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Sample records for catalytic reduction scr

  1. COST OF SELECTIVE CATALYTIC REDUCTION (SCR) APPLICATION FOR NOX CONTROL ON COAL-FIRED BOILERS

    Science.gov (United States)

    The report provides a methodology for estimating budgetary costs associated with retrofit applications of selective catalytic reduction (SCR) technology on coal-fired boilers. SCR is a postcombustion nitrogen oxides (NOx) control technology capable of providing NOx reductions >90...

  2. Selective catalytic reduction (SCR) NOx control for small natural gas-fired prime movers

    International Nuclear Information System (INIS)

    The application of selective catalytic reduction (SCR) to small natural gas-fired prime movers at cogeneration facilities and compressor stations could possibly increase due to regulatory forces to limit NOx from such sources. The natural gas industry is presently without a current database with which to evaluate the cost and operating characteristics of SCR under the conditions anticipated for small prime movers. This paper presents the results from a two-phase study undertaken to document SCR applications with emphasis on SCR system performance and costs. The database of small natural gas-fired prime mover SCR experience, focusing on prime mover characterization, SCR system performance, and SCR system costs will be described. Result from analysis of performance and cost data will be discussed, including analytical tools developed to project SCR system performance and costs

  3. Adaptive Model Predictive Control of Diesel Engine Selective Catalytic Reduction (SCR) Systems

    Science.gov (United States)

    McKinley, Thomas L.

    2009-01-01

    Selective catalytic reduction or SCR is coming into worldwide use for diesel engine emissions reduction for on- and off-highway vehicles. These applications are characterized by broad operating range as well as rapid and unpredictable changes in operating conditions. Significant nonlinearity, input and output constraints, and stringent performance…

  4. Chemical deactivation of Cu-SSZ-13 ammonia selective catalytic reduction (NH3-SCR) systems

    NARCIS (Netherlands)

    Lezcano-Gonzalez, I.; Deka, U.; van der Bij, H. E.; Paalanen, P.; Arstad, B.; Weckhuysen, B. M.; Beale, A. M.

    2014-01-01

    The chemical deactivation of Cu-SSZ-13 Ammonia Selective Catalytic Reduction (NH3-SCR) catalysts by Pt, Zn, Ca and P has been systematically investigated using a range of analytical techniques in order to study the influence on both the zeolitic framework and the active Cu2+ ions. The results obtain

  5. Optimization of internals for Selective Catalytic Reduction (SCR) for NO removal.

    Science.gov (United States)

    Lei, Zhigang; Wen, Cuiping; Chen, Biaohua

    2011-04-15

    This work tried to identify the relationship between the internals of selective catalytic reduction (SCR) system and mixing performance for controlling ammonia (NH(3)) slip. In the SCR flow section, arranging the flow-guided internals can improve the uniformity of velocity distribution but is unfavorable for the uniformity of NH(3) concentration distribution. The ammonia injection grids (AIG) with four kinds of nozzle diameters (i.e., 1.0 mm, 1.5 mm, 2.0 mm, and mixed diameters) were investigated, and it was found that the AIG with mixed nozzle diameters in which A3, A4, B3, and B4 nozzles' diameters are 1.0 mm and other nozzles' diameters are 1.5 mm is the most favorable for the uniformity of NH(3) concentration distribution. In the SCR reactor section, the appropriate space length between two catalyst layers, which serves as gas mixing in order to prevent maldistribution of gas concentrations into the second catalyst layer, under the investigated conditions is about 100, 1000, and 12 mm for honeycomb-like cordierite catalyst, plate-type catalysts with parallel channel arrangement, and with cross channel arrangement, respectively. Therefore, the cross channel arrangement is superior to the parallel channel arrangement in saving the SCR reactor volume.

  6. Selective catalytic reduction (SCR) of NO by urea loaded on activated carbon fibre (ACF) and CeO2/ACF at 30 degrees C: the SCR mechanism.

    Science.gov (United States)

    Zeng, Zheng; Lu, Pei; Li, Caiting; Zeng, Guangming; Jiang, Xiao; Zhai, Yunbo; Fan, Xiaopeng

    2012-06-01

    Selective catalytic reduction (SCR) of NO by urea loaded on rayon-based activated carbon fibre (ACF) and CeO2/ACF (CA) was studied at ambient temperature (30 degrees C) to establish a basic scheme for its reduction. Nitric oxide was found to be reduced to N2 with urea deposited on the ACF and CA. When oxygen was present, the greater the amount of loaded urea (20-60%), the greater the NO(x) conversions, which were between 72.03% and 77.30%, whereas the NO(x) conversions were about 50% when oxygen was absent. Moreover, when the urea was loaded on CA, a catalyst containing 40% urea/ACF loaded with 10% CeO2 (UCA4) could yield a NO(x) conversion of about 80% for 24.5 h. Based on the experimental results, the catalytic mechanisms of SCR with and without oxygen are discussed. The enhancing effect of oxygen resulted from the oxidation of NO to NO2, and urea was the main reducing agent in the SCR of loaded catalysts. ACF-C was the catalytic centre in the SCR of NO of ACF, while CeO2 of urea-loaded CA was the catalytic centre.

  7. Emission reduction from a diesel engine fueled by pine oil biofuel using SCR and catalytic converter

    Science.gov (United States)

    Vallinayagam, R.; Vedharaj, S.; Yang, W. M.; Saravanan, C. G.; Lee, P. S.; Chua, K. J. E.; Chou, S. K.

    2013-12-01

    In this work, we propose pine oil biofuel, a renewable fuel obtained from the resins of pine tree, as a potential substitute fuel for a diesel engine. Pine oil is endowed with enhanced physical and thermal properties such as lower viscosity and boiling point, which enhances the atomization and fuel/air mixing process. However, the lower cetane number of the pine oil hinders its direct use in diesel engine and hence, it is blended in suitable proportions with diesel so that the ignition assistance could be provided by higher cetane diesel. Since lower cetane fuels are prone to more NOX formation, SCR (selective catalyst reduction), using urea as reducing agent, along with a CC (catalytic converter) has been implemented in the exhaust pipe. From the experimental study, the BTE (brake thermal efficiency) was observed to be increased as the composition of pine oil increases in the blend, with B50 (50% pine oil and 50% diesel) showing 7.5% increase over diesel at full load condition. The major emissions such as smoke, CO, HC and NOX were reduced by 70.1%, 67.5%, 58.6% and 15.2%, respectively, than diesel. Further, the average emissions of B50 with SCR and CC assembly were observed to be reduced, signifying the positive impact of pine oil biofuel on atmospheric environment. In the combustion characteristics front, peak heat release rate and maximum in-cylinder pressure were observed to be higher with longer ignition delay.

  8. Effect of selective catalytic reduction (SCR) on fine particle emission from two coal-fired power plants in China

    Science.gov (United States)

    Li, Zhen; Jiang, Jingkun; Ma, Zizhen; Wang, Shuxiao; Duan, Lei

    2015-11-01

    Nitrogen oxides (NOx) emission abatement of coal-fired power plants (CFPPs) requires large-scaled installation of selective catalytic reduction (SCR), which would reduce secondary fine particulate matter (PM2.5) (by reducing nitrate aerosol) in the atmosphere. However, our field measurement of two CFPPs equipped with SCR indicates a significant increase of SO42- and NH4+ emission in primary PM2.5, due to catalytic enhancement of SO2 oxidation to SO3 and introducing of NH3 as reducing agent. The subsequent formation of (NH4)2SO4 or NH4HSO4 aerosol is commonly concentrated in sub-micrometer particulate matter (PM1) with a bimodal pattern. The measurement at the inlet of stack also showed doubled primary PM2.5 emission by SCR operation. This effect should therefore be considered when updating emission inventory of CFPPs. By rough estimation, the enhanced primary PM2.5 emission from CFPPs by SCR operation would offset 12% of the ambient PM2.5 concentration reduction in cities as the benefit of national NOx emission abatement, which should draw attention of policy-makers for air pollution control.

  9. Mercury Oxidation over Selective Catalytic Reduction (SCR) Catalysts - Ph.d. thesis Karin Madsen

    DEFF Research Database (Denmark)

    Madsen, Karin

    The vanadium-based SCR catalyst used for NOx-control promotes the oxidation of elemental mercury Hg0 to Hg2+ in flue gases from coal-fired power plants. Hg2+ is water soluble and can effectively be captured in a wet scrubber. This means that the combination of an SCR with a wet FGD can offer...... an effective control option for mercury. Laboratory experiments have been carried out to quantify the Hg0 oxidation that can be achieved over commercial SCR catalysts for different gas compositions, operating conditions and catalyst types. The following three net reactions have been identified as relevant...... for the mercury chemistry over the SCR: R1. 2 HCl + Hg0 + 1/2 O2 ↔ HgCl2 + H2O R2. 2 NH3 + 3 HgCl2 ↔ N2 + 3 Hg0 + 6 HCl R3. 2 NO + 2 NH3 + 1/2 O2 ↔ 2 N2 + 3 H2O where reaction R1 is the oxidation of Hg0 by HCl, reaction R2 is the reduction of HgCl2 by NH3 and reaction R3 is the DeNOx reaction. The importance...

  10. NH3-SCR performance of fresh and hydrothermally aged Fe-ZSM-5 in standard and fast selective catalytic reduction reactions.

    Science.gov (United States)

    Shi, Xiaoyan; Liu, Fudong; Xie, Lijuan; Shan, Wenpo; He, Hong

    2013-04-01

    Hydrothermal stability is one of the challenges for the practical application of Fe-ZSM-5 catalysts in the selective catalytic reduction (SCR) of NO with NH3 (NH(3)-SCR) for diesel engines. The presence of NO(3) in the exhaust gases can enhance the deNOx activity because of the fast SCR reaction. In this work, a Fe-ZSM-5 catalyst was prepared by a solid-state ion-exchange method and was hydrothermally deactivated at 800 °C in the presence of 10% H(2)O. The activity of fresh and hydrothermal aged Fe-ZSM-5 catalysts was investigated in standard SCR (NO(2)/NOx = 0) and in fast SCR with NO(2)/NOx = 0.3 and 0.5. In standard SCR, hydrothermal aging of Fe-ZSM-5 resulted in a significant decrease of low-temperature activity and a slight increase in high-temperature activity. In fast SCR, NOx conversion over aged Fe-ZSM-5 was significantly increased but was still lower than that over fresh catalyst. Additionally, production of N(2)O in fast SCR was much more apparent over aged Fe-ZSM-5 than over fresh catalyst. We propose that, in fast SCR, the rate of key reactions related to NO is slower over aged Fe-ZSM-5 than over fresh catalyst, thus increasing the probabilities of side reactions involving the formation of N(2)O. PMID:23477804

  11. NH3-SCR performance of fresh and hydrothermally aged Fe-ZSM-5 in standard and fast selective catalytic reduction reactions.

    Science.gov (United States)

    Shi, Xiaoyan; Liu, Fudong; Xie, Lijuan; Shan, Wenpo; He, Hong

    2013-04-01

    Hydrothermal stability is one of the challenges for the practical application of Fe-ZSM-5 catalysts in the selective catalytic reduction (SCR) of NO with NH3 (NH(3)-SCR) for diesel engines. The presence of NO(3) in the exhaust gases can enhance the deNOx activity because of the fast SCR reaction. In this work, a Fe-ZSM-5 catalyst was prepared by a solid-state ion-exchange method and was hydrothermally deactivated at 800 °C in the presence of 10% H(2)O. The activity of fresh and hydrothermal aged Fe-ZSM-5 catalysts was investigated in standard SCR (NO(2)/NOx = 0) and in fast SCR with NO(2)/NOx = 0.3 and 0.5. In standard SCR, hydrothermal aging of Fe-ZSM-5 resulted in a significant decrease of low-temperature activity and a slight increase in high-temperature activity. In fast SCR, NOx conversion over aged Fe-ZSM-5 was significantly increased but was still lower than that over fresh catalyst. Additionally, production of N(2)O in fast SCR was much more apparent over aged Fe-ZSM-5 than over fresh catalyst. We propose that, in fast SCR, the rate of key reactions related to NO is slower over aged Fe-ZSM-5 than over fresh catalyst, thus increasing the probabilities of side reactions involving the formation of N(2)O.

  12. HYBRID SELECTIVE NON-CATALYTIC REDUCTION (SNCR)/SELECTIVE CATALYTIC REDUCTION (SCR) DEMONSTRATION FOR THE REMOVAL OF NOx FROM BOILER FLUE GASES; FINAL

    International Nuclear Information System (INIS)

    The U. S. Department of Energy (DOE), Electric Power Research Institute (EPRI), Pennsylvania Electric Energy Research Council, (PEERC), New York State Electric and Gas and GPU Generation, Inc. jointly funded a demonstration to determine the capabilities for Hybrid SNCR/SCR (Selective Non-Catalytic Reduction/Selective Catalytic Reduction) technology. The demonstration site was GPU Generation's Seward Unit No.5 (147MW) located in Seward Pennsylvania. The demonstration began in October of 1997 and ended in December 1998. DOE funding was provided through Grant No. DE-FG22-96PC96256 with T. J. Feeley as the Project Manager. EPRI funding was provided through agreements TC4599-001-26999 and TC4599-002-26999 with E. Hughes as the Project Manager. This project demonstrated the operation of the Hybrid SNCR/SCR NO(sub x) control process on a full-scale coal fired utility boiler. The hybrid technology was expected to provide a cost-effective method of reducing NO(sub x) while balancing capital and operation costs. An existing urea based SNCR system was modified with an expanded-duct catalyst to provide increased NO(sub x) reduction efficiency from the SNCR while producing increased ammonia slip levels to the catalyst. The catalyst was sized to reduce the ammonia slip to the air heaters to less than 2 ppm while providing equivalent NO(sub x) reductions. The project goals were to demonstrate hybrid technology is capable of achieving at least a 55% reduction in NO(sub x) emissions while maintaining less than 2ppm ammonia slip to the air heaters, maintain flyash marketability, verify the cost benefit and applicability of Hybrid post combustion technology, and reduce forced outages due to ammonium bisulfate (ABS) fouling of the air heaters. Early system limitations, due to gas temperature stratification, restricted the Hybrid NO(sub x) reduction capabilities to 48% with an ammonia slip of 6.1 mg/Nm(sup 3) (8 ppm) at the catalyst inlet. After resolving the stratification problem

  13. HYBRID SELECTIVE NON-CATALYTIC REDUCTION (SNCR)/SELECTIVE CATALYTIC REDUCTION (SCR) DEMONSTRATION FOR THE REMOVAL OF NOx FROM BOILER FLUE GASES

    Energy Technology Data Exchange (ETDEWEB)

    Jerry B. Urbas

    1999-05-01

    The U. S. Department of Energy (DOE), Electric Power Research Institute (EPRI), Pennsylvania Electric Energy Research Council, (PEERC), New York State Electric and Gas and GPU Generation, Inc. jointly funded a demonstration to determine the capabilities for Hybrid SNCR/SCR (Selective Non-Catalytic Reduction/Selective Catalytic Reduction) technology. The demonstration site was GPU Generation's Seward Unit No.5 (147MW) located in Seward Pennsylvania. The demonstration began in October of 1997 and ended in December 1998. DOE funding was provided through Grant No. DE-FG22-96PC96256 with T. J. Feeley as the Project Manager. EPRI funding was provided through agreements TC4599-001-26999 and TC4599-002-26999 with E. Hughes as the Project Manager. This project demonstrated the operation of the Hybrid SNCR/SCR NO{sub x} control process on a full-scale coal fired utility boiler. The hybrid technology was expected to provide a cost-effective method of reducing NO{sub x} while balancing capital and operation costs. An existing urea based SNCR system was modified with an expanded-duct catalyst to provide increased NO{sub x} reduction efficiency from the SNCR while producing increased ammonia slip levels to the catalyst. The catalyst was sized to reduce the ammonia slip to the air heaters to less than 2 ppm while providing equivalent NO{sub x} reductions. The project goals were to demonstrate hybrid technology is capable of achieving at least a 55% reduction in NO{sub x} emissions while maintaining less than 2ppm ammonia slip to the air heaters, maintain flyash marketability, verify the cost benefit and applicability of Hybrid post combustion technology, and reduce forced outages due to ammonium bisulfate (ABS) fouling of the air heaters. Early system limitations, due to gas temperature stratification, restricted the Hybrid NO{sub x} reduction capabilities to 48% with an ammonia slip of 6.1 mg/Nm{sup 3} (8 ppm) at the catalyst inlet. After resolving the stratification

  14. The selective catalytic reduction (SCR) of NO with NH3 at vanadium oxide catalysts: Adsorption, diffusion, reaction

    International Nuclear Information System (INIS)

    The selective catalytic reduction (SCR) of NOx with NH3 over vanadium based metal-oxide (VOx) catalysts has been proven to be one of the most effective NOx reduction processes. Even though it is widely used in commercial applications details of the reaction mechanism are still under debate. Experiments show that adsorption, diffusion, and reactions with NO and (de)hydrogenation processes at the VOx surface contribute elementary steps. These processes are examined in theoretical studies employing density-functional theory together with gradient corrected functionals. The VOx substrate is modeled by clusters cut out from the ideal V2O5(010) surface where peripheral oxygen bonds are saturated by hydrogen. Apart from the perfect oxide surface also differently reduced surfaces are considered by introducing oxygen vacancies. NH3 is found to interact only weakly with the perfect V2O5(010) surface. In the presence of OH groups (Broensted acid sites) NH3 can form a surface NH4+ species. NH3 can also interact with the surface near oxygen vacancies, adsorbing at vanadium centers of lower coordination (Lewis acid sites). In contrast, NO interacts much more weakly with the surface. Further, simultaneous NO, NH3 adsorption and SCR reaction scenarios at Broensted and Lewis acid sites are examined. They result in different reaction paths and intermediates as will be discussed in detail.

  15. Fabrication of doped Titania (TiO2) nanofibers to serve as catalysts in NH3-Selective CatalyticReduction (SCR)

    DEFF Research Database (Denmark)

    Marani, Debora; Silva, Rafael Hubert; Dankeaw, Apiwat;

    2016-01-01

    of the NOx in exhausts via the NH3 SelectiveCatalytic Reduction (SCR) method. By combining electrospinning and sol-gel chemistry, materials areprocessed as nanofibers with the catalytic components (e. g. V2O5-WO3) incorporated as dopants into thesupporting anatase phase (e. g TiO2). Remarkable high NOx...... conversion efficiencies are obtained andassociated with the unique features deriving from the synergism among the doping approach, the nanoscaleconfinement, and the nano-fibrous texture. A novel concept of self-supported, lightweight and ultra-compactdesign SCR reactor is defined....

  16. Innovative clean coal technology (ICCT): demonstration of selective catalytic reduction (SCR) technology for the control of nitrogen oxide (NOx) emission from high-sulfur, coal-fired boilers - economic evaluation of commercial-scale SCR applications for utility boilers

    International Nuclear Information System (INIS)

    This report presents the results of an economic evaluation produced as part of the Innovative Clean Coal Technology project, which demonstrated selective catalytic reduction (SCR) technology for reduction of NOx emissions from utility boilers burning U.S. high-sulfur coal. The document includes a commercial-scale capital and O ampersand M cost evaluation of SCR technology applied to a new facility, coal-fired boiler utilizing high-sulfur U.S. coal. The base case presented herein determines the total capital requirement, fixed and variable operating costs, and levelized costs for a new 250-MW pulverized coal utility boiler operating with a 60-percent NOx removal. Sensitivity evaluations are included to demonstrate the variation in cost due to changes in process variables and assumptions. This report also presents the results of a study completed by SCS to determine the cost and technical feasibility of retrofitting SCR technology to selected coal-fired generating units within the Southern electric system

  17. Active sites, deactivation and stabilization of Fe-ZSM-5 for the selective catalytic reduction (SCR) of NO with NH(3).

    Science.gov (United States)

    Kröcher, Oliver; Brandenberger, Sandro

    2012-01-01

    Fe-ZSM-5 has been systematically investigated as catalyst for the selective catalytic reduction (SCR) of NO with NH(3), concentrating on the active sites, the deactivation mechanism during hydrothermal aging and the chemical possibilities to stabilize this type of SCR catalyst. Regarding the active SCR sites, it could be shown that monomeric species start to become active at the lowest temperatures (E(a,app) ≈ 36.3 ± 0.2 kJ/mol), followed by dimeric species at intermediate temperatures (E(a,app) ≈ 77 ± 16 kJ/mol) and oligomeric species at high temperatures. Experiments with Fe-ZSM-5 samples, in which the Brønsted acidity was specifically removed, proved that Brønsted acidity is not required for high SCR activity and that NH(3) can also be adsorbed on other acidic sites on the zeolite surface. The hydrothermal deactivation of Fe-ZSM-5 could be explained by the migration of active iron ions from the exchange sites. Parallel to the iron migration dealumination of the zeolite framework occurs, which has to be regarded as an independent process. The migration of iron can be reduced by the targeted reaction of the aluminum hydroxide groups in the lattice with trimethylaluminium followed by calcination. With respect to the application of iron zeolites in the SCR process in diesel vehicles, the most efficient stabilization method would be to switch from the ZSM-5 to the BEA structure type. The addition of NO(2) to the feed gas is another effective measure to increase the activity of even strongly deactivated iron zeolites tremendously. PMID:23211727

  18. Active sites, deactivation and stabilization of Fe-ZSM-5 for the selective catalytic reduction (SCR) of NO with NH(3).

    Science.gov (United States)

    Kröcher, Oliver; Brandenberger, Sandro

    2012-01-01

    Fe-ZSM-5 has been systematically investigated as catalyst for the selective catalytic reduction (SCR) of NO with NH(3), concentrating on the active sites, the deactivation mechanism during hydrothermal aging and the chemical possibilities to stabilize this type of SCR catalyst. Regarding the active SCR sites, it could be shown that monomeric species start to become active at the lowest temperatures (E(a,app) ≈ 36.3 ± 0.2 kJ/mol), followed by dimeric species at intermediate temperatures (E(a,app) ≈ 77 ± 16 kJ/mol) and oligomeric species at high temperatures. Experiments with Fe-ZSM-5 samples, in which the Brønsted acidity was specifically removed, proved that Brønsted acidity is not required for high SCR activity and that NH(3) can also be adsorbed on other acidic sites on the zeolite surface. The hydrothermal deactivation of Fe-ZSM-5 could be explained by the migration of active iron ions from the exchange sites. Parallel to the iron migration dealumination of the zeolite framework occurs, which has to be regarded as an independent process. The migration of iron can be reduced by the targeted reaction of the aluminum hydroxide groups in the lattice with trimethylaluminium followed by calcination. With respect to the application of iron zeolites in the SCR process in diesel vehicles, the most efficient stabilization method would be to switch from the ZSM-5 to the BEA structure type. The addition of NO(2) to the feed gas is another effective measure to increase the activity of even strongly deactivated iron zeolites tremendously.

  19. EMISSION REDUCTION FROM A DIESEL ENGINE FUELED BY CERIUM OXIDE NANO-ADDITIVES USING SCR WITH DIFFERENT METAL OXIDES COATED CATALYTIC CONVERTER

    Directory of Open Access Journals (Sweden)

    B. JOTHI THIRUMAL

    2015-11-01

    Full Text Available This paper reports the results of experimental investigations on the influence of the addition of cerium oxide in nanoparticle form on the major physiochemical properties and the performance of diesel. The fuel is modified by dispersing the catalytic nanoparticle by ultrasonic agitation. The physiochemical properties of sole diesel fuel and modified fuel are tested with ASTM standard procedures. The effects of the additive nanoparticles on the individual fuel properties, the engine performance, and emissions are studied, and the dosing level of the additive is optimized. Cerium oxide acts as an oxygen-donating catalyst and provides oxygen for the oxidation of CO during combustion. The active energy of cerium oxide acts to burn off carbon deposits within the engine cylinder at the wall temperature and prevents the deposition of non-polar compounds on the cylinder wall which results in reduction in HC emission by 56.5%. Furthermore, a low-cost metal oxide coated SCR (selective catalyst reduction, using urea as a reducing agent, along with different types of CC (catalytic converter, has been implemented in the exhaust pipe to reduce NOx. It was observed that a reduction in NOx emission is 50–60%. The tests revealed that cerium oxide nanoparticles can be used as an additive in diesel to improve complete combustion of the fuel and reduce the exhaust emissions significantly.

  20. Examination of surface phenomena of V₂O₅ loaded on new nanostructured TiO₂ prepared by chemical vapor condensation for enhanced NH₃-based selective catalytic reduction (SCR) at low temperatures.

    Science.gov (United States)

    Cha, Woojoon; Yun, Seong-Taek; Jurng, Jongsoo

    2014-09-01

    In this article, we describe the investigation and surface characterization of a chemical vapor condensation (CVC)-TiO2 support material used in a V2O5/TiO2 catalyst for enhanced selective catalytic reduction (SCR) activity and confirm the mechanism of surface reactions. On the basis of previous studies and comparison with a commercial TiO2 catalyst, we examine four fundamental questions: first, the reason for increased surface V(4+) ion concentrations; second, the origin of the increase in surface acid sites; third, a basis for synergistic influences on improvements in SCR activity; and fourth, a reason for improved catalytic activity at low reaction temperatures. In this study, we have cited the result of SCR with NH3 activity for removing NOx and analyzed data using the reported result and data from previous studies on V2O5/CVC-TiO2 for the SCR catalyst. In order to determine the properties of suitable CVC-TiO2 surfaces for efficient SCR catalysis at low temperatures, CVC-TiO2 specimens were prepared and characterized using techniques such as XRD, BET, HR-TEM, XPS, FT-IR, NH3-TPD, photoluminescence (PL) spectroscopy, H2-TPR, and cyclic voltammetry. The results obtained for the CVC-TiO2 materials were also compared with those of commercial TiO2.

  1. SELECTIVE CATALYTIC REDUCTION MERCURY FIELD SAMPLING PROJECT

    Science.gov (United States)

    A lack of data still exists as to the effect of selective catalytic reduction (SCR), selective noncatalytic reduction (SNCR), and flue gas conditioning on the speciation and removal of mercury (Hg) at power plants. This project investigates the impact that SCR, SNCR, and flue gas...

  2. Innovative Clean Coal Technology (ICCT). Demonstration of Selective Catalytic Reduction (SCR) technology for the control of nitrogen oxide (NO{sub x}) emissions from high-sulfur coal-fired boilers: Volume 1. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-10-01

    The objective of this project is to demonstrate and evaluate commercially available Selective Catalytic Reduction (SCR) catalysts from U.S., Japanese and European catalyst suppliers on a high-sulfur U.S. coal-fired boiler. SCR is a post-combustion nitrogen oxide (NO.) control technology that involves injecting ammonia into the flue gas generated from coal combustion in an electric utility boiler. The flue gas containing ammonia is then passed through a reactor that contains a specialized catalyst. In the presence of the catalyst, the ammonia reacts with NO. to convert it to nitrogen and water vapor. Although SCR is widely practiced in Japan and Europe on gas-, oil-, and low-sulfur coal- fired boilers, there are several technical uncertainties associated with applying SCR to U.S. coals. These uncertainties include: 1) potential catalyst deactivation due to poisoning by trace metal species present in U.S. coals that are not present in other fuels. 2) performance of the technology and effects on the balance-of- plant equipment in the presence of high amounts of SO{sub 2} and SO{sub 3}. 3) performance of a wide variety of SCR catalyst compositions, geometries and methods of manufacturer under typical high-sulfur coal-fired utility operating conditions. These uncertainties were explored by operating nine small-scale SCR reactors and simultaneously exposing different SCR catalysts to flue gas derived from the combustion of high sulfur U.S. coal. In addition, the test facility operating experience provided a basis for an economic study investigating the implementation of SCR technology.

  3. Urea thermolysis and NOx reduction with and without SCR catalysts

    International Nuclear Information System (INIS)

    Urea-selective catalytic reduction (SCR) has been a leading contender for removal of nitrogen oxides (deNOx) from diesel engine emissions. Despite its advantages, the SCR technology faces some critical detriments to its catalytic performance such as catalyst surface passivation (caused by deposit formation) and consequent stoichiometric imbalance of the urea consumption. Deposit formation deactivates catalytic performance by not only consuming part of the ammonia produced during urea decomposition but also degrading the structural and thermal properties of the catalyst surface. We have characterized the urea thermolysis with and without the urea-SCR catalyst using both spectroscopic (DRIFTS and Raman) and thermal techniques (thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC)) to identify the deposit components and their corresponding thermal properties. Urea thermolysis exhibits two decomposition stages, involving ammonia generation and consumption, respectively. The decomposition after the second stage leads to the product of melamine complexes, (HNC=NH)x(HNCO)y, that hinder catalytic performance. The presence of catalyst accompanied with a good spray of the urea solution helps to eliminate the second stage. In this work, kinetics of the direct reduction of NOx by urea is determined and the possibility of using additives to the urea solution in order to rejuvenate the catalyst surface and improve its performance will be discussed

  4. SELECTIVE CATALYTIC REDUCTION (SCR OF NO BY AMMONIA OVER V2O5/TiO2 CATALYST IN A CATALYTIC FILTER MEDIUM AND HONEYCOMB REACTOR: A KINETIC MODELING STUDY

    Directory of Open Access Journals (Sweden)

    M. Nahavandi

    2015-12-01

    Full Text Available Abstract The present study addresses a numerical modeling and simulation based on the available knowledge of SCR kinetics for prediction of NO conversion over a V2O3/TiO3 catalyst through a catalytic filter medium and honeycomb reactor. After introducing the NH3-SCR system with specific operational criteria, a reactor model was developed to evaluate the effect of various operating parameters such as flue gas temperature, velocity, NH3/NO molar ratio, etc., on the SCR process. Computational investigations were performed based on the proposed model and optimum operational conditions were identified. Simulation results indicate that SCR performance is substantially under the effects of reactant concentration and operating temperature, so that the concentration of unreacted ammonia emitted from reactor discharge (ammonia slip increases significantly at NH3/NO ratios of more than 1.14 and operating temperatures less than 360 ºC and 300 ºC, respectively, in the catalytic filter medium and honeycomb reactor. The results also show that there are three sections in NO conversion variation versus changing temperature and the required conversion with a maximum of almost 87% and low level of ammonia slip can be achieved at the NH3/NO ratio of 1 and temperature range of 240–360 ºC in both reactors.

  5. Innovative clean coal technology (ICCT): demonstration of selective catalytic reduction (SCR) technology for the control of nitrogen oxide (NO{sub x}) emission from high-sulfur, coal-fired boilers - economic evaluation of commercial-scale SCR applications for utility boilers

    Energy Technology Data Exchange (ETDEWEB)

    Healy, E.C.; Maxwell, J.D.; Hinton, W.S.

    1996-09-01

    This report presents the results of an economic evaluation produced as part of the Innovative Clean Coal Technology project, which demonstrated selective catalytic reduction (SCR) technology for reduction of NO{sub x} emissions from utility boilers burning U.S. high-sulfur coal. The document includes a commercial-scale capital and O&M cost evaluation of SCR technology applied to a new facility, coal-fired boiler utilizing high-sulfur U.S. coal. The base case presented herein determines the total capital requirement, fixed and variable operating costs, and levelized costs for a new 250-MW pulverized coal utility boiler operating with a 60-percent NO{sub x} removal. Sensitivity evaluations are included to demonstrate the variation in cost due to changes in process variables and assumptions. This report also presents the results of a study completed by SCS to determine the cost and technical feasibility of retrofitting SCR technology to selected coal-fired generating units within the Southern electric system.

  6. NOX REMOVAL WITH COMBINED SELECTIVE CATALYTIC REDUCTION AND SELECTIVE NONCATALYTIC REDUCTION: PILOT- SCALE TEST RESULTS

    Science.gov (United States)

    Pilot-scale tests were conducted to develop a combined nitrogen oxide (NOx) reduction technology using both selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). A commercially available vanadium-and titatnium-based composite honeycomb catalyst and enh...

  7. Modelling of an SCR catalytic converter for diesel exhaust after treatment: Dynamic effects at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Tronconi, Enrico; Nova, Isabella; Ciardelli, Cristian [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' G. Natta' , Politecnico di Milano, P.zza L. Da Vinci 32, 20133 Milano (Italy); Chatterjee, Daniel; Bandl-Konrad, Brigitte; Burkhardt, Thomas [DaimlerChrysler AG Abteilung RBP/C, HPC: 096-E220, D-70546 Stuttgart (Germany)

    2005-08-15

    As part of a fundamental and applied work on the development of an unsteady mathematical model of the NH{sub 3}-selective catalytic reduction (SCR) process for design and control of integrated after-treatment systems of heavy-duty engines, we present herein a transient kinetic analysis of the standard SCR NO+NH{sub 3} system which provides new insight in the catalytic kinetics and mechanism prevailing at low temperatures. Based on kinetic runs performed over a commercial powdered V{sub 2}O{sub 5}-WO{sub 3}-TiO{sub 2} catalyst in the 175-450{sup o}C T-range feeding NH{sub 3} and NO (1000ppm) in the presence of H{sub 2}O (1-10%, v/v) and O{sub 2} (2-6%, v/v), an original dual-site modified redox rate law is derived which effectively accounts for NH{sub 3} inhibition effects observed during transient reactive experiments at T<250{sup o}C. We also demonstrate that implementation of the novel modified redox kinetics into a fully predictive 1D+1D model of SCR monolith reactors can significantly improve simulations of SCR transient runs at different scales, including engine test bench experiments over full-scale SCR honeycomb catalysts.

  8. Economical way to synthesize SSZ-13 with abundant ion-exchanged Cu+ for an extraordinary performance in selective catalytic reduction (SCR) of NOx by ammonia.

    Science.gov (United States)

    Chen, Biaohua; Xu, Ruinian; Zhang, Runduo; Liu, Ning

    2014-12-01

    In this study, an economical way for SSZ-13 preparation with the essentially cheap choline chloride as template has been attempted. The as-synthesized SSZ-13 zeolite after ion exchange by copper nitrate solution exhibited a superior SCR performance (over 95% NOx conversion across a broad range from 150 to 400 °C) to the traditional zeolite-based catalysts of Cu-Beta and Cu-ZSM-5. Furthermore, the opportune size of pore opening (∼3.8 Å) made Cu-SSZ-13 exhibiting the best selectivity to N2 as well as satisfactory tolerance toward SO2 and C3H6 poisonings. The characterization (XRD, XPS, XRF, and H2-TPR) of samples confirmed that Cu-SSZ-13 possessed the most abundant Cu cations among three investigated Cu-zeolites; furthermore, either on the surface or in the bulk the ratio of Cu(+)/Cu(2+) ions for Cu-SSZ-13 is also the highest. New finding was announced that CHA-type topology is in favor of the formation of copper cations, especially generating much more Cu(+) ions than the others, rather than CuO. The activity test of Cu(CuCl)-ZSM-5 (prepared by a solid-state ion-exchange method) clearly indicated that Cu(+) ions could make a major contribution to the low-temperature deNOx activity. The activity of protonic zeolites (H-SSZ-13, H-Beta, H-ZSM-5) revealed the topology effect on SCR performances. PMID:25365767

  9. Economical way to synthesize SSZ-13 with abundant ion-exchanged Cu+ for an extraordinary performance in selective catalytic reduction (SCR) of NOx by ammonia.

    Science.gov (United States)

    Chen, Biaohua; Xu, Ruinian; Zhang, Runduo; Liu, Ning

    2014-12-01

    In this study, an economical way for SSZ-13 preparation with the essentially cheap choline chloride as template has been attempted. The as-synthesized SSZ-13 zeolite after ion exchange by copper nitrate solution exhibited a superior SCR performance (over 95% NOx conversion across a broad range from 150 to 400 °C) to the traditional zeolite-based catalysts of Cu-Beta and Cu-ZSM-5. Furthermore, the opportune size of pore opening (∼3.8 Å) made Cu-SSZ-13 exhibiting the best selectivity to N2 as well as satisfactory tolerance toward SO2 and C3H6 poisonings. The characterization (XRD, XPS, XRF, and H2-TPR) of samples confirmed that Cu-SSZ-13 possessed the most abundant Cu cations among three investigated Cu-zeolites; furthermore, either on the surface or in the bulk the ratio of Cu(+)/Cu(2+) ions for Cu-SSZ-13 is also the highest. New finding was announced that CHA-type topology is in favor of the formation of copper cations, especially generating much more Cu(+) ions than the others, rather than CuO. The activity test of Cu(CuCl)-ZSM-5 (prepared by a solid-state ion-exchange method) clearly indicated that Cu(+) ions could make a major contribution to the low-temperature deNOx activity. The activity of protonic zeolites (H-SSZ-13, H-Beta, H-ZSM-5) revealed the topology effect on SCR performances.

  10. EMISSION REDUCTION FROM A DIESEL ENGINE FUELED BY CERIUM OXIDE NANO-ADDITIVES USING SCR WITH DIFFERENT METAL OXIDES COATED CATALYTIC CONVERTER

    OpenAIRE

    B. JOTHI THIRUMAL; E, JAMES GUNASEKARAN; LOGANATHAN; C.G. Saravanan

    2015-01-01

    This paper reports the results of experimental investigations on the influence of the addition of cerium oxide in nanoparticle form on the major physiochemical properties and the performance of diesel. The fuel is modified by dispersing the catalytic nanoparticle by ultrasonic agitation. The physiochemical properties of sole diesel fuel and modified fuel are tested with ASTM standard procedures. The effects of the additive nanoparticles on the individual fuel properties, the engine performanc...

  11. Reduction of nitric oxide emissions of stationary diesel engines with SCR and urea as reduction agents. Stickstoffoxidminderung bei stationaeren Dieselmotoren mittels SCR und Harnstoff als Reduktionsmittel

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, M.; Elsener, M.; Eicher, H.P.

    1991-03-01

    Experiments were carried out to determine whether urea can replace ammonia in the selective catalytic reduction of nitric oxides. Pyrolysis experiments with aqueous urea solutions showed that it depended on the conditions of decomposition whether ammonia or urea was produced in changing quantities. Like pure ammonia the pyrolysis-gas mixture can be used in SCR catalytic converters with nitric oxides. Experiments with the exhaust gas of a diesel engine showed that the method also works in practice and is basically ready for application. Successfull application on a wider basis however can only start after overcoming the difficult technical problems of administering the reduction agent, process control, intermitting operation and service life of catalytic converter. (orig.).

  12. Chemical speciation of PM emissions from heavy-duty diesel vehicles equipped with diesel particulate filter (DPF) and selective catalytic reduction (SCR) retrofits

    Science.gov (United States)

    Biswas, Subhasis; Verma, Vishal; Schauer, James J.; Sioutas, Constantinos

    Four heavy-duty diesel vehicles (HDDVs) in six retrofitted configurations (CRT ®, V-SCRT ®, Z-SCRT ®, Horizon, DPX and CCRT ®) and a baseline vehicle operating without after--treatment were tested under cruise (50 mph), transient UDDS and idle driving modes. As a continuation of the work by Biswas et al. [Biswas, S., Hu, S., Verma, V., Herner, J., Robertson, W.J., Ayala, A., Sioutas, C., 2008. Physical properties of particulate matter (PM) from late model heavy-duty diesel vehicles operating with advanced emission control technologies. Atmospheric Environment 42, 5622-5634.] on particle physical parameters, this paper focuses on PM chemical characteristics (Total carbon [TC], Elemental carbon [EC], Organic Carbon [OC], ions and water-soluble organic carbon [WSOC]) for cruise and UDDS cycles only. Size-resolved PM collected by MOUDI-Nano-MOUDI was analyzed for TC, EC and OC and ions (such as sulfate, nitrate, ammonium, potassium, sodium and phosphate), while Teflon coated glass fiber filters from a high volume sampler were extracted to determine WSOC. The introduction of retrofits reduced PM mass emissions over 90% in cruise and 95% in UDDS. Similarly, significant reductions in the emission of major chemical constituents (TC, OC and EC) were achieved. Sulfate dominated PM composition in vehicle configurations (V-SCRT ®-UDDS, Z-SCRT ®-Cruise, CRT ® and DPX) with considerable nucleation mode and TC was predominant for configurations with less (Z-SCRT ®-UDDS) or insignificant (CCRT ®, Horizon) nucleation. The transient operation increases EC emissions, consistent with its higher accumulation PM mode content. In general, solubility of organic carbon is higher (average ˜5 times) for retrofitted vehicles than the baseline vehicle. The retrofitted vehicles with catalyzed filters (DPX, CCRT ®) had decreased OC solubility (WSOC/OC: 8-25%) unlike those with uncatalyzed filters (SCRT ®s, Horizon; WSOC/OC ˜ 60-100%). Ammonium was present predominantly in the

  13. INDUSTRIAL BOILER RETROFIT FOR NOX CONTROL: COMBINED SELECTIVE NONCATALYTIC REDUCTION AND SELECTIVE CATALYTIC REDUCTION

    Science.gov (United States)

    The paper describes retrofitting and testing a 590 kW (2 MBtu/hr), oil-fired, three-pass, fire-tube package boiler with a combined selective noncatalytic reduction (SNCR) and selective catalytic reduction (SCR) system. The system demonstrated 85% nitrogen oxides (NOx) reduction w...

  14. SCR-catalytic converter technology using urea for industrial and thermal power plants. SCR-Katalysatortechnik mit Harnstoff fuer Industrie- und Heizkraftwerke

    Energy Technology Data Exchange (ETDEWEB)

    Hartenstein, A. (H und H Innotech GmbH (Switzerland)); Mayer, A. (H und H Innotech GmbH (Switzerland))

    1994-01-01

    The subjects are dealt with in 6 chapters: 1. Fuels, pollutants, prices 2. fields of application of catalytic converter systems 3. system description of the SCR catalytic converter plant using area 4. catalytic converter reactor and applications 5. efficiencies of catalytic converter plants 6. examples and profitability. (HW)

  15. INVESTIGATION OF SELECTIVE CATALYTIC REDUCTION IMPACT ON MERCURY SPECIATION UNDER SIMULATED NOX EMISSION CONTROL CONDITIONS

    Science.gov (United States)

    Selective catalytic reduction (SCR) technology is being increasingly applied for controlling emissions of nitrogen oxides (NOx) from coal-fired boilers. Some recent field and pilot studies suggest that the operation of SCR could affect the chemical form of mercury in the coal com...

  16. Co3O4 based catalysts for NO oxidation and NOx reduction in fast SCR process

    International Nuclear Information System (INIS)

    Reaction activities of several developed catalysts for NO oxidation and NOx (NO + NO2) reduction have been determined in a fixed bed differential reactor. Among all the catalysts tested, Co3O4 based catalysts are the most active ones for both NO oxidation and NOx reduction reactions even at high space velocity (SV) and low temperature in the fast selective catalytic reduction (SCR) process. Over Co3O4 catalyst, the effects of calcination temperatures, SO2 concentration, optimum SV for 50% conversion of NO to NO2 were determined. Also, Co3O4 based catalysts (Co3O4-WO3) exhibit significantly higher conversion than all the developed DeNOx catalysts (supported/unsupported) having maximum conversion of NOx even at lower temperature and higher SV since the mixed oxide Co-W nanocomposite is formed. In case of the fast SCR, N2O formation over Co3O4-WO3 catalyst is far less than that over the other catalysts but the standard SCR produces high concentration of N2O over all the catalysts. The effect of SO2 concentration on NOx reduction is found to be almost negligible may be due to the presence of WO3 that resists SO2 oxidation. (author)

  17. GENERIC VERIFICATION PROTOCOL FOR DETERMINATION OF EMISSIONS REDUCTIONS FROM SELECTIVE CATALYTIC REDUCTIONS CONTROL TECHNOLOGIES FOR HIGHWAY, NONROAD, AND STATIONARY USE DIESEL ENGINES

    Science.gov (United States)

    The protocol describes the Environmental Technology Verification (ETV) Program's considerations and requirements for verification of emissions reduction provided by selective catalytic reduction (SCR) technologies. The basis of the ETV will be comparison of the emissions and perf...

  18. State Estimation for the Automotive SCR Process

    DEFF Research Database (Denmark)

    Zhou, Guofeng; Huusom, Jakob Kjøbsted; Jørgensen, John Bagterp

    2012-01-01

    Selective catalytic reduction (SCR) of NOx is a widely applied diesel engine exhaust gas aftertreatment technology. For advanced SCR process control, like model predictive control, full state information of the process is required. The ammonia coverage ratio inside the catalyst is difficult...... present for SCR in engine applications, we recommend to estimating the ammonia coverage using the extended Kalman filter....

  19. A consistent reaction scheme for the selective catalytic reduction of nitrogen oxides with ammonia

    DEFF Research Database (Denmark)

    Janssens, Ton V.W.; Falsig, Hanne; Lundegaard, Lars Fahl;

    2015-01-01

    For the first time, the standard and fast selective catalytic reduction of NO by NH3 are described in a complete catalytic cycle, that is able to produce the correct stoichiometry, while only allowing adsorption and desorption of stable molecules. The standard SCR reaction is a coupling of the ac......For the first time, the standard and fast selective catalytic reduction of NO by NH3 are described in a complete catalytic cycle, that is able to produce the correct stoichiometry, while only allowing adsorption and desorption of stable molecules. The standard SCR reaction is a coupling...... of the activation of NO by O2 with the fast SCR reaction, enabled by the release of NO2. According to the scheme, the SCR reaction can be divided in an oxidation of the catalyst by NO + O2 and a reduction by NO + NH3; these steps together constitute a complete catalytic cycle. Furthermore both NO and NH3...... spectroscopy (FTIR). A consequence of the reaction scheme is that all intermediates in fast SCR are also part of the standard SCR cycle. The calculated activation energy by density functional theory (DFT) indicates that the oxidation of an NO molecule by O2 to a bidentate nitrate ligand is rate determining...

  20. MERCURY OXIDATION PROMOTED BY A SELECTIVE CATALYTIC REDUCTION CATALYST UNDER SIMULATED POWDER RIVER BASIN COAL COMBUSTION CONDITIONS

    Science.gov (United States)

    A bench-scale reactor consisting of a natural gas burner and an electrically heated reactor housing a selective catalytic reduction (SCR) catalyst was constructed for studying elemental mercury oxidation under SCR conditions. A low sulfur Power River Basin (PRB) coal combustion ...

  1. Mesoporous Fe-containing ZSM-5 zeolite single crystal catalysts for selective catalytic reduction of nitric oxide by ammonia

    DEFF Research Database (Denmark)

    Kustov, Arkadii; Egeblad, Kresten; Kustova, Marina;

    2007-01-01

    Mesoporous and conventional Fe-containing ZSM-5 catalysts (0.5–8 wt% Fe) were prepared using a simple impregnationmethod and tested in NO selective catalytic reduction (SCR) with NH3. It was found that mesoporous Fe-ZSM-5 catalysts exhibit higher SCR activities than comparable conventional cataly...

  2. Catalytic Destruction of a Surrogate Organic Hazardous Air Pollutant as a Potential Co-benefit for Coal-fired Selective Catalyst Reduction Systems

    Science.gov (United States)

    Catalytic destruction of benzene (C6H6), a surrogate for organic hazardous air pollutants (HAPs) produced from coal combustion, was investigated using a commercial selective catalytic reduction (SCR) catalyst for evaluating the potential co-benefit of the SCR technology for reduc...

  3. SCR maintenance fundamentals

    Energy Technology Data Exchange (ETDEWEB)

    Wicker, K.; Staudt, J.

    2004-06-01

    The latest round of NOx emissions rules in the USA may afford power plant operators more flexibility in meeting air-quality standards. But complying with the rules can be somewhat confusing. Because a selective catalytic reduction (SCR) system is the first line of defence against excessive NOx emission, its proper maintenance is critical. This article explains how to monitor an SCR system for ammonia slip and manage its catalysts in a way that optimizes the system's performance. 9 figs.

  4. Selective catalytic reduction of nitrogen oxides with ammonia over microporous zeolite catalysts

    OpenAIRE

    VENNESTROM, PETER NICOLAI RAVNBORG

    2014-01-01

    With increasing legislative demands to remove nitrogen oxides (NOx) from automotive diesel exhaust, new catalyst systems are investigated and intensely studied in industry as well in academia. The most prevailing catalytic method of choice is the selective catalytic reduction (SCR) where non-toxic urea is used as a reductant for practical reasons. Usually urea is stored in a separate tank and once injected into the exhaust system it hydrolyses into the more aggressive reductant NH3 and CO2. ...

  5. SCR atmosphere induced reduction of oxidized mercury over CuO-CeO2/TiO2 catalyst.

    Science.gov (United States)

    Li, Hailong; Wu, Shaokang; Wu, Chang-Yu; Wang, Jun; Li, Liqing; Shih, Kaimin

    2015-06-16

    CuO-CeO2/TiO2 (CuCeTi) catalyst synthesized by a sol-gel method was employed to investigate mercury conversion under a selective catalytic reduction (SCR) atmosphere (NO, NH3 plus O2). Neither NO nor NH3 individually exhibited an inhibitive effect on elemental mercury (Hg(0)) conversion in the presence of O2. However, Hg(0) conversion over the CuCeTi catalyst was greatly inhibited under SCR atmosphere. Systematic experiments were designed to investigate the inconsistency and explore the in-depth mechanisms. The results show that the copresence of NO and NH3 induced reduction of oxidized mercury (Hg(2+), HgO in this study), which offset the effect of catalytic Hg(0) oxidation, and hence resulted in deactivation of Hg(0) conversion. High NO and NH3 concentrations with a NO/NH3 ratio of 1.0 facilitated Hg(2+) reduction and therefore lowered Hg(0) conversion. Hg(2+) reduction over the CuCeTi catalyst was proposed to follow two possible mechanisms: (1) direct reaction, in which NO and NH3 react directly with HgO to form N2 and Hg(0); (2) indirect reaction, in which the SCR reaction consumed active surface oxygen on the CuCeTi catalyst, and reduced species on the CuCeTi catalyst surface such as Cu2O and Ce2O3 robbed oxygen from adjacent HgO. Different from the conventionally considered mechanisms, that is, competitive adsorption responsible for deactivation of Hg(0) conversion, this study reveals that oxidized mercury can transform into Hg(0) under SCR atmosphere. Such knowledge is of fundamental importance in developing efficient and economical mercury control technologies for coal-fired power plants. PMID:25961487

  6. SCR atmosphere induced reduction of oxidized mercury over CuO-CeO2/TiO2 catalyst.

    Science.gov (United States)

    Li, Hailong; Wu, Shaokang; Wu, Chang-Yu; Wang, Jun; Li, Liqing; Shih, Kaimin

    2015-06-16

    CuO-CeO2/TiO2 (CuCeTi) catalyst synthesized by a sol-gel method was employed to investigate mercury conversion under a selective catalytic reduction (SCR) atmosphere (NO, NH3 plus O2). Neither NO nor NH3 individually exhibited an inhibitive effect on elemental mercury (Hg(0)) conversion in the presence of O2. However, Hg(0) conversion over the CuCeTi catalyst was greatly inhibited under SCR atmosphere. Systematic experiments were designed to investigate the inconsistency and explore the in-depth mechanisms. The results show that the copresence of NO and NH3 induced reduction of oxidized mercury (Hg(2+), HgO in this study), which offset the effect of catalytic Hg(0) oxidation, and hence resulted in deactivation of Hg(0) conversion. High NO and NH3 concentrations with a NO/NH3 ratio of 1.0 facilitated Hg(2+) reduction and therefore lowered Hg(0) conversion. Hg(2+) reduction over the CuCeTi catalyst was proposed to follow two possible mechanisms: (1) direct reaction, in which NO and NH3 react directly with HgO to form N2 and Hg(0); (2) indirect reaction, in which the SCR reaction consumed active surface oxygen on the CuCeTi catalyst, and reduced species on the CuCeTi catalyst surface such as Cu2O and Ce2O3 robbed oxygen from adjacent HgO. Different from the conventionally considered mechanisms, that is, competitive adsorption responsible for deactivation of Hg(0) conversion, this study reveals that oxidized mercury can transform into Hg(0) under SCR atmosphere. Such knowledge is of fundamental importance in developing efficient and economical mercury control technologies for coal-fired power plants.

  7. NH3 Measurements for Advanced SCR Applications

    NARCIS (Netherlands)

    Seykens, X.; Tillaart, E. van den; Lilova, V.; Nakatani, S.

    2016-01-01

    Since the introduction of Euro IV legislation [1, 2], Selective Catalytic Reduction (SCR) technology using liquid urea injection is (one of) the primary methods for NOx reduction in many applications. Ammonia (NH3) is the reagent and key element for the SCR system and its control calibration to meet

  8. Development of Optimal Catalyst Designs and Operating Strategies for Lean NOx Reduction in Coupled LNT-SCR Systems

    Energy Technology Data Exchange (ETDEWEB)

    Harold, Michael; Crocker, Mark; Balakotaiah, Vemuri; Luss, Dan; Choi, Jae-Soon; Dearth, Mark; McCabe, Bob; Theis, Joe

    2013-09-30

    Oxides of nitrogen in the form of nitric oxide (NO) and nitrogen dioxide (NO{sub 2}) commonly referred to as NO{sub x}, is one of the two chemical precursors that lead to ground-level ozone, a ubiquitous air pollutant in urban areas. A major source of NO{sub x} is generated by equipment and vehicles powered by diesel engines, which have a combustion exhaust that contains NO{sub x} in the presence of excess O{sub 2}. Catalytic abatement measures that are effective for gasoline-fueled engines such as the precious metal containing three-way catalytic converter (TWC) cannot be used to treat O2-laden exhaust containing NO{sub x}. Two catalytic technologies that have emerged as effective for NO{sub x} abatement are NO{sub x} storage and reduction (NSR) and selective catalytic reduction (SCR). NSR is similar to TWC but requires much larger quantities of expensive precious metals and sophisticated periodic switching operation, while SCR requires an on-board source of ammonia which serves as the chemical reductant of the NO{sub x}. The fact that NSR produces ammonia as a byproduct while SCR requires ammonia to work has led to interest in combining the two together to avoid the need for the cumbersome ammonia generation system. In this project a comprehensive study was carried out of the fundamental aspects and application feasibility of combined NSR/SCR. The project team, which included university, industry, and national lab researchers, investigated the kinetics and mechanistic features of the underlying chemistry in the lean NOx trap (LNT) wherein NSR was carried out, with particular focus on identifying the operating conditions such as temperature and catalytic properties which lead to the production of ammonia in the LNT. The performance features of SCR on both model and commercial catalysts focused on the synergy between the LNT and SCR converters in terms of utilizing the upstream-generated ammonia and alternative reductants such as propylene, representing the

  9. Review of state of the art technologies of selective catalytic reduction of NOx from diesel engine exhaust

    International Nuclear Information System (INIS)

    Increasingly stringent emission legislations, such as US 2010 and Euro VI, for NOx in mobile applications will require the use of intensification of NOx reduction aftertreatment technologies, such as the selective catalytic reduction (SCR). Due to the required higher deNOx efficiency, a lot of efforts have recently been concentrated on the optimization of the SCR systems for broadening the active deNOx temperature window as widely as possible, especially at low temperatures, enhancing the catalysts durability, and reducing the cost of the deNOx system. This paper provides a comprehensive overview of the state-of-the-art SCR technologies, including the alternative ammonia generation from the solid reductants, Vanadium-based, Cu-zeolite (CuZ) and Fe-zeolite (FeZ) based, and the novel chabazite zeolite with small pore size SCR catalysts. Furthermore, the progresses of the highly optimized hybrid approaches, involving combined CuZ and FeZ SCR, passive SCR, integration of DOC + (DPF, SCR), as well as SCR catalyst coated on DPF (referred as SCRF hereinafter) systems are well discussed. Even though SCR technology is considered as the leading NOx aftertreatment technology, attentions have been paid to the adverse by-products, such as NH3 and N2O. Relevant regulations have been established to address the issues. - Highlights: •The review of state of the art technologies of selective catalytic reduction of NOx. •The mainstream V-based, Cu- and Fe-zeolite, and chabazite catalysts are illustrated. •The development of highly optimized hybrid integration SCR systems are analyzed. •The by-products of SCR systems and the corresponding regulations are discussed. •The future perspectives of the advanced SCR technologies are described

  10. Comparisons of SCR and Active-set Methods for PAPR Reduction in OFDM Systems

    Directory of Open Access Journals (Sweden)

    Qihui Liang

    2010-04-01

    Full Text Available signal to clipping noise ratio (SCR and active-set methods are two existing methods for peak-to-average power ratio (PAPR reduction based on tone reservation. In this paper, the computational complexities of these two methods are analyzed and simulation is done for comparing their PAPR-reducing performance. The simulation results show that active-set method requires less computational complexity than that of SCR method while they achieve similar PAPR reduction performance. 

  11. Impacts of halogen additions on mercury oxidation, in a slipstream selective catalyst reduction (SCR), reactor when burning sub-bituminous coal.

    Science.gov (United States)

    Cao, Yan; Gao, Zhengyang; Zhu, Jiashun; Wang, Quanhai; Huang, Yaji; Chiu, Chengchung; Parker, Bruce; Chu, Paul; Pant, Wei-Ping

    2008-01-01

    This paper presents a comparison of impacts of halogen species on the elemental mercury (Hg(0)) oxidation in a real coal-derived flue gas atmosphere. It is reported there is a higher percentage of Hg(0) in the flue gas when burning sub-bituminous coal (herein Powder River Basin (PRB) coal) and lignite, even with the use of selective catalytic reduction (SCR). The higher Hg(0)concentration in the flue gas makes it difficult to use the wet-FGD process for the mercury emission control in coal-fired utility boilers. Investigation of enhanced Hg(0) oxidation by addition of hydrogen halogens (HF, HCl, HBr, and HI) was conducted in a slipstream reactor with and without SCR catalysts when burning PRB coal. Two commercial SCR catalysts were evaluated. SCR catalyst no. 1 showed higher efficiencies of both NO reduction and Hg(0) oxidation than those of SCR catalyst no. 2. NH3 addition seemed to inhibit the Hg(0) oxidation, which indicated competitive processes between NH3 reduction and Hg(0) oxidation on the surface of SCR catalysts. The hydrogen halogens, in the order of impact on Hg(0) oxidation, were HBr, HI, and HCl or HF. Addition of HBr at approximately 3 ppm could achieve 80% Hg(0) oxidation. Addition of HI at approximately 5 ppm could achieve 40% Hg(0) oxidation. In comparison to the empty reactor, 40% Hg(0) oxidation could be achieved when HCl addition was up to 300 ppm. The enhanced Hg(0) oxidation by addition of HBr and HI seemed not to be correlated to the catalytic effects by both evaluated SCR catalysts. The effectiveness of conversion of hydrogen halogens to halogen molecules or interhalogens seemed to be attributed to their impacts on Hg(0) oxidation.

  12. Novel high-efficienly H2-SCR spinel-type NiFe2O4 for catalytic reduction of NO%新型高效H2-SCR尖晶石型NiFe2 O4催化还原NO

    Institute of Scientific and Technical Information of China (English)

    乔凯; 罗雯军; 王吉; 曹礼梅; 沈玉然; 杨骥

    2014-01-01

    采用柠檬酸配位溶胶-凝胶法制备尖晶石型复合金属氧化物NiFe2 O4,以H2为还原剂,在固定床反应器中考察了该催化剂催化还原NO的性能,并借助X射线衍射( XRD)、扫描电子显微镜( SEM)、透射电子显微镜( TEM)、比表面积测定( BET)、程序升温还原( TPR)和程序升温脱附( TPD)等方法对样品的晶体结构、形貌等特性进行了表征.结果表明.在空速4500 h-1,H2/NO浓度比为1,温度为400℃下,H2催化还原NO的效率可达97.8%,高H2/NO浓度比对NO转化率提升不大,高空速对其催化活性无明显影响.所制备的NiFe2 O4催化剂具有典型的尖晶石结构,颗粒不规则,粒径大约为30-150 nm,并且具有良好的双官能团氧化还原性质.%Spinel-type complex oxide NiFe2 O4 was prepared by citric acid-ligand sol-gel method. The NO selective catalytic reduction ( SCR) activities by H2 were investigated in a fixed-bed reactor. The physical properties of the prepared samples were explored by means of X-ray diffraction ( XRD ) , scanning electron microscopy ( SEM ) , transmission electron microscopy ( TEM ) , surface area measurements ( BET ) , temperature-programmed reduction ( TPR ) and temperature-programmed desorption (TPD). The results indicated that when the space velocity was 4500 h-1,the molar ratio of H2/NO was 1, and the temperature was 400 ℃,the SCR conversion of NO reached 97.8%. The NO conversion rate increased slightly with increasing H2/NO ratio and the effect of space velocity on catalytic activity of SCR process was ngelsible. It was also found that the prepared NiFe2 O4 catalyst was intact spinel-type crystal structures as irregular particle with particle size of about 30-150 nm, and the catalyst had good bifunctional oxygen reducibility.

  13. Estimating SCR installation costs

    Energy Technology Data Exchange (ETDEWEB)

    Marano, M.; Sharp, G. [American Electric Power (United States)

    2006-01-15

    The EUCG surveyed 72 separate US installations of selective catalytic reduction (SCR) systems at coal-fired units totalling 41 GW of capacity to identify the systems' major cost drivers. The results, summarized in this article, provide excellent first-order estimates and guidance for utilities considering installing the downstream emissions-control technology. 4 figs., 1 tab.

  14. COMPARISON OF WEST GERMAN AND U.S. FLUE GAS DESULFURIZATION AND SELECTIVE CATALYTIC REDUCTION COSTS

    Science.gov (United States)

    The report documents a comparison of the actual cost retrofitting flue gas desulfurization (FGD) and selective catalytic reduction (SCR) on Federal Republic of German (FRG) boilers to cost estimating procedures used in the U.S. to estimate the retrofit of these controls on U.S. b...

  15. Subharmonic ripple reduction in SCR-type magnet power supplies

    International Nuclear Information System (INIS)

    Subharmonic ripple in a magnet power supply output can cause unwanted low-frequency field ripple in a magnet load. Among other things the ripple may be caused by SCR firing circuit imbalance. In critical applications, simply providing equally spaced SCR firing pulses, as is done in some all digital control schemes, may not be sufficient. This study discusses in general the causes of subharmonic ripple and some approaches to the problem. A negative feedback scheme utilizing bandpass filters is analyzed and applied to a group of twelve phase .5MW power supplies. Results are given which show a substantial improvement in power supply voltage and magnet field ripple content at 60, 120, and 180 Hz

  16. Atmospheric emissions from a passenger ferry with selective catalytic reduction.

    Science.gov (United States)

    Nuszkowski, John; Clark, Nigel N; Spencer, Thomas K; Carder, Daniel K; Gautam, Mridul; Balon, Thomas H; Moynihan, Paul J

    2009-01-01

    The two main propulsion engines on Staten Island Ferry Alice Austen (Caterpillar 3516A, 1550 hp each) were fitted with selective catalytic reduction (SCR) aftertreatment technology to reduce emissions of oxides of nitrogen (NOx). After the installation of the SCR system, emissions from the ferry were characterized both pre- and post-aftertreatment. Prior research has shown that the ferry operates in four modes, namely idle, acceleration, cruise, and maneuvering modes. Emissions were measured for both engines (designated NY and SI) and for travel in both directions between Manhattan and Staten Island. The emissions characterization used an analyzer system, a data logger, and a filter-based particulate matter (PM) measurement system. The measurement of NOx, carbon monoxide (CO), and carbon dioxide (CO2) were based on federal reference methods. With the existing control strategy for the SCR urea injection, the SCR provided approximately 64% reduction of NOx for engine NY and 36% reduction for engine SI for a complete round trip with less than 6.5 parts per million by volume (ppmv) of ammonia slip during urea injection. Average reductions during the cruise mode were 75% for engine NY and 47% for engine SI, which was operating differently than engine NY. Reductions for the cruise mode during urea injection typically exceeded 94% from both engines, but urea was injected only when the catalyst temperature reached a 300 degrees C threshold pre- and postcatalyst. Data analysis showed a total NOx mass emission split with 80% produced during cruise, and the remaining 20% spread across idle, acceleration, and maneuvering. Examination of continuous NOx data showed that higher reductions of NOx could be achieved on both engines by initiating the urea injection at an earlier point (lower exhaust temperature) in the acceleration and cruise modes of operation. The oxidation catalyst reduced the CO production 94% for engine NY and 82% for engine SI, although the high CO levels

  17. Selective reduction of NO by photo-SCR with ammonia in an annular fixed-film photoreactor

    Institute of Scientific and Technical Information of China (English)

    YiangChen CHOU; Young KU

    2012-01-01

    Gaseous NO was photocatalytically reduced at room temperature by photo-assisted selective catalytic reduction (photo-SCR) with ammonia over TiO2 in this study. NO reduction efficiency and N2 selectivity were determined from gases composition at the outlet stream of photoreactor. Effect of operating conditions, e.g. light intensity and inlet concentrations of ammonia and oxygen, on the NO reduction efficiency and N2 selectivity were discussed to determine the feasible operating condition for photocatalytic reduction of NO. Experimental results showed that selective catalytic reduction of NO with ammonia over TiO2 in the presence of oxygen was a spontaneous reaction in dark. The photoirradiation on the TiO2 surface caused remarkable photocatalytic reduction of NO to form N2, NO2, and N20 under 254 nm UV illuminations, while almost 90% of N2 selectivity was achieved in this study. The ammonia and oxygen molecules played the roles of reductant and oxidant for NO reduction and active sites regeneration, respectively. The reduction of NO was found to be increased with the increase of inlet ammonia and oxygen concentrations until specific concentrations because of the limited active sites on the surface of TiO2. The kinetic model proposed in this study can be used to reasonably describe the reaction mechanism of photo-SCR.

  18. Selective catalytic reduction operation with heavy fuel oil: NOx, NH3, and particle emissions.

    Science.gov (United States)

    Lehtoranta, Kati; Vesala, Hannu; Koponen, Päivi; Korhonen, Satu

    2015-04-01

    To meet stringent NOx emission limits, selective catalytic reduction (SCR) is increasingly utilized in ships, likely also in combination with low-priced higher sulfur level fuels. In this study, the performance of SCR was studied by utilizing NOx, NH3, and particle measurements. Urea decomposition was studied with ammonia and isocyanic acid measurements and was found to be more effective with heavy fuel oil (HFO) than with light fuel oil. This is suggested to be explained by the metals found in HFO contributing to metal oxide particles catalyzing the hydrolysis reaction prior to SCR. At the exhaust temperature of 340 °C NOx reduction was 85-90%, while at lower temperatures the efficiency decreased. By increasing the catalyst loading, the low temperature behavior of the SCR was enhanced. The drawback of this, however, was the tendency of particle emissions (sulfate) to increase at higher temperatures with higher loaded catalysts. The particle size distribution results showed high amounts of nanoparticles (in 25-30 nm size), the formation of which SCR either increased or decreased. The findings of this work provide a better understanding of the usage of SCR in combination with a higher sulfur level fuel and also of ship particle emissions, which are a growing concern.

  19. System and method for controlling an engine based on ammonia storage in multiple selective catalytic reduction catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Sun, MIn; Perry, Kevin L.

    2015-11-20

    A system according to the principles of the present disclosure includes a storage estimation module and an air/fuel ratio control module. The storage estimation module estimates a first amount of ammonia stored in a first selective catalytic reduction (SCR) catalyst and estimates a second amount of ammonia stored in a second SCR catalyst. The air/fuel ratio control module controls an air/fuel ratio of an engine based on the first amount, the second amount, and a temperature of a substrate disposed in the second SCR catalyst.

  20. Confirmation of Isolated Cu2+ Ions in SSZ-13 Zeolite as Active Sites in NH3-Selective Catalytic Reduction

    NARCIS (Netherlands)

    Deka, U.; Juhin, A.F.; Eilertsen, E.A.; Emerich, H.; Green, M.A.; Korhonen, S.T.; Weckhuysen, B.M.; Beale, A.M.

    2012-01-01

    NH3-Selective Catalytic Reduction (NH3-SCR) is a widely used technology for NOx reduction in the emission control systems of heavy duty diesel vehicles. Copper-based ion exchanged zeolites and in particular Cu-SSZ-13 (CHA framework) catalysts show both exceptional activity and hydrothermal stability

  1. Ammonia sensor for closed-loop SCR control

    NARCIS (Netherlands)

    Wang, D.Y.; Yao, S.; Shost, M.; Yoo, J.H.; Cabush, D.; Racine, D.; Cloudt, R.P.M.; Willems, F.P.T.

    2009-01-01

    Selective Catalytic Reduction (SCR) is the dominant solution for meeting future NOx reduction regulations for heavy-duty diesel powertrains. SCR systems benefit from closed-loop control if an appropriate exhaust gas sensor were available. An ammonia sensor has recently been developed for use as a fe

  2. Selective catalytic reduction system and process using a pre-sulfated zirconia binder

    Science.gov (United States)

    Sobolevskiy, Anatoly; Rossin, Joseph A.

    2010-06-29

    A selective catalytic reduction (SCR) process with a palladium catalyst for reducing NOx in a gas, using hydrogen as a reducing agent is provided. The process comprises contacting the gas stream with a catalyst system, the catalyst system comprising (ZrO.sub.2)SO.sub.4, palladium, and a pre-sulfated zirconia binder. The inclusion of a pre-sulfated zirconia binder substantially increases the durability of a Pd-based SCR catalyst system. A system for implementing the disclosed process is further provided.

  3. Low temperature selective catalytic reduction of NOx with NH3 over Mn-based catalyst: A review

    Directory of Open Access Journals (Sweden)

    TsungYu Lee

    2016-05-01

    Full Text Available The removals of NOx by catalytic technology at low temperatures (100–300 °C for industrial flue gas treatment have received increasing attention. However, the development of low temperature catalysts for selective catalytic reduction (SCR of NOx with ammonia is still a challenge especially in the presence of SO2. The current status of using Mn-based catalysts for low temperature SCR of NOx with ammonia (NH3-SCR is reviewed. Reaction mechanisms and effects of operating factors on low temperature NH3-SCR are addressed, and the SCR efficiencies of Mn-based metal oxides with and without SO2 poisoning have also been discussed with different supports and co-metals. The key factors for enhancing low temperature NH3-SCR efficiency and SO2 resistance with Mn-based catalysts are identified to be (1 high specific surface area; (2 high surface acidity; (3 oxidation states of manganese; (4 well dispersion of manganese oxide metals; (5 more surface adsorbed oxygen; (6 more absorbed NO3− on the catalyst surface; (7 easier decomposition of ammonium sulfates. Moreover, the regenerative methods such as water washing, acid and/or alkali washing and heat treatment to the poisoned catalysts could help to recover the low temperature SCR efficiency to its initial level.

  4. Using Acetylene for Selective Catalytic Reduction of NO in Excess Oxygen

    Institute of Scientific and Technical Information of China (English)

    YU Shan-Shan; WANG Xin-Ping; WANG Chong; XU Yan

    2006-01-01

    Acetylene as a reducing agent for selective catalytic reduction of NO (C2H2-SCR) was investigated over a series of metal exchanged HY catalysts, in the reaction system of 0.16% NO, 0.08% C2H2, and 9.95% O2 (volume percent)in He. 75% of NO conversion to N2 with hydrocarbon efficiency about 1.5 was achieved over a Ce-HY catalyst around 300 ℃. The NO removal level was comparable with that of selective catalytic reduction of NOx by C3H6reported in literatures, although only one third of the reducing agent in carbon moles was used in the C2H2-SCR of NO. The protons in zeolite were crucial to the C2H2-SCR of NO, and the performance of HY in the reaction was significantly promoted by cerium incorporation into the zeolite. NO2 was proposed to be the intermediate of NO reduction to N2, and the oxidation of NO to NO2 was rate-determining step of the C2H2-SCR of NO over Ce-HY.The suggestion was well supported by the results of the NO oxidation with O2, and the C2H2 consumption under the conditions in the presence or absence of NO.

  5. Multi-stage selective catalytic reduction of NOx in lean burn engine exhaust

    Energy Technology Data Exchange (ETDEWEB)

    Penetrante, B.M.; Hsaio, M.C.; Merritt, B.T.; Vogtlin, G.E. [Lawrence Livermore National Lab., CA (United States)

    1997-12-31

    Many studies suggest that the conversion of NO to NO{sub 2} is an important intermediate step in the selective catalytic reduction (SCR) of NO{sub x} to N{sub 2}. Some effort has been devoted to separating the oxidative and reductive functions of the catalyst in a multi-stage system. This method works fine for systems that require hydrocarbon addition. The hydrocarbon has to be injected between the NO oxidation catalyst and the NO{sub 2} reduction catalyst; otherwise, the first-stage oxidation catalyst will also oxidize the hydrocarbon and decrease its effectiveness as a reductant. The multi-stage catalytic scheme is appropriate for diesel engine exhausts since they contain insufficient hydrocarbons for SCR, and the hydrocarbons can be added at the desired location. For lean-burn gasoline engine exhausts, the hydrocarbons already present in the exhausts will make it necessary to find an oxidation catalyst that can oxidize NO to NO{sub 2} but not oxidize the hydrocarbon. A plasma can also be used to oxidize NO to NO{sub 2}. Plasma oxidation has several advantages over catalytic oxidation. Plasma-assisted catalysis can work well for both diesel engine and lean-burn gasoline engine exhausts. This is because the plasma can oxidize NO in the presence of hydrocarbons without degrading the effectiveness of the hydrocarbon as a reductant for SCR. In the plasma, the hydrocarbon enhances the oxidation of NO, minimizes the electrical energy requirement, and prevents the oxidation of SO{sub 2}. This paper discusses the use of multi-stage systems for selective catalytic reduction of NO{sub x}. The multi-stage catalytic scheme is compared to the plasma-assisted catalytic scheme.

  6. Method to monitor HC-SCR catalyst NOx reduction performance for lean exhaust applications

    Science.gov (United States)

    Viola, Michael B.; Schmieg, Steven J.; Sloane, Thompson M.; Hilden, David L.; Mulawa, Patricia A.; Lee, Jong H.; Cheng, Shi-Wai S.

    2012-05-29

    A method for initiating a regeneration mode in selective catalytic reduction device utilizing hydrocarbons as a reductant includes monitoring a temperature within the aftertreatment system, monitoring a fuel dosing rate to the selective catalytic reduction device, monitoring an initial conversion efficiency, selecting a determined equation to estimate changes in a conversion efficiency of the selective catalytic reduction device based upon the monitored temperature and the monitored fuel dosing rate, estimating changes in the conversion efficiency based upon the determined equation and the initial conversion efficiency, and initiating a regeneration mode for the selective catalytic reduction device based upon the estimated changes in conversion efficiency.

