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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. 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.

  6. 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.

  7. 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...

  8. 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

  9. 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

  10. 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

  11. 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.

  12. 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

  13. Performance evaluation of a urea-water selective catalytic reduction (SCR) for controlling the exhaust emissions from a diesel engine

    OpenAIRE

    SHAH, Asad Naeem; GE, Yun-Shan; Jiang, Lei; Liu, Zhi-Hua

    2009-01-01

    An integrated performance analysis of a vanadium-based urea-SCR system used for the reduction of exhaust emissions from a diesel engine was carried out. The engine was run on an AC electrical dynamometer in accordance with an 8-mode steady-state cycle. The number-size distribution of particles and carbonyls was analyzed using an electrical low pressure impactor (ELPI) and high performance liquid chromatography (HPLC), respectively. It was found that conversion and/or reduction effic...

  14. 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

  15. 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.

  16. 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.

  17. 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...

  18. 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

  19. 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.

  20. 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.

  1. 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...

  2. Heteropoly acid promoted Cu and Fe catalysts for the selective catalytic reduction of NO with ammonia

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Mossin, Susanne L.; Riisager, Anders; Fehrmann, Rasmus

    2011-01-01

    were studied and compared with the catalytic activity for the selective catalytic reduction (SCR) of NO with ammonia. The SCR activities and acidity values of heteropoly acid promoted catalysts were found to be much higher than unpromoted catalysts. The influence of potassium poisons on the SCR...... activity and acidity was lower for promoted catalysts than for unpromoted catalysts. In the heteropoly acid promoted catalysts the SCR active Cu and Fe metals were protected from potassium poisons by bonding of the potassium to the Brønsted acid centres. Thus heteropoly acid promoted catalysts might be...... suitable for biomass fired power plant SCR applications....

  3. Influence of Selective Catalytic Reduction (SCR system on stainless steel durability Influência do sistema de redução catalítica seletiva na durabilidade de aços inoxidáveis

    Directory of Open Access Journals (Sweden)

    Claudine Miraval

    2013-06-01

    Full Text Available Stainless steel is largely used in the car exhaust market and will be applied now for truck and off-road vehicles. In that field of application, designs are more and more complex with the integration of a catalytic converter and particle filter, consequence of more and more severe diesel depollution regulations. In particular, due to the necessity of reducing NOx emission established by Euro 5 standard (2009, Euro 6 (2014 and American Tier 4 (2014, new equipment were developed for diesel vehicles (truck as well as car. The most promising technology is called Selective Catalytic Reduction (SCR and takes advantage of the reduction feature of ammonia (NH3 on NOx. As NH3 cannot be stored directly within the vehicle for safety reasons (toxicity & flammability of ammonia urea in water solution was selected to initiate the reaction by means of a spraying nozzle. To get a better understanding of the involved hot corrosion mechanisms and afterward to improve material selection, a dedicated laboratory test was developed at Isbergues Research Center. The simulated test consists of spraying urea solution on cyclic heated stainless steel in a range from 200ºC to 600ºC. We evidenced a nitriding mechanism due to the urea decomposition on the surface of stainless steel at high temperature, and also the very different behaviours between austenitic and ferritic grades. The last one, in particular K41X (1.4509-441 and K33X (1.4513-molybdenum stabilized ferritic grades show the best performance in particular when compared to the standard 304 austenitic grade. The paper will review the test set-up, the result obtained and will discuss the stainless steel grade selection for the SCR application.O aço inoxidável é amplamente utilizado no sistema de exaustão de carros de passeio e será aplicado, agora, em caminhões e veículos off-road. Nesse campo de aplicação, os projetos são cada vez mais complexos com a integração de catalisador e filtro de part

  4. 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

  5. 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)

  6. 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...

  7. 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)

  8. 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...

  9. 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....

  10. 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...

  11. 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 ...

  12. 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

  13. 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

  14. 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. ...

  15. 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. 

  16. 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

  17. 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

  18. 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...

  19. Optimizacija SCR sistema

    OpenAIRE

    Berić, Sašo

    2013-01-01

    Računalniška dinamika tekočin predstavlja učinkovito orodje pri iskanju izboljšav na področju izpušnih sistemov kot je SCR (angl.: Selectiv Catalytic Reduction, Selektivna katalitična redukcija) sistem. Omogoča analiziranje tokovnih karakteristik znotraj izpušnega sistema, vpliva geometrije sistema na konverzijo dušikovih oksidov. V predstavljeni nalogi je prikazano iterativno optimiranje SCR sistema s pomočjo računalniške dinamike tekočin. Najprej je bila izvedena numerična analiza obstoj...

  20. 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

  1. Impact of selective catalytic reduction systems on the operation of coal and oil fired boilers and downstream equipment

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    The history of the development of selective catalytic reduction (SCR) technology has clearly demonstrated that whenever the technology arrives in a new region of the world new challenges are met. This paper discusses some of these historical challenges and their particular solutions in some detail. The paper shows that the design of successful SCR systems is extremely site-specific, but that the technology continues to evolve to meet these continuously changing demands. Most recently the increased power of CFD technology has enabled SCR to meet the more stringent North American emissions criteria through optimal fluid dynamic design. 4 figs.

  2. 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.

  3. PILOT-SCALE EVALUATION OF THE IMPACT OF SELECTIVE CATALYTIC REDUCTION FOR NOx ON MERCURY SPECIATION

    Energy Technology Data Exchange (ETDEWEB)

    Dennis L. Laudal; John H. Pavlish; Kevin C. Galbreath; Jeffrey S. Thompson; Gregory F. Weber; Everett Sondreal

    2000-12-01

    Full-scale tests in Europe and bench-scale tests in the United States have indicated that the catalyst, normally vanadium/titanium metal oxide, used in the selective catalytic reduction (SCR) of NO{sub x}, may promote the formation of Hg{sup 2+} and/or particulate-bound mercury (Hg{sub p}). To investigate the impact of SCR on mercury speciation, pilot-scale screening tests were conducted at the Energy & Environmental Research Center. The primary research goal was to determine whether the catalyst or the injection of ammonia in a representative SCR system promotes the conversion of Hg{sup 0} to Hg{sup 2+} and/or Hg{sub p} and, if so, which coal types and parameters (e.g., rank and chemical composition) affect the degree of conversion. Four different coals, three eastern bituminous coals and a Powder River Basin (PRB) subbituminous coal, were tested. Three tests were conducted for each coal: (1) baseline, (2) NH{sub 3} injection, and (3) SCR of NO{sub x}. Speciated mercury, ammonia slip, SO{sub 3}, and chloride measurements were made to determine the effect the SCR reactor had on mercury speciation. It appears that the impact of SCR of NO{sub x} on mercury speciation is coal-dependent. Although there were several confounding factors such as temperature and ammonia concentrations in the flue gas, two of the eastern bituminous coals showed substantial increases in Hg{sub p} at the inlet to the ESP after passing through an SCR reactor. The PRB coal showed little if any change due to the presence of the SCR. Apparently, the effects of the SCR reactor are related to the chloride, sulfur and, possibly, the calcium content of the coal. It is clear that additional work needs to be done at the full-scale level.

  4. 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

  5. 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.

  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. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Superior catalysts for selective catalytic reduction of nitric oxide. Quarterly technical progress report, July 1, 1995--September 30, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Li, W.B.; Yang, R.T.

    1995-12-31

    During the last quarter, we studied selective catalytic reduction (SCR) of NO with ethylene over Cu{sup 2+}-exchanged pillared clay and the important effect of O{sub 2} concentration. Also, the mechanism of the reaction was discussed. Details are presented in this report.

  13. 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

  14. 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...

  15. 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

  16. 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.

  17. 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...

  18. 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...

  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. Promoted selective non-catalytic reduction of nox from combustion effluent

    International Nuclear Information System (INIS)

    In last decade, a significant numbers of NOx reduction technologies have been developed and among these, the post combustion technologies, specifically, Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) technologies are being regarded most effective which are being well accepted and retrofitted to the existing industries. In comparison to SCR, SNCR is easier to retrofit and as it has no need catalytic bed, it is a cost effective method for controlling NOx emission in many industries. Yet, SNCR is limited by narrow temperature window, higher ammonia slip and low utilization of NOx reducing agents, these limitations can be greatly alleviated by promoted SNCR process, where the small amounts of different water dispersible inorganic or organic compounds are added with the NOx reducing agent and introducing the solution into an effluent from the combustion of a carbonaceous fuel under oxygen-rich condition. The SNCR can achieve a maximum of 70% NOx reduction, whilst in promoted SNCR the NOx reduction is reported about 80-90% by most researchers. The detailed mechanism of the SNCR, the additives and the techniques of using different additives are reviewed. A wide range of additives and NOx reducing agents and their simple and cheap techniques of application make the process highly acceptable to the industries

  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...... catalysts. Furthermore, conventional Fe-ZSM-5 catalysts have maximum activity at ~2.5 wt% Fe while for the mesoporous system, optimal NO conversion is obtained for the catalysts with ~6 wt % Fe....

  2. 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...

  3. 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}.

  4. 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}.

  5. Low Temperature Performance of Selective Catalytic Reduction of NO with NH3 under a Concentrated CO2 Atmosphere

    Directory of Open Access Journals (Sweden)

    Xiang Gou

    2015-10-01

    Full Text Available Selective catalytic reduction of NOx with NH3 (NH3-SCR has been widely investigated to reduce NOx emissions from combustion processes, which cause environmental challenges. However, most of the current work on NOx reduction has focused on using feed gas without CO2 or containing small amounts of CO2. In the future, oxy-fuel combustion will play an important role for power generation, and this process generates high concentrations of CO2 in flue gas. Therefore, studies on the SCR process under concentrated CO2 atmosphere conditions are important for future SCR deployment in oxy-fuel combustion processes. In this work, Mn- and Ce-based catalysts using activated carbon as support were used to investigate the effect of CO2 on NO conversion. A N2 atmosphere was used for comparison. Different process conditions such as temperature, SO2 concentration, H2O content in the feed gas and space velocity were studied. Under Mn-Ce/AC conditions, the results suggested that Mn metal could reduce the inhibition effect of CO2 on the NO conversion, while Ce metal increased the inhibition effect of CO2. High space velocity also resulted in a reduction of CO2 inhibition on the NO conversion, although the overall performance of SCR was greatly reduced at high space velocity. Future investigations to design novel Mn-based catalysts are suggested to enhance the SCR performance under concentrated CO2 atmosphere conditions.

  6. 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...

  7. 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。

  8. 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.

  9. 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.

  10. Selective catalytic reduction of NO by ammonia using mesoporous Fe-containing HZSM-5 and HZSM-12 zeolite catalysts: An option for automotive applications

    DEFF Research Database (Denmark)

    Kustov, Arkadii; Hansen, T. W.; Kustova, Marina;

    2007-01-01

    Mesoporous and conventional Fe-containing ZSM-5 and ZSM-12 catalysts (0.5–8 wt% Fe) were prepared using a simple impregnation method and tested in the selective catalytic reduction (SCR) of NO with NH3. It was found that for both Fe/HZSM-5 and Fe/HZSM-12 catalysts with similar Fe contents, the ac...

  11. 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...

  12. 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

  13. 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...

  14. 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

  15. 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

  16. 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.

  17. 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...

  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. 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. PMID:25167537

  20. 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.

  1. 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...

  2. 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

  3. 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)

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

    Directory of Open Access Journals (Sweden)

    Choi Cheolyong

    2015-11-01

    Full Text Available 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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...

  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. 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.)

  12. SELECTIVE CATALYTIC REDUCTION OF DIESEL ENGINE NOX EMISSIONS USING ETHANOL AS A REDUCTANT

    Energy Technology Data Exchange (ETDEWEB)

    (1)Kass, M; Thomas, J; Lewis, S; Storey, J; Domingo, N; Graves, R (2) Panov, A

    2003-08-24

    NOx emissions from a heavy-duty diesel engine were reduced by more than 90% and 80% utilizing a full-scale ethanol-SCR system for space velocities of 21000/h and 57000/h respectively. These results were achieved for catalyst temperatures between 360 and 400 C and for C1:NOx ratios of 4-6. The SCR process appears to rapidly convert ethanol to acetaldehyde, which subsequently slipped past the catalyst at appreciable levels at a space velocity of 57000/h. Ammonia and N2O were produced during conversion; the concentrations of each were higher for the low space velocity condition. However, the concentration of N2O did not exceed 10 ppm. In contrast to other catalyst technologies, NOx reduction appeared to be enhanced by initial catalyst aging, with the presumed mechanism being sulfate accumulation within the catalyst. A concept for utilizing ethanol (distilled from an E-diesel fuel) as the SCR reductant was demonstrated.

  13. 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

  14. 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...

  15. 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

  16. 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

  17. 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.

  18. Significant Promotion Effect of Mo Additive on a Novel Ce-Zr Mixed Oxide Catalyst for the Selective Catalytic Reduction of NO(x) with NH3.

    Science.gov (United States)

    Ding, Shipeng; Liu, Fudong; Shi, Xiaoyan; Liu, Kuo; Lian, Zhihua; Xie, Lijuan; He, Hong

    2015-05-13

    A novel Mo-promoted Ce-Zr mixed oxide catalyst prepared by a homogeneous precipitation method was used for the selective catalytic reduction (SCR) of NO(x) with NH3. The optimal catalyst showed high NH3-SCR activity, SO2/H2O durability, and thermal stability under test conditions. The addition of Mo inhibited growth of the CeO2 particle size, improved the redox ability, and increased the amount of surface acidity, especially the Lewis acidity, all of which were favorable for the excellent NH3-SCR performance. It is believed that the catalyst is promising for the removal of NO(x) from diesel engine exhaust. PMID:25894854

  19. 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.

  20. 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

  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. 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...

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

    Energy Technology Data Exchange (ETDEWEB)

    R. Q. LONG; R.T. YANG

    1998-09-30

    Selective catalytic reduction (SCR) of NO{sub x} by hydrocarbons was investigated on Pt doped MCM-41 and copper ion and/or cerium ion-exchanged Al-MCM-41 in the presence of excess oxygen. It was found that Pt/MCM-41 provided the highest specific NO reduction rates as compared with other Pt doped catalysts reported in the literature, such as Pt/Al{sub 2}O{sub 3} and Pt/ZSM-5. For different hydrocarbons, the catalytic activity decreased according to the sequence of C{sub 3}H{sub 6} {approx} C{sub 2}H{sub 4} >> C{sub 3}H{sub 8} > CH{sub 4}. This catalyst was also stable in the presence of H{sub 2}O and SO{sub 2}. Cu exchanged Al-MCM-41 and cerium promoted Cu-Al-MCM-41 (i.e., Ce-Cu-Al-MCM-41) were also found to be active in this reaction. Higher NO{sub x} conversions to N2 were obtained on the Ce-Cu-Al-MCM-41 as compared with Cu-Al-MCM-41. The activity of Ce-Cu-Al-MCM-41 was approximately the same as that of Cu-ZSM-5; but the former had a wider temperature window. TPR results indicated that only isolated Cu{sup 2+} and Cu{sup +} ions were detected in the Cu{sup 2+}-exchanged Al-MCM-41 samples, which may play an important role in the selective catalytic reduction of NO{sub x} to N{sub 2}. After some cerium ions were introduced into Cu-Al-MCM-41, Cu{sup 2+} in the molecular sieve became more easily reducible by H{sub 2}. This may be related to the increase of catalytic activity of NO{sub x} reduction by ethylene.

  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. 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.

  7. 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)

  8. 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

  9. 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...

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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)...

  17. 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.