  7. System and method for selective catalytic reduction of nitrogen oxides in combustion exhaust gases

    Science.gov (United States)

    Sobolevskiy, Anatoly; Rossin, Joseph A

    2014-04-08

    A multi-stage selective catalytic reduction (SCR) unit (32) provides efficient reduction of NOx and other pollutants from about 50-550.degree. C. in a power plant (19). Hydrogen (24) and ammonia (29) are variably supplied to the SCR unit depending on temperature. An upstream portion (34) of the SCR unit catalyzes NOx+NH.sub.3 reactions above about 200.degree. C. A downstream portion (36) catalyzes NOx+H.sub.2 reactions below about 260.degree. C., and catalyzes oxidation of NH.sub.3, CO, and VOCs with oxygen in the exhaust above about 200.degree. C., efficiently removing NOx and other pollutants over a range of conditions with low slippage of NH.sub.3. An ammonia synthesis unit (28) may be connected to the SCR unit to provide NH.sub.3 as needed, avoiding transport and storage of ammonia or urea at the site. A carbonaceous gasification plant (18) on site may supply hydrogen and nitrogen to the ammonia synthesis unit, and hydrogen to the SCR unit.

  8. Alkali resistivity of Cu based selective catalytic reduction catalysts

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Jensen, Anker Degn; Riisager, Anders;

    2012-01-01

    The deactivation of V2O5–WO3–TiO2, Cu–HZSM5 and Cu–HMOR plate type monolithic catalysts was investigated when exposed to KCl aerosols in a bench-scale reactor. Fresh and exposed catalysts were characterized by selective catalytic reduction (SCR) activity measurements, scanning electron microscope...... catalysts revealed that the potassium salt not only deposited on the catalyst surface, but also penetrated into the catalyst wall. Thus, the K/M ratio (M = V or Cu) was high on V2O5–WO3–TiO2 catalyst and comparatively less on Cu–HZSM5 and Cu–HMOR catalysts. NH3-TPD revealed that the KCl exposed Cu–HZSM5...

  9. Mercury oxidation promoted by a selective catalytic reduction catalyst under simulated Powder River Basin coal combustion conditions.

    Science.gov (United States)

    Lee, Chun W; Serre, Shannon D; Zhao, Yongxin; Lee, Sung Jun; Hastings, Thomas W

    2008-04-01

    A bench-scale reactor consisting of a natural gas burner and an electrically heated reactor housing a selective catalytic reduction (SCR) catalyst was constructed for studying elemental mercury (Hg(o)) oxidation under SCR conditions. A low sulfur Powder River Basin (PRB) subbituminous coal combustion fly ash was injected into the entrained-flow reactor along with sulfur dioxide (SO2), nitrogen oxides (NOx), hydrogen chloride (HCl), and trace Hg(o). Concentrations of Hg(o) and total mercury (Hg) upstream and downstream of the SCR catalyst were measured using a Hg monitor. The effects of HCl concentration, SCR operating temperature, catalyst space velocity, and feed rate of PRB fly ash on Hg(o) oxidation were evaluated. It was observed that HCl provides the source of chlorine for Hg(o) oxidation under simulated PRB coal-fired SCR conditions. The decrease in Hg mass balance closure across the catalyst with decreasing HCl concentration suggests that transient Hg capture on the SCR catalyst occurred during the short test exposure periods and that the outlet speciation observed may not be representative of steady-state operation at longer exposure times. Increasing the space velocity and operating temperature of the SCR led to less Hg(o) oxidized. Introduction of PRB coal fly ash resulted in slightly decreased outlet oxidized mercury (Hg2+) as a percentage of total inlet Hg and correspondingly resulted in an incremental increase in Hg capture. The injection of ammonia (NH3) for NOx reduction by SCR was found to have a strong effect to decrease Hg oxidation. The observations suggest that Hg(o) oxidation may occur near the exit region of commercial SCR reactors. Passage of flue gas through SCR systems without NH3 injection, such as during the low-ozone season, may also impact Hg speciation and capture in the flue gas. PMID:18422035

  10. Selective catalytic reduction of NO by ammonia over oil shale ash and fly ash catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Changtao Yue; Shuyuan Li [University of Petroleum, Beijing (China). State Key Lab of Heavy Oil Processing

    2003-07-01

    Acid rain and urban air pollution, produced mainly by pollutants such as SOX and NOX and other volatile organic compounds, has become the most serious environmental problem. The selective catalytic reduction (SCR) of NO with NH{sub 3} in the presence of oxygen is a wellproven method to limit the NOX emissions. The work in this field has been the subject of much research in recent years. In this paper, NO reduction with NH{sub 3} over oil shale ash or fly ash catalysts was studied. Fe, Cu, V or Ni as active elements was loaded by adding aqueous solutions of the metal nitrate over the oil shale ash or fly ash support. The activities of the catalysts for NO removal were measured in a fixed-bed reactor. According to the results, oil shale ash or fly ash, after pre-treatment, can be reasonably used as the SCR catalyst support to remove NO from flue gas. Cu gave the highest catalytic activity and NO conversion for fly ash while V for oil shale ash. As the support, fly ash is more feasible than oil shale ash. Because of their low cost and high efficiency, the catalysts should be used in the SCR process. Further research on this subject is necessary in the future to understand more details of the SCR system and issue of pollution control. 9 refs., 2 figs., 2 tabs.

  11. Determining the storage, availability and reactivity of NH3 within Cu-Chabazite-based Ammonia Selective Catalytic Reduction systems

    NARCIS (Netherlands)

    Lezcano-Gonzalez, I; Deka, U; Arstad, B; Van Yperen-De Deyne, A; Hemelsoet, K; Waroquier, M; Van Speybroeck, V; Weckhuysen, B M; Beale, A M

    2014-01-01

    Three different types of NH3 species can be simultaneously present on Cu(2+)-exchanged CHA-type zeolites, commonly used in Ammonia Selective Catalytic Reduction (NH3-SCR) systems. These include ammonium ions (NH4(+)), formed on the Brønsted acid sites, [Cu(NH3)4](2+) complexes, resulting from NH3 co

  12. The application of a low temperature selective catalytic reduction system for municipal and hazardous waste combustors

    Energy Technology Data Exchange (ETDEWEB)

    Hartenstein, H.U. [L. and C. Steinmueller GmbH, Gummersbach (Germany); Licata, A. [Licata Energy and Environmental Consultants, Inc., Yonkers, NY (United States)

    1996-09-01

    In Central Europe during the late 1980`s and through the early 1990`s, emission regulations on municipal and hazardous waste combustors (MWCs and HWCs) were tightened drastically. Among other pollutants, NO{sub x} emissions had to be limited to an extent that required the installation of special NO{sub x} control technologies and 70 mg NO{sub x}/Nm{sup 3} (56 ppmdv) (corrected to 11% O{sub 2} if the measured value exceeded 11% O{sub 2}). This became a commonly accepted value for most permitting agencies in Germany, Holland, Austria and Switzerland. The Selective Catalytic Reduction (SCR) technology became the preferred NO{sub x} control technology for retrofitting existing MWCs and HWCs, as well as for new facilities. This paper presents the Low Temperature SCR technology (LTSCR) as a major new development in SCR technology adapted to MWCs and HWCs. LTSCR`s can be operated at temperatures as low as 150 C (302 F) while SCR`s operate at temperatures above 280 C (536 F). The paper outlines the specific needs and restrictions of LTSCR, as well as its advantages. A detailed description of the correlation between required volume of catalyst, temperature, and specific catalytic activity is given. The application of LTSCR is shown for MWCs and HWCs, and for each case, one retrofit and one new facility are introduced. Finally, the paper reports on some two and a half years of operating experience with LTSCR and gives an outlook on further applications.

  13. System analysis regarding NO{sub x} reduction with combined SNCR/SCR; Systemstudie avseende kombinerad NO{sub x}-reducering med SNCR/SCR

    Energy Technology Data Exchange (ETDEWEB)

    Niemann, Therese; Henningsson, Claes [S.E.P. Scandinavian Energy Project AB, Stockholm (Sweden); Andersson, Christer [Vattenfall Utveckling AB, Stockholm (Sweden)

    2000-06-01

    Systems with combined SNCR/SCR on biomass fired CFB:s have been focused on lately since they are regarded as very load flexible. Furthermore, synergy effects between the two parts are supposed to result in better performance for the combined system than for the two systems separately. The aim of this study is to investigate whether the combined SNCR/SCR matches the outlined expectations above. The plant chosen for the measurements was Brista Kraft AB. This particular plant is equipped with a CFB boiler of 122 MW{sub th}, which in turn is equipped with the deNO{sub x} system mentioned above. The measurements are made by a 'concentration gradient measurement system', developed by Vattenfall. Consequently, the study indicates that it is very useful to add a catalyst to the SNCR system, both from an environmental- and an economical point of view. However, since the full scale data for the SCR alone is missing, the results for SCR compared with combined SNCR/SCR is harder to decide. Simulations indicate that both systems produces the same emission levels, although, the SCR system may be a bit more cost effective in the long run. The synergy effect between the systems in combination is obvious. Predominantly because the NO{sub x} reduction efficiency in the SNCR zone can be increased (in this case about 10-12%) since a higher amount of ammonia can be accepted downstream of the SNCR zone. Combined systems will achieve a comparable good load independence. The reduction in the SNCR will decrease at lower loads, simultaneously as the reduction in the SCR increases. Thus, the total reduction efficiency will almost be independent of the load. In the project investigations have been made to figure out if two points injection in SNCR give more or less mol distribution of NH{sub 3}/NO quota over the catalyst crosses sectional area. The measurements indicates that two point injection may cause a more uneven distribution of stoichiometries. However, the results seems to

  14. EVALUATION OF MERCURY SPECIATION AT POWER PLANTS USING SCR AND SNCR CONTROL TECHNOLOGIES

    Science.gov (United States)

    The paper describes the impact that selective catalytic reduction (SCR), selective noncatalytic reduction (SNCR), and flue gas-conditioning systems have on total mercury emissions and on the speciation of mercury. If SCR and/or SNCR systems enhance mercury conversion/capture, the...

  15. EVALUATION OF MERCURY SPECIATION AT POWER PLANTS USING SCR AND SNCR NOX CONTROL TECHNOLOGIES

    Science.gov (United States)

    The paper describes the impact that selective catalytic reduction (SCR), selective noncatalytic reduction (SNCR), and flue gas-conditioning systems have on total mercury emissions and on the speciation of mercury. If SCR and/or SNCR systems enhance mercury conversion/capture, the...

  16. Catalytic performance of Fe-ZSM-5 catalysts for selective catalytic reduction of nitric oxide by ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Long, R.Q.; Yang, R.T.

    1999-12-10

    A series of Fe-exchanged molecular sieves were studied as catalysts for the selective catalytic reduction (SCR) of NO with ammonia. It was found that Fe-ZSM-5 and Fe-mordenite catalysts were highly active for the SCR reaction. Nearly 100% NO conversions were obtained at 400--500 C under conditions with a high space velocity (GHSV = 4.6 x 10{sup 5} 1/h). However, Fe-Y and Fe-MCM-41 with larger pore sizes showed lower activities for this reaction. F or Fe-ZSM-5 catalysts, the SCR activity decreased with increasing Si/Al ratio in the zeolites. As the Fe-exchange level in the Fe-ZSM-5 catalysts was increased from 58 to 252%, NO conversion increased at lower temperatures (e.g., 300 C), but decreased at high temperatures (e.g., 600 C). Compared with the commercial vanadia catalyst, based on the first-order rate constants, the Fe-ZSM-5 catalyst was five times more active at 400 C and seven times more active at 450 C. It also functioned in a broader temperature window, produced only N{sub 2} (rather than N{sub 2}O) and H{sub 2}O, and showed a substantially lower activity for oxidation of SO{sub 2} to SO{sub 3}.

  17. Selective Catalytic Reduction of NO with Methane

    Institute of Scientific and Technical Information of China (English)

    Xiang Gao; Qi Yu; Limin Chen

    2003-01-01

    The removal of nitrogen oxides from exhaust gases has attracted great attention in recent years, and many approaches have been developed depending on the application. Methane, the main component of natural gas, has great potential as a NO reductant. In this paper, a number of catalysts previous reported for this catalytic reduction of NO have been reviewed, including a direct comparison of the relative activities and effective factors of the catalysts. Reaction mechanisms have also been explored preliminarily.

  18. Design and testing of an independently controlled urea SCR retrofit system for the reduction of NOx emissions from marine diesels.

    Science.gov (United States)

    Johnson, Derek R; Bedick, Clinton R; Clark, Nigel N; McKain, David L

    2009-05-15

    Diesel engine emissions for on-road, stationary and marine applications are regulated in the United States via standards set by the Environmental Protection Agency (EPA). A major component of diesel exhaust that is difficult to reduce is nitrogen oxides (NOx). Selective catalytic reduction (SCR) has been in use for many years for stationary applications, including external combustion boilers, and is promising for NOx abatement as a retrofit for mobile applications where diesel compression ignition engines are used. The research presented in this paper is the first phase of a program focused on the reduction of NOx by use of a stand-alone urea injection system, applicable to marine diesel engines typical of work boats (e.g., tugs). Most current urea SCR systems communicate with engine controls to predict NOx emissions based on signals such as torque and engine speed, however many marine engines in use still employ mechanical injection technology and lack electronic communication abilities. The system developed and discussed in this paper controls NOx emissions independentof engine operating parameters and measures NOx and exhaust flow using the following exhaust sensor inputs: absolute pressure, differential pressure, temperature, and NOx concentration. These sensor inputs were integrated into an independent controller and open loop architecture to estimate the necessary amount of urea needed, and the controller uses pulse width modulation (PWM) to power an automotive fuel injector for airless urea delivery. The system was tested in a transient test cell on a 350 hp engine certified at 4 g/bhp-hr of NOx, with a goal of reducing the engine out NOx levels by 50%. NOx reduction capabilities of 41-67% were shown on the non road transient cycle (NRTC) and ICOMIA E5 steady state cycles with system optimization during testing to minimize the dilute ammonia slip to cycle averages of 5-7 ppm. The goal of 50% reduction of NOx can be achieved dependent upon cycle. Further

  19. Design and testing of an independently controlled urea SCR retrofit system for the reduction of NOx emissions from marine diesels.

    Science.gov (United States)

    Johnson, Derek R; Bedick, Clinton R; Clark, Nigel N; McKain, David L

    2009-05-15

    Diesel engine emissions for on-road, stationary and marine applications are regulated in the United States via standards set by the Environmental Protection Agency (EPA). A major component of diesel exhaust that is difficult to reduce is nitrogen oxides (NOx). Selective catalytic reduction (SCR) has been in use for many years for stationary applications, including external combustion boilers, and is promising for NOx abatement as a retrofit for mobile applications where diesel compression ignition engines are used. The research presented in this paper is the first phase of a program focused on the reduction of NOx by use of a stand-alone urea injection system, applicable to marine diesel engines typical of work boats (e.g., tugs). Most current urea SCR systems communicate with engine controls to predict NOx emissions based on signals such as torque and engine speed, however many marine engines in use still employ mechanical injection technology and lack electronic communication abilities. The system developed and discussed in this paper controls NOx emissions independentof engine operating parameters and measures NOx and exhaust flow using the following exhaust sensor inputs: absolute pressure, differential pressure, temperature, and NOx concentration. These sensor inputs were integrated into an independent controller and open loop architecture to estimate the necessary amount of urea needed, and the controller uses pulse width modulation (PWM) to power an automotive fuel injector for airless urea delivery. The system was tested in a transient test cell on a 350 hp engine certified at 4 g/bhp-hr of NOx, with a goal of reducing the engine out NOx levels by 50%. NOx reduction capabilities of 41-67% were shown on the non road transient cycle (NRTC) and ICOMIA E5 steady state cycles with system optimization during testing to minimize the dilute ammonia slip to cycle averages of 5-7 ppm. The goal of 50% reduction of NOx can be achieved dependent upon cycle. Further

  20. PILLARED CLAYS AS SUPERIOR CATALYSTS FOR SELECTIVE CATALYTIC REDUCTION OF NITRIC OXIDE

    Energy Technology Data Exchange (ETDEWEB)

    R.Q. Long; N. Tharappiwattananon; W.B. Li; R.T. Yang

    2000-09-01

    Removal of NO{sub x} (NO + NO{sub 2}) from exhaust gases is a challenging subject. V{sub 2}O{sub 5}-based catalysts are commercial catalysts for selective catalytic reduction (SCR) with NH{sub 3} for stationary sources. However, for diesel and lean-burn gasoline engines in vehicles, hydrocarbons would be the preferred reducing agents over NH{sub 3} because of the practical problems associated with the use of NH{sub 3} (i.e., handling and slippage through the reactor). The noble-metal three-way catalysts are not effective under these conditions. The first catalyst found to be active for selective catalytic reduction of NO by hydrocarbons in the presence of excess oxygen was copper exchanged ZSM-5 and other zeolites, reported in 1990 by Iwamoto in Japan and Held et al. in Germany. Although Cu-ZSM-5 is very active and the most intensively studied catalyst, it suffers from severe deactivation in engine tests, mainly due to H{sub 2}O and SO{sub 2}. In this project, we found that ion-exchanged pillared clays and MCM-41 catalysts showed superior SCR activities of NO with hydrocarbon. All Cu{sup 2+}-exchanged pillared clays showed higher SCR activities than Cu-ZSM-5 reported in the literature. In particular, H{sub 2}O and SO{sub 2} only slightly deactivated the SCR activity of Cu-TiO{sub 2}-PILC, whereas severe deactivation was observed for Cu-ZSM-5. Moreover, Pt/MCM-41 provided the highest specific NO reduction rates as compared with other Pt doped catalysts, i.e., Pt/Al{sub 2}O{sub 3}, Pt/SiO{sub 2} and Pt/ZSM-5. The Pt/MCM-41 catalyst also showed a good stability in the presence of H{sub 2}O and SO{sub 2}.

  1. DRIFT studies on promotion mechanism of H3PW12O40 in selective catalytic reduction of NO with NH3.

    Science.gov (United States)

    Weng, Xiaole; Dai, Xiaoxia; Zeng, Qingshan; Liu, Yue; Wu, Zhongbiao

    2016-01-01

    Heteropoly acids (HPAs) have been effectively utilized in selective catalytic reduction (SCR) of NO to improve the NH3 absorption capacity and alkaline/alkali metal resistance for SCR catalysts. However, despite the promise on super-acidities, their other properties that would work on SCR process are still lack of exploration. In this study, a 12-tungstaphosphoric acid (H3PW12O40, HPW) was selected to modify a well-reported CeO2 catalyst. The resulted CeO2/HPW catalyst was subsequently utilized for SCR of NO with excess NH3, which revealed a significantly promoted performance in SCR reaction. DRIFT analyses showed that the unique NO2 absorption capacity of HPW could prevent the NO2 being further oxidized into nitrate species and the abundant Brønsted acid sites could effectively retain the NH3, avoiding them being over-oxidized at evaluated temperatures. The presence of NO2 was demonstrated able to induce a so called "fast SCR" reaction over the CeO2/HPW catalyst, which effectively facilitated the SCR reaction. Furthermore, we have also constructed a CeO2@HPW catalyst, which showed an enhanced SO2 poisoning resistance in SCR reaction.

  2. A study on the indirect urea dosing method in the Selective Catalytic Reduction system

    Science.gov (United States)

    Brzeżański, M.; Sala, R.

    2016-09-01

    This article presents the results of studies on concept solution of dosing urea in a gas phase in a selective catalytic reduction system. The idea of the concept was to heat-up and evaporate the water urea solution before introducing it into the exhaust gas stream. The aim was to enhance the processes of urea converting into ammonia, what is the target reductant for nitrogen oxides treatment. The study was conducted on a medium-duty Euro 5 diesel engine with exhaust line consisting of DOC catalyst, DPF filter and an SCR system with a changeable setup allowing to dose the urea in liquid phase (regular solution) and to dose it in a gas phase (concept solution). The main criteria was to assess the effect of physical state of urea dosed on the NOx conversion ratio in the SCR catalyst. In order to compare both urea dosing methods a special test procedure was developed which consisted of six test steps covering a wide temperature range of exhaust gas generated at steady state engine operation condition. Tests were conducted for different urea dosing quantities defined by the a equivalence ratio. Based on the obtained results, a remarkable improvement in NOx reduction was found for gas urea application in comparison to the standard liquid urea dosing. Measured results indicate a high potential to increase an efficiency of the SCR catalyst by using a gas phase urea and provide the basis for further scientific research on this type of concept.

  3. EFFECT OF SCR CATALYST ON MERCURY SPECIATION

    Science.gov (United States)

    A pilot-scale research study was conducted to investigate the effect of selective catalytic reduction (SCR) on elemental mercury speciation in bituminous and subbituminous coal combustion flue gases. Three different Illinois bituminous coals and one Powder River Basin (PRB) coal...

  4. Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic reduction of NOx with NH3

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Ja Hun; Tonkyn, Russell G.; Kim, Do Heui; Szanyi, Janos; Peden, Charles HF

    2010-10-21

    Superior activity and selectivity of a Cu ion-exchanged SSZ-13 zeolite in the selective catalytic reduction (SCR) of NOx with NH3 were observed, in comparison to Cu-beta and Cu-ZSM-5 zeolites. Cu-SSZ-13 was not only more active in the NOx SCR reaction over the entire temperature range studied (up to 550 °C), but also more selective toward nitrogen formation, resulting in significantly lower amounts of NOx by-products (i.e., NO2 and N2O) than the other two zeolites. In addition, Cu-SSZ-13 demonstrated the highest activity and N2 formation selectivity in the oxidation of NH3. The results of this study strongly suggest that Cu-SSZ-13 is a promising candidate as a catalyst for NOx SCR with great potential in after-treatment systems for either mobile or stationary sources.

  5. Kinetics of selective catalytic reduction of NO by NH3 on Fe-Mo/ZSM-5 catalyst

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The catalyst of Fe-Mo/ZSM-5 has been found to be more active than Fe-ZSM-5 and Mo/ZSM-5 separately for selective catalytic reduction (SCR) of nitric oxide (NO) with NH3. The kinetics of the SCR reaction in the presence of O2 was studied in this work. The results show that the observed reaction orders were 0.74-0.99, 0.01-0.13, and 0 for NO, O2 and NH3, respectively, at 350-450℃. And the apparent activation energy of the SCR was 65 kJ/mol on the Fe-Mo/ZSM-5 catalyst. The SCR mechanism was also deduced. Adsorbed NO species can react directly with adsorbed ammonia species on the active sites to form N2 and H2O. Gaseous O2 might serve as a reoxidizing agent for the active sites that have undergone reduction in the SCR process. It is also important to note that a certain amount of NO was decomposed directly over the Fe-Mo/ZSM-5 catalyst in the absence of NH3.

  6. PILOT-SCALE STUDY OF THE EFFECT OF SELECTIVE CATALYTIC REDUCTION CATALYST ON MERCURY SPECIATION IN ILLINOIS AND POWDER RIVER BASIN COAL COMBUSTION FLUE GASES

    Science.gov (United States)

    A study was conducted to investigate the effect of selective catalytic reduction (SCR) catalyst on mercury (Hg) speciation in bituminous and subbituminous coal combustion flue gases. Three different Illinois Basin bituminous coals (from high to low sulfur and chlorine) and one Po...

  7. Ethanol-selective catalytic reduction of NO by Ag/Al2O3 catalysts: Activity and deactivation by alkali salts

    DEFF Research Database (Denmark)

    Schill, Leonhard; Putluru, Siva Sankar Reddy; Jacobsen, Casper Funk;

    2012-01-01

    Ag/Al2O3 catalysts with and without potassium doping were prepared by incipient wetness impregnation and characterized by N2 physisorption, XRPD, NH3-TPD and SEM. The influence of the Ag content from 1 to 5 wt.% was investigated for the selective catalytic reduction (SCR) of NO with ethanol. The 3...

  8. Enhanced catalytic activity over MIL-100(Fe) loaded ceria catalysts for the selective catalytic reduction of NOx with NH₃ at low temperature.

    Science.gov (United States)

    Wang, Peng; Sun, Hong; Quan, Xie; Chen, Shuo

    2016-01-15

    The development of catalysts for selective catalytic reduction (SCR) reactions that are highly active at low temperatures and show good resistance to SO2 and H2O is still a challenge. In this study, we have designed and developed a high-performance SCR catalyst based on nano-sized ceria encapsulated inside the pores of MIL-100(Fe) that combines excellent catalytic power with a metal organic framework architecture synthesized by the impregnation method (IM). Transmission electron microscopy (TEM) revealed the encapsulation of ceria in the cavities of MIL-100(Fe). The prepared IM-CeO2/MIL-100(Fe) catalyst shows improved catalytic activity both at low temperatures and throughout a wide temperature window. The temperature window for 90% NOx conversion ranges from 196 to 300°C. X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) analysis indicated that the nano-sized ceria encapsulated inside MIL-100(Fe) promotes the production of chemisorbed oxygen on the catalyst surface, which greatly enhances the formation of the NO2 species responsible for fast SCR reactions. PMID:26414927

  9. EVALUATION OF THE EFFECT OF SCR ON MERCURY SPECIATION AND EMISSIONS

    Science.gov (United States)

    The paper presents the results of an investigation on the impact that selective catalytic reduction (SCR) has on both the total emissions and the speciation of mercury (Hg). SCR systems can be used as multipollutant technologies if they enhance Hg conversion/capture. Previous pil...

  10. 基于 PLC 的船用 SCR 废气减排与综合利用%SCR emission reduction and comprehensive utilization of the ship based on PLC

    Institute of Scientific and Technical Information of China (English)

    文超

    2015-01-01

    In recent years, the country pay more and more attention to the protection of the environment, to strengthen the control of all kinds of vehicle emission, to reduce emissions of the vehicle through a number of measures. The ship is a kind of large transportation tool, which make great contributions to the transportation industry and economic development at the same time, but also cause great pollution to the natural environment. Many of the nitrogen oxides is contained in the waste gas produced by the marine diesel engine, the fact proves that these oxides has great harm to the atmosphere. The diesel engine selective catalytic reduction system is a kind of technology especially for the nitrogen oxides control technology, which can reduce more than 50% reduction of ntrogen oxides in the waste gas produced by the marine diesel engine effectively. In this paper, the SCR emission reduction and comprehensive utilization system of ship are analyzed and studied based on the PLC technology.%近年来,国家越来越重视对环境的保护,加强对各种交通工具的排放控制,通过一些措施对其进行废气减排。船舶作为一种大型的交通运输工具,在为交通运输业与经济发展做出巨大贡献的同时,也对自然环境造成了较大污染。船用柴油机会产生很多的含有氮氧化物的废气,事实证明这些氮氧化物对大气具有很大危害。而选择性催化还原系统( SCR 系统)是一种专门针对氮氧化物的控制减排技术,可以有效的减少船舶柴油机废气中50%以上的氮氧化物。本文基于 PLC 技术,对船用的 SCR 废气减排与综合利用系统进行了系统的分析与研究。

  11. Enhanced Activity of Nanocrystalline Zeolites for Selective Catalytic Reduction of NOx

    International Nuclear Information System (INIS)

    Nanocrystalline zeolites with discrete crystal sizes of less than 100 nm have different properties relative to zeolites with larger crystal sizes. Nanocrystalline zeolites have improved mass transfer properties and very large internal and external surface areas that can be exploited for many different applications. The additional external surface active sites and the improved mass transfer properties of nanocrystalline zeolites offer significant advantages for selective catalytic reduction (SCR) catalysis with ammonia as a reductant in coal-fired power plants relative to current zeolite based SCR catalysts. Nanocrystalline NaY was synthesized with a crystal size of 15-20 nm and was thoroughly characterized using x-ray diffraction, electron paramagnetic resonance spectroscopy, nitrogen adsorption isotherms and Fourier Transform Infrared (FT-IR) spectroscopy. Copper ions were exchanged into nanocrystalline NaY to increase the catalytic activity. The reactions of nitrogen dioxides (NOx) and ammonia (NH3) on nanocrystalline NaY and CuY were investigated using FT-IR spectroscopy. Significant conversion of NO2 was observed at room temperature in the presence of NH3 as monitored by FT-IR spectroscopy. Copper-exchanged nanocrystalline NaY was more active for NO2 reduction with NH3 relative to nanocrystalline NaY

  12. Structural characterization and catalytic activity of Pt dendrimer encapsulated nanoparticles supported over Al2O3 for SCR of NOx.

    Science.gov (United States)

    Bae, HyunSook; Rao, Komateedi N; Ha, HeonPhil

    2011-07-01

    Pt/Al2O3 and Pt-Mg/Al2O3 nano composites were successfully prepared by dendrimer templated synthesis route. The obtained dendritic nanoparticles were dispersed in alumina support and they were evaluated for SCR of NOx using methane as reductant. Thermal analysis results of uncalcined samples revealed that the oxygen can accelerate the rate of dendrimer shell decomposition. X-ray diffractograms of 500 degrees C calcined samples disclosed the amorphous nature of materials, whereas 1000 degrees C air calcined samples showed enhanced crystallinity as well as diffraction pattern corresponding to Pt and PtO. HRTEM images of Pt40-G4OH dendritic nanoparticles showed uniform particulate distribution with average particle size of 2.4 nm. The STEM results of 0.5 Pt/Al2O3 sample calcined at 500 degrees C exhibited a wide range of particles between 2 and 20 nm. This indicates the huge segregation of platinum metal particles during impregnation and subsequent calcination. Among the synthesized materials 0.5 wt% Pt/Al2O3 sample showed excellent conversion and selectivity for SCR of NOx.

  13. PILLARED CLAYS AS SUPERIOR CATALYSTS FOR SELECTIVE CATALYTIC REDUCTION OF NITRIC OXIDE

    Energy Technology Data Exchange (ETDEWEB)

    R. T. Yang; R.Q. Long

    1999-03-31

    In the last annual reports, we reported Cu-exchanged pillared clays as superior selective catalytic reduction (SCR) catalysts. During the past year we explored the possibilities with MCM-41, a new class of molecular sieve. In this report, Rh exchanged Al-MCM-41 is studied for the SCR of NO by C{sub 3}H{sub 6} in the presence of excess oxygen. It shows a high activity in converting NO to N{sub 2} and N{sub 2}O at low temperatures. In situ FT-IR studies indicate that Rh-NO{sup +} species (1910-1898 cm{sup {minus}1}) is formed on the Rh-Al-MCM-41 catalyst in flowing NO/He, NO+O{sub 2}/He and NO+C{sub 3}H{sub 6}+O{sub 2}/He at 100-350 C. This species is quite active in reacting with propylene and/or propylene adspecies (e.g., {pi}-C{sub 3}H{sub 5}, polyene, etc.) at 250 C in the presence/absence of oxygen, leading to the formation of the isocyanate species (Rh-NCO, at 2174 cm{sup {minus}1}), CO and CO{sub 2}. Rh-NCO is also detected under reaction conditions. A possible reaction pathway for reduction of NO by C{sub 3}H{sub 6} is proposed. In the SCR reaction, Rh-NO{sup +} and propylene adspecies react to generate the Rh-NCO species, then Rh-NCO reacts with O{sub 2}, NO and NO{sub 2} to produce N{sub 2}, N{sub 2}O and CO{sub 2}. Rh-NO{sup +} and Rh-NCO species are two main intermediates for the SCR reaction on Rh-Al-MCM-41 catalyst.

  14. Side reactions in the selective catalytic reduction of NO with NH{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Madia, G.; Koebel, M.; Elsener, M.; Wokaun, A.

    2002-03-01

    The main and the side reactions of the SCR reaction with ammonia over TiO{sub 2}-WO{sub 3}-V{sub 2}O{sub 5} catalysts have been investigated using synthetic gas mixtures matching the composition of diesel exhaust. At high temperatures the selective catalytic oxidation of ammonia (SCO) and the formation of nitrous oxide compete with the SCR reaction. Water strongly inhibits the SCO of ammonia and the formation of nitrous oxide thus increasing the selectivity of the SCR reaction. However, water also inhibits SCR activity, most pronounced at low temperatures. (author)

  15. Oxidation of diesel-generated volatile organic compounds in the selective catalytic reduction process

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, M.; Elsener, M. [Paul Scherrer Inst., Villigen (Switzerland). Combustion Research

    1998-10-01

    The main part of the VOCs (volatile organic compounds) contained in diesel exhaust ({approx}80%) is oxidized to CO and CO{sub 2} over an SCR (selective catalytic reduction) catalyst. CO is the major product of this oxidation, representing about 50--70% of the formed products (CO + CO{sub 2}). This preferential formation of CO leads to a pronounced increase of CO emissions when an SCR process is added to a diesel engine. A small fraction of the VOCs is selectively oxidized to carboxylic acids over the SCR catalyst. This selectivity is due to the acidic properties of the catalyst causing the preferential desorption at the oxidation state of the acid. The main products of these oxidation reactions are the lower monocarboxylic acids and some dicarboxylic acids forming stable anhydrides, especially maleic and phthalic acid. The highest emissions of these acids are found at low temperatures; they decrease at higher temperatures. Formic acid is preferentially decomposed into carbon monoxide and water. It must therefore be assumed that the strong increase of CO mentioned above is due to a mechanism involving the thermal decomposition of formic acid formed from various primary VOCs.

  16. Impact of selective catalytic reduction on exhaust particle formation over excess ammonia events.

    Science.gov (United States)

    Amanatidis, Stavros; Ntziachristos, Leonidas; Giechaskiel, Barouch; Bergmann, Alexander; Samaras, Zissis

    2014-10-01

    The introduction of selective catalytic reduction (SCR) aftertreatment to meet stringent diesel NOx emission standards around the world increases exhaust ammonia. Further to the direct air quality and health implications of ammonia, this may also lead to particle formation in the exhaust. In this study, an ammonia SCR system was examined with respect to its impact on both solid and total exhaust particle number and size distribution, downstream of a diesel particulate filter (DPF). Fuel post-injection was conducted in some tests to investigate the effect of ammonia during active DPF regeneration. On average, the post-DPF solid >23 nm and total <23 nm particle number emissions were increased by 129% (range 80-193%) and by 67% (range 26-136%), respectively, when 100 ppm ammonia level was induced downstream of the SCR catalyst. This is a typical level during ammonia overdosing, often practiced for efficient NOx control. Ammonia did not have a significant additional effect on the high particle concentrations measured during DPF regeneration. Based on species availability and formation conditions, sulfate, nitrate, and chloride salts with ammonium are possible sources of the new particles formed. Ammonia-induced particle formation corresponds to an environmental problem which is not adequately addressed by current regulations.

  17. Superior Fe-ZSM-5 catalyst for selective catalytic reduction of nitric oxide by ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Long, R.Q.; Yang, R.T. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering

    1999-06-16

    Nitrogen oxides in the exhaust gases from combustion of fossil fuels remain a major source for air pollution and acid rain. The current technology for reducing NO{sub x} (NO + NO{sub 2}) emissions from power plants is selective catalytic reduction (SCR) with ammonia in the presence of oxygen. For the SCR reaction, V{sub 2}O{sub 5} + WO{sub 3} (or MoO{sub 3}) supported on TiO{sub 2} are the commercial catalysts. The mechanism of the reaction on the vanadia catalysts has been studied extensively, and several different mechanisms have been proposed. Ion-exchanged zeolite catalysts have also been studied, e.g., Fe-Y, Cu-ZSM-5, and Fe-ZSM-5, but the reported activities were lower than that of the commercial vanadia catalysts. The SCR technology based on vanadia catalysts is being used in Europe and Japan and is being quickly adopted in the US. However, problems associated with vanadia catalysts remain, e.g., high activity for oxidation of SO{sub 2} to SO{sub 3}, toxicity of vanadia, and formation of N{sub 2}O at high temperature. Hence, there are continuing efforts in developing new catalysts. In this paper, the authors report a superior Fe-ZSM-5 catalyst that is much more active than the commercial vanadia catalysts and does not have the deficiencies that are associated with the vanadia catalysts.

  18. INVESTIGATION OF AMMONIA ADSORPTION ON FLY ASH DUE TO INSTALLATION OF SELECTIVE CATALYTIC REDUCTION SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    G.F. Brendel; J.E. Bonetti; R.F. Rathbone; R.N. Frey Jr.

    2000-11-01

    This report summarizes an investigation of the potential impacts associated with the utilization of selective catalytic reduction (SCR) systems at coal-fired power plants. The study was sponsored by the U.S. Department of Energy Emission Control By-Products Consortium, Dominion Generation, the University of Kentucky Center for Applied Energy Research and GAI Consultants, Inc. SCR systems are effective in reducing nitrogen oxides (NOx) emissions as required by the Clean Air Act (CAA) Amendments. However, there may be potential consequences associated with ammonia contamination of stack emissions and combustion by-products from these systems. Costs for air quality, landfill and pond environmental compliance may increase significantly and the marketability of ash may be seriously reduced, which, in turn, may also lead to increased disposal costs. The potential impacts to air, surface water, groundwater, ash disposal, ash utilization, health and safety, and environmental compliance can not be easily quantified based on the information presently available. The investigation included: (1) a review of information and data available from published and unpublished sources; (2) baseline ash characterization testing of ash samples produced from several central Appalachian high-volatile bituminous coals from plants that do not currently employ SCR systems in order to characterize the ash prior to ammonia exposure; (3) an investigation of ammonia release from fly ash, including leaching and thermal studies; and (4) an evaluation of the potential impacts on plant equipment, air quality, water quality, ash disposal operations, and ash marketing.

  19. Vanadia supported on zeolites for SCR of NO by ammonia

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Riisager, Anders; Fehrmann, Rasmus

    2010-01-01

    in the selective catalytic reduction (SCR) of NO with ammonia. The SCR activity was found to correlate directly with the total acidity of the catalysts and showed high poisoning resistivity after doping with potassium oxide (100 mu mol/g). The poisoning resistance was due to unique combination of high surface area......, acidity and micropore structure of the support. Apparently the support hosted the potassium oxide on the acid sites, thereby protecting the active vanadium species from poisoning. Zeolite based catalysts might therefore prove useful for SCR of NO in alkali-containing flue gases from, e.g. biomass fired...

  20. Physico-Chemical Property and Catalytic Activity of a CeO2-Doped MnO(x)-TiO2 Catalyst with SO2 Resistance for Low-Temperature NH3-SCR of NO(x).

    Science.gov (United States)

    Shin, Byeongkil; Chun, Ho Hwan; Cha, Jin-Sun; Shin, Min-Chul; Lee, Heesoo

    2016-05-01

    The effects of CeO2 addition on the catalytic activity and the SO2 resistance of CeO2-doped MnO(x)-TiO2 catalysts were investigated for the low-temperature selective catalytic reduction (SCR) with NH3 of NO(x) emissions in marine applications. The most active catalyst was obtained from 30 wt% CeO2-MnO(x)-TiO2 catalyst in the whole temperature range of 100-300 degrees C at a low gas hourly space velocity (GHSV) of 10,000 h(-)1, and its de-NO(x) efficiency was higher than 90% over 250 degrees C. The enhanced catalytic activity may contribute to the dispersion state and catalytic acidity on the catalyst surface, and the highly dispersed Mn and Ce on the nano-scaled TiO2 catalyst affects the increase of Lewis and Brønsted acid sites. A CeO2-rich additive on MnO(x)-TiO2 could provide stronger catalytic acid sites, associated with NH3 adsorption and the SCR performance. As the results of sulfur resistance in flue gas that contains SO2, the de-NO(x) efficiency of MnO(x)-TiO2 decreased by 15% over 200 degrees C, whereas that of 30 wt% ceria-doped catalyst increased by 14-21% over 150 degrees C. The high SO2 resistance of CeO2-MnO(x)-TiO2 catalysts that resulted from the addition of ceria suppressed the formation of Mn sulfate species, which led to deactivation on the surface of nano-catalyst. PMID:27483759

  1. Physico-Chemical Property and Catalytic Activity of a CeO2-Doped MnO(x)-TiO2 Catalyst with SO2 Resistance for Low-Temperature NH3-SCR of NO(x).

    Science.gov (United States)

    Shin, Byeongkil; Chun, Ho Hwan; Cha, Jin-Sun; Shin, Min-Chul; Lee, Heesoo

    2016-05-01

    The effects of CeO2 addition on the catalytic activity and the SO2 resistance of CeO2-doped MnO(x)-TiO2 catalysts were investigated for the low-temperature selective catalytic reduction (SCR) with NH3 of NO(x) emissions in marine applications. The most active catalyst was obtained from 30 wt% CeO2-MnO(x)-TiO2 catalyst in the whole temperature range of 100-300 degrees C at a low gas hourly space velocity (GHSV) of 10,000 h(-)1, and its de-NO(x) efficiency was higher than 90% over 250 degrees C. The enhanced catalytic activity may contribute to the dispersion state and catalytic acidity on the catalyst surface, and the highly dispersed Mn and Ce on the nano-scaled TiO2 catalyst affects the increase of Lewis and Brønsted acid sites. A CeO2-rich additive on MnO(x)-TiO2 could provide stronger catalytic acid sites, associated with NH3 adsorption and the SCR performance. As the results of sulfur resistance in flue gas that contains SO2, the de-NO(x) efficiency of MnO(x)-TiO2 decreased by 15% over 200 degrees C, whereas that of 30 wt% ceria-doped catalyst increased by 14-21% over 150 degrees C. The high SO2 resistance of CeO2-MnO(x)-TiO2 catalysts that resulted from the addition of ceria suppressed the formation of Mn sulfate species, which led to deactivation on the surface of nano-catalyst.

  2. SCR氨区的运行维护%Operation and uphold of area of liquid ammonia in Selective Catalytic Reduction

    Institute of Scientific and Technical Information of China (English)

    陈建明

    2014-01-01

    液氨是选择性催化还原脱硝法( SCR)工艺首选的脱硝反应剂,它属于危险化学品。氨区的安全运行是SCR系统安全运行的基础保障。从氨区的运行、维护、人员防护和事故处理等方面阐述了SCR系统运行维护中需要注意的一些关键点。%Liquid ammonia is the first choice of reductant in selective catalytic reduction,it is a sort of dangerous chemical. The safe operation in the area of liquid ammonia is foundation of SCR. lt describes take notice of SCR from the operation,uphold,physical protection and accident handling in the area of liquid ammonia.

  3. Operation and uphold of area of liquid ammonia in Selective Catalytic Reduction%SCR氨区的运行维护

    Institute of Scientific and Technical Information of China (English)

    陈建明

    2014-01-01

    液氨是选择性催化还原脱硝法( SCR)工艺首选的脱硝反应剂,它属于危险化学品。氨区的安全运行是SCR系统安全运行的基础保障。从氨区的运行、维护、人员防护和事故处理等方面阐述了SCR系统运行维护中需要注意的一些关键点。%Liquid ammonia is the first choice of reductant in selective catalytic reduction,it is a sort of dangerous chemical. The safe operation in the area of liquid ammonia is foundation of SCR. lt describes take notice of SCR from the operation,uphold,physical protection and accident handling in the area of liquid ammonia.

  4. HYBRID SNCR-SCR TECHNOLOGIES FOR NOX CONTROL: MODELING AND EXPERIMENT

    Science.gov (United States)

    The hybrid process of homogeneous gas-phase selective non-catalytic reduction (SNCR) followed by selective catalytic reduction (SCR) of nitric oxide (NO) was investigated through experimentation and modeling. Measurements, using NO-doped flue gas from a gas-fired 29 kW test combu...

  5. Long-time experience in catalytic flue gas cleaning and catalytic NO{sub x} reduction in biofueled boilers

    Energy Technology Data Exchange (ETDEWEB)

    Ahonen, M. [Tampella Power Inc., Tampere (Finland)

    1996-12-31

    NO emissions are reduced by primary or secondary methods. Primary methods are based on NO reduction in the combustion zone and secondary methods on flue gas cleaning. The most effective NO reduction method is selective catalytic reduction (SCR). It is based on NO reduction by ammonia on the surface of a catalyst. Reaction products are water and nitrogen. A titanium-dioxide-based catalyst is very durable and selective in coal-fired power plants. It is not poisoned by sulphur dioxide and side reactions with ammonia and sulphur dioxide hardly occur. The long time experience and suitability of a titanium-dioxide-based catalyst for NO reduction in biofuel-fired power plants was studied. The biofuels were: peat, wood and bark. It was noticed that deactivation varied very much due to the type of fuel and content of alkalinities in fuel ash. The deactivation in peat firing was moderate, close to the deactivation noticed in coal firing. Wood firing generally had a greater deactivation effect than peat firing. Fuel and fly ash were analyzed to get more information on the flue gas properties. The accumulation of alkali and alkaline earth metals and sulphates was examined together with changes in the physical composition of the catalysts. In the cases where the deactivation was the greatest, the amount of alkali and alkaline earth metals in fuels and fly ashes and their accumulation were very significant. (author) (3 refs.)

  6. Experimental demonstration of a new model-based SCR control strategy for cleaner heavy-duty diesel engines

    NARCIS (Netherlands)

    Willems, F.P.T.; Cloudt, R.P.M.

    2011-01-01

    Selective catalytic reduction (SCR) is a promising diesel aftertreatment technology that enables low nitrogen oxides (NOx) tailpipe emissions with relatively low fuel consumption. Future emission legislation is pushing the boundaries for SCR control systems to achieve high NOx conversion within a ta

  7. Bauxite-supported Transition Metal Oxides: Promising Low-temperature and SO2-tolerant Catalysts for Selective Catalytic Reduction of NOx

    OpenAIRE

    Xiuyun Wang; Wen Wu; Zhilin Chen; Ruihu Wang

    2015-01-01

    In order to develop low-temperature (below 200 °C) and SO2-tolerant catalysts for selective catalytic reduction (SCR) of NOx, a series of cheap M/bauxite (M = Mn, Ni and Cu) catalysts were prepared using bauxite as a support. Their SCR performances are much superior to typical V2O5/TiO2, the addition of M into bauxite results in significant promotion of NOx removal efficiency, especially at low temperature. Among the catalysts, Cu/bauxite exhibits wide temperature window over 50–400 °C, stron...

  8. Influence of hydrogen treatment on SCR catalysts

    DEFF Research Database (Denmark)

    Due-Hansen, Johannes

    reduction (SCR) process, i.e. the catalytic removal of NOx from the flue gas. A series of experiments was conducted to reveal the impact on the NO SCR activity of a industrial DeNOX catalyst (3%V2O5-7%WO3/TiO2) by treatment of H2. Standard conditions were treatment of the SCR catalyst for 60 min with three...... different concentrations of H2 (0-2%) in a 8% O2/N2 mixture, where the SCR activity was measured before and after the hydrogen treatment. The results show that the activity of the SCR catalyst is only negligible affected during exposure to the H2/O2 gas and in all cases it returned reversibly to the initial...... NOx conversion (temporarily higher) after reexposure to the standard NO SCR gas. Electron paramagnetic resonance (EPR) suggests that a fraction of both V(IV) and V(V) were reduced to V(III) during exposure to 2% H2 + 8% O2. However, the distribution of vanadium in oxidation state V(III)-V(V) quickly...

  9. The Significance of Lewis Acid Sites for the Selective Catalytic Reduction of Nitric Oxide on Vanadium-Based Catalysts.

    Science.gov (United States)

    Marberger, Adrian; Ferri, Davide; Elsener, Martin; Kröcher, Oliver

    2016-09-19

    The long debated reaction mechanisms of the selective catalytic reduction (SCR) of nitric oxide with ammonia (NH3 ) on vanadium-based catalysts rely on the involvement of Brønsted or Lewis acid sites. This issue has been clearly elucidated using a combination of transient perturbations of the catalyst environment with operando time-resolved spectroscopy to obtain unique molecular level insights. Nitric oxide reacts predominantly with NH3 coordinated to Lewis sites on vanadia on tungsta-titania (V2 O5 -WO3 -TiO2 ), while Brønsted sites are not involved in the catalytic cycle. The Lewis site is a mono-oxo vanadyl group that reduces only in the presence of both nitric oxide and NH3 . We were also able to verify the formation of the nitrosamide (NH2 NO) intermediate, which forms in tandem with vanadium reduction, and thus the entire mechanism of SCR. Our experimental approach, demonstrated in the specific case of SCR, promises to progress the understanding of chemical reactions of technological relevance.

  10. The Significance of Lewis Acid Sites for the Selective Catalytic Reduction of Nitric Oxide on Vanadium-Based Catalysts.

    Science.gov (United States)

    Marberger, Adrian; Ferri, Davide; Elsener, Martin; Kröcher, Oliver

    2016-09-19

    The long debated reaction mechanisms of the selective catalytic reduction (SCR) of nitric oxide with ammonia (NH3 ) on vanadium-based catalysts rely on the involvement of Brønsted or Lewis acid sites. This issue has been clearly elucidated using a combination of transient perturbations of the catalyst environment with operando time-resolved spectroscopy to obtain unique molecular level insights. Nitric oxide reacts predominantly with NH3 coordinated to Lewis sites on vanadia on tungsta-titania (V2 O5 -WO3 -TiO2 ), while Brønsted sites are not involved in the catalytic cycle. The Lewis site is a mono-oxo vanadyl group that reduces only in the presence of both nitric oxide and NH3 . We were also able to verify the formation of the nitrosamide (NH2 NO) intermediate, which forms in tandem with vanadium reduction, and thus the entire mechanism of SCR. Our experimental approach, demonstrated in the specific case of SCR, promises to progress the understanding of chemical reactions of technological relevance. PMID:27553251

  11. Numerical analysis of NOx reduction for compact design in marine urea-SCR system

    Science.gov (United States)

    Choi, Cheolyong; Sung, Yonmo; Choi, Gyung Min; Kim, Duck Jool

    2015-11-01

    In order to design a compact urea selective catalytic reduction system, numerical simulation was conducted by computational fluid dynamics tool. A swirl type static mixer and a mixing chamber were considered as mixing units in the system. It had great influence on flow characteristics and urea decomposition into ammonia. The mixer caused flow recirculation and high level of turbulence intensity, and the chamber increased residence time of urea-water-solution injected. Because of those effects, reaction rates of urea decomposition were enhanced in the region. When those mixing units were combined, it showed the maximum because the recirculation zone was significantly developed. NH3 conversion was maximized in the zone due to widely distributed turbulence intensity and high value of uniformity index. It caused improvement of NOx reduction efficiency of the system. It was possible to reduce 55% length of the chamber and connecting pipe without decrease of NOx reduction efficiency.

  12. Understanding ammonia selective catalytic reduction kinetics over Cu-SSZ-13 from motion of the Cu ions

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Walter, Eric D.; Kollar, Marton; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

    2014-11-01

    Cu-SSZ-13 catalysts with three Si/Al ratios, at 6, 12 and 35, are synthesized with solution ion exchange. Catalysts are characterized with surface area/pore volume measurements, temperature programmed reduction (TPR), and electron paramagnetic resonance (EPR) spectroscopy. Catalytic properties are examined using NO oxidation, ammonia oxidation, and standard ammonia selective catalytic reduction (NH3-SCR) reactions. By varying Si/Al ratios and Cu loadings, it is possible to synthesize catalysts with one dominant type of isolated Cu2+ ion species. Prior to full dehydration of the zeolite catalyst, hydrated Cu2+ ions are found to be very mobile as judged from EPR. NO oxidation is catalyzed by O-bridged Cu-dimer species that form at relatively high Cu loadings and in the presence of O2. For NH3 oxidation and standard SCR reactions, transient Cu-dimers even form at much lower Cu loadings; and these are proposed to be the active sites for reaction temperatures ≤ 350 °C. These dimer species can be viewed as in equilibrium with monomeric Cu ion complexes. Between ~250 and 350 °C, these moieties become less stable causing SCR reaction rates to decrease. At temperatures above 350 °C and at low Cu loadings, Cu-dimers completely dissociate to regenerate isolated Cu2+ monomers that then locate at ion-exchange sites of the zeolite lattice. At low Cu loadings, these Cu species are the high-temperature active SCR catalytic centers. At high Cu loadings, on the other hand, both Cu-dimers and monomers are highly active in the high temperature kinetic regime, yet Cu-dimers are less selective in SCR. Brönsted acidity is also very important for SCR reactivity in the high-temperature regime. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national

  13. Impacts of acid gases on mercury oxidation across SCR catalyst

    International Nuclear Information System (INIS)

    A series of bench-scale experiments were completed to evaluate acid gases of HCl, SO2, and SO3 on mercury oxidation across a commercial selective catalytic reduction (SCR) catalyst. The SCR catalyst was placed in a simulated flue gas stream containing O2, CO2, H2O, NO, NO2, and NH3, and N2. HCl, SO2, and SO3 were added to the gas stream either separately or in combination to investigate their interactions with mercury over the SCR catalyst. The compositions of the simulated flue gas represent a medium-sulfur and low- to medium-chlorine coal that could represent either bituminous or subbituminous. The experimental data indicated that 5-50 ppm HCl in flue gas enhanced mercury oxidation within the SCR catalyst, possibly because of the reactive chlorine species formed through catalytic reactions. An addition of 5 ppm HCl in the simulated flue gas resulted in mercury oxidation of 45% across the SCR compared to only 4% mercury oxidation when 1 ppm HCl is in the flue gas. As HCl concentration increased to 50 ppm, 63% of Hg oxidation was reached. SO2 and SO3 showed a mitigating effect on mercury chlorination to some degree, depending on the concentrations of SO2 and SO3, by competing against HCl for SCR adsorption sites. High levels of acid gases of HCl (50 ppm), SO2 (2000 ppm), and SO3 (50 ppm) in the flue gas deteriorate mercury adsorption on the SCR catalyst. (author)

  14. The Cu-CHA deNOx Catalyst in Action: Temperature-Dependent NH3-Assisted Selective Catalytic Reduction Monitored by Operando XAS and XES.

    Science.gov (United States)

    Lomachenko, Kirill A; Borfecchia, Elisa; Negri, Chiara; Berlier, Gloria; Lamberti, Carlo; Beato, Pablo; Falsig, Hanne; Bordiga, Silvia

    2016-09-21

    The small-pore Cu-CHA zeolite is today the object of intensive research efforts to rationalize its outstanding performance in the NH3-assisted selective catalytic reduction (SCR) of harmful nitrogen oxides and to unveil the SCR mechanism. Herein we exploit operando X-ray spectroscopies to monitor the Cu-CHA catalyst in action during NH3-SCR in the 150-400 °C range, targeting Cu oxidation state, mobility, and preferential N or O ligation as a function of reaction temperature. By combining operando XANES, EXAFS, and vtc-XES, we unambiguously identify two distinct regimes for the atomic-scale behavior of Cu active-sites. Low-temperature SCR, up to ∼200 °C, is characterized by balanced populations of Cu(I)/Cu(II) sites and dominated by mobile NH3-solvated Cu-species. From 250 °C upward, in correspondence to the steep increase in catalytic activity, the largely dominant Cu-species are framework-coordinated Cu(II) sites, likely representing the active sites for high-temperature SCR. PMID:27532483

  15. Urea-SCR Temperature Investigation for NOx Control of Diesel Engine

    Directory of Open Access Journals (Sweden)

    Asif Muhammad

    2015-01-01

    Full Text Available SCR (selective catalytic reduction system is continuously being analyzed by many researchers worldwide on various concerns due to the stringent nitrogen oxides (NOx emissions legislation for heavy-duty diesel engines. Urea-SCR includes AdBlue as urea source, which subsequently decomposes to NH3 (ammonia being the reducing agent. Reaction temperature is a key factor for the performance of urea-SCR system, as urea decomposition rate is sensitive to a specific temperature range. This particular study was directed to investigate the temperature of the SCR system in diesel engine with the objective to confirm that whether the appropriate temperature is attained for occurrence of urea based catalytic reduction or otherwise and how the system performs on the prescribed temperature range. Diesel engine fitted with urea-SCR exhaust system has been operated on European standard cycle for emission testing to monitor the temperature and corresponding nitrogen oxides (NOx values on specified points. Moreover, mathematical expressions for approximation of reaction temperature are also proposed which are derived by applying energy conservation principal and gas laws. Results of the investigation have shown that during the whole testing cycle system temperature has remained in the range where urea-SCR can take place with best optimum rate and the system performance on account of NOx reduction was exemplary as excellent NOx conversion rate is achieved. It has also been confirmed that selective catalytic reduction (SCR is the best suitable technology for automotive engine-out NOx control.

  16. Lewis-acid and redox-active zeolite catalysts for the activation of methane and lower hydrocarbons in the selective catalytic reduction of NO{sub x}. Subproject: structural characterization and kinetic modelling. Final report; Lewis-acide und redox-aktive Zeolith-Katalysatoren fuer die Aktivierung von Methan und Fluessiggas-Kohlenwasserstoffen in der SCR von NO{sub x}. Teilprojekt: Strukturelle Katalysatorcharakterisierung und Modellierung der Reaktionskinetik. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Gruenert, W. [Bochum Univ. (Germany). Technische Chemie; Sowade, T.; Schmidt, C.; Stroeder, U. [Heraeus (W.C.) GmbH, Hanau (Germany)

    2001-12-01

    Zeolites (in particular ZSM-5) modified by indium and additionally promoted by ceria have been studied as catalysts for selective reduction of NO by methane. The structural properties of the catalysts have been investigated by XRD, FTIR, EXAFS, electron microscopy and XPS. The ceria promotor may be added to In-ZSM-5 by precipitation onto the external zeolite surface or by physically admixing a high surface-area powder. The preparation of the basic In-ZSM-5 system has a large influence on the properties of the catalyst. Preparation by aqueous exchange leads in most cases to a coexistence of a small amount of intra-zeolite indium species and extra-zeolite indium phases. Only at low pH, exclusively intra-zeolite indium is formed to a low extent (<10% exchange degree). Intrazeolite indium can be also obtained by dry preparations using InCl{sub 3} (solid-state ion exchange, sublimation, transport reaction). The In species formed carry Cl ligands, the stability of which depends on the indium content: after washing and calcination steps, Cl ligands could no longer be detected only in samples with low In content. Reductive solid-state ion exchange is a further method to prepare intra-zeolite In species. In mixtures containing excess indium, oligometric intra-zeolite In species are formed via this route. Intra-zeolite Cl-free In species exhibit significant SCR activity while Cl-containing In-species activate methane with low SCR selectivity. In ceria-promoted systems, the ceria provides full NO{sub 2} supply by catalysing the NO oxidation. With sufficient NO{sub 2} supply, the even Cl-containing In sites provide high SCR activities. Since the relevance of acidic sites was established e.g. by poisoning experiments, the reaction mechanism can by visualised by proceeding via methane activation over In sites, reaction of activated methane with NO{sub 2} to a volatile intermediate (e.g. nitromethane), which is then decomposed over the acidic sites. The reaction kinetics of the

  17. Laboratory test reactor for the investigation of liquid reducing agents in the selective catalytic reduction of NOx

    Science.gov (United States)

    Peitz, D.; Bernhard, A.; Elsener, M.; Kröcher, O.

    2011-08-01

    A test reactor was designed and built for investigating liquid reducing agents in the selective catalytic reduction (SCR) process in the laboratory. The design of the experimental setup is described in detail and its performance was evaluated. Using a glass nebulizer, liquid reducing agents were sprayed directly onto a catalyst positioned in a heated glass reactor with a length of 250 mm and an internal diameter of 20.4 mm or 40 mm. Model exhaust gases were mixed from individual gas components and were heated up to 450 °C in a heat exchanger before entering the reactor. The off-gas was analyzed using two complimentary techniques, a multi-component online FTIR gas analysis and a liquid quench gas absorption setup, to detect higher molecular compounds and aerosols. Due to the versatility of construction, processes not related to SCR, but involving three-phase reactions with gases, liquids and a catalyst, can also be investigated.

  18. Isolation of the Copper Redox Steps in the Standard Selective Catalytic Reduction on Cu-SSZ-13

    Energy Technology Data Exchange (ETDEWEB)

    Paolucci, Christopher; Verma, Anuj A.; Bates, Shane A.; Kispersky, Vincent F.; Miller, Jeffrey T.; Gounder, Rajmani; Delgass, Nick; Ribeiro, Fabio; Schneider, William F.

    2014-10-27

    Operando X-ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu-exchanged SSZ-13. Catalysts prepared to contain only isolated, exchanged CuII ions evidence both CuII and CuI ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH3 together are necessary for CuII reduction to CuI. DFT calculations show that NO-assisted NH3 dissociation is both energetically favorable and accounts for the observed CuII reduction. The calculations predict in situ generation of Brønsted sites proximal to CuI upon reduction, which we quantify in separate titration experiments. Both NO and O2 are necessary for oxidation of CuI to CuII, which DFT suggests to occur by a NO2 intermediate. Reaction of Cu-bound NO2 with proximal NH4 + completes the catalytic cycle. N2 is produced in both reduction and oxidation half-cycles.

  19. Isolation of the copper redox steps in the standard selective catalytic reduction on Cu-SSZ-13.

    Science.gov (United States)

    Paolucci, Christopher; Verma, Anuj A; Bates, Shane A; Kispersky, Vincent F; Miller, Jeffrey T; Gounder, Rajamani; Delgass, W Nicholas; Ribeiro, Fabio H; Schneider, William F

    2014-10-27

    Operando X-ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu-exchanged SSZ-13. Catalysts prepared to contain only isolated, exchanged Cu(II) ions evidence both Cu(II) and Cu(I) ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH3 together are necessary for Cu(II) reduction to Cu(I). DFT calculations show that NO-assisted NH3 dissociation is both energetically favorable and accounts for the observed Cu(II) reduction. The calculations predict in situ generation of Brønsted sites proximal to Cu(I) upon reduction, which we quantify in separate titration experiments. Both NO and O2 are necessary for oxidation of Cu(I) to Cu(II), which DFT suggests to occur by a NO2 intermediate. Reaction of Cu-bound NO2 with proximal NH4(+) completes the catalytic cycle. N2 is produced in both reduction and oxidation half-cycles. PMID:25220217

  20. Heteropoly acid promoted catalyst for SCR of NOx with ammonia

    DEFF Research Database (Denmark)

    2012-01-01

    comprising alkali or earth alkali metals. Such gases comprise for example flue gases arising from the burning of biomass, combined biomass and fossil fuel, and from waste incineration units. The process comprises the selective catalytic reduction (SCR) of NOx, such as nitrogen dioxide (NO2) and nitrogen...

  1. Fe Promotion Effect in Mn/USY for Low-temperature Selective Catalytic Reduction of NO with NH3

    Institute of Scientific and Technical Information of China (English)

    Qi Chun LIN; Ji Ming HAO; Jun Hua LI

    2006-01-01

    A series of catalysts of Mn/USY and Mn-Fe/USY prepared by impregnation were studied for low-temperature selective catalytic reduction (SCR) of NO with NH3 in the presence of excess of oxygen. It was found that the addition of Fe enhanced the catalytic performance at low-temperature. Mn-Fe/USY catalyst yielded nearly 100% NO conversion in a range of manganese and iron oxides enhanced the dispersion of the supported oxides, no visible phase of the oxides can be observed on catalyst. The addition of Fe enhanced the number and strength of the Bronsted and Lewis acid sites on the surface of the catalyst, which might promote the absorption of NH3 to form active intermediate and enhance the catalytic performance at low-temperature.

  2. Elementary steps of the catalytic NO{sub x} reduction with NH{sub 3}: Cluster studies on reaction paths and energetics at vanadium oxide substrate

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, M.; Hermann, K. [Inorganic Chemistry Department, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Germany)

    2013-12-28

    We consider different reaction scenarios of the selective catalytic reduction (SCR) of NO in the presence of ammonia at perfect as well as reduced vanadium oxide surfaces modeled by V{sub 2}O{sub 5}(010) without and with oxygen vacancies. Geometric and energetic details as well as reaction paths are evaluated using extended cluster models together with density-functional theory. Based on earlier work of adsorption, diffusion, and reaction of the different surface species participating in the SCR we confirm that at Brønsted acid sites (i.e., OH groups) of the perfect oxide surface nitrosamide, NH{sub 2}NO, forms a stable intermediate. Here adsorption of NH{sub 3} results in NH{sub 4} surface species which reacts with gas phase NO to produce the intermediate. Nitrosamide is also found as intermediate of the SCR near Lewis acid sites of the reduced oxide surface (i.e., near oxygen vacancies). However, here the adsorbed NH{sub 3} species is dehydrogenated to surface NH{sub 2} before it reacts with gas phase NO to produce the intermediate. The calculations suggest that reaction barriers for the SCR are overall higher near Brønsted acid sites of the perfect surface compared with Lewis acid sites of the reduced surface, examined for the first time in this work. The theoretical results are consistent with experimental findings and confirm the importance of surface reduction for the SCR process.

  3. Spectroscopic and Kinetic Study of Copper-Exchanged Zeolites for the Selective Catalytic Reduction of NOx with Ammonia

    OpenAIRE

    Bates, Shane Adam

    2013-01-01

    The recent application of metal-exchanged, small-pore zeolites for use in the selective catalytic reduction (SCR) of NOx with ammonia NH3 for automotive deNOx applications has been a great stride in achieving emission standard goals. Copper-exchanged SSZ-13 (Cu-SSZ-13), the small-pore zeolite in this study, has been shown to be very hydrothermally stable and active under conditions presented in the exhaust of the lean-burn diesel engine. In this work, detailed studies were performed to identi...

  4. Selective Catalytic Reduction of Nitric Oxide in Diesel Engine Exhaust over Monolithic

    Directory of Open Access Journals (Sweden)

    Ahmad Zuhairi Abdullah

    2009-01-01

    Full Text Available Selective catalytic reduction (SCR of nitric oxide (NO in diesel engine exhaust over Cu-Zn/ZSM-5 washcoated ceramic monolithic catalysts is reported. The washcoat component was prepared by ion-exchanging ZSM-5 (Si/Al=40 with zinc while copper was incorporated through impregnation. The dispersed washcoat component was then incorporated into 400 cpsi ceramic monolith through a dipping process with the final loadings between 19.6 wt. % and 31.4 wt. %. The SCR process was studied with a feed comprising of 900 ppm NO, 2,000 ppm iso butane and 3 % oxygen at gas hourly space velocities (GHSV between 5,000 and 13,000 h-1. NO conversion increased until a loading of 23.6 wt. % to give a conversion of 88 % at 400 °C. The activity dropped at higher loadings due to the partial blockage of cell openings and diffusion limitations while unstable washcoating adherence was also demonstrated. After an initial deactivation of about 10 % in the first 48 h, this catalyst showed stable residual activity. Between 325 and 375 °C, minimal effect on the activity was detected when the space time was reduced from 0.94 s to 0.24 s, suggesting the absence of external mass transfer limitations for up to a GHSV of 16,000 h-1.

  5. Selective catalytic reduction of NO in a reverse-flow reactor: Modelling and experimental validation

    International Nuclear Information System (INIS)

    Highlights: • Reverse-flow reactors easily overcome feed concentration disturbances. • Central feeding improves ammonia adsorption in reverse-flow reactors. • Dynamic heterogeneous model validated with bench-scale experiments. • Optimum reverse-flow reactor design improves efficiency and reduces reactor size. - Abstract: The abatement of nitrogen oxides produced in combustion processes and in the chemical industry requires efficient and reliable technologies capable of fulfilling strict environmental regulations. Selective catalytic reduction (SCR) with ammonia in fixed-bed (monolithic) reactors has stood out among other techniques in the last decades. In this work, the use of reverse-flow reactors, operated under the forced un-steady state generated by the periodic reversal of the flow direction, is studied for improving the SCR performance. This reactor can take advantage of ammonia adsorption in the catalyst to enhance concentration profiles in the reactor, increasing reaction rate, efficiency and reducing the emission of un-reacted ammonia. The process has been studied experimentally in a bench-scale device using a commercial monolithic catalyst. The optimum operating conditions, best ammonia feed configuration (side or central) and capacity of the reactor to deal with feed concentration disturbances is analysed. The experiments have also been used for validating a mathematical model of the reactor based on mass conservation equations, and the model has been used to design a full-size reverse-flow reactor able of operating at industrial conditions

  6. Utility experience with SCR in Germany

    Energy Technology Data Exchange (ETDEWEB)

    Hartenstein, H.U.; Gutberlet, H.; Licata, A.

    1999-07-01

    The selective catalytic reduction (SCR) technology was primarily developed by Japanese industry for the reduction of NOx concentrations from power plant flue gas emissions. The first commercial Japanese DeNOx plant began operation in 1980 while the first German high dust SCR plant started up in 1985 and the first German tail end SCR plant started up in 1986. Two German environmental resolutions (GFAVO of June, 1983 and UMK of April, 1984) enhanced the adaptation of the SCR technique in German power plants. From the end of 1984 to 1987 most German utility owners ran pilot plant studies in order to become acquainted with this technology and to determine whether there are special deterioration mechanisms. The first full-scale plant started operation at the end of 1985. Since then, around 120 SCR plants have been installed on coal, oil and gas fired utility power plants. SCR technology for NOx control has also been applied on waste-to-energy plants, wood fired boilers, chemical plants, hazardous waste incinerators, glass smelters, refinery crackers, stationary diesel generators and sewage sludge incinerators. In addition, a special catalyst was developed to control dioxin/furan emissions in waste-to-energy plants, hazardous waste incinerators, sewage sludge incinerators, crematoria, iron ore sintering plants, and other thermal processes requiring dioxin/furan control. The German NOx emission limit for utility power plants is 200 mg/Nm{sup 3} at 6% O{sub 2} for dry bottom boilers and 5% O{sub 2} for wet bottom boilers or about 117 ppmv NOx at 3% O{sub 2}. This is approximately 0.12 lbs/MMBtu. Many German SCR units achieve high online availability on an annual basis. In the following paper, the authors will emphasize some aspects of the SCR process: (a) The chemical and physical/chemical properties of the catalyst; (b) The chemical engineering design of the catalyst volume; (c) The deterioration of catalytic activity with time; and (d) The effect of NH{sub 3} slip

  7. Determining the storage, availability and reactivity of NH3 within Cu-Chabazite-based Ammonia Selective Catalytic Reduction systems.

    Science.gov (United States)

    Lezcano-Gonzalez, I; Deka, U; Arstad, B; Van Yperen-De Deyne, A; Hemelsoet, K; Waroquier, M; Van Speybroeck, V; Weckhuysen, B M; Beale, A M

    2014-01-28

    Three different types of NH3 species can be simultaneously present on Cu(2+)-exchanged CHA-type zeolites, commonly used in Ammonia Selective Catalytic Reduction (NH3-SCR) systems. These include ammonium ions (NH4(+)), formed on the Brønsted acid sites, [Cu(NH3)4](2+) complexes, resulting from NH3 coordination with the Cu(2+) Lewis sites, and NH3 adsorbed on extra-framework Al (EFAl) species, in contrast to the only two reacting NH3 species recently reported on Cu-SSZ-13 zeolite. The NH4(+) ions react very slowly in comparison to NH3 coordinated to Cu(2+) ions and are likely to contribute little to the standard NH3-SCR process, with the Brønsted groups acting primarily as NH3 storage sites. The availability/reactivity of NH4(+) ions can be however, notably improved by submitting the zeolite to repeated exchanges with Cu(2+), accompanied by a remarkable enhancement in the low temperature activity. Moreover, the presence of EFAl species could also have a positive influence on the reaction rate of the available NH4(+) ions. These results have important implications for NH3 storage and availability in Cu-Chabazite-based NH3-SCR systems. PMID:24322601

  8. Alkali deactivation of high-dust SCR catalysts used for NOx reduction exposed to flue gas from 100MW-scale biofuel and peat fired boilers. Influence of flue gas composition

    International Nuclear Information System (INIS)

    Deactivation of vanadium-titanium deNOx SCR (selective catalytic reduction) catalysts in high-dust position have been investigated in three 100MW-scale boilers during biofuel and peat combustion. The deactivation of the catalyst samples has been correlated to the corresponding flue gas composition in the boilers. To investigate the effect on catalyst deactivation a sulphate-containing additive was sprayed into one of the furnaces. Increased alkali content on the SCR catalyst samples decreased the catalytic deNOx activity. The study has shown a linear correlation between exposure time in the boilers and alkali concentration (mainly potassium) on the samples. The results imply that mainly alkali in ultra fine particles (<100nm) in the flue gas increased the alkali accumulation on the catalyst samples. Low correlation was found between particles larger than 100nm and the catalyst deactivation. It was not possible to decrease the deactivation of the catalyst samples by the sulphate-containing additive. Although the additive had an effect in sulphating potassium chloride to potassium sulphate, it did not decrease the amount of potassium in ultra fine particles or the deactivation of the catalyst samples. (author)

  9. One-pot hydrothermal synthesis of CuBi co-doped mesoporous zeolite Beta for the removal of NOx by selective catalytic reduction with ammonia

    Science.gov (United States)

    Xie, Zhiguo; Zhou, Xiaoxia; Wu, Huixia; Chen, Lisong; Zhao, Han; Liu, Yan; Pan, Linyu; Chen, Hangrong

    2016-07-01

    A series of CuBi co-doped mesoporous zeolite Beta (CuxBiy-mBeta) were prepared by a facile one-pot hydrothermal treatment approach and were characterized by XRD, N2 adsorption-desorption, TEM/SEM, XPS, H2-TPR, NH3-TPD and in situ DRIFTS. The catalysts CuxBiy-mBeta were applied to the removal of NOx by selective catalytic reduction with ammonia (NH3-SCR), especially the optimized Cu1Bi1-mBeta achieved the high efficiency for the removal of NOx and N2 selectivity, superior water and sulfur resistance as well as good durability. The excellent catalytic performance could be attributed to the acid sites of the support and the synergistic effect between copper and bismuth species. Moreover, in situ DRIFTS results showed that amides NH2 and NH4+ generated from NH3 adsorption could be responsible for the high selective catalytic reduction of NOx to N2. In addition, a possible catalytic reaction mechanism on Cu1Bi1-mBeta for the removal of NOx by NH3-SCR was proposed for explaining this catalytic process.

  10. One-pot hydrothermal synthesis of CuBi co-doped mesoporous zeolite Beta for the removal of NOx by selective catalytic reduction with ammonia.

    Science.gov (United States)

    Xie, Zhiguo; Zhou, Xiaoxia; Wu, Huixia; Chen, Lisong; Zhao, Han; Liu, Yan; Pan, Linyu; Chen, Hangrong

    2016-01-01

    A series of CuBi co-doped mesoporous zeolite Beta (CuxBiy-mBeta) were prepared by a facile one-pot hydrothermal treatment approach and were characterized by XRD, N2 adsorption-desorption, TEM/SEM, XPS, H2-TPR, NH3-TPD and in situ DRIFTS. The catalysts CuxBiy-mBeta were applied to the removal of NOx by selective catalytic reduction with ammonia (NH3-SCR), especially the optimized Cu1Bi1-mBeta achieved the high efficiency for the removal of NOx and N2 selectivity, superior water and sulfur resistance as well as good durability. The excellent catalytic performance could be attributed to the acid sites of the support and the synergistic effect between copper and bismuth species. Moreover, in situ DRIFTS results showed that amides NH2 and NH4(+) generated from NH3 adsorption could be responsible for the high selective catalytic reduction of NOx to N2. In addition, a possible catalytic reaction mechanism on Cu1Bi1-mBeta for the removal of NOx by NH3-SCR was proposed for explaining this catalytic process. PMID:27445009

  11. One-pot hydrothermal synthesis of CuBi co-doped mesoporous zeolite Beta for the removal of NOx by selective catalytic reduction with ammonia

    Science.gov (United States)

    Xie, Zhiguo; Zhou, Xiaoxia; Wu, Huixia; Chen, Lisong; Zhao, Han; Liu, Yan; Pan, Linyu; Chen, Hangrong

    2016-01-01

    A series of CuBi co-doped mesoporous zeolite Beta (CuxBiy-mBeta) were prepared by a facile one-pot hydrothermal treatment approach and were characterized by XRD, N2 adsorption-desorption, TEM/SEM, XPS, H2-TPR, NH3-TPD and in situ DRIFTS. The catalysts CuxBiy-mBeta were applied to the removal of NOx by selective catalytic reduction with ammonia (NH3-SCR), especially the optimized Cu1Bi1-mBeta achieved the high efficiency for the removal of NOx and N2 selectivity, superior water and sulfur resistance as well as good durability. The excellent catalytic performance could be attributed to the acid sites of the support and the synergistic effect between copper and bismuth species. Moreover, in situ DRIFTS results showed that amides NH2 and NH4+ generated from NH3 adsorption could be responsible for the high selective catalytic reduction of NOx to N2. In addition, a possible catalytic reaction mechanism on Cu1Bi1-mBeta for the removal of NOx by NH3-SCR was proposed for explaining this catalytic process. PMID:27445009

  12. Pt-Doped NiFe₂O₄ Spinel as a Highly Efficient Catalyst for H₂ Selective Catalytic Reduction of NO at Room Temperature.

    Science.gov (United States)

    Sun, Wei; Qiao, Kai; Liu, Ji-Yuan; Cao, Li-Mei; Gong, Xue-Qing; Yang, Ji

    2016-04-11

    H2 selective catalytic reduction (H2-SCR) has been proposed as a promising technology for controlling NOx emission because hydrogen is clean and does not emit greenhouse gases. We demonstrate that Pt doped into a nickel ferrite spinel structure can afford a high catalytic activity of H2-SCR. A superior NO conversion of 96% can be achieved by employing a novel NiFe1.95Pt0.05O4 spinel-type catalyst at 60 °C. This novel catalyst is different from traditional H2-SCR catalysts, which focus on the role of metallic Pt species and neglect the effect of oxidized Pt states in the reduction of NO. The obtained Raman and XPS spectra indicate that Pt in the spinel lattice has different valence states with Pt(2+) occupying the tetrahedral sites and Pt(4+) residing in the octahedral ones. These oxidation states of Pt enhance the back-donation process, and the lack of filling electrons of the 5d band causes Pt to more readily hybridize with the 5σ orbital of the NO molecule, especially for octahedral Pt(4+), which enhances the NO chemisorption on the Pt sites. We also performed DFT calculations to confirm the enhancement of adsorption of NO onto Pt sites when doped into the Ni-Fe spinel structure. The prepared Pt/Ni-Fe catalysts indicate that increasing the dispersity of Pt on the surfaces of the individual Ni-Fe spinel-type catalysts can efficiently promote the H2-SCR activity. Our demonstration provides new insight into designing advanced catalysts for H2-SCR. PMID:26982816

  13. Reaction pathway investigation on the selective catalytic reduction of NO with NH3 over Cu/SSZ-13 at low temperatures.

    Science.gov (United States)

    Su, Wenkang; Chang, Huazhen; Peng, Yue; Zhang, Chaozhi; Li, Junhua

    2015-01-01

    The mechanism of the selective catalytic reduction of NO with NH3 was studied using Cu/SSZ-13. The adspecies of NO and NH3 as well as the active intermediates were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy and temperature-programmed surface reaction. The results revealed that three reactions were possible between adsorbed NH3 and NOx. NO2(-) could be generated by direct formation or NO3(-) reduction via NO. In a standard selective catalytic reduction (SCR) reaction, NO3(-) was hard to form, because NO2(-) was consumed by ammonia before it could be further oxidized to nitrates. Additionally, adsorbed NH3 on the Lewis acid site was more active than NH4(+). Thus, SCR mainly followed the reaction between Lewis acid site-adsorbed NH3 and directly formed NO2(-). Higher Cu loading could favor the formation of active Cu-NH3, Cu-NO2(-), and Cu-NO3(-), improving the SCR activity at low temperature. PMID:25485842

  14. Retrofit SCR system for NOx control from heavy-duty mining equipment

    International Nuclear Information System (INIS)

    Diesel engines are used extensively in the mining industry and offer many advantages. However, particulate matter (PM) emissions and nitrogen oxide emissions (NOx) are among its disadvantages. A significant concern related to PM and NOx in an underground mine involves the use of diesel exhaust after treatment systems such as diesel particulate filters and selective catalytic reduction (SCR). This presentation discussed NOx and PM control and provided a description of an SCR system and examples of SCR retrofits. Options for NOx control were discussed and a case study involving the installation of an SCR retrofit system in an underground mine operated by Sifto Salt was also presented. The purpose of the case study was to identify cost effective retrofit solutions to lower nitrogen dioxide emissions from heavy-duty trucks operating in underground mines. The case study illustrated and presented the candidate vehicle, baseline emissions, a BlueMax SCR retrofit solution, and BlueMax installation. 1 tab., 6 figs.

  15. Effect of manufacturing methods of AgCl/Al2O3 catalyst on selective catalytic reduction of NOx

    Institute of Scientific and Technical Information of China (English)

    Satoshi Kishida; Dong-Ying Ju; Hirofumi Aritani

    2011-01-01

    The AgCl/Al2O3 catalyst has potential for use in the selective catalytic reduction (SCR) of NOx. A compound hydrocarbon, following oxygenation is used as a type of reducing agent. In this experiment, the AgCl/Al2O3 catalyst was produced by four different methods,and the differences among their reduction catalysis of NOx were compared. Ethanol was used as a type of reducing agent. X-ray diffraction analysis was performed to study the crystalline structure and scanning electron microscope and transmission electron microscope (TEM) were applied to determine the microindentation. The results indicated that, in the range of 350-400℃, there was no significant difference on the NOx reduction rate; however, there was dispersion at high and low temperature ranges. The size of the AgCl particles was about 20-100 nm.

  16. Reduction of nitrate from groundwater: powder catalysts and catalytic membrane

    Institute of Scientific and Technical Information of China (English)

    CHEN Ying-xu; ZHANG Yan; LIU Hong-yuan

    2003-01-01

    The reduction of nitrate contaminant in groundwater has gained renewed and intensive attention due to the environmental problems and health risks. Catalytic denetrification presents one of the most promising approaches for the removal of nitrate from water. Catalytic nitrate reduction from water by powder catalysts and catalytic membrane in a batch reactor was studied. And the effects of the initial concentration, the amounts of catalyst, and the flux H2 on the nitrate reduction were also discussed. The results demonstrated that nitrate reduction activity and the selectivity to nitrogen gas were mainly controlled by diffusion limitations and the mass transfer of the reactants. The selectivity can improved while retaining a high catalytic activity under controlled diffusion condition or the intensification of the mass transfer, and a good reaction condition. The total nitrogen removal efficiency reached above 80%. Moreover, catalytic membrane can create a high effective gas/liquid/solid interface, and show a good selectivity to nitrogen in comparative with the powder catalyst, the selectivity to nitrogen was improved from 73.4% to 89.4%.

  17. State Estimation in the Automotive SCR DeNOx Process

    DEFF Research Database (Denmark)

    Zhou, Guofeng; Jørgensen, John Bagterp; Duwig, Christophe;

    2012-01-01

    Selective catalytic reduction (SCR) of nitrogen oxides (NOx) is a widely applied diesel engine exhaust gas after-treatment technology. For effective NOx removal in a transient operating automotive application, controlled dosing of urea can be used to meet the increasingly restrictive legislations...... on exhaust gas emissions. For advanced control, e.g. Model Predictive Control (MPC), of the SCR process, accurate state estimates are needed. We investigate the performance of the ordinary and the extended Kalman filters based on a simple first principle system model. The performance is tested through...

  18. Ammonia Generation and Utilization in a Passive SCR (TWC+SCR) System on Lean Gasoline Engine

    Energy Technology Data Exchange (ETDEWEB)

    Prikhodko, Vitaly Y [ORNL; Parks, II, James E [ORNL; Pihl, Josh A [ORNL; Toops, Todd J [ORNL

    2016-01-01

    Lean gasoline engines offer greater fuel economy than the common stoichiometric gasoline engine, but the current three-way catalyst (TWC) on stoichiometric engines is unable to control nitrogen oxide (NOX) emissions in the oxygen-rich exhaust. Thus, lean NOX emission control is required to meet existing Tier 2 and upcoming Tier 3 emission regulations set by the U.S. Environmental Protection Agency (EPA). While urea-based selective catalytic reduction (SCR) has proven effective in controlling NOX from diesel engines, the urea storage and delivery components can add significant size and cost. As such, onboard NH3 production via a passive SCR approach is of interest. In a passive SCR system, NH3 is generated over a close-coupled TWC during periodic slightly rich engine operation and subsequently stored on an underfloor SCR catalyst. Upon switching to lean operation, NOX passes through the TWC and is reduced by the stored NH3 on the SCR catalyst. In this work, a passive SCR system was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine to assess NH3 generation over a Pd-only TWC and utilization over a Cu-based SCR catalyst. System NOX reduction efficiency and fuel efficiency improvement compared to stoichiometric engine operation were measured. A feedback control strategy based on cumulative NH3 produced by the TWC during rich operation and NOX emissions during lean operation was implemented on the engine to control lean/rich cycle timing. 15% excess NH3 production over a 1:1 NH3:NOX ratio was required (via longer rich cycle timing) to achieve 99.7% NOX conversion at an SCR average inlet temperature of 350 C. Increasing NH3 generation further resulted in even higher NOX conversion; however, tailpipe NH3 emissions resulted. At higher temperatures, NH3 oxidation becomes important and limits NH3 availability for NOX reduction. At the engine conditions studied here, greater than 99% NOX conversion was achieved with passive SCR while delivering fuel

  19. Influence of Sulfation on the Catalytic Activity of Ni-ZrO2 for NO Reduction with Propane in Excess Oxygen

    Institute of Scientific and Technical Information of China (English)

    Shujuan Zhang; Landong Li; Fuxiang Zhang; Naijia Guan

    2005-01-01

    Selective catalytic reduction (SCR) of nitric oxide with propane in excess oxygen was investigated on Ni-ZrO2 (NZ) and sulfated Ni-ZrO2 (SNZ), prepared by coprecipitation from a mixture of nickel nitrate-zirconium oxychloride followed by modifying with (NH4)2SO4. It was found that sulfated Ni-ZrO2catalyst showed higher activity for the SCR of NO with propane than that of Ni-ZrO2. The structural and surface properties of catalysts were studied by XRD, BET, SEM and FT-IR of pyridine adsorption. The experimental results indicated that the modification of (NH4)2SO4 resulted in the generation of strong Bronsted and Lewis acid sites and promoted the dispersion of the Ni species, which could lead to higher NO conversion and propane efficiency in NO reduction.

  20. Modeling Species Inhibition of NO Oxidation in Urea-SCR Catalysts for Diesel Engine NOx Control

    Energy Technology Data Exchange (ETDEWEB)

    Devarakonda, Maruthi N.; Tonkyn, Russell G.; Tran, Diana N.; Lee, Jong H.; Herling, Darrell R.

    2011-04-20

    Urea-selective catalytic reduction (SCR) catalysts are regarded as the leading NOx aftertreatment technology to meet the 2010 NOx emission standards for on-highway vehicles running on heavy-duty diesel engines. However, issues such as low NOx conversion at low temperature conditions still exist due to various factors, including incomplete urea thermolysis, inhibition of SCR reactions by hydrocarbons and H2O. We have observed a noticeable reduction in the standard SCR reaction efficiency at low temperature with increasing water content. We observed a similar effect when hydrocarbons are present in the stream. This effect is absent under fast SCR conditions where NO ~ NO2 in the feed gas. As a first step in understanding the effects of such inhibition on SCR reaction steps, kinetic models that predict the inhibition behavior of H2O and hydrocarbons on NO oxidation are presented in the paper. A one-dimensional SCR model was developed based on conservation of species equations and was coded as a C-language S-function and implemented in Matlab/Simulink environment. NO oxidation and NO2 dissociation kinetics were defined as a function of the respective adsorbate’s storage in the Fe-zeolite SCR catalyst. The corresponding kinetic models were then validated on temperature ramp tests that showed good match with the test data. Such inhibition models will improve the accuracy of model based control design for integrated DPF-SCR aftertreatment systems.

  1. Studies on catalytic reduction of nitrate in groundwater

    Institute of Scientific and Technical Information of China (English)

    GENG Bing; ZHU Yanfang; JIN Zhaohui; LI Tielong; KANG Haiyan; WANG Shuaima

    2007-01-01

    Catalytic reduction of nitrate in groundwater by sodium formate over the catalyst was investigated.Pd-Cu/γ-Al2O3 catalyst was prepared by impregnation and characterized by brunauer-emmett-teller (BET),inductive coupled plasma (ICP),X-ray diffraction (XRD),transmission electron microscopy (TEM) and energy dispersive X-ray (EDX).It was found that total nitrogen was effectively removed from the nitrate solution (100 mg/L) and the removal efficiency was 87%.The catalytic activity was affected by pH,catalyst amount used,concentration of sodium formate,and initial concentration of nitrate.As sodium formate was used as reductant,precise control in the initial pH was needed.Excessively high or low initial pH (7.0 or 3.0) reduced catalytic activity.At initial pH of 4.5,catalytic activity was enhanced by reducing the amount of catalyst,while concentrations of sodium formate increased with a considerable decrease in N2 selectivity.In which case,catalytic reduction followed the first order kinetics.

  2. Introduction manner of sulfate acid for improving the performance of SO42-/CeO2 on selective catalytic reduction of NO by NH3

    Institute of Scientific and Technical Information of China (English)

    宋忠贤; 张秋林; 宁平; 刘昕; 樊洁; 黄真真

    2016-01-01

    A series of sulfated CeO2 catalysts were synthesized by impregnation and sol-gel methods and used for selective catalytic reduction (SCR) of NOx by NH3. The results showed that the sulfated CeO2 catalysts prepared by sol-gel method showed excellent catalytic activity at 150–450 °C, and more than 90% NOx conversion was obtained at 232–450 °C with a gas hourly space velocity of 60000 h–1. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption, Raman, thermogravimetry (TG), H2-tem-perature-programmed reduction (H2-TPR) and Py-infrared spectroscopy (Py-IR). The excellent SCR performance was associated with the surface acidity and the micro-structure. The introduction of sulfate acid into CeO2 could increase the amount of Brönsted and Lewis acid sites over the catalysts, resulting in the improvement of the low temperature activity. The sulfated CeO2 catalysts prepared by sol-gel method possessed lower crystallization degree, excellent redox property and larger specific surface areas, which were re-sponsible for the superior SCR performance.

  3. Activity and hydrothermal stability of CeO2-ZrO2-WO3 for the selective catalytic reduction of NOx with NH3.

    Science.gov (United States)

    Song, Zhongxian; Ning, Ping; Zhang, Qiulin; Li, Hao; Zhang, Jinhui; Wang, Yancai; Liu, Xin; Huang, Zhenzhen

    2016-04-01

    A series of CeO2-ZrO2-WO3 (CZW) catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction (SCR) of NO with NH3 over a wide temperature of 150-550°C. The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H2O. The fresh catalyst showed above 90% NOx conversion at 201-459°C, which is applicable to diesel exhaust NOx purification (200-440°C). The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures (below 300°C), while the activity was notably enhanced at high temperature (above 450°C). The aged CZW catalyst (hydrothermal aging at 700°C for 8hr) showed almost 80% NOx conversion at 229-550°C, while the V2O5-WO3/TiO2 catalyst presented above 80% NOx conversion at 308-370°C. The effect of structural changes, acidity, and redox properties of CZW on the SCR activity was investigated. The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO2-ZrO2 solid solution, amorphous WO3 phase and optimal acidity. In addition, the formation of WO3 clusters increased in size as the hydrothermal aging temperature increased, resulting in the collapse of structure, which could further affect the acidity and redox properties. PMID:27090708

  4. Hydrothermally stable, low-temperature NO.sub.x reduction NH.sub.3-SCR catalyst

    Science.gov (United States)

    Narula, Chaitanya K; Yang, Xiaofan

    2015-03-24

    A catalyst composition includes a heterobimetallic zeolite characterized by a chabazite structure loaded with copper ions and at least one trivalent metal ion other than Al.sup.3+. The catalyst composition decreases NO.sub.x emissions in diesel exhaust and is suitable for operation in a catalytic converter.

  5. Hydrothermally stable, low-temperature NO.sub.x reduction NH.sub.3-SCR catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Narula, Chaitanya K.; Yang, Xiaofan

    2016-10-25

    A catalyst composition includes a heterobimetallic zeolite characterized by a chabazite structure loaded with copper ions and at least one trivalent metal ion other than Al.sup.3+. The catalyst composition decreases NO.sub.x emissions in diesel exhaust and is suitable for operation in a catalytic converter.

  6. Selective catalytic reduction of NO with NH3 over CeO2-ZrO2-WO3 catalysts prepared by different methods

    Science.gov (United States)

    Ning, Ping; Song, Zhongxian; Li, Hao; Zhang, Qiulin; Liu, Xin; Zhang, Jinhui; Tang, Xiaosu; Huang, Zhenzhen

    2015-03-01

    The selective catalytic reduction (SCR) of NO by NH3 has been investigated over the CeO2-ZrO2-WO3 (CZW) catalysts prepared by hydrothermal synthesis, incipient impregnation, co-precipitation and sol-gel methods. The results indicate that the CZW catalyst prepared by hydrothermal method shows the best SCR activity, and more than 90% NO conversion is obtained at 195-450 °C with a gas hourly space velocity of 50,000 h-1. The samples are characterized by XRD, N2 adsorption-desorption, SEM, EDS, XPS, H2-TPR, NH3-TPD and Pyridine-IR techniques. The results imply that the superior SCR activity of CZW catalyst is contributed to the excellent redox property, strong acidity and highest content of chemisorbed oxygen species. Furthermore, the larger surface area and greater total pore volume improve the redox ability and enhance NO conversion at low temperature, while the co-existence of Lewis and Brønsted acid sites enhance the SCR activity at high temperature.

  7. Selective catalytic reduction of NO by C2H2 over Ce-Al2O3 catalyst with rate-determining step of NO oxidation

    Institute of Scientific and Technical Information of China (English)

    Suhua Yan; Xinping Wang; Wenchen Wang; Zequn Liu; Jiahao Niu

    2012-01-01

    Ce-Al2O3 catalysts prepared by co-precipitation are investigated both in NO oxidation by O2 and in selective catalytic reduction of NO by C2H2 (C2H2-SCR).It is found that C2H2-SCR is initiated and controlled by NO oxidation to NO2 over A12O3.Ce loading on Al2O3 is almost inactive for NO oxidation below 350 ℃,since NO2 strongly adsorbs on cerium oxide,leading to the active sites being blocked,which was characterized by temperature-programmed desorption of NO and NO2 and Fourier transform infrared spectroscopy after NO+O2 coadsorption over the samples.However,in the case of C2H2-SCR,Ce loading on Al2O3 significantly improves the reaction by accelerating the NO oxidation step in the temperature range of 250-450 ℃,since the nitrate species produced by NO2 adsorption is an active intermediate required by C2H2-SCR.

  8. DEVELOPMENT OF HIGH ACTIVITY, CATALYTIC SYSTEMS FOR NOx REDUCTION

    Energy Technology Data Exchange (ETDEWEB)

    Unknown

    2001-12-01

    This project was directed at an investigation of catalytic NO{sub x} reduction on carbonaceous supports at low temperatures. The experimental work was conducted primarily in a packed bed reactor/gas flow system that was constructed for this work. The analytical techniques employed were mass spectrometry, NO{sub x} chemiluminescence, and gas chromatography. The experimental plan was focused on steady-state reactivity experiments, followed by temperature programmed desorption (TPD) of surface intermediates, and also selected temperature-programmed reaction (TPR) experiments. Both uncatalyzed and catalyzed (potassium-promoted) phenolic resin char, were investigated as well as the catalytic effect of additional CO in the gas phase.

  9. 40 CFR 1033.112 - Emission diagnostics for SCR systems.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Emission diagnostics for SCR systems....112 Emission diagnostics for SCR systems. Engines equipped with SCR systems using separate reductant.... This section does not apply for SCR systems using the engine's fuel as the reductant. (a)...

  10. Deactivation of SCR catalysts in biomass fired power plants

    DEFF Research Database (Denmark)

    Olsen, Brian Kjærgaard

    in such biomass fuels, however, causes enhanced strain on the different equipment in these power plants. One of the affected units is the catalyst for selective catalytic reduction (SCR) of nitrogen oxides, which undergoes accelerated deactivation due to deposition of potassium rich particles and subsequent...... poisoning. The potassium poisoning of commercial vanadia based SCR catalysts have been studied for more than two decades, and a broad understanding have been obtained. However, more detailed information on the overall mechanism of deposition, reaction and transport of potassium, and its function of catalyst...... composition and operating conditions, is not available. The main objective of the work presented in this thesis has been to conduct an in depth investigation of the deactivation mechanism of vanadia based SCR catalysts, when subjected to potassium rich aerosols. It has furthermore been a goal to suggest...

  11. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    Science.gov (United States)

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  12. The Effect of Copper Loading on the Selective Catalytic Reduction of Nitric Oxide by Ammonia Over Cu-SSZ-13

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Ja Hun; Tran, Diana N.; Szanyi, Janos; Peden, Charles HF; Lee, Jong H.

    2012-03-01

    The effect of Cu loading on the selective catalytic reduction of NOx by NH3 was examined over 20-80% ion-exchanged Cu-SSZ-13 zeolite catalysts. High NO reduction efficiency (80-95%) was obtained over all catalyst samples between 250 and 500°C, and the gas hourly space velocity of 200,000 h-1. Both NO reduction and NH3 oxidation activities under these conditions were found to increase slightly with increasing Cu loading at low temperatures. However, NO reduction activity was suppressed with increasing Cu loadings at high temperatures (>500oC) due to excess NH3 oxidation. The optimum Cu ion exchange level appears to be ~40-60% as higher than 80% NO reduction efficiency was obtained over 50% Cu ion-exchanged SSZ-13 up to 600oC. The NO oxidation activity of Cu-SSZ-13 was found to be low regardless of Cu loading, although it was somewhat improved with increasing Cu ion exchange level at high temperatures. During the “fast” SCR (i.e., NO/NO2 =1), only a slight improvement in NOx reduction activity was obtained for Cu-SSZ-13. Regardless of Cu loading, near 100% selectivity to N2 was observed; only a very small amount of N2O was produced even in the presence of NO2. Based on the Cu loading, the apparent activation energies for NO oxidation and NO SCR were estimated to be ~58 kJ/mol and ~41 kJ/mol, respectively.

  13. Alkali resistant Fe-zeolite catalysts for SCR of NO with NH3 in flue gases

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Jensen, Anker Degn; Riisager, Anders;

    2011-01-01

    , towards e.g. potassium salts in flue gases from biomass fired power plants. These properties allowed both undoped and potassium doped Fe-zeolite catalysts to posses high activity during the selective catalytic reduction (SCR) of NO with NH3. The extent of deactivation of the Fe-zeolite catalysts...

  14. EVALUATION OF SCR CATALYSTS FOR COMBINED CONTROL OF NOX AND MERCURY

    Science.gov (United States)

    The report documents two-task, bench- and pilot-scale research on the effect of selective catalytic reduction (SCR) catalysts on mercury speciation in Illinois and Powder River Basin (PRB) coal combustion flue gases. In task I, a bench-scale reactor was used to study the oxidatio...

  15. Catalytic NO reduction with ammonia at low temperatures on V2O5/AC catalysts. Effect of metal oxides addition and SO2

    International Nuclear Information System (INIS)

    The catalytic behavior of the V-M/AC (M=W, Mo, Zr, and Sn) catalysts were studied for the NO reduction with ammonia at low temperatures, especially in the presence of SO2. The presence of the metal oxides does not increase the V2O5/AC activity but decreases it. Except V-Mo/AC, the other catalysts are promoted by SO2 at 250C, especially for V-Sn/AC. However, the promoting effect of SO2 is gradually depressed by catalyst deactivation. Changes in catalyst preparation method can improve the catalyst stability in short-term but cannot completely prevent the catalyst from a long-term deactivation. Mechanisms of the promoting effect and the deactivation of V-Sn/AC catalyst by SO2 were studied using Fourier transform infrared spectroscopy (FT-IR) spectra and measurement of catalyst surface area and pore volume. The results showed that both the SO2 promotion and deactivation are associated with the formation of sulfate species on the catalyst surface. In the initial period of the selective catalytic reduction (SCR) reaction in the presence of SO2, the formed sulfate species provide new acid sites to enhance ammonia adsorption and thus the catalytic activity. However, as the SCR reaction proceeds, excess amount of sulfate species and then ammonium-sulfate salts are formed which is stabilized by the presence of tin oxide, resulting in gradual plugging of the pore structures and the catalyst deactivation

  16. In situ DRIFTS studies on MnOx nanowires supported by activated semi-coke for low temperature selective catalytic reduction of NOx with NH3

    Science.gov (United States)

    Chen, Yan; Zhang, Zuotai; Liu, Lili; Mi, Liang; Wang, Xidong

    2016-03-01

    To mitigate the threat of NOx on the environment, MnOx nanowires were fabricated on activated semi-coke (MnOx NW/ASC) for the first time. The prepared MnOx NW/ASC was used for the low temperature selective catalytic reduction (SCR) of NOx with NH3, which achieved an efficiency of over 90% with a low loading content of 1.64 wt% at 150-210 °C. This high performance could be ascribed to synergistic effect between MnOx and ASC. Specifically, the large specific surface area and reducible property of ASC facilitated the dispersion of MnOx and the formation of Mn3+, respectively. Meanwhile, MnOx nanowires provided more redox sites and lattice oxygen species due to the coexistence of Mn3+ and Mn4+, which accelerated the catalytic cycle. The in situ DRIFTS studies revealed that ASC was conducive to the adsorption of NO and NH3. Most importantly, the existence of Mn3+ favored the formation of amide species and the subsequent reduction reaction. Furthermore, the Langmuir-Hinshelwood (L-H) route between coordinated NH3 and bidentate nitrate was predominating in the SCR process and responsible for the high catalytic activity at low temperature.

  17. IDENTIFICATION AND RESPONSES TO POTENTIAL EFFECTS OF SCR AND WET SCRUBBERS ON SUBMICRON PARTICULATE EMISSIONS AND PLUME CHARACTERISTICS

    Science.gov (United States)

    Applications of selective catalytic reduction (SCR) systems and wet flue gas desulfurization (FGD) scrubbers on coal-fired boilers have led to substantial reductions in emissions of nitrogen oxides (NOX) and sulfur dioxide (SO2). However, observations of pilot- and full-scale tes...

  18. Study of the "Fast SCR" -like mechanism of H2-assisted SCR of NOx with ammonia over Ag/Al2O3

    DEFF Research Database (Denmark)

    Doronkin, Dmitry E.; Fogel, Sebastian; Tamm, Stefanie;

    2012-01-01

    It is shown that Ag/Al2O3 is a unique catalytic system for H2-assisted selective catalytic reduction of NOx by NH3 (NH3-SCR) with both Ag and alumina being necessary components of the catalyst. The ability of Ag/Al2O3 and pure Al2O3 to catalyse SCR of mixtures of NO and NO2 by ammonia...... is demonstrated, the surface species occurring discussed, and a "Fast SCR" -like mechanism of the process is proposed. The possibility of catalyst surface blocking by adsorbed NOx and the influence of hydrogen on desorption of NOx were evaluated by FTIR and DFT calculations. © 2011 Elsevier B.V....

  19. Mechanism of propene poisoning on Fe-ZSM-5 for selective catalytic reduction of NO(x) with ammonia.

    Science.gov (United States)

    Li, Junhua; Zhu, Ronghai; Cheng, Yisun; Lambert, Christine K; Yang, Ralph T

    2010-03-01

    Application of Fe-zeolites for urea-SCR of NO(x) in diesel engine is limited by catalyst deactivation with hydrocarbons. In this work, we investigated the effect of propene on the activity of Fe-ZSM-5 for selective catalytic reduction of NO(x) with ammonia (NH(3)-SCR), and proposed a deactivation mechanism of Fe(3+) active site blockage by propene residue. The NO conversion decreased in the presence of propene at various temperatures, while the effect was not significant when NO was replaced by NO(2) in the feed, especially at low temperatures (<300 degrees C). The surface area and pore volume were decreased due to carbonaceous deposition. The site blockage was mainly on Fe(3+) sites on which NO was to be oxidized to NO(2). The activity for NO oxidation to NO(2) was significantly inhibited on a propene poisoned catalyst below 400 degrees C. The adsorption of NH(3) on the Bronsted acid sites to form NH(4)(+) was not hindered even on the propene poisoned catalyst, and the amount of absorbed NH(3) was still abundant and enough to react with NO(2) to generate N(2). The hydrocarbon oxygenates such as formate, acetate, and containing nitrogen organic compounds were observed on catalyst surface, however, no graphitic carbonaceous deposit was formed. PMID:20136123

  20. Significance of RuO2 modified SCR catalyst for elemental mercury oxidation in coal-fired flue gas.

    Science.gov (United States)

    Yan, Naiqiang; Chen, Wanmiao; Chen, Jie; Qu, Zan; Guo, Yongfu; Yang, Shijian; Jia, Jinping

    2011-07-01

    Catalytic conversion of elemental mercury (Hg(0)) to its oxidized form has been considered as an effective way to enhance mercury removal from coal-fired power plants. In order to make good use of the existing selective catalytic reduction of NO(x) (SCR) catalysts as a cobenefit of Hg(0) conversion at lower level HCl in flue gas, various catalysts supported on titanium dioxide (TiO(2)) and commercial SCR catalysts were investigated at various cases. Among the tested catalysts, ruthenium oxides (RuO(2)) not only showed rather high catalytic activity on Hg(0) oxidation by itself, but also appeared to be well cooperative with the commercial SCR catalyst for Hg(0) conversion. In addition, the modified SCR catalyst with RuO(2) displayed an excellent tolerance to SO(2) and ammonia without any distinct negative effects on NO(x) reduction and SO(2) conversion. The demanded HCl concentration for Hg(0) oxidation can be reduced dramatically, and Hg(0) oxidation efficiency over RuO(2) doped SCR catalyst was over 90% even at about 5 ppm HCl in the simulated gases. Ru modified SCR catalyst shows a promising prospect for the cobenefit of mercury emission control.

  1. Roles of Promoters in V2O5/TiO2 Catalysts for Selective Catalytic Reduction of NOx with NH3: Effect of Order of Impregnation.

    Science.gov (United States)

    Youn, Seunghee; Song, Inhak; Kim, Do Heui

    2016-05-01

    Recently, various promoters for commercial selective catalytic reduction (SCR) catalysts are used to improve DeNOx activity at low temperature. We aimed at finding the optimum condition to prepare V2O5/TiO2 catalyst by changing promoters (W, Ce, Zr and Mn), not only for improving SCR reactivity, but also for reducing N2O formation at high temperature. In addition, we changed the order of impregnation between promoter and vanadium precursors on TiO2 support and observed its effect on activity and N2O selectivity. We utilized various analytical techniques, such as N2 adsorption-desorption, X-ray Diffraction (XRD), Raman spectroscopy, UV-visible Diffuse Reflectance Spectroscopy (UV-vis DRS) and Temperature Programmed Reduction with hydrogen (H2-TPR) to investigate the physicochemical properties of V2O5/TiO2 catalysts. It was found that W and Ce added V2O5/TiO2 catalysts showed the most active DeNOx properties at low temperature. Additionally, the difference in impregnation order affected the SCR activity. The superiority of low temperature activity of the vanadium firstly added catalysts (W or Ce/V/TiO2) is attributed to the formation of more polymerized V2O5 on the sample. PMID:27483756

  2. Promotional Effect of Ce on Iron-Based Catalysts for Selective Catalytic Reduction of NO with NH3

    Directory of Open Access Journals (Sweden)

    Xiaobo Wang

    2016-07-01

    Full Text Available A series of Fe–Ce–Ti catalysts were prepared via co-precipitation method to investigate the effect of doping Ce into Fe–Ti catalysts for selective catalytic reduction of NO with NH3. The NO conversion over Fe–Ce–Ti catalysts was considerably improved after Ce doping compared to that of Fe–Ti catalysts. The Fe(0.2–Ce(0.4–Ti catalysts exhibited superior catalytic activity to that of Fe(0.2–Ti catalysts. The obtained catalysts were characterized by N2 adsorption (BET, X-ray diffraction (XRD, temperature programmed reduction (H2-TPR, temperature programmed desorption (NH3-TPD, Fourier transform infrared (FT-IR spectrophotometry, thermogravimetric analysis (TGA, and X-ray photoelectron spectroscopy (XPS. The data showed that the introduction of Ce results in higher surface area and better dispersion of active components on the catalyst surface and enhances the amount of surface acid sites. The interactions between Fe and Ce species were found to improve the redox ability of the catalyst, which promotes catalytic performance at low temperature. The XPS results revealed that Fe3+/Fe2+ and Ce4+/Ce3+ coexisted on the catalyst surface and that Ti was in 4+ oxidation state on catalyst surface. Ce doping increased the atomic ratio of Fe/Ti and Ce/Ti and enhanced the surface adsorbed oxygen species. In addition, Fe(0.2–Ce(0.4–Ti catalyst also showed better tolerance to H2O and SO2 and up to 92% NO conversion at 270 °C with 200 ppm SO2 added over 25 h, which suggests that it is a promising industrial catalyst for mid-low temperature NH3–selective catalytic reduction (SCR reaction.

  3. Selective Catalytic Reduction of Oxides of Nitrogen with Ethanol/Gasoline Blends over a Silver/Alumina Catalyst on Lean Gasoline Engine

    Energy Technology Data Exchange (ETDEWEB)

    Prikhodko, Vitaly Y [ORNL; Pihl, Josh A [ORNL; Toops, Todd J [ORNL; Thomas, John F [ORNL; Parks, II, James E [ORNL; West, Brian H [ORNL

    2015-01-01

    Ethanol is a very effective reductant of nitrogen oxides (NOX) over silver/alumina (Ag/Al2O3) catalysts in lean exhaust environment. With the widespread availability of ethanol/gasoline-blended fuel in the USA, lean gasoline engines equipped with an Ag/Al2O3 catalyst have the potential to deliver higher fuel economy than stoichiometric gasoline engines and to increase biofuel utilization while meeting exhaust emissions regulations. In this work a pre-commercial 2 wt% Ag/Al2O3 catalyst was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine for the selective catalytic reduction (SCR) of NOX with ethanol/gasoline blends. The ethanol/gasoline blends were delivered via in-pipe injection upstream of the Ag/Al2O3 catalyst with the engine operating under lean conditions. A number of engine conditions were chosen to provide a range of temperatures and space velocities for the catalyst performance evaluations. High NOX conversions were achieved with ethanol/gasoline blends containing at least 50% ethanol; however, higher C1/N ratio was needed to achieve greater than 90% NOX conversion, which also resulted in significant HC slip. Temperature and HC dosing were important in controlling selectivity to NH3 and N2O. At high temperatures, NH3 and N2O yields increased with increased HC dosing. At low temperatures, NH3 yield was very low, however, N2O levels became significant. The ability to generate NH3 under lean conditions has potential for application of a dual SCR approach (HC SCR + NH3 SCR) to reduce fuel consumption needed for NOX reduction and/or increased NOX conversion, which is discussed in this work.

  4. Reduction of greenhouse gas emissions by catalytic processes

    International Nuclear Information System (INIS)

    Catalytic technologies for the abatement of greenhouse gases (GGs) can be an effective possibility for limiting the increasing tropospheric concentration of GGs and reducing their contribution to global warming. Two different cases are discussed: (1) reduction of anthropogenic emissions of non-CO2 GGs (N2O and CH4) and (2) reduction or conversion of CO2. In methane conversion waste gases containing diluted methane can be converted at low temperature using Pd supported on titania-ceria catalysts which show also a good resistance to deactivation. Rh supported on modified zirconia-alumina catalysts are effective and stable catalysts in low temperature decomposition of N2O. The concept of reduction of CO2 back to fuels in a photo-electrocatalytic reactor is also presented

  5. WO3/CeO2/TiO2 Catalysts for Selective Catalytic Reduction of NO(x) by NH3: Effect of the Synthesis Method.

    Science.gov (United States)

    Michalow-Mauke, Katarzyna A; Lu, Ye; Ferri, Davide; Graule, Thomas; Kowalski, Kazimierz; Elsener, Martin; Kröcher, Oliver

    2015-01-01

    WO3/CeO2/TiO2, CeO2/TiO2 and WO3/TiO2 catalysts were prepared by wet impregnation. CeO2/TiO2 and WO3/TiO2 showed activity towards the selective catalytic reduction (SCR) of NO(x) by NH3, which was significantly improved by subsequent impregnation of CeO/TiO2 with WO3. Catalytic performance, NH3 oxidation and NH3 temperature programmed desorption of wet-impregnated WO3/CeO2/TiO2 were compared to those of a flame-made counterpart. The flame-made catalyst exhibits a peculiar arrangement of W-Ce-Ti-oxides that makes it very active for NH3-SCR. Catalysts prepared by wet impregnation with the aim to mimic the structure of the flame-made catalyst were not able to fully reproduce its activity. The differences in the catalytic performance between the investigated catalysts were related to their structural properties and the different interaction of the catalyst components.

  6. Influence of calcination temperature on selective catalytic reduction of NOx with NH3 over CeO2-ZrO2-WO3 catalyst

    Institute of Scientific and Technical Information of China (English)

    李军燕; 宋忠贤; 宁平; 张秋林; 刘昕; 李昊; 黄真真

    2015-01-01

    A series of CeO2-ZrO2-WO3 catalysts for the selective catalytic reduction (SCR) of NO with NH3 were prepared by hydro-thermal method. The influence of calcination temperature on the catalytic activity, microstructure, surface acidity and redox behavior of CeO2-ZrO2-WO3 catalyst was investigated using various characterization methods. It was found that the CeO2-ZrO2-WO3 catalyst calcined at 600 ºC showed the best catalytic performance and excellent N2 selectivity, and yielded more than 90% NO conversion in a wide temperature range of 250–500 ºC with a space velocity (GHSV) of 60000 h–1. As the calcination temperature was increased from 400 to 600 ºC, the NO conversion obviously increased, but decreased at higher calcination temperature. The results implied that the higher surface area, the strongest synergistic interaction, the superior redox property and the highly dispersed or amorphous WO3 species contributed to the excellent SCR activity of the CeO2-ZrO2-WO3 catalyst calcined at 600 ºC.

  7. Comparison study of Cu-Fe-Ti and Co-Fe-Ti oxide catalysts for selective catalytic reduction of NO with NH3 at low temperature.

    Science.gov (United States)

    Zhu, Lin; Zhong, Zhaoping; Yang, Han; Wang, Chunhua

    2016-09-15

    In this paper, a series of Cu-Fe-Ti and Co-Fe-Ti oxide catalysts were prepared by sol gel method. Cu-Fe-Ti and Co-Fe-Ti oxide catalysts showed the moderate catalytic activity for selective catalytic reduction (SCR) of NO with NH3 at low temperature. The catalysts with the molar ratio as 4:1:10 (M:Fe:Ti) were selected as the representatives for comparison of reaction properties and H2O resistance, which were denoted as Cu-Fe/TiO2 and Co-Fe/TiO2 respectively. The characterization results manifested Co-Fe/TiO2 owned more adsorption capacity of the reactants and Cu-Fe/TiO2 had better redox ability. The in situ DRIFTS experiments indicated that adsorbed NH3 species and nitrate species both exhibited reaction activity for Co-Fe/TiO2, while nitric oxide was only be reduced by adsorbed NH3 species through Eley-Rideal mechanism for Cu-Fe/TiO2 at 150°C. Co-Fe/TiO2 exhibited the better resistance to H2O and its temperature window shifted towards the higher temperature in presence of 10vol% H2O, while the SCR activity of Cu-Fe/TiO2 was inhibited significantly in the whole temperature range investigated. The suppression of adsorption and activation for NH3 and NOx might be the reasons for the reversible inactivation, which was confirmed by the inhibitation of catalytic activities for separation NH3 and NO oxidation under the wet condition. We speculated that different thermal stability of adsorbed species and redox capacity of catalysts leaded to the different SCR behavior in absence and presence of H2O. PMID:27280535

  8. Numerical Simulation of Internal Flow Field and Structure Optimization of SCR Catalytic Converter%SCR催化转化器内流场数值模拟与结构改进

    Institute of Scientific and Technical Information of China (English)

    高伟; 邓召文

    2012-01-01

    利用计算流体动力学(CFD)软件,对结构改进前后的SCR催化转化器内流场进行了三维稳态流动数值模拟,对比分析了改进前后两种不同结构的催化转化器内流动特性.模拟结果显示:结构因素对催化转化器的内流动特性有很大影响,通过结构改进,减小了压力损失,使其内部速度分布和温度分布更加均匀.%The numerical simulation of three-dimension steady state flow is carried out on the internal flow filed of SCR catalytic converters before and after structure optimization, by using the computational fluid dynamics ( CFD) code. The internal flow characteristics of two different SCR catalytic converters have been contrastively analyzed. The results show that; the structure factor has a great impact on the flow of catalytic converters. Through the improvement of structure, the pressure loss can be reduced, which makes velocity and temperature distribution in the catalytic converters to be more uniform.

  9. Study on the mechanism of NH3-selective catalytic reduction over CuCexZr1-x/TiO2

    Science.gov (United States)

    Chen, Xujuan; Sun, Xiaoliang; Gong, Cairong; Lv, Gang; Song, Chonglin

    2016-06-01

    Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NOx. The reaction mechanism was proposed on the basis of results from in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH3 is introduced, ammonia bonded to Lewis acid sites is more stable over CuCe0.25Zr0.75/TiO2 at high temperature, while Brønsted acid sites are more important than Lewis acid sites at low temperature. For the NH3+NO+O2 co-adsorption, NH3 species occupy most of activity sites on CuCe0.25Zr0.75/TiO2 catalyst, and mainly exist in the forms of NH4 + (at low temperature) and NH3 coordinated (at high temperature), playing a crucial role in the NH3-SCR process. Two different reaction routes, the L-H mechanism at low temperature ( 200°C), are presented for the SCR reaction over CuCe0.25Zr0.75/TiO2 catalyst.

  10. Study on methane selective catalytic reduction of NO on Pt/Ce0.67Zr0.33O2 and its application

    Institute of Scientific and Technical Information of China (English)

    Zhimin Liu; Kangcai Wang; Xiaoyu Zhang; Jianli Wang; Hongyan Cao; Maochu Gong; Yaoqiang Chen

    2009-01-01

    Monolithic catalysts of Pt/La-Al2O3 and Pt/Ce0.67Zr0.33O2 were prepared to investigate methane selective catalytic reduction (SCR) of NO.The results indicate that Pt/Ce0.67Zr0.33O2 shows high activity and both NO and CH4 can be converted completely at 450 ℃.Meanwhile,NO and CH4 can be converted completely when there exists excess oxygen.The Pt/Ce0.67Zr0.33O2 catalyst were further investigated by using methane as reducing agent to SCR NO in a novel equipment which combined the CH4 selective catalytic reduction of NO with methane combustion.The result shows that the catalyst is high active and the novel equipment is very effective.The conversion of NO is above 92% under the conditions used in this work.The prepared burner and catalysts have great potential for application.

  11. Highly selective catalytic reduction of NO via SO2/H2O-tolerant spinel catalysts at low temperature.

    Science.gov (United States)

    Cai, Xuanxuan; Sun, Wei; Xu, Chaochao; Cao, Limei; Yang, Ji

    2016-09-01

    Selective catalytic reduction of NO X by hydrogen (H2-SCR) in the presence of oxygen has been investigated over the NiCo2O4 and Pd-doped NiCo2O4 catalysts under varying conditions. The catalysts were prepared by a sol-gel method in the presence of oxygen within 50-350 °C and were characterized using XRD, BET, EDS, XPS, Raman, H2-TPR, and NH3-TPD analysis. The results demonstrated that the doped Pd could improve the catalyst reducibility and change the surface acidity and redox properties, resulting in a higher catalytic performance. The performance of NiCo1.95Pd0.05O4 was consistently better than that of NiCo2O4 within the 150-350 °C range at a gas hourly space velocity (GHSV) of 4800 mL g(-1) h(-1), with a feed stream containing 1070 ppm NO, 10,700 ppm H2, 2 % O2, and N2 as balance gas. The effects of GHSV, NO/H2 ratios, and O2 feed concentration on the NO conversion over the NiCo2O4 and NiCo1.95Pd0.05O4 catalysts were also investigated. The two samples similarly showed that an increase in GHSV from 4800 to 9600 mL h(-1) g(-1), the NO/H2 ratio from 1:10 to 1:1, and the O2 content from 0 to 6 % would result in a decrease in NO conversion. In addition, 2 %, 5 %, and 8 % H2O into the feed gas had a slightly negative influence on SCR activity over the two catalysts. The effect of SO2 on the SCR activity indicated that the NiCo1.95Pd0.05O4 possesses better SO2 tolerance than NiCo2O4 catalyst does. Graphical abstract The NiCo1.95Pd0.05O4 catalyst achieved over 90 % NO conversion with N2 selectivity of 100 % in the 200∼250 °C range than the maximum 40.5 % NO conversion over NiCo2O4 with N2 selectivity of approximately 80 % in 350 °C. PMID:27301438

  12. Transformation of mercury speciation through the SCR system in power plants.

    Science.gov (United States)

    Yang, Hong-min; Pan, Wei-ping

    2007-01-01

    Coal-fired utility boilers are now identified as the largest source of mercury in the United States. There is speculation that the installation of selective catalytic reduction (SCR) system for reduction of NOx can also prompt the oxidation and removal of mercury. In this paper, tests at six full-scale power plants with similar type of the SCR systems are conducted to investigate the effect of the SCR on the transformation of mercury speciation. The results show that the SCR system can achieve more than 70%-80% oxidation of elemental mercury and enhance the mercury removal ability in these units. The oxidation of elemental mercury in the SCR system strongly depends on the coal properties and the operation conditions of the SCR systems. The content of chloride in the coal is the key factor for the oxidization process and the maximum oxidation of elemental mercury is found when chloride content changes from 400 to 600 ppm. The sulfur content is no significant impact on oxidation of elemental mercury.

  13. Transformation of mercury speciation through the SCR system in power plants

    Institute of Scientific and Technical Information of China (English)

    YANG Hong-min; PAN Wei-ping

    2007-01-01

    Coal-fired utility boilers are now identified as the largest source of mercury in the United States. There is speculation that the installation of selective catalytic reduction (SCR) system for reduction of NOx can also prompt the oxidation and removal of mercury.In this paper, tests at six full-scale power plants with similar type of the SCR systems are conducted to investigate the effect of the SCR on the transformation of mercury speciation. The results show that the SCR system can achieve more than 70%-80% oxidation of elemental mercury and enhance the mercury removal ability in these units. The oxidation of elemental mercury in the SCR system strongly depends on the coal properties and the operation conditions of the SCR systems. The content of chloride in the coal is the key factor for the oxidization process and the maximum oxidation of elemental mercury is found when chloride content changes from 400 to 600 ppm. The sulfur content is no significant impact on oxidation of elemental mercury.

  14. Selective catalytic reduction of NO over Fe-ZSM-5: mechanistic insights by operando HERFD-XANES and valence-to-core X-ray emission spectroscopy.

    Science.gov (United States)

    Boubnov, Alexey; Carvalho, Hudson W P; Doronkin, Dmitry E; Günter, Tobias; Gallo, Erik; Atkins, Andrew J; Jacob, Christoph R; Grunwaldt, Jan-Dierk

    2014-09-17

    An in-depth understanding of the active site requires advanced operando techniques and the preparation of defined catalysts. We elucidate here the mechanism of the selective catalytic reduction of NO by NH3 (NH3-SCR) over a Fe-ZSM-5 zeolite catalyst. 1.3 wt % Fe-ZSM-5 with low nuclearity Fe sites was synthesized, tested in the SCR reaction and characterized by UV-vis, X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopy. Next, this defined Fe-zeolite catalyst was studied by complementary high-energy-resolution fluorescence-detected XANES (HERFD-XANES) and valence-to-core X-ray emission spectroscopy (V2C XES) under different model in situ and realistic working (operando) conditions identical to the catalyst test bench including the presence of water vapor. HERFD-XANES uncovered that the coordination (between 4 and 5), geometry (tetrahedral, partly 5-fold), and oxidation state of the Fe centers (reduced in NH3, partly in SCR mixture, slight reduction in NO) strongly changed. V2C XES supported by DFT calculations provided important insight into the chemical nature of the species adsorbed on Fe sites. The unique combination of techniques applied under realistic reaction conditions and the corresponding catalytic data unraveled the adsorption of ammonia via oxygen on the iron site. The derived reaction model supports a mechanism where adsorbed NOx reacts with ammonia coordinated to the Fe(3+) site yielding Fe(2+) whose reoxidation is slow. PMID:25105343

  15. STUDY OF MERCURY OXIDATION BY SCR CATALYST IN AN ENTRAINED-FLOW REACTOR UNDER SIMULATED PRB CONDITIONS

    Science.gov (United States)

    A bench-scale entrained-flow reactor system was constructed for studying elemental mercury oxidation under selective catalytic reduction (SCR) reaction conditions. Simulated flue gas was doped with fly ash collected from a subbituminous Powder River Basin (PRB) coal-fired boiler ...

  16. STUDY OF THE EFFECT OF CHLORINE ADDITION ON MERCURY OXIDATION BY SCR CATALYST UNDER SIMULATED SUBBITUMINOUS COAL FLUE GAS

    Science.gov (United States)

    An entrained flow reactor is used to study the effect of addition of chlorine-containing species on the oxidation of elemental mercury (Hgo)by a selective catalytic reduction (SCR) catalyst in simulated subbituminous coal combustion flue gas. The combustion flue gas was doped wit...

  17. The effect of soot on ammonium nitrate species and NO2 selective catalytic reduction over Cu-zeolite catalyst-coated particulate filter.

    Science.gov (United States)

    Mihai, Oana; Tamm, Stefanie; Stenfeldt, Marie; Olsson, Louise

    2016-02-28

    A selective catalytic reduction (SCR)-coated particulate filter was evaluated by means of dynamic tests performed using NH3, NO2, O2 and H2O. The reactions were examined both prior to and after soot removal in order to study the effect of soot on ammonium nitrate formation and decomposition, ammonia storage and NO2 SCR. A slightly larger ammonia storage capacity was observed when soot was present in the sample, which indicated that small amounts of ammonia can adsorb on the soot. Feeding of NO2 and NH3 in the presence of O2 and H2O at low temperature (150, 175 and 200°C) leads to a large formation of ammonium nitrate species and during the subsequent temperature ramp using H2O and argon, a production of nitrous oxides was observed. The N2O formation is often related to ammonium nitrate decomposition, and our results showed that the N2O formation was clearly decreased by the presence of soot. We therefore propose that in the presence of soot, there are fewer ammonium nitrate species on the surface due to the interactions with the soot. Indeed, we do observe CO2 production during the reaction conditions also at 150°C, which shows that there is a reaction with these species and soot. In addition, the conversion of NOx due to NO2 SCR was significantly enhanced in the presence of soot; we attribute this to the smaller amount of ammonium nitrate species present in the experiments where soot is available since it is well known that ammonium nitrate formation is a major problem at low temperature due to the blocking of the catalytic sites. Further, a scanning electron microscopy analysis of the soot particles shows that they are about 30-40 nm and are therefore too large to enter the pores of the zeolites. There are likely CuxOy or other copper species available on the outside of the zeolite crystallites, which could have been enhanced due to the hydrothermal treatment at 850°C of the SCR-coated filter prior to the soot loading. We therefore propose that soot is

  18. The effect of soot on ammonium nitrate species and NO2 selective catalytic reduction over Cu-zeolite catalyst-coated particulate filter.

    Science.gov (United States)

    Mihai, Oana; Tamm, Stefanie; Stenfeldt, Marie; Olsson, Louise

    2016-02-28

    A selective catalytic reduction (SCR)-coated particulate filter was evaluated by means of dynamic tests performed using NH3, NO2, O2 and H2O. The reactions were examined both prior to and after soot removal in order to study the effect of soot on ammonium nitrate formation and decomposition, ammonia storage and NO2 SCR. A slightly larger ammonia storage capacity was observed when soot was present in the sample, which indicated that small amounts of ammonia can adsorb on the soot. Feeding of NO2 and NH3 in the presence of O2 and H2O at low temperature (150, 175 and 200°C) leads to a large formation of ammonium nitrate species and during the subsequent temperature ramp using H2O and argon, a production of nitrous oxides was observed. The N2O formation is often related to ammonium nitrate decomposition, and our results showed that the N2O formation was clearly decreased by the presence of soot. We therefore propose that in the presence of soot, there are fewer ammonium nitrate species on the surface due to the interactions with the soot. Indeed, we do observe CO2 production during the reaction conditions also at 150°C, which shows that there is a reaction with these species and soot. In addition, the conversion of NOx due to NO2 SCR was significantly enhanced in the presence of soot; we attribute this to the smaller amount of ammonium nitrate species present in the experiments where soot is available since it is well known that ammonium nitrate formation is a major problem at low temperature due to the blocking of the catalytic sites. Further, a scanning electron microscopy analysis of the soot particles shows that they are about 30-40 nm and are therefore too large to enter the pores of the zeolites. There are likely CuxOy or other copper species available on the outside of the zeolite crystallites, which could have been enhanced due to the hydrothermal treatment at 850°C of the SCR-coated filter prior to the soot loading. We therefore propose that soot is

  19. Poisoning of vanadia based SCR catalysts by potassium:influence of catalyst composition and potassium mobility

    DEFF Research Database (Denmark)

    Olsen, Brian Kjærgaard; Kügler, Frauke; Jensen, Anker Degn

    2016-01-01

    The deactivation of V2O5–(WO3)/TiO2 catalysts for selective catalytic reduction (SCR) of NOx upon exposure to aerosols of KCl or K2SO4, at different temperatures, has been studied. All samples exposed for more than 240 hours lost a substantial fraction of their initial activity although lower...... the transport of potassium. Using a newly developed experimental protocol consisting of two-layer pellets of SCR catalysts, where one side is impregnated with KCl or K2SO4, the potassium transport in such systems, which is assumed to take place through reactionand diffusion over acid sites, was investigated...

  20. Selective catalytic reduction of NO and NO{sub 2} at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, Manfred; Madia, Giuseppe; Elsener, Martin [Paul Scherrer Institute, CH-5232 PSI Villigen (Switzerland)

    2002-04-15

    The fast SCR reaction using equimolar amounts of NO and NO{sub 2} is a powerful means to enhance the NO{sub x} conversion over a given SCR catalyst. NO{sub 2} fractions in excess of 50% of total NO{sub x} should be avoided because the reaction with NO{sub 2} only is slower than the standard SCR reaction. At temperatures below 200C, due to its negative temperature coefficient, the ammonium nitrate reaction gets increasingly important. Half of each NH{sub 3} and NO{sub 2} react to form dinitrogen and water in analogy to a typical SCR reaction. The other half of NH{sub 3} and NO{sub 2} form ammonium nitrate in close analogy to a NO{sub x} storage-reduction catalyst. Ammonium nitrate tends to deposit in solid or liquid form in the pores of the catalyst and this will lead to its temporary deactivation.The various reactions have been studied experimentally in the temperature range 150-450C for various NO{sub 2}/NO{sub x} ratios. The fate of the deposited ammonium nitrate during a later reheating of the catalyst has also been investigated. In the absence of NO, the thermal decomposition yields mainly ammonia and nitric acid. If NO is present, its reaction with nitric acid on the catalyst will cause the formation of NO{sub 2}.

  1. Coke formation over zeolites and CeO2-zeolites and its influence on selective catalytic reduction of NOx

    International Nuclear Information System (INIS)

    Selective catalytic reduction, various possible reasons of coke formation, and temperature programmed oxidation of coke deposits are studied over HFER, HZSM-5 and 15|wt% CeO2-H zeolites. The materials are characterised by TGA, NH3-TPD and in-situ FTIR measurements. HFER based catalysts showed superior NOx (NO+NO2) conversion in SCR with propene compared with HZSM-5 based catalysts. It is found that NO2 (formed by the oxidation of NO) is not the only important intermediate in determining the extent of NOx conversion. The topology and acidity of the zeolites play an important role in selective activation of propene and its reaction with NO2. Over HZSM-5 based catalysts the rate of deposition of carbonaceous compounds is higher than the rate of reaction of activated propene with NO2, leading to unselective reduction to NO. The nature and the amount of the carbonaceous products deposited over the zeolites are found to depend on the acidity, structure of the zeolite and reaction conditions (inert or oxidative atmosphere). Coke deposition rate is enhanced in the presence of oxygen and most of the coke is retained by the zeolite which is detrimental for NOx reduction. in-situ IR studies show that hydrocarbon deposits are more heterogeneous and carbon rich over HZSM-5 compared with HFER. TPO studies show that only a negligible fraction of hydrocarbon deposits are active in NOx conversion

  2. Selective catalytic reduction of nitric oxide with acetaldehyde over NaY zeolite catalyst in lean exhaust feed

    International Nuclear Information System (INIS)

    Steady-state selective catalytic reduction (SCR) of nitric oxide (NO) was investigated under simulated lean-burn conditions using acetaldehyde (CH3CHO) as the reductant. This work describes the influence of catalyst space velocity and the impact of nitric oxide, acetaldehyde, oxygen, sulfur dioxide, and water on NOx reduction activity over NaY zeolite catalyst. Results indicate that with sufficient catalyst volume 90% NOx conversion can be achieved at temperatures relevant to light-duty diesel exhaust (150-350C). Nitric oxide and acetaldehyde react to form N2, HCN, and CO2. Oxygen is necessary in the exhaust feed stream to oxidize NO to NO2 over the catalyst prior to reduction, and water is required to prevent catalyst deactivation. Under conditions of excess acetaldehyde (C1:N>6:1) and low temperature (x conversion is apparently very high; however, the NOx conversion steadily declines with time due to catalytic oxidation of some of the stored (adsorbed) NO to NO2, which can have a significant impact on steady-state NOx conversion. With 250ppm NO in the exhaust feed stream, maximum NOx conversion at 200C can be achieved with =400ppm of acetaldehyde, with higher acetaldehyde concentrations resulting in production of acetic acid and breakthrough of NO2 causing lower NOx conversion levels. Less acetaldehyde is necessary at lower NO concentrations, while more acetaldehyde is required at higher temperatures. Sulfur in the exhaust feed stream as SO2 can cause slow deactivation of the catalyst by poisoning the adsorption and subsequent reaction of nitric oxide and acetaldehyde, particularly at low temperature

  3. How NO{sub 2} affects the reaction mechanism of the SCR reaction

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, M.; Madia, G.; Raimondo, F.; Wokaun, A.

    2003-03-01

    The rate of the selective catalytic reduction (SCR) of NO with N-containing reducing agents may be considerably enhanced by converting part of the NO into NO{sub 2}. The reaction using an equimolar mixture of NO and NO{sub 2} is known as 'fast SCR reaction' and the rate enhancement is most pronounced at low temperatures (T<300{sup o}C). In the present work the possible role of NO{sub 2} on catalysts based on TiO{sub 2}-WO{sub 3}-V{sub 2}O{sub 5} was investigated by in-situ Raman spectroscopy. The experiments suggest that the V{sup +4} species formed during the reduction of NO with ammonia are reoxidized faster by NO{sub 2} than by oxygen, resulting in an increased reaction rate of the fast SCR reaction. (author)

  4. Progress of Research on Selective Catalytic Reduction Technology for Vehicle Diesel Engine%车用柴油机选择性催化还原技术研究进展

    Institute of Scientific and Technical Information of China (English)

    楼狄明; 张正兴; 谭丕强; 马滨

    2009-01-01

    Selective Catalyst Reduction Technology (SCR) is at present the unique technology which can improve the emission and reduce oil consumption simultaneously. And SCR technology using NH_3 as reductant (NH_3-SCR) is most maturely developed and has the brightest foreground In this paper, the chemical reaction mechanism of Selective Catalytic Reduction technology was expatiated,and the effect of temperature on NO_x conversion rate was analyzed: the function of main parts of SCR system was introduced, as well as the specifications of AdBlue: a summarization of open loop and closed loop control strategies was made, and the advantages and disadvantages of each were analyzed; then the two different modes for the integration of SCR and DPF in diesel aftertreatment system were referred and contrasted: finally, the problems which block the popularization ofSCR was put forward.%选择性催化还原技术(SCR)是目前唯一可以同时改善柴油机排放和燃油经济性的氮氧化物(NO_x)净化技术,而以NH_2作为还原剂的SCR技术(NH_3-SCR)又是目前最成熟,最具推广前景的SCR技术.文章详细阐述了用于车用柴油机的NH_3-SCR技术的反应机理,介绍了温度对SCR反应的影响;列举了典型SCR系统的主要部件并介绍了各部分的功能,以及法规中对车用尿素水溶液(AdBiue)主要指标的规定;总结了目前应用较多的开环、闭环两种控制策略的工作流程及特点,并且分析了各自的优缺点;在柴油机后处理系统集成的角度对SCR与颗粒捕集器(DPF)的两种整合方案进行了分析,对比了两种方案的优缺点;最后分析了SCR技术目前存在的几个问题.

  5. Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

    Directory of Open Access Journals (Sweden)

    Mickael Seneque

    2015-09-01

    Full Text Available The selective catalytic reduction (SCR of NOx by NH3 has been extensively studied in the literature, mainly because of its high potential to remediate the pollution of diesel exhaust gases. The implementation of the NH3-SCR process into passenger cars requires the use of an ammonia precursor, provided by a urea aqueous solution in the conventional process. Although the thermal decomposition and hydrolysis mechanisms of urea are well documented in the literature, the influence of the direct use of urea on the NOx reduction over SCR catalysts may be problematic. With the aim to evaluate prototype powdered catalysts, a specific synthetic gas bench adjusted to powdered material was developed, allowing the use of NH3 or urea as reductant for direct comparison. The design of the experimental setup allows vaporization of liquid urea at 200 °C under 10 bar using an HPLC pump and a micro injector of 50 μm diameter. This work presents the experimental setup of the catalytic test and some remarkable catalytic results towards further development of new catalytic formulations specifically dedicated to urea-SCR. Indeed, a possible divergence in terms of DeNOx efficiency is evidenced depending on the nature of the reductant, NH3 or urea solution. Particularly, the evaluated catalyst may not allow an optimal NOx conversion because of a lack in ammonia availability when the urea residence time is shortened. This is attributed to insufficient activity of isocyanic acid (HNCO hydrolysis, which can be improved by addition upstream of an active solid for the hydrolysis reaction such as ZrO2. Thus, this µ-scale synthetic gas bench adjusted to powdered materials enables the specific behaviour of urea use for NOx reduction to be demonstrated.

  6. Zeolites as nanoporous, gas-sensitive materials for in situ monitoring of DeNO(x)-SCR.

    Science.gov (United States)

    Simons, Thomas; Simon, Ulrich

    2012-01-01

    In a proof-of-concept study we demonstrate in situ reaction monitoring of DeNO(x)-SCR on proton-conducting zeolites serving as catalyst and gas sensor at the same time. By means of temperature-dependent impedance spectroscopy we found that the thermally induced NH(3) desorption in H-form and in Fe-loaded zeolite H-ZSM-5 follow the same process, while a remarkable difference under DeNO(x)-SCR reaction conditions was found. The Fe-loaded catalyst shows a significantly lower onset temperature, and time-dependent measurements suggest different SCR reaction mechanisms for the two catalysts tested. These results may help in the development of catalysts for the reduction of NO(x) emissions and ammonia consumption, and provide insight into the elementary catalytic process promoting a full description of the NH(3)-SCR reaction system.

  7. Sulfate Promoted Zirconia as Promising Alkali-Resistant Support for Catalytic NOx Removal

    OpenAIRE

    Due-Hansen, Johannes; Kustov, Arkadii; Christensen, Claus H.; Fehrmann, Rasmus

    2007-01-01

    The use of bio-fuels as alternatives to traditional fossil fuels has attracted much attention recent years since bio-fuels belong to a family of renewable types of energy sources and do not contribute to the green-house effect. Selective catalytic reduction (SCR) of NOx with ammonia as reductant is the most efficient method to eliminate NOx from flue gases in stationary sources. The traditional SCR catalyst suffers significant deactivation with time due to the presence of relative large amoun...

  8. Optimization on structural parameters of diesel SCR catalytic reactor%柴油机SCR催化器载体结构参数优化

    Institute of Scientific and Technical Information of China (English)

    龚金科; 张福杰; 鄂加强; 刘恒语; 杜佳; 陈韬; 江俊豪

    2012-01-01

    提出一种柴油机选择催化还原(SCR)催化器载体结构参数优化的设计方法,根据车用柴油机排量,将SCR催化器载体分为4类,选取载体体积、长度、目数、壁厚和涂层厚5个结构参数为设计变量,以高NO。转化率及低压力损失为优化目标,利用拉丁超立方实验设计选择样本点进行数值模拟,在构建的Kriging近似模型基础上,对载体结构参数采用改进的非支配排序遗传算法NSGA—II(non—dominatedsortinggeneticalgorithm—II)进行优化设计。结果表明:Kriging近似模型的拟合精度较高,结合NSGA—II算法对SCR催化器载体结构参数进行优化是可行的、有效的,不同排量下的优化结果均能够较好地满足设计要求。%The optimal design method of structural parameters for diesel urea-SCR was proposed. Accord- ing to the differences of diesel engine displacement, the urea-selective catalytic reactor can be divided into four subclasses. Taking high conversion ratio of NO and small pressure loss as the optimization goal, with monolith volume, length,cell per square inch,wall thickness and washcoat thickness as design variables, Latin Hypercube method was used to carry out sampling of parameters. The obtained samples were analyzed with numerical simula- tion. On this basis, the optimization was solved by NSGA-Ⅱ (non-dominated sorting genetic algorithm-Ⅱ ) , using Kriging model as the approximate model. The results show that the Kriging model has high fitting accuracy,dem- onstrate the efficiency and applicability of the optimal design method. The optimization results of different diesel engine displacement show that the method can obtain structural parameters which meet design requirements.

  9. Evaluation of Mercury Emissions from Coal-Fired Facilities with SCR and FGD Systems

    Energy Technology Data Exchange (ETDEWEB)

    J. A. Withum; S. C. Tseng; J. E. Locke

    2006-01-31

    CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)--wet flue gas desulfurization (FGD) combination or a spray dyer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The principal purpose of this work is to develop a better understanding of the potential mercury removal ''co-benefits'' achieved by NO{sub x}, and SO{sub 2} control technologies. It is expected that these data will provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. Ultimately, this insight could help to design and operate SCR and FGD systems to maximize mercury removal. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of SCR catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the ninth in a series of topical reports, describes the results and analysis of mercury sampling performed on Unit 1 at Plant 7, a 566 MW unit burning a bituminous coal containing 3.6% sulfur. The unit is equipped with a SCR, ESP, and wet FGD to control NO{sub x}, particulate, and SO

  10. [Deactivation by SO2 of transition metal oxides modified low-temperature SCR catalyst for NOx reduction with NH3].

    Science.gov (United States)

    Shen, Bo-xiong; Liu, Ting; Yang, Ting-ting; Xiong, Li-xian; Wang, Jing

    2009-08-15

    MnOx-CeOx/ACF catalyst was prepared by impregnation method, which exhibited high activity for low-temperature selective catalytic reduction of NOx over the temperature range 110-230 degrees C. Experiments results indicated that the catalyst yielded 80% NO conversion at 150 degrees C and 90% at 230 degrees C. The Oxides of Fe,Cu and V were added to the catalysts based on MnOx-CeOx/ACF. The additions of these transition metal oxides had a negative effect on the activity of the catalysts. Compared with MnOx-CeOx/ACF and Cu and V modified catalysts, NO conversion for Fe-MnOx-CeOx/ACF catalyst leveled off at nearly 75% in the first 6 h in the presence of SO2. Two mechanisms of catalyst deactivation by SO2 were discovered by the methods of X-ray photoelectron spectrum (XPS) and Fourier transform infrared spectra (FTIR), indicating that the catalysts were covered by ammonium sulfates and the metal oxides, acting as active components, were also sulfated by SO2 to form metal sulfates.

  11. The Key Role of pH Value in the Synthesis of Titanate Nanotubes-Loaded Manganese Oxides as a Superior Catalyst for the Selective Catalytic Reduction of NO with NH3

    Directory of Open Access Journals (Sweden)

    Xiongbo Chen

    2013-01-01

    Full Text Available Titanate nanotubes (TNTs synthesized by hydrothermal method were increasingly used as the catalyst support for the selective catalytic reduction (SCR of NO with ammonia. This paper reports the critical process of postwashing to prepare satisfactory TNTs for the uses of SCR catalysts. Herein, alkaline TNTs (TNTs-AL, acidic TNTs (TNTs-AC, and neutral TNTs (TNTs-NE were synthesized by controlling washing pH value. When these TNTs were utilized as the catalyst supports for manganese oxides (Mn/TNTs-AL, Mn/TNTs-AC, and Mn/TNTs-NE, the key role of pH value was found. Titanate nanosheets, titanate nanorods and titanate nanotubes were dominated in Mn/TNTs-AL, Mn/TNTs-AC, and Mn/TNTs-NE, respectively. MnO2 crystal was observed when using TNTs-AC or TNTs-NE as the support. By contrast, Mn3O4 and NaNO3 were observed when using TNTs-AL as the support. Mn/TNTs-NE showed the best SCR activity, in line with the largest surface area, the best dispersion, and the most active redox property of manganese oxides. Mn/TNTs-AL showed negligible SCR activity, resulting from the minimum surface area, the Mn3O4-dominating crystal structure, and the bad dispersion of manganese oxides.

  12. SCR optimisation in Danish coal-fired plants

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, Jimmy [DONG Energy Power, Esbjerg (Denmark); Christensen, Soeren [DONG Energy Power, Fredericia (Denmark); Hvidberg, Jan

    2011-07-01

    From 1 January 2010, a new Danish tax on NO{sub x} emissions (0.7 EUR/kg NO{sub x}) worked as an incentive for minimising NO{sub x} emissions from power plants. Previously, an emission limit of 200 mg NO{sub x}/Nm{sup 3} had to be complied with, which was easily achieved, since all major Danish coal-fired power plants are equipped with high dust SCR (Selective Catalytic Reduction of NO{sub x}) systems. With the new NO{sub x} tax, a number of initiatives have been taken in order to maximise the DENOX capacity of the SCR systems. All efforts have led to a significant decrease in NO{sub x} emissions from DONG Energy's coal-fired power plants. (orig.)

  13. Using SCR methods to analyze requirements documentation

    Science.gov (United States)

    Callahan, John; Morrison, Jeffery

    1995-01-01

    Software Cost Reduction (SCR) methods are being utilized to analyze and verify selected parts of NASA's EOS-DIS Core System (ECS) requirements documentation. SCR is being used as a spot-inspection tool. Through this formal and systematic approach of the SCR requirements methods, insights as to whether the requirements are internally inconsistent or incomplete as the scenarios of intended usage evolve in the OC (Operations Concept) documentation. Thus, by modelling the scenarios and requirements as mode charts using the SCR methods, we have been able to identify problems within and between the documents.

  14. Low-temperature selective catalytic reduction of NO with NH3 over nanoflaky MnOx on carbon nanotubes in situ prepared via a chemical bath deposition route

    Science.gov (United States)

    Fang, Cheng; Zhang, Dengsong; Cai, Sixiang; Zhang, Lei; Huang, Lei; Li, Hongrui; Maitarad, Phornphimon; Shi, Liyi; Gao, Ruihua; Zhang, Jianping

    2013-09-01

    Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD). The SEM, TEM, XRD results and N2 adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnOx and the obtained catalyst exhibited a large surface area as well. Compared with the MnOx/CNT and MnOx/TiO2 catalysts prepared by an impregnation method, the nf-MnOx@CNTs presented better NH3-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn4+ and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnOx@CNTs. The H2-TPR and NH3-TPD results demonstrated that the nf-MnOx@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnOx@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N2 with NH3. In addition, the nf-MnOx@CNT catalyst also presented favourable stability and H2O resistance.Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature

  15. Diesel Engine Emission Reduction Using Catalytic Nanoparticles: An Experimental Investigation

    Directory of Open Access Journals (Sweden)

    Ajin C. Sajeevan

    2013-01-01

    Full Text Available Cerium oxide being a rare earth metal with dual valance state existence has exceptional catalytic activity due to its oxygen buffering capability, especially in the nanosized form. Hence when used as an additive in the diesel fuel it leads to simultaneous reduction and oxidation of nitrogen dioxide and hydrocarbon emissions, respectively, from diesel engine. The present work investigates the effect of cerium oxide nanoparticles on performance and emissions of diesel engine. Cerium oxide nanoparticles were synthesized by chemical method and techniques such as TEM, EDS, and XRD have been used for the characterization. Cerium oxide was mixed in diesel by means of standard ultrasonic shaker to obtain stable suspension, in a two-step process. The influence of nanoparticles on various physicochemical properties of diesel fuel has also been investigated through extensive experimentation by means of ASTM standard testing methods. Load test was done in the diesel engine to investigate the effect of nanoparticles on the efficiency and the emissions from the engine. Comparisons of fuel properties with and without additives are also presented.