  18. Effects of calcination temperature on Mn species and catalytic activities of Mn/ZSM-5 catalyst for selective catalytic reduction of NO with ammonia

    International Nuclear Information System (INIS)

    A series of Mn/ZSM-5 catalysts for the selective catalytic reduction of NO with NH3 was prepared by precipitation method at different calcination temperature. X-ray diffraction, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction and N2 adsorption/desorption technologies were conducted to explore the effects of calcination temperature on the physical and chemical properties of Mn/ZSM-5 catalysts. Results suggested that when calcined at lower temperatures (x existed in the form of Mn3O4 and amorphous MnO2 on the catalyst surface. However, when calcined at 600 °C Mn2O3 species which is unfavorable for the SCR process were formed and became the major phase at 700 °C. On the other hand, with the increase of calcination temperatures, the surface Mn concentration and the specific surface area of catalysts both decreased. The catalytic activity test indicated that the Mn/ZSM-5 catalyst calcined at 300 °C demonstrated the best performance for NO removal, with almost 100% NO conversion in the range of 150–390 °C. According to the characterization results, the enrichment of surface Mn, surface Mn3O4 and amorphous MnO2 species may account for its superior catalytic activity.

  19. 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...

  20. 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%.

  1. 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

  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. 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.

  4. 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.

  5. 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...

  6. 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...

  7. 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...

  8. 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....

  9. 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.

  10. The Effect of Acidic and Redox Properties of V2O5/CeO2-ZrO2 Catalysts in Selective Catalytic Reduction of NO by NH3

    DEFF Research Database (Denmark)

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

    2009-01-01

    V2O5 supported ZrO2 and CeO2–ZrO2 catalysts were prepared and characterized by N2 physisorption, XRPD, TPR, and NH3-TPD methods. The influence of calcination temperature from 400 to 600 °C on crystallinity, acidic and redox properties were studied and compared with the catalytic activity in the...... selective catalytic reduction (SCR) of NO with ammonia. The surface area of the catalysts decreased gradually with increasing calcination temperature. The SCR activity of V2O5/ZrO2 catalysts was found to be related with the support crystallinity, whereas V2O5/CeO2–ZrO2 catalysts were also dependent on...... acidic and redox properties of the catalyst. The V2O5/CeO2–ZrO2 catalysts showed high activity and selectivity for reduction of NO with NH3....

  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. 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

  14. 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.

  15. Catalytic reduction of 4-nitrophenol by magnetically recoverable Au nanocatalyst.

    Science.gov (United States)

    Chang, Yang-Chuang; Chen, Dong-Hwang

    2009-06-15

    A novel magnetically recoverable Au nanocatalyst was fabricated by the simple adsorption-reduction of Au(III) ions on chitosan-coated iron oxide magnetic nanocarrier. Au nanoparticles with a mean diameter of 3.14 nm were well loaded on the surface of magnetic nanocarrier because chitosan layer provided an effective driving force in the formation and stabilization of Au nanoparticles. The resultant magnetically recoverable Au nanocatalyst exhibited excellent catalytic activity to the reduction of 4-nitrophenol (4-NP) with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increasing the amount of Au nanocatalyst, decreasing the initial 4-NP concentration, and increasing the temperature. Also, the kinetic data suggested that this catalytic reaction was diffusion controlled owing to the presence of chitosan layer. In addition, catalyst reuse showed no trace of deactivation or poisoning during the catalytic and separation processes, revealing the stable nature and good catalytic ability of this nanocatalyst. PMID:19022566

  16. Development of a chronocoulometric method for uranium traces determination with basis on nitrate catalytic reduction

    International Nuclear Information System (INIS)

    The application of chronocoulometric technique with catalytic reduction of uranium/nitrate with catalytic reduction of uranium/nitrate system is described to give a detection limits on the sub-nanomolar region of uranium. (author)

  17. Copper-impregnated Al-Ce-pillared clay for selective catalytic reduction of NO by C3H6

    International Nuclear Information System (INIS)

    The selective catalytic reduction (SCR) of NO by hydrocarbon is an efficient way to remove NO emission from lean-burn gasoline and diesel exhaust. In this paper, a thermally and hydrothermally stable Al-Ce-pillared clay (Al-Ce-PILC) was synthesized and then modified by SO42-, whose surface area and average pore diameter calcined at 773 K were 161 m2/g and 12.15 nm, respectively. Copper-impregnated Al-Ce-pillared clay catalyst (Cu/SO42-/Al-Ce-PILC) was applied for the SCR of NO by C3H6 in the presence of oxygen. The catalyst 2 wt% Cu/SO42-/Al-Ce-PILC showed good performance over a broad range of temperature, its maximum conversion of NO was 56% at 623 K and remained as high as 22% at 973 K. Furthermore, the presence of 10% water slightly decreased its activity, and this effect was reversible following the removal of water from the feed. Py-IR results showed SO42- modification greatly enhanced the number and strength of Broensted acidity on the surface of Cu/SO42-/Al-Ce-PILC, which played a vital role in the improvement of NO conversion. TPR and XPS results indicated that both Cu+ and isolated Cu2+ species existed on the optimal catalyst, mainly Cu+, as Cu content increased to 5 wt%, another species CuO aggregates which facilitated the combustion of C3H6 were formed. (author)

  18. 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

  19. Low-temperature selective catalytic reduction of NO on CeO2-CuO/Al2O3 catalysts prepared by different methods.

    Science.gov (United States)

    Guo, Rui-Tang; Zhen, Wen-Long; Pan, Wei-Guo; Hong, Jie-Nan; Jin, Qiang; Ding, Cheng-Gang; Guo, Shi-Yi

    2014-08-01

    CeO2-CuO/Al2O3 catalysts were prepared by three different methods and their activities for selective catalytic reduction (SCR) of NO with NH3 were investigated. As can be seen from the experimental results, the catalyst prepared by the single-step sol-gel (SG) method showed the best SCR activity and resistance to SO2 and H2O. In order to investigate the relationship between the preparation method and the performance of SCR catalysts, the catalysts were characterized by using Brunauer-Emmett-Teller, X-ray diffraction, temperature programmed reduction with hydrogen, temperature programmed desorption with ammonia, X-ray photoelectron spectroscopy, Fourier transform infrared and thermo-gravimetric analysis techniques. It was found that the excellent performance of CeO2-CuO/Al2O3 catalyst prepared by the single-step SG method should be resulted from its large surface area, low crystallinity, high oxygen storage capacity, high NH3 adsorption capacity, high concentration of surface chemisorbed oxygen, weak sulphation process and weak water absorption. PMID:24956769

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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 ...

  5. 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...

  6. 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

  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. 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...

  9. Study on the mechanism of NH3-selective catalytic reduction over CuCe x Zr1-x /TiO2

    Science.gov (United States)

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

    2016-03-01

    Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NO x . 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 NH{4/+} (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 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.

  11. 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.

  12. Particulate filters and SCR exhaust treatment technologies for Euro 4 standards; Partikelfilter und SCR Abgasnachbehandlungstechnologien fuer Euro 4-Anforderungen

    Energy Technology Data Exchange (ETDEWEB)

    Frank, W.; Huethwohl, G.; Maurer, B.; Neumann, P. [PUREM Abgassysteme GmbH und Co. KG (Germany)

    2001-07-01

    Due to the EURO 4 and EURO 5 emission standards efficient exhaust aftertreatment systems for commercial vehicles will be necessary. Practicable exhaust aftertreatment systems are particulate traps, SCR catalysts (Selective Catalytic Reduction), and combinations of both systems. As sintered metal allows variable design it possesses the highest potential as trap material. At the moment a low maintenance concept is possible with a sintered metal trap. For SCR systems the gaseous dosing of ammonia as reducing agent into the exhaust gas is an advantage for designing compact combination systems. The direct use of liquid ammonia is presented regarding technical realization, availability, setting up logistics, operating range, operating costs, and registration's ability. (orig.) [German] Die im Rahmen von EURO 4 und EURO 5 festgesetzten Abgasgrenzwerte erfordern den Einsatz einer effizienten Abgasnachbehandlung bei Nutzfahrzeugen. Moegliche Abgasreinigungssysteme sind Partikelfilter, SCR-Katalysatoren (Selective Catalytic Reduction) sowie Kombinationen aus beiden Verfahren. Bei Partikelfiltern wird angesichts der Moeglichkeit einer variablen Stroemungsfuehrung und eines flexiblen Aufbaus dem Sintermetall als Filtermaterial das groesste Potential eingeraeumt. Dabei ist derzeit nur mit dem Sintermetallfilter ein wartungsarmes Konzept zur Aschereinigung darstellbar. Fuer die DCR-Systeme ist die gasfoermige Dosierung von Ammoniak als Reduktionsmittel in den Abgasstrang vorteilhaft, um sehr kompakte Kombinationssysteme aufzubauen. Die direkte Verwendung von Fluessigammoniak wird anhand der technischen Umsetzung, Verfuegbarkeit, Aufbau der Logistik, Reichweite, Betriebskosten sowie Zulassungsfaehigkeit vorgestellt. (orig.)

  13. 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.

  14. Optimal SCR Control Using Data-Driven Models

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, Andrew J.; Sun, Yannan; Lian, Jianming; Devarakonda, Maruthi N.; Parker, Gordon

    2013-04-16

    We present an optimal control solution for the urea injection for a heavy-duty diesel (HDD) selective catalytic reduction (SCR). The approach taken here is useful beyond SCR and could be applied to any system where a control strategy is desired and input-output data is available. For example, the strategy could also be used for the diesel oxidation catalyst (DOC) system. In this paper, we identify and validate a one-step ahead Kalman state-space estimator for downstream NOx using the bench reactor data of an SCR core sample. The test data was acquired using a 2010 Cummins 6.7L ISB production engine with a 2010 Cummins production aftertreatment system. We used a surrogate HDD federal test procedure (FTP), developed at Michigan Technological University (MTU), which simulates the representative transients of the standard FTP cycle, but has less engine speed/load points. The identified state-space model is then used to develop a tunable cost function that simultaneously minimizes NOx emissions and urea usage. The cost function is quadratic and univariate, thus the minimum can be computed analytically. We show the performance of the closed-loop controller in using a reduced-order discrete SCR simulator developed at MTU. Our experiments with the surrogate HDD-FTP data show that the strategy developed in this paper can be used to identify performance bounds for urea dose controllers.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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...

  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. 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

  4. 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...

  5. 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.

  6. 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

  7. 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...

  8. 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...

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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.

  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. 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

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. 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

  5. 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 ...

  6. 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...

  7. 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.

  8. Demonstration of Selective Catalytic Reduction Technology to Control Nitrogen Oxide Emissions From High-Sulfur, Coal-Fired Boilers: A DOE Assessment

    International Nuclear Information System (INIS)

    The goal of the U.S. Department of Energy (DOE) Clean Coal Technology (CCT) program is to furnish the energy marketplace with a number of advanced, more efficient, and environmentally responsible coal utilization technologies through demonstration projects. These projects seek to establish the commercial feasibility of the most promising advanced coal technologies that have developed beyond the proof-of-concept stage. This document serves as a DOE post-project assessment of a project selected in CCT Round 2. The project is described in the report ''Demonstration of Selective Catalytic Reduction (SCR) Technology for the Control of Nitrogen Oxide (NO(sub x)) Emissions from High-Sulfur, Coal-Fired Boilers'' (Southern Company Services 1990). In June 1990, Southern Company Services (Southern) entered into a cooperative agreement to conduct the study. Southern was a cofunder and served as the host at Gulf Power Company's Plant Crist. Other participants and cofunders were EPRI (formerly the Electric Power Research Institute) and Ontario Hydro. DOE provided 40 percent of the total project cost of$23 million. The long-term operation phase of the demonstration was started in July 1993 and was completed in July 1995. This independent evaluation is based primarily on information from Southern's Final Report (Southern Company Services 1996). The SCR process consists of injecting ammonia (NH(sub 3)) into boiler flue gas and passing the 3 flue gas through a catalyst bed where the NO(sub x) and NH(sub 3) react to form nitrogen and water vapor. The objectives of the demonstration project were to investigate: Performance of a wide variety of SCR catalyst compositions, geometries, and manufacturing methods at typical U.S. high-sulfur coal-fired utility operating conditions; Catalyst resistance to poisoning by trace metal species present in U.S. coals but not present, or present at much lower concentrations, in fuels from other countries; and Effects on the balance-of-plant equipment

  9. 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)

  10. 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

  11. 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

  12. 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

  13. 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

  14. ENVIRONMENTAL ASSESSMENT OF A RECIPROCATING ENGINE RETROFITTED WITH NONSELECTIVE CATALYTIC REDUCTION. VOLUME 2. DATA SUPPLEMENT

    Science.gov (United States)

    The two-volume report describes results from testing a rich-burn reciprocating internal combustion engine retrofitted with a nonselective catalytic reduction system for NOx reduction. A comprehensive test program was performed to characterize catalyst inlet and outlet organic and...

  15. ENVIRONMENTAL ASSESSMENT OF A RECIPROCATING ENGINE RETROFITTED WITH NONSELECTIVE CATALYTIC REDUCTION. VOLUME 1. TECHNICAL RESULTS

    Science.gov (United States)

    The two-volume report describes results from testing a rich-burn reciprocating internal combustion engine retrofitted with a nonselective catalytic reduction system for NOx reduction. A comprehensive test program was performed to characterize catalyst inlet and outlet organic and...

  16. Numerical Study on Selective Catalytic Reduction System to Determine DeNOx Efficiency in Diesel Engine

    Directory of Open Access Journals (Sweden)

    Manoj Kumar A.P

    2012-06-01

    Full Text Available Environmental Pollution is the major problem in the world, and the main cause for this is Vehicle Exhaust Gases. NOx is the major pollutant coming out from vehicles, which need to be controlled in order to meet stringent limits on emission standards (EuroV .Several researchers had carried out experiments using different aftertreatment devices in order to achieve maximum DeNOx conversion. Results showed that Urea-SCR system is a promising approach to achieve substantial NOx reduction performance. The Present study focuses on one dimensional (1D steady state kinetic simulation of SCR using CFD code AVL BOOST. The relevant reactions and boundary conditions are considered for a simulation in a square celled catalyst. The conversion of NOx and NH3 are obtained from the simulation. The results are validated through AVL code FIRE which considers the three dimensional flow inside the catalyst. Similar boundary conditions and reactions are taken into account as given in BOOST. The results are also validated through experimental results obtained from the literature.

  17. 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%。

  18. 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.

  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. Partitioning of mercury, arsenic, selenium, boron, and chloride in a full-scale coal combustion process equipped with selective catalytic reduction, electrostatic precipitation, and flue gas desulfurization systems

    Energy Technology Data Exchange (ETDEWEB)

    Chin-Min Cheng; Pauline Hack; Paul Chu; Yung-Nan Chang; Ting-Yu Lin; Chih-Sheng Ko; Po-Han Chiang; Cheng-Chun He; Yuan-Min Lai; Wei-Ping Pan [Western Kentucky University, Bowling Green, KY (United States). Institute for Combustion Science and Environmental Technology

    2009-09-15

    A full-scale field study was carried out at a 795 MWe coal-fired power plant equipped with selective catalytic reduction (SCR), an electrostatic precipitator (ESP), and wet flue gas desulfurization (FGD) systems to investigate the distribution of selected trace elements (i.e., mercury, arsenic, selenium, boron, and chloride) from coal, FGD reagent slurry, makeup water to flue gas, solid byproduct, and wastewater streams. Flue gases were collected from the SCR outlet, ESP inlet, FGD inlet, and stack. Concurrent with flue gas sampling, coal, bottom ash, economizer ash, and samples from the FGD process were also collected for elemental analysis. By combining plant operation parameters, the overall material balances of selected elements were established. The removal efficiencies of As, Se, Hg, and B by the ESP unit were 88, 56, 17, and 8%, respectively. Only about 2.5% of Cl was condensed and removed from flue gas by fly ash. The FGD process removed over 90% of Cl, 77% of B, 76% of Hg, 30% of Se, and 5% of As. About 90% and 99% of the FGD-removed Hg and Se were associated with gypsum. For B and Cl, over 99% were discharged from the coal combustion process with the wastewater. Mineral trona (trisodium hydrogendicarbonate dehydrate, Na{sub 3}H(CO{sub 3}){sub 2}.2H{sub 2}O) was injected before the ESP unit to control the emission of sulfur trioxide (SO{sub 3}). By comparing the trace elements compositions in the fly ash samples collected from the locations before and after the trona injection, the injection of trona did not show an observable effect on the partitioning behaviors of selenium and arsenic, but it significantly increased the adsorption of mercury onto fly ash. The stack emissions of mercury, boron, selenium, and chloride were for the most part in the gas phase. 47 refs., 3 figs., 11 tabs.