  16. Method and apparatus for monitoring a hydrocarbon-selective catalytic reduction device

    Energy Technology Data Exchange (ETDEWEB)

    Schmieg, Steven J; Viola, Michael B; Cheng, Shi-Wai S; Mulawa, Patricia A; Hilden, David L; Sloane, Thompson M; Lee, Jong H

    2014-05-06

    A method for monitoring a hydrocarbon-selective catalytic reactor device of an exhaust aftertreatment system of an internal combustion engine operating lean of stoichiometry includes injecting a reductant into an exhaust gas feedstream upstream of the hydrocarbon-selective catalytic reactor device at a predetermined mass flowrate of the reductant, and determining a space velocity associated with a predetermined forward portion of the hydrocarbon-selective catalytic reactor device. When the space velocity exceeds a predetermined threshold space velocity, a temperature differential across the predetermined forward portion of the hydrocarbon-selective catalytic reactor device is determined, and a threshold temperature as a function of the space velocity and the mass flowrate of the reductant is determined. If the temperature differential across the predetermined forward portion of the hydrocarbon-selective catalytic reactor device is below the threshold temperature, operation of the engine is controlled to regenerate the hydrocarbon-selective catalytic reactor device.

  17. Selective catalytic reduction of NO with NH{sub 3} at V{sub 2}O{sub 5}(010) and silica supported vanadium oxide: DFT studies

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, Mathis; Hermann, Klaus [Fritz-Haber-Institut der MPG, Sfb 546, Berlin (Germany)

    2011-07-01

    The selective catalytic reduction (SCR) of NO{sub x} with NH{sub 3} over vanadium based metal-oxide (VO{sub x}) catalysts has been proven to be one of the most effective NO{sub x} reduction processes. Details of the reaction mechanism are still under debate. Adsorption, (de)hydrogenation, reactions with NO, and surface water formation at the VO{sub x} catalyst contribute elementary steps. These processes are examined in theoretical studies employing density-functional theory together with gradient corrected functionals. The VO{sub x} substrate is modeled by clusters cut out from the clean V{sub 2}O{sub 5}(010) surface where peripheral oxygen bonds are saturated by hydrogen. Reduced surfaces are represented by introducing oxygen vacancies. In addition, silica supported vanadium oxide clusters are considered. NH{sub 3} is found to interact with the clean V{sub 2}O{sub 5}(010) surface only in the presence of OH groups (Boernsted acid sites) where it can form a rather stable surface NH{sub 4}{sup +} species. Further, NH{sub 3} can adsorb at vanadium centers of lower coordination at the reduced surface (Lewis acid sites). This leads to two different SCR reaction scenarios transferring NH{sub 3} and NO to N{sub 2} and H{sub 2}O which are discussed by corresponding reaction paths and intermediates.

  18. Synergy of CuO and CeO2 combination for mercury oxidation under low-temperature selective catalytic reduction atmosphere

    KAUST Repository

    Li, Hailong

    2016-07-19

    Synergy for low temperature Hg0 oxidation under selective catalytic reduction (SCR) atmosphere was achieved when copper oxides and cerium oxides were combined in a CuO-CeO2/TiO2 (CuCeTi) catalyst. Hg0 oxidation efficiency as high as 99.0% was observed on the CuCeTi catalyst at 200 °C, even the gas hourly space velocity was extremely high. To analyze the synergistic effect, comparisons of catalyst performance in the presence of different SCR reaction gases were systematically conducted over CuO/TiO2 (CuTi), CeO2/TiO2 (CeTi) and CuCeTi catalysts prepared by sol-gel method. The interactions between copper oxides and cerium oxides in CuCeTi catalyst yielded more surface chemisorbed oxygen, and facilitated the conversion of gas-phase O2 to surface oxygen, which are favorable for Hg0 oxidation. Copper oxides in the combination interacted with NO forming more chemisorbed oxygen for Hg0 oxidation in the absence of gas-phase O2. Cerium oxides in the combination promoted Hg0 oxidation through enhancing the transformations of NO to NO2. In the absence of NO, NH3 exhibited no inhibitive effect on Hg0 oxidation, because enough Lewis acid sites due to the combination of copper oxides and cerium oxides scavenged the competitive adsorption between NH3 and Hg0. In the presence of NO, although NH3 lowered Hg0 oxidation rate through inducing reduction of oxidized mercury, complete recovery of Hg0 oxidation activity over the CuCeTi catalyst was quickly achieved after cutting off NH3. This study revealed the synergistic effect of the combination of copper oxides and cerium oxides on Hg0 oxidation, and explored the involved mechanisms. Such knowledge would help obtaining maximum Hg0 oxidation co-benefit from SCR units in coal-fired power plants.

  19. The influence of a silica pillar in lamellar tetratitanate for selective catalytic reduction of NO{sub x} using NH{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira da Cunha, Beatriz; Gonçalves, Alécia Maria; Gomes da Silveira, Rafael [Institute of Chemistry, Federal University of Goiás, C. Postal 131, CEP 74001-970 Goiânia, GO (Brazil); Urquieta-González, Ernesto A. [Laboratory of Applied Catalysis, Department of Chemical Engineering, Federal University of Sao Carlos, Rodovia Washington Luis Km 235, C. Postal 676, CEP 13565-905 São Carlos, SP (Brazil); Magalhães Nunes, Liliane, E-mail: lilianemnunes@gmail.com [Institute of Chemistry, Federal University of Goiás, C. Postal 131, CEP 74001-970 Goiânia, GO (Brazil)

    2015-01-15

    Highlights: • Potassium ions significantly affected the SCR. • The introduction of silica in the catalyst promotes the NH{sub 3}-SCR reaction. • The catalysts activities were not significantly influenced by SO{sub 2} addition. - Abstract: Silica-pillared layered titanate (SiO{sub 2}–Ti{sub 4}O{sub 9}) was prepared by intercalating organosilanes into the interlayers of a layered K{sub 2}Ti{sub 4}O{sub 9} followed by calcination at 500 °C. The lamellar titanates produced were used as a support to prepare vanadium catalysts (1 and 2 wt%) through wet impregnation for selective catalytic reduction (SCR) of NO. The catalysts were characterized using nitrogen adsorption (BET), X-ray diffraction (XRD), temperature programmed reduction (H{sub 2}-TPR), nuclear magnetic resonance ({sup 29}Si NMR), and infrared spectroscopy (FT-IR). Reduction of NO by NH{sub 3} was studied in a fixed-bed reactor packed with the catalysts and fed a mixture comprising 1% NH{sub 3}, 1% NO, 10% O{sub 2}, and 34 ppm SO{sub 2} (when used) in helium. The results demonstrate that activity is correlated with the support, i.e., with acidic strength of catalysts. The potassium in the support, K{sub 2}Ti{sub 4}O{sub 9}, significantly affected the reaction and level of vanadium species reduction. The catalyst (1VSiT) with 1 wt% vanadium impregnated on the SiO{sub 2}–Ti{sub 4}O{sub 9} support reduced ∼80% of the NO. Approximately the same conversion rate was generated on the catalyst (2VSiT) with 2 wt% vanadium using the same support. The increased NH{sub 3} adsorption demonstrate that introduction of silica in the catalyst promotes the NH{sub 3}-SCR reaction. More importantly, 2VSiT and 1VSiT were strongly resistant to SO{sub 2} poisoning.

  20. Catalytic reduction of NO{sub x}. Final report; Katalytisk Reduktion av NO{sub x}. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    Khodayari, Raziyeh; Odenbrand, Ingemar [Lund Univ. (Sweden). Chemical Engineering II

    2002-02-01

    This report is intended to show the work regarding the SCR technique performed at Chemical Engineering II, Lund Inst. of Tech. since the start in 1982. The emphasis is on work performed the last 7 years which deals with deactivation and regeneration of SCR catalysts. In chapter 1 a short general introduction to the SCR technique is given. Chapter 2 describes the work performed up to 1995. It shows the kinetics for the reaction between NO and NH{sub 3}, reactions between NO{sub 2} and NH{sub 3} as well as patents for a new process for cleaning flue gases based on our research results. Later work on using zeolites as catalysts for the reduction and for the oxidation of NO was presented. Then a series of characterisations were performed on model catalysts consisting of 2-30 wt.% V{sub 2}O{sub 5} on a coprecipitated silica-titania support. The formation of nitrous oxide was studied and found to be noticeable when water is not present in the gas and on a catalyst which contains large amounts of crystallites of V{sub 2}O{sub 5}. Chapter 3 deals with international research in the area of deactivation of SCR catalysts in i.e. biofuelled applications. Material from a literature search from December 2001 is presented. It contains general material on the deactivation with alkali metals and SO{sub 2}. Chapter 4 deals with our studies of deactivated SCR catalysts. During 1995-2001 we have studied the deactivation of catalysts in a number of Swedish plants. The sensitivity of zeolites to poisoning in waste combustion (GRAAB) was tested by artificial poisoning with 2 wt.% metal of the elements; Na, K, Mg, Fe, Zn, Cu, Al, Ni and Cr. The combustion of waste at SYSAV gave high contents of Na, Y, Ca, Pb and Zn on the catalyst after 2000 hours on stream. Activity measurements showed that low concentrations of ammonium sulphate, 1-5 vol.%, promotes the SCR reaction. A maximal activity is obtained at around 5 vol.%. There exists an optimal content of ammonium sulphate on the catalyst

  1. Low absorption vitreous carbon reactors for operando XAS: a case study on Cu/Zeolites for selective catalytic reduction of NO(x) by NH3.

    Science.gov (United States)

    Kispersky, Vincent F; Kropf, A Jeremy; Ribeiro, Fabio H; Miller, Jeffrey T

    2012-02-21

    We describe the use of vitreous carbon as an improved reactor material for an operando X-ray absorption spectroscopy (XAS) plug-flow reactor. These tubes significantly broaden the operating range for operando experiments. Using selective catalytic reduction (SCR) of NO(x) by NH(3) on Cu/Zeolites (SSZ-13, SAPO-34 and ZSM-5) as an example reaction, we illustrate the high-quality XAS data achievable with these reactors. The operando experiments showed that in Standard SCR conditions of 300 ppm NO, 300 ppm NH(3), 5% O(2), 5% H(2)O, 5% CO(2) and balance He at 200 °C, the Cu was a mixture of Cu(I) and Cu(II) oxidation states. XANES and EXAFS fitting found the percent of Cu(I) to be 15%, 45% and 65% for SSZ-13, SAPO-34 and ZSM-5, respectively. For Standard SCR, the catalytic rates per mole of Cu for Cu/SSZ-13 and Cu/SAPO-34 were about one third of the rate per mole of Cu on Cu/ZSM-5. Based on the apparent lack of correlation of rate with the presence of Cu(I), we propose that the reaction occurs via a redox cycle of Cu(I) and Cu(II). Cu(I) was not found in in situ SCR experiments on Cu/Zeolites under the same conditions, demonstrating a possible pitfall of in situ measurements. A Cu/SiO(2) catalyst, reduced in H(2) at 300 °C, was also used to demonstrate the reactor's operando capabilities using a bending magnet beamline. Analysis of the EXAFS data showed the Cu/SiO(2) catalyst to be in a partially reduced Cu metal-Cu(I) state. In addition to improvements in data quality, the reactors are superior in temperature, stability, strength and ease of use compared to previously proposed borosilicate glass, polyimide tubing, beryllium and capillary reactors. The solid carbon tubes are non-porous, machinable, can be operated at high pressure (tested at 25 bar), are inert, have high material purity and high X-ray transmittance.

  2. Low Absorption Vitreous Carbon Reactors for Operando XAS: A Case Study on Cu/Zeolites for Selective Catalytic Reduction of NOx by NH3

    Energy Technology Data Exchange (ETDEWEB)

    Kispersky, Vincent F.; Kropf, Jeremy; Ribeiro, Fabio H; Miller, Jeffrey T

    2012-01-01

    We describe the use of vitreous carbon as an improved reactor material for an operando X-ray absorption spectroscopy (XAS) plug-flow reactor. These tubes significantly broaden the operating range for operando experiments. Using selective catalytic reduction (SCR) of NOx by NH₃ on Cu/Zeolites (SSZ-13, SAPO-34 and ZSM-5) as an example reaction, we illustrate the high-quality XAS data achievable with these reactors. The operando experiments showed that in Standard SCR conditions of 300 ppm NO, 300 ppm NH₃, 5% O₂, 5% H₂O, 5% CO₂ and balance He at 200 °C, the Cu was a mixture of Cu(I) and Cu(II) oxidation states. XANES and EXAFS fitting found the percent of Cu(I) to be 15%, 45% and 65% for SSZ-13, SAPO-34 and ZSM-5, respectively. For Standard SCR, the catalytic rates per mole of Cu for Cu/SSZ-13 and Cu/SAPO-34 were about one third of the rate per mole of Cu on Cu/ZSM-5. Based on the apparent lack of correlation of rate with the presence of Cu(I), we propose that the reaction occurs via a redox cycle of Cu(I) and Cu(II). Cu(I) was not found in in situSCR experiments on Cu/Zeolites under the same conditions, demonstrating a possible pitfall of in situ measurements. A Cu/SiO₂ catalyst, reduced in H₂ at 300 °C, was also used to demonstrate the reactor's operando capabilities using a bending magnet beamline. Analysis of the EXAFS data showed the Cu/SiO₂ catalyst to be in a partially reduced Cu metal–Cu(I) state. In addition to improvements in data quality, the reactors are superior in temperature, stability, strength and ease of use compared to previously proposed borosilicate glass, polyimide tubing, beryllium and capillary reactors. The solid carbon tubes are non-porous, machinable, can be operated at high pressure (tested at 25 bar), are inert, have high material purity and high X-ray transmittance.

  3. Low absorption vitreous carbon reactors for operando XAS: a case study on Cu/Zeolites for selective catalytic reduction of NO(x) by NH3.

    Science.gov (United States)

    Kispersky, Vincent F; Kropf, A Jeremy; Ribeiro, Fabio H; Miller, Jeffrey T

    2012-02-21

    We describe the use of vitreous carbon as an improved reactor material for an operando X-ray absorption spectroscopy (XAS) plug-flow reactor. These tubes significantly broaden the operating range for operando experiments. Using selective catalytic reduction (SCR) of NO(x) by NH(3) on Cu/Zeolites (SSZ-13, SAPO-34 and ZSM-5) as an example reaction, we illustrate the high-quality XAS data achievable with these reactors. The operando experiments showed that in Standard SCR conditions of 300 ppm NO, 300 ppm NH(3), 5% O(2), 5% H(2)O, 5% CO(2) and balance He at 200 °C, the Cu was a mixture of Cu(I) and Cu(II) oxidation states. XANES and EXAFS fitting found the percent of Cu(I) to be 15%, 45% and 65% for SSZ-13, SAPO-34 and ZSM-5, respectively. For Standard SCR, the catalytic rates per mole of Cu for Cu/SSZ-13 and Cu/SAPO-34 were about one third of the rate per mole of Cu on Cu/ZSM-5. Based on the apparent lack of correlation of rate with the presence of Cu(I), we propose that the reaction occurs via a redox cycle of Cu(I) and Cu(II). Cu(I) was not found in in situ SCR experiments on Cu/Zeolites under the same conditions, demonstrating a possible pitfall of in situ measurements. A Cu/SiO(2) catalyst, reduced in H(2) at 300 °C, was also used to demonstrate the reactor's operando capabilities using a bending magnet beamline. Analysis of the EXAFS data showed the Cu/SiO(2) catalyst to be in a partially reduced Cu metal-Cu(I) state. In addition to improvements in data quality, the reactors are superior in temperature, stability, strength and ease of use compared to previously proposed borosilicate glass, polyimide tubing, beryllium and capillary reactors. The solid carbon tubes are non-porous, machinable, can be operated at high pressure (tested at 25 bar), are inert, have high material purity and high X-ray transmittance. PMID:22158950

  4. An Experimental Study on the Performance Matching of Urea-SCR Catalytic Converter with Engine%尿素-SCR催化器与发动机性能匹配试验研究

    Institute of Scientific and Technical Information of China (English)

    郭红松; 姜艳; 包俊江; 景晓军

    2011-01-01

    A power, fuel economy and emission performances matching test is conducted on a stage-IV heavy duty diesel engine equipped with 3 typical commercial urea-SCR catalytic converters produced by different manufacturers, focusing on the study on performances including pressure drop and light-off characteristics as well as the dynamic response and pollutant conversion rates of catalytic converter. The results show that the fewer the mesh number of converter, the smaller its pressure drop; the catalytic converter with lower light-off temperature and quicker dynamic response has better control result for not only NOX, but also NH3, SO2, N2O and NO2. With same size and structure of SCR, the formula and coating process of catalyst basically have no effects on the power and fuel e-conomy of engine.%对一台国IV重型柴油机装用不同厂家生产的3种典型商用尿素-SCR催化转化器在台架上进行了动力性、经济性和排放等性能匹配试验,重点研究催化转化器的压降特性、起燃特性、动态响应和转化效率等性能.结果表明,催化器目数越少,其压降越小;起燃温度低,动态响应快的催化器具有较好的NOx控制效果,且在减少NH3、SO2、N2O和NO2排放方面效果也较好.SCR尺寸和结构相同时,发动机动力性和经济性基本不受催化剂配方和涂层工艺的影响.

  5. Investigation into selective catalytic reduction (SCR)of NOx%选择性催化还原(SCR)脱除NOx的实验研究

    Institute of Scientific and Technical Information of China (English)

    薛红丹; 董国君; 龚凡; 韩成喜

    2006-01-01

    制备以堇青石蜂窝陶瓷为载体,以Cu、Cu-NiO、Cu-NiO-La2O3、Cu-NiO-Ce2O3为活性组分,以尿素为还原剂,选择催化还原氮氧化物的催化剂,并对催化剂的活性在423~623 K范围内进行了评价和比较,筛选出活性较高、较有研究前景的催化剂.

  6. LPV gain-scheduled control of SCR aftertreatment systems

    Science.gov (United States)

    Meisami-Azad, Mona; Mohammadpour, Javad; Grigoriadis, Karolos M.; Harold, Michael P.; Franchek, Matthew A.

    2012-01-01

    Hydrocarbons, carbon monoxide and some of other polluting emissions produced by diesel engines are usually lower than those produced by gasoline engines. While great strides have been made in the exhaust aftertreatment of vehicular pollutants, the elimination of nitrogen oxide (NO x ) from diesel vehicles is still a challenge. The primary reason is that diesel combustion is a fuel-lean process, and hence there is significant unreacted oxygen in the exhaust. Selective catalytic reduction (SCR) is a well-developed technology for power plants and has been recently employed for reducing NO x emissions from automotive sources and in particular, heavy-duty diesel engines. In this article, we develop a linear parameter-varying (LPV) feedforward/feedback control design method for the SCR aftertreatment system to decrease NO x emissions while keeping ammonia slippage to a desired low level downstream the catalyst. The performance of the closed-loop system obtained from the interconnection of the SCR system and the output feedback LPV control strategy is then compared with other control design methods including sliding mode, and observer-based static state-feedback parameter-varying control. To reduce the computational complexity involved in the control design process, the number of LPV parameters in the developed quasi-LPV (qLPV) model is reduced by applying the principal component analysis technique. An LPV feedback/feedforward controller is then designed for the qLPV model with reduced number of scheduling parameters. The designed full-order controller is further simplified to a first-order transfer function with a parameter-varying gain and pole. Finally, simulation results using both a low-order model and a high-fidelity and high-order model of SCR reactions in GT-POWER interfaced with MATLAB/SIMULINK illustrate the high NO x conversion efficiency of the closed-loop SCR system using the proposed parameter-varying control law.

  7. Regeneration of Pt-catalysts deactivated in municipal waste flue gas with H2/N2 and the effect of regeneration step on the SCR catalyst

    DEFF Research Database (Denmark)

    Due-Hansen, Johannes; Rasmussen, Søren Birk; Kustov, Arkadii;

    stream, i.e. by in situ treatment of the Pt-catalyst by reductive H2-gas. However, introduction of H2 gas in the gas stream could also affect other units in the tail pipe gas cleaning system. Of special interest here, is the effect of hydrogen gas on the performance of the deNOx + SCR catalytic process...

  8. Improved Automotive NO (x) Aftertreatment System: Metal Ammine Complexes as NH3 Source for SCR Using Fe-Containing Zeolite Catalysts

    DEFF Research Database (Denmark)

    Johannessen, Tue; Schmidt, Henning; Frey, Anne Mette;

    2009-01-01

    Ammonia storage is a challenge in the selective catalytic reduction of NO (x) in vehicles. We propose a new system, based on metal ammines as the ammonia source. In combination with iron containing zeolites as the SCR catalyst it should be possible to obtain a low temperature system for NO (x...

  9. Destruction of PCDD/Fs by SCR from flue gases of municipal waste incinerator and metal smelting plant.

    Science.gov (United States)

    Chang, Moo Been; Chi, Kai Hsien; Chang, Shu Hao; Yeh, Jhy Wei

    2007-01-01

    Partitioning of PCDD/F congeners between vapor/solid phases and removal and destruction efficiencies achieved with selective catalytic reduction (SCR) system for PCDD/Fs at an existing municipal waste incinerator (MWI) and metal smelting plant (MSP) in Taiwan are evaluated via stack sampling and analysis. The MWI investigated is equipped with electrostatic precipitators (EP, operating temperature: 230 degrees C), wet scrubbers (WS, operating temperature: 70 degrees C) and SCR (operating temperature: 220 degrees C) as major air pollution control devices (APCDs). PCDD/F concentration measured at stack gas of the MWI investigated is 0.728 ng-TEQ/Nm(3). The removal efficiency of WS+SCR system for PCDD/Fs reaches 93% in the MWI investigated. The MSP investigated is equipped with EP (operating temperature: 240 degrees C) and SCR (operating temperature: 290 degrees C) as APCDs. The flue gas sampling results also indicate that PCDD/F concentration treated with SCR is 1.35 ng-TEQ/Nm(3). The SCR system adopted in MSP can remove 52.3% PCDD/Fs from flue gases (SCR operating temperature: 290 degrees C, Gas flow rate: 660 kN m(3)/h). In addition, the distributions of PCDD/F congeners observed in the flue gases of the MWI and MSP investigated are significantly different. This study also indicates that the PCDD/F congeners measured in the flue gases of those two facilities are mostly distributed in vapor phase prior to the SCR system and shift to solid phase (vapor-phase PCDD/Fs are effectively decomposed) after being treated with catalyst. Besides, the results also indicate that with SCR highly chlorinated PCDD/F congeners can be transformed to lowly chlorinated PCDD/F congeners probably by dechlorination, while the removal efficiencies of vapor-phase PCDD/Fs increase with increasing chlorination.

  10. The poisoning effect of Na and K on Mn/TiO2 catalyst for selective catalytic reduction of NO with NH3: A comparative study

    Science.gov (United States)

    Guo, Rui-tang; Wang, Qing-shan; Pan, Wei-guo; Zhen, Wen-long; Chen, Qi-lin; Ding, Hong-lei; Yang, Ning-zhi; Lu, Chen-zi

    2014-10-01

    Mn/TiO2 catalyst is of high activity for low temperature selective catalytic reduction (SCR) of NO with NH3. And the deposition of alkali metal would lead to the deactivation of Mn/TiO2 catalyst. In this paper, the poisoning effect of Na and K on Mn/TiO2 was investigated based on experimental and theoretical study. It was found that K had a stronger poisoning effect than that of Na. The bad performance of K-Mn/TiO2 may be due to its small surface area, high crystallinity, weak surface acidity, low content of Mn4+ and chemisorbed oxygen, and bad redox ability. The interpretation of the experimental results is supported by DFT calculations.

  11. 环境友好的选择性催化还原氮氧化物催化剂%Environmental-friendly catalysts for the selective catalytic reduction of NOx

    Institute of Scientific and Technical Information of China (English)

    贺泓; 刘福东; 余运波; 单文坡

    2012-01-01

    Selective catalytic reduction (SCR) of nitrogen oxides (Nox) under oxygen-rich conditions is a research hotspot in the field of environmental catalysis, of which the core problem is to develop environmental-friendly, highly effective and stable SCR catalyst systems. At present, the NH3-SCR technique using urea/NH3 as reducing agent has already been widely applied for stationary flue gas denitrogenation and diesel engine exhaust purification. The HC-SCR technique using hydrogen carbons (HC) as reducing agent is also promising for practical application. For urea/NH3-SCR system, in this paper, the research progress of iron titanate catalyst, cerium-based oxide catalysts and small-pore zeolite catalysts is comprehensively summarized, including the catalyst structure, the SCR reaction mechanism, the improvement of low temperature activity and also the poisoning resistance performance. For HC-SCR system, herein, the SCR of NO* by higher HCs/diesel, and the achievements in the mechanism study of HC-SCR are summarized systematically, which can provide new guideline for the development and application of diesel-SCR technique.%富氧条件下的氮氧化物(NOx)选择性催化还原(SCR)是目前环境催化领域的研究热点,其核心问题是研发环境友好、高效稳定的SCR催化剂.目前,以NH3为还原剂的NH3-SCR已经大规模应用于固定源烟气脱硝和柴油车尾气净化,以碳氢化合物(HC)为还原剂的HC-SCR也有望实际应用.针对NH3-SCR,本文以作者研究的铁钛复合氧化物催化剂、铈基氧化物催化剂以及国际上新兴的小孔分子筛催化剂为例,从催化剂结构、SCR反应机理、催化剂低温活性改进以及抗中毒性能等诸多方面对该领域的研究进展做了较为全面的论述.针对HC-SCR催化剂,本文在综述长链HC及柴油选择性还原NOx研究现状的基础上,结合作者在HC-SCR反应机理方面的研究成果,展望了实现柴油-SCR的发展方向.

  12. Alternative SILP-SCR Catalysts based on Guanidinium Chromates

    DEFF Research Database (Denmark)

    Due-Hansen, Johannes; Riisager, Anders; Ståhl, Kenny;

    There is an increasing global concern about human caused emissions of pollutants like sulfur and nitrogen oxides to the atmosphere leading to, e.g. smog and acid rain damaging to the human health and the environment. Selective catalytic reduction (SCR) of NOx with ammonia as reductant is the most...... efficient method to eliminate NOx from flue gases in stationary sources via the reaction: 4NH3 + 4NO + O2 → 4N2 + 6H2O. The traditionally used heterogeneous SCR catalyst, V2O5-WO3/TiO2, suffers significant deactivation with time due to the presence of relatively large amounts of potassium in the fly ash...... from bio-fuels. Some of the alkali particles reach the SCR catalyst and deactivate the catalyst both by physical pore blocking as well as by chemically deactivating the oxo vanadium sites. Furthermore, the catalyst operates around 375ºC and thus has to be placed in a certain position in the flue gas...

  13. Evaluation of Mercury Emissions from Coal-Fired Facilities with SCR and FGD Systems

    Energy Technology Data Exchange (ETDEWEB)

    J. A. Withum; J. E. Locke

    2006-02-01

    CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)--wet flue gas desulfurization (FGD) combination or a spray dyer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The principal purpose of this work is to develop a better understanding of the potential mercury removal ''co-benefits'' achieved by NO{sub x}, and SO{sub 2} control technologies. It is expected that this data will provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. Ultimately, this insight could help to design and operate SCR and FGD systems to maximize mercury removal. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of SCR catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the tenth in a series of topical reports, describes the results and analysis of mercury sampling performed on two 468 MW units burning bituminous coal containing 1.3-1.7% sulfur. Unit 2 is equipped with an SCR, ESP, and wet FGD to control NO{sub x}, particulate, and SO{sub 2} emissions

  14. Influence on the oxidative potential of a heavy-duty engine particle emission due to selective catalytic reduction system and biodiesel blend.

    Science.gov (United States)

    Godoi, Ricardo H M; Polezer, Gabriela; Borillo, Guilherme C; Brown, Andrew; Valebona, Fabio B; Silva, Thiago O B; Ingberman, Aline B G; Nalin, Marcelo; Yamamoto, Carlos I; Potgieter-Vermaak, Sanja; Penteado Neto, Renato A; de Marchi, Mary Rosa R; Saldiva, Paulo H N; Pauliquevis, Theotonio; Godoi, Ana Flavia L

    2016-08-01

    Although the particulate matter (PM) emissions from biodiesel fuelled engines are acknowledged to be lower than those of fossil diesel, there is a concern on the impact of PM produced by biodiesel to human health. As the oxidative potential of PM has been suggested as trigger for adverse health effects, it was measured using the Electron Spin Resonance (OP(ESR)) technique. Additionally, Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) was employed to determine elemental concentration, and Raman Spectroscopy was used to describe the amorphous carbon character of the soot collected on exhaust PM from biodiesel blends fuelled test-bed engine, with and without Selective Catalytic Reduction (SCR). OP(ESR) results showed higher oxidative potential per kWh of PM produced from a blend of 20% soybean biodiesel and 80% ULSD (B20) engine compared with a blend of 5% soybean biodiesel and 95% ULSD (B5), whereas the SCR was able to reduce oxidative potential for each fuel. EDXRF data indicates a correlation of 0.99 between concentration of copper and oxidative potential. Raman Spectroscopy centered on the expected carbon peaks between 1100cm(-1) and 1600cm(-1) indicate lower molecular disorder for the B20 particulate matter, an indicative of a more graphitic carbon structure. The analytical techniques used in this study highlight the link between biodiesel engine exhaust and increased oxidative potential relative to biodiesel addition on fossil diesel combustion. The EDXRF analysis confirmed the prominent role of metals on free radical production. As a whole, these results suggest that 20% of biodiesel blends run without SCR may pose an increased health risk due to an increase in OH radical generation. PMID:27101453

  15. Final Report of a CRADA Between Pacific Northwest National Laboratory and the General Motors Company (CRADA No. PNNL/271): “Degradation Mechanisms of Urea Selective Catalytic Reduction Technology”

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Do Heui; Lee, Jong H.; Peden, Charles HF; Howden, Ken; Kim, Chang H.; Oh, Se H.; Schmieg, Steven J.; Wiebenga, Michelle H.

    2011-12-13

    Diesel engines can offer substantially higher fuel efficiency, good driving performance characteristics, and reduced carbon dioxide (CO2) emission compared to stoichiometric gasoline engines. Despite the increasing public demand for higher fuel economy and reduced dependency on imported oil, however, meeting the stringent emission standards with affordable methods has been a major challenge for the wide application of these fuel-efficient engines in the US market. The selective catalytic reduction of NOx by urea (urea-SCR) is one of the most promising technologies for NOx emission control for diesel engine exhausts. To ensure successful NOx emission control in the urea-SCR technology, both a diesel oxidation catalyst (DOC) and a urea-SCR catalyst with high activity and durability are critical for the emission control system. Because the use of this technology for light-duty diesel vehicle applications is new, the relative lack of experience makes it especially challenging to satisfy the durability requirements. Of particular concern is being able to realistically simulate actual field aging of the catalyst systems under laboratory conditions, which is necessary both as a rapid assessment tool for verifying improved performance and certifiability of new catalyst formulations. In addition, it is imperative to develop a good understanding of deactivation mechanisms to help develop improved catalyst materials. In this CRADA program, General Motors Company and PNNL have investigated fresh, laboratory- and vehicle-aged DOC and SCR catalysts. The studies have led to a better understanding of various aging factors that impact the long-term performance of catalysts used in the urea-SCR technology, and have improved the correlation between laboratory and vehicle aging for reduced development time and cost. This Final Report briefly highlights many of the technical accomplishments and documents the productivity of the program in terms of peer-reviewed scientific publications

  16. Design of a periodically operated SCR reactor

    International Nuclear Information System (INIS)

    A new NOx abatement process uses the rotating Ljungstroem air heater of the power plant for the selective catalytic reduction (SCR) of nitrogen monoxide with ammonia. For this purpose the air heater elements are covered by a catalytically active layer. The transformation can be carried out by simple replacement of the original air heater elements. Thus nitrogen monoxide control is possible without requiring major modifications of existing power plant equipment. Two oxidic catalysts have been developed to be employed in the different temperature sections of the air heater. The activity of the catalysts has been quantified with the aid of laboratory scale experiments. The results can be described using a simple expression for the rate of the chemical reaction. NO conversion and NH3 slip to be expected in a catalytically active Ljungstroem heat exchanger are calculated with a reactor model taking into account the gas phase mass transfer resistances. The calculations show that the proposed device can be used if the NO concentration in the flue gas does not exceed 300 ppm. Recently Kraftanlagen AG, Heidelberg, installed a catalyst air heater system at Mandalay Generating Station in Oxnard, California. The comparison of the predicted results with preliminary experimental data proves the validity of the chosen reactor model. Under the given conditions NO conversions of more than 60% can be achieved maintaining the NH3 slip below the specified value of 10 ppm. (orig.). 19 figs., 35 refs

  17. XAFS Study of Active Tungsten Species on WO3/TiO2 as a Catalyst for Photo-SCR

    International Nuclear Information System (INIS)

    The activity of the photo-assisted selective catalytic reduction of NO with NH3 (photo-SCR) was enhanced by the addition of WO3 to TiO2. From the result of XAFS analysis, the W species on TiO2 had a WO4 tetrahedral structure and agglutination took place as the addition of WO3 was increased. We conclude that the isolated W species enhances the surface acidity and photo-SCR activity whereas the agglutinated W species is an inactive species

  18. Effect of metal ions doping (M = Ti4+, Sn4+) on the catalytic performance of MnOx/CeO2 catalyst for low temperature selective catalytic reduction of NO with NH3

    Science.gov (United States)

    Xiong, Yan; Tang, Changjin; Dong, Lin

    2015-04-01

    Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China The abatement of nitrogen oxides (NOx) emission from exhaust gases of diesel and stationary sources is a significant challenge for economic and social development. Ceria-based solid solutions were synthesized and used as supports to prepare MnOx/Ce0.8Ti0.2O2 and MnOx/Ce0.8Sn0.2O2 catalysts (Mn/CeTi and Mn/CeSn) for low temperature selective catalytic reduction of NO by NH3 (NH3-SCR). The effects of Ti or Sn doping on the catalytic performance of MnOx/CeO2 catalyst were investigated. Experimental results show that doping of Ti or Sn increases the NO removal efficiency of MnOx/CeO2. The NO conversion of Mn/CeTi catalyst is more than 90 % at temperature window of 175 ~ 300 °C under a gas hour space velocity of 60,000 mL.g-1.h-1. Modified catalysts are also found to exhibit greatly improved resistance to sulfur-poisoning. NH3-TPD results suggest that NH3 desorption on the catalysts is observed over a wide temperature range, due to the variability of adsorbed NH3 species with different thermal stabilities. Doping of Ti and Sn into Mn/CeO2 greatly increased the NH3 adsorption ability of the composites which could promote the SCR reaction. Characterization results also indicate that doping of Ti or Sn brings about catalysts with higher BET surface area, enhanced oxygen storage capacity and increased surface acidity.

  19. The poisoning effect of potassium ions doped on MnOx/TiO2 catalysts for low-temperature selective catalytic reduction

    Science.gov (United States)

    Zhang, Liangjing; Cui, Suping; Guo, Hongxia; Ma, Xiaoyu; Luo, Xiaogen

    2015-11-01

    The poisoning of alkali metal on MnOx/TiO2 catalysts used for selective catalytic reduction (SCR) of NOx by NH3 was investigated. KNO3, KCl and K2SO4 were doped on MnOx/TiO2 catalysts by sol-gel method, respectively. The SCR activity of each catalyst was measured for the removal of NOx with NH3 in the temperature range 90-330 °C. The experimental results showed that catalyst with KNO3 have a stronger deactivation effect than other catalysts. The properties of the catalysts were characterized by XRD, BET, SEM, XPS, H2-TPR, NH3-TPD and in situ DRIFTS analyses. The characterized results indicated that KNO3, KCl and K2SO4 caused the similar decrease of specific surface area and pore volume, but the quantity of acid sites for KNO3-MnOx/TiO2 catalyst reduced sharply. The main reason for catalyst deactivation is attributed to two aspects: one was physical influences for the decrease of surface area and pore volume, another was chemical influences that the K+ ions decomposed by KNO3 neutralized Brønsted acid sites of catalyst and reduced their reducibility. The chemical influence played a leading role on the deactivation of catalysts.

  20. Identification of the arsenic resistance on MoO3 doped CeO2/TiO2 catalyst for selective catalytic reduction of NOx with ammonia.

    Science.gov (United States)

    Li, Xiang; Li, Xiansheng; Li, Junhua; Hao, Jiming

    2016-11-15

    Arsenic resistance on MoO3 doped CeO2/TiO2 catalysts for selective catalytic reduction of NOx with NH3 (NH3-SCR) is investigated. It is found that the activity loss of CeO2-MoO3/TiO2 caused by As oxide is obvious less than that of CeO2/TiO2 catalysts. The fresh and poisoned catalysts are compared and analyzed using XRD, Raman, XPS, H2-TPR and in situ DRIFTS. The results manifest that the introduction of arsenic oxide to CeO2/TiO2 catalyst not only weakens BET surface area, surface acid sites and adsorbed NOx species, but also destroy the redox circle of Ce(4+) to Ce(3+) because of interaction between Ce and As. When MoO3 is added into CeO2/TiO2 system, the main SCR reaction path are found to be changed from the reaction between coordinated NH3 and ad-NOx species to that between an amide and gaseous NO. Additionally, for CeO2-MoO3/TiO2 catalyst, As toxic effect on active sites CeO2 can be released because of stronger As-Mo interaction. Moreover, not only are the reactable Brønsted and Lewis acid sites partly restored, but the cycle of Ce(4+) to Ce(3+) can also be free to some extent.

  1. Selective catalytic reduction of NO with NH{sub 3} over CeO{sub 2}–ZrO{sub 2}–WO{sub 3} catalysts prepared by different methods

    Energy Technology Data Exchange (ETDEWEB)

    Ning, Ping; Song, Zhongxian; Li, Hao [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Zhang, Qiulin, E-mail: qiulinzhang_kmust@163.com [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Liu, Xin; Zhang, Jinhui; Tang, Xiaosu [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Huang, Zhenzhen [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China)

    2015-03-30

    Graphical abstract: The CeO{sub 2}–ZrO{sub 2}–WO{sub 3} (CZW) catalysts are prepared by different methods for the selective catalytic reduction of NO by NH{sub 3}. The CZW (HT) catalyst (synthesized by hydrothermal method) shows the best catalytic activity and above 90% NO conversion is obtained at 195–450 °C. Furthermore, the CZW (HT) also exhibits the excellent performance in the presence of H{sub 2}O and SO{sub 2}. Besides, the hydrothermal method contributes to the formation of Brønsted acid sites and then results in the exceptional high-temperature activity. - Highlights: • The CeO{sub 2}–ZrO{sub 2}–WO{sub 3} catalyst exhibits the superior SCR activity at 175–450 °C. • The hydrothermal method is beneficial to the formation of Brønsted acid sites. • The CeO{sub 2}–ZrO{sub 2}–WO{sub 3} catalyst shows the excellent resistance to SO{sub 2} + H{sub 2}O. • The highly dispersed tungsten oxide species result in the excellent performance. - Abstract: The selective catalytic reduction (SCR) of NO by NH{sub 3} has been investigated over the CeO{sub 2}–ZrO{sub 2}–WO{sub 3} (CZW) catalysts prepared by hydrothermal synthesis, incipient impregnation, co-precipitation and sol–gel methods. The results indicate that the CZW catalyst prepared by hydrothermal method shows the best SCR activity, and more than 90% NO conversion is obtained at 195–450 °C with a gas hourly space velocity of 50,000 h{sup −1}. The samples are characterized by XRD, N{sub 2} adsorption–desorption, SEM, EDS, XPS, H{sub 2}-TPR, NH{sub 3}-TPD and Pyridine-IR techniques. The results imply that the superior SCR activity of CZW catalyst is contributed to the excellent redox property, strong acidity and highest content of chemisorbed oxygen species. Furthermore, the larger surface area and greater total pore volume improve the redox ability and enhance NO conversion at low temperature, while the co-existence of Lewis and Brønsted acid sites enhance the SCR activity at

  2. Novel, Regenerable Microlith Catalytic Reactor for CO2 Reduction via Bosch Process Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Precision Combustion, Inc. (PCI) proposes to develop an extremely compact, lightweight and regenerable MicrolithREG catalytic CO2 reduction reactor, capable of...

  3. State of the art and potential of development of catalysts for the SCR procedure at waste incinerators; Stand der Technik und Entwicklungspotential von Katalysatoren fuer SCR-Verfahren bei Abfallverbrennungsanlagen

    Energy Technology Data Exchange (ETDEWEB)

    Schuettenhelm, Wolfgang

    2012-11-01

    The optimal implementation of the SCR technology (SCR - selective catalytic reduction) into the overall plant concept enables a cost efficient deposition of NO{sub x} with a very large performance and a low ammonia slippage. Especially the raw gas switchings with and without preceding electro filters as well as the low temperature SCR plants arranged by optimized dry and semi-dry procedures of exhaust gas purification are the trend. The areas of application of the SCR procedure in waste incinerators, substitute fuels power plants and biomass conversion plants are enlarged clearly. The energy efficiency of the overall facility can be enhanced by a subsequent heat recycling. Especially, within the scope of the catalyst technology it could be shown that SINO{sub x} plate catalysts are particularly suitable for raw gas switchings due to its intoxication resistance and deposits of dusts. Due to the numerous advantages of the SCR procedure a manifold of new combustion plants are provided with the SCR technology.

  4. Ammonia measurement with a pH electrode in the ammonia/urea-SCR process

    Science.gov (United States)

    Kröcher, Oliver; Elsener, Martin

    2007-03-01

    The selective catalytic reduction of nitrogen oxides with ammonia (ammonia SCR) and urea (urea SCR), respectively, is a widespread process to clean flue and diesel exhaust gases due to its simplicity and efficiency. The main challenge of the process is to minimize the ammonia emissions downstream of the SCR catalyst. We found that ammonia emissions of >10 ppm can reliably be detected with a simple pH electrode in the presence of CO2, SOx, NOx, and moderately weak organic acids. 10-20 ppm of ammonia in the exhaust gas are sufficient to neutralize the acids and to increase the pH value from 3 to 6. On this basis a continuous measuring method for ammonia was developed, which was used to control the dosage of urea in the SCR process. While keeping the ammonia emissions after the SCR catalyst at 5-30 ppm an average NOx removal efficiency (DeNOx) of >95% were achieved at a diesel test rig. The method can also be applied for exhaust gases with higher acid contents, if a basic pre-filter is added adsorbing the acidic exhaust components. Compared to water as absorption solution, more precise ammonia measurements are possible, if a 0.1 M NH4Cl absorption solution is applied, whose pH value is changing as a Nernst function of the ammonia concentration.

  5. Catalytic Radical Reduction in Aqueous Solution by a Ruthenium Hydride Intermediate.

    Science.gov (United States)

    Htet, Yamin; Tennyson, Andrew G

    2016-07-18

    Some manganese complexes can catalyze both antioxidant and pro-oxidant reactions, whereby the disparate reactivity modes are determined by the catalyst environment and afford distinct therapeutic effects. We recently reported the reduction of radicals in buffered aqueous solution catalyzed by a ruthenium complex with biologically relevant non-tertiary alcohols as terminal reductants. Mechanistic evidence is presented, indicating that this catalytic radical reduction is achieved by a Ru-hydride intermediate formed by β-hydride elimination from a Ru-alkoxide species. A similar mechanism and Ru-hydride intermediate was previously reported to kill cancer cells with catalytic pro-oxidant effects. Therefore, our demonstration of catalytic antioxidant effects by the same type of intermediate reveals new potential therapeutic strategies and applications for catalytic systems that form Ru-hydride intermediates. PMID:27254303

  6. Sulfate Promoted Zirconia as Promising Alkali-Resistant Support for Catalytic NOx Removal

    DEFF Research Database (Denmark)

    Due-Hansen, Johannes; Kustov, Arkadii; Christensen, Claus H.;

    The use of bio-fuels as alternatives to traditional fossil fuels has attracted much attention recent years since bio-fuels belong to a family of renewable types of energy sources and do not contribute to the green-house effect. Selective catalytic reduction (SCR) of NOx with ammonia as reductant...

  7. Sulfated Zirconia as Alkali-Resistant Support for Catalytic NOx Removal

    DEFF Research Database (Denmark)

    The use of bio-fuels as alternatives to traditional fossil fuels has attracted much attention recent years since bio-fuels belong to a family of renewable types of energy sources and do not contribute to the green-house effect. Selective catalytic reduction (SCR) of NOx with ammonia as reductant...

  8. SCR SYSTEMS FOR HEAVY DUTY TRUCKS: PROGRESS TOWARDS MEETING EURO 4 EMISSION STANDARDS IN 2005

    Energy Technology Data Exchange (ETDEWEB)

    Frank, W; Huethwohl, G; Maurer, B

    2003-08-24

    Emissions of diesel engines contain some components, which support the generation of smog and which are classified hazardous. Exhaust gas aftertreatment is a powerful tool to reduce the NOx and Particulate emissions. The NOx-emission can be reduced by the SCR technology. SCR stands for Selective Catalytic Reduction. A reduction agent has to be injected into the exhaust upstream of a catalyst. On the catalyst the NOx is reduced to N2 (Nitrogen) and H2O (Water). This catalytic process was developed in Japan about 30 years ago to reduce the NOx emission of coal-fired power plants. The first reduction agent used was anhydrous ammonia (NH3). SCR technology was used with diesel engines starting mid of the 80s. First applications were stationary operating generator-sets. In 1991 a joint development between DaimlerChrysler, MAN, IVECO and Siemens was started to use SCR technology for the reduction of heavy duty trucks. Several fleet tests demonstrated the durability of the systems. To day, SCR technology is the most promising technology to fulfill the new European Regulations EURO 4 and EURO 5 being effective Oct. 2005 and Oct. 2008. The efficient NOx reduction of the catalyst allows an engine calibration for low fuel consumption. DaimlerChrysler decided to use the SCR technology on every heavy duty truck and bus in Europe and many other truck manufacturers will introduce SCR technology to fulfill the 2005 emission regulation. The truck manufacturers in Europe agreed to use aqueous solution of Urea as reducing agent. The product is called AdBlue. AdBlue is a non toxic, non smelling liquid. The consumption is about 5% of the diesel fuel consumption to reduce the NOx emissions. A small AdBlue tank has to be installed to the vehicle. With an electronically controlled dosing system the AdBlue is injected into the exhaust. The dosing system is simple and durable. It has proven its durability during winter and summer testing as well as in fleet tests. The infrastructure for Ad

  9. Performance of optimised SCR retrofit buses under urban driving and controlled conditions

    Science.gov (United States)

    Carslaw, David C.; Priestman, Max; Williams, Martin L.; Stewart, Gregor B.; Beevers, Sean D.

    2015-03-01

    This work presents the first comprehensive real-world emissions results from urban buses retrofitted with an optimised low-NO2 selective catalytic reduction (SCR) system. The SCRT system combines a CRT (Continuously Regenerating Trap) to reduce particle emissions and SCR to reduce NOx emissions. The optimised low-NO2 SCRT was designed to work under urban conditions where the vehicle exhaust gas temperature is often too low for many SCR systems to work efficiently. The system was extensively tested through on-road and test track measurements using a vehicle emission remote sensing instrument capable of measuring both nitric oxide (NO) and nitrogen dioxide (NO2). Over 700 on-road measurements of the SCRT system were made in London. Compared with identical buses operating under the same conditions fitted with a CRT, NO2 emissions were reduced by 61% and total NOx by 45%. Under test track conditions reductions in NOx of 77% were observed. The test track results do reveal however that compared with an original Euro III bus without a CRT, the SCRT retrofit bus emissions of NO2 are 50% higher. Engine-out and tailpipe measurements of several important engine parameters under test track conditions showed the important effect of SCR inlet temperature on NOx conversion efficiency. Overall, we conclude that retrofitting urban buses to use low-NO2 SCRT systems is an effective method for delivering NOx and NO2 emissions reduction.

  10. The reaction mechanism for the SCR process on monomer V(5+) sites and the effect of modified Brønsted acidity.

    Science.gov (United States)

    Arnarson, Logi; Falsig, Hanne; Rasmussen, Søren B; Lauritsen, Jeppe V; Moses, Poul Georg

    2016-06-22

    The energetics, structures and activity of a monomeric VO3H/TiO2(001) catalyst are investigated for the selective catalytic reduction (SCR) reaction by the use of density functional theory (DFT). Furthermore we study the influences of a dopant substitute in the TiO2 support and its effects on the known properties of the SCR system such as Brønsted acidity and reducibility of vanadium. We find for the reduction part of the SCR mechanism that it involves two Ti-O-V oxygen sites. One is a hydroxyl possessing Brønsted acidity which contributes to the formation of NH4(+), while the other accepts a proton which charge stabilizes the reduced active site. In the reduction the proton is donated to the latter due to a reaction between NH3 and NO that forms a H2NNO molecule which decomposes into N2(g) and H2O(g). A dopant substitution of 10 different dopants: Si, Ge, Se, Zr, Sn, Te, Hf, V, Mo and W at each of the sites, which participate in the reaction, modifies the energetics and therefore the SCR activity. We find that Brønsted acidity is a descriptor for the SCR activity at low temperatures. Based on this descriptor we find that Zr, Hf and Sn have a positive effect as they decrease the activation energy for the SCR reaction. PMID:27297567

  11. The reaction mechanism for the SCR process on monomer V(5+) sites and the effect of modified Brønsted acidity.

    Science.gov (United States)

    Arnarson, Logi; Falsig, Hanne; Rasmussen, Søren B; Lauritsen, Jeppe V; Moses, Poul Georg

    2016-06-22

    The energetics, structures and activity of a monomeric VO3H/TiO2(001) catalyst are investigated for the selective catalytic reduction (SCR) reaction by the use of density functional theory (DFT). Furthermore we study the influences of a dopant substitute in the TiO2 support and its effects on the known properties of the SCR system such as Brønsted acidity and reducibility of vanadium. We find for the reduction part of the SCR mechanism that it involves two Ti-O-V oxygen sites. One is a hydroxyl possessing Brønsted acidity which contributes to the formation of NH4(+), while the other accepts a proton which charge stabilizes the reduced active site. In the reduction the proton is donated to the latter due to a reaction between NH3 and NO that forms a H2NNO molecule which decomposes into N2(g) and H2O(g). A dopant substitution of 10 different dopants: Si, Ge, Se, Zr, Sn, Te, Hf, V, Mo and W at each of the sites, which participate in the reaction, modifies the energetics and therefore the SCR activity. We find that Brønsted acidity is a descriptor for the SCR activity at low temperatures. Based on this descriptor we find that Zr, Hf and Sn have a positive effect as they decrease the activation energy for the SCR reaction.

  12. Investigation of PCDD/F emissions from mobile source diesel engines: impact of copper zeolite SCR catalysts and exhaust aftertreatment configurations.

    Science.gov (United States)

    Liu, Z Gerald; Wall, John C; Barge, Patrick; Dettmann, Melissa E; Ottinger, Nathan A

    2011-04-01

    This study investigated the impact of copper zeolite selective catalytic reduction (SCR) catalysts and exhaust aftertreatment configurations on the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from mobile source diesel engines. Emissions of PCDD/Fs, reported as the weighted sum of 17 congeners called the toxic equivalency quotient (TEQ), were measured using a modified EPA Method 0023A in the absence and presence of exhaust aftertreatment. Engine-out emissions were measured as a reference, while aftertreatment configurations included various combinations of diesel oxidation catalyst (DOC), diesel particulate filter (DPF), Cu-zeolite SCR, Fe-zeolite SCR, ammonia oxidation catalyst (AMOX), and aqueous urea dosing. In addition, different chlorine concentrations were evaluated. Results showed that all aftertreatment configurations reduced PCDD/F emissions in comparison to the engine-out reference, consistent with reduction mechanisms such as thermal decomposition or combined trapping and hydrogenolysis reported in the literature. Similarly low PCDD/F emissions from the DOC-DPF and the DOC-DPF-SCR configurations indicated that PCDD/F reduction primarily occurred in the DOC-DPF with no noticeable contribution from either the Cu- or Fe-zeolite SCR systems. Furthermore, experiments performed with high chlorine concentration provided no evidence that chlorine content has an impact on the catalytic synthesis of PCDD/Fs for the chlorine levels investigated in this study.

  13. DEVELOPMENT OF IMPROVED CATALYSTS FOR THE SELECTIVE CATALYTIC REDUCTION OF NITROGEN OXIDES WITH HYDROCARBONS

    Energy Technology Data Exchange (ETDEWEB)

    Ates Akyurtlu; Jale F. Akyurtlu

    2003-11-30

    Significant work has been done by the investigators on the cerium oxide-copper oxide based sorbent/catalysts for the combined removal of sulfur and nitrogen oxides from the flue gases of stationary sources. Evaluation of these sorbents as catalysts for the selective reduction of NO{sub x} gave promising results with methane. Since the replacement of ammonia by methane is commercially very attractive, in this project, the effect of promoters on the activity and selectivity of copper oxide/cerium oxide-based catalysts and the reaction mechanism for the SCR with methane was investigated. Unpromoted and promoted catalysts were investigated for their SCR activity with methane in a microreactor setup and also, by the temperature-programmed desorption (TPD) technique. The results from the SCR experiments indicated that manganese is a more effective promoter than the other metals (Rh, Li, K, Na, Zn, and Sn) for the supported copper oxide-ceria catalysts under study. The effectiveness of the promoter increased with the increase in Ce/Cu ratio. Among the catalysts tested, the Cu1Ce3 catalyst promoted with 1 weight % Mn was found to be the best catalyst for the SCR of NO with methane. This catalyst was subjected to long-term testing at the facilities of our industrial partner TDA Research. TDA report indicated that the performance of this catalyst did not deteriorate during 100 hours of operation and the activity and selectivity of the catalyst was not affected by the presence of SO{sub 2}. The conversions obtained by TDA were significantly lower than those obtained at Hampton University due to the transport limitations on the reaction rate in the TDA reactor, in which 1/8th inch pellets were used while the Hampton University reactor contained 250-425-{micro}m catalyst particles. The selected catalyst was also tested at the TDA facilities with high-sulfur heavy oil as the reducing agent. Depending on the heavy oil flow rate, up to 100% NO conversions were obtained. The

  14. Session 6: Active Sites for the Selective Catalytic Reduction of NO with NH{sub 3} or Isobutane over Fe-ZSM-5: A New View onto a Controversial Question

    Energy Technology Data Exchange (ETDEWEB)

    Schwidder, M.; Klementiev, K.; GrUnert, W. [Bochum Ruhr Univ., Lab. of Industrial Chemistry (Germany); Matam, S.K.; Bentrup, U.; Bruckner, A. [Institute of Applied Chemistry Berlin-Adlershof (ACA), Berlin (Germany)

    2004-07-01

    In recent work, we have demonstrated that Fe-ZSM-5 catalysts prepared via CVD of FeCl{sub 3} contain iron species of a broad distribution of nuclearity, from monomeric species up to large oxide crystals. While this distribution is strongly affected by the nature of catalyst pretreatments, the resulting effects on the activity in HC-SCR are small. To elucidate the origin of this effect we have adopted a methodology that includes new spectroscopic techniques capable of differentiating coexisting iron species (UV-Vis, EPR), extends to new preparation routes with the goal of creating as much homogeneity in site structure as possible, and employs in-situ spectroscopic studies (IR, UV-Vis, EPR) to differentiate between catalytically relevant sites and spectators. Given the technological importance of NH{sub 3}-SCR and the likely role of NH{sub 3} as the actual reducing agent in HC-SCR we have included the NH{sub 3} reductant in our research. (authors)

  15. Tuning the catalytic activity of graphene nanosheets for oxygen reduction reaction via size and thickness reduction.

    Science.gov (United States)

    Benson, John; Xu, Qian; Wang, Peng; Shen, Yuting; Sun, Litao; Wang, Tanyuan; Li, Meixian; Papakonstantinou, Pagona

    2014-11-26

    Currently, the fundamental factors that control the oxygen reduction reaction (ORR) activity of graphene itself, in particular, the dependence of the ORR activity on the number of exposed edge sites remain elusive, mainly due to limited synthesis routes of achieving small size graphene. In this work, the synthesis of low oxygen content (graphene nanosheets with lateral dimensions smaller than a few hundred nanometers were achieved using a combination of ionic liquid assisted grinding of high purity graphite coupled with sequential centrifugation. We show for the first time that the graphene nanosheets possessing a plethora of edges exhibited considerably higher electron transfer numbers compared to the thicker graphene nanoplatelets. This enhanced ORR activity was accomplished by successfully exploiting the plethora of edges of the nanosized graphene as well as the efficient electron communication between the active edge sites and the electrode substrate. The graphene nanosheets were characterized by an onset potential of -0.13 V vs Ag/AgCl and a current density of -3.85 mA/cm2 at -1 V, which represent the best ORR performance ever achieved from an undoped carbon based catalyst. This work demonstrates how low oxygen content nanosized graphene synthesized by a simple route can considerably impact the ORR catalytic activity and hence it is of significance in designing and optimizing advanced metal-free ORR electrocatalysts.

  16. NH3-SCR denitration catalyst performance over vanadium-titanium with the addition of Ce and Sb.

    Science.gov (United States)

    Xu, Chi; Liu, Jian; Zhao, Zhen; Yu, Fei; Cheng, Kai; Wei, Yuechang; Duan, Aijun; Jiang, Guiyuan

    2015-05-01

    Selective catalytic reduction technology using NH3 as a reducing agent (NH3-SCR) is an effective control method to remove nitrogen oxides. TiO2-supported vanadium oxide catalysts with different levels of Ce and Sb modification were prepared by an impregnation method and were characterized by X-ray diffractometer (XRD), Brunauer-Emmett-Teller (BET), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), Raman and Hydrogen temperature-programmed reduction (H2-TPR). The catalytic activities of V5CexSby/TiO2 catalysts for denitration were investigated in a fixed bed flow microreactor. The results showed that cerium, vanadium and antimony oxide as the active components were well dispersed on TiO2, and the catalysts exhibited a large number of d-d electronic transitions, which were helpful to strengthen SCR reactivity. The V5CexSby/TiO2 catalysts exhibited a good low temperature NH3-SCR catalytic activity. In the temperature range of 210 to 400°C, the V5CexSby/TiO2 catalysts gave NO conversion rates above 90%. For the best V5Ce35Sb2/TiO2 catalyst, at a reaction temperature of 210°C, the NO conversion rate had already reached 90%. The catalysts had different catalytic activity with different Ce loadings. With the increase of Ce loading, the NO conversion rate also increased.

  17. Low-temperature SCR of NO with NH3 over activated semi-coke composite-supported rare earth oxides

    International Nuclear Information System (INIS)

    The catalysts with different rare earth oxides (La, Ce, Pr and Nd) loaded onto activated semi-coke (ASC) via hydrothermal method are prepared for the selective catalytic reduction (SCR) of NO with NH3 at low temperature (150–300 °C). It is evidenced that CeO2 loaded catalysts present the best performance, and the optimum loading amount of CeO2 is about 10 wt%. Composite catalysts by doping La, Pr and Nd into CeO2 are prepared to obtain further improved catalytic properties. The SCR mechanism is investigated through various characterizations, including XRD, Raman, XPS and FT-IR, the results of which indicate that the oxygen defect plays an important role in SCR process and the doped rare earth elements effectively serve as promoters to increase the concentration of oxygen vacancies. It is also found that the oxygen vacancies in high concentration are favored for the adsorption of O2 and further oxidation of NO, which facilitates a rapid progressing of the following reduction reactions. The SCR process of NO with NH3 at low temperature over the catalysts of ASC composite-supported rare earth oxides mainly follows the Langmuir–Hinshlwood mechanism.

  18. Reductive cyclodimerization of arylmethylidenemalononitriles promoted by samarium and catalytic amount of iodine: facile synthesis of cyclopentene derivatives

    Institute of Scientific and Technical Information of China (English)

    陈珏; 张永敏

    2004-01-01

    Samarium and a catalytic amount of iodine were used to obtain functionalized cyclopentenes by reductive dimerization followed by intramolecular cyclization of 1, 1-dicyanoalkenes under mild conditions.

  19. 焙烧条件对Fe - Mo/ZSM-5催化剂上NO选择性催化还原性能的影响%Effects of calcination conditions on catalytic performance of Fe-Mo/ZSM-5 catalyst for SCR reaction of NO

    Institute of Scientific and Technical Information of China (English)

    王晓丽; 娄晓荣; 黄伟; 李哲

    2011-01-01

    Fe-Mo/ZSM-5 catalyst with to ( Fe): m ( Mo) =1 was prepared by co-impregnation method under different calcination conditions. Their catalytic performance for selective catalytic reduction (SCR) for nitrogen oxides was investigated. The results showed that the calcination conditions had evident influence on the performance of Fe-Mo/ZSM-5 catalyst. The catalyst calcinated at 600 ℃ for 6 h exhibited better performance for SCR of nitrogen oxides;the curve of Nox conversion was shifted to higher temperature with the increase of calcination time and calcination temperature. The catalytic activity of the catalyst calcined at 800 ℃ was dropped obviously. The bulk phase and surface properties of Fe-Mo/ZSM-5 catalyst were also characterized by XRD and BET techniques. The results indicated that the lattice constants and the surface area of Fe-Mo/ZSM-5 catalysts were changed under different calcination conditions. When cal-canation temperature was 800 ℃, the surface area was reduced obviously, which could be the main cause of activity reduction of the catalyst. The residual nitrous species on the catalyst surface after calcination had important influence on the activity of Fe-Mo/ZSM-5 catalyst for the selective catalytic reduction of nitrogen oxides.%采用共浸渍法制备了m(Fe):m(Mo)=1的Fe - Mo/ZSM -5催化剂,并对其在不同焙烧条件所得样品上NO选择性催化还原反应活性进行了测试.结果表明,焙烧条件对Fe - Mo/ZSM -5催化性能影响明显,600℃焙烧6h的样品在低温范围具有较好的催化性能,随着焙烧时间或焙烧温度的增加,其NOx转化率依次向高温方向移动,在800℃焙烧后的样品催化活性明显下降.采用XRD和BET对Fe - Mo/ZSM -5样品的体相结构和表面性能进行了研究.结果表明,不同焙烧条件下Fe - Mo/ZSM -5催化剂的晶胞参数和比表面积产生了差别,特别是焙烧温度达到800℃时,其比表面积显著减小,这可能是导致Fe - Mo/ZSM -5催化性能突

  20. 富氧条件下Co/MOR催化剂上甲烷选择催化还原NO%Selective catalytic reduction of NO by methane over the Co/MOR catalysts in the presence of oxygen

    Institute of Scientific and Technical Information of China (English)

    王虹; 李滨; 卢学斌; 李翠清; 丁福臣; 宋永吉

    2015-01-01

    A series of Co/MOR catalysts were prepared by impregnation method and used in the selective catalytic reduction of nitric oxide with methane ( CH4-SCR) . These catalysts were characterized by XRD, BET, TG-MS, H2-TPR, NH3-TPD and NO-TPD; their performance in the CH4-SCR of NO was investigated. The results showed that cobalt species exist as Co3 O4 spinal in the Co/MOR catalysts;the acidity and redox and NO absorption/desorption ability of the Co/MOR catalysts are changed after the incorporation of cobalt in MOR zeolite, in comparison with pure MOR zeolite. The catalytic performance of Co/MOR is closely related to its redox and NO adsorption/desorption ability, which are dependent on the cobalt loading. The Co ( 10 )/MOR catalyst with a cobalt loading of 10% exhibits high activity in the CH4-SCR of NO; over it the conversion of nitric oxide reaches 54 . 2% at 330℃.%采用浸渍法制备了一系列用于甲烷选择催化还原( CH4-SCR)氮氧化物的 Co/MOR 催化剂。采用 XRD、BET、TG-MS、H2-TPR、NH3-TPD和NO-TPD等手段对催化剂进行表征,并对其在甲烷选择催化还原氮氧化物反应中的活性进行评价。结果表明,钴物种以Co3 O4尖晶石形态存在于Co/MOR催化剂中;与MOR载体相比,引入钴物种后,催化剂的酸性、氧化还原能力和对NO的吸脱附能力均发生了变化。在甲烷选择催化还原氮氧化物反应中,Co/MOR的催化活性与其氧化还原性能和对NO的吸脱附性能直接相关;其中, Co 负载量为10%的 Co (10)/MOR 催化剂的 CH4-SCR 脱硝活性最好,在330℃下NO的转化率达54.2%。

  1. Water Soluble Iron aminoclay for Catalytic Reduction of Nitrophenol

    Directory of Open Access Journals (Sweden)

    S. ANBU ANJUGAM VANDARKUZHALI

    2013-06-01

    Full Text Available Water soluble iron decorated phyllosilicate is synthesized through one pot sol-gel synthesis by a wet chemical method using NaBH4 as reducing agent. The as-synthesized nanocomposite is characterized by powder-XRD and TGA techniques. The morphology of the composite is obtained using HRSEM and HRTEM. The prepared nanocomposite is an efficient catalyst for the reduction of nitrophenol.

  2. In-line localized monitoring of catalyst activity in selective catalytic NO.sub.x reduction systems

    Science.gov (United States)

    Muzio, Lawrence J.; Smith, Randall A.

    2009-12-22

    Localized catalyst activity in an SCR unit for controlling emissions from a boiler, power plant, or any facility that generates NO.sub.x-containing flue gases is monitored by one or more modules that operate on-line without disrupting the normal operation of the facility. Each module is positioned over a designated lateral area of one of the catalyst beds in the SCR unit, and supplies ammonia, urea, or other suitable reductant to the catalyst in the designated area at a rate that produces an excess of the reductant over NO.sub.x on a molar basis through the designated area. Sampling probes upstream and downstream of the designated area draw samples of the gas stream for NO.sub.x analysis, and the catalyst activity is determined from the difference in NO.sub.x levels between the two probes.

  3. EVALUATION OF MERCURY EMISSIONS FROM COAL-FIRED FACILITIES WITH SCR AND FGD SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    J. A. Withum; S.C. Tseng; J. E. Locke

    2004-10-31

    CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP) - wet flue gas desulfurization (FGD) combination or a spray dyer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on Hg speciation and the efficacy of different FGD technologies for Hg capture. This document, the second in a series of topical reports, describes the results and analysis of mercury sampling performed on a 330 MW unit burning a bituminous coal containing 1.0% sulfur. The unit is equipped with a SCR system for NOx control and a spray dryer absorber for SO{sub 2} control followed by a baghouse unit for particulate emissions control. Four sampling tests were performed in March 2003. Flue gas mercury speciation and concentrations were determined at the SCR inlet, air heater outlet (ESP inlet), and at the stack (FGD outlet) using the Ontario Hydro method. Process stream samples for a mercury balance were collected to coincide with the flue gas measurements. Due to mechanical problems with the boiler feed water pumps, the actual gross output was between 195 and 221 MW during the tests. The results showed that the SCR/air heater combination oxidized nearly 95% of the elemental mercury. Mercury removal, on a

  4. Catalytic enantioselective reductions and allylations of prochiral ketones

    CERN Document Server

    Cunningham, A

    2002-01-01

    The use of LiGaH sub 4 in combination with the S,O-chelate 2-hydroxy-2'-mercapto-1,1'-binaphthyl (monothiobinaphthol, MTBH sub 2), forms an active catalyst (2 mol %) for the asymmetric reduction of prochiral ketones, when using catecholborane as the hydride source. This catalyst has successfully been applied to the enantioselective reduction of aryl/n-alkyl ketones, providing the chiral sec-alcohols in yields of 82 - 96% and with enantiomeric excess values of 59 - 93%. Alkyl/methyl ketones are reduced in yields of 72 - 93% and in 46 - 79% enantiomeric excess. Enantioface differentiation is on the basis of the steric requirements of the ketone substituents. The X-ray structure of the pre-catalyst, Li(THF) sub 3 Ga(MTB) sub 2 has been determined and in solution is in equilibrium with a dimeric species of constitution Li sub 2 Ga sub 2 (MTB) sub 4. An indium analogue whose X-ray structure was determined as Li sub 2 (THF) sub 5 lnCI(MTB) sub 2 has also been prepared. The indium- based catalyst does not form an en...

  5. A Comparative Study of N2O Formation during the Selective Catalytic Reduction of NOx with NH3 on Zeolite Supported Cu Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hai-Ying; Wei, Zhehao; Kollar, Marton; Gao, Feng; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

    2015-09-01

    A comparative study was carried out on a small-pore CHA.Cu and a large-pore BEA.Cu zeolite catalyst to understand the lower N2O formation on small-pore zeolite supported Cu catalysts in the selective catalytic reduction (SCR) of NOx with NH3. On both catalysts, the N2O yield increases with an increase in the NO2/NOx ratios of the feed gas, suggesting N2O formation via the decomposition of NH4NO3. Temperature-programmed desorption experiments reveal that NH4NO3 is more stable on CHA.Cu than on BEA.Cu. In situ FTIR spectra following stepwise (NO2 + O2) and (15NO + NH3 + O2) adsorption and reaction, and product distribution analysis using isotope-labelled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH4NO3. Furthermore, CHA.Cu is shown to be considerably less active than BEA.Cu in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH4NO3 on CHA.Cu, and (2) the lower activity for this catalyst to catalyze NO oxidation and the subsequent formation of surface nitrates, likely contribute to the higher SCR selectivity with less N2O formation on this catalyst as compared to BEA.Cu. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH4NO3 on the catalysts.

  6. Synthesis of chitosan supported palladium nanoparticles and its catalytic activity towards 2-nitrophenol reduction

    Science.gov (United States)

    Dhanavel, S.; Nivethaa, E. A. K.; Esther, G.; Narayanan, V.; Stephen, A.

    2016-05-01

    Chitosan supported Palladium nanoparticles were synthesized by a simple cost effective chemical reduction method using NaBH4. The prepared nanocomposite was characterized by X-Ray diffraction analysis, FESEM and Energy dispersive spectroscopy analysis of X-rays (EDAX). The catalytic performance of the nanocomposite was evaluated on the reduction of 2-Nitrophenol to the 2-Amino phenol with rate constant 1.08 × 10-3 S-1 by NaBH4 using Spectrophotometer.

  7. Combined effects Na and SO2 in flue gas on Mn-Ce/TiO2 catalyst for low temperature selective catalytic reduction of NO by NH3 simulated by Na2SO4 doping

    Science.gov (United States)

    Zhou, Aiyi; Yu, Danqing; Yang, Liu; Sheng, Zhongyi

    2016-08-01

    A series of Mn-Ce/TiO2 catalysts were synthesized through an impregnation method and used for low temperature selective catalytic reduction (SCR) of NOx with ammonia (NH3). Na2SO4 was added into the catalyst to simulate the combined effects of alkali metal and SO2 in the flue gas. Experimental results showed that Na2SO4 had strong and fluctuant influence on the activity of Mn-Ce/TiO2, because the effect of Na2SO4 included pore occlusion and sulfation effect simultaneously. When Na2SO4 loading content increased from 0 to 1 wt.%, the SCR activities of Na2SO4-doped catalysts decreased greatly. With further increasing amount of Na2SO4, however, the catalytic activity increased gradually. XRD results showed that Na2SO4 doping could induce the crystallization of MnOx phases, which were also confirmed by TEM and SEM results. BET results showed that the surface areas decreased and a new bimodal mesoporous structure formed gradually with the increasing amount of Na2SO4. XPS results indicated that part of Ce4+ and Mn3+ were transferred to Ce3+ and Mn4+ due to the sulfation after Na2SO4 deposition on the surface of the catalysts. When the doped amounts of Na2SO4 increased, NH3-TPD results showed that the Lewis acid sites decreased and the Brønsted acid sites of Mn-Ce/TiO2 increased quickly, which could be considered as another reason for the observed changes in the catalytic activity. The decreased Mn and Ce atomic concentration, the changes of their oxidative states, and the variation in acidic properties on the surface of Na2SO4-doped catalysts could be the reasons for the fluctuant changes of the catalytic activity.

  8. Performance and mechanism study for low-temperature SCR of NO with propylene in excess oxygen over Pt/TiO2 catalyst.

    Science.gov (United States)

    Zhang, Zhixiang; Chen, Mingxia; Jiang, Zhi; Shangguan, Wenfeng

    2010-01-01

    A 0.5 wt.% Pt/TiO2 catalyst was prepared and used for the low-temperature selective catalytic reduction (SCR) of NO with C3H6 in the presence of excess oxygen. The effects of Pt loading and O2 concentration on Pt/TiO2 catalytic performance for low-temperature SCR were investigated. It was found that optimal Pt loading was 0.5 wt.% and excess O2 favored low-temperature SCR of NOx. The mechanism of low-temperature SCR of NO with C3H6 was investigated with respect to the behavior of adsorbed species over Pt/TiO2 at 150 degrees C using in situ DRIFTS. The results indicated that surface nitrosyl species (Ptdelta(+)-NO and Ti3(+)-NO) and Pt2(+)-CO are main reaction intermediates during the interactions of NO, C3H6 and O2. A simplified NO decomposition mechanism for the low-temperature SCR of NO with C3H6 was proposed.

  9. Effect of water vapor on NH3-NO/NO2 SCR performance of fresh and aged MnOx-NbOx-CeO2 catalysts.

    Science.gov (United States)

    Chen, Lei; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Wu, Zhenwei

    2015-05-01

    A MnOx-NbOx-CeO2 catalyst for low temperature selective catalytic reduction (SCR) of NOx with NH3 was prepared by a sol-gel method, and characterized by NH3-NO/NO2 SCR catalytic activity, NO/NH3 oxidation activity, NOx/NH3 TPD, XRD, BET, H2-TPR and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results indicate that the MnOx-NbOx-CeO2 catalyst shows excellent low temperature NH3-SCR activity in the temperature range of 150-300°C. Water vapor inhibits the low temperature activity of the catalyst in standard SCR due to the inhibition of NOx adsorption. As the NO2 content increases in the feed, water vapor does not affect the activity in NO2 SCR. Meanwhile, water vapor significantly enhances the N2 selectivity of the fresh and the aged catalysts due to its inhibition of the decomposition of NH4NO3 into N2O.