  1. 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. PMID:27474851

  2. 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.

  3. 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.

  4. Catalytic Leuckart-Wallach-type reductive amination of ketones.

    Science.gov (United States)

    Kitamura, Masato; Lee, Donghyun; Hayashi, Shinnosuke; Tanaka, Shinji; Yoshimura, Masahiro

    2002-11-29

    A CpRh(III) complex catalyzes reductive amination of ketones using HCOONH(4) at 50-70 degrees C to give the corresponding primary amines in high yields. The reaction is clean and operationally simple and proceeds at a lower temperature and with higher chemoselectivity than the original Leuckart-Wallach reaction. The new method has been applied to the synthesis of alpha-amino acids directly from alpha-keto acids. PMID:12444661

  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. Carbon based catalytic briquettes for the reduction of NO. Catalyst scale-up

    International Nuclear Information System (INIS)

    Exhaust gases from small and medium stationary sources contain NOx that will be regulated by new European legislation in the coming years. Among all the processes the SCR-NH3 seems to be the more promising one. However, the application of commercial catalysts to these new facilities presents some drawbacks such as the high and narrow operation temperature, its low withdraw to SO2 or its high cost production. In order to improve this technology, in previous works, carbon-supported catalytic briquettes have shown a good kinetic performance under the above commented conditions. In this study, other aspects such as thermal stability, long-term performance, spatial velocity influence and mechanical resistance were evaluated. Finally, a simple economic assessment was carried out providing a three times lower cost production than commercial catalysts. From all the data collected, there are some evidences that these catalyst briquettes will have a good performance in small and medium facilities, being an interesting alternative to commercial ones. (author)

  7. Azeotropic distillation assisted fabrication of silver nanocages and their catalytic property for reduction of 4-nitrophenol.

    Science.gov (United States)

    Min, Jianzhong; Wang, Fei; Cai, Yunliang; Liang, Shuai; Zhang, Zhenwei; Jiang, Xingmao

    2015-01-14

    Monodisperse silver nanocages (AgNCs) with specific interiors were successfully synthesized by an azeotropic distillation (AD) assisted method and exhibited excellent catalytic activities for reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) due to the unique hollow morphology and small thickness of the silver shell. PMID:25421649

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

    Science.gov (United States)

    Wu, Xiao-Qiong; Wu, Xing-Wen; Huang, Qing; Shen, Jiang-Shan; Zhang, Hong-Wu

    2015-03-01

    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-AuIII 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 (NaBH4). Experimental conditions of synthesizing Au nanoparticles, including pH, concentration of AuIII, 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 NaBH4 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 of this catalytic system.

  9. ENVIRONMENTAL ASSESSMENT OF A RECIPROCATING ENGINE RETROFITTED WITH SELECTIVE CATALYTIC REDUCTION. VOLUME 2. DATA SUPPLEMENT

    Science.gov (United States)

    The report gives results of comprehensive emission measurements and 15-day continuous emission monitoring for a 1,500 kW (2000 hp) gas-fired, four-stroke turbocharged reciprocating engine equipped with an ammonia-based selective catalytic reduction system for NOx control.

  10. ENVIRONMENTAL ASSESSMENT OF A RECIPROCATING ENGINE RETROFITTED WITH SELECTIVE CATALYTIC REDUCTION. VOLUME 1. TECHNICAL RESULTS

    Science.gov (United States)

    The report gives results of comprehensive emission measurements and 15-day continuous emission monitoring for a 1,500 kW (2000 hp) gas-fired, four-stroke turbocharged reciprocating engine equipped with an ammonia-based selective catalytic reduction system for NOx control.

  11. Preparation of Copper Nanoparticles and Catalytic Properties for the Reduction of Aromatic Nitro Compounds

    International Nuclear Information System (INIS)

    A novel copper nanoparticles were synthesized from cupric sulfate using hydrazine as reducing reagents. A series of aromatic nitro compounds were reacted with sodium borohydride in the presence of the copper nanoparticles catalysts to afford the aromatic amino compounds in high yields. Additionally, the catalysts system can be recycled and maintain a high catalytic effect in the reduction of aromatic nitro compounds

  12. 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.

  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. 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.

  15. 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.

  16. 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...

  17. 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.

  18. 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.

  19. 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...

  20. 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

  1. Two-dimensional structure Au nanosheets are super active for the catalytic reduction of 4-nitrophenol.

    Science.gov (United States)

    Zhang, Yan; Cui, Zhimin; Li, Lidong; Guo, Lin; Yang, Shihe

    2015-06-14

    Two-dimensional structure Au nanosheets with a polygon morphology and controlled thicknesses of ∼15 nm, ∼35 nm, and ∼50 nm were successfully synthesized by a one-step solution reduction method. Scanning and transmission electron microscopy (SEM and TEM), selected area electron diffraction (SEAD) analyses, and X-ray diffraction (XRD) were used to thoroughly study the structure and the formation mechanism of the nanosheets. The catalytic activity of the Au nanosheets was investigated for the reduction of 4-nitrophenol (4-NP) by UV-visible absorption spectroscopy. Against all expectation, the Au nanosheets with such a big lateral (more than 1 μm) size exhibited superior catalytic activity on the selective reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4. On the other hand, the catalytic activity does closely depend on the thickness of the nanosheets; that is, it decreases with increasing thickness. The reaction can be completed in less than 1 min when catalyzed by Au nanosheets about 15 nm thick. The 100% conversion efficiency was further demonstrated after two catalytic cycles with the thinnest Au nanosheets. PMID:25971868

  2. 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.

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

    International Nuclear Information System (INIS)

    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-AuIII 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 (NaBH4). Experimental conditions of synthesizing Au nanoparticles, including pH, concentration of AuIII, 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 NaBH4 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 of this catalytic system

  4. 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

  5. Energy efficient NO{sub x} reduction due to modern fuel technology; Energieeffiziente NO{sub x}-Minderung dank moderner Feuerungstechnik

    Energy Technology Data Exchange (ETDEWEB)

    Gohlke, Oliver; Schmidt, Wolfgang [Martin GmbH fuer Umwelt- und Energietechnik, Muenchen (Germany); Baj, Peter; Papa, Georg [ZAW Coburg (Germany)

    2012-07-15

    The increasing claims for the protection of the environment cause an increase of the requirements on the emissions of pollutants. This is equal to a significant reduction of the limiting values of the emission. Further components are necessary for the purification of exhaust gases. In combination with the SNCR system (SNCR = selective non-catalytic reduction) the Martin VLN procedure reduces the emission of nitrogen oxide at waste incinerators also without SCR catalysts (SCR = selective catalytic reduction) beneath a value of 100 milligram per standard cubic meter (mg/Nm{sup 3}). The first commercial European pilot plant was brought on line in Coburg (Federal Republic of Germany) in the autumn of 2011.

  6. 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)

  7. 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.

  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.

    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. PMID:25217745

  9. 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...

  10. 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.

  11. 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.)

  12. 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.

  13. 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...

  14. First results of the urea injection SCR DeNO{sub x} system on Euro 5 buses; Premiers resultats de systeme DeNO{sub x} SCR par injection d'uree sur BUS Euro 5

    Energy Technology Data Exchange (ETDEWEB)

    Plassat, G.

    2005-07-15

    In the framework of the 'clean buses' French national program, this document presents the results obtained on a diesel Euro 5 Irisbus vehicle fitted with a selective catalytic reduction (SCR) DeNO{sub x} system. The methodology developed by the French agency of environment and energy mastery (Ademe) is used to quantify the efficiency of this technology and its reliability. The first results about the pollutant emissions, and the diesel and urea consumptions are encouraging. The over-cost due to the urea consumption is compensated by the abatement of the diesel consumption due to the use of the SCR technology. This first status in quasi-real conditions is positive and must be confirmed by a test performed over a full year. (J.S.)

  15. 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.

  16. 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 ...

  17. 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

  18. 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

  19. 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-.

  20. 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....

  1. Pillared clays as superior catalysts for selective catalytic reduction of nitric oxide. Second semiannual report, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Yang, R.T.; Li, W.B.; Sirilumpen, M.; Tharapiwattananon, N.

    1997-08-01

    During the first six months of the program, the work has progressed as planned. We have constructed a reactor system and assembled all laboratory essentials for conducting the three-year project. First, the catalytic activities of the Cu(2+) ion exchanged alumina-pillared clay for the selective catalytic reduction of NO by ethylene were measured. The temperature range was 250-500{degrees}C. The activities of this catalyst were substantially higher than the catalyst that has been extensively studied in the literature, Cu-ZSM-5. Fourier Transform Infrared Spectroscopy (FTIR) was used to study the acidity of the catalyst. The second part of the work was an in-depth FTIR study of the NO decomposition mechanism on the catalyst. This was planned as the first and the key step to obtain an understanding of the reaction mechanism. Key surface intermediates were identified from the FTIR spectra, and a redox type Eley-Rideal mechanism was proposed for the NO decomposition on this catalyst. This report will be divided into two parts. In Part One, we report results on the catalytic activities of the Cu-alumina-pillared clay and a direct comparison with other known catalysts. In Part two, we focus on the FTIR study and from the results, we propose a NO decomposition mechanism on this new catalyst. Plans for the next six months include tests of different pillared clays as well as the catalytic mechanism. The micro reactor will continue to be the key equipment for measuring the catalytic activities. FTIR will continue to be the major technique for identifying surface species and hence understanding the reaction mechanism.

  2. 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 ...... interact with potassium stronger than active metal species. Among potential carriers, sulfated zirconia is of high interest because its acidic and textural properties can be modified by varying preparation conditions....

  3. Impact of the spray-wall-interaction-model on the prediction of the ammonia homogenization in automotive SCR systems; Einfluss des Tropfen-Wand-Interaktions-Modells auf die Vorhersage der Ammoniak-Homogenisierung in PKW-SCR-Systemen

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, S.; Smith, H.; Lauer, T.; Geringer, B. [Technische Univ. Wien (Austria). Inst. fuer Fahrzeugantriebe und Automobiltechnik; Pessl, G.; Krenn, C. [BMW Motoren GmbH, Steyr (Austria)

    2012-11-01

    Nitrogen oxide emissions of diesel engine powered vehicles have to be significantly reduced in order to meet future international legislative restrictions. The Selective Catalytic Reduction (SCR) has meanwhile been established as a promising technology to cope with the challenging limits in the sector of mid-sized and large passenger cars. Despite its successful market launch, high optimization potentials remain for the automotive SCR system with respect to the fast preparation of the injected urea-water solution (UWS) and a sufficient ammonia homogenization at the SCR catalyst. In cooperation with BMW Motoren GmbH Steyr, the Institute for Powertrains and Automotive Technology from Vienna University of Technology implemented a CFD-simulation model of the UWS preparation and mixing processes upstream of the SCR-catalyst. A series type passenger car SCR system with a swirl mixing element has been investigated, to analyze the impact of the droplet-wall-interaction and liquid-film formation on the ammonia homogenization for a wide range of exhaust gas conditions. An optimized numerical description of the UWS-droplet-interaction with the hot surfaces of the exhaust system has been established and validated with engine test bed measurements of the ammonia homogenization. A remarkable correlation between a fast formation of ammonia and a high degree of uniformity at the catalyst was proven by the CFD. Especially for high exhaust temperatures an early UWS decomposition was hindered by the Leidenfrost effect, which leads to a high amount of droplets that reach the catalyst and a relatively low level of homogenization. (orig.)

  4. Green synthesis of gold nanoparticles using aspartame and their catalytic activity for p-nitrophenol reduction

    Science.gov (United States)

    Wu, Shufen; Yan, Songjing; Qi, Wei; Huang, Renliang; Cui, Jing; Su, Rongxin; He, Zhimin

    2015-05-01

    We demonstrated a facile and environmental-friendly approach to form gold nanoparticles through the reduction of HAuCl4 by aspartame. The single-crystalline structure was illustrated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared (FTIR) results indicated that aspartame played a pivotal role in the reduction and stabilization of the gold crystals. The crystals were stabilized through the successive hydrogen-bonding network constructed between the water and aspartame molecules. Additionally, gold nanoparticles synthesized through aspartame were shown to have good catalytic activity for the reduction of p-nitrophenol to p-aminophenol in the presence of NaBH4.

  5. 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

  6. 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.

  7. VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging

    OpenAIRE

    Adrian Marberger; Martin Elsener; Davide Ferri; Oliver Kröcher

    2015-01-01

    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 activ...

  8. Glucomannan-mediated facile synthesis of gold nanoparticles for catalytic reduction of 4-nitrophenol

    Science.gov (United States)

    Gao, Zhao; Su, Rongxin; Huang, Renliang; Qi, Wei; He, Zhimin

    2014-08-01

    A facile one-pot approach for synthesis of gold nanoparticles with narrow size distribution and good stability was presented by reducing chloroauric acid with a polysaccharide, konjac glucomannan (KGM) in alkaline solution, which is green and economically viable. Here, KGM served both as reducing agent and stabilizer. The effects of KGM on the formation and stabilization of as-synthesized gold nanoparticles were studied systematically by a combination of UV-visible (UV-vis) absorption spectroscopy, transmission electron microscopy, X-ray diffraction, dynamic light scattering, and Fourier transform infrared spectroscopy. Furthermore, the gold nanoparticles exhibited a notable catalytic activity toward the reduction of 4-nitrophenol to 4-aminophenol.

  9. 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.

  10. Development of a choronocoulometric method for determining traces of uranium using the catalytic nitrate reduction

    International Nuclear Information System (INIS)

    With the aim of improving the sensitivity of the electroanalytical determination of uranium at trace levels. The uranium catalyzed reduction of nitrate on mercury electrode and the technique of chronocoulometry were used. Several experimental parameters were investigated (electrolyte composition, potential program, integration time, blank correction, temperature, previous separation) and adequate conditions were selected for the analytical determination. Under these conditions it was possible to exceed the best reported sensitivity for the catalytic determination, extending the detection limit to 3.10-10M. Exploratory study of the combination of this procedure with pre-concentration of uranium ions on the electrode revealed a detection limit ten limes lower. (author)

  11. 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

  12. 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

  13. 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

  14. 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

  15. [Study on deactivation of Cu/Al-Ce-PILC in the selective catalytic reduction of NO by propylene].

    Science.gov (United States)

    Lin, Qi-Chun; Hao, Ji-Ming; Li, Jun-Hua; Fu, Li-Xin; Lin, Wei-Ming

    2007-03-01

    New pillared clay catalysts were studied for NO removal by hydrocarbon in the presence of oxygen. The purpose of this work is to study the deactivation of Cu/Al-Ce-PILC in the SCR of NO. Montmorillonite was pillared by multi oligomeric hydroxyl cation to synthesize Al-Ce-PILC and treated by (NH4) 2SO4, then it was used as catalyst support. Cu/Al-Ce-PILC catalyst was prepared by impregnation and applied to the SCR of NO by C3 H6. The NO conversion to N2 reached its maximum of 56% at 350 degrees C and decreased to 22% at 700 degrees C. To study the deactivation of Cu/Al-Ce-PILC in the SCR of NO at high temperature, the fresh and post-reaction catalysts were characterized by XPS, TPR, TGA, Py-IR and DSC. The results showed that only Cu+ species existed on the fresh catalyst pretreated in hydrogen, while another species CuO was detected on the post-reaction catalyst. The loss of structural hydroxyl and SO4(2-) on Al-Ce-PILC weakened the surface acidity of the catalyst at high reaction temperature. Furthermore, the coke deposition on the catalyst covered part of the active sites and blocked the pores of the catalyst. The deactivation of Cu/Al-Ce-PILC may be due to the combined effects of CuO formation, the decrease on acidity and the coke deposition, which facilitated propylene combustion and inhibited NO reduction. PMID:17633621

  16. 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.