  10. In situ IR studies of Co and Ce doped Mn/TiO2 catalyst for low-temperature selective catalytic reduction of NO with NH3

    Science.gov (United States)

    Qiu, Lu; Pang, Dandan; Zhang, Changliang; Meng, Jiaojiao; Zhu, Rongshu; Ouyang, Feng

    2015-12-01

    The Mn-Co-Ce/TiO2 catalyst was prepared by wet co-impregnation method for selective catalytic reduction of NO by NH3 in the presence of oxygen. The adsorption and co-adsorption of NH3, NO and O2 on catalysts were investigated by in situ FTIR spectroscopy. The results suggested that addition of cobalt and cerium oxides increased the numbers of acid and redox sites. Especially, the cobalt oxide produced lots of Brønsted acid sites, which favor to the adsorption of coordinated NH3 through NH3 migration. Ce addition improved amide ions formation to reach best NO reduction selectivity. A mechanistic pathway over Mn-Co-Ce/TiO2 was proposed. At low-temperature SCR reaction, coordinated NH3 reacted with NO2-, and amide reacted with NO (ad) or NO (g) to form N2. NO2 was related to the formation of nitrite on Co-contained catalysts and the generation of sbnd NH2- on Ce-contained catalysts. At high temperature, the other branch reaction also occurred between the coordinated NH3 and nitrate species, resulting in N2O yield increase.

  11. Integrated Removal of NOx with Carbon Monoxide as Reductant, and Capture of Mercury in a Low Temperature Selective Catalytic and Adsorptive Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Neville Pinto; Panagiotis Smirniotis; Stephen Thiel

    2010-08-31

    Coal will likely continue to be a dominant component of power generation in the foreseeable future. This project addresses the issue of environmental compliance for two important pollutants: NO{sub x} and mercury. Integration of emission control units is in principle possible through a Low Temperature Selective Catalytic and Adsorptive Reactor (LTSCAR) in which NO{sub x} removal is achieved in a traditional SCR mode but at low temperature, and, uniquely, using carbon monoxide as a reductant. The capture of mercury is integrated into the same process unit. Such an arrangement would reduce mercury removal costs significantly, and provide improved control for the ultimate disposal of mercury. The work completed in this project demonstrates that the use of CO as a reductant in LTSCR is technically feasible using supported manganese oxide catalysts, that the simultaneous warm-gas capture of elemental and oxidized mercury is technically feasible using both nanostructured chelating adsorbents and ceria-titania-based materials, and that integrated removal of mercury and NO{sub x} is technically feasible using ceria-titania-based materials.

  12. On the Effect of Preparation Methods of PdCe-MOR Catalysts as NOx CH4-SCR System for Natural Gas Vehicles Application

    Directory of Open Access Journals (Sweden)

    Acácio Nobre Mendes

    2015-10-01

    Full Text Available In the present work, the effect of several parameters involved in the preparation of PdCe-HMOR catalysts active for NOx selective catalytic reduction with methane (NOx CH4-SCR was studied. Results show that the catalytic performance of Pd-HMOR is better when palladium is introduced by ion-exchange, namely at room temperature. It was also shown that Pd loading does not influence the formation of cerium species, namely surface Ce4+ (CeO2 species and CeO2 species in interaction with Pd. However, when Ce is introduced before Pd, more surface CeO2 species are stabilized in the support and less CeO2 become in interaction with Pd, which results in a worse NOx CH4-SCR catalytic performance.

  13. Low temperature selective catalytic reduction of NO by C3H6 over CeOx loaded on AC treated by HNO3

    Institute of Scientific and Technical Information of China (English)

    楚英豪; 尹华强; 张腾腾; 朱晓帆; 郭家秀; 刘勇军; 刘超

    2015-01-01

    The activated carbons from coal were treated by HNO3 (named as NAC) and used as carriers to load 7% Ce (named as Ce(0.07)/NAC) by impregnation method. The physical and chemical properties were investigated by thermogravimetric-differential thermal analysis (TG-DTA), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM) and NH3-temperature programmed desorption (NH3-TPD) and NO-temperature programmed desorption techniques. The catalytic activities of Ce(0.07)/NAC were evaluated for the low temperature selective catalytic reduction (SCR) of NO with C3H6 using temperature-programmed reaction (TP-reaction) in NO, C3H6, O2 and N2 as a balance. The results showed that the specific surface area of Ce(0.07)/NAC was 850.8 m2/g and less than NAC, but Ce oxides could be dispersed highly on the acti-vated carbons. Ce oxides could change acid sites and NO adsorption as well as oxygen-containing functional groups of activated car-bons, and Ce4+ and Ce3+ coexisted in catalysts. The conversion of NO with C3H6 achieved 70% at 280 °C over Ce(0.07)/NAC, but with the increase of O2 concentration, heat accumulation and nonselective combustion were exacerbated, which could cause surface ashing and roughness, resulting in a sharp decrease of catalytic activities. The optimum O2 concentration used in the reaction system was 3% and achieved the high conversion of NO and the widest temperature window. The conversion of NO was closely related to the NO concentrations and [NO]/[C3H6] ratios, and the stoichiometric number was just close to 2:1, but the presence of H2O could af-fect the denitration efficiency of catalyst.

  14. Catalytic Activity of Iridium Dioxide With Different Morphologies for Oxygen Reduction Reaction

    Institute of Scientific and Technical Information of China (English)

    WANG Guangjin; HUANG Fei; XU Tian; YU Yi; CHENG Feng; ZHANG Yue; PAN Mu

    2015-01-01

    Iridium dioxide with different morphologies (nanorod and nanogranular) is successfully prepared by a modiifed sol-gel and Adams methods. The catalytic activity of both samples for oxygen reduction reaction is investigated in an alkaline solution. The electrochemical results show that the catalytic activity of the nanogranular IrO2 sample is superior to that of the nanorod sample due to its higher onset potential for oxygen reduction reaction and higher electrode current density in low potential region. The results of Koutecky-Levich analysis indicate that the oxygen reduction reaction catalyzed by both samples is a mixture transfer pathway. It is dominated by four electron transfer pathway for both samples in high overpotential area, while it is controlled by two electron transfer process for both samples in low overpotential area.

  15. In situ synthesized gold nanoparticles in hydrogels for catalytic reduction of nitroaromatic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiao-Qiong; Wu, Xing-Wen; Huang, Qing [Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Shen, Jiang-Shan, E-mail: jsshen@iue.ac.cn [Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Ningbo Urban Environment Observation and Research Station, Chinese Academy of Sciences, Ningbo 315800 (China); Zhang, Hong-Wu, E-mail: hwzhang@iue.ac.cn [Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China)

    2015-03-15

    Graphical abstract: - Highlights: • In situ preparing Au nanoparticles by photoreduction in chitosan hydrogels was firstly achieved. • In situ photoreduction for creating Au nanoparticles is environmentally friendly and the operation procedure is very simple. • The as-prepared Au nanoparticles have good catalytic performance. • Affording an effective strategy for converting some high explosive compounds such as 2,4,6-tNT to nonexplosive. - Abstract: Developing hydrogel systems featured by catalytic active is of importance to construct highly effective platforms for removing environmental pollutants/hazardous substances or for bio-/chemosensing. Reported herein are our recent finding that Au nanoparticles could be in situ prepared in chitosan-Au{sup III} hydrogel system via photoreduction, and the as-prepared Au nanoparticles could be employed for the catalytic reduction of a series of nitroaromatic compounds by sodium borohydride (NaBH{sub 4}). Experimental conditions of synthesizing Au nanoparticles, including pH, concentration of Au{sup III}, and light irradiation time were systematically investigated. The as-prepared Au nanoparticles were characterized by UV–vis absorption spectroscopy, X-ray diffraction (XRD), transmission and field emission scanning electron microscopy (TEM and FESEM). This is the first example for in situ formed metal nanoparticles in chitosan hydrogel systems via photoreduction. The effectiveness of the as-prepared Au nanoparticles as nanocatalysts was evaluated by employing the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH{sub 4} as a model reaction. The catalytic reduction reaction was found to be very efficient and to follow a pseudo-first-order kinetics. The as-prepared Au nanoparticles demonstrated good reusability and stability. The reduction of a series of other nitroaromatic compounds including highly explosives 2,4,6-trinitrophenol (2,4,6-tNP) and 2,4,6-trinitrotoluene (2,4,6-tNT) was achieved by means

  16. Development of a hydrophilic interaction liquid chromatography-mass spectrometry method for detection and quantification of urea thermal decomposition by-products in emission from diesel engine employing selective catalytic reduction technology.

    Science.gov (United States)

    Yassine, Mahmoud M; Dabek-Zlotorzynska, Ewa; Celo, Valbona

    2012-03-16

    The use of urea based selective catalytic reduction (SCR) technology for the reduction of NOx from the exhaust of diesel-powered vehicles has the potential to emit at least six thermal decomposition by-products, ammonia, and unreacted urea from the tailpipe. These compounds may include: biuret, dicyandiamine, cyanuric acid, ammelide, ammeline and melamine. In the present study, a simple, sensitive and reliable hydrophilic interaction liquid chromatography (HILIC)-electrospray ionization (ESI)/mass spectrometry (MS) method without complex sample pre-treatment was developed for identification and determination of urea decomposition by-products in diesel exhaust. Gradient separation was performed on a SeQuant ZIC-HILIC column with a highly polar zwitterionic stationary phase, and using a mobile phase consisting of acetonitrile (eluent A) and 15 mM ammonium formate (pH 6; eluent B). Detection and quantification were performed using a quadrupole ESI/MS operated simultaneously in negative and positive mode. With 10 μL injection volume, LODs for all target analytes were in the range of 0.2-3 μg/L. The method showed a good inter-day precision of retention time (RSDfilter (DPF) and urea based SCR technology showed the presence of five target analytes with cyanuric acid and ammelide the most abundant compounds in the exhaust.

  17. Research advance in non-thermal plasma induced selective catalytic reduction NOx with low hydrocarbon compounds%低温等离子体诱导低碳烃选择性催化还原NOx研究进展

    Institute of Scientific and Technical Information of China (English)

    苏清发; 刘亚敏; 陈杰; 潘华; 施耀

    2009-01-01

    The emission of nitrogen oxides (NOx) from stationary sources, primarily from power stations, industrial heaters and cogeneration plants, represents a major environmental problem. This paper intends to give a general review over the advances in non-thermal plasma assisted selective catalytic reduction (SCR) of NOx with lower hydrocarbon compounds. In the last decade, the non-thermal plasma induced SCR of nitrogen oxide with low hydrocarbon compounds has received much attention. The different hydrocarbons (≤C3) used in the research are discussed. As we know,methane is more difficultly activated than non-methane hydrocarbons, such as ethylene and propylene etc. The reduction mechanism is also discussed. In addition, aiming at the difficulties existed, the direction for future research is prospected.%综述了近年来低温等离子体诱导低碳烃选择性催化还原NOx的研究进展,详细介绍了难活化的甲烷及较易活化的非甲烷低碳烃气体如乙烯、丙烯及丙烷等的研究现状,探讨了低温等离子体诱导低碳烃选择性催化还原NOx的反应机理,并展望了低温等离子体诱导低碳烃选择性催化还原NOx今后研究方向.

  18. A feasibility study of catalytic reduction method for tritium recovery from tritiated water

    International Nuclear Information System (INIS)

    Feasibility of catalytic reduction method for the application to the tritium recovery process in the fusion fuel cleanup system and the blanket tritium recovery system was studied by experimental work and the thermodynamic analysis. Reduction experiments of H2O vapor with Ar carrier were carried out under the following conditions: temperature; 350 -- 650 K, H2O vapor concentration in feed gas; 103 -- 104 ppm, mole ratio of CO to H2O; 1 -- 10, space velocity; 2 x 102 -- 2 x 104 hr-1. Catalyst was the mixture of CuO, ZnO and Cr2O3, which has been used as the catalyst for the water-gas shift reaction H2O(g) + CO(g) reversible H2(g) + CO2(g). Relations between the conversion factor for H2O vapor and the operating conditions such as temperature, feed composition and feed flow rate were obtained by the experiments. Catalytic reaction rate equation and the rate constants, which can be used for designing a practicable catalytic reduction bed, were also determined by the treatment of the second order reaction. Advantages of the tritium recovery system composed of the reduction bed and palladium diffusers were verified by the present experiments and the study of several tritium recovery systems. Very high recovery ratio will be obtained at low operation temperature by the systems. (author)

  19. SCR in biomass and waste fuelled plants. Benchmarking of Swedish and European plants; SCR i biobraensle- och avfallseldade anlaeggningar. Erfarenheter fraan svenska och europeiska anlaeggningar

    Energy Technology Data Exchange (ETDEWEB)

    Goldschmidt, Barbara; Olsson, Henrik; Lindstroem, Erica

    2010-11-15

    In this report the state-of-art of SCR technology in biomass and waste fired plants is investigated. The aim of the investigation is to answer the question why new Swedish biomass combustion and co-combustion plants often prefer SNCR technology, whilst European waste combustion plants often choose SCR technology. In the report positives and negatives of various types of SCR installations are discussed, high-dust versus tail-end, 'normal' SCR versus low-temperature SCR, etc. Experiences, e g catalyst lifetime, deactivation and maintenance requirement, are discussed. The investigation is based partly on literature, but mainly on interviews with plant owners and with suppliers of SCR installations. The interviewed suppliers are mentioned in the reference list and the interviewed plant owners are mentioned in appendix A and B. The experiences from the Swedish and European plants are quite similar. Tail-end SCR is often operated without serious problems in both biomass and waste fuelled plants. The catalyst lifetimes are as long or even longer than for coal fired plants with high-dust SCR. In waste incineration plants high-dust SCR causes big problems and these plants are almost always equipped with tail-end SCR. In co-combustion boilers, where coal and biomass is co-combusted, high-dust SCR is more common, especially if the boilers were originally coal fired. In plants with both SNCR and high-dust SCR, i.e. slip-SCR, the SCR installation is considered to be much less of a problem. Although the activity loss of the catalyst is as quick as in conventional high-dust SCR, the catalyst can be changed less often. This is due to the fact that installed slip-SCR catalysts often are as large as conventional SCR catalysts, although less NO{sub x} reduction is required after the initial SNCR step. Thus, the catalyst lifetime is prolonged.

  20. Aligned carbon nanotube with electro-catalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

    2010-08-03

    A catalyst for an electro-chemical oxygen reduction reaction (ORR) of a bundle of longitudinally aligned carbon nanotubes having a catalytically active transition metal incorporated longitudinally in said nanotubes. A method of making an electro-chemical catalyst for an oxygen reduction reaction (ORR) having a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes, where a substrate is in a first reaction zone, and a combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into the first reaction zone which is maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is then introduced to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes over the substrate with a catalytically active transition metal incorporated throughout the nanotubes.

  1. SCR during co-combustion of biofuel and recycled fuels; SCR vid sameldning av biobraenslen och returbraenslen

    Energy Technology Data Exchange (ETDEWEB)

    Kling, Aasa; Myringer, Aase [Vattenfall Utveckling AB, Aelvkarleby (Sweden); Eskilsson, David [SP Swedish National Testing and Research Inst., Boraas (Sweden); Aurell, Johanna; Marklund, Stellan [Umeaa Univ. (Sweden). Environmental Chemistry

    2005-06-01

    An increased cost for wood fuels in combination with higher taxes on fossil fuels have led to an increased interest for less costly recycled fuels. Two examples on recycle fuels are demolition wood and refuse energy waste. These fuels are becoming a larger amount of the heat and electricity production in Sweden, not the least since the prohibition against deposition of combustible waste 2002. One of the environmental problems with combustion of bio based fuels are emissions of nitrogen oxides, NO{sub x}. The commercial flue gas cleaning method that gives the highest reduction in NO{sub x} is SCR, selective catalytic reduction, which can reduce more than 90% of the emissions. The planned raise in NO{sub x}-fee from 40 SEK to 50 SEK per kg/NO{sub x} increases the potential for advanced flue gas cleaning techniques. Today there is unique knowledge about SCR in combination with biofuel in Sweden. During cocombustion of recycle wood and wood fuels there is however, besides the deactivating compounds that dominate during wood combustion, mainly alkali, also other potentially poisonous compounds that can deactivate the catalyst. The goal for the study was to investigate the potential and risk with SCR during cocombustion of wood fuels and recycle wood. The project aimed at describing which components in the fuel/flue gas that leads to an eventual increase in deactivation and compare this with previous studies on wood fuels. The project also aimed at in full scale verify reduction of dioxin over a SCR deNO{sub x} catalyst during combustion of wood fuels and recycle wood. The deactivation of a SCR catalyst increases with an increased amount of recycled wood. During co-combustion of bark and 30 % demolition wood the deactivation increased from 30 % loss of catalytic activity during pure wood fuel combustion to 40 % loss of catalytic activity after 1500 hours of exposure. During combustion of 100% refuse energy fuel the loss of activity was 80% after 1500 hours of exposure

  2. Chemically enhanced biological NOx removal from flue gases : nitric oxide and ferric EDTA reduction in BioDeNox reactors

    OpenAIRE

    Maas,, F.

    2005-01-01

    The emission of nitrogen oxides (NOx) to the atmosphere is a major environmental problem. To abate NOx emissions from industrial flue gases, to date, mainly chemical processes like selective catalytic reduction (SCR) are applied. All these processes require high temperatures (>300 °C) and expensive catalysts. Therefore, biological NOx removal techniques using denitrification may represent promising alternatives for the conventional SCR techniques. However, water based biofiltration require...

  3. Research on Catalytic Properties of Palladium Catalyst Prepared by Biological Reduction Method

    Institute of Scientific and Technical Information of China (English)

    Zhang Feng; Fu Jiquan

    2013-01-01

    This paper relates to highly dispersed supported Pd/MWCNTs and Pd/α-Al2O3 catalysts prepared by biological reduction method. The physico-chemical properties and the difference in catalytic activity of Pd catalysts prepared by bio-logical reduction method and chemical method, respectively, were investigated using XRD, TEM and speciifc surface char-acterization methods. The catalytic properties of catalysts were studied through activity evaluation means. The test results showed that the catalysts prepared by biological method were characteristic of small Pd nanoparticle size, good dispersion and low agglomeration, while possessing a high activity and stability in styrene hydrogenation reaction in comparison with catalysts prepared via the chemical method.

  4. Selective catalytic reduction of nitrogen oxides from industrial gases by hydrogen or methane

    International Nuclear Information System (INIS)

    This work deals with the selective catalytic reduction of nitrogen oxides (NOx), contained in the effluents of industrial plants, by hydrogen or methane. The aim is to replace ammonia, used as reducing agent, in the conventional process. The use of others reducing agents such as hydrogen or methane is interesting for different reasons: practical, economical and ecological. The catalyst has to convert selectively NO into N2, in presence of an excess of oxygen, steam and sulfur dioxide. The developed catalyst is constituted by a support such as perovskites, particularly LaCoO3, on which are dispersed noble metals (palladium, platinum). The interaction between the noble metal and the support, generated during the activation of the catalyst, allows to minimize the water and sulfur dioxide inhibitor phenomena on the catalytic performances, particularly in the reduction of NO by hydrogen. (O.M.)

  5. Experiment and CFD simulation of hybrid SNCR-SCR using urea solution in a pilot-scale reactor

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, T.D.B.; Lim, Y.I.; Eom, W.H.; Kim, S.J.; Yoo, K.S. [Hankyong National University, Gyonggi Do (Republic of Korea). Dept. of Chemical Engineering

    2010-10-12

    The urea-based selective non-catalytic reduction (SNCR) experiment and modeling previously presented by Nguyen, Lim, et al. (2008) was extended in this study to the hybrid SNCR-SCR process for nitrogen oxides (NOx) removal in a pilot-scale flow reactor. The 5 wt% urea-water solution was sprayed into the SNCR zone and a commercial V{sub 2}O{sub 5}-WO{sub 3}/TiO{sub 2} catalyst in the form of monolith honeycomb was applied in the SCR zone. The NOx reduction efficiency of 91% was obtained from hybrid SNCR-SCR experiments, while 81% of NOx was reduced from the SNCR zone at 940{sup o}C and a normalized stoichiometric ratio (NSR) of 2.0. The turbulent reacting flow computational fluid dynamics (CFD) model with a nonuniform droplet size distribution was used, incorporating with the reduced seven-step reactions of SNCR and one Arrhenius-type SCR kinetics. The CFD simulation results showed a reasonable agreement with the experimental data in the temperature range between 900 and 980{sup o}C.

  6. Solid-phase reduction of Cr2O3 under chemical catalytic conditions

    Science.gov (United States)

    Simonov, V. K.; Grishin, A. M.

    2016-06-01

    The kinetics of the solid-phase reduction of Cr2O3 with carbon under chemical catalytic action on the reacting system is studied. A significant intensification of the process in the presence of small amounts of potassium and sodium salts is established. The concepts of the catalyst action mechanism are considered and experimentally substantiated. Manufacture of iron-chromium master alloys with a restricted content of carbon can be organized at low temperatures, and they can be used in steelmaking.

  7. Catalytic reduction of NO by methane using a Pt/C/polybenzimidazole/Pt/C fuel cell

    DEFF Research Database (Denmark)

    Petrushina, Irina; Cleemann, Lars Nilausen; Refshauge, Rasmus;

    2007-01-01

    The catalytic NO reduction by methane was studied using a (NO,CH4,Ar),Pt|polybenzimidazole(PBI)–H3PO4|Pt,(H2,Ar) fuel cell at 135 and 165°C. It has been found that, without any reducing agent (like CH4), NO can be electrochemically reduced in the (NO, Ar), Pt/C|PBI–H3PO4|Pt/C, (H2,Ar) fuel cell...

  8. Environmental Technology Verification: Test Report of Mobile Source Selective Catalytic Reduction--Nett Technologies, Inc., BlueMAX 100 version A urea-based selective catalytic reduction technology

    Science.gov (United States)

    Nett Technologies’ BlueMAX 100 version A Urea-Based SCR System utilizes a zeolite catalyst coating on a cordierite honeycomb substrate for heavy-duty diesel nonroad engines for use with commercial ultra-low–sulfur diesel fuel. This environmental technology verification (ETV) repo...

  9. Environmental Technology Verification Test Report of Mobile Source Selective Catalytic Reduction, Johnson Matthey SCCRT, Version 1, Selective Catalytic Reduction Technology with a Catalyzed Continuously Regenerating Trap

    Science.gov (United States)

    The Johnson Matthey SCCRT, v.1 technology is a urea-based SCR system combined with a CCRT filter designed for on-highway light, medium, and heavy heavy-duty diesel, urban and non-urban, bus exhaust gas recirculation (EGR)-or non-EGR-equipped engines for use with commercial ultra-...

  10. Low-temperature SCR of NO with NH{sub 3} over activated semi-coke composite-supported rare earth oxides

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jinping; Yan, Zheng; Liu, Lili; Zhang, Yingyi; Zhang, Zuotai; Wang, Xidong, E-mail: xidong@pku.edu.cn

    2014-08-01

    The catalysts with different rare earth oxides (La, Ce, Pr and Nd) loaded onto activated semi-coke (ASC) via hydrothermal method are prepared for the selective catalytic reduction (SCR) of NO with NH{sub 3} at low temperature (150–300 °C). It is evidenced that CeO{sub 2} loaded catalysts present the best performance, and the optimum loading amount of CeO{sub 2} is about 10 wt%. Composite catalysts by doping La, Pr and Nd into CeO{sub 2} are prepared to obtain further improved catalytic properties. The SCR mechanism is investigated through various characterizations, including XRD, Raman, XPS and FT-IR, the results of which indicate that the oxygen defect plays an important role in SCR process and the doped rare earth elements effectively serve as promoters to increase the concentration of oxygen vacancies. It is also found that the oxygen vacancies in high concentration are favored for the adsorption of O{sub 2} and further oxidation of NO, which facilitates a rapid progressing of the following reduction reactions. The SCR process of NO with NH{sub 3} at low temperature over the catalysts of ASC composite-supported rare earth oxides mainly follows the Langmuir–Hinshlwood mechanism.

  11. Kinetics of Carbothermic Reduction of MnO2 and Catalytic Effect of La2O3

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Kinetics of carbothermic reduction of manganese oxide and the catalytic effect of La2O3 on the reduction have been studied by the measurement of mass loss in N2 atmosphere at different temperatures and followed by SEM analysis. It is concluded that the kinetics of carbothermic reduction of manganese oxide is divided into three stages: gas diffusion controlling stage, carbon gasification controlling stage and solid state diffusion controlling stage. La2O3 has catalytic effect on the reduction. The catalytic effect of La2O3 increases with the added amount of La2O3. SEM analysis shows that the catalytic mechanism is that Laa2O3 promotes the transfer of oxygen ions so that carbon gasifying is catalyzed and thus carbothermic reduction of MnO3 is catalyzed.

  12. Catalytic reduction of NO by methane using a Pt/C/polybenzimidazole/Pt/C fuel cell

    OpenAIRE

    Petrushina, Irina; Cleemann, Lars Nilausen; Refshauge, Rasmus; Bjerrum, Niels; Bandur, Viktor

    2007-01-01

    The catalytic NO reduction by methane was studied using a (NO,CH4,Ar),Pt|polybenzimidazole(PBI)–H3PO4|Pt,(H2,Ar) fuel cell at 135 and 165°C. It has been found that, without any reducing agent (like CH4), NO can be electrochemically reduced in the (NO, Ar), Pt/C|PBI–H3PO4|Pt/C, (H2,Ar) fuel cell with participation of H+ or electrochemically produced hydrogen. When added, methane partially suppresses the electrochemical reduction of NO. Methane outlet concentration monitoring has shown the CH4 ...

  13. Urea SCR systems in focus. New challenges in the development of exhaust systems; Harnstoff-SCR-Systeme im Fokus. Neue Herausforderungen bei der Entwicklung von Abgasanlagen

    Energy Technology Data Exchange (ETDEWEB)

    Calvo Zueco, S.; Neumann, F.; Oesterle, J.J.; Rudelt, J.; Toebben, H. [J. Eberspaecher GmbH und Co.KG, Esslingen (Germany); Halbei, J. [Audi AG (Germany)

    2007-09-15

    One of the main thrusts of development when it comes to exhaust systems with integrated SCR technology for cars and commercial vehicles lies in the area of urea processing before the SCR catalytic converter. In contrast to conventional exhaust systems with single-phase gas flow, the complex processes in this area call both for new development methods and new components in the exhaust system. For the SCR applications, Eberspaecher has developed various mixers which significantly shorten the necessary mixing section and in some cases actually make possible the constructive use of SCR technology. (orig.)

  14. The selective catalytic reduction of NO with NH3 over a novel Ce-Sn-Ti mixed oxides catalyst: Promotional effect of SnO2

    Science.gov (United States)

    Yu, Ming'e.; Li, Caiting; Zeng, Guangming; Zhou, Yang; Zhang, Xunan; Xie, Yin'e.

    2015-07-01

    A series of novel catalysts (CexSny) for the selective catalytic reduction of NO by NH3 were prepared by the inverse co-precipitation method. The aim of this novel design was to improve the NO removal efficiency of CeTi by the introduction of SnO2. It was found that the Ce-Sn-Ti catalyst was much more active than Ce-Ti and the best Ce:Sn molar ratio was 2:1. Ce2Sn1 possessed a satisfied NO removal efficiency at low temperature (160-280 °C), while over 90% NO removal efficiency maintained in the temperature range of 280-400 °C at the gas hourly space velocity (GHSV) of 50,000 h-1. Besides, Ce2Sn1 kept a stable NO removal efficiency within a wide range of GHSV and a long period of reacting time. Meanwhile, Ce2Sn1 exhibited remarkable resistance to both respectively and simultaneously H2O and SO2 poisoning due to the introduction of SnO2. The promotional effect of SnO2 was studied by N2 adsorption-desorption, X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reduction (H2-TPR) for detail information. The characterization results revealed that the excellent catalytic performance of Ce2Sn1 was associated with the higher specific surface area, larger pore volume and poorer crystallization. Besides, the introduction of SnO2 could result in not only greater conversion of Ce4+ to Ce3+ but also the increase amount of chemisorbed oxygen, which are beneficial to improve the SCR activity. More importantly, a novel peak appearing at lower temperatures through the new redox equilibrium of 2Ce4+ + Sn2+ ↔ 2Ce3+ + Sn4+ and higher total H2 consumption can be obtained by the addition of SnO2. Finally, the possible reaction mechanism of the selective catalytic reduction over Ce2Sn1 was also proposed.

  15. EVALUATION OF MERCURY EMISSIONS FROM COAL-FIRED FACILITIES WITH SCR AND FGD SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    J.A. Withum; S.C. Tseng; J.E. Locke

    2005-11-01

    CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)--wet flue gas desulfurization (FGD) combination or a spray dryer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the seventh in a series of topical reports, describes the results and analysis of mercury sampling performed on a 1,300 MW unit burning a bituminous coal containing three percent sulfur. The unit was equipped with an ESP and a limestone-based wet FGD to control particulate and SO2 emissions, respectively. At the time of sampling an SCR was not installed on this unit. Four sampling tests were performed in September 2003. Flue gas mercury speciation and concentrations were determined at the ESP outlet (FGD inlet), and at the stack (FGD outlet) using the Ontario Hydro method. Process stream samples for a mercury balance were collected to coincide with the flue gas measurements. The results show that the FGD inlet flue gas oxidized:elemental mercury ratio was roughly 2:1, with 66% oxidized mercury and 34% elemental mercury. Mercury removal, on a coal

  16. Selective catalytic reduction of nitric oxide by ammonia over Cu-exchanged Cuban natural zeolites

    International Nuclear Information System (INIS)

    The catalytic selective reduction of NO over Cu-exchanged natural zeolites (mordenite (MP) and clinoptilolite (HC)) from Cuba using NH3 as reducing agent and in the presence of excess oxygen was studied. Cu(II)-exchanged zeolites are very active catalysts, with conversions of NO of 95%, a high selectivity to N2 at low temperatures, and exhibiting good water tolerance. The chemical state of the Cu(II) in exchanged zeolites was characterized by H2-TPR and XPS. Cu(II)-exchanged clinoptilolite underwent a severe deactivation in the presence of SO2. However, Cu(II)-exchanged mordenite not only maintained its catalytic activity, but even showed a slight improvement after 20h of reaction in the presence of 100ppm of SO2

  17. Communication: Towards catalytic nitric oxide reduction via oligomerization on boron doped graphene

    Science.gov (United States)

    Cantatore, Valentina; Panas, Itai

    2016-04-01

    We use density functional theory to describe a novel way for metal free catalytic reduction of nitric oxide NO utilizing boron doped graphene. The present study is based on the observation that boron doped graphene and O—N=N—O- act as Lewis acid-base pair allowing the graphene surface to act as a catalyst. The process implies electron assisted N=N bond formation prior to N—O dissociation. Two N2 + O2 product channels, one of which favoring N2O formation, are envisaged as outcome of the catalytic process. Besides, we show also that the N2 + O2 formation pathways are contrasted by a side reaction that brings to N3O3- formation and decomposition into N2O + NO2-.

  18. Low temperature SCR of NO with catalysts prepared by modified ACF loading Mn and Ce: effects of modification method.

    Science.gov (United States)

    Li, Ping; Lu, Pei; Zhai, Yunbo; Li, Caiting; Chen, Ting; Qing, Renpeng; Zhang, Wei

    2015-01-01

    Achievement of a higher NOx conversion ratio in selective catalytic reduction (SCR) at low temperature is challenging. In this work, pure activated carbon fibres (ACFs) were modified with different ratios of H2O (g), NaOH, CO2 and HNO3, respectively (named as modified ACF). The chemical and physical properties of modified ACFs were identified by Brunauer-Emmett-Teller, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy methods. The NOx conversion ratio of ACF was improved from 56.1% to 82.4% at 80°C after modification with 30% (mass ratio) NaOH. These modified ACFs were further loaded with the mixture of MnO2 and CeO2 in the form of metal salt solutions (named as Mn0.5Ce0.5O2/modified ACF). The NOx conversion ratio of 30% SHACF remained similar at 80°C but was increased from 60.0% to 98.5% at 360°C after loading with Mn and Ce, which showed the best performance in SCR of NOx at low temperature. It could be seen that ACF delivered higher performance in low temperature SCR after being modified with the aforementioned reactants and further loading with metals. Based on chemical and physical characterization and the performance of the catalysts, the reasons for different performances of these catalysts in low temperature SCR are discussed.

  19. Gaseous emissions from a heavy-duty engine equipped with SCR aftertreatment system and fuelled with diesel and biodiesel: assessment of pollutant dispersion and health risk.

    Science.gov (United States)

    Tadano, Yara S; Borillo, Guilherme C; Godoi, Ana Flávia L; Cichon, Amanda; Silva, Thiago O B; Valebona, Fábio B; Errera, Marcelo R; Penteado Neto, Renato A; Rempel, Dennis; Martin, Lucas; Yamamoto, Carlos I; Godoi, Ricardo H M

    2014-12-01

    The changes in the composition of fuels in combination with selective catalytic reduction (SCR) emission control systems bring new insights into the emission of gaseous and particulate pollutants. The major goal of our study was to quantify NOx, NO, NO2, NH3 and N2O emissions from a four-cylinder diesel engine operated with diesel and a blend of 20% soybean biodiesel. Exhaust fume samples were collected from bench dynamometer tests using a heavy-duty diesel engine equipped with SCR. The target gases were quantified by means of Fourier transform infrared spectrometry (FTIR). The use of biodiesel blend presented lower concentrations in the exhaust fumes than using ultra-low sulfur diesel. NOx and NO concentrations were 68% to 93% lower in all experiments using SCR, when compared to no exhaust aftertreatment. All fuels increased NH3 and N2O emission due to SCR, a precursor secondary aerosol, and major greenhouse gas, respectively. An AERMOD dispersion model analysis was performed on each compound results for the City of Curitiba, assumed to have a bus fleet equipped with diesel engines and SCR system, in winter and summer seasons. The health risks of the target gases were assessed using the Risk Assessment Information System For 1-h exposure of NH3, considering the use of low sulfur diesel in buses equipped with SCR, the results indicated low risk to develop a chronic non-cancer disease. The NOx and NO emissions were the lowest when SCR was used; however, it yielded the highest NH3 concentration. The current results have paramount importance, mainly for countries that have not yet adopted the Euro V emission standards like China, India, Australia, or Russia, as well as those already adopting it. These findings are equally important for government agencies to alert the need of improvements in aftertreatment technologies to reduce pollutants emissions.

  20. Selective catalytic reduction of sulfur dioxide to elemental sulfur. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W.; Flytzani-Stephanopoulos, M.; Sarofim, A.F.

    1995-06-01

    This project has investigated new metal oxide catalysts for the single stage selective reduction of SO{sub 2} to elemental sulfur by a reductant, such as CO. Significant progress in catalyst development has been made during the course of the project. We have found that fluorite oxides, CeO{sub 2} and ZrO{sub 2}, and rare earth zirconates such as Gd{sub 2}Zr{sub 2}O{sub 7} are active and stable catalysts for reduction Of SO{sub 2} by CO. More than 95% sulfur yield was achieved at reaction temperatures about 450{degrees}C or higher with the feed gas of stoichiometric composition. Reaction of SO{sub 2} and CO over these catalysts demonstrated a strong correlation of catalytic activity with the catalyst oxygen mobility. Furthermore, the catalytic activity and resistance to H{sub 2}O and CO{sub 2} poisoning of these catalysts were significantly enhanced by adding small amounts of transition metals, such as Co, Ni, Co, etc. The resulting transition metal-fluorite oxide composite catalyst has superior activity and stability, and shows promise in long use for the development of a greatly simplified single-step sulfur recovery process to treat variable and dilute SO{sub 2} concentration gas streams. Among various active composite catalyst systems the Cu-CeO{sub 2} system has been extensively studied. XRD, XPS, and STEM analyses of the used Cu-CeO{sub 2} catalyst found that the fluorite crystal structure of ceria was stable at the present reaction conditions, small amounts of copper was dispersed and stabilized on the ceria matrix, and excess copper oxide particles formed copper sulfide crystals of little contribution to catalytic activity. A working catalyst consisted of partially sulfated cerium oxide surface and partially sulfided copper clusters. The overall reaction kinetics were approximately represented by a first order equation.

  1. Study of tritium labelling by solid-state catalytic reductive dehalogenation

    Energy Technology Data Exchange (ETDEWEB)

    Filikov, A.V.; Myasoedov, N.F. (AN SSSR, Moscow. Inst. Molekulyarnoj Genetiki)

    1984-04-02

    A reaction mechanism is proposed for tritium labelling by the solid-state catalytic reductive dehalogenation (SCRD) method based on hydrogen spillover. A model system (palladium membrane with a layer of the original organic compound) is used for a kinetic study of the debromination of 5-bromouracil and the isotope exchange of ..cap alpha..-alanine at pressure of 0.07-20 kPa. A kinetic model is considered for the spillover stoppage due to the contamination of penetration centres by the reaction product. Other possible causes of the spillover stoppage are discussed. 6 refs.; 3 figs.

  2. Aromaticity as stabilizing element in the bidentate activation for the catalytic reduction of carbon dioxide.

    Science.gov (United States)

    Lu, Zhenpin; Hausmann, Heike; Becker, Sabine; Wegner, Hermann A

    2015-04-29

    A new transition-metal-free mode for the catalytic reduction of carbon dioxide via bidentate interaction has been developed. In the presence of Li2[1,2-C6H4(BH3)2], CO2 can be selectively transformed to either methane or methanol, depending on the reducing agent. The bidentate nature of binding is supported by X-ray analysis of an intermediate analogue, which experiences special stabilization due to aromatic character in the bidentate interaction. Kinetic studies revealed a first-order reaction rate. The transformation can be conducted without any solvent. PMID:25871326

  3. Isolated metal active site concentration and stability control catalytic CO2 reduction selectivity.

    Science.gov (United States)

    Matsubu, John C; Yang, Vanessa N; Christopher, Phillip

    2015-03-01

    CO2 reduction by H2 on heterogeneous catalysts is an important class of reactions that has been studied for decades. However, atomic scale details of structure-function relationships are still poorly understood. Particularly, it has been suggested that metal particle size plays a unique role in controlling the stability of CO2 hydrogenation catalysts and the distribution of active sites, which dictates reactivity and selectivity. These studies often have not considered the possible role of isolated metal active sites in the observed dependences. Here, we utilize probe molecule diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with known site-specific extinction coefficients to quantify the fraction of Rh sites residing as atomically dispersed isolated sites (Rhiso), as well as Rh sites on the surface of Rh nanoparticles (RhNP) for a series of TiO2 supported Rh catalysts. Strong correlations were observed between the catalytic reverse water gas shift turn over frequency (TOF) and the fraction of Rhiso sites and between catalytic methanation TOF and the fraction of RhNP sites. Furthermore, it was observed that reaction condition-induced disintegration of Rh nanoparticles, forming Rhiso active sites, controls the changing reactivity with time on stream. This work demonstrates that isolated atoms and nanoparticles of the same metal on the same support can exhibit uniquely different catalytic selectivity in competing parallel reaction pathways and that disintegration of nanoparticles under reaction conditions can play a significant role in controlling stability. PMID:25671686

  4. Low-temperature SCR of NOx with NH3 over Nomex rejects-based activated carbon fibre composite-supported manganese oxides. Part 1. Effect of pre-conditioning of the carbonaceous support

    International Nuclear Information System (INIS)

    Nomex rejects-based activated carbon fibre composites, recently developed at our laboratory, were tested as catalytic supports for the low-temperature selective catalytic reduction (SCR) of nitric oxide with ammonia. Impregnation of the support was performed by equilibrium adsorption of a diluted aqueous solution of manganese acetate. Prior to impregnation, different pre-conditioning procedures of the carbonaceous support were investigated. These comprised steam activation and oxidation with air and different liquids. The modified supports were characterised by different techniques and the impregnated catalysts were tested for SCR of NO at 150C. The best catalytic results were achieved after support activation at 20wt.% (SBET∼1000m2g-1) and oxidation with nitric acid at 90C for 1-2h

  5. Combination of biodiesel-ethanol-diesel fuel blend and SCR catalyst assembly to reduce emissions from a heavy-duty diesel engine.

    Science.gov (United States)

    Shi, Xiaoyan; Yu, Yunbo; He, Hong; Shuai, Shijin; Dong, Hongyi; Li, Rulong

    2008-01-01

    In this study, the efforts to reduce NOx and particulate matter (PM) emissions from a diesel engine using both ethanol-selective catalytic reduction (SCR) of NOx over an Ag/Al2O3 catalyst and a biodiesel-ethanol-diesel fuel blend (BE-diesel) on an engine bench test are discussed. Compared with diesel fuel, use of BE-diesel increased PM emissions by 14% due to the increase in the soluble organic fraction (SOF) of PM, but it greatly reduced the Bosch smoke number by 60%-80% according to the results from 13-mode test of European Stationary Cycle (ESC) test. The SCR catalyst was effective in NOx reduction by ethanol, and the NOx conversion was approximately 73%. Total hydrocarbons (THC) and CO emissions increased significantly during the SCR of NOx process. Two diesel oxidation catalyst (DOC) assemblies were used after Ag/Al2O3 converter to remove CO and HC. Different oxidation catalyst showed opposite effect on PM emission. The PM composition analysis revealed that the net effect of oxidation catalyst on total PM was an integrative effect on SOF reduction and sulfate formation of PM. The engine bench test results indicated that the combination of BE-diesel and a SCR catalyst assembly could provide benefits for NOx and PM emissions control even without using diesel particle filters (DPFs).

  6. Technical presentation of SCR

    CERN Multimedia

    FI Department

    2008-01-01

    SCR Société des Composants Record, Montierchaume, France Monday 20 October 2008 from 9:45 to 12:00 – Room A Main Building (Bldg. 61/1-017) http://www.scr.fr SCR develops, manufactures and markets plastic dielectric capacitors (polypropylene, polyester, Teflon) for use in various applications: audio amplifiers, high-end loudspeakers, fans and extractors (multi-capacitance capacitors), pulsed lasers, flash lamps, defibrillators, beacons, power supplies, converters for rail traction drives, railway signalling devices, voltage dividers and multipliers, high voltage laboratories, etc. The company is renowned for its precision wire-wound resistors for use in power electronics and consumer electronics marketed under the SETA brand name. SCR is also experienced in the design and production of electronic circuits for various applications, such as speed variators for mono and three-phase motors, dimmers, passive filters for audio speakers, etc. Contact : M. Urs V. Rölli, e-mail: mailto:info@technictrade.ch.

  7. Catalytic Reductive Degradation of Methyl Orange Using Air Resilient Copper Nanostructures

    Directory of Open Access Journals (Sweden)

    Razium Ali Soomro

    2015-01-01

    Full Text Available The study describes the application of oxidation resistant copper nanostructures as an efficient heterogeneous catalyst for the treatment of organic dye containing waste waters. Copper nanostructures were synthesized in an aqueous environment using modified surfactant assisted chemical reduction route. The synthesized nanostructures have been characterized by UV-Vis, Fourier transform infrared spectroscopy FTIR spectroscopy, Atomic force microscopy (AFM, Scanning Electron Microscopy (SEM, and X-ray diffractometry (XRD. These surfactant capped Cu nanostructures have been used as a heterogeneous catalyst for the comparative reductive degradation of methyl orange (MO in the presence of sodium borohydride (NaBH4 used as a potential reductant. Copper nanoparticles (Cu NPs were found to be more efficient compared to copper nanorods (Cu NRds with the degradation reaction obeying pseudofirst order reaction kinetics. Shape dependent catalytic efficiency was further evaluated from activation energy (EA of reductive degradation reaction. The more efficient Cu NPs were further employed for reductive degradation of real waste water samples containing dyes collected from the drain of different local textile industries situated in Hyderabad region, Pakistan.

  8. Poly(N-isopropylacrylamide-co-methacrylic acid microgel stabilized copper nanoparticles for catalytic reduction of nitrobenzene

    Directory of Open Access Journals (Sweden)

    Farooqi Zahoor H.

    2015-09-01

    Full Text Available Poly(N-isopropylacrylamide-co-methacrylic acid microgels [p(NIPAM-co-MAAc] were synthesized by precipitation polymerization of N-isopropylacrylamide and methacrylic acid in aqueous medium. These microgels were characterized by dynamic light scattering and Fourier transform infrared spectroscopy. These microgels were used as micro-reactors for in situ synthesis of copper nanoparticles using sodium borohydride (NaBH4 as reducing agent. The hybrid microgels were used as catalysts for the reduction of nitrobenzene in aqueous media. The reaction was performed with different concentrations of cat­alyst and reducing agent. A linear relationship was found between apparent rate constant (kapp and amount of catalyst. When the amount of catalyst was increased from 0.13 to 0.76 mg/mL then kapp was increased from 0.03 to 0.14 min-1. Activation parameters were also determined by performing reaction at two different temperatures. The catalytic process has been discussed in terms of energy of activation, enthalpy of activation and entropy of activation. The synthesized particles were found to be stable even after 14 weeks and showed catalytic activity for the reduction of nitrobenzene.

  9. On reasons of different catalytic activity of 4B-6B subgroup metallocenedichlorides in carbon monoxide amalgam reduction

    International Nuclear Information System (INIS)

    A study was made on catalytic activity of metallocenedichlorides of 4B-6B subgroup elements (Ti, Nb, Mo, W) in carbon monoxide amalgam reduction in THP and DMFA medium. It is shown that the difference in catalytic activity of these elements is conditioned by thermodynamic factors, which dictate impossibility of amalgam reduction of catalyst-substrate complex (4th subgroup), as well as by the difference in stability of corresponding metallocenes (5B and 6B subgroups). Amalgam reduction of CO bounded in complex with metallocene proceeds under conditions of the first electron transfer opposite to potential gradient

  10. Selective catalytic reduction of NO with NH3 over V2O5 supported on TiO2 and Al2O3: A comparative study

    Science.gov (United States)

    Huang, Xianming; Zhang, Shule; Chen, Huinan; Zhong, Qin

    2015-10-01

    This study aimed at investigating the interaction of V2O5 species with TiO2 and Al2O3 supports to understand the effect of supports on SCR reaction. Analysis by XRD, BET, UV-vis, and DFT theoretical calculations, XPS, EPR and in situ DRIFT showed that the two kinds of supports could interact with V2O5. The interaction of electron excitation and charge transfer of supports to V2O5 species was important to the formation of the reduced V2O5. These aspects increased the formation of superoxide ions that could improve the NO oxidation over V2O5/TiO2. It was responsible for the higher SCR catalytic activity of V2O5/TiO2 than V2O5/Al2O3.

  11. Ti or Sn doping as a way to increase activity and sulfur tolerance of Mn/CeO2 catalyst for low temperature NH3 selective catalytic reduction of NO

    Science.gov (United States)

    Xiong, Yan; Tang, Changjin; Dong, Lin

    2015-04-01

    Mn/CeO2 catalysts modified by doping of Ti or Sn were investigated for low temperature selective catalytic reduction (SCR) of NO by NH3 with the aim of studying the effects of Ti, Sn doping on the catalytic performance. Ceria-based solid solutions (Ce0.8Ti0.2O2 and Ce0.8Sn0.2O2) were synthesized via inverse co-precipitation, and used as supports to prepare MnOx/Ce0.8M0.2O2 (M =Ti4+, Sn4+) catalysts through wetness impregnation method. The results showed that doping of Ti or Sn to the CeO2 support increase the NO removal efficiency. A NO conversion of more than 90 % was obtained over the Mn/CeTi catalyst at the temperature window of 175 ~ 300 °C under a gas hourly space velocity (GHSV) of 60,000 mL•g-1•h-1. Catalysts modified by Ti and Sn were also found to obtain higher SO2 resistance than Mn/CeO2 catalyst. More than 90% NO conversion and 95% N2 selectivity could be provided by Mn/CeTi catalyst in the presence of 100 ppm SO2 at 250 °C for 10 h. A series of characterization techniques, namely XRD, BET, H2-TPR, XPS, NH3-TPD and in situ DRIFTS were used to elucidate the structure and surface properties of the obtained supports and catalysts. The results indicate that doping of Ti or Sn brings about catalysts with favorable properties such as higher BET surface area, better oxygen storage capacity and stronger surface acidity. The relative amount of Mn4+, Ce3+, adsorbed oxygen species and oxygen vacancies on the surface of catalysts are in the order of Mn/CeTi>Mn/CeSn>Mn/CeO2, which is thought to make positive a contribution to the low-temperature SCR activity. The promoted SCR activity is considered as well to be related to the dual redox cycles in Mn/CeTi (Mn4+ + Ce3+ ↔ Mn3+ + Ce4+, Ce4+ + Ti3+ ↔ Ce3+ + Ti4+) and Mn/CeSn (Mn4+ + Ce3+ ↔ Mn3+ + Ce4+, Ce4+ + Sn2+ ↔ Ce3+ + Sn4+ ) catalysts.

  12. Combination of Ag/Al2O3 and Fe-BEA for High-Activity Catalyst System for H2-Assisted NH3-SCR of NO x for Light-Duty Diesel Car Applications

    DEFF Research Database (Denmark)

    Fogel, S.; Doronkin, D. E.; Høj, J. W.;

    2013-01-01

    Low-temperature active Ag/Al2O3 and high-temperature active Fe-BEA zeolite were combined and tested for H2-assisted NH3-selective catalytic reduction (SCR) of NO x . The catalysts were either washcoated onto separate monoliths that were placed up- or downstream of each other (dual-brick layout......-BEA through the “fast”-SCR reaction when Fe-BEA was placed downstream or as inner layer. When no H2, which is needed for the SCR reaction over Ag/Al2O3, was added, the dual-layer layout was preferred. The shorter diffusion distance between the layers is a probable explanation....

  13. Selective catalytic reduction of NOx by hydrocarbons over Fe/ZSM5 prepared by sublimation of FeCl3

    OpenAIRE

    Battiston, A.A.

    2003-01-01

    Selective Catalytic Reduction of NOx by Hydrocarbons over Fe/ZSM5 Prepared by Sublimation of FeCl3. Characterization and Catalysis Nitrogen oxides (NOx) are unwanted by-products of combustion. They are generated primarily from motor vehicles and stationary sources, like power stations and industrial heaters. New catalytic materials are constantly developed in order to improve the efficiency of the cleaning-up technologies for NOx. With this respect an important breakthrough has recently been ...

  14. Effect of process parameters and injector position on the efficiency of NOx reduction by selective non catalytic reduction technique

    International Nuclear Information System (INIS)

    An experimental investigation has been performed to study the effect of atomizer pressure dilution of the reducing reagent and the injector position on the efficiency or the NOx reduction by a selective non-catalytic reduction technique using urea as a reducing agent. Experiments were performed with a flow reactor in which flue gas was generated by the combustion of methane in air at stoichiometric amount of oxygen and the desired levels of initial NOx (400-450 ppm) were achieved by doping the flame with ammonia. The work was directed to investigate the effect of atomizer pressure, dilution of urea reagent and the injector position. The atomizer pressure was varied from 1 to 3bar and 20-25% increase in efficiency was observed by decreasing the pressure. Effect of dilution of urea solution was investigated by varying the strength of the solution from the 8 to 32% and 40-45% increase in the efficiency was observed. Effects of injector position was investigated by injecting the urea solution both in co current and counter current direction of the flue gases and 20-25% increase in the efficiency was observed in counter current direction. (author)

  15. Characterization and performance of Pt/SBA-15 for low-temperature SCR of NO by C3H6.

    Science.gov (United States)

    Liu, Xinyong; Jiang, Zhi; Chen, Mingxia; Shi, Jianwei; Shangguan, Wenfeng; Teraoka, Yasutake

    2013-05-01

    Pt supported on mesoporous silica SBA-15 was investigated as a catalyst for low temperature selective catalytic reduction (SCR) of NO by C3H6 in the presence of excess oxygen. The prepared catalysts were characterized by means of XRD, BET surface area, TEM, NO-TPD, NO/C3H6-TPO, NH3-TPD, XPS and 27Al MAS NMR. The effects of Pt loading amount, O2/C3H6 concentration, and incorporation of Al into SBA-15 have been studied. It was found that the removal efficiency increased significantly after Pt loading, but an optimal loading amount was observed. In particular, under an atmosphere of 150 ppm NO, 150 ppm C3H6, and 18 vol.% O2, 0.5% Pt/SBA-15 showed remarkably high catalytic performance giving 80.1% NOx reduction and 87.04% C3H6 conversion simultaneously at 140 degrees C. The enhanced SCR activity of Pt/SBA-15 is associated with its outstanding oxidation activities of NO to NO2 and C3H6 to CO2 in low temperature range. The research results also suggested that higher concentration of O2 and higher concentration of C3H6 favored NO removal. The incorporation of Al into SBA-15 improved catalytic performance, which could be ascribed to the enhancement of catalyst surface acidity caused by tetrahedrally coordinated AlO4. Moreover, the catalysts could be easily reused and possessed good stability.

  16. Designed copper-amine complex as an efficient template for one-pot synthesis of Cu-SSZ-13 zeolite with excellent activity for selective catalytic reduction of NOx by NH3.

    Science.gov (United States)

    Ren, Limin; Zhu, Longfeng; Yang, Chengguang; Chen, Yanmei; Sun, Qi; Zhang, Haiyan; Li, Caijin; Nawaz, Faisal; Meng, Xiangju; Xiao, Feng-Shou

    2011-09-21

    Low-cost copper-amine complex was rationally designed to be a novel template for one-pot synthesis of Cu-SSZ-13 zeolites. Proper confirmation and appropriate size make this complex fit well with CHA cages as an efficient template. The products exhibit superior catalytic performance on NH(3)-SCR reaction. PMID:21625721

  17. Selective catalytic reduction of NO and NO{sub 2} at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, M.; Madia, G.; Elsener, M.

    2001-03-01

    A feed gas containing both NO and NO{sub 2} can react with NH{sub 3} according to two different reaction pathways at low temperatures: The fast SCR reaction has a positive and the ammonium nitrate reaction has a negative temperature coefficient. The deposition of ammonium nitrate in the pores of the catalyst may lead to its temporary deactivation. (author)

  18. SCR系统对公交车NOX排放降低效果的研究%A Research on the NO X Reduction Effects of SCR Systems in City Buses

    Institute of Scientific and Technical Information of China (English)

    郭佳栋; 葛蕴珊; 郝利君; 谭建伟; 彭子航; 张传桢

    2015-01-01

    使用便携排放测试系统测试了3辆带有SCR系统的公交车在实际运行条件下的NOX排放,对比喷射和不喷射尿素两种情况下的NOX排放因子,计算了SCR系统对NOX的降低率。结果表明:国Ⅳ柴油车由于其排气温度低,催化剂体积小,SCR系统对NOX的降低率最低,只当车速高于30 km/h以后才能逐步显现出催化效果,NOX平均降低率只有10%;国Ⅴ天然气车SCR系统对NOX 的降低率最高,它在低速时排气温度就很高,且NOX排放中NO2的比例较高,使其SCR系统对NOX 的降低率基本上不随车速而变化,NOX 平均降低率达85%;国V柴油车介乎两者之间,使其SCR系统对NOX 的降低率约为70%。至于NOX+HC排放,则是国V柴油车最低,国IV柴油车最高,国V天然气车由于其甲烷的排放量很高,使其NOX+HC排放接近而稍低于国Ⅳ柴油车。%NOX emissions from three buses with SCR systems are measured by using portable emission measurement system in real-world conditions, the NOX emission factors in both conditions ( with and without urea in-jection) are compared and their NOX reduction rates of SCR systems are calculated. The results show that the State-IV diesel bus has the lowest NOx reduction rate of SCR system due to its low exhaust temperature and less volume of catalyst, whose effects gradually become apparent only when vehicle speed is higher than 30km/h, with an average NOX reduction rate of only 10 %;the State-V CNG bus has the highest NOX reduction rate due to its high exhaust temperature even at low speed and higher proportion of NO2 in NOX emission, and its NOX reduction rate basically does not change with vehicle speed, resulting in an average NOX reduction rate of 85%; while the NOX reduction rate of State-V diesel bus is in-between with an average NOX reduction rate of around 70%. As for the emission of NOX+ HC, the lowest is the State-V diesel bus, the highest is the State-IV diesel bus, while the NOX+HC emission of State

  19. Development of a hydrophilic interaction liquid chromatography-mass spectrometry method for detection and quantification of urea thermal decomposition by-products in emission from diesel engine employing selective catalytic reduction technology.

    Science.gov (United States)

    Yassine, Mahmoud M; Dabek-Zlotorzynska, Ewa; Celo, Valbona

    2012-03-16

    The use of urea based selective catalytic reduction (SCR) technology for the reduction of NOx from the exhaust of diesel-powered vehicles has the potential to emit at least six thermal decomposition by-products, ammonia, and unreacted urea from the tailpipe. These compounds may include: biuret, dicyandiamine, cyanuric acid, ammelide, ammeline and melamine. In the present study, a simple, sensitive and reliable hydrophilic interaction liquid chromatography (HILIC)-electrospray ionization (ESI)/mass spectrometry (MS) method without complex sample pre-treatment was developed for identification and determination of urea decomposition by-products in diesel exhaust. Gradient separation was performed on a SeQuant ZIC-HILIC column with a highly polar zwitterionic stationary phase, and using a mobile phase consisting of acetonitrile (eluent A) and 15 mM ammonium formate (pH 6; eluent B). Detection and quantification were performed using a quadrupole ESI/MS operated simultaneously in negative and positive mode. With 10 μL injection volume, LODs for all target analytes were in the range of 0.2-3 μg/L. The method showed a good inter-day precision of retention time (RSD<0.5%) and peak area (RSD<3%). Satisfactory extraction recoveries from spiked blanks ranged between 96 and 98%. Analyses of samples collected during transient chassis dynamometer tests of a bus engine equipped with a diesel particulate filter (DPF) and urea based SCR technology showed the presence of five target analytes with cyanuric acid and ammelide the most abundant compounds in the exhaust. PMID:22318005

  20. Chemical deactivation of V{sub 2}O{sub 5}/WO{sub 3}-TiO{sub 2} SCR catalysts by additives and impurities from fuels, lubrication oils, and urea solution. Part 1. Catalytic studies

    Energy Technology Data Exchange (ETDEWEB)

    Kroecher, Oliver; Elsener, Martin [Paul Scherrer Institute, 5232 Villigen PSI (Switzerland)

    2008-01-10

    The influence of the combustion products of different lubrication oil additives (Ca, Mg, Zn, P, B, Mo) and impurities in Diesel fuel (K from raps methyl ester) or urea solution (Ca, K) on the activity and selectivity of vanadia-based SCR catalysts were investigated. Standard V{sub 2}O{sub 5}/WO{sub 3}-TiO{sub 2} catalysts coated on metal substrates (400 cpsi) were impregnated with water soluble compounds of these elements and calcined at 400 and 550 C, in order to investigate the chemical deactivation potential of different elements and combinations of them. It was found that potassium strongly reduced the adsorption equilibrium constant K{sub NH{sub 3}} of ammonia. At small ammonia concentrations in the feed, only part of the active sites were covered with ammonia resulting in a reduced SCR reaction rate. At high ammonia concentrations, the surface coverage and SCR reaction rate increased, but high SCR activity at concurrent low ammonia emissions was impossible. Calcium caused less deactivation than potassium and did not affect the ammonia adsorption to the same extent, but it lowered the intrinsic SCR reaction rate. Moreover, deactivation by calcium was much reduced if counter-ions of inorganic acids were present (order of improvement: SO{sub 4}{sup 2-} > PO{sub 4}{sup 3-} > BO{sub 3}{sup 3-}). Zinc was again less deactivating than calcium, but the positive effect of the counter-ions was weaker than in case of calcium. The degree of N{sub 2}O production at T > 500 C, which is typical for V{sub 2}O{sub 5}/WO{sub 3}-TiO{sub 2} catalysts, was not influenced by the different compounds, except for molybdenum, which induced a small increase in N{sub 2}O formation. (author)

  1. NOx emissions from Euro IV busses with SCR systems associated with urban, suburban and freeway driving patterns.

    Science.gov (United States)

    Fu, Mingliang; Ge, Yunshan; Wang, Xin; Tan, Jianwei; Yu, Linxiao; Liang, Bin

    2013-05-01

    NOx and particulate matter (PM) emissions from heavy-duty diesel vehicles (HDVs) have become the most important sources of pollutants affecting urban air quality in China. In recent years, a series of emission control strategies and diesel engine polices have been introduced that require advanced emission control technology. China and Europe mostly have used Selective Catalytic Reduction (SCR) with urea to meet the Euro IV diesel engine emission standard. In this study, two Euro IV busses with SCR were tested by using potable emission measurement system (PEMS) to assess NOx emissions associated with urban, suburban and freeway driving patterns. The results indicated that with the SCR system, the urea injection time for the entire driving period increased with higher vehicle speed. For freeway driving, the urea injection time covered 71%-83% of the driving period; the NOx emission factors from freeway driving were lower than those associated with urban and suburban driving. Unfortunately, the NOx emission factors were 2.6-2.8-, 2.3-2.7- and 2.2-2.3-fold higher than the Euro IV standard limits for urban, suburban and freeway driving, respectively; NOx emission factors (in g/km and g/(kW·h)) from the original vehicles (without SCR) were higher than their corresponding vehicles with SCR for suburban and freeway driving. Compared with the IVE model results, the measured NOx emission factors were 1.60-1.16-, 1.77-1.27-, 2.49-2.44-fold higher than the NOx predicted by the IVE model for urban and suburban driving, respectively. Thus, an adjustment of emission factors is needed to improve the estimation of Euro IV vehicle emissions in China.

  2. Co$_9$S$_8$ nanotubes: facile synthesis and application in the catalytic reduction of 4-nitrophenol

    Indian Academy of Sciences (India)

    TAO GENG; YONGHONG NI; HONGYAN WANG; XIA ZHOU

    2016-10-01

    Co$_9$S$_8$ nanotubes have been successfully synthesized via a facile two-step solvothermal method without the assistance of any template or surfactant, using cobalt sulphate (CoSO$_4$·7H$_2$O), urea and sodium sulphide (Na$_2$S·9H$_2$O) as starting reactants, and deionized water and glycol as the reactive medium. The phase and the morphologyof the as-obtained product were characterized by means of powder X-ray diffraction, energy dispersive spectrometry and scanning electron microscopy. The result displays that the Co9S8 nanotubes have hexagonal crosssections,the diameter of the nanotubes is about 200 nm and the wall thickness is of 50 nm. The experiments showed that the Co$_9$S$_8$ nanotubes could be used as new-type catalysts for the reduction of 4-nitrophenol. It was found thatthe as-obtained Co$_9$S$_8$ nanotubes contributed to the best catalytic activity.

  3. Direct Comparison of Electrochemical and Spectrochemical Kinetics for Catalytic Oxygen Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Wasylenko, Derek J.; Rodriguez, Carlos; Pegis, Michael L.; Mayer, James M.

    2014-09-10

    We describe here a direct comparison of electrochemical and spectrochemical experiments to determine rates and selectivity of oxygen reduction catalyzed by iron 5,10,15,20-meso-tetraphenylporphyrin chloride. Strong agreement was found between the two methods suggesting the same mechanism is occurring under both conditions, with the same overall third order rate constant kcat = (1.1 ± 0.1) × 106 M-2 s-1. This report provides a rare example of characterization of a redox catalytic process by two common but very different methods. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

  4. Electro-catalytic effect of manganese oxide on oxygen reduction at teflonbonded carbon electrode

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Oxygen reduction(OR)on Teflon-bonded carbon electrodes with manganese oxide as catalyst in 6 mol/L KOH solution was investigated using AC impedance spectroscopy combined with other techniques. For OR at this electrode, the Tafel slope is-0.084V/dec and the apparent exchange current density is (1.02-3.0)×10-7 A/cm2. In the presence of manganese oxide on carbon electrode,the couple Mn3+/Mn4+ reacts with the O2 adsorbed on carbon sites forming O2- radicals and acceletes the dismutation of O2-, which contributes to the catalytic effect of manganese oxide for OR reaction.

  5. Ammonia generators for GD-KAT (advanced SCR) systems; Ammoniakgeneratoren fuer GD-KAT-Systeme

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, E. [MAN Nutzfahrzeuge AG, Nuernberg (Germany)

    2004-07-01

    Catalyzed thermal decomposition of aqueous solution of urea (AdBlue) or solid urea is the preferred way to generate the reducing agent ammonia, NH{sub 3}, for selective catalytic reduction (SCR) of NO{sub x} in the diesel engine exhaust gas. Various types of decomposition reactors, called ammonia generators, are possible which differ in their effectiveness to produce ammonia from urea. For reasons of simplicity, the decomposition is usually performed by atomizing AdBlue directly into the hot exhaust. However, this technique suffers from high space velocities (SV), leading to incomplete vaporization of water and only slight decomposition into NH{sub 3} and HNCO and causing a significant performance loss of the SCR catalyst. The catalyzed thermohydrolysis out of the main exhaust stream allows much decreased SV for the urea decomposition. A catalytic reactor utilizing a partial or an auxilliary (for solid urea only) stream of the exhaust gas seems particularly promising, leading to NH{sub 3} practically free from HNCO. (orig.)

  6. Nitrogen oxides from waste incineration: control by selective non-catalytic reduction.

    Science.gov (United States)

    Zandaryaa, S; Gavasci, R; Lombardi, F; Fiore, A

    2001-01-01

    An experimental study of the selective non-catalytic reduction (SNCR) process was carried out to determine the efficiency of NOx removal and NH3 mass balance, the NOx reducing reagent used. Experimental tests were conducted on a full-scale SNCR system installed in a hospital waste incineration plant. Anhydrous NH3 was injected at the boiler entrance for NOx removal. Ammonia was analyzed after each flue-gas treatment unit in order to establish its mass balance and NH3 slip in the stack gas was monitored as well. The effective fraction of NH3 for the thermal NOx reduction was calculated from measured values of injected and residual NH3. Results show that a NOx reduction efficiency in the range of 46.7-76.7% is possible at a NH3/NO molar ratio of 0.9-1.5. The fraction of NH3 used in NOx removal was found to decrease with rising NH3/NO molar ratio. The NH3 slip in the stack gas was very low, below permitted limits, even at the higher NH3 dosages used. No direct correlation was found between the NH3/NO molar ratio and the NH3 slip in the stack gas since the major part of the residual NH3 was converted into ammonium salts in the dry scrubbing reactor and subsequently collected in the fabric filter. Moreover, another fraction of NH3 was dissolved in the scrubbing liquor.

  7. Gaseous emissions from a heavy-duty engine equipped with SCR aftertreatment system and fuelled with diesel and biodiesel: Assessment of pollutant dispersion and health risk

    International Nuclear Information System (INIS)

    The changes in the composition of fuels in combination with selective catalytic reduction (SCR) emission control systems bring new insights into the emission of gaseous and particulate pollutants. The major goal of our study was to quantify NOx, NO, NO2, NH3 and N2O emissions from a four-cylinder diesel engine operated with diesel and a blend of 20% soybean biodiesel. Exhaust fume samples were collected from bench dynamometer tests using a heavy-duty diesel engine equipped with SCR. The target gases were quantified by means of Fourier transform infrared spectrometry (FTIR). The use of biodiesel blend presented lower concentrations in the exhaust fumes than using ultra-low sulfur diesel. NOx and NO concentrations were 68% to 93% lower in all experiments using SCR, when compared to no exhaust aftertreatment. All fuels increased NH3 and N2O emission due to SCR, a precursor secondary aerosol, and major greenhouse gas, respectively. An AERMOD dispersion model analysis was performed on each compound results for the City of Curitiba, assumed to have a bus fleet equipped with diesel engines and SCR system, in winter and summer seasons. The health risks of the target gases were assessed using the Risk Assessment Information System For 1-h exposure of NH3, considering the use of low sulfur diesel in buses equipped with SCR, the results indicated low risk to develop a chronic non-cancer disease. The NOx and NO emissions were the lowest when SCR was used; however, it yielded the highest NH3 concentration. The current results have paramount importance, mainly for countries that have not yet adopted the Euro V emission standards like China, India, Australia, or Russia, as well as those already adopting it. These findings are equally important for government agencies to alert the need of improvements in aftertreatment technologies to reduce pollutants emissions. - Highlights: • Emission, dispersion and risk assessment from Euro 5 engine by diesel and biodiesel. • All fuels

  8. Gaseous emissions from a heavy-duty engine equipped with SCR aftertreatment system and fuelled with diesel and biodiesel: Assessment of pollutant dispersion and health risk

    Energy Technology Data Exchange (ETDEWEB)

    Tadano, Yara S.; Borillo, Guilherme C.; Godoi, Ana Flávia L.; Cichon, Amanda; Silva, Thiago O.B.; Valebona, Fábio B.; Errera, Marcelo R. [Environmental Engineering Department, Federal University of Parana, 210 Francisco H. dos Santos St., Curitiba, PR, 81531-980 Brazil (Brazil); Penteado Neto, Renato A.; Rempel, Dennis; Martin, Lucas [Institute of Technology for Development, Lactec–Leme Division, 01 LothárioMeissner Ave., Curitiba, PR, 80210-170 (Brazil); Yamamoto, Carlos I. [Chemical Engineering Department, Federal University of Parana, 210 Francisco H. dos Santos St., Curitiba, PR, 81531-980 Brazil (Brazil); Godoi, Ricardo H.M., E-mail: rhmgodoi@ufpr.br [Environmental Engineering Department, Federal University of Parana, 210 Francisco H. dos Santos St., Curitiba, PR, 81531-980 Brazil (Brazil)

    2014-12-01

    The changes in the composition of fuels in combination with selective catalytic reduction (SCR) emission control systems bring new insights into the emission of gaseous and particulate pollutants. The major goal of our study was to quantify NO{sub x}, NO, NO{sub 2}, NH{sub 3} and N{sub 2}O emissions from a four-cylinder diesel engine operated with diesel and a blend of 20% soybean biodiesel. Exhaust fume samples were collected from bench dynamometer tests using a heavy-duty diesel engine equipped with SCR. The target gases were quantified by means of Fourier transform infrared spectrometry (FTIR). The use of biodiesel blend presented lower concentrations in the exhaust fumes than using ultra-low sulfur diesel. NO{sub x} and NO concentrations were 68% to 93% lower in all experiments using SCR, when compared to no exhaust aftertreatment. All fuels increased NH{sub 3} and N{sub 2}O emission due to SCR, a precursor secondary aerosol, and major greenhouse gas, respectively. An AERMOD dispersion model analysis was performed on each compound results for the City of Curitiba, assumed to have a bus fleet equipped with diesel engines and SCR system, in winter and summer seasons. The health risks of the target gases were assessed using the Risk Assessment Information System For 1-h exposure of NH{sub 3}, considering the use of low sulfur diesel in buses equipped with SCR, the results indicated low risk to develop a chronic non-cancer disease. The NO{sub x} and NO emissions were the lowest when SCR was used; however, it yielded the highest NH{sub 3} concentration. The current results have paramount importance, mainly for countries that have not yet adopted the Euro V emission standards like China, India, Australia, or Russia, as well as those already adopting it. These findings are equally important for government agencies to alert the need of improvements in aftertreatment technologies to reduce pollutants emissions. - Highlights: • Emission, dispersion and risk assessment

  9. Low Temperature Selective Catalytic Reduction of Nitrogen Oxides in Production of Nitric Acid by the Use of Liquid

    Directory of Open Access Journals (Sweden)

    Kabljanac, Ž.

    2011-11-01

    Full Text Available This paper presents the application of low-temperature selective catalytic reduction of nitrous oxides in the tail gas of the dual-pressure process of nitric acid production. The process of selective catalytic reduction is carried out using the TiO2/WO3 heterogeneous catalyst applied on a ceramic honeycomb structure with a high geometric surface area per volume. The process design parameters for nitric acid production by the dual-pressure procedure in a capacity range from 75 to 100 % in comparison with designed capacity for one production line is shown in the Table 1. Shown is the effectiveness of selective catalytic reduction in the temperature range of the tail gas from 180 to 230 °C with direct application of liquid ammonia, without prior evaporation to gaseous state. The results of inlet and outlet concentrations of nitrous oxides in the tail gas of the nitric acid production process are shown in Figures 1 and 2. Figure 3 shows the temperature dependence of the selective catalytic reduction of nitrous oxides expressed as NO2in the tail gas of nitric acid production with the application of a constant mass flow of liquid ammonia of 13,0 kg h-1 and average inlet mass concentration of the nitrous oxides expressed as NO2of 800,0 mgm-3 during 100 % production capacity. The specially designed liquid-ammonia direct-dosing system along with the effective homogenization of the tail gas resulted in emission levels of nitrous oxides expressed as NO2 in tail gas ranging from 100,0 to 185,0 mg m-3. The applied low-temperature selective catalytic reduction of the nitrous oxides in the tail gases by direct use of liquid ammonia is shown in Figure 4. It is shown that low-temperature selective catalytic reduction with direct application of liquid ammonia opens a new opportunity in the reduction of nitrous oxide emissions during nitric acid production without the risk of dangerous ammonium nitrate occurring in the process of subsequent energy utilization of

  10. Investigation of Catalytic NOx, reduction with transient techniques, isotopic exchange and FT-IR spectroscopy

    International Nuclear Information System (INIS)

    Emissions from vehicles are suppressed by catalytic conversion, i.e. total oxidation of carbon monoxide and hydrocarbons and reduction of nitrogen oxides. The on-going demand for lower emissions requires more detailed knowledge about the catalytic reaction mechanisms and kinetics on the level of elementary steps, especially because of the mutual interactions in the complex reaction mixture. The reaction mechanisms for the abatement of nitrogen oxides (NOx) are of particular interest, since they are environmentally very unfriendly compounds. Transient experimental techniques can be used as a tool to understand the reaction mechanisms and to develop mathematical models allowing simulation and optimisation of the behaviour of three-way catalyst converters. In chemical kinetics, isotope-labelled reactants are frequently employed to follow reaction pathways and to determine reaction mechanisms. The kinetics and mechanisms of the catalytic reduction of nitrogen oxide (NO) by hydrogen as well as self-decomposition of NO and N2O were studied over alumina based palladium and rhodium-alumina monoliths. In addition, NO reduction with H2 and D2, isotope exchange of hydrogen atoms in water, ammonia and hydrogen with deuterium, as well as adsorption of ammonia and water on the Pd-monolith were studied with transient experiments. Transient step-response experiments, isotopic jumping techniques, steady- state isotopic-transient analysis, temperature programmed desorption (TPD) and Fourier-transformed infrared spectroscopy (FT-IR) were used as experimental techniques. The catalysts were characterised by carbon monoxide chemisorption, nitrogen physisorption and X-ray photoelectron spectroscopy (XPS). Nitrogen, nitrous oxide, ammonia, and water were detected as reaction products in NO reduction by hydrogen. The transient and FT-IR experiments yielded information about the surface reaction mechanisms. The dissociation of NO on the catalyst surface is the crucial step, dominating the

  11. Data and Summaries for Catalytic Destruction of a Surrogate Organic Hazardous Air Pollutant as a Potential Co-benefit for Coal-Fired Selective Catalytic Reduction Systems

    Data.gov (United States)

    U.S. Environmental Protection Agency — Table 1 summarizes and explanis the Operating Conditions of the SCR Reactor used in the Benzene-Destruction. Table 2 summarizes and explains the Experimental Design...

  12. Catalytic activity of various pepsin reduced Au nanostructures towards reduction of nitroarenes and resazurin

    International Nuclear Information System (INIS)

    Pepsin, a digestive protease enzyme, could function as a reducing as well as stabilizing agent for the synthesis of Au nanostructures of various size and shape under different reaction conditions. The simple tuning of the pH of the reaction medium led to the formation of spherical Au nanoparticles, anisotropic Au nanostructures such as triangles, hexagons, etc., as well as ultra small fluorescent Au nanoclusters. The activity of the enzyme was significantly inhibited after its participation in the formation of Au nanoparticles due to conformational changes in the native structure of the enzyme which was studied by fluorescence, circular dichroism (CD), and infra red spectroscopy. However, the Au nanoparticle-enzyme composites served as excellent catalyst for the reduction of p-nitrophenol and resazurin, with the catalytic activity varying with size and shape of the nanoparticles. The presence of pepsin as the surface stabilizer played a crucial role in the activity of the Au nanoparticles as reduction catalysts, as the approach of the reacting molecules to the nanoparticle surface was actively controlled by the stabilizing enzyme

  13. Catalytic activity of various pepsin reduced Au nanostructures towards reduction of nitroarenes and resazurin

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Bhagwati; Mandani, Sonam; Sarma, Tridib K., E-mail: tridib@iiti.ac.in [Indian Institute of Technology Indore, Discipline of Chemistry, School of Basic Sciences (India)

    2015-01-15

    Pepsin, a digestive protease enzyme, could function as a reducing as well as stabilizing agent for the synthesis of Au nanostructures of various size and shape under different reaction conditions. The simple tuning of the pH of the reaction medium led to the formation of spherical Au nanoparticles, anisotropic Au nanostructures such as triangles, hexagons, etc., as well as ultra small fluorescent Au nanoclusters. The activity of the enzyme was significantly inhibited after its participation in the formation of Au nanoparticles due to conformational changes in the native structure of the enzyme which was studied by fluorescence, circular dichroism (CD), and infra red spectroscopy. However, the Au nanoparticle-enzyme composites served as excellent catalyst for the reduction of p-nitrophenol and resazurin, with the catalytic activity varying with size and shape of the nanoparticles. The presence of pepsin as the surface stabilizer played a crucial role in the activity of the Au nanoparticles as reduction catalysts, as the approach of the reacting molecules to the nanoparticle surface was actively controlled by the stabilizing enzyme.

  14. Catalytic pyrolysis of LDPE leads to valuable resource recovery and reduction of waste problems

    International Nuclear Information System (INIS)

    confirmed by Bromine number tests. The values of which lie in the range of 0.1-12.8 g/ml, which fall in the range for olefin mixture. Phenol and carbonyl contents were quantified using UV/Visible spectroscopy and the values lie in the range of 1-8920 μg/ml and 5-169 μg/ml for both phenols and carbonyls respectively. The components of different hydrocarbons in the oil mixture were separated by using column chromatography and fractional distillation followed by characterization with FT-IR spectroscopy. The interpretation of FT-IR spectra shows that catalytic pyrolysis of LDPE leads to the formation of a complex mixture of alkanes, alkenes, carbonyl group containing compounds like aldehydes, ketones, aromatic compounds and substituted aromatic compounds like phenols. It could be concluded, that catalytic pyrolysis of LDPE leads to valuable resource recovery and reduction of waste problem.

  15. Catalytic pyrolysis of LDPE leads to valuable resource recovery and reduction of waste problems

    Energy Technology Data Exchange (ETDEWEB)

    Shah, Jasmin [Institute of Chemical Sciences, University of Peshawar, N.W.F.P. (Pakistan); Jan, M. Rasul [University of Malakand, Chakdara, N.W.F.P. (Pakistan); Mabood, Fazal [Department of Chemistry, University of Malakand, Chakdara, N.W.F.P. (Pakistan); Jabeen, Farah [Department of Chemistry, Sarhad University, N.W.F.P. (Pakistan)

    2010-12-15

    . This was further confirmed by Bromine number tests. The values of which lie in the range of 0.1-12.8 g/ml, which fall in the range for olefin mixture. Phenol and carbonyl contents were quantified using UV/Visible spectroscopy and the values lie in the range of 1-8920 {mu}g/ml and 5-169 {mu}g/ml for both phenols and carbonyls respectively. The components of different hydrocarbons in the oil mixture were separated by using column chromatography and fractional distillation followed by characterization with FT-IR spectroscopy. The interpretation of FT-IR spectra shows that catalytic pyrolysis of LDPE leads to the formation of a complex mixture of alkanes, alkenes, carbonyl group containing compounds like aldehydes, ketones, aromatic compounds and substituted aromatic compounds like phenols. It could be concluded, that catalytic pyrolysis of LDPE leads to valuable resource recovery and reduction of waste problem. (author)

  16. One-step selective synthesis of branched 1-O-alkyl-glycerol/diglycerol monoethers by catalytic reductive alkylation of ketones

    Institute of Scientific and Technical Information of China (English)

    DAYOUB; Wissam; LEMAIRE; Marc

    2010-01-01

    Branched 1-O-alkyl glycerol and diglycerol monoethers were obtained in good yields and high selectivity by a straightforward catalytic reductive alkylation of glycerol with relevant ketones in the presence of 0.5 mol% of Pd/C under 10 bar of hydrogen pressure using a Brφnsted acid as the co-catalyst.

  17. Towards chiral diamines as chiral catalytic precursors for the borane-mediated enantioselective reduction of prochiral ketones

    Indian Academy of Sciences (India)

    Deevi Basavaiah; Utpal Das; Suparna Roy

    2009-11-01

    Two chiral diamines (3)-3-anilinomethyl-1,2,3,4-tetrahydroisoquinoline (1) and (2)-2-anilinomethylpiperidine (2) have been employed as chiral catalytic sources in the borane-mediated asymmetric reduction of prochiral ketones thus providing the resulting secondary alcohols in good enantiomeric purities (up to 81% ).

  18. Selective catalytic reduction of NOx by hydrocarbons over Fe/ZSM5 prepared by sublimation of FeCl3

    NARCIS (Netherlands)

    Battiston, A.A.

    2003-01-01

    Selective Catalytic Reduction of NOx by Hydrocarbons over Fe/ZSM5 Prepared by Sublimation of FeCl3. Characterization and Catalysis Nitrogen oxides (NOx) are unwanted by-products of combustion. They are generated primarily from motor vehicles and stationary sources, like power stations and indust

  19. Low-temperature SCR of NOx with NH3 over activated carbon fiber composite-supported metal oxides

    International Nuclear Information System (INIS)

    In previous works, the authors were involved in the preparation and optimization of Nomex-based activated carbon fibers (ACFs) monoliths and their use as catalytic supports of manganese oxides for the selective catalytic reduction (SCR) of NOx with NH3 at low temperature. Thus, a low density monolith made of carbonized Nomex rejects was fabricated and submitted to different surface conditioning treatments in order to maximize the dispersion and loading of manganese oxides which were highly active in the SCR process. In order to complete the study, in this work different carbon fibers were used to fabricate the monolithic support, and the catalytic activity of the derived manganese oxide-based catalysts was analyzed and compared to that of the standard Nomex-supported catalyst. These fibers were coal Pitch-, Rayon-, PAN-, and phenolic Resin-based carbon fibers. Additionally, catalysts based on other metal oxides (nickel, chromium, vanadium and iron) were prepared via equilibrium adsorption (EA) and pore volume impregnation (PVI) of the strategically modified supports, in an attempt to surpass the catalytic performance of the already highly active manganese oxide-based catalysts and to tackle one of the main drawbacks for the utilization of these catalysts under practical conditions; the SO2 deactivation. For all the prepared catalysts the following parameters were evaluated at a standard reaction temperature of 150C: catalytic activity, selectivity, extent of support gasification, H2O inhibition and SO2 deactivation. Additionally temperature programmed desorption (TPD) of NO was conducted on specific samples in order to analyze the different adsorption modes of NO on the catalyst surface. All this research procedure has eventually derived in the selection of a catalyst (Nomex rejects-based activated carbon fiber composite (ACFC) supported iron oxides) which constitutes a compromise between high catalytic performance and moderate SO2 deactivation

  20. Improvement of activity and SO₂ tolerance of Sn-modified MnOx-CeO₂ catalysts for NH₃-SCR at low temperatures.

    Science.gov (United States)

    Chang, Huazhen; Chen, Xiaoyin; Li, Junhua; Ma, Lei; Wang, Chizhong; Liu, Caixia; Schwank, Johannes W; Hao, Jiming

    2013-05-21

    The performances of fresh and sulfated MnOx-CeO₂ catalysts for selective catalytic reduction of NOx by NH₃ (NH₃-SCR) in a low-temperature range (T role of additive and the effect of sulfation. The catalyst having a Sn:Mn:Ce = 1:4:5 molar ratio showed the widest SCR activity improvement with near 100% NOx conversion at 110-230 °C. Raman and X-ray photoelectron spectroscopy (XPS) indicated that Sn modification significantly increases the concentration of oxygen vacancies that may facilitate NO oxidation to NO₂. NH₃-TPD characterization showed that the low-temperature NH₃-SCR activity is well correlated with surface acidity for NH3 adsorption, which is also enhanced by Sn modification. Furthermore, as compared to MnOx-CeO₂, Sn-modified MnOx-CeO₂ showed remarkably improved tolerance to SO₂ sulfation and to the combined effect of SO₂ and H₂O. In the presence of SO₂ and H₂O, the Sn-modified MnOx-CeO₂ catalyst gave 62% and 94% NOx conversions as compared to 18% and 56% over MnOx-CeO₂ at temperatures of 110 and 220 °C, respectively. Sulfation of SnO₂-modified MnOx-CeO₂ may form Ce(III) sulfate that could enhance the Lewis acidity and improve NO oxidation to NO₂ during NH₃-SCR at T > 200 °C. PMID:23582170

  1. Effects of Alkali and Alkaline Earth Cocations on the Activity and Hydrothermal Stability of Cu/SSZ-13 NH3-SCR Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Wang, Yilin; Washton, Nancy M.; Kollar, Marton; Szanyi, Janos; Peden, Charles HF

    2015-10-13

    Using a three-step aqueous solution ion-exchange method, cocation modified Cu/SSZ-13 SCR catalysts were synthesized. These catalysts, in both fresh and hydrothermally aged forms, were characterized with several methods including temperature-programmed reduction by H2 (H2-TPR), temperature-programmed desorption of NH3 (NH3-TPD), and 27Al solid-state nuclear magnetic resonance (NMR) and diffuse reflectance Infrared Fourier Transform (DRIFT) spectroscopies. Their catalytic performance was probed using steady-state standard NH3-SCR. Characterization results indicate that cocations weaken interactions between Cu-ions and the CHA framework making them more readily reducible. By removing a portion of Brønsted acid sites, cocations also help to mitigate hydrolysis of the zeolite catalysts during hydrothermal aging as evidenced from 27Al NMR. Reaction tests show that certain cocations, especially Li+ and Na+, promote low-temperature SCR rates while others show much less pronounced effects. In terms of applications, our results indicate that introducing cocations can be a viable strategy to improve both low- and high-temperature performance of Cu/SSZ-13 SCR catalysts.

  2. Improvement of activity and SO₂ tolerance of Sn-modified MnOx-CeO₂ catalysts for NH₃-SCR at low temperatures.

    Science.gov (United States)

    Chang, Huazhen; Chen, Xiaoyin; Li, Junhua; Ma, Lei; Wang, Chizhong; Liu, Caixia; Schwank, Johannes W; Hao, Jiming

    2013-05-21

    The performances of fresh and sulfated MnOx-CeO₂ catalysts for selective catalytic reduction of NOx by NH₃ (NH₃-SCR) in a low-temperature range (T SCR activity improvement with near 100% NOx conversion at 110-230 °C. Raman and X-ray photoelectron spectroscopy (XPS) indicated that Sn modification significantly increases the concentration of oxygen vacancies that may facilitate NO oxidation to NO₂. NH₃-TPD characterization showed that the low-temperature NH₃-SCR activity is well correlated with surface acidity for NH3 adsorption, which is also enhanced by Sn modification. Furthermore, as compared to MnOx-CeO₂, Sn-modified MnOx-CeO₂ showed remarkably improved tolerance to SO₂ sulfation and to the combined effect of SO₂ and H₂O. In the presence of SO₂ and H₂O, the Sn-modified MnOx-CeO₂ catalyst gave 62% and 94% NOx conversions as compared to 18% and 56% over MnOx-CeO₂ at temperatures of 110 and 220 °C, respectively. Sulfation of SnO₂-modified MnOx-CeO₂ may form Ce(III) sulfate that could enhance the Lewis acidity and improve NO oxidation to NO₂ during NH₃-SCR at T > 200 °C.

  3. Low-Temperature NH3–SCR of NO on Mesoporous Mn0.6Fe0.4/TiO2 Prepared by a Hydrothermal Method

    DEFF Research Database (Denmark)

    Schill, Leonhard; Putluru, Siva Sankar Reddy; Fehrmann, Rasmus;

    2014-01-01

    Mesoporous 30 wt% Mn0.6Fe0.4/TiO2 has been prepared by a novel hydrothermal method using a structure directing agent and characterized by N2 adsorption, SEM, XRD, EDX, H2-TPR and the catalytic activity for the selective catalytic reduction (SCR) of NO by ammonia was measured under power plant flue...... higher (NH4)2SO4 tolerance at 150 °C compared to the impregnation preparation method. Regeneration of the (NH4)2SO4 loaded samples by heating to 400 °C was not possible whereas water washing yielded better regeneration. The catalysts are significantly more active than a commercial VWT SCR catalyst...

  4. Fast SCR Thyratron Driver

    International Nuclear Information System (INIS)

    As part of an improvement project on the linear accelerator at SLAC, it was necessary to replace the original thyratron trigger generator, which consisted of two chassis, two vacuum tubes, and a small thyratron. All solid-state, fast rise, and high voltage thyratron drivers, therefore, have been developed and built for the 244 klystron modulators. The rack mounted, single chassis driver employs a unique way to control and generate pulses through the use of an asymmetric SCR, a PFN, a fast pulse transformer, and a saturable reactor. The resulting output pulse is 2 kV peak into 50 (Omega) load with pulse duration of 1.5 μs FWHM at 180 Hz. The pulse risetime is less than 40 ns with less than 1 ns jitter. Various techniques are used to protect the SCR from being damaged by high voltage and current transients due to thyratron breakdowns. The end-of-line clipper (EOLC) detection circuit is also integrated into this chassis to interrupt the modulator triggering in the event a high percentage of line reflections occurred

  5. Catalytic activities enhanced by abundant structural defects and balanced N distribution of N-doped graphene in oxygen reduction reaction

    Science.gov (United States)

    Bai, Xiaogong; Shi, Yantao; Guo, Jiahao; Gao, Liguo; Wang, Kai; Du, Yi; Ma, Tingli

    2016-02-01

    N-doped graphene (NG) is a promising candidate for oxygen reduction reaction (ORR) in the cathode of fuel cells. However, the catalytic activity of NG is lower than that of commercial Pt/C in alkaline and acidic media. In this study, NG samples were obtained using urea as N source. The structural defects and N distribution in the samples were adjusted by regulating the pyrolysis temperature. The new NG type exhibited remarkable catalytic activities for ORR in both alkaline and acidic media.

  6. Controllable Synthesis of Mesoporous Iron Oxide Nanoparticle Assemblies for Chemoselective Catalytic Reduction of Nitroarenes.

    Science.gov (United States)

    Papadas, Ioannis T; Fountoulaki, Stella; Lykakis, Ioannis N; Armatas, Gerasimos S

    2016-03-18

    Iron(III) oxide is a low-cost material with applications ranging from electronics to magnetism, and catalysis. Recent efforts have targeted new nanostructured forms of Fe2O3 with high surface area-to-volume ratio and large pore volume. Herein, the synthesis of 3D mesoporous networks consisting of 4-5 nm γ-Fe2O3 nanoparticles by a polymer-assisted aggregating self-assembly method is reported. Iron oxide assemblies obtained from the hybrid networks after heat treatment have an open-pore structure with high surface area (up to 167 m(2)g(-1)) and uniform pores (ca. 6.3 nm). The constituent iron oxide nanocrystals can undergo controllable phase transition from γ-Fe2O3 to α-Fe2O3 and to Fe3O4 under different annealing conditions while maintaining the 3D structure and open porosity. These new ensemble structures exhibit high catalytic activity and stability for the selective reduction of aryl and alkyl nitro compounds to the corresponding aryl amines and oximes, even in large-scale synthesis. PMID:26880681

  7. DEVELOPMENT OF HIGH ACTIVITY, COAL-DERIVED, PROMOTED CATALYTIC SYSTEMS FOR NOx REDUCTION AT LOW TEMPERATURES

    Energy Technology Data Exchange (ETDEWEB)

    Joseph M. Calo

    2000-07-21

    This project is directed at an investigation of catalytic NO{sub x} reduction mechanisms on coal-derived, activated carbon supports at low temperatures. Promoted carbon systems offer some potentially significant advantages for heterogeneous NO{sub x} reduction. These include: low cost; high activity at low temperatures, which minimizes carbon loss; oxygen resistance; and a support material which can be engineered with respect to porosity, transport and catalyst dispersion characteristics. During the reporting period, the following has been accomplished: (1) Steady-state reactivity studies in the packed bed reactor were extended to the NO/CO-carbon reaction system as a function of temperature and NO and CO concentrations. It was found that the NO reaction rate increased in the presence of CO, and the apparent activation energy decreased to about 75 {+-} 8 kJ/mol. In addition, the influence of mass transfer limitations were noted at low NO and CO concentrations. (2) The packed bed reactor/gas flow system has been applied to performing post-reaction temperature programmed desorption (TPD) studies of intermediate surface complexes following steady-state reaction. It was found that the amount of CO-evolving intermediate surface complexes exceeded that of the N{sub 2}-evolving surface complexes, and that both increased with reaction temperature. The TPD spectra indicates that both types of complexes desorb late, suggesting that they have high desorption activation energies. Plans for the next reporting period include extending the temperature programmed desorption studies in the packed bed reactor system to the NO/CO reaction system, including exposure to just CO, as well as NO/CO mixtures.

  8. High performance vanadia-anatase nanoparticle catalysts for the selective catalytic reduction of NO by ammonia

    DEFF Research Database (Denmark)

    Kristensen, Steffen Buus; Kunov-Kruse, Andreas Jonas; Riisager, Anders;

    2011-01-01

    Highly active nanoparticle SCR deNO(x) catalysts composed of amorphous vanadia on crystalline anatase have been prepared by a sol-gel, co-precipitation method using decomposable crystallization seeds. The catalysts were characterized by means of XRPD, TEM/SEM, FT-IR, nitrogen physisorption and NH(3......) catalysts reported in the literature in the examined temperature range of 200-400 degrees C. The catalysts showed very high resistivity towards potassium poisoning maintaining a 15-30 times higher activity than the equally poisoned industrial reference catalyst, upon impregnation by 280 mu mole potassium...

  9. Thermal stability of vanadia-tungsta-titania catalysts in the SCR process

    Energy Technology Data Exchange (ETDEWEB)

    Madia, G.; Elsener, M.; Koebel, M.; Raimondi, F.; Wokaun, A. [Paul Scherrer Institute, CH-5232 PSI Villigen (Switzerland)

    2002-11-28

    The thermal behaviour of TiO{sub 2}-WO{sub 3}-V{sub 2}O{sub 5} catalysts with various vanadia contents (1, 2 and 3wt.% V{sub 2}O{sub 5}) was investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and BET surface area determination. The activity and selectivity of the new and thermally treated catalysts were tested in the SCR reaction. Both structural and catalytic investigations have shown that the vanadia content has a strong effect on the thermal behaviour of the SCR catalysts. The structural investigations evidenced anatase sintering, increase of polymeric vanadyl surface species and three-dimensional growth of supported vanadia upon ageing. The catalytic tests have shown that the SCR activity of catalysts containing 1 or 2% V{sub 2}O{sub 5} increased upon ageing, whereas the SCR performance of the catalyst with 3% V{sub 2}O{sub 5} decreased. The observed improvement of the SCR performance is attributed to an increase of the amount of polymeric vanadyl surface species upon ageing. The decrease of the SCR performance of the catalyst with 3% V{sub 2}O{sub 5} is due to the extensive loss of surface area and to the three-dimensional growth of supported vanadia upon ageing. The catalyst containing 2% V{sub 2}O{sub 5} represents the best compromise between high SCR activity and good thermal stability.

  10. Comparison of preparation methods for ceria catalyst and the effect of surface and bulk sulfates on its activity toward NH3-SCR.

    Science.gov (United States)

    Chang, Huazhen; Ma, Lei; Yang, Shijian; Li, Junhua; Chen, Liang; Wang, Wei; Hao, Jiming

    2013-11-15

    A series of CeO2 catalysts prepared with sulfate (S) and nitrate (N) precursors by hydrothermal (H) and precipitation (P) methods were investigated in selective catalytic reduction of NOx by NH3 (NH3-SCR). The catalytic activity of CeO2 was significantly affected by the preparation methods and the precursor type. CeO2-SH, which was prepared by hydrothermal method with cerium (IV) sulfate as a precursor, showed excellent SCR activity and high N2 selectivity in the temperature range of 230-450 °C. Based on the results obtained by temperature-programmed reduction (H2-TPR), transmission infrared spectra (IR) and thermal gravimetric analysis (TGA), the excellent performance of CeO2-SH was correlated with the surface sulfate species formed in the hydrothermal reaction. These results indicated that sulfate species bind with Ce(4+) on the CeO2-SH catalyst, and the specific sulfate species, such as Ce(SO4)2 or CeOSO4, were formed. The adsorption of NH3 was promoted by these sulfate species, and the probability of immediate oxidation of NH3 to N2O on Ce(4+) was reduced. Accordingly, the selective oxidation of NH3 was enhanced, which contributed to the high N2 selectivity in the SCR reaction. However, the location of sulfate on the CeO2-SP catalyst was different. Plenty of sulfate species were likely deposited on CeO2-SP surface, covering the active sites for NO oxidation, which resulted in poor SCR activity in the test temperature range. Moreover, the resistance to alkali metals, such as Na and K, was improved over the CeO2-SH catalyst.

  11. System Study of Rich Catalytic/Lean burn (RCL) Catalytic Combustion for Natural Gas and Coal-Derived Syngas Combustion Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Shahrokh Etemad; Lance Smith; Kevin Burns

    2004-12-01

    Rich Catalytic/Lean burn (RCL{reg_sign}) technology has been successfully developed to provide improvement in Dry Low Emission gas turbine technology for coal derived syngas and natural gas delivering near zero NOx emissions, improved efficiency, extending component lifetime and the ability to have fuel flexibility. The present report shows substantial net cost saving using RCL{reg_sign} technology as compared to other technologies both for new and retrofit applications, thus eliminating the need for Selective Catalytic Reduction (SCR) in combined or simple cycle for Integrated Gasification Combined Cycle (IGCC) and natural gas fired combustion turbines.

  12. On the Major Influencing Factors of Selective Catalytic Reduction (SCR)%浅析SCR脱硝技术的主要影响因素

    Institute of Scientific and Technical Information of China (English)

    龙勇

    2011-01-01

    SCR工艺是目前火电厂的主要采用的烟气脱硝技术,催化剂是SCR脱硝工艺的重点内容,催化剂性能直接关系到脱硝效率.文章简述了SCR脱硝技术的概念及原理,分析了影响SCR法脱硝效率的主要因素,并针对影响因素提出了一些控制措施.

  13. Multiphase catalysts for selective reduction of NOx with hydrocarbons

    OpenAIRE

    Maisuls, Sergio Eduardo

    2000-01-01

    The combustion of fuels, to meet the society demands for energy, result in the emissi of large quantities of nitrogen oxides (NOx) to the environment. These pollutants cause severe environmental problems and present a serious hazard to the health. Nowadays, two methods for the control of NOx emission are employed. The selective catalytic reduction of NOx with NH3 (SCR), (for stationary sources such as power plants) and the three way catalyst (TWC), (for mobile sources such as automobiles). Th...

  14. Low-temperature SCR of NOx with NH3 over carbon-ceramic supported catalysts

    International Nuclear Information System (INIS)

    A new method for preparing vanadium oxide supported on carbon-ceramic cellular monoliths is described. This includes a support oxidation step with HNO3, followed by ionic exchange with a NaOH solution, equilibrium adsorption impregnation of VO2+ and thermal treatment. As a result an active catalyst for low-temperature selective catalytic reduction (SCR) reaction is obtained. The V-catalyst is more resistant to SO2 poisoning than the previously developed Mn-catalyst. Inhibition by water is reversible for both types of catalysts. Testing of the vanadium catalyst after subjecting it to the outlet gas stream of a power plant shows fast deactivation until constant residual activity is reached. Deactivation seems to be caused by arsenic poisoning and the formation of superficial sulphates

  15. Zeolite Based SCR Catalysts - An Interesting Alternative To Vanadia-Titania Systems

    Energy Technology Data Exchange (ETDEWEB)

    Devadas, M.; Kroecher, O.; Wokaun, A.

    2004-03-01

    Metal exchanged zeolite catalysts were tested for the selective catalytic reduction of NO{sub x} with ammonia (NH{sub 3}-SCR) and compared with a vanadia based catalyst. With pure NO in the feed Cu-ZSM5 exhibited a better NO{sub x} conversion than Fe-ZSM5 and V{sub 2}O{sub 5}/WO{sub 3}-TiO{sub 2} at all temperatures. The main drawback of Cu-ZSM5 is the required excess of ammonia due to oxidation of NH{sub 3} to N{sub 2} (SCO). For a feed ratio of NO:NO{sub 2} = 0.5, all catalysts showed a high activity at elevated temperatures, but Fe-ZSM5 and Cu-ZSM5 performed better than the vanadia catalyst at lower temperatures. (author)

  16. CFD aided optimization of an innovative SCR catalyst design for heavy-duty marine diesel engines

    Science.gov (United States)

    Krastev, V. K.; Russo, S.; Verdemare, D.; Recine, G.; Biferale, L.; Falcucci, G.

    2016-06-01

    In this paper, the design of a new system for reducing NOx from exhaust gases from marine engines is shown. The core of the system is represented by the Selective Catalytic Reduction (SCR) reactor, in which the catalyst is made of titanium dioxide nano-fibers functionalized with metal oxides and deposited by electrospinning on a corrugated metal support. Compared to the current monolithic reactor designs, the high specific surface offered by the fibers allows in principle to satisfy the TIER III emission standards, with a consistent saving in the reactor volume. To optimize the reactor design process, a Computational Fluid Dynamics (CFD) model has been developed, alongside experimental measurements and numerical simulations. Results of different configurations are reported and critically assessed.

  17. Regeneration of Pt-catalysts deactivated in municipal waste flue gas with H2/N2 and the effect of regeneration step on the SCR catalyst

    DEFF Research Database (Denmark)

    Due-Hansen, Johannes; Rasmussen, Søren Brik; Kustov, Arkady;

    on reduction with hydrogen. This procedure had negligible effect on the performance of the SCR catalyst. After treatment with 2% H2, 8% O2 in N2 for one hour, a slight better NO SCR activity was observed due to increase in the concentration V4+ sites. However, after exposure in normal NO SCR gases the activity...

  18. Selective catalytic reduction system and process for treating NOx emissions using a palladium and rhodium or ruthenium catalyst

    Science.gov (United States)

    Sobolevskiy, Anatoly; Rossin, Joseph A.; Knapke, Michael J.

    2011-07-12

    A process for the catalytic reduction of nitrogen oxides (NOx) in a gas stream (29) in the presence of H.sub.2 is provided. The process comprises contacting the gas stream with a catalyst system (38) comprising zirconia-silica washcoat particles (41), a pre-sulfated zirconia binder (44), and a catalyst combination (40) comprising palladium and at least one of rhodium, ruthenium, or a mixture of ruthenium and rhodium.

  19. ADVANCED BYPRODUCT RECOVERY: DIRECT CATALYTIC REDUCTION OF SO2 TO ELEMENTAL SULFUR

    Energy Technology Data Exchange (ETDEWEB)

    Robert S. Weber

    1999-05-01

    Arthur D. Little, Inc., together with its commercialization partner, Engelhard Corporation, and its university partner Tufts, investigated a single-step process for direct, catalytic reduction of sulfur dioxide from regenerable flue gas desulfurization processes to the more valuable elemental sulfur by-product. This development built on recently demonstrated SO{sub 2}-reduction catalyst performance at Tufts University on a DOE-sponsored program and is, in principle, applicable to processing of regenerator off-gases from all regenerable SO{sub 2}-control processes. In this program, laboratory-scale catalyst optimization work at Tufts was combined with supported catalyst formulation work at Engelhard, bench-scale supported catalyst testing at Arthur D. Little and market assessments, also by Arthur D. Little. Objectives included identification and performance evaluation of a catalyst which is robust and flexible with regard to choice of reducing gas. The catalyst formulation was improved significantly over the course of this work owing to the identification of a number of underlying phenomena that tended to reduce catalyst selectivity. The most promising catalysts discovered in the bench-scale tests at Tufts were transformed into monolith-supported catalysts at Engelhard. These catalyst samples were tested at larger scale at Arthur D. Little, where the laboratory-scale results were confirmed, namely that the catalysts do effectively reduce sulfur dioxide to elemental sulfur when operated under appropriate levels of conversion and in conditions that do not contain too much water or hydrogen. Ways to overcome those limitations were suggested by the laboratory results. Nonetheless, at the end of Phase I, the catalysts did not exhibit the very stringent levels of activity or selectivity that would have permitted ready scale-up to pilot or commercial operation. Therefore, we chose not to pursue Phase II of this work which would have included further bench-scale testing

  20. DEVELOPMENT OF HIGH ACTIVITY, COAL-DERIVED, PROMOTED CATALYTIC SYSTEMS FOR NOx REDUCTION AT LOW TEMPERATURES

    Energy Technology Data Exchange (ETDEWEB)

    Joseph M. Calo

    2000-07-24

    This project is directed at an investigation of catalytic NO{sub x} reduction mechanisms on coal-derived, activated carbon supports at low temperatures. Promoted carbon systems offer some potentially significant advantages for heterogeneous NO{sub x} reduction. These include: low cost; high activity at low temperatures, which minimizes carbon loss; oxygen resistance; and a support material which can be engineered with respect to porosity, transport and catalyst dispersion characteristics. During the reporting period, TPD studies were conducted following steady-state reaction in NO/CO mixtures in helium. From these studies, the following points have been concluded: (1) The total amount of CO and N{sub 2} evolved following reaction in NO increases with reaction temperature. The TPD spectra are skewed to high temperatures, indicating more stable surface complexes with high desorption activation energies. (2) The total amount of CO evolved following exposure of the char sample to CO at reaction temperatures decreases with reaction temperature, similar to chemisorption behavior. The CO TPD spectra are shifted to lower temperatures, indicating more labile oxygen surface complexes with lower desorption activation energies. (3) The total amount of CO evolved following reaction in NO/CO mixtures decreases with reaction temperature, while the evolved N{sub 2} still increases with reaction temperature. The CO TPD spectra appear more similar to those obtained following exposure to pure CO, while the N{sub 2} TPD spectra are more similar to those obtained followed reaction in just CO. Based on the preceding observations, a simple mechanism was formulated whereby two different types of surface complexes are formed by NO and CO; the former are more stable, and the latter more labile. This produces two parallel routes for the NO-carbon reaction: (a) the C(O) complexes formed directly by NO desorb as CO; and (b) The C(CO) complexes formed by CO, react with NO to produce CO{sub 2

  1. Photo catalytic reduction of benzophenone on TiO{sub 2}: Effect of preparation method and reaction conditions

    Energy Technology Data Exchange (ETDEWEB)

    Albiter E, E.; Valenzuela Z, M. A.; Alfaro H, S.; Flores V, S. O.; Rios B, O.; Gonzalez A, V. J.; Cordova R, I., E-mail: mavalenz@ipn.m [IPN, Escuela Superior de Ingenieria Quimica e Industrias Extractivas, Laboratorio de Catalisis y Materiales, Zacatenco, 07738 Mexico D. F. (Mexico)

    2010-07-01

    The photo catalytic reduction of benzophenone was studied focussing on improving the yield to benzhydrol. TiO{sub 2} was synthesized by means of a hydrothermal technique. TiO{sub 2} (Degussa TiO{sub 2}-P25) was used as a reference. Catalysts were characterized by X-ray diffraction and nitrogen physisorption. The photo catalytic reduction was carried out in a batch reactor at 25 C under nitrogen atmosphere, acetonitrile as solvent and isopropanol as electron donor. A 200 W Xe-Hg lamp ({lambda}= 360 nm) was employed as irradiation source. The chemical composition of the reaction system was determined by HPLC. Structural and textural properties of the synthesized TiO{sub 2} depended on the type of acid used during sol formation step. Using HCl, a higher specific surface area and narrower pore size distribution of TiO{sub 2} was obtained in comparison with acetic acid. As expected, the photochemical reduction of benzophenone yielded benzopinacol as main product, whereas, benzhydrol is only produced in presence of TiO{sub 2} (i.e. photo catalytic route). In general, the hydrothermally synthesized catalysts were less active and with a lower yield to benzhydrol. The optimal reaction conditions to highest values of benzhydrol yield (70-80%) were found at 2 g/L (catalyst loading) and 0.5 m M of initial concentration of benzophenone, using commercial TiO{sub 2}-P25. (Author)

  2. Electrochemical characterization of praseodymia doped zircon. Catalytic effect on the electrochemical reduction of molecular oxygen in polar organic solvents

    Energy Technology Data Exchange (ETDEWEB)

    Domenech, Antonio, E-mail: antonio.domenech@uv.es [Departament de Quimica Analitica, Universitat de Valencia, Dr. Moliner, 50, 46100 Burjassot, Valencia (Spain); Montoya, Noemi; Alarcon, Javier [Departament de Quimica Inorganica, Universitat de Valencia, Dr. Moliner, 50, 46100 Burjassot, Valencia (Spain)

    2011-08-01

    Highlights: > Electrochemical characterization of Pr centers in praseodymia-doped zircon. > Study of the catalytic effect on the reduction of peroxide radical anion in nonaqueous solvents. > Assessment of non-uniform distribution of Pr centers in the zircon grains. - Abstract: The voltammetry of microparticles and scanning electrochemical microscopy methodologies are applied to characterize praseodymium centers in praseodymia-doped zircon (Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4}; y + z = x; 0.02 < x < 0.10) specimens prepared via sol-gel synthetic routes. In contact with aqueous electrolytes, two overlapping Pr-centered cathodic processes, attributable to the Pr (IV) to Pr (III) reduction of Pr centers in different sites are obtained. In water-containing, air-saturated acetone and DMSO solutions as solvent, Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4} materials produce a significant catalytic effect on the electrochemical reduction of peroxide radical anion electrochemically generated. These electrochemical features denote that most of the Pr centers are originally in its 4+ oxidation state in the parent Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4} specimens. The variation of the catalytic performance of such specimens with potential scan rate, water concentration and Pr loading suggests that Pr is not uniformly distributed within the zircon grains, being concentrated in the outer region of such grains.

  3. Onboard measurements of nanoparticles from a SCR-equipped marine diesel engine.

    Science.gov (United States)

    Hallquist, Åsa M; Fridell, Erik; Westerlund, Jonathan; Hallquist, Mattias

    2013-01-15

    In this study nanoparticle emissions have been characterized onboard a ship with focus on number, size, and volatility. Measurements were conducted on one of the ship's four main 12,600 kW medium-speed diesel engines which use low sulfur marine residual fuel and have a Selective Catalytic Reduction (SCR) system for NO(X) abatement. The particles were measured after the SCR with an engine exhaust particle sizer spectrometer (EEPS), giving particle number and mass distributions in the size range of 5.6-560 nm. The thermal characteristics of the particles were analyzed using a volatility tandem DMA system (VTDMA). A dilution ratio of 450-520 was used which is similar to the initial real-world dilution. At a stable engine load of 75% of the maximum rated power, and after dilution and cooling of the exhaust gas, there was a bimodal number size distribution, with a major peak at ∼10 nm and a smaller peak at around 30-40 nm. The mass distribution peaked around 20 nm and at 50-60 nm. The emission factor for particle number, EF(PN), for an engine load of 75% in the open-sea was found to be 10.4 ± 1.6 × 10(16) (kg fuel)(-1) and about 50% of the particles by number were found to have a nonvolatile core at 250 °C. Additionally, 20 nm particles consist of ∼40% of nonvolatile material by volume (evaporative temperature 250 °C), while the particles with a particle diameter SCR and fuel with low sulfur content.

  4. Improvement of flue gas selective catalytic reduction technology and equipment for propane dehydrogenation (PDH) unit%丙烷脱氢装置烟气脱硝技术与设备改造

    Institute of Scientific and Technical Information of China (English)

    刘唯奇; 张国甫; 高海见; 陈金锋

    2016-01-01

    为降低烟气中的氮氧化物含量,采用丹麦托普索公司催化剂和工艺技术,在烟气余热锅炉内增加脱硝段,以满足达标排放的目的.并与工程公司合作,优化脱硝注氨系统的工艺流程,减少氨水消耗量,降低氨逃逸浓度.技术与设备改进后,烟色得到改善,烟气中的NOx含量大幅降低,同时氨水消耗量低于设计值,产生了良好的环境效益和经济效益.%The NOx concentration in the flue gas is reduced for standardized emission by a selective catalytic reduction (SCR) reactor installed in the waste heat boiler.The catalyst and reactor design are provided by Denmark HALDOR TOPSOE.New ammonia injection process is studied with engineering company to reduce ammonia consumption and slip concentration.After the improvement of process and equipment,the colour of flue gas looks better than before.The flue gas NOx concentration is significantly decreased and ammonia consumption is lower than hte design value,which produce good environmental and economic benefits.

  5. Selective catalytic reduction of NOx from diesel engine exhaust using injection of urea. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Hultermans, R.J.

    1995-09-25

    ;Contents: Diesel exhaust NOx formation and abatement (Diesel DeNOxing literature, System Considerations, Summary); Catalytic testing (Experimental facilities for testing catalysts, transport phenomena in steady state fixed bed reactors, Catalyst testing); Development of a urea injection system.

  6. Novel Catalytic Reactor for CO2 Reduction via Sabatier Process Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Precision Combustion, Inc. (PCI) proposes to develop a novel, efficient, and lightweight catalytic Sabatier CO2 methanation unit, capable of converting a mixture of...

  7. Active sites for NO reduction over Fe-ZSM-5 catalysts.

    Science.gov (United States)

    Schwidder, M; Santhosh Kumar, M; Brückner, A; Grünert, W

    2005-02-14

    A study of Fe-ZSM-5 catalysts with variable amounts of isolated, oligomeric and heavily aggregated Fe3+ oxo sites (as evidenced by UV-Vis and EPR spectroscopic data) and their catalytic properties in the selective catalytic reduction of NO by isobutane or by NH3 is presented, which allows development of a unified concept of the active Fe sites in these reactions, according to which isolated Fe sites catalyse both SCR reactions while oligomeric sites, though also involved in the selective reduction path, limit the catalyst performance by causing the total oxidation of the reductant. PMID:15685345

  8. Reactivity of Surface Nitrates in H2-Assisted SCR of NOx Over Ag/Al2O3 Catalyst

    DEFF Research Database (Denmark)

    Sadokhina, N. A.; Doronkin, Dmitry E.; Baeva, G. N.;

    2013-01-01

    The role of nitrate ad-species in H2-assisted SCR over Ag/Al2O3 was compared in NH3-SCR and n-C6H14-SCR processes. It was found that nitrates could be reduced by NH3 or n-C6H14 at similar rates with H2 co-feeding which indicates a common rate-limiting step. However, contributions of surface nitrate...... reduction to the overall NH3-SCR or n-C6H14-SCR are different as revealed by comparing the rates of nitrate reduction with the rates of steady-state processes. The rate of the steady-state n-C6H14-SCR is virtually identical to the rate of surface nitrate reduction suggesting a significant contribution...... of the surface nitrates reduction to the overall n-C6H14-SCR process. On the other hand, the steady-state rate of NH3-SCR is by ~15 times higher, which indicates that the reduction of surface nitrates plays a marginal role in the overall NH3-SCR....

  9. Selective catalytic reduction of NOx from exhaust of lean-burn engine over Ag-Al2O3/cordierite catalyst

    Institute of Scientific and Technical Information of China (English)

    LI Junhua; KANG Shoufang; FU Lixin; HAO Jiming

    2007-01-01

    A highly effective Ag-Al2O3 catalyst was prepared using the in-situ sol-gel method,and characterized by surface area using nitrogen adsorption,scanning electron microscopy(SEM),and transmission electron microscopy(TEM)techniques.The catalyst performance was tested on a real lean-burn gasoline engine.Only unburned hydrocarbons and carbon monoxide in the exhaust were directly used as reductant(without any external reductant),the maximum NOx conversion could only reach 40% at 450℃.When an external reductant,ethanol was added,the average NOx conversion was greater than 60%.At exhaust gas temperature range of 350-500℃.the maximum NOx conversion reached about 90%.CO and HC could be efficiently oxidized with Pt-AlO3 oxidation catalyst placed at the end of SCR converter.However,NOx conversion drastically decreased because of the oxidation of some intermediates to NOx again.The possible reaction mechanism was proposed as two typical processes,nitration,and reduction in HC-SCR over Ag-Al2O3.

  10. Ultra Low NOx Catalytic Combustion for IGCC Power Plants

    Energy Technology Data Exchange (ETDEWEB)

    Shahrokh Etemad; Benjamin Baird; Sandeep Alavandi; William Pfefferle

    2008-03-31

    to be active in ammonia reduction in fuel allowing potential reductions in the burner NOx production. These reductions of NOx emissions and expanded alternative fuel capability make the rich catalytic combustor uniquely situated to provide reductions in capital costs through elimination of requirements for SCR, operating costs through reduction in need for NOx abating dilution, SCR operating costs, and need for co-firing fuels allowing use of lower value but more available fuels, and efficiency of an engine through reduction in dilution flows.

  11. NH3选择性还原NOx技术在重型柴油车尾气净化中的应用%Selective catalytic reduction of NOx by NH3 for heavy-duty diesel vehicles

    Institute of Scientific and Technical Information of China (English)

    刘福东; 单文坡; 潘大伟; 李腾英; 贺泓

    2014-01-01

    基于实验室对柴油车用V2O5-WO3/TiO2催化剂配方以及涂覆成型技术的大量研究,设计了一条产量为6000只/月的NH3选择性催化还原NOx (NH3-SCR)催化剂中试生产线,并对生产的催化剂产品进行了发动机台架测试。结果表明,实验室制备的V2O5-WO3/TiO2粉体催化剂和生产线产品,在空速为50000 h-1和200-450°C条件下NOx转化率均可达80%以上;采用大尺寸堇青石载体涂覆后制备的V2O5-WO3/TiO2整体催化剂经实验室小样测试,在空速为10000-30000 h-1和250-450°C条件下NOx转化率也为80%以上。发动机台架测试结果表明,该催化剂产品可使重型柴油机NOx排放达到国IV标准中欧洲稳态循环(ESC)和欧洲瞬态循环(ETC)排放限值的要求。该生产线经适当调整后也可用于生产非钒基NH3-SCR整体催化剂,以满足未来钒基NH3-SCR催化剂更新换代的需求。%A catalyst production line with a production capacity of 6000 catalyst monoliths per month for the selective catalytic reduction of NOx by NH3 (NH3-SCR) for NOx abatement in diesel vehicle exhaust was set up based on a detailed laboratory study of the catalyst formulation and washcoating tech-nology for V2O5-WO3/TiO2 catalyst. The catalyst produced by this line was tested on a bench scale diesel engine. The V2O5-WO3/TiO2 powder catalyst prepared in the laboratory and production line both achieved>80%NOx conversion at 200-450 °C and a GHSV of 50000 h-1. The washcoated cata-lyst used a large cordierite support and gave>80%NOx conversion at 250-450 °C and GHSVs of 10000-30000 h-1. The engine bench tests showed that after treatment by the catalyst, the NOx emis-sion met the European steady-state cycle (ESC) and European transient cycle (ETC) limits of the China IV standard. The production line can also be used for the production of vanadium-free NH3-SCR catalysts to meet the required replacement of the present vanadium-based NH3-SCR cata-lyst in the future.

  12. Chitosan based polymer matrix with silver nanoparticles decorated multiwalled carbon nanotubes for catalytic reduction of 4-nitrophenol.

    Science.gov (United States)

    Alshehri, Saad M; Almuqati, Turki; Almuqati, Naif; Al-Farraj, Eida; Alhokbany, Norah; Ahamad, Tansir

    2016-10-20

    A novel catalyst for the reduction of 4-nitrophenol (4-NP) was prepared using carboxyl group-functionalized multiwalled carbon nanotubes (MWCNTs), polymer matrix, and silver nanoparticles (AgNPs). The AgNPs were prepared by the reduction of silver nitrate by trisodium citrate in the MWCNTs-polymer nanocomposite; the size of the synthesized AgNPs was found to be 3nm (average diameter). The synthesized nanocomposites were characterized using several analytical techniques. Ag@MWCNTs-polymer composite in the presence of sodium borohydride (NaBH4) in aqueous solution is an effective catalyst for the reduction of 4-NP. The apparent kinetics of reduction has a pseudo-first-order kinetics, and the rate constant and catalytic activity parameter were found to be respectively 7.88×10(-3)s(-1)and 11.64s(-1)g(-1). The MWCNTs-polymer nanocomposite renders stability to AgNPs against the environment and the reaction medium, which means that the Ag@MWCNTs-polymer composite can be re-used for many catalytic cycles. PMID:27474552

  13. Uniform Ni/SiO2@Au magnetic hollow microspheres: rational design and excellent catalytic performance in 4-nitrophenol reduction

    Science.gov (United States)

    Zhang, Shenghuan; Gai, Shili; He, Fei; Dai, Yunlu; Gao, Peng; Li, Lei; Chen, Yujin; Yang, Piaoping

    2014-05-01

    A unique and rational design was presented to fabricate Ni/SiO2@Au magnetic hollow microspheres (MHMs) with interesting structures and well-dispersed metal nanoparticles. Hierarchical nickel silicate hollow microspheres were synthesized using silica colloidal spheres as a chemical template. Then, Ni/SiO2 MHMs with well-dispersed Ni nanoparticles were prepared via an in situ reduction approach. Ni/SiO2@Au MHMs were finally obtained by immobilizing uniform Au nanoparticles onto Ni/SiO2 support through a low-temperature chemical reduction process. It was found that Ni/SiO2@Au MHMs inherit the shape and uniformity of the original silica scaffold, and Ni NPs and Au NPs, which were less than 5 nm in size, were well dispersed on the mesoporous silica shell with narrow size distribution. Both Ni/SiO2 and Ni/SiO2@Au MHMs showed excellent catalytic activity in the 4-nitrophenol reduction reaction. Importantly, introduction of a small amount of Au NPs onto Ni/SiO2 MHMs markedly improved the catalytic activity. In particular, Ni/SiO2@Au MHMs showed high conversion even after re-use for several cycles with magnetic separation. The unique structure, high catalytic performance, and ease of separation make Ni/SiO2@Au MHMs highly promising candidates for diverse applications.A unique and rational design was presented to fabricate Ni/SiO2@Au magnetic hollow microspheres (MHMs) with interesting structures and well-dispersed metal nanoparticles. Hierarchical nickel silicate hollow microspheres were synthesized using silica colloidal spheres as a chemical template. Then, Ni/SiO2 MHMs with well-dispersed Ni nanoparticles were prepared via an in situ reduction approach. Ni/SiO2@Au MHMs were finally obtained by immobilizing uniform Au nanoparticles onto Ni/SiO2 support through a low-temperature chemical reduction process. It was found that Ni/SiO2@Au MHMs inherit the shape and uniformity of the original silica scaffold, and Ni NPs and Au NPs, which were less than 5 nm in size, were well

  14. Plasma-catalytic Selective Reduction of NO with C2H4 in the Presence of Excess Oxygen

    Institute of Scientific and Technical Information of China (English)

    Qi SUN; Ai Min ZHU; Xue Feng YANG; Jin Hai NIU; Yong XU; Zhi Min SONG; Jing LIU

    2005-01-01

    This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at250 ℃ in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor.With the reactant gas mixture of 530 ppm NO, 650 ppm C2H4, 5.8% O2 in N2and GHSV = 12000h-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasmacatalytic (in the POC reactor) NOx conversion are 39%, 1.5% and 79%, respectively. The in-situ optical emission spectra of the reactive systems imply some short-lived active species formed from plasma-induced and plasma-catalytic processes may be responsible to the observed synergistic effects in this one-stage POC system.

  15. Effect of Ce doping of TiO2 support on NH3-SCR activity over V2O5-WO3/CeO2-TiO2 catalyst.

    Science.gov (United States)

    Cheng, Kai; Liu, Jian; Zhang, Tao; Li, Jianmei; Zhao, Zhen; Wei, Yuechang; Jiang, Guiyuan; Duan, Aijun

    2014-10-01

    CeO2-TiO2 composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5-WO3/CeO2-TiO2 catalysts for the selective catalytic reduction (SCR) of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV-Vis, Raman and XPS techniques. The results showed that the catalytic activity of V2O5-WO3/TiO2 was greatly enhanced by Ce doping (molar ratio of Ce/Ti=1/10) in the TiO2 support. The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning. PMID:25288555

  16. Effect of Ce doping of TiO2 support on NH3-SCR activity over V2O5-WO3/CeO2-TiO2 catalyst.

    Science.gov (United States)

    Cheng, Kai; Liu, Jian; Zhang, Tao; Li, Jianmei; Zhao, Zhen; Wei, Yuechang; Jiang, Guiyuan; Duan, Aijun

    2014-10-01

    CeO2-TiO2 composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5-WO3/CeO2-TiO2 catalysts for the selective catalytic reduction (SCR) of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV-Vis, Raman and XPS techniques. The results showed that the catalytic activity of V2O5-WO3/TiO2 was greatly enhanced by Ce doping (molar ratio of Ce/Ti=1/10) in the TiO2 support. The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning.

  17. Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium.

    Science.gov (United States)

    Pullamsetty, Ashok; Sundara, Ramaprabhu

    2016-10-01

    Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts. PMID:27393888

  18. Evaluation of the first SCR-plants in Sweden; Utvaerdering av de foersta SCR-anlaeggningarna i Sverige

    Energy Technology Data Exchange (ETDEWEB)

    Hanell, B. [Vattenfall AB, Stockholm (Sweden)] [and others

    1996-05-01

    This report presents operational experience of SCR systems at five power plants in Sweden; the diesel cogeneration plants in Linkoeping, Oskarshamn, Skultuna and Visby and the coal fired power plant in Vaesteraas. The experience represents the first years of operation of the SCR systems. The SCR-systems involved in this project achieve the following: * Uneven flue gas flow and concentration of ammonia and NO{sub x} through the SCR reactor results in lower efficiency. Hence it is important to achieve a thorough mixing of the ammonia in the flue gas in order to achieve high NO{sub x} reduction efficiencies, * Inferior control systems can cause unnecessary ammonia slip, * The diesel plants with an operating time of a couple of thousand hours have had major problems with deposits on the catalyst surface, * Guarantees regarding the lifetime of the catalyst are important. At commissioning the catalyst has to be over-dimensioned since the system has to reach the guaranteed emissions during the whole guarantee period, * There should be enough space in the reactor to install additional catalyst layers. This project verifies that additional layers need to be installed at later stages, * The mechanical construction of the SCR-reactor is important. The efficiency decreases when there is a leakage of flue gases past the reactor, * No considerable amounts of N{sub 2}O are generated by the catalyst. 21 refs, 27 figs, 47 tabs

  19. Characterization and performance of Pt/SBA-15 for low-temperature SCR of NO by C3H6

    Institute of Scientific and Technical Information of China (English)

    Xinyong Liu; Zhi Jiang; Mingxia Chen; Jianwei Shi; Wenfeng Shangguan; Yasutake Teraoka

    2013-01-01

    Pt supported on mesoporous silica SBA-15 was investigated as a catalyst for low temperature selective catalytic reduction (SCR) of NO by C3H6 in the presence of excess oxygen.The prepared catalysts were characterized by means of XRD,BET surface area,TEM,NO-TPD,NO/C3H6-TPO,NH3-TPD,XPS and 27Al MAS NMR.The effects of Pt loading amount,O2/C3H6 concentration,and incorporation of Al into SBA-15 have been studied.It was found that the removal efficiency increased significantly after Pt loading,but an optimal loading amount was observed.In particular,under an atmosphere of 150 ppm NO,150 ppm C3H6,and 18 vol.% O2,0.5% Pt/SBA-15 showed remarkably high catalytic performance giving 80.1% NOx reduction and 87.04% C3H6 conversion simultaneously at 140℃.The enhanced SCR activity of Pt/SBA-15 is associated with its outstanding oxidation activities of NO to NO2 and C3H6 to CO2 in low temperature range.The research results also suggested that higher concentration of O2 and higher concentration of C3H6 favored NO removal.The incorporation of A1 into SBA-15 improved catalytic performance,which could be ascribed to the enhancement of catalyst surface acidity caused by tetrahedrally coordinated AlO4.Moreover,the catalysts could be easily reused and possessed good stability.

  20. The role of isolated Cu2+ location in structural stability of Cu-modified SAPO-34 in NH3-SCR of NO.

    Science.gov (United States)

    Yan, Chundi; Cheng, Hao; Yuan, Zhongshan; Wang, Shudong

    2015-01-01

    In this study, three different methods (ion exchange, wet mixing and impregnation) were employed to prepare Cu-modified SAPO-34 molecular sieves. All these freshly prepared catalysts showed excellent activities towards the selective catalytic reduction (SCR) of NO with NH3 (NH3-SCR) no matter which preparation method was used. However, hydrothermal ageing significantly reduced the catalytic activities of those catalysts prepared by the wet-mixing and impregnation methods, respectively. The results of X-ray powder diffraction, H2-TPR and electron paramagnetic resonance measurements for these catalysts suggested that the decrease in catalytic activity may be attributed to the migration of Cu2+ ion to the centre of the hexagonal prism (site III), the formation of CuxOy and the collapse of the molecular framework during hydrothermal ageing. The degrees of structural collapse of each Cu-modified molecular sieve were different, probably due to Cu2+ species in different sites (in the ellipsoidal cavity (site I) for ion-exchange sample, near the eight-ring window (site IV) for the wet-mixing and impregnation samples). Cu2+ located at site I was more stable than that located at site IV.

  1. Selective Catalytic Reduction of NO with NH3 Over V-MCM-41 Catalyst.

    Science.gov (United States)

    Kwon, Woo Hyun; Park, Sung Hoon; Kim, Ji Man; Park, Su Bin; Jung, Sang-Chul; Kim, Sang Chai; Jeon, Jong-Ki; Park, Young-Kwon

    2016-02-01

    V-MCM-41, a mesoporous catalyst doped with V2O5, was applied for the first time to the removal of atmospheric NO. The quantity of V2O5 added was 10 wt% and 30 wt%. The characteristics of the synthesized catalysts were examined using XRD, N2 soprtion, and NH3-TPD. With increasing quantity of V2O5 added, specific surface area decreased and pore size increased. When the quantity of V2O5 was 10 wt%, the MCM-41 structure was retained, whereas considerable collapse of mesoporous structure was observed when 30 wt% V2O5 was added. The examination of acid characteristics using NH3-TPD showed that 30 wt% V-MCM-41 had the higher NH3 adsorption ability, implying that it would exhibit high activity for NH3 SCR reaction. In the NO removal experiments, 30 wt% V-MCM-41 showed much higher NO removal efficiency than 10 wt% V-MCM-41, which was attributed to its high NH3 adsorption ability. PMID:27433662

  2. Highly active Ag clusters stabilized on TiO2 nanocrystals for catalytic reduction of p-nitrophenol

    Science.gov (United States)

    Wang, Xin; Zhao, Zhe; Ou, Dingrong; Tu, Baofeng; Cui, Daan; Wei, Xuming; Cheng, Mojie

    2016-11-01

    Ag/TiO2 nanocomposites comprising of Ag clusters on TiO2 nanocrystal surfaces are of great significance in catalysts and advanced functional materials. Herein a novel method to synthesize Ag/TiO2 nanocomposites with Ag clusters under 2 nm on TiO2 nanocrystal surfaces have been developed. The success of this method relies on a silver mirror reaction in toluene, which refers to the reduction of silver-dodecylamine complexes by acetaldehyde in the presence of mono-dispersed TiO2 nanocrystals. The prepared Ag/TiO2 nanocomposites have been characterized by FT-IR spectra, UV-vis absorption spectra, X-ray diffraction (XRD) analysis, ultra high resolution scanning electron microscope (Ultra-HRSEM), high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectra (XPS). Catalytic activity of Ag/TiO2 nanocomposites is evaluated for the reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) by NaBH4. Results demonstrate that Ag/TiO2 nanocomposites have shown an outstanding catalytic activity as well as a good stability in successive reduction of 4-NP. Noticeably, TOF of Ag/TiO2-0.75 nanocomposites obtained in this work is the highest among Ag based catalysts previously reported.

  3. Modelling of catalytic oxidation of NH3 and reduction of NO on limestone during sulphur capture

    DEFF Research Database (Denmark)

    Kiil, Søren; Bhatia, Suresh K.; Dam-Johansen, Kim

    1996-01-01

    A theoretical study of the complex transient system of simultaneous sulphur capture and catalytic reactions of N-containing compounds taking place on a single limestone particle is conducted. The numerical technique developed previously by the authors (Kiil et al. 1994) based on collocation...... on moving finite elements is used to solve the model equations. To our knowledge, this is the first serious attempt to model such transient systems in detail. The particle is divided into moving zones, described by the reaction between limestone and SO2, and each zone is assigned a certain catalytic...... activity with respect to each species involved. An existing particle model, the Grain-Micrograin Model, which simulates sulphur capture on limestone under oxidizing conditions is considered in the modelling. Simulation results in good qualitative agreement with experimental data are obtained here...

  4. Experimental Study of Selective Catalytic Reduction System On CI Engine Fuelled with Diesel-Ethanol Blend for NOx Reduction with Injection of Urea Solutions

    Directory of Open Access Journals (Sweden)

    R. Praveen

    2014-05-01

    Full Text Available Nowadays exhaust emission control from internal combustion engines have become one of the most important challenges. Oxides of nitrogen (NOx are one of the major hazardous pollutants that come out from diesel engines. There are various techniques existing for NOx control but each techniques has its own advantages and disadvantages. Technologies available for NOx reductions either increase other polluting gas emission or increase fuel consumption. The objective of this paper is to determine the maximum reduction of NOx emissions by varying concentration of urea solution with reduction catalyst. An aqueous solution of urea was injected in engine exhaust pipe for reducing NOx emissions in single cylinder light duty stationery DI diesel engine fuelled with diesel and diesel- (10% ethanol blend. A concentration of urea solution varying from 30 to 35% by weight with constant flow rates and tested with fitting Titanium dioxide (TiO2 coated catalyst which controls by products of ammonia and water vapour. Results indicated that a maximum of 70 % of NOx reduction was achieved an engine fuelled with diesel-ethanol blend and constant flow rate of 0.75 lit/hr with an urea concentration of 35% and 66% NOx of reduced with neat diesel using Titanium dioxide catalyst in Selective Catalytic Reduction system.

  5. Influence of real-world engine load conditions on nanoparticle emissions from a DPF and SCR equipped heavy-duty diesel engine.

    Science.gov (United States)

    Thiruvengadam, Arvind; Besch, Marc C; Carder, Daniel K; Oshinuga, Adewale; Gautam, Mridul

    2012-02-01

    The experiments aimed at investigating the effect of real-world engine load conditions on nanoparticle emissions from a Diesel Particulate Filter and Selective Catalytic Reduction after-treatment system (DPF-SCR) equipped heavy-duty diesel engine. The results showed the emission of nucleation mode particles in the size range of 6-15 nm at conditions with high exhaust temperatures. A direct result of higher exhaust temperatures (over 380 °C) contributing to higher concentration of nucleation mode nanoparticles is presented in this study. The action of an SCR catalyst with urea injection was found to increase the particle number count by over an order of magnitude in comparison to DPF out particle concentrations. Engine operations resulting in exhaust temperatures below 380 °C did not contribute to significant nucleation mode nanoparticle concentrations. The study further suggests the fact that SCR-equipped engines operating within the Not-To-Exceed (NTE) zone over a critical exhaust temperature and under favorable ambient dilution conditions could contribute to high nanoparticle concentrations to the environment. Also, some of the high temperature modes resulted in DPF out accumulation mode (between 50 and 200 nm) particle concentrations an order of magnitude greater than typical background PM concentrations. This leads to the conclusion that sustained NTE operation could trigger high temperature passive regeneration which in turn would result in lower filtration efficiencies of the DPF that further contributes to the increased solid fraction of the PM number count.

  6. MnO{sub x}-Nb{sub 2}O{sub 3}-CeO{sub 2} - A New Catalyst For Low-Temperature SCR With Reduced N{sub 2}O Formation

    Energy Technology Data Exchange (ETDEWEB)

    Kroecher, O.; Elsener, M.

    2005-03-01

    MnOx-CeO2 was found to be up to 5 times more active for the selective catalytic reduction of NO{sub x} with ammonia (SCR) than the established V{sub 2}O{sub 5}/WO{sub 3}-TiO{sub 2} catalysts at temperatures below 250 C. The SCR activity of MnO{sub x}-CeO{sub 2} itself was further improved by a factor of 1.3-65 by the addition of Nb{sub 2}O{sub 3}, depending on the temperature (125-350 C). Moreover, a strong decrease in the selectivity to the side-product N{sub 2}O was observed, especially in the low-temperature range. (author)

  7. Promotional effect of CO pretreatment on CuO/CeO2 catalyst for catalytic reduction of NO by CO

    Institute of Scientific and Technical Information of China (English)

    顾贤睿; 李昊; 刘礼晨; 汤常金; 高飞; 董林

    2014-01-01

    The CuO/CeO2 catalysts were investigated by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectronic spectroscopy (XPS), temperature-programmed reduction (TPR), in situ Fourier transform infrared spectroscopy (FTIR) and NO+CO reaction. The results revealed that the low temperature (<150 °C) catalytic performances were enhanced for CO pretreated samples. During CO pretreatment, the surface Cu+/Cu0 and oxygen vacancies on ceria surface were present. The low va-lence copper species activated the adsorbed CO and surface oxygen vacancies facilitated the NO dissociation. These effects in turn led to higher activities of CuO/CeO2 for NO reduction. The current study provided helpful understandings of active sites and reaction mechanism in NO+CO reaction.

  8. Analysis and study on the performance variation of SCR DeNOx catalyst of Coal-Fired Boilers

    International Nuclear Information System (INIS)

    Nitrogen oxides (NOx) are one kind of harmful substances from the burning process of fossil fuel and air at high temperature. NOx emissions cause serious pollution on atmospheric environment. In this paper, coal-fired utility boilers were chosen as the object, NOx formation mechanism and control were studied, and SCR deNOx technology was used to control NOx emissions from coal-fired boilers. Analyzed the relationship between deNOx efficiency and characteristics of SCR DeNOx catalyst. Through analysis, affecting SCR DeNOx catalyst failure factors, change law of catalytic properties and technical measures to extend the service life of the catalyst were gotten. (author)

  9. Impact of Substituents Attached to N-Heterocyclic Carbenes on the Catalytic Activity of Copper Complexes in the Reduction of Carbonyl Compounds with Triethoxysilane

    Institute of Scientific and Technical Information of China (English)

    PENG, Jiajian; CHEN, Lingzhen; XU, Zheng; HU, Yingqian; LI, Jiayun; BAI, Ying; QIU, Huayu; LAI, Guoqiao

    2009-01-01

    By using functionalized imidazolium salts such as 1-allyl-3-alkylimidazolium or 1-alkyi-3-vinylimidazolium salts as carbene ligand precursors, the reduction of aryl ketones with triethoxysilane may be catalyzed by copper salt/imidazolium salt/KO~tBu systems. The functional substituents attached to the N-heterocyclic carbene (NHC) serve to enhance the catalytic activity. Different copper salts also have an effect on the catalytic activity, with copper(Ⅱ) acetate monohydrate being superior to copper(I) chloride.

  10. The selective catalytic reduction of NO with NH{sub 3} over a novel Ce–Sn–Ti mixed oxides catalyst: Promotional effect of SnO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ming’e [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Li, Caiting, E-mail: ctli@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Zeng, Guangming; Zhou, Yang; Zhang, Xunan; Xie, Yin’e [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China)

    2015-07-01

    Graphical abstract: - Highlights: • A novel catalyst was developed for selective catalytic reduction of NO with NH{sub 3}. • The NO removal efficiency of CeTi catalyst was improved by the addition of SnO{sub 2}. • The novel catalyst possessed remarkable resistance to H{sub 2}O and SO{sub 2}. • The promotional effects of SnO{sub 2} were investigated in detail. • Possible reaction mechanism over the novel catalyst was discussed. - Abstract: A series of novel catalysts (CexSny) for the selective catalytic reduction of NO by NH{sub 3} were prepared by the inverse co-precipitation method. The aim of this novel design was to improve the NO removal efficiency of CeTi by the introduction of SnO{sub 2}. It was found that the Ce–Sn–Ti catalyst was much more active than Ce–Ti and the best Ce:Sn molar ratio was 2:1. Ce2Sn1 possessed a satisfied NO removal efficiency at low temperature (160–280 °C), while over 90% NO removal efficiency maintained in the temperature range of 280–400 °C at the gas hourly space velocity (GHSV) of 50,000 h{sup −1}. Besides, Ce2Sn1 kept a stable NO removal efficiency within a wide range of GHSV and a long period of reacting time. Meanwhile, Ce2Sn1 exhibited remarkable resistance to both respectively and simultaneously H{sub 2}O and SO{sub 2} poisoning due to the introduction of SnO{sub 2}. The promotional effect of SnO{sub 2} was studied by N{sub 2} adsorption–desorption, X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS) and H{sub 2} temperature programmed reduction (H{sub 2}-TPR) for detail information. The characterization results revealed that the excellent catalytic performance of Ce2Sn1 was associated with the higher specific surface area, larger pore volume and poorer crystallization. Besides, the introduction of SnO{sub 2} could result in not only greater conversion of Ce{sup 4+} to Ce{sup 3+} but also the increase amount of chemisorbed oxygen, which are beneficial to improve the SCR

  11. Low-temperature SCR of NO{sub x} with NH{sub 3} over carbon-ceramic supported catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Valdes-Solis, Teresa; Marban, Gregorio; Fuertes, Antonio B. [Instituto Nacional del Carbon (CSIC), c/Francisco Pintado Fe No. 26, 33011 Oviedo (Spain)

    2003-11-10

    A new method for preparing vanadium oxide supported on carbon-ceramic cellular monoliths is described. This includes a support oxidation step with HNO{sub 3}, followed by ionic exchange with a NaOH solution, equilibrium adsorption impregnation of VO{sup 2+} and thermal treatment. As a result an active catalyst for low-temperature selective catalytic reduction (SCR) reaction is obtained. The V-catalyst is more resistant to SO{sub 2} poisoning than the previously developed Mn-catalyst. Inhibition by water is reversible for both types of catalysts. Testing of the vanadium catalyst after subjecting it to the outlet gas stream of a power plant shows fast deactivation until constant residual activity is reached. Deactivation seems to be caused by arsenic poisoning and the formation of superficial sulphates.

  12. Novel Catalytic Reactor for CO2 Reduction via Sabatier Process Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A novel short contact time Microlith Sabatier reactor system for CO2 reduction offers a significant advance in support of manned spaceflight. Compared to current...

  13. A facile approach to fabricate Au nanoparticles loaded SiO2 microspheres for catalytic reduction of 4-nitrophenol

    International Nuclear Information System (INIS)

    Hydrophilic and biocompatible macromolecules were used to improve and simplify the process for the fabrication of core/shell SiO2@Au composite particles. The influence of polymers on the morphology of SiO2@Au particles with different size of SiO2 cores was analyzed by transmission electron microscopy and scanning electron microscopy. The optical property of the SiO2@Au particles was studied with UV–Vis spectroscopy. The results indicate that the structure and composition of macromolecules affect the morphology of Au layers on SiO2 microspheres. The SiO2@Au particles prepared in the presence of polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) have thin and complete Au nanoshells owing to their inducing act in preferential growth of Au nanoparticles along the surface of SiO2 microspheres. SiO2@Au particles can be also prepared from SiO2 microspheres modified with 3-aminopropyltrimethoxysilane in the presence of PVA or PVP. This offers a simple way to fabricate a Au layer on SiO2 or other microspheres. The SiO2@Au particles demonstrated high catalytic activity in the reduction of 4-nitrophenol. - Highlights: • Facile direct deposition method for Au nanoparticles on silica microspheres. • Influence of different types of macromolecule on the formation of Au shell. • High catalytic performance of Au nanoparticles on silica microspheres

  14. A facile approach to fabricate Au nanoparticles loaded SiO{sub 2} microspheres for catalytic reduction of 4-nitrophenol

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Mingyi, E-mail: mingyitjucu@163.com [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Huang, Guanbo, E-mail: gbhuang2007@hotmail.com [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China); Li, Xianxian; Pang, Xiaobo [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Qiu, Haixia [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China)

    2015-07-15

    Hydrophilic and biocompatible macromolecules were used to improve and simplify the process for the fabrication of core/shell SiO{sub 2}@Au composite particles. The influence of polymers on the morphology of SiO{sub 2}@Au particles with different size of SiO{sub 2} cores was analyzed by transmission electron microscopy and scanning electron microscopy. The optical property of the SiO{sub 2}@Au particles was studied with UV–Vis spectroscopy. The results indicate that the structure and composition of macromolecules affect the morphology of Au layers on SiO{sub 2} microspheres. The SiO{sub 2}@Au particles prepared in the presence of polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) have thin and complete Au nanoshells owing to their inducing act in preferential growth of Au nanoparticles along the surface of SiO{sub 2} microspheres. SiO{sub 2}@Au particles can be also prepared from SiO{sub 2} microspheres modified with 3-aminopropyltrimethoxysilane in the presence of PVA or PVP. This offers a simple way to fabricate a Au layer on SiO{sub 2} or other microspheres. The SiO{sub 2}@Au particles demonstrated high catalytic activity in the reduction of 4-nitrophenol. - Highlights: • Facile direct deposition method for Au nanoparticles on silica microspheres. • Influence of different types of macromolecule on the formation of Au shell. • High catalytic performance of Au nanoparticles on silica microspheres.

  15. Low-temperature selective catalytic reduction of NO with NH3 based on MnOx-CeOx/ACFN

    Institute of Scientific and Technical Information of China (English)

    Boxiong SHEN; Ting LIU; Zhanliang SHI; Jianwei SHI; Tingting YANG; Ning ZHAO

    2008-01-01

    MnOx-CeOx/ACFN were prepared by the impregnation method and used as catalyst for selective catalytic reduction of NO with NH3 at 80℃-150℃.The catalyst was characterized by N2-BET,scanning electron microscopy (SEM) and Fourier transform infrared spec-troscopy (FT-IR).The fraction of the mesopore and the oxygen functional groups on the surface of activated car-bon fiber (ACF) increased after the treatment with nitric acid,which was favorable to improve the catalytic activ-ities of MnOx-CeOx/ACFN.The experimental results show that the conversion of NO is nearly 100% in the range 100℃-150℃ under the optimal preparation condi-tions of MnOx-CeOx/ACFN.In addition,the effects of a series of performance parameters,including initial NH3 concentration,NO concentration and O2 concentration,on the conversion of NO were studied.

  16. Mesoporous titania-alumina mixed oxide: A preliminary study on synthesis and application in selective catalytic reduction of NOx

    International Nuclear Information System (INIS)

    Titania-alumina mixed oxide was synthesized hydrothermally using tetrapropylammonium hydroxide (TPAOH) as the template. The dried, calcined and palladium loaded samples were characterized for particle morphology, weight loss, nitrogen adsorption/desorption at liquid nitrogen temperature, texture and metal dispersion. The Pd loaded material was tested for NO reduction in a fixed bed catalytic reactor using a simulated gas mixture closely resembling lean burn engine exhaust. Scanning electron microscopy of the dried and calcined samples revealed a well developed tubular fibrous network of titania-alumina. Thermogravimetry (TG) of the dried sample indicated about 16% weight loss due to decomposition of an oxy-hydroxide structure of the material, mostly boehmite, which was confirmed by X-ray diffraction (XRD) measurements. The boehmite phase changed to poorly crystalline γ-alumina upon calcination where as titania remained as anatase. BET specific surface area, adsorption-desorption isotherms and BJH pore size distributions indicated formation of a mesoporous structure. The surface area of the dried material increased when calcined at 600 deg. C but the pore size distribution patterns for the dried, calcined and palladium dispersed materials remained unchanged. These observations along with TG and XRD analyses suggest that a thermo-resistant, mesoporous, high surface area, crystalline titania-alumina framework can be prepared using the hydrothermal synthesis route. A peak NOx conversion of 75% with the palladium dispersed catalyst indicates high catalytic activity, possibly due to high dispersion of Pd confirmed by CO chemisorption studies

  17. Fe-MCM-41 from Coal-Series Kaolin as Catalysts for the Selective Catalytic Reduction of NO with Ammonia

    Science.gov (United States)

    Li, Shuiping; Wu, Qisheng; Lu, Guosen; Zhang, Changsen; Liu, Xueran; Cui, Chong; Yan, Zhiye

    2013-12-01

    Fe-MCM-41, one kind of high-ordered mesoporous materials catalysts, with molar ratio of Fe/Si = 0.01-0.1, was synthesized by hydrothermal method from coal-series kaolin. Fe-MCM-41 catalysts were characterized by Fourier transform infrared spectroscopy, high resolution transmission electron microscopy, N2 adsorption-desorption, x-ray photoelectron spectroscopy, and UV-vis spectroscopy. The results clearly indicated that: (1) all the samples exhibited typical hexagonal arrangement of mesoporous structure; (2) the incorporation of tiny amount of Fe3+ onto the surface and pore channel of MCM-41 mesoporous materials could efficiently promote the deNO x activity of these catalysts. Moreover, the Fe-MCM-41 mesoporous materials were evaluated in the selective catalytic reduction of NO with NH3. The results showed that Fe-MCM-41 catalyst with Fe/Si = 0.05 showed the highest catalytic activity at 350 °C, a gas hourly space velocity of 5000 h-1, n(NH3)/ n(NO) = 1.1, and O2% = 2.5%.