  17. In situ generation of silver nanoparticles within crosslinked 3D guar gum networks for catalytic reduction.

    Science.gov (United States)

    Zheng, Yian; Zhu, Yongfeng; Tian, Guangyan; Wang, Aiqin

    2015-02-01

    The direct use of guar gum (GG) as a green reducing agent for the facile production of highly stable silver nanoparticles (Ag NPs) within this biopolymer and subsequent crosslinking with borax to form crosslinked Ag@GG beads with a 3D-structured network are presented here. These crosslinked Ag@GG beads were characterized using UV-vis absorption spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy, and then tested as a solid-phase heterogenerous catalyst for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of excess borohydride. The results indicate that these crosslinked Ag@GG beads show excellent catalytic performance for the reduction of 4-NP within 20 min and can be readily used for 10 successive cycles. PMID:25445685

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. 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

  3. 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

  4. 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 ...

  5. 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

  6. 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.

  7. Catalytic Tar Reduction for Assistance in Thermal Conversion of Space Waste for Energy Production

    Science.gov (United States)

    Caraccio, Anne Joan; Devor, Robert William; Hintze, Paul E.; Muscatello, Anthony C.; Nur, Mononita

    2014-01-01

    The Trash to Gas (TtG) project investigates technologies for converting waste generated during spaceflight into various resources. One of these technologies was gasification, which employed a downdraft reactor designed and manufactured at NASA's Kennedy Space Center (KSC) for the conversion of simulated space trash to carbon dioxide. The carbon dioxide would then be converted to methane for propulsion and water for life support systems. A minor byproduct of gasification includes large hydrocarbons, also known as tars. Tars are unwanted byproducts that add contamination to the product stream, clog the reactor and cause complications in analysis instrumentation. The objective of this research was to perform reduction studies of a mock tar using select catalysts and choose the most effective for primary treatment within the KSC downdraft gasification reactor. Because the KSC reactor is operated at temperatures below typical gasification reactors, this study evaluates catalyst performance below recommended catalytic operating temperatures. The tar reduction experimentation was observed by passing a model tar vapor stream over the catalysts at similar conditions to that of the KSC reactor. Reduction in tar was determined using gas chromatography. Tar reduction efficiency and catalyst performances were evaluated at different temperatures.

  8. 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

  9. 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)

  10. Influence of the addition of transition metals (Cr, Zr, Mo) on the properties of MnOx-FeOx catalysts for low-temperature selective catalytic reduction of NOx by Ammonia.

    Science.gov (United States)

    Zhou, Changcheng; Zhang, Yaping; Wang, Xiaolei; Xu, Haitao; Sun, Keqin; Shen, Kai

    2013-02-15

    The co-precipitation and citric acid methods were employed to prepare MnO(x)-FeO(x) catalysts for the low-temperature selective catalytic reduction (SCR) of NO(x) by ammonia. It was found that the Mn-Fe (CP) sample obtained from the co-precipitation method, which exhibited low crystalline of manganese oxides on the surface, high specific surface area and abundant acid sites at the surface, had better catalytic activity. The effects of doping different transition metals (Mo, Zr, Cr) in the Mn-Fe (CP) catalysts were further investigated. The study suggested that the addition of Cr can obviously reduce the take-off temperature of Mn-Fe catalyst to 90°C, while the impregnation of Zr and Mo raised that remarkably. The texture and micro-structure analysis revealed that for the Cr-doped Mn-Fe catalysts, the active components had better dispersion with less agglomeration and sintering and the largest BET surface specific area. In situ FTIR study indicated that the addition of Cr can increase significantly the surface acidity, especially, the Lewis acid sites, and promote the formation of the intermediate -NH(3)(+). H(2)-TPR results confirmed the better low-temperature redox properties of Mn-Fe-Cr. PMID:23142012

  11. 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...

  12. Facile route to silver submicron-sized particles and their catalytic activity towards 4-nitrophenol reduction

    International Nuclear Information System (INIS)

    Research highlights: → Submicron-sized Ag particles can be prepared by using EDTA as a reducing agent. → By varying the amount of EDTA, the size of Ag particles can be controlled. → By varying the hydrothermal reaction time, the size of Ag particles can be controlled. → In comparison with Ag nanoparticles, the submicron-sized Ag particles have a comparable catalytic activity. - Abstract: A facile, efficient, and environmentally friendly synthetic route was developed to fabricate silver submicron-sized particles by reducing silver nitrate with EDTA in aqueous solution. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) analysis revealed the formation of silver particles, with sizes ranging from 100 to 800 nm. By varying the amount of EDTA utilized in the reaction medium and/or hydrothermal reaction time, the size of prepared silver particles can be readily controlled. Compared with silver nanoparticles, the as-synthesized submicron-sized silver particles were found to show a comparable catalytic activity towards the reduction of 4-nitrophenol to 4-aminophenol in the presence of an excess amount of NaBH4.

  13. Facile route to silver submicron-sized particles and their catalytic activity towards 4-nitrophenol reduction

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Deli [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Xie Jimin, E-mail: Xiejm391@sohu.com [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Chen Min; Li Di; Zhu Jianjun; Qin Huiru [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

    2011-02-03

    Research highlights: > Submicron-sized Ag particles can be prepared by using EDTA as a reducing agent. > By varying the amount of EDTA, the size of Ag particles can be controlled. > By varying the hydrothermal reaction time, the size of Ag particles can be controlled. > In comparison with Ag nanoparticles, the submicron-sized Ag particles have a comparable catalytic activity. - Abstract: A facile, efficient, and environmentally friendly synthetic route was developed to fabricate silver submicron-sized particles by reducing silver nitrate with EDTA in aqueous solution. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) analysis revealed the formation of silver particles, with sizes ranging from 100 to 800 nm. By varying the amount of EDTA utilized in the reaction medium and/or hydrothermal reaction time, the size of prepared silver particles can be readily controlled. Compared with silver nanoparticles, the as-synthesized submicron-sized silver particles were found to show a comparable catalytic activity towards the reduction of 4-nitrophenol to 4-aminophenol in the presence of an excess amount of NaBH{sub 4}.

  14. 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.

  15. 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.

  16. Nanocomposite of montmorillonite and silver nanoparticles: Characterization and application in catalytic reduction of 4-nitrophenol

    Energy Technology Data Exchange (ETDEWEB)

    Praus, Petr, E-mail: petr.praus@vsb.cz [Department of Analytical Chemistry and Material Testing, VŠB-Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava-Poruba (Czech Republic); Turicová, Martina [Department of Analytical Chemistry and Material Testing, VŠB-Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava-Poruba (Czech Republic); Karlíková, Martina; Kvítek, Libor [Department of Physical Chemistry, Palacký University, 17. listopadu 12, 771 46 Olomouc (Czech Republic); Dvorský, Richard [Institute of Physics, VŠB-Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava-Poruba (Czech Republic)

    2013-07-15

    Silver ions previously intercalated into a montmorillonite (MMT) interlayer were reduced by sodium borohydride forming a nanocomposite of MMT and silver nanoparticles (Ag–MMT) with no other stabilizing additives. Within 360 min no coagulation of an aqueous Ag–MMT dispersion was observed. However, after 24 h the coagulation was indicated by a red shift of absorption maximum from 408 nm to 434 nm and by broadening of the absorbance band. The nanocomposite was characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and measurements of specific surface area (SSA). It contained 4.94 wt. % of silver. Ag nanoparticles with an average size of 6.9 nm were located on the external MMT surface, mostly in its pores. Ag–MMT was used as a catalyst for reduction of 4-nitrophenol with sodium borohydride forming 4-aminophenol. After 30 s the reaction kinetics changed from zero order to first order, which was explained by means of the Langmuir–Hinshelwood model. The whole reduction was completed after 290 s. During this time min. 95 wt. % of Ag nanoparticles stayed fixed on the MMT support. - Highlights: • Ag nanoparticles with an average size of 6.9 nm were reduced on montmorillonite. • Ag nanoparticles were fixed in montmorillonite pores forming a stable nanocomposite. • Ag in the nanocomposite showed catalytic activity for reduction of 4-nitrophenol. • Reaction kinetics was explained by the Langmuir–Hinshelwood model.

  17. Nanocomposite of montmorillonite and silver nanoparticles: Characterization and application in catalytic reduction of 4-nitrophenol

    International Nuclear Information System (INIS)

    Silver ions previously intercalated into a montmorillonite (MMT) interlayer were reduced by sodium borohydride forming a nanocomposite of MMT and silver nanoparticles (Ag–MMT) with no other stabilizing additives. Within 360 min no coagulation of an aqueous Ag–MMT dispersion was observed. However, after 24 h the coagulation was indicated by a red shift of absorption maximum from 408 nm to 434 nm and by broadening of the absorbance band. The nanocomposite was characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and measurements of specific surface area (SSA). It contained 4.94 wt. % of silver. Ag nanoparticles with an average size of 6.9 nm were located on the external MMT surface, mostly in its pores. Ag–MMT was used as a catalyst for reduction of 4-nitrophenol with sodium borohydride forming 4-aminophenol. After 30 s the reaction kinetics changed from zero order to first order, which was explained by means of the Langmuir–Hinshelwood model. The whole reduction was completed after 290 s. During this time min. 95 wt. % of Ag nanoparticles stayed fixed on the MMT support. - Highlights: • Ag nanoparticles with an average size of 6.9 nm were reduced on montmorillonite. • Ag nanoparticles were fixed in montmorillonite pores forming a stable nanocomposite. • Ag in the nanocomposite showed catalytic activity for reduction of 4-nitrophenol. • Reaction kinetics was explained by the Langmuir–Hinshelwood model

  18. Effects of a TiC substrate on the catalytic activity of Pt for NO reduction.

    Science.gov (United States)

    Chu, Xingli; Fu, Zhaoming; Li, Shasha; Zhang, Xilin; Yang, Zongxian

    2016-05-11

    Density functional theory calculations are used to elucidate the catalytic properties of a Pt monolayer supported on a TiC(001) substrate (Pt/TiC) toward NO reduction. It is found that the compound system of Pt/TiC has a good stability due to the strong Pt-TiC interaction. The diverse dissociation paths (namely the direct dissociation mechanism and the dimeric mechanism) are investigated. The transition state searching calculations suggest that NO has strong diffusion ability and small activation energy for dissociation on the Pt/TiC. For NO reduction on the Pt/TiC surface, we have found that the direct dissociation mechanisms (NO + N + O → NO2 + N and NO + N + O → N2 + O + O) are easier with a smaller dissociation barrier than those on the Pt(111) surface; and the dimeric process (NO + NO → (NO)2 → N2O + O → N2 + O + O) is considered to be dominant or significant with even a lower energy barrier than that of the direct dissociation. The results show that Pt/TiC can serve as an efficient catalyst for NO reduction. PMID:27117987

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

    OpenAIRE

    Kabljanac, Ž.; Herjavec, I.; Mikoč, K.; Vdović, D.; Ljubičić, M.; Zečević, N.

    2011-01-01

    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 comp...

  20. 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...

  1. 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

  2. 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

  3. A novel green synthesis and characterization of Ag NPs with its ultra-rapid catalytic reduction of methyl green dye

    International Nuclear Information System (INIS)

    Ampicillin derived silver nanoparticles were synthesized in an aqueous medium. Particle size and shape were determined by Transmission electron microscopy which showed the monodispersed morphology. The Fourier transform infrared spectra were represented the interaction of Ampicillin with surface of Ampicillin derived silver nanoparticles. X-ray powder diffraction study gave crystalline nature of the Ampicillin derived silver nanoparticles which exhibited exceptional catalytic activity for the reduction of Methylene Green dye. However, complete reduction of dye was accomplished by Ampicillin derived silver nanoparticles within 4 min only. The catalytic performance of these nanoparticles was adsorbed on glass. They were recovered easily from reaction medium and reused with enhanced catalytic potential. Based upon these results it has been concluded that Ampicillin derived silver nanoparticles are novel, rapid and highly economical alternative for environmental safety against pollution by dyes and extendable for control of other reducible contaminants as well.

  4. 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...

  5. Application of chronocoulomentry for trace levels uranium determination using catalytic nitrate reduction on mercury electrode

    International Nuclear Information System (INIS)

    With the aim of improving the sensitivity of the electro-analytical determination of uranium at trace levels, the uranium catalyzed reduction of nitrate on mercury electrodes was used and the technique of chronocoulometry was compared with other voltammetric techniques. The catalytic process offers high sensitivity in comparison with uranyl reduction in absence of nitrate. The chronocoulometry, virtually unexplored for analytical applications, was found to be specially well suited for determinations based on this kind of electrode process, when using current integration times in the range of several seconds. Under these conditions the interference from diffusion controlled faradaic processes is reduced to a minimum. Several experimental parameters were investigated (eletrolyte composition, potential program, integration time, blank correction, temperature, previous separation) and adequate conditions were selected for the analytical determination of pure and real samples. The proposed method was applied and evaluated with real and, when necessary, an adapted liquid-liquid extraction procedure was used. Reference materials with complex matrices like rocks were first solubilized by hot digestion under pressure. The obtained results are in good agreement with the values obtained with other techniques such as X-ray fluorescence, mass spectrometry-isotope dilution and epithermal netron activation analysis. (author)

  6. 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

  7. 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.

  8. 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.

  9. Electrodeposition of Sb2Se3 on TiO2 nanotube arrays for catalytic reduction of p-nitrophenol

    International Nuclear Information System (INIS)

    TiO2 nanotube arrays decorated with Sb2Se3 particles were successfully fabricated through a simple and efficient electrodeposition strategy, which exhibited excellent catalytic performance for the reduction of p-nitrophenol. The formation of Sb2Se3 was confirmed to follow a co-deposition mechanism. - Highlights: • TiO2 nanotube arrays decorated with Sb2Se3 particles were successfully fabricated by electrodeposition. • The deposition potential plays a major role on the chemical composition and morphologies of Sb2Se3/TNAs. • Sb2Se3/TNAs obtained at −0.7 V exhibited the highest catalytic performance for the reduction of p-nitrophenol to p-aminophenol. • The formation of Sb2Se3 was confirmed to follow a co-deposition mechanism. - Abstract: Titanium dioxide (TiO2) nanotube arrays (TNAs) decorated with antimony selenide (Sb2Se3) particles were successfully fabricated through a simple and efficient electrodeposition strategy, which exhibited excellent catalytic performance for the reduction of p-nitrophenol. The electrodeposition mechanism was investigated by electrochemical methods. The microstructure, chemical composition and morphologies of the Sb2Se3/TNAs prepared at different deposition potentials were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The formation of Sb2Se3 was confirmed to follow a co-deposition mechanism. It was found that Sb2Se3/TNAs with homogeneous morphology could be obtained at −0.7 V, which exhibited the highest catalytic performance for the reduction of p-nitrophenol to p-aminophenol. The conversion rate of p-nitrophenol reached as high as 93.5% within 80 min. Such good catalytic performance could be attributed to the large surface area of TNAs that facilitate electrodeposition of Sb2Se3 and hence improve its catalytic performance

  10. 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.; Gabrielsson, P.; Dahl, S.

    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) or......-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....

  11. 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

  12. 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.

  13. 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% ).

  14. 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.

  15. 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.

  16. Defect-meditated efficient catalytic activity toward p-nitrophenol reduction: A case study of nitrogen doped calcium niobate system

    Energy Technology Data Exchange (ETDEWEB)

    Su, Yiguo; Huang, Shushu; Wang, Tingting; Peng, Liman; Wang, Xiaojing, E-mail: wang_xiao_jing@hotmail.com

    2015-09-15

    Graphical abstract: A series of nitrogen doped Ca{sub 2}Nb{sub 2}O{sub 7} was successfully prepared via ion-exchange method, which was found to be an efficient and green noble-metal-free catalyst toward catalytic reduction of p-nitrophenol. - Highlights: • Nitrogen doped Ca{sub 2}Nb{sub 2}O{sub 7} was found to be an efficient and green noble-metal-free catalyst toward catalytic reduction of p-nitrophenol. • Defective nitrogen and oxygen species were found to play synergetic roles in the reduction of p-nitrophenol. • Nitrogen doped Ca{sub 2}Nb{sub 2}O{sub 7} showed photo-synergistic promotion effects toward p-nitrophenol reduction under UV light irradiation. - Abstract: This work reported on the synthesis of a series of nitrogen doped Ca{sub 2}Nb{sub 2}O{sub 7} with tunable nitrogen content that were found to be efficient and green noble-metal-free catalysts toward catalytic reduction of p-nitrophenol. XPS and ESR results indicated that the introduction of nitrogen in Ca{sub 2}Nb{sub 2}O{sub 7} gave rise to a large number of defective nitrogen and oxygen species. Defective nitrogen and oxygen species were found to play synergetic roles in the reduction of p-nitrophenol. The underlying mechanism is completely different from those reported for metallic nanoparticles. Moreover, the more negative conduction band edge potential enabled nitrogen doped Ca{sub 2}Nb{sub 2}O{sub 7} to show photo-synergistic effects that could accelerate the reduction rate toward p-nitrophenol under UV light irradiation. This work may provide a strategy for tuning the catalytic performance by modulating the chemical composition, electronic structure as well as surface defect chemistry.