  18. Onboard measurements of nanoparticles from a SCR-equipped marine diesel engine.

    Science.gov (United States)

    Hallquist, Åsa M; Fridell, Erik; Westerlund, Jonathan; Hallquist, Mattias

    2013-01-15

    In this study nanoparticle emissions have been characterized onboard a ship with focus on number, size, and volatility. Measurements were conducted on one of the ship's four main 12,600 kW medium-speed diesel engines which use low sulfur marine residual fuel and have a Selective Catalytic Reduction (SCR) system for NO(X) abatement. The particles were measured after the SCR with an engine exhaust particle sizer spectrometer (EEPS), giving particle number and mass distributions in the size range of 5.6-560 nm. The thermal characteristics of the particles were analyzed using a volatility tandem DMA system (VTDMA). A dilution ratio of 450-520 was used which is similar to the initial real-world dilution. At a stable engine load of 75% of the maximum rated power, and after dilution and cooling of the exhaust gas, there was a bimodal number size distribution, with a major peak at ∼10 nm and a smaller peak at around 30-40 nm. The mass distribution peaked around 20 nm and at 50-60 nm. The emission factor for particle number, EF(PN), for an engine load of 75% in the open-sea was found to be 10.4 ± 1.6 × 10(16) (kg fuel)(-1) and about 50% of the particles by number were found to have a nonvolatile core at 250 °C. Additionally, 20 nm particles consist of ∼40% of nonvolatile material by volume (evaporative temperature 250 °C), while the particles with a particle diameter Emission factors for NO(X), CO, and CO(2) for an engine load of 75% in the open-sea were determined to 4.06 ± 0.3 g (kg fuel)(-1), 2.15 ± 0.06 g (kg fuel)(-1), and 3.23 ± 0.08 kg (kg fuel)(-1), respectively. This work contributes to an improved understanding of particle emissions from shipping using modern pollution reduction measures such as SCR and fuel with low sulfur content. PMID:23163334

  19. A Comparative Kinetics Study between Cu/SSZ-13 and Fe/SSZ-13 SCR Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Wang, Yilin; Kollar, Marton; Washton, Nancy M.; Szanyi, Janos; Peden, Charles HF

    2015-11-09

    Cu- and Fe/SSZ-13 catalysts with the same Cu(Fe)/Al ratios are synthesized using the same parent SSZ-13 starting material. The catalytic performance for both fresh and hydrothermally aged catalysts is tested with NO and NH3 oxidation, and standard SCR reactions under steady-state conditions, and standard and fast SCR under temperature-programmed conditions. For standard SCR, Cu/SSZ-13 shows much better low-temperature performance which can be explained by NH3-inhibition of Fe/SSZ-13. During hydrothermal aging, both catalysts undergo dealumination but Fe/SSZ-13 dealuminates more severely. For aged catalysts, Cu/SSZ-13 gains oxidation activities due to formation of CuOx. However, Fe/SSZ-13 loses oxidation activities although formation of FeOx clusters and FeAlOx species also occur. Because of such physical properties differences, aged Cu/SSZ-13 loses while Fe/SSZ-13 maintains high-temperature SCR selectivities. A physical mixture of aged catalysts provides stable SCR performance in a wide temperature range and is able to decrease N2O formation at high reaction temperatures. This suggests that Fe/SSZ-13 can be used as a cocatalyst for Cu/SSZ-13 for transportation applications. During temperature-programmed SCR reactions, weak hysteresis is found during standard SCR due to NH3 inhibition. For fast SCR, hysteresis caused by NH4NO3 inhibition is much more significant. NH4NO3 deposition is greatly enhanced by Brønsted and Lewis acidity of the catalysts.

  20. Selective catalytic reduction of NO over commercial DeNO{sub x} catalysts: Comparison of the measured and calculated performance

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, M.; Elsener, M. [Paul Scherrer Inst., Villigen (Switzerland)

    1998-02-01

    The performance of selective catalytic reduction monolithic catalysts may best be characterized by plotting the ammonia slip as a function of the percentage of NO{sub x} conversion achieved. Experimental results obtained on a Diesel engine test stand have been compared with predicted values obtained by model calculations. In this way the possibilities and limits of such calculations could be shown. The model has no adjustable parameters. An exact prediction of performance is not possible under all conditions due to minor differences in composition between the real exhaust and the test gas mixtures used in the determination of the intrinsic catalyst properties. The value of such a model therefore lies in the prediction of the performance of new catalysts (e.g., layer catalysts) or under changed operating conditions (other temperature or GHSV).

  1. Size Control of Iron Oxide Nanoparticles Using Reverse Microemulsion Method: Morphology, Reduction, and Catalytic Activity in CO Hydrogenation

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Housaindokht

    2013-01-01

    Full Text Available Iron oxide nanoparticles were prepared by microemulsion method and evaluated in Fischer-Tropsch synthesis. The precipitation process was performed in a single-phase microemulsion operating region. Different HLB values of surfactant were prepared by mixing of sodium dodecyl sulfate (SDS and Triton X-100. Transmission electron microscopy (TEM, surface area, pore volume, average pore diameter, pore size distribution, and XRD patterns were used to analyze size distribution, shape, and structure of precipitated hematite nanoparticles. Furthermore, temperature programmed reduction (TPR and catalytic activity in CO hydrogenation were implemented to assess the performance of the samples. It was found that methane and CO2 selectivity and also the syngas conversion increased as the HLB value of surfactant decreased. In addition, the selectivity to heavy hydrocarbons and chain growth probability (α decreased by decreasing the catalyst crystal size.

  2. Species active in the selective catalytic reduction of no with iso-butane on iron-exchanged ZSM-5 zeolites

    Directory of Open Access Journals (Sweden)

    M. S. Batista

    2005-09-01

    Full Text Available Fe-ZSM-5 catalysts were prepared by ion exchange in aqueous medium or in the solid state and tested in the catalytic reduction of NO with iso-butane. X-ray powder diffraction (XRD, atomic absorption spectroscopy (AAS, electron paramagnetic resonance spectroscopy (EPR, X-ray absorption spectroscopy (XANES, EXAFS, temperature-programmed reduction by H2 (H2-TPR and Mössbauer spectroscopy (MÖS-S were used for sample characterisation. Irrespective of the method used in catalyst preparation, EPR, XANES and MÖS-S showed Fe atoms in the oxidation state of 3+. MÖS-S and H2-TPR data on Fe-ZSM-5 prepared by ion exchange in the solid state allowed quantification of a lower hematite (Fe2O3 concentration and a higher proportion of Fe cations than samples prepared in an aqueous medium. In all the catalysts studied these Fe cations were the active sites in the reduction of NO to N2 and in the oxidation of iso-butane. It is further suggested that coordination of Fe species is another important aspect to be considered in their behaviour.

  3. Role of iron oxide catalysts in selective catalytic reduction of NOx and soot from vehicular emission

    International Nuclear Information System (INIS)

    This study deals with Iron containing catalysts i.e Iron oxide Fe/sub 2/O/sub 3/) Iron potassium oxide Fe/sub 1.9/K/sub 0.1/O/sub 3/, copper iron oxide Cu/sub 0.9/K/sub 0.1/, Fe/sub 2/O/sub 3/, nickel iron oxide Ni Fe/sub 2/O/sub 4/, and Nickel potassium iron oxide Ni/sub 0.95/K/sub 0.05/ Fe/sub 2/O/sub 4/ catalyst were synthesized by using PVA technique. By X-ray Diffraction technique these catalysts were characterized to ensure the formation of crystalline structure. Energy Dispersive X-rays analysis (EDX) was used for the confirmation of presence of different metals and Scanning Electron Microscopy (SEM) for Surface Morphology. Then the catalytic investigations of the prepared catalyst were carried out for their activity measurement toward simultaneous conversion of NOx and Soot from an engine exhaust. Some Iron containing oxide catalysts were partially modified by alkali metal potassium and were used for NOx -Soot reaction in a model exhaust gas. Fe/sub 1.9 K /sub 0.1/O/sub 3/ show high catalytic performance for N/sub 2/ formation in the prepared catalyst. Further studies have shown that Fe/sub 1.9/ K/sub 0.1/ O/sub 3/ was deactivated in a substantial way after about 20 Temperature. Temperature Programmed Reaction (TPR) experiments due to agglomeration of the promoter potassium. Experiments carried out over the aged Fe/sub 1.9/K/sub 0.1/O/sub 3/ catalyst have shown that NOx-soot reaction was suppressed at higher oxygen concentration, since O/sub 2/-soot conversion was kindly favored. More over nitrite species formed at the catalyst surface might play an important role in NOx-soot conversion. (author)

  4. Formation of catalytically active gold-polymer microgel hybrids via a controlled in situ reductive process

    NARCIS (Netherlands)

    Agrawal, Garima; Schuerings, Marco Philipp; van Rijn, Patrick; Pich, Andrij

    2013-01-01

    A newly developed N-vinylcaprolactam/acetoacetoxyethyl methacrylate/acrylic acid based microgel displays in situ reductive reactivity towards HAuCl4, forming hybrid polymer-gold nanostructures at ambient temperature without additional reducing agents. The colloidal gold nanostructure is selectively

  5. Zeolite catalysts and their use in selective catalytic reduction of NOx

    NARCIS (Netherlands)

    Seijger, G.B.F.; Van den Bleek, C.M.; Calis, H.P.A.

    2003-01-01

    The invention is directed to catalyst compositions comprising a zeolite, as well as to processes for the reduction of nitrogen oxides (NOx) employing these catalyst compositions. The catalyst compositions of the invention comprise a zeolite of the ferrierite type (FER), which zeolite is ion exchange

  6. Fe-BEA Zeolite Catalysts for NH3-SCR of NOx

    DEFF Research Database (Denmark)

    Frey, Anne Mette; Mert, Selcuk; Due-Hansen, Johannes;

    2009-01-01

    Iron-containing zeolites are known to be promising catalysts for the NH3-SCR reaction. Here, we will investigate the catalytic activity of iron-based BEA catalysts, which was found to exhibit improved activities compared to previously described iron-containing zeolite catalysts, such as ZSM-5...... and ZSM-12. Series of Fe-BEA zeolite catalysts were prepared using a range of different preparation methods. Furthermore, we found that an iron concentration around 3 wt% on BEA showed a small optimum in SCR activity compared to the other iron loadings studied....

  7. Design of multi-shell Fe2O3@MnOx@CNTs for the selective catalytic reduction of NO with NH3: improvement of catalytic activity and SO2 tolerance

    Science.gov (United States)

    Cai, Sixiang; Hu, Hang; Li, Hongrui; Shi, Liyi; Zhang, Dengsong

    2016-02-01

    Manganese based catalysts are highly active in the NH3-SCR reaction for NOx removal. Unfortunately, manganese oxides can be easily deactivated by sulfur dioxide in the flow gas, which has become the main obstacle for their practical applications. To address this problem, we presented a green and facile method for the synthesis of multi-shell Fe2O3@MnOx@CNTs. The morphology and structural properties of the catalysts were systematically investigated. The results revealed that the MnOx@CNT core-shell structure was formed during the chemical bath deposition, while the outermost MnOx species were transformed to Fe2O3 after the galvanic replacement reaction. The formation of the multi-shell structure induced the enhancement of the active oxygen species, reducible species as well as adsorption of the reactants, which brought about excellent de-NOx performance. Moreover, the Fe2O3 shell could effectively suppress the formation of the surface sulfate species, leading to the desirable SO2 resistance to the multi-shell catalyst. Hence, the synthesis protocol could provide guidance for the preparation and elevation of manganese based catalysts.Manganese based catalysts are highly active in the NH3-SCR reaction for NOx removal. Unfortunately, manganese oxides can be easily deactivated by sulfur dioxide in the flow gas, which has become the main obstacle for their practical applications. To address this problem, we presented a green and facile method for the synthesis of multi-shell Fe2O3@MnOx@CNTs. The morphology and structural properties of the catalysts were systematically investigated. The results revealed that the MnOx@CNT core-shell structure was formed during the chemical bath deposition, while the outermost MnOx species were transformed to Fe2O3 after the galvanic replacement reaction. The formation of the multi-shell structure induced the enhancement of the active oxygen species, reducible species as well as adsorption of the reactants, which brought about excellent de

  8. Carbon nanotubes loaded with vanadium oxide for reduction NO with NH3 at low temperature☆

    Institute of Scientific and Technical Information of China (English)

    Shuli Bai; Shengtao Jiang; Huanying Li; Yujiang Guan

    2015-01-01

    The catalytic activity of carbon nanotubes-supported vanadium oxide (V2O5/CNTs) catalysts in the selective catalytic reduction (SCR) of NO with NH3 at low temperatures (≤250 °C) was investigated. The effects of V2O5 loading, reaction temperature, and presence of SO2 on the SCR activity were evaluated. The results show that V2O5/CNTs catalysts exhibit high activity for NO reduction with NH3 at low-temperatures. The catalysts also show very high stability in the presence of SO2. More interestingly, their activities are significantly promoted in-stead of being poisoned by SO2. The promoting effect of SO2 is distinctly associated with V2O5 loading, particularly maximized at low V2O5 loading, which indicated the role of CNTs support in this effect. The promoting effect of SO2 at low temperatures suggests that V2O5/CNTs catalysts are promising catalytic materials for low-temperature SCR reactions.

  9. Identification of intrinsic catalytic activity for electrochemical reduction of water molecules to generate hydrogen

    KAUST Repository

    Shinagawa, Tatsuya

    2015-01-01

    Insufficient hydronium ion activities at near-neutral pH and under unbuffered conditions induce diffusion-limited currents for hydrogen evolution, followed by a reaction with water molecules to generate hydrogen at elevated potentials. The observed constant current behaviors at near neutral pH reflect the intrinsic electrocatalytic reactivity of the metal electrodes for water reduction. This journal is © the Owner Societies.

  10. Kinetic Study of Co-β-Zeolite for Selective Catalytic Reduction of NOx with Propane

    Institute of Scientific and Technical Information of China (English)

    毛树红; 王润平; 池永庆; 王艳; 张清华; 丛燕青

    2011-01-01

    The effects of grain size, space velocity, temperature and reactant concentration on the kinetics of NOx reduction with propane over Co-β-zeolite catalyst were investigated. The external mass transfer phenomenon was examined by varying the space velocity. The results show that the transfer can be negligible when the space velocity is greater than 60000 h-1 in low temperature range. However, the transfer exists at high temperatures even when the space velocity reaches a high level.Variation of the catalyst grain size from 0.05 to 0.125 mm does not change the conversion rate of NOx. The concentrations of components, NOx, C3H8 and O2, were also investigated to have a better understanding of mechanism. Based on the experimental data, the selectivity formula was proposed. The results shows that lower temperature is helpful to get higher selectivity as the activation energy of hydrocarbon oxidation, Ea,2, is greater than that of NOx reduction, Ea,1, (Ea,2>Ea,l). High NOx concentration and low C3H8 concentration are beneficial to high selectivity. However in order to maintain high activity simultaneously, the temperature and C3H8 concentration should be high enough to promote NOx reduction. 10%(φ) H2O and 75×i0-6(φ) SO2 were introduced into the reaction system, and Co-β-zeolite shows strong resistance to water and SO2.

  11. Selective catalytic reduction of nitric oxide with ammonia on Fe-ZSM-5 catalysts prepared by different methods

    Energy Technology Data Exchange (ETDEWEB)

    Delahay, Gerard; Valade, David; Guzman-Vargas, Ariel; Coq, Bernard [Laboratoire de Materiaux Catalytiques et Catalyse en Chimie Organique, UMR CNRS-ENSCM 5618, ENSCM, 8 rue d l' Ecole Normale, 34296 Montpellier Cedex 5 (France)

    2005-01-28

    Fe-ZSM-5 catalysts, prepared by different methods, have been characterized by TPR and XRD and tested in the NO-SCR by NH{sub 3.} The sublimation method leads to the most active catalysts. Nevertheless the preparation starting from Fe(acac){sub 3}, which is a preparation easy to implement from an industrial point of view, seems to be a very attractive alternative way. On the most active catalyst, Fe(0.83){sub sub}ZSM-5, prepared starting from FeCl{sub 3}, a study of the mechanism was undertaken. In the initial step of the SCR reaction, the oxidation of NO in NO{sub 2}, the re-oxidation of Fe{sup II} species in the active iron oxo species is the slow phase.

  12. [Research on SCR denitrification of MnOx/Al2O3 modified by CeO2 and its mechanism at low temperature].

    Science.gov (United States)

    Guo, Jing; Li, Cai-Ting; Lu, Pei; Cui, Hua-Fei; Peng, Dun-Liang; Wen, Qing-Bo

    2011-08-01

    The Al2O3,which has large specific surface area and is used as carrier,was prepared by sol-gel method in this study. Series catalysts of MnOx, CeO2 plus MnOx supported on Al2O3 by isometric impregnation method. The SCR denitrification experimental conditions were as follows: NH3 as reductive agent, certain gas velocity and suitable ratio of gas mixed was setup. Furthermore, the experiments of BET, XRD and SEM were also carried out respectively in order to obtain physicochemical properties of the prepared catalysts. The experimental results showed that the loading of active component and calcination temperature made a big difference to the catalysts' performance. With appropriate addition of CeO2, MnOx/Al2O3 exhibits better activity and stability. For MnOx/Al2O3, the catalytic activity on NO was greatly influenced by its loaded content, and 7% MnOx/Al2O3 showed superior catalytic activity among the MnOx/Al2O3. The addition of CeO2 could greatly improve the dispersibility of MnOx on the carrier and increase its catalytic activity. The 4% CeO2 addition was the optimum loaded mass precent. Forthermore, 550 degrees C is the best calcination temperature, as MnOx formed different crystalline phases with temperature, at the same time, the addition of CeO2 could affect MnOx crystalline phase. The catalytic mechanism of SCR on NO was also discussed.

  13. Green synthesis of silver nanoparticles using Terminalia cuneata and its catalytic action in reduction of direct yellow-12 dye

    Science.gov (United States)

    Edison, Thomas Nesakumar Jebakumar Immanuel; Lee, Yong Rok; Sethuraman, Mathur Gopalakrishnan

    2016-05-01

    Facile green synthesis of silver nanoparticles (AgNPs) using aqueous bark extract of Terminalia cuneata has been reported in this article. The effects of concentration of the extract, reaction time and pH were studied by UV-Vis spectroscopy. Appearance of yellow color with λmax around ~ 420 nm suggested the formation of AgNPs. The stable AgNPs were further characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS) with zeta potential and high resolution transmission electron microscopy (HR-TEM) with energy dispersive X-ray spectroscopy (EDS) analysis. The synthesized AgNPs were in the size range of 25-50 nm with a distorted spherical shape identified from HR-TEM analysis. The catalytic activity of AgNPs on the reduction of direct yellow-12 using NaBH4 was analyzed using a UV-Vis spectrophotometer. This study showed the efficacy of biogenic AgNPs in catalyzing the reduction of direct yellow-12.

  14. Selective catalytic reduction of nitric oxide by methane over cerium and silver ion-exchanged ZSM-5 zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhijiang; Flytzani-Stephanopoulos, Maria [Department of Chemical Engineering, Tufts University, Medford, MA (United States)

    1997-12-31

    A new catalyst comprising cerium and silver ion-exchanged ZSM-5 zeolite is reported in this paper, for the reduction of nitric oxide by methane in the presence of excess oxygen. The bi-cation exchanged Ce-Ag-ZSM-5 catalyst was very active for this reaction, while either Ce-ZSM-5 or Ag-ZSM-5 alone showed low activity. The presence of oxygen in the feed gas mixture enhanced the activity of the catalyst and the NO conversion to N{sub 2} increased with the CH{sub 4}/NO ratio and Ag loading of the zeolite. The presence of water vapor had a small adverse effect on the catalyst activity. The coexistence of Ce and Ag ions in the zeolite is crucial for achieving high NO conversion to N{sub 2}. A small amount of cerium is adequate to promote the selective catalytic reduction of NO. The two main functions of Ce ions are (1) to provide the Ag ion sites with NO{sub 2} by catalyzing the oxidation of NO to NO{sub 2} and (2) to suppress the direct CH{sub 4} oxidation to CO{sub 2}. The Ag sites are the active centers where the reaction of NO{sub 2} with CH{sub 4} takes place

  15. Study on SCR De NOx mechanism through in situ electrical conductivity measurements on V2O5-WO3/TiO2 catalysts

    Institute of Scientific and Technical Information of China (English)

    HA Heon Phil; JUNG Soon Hyo; LEE Jun Yub; HONG Sung Ho

    2006-01-01

    V2O5-WO3/TiO2 catalysts were prepared by impregnation method and in situ electrical conductivity measurements were carried out to investigate the reaction mechanism for ammonia SCR (selective catalytic reduction) of NOx.The electrical conductivity change with ammonia supply and the increase of electrical conductivity were mainly caused by reduction of the labile surface oxygen.The electrical conductivity change of catalysts shows close relationship with the conversion rate of NOx.Variation of conversion rate in atmosphere without gaseous oxygen also supports that the labile lattice oxygen is indispensable in the initial stage of the de NOx reaction.These results suggest that the liable lattice oxygen acts decisive role in the de NOx mechanism.They also support that De NOx reaction occurs through the Eley-Rideal type mechanism.The amount of labile oxygen can be estimated from the measurement of electrical conductivity change for catalysts with ammonia supply.

  16. Study on Selective Catalytic Reduction Reaction Properties of LaCoO3 Perovskite Catalyst for Diesel NOx Emission Removal%LaCoO3钙钛矿型催化剂对柴油机NOx净化性能研究

    Institute of Scientific and Technical Information of China (English)

    郝斌; 杨铁皂; 吕刚; 宋崇林; 宾峰

    2012-01-01

    LaCoO3 perovskite catalyst was prepared by citric acid complex method and characterized for its physic - chemical properties. Catalytic performance in the SCR of NO, by NH3 was studied and results showed that: pure LaCoO3 granule has a certain ability of catalytic reduction of NOx, especially between 250 to 45℃. However, the undesired catalytic activity for the oxidation of NH3 was too high and could be even largely promoted by a higher temperature. When LaCoO3 was used as SCR catalyst, it showed a certain degree of purification ability of NOx, below 400℃ , but if the temperature was higher than 400℃ , NOx elimination is deteriorated. Moreover, LaCo03 perovskite catalyst was highly capable of enhancing the oxidation of HC and CO regardless of their gas compositions.%采用柠檬酸络合法制备了LaCoO3钙钛矿型催化剂.对其理化特性及NH3-选择性催化还原催化性能的研究结果表明:纯LaCoO3颗粒具有一定的NOx催化还原能力,在250~450℃活性较高;但该催化剂对NH3具有较高的氧化活性,且催化活性随反应温度的升高而提高;在SCR反应中,在400℃以下时,该催化剂显示出一定的NOx净化能力,但当温度超过400℃以后,还原剂的加入反而恶化了NOx排放.不管反应气组成如何,LaCoO3钙钛矿型催化剂对HC和CO都具有良好的催化性能.

  17. Catalytic reduction of nitrate and nitrite ions by hydrogen : investigation of the reaction mechanism over Pd and Pd-Cu catalysts

    NARCIS (Netherlands)

    Ilinitch, OM; Nosova, LV; Gorodetskii, VV; Ivanov, VP; Trukhan, SN; Gribov, EN; Bogdanov, SV; Cuperus, FP

    2000-01-01

    The catalytic behavior of mono- and bimetallic catalysts with Pd and/or Cu supported over gamma-Al2O3 in the reduction of aqueous nitrate and nitrite ions by hydrogen was investigated. The composition of the supported metal catalysts was analysed using secondary ion mass spectroscopy (SIMS) and X-ra

  18. Study on Simultaneous Catalytic Reduction of Sulfur Dioxide and Nitric Oxide on Rare Earth Mixed Compounds

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    CeO2/γ-Al2O3, La2O3/γ-Al2O3, CeO2-La2O3/γ-Al2O3 and CeO2-La2O3, which were prepared by impregnating in certain ratio, were used as the catalysts for the reduction of SO2 and NO by CO. Separate and simultaneous removal of SO2 and NO over La2O3/γ-Al2O3, CeO2/γ-Al2O3, CeO2-La2O3/γ-Al2O3 were investigated. The phase characteristics of catalysts were also analyzed by X-ray diffraction. The result shows that the conversions of SO2 and NO are above 98% over CeO2/γ-Al2O3 and CeO2-La2O3/γ-Al2O3. After SO2 is added in the NO-CO-N2 system (NO∶SO2=1∶2~1∶3), the conversions of SO2 and NO are both above 98%. Furthermore, it is found that CeO2-La2O3 with various ratios has different activity for the simultaneous reduction of SO2 and NO.

  19. Formic acid as an alternative reducing agent for the catalytic nitrate reduction in aqueous media

    Institute of Scientific and Technical Information of China (English)

    Eun-kyoung Choi; Kuy-hyun Park; Ho-bin Lee; Misun Cho; Samyoung Ahn

    2013-01-01

    Formic acid was used for the nitrate reduction as a reductant in the presence of Pd∶Cu/γ-alumina catalysts.The surfatce characteristics of the bimetallic catalyst synthesized by wet impregnation were investigated by SEM,TEM-EDS.The metals were not distributed homogeneously on the surface of catalyst,although the total contents of both metals in particles agreed well with the theoretical values.Formic acid decomposition on the catalyst surface,its influence on solution pH and nitrate removal efficacy was investigated.The best removal of nitrate (50 ppm) was obtained under the condition of 0.75 g/L catalyst with Pd∶Cu ratio (4∶1) and two fold excess of formic acid.Formic acid decay patterns resembled those of nitrate removal,showing a linear relationship between kf (formic acid decay) and k (nitrate removal).Negligible amount of ammonia was detected,and no nitrite was detected,possibly due to buffering effect of bicarbonate that is in situ produced by the decomposition of formic acid,and due to the sustained release of H2 gas.

  20. Copper nanoparticles supported on permeable monolith with carboxylic acid surface functionality: Stability and catalytic properties under reductive conditions

    Energy Technology Data Exchange (ETDEWEB)

    Poupart, Romain; Le Droumaguet, Benjamin, E-mail: ledroumaguet@icmpe.cnrs.fr; Guerrouache, Mohamed; Carbonnier, Benjamin, E-mail: carbonnier@icmpe.cnrs.fr

    2015-08-01

    This work reported on the immobilization of copper metallic nanoparticles at the interface of mercaptosuccinic acid-functionalized N-acryloxysuccinimide-based monoliths. Upon photochemically-mediated free radical copolymerization of N-acryloxysuccinimide reactive monomer with ethylene glycol dimethacrylate cross-linker, reactive monoliths were obtained. Nucleophilic substitution of the N-hydroxysuccinimide moieties with allylamine, allowed for the synthesis of an olefin-functionalized monolith, as demonstrated by Raman spectroscopy. Mercaptosuccinic acid was anchored at the surface of the porous polymeric material through photochemically-driven thiol-ene “click” addition. In a final step, adsorption of copper nanoparticles at the surface of the resulting carboxylic acid functionalized monolith was achieved via two distinct pathways. It was either realized by percolation of a suspension of pre-formed copper nanoparticles through the capillary or by in situ reduction of Cu{sup (II)}Br{sub 2} salt solution preliminary flown through the monolith. After characterization of the resulting hybrids by scanning electron microscopy and energy-dispersive X-ray spectroscopy, investigations were further pursued regarding the catalytic behavior of such hybrid materials. The possibility to reduce 2-nitrophenol into the corresponding 2-aminophenol within a few minutes via a flow-through process inside the hybrid monolithic capillary was notably successfully demonstrated. - Graphical abstract: Display Omitted - Highlights: • Monolithic micro-reactors with surface immobilized copper nanoparticle for flow through catalytic processes. • Porous polymer-stabilized copper nanoparticles. • Photothiol-ene click chemistry for the effective surface functionalization of porous monolithic polymers. • Surface adsorption of copper nanoparticles through in-situ and ex-situ strategies.

  1. Explore the principle of SCR technology%SCR技术原理探讨

    Institute of Scientific and Technical Information of China (English)

    徐鹏

    2015-01-01

    文章介绍车辆排放后处理系统--SCR(发动机排气催化净化技术)技术发展必要性及SCR技术原理。本篇文章是对SCR的一个基本介绍,SCR系统会随着车辆及发动机在硬、软件上配置的变化而发生改变。%This paper introduces the vehicle emission treatment system --SCR (engine exhaust catalytic technology) technology and necessity. This article is a basic introduction to the SCR, SCR systems will change with the vehicles and engines in the hardware and software configuration and change.

  2. SCR技术原理探讨%Explore the principle of SCR technology

    Institute of Scientific and Technical Information of China (English)

    徐鹏

    2015-01-01

    This paper introduces the vehicle emission treatment system --SCR (engine exhaust catalytic technology) technology and necessity. This article is a basic introduction to the SCR, SCR systems will change with the vehicles and engines in the hardware and software configuration and change.%文章介绍车辆排放后处理系统--SCR(发动机排气催化净化技术)技术发展必要性及SCR技术原理。本篇文章是对SCR的一个基本介绍,SCR系统会随着车辆及发动机在硬、软件上配置的变化而发生改变。

  3. Combined Particle Filter and Selective Catalytic Reduction Catalyst for Diesel Engines

    DEFF Research Database (Denmark)

    Hvam, Jeanette

    for exhaust gas purification. By combining the particulate filtration application with the application as catalyst support for NOx reduction, the low emissions standards can be met. This project was initiated as a result of the need for new and improved filters with characteristics making it suitable...... them ideal for multiple applications like high power electronic devices, heating elements, abrasive materials and cutting tools. Porous silicon carbide is suitable for electrode and catalyst support material as well as hot gas filter units or a combination of these. The automotive industry demands new...... here. A new and improved filter was developed on the basis of the research results concerning copper as partner additive. In comparison to filters produced with aluminium as sole additive, these new filters exhibit enhanced mechanical stability, enhanced microstructure and controllable surface...

  4. Catalytic activity trends of oxygen reduction reaction for nonaqueous Li-air batteries.

    Science.gov (United States)

    Lu, Yi-Chun; Gasteiger, Hubert A; Shao-Horn, Yang

    2011-11-30

    We report the intrinsic oxygen reduction reaction (ORR) activity of polycrystalline palladium, platinum, ruthenium, gold, and glassy carbon surfaces in 0.1 M LiClO(4) 1,2-dimethoxyethane via rotating disk electrode measurements. The nonaqueous Li(+)-ORR activity of these surfaces primarily correlates to oxygen adsorption energy, forming a "volcano-type" trend. The activity trend found on the polycrystalline surfaces was in good agreement with the trend in the discharge voltage of Li-O(2) cells catalyzed by nanoparticle catalysts. Our findings provide insights into Li(+)-ORR mechanisms in nonaqueous media and design of efficient air electrodes for Li-air battery applications. PMID:22044022

  5. Comparison of preparation methods for ceria catalyst and the effect of surface and bulk sulfates on its activity toward NH3-SCR

    International Nuclear Information System (INIS)

    Highlights: • The CeO2-SH catalyst showed >97% conversion of NOx at 230–450 °C. • The resistance to Na and K of the CeO2 catalyst was enhanced significantly. • Surface sulfate species bind to Ce4+ improve the N2 selectivity in NH3-SCO. -- Abstract: A series of CeO2 catalysts prepared with sulfate (S) and nitrate (N) precursors by hydrothermal (H) and precipitation (P) methods were investigated in selective catalytic reduction of NOx by NH3 (NH3-SCR). The catalytic activity of CeO2 was significantly affected by the preparation methods and the precursor type. CeO2-SH, which was prepared by hydrothermal method with cerium (IV) sulfate as a precursor, showed excellent SCR activity and high N2 selectivity in the temperature range of 230–450 °C. Based on the results obtained by temperature-programmed reduction (H2-TPR), transmission infrared spectra (IR) and thermal gravimetric analysis (TGA), the excellent performance of CeO2-SH was correlated with the surface sulfate species formed in the hydrothermal reaction. These results indicated that sulfate species bind with Ce4+ on the CeO2-SH catalyst, and the specific sulfate species, such as Ce(SO4)2 or CeOSO4, were formed. The adsorption of NH3 was promoted by these sulfate species, and the probability of immediate oxidation of NH3 to N2O on Ce4+ was reduced. Accordingly, the selective oxidation of NH3 was enhanced, which contributed to the high N2 selectivity in the SCR reaction. However, the location of sulfate on the CeO2-SP catalyst was different. Plenty of sulfate species were likely deposited on CeO2-SP surface, covering the active sites for NO oxidation, which resulted in poor SCR activity in the test temperature range. Moreover, the resistance to alkali metals, such as Na and K, was improved over the CeO2-SH catalyst

  6. Circuit controls transients in SCR inverters

    Science.gov (United States)

    Moore, E. T.; Wilson, T. G.

    1964-01-01

    Elimination of starting difficulties in SCR inverters is accomplished by the addition of two taps of the output winding of the inverter. On starting or under transient loads, the two additional taps deliver power through diodes without requiring quenching of SCR currents in excess of normal starting load.

  7. Using a PFET To Commutate an SCR

    Science.gov (United States)

    Edwards, D. B.; Ripple, W. E.

    1984-01-01

    Accidental turn-on prevented. PFET diverts load current around SCR to prevent false SCR triggering from current and voltage switching transients. New circuit used in all types of single phase and polyphase inverters and in buck-boost-, and flyback regulators.

  8. Technology Roadmap: Energy and GHG reductions in the chemical industry via catalytic processes

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2013-06-01

    The chemical industry is a large energy user; but chemical products and technologies also are used in a wide array of energy saving and/or renewable energy applications so the industry has also an energy saving role. The chemical and petrochemical sector is by far the largest industrial energy user, accounting for roughly 10% of total worldwide final energy demand and 7% of global GHG emissions. The International Council of Chemical Associations (ICCA) has partnered with the IEA and DECHEMA (Society for Chemical Engineering and Biotechnology) to describe the path toward further improvements in energy efficiency and GHG reductions in the chemical sector. The roadmap looks at measures needed from the chemical industry, policymakers, investors and academia to press on with catalysis technology and unleash its potential around the globe. The report uncovers findings and best practice opportunities that illustrate how continuous improvements and breakthrough technology options can cut energy use and bring down greenhouse gas (GHG) emission rates. Around 90% of chemical processes involve the use of catalysts – such as added substances that increase the rate of reaction without being consumed by it – and related processes to enhance production efficiency and reduce energy use, thereby curtailing GHG emission levels. This work shows an energy savings potential approaching 13 exajoules (EJ) by 2050 – equivalent to the current annual primary energy use of Germany.

  9. Catalytic reductive dechlorination of p-chlorophenol in water using Ni/Fe nanoscale particles

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wei-hua; QUAN Xie; ZHANG Zhuo-yong

    2007-01-01

    Nanoscale bimetallic Ni/Fe particles were synthesized from the reaction of sodium borohydride (NaBH4)with reduction of Ni2+and Fe2+ in aqueous solution.The obtained Ni/Fe particles were characterized by TEM(transmission electron microscope),XRD(X-ray diffractometer),and N2-BET The dechlorination activity of the Ni/Fe was investigated using P-chlorophenol (p-CP)as a pmbe agent.Results demonstrated that the nanoscale Ni/Fe could effectively dechlorinate P-CP at relatively low metal to solution ratio of 0.4 g/L (Ni 5 wt%).The target with initial concentration of P-CP O.625 mmol/L was dechlorinted completely in 60 min under ambient temperature and pressure.Factors affecting dechlorination efficiency,including reaction temperature,pH,Ni loading percentage over Fe,and metal to solution ratio.were investigated.The possible mechanism of dechlorination of P-CP was proposed and discussed.The pseudo-first-order reaction took place on the surface of the Ni/Fe bimetallic particles,and the activation energy of the dechlorination reaction was determined to be 21.2 kJ/mol at the temperature rang of 287-313 K.

  10. Screening of catalytic oxygen reduction reaction activity of metal-doped graphene by density functional theory

    Science.gov (United States)

    Chen, Xin; Chen, Shuangjing; Wang, Jinyu

    2016-08-01

    Graphene doping is a promising direction for developing effective oxygen reduction reaction (ORR) catalysts. In this paper, we computationally investigated the ORR performance of 10 kinds of metal-doped graphene (M-G) catalysts, namely, Al-, Si-, Mn-, Fe-, Co-, Ni-, Pd-, Ag-, Pt-, and Au-G. The results shown that the binding energies of the metal atoms incorporated into the graphene vacancy are higher than their bulk cohesive energies, indicating the formed M-G catalysts are even more stable than the corresponding bulk metal surfaces, and thus avoid the metals dissolution in the reaction environment. We demonstrated that the linear relation among the binding energies of the ORR intermediates that found on metal-based materials does not hold for the M-G catalysts, therefore a single binding energy of intermediate alone is not sufficient to evaluate the ORR activity of an arbitrary catalyst. By analysis of the detailed ORR processes, we predicted that the Au-, Co-, and Ag-G materials can be used as the ORR catalysts.

  11. SCR in biofuel combustion - stage 3. Regeneration at full-scale; SCR vid biobraensleeldning - etapp 3. Regenerering i full skala

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Christer; Kling, Aasa; Odenbrand, Ingemar; Khodayari, Raziyeh

    2002-04-01

    This is the third and last part of a project that started in 1996. The overall goal of the project was to increase the possibilities to use SCR at bio fuel combustion under reasonable technical and economical conditions. This part of the project has focused on full-scale applications of the reactivation methods that were developed during phase 1 and 2. There are quite large differences in deactivation rate between different types of catalysts. A high active Biocomb catalyst deactivates more slowly then a catalyst that contains less vanadium and is less active. A high active catalyst also catalysts the oxidation from SO{sub 2} to SO{sub 3}. Practical consequences of this for low sulphur fuels should be investigated. Two new reactivation methods, sulphation and sulphation in combination with water wash, give an activity increase of 80 and 90% relative activity respectively for the evaluated catalyst (Biocomb Type B). The water washed and sulphated samples deactivate with approximately the same deactivation rate as not regenerated samples regardless of flue gas exposure temperatures. The samples that were regenerated with sulphation deactivates less fast than not regenerated samples when they are exposed to flue gas temperatures lower then 340 deg C. At higher temperatures they deactivates relatively fast. The plate-type catalyst has been regenerated with water wash in combination with sulphation as well as water and sulphuric acid wash up to a relative activity of 80%. The deactivation has been faster for the water washed and sulphated samples compared to the water and sulphuric acid washed samples (which deactivates with the same rate as fresh samples). At full-scale sulphation tests at the Brista Kraft plant, the catalytic activity was raised with 23% by sulphation with 260 ppm SO{sub 2} during 25 hours (dosage of 3 tons of elementary sulphur with the fuel). The sulphation led to a reduction on the NO{sub x}, emissions by half. The catalyst, which works in a flue

  12. VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging

    Directory of Open Access Journals (Sweden)

    Adrian Marberger

    2015-10-01

    Full Text Available V2O5/WO3-TiO2 selective catalytic reduction (SCR catalysts with a V2O5 loading of 1.7, 2.0, 2.3, 2.6, 2.9, 3.2 and 3.5 wt. % were investigated in the fresh state and after hydrothermal aging at 600 °C for 16 h. The catalysts were characterized by means of nitrogen physisorption, X-ray diffraction and X-ray absorption spectroscopy. In the fresh state, the SCR activity increased with increasing V loading. Upon aging, the catalysts with up to 2.3 wt. % V2O5 exhibited higher NOx reduction activity than in the fresh state, while the catalysts with more than 2.6 wt. % V2O5 showed increasing deactivation tendencies. The observed activation and deactivation were correlated with the change of the VOx and WOx surface coverages. Only catalysts with a VOx coverage below 50% in the aged state did not show deactivation tendencies. With respect to tungsten, above one monolayer of WOx, WO3 particles were formed leading to loss of surface acidity, sintering, catalyst deactivation and early NH3 slip. An optimal compromise between activity and hydrothermal aging resistance could be obtained only with V2O5 between 2.0 and 2.6 wt. %.

  13. Energy optimization of a Tail End SCR plant. Case study; Energieoptimierung einer Tail End SCR Anlage. Fallbeispiel

    Energy Technology Data Exchange (ETDEWEB)

    Ebinger, Maximilian [Ebinger Katalysatorservice GmbH und Co. KG, Wildeshausen (Germany); Martinett, Udo [MVA Weisweiler GmbH und Co. KG, Eschweiler (Germany)

    2012-11-01

    In 2009, the waste incinerator Weisweiler (Federal Republic of Germany) decided to rebuild the wet purification of exhaust gases to a dry purification process at three incineration lines. The reduction of NO{sub x} emissions requires an operation of the existing Tail End SCR plant with four installed layers of catalyst at a temperature of 180 Celsius instead of 360 Celsius. Within the by-pass phases in the years 2010 and 2011 the catalyst was regenerated and chemically modified by Ebinger GmbH (Cologne, Federal Republic of Germany) in order to fulfill the new requirements. Ultrasonics is used for the regeneration of SCR DeNO{sub x} catalysts in a stationary plant as a central procedural step.

  14. Structural characterization and catalytic properties of bis(1,1,3,3-tetramethylguanidinium) dichromate

    DEFF Research Database (Denmark)

    Due-Hansen, Johannes; Ståhl, Kenny; Boghosian, Soghomon;

    2011-01-01

    of dichromate anions (Cr2O72-) stabilized by tetramethylguanidinium cations ([H2NC(N(CH3)2)2]+ or [TMGH]+). Phase transitions of [TMGH]2Cr2O7 were determined by differential scanning calorimetry, thermal gravimetric analysis and in situ Raman spectroscopy, where the decomposition of the matrix into Cr......OX was found at 171-172ºC. Further heat treatment to above 400ºC resulted in formation of the thermodynamically stable Cr2O3, most likely with the [TMGH]+ cation as reductant. The catalytic activity of [TMGH]2Cr2O7 supported on TiO2 anatase in the selective catalytic reduction (SCR) of nitrogen oxide was also...

  15. Fabrication and catalytic activity of FeNi@Ni nanocables for the reduction of p-nitrophenol.

    Science.gov (United States)

    Zhou, Linyi; Wen, Ming; Wu, Qingsheng; Wu, Dandan

    2014-06-01

    Magnetic FeNi@Ni nanocables were prepared as a superior recyclable catalyst towards the hydrogenation reduction of p-nitrophenol to p-aminophenol through a two-step tunable assembly process in a solvothermal system. The proposed fabrication mechanism was verified through characterization by SEM, TEM, XRD, XPS, and UV-Vis. The as-prepared FeNi@Ni nanocomposites are core-shell-structured nanocables with Ni nanoparticles (NPs) attached on FeNi nanorods (NRs) surface loosely. The catalytic reactivity monitored by means of a UV-vis dynamic process shows FeNi@Ni nanocables can catalyse the transformation of p-nitrophenol to p-aminophenol completely under an ambient atmosphere at room temperature, and enable the catalysis to be more efficient than its counterparts FeNi NRs and Ni NPs due to the interfacial synergistic effect. Additionally, the resultant hierarchical metal-alloy nanocomposites possess ferromagnetic behaviour, and can be easily separated and recycled by an external magnet field for application. PMID:24714959

  16. [Low-temperature catalytic reduction of NO over Fe-MnOx-CeO2/ZrO2 catalyst].

    Science.gov (United States)

    Liu, Rong; Yang, Zhi-Qin

    2012-06-01

    Fe-MnOx-CeO2/ZrO2 catalysts were prepared through impregnation method with nanometer ZrO2 as a carrier and used in selective catalytic reduction of NO with NH3 at low temperature. Effects of active component ratio and loading of promoter on the catalyst activity were investigated. The catalysts were characterized by means of XRD, SEM, EDS and BET. The effects of temperature, SO2 and H2O on NO conversion were studied and the results showed that in the absence of SO2 and H2O, the catalyst of 8% Fe-10% MnOx-CeO2/ZrO2 had good activity and stability as well as the NOx removal efficiency reached 85.23% at 120 degrees C and 92.0% at 180 degrees C. The presence of SO2 and H2O results in the catalyst deactivated. Properties of the catalyst on different reaction stages were characterized by FT-IR to study the inactivation mechanism of the catalyst. The results showed that the catalyst deactivation was due to the deposition of ammonium sulfate on the catalyst and the sulphation of the catalyst.

  17. Fabrication of Bi-Fe3O4@RGO hybrids and their catalytic performance for the reduction of 4-nitrophenol

    International Nuclear Information System (INIS)

    Nanocatalysts are frequently connected to magnetic nanoparticles. These composites are easy to be retrieved from the reaction system under a magnetic field because of their magnetic properties. Magnetic separation is particularly promising in industry since it can solve many issues present in filtration, centrifugation, or gravitation separation. Herein, a facile method to prepare bismuth and Fe3O4 nanoparticles loaded on reduced graphene oxide magnetic hybrids (Bi-Fe3O4@RGO) using soluble starch as a dispersant is demonstrated. The magnetic Fe3O4 nanoparticles were synthesized by the co-precipitation of Fe2+ and Fe3+ ions, and Bi nanoparticles were fabricated by the redox reactions between sodium borohydride and ammonium bismuth citrate in the presence of soluble starch. Transmission electron microscopy images demonstrate that the average diameter of the Fe3O4 nanoparticles is about 5 nm and the diameters of Bi nanoparticles range from 10 to 20 nm. The magnetic Bi-Fe3O4@RGO hybrids exhibit high catalytic activity in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 with a first-order rate constant (K) of 0.00808 s−1 and is magnetically recyclable for at least five cycles. This strategy provides an efficient and recyclable catalyst for the use in environmental protection applications

  18. Strongly coupled Pd nanotetrahedron/tungsten oxide nanosheet hybrids with enhanced catalytic activity and stability as oxygen reduction electrocatalysts.

    Science.gov (United States)

    Lu, Yizhong; Jiang, Yuanyuan; Gao, Xiaohui; Wang, Xiaodan; Chen, Wei

    2014-08-20

    The design and synthesis of highly active oxygen reduction reaction (ORR) catalysts with strong durability at low cost is extremely desirable but still remains a significant challenge. Here we develop an efficient strategy that utilizes organopalladium(I) complexes containing palladium-palladium bonds as precursors for the synthesis of strongly coupled Pd tetrahedron-tungsten oxide nanosheet hybrids (Pd/W18O49) to improve the electrocatalytic activity and stability of Pd nanocrystals. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of Pd tetrahedral nanocrystals on the in situ-synthesized W18O49 nanosheets. Compared to supportless Pd nanocrystals and W18O49, their hybrids exhibited not only surprisingly high activity but also superior stability to Pt for the ORR in alkaline solutions. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrochemical analyses indicated that the enhanced electrocatalytic activity and durability are associated with the increased number and improved catalytic activity of active sites, which is induced by the strong interaction between the Pd tetrahedrons and W18O49 nanosheet supports. The present study provides a novel strategy for synthesizing hybrid catalysts with strong chemical attachment and electrical coupling between nanocatalysts and supports. The strategy is expected to open up exciting opportunities for developing a novel class of metal-support hybrid nanoelectrocatalysts with improved ORR activity and durability for both fuel cells and metal-air batteries. PMID:25054583

  19. 选择催化还原SCR脱硝技术在电站锅炉的应用%APPLICATION OF SELECTIVE CATALYST REDUCTION (SCR) DENITRIFICATION TECHNOLOGY FOR UTILITY BOILERS

    Institute of Scientific and Technical Information of China (English)

    杨卫娟; 周俊虎; 刘建忠; 岑可法

    2005-01-01

    详细介绍了选择催化还原技术(SCR)在世界各国的推广应用情况及其系统的3种典型布置方式和特点,总结分析了SCR系统运行对电站锅炉运行带来的不利影响.催化剂是SCR系统的重要部分,分析了SCR运行中引起催化剂失效的各种原因,指出了当前催化剂和新型SCR技术的研究热点.

  20. ARGONAUTE1 acts in Arabidopsis root radial pattern formation independently of the SHR/SCR pathway.

    Science.gov (United States)

    Miyashima, Shunsuke; Hashimoto, Takashi; Nakajima, Keiji

    2009-03-01

    The formation of radially symmetric tissue patterns is one of the most basic processes in the development of vascular plants. In Arabidopsis thaliana, plant-specific GRAS-type transcription factors, SHORT-ROOT (SHR) and SCARECROW (SCR), are required for asymmetric cell divisions that separate two ground tissue cell layers, the endodermis and cortex, as well as for endodermal cell fate specification. While loss of SHR or SCR results in a single-layered ground tissue, radially symmetric cellular patterns are still maintained, suggesting that unknown regulatory mechanisms act independently of the SHR/SCR-dependent pathway. In this study, we identified a novel root radial pattern mutant and found that it is a new argonaute1 (ago1) allele. Multiple ago1 mutant alleles contained supernumerary ground tissue cell layers lacking a concentric organization, while expression patterns of SHR and SCR were not affected, revealing a previously unreported role for AGO1 in root ground tissue patterning. Analyses of ago1 scr double mutants demonstrated that the simultaneous loss of the two pathways caused a dramatic reduction in cellular organization and ground tissue identity as compared with the single mutants. Based on these results, we propose that highly symmetric root ground tissue patterns are maintained by the actions of two independent pathways, one using post-transcriptional regulation mediated by AGO1 and the other using the SHR/SCR transcriptional regulator.

  1. Catalytic reduction of methane/unburned hydrocarbons in smoke from lean-burn gas engines

    International Nuclear Information System (INIS)

    The aim of this project has been: To describe the flue gas conditions of typical stationary gas engines for cogeneration; To evaluate the predominant causes of deactivation of oxidation catalysts under realistic operation conditions; To develop improved long-term stable oxidation catalysts; To evaluate alternative catalyst-based methane reduction technologies. Most gas engines for stationary purposes are efficient lean-burn gas engines. Both the high efficiency and the very lean operation lead to low exhaust temperatures. However, there is now a tendency to design engines with un-cooled exhaust manifolds. This leads to higher shaft efficiency and increases the exhaust temperature. Exhaust gas composition and temperatures during continuous operation and start/stops are given in this report. Analyses have been made of catalyst samples to find predominant causes for oxidation catalyst deactivation. The analyses have shown that the presence of sulphur dioxide in the flue gas causes sulphur poisoning on the active catalyst surface. This effect is dependent on both the catalyst formulation and the catalyst support material composition. Neither sintering, nor other poisoning components than sulphur have been on the examined catalyst samples. The sulphur dioxide in the exhaust is a result of the sulphur in the odorisation additive used in the natural gas (approx. 10 mg/n3 m THT) and of the sulphur present in combusted lubrication oil. These sources leads to a level of approx. 0.3 - 0.6 ppm (vol) SO2 in the exhaust gas. Based on a large number of laboratory tests, a new oxidation catalyst formulation has been developed and successfully tested over 5000 hours of operation at a commercial cogeneration plant. This long-term testing has been additionally supplemented by short-term testings at test sites to see performance under other operation conditions. It has been shown that a rise in flue gas temperature (from e.g. 450 deg. C) will significantly reduce the necessary

  2. Propene poisoning on three typical Fe-zeolites for SCR of NOχ with NH₃: from mechanism study to coating modified architecture.

    Science.gov (United States)

    Ma, Lei; Li, Junhua; Cheng, Yisun; Lambert, Christine K; Fu, Lixin

    2012-02-01

    Application of Fe-zeolites for urea-SCR of NO(x) in diesel engine is limited by catalyst deactivation with hydrocarbons (HCs). In this work, a series of Fe-zeolite catalysts (Fe-MOR, Fe-ZSM-5, and Fe-BEA) was prepared by ion exchange method, and their catalytic activity with or without propene for selective catalytic reduction of NO(x) with ammonia (NH(3)-SCR) was investigated. Results showed that these Fe-zeolites were relatively active without propene in the test temperature range (150-550 °C); however, all of the catalytic activity was suppressed in the presence of propene. Fe-MOR kept relatively higher activity with almost 80% NO(x) conversion even after propene coking at 350 °C, and 38% for Fe-BEA and 24% for Fe-ZSM-5 at 350 °C, respectively. It was found that the pore structures of Fe-zeolite catalysts were one of the main factors for coke formation. As compared to ZSM-5 and HBEA, MOR zeolite has a one-dimensional structure for propene diffusion, relatively lower acidity, and is not susceptible to deactivation. Nitrogenated organic compounds (e.g., isocyanate) were observed on the Fe-zeolite catalyst surface. The site blockage was mainly on Fe(3+) sites, on which NO was activated and oxidized. Furthermore, a novel fully formulated Fe-BEA monolith catalyst coating modified with MOR was designed and tested, the deactivation due to propene poisoning was clearly reduced, and the NO(x) conversion reached 90% after 700 ppm C(3)H(6) exposure at 500 °C.

  3. Preparation of Fe-ZSM-5 with enhanced activity and stability for SCR of NOx

    International Nuclear Information System (INIS)

    Fe-ZSM-5 catalysts are prepared by 320 and 700oC FeCl3 sublimation into H-ZSM-5 and are characterised by XRD, H2-TPR, NH3-TPD, 27Al MAS NMR, and NO adsorption by DRIFT. Selective catalytic reduction of NO with NH3 and i-C4H10 and NO oxidation to NO2 have been studied. Fe-ZSM-5 prepared by 700oC FeCl3 sublimation is more active compared with Fe-ZSM-5 prepared by 320oC FeCl3 sublimation. NO adsorption study by DRIFT shows that FeCl3 sublimation temperature effects the relative distribution of different iron species in Fe-ZSM-5. High temperature FeCl3 sublimation leads to isolated and hydroxylated iron species (-Fe(OH)2) attached to the ion-exchange positions of ZSM-5. Isolated iron species are intrinsically more active in SCR of NO with NH3 and i-C4H10, and NO oxidation to NO2. All Fe-ZSM-5 catalysts deactivate under simulated exhaust gases at 600oC. Deactivation is due to extensive detachment of iron species from the ion-exchange positions followed by dealumination of zeolite. (author)

  4. Combination of photocatalysis and HC/SCR for improved activity and durability of DeNOx catalysts.

    Science.gov (United States)

    Heo, Iljeong; Kim, Mun Kyu; Sung, Samkyung; Nam, In-Sik; Cho, Byong K; Olson, Keith L; Li, Wei

    2013-04-16

    A photocatalytic HC/SCR system has been developed and its high deNOx performance (54.0-98.6% NOx conversion) at low temperatures (150-250 °C) demonstrated by using a representative diesel fuel hydrocarbon (dodecane) as the reductant over a hybrid SCR system of a photocatalytic reactor (PCR) and a dual-bed HC/SCR reactor. The PCR generates highly active oxidants such as O3 and NO2 from O2 and NO in the feed stream, followed by the subsequent formation of highly efficient reductants such as oxygenated hydrocarbon (OHC), NH3, and organo-nitrogen compounds. These reductants are the key components for enhancing the low temperature deNOx performance of the dual-bed HC/SCR system containing Ag/Al2O3 and CuCoY in the front and rear bed of the reactor, respectively. The OHCs are particularly effective for both NOx reduction and NH3 formation over the Ag/Al2O3 catalyst, while NH3 and organo-nitrogen compounds are effective for NOx reduction over the CuCoY catalyst. The hybrid HC/SCR system assisted by photocatalysis has shown an overall deNOx performance comparable to that of the NH3/SCR, demonstrating its potential as a promising alternative to the current urea/SCR and LNT technologies. Superior durability of HC/SCR catalysts against coking by HCs has also been demonstrated by a PCR-assisted regeneration scheme for deactivating catalysts.

  5. Optimizing the crystallinity and acidity of H-SAPO-34 by fluoride for synthesizing Cu/SAPO-34 NH3-SCR catalyst.

    Science.gov (United States)

    Ma, Jing; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Ma, Yue

    2016-03-01

    A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F(-) anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species. PMID:26969071

  6. Optimizing the crystallinity and acidity of H-SAPO-34 by fluoride for synthesizing Cu/SAPO-34 NH3-SCR catalyst.

    Science.gov (United States)

    Ma, Jing; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Ma, Yue

    2016-03-01

    A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F(-) anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species.

  7. Influence of MnO2 modification methods on the catalytic performance of CuO/CeO2 for NO reduction by CO

    Institute of Scientific and Technical Information of China (English)

    姚小江; 熊燕; 孙敬方; 高飞; 邓昱; 汤常金; 董林

    2014-01-01

    In order to investigate the influence of MnO2 modification methods on the catalytic performance of CuO/CeO2 catalyst for NO reduction by CO, two series of catalysts (xCuyMn/Ce and xCu/yMn/Ce) were prepared by co-impregnation and step-wise-impregnation methods, and characterized by means of X-ray diffraction (XRD), Raman spectra, H2-temperature programmed reduction (H2-TPR), in situ diffuse reflectance infrared Fourier transform spectra (in situ DRIFTS) techniques. Furthermore, the cata-lytic performances of these catalysts were evaluated by NO+CO model reaction. The obtained results indicated that:(1) The catalysts acquired by co-impregnation method exhibited stronger interaction owing to the more sufficient contact among each component of the catalysts compared with the catalysts obtained by stepwise-impregnation method, which was beneficial to the improvement of the reduction behavior;(2) The excellent reduction behavior was conducive to the formation of low valence state copper species (Cu+/Cu0) and more oxygen vacancies (especially the surface synergetic oxygen vacancies (SSOV, Cu+-Mn(4-x)+)) during the reaction process, which were beneficial to the adsorption of CO species and the dissociation of NO species, respectively, and further promoted the en-hancement of the catalytic performance. Finally, in order to further understand the difference between the catalytic performances of these catalysts prepared by co-impregnation and stepwise-impregnation methods, a possible reaction mechanism (schematic diagram) was tentatively proposed.

  8. Effects of alkali metals on catalyst of MnOx-CeO2/ZrO2-PILC in the low-temperature selective catalytic reduction%碱土金属对MnOx-CeO2/ZrO2-PILC催化剂SCR活性影响研究

    Institute of Scientific and Technical Information of China (English)

    沈伯雄; 陈建宏; 姚燕; 胡国丽

    2012-01-01

    The poisoning effects of alkali metals on low-temperature selective catalytic reduction (SCR) catalyst MnOx-CeO2/ZrO2-PILC were invested by the method of impregnation in the laboratory. It was indicated that the addition of Ca/Mg would decrease the activities of the catalyst, and the poisoning effects were contacted with the amount and acidity of the doped-alkali metal. X-ray diffraction (XRD) , H2-temperature programmed reduction (H2-TPR) , N2 adsorption-desorption and temperature-programmed desorption of NH3(NH3-TPD) were used to characterize the properties of the fresh and alkali earth doped catalysts. According to the results, the doped-alkali metals would inhibit the reduction properties, induce the loss in surface area and surface acidity.%采用浸渍法模拟低温选择性催化还原(SCR)催化剂MnOx-CeO2/ZrO2-PILC的碱土金属中毒特性,研究了碱土金属及其负载量对中毒程度的影响.实验表明,钙/镁的添加会引起催化剂中毒,催化剂中毒失活程度与碱土金属的负载量有关.运用X射线衍射(XRD)、H2程序升温还原(H2-TPR)、氮气吸脱附及NH3程序升温脱附(NH3-TPD)对新鲜催化剂以及碱土金属中毒后的催化剂进行了表征.结果表明,钙/镁中毒后催化剂的比表面积降低、催化剂氧化还原性和表面酸性减少,进而造成催化剂失活.

  9. Hydrolysis of isocyanic acid on SCR catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Elsener, M.; Kleemann, M.; Koebel, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Standard SCR catalysts possess high activity for the hydrolysis of HNCO and thus explain the suitability of urea as a selective reducing agent for NO{sub x}. At high space velocities HNCO-slip can get perceptible over the entire temperature range. This can be attributed to the fact that the temperature dependence is strong for the SCR reaction, but weak for the hydrolysis reaction. (author) 3 figs., 5 refs.

  10. Reduction of NO with methane over Fe/ZSM-5 catalysts

    Institute of Scientific and Technical Information of China (English)

    Li

    2010-01-01

    The catalytic activity of Fe/ZSM-5 for the selective reduction of NO to N2 with methane in the presence of excess O2 was studied. Fe/ZSM-5 catalysts with various Fe loadings were prepared by impregnation method. It is well known that methane is inactive when Fe/ZSM-5 as the catalyst for the selective catalytic reduction (SCR) of NO with methane. However, this paper shows that when the content of Fe was about 0.5%, Fe/ZSM-5 showed higher catalytic activity and selectivity of methane, and put forward measurable activation for CH4 is an important factor for the reaction of removal of NOx with CH4.

  11. The co-effect of Sb and Nb on the SCR performance of the V2O5/TiO2 catalyst.

    Science.gov (United States)

    Du, Xuesen; Gao, Xiang; Fu, Yincheng; Gao, Feng; Luo, Zhongyang; Cen, Kefa

    2012-02-15

    The effect of the Sb and Nb additives on the V(2)O(5)/TiO(2) catalyst for the selective catalytic reduction (SCR) of NO with NH(3) was investigated. The experimental results show that either Nb or Sb can improve the activity of V(2)O(5)/TiO(2) catalyst. Higher Nb loading led to higher N(2) selectivity. The co-doping of Sb and Nb showed higher improving effect than the single doping of Sb or Nb. The V(2)O(5)/TiO(2) catalyst doped with Sb and Nb had a better H(2)O resistance than the V(2)O(5)/TiO(2) catalyst. The addition of Sb and Nb also enhance the resistance of the V(2)O(5)/TiO(2) catalyst to K(2)O poisoning. The catalysts were characterized by BET, XRD, TEM, and XPS. The results showed that the active components of V, Sb, and Nb were well interacting with each other. The coexistence of Sb and Nb will enhance the redox ability and surface acidity and thus promote the SCR performance.

  12. Synergetic catalysis of ceria and titania for selective reduction of NO

    Institute of Scientific and Technical Information of China (English)

    SHEN Yuesong; ZHENG Dahai; YANG Bo; NI Songbo; ZHU Shemin

    2012-01-01

    The promotional effect of the interaction between titania and ceria on the catalytic performance for selective reduction of NO was studied.The catalysts,CeO2,TiO2,CeO2/TiO2 and TixCe1-xO2,were synthesized and tested in NH3-Selective catalytic reduction (SCR) of NO,and the samples were characterized by the Brunaller,Emmett and Teller (BET absorbed gas N2),X-ray diffraction (XRD),high resolution transmission electron microscopy (HR-TEM),and temperature programmed desorption (TPD NH3) techniques.The improvement mechanism of the interaction between the titania and ceria had been explored and discussed from two aspects of micro-structure and surface acidity.The interaction between the titania and ceria greatly improved the catalytic activity but had little effect on the active temperature.It was first reported that the acid amount determined the catalytic activity and the acid strength determined the active temperature for NH3-SCR of NO.

  13. Effect of Mole Percentage of Crosslinker of Silver-poly(N-isopropylacrylamide-co-acrylic acid Hybrid Microgels on Catalytic Reduction of Nitrobenzene

    Directory of Open Access Journals (Sweden)

    Zahoor H. FAROOQI

    2015-02-01

    Full Text Available Poly(N-isopropylacrylamide-co-acrylic acid microgels [P(NIPAM-co-AAc] with 2, 4, 6 and 8 mole percentage of N,N-methylene-bis-acrylamide were used as micro-reactors for the fabrication of Ag nanoparticles using the in situ reduction method. The pure and hybrid microgels were characterized by Fourier transform infrared and Ultraviolet-Visible spectroscopies. Silver-poly(N-isopropylacrylamide-co-acrylic acid hybrid microgels [Ag-P(NIPAM-co-AAc] with different crosslinker contents were used as catalysts for reduction of nitrobenzene (NB in aqueous medium in order to investigate the effect of crosslinker content on the value of apparent rate constant (kapp. 0.041, 0.146, 0.2388 and 0.255 min-1 were found as values of kapp for catalytic reduction of NB using hybrid microgels with 2, 4, 6 and 8 mole percentage of crosslinker, respectively. The effect of crosslinker feed content of hybrid microgels on catalytic activity for reduction of NB was compared to that of reduction of p-nitrophenol in aqueous medium.

  14. Preparation of Fe-Mo/ZSM-5 honeycomb catalyst and its performance for catalytic reduction of NOx%蜂窝状Fe-Mo/ZSM-5催化剂制备及其对NOx催化还原性能的影响

    Institute of Scientific and Technical Information of China (English)

    娄晓荣; 李伟; 李哲

    2012-01-01

    以具有较低热膨胀系数和较好抗热冲击性的堇青石蜂窝状陶瓷为载体、Fe-Mo/ZSM-5为活性组分制备了蜂窝状催化剂,研究了表面活性剂、载体和涂覆方法等条件对蜂窝状催化剂性能及其催化活性的影响.采用XRD、FT-IR、BET和SEM等技术对蜂窝状催化剂的体相结构、表面离子形态等进行了表征和研究.结果表明,以羧甲基纤维素为表面活性剂、美国康宁公司的堇青石蜂窝状陶瓷为载体和超声波法涂覆的蜂窝状催化剂具有最佳的催化活性,300℃时NOx催化转化率达100%,且随着温度的升高保持不变.%A series of monolithic catalysts supported with Fe-Mo/ZSM-5 and based on cordierite honeycomb ceramic substrate were prepared and tested for selective catalytic reduction of NOx with NH3. The effects of surface active agent, substrate and coating methods on the SCR activity of monolithic catalysts were investigated simultaneously. The bulk structures and the surface ionic forms of these catalysts were also characterized by XRD, FT-IR, BET and SEM technologies. The results indicated that the monolithic catalyst, prepared with carboxymethyl cellulose as the surface active agent and Corning cordierite honeycomb ceramics as the substrate by ultrasonic method, exhibited the best catalytic activity, and NOx conversion rate over the catalyst reached 100% at 300 ℃.

  15. Selective catalytic reduction of NOx with NH3 over a Cu-SSZ-13 catalyst prepared by a solid state ion exchange method

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Di; Gao, Feng; Peden, Charles HF; Li, Junhui; Kamasamudram, Krishna; Epling, William S.

    2014-06-01

    A novel solid state method was developed to synthesize Cu-SSZ-13 catalysts with excellent NH3-SCR performance and durable hydrothermal stability. After the solid state ion exchange (SSIE) process, the SSZ framework structure and surface area was maintained. In-situ DRIFTS and NH3-TPD experiments provide evidence that isolated Cu ions were successfully exchanged into the pores, which are the active centers for the NH3-SCR reaction.

  16. Using the SCR Specification Technique in a High School Programming Course.

    Science.gov (United States)

    Rosen, Edward; McKim, James C., Jr.

    1992-01-01

    Presents the underlying ideas of the Software Cost Reduction (SCR) approach to requirements specifications. Results of applying this approach to the teaching of programing to high school students indicate that students perform better in writing programs. An appendix provides two examples of how the method is applied to problem solving. (MDH)

  17. One-pot synthesis of hierarchical FeZSM-5 zeolites from natural aluminosilicates for selective catalytic reduction of NO by NH3

    Science.gov (United States)

    Yue, Yuanyuan; Liu, Haiyan; Yuan, Pei; Yu, Chengzhong; Bao, Xiaojun

    2015-03-01

    Iron-modified ZSM-5 zeolites (FeZSM-5s) have been considered to be a promising catalyst system to reduce nitrogen oxide emissions, one of the most important global environmental issues, but their synthesis faces enormous economic and environmental challenges. Herein we report a cheap and green strategy to fabricate hierarchical FeZSM-5 zeolites from natural aluminosilicate minerals via a nanoscale depolymerization-reorganization method. Our strategy is featured by neither using any aluminum-, silicon-, or iron-containing inorganic chemical nor involving any mesoscale template and any post-synthetic modification. Compared with the conventional FeZSM-5 synthesized from inorganic chemicals with the similar Fe content, the resulting hierarchical FeZSM-5 with highly-dispersed iron species showed superior catalytic activity in the selective catalytic reduction of NO by NH3.

  18. Safety system of a submersible compact reactor SCR for under-sea research vessel

    International Nuclear Information System (INIS)

    The SCR is an integral type PWR with thermal output of 1.25 MW for under-sea research vessel. The primary system of the reactor is cooled by natural circulation and pressurized by self-pressurization. The SCR adopts a passive safety system consisting of a water filled containment vessel, the emergency decay heat removal system and the pressure reduction makeup system. This paper describes design of safety system of the SCR and safety analysis, carried out by the RELAP5 code to confirm the function of keeping core flooding and removing residual heat by natural circulation for postulated accidents. The analysis results show that in case of loss of coolant accident and loss of feedwater accident, the core is always flooded and cooled down by rejecting the decay heat to the sea water through the containment wall. (author)

  19. Performance and kinetic study on selective catalytic reduction of NOx with NH3 of MnOx-WO3/TiO2 catalyst%MnOx-WO3/TiO2NH3选择性还原NOx的催化性能与动力学

    Institute of Scientific and Technical Information of China (English)

    吴碧君; 肖萍; 刘晓勤

    2011-01-01

    研究了Mn-W/TiO2用于NH3选择性催化还原NOx体系的催化反应性能,在很宽的温度范围和各种气体条件下,该催化剂显示了较高的催化活性.在GHSV 18900 h-1、100~350℃条件下,NOx转化率高达80.3%~99.6%,Nz选择性达98.7%~100%;当反应气体中有0.01%SO2(分压比,下同)和6%H2O,120℃转化率可维持在98.5%;SO2浓度高达0.07%,300℃转化率可长期稳定在99%,达到了商用V-W/TiO2催化剂的水平.稳态动力学实验发现,O2对Mn-W/TiO2NH3-SCR NOx催化体系起促进作用,O2含量在1.5%以下时转化率随O2浓度的增加而显著提高;当有过量O2和过量H2O存在时,反应为关于NO浓度的一级反应,关于NH3浓度的零级反应.由各温度下的动力学实验结果推导出Mn-W/TiO2催化反应的活化能为6.24 kJ·mol-1,较文献报道的其他催化剂的活化能低得多,为NH3选择性还原NOx较好的催化剂.%The catalytic activities of MnOx-WO3/TiO2 catalyst in a wide temperature range were investigated for selective catalytic reduction (SCR) of NO with NH3.It yields 80.3%-99.6% NOx conversion and 98.7%-100% selectivity for N2 product from 100℃ to 350℃ at GHSV 18900 h-1. In the presence of 0. 01% SO2 and 6% H2O at 120℃, the NOx conversion maintains at 98. 5%. At 300℃ and with 0.07% SO2 in the reactant stream, the NOx conversion is 99%, as high as that of the commercial V-W/ TiO2 catalyst. The steady-state kinetic study shows that O2 plays a promoting role. When O2 content is less than 1.5%, the NOx conversion increases sharply with O2 concentration. The reaction order is zero with respect to NH3 and first with respect to NO with excess O2 and H2O. The active energy of Mn-W/TiO2 calculated is 6.24 kJ · mol-1 according to the kinetic experiments at various temperatures, much lower than other catalysts reported in the literatures. Thus Mn-W/TiO2 is an excellent catalyst for SCR NO with NH3.

  20. Deactivation of SCR Catalysts by Additives

    DEFF Research Database (Denmark)

    Castellino, Francesco

    2008-01-01

    , som anvendes på kraftværkerne i forbindelse med SCR processen. Både P og Ca er kendt som komponenter, der deaktiverer disse vanadium baserede katalysatorer, der normalt anvendes i SCR anlæg, og det har derfor ført til bekymring i forbindelse med deres anvendelse i fuldskalaanlæg. Hovedformålet med...... dette studie har været at undersøge deaktiveringspotentiale og -mekanismer af P and Ca additiver overfor kommercielle vanadium baserede SCR katalysatorer under veldefinerede realistiske driftsbetingelser. I den første del af studiet blev kommercielle vanadiumbaserede SCR katalysatorer eksponeret...... blev kommercielle vanadium baserede SCR katalysatorer i fuld længde eksponeret for aerosoler dannet ved injektion af en vandig opløsning af K3PO4 i den varme røggas (T > 850 °C) fra naturgasbrænderen. Disse aerosoler kan dannes, når der anvendes brændstoffer med højt indhold af K- og P...

  1. Synthesis of Au nanoparticles decorated graphene oxide nanosheets: Noncovalent functionalization by TWEEN 20 in situ reduction of aqueous chloroaurate ions for hydrazine detection and catalytic reduction of 4-nitrophenol

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Wenbo [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin (China); Ning, Rui [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Qin, Xiaoyun; Zhang, Yingwei; Chang, Guohui; Liu, Sen; Luo, Yonglan [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin (China); Sun, Xuping, E-mail: sunxp@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin (China)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer TWEEN 20 is used as a stabilizing agent for GO as well as a reducing and immobilizing agent for Au nanoparticles. Black-Right-Pointing-Pointer The hydrazine sensor based on the nanocomposites has a fast amperometric response. Black-Right-Pointing-Pointer The detection limit of the hydrazine sensor is estimated to be 78 nM. Black-Right-Pointing-Pointer The nanocomposites also exhibit good catalytic activity toward 4-nitrophenol reduction. - Abstract: In this paper, we develop a cost-effective and simple route for the synthesis of Au nanoparticles (AuNPs) decorated graphene oxide (GO) nanosheets using polyoxyethylene sorbitol anhydride monolaurate (TWEEN 20) as a stabilizing agent for GO as well as a reducing and immobilizing agent for AuNPs. The AuNPs assemble on the surface of TWEEN-functionalized GO by the in situ reduction of HAuCl{sub 4} aqueous solution. The morphologies of these composites were characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is found that the resultant AuNPs decorated GO nanosheets (AuNPs/TWEEN/GO) exhibit remarkable catalytic performance for hydrazine oxidation. This hydrazine sensor has a fast amperometric response time of less than 3 s. The linear range is estimated to be from 5 {mu}M to 3 mM (r = 0.999), and the detection limit is estimated to be 78 nM at a signal-to-noise ratio of 3. The AuNPs/TWEEN/GO composites also exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GO supports also enhance the catalytic activity via a synergistic effect.

  2. Local Environment and Nature of Cu Active Sites in Zeolite-Based Catalysts for the Selective Catalytic Reduction of NOx

    NARCIS (Netherlands)

    Deka, U.; Lezcano-Gonzalez, I.; Weckhuysen, B.M.; Beale, A.M.

    2013-01-01

    Cu-exchanged zeolites have demonstrated widespread use as catalyst materials in the abatement of NOx, especially from mobile sources. Recent studies focusing on Cu-exchanged zeolites with the CHA structure have demonstrated them to be excellent catalysts in the ammonia-assisted selective catalytic r

  3. Technical and commercial considerations in selecting NOx reduction technology for utility boilers

    International Nuclear Information System (INIS)

    A technical and economic evaluation of technologies commercially available for the reduction of nitrous oxides is presented. The study was based on nitrogen oxide control alternatives for a 500 MW pulverized coal and oil fired utility boiler, with emphasis on post-combustion technologies. A combustion related technology examined was the XCL type DRB burner in combination with an overfire air system. Post-combustion technologies examined included selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR). It was concluded that if modest nitrogen oxides reduction is required for large utility boiler application, combustion related technologies such as low nitrogen oxide burners and overfire air systems should be given first consideration. If required reductions are beyond the capabilities of these systems, post combustion technologies must be considered. The lower capital cost of SNCR nitrogen oxide control systems is attractive, but technical risk, lack of large scale operating experience, and life cycle cost render it less attractive than SCR over 25 years of expected boiler operating life. 2 refs., 4 figs., 2 tabs

  4. Modeling Species Inhibition and Competitive Adsorption in Urea-SCR Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Devarakonda, Maruthi N.; Tonkyn, Russell G.; Lee, Jong H.

    2012-04-16

    Although the urea-SCR technology exhibits high NOx reduction efficiency over a wide range of temperatures among the lean NOx reduction technologies, further improvement in low-temperature performance is required to meet the future emission standards and to lower the system cost. In order to improve the catalyst technologies and optimize the system performance, it is critical to understand the reaction mechanisms and catalyst behaviors with respect to operating conditions. Urea-SCR catalysts exhibit poor NOx reduction performance at low temperature operating conditions (T < 150 C). We postulate that the poor performance is either due to NH3 storage inhibition by species like hydrocarbons or due to competitive adsorption between NH3 and other adsorbates such as H2O and hydrocarbons in the exhaust stream. In this paper we attempt to develop one-dimensional models to characterize inhibition and competitive adsorption in Fe-zeolite based urea-SCR catalysts based on bench reactor experiments. We further use the competitive adsorption (CA) model to develop a standard SCR model based on previously identified kinetics. Simulation results indicate that the CA model predicts catalyst outlet NO and NH3 concentrations with minimal root mean square error.

  5. Surface Contour Radar (SCR) contributions to FASINEX

    Science.gov (United States)

    Walsh, E. J.

    1988-01-01

    The SCR was asked to participate in the Frontal Air-Sea Interaction Experiment (FASINEX) to provide directional wave spectra. The NASA P-3 carrying the SCR, the Radar Ocean Wave Spectrometer, and the Airborne Oceanographic Lidar was one of five aircrafts and two ocean research ships participating in this coordinated study of the air sea interaction in the vicinity of a sea surface temperature front near 28 deg N, 70 deg W. Analysis of data from the February 1986 experiment is still ongoing, but results already submitted for publication strengthen the hypothesis that off-nadir radar backscatter is closely correlated to wind stress. The SCR provided valuable information on the directional wave spectrum and its spatial variation.

  6. Development and analysis of SCR requirements tables for system scenarios

    Science.gov (United States)

    Callahan, John R.; Morrison, Jeffery L.

    1995-01-01

    We describe the use of scenarios to develop and refine requirement tables for parts of the Earth Observing System Data and Information System (EOSDIS). The National Aeronautics and Space Administration (NASA) is developing EOSDIS as part of its Mission-To-Planet-Earth (MTPE) project to accept instrument/platform observation requests from end-user scientists, schedule and perform requested observations of the Earth from space, collect and process the observed data, and distribute data to scientists and archives. Current requirements for the system are managed with tools that allow developers to trace the relationships between requirements and other development artifacts, including other requirements. In addition, the user community (e.g., earth and atmospheric scientists), in conjunction with NASA, has generated scenarios describing the actions of EOSDIS subsystems in response to user requests and other system activities. As part of a research effort in verification and validation techniques, this paper describes our efforts to develop requirements tables from these scenarios for the EOSDIS Core System (ECS). The tables specify event-driven mode transitions based on techniques developed by the Naval Research Lab's (NRL) Software Cost Reduction (SCR) project. The SCR approach has proven effective in specifying requirements for large systems in an unambiguous, terse format that enhance identification of incomplete and inconsistent requirements. We describe development of SCR tables from user scenarios and identify the strengths and weaknesses of our approach in contrast to the requirements tracing approach. We also evaluate the capabilities of both approach to respond to the volatility of requirements in large, complex systems.

  7. Fabrication of magnetically recyclable Fe3O4@Cu nanocomposites with high catalytic performance for the reduction of organic dyes and 4-nitrophenol

    International Nuclear Information System (INIS)

    A facile and efficient approach to synthesize Fe3O4@Cu nanocomposites using L-Lysine as a linker was developed. The morphology, composition and crystallinity of the Fe3O4@Cu nanocomposites were characterized by Fourier Transform infrared spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and powder X-ray diffraction. In addition, the magnetic properties were determined with vibrating sample magnetometer. The surface of the Fe3O4 contained many small Cu nanoparticles with sizes of about 3 nm. It was found that the Fe3O4@Cu nanocomposites could catalyze the degradation of organic dyes. The catalytic activities of the Fe3O4@Cu nanocomposites for the reduction of nitrophenol were also studied. The Fe3O4@Cu nanocomposites are more efficient catalysts compared with Cu nanoparticles and can easily be recovered from the reaction mixture with magnet. The cost effective and recyclable Fe3O4@Cu nanocomposites provide an exciting new material for environmental protection applications. - Highlights: • Cu nanoparticles as small as 3 nm are synthesized. • Low cost Fe3O4@Cu magnetical nanoparticles show catalytic activity for organic dyes and 4-nitrophenol. • The Fe3O4@Cu display high catalytic activity after 13 cycles

  8. The Poisoning Effect of Na Doping over Mn-Ce/TiO2 Catalyst for Low-Temperature Selective Catalytic Reduction of NO by NH3

    Directory of Open Access Journals (Sweden)

    Liu Yang

    2014-01-01

    Full Text Available Sodium carbonate (Na2CO3, sodium nitrate (NaNO3, and sodium chloride (NaCl were chosen as the precursors to prepare the Na salts deposited Mn-Ce/TiO2 catalysts through an impregnation method. The influence of Na on the performance of the Mn-Ce/TiO2 catalyst for low-temperature selective catalytic reduction of NOx by NH3 was investigated. Experimental results showed that Na salts had negative effects on the activity of Mn-Ce/TiO2 and the precursors of Na salts also affected the catalytic activity. The precursor Na2CO3 had a greater impact on the catalytic activity, while NaNO3 had minimal effect. The characterization results indicated that the significant changes in physical and chemical properties of Mn-Ce/TiO2 were observed after Na was doped on the catalysts. The significant decreases in surface areas and NH3 adsorption amounts were observed after Na was doped on the catalysts, which could be considered as the main reasons for the deactivation of Na deposited Mn-Ce/TiO2.

  9. SCR at bio fuel combustion

    International Nuclear Information System (INIS)

    by sulphatisation with sulphur dioxide. After a sulphatisation procedure with 500 ppm SO2 (without washing) the activity was regained to at least 90 % even for heavily deactivated samples. The use of sulphatisation, periodic washing, lower flue gas temperature and use of an optimised catalyst are very promising measures to increase the catalyst lifetime and to reduce the operation costs for SCR in bio fuel fluidized bed based power plants. Therefore, a thorough investigation of these measures is warranted Figures and tables with text in English. 36 refs, 26 figs, 5 tabs

  10. Industrial H2-SCR of NO on a novel Pt/MgO-CeO2 catalyst

    International Nuclear Information System (INIS)

    We describe here the performance of a novel MgO-CeO2-supported Pt (0.1 wt%) catalyst towards the selective conversion of NO into N2 (SN2 > 80%) by using H2 (H2-SCR) under process conditions similar to those encountered in the NH3-SCR in the low-temperature range of 150-200 C. At 200 C, 100% conversion of NO and 85% N2-selectivity were obtained with a feed stream containing 1000 ppm NO, 5% O2, 5% H2O, 10% CO2, 0-0.5% CO, and using 1.5% H2 in the feed as reducing agent (GHSV = 40,000 h-1). Thus, a N2-yield of 85% similar to that obtained in most NH3-SCR applications could make H2-SCR as the most environmentally friendly NOx control catalytic technology with great potential to replace the existing NH3-SCR technology. The latter is currently used industrially mainly in power and nitric acid plants, gas turbines, furnaces, boilers, and waste incinerators for the elimination of NOx. However, this technology faces several problems such as catalyst deterioration, emissions of non-reacted toxic NH3 (ammonia slip), ash odor, air-heaters fouling, and a high running cost. (author)

  11. Relevance of Co, Ag-ferrierite catalysts acidity and cation siting to CH4-NOx-SCR activity

    International Nuclear Information System (INIS)

    The influence of acidity on Ag.Co exchanged ferrierite obtained from different parent forms was tested in CH4-DeNOx reaction. Ag and Co cation siting distribution and residual zeolite acidity were evaluated by means of a quantitative evaluation of catalyst acidity through NH3-TPD experiments and a detailed structural catalyst characterization by Rietveld refinement. A new nomenclature for the cation sites in hydrated and dehydrated cation exchange ferrierites was introduced for sake of clarity. The sites relative populations obtained by the UV-Vis spectra did not agree with the values given by the Rietveld refinement and the SCR. activity scale since the high abundance of Co cations in the retained most active position. Co2a, was shown by the less active catalyst obtained from the Na,K form. It was concluded that SCR activity does not only depend on Co and Ag siting within the zeolite framework but also by the presence of residual acidity evidenced on the most active catalysts. CH4 combustion tests showed that the presence of residual acidity appears relevant to SCR catalytic performances, likely related to its ability in methane activation. The importance of the coexistence of Co and zeolitic, acid sites for the HC-SCR suggested that SCR reaction could proceed on a dual site.

  12. 40 CFR 1042.110 - Recording reductant use and other diagnostic functions.

    Science.gov (United States)

    2010-07-01

    ... other diagnostic functions. (a) Engines equipped with SCR systems using a reductant other than the... or printed by the operator. (3) SCR systems must also conform to the provisions of paragraph (d) of... paragraph (a) of this section also apply for SCR systems covered by this paragraph (d). For engines...

  13. Effect of Ce/Zr molar ratio on the performance of Cu–Ce{sub x}–Zr{sub 1−x}/TiO{sub 2} catalyst for selective catalytic reduction of NO{sub x} with NH{sub 3} in diesel exhaust

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xiaoliang [School of Material Science and Engineering, Tianjin University, Tianjin 300072 (China); Gong, Cairong, E-mail: gcr@tju.edu.cn [School of Material Science and Engineering, Tianjin University, Tianjin 300072 (China); Lv, Gang; Bin, Feng; Song, Chonglin [State Key Laboratory of Engines, Tianjin University, Tianjin 300072 (China)

    2014-12-15

    Graphical abstract: The Cu–Ce{sub 0.25}–Zr{sub 0.75}/TiO{sub 2} catalyst exhibited excellent SCR activity at 165–450 °C within the range of exhaust temperatures of diesel engines. - Highlights: • Cu–Ce{sub x}–Zr{sub 1−x}/TiO{sub 2} catalysts were prepared by a wet impregnation method. • The property for NH{sub 3}-selective catalytic reduction of NO{sub x} were investigated. • The Ce/Zr molar ratio had effects on the performance of Cu–Ce–Zr/TiO{sub 2} catalysts. • The Cu–Ce{sub 0.25}–Zr{sub 0.75}/TiO{sub 2} sample exhibited 100% NO{sub x} conversion between 165 °C and 450 °C. • The factors that govern the activity enhancement were extensively investigated. - Abstract: Copper–cerium–zirconium catalysts loaded on TiO{sub 2} prepared by a wet impregnation method were investigated for NH{sub 3}-selective catalytic reduction of NO{sub x}, aiming to study the effects of the Ce/Zr molar ratio on the performance of Cu–Ce–Zr/TiO{sub 2} catalysts. The Cu–Ce{sub 0.25}–Zr{sub 0.75}/TiO{sub 2} sample exhibited nearly 100% NO{sub x} conversion over a wide temperature range (165–450 °C), which is strikingly superior to that of Cu/TiO{sub 2} (210–389 °C) within the range of exhaust temperatures of diesel engines. The factors that govern the activity enhancement were extensively investigated by using a series of characterization techniques, namely X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H{sub 2}-TPR). The results showed that the addition of zirconium and/or cerium refined the copper dispersion, prevented copper crystallization and partially incorporated the copper ions into the zirconia (ceira) lattice, which led to enhance the redox abilities of Cu–Ce–Zr/TiO{sub 2} catalysts.

  14. Excellent performance of one-pot synthesized Cu-SSZ-13 catalyst for the selective catalytic reduction of NOx with NH3.

    Science.gov (United States)

    Xie, Lijuan; Liu, Fudong; Ren, Limin; Shi, Xiaoyan; Xiao, Feng-Shou; He, Hong

    2014-01-01

    Cu-SSZ-13 samples prepared by a novel one-pot synthesis method achieved excellent NH3-SCR performance and high N2 selectivity from 150 to 550 °C after ion exchange treatments. The selected Cu3.8-SSZ-13 catalyst was highly resistant to large space velocity (800 000 h(-1)) and also maintained high NOx conversion in the presence of CO2, H2O, and C3H6 in the simulated diesel exhaust. Isolated Cu(2+) ions located in three different sites were responsible for its excellent NH3-SCR activity. Primary results suggest that the one-pot synthesized Cu-SSZ-13 catalyst is a promising candidate as an NH3-SCR catalyst for the NOx abatement from diesel vehicles. PMID:24295053

  15. Octonionic representations of GL(8,scr(R)) and GL(4,scr(C))

    International Nuclear Information System (INIS)

    Octonionic algebra being nonassociative is difficult to manipulate. We introduce left/right octonionic barred operators which enable us to reproduce the associative GL(8,scr(R)) group. Extracting the basis of GL(4,scr(C)), we establish an interesting connection between the structure of left/right octonionic barred operators and generic 4x4 complex matrices. As an application we give an octonionic representation of the four-dimensional Clifford algebra. copyright 1997 American Institute of Physics

  16. Preparation of FeO(OH Modified with Polyethylene Glycol and Its Catalytic Activity on the Reduction of Nitrobenzene with Hydrazine Hydrate

    Directory of Open Access Journals (Sweden)

    Ke Ying Cai

    2016-10-01

    Full Text Available Iron oxyhydroxide was prepared by dropping ammonia water to Fe(NO33.9H2O dispersed in polyethylene glycol (PEG 1000. The catalyst was characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and laser particle size analyzer. The results showed the catalyst modified with polyethylene glycol was amorphous. The addition of PEG during the preparation make the particle size of the catalyst was smaller and more uniform. The catalytic performance was tested in the reduction of nitroarenes to corresponding amines with hydrazine hydrate, and the catalyst showed excellent activity and stability. Copyright © 2016 BCREC GROUP. All rights reserved Received: 2nd February 2016; Revised: 26th April 2016; Accepted: 7th June 2016 How to Cite: Cai, K.Y., Liu, Y.S., Song, M., Zhou, Y.M., Liu, Q., Wang, X.H. (2016. Preparation of FeO(OH Modified with Polyethylene Glycol and Its Catalytic Activity on the Reduction of Nitrobenzene with Hydrazine Hydrate. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (3: 363-368 (doi:10.9767/bcrec.11.3.576.363-368 Permalink/DOI: http://doi.org/10.9767/bcrec.11.3.576.363-368

  17. Advanced byproduct recovery: Direct catalytic reduction of sulfur dioxide to elemental sulfur. Quarterly report, April 1--June 30, 1997

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    The team of Arthur D. Little, Tufts University and Engelhard Corporation are conducting Phase 1 of a four and a half year, two-phase effort to develop and scale-up an advanced byproduct recovery technology that is a direct, single-stage, catalytic process for converting sulfur dioxide to elemental sulfur. This catalytic process reduces SO{sub 2} over a fluorite-type oxide (such as ceria and zirconia). The catalytic activity can be significantly promoted by active transition metals, such as copper. More than 95% elemental sulfur yield, corresponding to almost complete sulfur dioxide conversion, was obtained over a Cu-Ce-O oxide catalyst as part of an on-going DOE-sponsored, University Coal Research Program. This type of mixed metal oxide catalyst has stable activity, high selectivity for sulfur production, and is resistant to water and carbon dioxide poisoning. Tests with CO and CH{sub 4} reducing gases indicate that the catalyst has the potential for flexibility with regard to the composition of the reducing gas, making it attractive for utility use. The performance of the catalyst is consistently good over a range of SO{sub 2} inlet concentration (0.1 to 10%) indicating its flexibility in treating SO{sub 2} tail gases as well as high concentration streams. The principal objective of the Phase 1 program is to identify and evaluate the performance of a catalyst which is robust and flexible with regard to choice of reducing gas. In order to achieve this goal, the authors have planned a structured program including: Market/process/cost/evaluation; Lab-scale catalyst preparation/optimization studies; Lab-scale, bulk/supported catalyst kinetic studies; Bench-scale catalyst/process studies; and Utility review. Progress is reported from all three organizations.

  18. Innovative Clean Coal Technology (ICCT). Demonstration of Selective Catalytic Reduction (SCR) technology for the control of nitrogen oxide (NO{sub x}) emissions from high-sulfur coal-fired boilers: Volume 3, Appendices O--T. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-10-01

    Volume 3 contains the following appendices: Appendix O, Second Series-Manual APH Tests; Appendix P, Third Series-Manual APH Tests; Appendix Q, ABB Analysis of Air Preheaters-Final Report; Appendix R, ABB Corrosion Analysis Study; Appendix S, SRI Waste Stream Impacts Study; and Appendix T, Economic Evaluation.

  19. Characterization of the major promoter for the plasmid-encoded sucrose genes scrY, scrA, and scrB.

    OpenAIRE

    Cowan, P J; Nagesha, H; Leonard, L.; Howard, J. L.; Pittard, A. J.

    1991-01-01

    Sucrose genes from a Salmonella thompson plasmid were cloned in Escherichia coli K-12. A physical map and a genetic map of the genes were constructed, revealing strong homology with the scr regulon from the Salmonella typhimurium plasmid pUR400. Two promoters were examined after being subcloned into transcriptional fusion vectors. Primer extension analysis and site-directed mutagenesis were used to identify the precise location of the promoter of scrY, scrA, and scrB. Transcription from this ...

  20. Catalytic role of Cu(II) in the reduction of Cr(VI) by citric acid under an irradiation of simulated solar light.

    Science.gov (United States)

    Li, Ying; Chen, Cheng; Zhang, Jing; Lan, Yeqing

    2015-05-01

    The catalytic role of Cu(II) in the reduction of Cr(VI) by citric acid with simulated solar light was investigated. The results demonstrated that Cu(II) could significantly accelerate Cr(VI) reduction and the reaction obeyed to pseudo zero-order kinetics with respect to Cr(VI). The removal of Cr(VI) was related to the initial concentrations of Cu(II), citric acid, and the types of organic acids. The optimal removal of Cr(VI) was achieved at pH 4, and the rates of Cu(II) photocatalytic reduction of Cr(VI) by organic acids were in the order: tartaric acid (two α-OH groups, two -COOH groups)>citric acid (one α-OH group, three -COOH groups)>malic acid (one α-OH group, two -COOH groups)>lactic acid (one α-OH group, one -COOH group)≫succinic acid (two -COOH groups), suggesting that the number of α-OH was the key factor for the reaction, followed by the number of -COOH. The formation of Cu(II)-citric acid complex could generate Cu(I) and radicals through a pathway of metal-ligand-electron transfer, promoting the reduction of Cr(VI). This study is helpful to fully understanding the conversion of Cr(VI) in the existence of both organic acids and Cu(II) with solar light in aquatic environments.

  1. A Close Analysis of Developments in Diesel Engine Emission Reduction Technologies

    Directory of Open Access Journals (Sweden)

    Raghav Ahuja

    2013-06-01

    Full Text Available Diesel engines have the potential to significantly increase vehicle fuel economy and decrease CO 2 emissions; however, efficient removal of NO x and particulate matter from the engine exhaust is required to meet stringent emission standards. Diesel aftertreatment systems being used consists of a Diesel Oxidation Catalyst (DOC, a urea-based Selective Catalyst Reduction (SCR catalyst and a diesel particulate filter (DPF, and is widely used to meet the most recent NO x (nitrogen oxides comprising NO and NO 2 and particulate matter (PM emission standards for medium and heavy-duty sport utility and truck vehicles. The most efficient way and the best available technology (BAT to radically reduce the critical Diesel emission components particles (PM&NP and nitric oxides (NO x are combined exhaust gas aftertreatment systems (DPF+SCR. SCR (selective catalytic reduction is regarded as the most efficient deNO x -system, diesel particle filters are most efficient for soot abatement. Today, several suppliers offer combined systems for retrofitting of HD vehicles.

  2. Durability of ZSM5-supported Co-Pd catalysts in the reduction of NOx with methane

    International Nuclear Information System (INIS)

    Selective catalytic reduction (SCR) of NO with CH4 was studied over ZSM5-based cobalt and palladium catalysts in the presence of oxygen and water. Pore volume impregnation of cobalt was found to be more efficient and much simpler than the common (wet) ion-exchange method. In the case of Pd, wet ion-exchange was found to give superior activity. As compared to alternative catalytic systems reported in literature for CH4-SCR in the presence of water, ZSM5-supported Co-Pd combination catalysts are very active and selective. The activity of the ZSM5-based Co-Pd combination catalysts, however, decreases strongly with time-on-stream. Strikingly, this deactivation is not (predominantly) caused by steam dealumination of the zeolites: loss of SCR activity with time-on-stream occurs irrespective of the presence or absence of water in the feed. The higher the temperature of calcination the lower the initial activity and the faster the deactivation. In addition to this, the deactivation is also more pronounced at higher reaction temperatures. These observations are consistent with a temperature-induced mechanism of ion migration and sintering as also confirmed by TPR analysis. The role of water in this migration process is not obvious. Hence, the limited thermal stability of ZSM5-supported metal (ion) catalysts leads to two demands, which have yet to be made for application of zeolites in CH4-SCR: (1) stabilisation of the ionic phases in zeolite pores of different geometry; and (2) further improved activity and selectivity allowing one to operate at temperatures that do not exceed 350-400C, where deactivation is not significant

  3. Synthesis and Evaluation of Cu/SAPO-34 Catalysts for NH3-SCR 2: Solid-state Ion Exchange and One-pot Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Walter, Eric D.; Washton, Nancy M.; Szanyi, Janos; Peden, Charles HF

    2015-01-01

    Cu-SAPO-34 catalysts are synthesized using two methods: solid-state ion exchange (SSIE) and one-pot synthesis. SSIE is conducted by calcining SAPO-34/CuO mixtures at elevated temperatures. For the one-pot synthesis method, Cu-containing chemicals (CuO and CuSO4) are added during gel preparation. A high-temperature calcination step is also needed for this method. Catalysts are characterized with surface area/pore volume measurements, temperature programmed reduction (TPR), electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopies, and scanning electron microscopy (SEM). Catalytic properties are examined using standard ammonia selective catalytic reduction (NH3-SCR) and ammonia oxidation reactions. In Cu-SAPO-34 samples formed using SSIE, Cu presents both as isolated Cu2+ ions and unreacted CuO. The former is highly active and selective in NH3-SCR, while the latter catalyzes a side reaction; notably, the non-selective oxidation of NH3 above 350 ºC. Using the one-pot method followed by a high-temperature aging treatment, it is possible to form Cu SAPO-34 samples with predominately isolated Cu2+ ions at low Cu loadings. However at much higher Cu loadings, isolated Cu2+ ions that bind weakly with the CHA framework and CuO clusters also form. These Cu moieties are very active in catalyzing non-selective NH3 oxidation above 350 ºC. Low-temperature reaction kinetics indicate that Cu-SAPO-34 samples formed using SSIE have core-shell structures where Cu is enriched in the shell layers; while Cu is more evenly distributed within the one-pot samples. Reaction kinetics also suggest that at low temperatures, the local environment next to Cu2+ ion centers plays little role on the overall catalytic properties. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental

  4. Preparation of Fe-ZSM-5 with enhanced activity and stability for SCR of NO{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Krishna, K.; Makkee, M. [Reactor and Catalysis Engineering, DelftChemTech, Delft University of Technology, Julianalaan 136, NL 2628 BL Delft (Netherlands)

    2006-04-30

    Fe-ZSM-5 catalysts are prepared by 320 and 700{sup o}C FeCl{sub 3} sublimation into H-ZSM-5 and are characterised by XRD, H{sub 2}-TPR, NH{sub 3}-TPD, {sup 27}Al MAS NMR, and NO adsorption by DRIFT. Selective catalytic reduction of NO with NH{sub 3} and i-C{sub 4}H{sub 10} and NO oxidation to NO{sub 2} have been studied. Fe-ZSM-5 prepared by 700{sup o}C FeCl{sub 3} sublimation is more active compared with Fe-ZSM-5 prepared by 320{sup o}C FeCl{sub 3} sublimation. NO adsorption study by DRIFT shows that FeCl{sub 3} sublimation temperature effects the relative distribution of different iron species in Fe-ZSM-5. High temperature FeCl{sub 3} sublimation leads to isolated and hydroxylated iron species (-Fe(OH){sub 2}) attached to the ion-exchange positions of ZSM-5. Isolated iron species are intrinsically more active in SCR of NO with NH{sub 3} and i-C{sub 4}H{sub 10}, and NO oxidation to NO{sub 2}. All Fe-ZSM-5 catalysts deactivate under simulated exhaust gases at 600{sup o}C. Deactivation is due to extensive detachment of iron species from the ion-exchange positions followed by dealumination of zeolite. (author)

  5. Experimental Studies for CPF and SCR Model, Control System, and OBD Development for Engines Using Diesel and Biodiesel Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, John; Naber, Jeffrey; Parker, Gordon; Yang, Song-Lin; Stevens, Andrews; Pihl, Josh

    2013-04-30

    The research carried out on this project developed experimentally validated Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), and Selective Catalytic Reduction (SCR) high‐fidelity models that served as the basis for the reduced order models used for internal state estimation. The high‐fidelity and reduced order/estimator codes were evaluated by the industrial partners with feedback to MTU that improved the codes. Ammonia, particulate matter (PM) mass retained, PM concentration, and NOX sensors were evaluated and used in conjunction with the estimator codes. The data collected from PM experiments were used to develop the PM kinetics using the high‐fidelity DPF code for both NO2 assisted oxidation and thermal oxidation for Ultra Low Sulfur Fuel (ULSF), and B10 and B20 biodiesel fuels. Nine SAE papers were presented and this technology transfer process should provide the basis for industry to improve the OBD and control of urea injection and fuel injection for active regeneration of the PM in the DPF using the computational techniques developed. This knowledge will provide industry the ability to reduce the emissions and fuel consumption from vehicles in the field. Four MS and three PhD Mechanical Engineering students were supported on this project and their thesis research provided them with expertise in experimental, modeling, and controls in aftertreatment systems.

  6. A kinetic model of the hydrogen assisted selective catalytic reduction of NO with ammonia over Ag/Al2O3

    DEFF Research Database (Denmark)

    Tamm, Stefanie; Olsson, Louise; Fogel, Sebastian;

    2013-01-01

    and NO, oxidation of H2, and the adsorption and desorption of NH3. The model was fitted to the results of an NH3-TPD experiment, an NH3 oxidation experiment, and a series of H2-assisted NH3-SCR steady-state experiments. The model predicts the conversion of NOx well even during transient experiments....

  7. Final Report of a CRADA Between Pacific Northwest National Laboratory and the Ford Motor Company (CRADA No. PNNL/265): “Deactivation Mechanisms of Base Metal/Zeolite Urea Selective Catalytic Reduction Materials, and Development of Zeolite-Based Hydrocarbon Adsorber Materials”

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Kwak, Ja Hun; Lee, Jong H.; Tran, Diana N.; Peden, Charles HF; Howden, Ken; Cheng, Yisun; Lupescu, Jason; Cavattaio, Giovanni; Lambert, Christine; McCabe, Robert W.

    2013-02-14

    Reducing NOx emissions and particulate matter (PM) are primary concerns for diesel vehicles required to meet current LEV II and future LEV III emission standards which require 90+% NOx conversion. Currently, urea SCR as the NOx reductant and a Catalyzed Diesel Particulate Filter (CDPF) are being used for emission control system components by Ford Motor Company for 2010 and beyond diesel vehicles. Because the use of this technology for vehicle applications is new, the relative lack of experience makes it especially challenging to satisfy durability requirements. Of particular concern is being able to realistically simulate actual field aging of the catalyst systems under laboratory conditions. This is necessary both as a rapid assessment tool for verifying improved performance and certifiability of new catalyst formulations, and to develop a good understanding of deactivation mechanisms that can be used to develop improved catalyst materials. In addition to NOx and PM, the hydrocarbon (HC) emission standards are expected to become much more stringent during the next few years. Meanwhile, the engine-out HC emissions are expected to increase and/or be more difficult to remove. Since HC can be removed only when the catalyst becomes warm enough for its oxidation, three-way catalyst (TWC) and diesel oxidation catalyst (DOC) formulations often contain proprietary zeolite materials to hold the HC produced during the cold start period until the catalyst reaches its operating temperature (e.g., >200°C). Unfortunately, much of trapped HC tends to be released before the catalyst reaches the operating temperature. Among materials effective for trapping HC during the catalyst warm-up period, siliceous zeolites are commonly used because of their high surface area and high stability under typical operating conditions. However, there has been little research on the physical properties of these materials related to the adsorption and release of various hydrocarbon species found in

  8. TiO2-Supported Binary Metal Oxide Catalysts for Low-temperature Selective Catalytic Reduction of NOx with NH3

    Institute of Scientific and Technical Information of China (English)

    WU Bi-jun; LIU Xiao-qin; XIAO Ping; WANG Shu-gang

    2008-01-01

    Binary metal oxide(MnOx-A/TiO2) catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide(TiO2),where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order:Mn-W/TiO2>Mn-Fe/TiO2>Mn-Cr/TiO2>Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order:Mn-Fe/TiO2>Mn-W/TiO2>Mn-Mo/TiO2>Mn-Cr/TiO2.In the presence of 0.01% SO2 and 6% H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8% and 94.2%,respectively,after 8 h at 120 ℃ at GHSV 12600 h-1.As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared(FTIR) spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.

  9. Catalyst for reduction of nitrogen oxides

    Science.gov (United States)

    Ott, Kevin C.

    2010-04-06

    A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  10. Catalytic, Conjugate Reduction-Aldol Addition Reaction of β'Oxoal kyl α, β-Unsatu rated Carboxylates%Catalytic, Conjugate Reduction-Aldol Addition Reaction of β'Oxoal kyl α, β-Unsatu rated Carboxylates

    Institute of Scientific and Technical Information of China (English)

    郑爱军; 姜岚; 李争宁

    2012-01-01

    Intramolecular conjugate reduction-aldol addition reactions of β'-oxoalkyl a,fl-unsaturated carboxylates were performed in the presence of copper catalysts generated in situ from copper salts, phosphine ligands and silanes. Moderate to good yields and high diastereoselectivities were obtained in 15 min to 3 h using bis[(2-diphenyl- phosphino)phenyl] ether as the ligand.

  11. Branch number matters: Promoting catalytic reduction of 4-nitrophenol over gold nanostars by raising the number of branches and coating with mesoporous SiO2.

    Science.gov (United States)

    Ndokoye, Pancras; Zhao, Qidong; Li, Xinyong; Li, Tingting; Tade, Moses O; Wang, Shaobin

    2016-09-01

    In this study, we demonstrate for the first time that highly branched gold nanostars (AuNSs) and silica-coated AuNSs (AuNSs@mSiO2) could potentially serve as efficient hydrogenation catalysts. The catalytic activity could be promoted by raising the number of tipped-branches of AuNSs, which reveals that the tips play an important role as active sites. The fabricated sharply-pointed AuNSs benefit the electron transfer from BH4 anions to 4-nitrophenol. Coating AuNSs with mesoporous silica (AuNSs@mSiO2) further enhanced the reduction rate and recyclability, and also contributed to reducing the induction period. The AuNSs@mSiO2 (50-100nm in diameter) are large enough to be catalytically inactive, but they consist of sharply-pointed tips with the radius of 2.6-3.6nm, which are rich in coordinately unsaturated sites similar to those of nanoparticles and clusters. Such features in structure and activity would also extend their application range in heterogeneous catalysis. PMID:27235790

  12. Engineered materials as potential geocatalysts in deep geological nuclear waste repositories: A case study of the stainless steel catalytic effect on nitrate reduction by hydrogen

    International Nuclear Information System (INIS)

    Highlights: • We demonstrate that stainless steels (316L and Hastelloy) can catalyse nitrate reduction in the presence of hydrogen. • Hydrogen is the sole electron donor. • The reaction proceeds via nitrate sorption at the steel surface up to pH = 9 following Langmuir–Hinshelwood mechanism. • The reaction is inhibited by the presence of phosphate anions which compete with nitrate for the steel sorption sites. - Abstract: The reduction of NO3- in natural waters is commonly promoted by biological activity. In the context of deep geological nuclear waste repositories with potentially high H2 pressure, abiotic redox reactions may be envisaged. Here, the catalytic effect of “inert” metallic surfaces, in part used for nuclear waste canisters, on NO3- reduction under H2 pressure is evaluated. The study is focused on stainless steels by testing the 316L and Hastelloy C276 steels. A parametric kinetic study (0 < P(H2) < 10 bar, 0.1 < [NO3-] < 10 mM, 90 < T° < 150 °C, 4 < pHin situ < 9) reveals that NO3- reduction, in the presence of stainless steel 316L and Hastelloy C276, proceeds via a pH-independent reaction requiring H2 as an electron donor. No corrosion of these steels is observed indicating a true catalytic process. The reaction is inhibited in the presence of PO43-. Activation energies assuming a first-order reaction in the 90–150 °C temperature range are found to be 46 kJ/mol for stainless steel 316L and 186 kJ/mol for Hastelloy C276, making the reaction efficient at lower temperature and on a human time scale. Nitrate sorption at the metallic surface being thought to be the limiting step, sorption and competitive sorption isotherms of several oxyanions were performed at 90 °C on 316L. Nitrate and PO43- are more strongly sorbed than SO42-, likely as inner sphere complexes, and in a large pH range, from acidic to pH 9. The Langmuir–Hinshelwood formalism best fits the kinetic data. The nature of the surface complex, and the competition for

  13. Design strategies for development of SCR catalyst: improvement of alkali poisoning resistance and novel regeneration method.

    Science.gov (United States)

    Peng, Yue; Li, Junhua; Shi, Wenbo; Xu, Jiayu; Hao, Jiming

    2012-11-20

    Based on the ideas of the additives modification and regeneration method update, two different strategies were designed to deal with the traditional SCR catalyst poisoned by alkali metals. First, ceria doping on the V(2)O(5)-WO(3)/TiO(2) catalyst could promote the SCR performance even reducing the V loading, which resulted in the enhancement of the catalyst's alkali poisoning resistance. Then, a novel method, electrophoresis treatment, was employed to regenerate the alkali poisoned V(2)O(5)-WO(3)/TiO(2) catalyst. This novel technique could dramatically enhance the SCR activities of the alkali poisoned catalysts by removing approximately 95% K or Na ions from the catalyst and showed less hazardous to the environment. Finally, the deactivation mechanisms by the alkali metals were extensively studied by employing both the experimental and DFT theoretical approaches. Alkali atom mainly influences the active site V species rather than W oxides. The decrease of catalyst surface acidity might directly reduce the catalytic activity, while the reducibility of catalysts could be another important factor.

  14. The homogeneous reduction of CO₂ by [Ni(cyclam)]⁺: increased catalytic rates with the addition of a CO scavenger.

    Science.gov (United States)

    Froehlich, Jesse D; Kubiak, Clifford P

    2015-03-18

    The homogeneous electrochemical reduction of CO2 by the molecular catalyst [Ni(cyclam)](2+) is studied by electrochemistry and infrared spectroelectrochemistry. The electrochemical kinetics are probed by varying CO2 substrate and proton concentrations. Products of CO2 reduction are observed in infrared spectra obtained from spectroelectrochemical experiments. The two major species observed are a Ni(I) carbonyl, [Ni(cyclam)(CO)](+), and a Ni(II) coordinated bicarbonate, [Ni(cyclam)(CO2OH)](+). The rate-limiting step during electrocatalysis is determined to be CO loss from the deactivated species, [Ni(cyclam)(CO)](+), to produce the active catalyst, [Ni(cyclam)](+). Another macrocyclic complex, [Ni(TMC)](+), is deployed as a CO scavenger in order to inhibit the deactivation of [Ni(cyclam)](+) by CO. Addition of the CO scavenger is shown to dramatically increase the catalytic current observed for CO2 reduction. Evidence for the [Ni(TMC)](+) acting as a CO scavenger includes the observation of [Ni(TMC)(CO)](+) by IR. Density functional theory (DFT) calculations probing the optimized geometry of the [Ni(cyclam)(CO)](+) species are also presented. PMID:25714353

  15. Effect of Ni+2-substituted Fe2TiO5 on the H2-reduction and CO2 Catalytic Decomposition Reactions at 500℃

    Institute of Scientific and Technical Information of China (English)

    M.H.Khedr

    2006-01-01

    CO2 is a major component of the greenhouse gases, which causes the global warming. To reduce CO2 gas,high activity nanosized Ni+2 substituted Fe2TiO5 samples were synthesized by conventional ceramic method.The effect of the composition of the synthesized ferrite on the H2-reduction and CO2-catalytic decomposition was investigated. Fe2TiO5 (iron titanate) phase that has a nanocrystallite size of ~80 nm is formed as a result of heating Fe2O3 and TiO2 while the addition of NiO leads to the formation of new phases (~80 nm)NiTiO3 and NiFe2O4, but the mixed solid of NiO and Fe2O3 results in the formation of NiFe2O4 only.Samples with Ni+2=0 shows the lowest reduction extent (20%); as the extent of Ni+2 increases, the extent of reduction increases. The increase in the reduction percent is attributed to the presence of NiTiO3 and NiFe2O4 phases, which are more reducible phases than Fe2TiO5. The CO2 decomposition reactions were monitored by thermogravimetric analysis (TGA) experiments. The oxidation of the H2-reduced Ni+2 substituted Fe2TiO5 at 500℃ was investigated. As Ni+2 increases, the rate of reoxidation increases. Samples with the highest reduction extents gave the highest reoxidation extent, which is attributed to the highly porous nature and deficiency in oxygen due to the presence of metallic Fe, Ni and/or FeNi alloy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) of oxidized samples show also the presence of carbon in the sample containing Ni+2>0, which appears in the form of nanotubes (25 nm).

  16. The Cooperative Effect of In2O2 and In/HZSM-5 for Reduction of Nitric Oxide with Methane

    OpenAIRE

    Lili Ren

    2014-01-01

    Compared with In/HZSM-5 catalyst, In/HZSM-5/In2O3 catalyst that contained two different kinds of In induced by the impregnation and the physical mixing method, respectively, has shown remarkable activity for methane selectively catalytic reduction (CH4-SCR) of NOx. The addition of In2O3 to In/HZSM-5 could improve the NO conversion. When a little In2O3 was added to the In/HZSM-5, the active sites of InO+ which can adsorb NO2 were increased. Moreover, at the internal surface of HZSM-5, highly d...

  17. Characterization and activity of alkaline earth metals loaded CeO{sub 2}–MO{sub x} (M = Mn, Fe) mixed oxides in catalytic reduction of NO

    Energy Technology Data Exchange (ETDEWEB)

    Mousavi, Seyed Mahdi [Department of Applied Chemistry and Chemical Engineering, Faculty of Chemistry, University of Tabriz, 5166616471 Tabriz (Iran, Islamic Republic of); Niaei, Aligholi, E-mail: niaei@yahoo.com [Department of Applied Chemistry and Chemical Engineering, Faculty of Chemistry, University of Tabriz, 5166616471 Tabriz (Iran, Islamic Republic of); Illán Gómez, María José [Carbon Materials and Environment Research Group, Department of Inorganic Chemistry, Faculty of Science, Universidad de Alicante, Alicante (Spain); Salari, Dariush; Nakhostin Panahi, Parvaneh [Department of Applied Chemistry and Chemical Engineering, Faculty of Chemistry, University of Tabriz, 5166616471 Tabriz (Iran, Islamic Republic of); Abaladejo-Fuentes, Vicente [Carbon Materials and Environment Research Group, Department of Inorganic Chemistry, Faculty of Science, Universidad de Alicante, Alicante (Spain)

    2014-02-14

    Nanocrystalline CeO{sub 2}–MO{sub x} mixed oxides (M = Mn, Fe) with different M/(M + Ce) molar ratio are prepared by sol–gel combustion method. X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Temperature Programmed Reduction with H{sub 2} (H{sub 2}-TPR) and N{sub 2}-adsorption (BET) analyses are conducted to characterize the physical–chemical properties of the catalysts. The activity of catalysts for reduction of NOx with ammonia has been evaluated. The CeO{sub 2}–MnO{sub x} catalysts showed better low temperature activity than CeO{sub 2}–FeO{sub x}. The superior activity of CeO{sub 2}–MnO{sub x} with Mn/(Mn + Ce) molar ratio of 0.25 respect to other catalysts (with 83% NO conversion and 68% N{sub 2} yield at 200 °C) is associated to nanocrystalline structure, reducibility at low temperature and synergistic effect between Ce and Mn that are observed by XRD, TEM and H{sub 2}-TPR. The CeO{sub 2}–FeO{sub x} catalysts were found to be active at high temperature, being Ce–Fe the best catalyst yielded 82% NO conversion at 300 °C. The effect of alkaline earth metals (Ca, Mg, Sr and Ba) loading on the structure and catalytic activity of cerium mixed oxides are also investigated. Loading of Ba enhanced the NO reduction activity of mixed oxides due to the increase of number of basic sites. Highest performance with 91% NO conversion and 80% N{sub 2} yield attained over CeO{sub 2}–MnO{sub x} (0.25)-Ba (7%) catalyst at 200 °C. - Highlights: • CeO{sub 2}–MO{sub x} mixed oxides (M = Mn, Fe) were synthesized by sol–gel combustion method. • The activity of mixed oxides is evaluated in catalytic reduction of NO with NH{sub 3}. • The CeO{sub 2}–MnO{sub x} showed better activity than CeO{sub 2}–FeO{sub x} due to better redox properties. • Ba loading enhanced the activity due to the increase of number of basic sites. • 91% NO conversion and 80% N{sub 2} yield attained over 7%Ba–Ce{sub 0.75}Mn{sub 0.25}O{sub 2} at 200 °C.

  18. 中温商业SCR催化剂碱和碱土中毒特性研究%Study on alkali and alkaline earths poisoning characteristics for a commercial SCR catalyst

    Institute of Scientific and Technical Information of China (English)

    沈伯雄; 卢凤菊; 高兰君; 岳时吉

    2016-01-01

    The poisoning of a commercial selective catalytic reduction ( SCR ) catalysts by alkali ( K ) and alkaline earths ( Ca) has been simulated in the laboratory. The techniques of N2 adsorption, scanning electronic microscopy, X-ray photoelectron spectroscopy, NH3-temperature program desorption, H2-temperature program reduction were used to identify the changes of physical chemical characteristics of the catalysts before and after the simulated poisoning. The results indicated that the poisoning of K and Ca did not damage the basic pore structure of the SCR catalyst, but decreased the BET surface area and pore volume. The poisoning by K and Ca changed the chemical valence state of V and decreased the reducibility of V. The poisoning by K and Ca decreased the amount of chemically adsorbed oxygen on the catalyst surface as well as acidity of the catalysts. The poisoning by K and Ca lowered the SCR activity of the catalysts and the poisoning by Ca was more serious than K.%在实验室条件下对选择性催化还原( SCR)商业催化剂的碱( K)和碱土( Ca)中毒进行了模拟,并采用液氮吸附、扫描电镜、能谱分析、NH3-程序升温脱附、H2-程序升温还原等方法对催化剂中毒前后的物理化学性质变化进行了表征。结果表明, K和Ca的中毒没有破坏商业中温SCR催化剂孔的基本结构,但K和Ca的中毒使催化剂的比表面积和孔容减小。 K和Ca的中毒在一定程度上改变了催化剂表面钒的价态,导致了钒的还原能力减弱,同时降低催化剂表面化学吸附氧。钾中毒和钙中毒使催化剂的表面酸量降低。钾和钙中毒造成中温SCR催化剂的脱硝活性降低,并且Ca中毒造成的催化剂活性降低要明显高于K中毒。

  19. Estimation of Kinetic Parameters in an Automotive SCR Catalyst Model

    DEFF Research Database (Denmark)

    Åberg, Andreas; Widd, Anders; Abildskov, Jens;

    2016-01-01

    A challenge during the development of models for simulation of the automotive Selective Catalytic Reduction catalyst is the parameter estimation of the kinetic parameters, which can be time consuming and problematic. The parameter estimation is often carried out on small-scale reactor tests, or p...

  20. Tensoring with infinite-dimensional modules in $\\scr O_0$

    OpenAIRE

    Kåhrström, Johan

    2007-01-01

    We show that the principal block $\\scr O_0$ of the BGG category $\\scr O$ for a semisimple Lie algebra $\\germ g$ acts faithfully on itself via exact endofunctors which preserve tilting modules, via right exact endofunctors which preserve projective modules and via left exact endofunctors which preserve injective modules. The origin of all these functors is tensoring with arbitrary (not necessarily finite-dimensional) modules in the category $\\scr O$. We study such functors, describe their adjo...

  1. The J3 SCR model applied to resonant converter simulation

    Science.gov (United States)

    Avant, R. L.; Lee, F. C. Y.

    1985-01-01

    The J3 SCR model is a continuous topology computer model for the SCR. Its circuit analog and parameter estimation procedure are uniformly applicable to popular computer-aided design and analysis programs such as SPICE2 and SCEPTRE. The circuit analog is based on the intrinsic three pn junction structure of the SCR. The parameter estimation procedure requires only manufacturer's specification sheet quantities as a data base.

  2. Oxidation of elemental mercury by modified spent TiO2-based SCR-DeNOx catalysts in simulated coal-fired flue gas.

    Science.gov (United States)

    Zhao, Lingkui; Li, Caiting; Zhang, Xunan; Zeng, Guangming; Zhang, Jie; Xie, Yin'e

    2016-01-01

    In order to reduce the costs, the recycle of spent TiO2-based SCR-DeNOx catalysts were employed as a potential catalytic support material for elemental mercury (Hg(0)) oxidation in simulated coal-fired flue gas. The catalytic mechanism for simultaneous removal of Hg(0) and NO was also investigated. The catalysts were characterized by Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) method. Results indicated that spent TiO2-based SCR-DeNOx catalyst supported Ce-Mn mixed oxides catalyst (CeMn/SCR1) was highly active for Hg(0) oxidation at low temperatures. The Ce1.00Mn/SCR1 performed the best catalytic activities, and approximately 92.80% mercury oxidation efficiency was obtained at 150 °C. The inhibition effect of NH3 on Hg(0) oxidation was confirmed in that NH3 consumed the surface oxygen. Moreover, H2O inhibited Hg(0) oxidation while SO2 had a promotional effect with the aid of O2. The XPS results illustrated that the surface oxygen was responsible for Hg(0) oxidation and NO conversion. Besides, the Hg(0) oxidation and NO conversion were thought to be aided by synergistic effect between the manganese and cerium oxides. PMID:26370819

  3. Oxidation of elemental mercury by modified spent TiO2-based SCR-DeNOx catalysts in simulated coal-fired flue gas.

    Science.gov (United States)

    Zhao, Lingkui; Li, Caiting; Zhang, Xunan; Zeng, Guangming; Zhang, Jie; Xie, Yin'e

    2016-01-01

    In order to reduce the costs, the recycle of spent TiO2-based SCR-DeNOx catalysts were employed as a potential catalytic support material for elemental mercury (Hg(0)) oxidation in simulated coal-fired flue gas. The catalytic mechanism for simultaneous removal of Hg(0) and NO was also investigated. The catalysts were characterized by Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) method. Results indicated that spent TiO2-based SCR-DeNOx catalyst supported Ce-Mn mixed oxides catalyst (CeMn/SCR1) was highly active for Hg(0) oxidation at low temperatures. The Ce1.00Mn/SCR1 performed the best catalytic activities, and approximately 92.80% mercury oxidation efficiency was obtained at 150 °C. The inhibition effect of NH3 on Hg(0) oxidation was confirmed in that NH3 consumed the surface oxygen. Moreover, H2O inhibited Hg(0) oxidation while SO2 had a promotional effect with the aid of O2. The XPS results illustrated that the surface oxygen was responsible for Hg(0) oxidation and NO conversion. Besides, the Hg(0) oxidation and NO conversion were thought to be aided by synergistic effect between the manganese and cerium oxides.

  4. Saraca indica bark extract mediated green synthesis of polyshaped gold nanoparticles and its application in catalytic reduction

    Science.gov (United States)

    Dash, Shib Shankar; Majumdar, Rakhi; Sikder, Arun Kanti; Bag, Braja Gopal; Patra, Biplab Kumar

    2014-04-01

    The bark extract of the traditional ayurvedic medicinal plant Saraca indica containing redox active polyphenolic compounds has been utilized for the one-step synthesis of gold nanoparticles at room temperature. The polyphenolic compounds acted as the reducing agent as well as the stabilizing agent without any additional capping agent. The synthesis of the gold nanoparticles of 15-23 nm size was complete in several minutes and no photo irradiation or heat treatment was necessary. Surface plasmon resonance, HRTEM, AFM, X-ray diffraction, and FTIR studies have been carried out to characterize the nanoparticles. Gold nanoparticles synthesized were of triangular, tetragonal, pentagonal, hexagonal, and spherical shapes. The synthesized gold nanoparticles have been used as a catalyst for the reduction of 4-nitrophenol to 4-aminophenol at room temperature and the kinetics of the reduction reaction has been studied spectrophotometrically.

  5. Catalytic Activity Enhancement for Oxygen Reduction on Epitaxial Perovskite Thin Films for Solid-Oxide Fuel Cells

    KAUST Repository

    la O', Gerardo Jose

    2010-06-22

    Figure Presented The active ingredient: La0.8Sr 0.2CoO3-δ (LSC) epitaxial thin films are prepared on (001 )-oriented yttria-stabilized zirconia (YSZ) single crystals with a gadolinium-doped ceria (GDC) buffer layer (see picture). The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC. The enhanced activity is attributed in part to higher oxygen nonstoichiometry. © 2010 Wiley-VCH Verlag GmbH & Co. KCaA, Weinheim.

  6. Highly Robust Hybrid Photocatalyst for Carbon Dioxide Reduction: Tuning and Optimization of Catalytic Activities of Dye/TiO2/Re(I) Organic-Inorganic Ternary Systems.

    Science.gov (United States)

    Won, Dong-Il; Lee, Jong-Su; Ji, Jung-Min; Jung, Won-Jo; Son, Ho-Jin; Pac, Chyongjin; Kang, Sang Ook

    2015-10-28

    Herein we report a detailed investigation of a highly robust hybrid system (sensitizer/TiO2/catalyst) for the visible-light reduction of CO2 to CO; the system comprises 5'-(4-[bis(4-methoxymethylphenyl)amino]phenyl-2,2'-dithiophen-5-yl)cyanoacrylic acid as the sensitizer and (4,4'-bis(methylphosphonic acid)-2,2'-bipyridine)Re(I)(CO)3Cl as the catalyst, both of which have been anchored on three different types of TiO2 particles (s-TiO2, h-TiO2, d-TiO2). It was found that remarkable enhancements in the CO2 conversion activity of the hybrid photocatalytic system can be achieved by addition of water or such other additives as Li(+), Na(+), and TEOA. The photocatalytic CO2 reduction efficiency was enhanced by approximately 300% upon addition of 3% (v/v) H2O, giving a turnover number of ≥570 for 30 h. A series of Mott-Schottky (MS) analyses on nanoparticle TiO2 films demonstrated that the flat-band potential (V(fb)) of TiO2 in dry DMF is substantially negative but positively shifts to considerable degrees in the presence of water or Li(+), indicating that the enhancement effects of the additives on the catalytic activity should mainly arise from optimal alignment of the TiO2 V(fb) with respect to the excited-state oxidation potential of the sensitizer and the reduction potential of the catalyst in our ternary system. The present results confirm that the TiO2 semiconductor in our heterogeneous hybrid system is an essential component that can effectively work as an electron reservoir and as an electron transporting mediator to play essential roles in the persistent photocatalysis activity of the hybrid system in the selective reduction of CO2 to CO. PMID:26456369

  7. Impact of Biodiesel Impurities on the Performance and Durability of DOC, DPF and SCR Technologies: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Williams, A.; McCormick, R.; Luecke, J.; Brezny, R.; Geisselmann, A.; Voss, K.; Hallstrom, K.; Leustek, M.; Parsons, J.; Abi-Akar, H.

    2011-04-01

    An accelerated durability test method determined the potential impact of biodiesel ash impurities, including engine testing with multiple diesel particulate filter substrate types, as well as diesel oxidation catalyst and selective catalyst reduction catalysts. The results showed no significant degradation in the thermo-mechanical properties of a DPF after exposure to 150,000-mile equivalent biodiesel ash and thermal aging. However, exposure to 435,000-mile equivalent aging resulted in a 69% decrease in thermal shock resistance. A decrease in DOC activity was seen after exposure to 150,000-mile equivalent aging, resulting in higher hydrocarbon slip and a reduction in NO2 formation. The SCR catalyst experienced a slight loss in activity after exposure to 435,000-mile equivalent aging. The SCR catalyst, placed downstream of the DPF and exposed to B20 exhaust suffered a 5% reduction in overall NOx conversion activity over the HDDT test cycle. It is estimated that the additional ash from 150,000 miles of biodiesel use would also result in a moderate increases in exhaust backpressure for a DPF. The results of this study suggest that long-term operation with B20 at the current specification limits for alkali and alkaline earth metal impurities will adversely impact the performance of DOC, DPF and SCR systems.

  8. The deactivation mechanism of Cl on Ce/TiO2 catalyst for selective catalytic reduction of NO with NH3

    Science.gov (United States)

    Yang, Ning-zhi; Guo, Rui-tang; Pan, Wei-guo; Chen, Qi-lin; Wang, Qing-shan; Lu, Chen-zi; Wang, Shu-xian

    2016-08-01

    The poisoning mechanism of Cl on Ce/TiO2 catalyst was investigated based on temperature programmed desorption (TPD) and the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) studies. The results of NH3-TPD and NO-TPD indicated that the addition of Cl on Ce/TiO2 catalyst would inhibit the adsorption of NH3 species and NOx species on it. As can be seen from the results of in situ DRIFT study, the NH3-SCR reaction over Ce/TiO2 and Ce/TiO2-Cl were all followed both the Eley-Rideal mechanism and the Langmuir-Hinshelwood mechanism. And the decreased adsorption ability of NH3 species and NOx species on the surface of Ce/TiO2-Cl should be mainly responsible for its low SCR activity.

  9. The addition of bio-butanol to GHGenius and a review of the GHG emissions from diesel engines with urea SCR

    International Nuclear Information System (INIS)

    The GHGenius model was developed to analyze the emissions of contaminants associated with the use and production of traditional and alternative transportation fuels. Over 140 vehicle and fuel combinations can be used with the model, which is continuously updated with new information on existing processes, new pathways, and new features. This paper provided details of the addition of a butanol production pathway and a urea system for heavy duty diesel engines. Butanol has recently been proposed as a gasoline additive for use with ethanol or as an alternative to ethanol in low-level gasoline blends. A corn to butanol pathway for low level blends was considered as the most appropriate pathway for North American applications. Estimates of energy required were made based on economic assessments and the estimated cost of energy at the time the estimates were made. In the second approach, an ethanol process model was modified to have the same water and feedstock ratios as a butanol feedstock. Total energy balances for the traditional butanol production system were poor due to the large energy requirement in the butanol production process. Low butanol concentrations were attributed to butanol toxicity to fermentation organisms. However, energy credits from co-products were large compared to many other pathways, and were attributed to the energy intensity of hydrogen and acetone. This report also provided details of selective catalytic reduction (SCR) processes that used ammonia or urea with a catalyst to produce water and gaseous nitrogen. Total energy balances and emissions impacts on the full lifecycle of SCR systems for diesel engines were provided. 13 refs., 17 tabs., 8 figs

  10. SCR optimization in Danish coal fired power plants

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, Jimmy [DONG Energy Power, Esbjerg (Denmark); Christensen, Soeren; Hvidberg, Jan [DONG Energy Power, Fredericia (Denmark)

    2010-07-01

    From January 1st 2010 a new Danish tax on NO{sub x} emissions (0.7 Euro/kg NO{sub x}) worked as an incentive for minimizing NO{sub x} emissions from power plants. Previously an emission limit of 200 mg NO{sub x}/Nm{sup 3} had to be kept, which was easily done, since all major Danish coal fired power plants are equipped with high dust SCR systems. With the new NO{sub x} tax a number of initiatives have been taken, in order to maximize the deNO{sub x} capacity of the SCR systems. Screening NO{sub x} measurements after the catalysts layers was performed on all units in order to investigate, if the distribution of ammonia and NO{sub x} before the catalysts is appropriate. If a skewed NOx profile was observed, the ammonia distribution was adjusted, this effort resulted typically in an increase in the NO{sub x} removal degree of 2-5 %. In situ laser based ammonia slip analyzers have been installed on all units. Implementation of these ammonia slip measurements in the SCR control system has helped optimizing the quantity of ammonia added, without exceeding the concentration limits for ammonia in the fly ash. A test campaign has showed a reasonable proportionality between ammonia slip and the quantity of ammonia found in the fly ash. During low load operation of the power plants, the temperature in the catalyst section often becomes so low, that it has been necessary stop ammonia addition, in order to avoid ammonium-bisulphate (ABS) formation. An intensive study of the formation of ABS has led to the implementation of ''an intelligent'' minimum temperature control, which makes it possible to keep ammonia addition enabled during low load operations. All of the above mentioned efforts have led to a significant decrease in NO{sub x} emissions from DONG Energy's coal fired power plants. In 2009 the specific NO{sub x} emission was on average 38 mg/MJ fired whereas the first three months of 2010 show a reduction to 25 mg/MJ fired. (orig.)

  11. Deactivation Mechanisms of Base Metal/Zeolite Urea Selective Catalytic Reduction Materials, and Development of Zeolite-Based Hydrocarbon Adsorber Materials

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Ja Hun; Lee, Jong H.; Kim, Do Heui; Li, Xiaohong S.; Tran, Diana N.; Peden, Charles HF

    2011-12-22

    This annual report describes recent progress on a collaborative project between scientists and engineers in the Institute for Integrated Catalysis at PNNL and at Ford Motor Company, involving investigations of laboratory- and engine-aged SCR catalysts, containing mainly base metal zeolites. These studies are leading to a better understanding of various aging factors that impact the long-term performance of SCR catalysts and improve the correlation between laboratory and engine aging, saving experimental time and cost. We are investigating SCR catalysts with reduced ammonia slip, increased low temperature activity, and increased product selectivity to N2. More recent recognition that high temperature performance, under regimes that sometimes cause deactivation, also needs to be improved is driving current work focused on catalyst materials modifications needed to achieve this enhanced performance. We are also studying materials effective for the temporary storage of HC species during the cold-start period. In particular, we examine the adsorption and desorption of various HC species produced during the combustion with different fuels (e.g., gasoline, E85, diesel) over potential HC adsorber materials, and measure the kinetic parameters to update Ford’s HC adsorption model.

  12. Synthesis of magnetically recyclable MnFe2O4@SiO2@Ag nanocatalyst: Its high catalytic performances for azo dyes and nitro compounds reduction

    Science.gov (United States)

    Kurtan, U.; Amir, Md.; Yıldız, A.; Baykal, A.

    2016-07-01

    In this study, magnetically recycable MnFe2O4@SiO2@Ag nanocatalyst (MnFe2O4@SiO2@Ag MRCs) has been synthesized through co-precipition and chemical reduction method. XRD analysis confirmed the synthesis of single phase nanoproduct with crystallite size of 10 nm. VSM measurements showed the superparamagnetic property of the product. Catalytic studies showed that MnFe2O4@SiO2@Ag MRC could catalyze the reduction of the various azo compounds like methyl orange (MO), methylene blue (MB), eosin Y (EY), and rhodamine B (RhB) and also aromatic nitro compounds such as 4-nitrophenol (4-NP), 4-nitroaniline (4-NA) and 2-nitroaniline (2-NA). Moreover, the magnetic nanocatalyst showed an excellent reusability properties that remained unchanged after several cycles. Therefore, MnFe2O4@SiO2@Ag is the potential candidate for the application of organic pollutants for wastewater treatment.

  13. A Catalytic Path for Electrolyte Reduction in Lithium-Ion Cells Revealed by in Situ Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy

    KAUST Repository

    Shi, Feifei

    2015-03-11

    © 2015 American Chemical Society. Although controlling the interfacial chemistry of electrodes in Li-ion batteries (LIBs) is crucial for maintaining the reversibility, electrolyte decomposition has not been fully understood. In this study, electrolyte decomposition on model electrode surfaces (Au and Sn) was investigated by in situ attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. Simultaneously obtained ATR-FTIR spectra and cyclic voltammetry measurements show that lithium ethylene dicarbonate and lithium propionate form on the Au electrode at 0.6 V, whereas diethyl 2,5-dioxahexane dicarboxylate and lithium propionate form on the Sn electrode surface at 1.25 V. A noncatalytic reduction path on the Au surface and a catalytic reduction path on the Sn surface are introduced to explain the surface dependence of the overpotential and product selectivity. This represents a new concept for explaining electrolyte reactions on the anode of LIBs. The present investigation shows that catalysis plays a dominant role in the electrolyte decomposition process and has important implications in electrode surface modification and electrolyte recipe selection, which are critical factors for enhancing the efficiency, durability, and reliability of LIBs.

  14. Structural insights into omega-class glutathione transferases: a snapshot of enzyme reduction and identification of a non-catalytic ligandin site.

    Directory of Open Access Journals (Sweden)

    Joseph Brock

    Full Text Available Glutathione transferases (GSTs are dimeric enzymes containing one active-site per monomer. The omega-class GSTs (hGSTO1-1 and hGSTO2-2 in humans are homodimeric and carry out a range of reactions including the glutathione-dependant reduction of a range of compounds and the reduction of S-(phenacylglutathiones to acetophenones. Both types of reaction result in the formation of a mixed-disulfide of the enzyme with glutathione through the catalytic cysteine (C32. Recycling of the enzyme utilizes a second glutathione molecule and results in oxidized glutathione (GSSG release. The crystal structure of an active-site mutant (C32A of the hGSTO1-1 isozyme in complex with GSSG provides a snapshot of the enzyme in the process of regeneration. GSSG occupies both the G (GSH-binding and H (hydrophobic-binding sites and causes re-arrangement of some H-site residues. In the same structure we demonstrate the existence of a novel "ligandin" binding site deep within in the dimer interface of this enzyme, containing S-(4-nitrophenacylglutathione, an isozyme-specific substrate for hGSTO1-1. The ligandin site, conserved in Omega class GSTs from a range of species, is hydrophobic in nature and may represent the binding location for tocopherol esters that are uncompetitive hGSTO1-1 inhibitors.

  15. Reduction of CO2 to low carbon alcohols on CuO FCs/Fe2O3 NTs catalyst with photoelectric dual catalytic interfaces.

    Science.gov (United States)

    Li, Peiqiang; Wang, Huying; Xu, Jinfeng; Jing, Hua; Zhang, Jun; Han, Haixiang; Lu, Fusui

    2013-12-01

    In this paper, the CuO FCs/Fe2O3 NTs catalyst was obtained after Fe2O3 nanotubes (Fe2O3 NTs) were decorated with CuO flower clusters (CuO FCs) by the pulse electrochemical deposition method. The in situ vertically aligned Fe2O3 NTs were prepared on the ferrous substrate by a potentiostatic anodization method. The SEM result showed the volcano-like Fe2O3 NTs were arranged in order and the CuO FCs constituted of flaky CuO distributed on the Fe2O3 NTs surface uniformly. After CuO FCs were loaded on Fe2O3 NTs, the absorption of visible light was enhanced noticeably, and its band gap narrowed to 1.78 eV from 2.03 eV. The conduction band and valence band locating at -0.73 eV and 1.05 eV, respectively were further obtained. In the PEC reduction of CO2 process, methanol and ethanol were two major products identified by chromatography. Their contents reached 1.00 mmol L(-1) cm(-2) and 107.38 μmol L(-1) cm(-2) after 6 h, respectively. This high-efficiency catalyst with photoelectric dual catalytic interfaces has a great guidance and reference significance for CO2 reduction to liquid carbon fuels.

  16. Artificial neural networks study of the catalytic reduction of resazurin: stopped-flow injection kinetic-spectrophotometric determination of Cu(II) and Ni(II)

    Energy Technology Data Exchange (ETDEWEB)

    Magni, Diana M. [Departamento de Quimica, Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2829, S3000AOM Santa Fe (Argentina); Olivieri, Alejandro C. [Departamento de Quimica Analitica, Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario (Argentina); Bonivardi, Adrian L. [Departamento de Quimica, Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2829, S3000AOM Santa Fe (Argentina) and Instituto de Desarrollo Tecnologico para la Industria Quimica, Gueemes 3450, S3000GLN Santa Fe (Argentina)]. E-mail: bonivar@fiqus.unl.edu.ar

    2005-01-10

    An artificial neural network (ANN) procedure was used in the development of a catalytic spectrophotometric method for the determination of Cu(II) and Ni(II) employing a stopped-flow injection system. The method is based on the catalytic action of these ions on the reduction of resazurin by sulfide. ANNs trained by back-propagation of errors allowed us to model the systems in a concentration range of 0.5-6 and 1-15 mg l{sup -1} for Cu(II) and Ni(II), respectively, with a low relative error of prediction (REP) for each cation: REP{sub Cu(II)} = 0.85% and REP{sub Ni(II)} = 0.79%. The standard deviations of the repeatability (s{sub r}) and of the within-laboratory reproducibility (s{sub w}) were measured using standard solutions of Cu(II) and Ni(II) equal to 2.75 and 3.5 mg l{sup -1}, respectively: s{sub r}[Cu(II)] = 0.039 mg l{sup -1}, s{sub r}[Ni(II)] = 0.044 mg l{sup -1}, s{sub w}[Ni(II)] = 0.045 mg l{sup -1} and s{sub w}[Ni(II)] = 0.050 mg l{sup -1}. The ANNs-kinetic method has been applied to the determination of Cu(II) and Ni(II) in electroplating solutions and provided satisfactory results as compared with flame atomic absorption spectrophotometry method. The effect of resazurin, NaOH and Na{sub 2}S concentrations and the reaction temperature on the analytical sensitivity is discussed.

  17. Characterization of gamma-Ga2O3-Al2O3 prepared by solvothermal method and its performance for methane-SCR of NO.

    Science.gov (United States)

    Nakatani, Tetsu; Watanabe, Tsunenori; Takahashi, Masaru; Miyahara, Yuya; Deguchi, Hiroshi; Iwamoto, Shinji; Kanai, Hiroyoshi; Inoue, Masashi

    2009-06-25

    The gamma-Ga(2)O(3)-Al(2)O(3) mixed oxides with a spinel structure were prepared by the solvothermal reaction of gallium acetylacetonate and aluminum isopropoxide in diethylenetriamine. In the crystal structures of the catalysts obtained by the calcination of these mixed oxides, Ga(3+) and Al(3+) ions preferentially occupied tetrahedral and octahedral sites, respectively. The catalysts with low Ga contents had a unique structure with high surface areas and a concentration gradient of decreasing Ga content from the surface to the bulk. In methane-selective catalytic reduction (SCR) of NO, higher NO conversion to N(2) was attained on the catalyst with high occupation of Ga(3+) ions at tetrahedral sites and Al(3+) ions at octahedral sites. For the gamma-Ga(2)O(3)-Al(2)O(3) mixed oxide with a charged Ga molar content of 0.3 (ST(0.3)), tetrahedral and octahedral sites were solely occupied by Ga(3+) and Al(3+) ions, respectively, and the catalyst exhibited the highest NO conversion to N(2). Therefore, it was concluded that the active site for methane-SCR of NO is tetrahedral Ga(3+) ion and octahedral Al(3+) ion, which are linked to each other. Nitrogen monoxide is adsorbed on the isolated hydroxyl group attached to Al(3+) ions and then oxidized by O(2) yielding surface nitrate species. Tetrahedral Ga(3+) ions work as Lewis acid sites for the activation of methane because of their coordinative unsaturation. The Ga(3+) ions in the gamma-Ga(2)O(3)-Al(2)O(3) catalyst have a redox property, which plays important roles in both the oxidation of NO to surface nitrate species and the activation of methane. The most important factor for this catalyst is that the sites for the formation of surface nitrate species reside next to the methane activation sites, which facilitates the reaction between surface nitrate species and the activated species derived from methane, thus mitigating the consumption of methane by simple combustion with O(2). Therefore, ST(0.3), which has the largest

  18. Experimental study on a room temperature urea-SCR of NO over activated carbon fibre-supported CeO2-CuO.

    Science.gov (United States)

    Jiang, Xiao; Lu, Pei; Li, Caiting; Zeng, Zheng; Zeng, Guangming; Hu, Luping; Mai, Lei; Li, Zhi

    2013-01-01

    In order to establish a desirable method for NO reduction, selective catalytic reduction (SCR) of NO by urea-CeO2/ACF and urea-CeO2-CuO/ACF was carried out at room temperature. The experimental results showed that 10% urea-9% CeO2/ACF could yield the highest NO conversion of 85% among the series of urea-CeO2/ACF prepared. When urea-CeO2-CuO/ACF was compared with urea-CeO2/ACF, it achieved higher NO conversion to a certain degree with the addition of CuO, which was attributed to the synergistic effect between cerium and copper. The effect of the mass ratio of CeO2 and CuO was also observed. The desirable mass ratio of CeO2 and CuO was 1:1, which yielded about 90% NO conversion when ACF was loaded with 10% urea. Furthermore, the influence of O2 concentration and NO concentration was also observed. In this study, NO conversion increased with increasing O2 concentration. In addition, some samples were further characterized by BET, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared methods.

  19. Synthesis of honeycomb-like palladium nanostructures by using cucurbit[7]uril and their catalytic activities for reduction of 4-nitrophenol

    Energy Technology Data Exchange (ETDEWEB)

    Premkumar, Thathan [Department of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); The University College/Department of Chemistry, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Geckeler, Kurt E., E-mail: keg@gist.ac.kr [Department of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); Department of Nanobio Materials and Electronics (WCU), Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of)

    2014-12-15

    An eco-friendly one-pot method to synthesize self-assembled palladium nanoclusters using a macrocycle, namely cucurbit[7]uril, in the alkaline medium without employing any special reducing or capping agents and/or external energy at room temperature is described. This greener approach, which utilizes water as a benign solvent and biocompatible cucurbit[7]uril as both reducing and protecting agents, can be applied to synthesize other noble metal nanoparticles such as gold, silver, and platinum. Owing to unique structural arrangement of cucurbit[7]uril, it was possible to prepare palladium nanoclusters of honeycomb-like structure irrespective of the reaction conditions. The honeycomb-like palladium nanoclusters were characterized using transmission electron microscopy (TEM), higher-resolution TEM (HR-TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), UV–vis, and FT-IR spectroscopy. Significantly, the synthesized palladium nanoclusters exhibited catalytic activity for the reduction reaction of 4-nitrophenol at room temperature. The approach launched here is easy, green, and user-friendly in contrast to the conventional techniques using polymers or surfactants and harsh reductants. - Highlights: • A simple and one-pot method to synthesis palladium nanostructures with honey-comb like structure. • The strategy established here does not require any harsh and toxic reducing agents. • It has a potential to be a general method for the synthesis of metal nanoparticles in water medium. • Palladium nanoclusters can be used as catalyst for the reduction reaction of 4-nitrophenol. • This system makes a novel platform for industrial and biomedical applications.

  20. Intercalation assembly of Li3VO4 nanoribbons/graphene sandwich-structured composites with enhanced oxygen reduction catalytic performance

    International Nuclear Information System (INIS)

    Novel sandwich-like nanocomposites of alternative stacked ultrathin Li3VO4 nanoribbons and graphene sheets (LVO-G) were successfully developed by a facile intercalation assembly method with a post heating treatment. The characterization results demonstrate that the average size of the Li3VO4 nanoribbons with a non-layered crystal structure is a few micrometers in length, 50–100 nm in width and a few atomic layers in height. The addition of graphene sheets can modify the preferred orientation of the Li3VO4 nanoribbons from (110) to (011) plane and restrict the growth of impurity phase at the same time. In addition, EIS analysis has also verified the reduced resistance and thus the enhance conductivity of LVO-G nanocomposites compared with bare Li3VO4 nanoribbons. What's more, the electrocatalytic performances of these novel LVO-G nanocomposites for oxygen reduction reaction (ORR) in alkaline solution are further investigated by cyclic voltammetry (CV), rotating disk electrode (RDE) and chronoamperometry test. It is found that the enhanced activity and stability of LVO-G can be attributed to the synergistic effect between the Li3VO4 nanoribbons and graphene sheets with a larger reduction current density and a smaller onset potential value for LVO-G25 compared with LVO-G50 due to the change of components. - Highlights: • Novel sandwich-structured LVO-G by a facile intercalation assembly method. • Addition of G sheets can modify the preferred orientation of Li3VO4 nanoribbon. • Enhanced ORR activity and stability due to synergistic effect are demonstrated