  17. Defect-meditated efficient catalytic activity toward p-nitrophenol reduction: A case study of nitrogen doped calcium niobate system

    International Nuclear Information System (INIS)

    Graphical abstract: A series of nitrogen doped Ca2Nb2O7 was successfully prepared via ion-exchange method, which was found to be an efficient and green noble-metal-free catalyst toward catalytic reduction of p-nitrophenol. - Highlights: • Nitrogen doped Ca2Nb2O7 was found to be an efficient and green noble-metal-free catalyst toward catalytic reduction of p-nitrophenol. • Defective nitrogen and oxygen species were found to play synergetic roles in the reduction of p-nitrophenol. • Nitrogen doped Ca2Nb2O7 showed photo-synergistic promotion effects toward p-nitrophenol reduction under UV light irradiation. - Abstract: This work reported on the synthesis of a series of nitrogen doped Ca2Nb2O7 with tunable nitrogen content that were found to be efficient and green noble-metal-free catalysts toward catalytic reduction of p-nitrophenol. XPS and ESR results indicated that the introduction of nitrogen in Ca2Nb2O7 gave rise to a large number of defective nitrogen and oxygen species. Defective nitrogen and oxygen species were found to play synergetic roles in the reduction of p-nitrophenol. The underlying mechanism is completely different from those reported for metallic nanoparticles. Moreover, the more negative conduction band edge potential enabled nitrogen doped Ca2Nb2O7 to show photo-synergistic effects that could accelerate the reduction rate toward p-nitrophenol under UV light irradiation. This work may provide a strategy for tuning the catalytic performance by modulating the chemical composition, electronic structure as well as surface defect chemistry

  18. 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....

  19. 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.

  20. Catalytic Reduction of Noble Metal Salts by Sodium Hypophosphite Promoted by the Film Poly-(p-Allyl Ether Benzenesulfonic Acid).

    Science.gov (United States)

    Costa, M I C F; Steter, J R; Purgato, F L S; Romero, J R

    2011-01-01

    Glassy carbon electrodes were coated with the film poly-(p-allyl ether benzenesulfonic acid) by an anodic procedure. Nickel, platinum, and palladium ions were introduced into the film by ion exchange of H(+) with the corresponding salts. These ions were catalytically reduced to their corresponding metals using the known electroless reducing agent sodium hypophosphite. Scanning electron microcopy and energy dispersive X-ray spectroscopy were carried out to demonstrate the occurrence of the catalytic process. To compare this method with another one carried out in our laboratory, the electrocatalytic reduction of H(+) was studied using the same modified electrodes. A suggested mechanism for the catalysis is proposed. PMID:24052832

  1. 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...

  2. 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...

  3. Catechin-capped gold nanoparticles: green synthesis, characterization, and catalytic activity toward 4-nitrophenol reduction

    Science.gov (United States)

    Choi, Yoonho; Choi, Myung-Jin; Cha, Song-Hyun; Kim, Yeong Shik; Cho, Seonho; Park, Youmie

    2014-03-01

    An eco-friendly approach is described for the green synthesis of gold nanoparticles using catechin as a reducing and capping agent. The reaction occurred at room temperature within 1 h without the use of any external energy and an excellent yield (99%) was obtained, as determined by inductively coupled plasma mass spectrometry. Various shapes of gold nanoparticles with an estimated diameter of 16.6 nm were green-synthesized. Notably, the capping of freshly synthesized gold nanoparticles by catechin was clearly visualized with the aid of microscopic techniques, including high-resolution transmission electron microscopy, atomic force microscopy, and field emission scanning electron microscopy. Strong peaks in the X-ray diffraction pattern of the as-prepared gold nanoparticles confirmed their crystalline nature. The catalytic activity of the as-prepared gold nanoparticles was observed in the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The results suggest that the newly prepared gold nanoparticles have potential uses in catalysis.

  4. 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.

  5. 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

  6. Does Density of Cationic Sites Affect Catalytic Activity of Co Zeolites in Selective Catalytic Reduction of NO with Methane?

    Czech Academy of Sciences Publication Activity Database

    Dědeček, Jiří; Kaucký, Dalibor; Wichterlová, Blanka

    2002-01-01

    Roč. 18, 3/4 (2002), s. 283-290. ISSN 1022-5528 R&D Projects: GA AV ČR IBS4040016 Institutional research plan: CEZ:AV0Z4040901 Keywords : Co zeolites * ZSM-5 * NO reduction Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.648, year: 2002

  7. DEVELOPMENT OF HIGH ACTIVITY, COAL DERIVED, PROMOTED CATALYTIC SYSTEMS FOR NOx REDUCTION AT LOW TEMPERATURES

    Energy Technology Data Exchange (ETDEWEB)

    Joseph M. Calo

    1998-12-31

    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) A MS-TGA (mass spectrometric-thermogravimetric analysis) apparatus, which is one of the primary instruments that will be used in these studies, has been refurbished and modified to meet the requirements of this project. A NO{sub x} chemiluminescence analyzer (ThermoElectron, Model 10) has been added to the instrument to monitor NO{sub x} concentrations in the feed and product streams. Computer control and data acquisition system has been updated and modified to accommodate the requirements of the specific types of experiments planned. The diffusion pumps used to maintain vacuum for the mass spectrometer system have been replaced with turbomolecular pumps (Varian 300 HT). (2) A packed bed reactor/gas flow system has been assembled for performing reactivity studies. This system employs a Kin-Tek gas calibration/mixing system for varying NO and CO concentrations in the feed gas to the packed bed, a NO{sub x} chemiluminescence analyzer (ThermoElectron, Model 10), and a quadrupole mass spectrometer (Dycor). This system is required for steady-state reactivity studies, as well as mechanistic studies on the effects of NO and CO in the gas phase on intermediate oxygen surface complex populations on the carbon substrates. (3) Work has continued on the application of contrast matching, small angle neutron scattering to the characterization and development of char porosity. Contrast matching with perdeuterated toluene has

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction

    Science.gov (United States)

    Chen, Dong; Ye, Feng; Liu, Hui; Yang, Jun

    2016-04-01

    Precisely tailoring the structure and fully making use of the components of nanoparticles are effective to enhance their catalytic performance for a given reaction. We herein demonstrate the design of cage-bell structured Pt-Pd nanoparticles, where a Pd shell is deliberately selected to enhance the catalytic property and methanol tolerance of Pt for oxygen reduction reaction. This strategy starts with the synthesis of core-shell Pt@Ag nanoparticles, followed by galvanic replacement reaction between the Ag shell and Pd2+ ions to form core-shell-shell Pt@Ag@Ag-Pd nanoparticles with a Pt core and double shells composed of Ag at inner and alloy Ag-Pd at outer, respectively. Then, the core-shell-shell templates are agitated with saturated NaCl solution to eliminate the Ag component from the double shells, leading to the formation of bimetallic Pt-Pd nanoparticles with a cage-bell structure, defined as a movable Pt core enclosed by a porous Pd shell, which show enhanced catalytic activity for oxygen reduction compared with that of the Pt seeds due to the additional catalysis from Pd shell. In addition, owing to the different diffusion behavior of methanol and oxygen molecules in the porous Pd shell, the Pt-Pd cage-bell nanostructures also exhibit superior methanol tolerant property in catalyzing the oxygen reduction.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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...

  19. Conversion of chicken feather waste to N-doped carbon nanotubes for the catalytic reduction of 4-nitrophenol.

    Science.gov (United States)

    Gao, Lei; Li, Ran; Sui, Xuelin; Li, Ren; Chen, Changle; Chen, Qianwang

    2014-09-01

    Poultry feather is renewable, inexpensive and abundantly available. It holds great business potentials if poultry feather can be converted into valuable functional materials. Herein, we describe a strategy for the catalytic conversion of chicken feather waste to Ni3S2-carbon coaxial nanofibers (Ni3S2@C) which can be further converted to nitrogen doped carbon nanotubes (N-CNTs). Both Ni3S2@C and N-CNTs exhibit high catalytic activity and good reusability in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 with a first-order rate constant (k) of 0.9 × 10(-3) s(-1) and 2.1 × 10(-3) s(-1), respectively. The catalytic activity of N-CNTs is better than that of N-doped graphene and comparable to commonly used noble metal catalysts. The N content in N-CNTs reaches as high as 6.43%, which is responsible for the excellent catalytic performance. This strategy provides an efficient and low-cost method for the comprehensive utilization of chicken feathers. Moreover, this study provides a new direction for the application of N-CNTs. PMID:25089346

  20. 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)

  1. Electrochemical characterization of praseodymia doped zircon. Catalytic effect on the electrochemical reduction of molecular oxygen in polar organic solvents

    International Nuclear Information System (INIS)

    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 (PrxZr(1-y)Si(1-z)O4; y + z = x; 0.02 xZr(1-y)Si(1-z)O4 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 PrxZr(1-y)Si(1-z)O4 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.

  2. SCR technology for commercial vehicles; SCR-Technologie fuer Nutzfahrzeuge

    Energy Technology Data Exchange (ETDEWEB)

    Frank, W.; Huethwohl, G.; Maurer, B. [Purem Abgassysteme GmbH und Co.KG, Unna (Germany)

    2004-09-01

    All industrial nations make sure that laws and guidelines limit the exhaust gas emissions caused by vehicles. In the face of steadily growing vehicle numbers, this is an effective way of reducing harmful substances emitted by traffic. However, the future Euro 4 and Euro 5 emissions limits represent an enormous challenge for the industry. It is possible, however, to meet the new limits with progressive SCR technology, as shown in this article by Purem GmbH, Unna, Germany. (orig.)

  3. 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

  4. Catalytic reduction of NO{sub x}; Katalytisk reduktion av NO{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Odenbrand, I. [Lund Univ. (Sweden). Dept. of Chemical Engineering

    2001-10-01

    In the project conventional and bio-modified SCR catalysts and the possibilities to regenerate deactivated ones have been studied. The catalysts were deactivated by use in commercial plants in the CFB furnaces at Brista and Vaexjoe and in the PC burner at Drefviken. The methods for regeneration that were applied were: a) washing with water, sulphuric acid or ammonium salts and b) sulphation by sulphur dioxide. The catalysts are deactivated when used by the enrichment of alkali and alkaline earth metals on their surface and in their pores. At bio-fuelled furnaces the accumulation of potassium is the major problem. When these deactivated catalysts are washed with water, potassium and some acidic components (sulphates) are dissolved from both types of catalysts. In addition small amounts of the active component vanadium are dissolved. When sulphuric acid is used an optimal activity after regeneration is obtained at 0.5 M sulphuric acid. At higher concentrations the leached amount of vanadia is too large counteracting the removal of potassium. The same tendency, with an optimum at 0.5 M, was obtained when the washing was performed with ammonium sulphate solutions. It is not possible to regenerate strongly deactivated catalysts by only washing with water. It is necessary to either wash with sulphuric acid/ammonium sulphate solutions or to sulphate with sulphur dioxide after washing with water. The thermal stability of introduced sulphate groups is good at least up to 420 deg C. A catalyst, which has been sulphated and contains large amounts of potassium, is not chemically stable in an SCR environment (in the presence of ammonia, nitric oxide and water) at 400 deg C. At 350 deg C it is stable however. Electron microscopy using X-ray analysis showed that a washing time of 60 minutes was enough to remove all visual deposits from the catalyst surface. The analysis did also show that potassium is distributed homogeneously throughout the monolith material both before and

  5. 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.

  6. 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

  7. 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

  8. Inrush Current Limitation in Wind Generators by SCR Based Soft-starter during grid connection

    OpenAIRE

    Sanjay Mishra

    2013-01-01

    High Inrush current & harmonics is a generic problem wind generators during grid connection.The designed SCR based soft-starter successfully limits the high inrush current during the connection of the wind-turbine system to the grid. The proposed SCR based soft starter using will be simulating in PSCAD on a three-phase induction generator. Expected results will show a significant reduction in high inrush current and smooth connection of the three phase induction generator to the grid with sm...

  9. 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.

  10. 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

  11. Effect of Ce/Zr molar ratio on the performance of Cu–Cex–Zr1−x/TiO2 catalyst for selective catalytic reduction of NOx with NH3 in diesel exhaust

    International Nuclear Information System (INIS)

    Graphical abstract: The Cu–Ce0.25–Zr0.75/TiO2 catalyst exhibited excellent SCR activity at 165–450 °C within the range of exhaust temperatures of diesel engines. - Highlights: • Cu–Cex–Zr1−x/TiO2 catalysts were prepared by a wet impregnation method. • The property for NH3-selective catalytic reduction of NOx were investigated. • The Ce/Zr molar ratio had effects on the performance of Cu–Ce–Zr/TiO2 catalysts. • The Cu–Ce0.25–Zr0.75/TiO2 sample exhibited 100% NOx conversion between 165 °C and 450 °C. • The factors that govern the activity enhancement were extensively investigated. - Abstract: Copper–cerium–zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction of NOx, aiming to study the effects of the Ce/Zr molar ratio on the performance of Cu–Ce–Zr/TiO2 catalysts. The Cu–Ce0.25–Zr0.75/TiO2 sample exhibited nearly 100% NOx conversion over a wide temperature range (165–450 °C), which is strikingly superior to that of Cu/TiO2 (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 (H2-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/TiO2 catalysts

  12. Selective catalytic reduction of nitrogen oxide. Pt. 2. Side flow system for the provision of gaseous ammonia; Selektive katalytische Reduktion von Strickoxiden. T. 2. Nebenstromverfahren zur Bereitstellung gasfoermigen Ammoniaks

    Energy Technology Data Exchange (ETDEWEB)

    Heubuch, Alexander; Wachtmeister, Georg [Technische Univ. Muenchen (Germany). Lehrstuhl fuer Verbrennungskraftmaschinen; Toshev, Plamen [MAN Diesel and Turbo SE, Augsburg (Germany); Sattelmayer, Thomas [Technische Univ. Muenchen (Germany). Lehrstuhl fuer Thermodynamik

    2012-12-01

    The limitation of NO{sub x} emissions from diesel engines has been significantly tightened, among other things by the introduction of Euro 5 and Euro 6. In numerous applications on passenger car diesel engines, SCR catalytic converters were introduced to reduce NO{sub x} emissions in order to comply with the strict standards. Insufficient properties make the use of the required aqueous urea solution more difficult. The first part of this article published in MTZ 11 reported on the findings achieved at the Paul Scherrer Institute on the use of guanidinium formiate (GuFo) and its properties as an alternative to established urea SCR technology. In the second part, the TU Munich presents the application on a diesel engine and the ammonia generator (NH{sub 3} generator) with a bypass system developed for this purpose.

  13. Catalytic reduction of emissions from small scale wood combustion. State of the art

    Energy Technology Data Exchange (ETDEWEB)

    Hargitai, T.; Silversand, F.A. [Katator AB, Lund (Sweden)

    1998-12-31

    Small-scale combustion of big-fuel often results in excessive emissions of volatile organic compounds (VOC), polyaromatic compounds (PAM) and carbon monoxide (CO). These compounds have a negative impact on human health and urban air quality. The predominant volatile organic compounds present in flue gases from big-fuel combustion are propylene, ethylene, butadiene, methanol, ethanol, methane, phenol and benzene. The poor combustion performance of some wood stoves has in certain cases led to legislation against small-scale combustion of big-fuel in urban areas. Catalytic cleaning is one very efficient way of decreasing the environmental impacts of big-fuel combustion. Several studies concerning catalytic purification of flue gases from big-fuel combustion have been presented over the years. Several problems must be addressed when designing a catalyst for this application: Clogging problems from deposition of ashes and particulates in the catalyst; Catalyst poisoning by sulphur, phosphorus, alkali metals etc.; Catalyst fouling due to deposition of ashes and particulates; Catalyst overheating at high flue-gas temperatures and Poor catalyst performance during start-up Most studies have been focused on monolith-type catalysts and- the conversion of CO, VOC and PAH typically is above 80 %. The observed problems are associated with increased pressure drop due to catalyst clogging and decreased catalyst performance due to fouling and poisoning. In most cases precious metals, preferably Pt. have been used as active combustion catalyst. Precious metals have a high activity for the combustion of CO and hydrocarbons and a fair stability against poisoning with compounds present in flue gases from big-fuel, e.g. sulphur and alkali metals. The majority of the studies on precious metals have been focused on Pt. Rh and Pd, which are especially active in catalytic combustion. Some metal oxides are used in catalytic combustion, especially at low temperatures (e.g. in VOC abatement

  14. 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....

  15. 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.

  16. Abroma augusta Linn bark extract-mediated green synthesis of gold nanoparticles and its application in catalytic reduction

    Science.gov (United States)

    Das, Subhajit; Bag, Braja Gopal; Basu, Ranadhir

    2014-11-01

    The bark extract of Abroma augusta Linn is rich in medicinally important phytochemicals including antioxidants and polyphenols. First one step green synthesis of gold nanoparticles (AuNPs) has been described utilizing the bark extract of Abroma augusta L. and chloroauric acid under very mild reaction conditions. The phytochemicals present in the bark extract acted both as a reducing as well as a stabilizing agent, and no additional stabilizing and capping agents were needed. Detailed characterizations of the stabilized AuNPs were carried out by surface plasmon resonance spectroscopy, high resolution transmission electron microscopy, and X-ray diffraction studies. The catalytic activity of the freshly synthesized gold nanoparticles has been demonstrated for the sodium borohydride reduction of 4-nitrophenol to 4-aminophenol, and the kinetics of the reduction reaction have been studied spectrophotometrically.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. Reductant and sequence effects on the morphology and catalytic activity of peptide-capped Au nanoparticles.

    Science.gov (United States)

    Briggs, Beverly D; Li, Yue; Swihart, Mark T; Knecht, Marc R

    2015-04-29

    The use of peptides as capping ligands for materials synthesis has been widely explored. The ambient conditions of bio-inspired syntheses using molecules such as peptides represent an attractive route for controlling the morphology and activity of nanomaterials. Although various reductants can be used in such syntheses, no comprehensive comparison of the same bio-based ligand with different reductants has been reported. In this contribution, peptides AuBP1, AuBP2, and Pd4 are used in the synthesis of Au nanoparticles. The reductant strength is varied by using three different reducing agents: NaBH4, hydrazine, and ascorbic acid. These changes in reductant produce significant morphological differences in the final particles. The weakest reductant, ascorbic acid, yields large, globular nanoparticles with rough surfaces, whereas the strongest reductant, NaBH4, yields small, spherical, smooth nanomaterials. Studies of 4-nitrophenol reduction using the Au nanoparticles as catalysts reveal a decrease in activation energy for the large, globular, rough materials relative to the small, spherical, smooth materials. These studies demonstrate that modifying the reductant is a simple way to control the activity of peptide-capped nanoparticles. PMID:25839335

  2. Preparation of Au Nanoparticles Immobilized Cross-Linked Poly(4-vinylpyridine) Nanofibers and Their Catalytic Application for the Reduction of 4-Nitrophenol.

    Science.gov (United States)

    Qin, Qi-Hu; Na, Hui; Zhang, Chunyu; Yu, Qizhou; Zhang, Xue-Quan; Zhang, He-Xin

    2015-05-01

    Catalytic nanofibers are prepared by the immobilization of Au nanoparticles (AuNPs) onto the surface of cross-linked electrospun poly(4-vinylpyridine) (P4VP) nanofibers. The crosslinking of the P4VP nanofibers by 1,4-diiodobutane via quaternization reaction greatly enhances the stability of the nanofibers against the solvent dissolution, which can then be used as promising platform for the immobilization of catalytic metal nanoparticles. The AuNPs immobilized cross-linked P4VP nanofibers have shown a good catalytic activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). PMID:26505022

  3. 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。

  4. 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.

  5. 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...

  6. 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

  7. Green synthesis of gold nanoparticles using aspartame and their catalytic activity for p-nitrophenol reduction

    OpenAIRE

    Wu, Shufen; Yan, Songjing; Qi, Wei; Huang, Renliang; Cui, Jing; Su, Rongxin; He, Zhimin

    2015-01-01

    We demonstrated a facile and environmental-friendly approach to form gold nanoparticles through the reduction of HAuCl4 by aspartame. The single-crystalline structure was illustrated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared (FTIR) results indicated that aspartame played a pivotal role in the reduction and stabilization of the gold crystals. The crystals were stabilized through the succe...

  8. The effect of the nano-silica support on the catalytic reduction of water by gold, silver and platinum nanoparticles--nanocomposite reactivity.

    Science.gov (United States)

    Zidki, T; Bar-Ziv, R; Green, U; Cohen, H; Meisel, D; Meyerstein, D

    2014-08-01

    Pt°-NPs, prepared by the reduction of Pt(IV) salts with borohydride, do not catalyse the reduction of water in the presence of the strongly-reducing ˙C(CH3)2OH radicals. However, supporting the same metal nanoparticles (M°-NPs) with SiO2 alters the catalytic properties enabling the reaction. This effect depends both on the nature of M° and concentration of the composite nanoparticles. At low nanocomposite concentration: for M = Au nearly no effect is observed; for M = Ag the support decreases the catalytic reduction of water and for M = Pt the support initiates the catalytic process. At high nanocomposite concentration: for M = Au the reactivity is considerably lower and for M = Ag or Pt no catalysis is observed. Furthermore, for M = Ag or Pt H2 reduces the ˙C(CH3)2OH radicals. PMID:24947417

  9. 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

  10. 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%.

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. Testing of Performance of a Scroll Pump in Support of Improved Vapor Phase Catalytic Ammonia Removal (VPCAR) Mass Reduction

    Science.gov (United States)

    Nahra, Henry K.; Kraft, Thomas G.; Yee, Glenda F.; Jankovsky, Amy L.; Flynn, Michael

    2006-01-01

    This paper describes the results of ground testing of a scroll pump with a potential of being a substitute for the current vacuum pump of the Vapor Phase Catalytic Ammonia Reduction (VPCAR). Assessments of the pressure-time, pump-down time, pump power and the pump noise were made for three configurations of the pump the first of which was without the gas ballast, the second with the gas ballast installed but not operating and the third with the gas ballast operating. The tested scroll pump exhibited optimum characteristics given its mass and power requirements. The pump down time required to reach a pressure of 50 Torr ranged from 60 minutes without the ballast to about 120 minutes with the gas ballast operational. The noise emission and the pump power were assessed in this paper as well.

  17. 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. %.

  18. 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

  19. 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)

  20. 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

  1. 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

  2. CATALYTIC REDUCTION OF NITROGEN OXIDES WITH AMMONIA: UTILITY PILOT PLANT OPERATION

    Science.gov (United States)

    The report describes work to demonstrate, on a utility pilot plant scale, the performance, reliability, and practicability of reducing nitrogen oxides (NOx) emissions from steam boilers by reduction of NOx with ammonia over a platinum catalyst. A utility pilot plant treating a sl...

  3. Laboratory investigation of the catalytic reduction technique for measurement of atmospheric NO y

    Science.gov (United States)

    Kliner, Dahv A. V.; Daube, Bruce C.; Burley, Joel D.; Wofsy, Steven C.

    1997-05-01

    We report laboratory studies of the detection scheme employed for in situ measurement of NOy in the atmosphere. In this technique, an air stream is passed over a hot metal (usually 24 karat (k) Au) catalyst in the presence of a reducing agent (usually CO), which converts the NOx compounds to NOx Using the NOy species NO, NO2, HNO3, and isopropyl nitrate and the potential interferences HCN, CH3CN, NH3, and N2O, we investigated: (1) conversion efficiencies as a function of pressure and catalyst temperature; (2) conversion efficiencies as a function of reducing-agent concentration with both H2 and CO; (3) the effect of humidity and O3 on conversion efficiency; (4) loss of NO in the catalyst; and (5) the efficacy and suitability as catalytic converters (or inlets) of several metals (24 k Au, 18k Au, Au with 1% Co, Ag, Pt, stainless steel) and quartz. The most significant results are the discovery of a gas-phase process that contributes to the conversion of HNO3 to NO and the identification of conditions under which HCN, CH3CN, and NH3 are converted to NO with high efficiency. We discuss the implications of these results for in situ measurement of atmospheric NOy.

  4. 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.

  5. 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.

  6. The heterogeneous catalytic reduction of NO and N2O mixture by carbon monoxide

    International Nuclear Information System (INIS)

    Kinetics of the simultaneous reduction N2O and NO by CO on CuCo2O4 has been studied. The reactants are adsorbed onto the coordination-unsaturated cations of the catalyst. The studies showed that the reactions of N2O and CO and of NO and CO occur between the adsorbed reactants on the catalyst surface; the catalyst surface is partially reduced during both these reactions. It was found that NO inhibits the reaction between N2O and CO, because N2O and NO compete for the active surface sites. The adsorption capacity of the catalyst is significantly higher for NO than for N2O and hence NO displaces N2Oads from the surface. The inhibition occurs on strongly localized sites and does not affect on the behaviour of the remaining free sites. At such blockage, the N2O reduction rate decreases in direct proportion to the amount of adsorbed NO

  7. 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.

  8. 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.

  9. AuCu@Pt Nanoalloys for Catalytic Application in Reduction of 4-Nitrophenol

    Directory of Open Access Journals (Sweden)

    Sadia Mehmood

    2016-01-01

    Full Text Available To enhance and optimize nanocatalyst ability for nitrophenol (4-NP reduction reaction we look beyond Au-metal nanoparticles and describe a new class of Au nanoalloys with controlled composition for core of AuCu-metals and Pt-metal shell. The reduction of 4-NP was investigated in aqueous media spectroscopically on 7.8 nm Au nanospheres (AuNSs, 8.3 nm AuCuNSs, and 9.1 nm AuCu@Pt core-shell NSs in diameter. The rate constants of the catalyzed reaction at room temperature, activation energies, and entropies of activation of reactions catalyzed by the AuCu@Pt core-shell NSs are found to have different values to those of the pure metal NSs. The results strongly support the proposal that catalysis by nanoparticles is taking place efficiently on the surface of NSs. These core-shell nanocatalysts exhibited stability throughout the reduction reaction and proved that heterogonous type mechanisms are most likely to be dominant in nanoalloy based catalysis if the surface of the NSs is not defected upon shell incorporation.

  10. Morphology-controllable synthesis of CuO nanostructures and their catalytic activity for the reduction of 4-nitrophenol

    Science.gov (United States)

    Che, Wei; Ni, Yonghong; Zhang, Yuxing; Ma, Yue

    2015-02-01

    The investigation on the correlation between properties and shapes of nanomaterials always draws increased interest. However, the correlation between properties and shapes of CuO nanostructures was rarely reported in the previous works. The shape-controlled preparation of CuO nanostructures was successfully realized in the present work via a simple oil-bath route in air at 170 °;C for 30 min, employing CuCl2•2H2O and NaOH as the reactants. It was found that CuO nanocrystals with leaf-like, dumbbell-like and flowerlike structures were obtained through introducing various additives. At the same time, the correlation between properties and shapes was investigated. It was found that the catalytic performances of the as-prepared CuO nanostructures for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in NaBH4 aqueous solution were dependent on its morphologies. Experiments showed that the first-order rate constants for CuO nanostructures with various shapes were in turn 35.5‧ 10-3 s-1 (leaf-like nanosheets), 4.77‧ 10-3 s-1 (dumbbell-like architectures), 10.6‧ 10-3 s-1 (flowerlike nanostructures). The present research provides a new catalyst selection for the reduction of 4-NP to 4-AP in excess NaBH4 aqueous solution, which has potential application in industrial production.

  11. 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.

  12. Theoretical insights on the catalytic activity and mechanism for oxygen reduction reaction at Fe and P codoped graphene.

    Science.gov (United States)

    He, Feng; Li, Kai; Xie, Guangyou; Wang, Ying; Jiao, Menggai; Tang, Hao; Wu, Zhijian

    2016-05-14

    The non-precious metal graphene catalyst doped with Fe-Px are recently proposed as a promising candidate in substituting Pt for catalyzing oxygen reduction reaction (ORR) in fuel cells. Systematic DFT calculations are performed to investigate the catalytic activity and the ORR mechanism on the Fe-Px (x = 1-4) system in acid medium in this work. Our results indicated that the configuration with one Fe and two P atoms codoped at zigzag edge site (Fe-P2-zig-G) is the most stable, in excellent agreement with the experimental observation that the ratio of Fe and P is nearly 1 : 2. The four-electron reduction mechanism for ORR on the Fe-P2-zig-G is via the competing OOH hydrogenation pathways (to form either OH + OH or O + H2O). The rate determining step is the O2 hydrogenation with an energy barrier of 0.43 eV, much smaller that of calculated 0.80 eV for pure Pt. In addition, the highest energy barrier of the studied ORR mechanism is the O2 dissociation with an energy barrier of 0.70 eV, a value also smaller than that of pure Pt. This demonstrated that the zigzag edge site of the Fe-P2 codoped graphene should be active for the ORR. PMID:27094325

  13. 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.

  14. 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)

  15. Copper nanoparticles supported on permeable monolith with carboxylic acid surface functionality: Stability and catalytic properties under reductive conditions

    International Nuclear Information System (INIS)

    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(II)Br2 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

  16. 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.

  17. Experimental and modeling study of the effect of CH(4) and pulverized coal on selective non-catalytic reduction process.

    Science.gov (United States)

    Zhang, Yanwen; Cai, Ningsheng; Yang, Jingbiao; Xu, Bo

    2008-10-01

    The reduction of nitric oxide using ammonia combined with methane and pulverized coal additives has been studied in a drop tube furnace reactor. Simulated flue gas with 1000 ppm NO(x) and 3.4% excess oxygen was generated by cylinder gas. Experiments were performed in the temperature range of 700-1200 degrees C to investigate the effects of additives on the DeNO(x) performance. Subsequently, a kinetic mechanism was modified and validated based on experimental results, and a computational kinetic modeling with CHEMKIN was conducted to analyze the secondary pollutants. For both methane and pulverized coal additives, the temperature window is shifted towards lower temperatures. The appropriate reaction temperature is shifted to about 900 and 800 degrees C, respectively with 1000 ppm methane and 0.051 g min(-1) pulverized lignite coal. The addition of methane and pulverized coal widens the temperature window towards lower temperature suggesting a low temperature application of the process. Furthermore, selective non-catalytic reduction (SNCR) reaction rate is accelerated evidently with additives and the residence time to complete the reaction is shortened distinctly. NO(x) reduction efficiency with 80% is achieved in about 0.3s without additive at 1000 degrees C. However, it is achieved in only about 0.2s with 100 ppm methane as additive, and only 0.07 and 0.05s are needed respectively for the cases of 500 and 1000 ppm methane. The modified kinetic modeling agrees well with the experimental results and reveals additional information about the process. Investigation on the byproducts where NO(2) and N(2)O were analyzed by modeling and the others were investigated by experimental means indicates that emissions would not increase with methane and pulverized coal additions in SNCR process and the efficacious temperature range of SNCR reaction is widened approximately with 100 degrees C. PMID:18727998

  18. 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

  19. Combined Particle Filter and Selective Catalytic Reduction Catalyst for Diesel Engines

    DEFF Research Database (Denmark)

    Hvam, Jeanette

    oxidation of the silicon carbide crystals, ideal for catalyst adhesive layer. The silicon carbide filter, produced with trace amounts of copper, still fulfills the requirements for macroporosity and accessible porosity in excess of 50%, and is thus superior for the purpose of combined diesel particulate...... 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...... 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...

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. Kinetic spectrophotometric determination of trace copper(II) ions by their catalytic effect on the reduction of brilliant cresyl blue by ascorbic acid

    OpenAIRE

    ULUSOY, Halil İbrahim; GÜRKAN, Ramazan; AKÇAY, Mehmet

    2011-01-01

    In the present study, a novel catalytic-kinetic spectrophotometric method was developed for the determination of trace amounts of copper. It is based on the catalytic effect of Cu(II) on the reduction of brilliant cresyl blue (BCB) by ascorbic acid in pH 5.0 acetate buffer medium. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of BCB at 624 nm. The operating conditions regarding concentration of reagents, pH, time, and temperature were esta...

  5. Selective catalytic reduction system and process for control of NO.sub.x emissions in a sulfur-containing gas stream

    Science.gov (United States)

    Sobolevskiy, Anatoly

    2015-08-11

    An exhaust gas treatment process, apparatus, and system for reducing the concentration of NOx, CO and hydrocarbons in a gas stream, such as an exhaust stream (29), via selective catalytic reduction with ammonia is provided. The process, apparatus and system include a catalytic bed (32) having a reducing only catalyst portion (34) and a downstream reducing-plus-oxidizing portion (36). Each portion (34, 36) includes an amount of tungsten. The reducing-plus-oxidizing catalyst portion (36) advantageously includes a greater amount of tungsten than the reducing catalyst portion (36) to markedly limit ammonia salt formation.

  6. 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. PMID:22169236

  7. Ultrasound-assistant preparation of Cu-SAPO-34 nanocatalyst for selective catalytic reduction of NO by NH3.

    Science.gov (United States)

    Panahi, Parvaneh Nakhostin; Niaei, Ali; Salari, Darush; Mousavi, Seyed Mahdi; Delahay, Gérard

    2015-09-01

    The influence of the various preparation methods of Cu-SAPO-34 nanocatalysts on the selective catalytic reduction of NO with NH3 under excess oxygen was studied. Cu-SAPO-34 nanocatalysts were prepared by using four techniques: conventional impregnation (IM), ultrasound-enhanced impregnation (UIM), conventional deposition precipitation (DP) using NaOH and homogeneous deposition precipitation (HDP) using urea. These catalysts were characterized in detail by various techniques such as N2-sorption, XRD, TEM, H2-TPR, NH3-TPD and XPS to understand the catalyst structure, the nature and the dispersed state of the copper species, and the acid sites for NH3 adsorption. All of the nanocatalysts showed high activities for NO removal. However, the activities were different and followed the sequence of Cu-SAPO-34 (UIM)>Cu-SAPO-34 (HDP)>Cu-SAPO-34 (IM)>Cu-SAPO-34 (DP). Based on the obtained results, it was concluded that the NO conversion on Cu-SAPO-34 nanocatalysts was mainly related to the high reducibility of the isolated Cu(2+) ions and CuO species, the number of the acid sites and the dispersion of CuO species on SAPO-34. PMID:26354702

  8. 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

  9. 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

  10. Evaluating the Catalytic Effects of Carbon Materials on the Photocatalytic Reduction and Oxidation Reactions of TiO2

    International Nuclear Information System (INIS)

    TiO2 composites with seven different carbon materials (activated carbons, graphite, carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene oxides, and reduced graphene oxides) that are virgin or treated with nitric acid are prepared through an evaporation method. The photocatalytic activities of the as-prepared samples are evaluated in terms of H2 production from aqueous methanol solution (photo-catalytic reduction: PCR) and degradation of aqueous pollutants (phenol, methylene blue, and rhodamine B) (photocatalytic oxidation: PCO) under AM 1.5-light irradiation. Despite varying effects depending on the kinds of carbon materials and their surface treatment, composites typically show enhanced PCR activity with maximum 50 times higher H2 production as compared to bare TiO2. Conversely, the carbon-induced synergy effects on PCO activities are insignificant for all three substrates. Colorimetric quantification of hydroxyl radicals supports the absence of carbon effects. However, platinum deposition on the binary composites displays the enhanced effect on both PCR and PCO reactions. These differing effects of carbon materials on PCR and PCO reactions of TiO2 are discussed in terms of physicochemical properties of carbon materials, coupling states of TiO2/carbon composites, interfacial charge transfers. Various surface characterizations of composites (UV-Vis diffuse reflectance, SEM, FTIR, surface area, electrical conductivity, and photoluminescence) are performed to gain insight on their photocatalytic redox behaviors

  11. 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

  12. Investigation of the Cu-Zr-Y oxides activity in the carbon black catalytic oxidation by differential thermal analysis and temperature programmed reduction

    International Nuclear Information System (INIS)

    Different copper/zirconium-yttrium catalysts have been tested in carbon black oxidation reaction. Supported mainly on differential thermal analysis and temperature programmed reduction, two different mechanisms have been proposed to explain the catalytic results. In the absence of copper, it has been shown that Zr3+ ions and associated anionic vacancies are responsible to the catalytic enhancement observed in the mixed oxides, oxygen species being activated on these sites. Among mixed zirconia-yttria solids, ZrO2-5 mol%Y2O3 is the most active catalyst. Copper impregnation on these oxides leads to the formation of different copper species. Small particles of CuO in low interaction with the support, induce a catalytic improvement due to the highest reducibility of these species. Moreover, in order to be more efficient, CuO species should have some interactions with the support, since impregnated samples are more active than the simple mechanical mixtures

  13. 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)

  14. 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...

  15. Catalytic reduction of nitrate in secondary effluent of wastewater treatment plants by Fe(0) and Pd-Cu/γ-Al2O3.

    Science.gov (United States)

    Yun, Yupan; Li, Zifu; Chen, Yi-Hung; Saino, Mayiani; Cheng, Shikun; Zheng, Lei

    2016-01-01

    Total nitrogen, in which NO3(-) is dominant in the effluent of most wastewater treatment plants, cannot meet the requirements of the Chinese wastewater discharge standard (making nitrate (NO3(-)) elimination attract considerable attention. In this study, reductant iron (Fe(0)) and γ-Al2O3 supported palladium-copper bimetallic catalysts (Pd-Cu/γ-Al2O3) were innovatively used for the chemical catalytic reduction of nitrate in wastewater. A series of specific operational conditions (such as mass ratio of Pd:Cu, catalyst amounts, reaction time and pH of solution) were optimized for nitrate reduction in the artificial solution, and then the selected optimal conditions were further applied for investigating the nitrate elimination of secondary effluent of a wastewater treatment plant in Beijing, China. Results indicated that a better catalytic performance (74% of nitrate removal and 62% of N2 selectivity) could be obtained under the optimal condition: 5 g/L Fe(0), 3:1 mass ratio (Pd:Cu), 4 g/L catalyst, 2 h reaction time and pH 5.1. It is noteworthy to point out that nitrogen gas (N2) predominated in the byproducts without another system to treat ammonium and nitrite. Therefore, the chemical catalytic reduction combining Fe(0) with Pd-Cu/γ-Al2O3 could be regarded as a better alternative for nitrate removal in wastewater treatment. PMID:27232406

  16. 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)

  17. DRIFT study of CuO-CeO₂-TiO₂ mixed oxides for NOx reduction with NH₃ at low temperatures.

    Science.gov (United States)

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

    2014-06-11

    A CuO-CeO2-TiO2 catalyst for selective catalytic reduction of NOx with NH3 (NH3-SCR) at low temperatures was prepared by a sol-gel method and characterized by X-ray diffraction, Brunner-Emmett-Teller surface area, ultraviolet-visible spectroscopy, H2 temperature-programmed reduction, scanning electron microscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). The CuO-CeO2-TiO2 ternary oxide catalyst shows excellent NH3-SCR activity in a low-temperature range of 150-250 °C. Lewis acid sites generated from Cu(2+) are the main active sites for ammonia activation at low temperature, which is crucial for low temperature NH3-SCR activity. The introduction of ceria results in increased reducibility of CuO species and strong interactions between CuO particles with the matrix. The interactions between copper, cerium and titanium oxides lead to high dispersion of metal oxides with increased active oxygen and enhanced catalyst acidity. Homogeneously mixed metal oxides facilitate the "fast SCR" reaction among Cu(2+)-NO, nitrate (coordinated on cerium sites) and ammonia (on titanium sites) on the CuO-CeO2-TiO2 catalyst at low temperatures. PMID:24848157

  18. 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.

  19. 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.

  20. 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.

  1. Catalytic reduction of SO{sub 2} with methane over molybdenum catalyst. Quarterly technical report, September 1, 1994--November 30, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Wiltowski, T.

    1995-03-01

    One of the primary concerns in coal utilization is the emission of sulfur compounds, especially SO{sub 2}. This project deals with catalytic reduction of SO{sub 2} with methane using molybdenum sulfide catalyst supported on different activated carbons: Darco TRS, Norit ROZ-3, and an activated carbon prepared from Illinois coal IBC-110. The work conducted during this quarter has concentrated on catalyst preparation and characterization along with synthesis of activated carbon from IBC-110 coal, as well as, construction of the apparatus for catalytic tests of SO{sub 2} reduction with methane. It was found that Darco TRS supported catalysts have larger surface area than the pure activated carbon, whereas the impregnation of Norit ROZ-3 did not significantly change the BET surface area. Also, the synthesis of activated carbon support from IBC-110 is in progress.

  2. Pt/YSZ electrochemical catalysts prepared by electrostatic spray deposition for selective catalytic reduction of NO by C{sub 3}H{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Lintanf, A.; Djurado, E. [Laboratoire d' Electrochimie et de Physico-Chimie des Materiaux et des Interfaces (LEPMI), ENSEEG/INPG/UJF/CNRS Institut National Polytechnique de Grenoble Domaine Universitaire, BP 75, 1130 rue de la Piscine, 38402 St Martin d' Heres Cedex (France); Vernoux, P. [Universite de Lyon, Institut de Recherches sur la Catalyse et l' Environnement de Lyon, UMR 5256, CNRS, Universite Claude Bernard Lyon 1, 2 avenue A. Einstein, 69626 Villeurbanne (France)

    2008-03-15

    Due to the great importance of automotive exhaust gas treatment, the catalytic activity was investigated in selective catalytic reduction of NO by propene on Pt films - with controlled microstructure - deposited on YSZ (8 mol% Y{sub 2}O{sub 3}-doped ZrO{sub 2}) by electrostatic spray deposition. This technique requires low Pt loadings in order to reduce costs and also to achieve high Pt particles dispersion with good reproducibility. This kind of electrochemical catalysts was found to be effective for NO reduction by propene in the presence of oxygen. A dense Pt film was found to be the most suitable. Furthermore, we have demonstrated that these electrochemical catalysts can implement the concept of electrochemical promotion of catalysis (EPOC). (author)

  3. 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

  4. 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.

  5. Fabrication and characterisation of gold nano-particle modified polymer monoliths for flow-through catalytic reactions and their application in the reduction of hexacyanoferrate

    International Nuclear Information System (INIS)

    Polymer monoliths in capillary (100 μm i.d.) and polypropylene pipette tip formats (vol: 20 μL) were modified with gold nano-particles (AuNP) and subsequently used for flow-through catalytic reactions. Specifically, methacrylate monoliths were modified with amine-reactive monomers using a two-step photografting method and then reacted with ethylenediamine to provide amine attachment sites for the subsequent immobilisation of 4 nm, 7 nm or 16 nm AuNP. This was achieved by flushing colloidal suspensions of gold nano-particles through each aminated polymer monolith which resulted in a multi-point covalent attachment of gold via the lone pair of electrons on the nitrogen of the free amine groups. Field emission scanning electron microscopy and scanning capacitively coupled conductivity detection was used to characterise the surface coverage of AuNP on the monoliths. The catalytic activity of AuNP immobilised on the polymer monoliths in both formats was then demonstrated using the reduction of Fe(III) to Fe(II) by sodium borohydride as a model reaction by monitoring the reduction in absorbance of the hexacyanoferrate (III) complex at 420 nm. Catalytic activity was significantly enhanced on monoliths modified with smaller AuNP with almost complete reduction (95 %) observed when using monoliths agglomerated with 7 nm AuNPs. (author)

  6. The Synthesis and Characterization of Multifunctional Titania-based Materials for the Photo/Thermal Catalytic Reduction of CO2

    Science.gov (United States)

    Schwartzenberg, Kevin

    The work presented in this dissertation is aimed at improving our understanding of the fundamental processes required for the photocatalytic reduction of CO2. A QCM reactor system for measuring CO2 adsorption under a range of conditions was designed, constructed, and characterized. Measurements on catalyst films revealed sufficient sensitivity to detect CO2 adsorption on the order of 0.1 molecules/nm2. Adsorption experiments were repeatable across multiple measurements for the same film. However, variation across multiple films prepared using the same mass of catalyst highlights the large contribution of surface roughness to frequency response and the importance of uniform, reproducible film preparation. The design of a multifunctional photo/thermal catalyst was explored through the concept of MnOx-TiO2 composites with thermally generated oxygen vacancies as the active sites for CO2 activation. MnOx-TiO 2 were prepared by incipient wetness impregnation of titania supports with one of two Mn precursors, and were characterized and screened for catalytic activity. The results were compared with predictions from theoretical modeling studies. Through TPR, UV-vis spectroscopy, and XANES, it was observed that a Mn(NO 3)2•4H2O precursor led to bulk-like domains of MnOx whereas a Mn(CH3COO)2•4H2O precursor led to a dispersed surface oxide. This precursor effect was less pronounced on rutile than on anatase support. As predicted by theory, the MnOx-TiO 2 exhibited the reversible generation of oxygen vacancies at mild temperatures (failed to show evidence of nonvolatile CO2 reduction products. However, several carbonate, bicarbonate, and carboxylate species were observed, confirming the interaction of CO 2 with oxygen vacancies on the surface. UV illumination of the catalysts led to some desorption of these species on rutile supported composites, and very little change in adsorbed species on anatase-supported composites. For all of the materials, illumination resulted in

  7. The influence of sulphate on the catalytic properties of V{sub 2}O{sub 5}-TiO{sub 2} and WO{sub 3}-TiO{sub 2} in the reduction of nitric oxide with ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Ciambelli, P.; Fortuna, M.E.; Sannino, D. [Dipartimento di Ingegneria Chimica e Alimentare, Universita di Salerno, Fisciano (Italy); Baldacci, A. [ENEL-CRT, Pisa (Italy)

    1996-05-31

    The effect of sulphate on the catalytic properties of V{sub 2}O{sub 5}/TiO{sub 2} and WO{sub 3}/TiO{sub 2} in the selective reduction of NO with NH{sub 3} has been investigated. For both catalytic systems, the presence of sulphate results in the enhancement of catalytic activity without reduction of selectivity to nitrogen. The rate of NO reduction depends on the sulphate content, which is affected by the original composition of titania, the method of catalyst preparation and the metal oxide loading

  8. 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 ℃.

  9. Multifunctional nanocomposites of Fe3O4-graphene-Au for repeated use in simultaneous adsorption, in situ SERS detection and catalytic reduction of 4-nitrophenol in water

    International Nuclear Information System (INIS)

    This work is directed towards the synthesis of a ternary nanocomposite of Fe3O4-graphene-Au, i.e. Fe3O4 nanoparticles (∼300 nm in size) and Au nanoparticles (∼50 nm in size) loaded on the carbon basal planes of reduced graphene oxide, aimed for repeated use in simultaneous adsorption, in situ SERS detection and catalytic reduction of 4-nitrophenol (4-NP) in water, and also for recovering the useful reduction product of 4-aminophenol (4-AP). The results indicate that the amount of 4-NP and 4-AP absorbed to the prepared Fe3O4-graphene-Au nanocomposite can reach 170 mg g−1 and 447 mg g−1, respectively. The reduction reaction of 4-NP to 4-AP by NaBH4 with the Fe3O4-graphene-Au nanocomposite as a catalyst follows first-order kinetics with a rate constant (k) of about 0.4964 min−1, remarkably superior to the 0.1199 min−1 for the reduction reaction with the bare Au nanoparticles under the same conditions. In addition, in situ SERS can also be carried out to detect 4-NP and to monitor the reduction reaction with Fe3O4-graphene-Au as the substrate. Recycling of the composite can be achieved by simply applying an external magnetic field and the results demonstrate that it can be reused at least eight times with almost unaffected catalytic efficiency. (paper)

  10. Multifunctional nanocomposites of Fe3O4-graphene-Au for repeated use in simultaneous adsorption, in situ SERS detection and catalytic reduction of 4-nitrophenol in water

    Science.gov (United States)

    Chen, Fenghua; Wang, Yongwei; Chen, Qingtao; Han, Lifeng; Chen, Zhijun; Fang, Shaoming

    2014-12-01

    This work is directed towards the synthesis of a ternary nanocomposite of Fe3O4-graphene-Au, i.e. Fe3O4 nanoparticles (˜300 nm in size) and Au nanoparticles (˜50 nm in size) loaded on the carbon basal planes of reduced graphene oxide, aimed for repeated use in simultaneous adsorption, in situ SERS detection and catalytic reduction of 4-nitrophenol (4-NP) in water, and also for recovering the useful reduction product of 4-aminophenol (4-AP). The results indicate that the amount of 4-NP and 4-AP absorbed to the prepared Fe3O4-graphene-Au nanocomposite can reach 170 mg g-1 and 447 mg g-1, respectively. The reduction reaction of 4-NP to 4-AP by NaBH4 with the Fe3O4-graphene-Au nanocomposite as a catalyst follows first-order kinetics with a rate constant (k) of about 0.4964 min-1, remarkably superior to the 0.1199 min-1 for the reduction reaction with the bare Au nanoparticles under the same conditions. In addition, in situ SERS can also be carried out to detect 4-NP and to monitor the reduction reaction with Fe3O4-graphene-Au as the substrate. Recycling of the composite can be achieved by simply applying an external magnetic field and the results demonstrate that it can be reused at least eight times with almost unaffected catalytic efficiency.

  11. 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.

  12. 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)

  13. 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.

  14. 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.

  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. 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

  17. 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 ...

  18. 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.

  19. 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...

  20. Catalytic activity of copper-supported catalyst for NO reduction in the presence of oxygen: Fitting of calcination temperature and copper loading

    International Nuclear Information System (INIS)

    The effects of different calcination temperatures (300, 400 and 500 deg. C) and copper loading (1, 3 and 5 wt.%) on the properties of the copper supported on activated carbon (AC) were investigated along with the catalytic activity of NO reduction. The results showed that the properties and copper species of Cu/AC catalysts were significantly affected by calcination temperature and copper loading. The NO reduction of the Cu/AC-300 catalysts with different copper loading follows the order 5Cu/AC-300 > 3Cu/AC-300 > 1Cu/AC-300. However, the NO reduction increased insignificantly when the loading of copper exceeds 3 wt.%. Choosing 3Cu/AC-300 as a catalyst in NO reduction is more economical than other catalysts. Moreover, the catalyst calcined at 300 deg. C showed the highest activity with 52.9% NO reduction in 6% O2 at 275 deg. C. The good dispersion of the copper particles and the species of CuO and Cu2O that existed in 3Cu/AC-300 catalysts were the determinant parameters for NO reduction. The optimum reaction conditions for NO reduction were identified as 6% O2 at 275 deg. C with 0.2 g of catalyst.

  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. Co-processing, catalytic reduction and remote controlled oxalate precipitation - a new route for 233U/Th MOX

    International Nuclear Information System (INIS)

    Reprocessing and recycling of fissile and fertile nuclides together without their individual separation is considered to be one of the few proliferation resistant approaches for closing the nuclear fuel cycle. The present paper explores the possibility of reducing the uranium to U4+ catalytically using H2 gas, co-precipitating both Th and U as oxalate and final conversion to oxide

  3. 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

  4. Fine tuning of the catalytic effect of a metal-free porphyrin on the homogeneous oxygen reduction

    Czech Academy of Sciences Publication Activity Database

    Trojánek, Antonín; Langmaier, Jan; Šebera, Jakub; Záliš, Stanislav; Barbe, J.-M.; Girault, H. H.; Samec, Zdeněk

    2011-01-01

    Roč. 47, č. 19 (2011), s. 5446-5448. ISSN 1359-7345 R&D Projects: GA ČR GAP208/11/0697 Institutional research plan: CEZ:AV0Z40400503 Keywords : porphyrins * catalytic effects Subject RIV: CG - Electrochemistry Impact factor: 6.169, year: 2011

  5. 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)

  6. 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.

  7. Ag Active Sites, Surface Intermediates and Hydrogen Function at decane-SCR-Nox over Ag/Alumina

    Czech Academy of Sciences Publication Activity Database

    Sazama, Petr; Wichterlová, Blanka; Sobalík, Zdeněk; Nováková, Jana; Dědeček, Jiří

    2007-01-01

    Roč. 172, - (2007), s. 501-504. ISSN 0167-2991. [Tokyo Conference in Advanced Catalytic Science and Technology /5./. Tokyo, 23.07.2007-28.07.2007] R&D Projects: GA AV ČR 1ET400400413; GA ČR GD203/03/H140 Institutional research plan: CEZ:AV0Z40400503 Keywords : SCR -NOx * Ag active sites * surface intermediates Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.307, year: 2005

  8. Solvothermal synthesis of octahedral NiFe2O4 nanocrystals and catalytic properties for the reduction of some aromatic nitrocompounds

    International Nuclear Information System (INIS)

    In this paper, we report the successful synthesis of octahedral NiFe2O4 nanocrystals with room-temperature ferrimagnetism via a mixed solvothermal process at 170 °C for 15 h, using Fe(NO3)3 and NiCl2 as starting reactants. The phase and morphology of the as-prepared product is characterized by means of powder X-ray diffraction, energy dispersive spectrometry, selected area electron diffraction (SAED), (high resolution) transmission electron microscopy, and scanning electron microscopy. Experiments showed that the as-prepared octahedral NiFe2O4 nanocrystals owned strong catalytic activity for the reduction of some aromatic nitro-compounds such as 4-nitrophenol, 2-nitroaniline, 4-nitroaniline, and 2,4-dinitrophenol. Under the presence of 9 mg NiFe2O4 nanocrystals, the rate constants of the reductive reactions were in turn 3.16 × 10−2 min−1 for 4-nitrophenol, 4.28 × 10−2 min−1 for 2-nitroaniline, 6.79 × 10−2 min−1 for 4-nitroaniline, and 3.26 × 10−2 min−1 for 2,4-dinitrophenol. Moreover, the present catalyst could be conveniently recycled due to its magnetism. After ten cycles, its catalytic efficiency did not obviously decrease. - Highlights: • Octahedral NiFe2O4 nanocrystals were successfully prepared by an emulsion-solvothermal route. • NiFe2O4 nanocrystals with the room-temperature magnetism could be used as a recyclable catalyst. • NiFe2O4 nanocrystals showed strong catalytic activity for the reduction of 4-NP in NaBH4 solution

  9. Solvothermal synthesis of octahedral NiFe{sub 2}O{sub 4} nanocrystals and catalytic properties for the reduction of some aromatic nitrocompounds

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Hangsong [College of Chemistry and Materials Science, Key Laboratory of Functional Molecular Solids of Ministry of Education, Anhui Laboratory of Molecule-Based Materials, Anhui Key Laboratory of Functional Molecular Solids, Anhui Normal University, 1 Beijing Eastern Road, Wuhu 241000 (China); Ni, Yonghong, E-mail: niyh@mail.ahnu.edu.cn [College of Chemistry and Materials Science, Key Laboratory of Functional Molecular Solids of Ministry of Education, Anhui Laboratory of Molecule-Based Materials, Anhui Key Laboratory of Functional Molecular Solids, Anhui Normal University, 1 Beijing Eastern Road, Wuhu 241000 (China); Xiang, Nannan [College of Chemistry and Materials Science, Key Laboratory of Functional Molecular Solids of Ministry of Education, Anhui Laboratory of Molecule-Based Materials, Anhui Key Laboratory of Functional Molecular Solids, Anhui Normal University, 1 Beijing Eastern Road, Wuhu 241000 (China); Ma, Xiang [Center of Modern Analyses, Nanjing University, Nanjing 210093 (China); Wan, Fengying [Library of Anhui Normal University, 1 Beijing Eastern Road, Wuhu 241000 (China)

    2015-05-05

    In this paper, we report the successful synthesis of octahedral NiFe{sub 2}O{sub 4} nanocrystals with room-temperature ferrimagnetism via a mixed solvothermal process at 170 °C for 15 h, using Fe(NO{sub 3}){sub 3} and NiCl{sub 2} as starting reactants. The phase and morphology of the as-prepared product is characterized by means of powder X-ray diffraction, energy dispersive spectrometry, selected area electron diffraction (SAED), (high resolution) transmission electron microscopy, and scanning electron microscopy. Experiments showed that the as-prepared octahedral NiFe{sub 2}O{sub 4} nanocrystals owned strong catalytic activity for the reduction of some aromatic nitro-compounds such as 4-nitrophenol, 2-nitroaniline, 4-nitroaniline, and 2,4-dinitrophenol. Under the presence of 9 mg NiFe{sub 2}O{sub 4} nanocrystals, the rate constants of the reductive reactions were in turn 3.16 × 10{sup −2} min{sup −1} for 4-nitrophenol, 4.28 × 10{sup −2} min{sup −1} for 2-nitroaniline, 6.79 × 10{sup −2} min{sup −1} for 4-nitroaniline, and 3.26 × 10{sup −2} min{sup −1} for 2,4-dinitrophenol. Moreover, the present catalyst could be conveniently recycled due to its magnetism. After ten cycles, its catalytic efficiency did not obviously decrease. - Highlights: • Octahedral NiFe{sub 2}O{sub 4} nanocrystals were successfully prepared by an emulsion-solvothermal route. • NiFe{sub 2}O{sub 4} nanocrystals with the room-temperature magnetism could be used as a recyclable catalyst. • NiFe{sub 2}O{sub 4} nanocrystals showed strong catalytic activity for the reduction of 4-NP in NaBH{sub 4} solution.

  10. 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 2, Appendices A--N. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-10-01

    Volume 2 contains the following appendices: Appendix A, Example Material Safety Data Sheet; Appendix B, Initial Site Characterization Test Results; Appendix C, Testing Proposal, Southern Research Institute; Appendix D, Example Laboratory Catalyst Test Protocol; Appendix E, Detailed Coal Analysis Data; Appendix F, Standard Methods-QA/QC Document; Appendix G, Task No. 1 Commissioning Tests; Appendix H, Task No. 2 Commissioning Tests; Appendix I, First Parametric Sequence Spreadsheets; Appendix J, Second Parametric Sequence Spreadsheets; Appendix K, Third Parametric Sequence Spreadsheets; Appendix L, Fourth Parametric Sequence Spreadsheets; Appendix M, Fifth Parametric Sequence Spreadsheets; and Appendix N, First Series-Manual APH Tests.

  11. 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.

  12. Feststoff-SCR auf Basis von Ammoniumcarbamat

    OpenAIRE

    Mayer, Thorsten

    2005-01-01

    Die Erfüllung zukünftiger länderspezifischer Emissionsgrenzwerte rein mittels motorischer Maßnahmen zu realisieren, stößt an die Grenze der Machbarkeit. Aus diesem Grunde bedarf es der Entwicklung neuartiger Abgasnachbehandlungssysteme. Im Falle der dieselmotorbetriebenen Kraftfahrzeuge stellt das SCR-Verfahren eine vielversprechende Technologie dar. Mit dieser katalytischen Abgasnachbehandlungsmethode werden sowohl die Stickoxid- als auch in geringem Maße die Partikelemissionen gemindert. Di...

  13. 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

  14. 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.

  15. Fabrication of magnetically recyclable Fe{sub 3}O{sub 4}@Cu nanocomposites with high catalytic performance for the reduction of organic dyes and 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); Zhang, Sai; Li, Xianxian; Pang, Xiaobo [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Qiu, Haixia [School of Science, Tianjin University, Tianjin 300072 (China)

    2014-12-15

    A facile and efficient approach to synthesize Fe{sub 3}O{sub 4}@Cu nanocomposites using L-Lysine as a linker was developed. The morphology, composition and crystallinity of the Fe{sub 3}O{sub 4}@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 Fe{sub 3}O{sub 4} contained many small Cu nanoparticles with sizes of about 3 nm. It was found that the Fe{sub 3}O{sub 4}@Cu nanocomposites could catalyze the degradation of organic dyes. The catalytic activities of the Fe{sub 3}O{sub 4}@Cu nanocomposites for the reduction of nitrophenol were also studied. The Fe{sub 3}O{sub 4}@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 Fe{sub 3}O{sub 4}@Cu nanocomposites provide an exciting new material for environmental protection applications. - Highlights: • Cu nanoparticles as small as 3 nm are synthesized. • Low cost Fe{sub 3}O{sub 4}@Cu magnetical nanoparticles show catalytic activity for organic dyes and 4-nitrophenol. • The Fe{sub 3}O{sub 4}@Cu display high catalytic activity after 13 cycles.

  16. 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.

  17. 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

  18. 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.

  19. 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...

  20. 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.

  1. 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

  2. Simple one-pot synthesis of platinum-palladium nanoflowers with enhanced catalytic activity and methanol-tolerance for oxygen reduction in acid media

    International Nuclear Information System (INIS)

    Graphical abstract: PtPd nanoflowers were fabricated by one-pot solvothermal co-reduction method in oleylamine system, which exhibited the improved electrocatalytic activity and higher methanol tolerance for oxygen reduction, compared with commercial Pt and Pd black catalysts. - Highlights: • Bimetallic alloyed PtPd nanoflowers are prepared by a simple one-pot solvothermal co-reduction method. • PtPd nanoflowers display high catalytic performance for ORR dominated by a four-electron pathway. • PtPd nanoflowers show good methanol tolerance for ORR. - Abstract: In this work, bimetallic alloyed platinum-palladium (PtPd) nanoflowers are fabricated by one-pot solvothermal co-reduction of Pt (II) acetylacetonate and Pd (II) acetylacetonate in oleylamine system. The as-prepared nanostructures show the enhanced electrocatalytic activity for oxygen reduction reaction (ORR), dominated by a four-electron pathway based on the Koutecky-Levich plots, mainly owing to the inhibition of the formation of Pt–OHad via the downshift of d-band center for Pt. Meanwhile, PtPd nanoflowers display good methanol tolerance and improved stability for ORR. The chronoamperometry test reveals that the current of PtPd nanoflowers remains 45.9% of its original value within 6000 s, much higher than those of commercial Pt (36.7%) and Pd (32.2%) black catalysts. Therefore, PtPd nanoflowers with unique interconnected structures can be used as a promising cathode catalyst in direct methanol fuel cells

  3. Mussel-inspired synthesis of boron nitride nanosheet-supported gold nanoparticles and their application for catalytic reduction of 4-nitrophenol

    Science.gov (United States)

    Kumer Roy, Arup; Park, Sung Young; In, Insik

    2015-03-01

    Gold nanoparticle (AuNP)-decorated boron nitride nanosheet (BNNS) was successfully prepared through the simultaneous reduction of Au3+ ions and the growth of AuNPs on polydopamine (PDA)-grafted BNNS. Both BNNS-AuNP and PDA-BNNS are successfully synthesized in an aqueous buffer solution (pH 8.5) in the absence of any chemical reducing agent and organic reaction, which is therefore environmentally friendly and highly beneficial for the mass production of green catalysts from 2D nanomaterials. BNNS-AuNP showed remarkable dispersion stability in aqueous media and revealed high catalytic efficiency for the reduction of nitrophenol as (4-NP) into 4-aminophenol (4-AP) within 8 min in water. The 2D structural feature of BNNS-AuNP also enables isolation and recycling of catalyst from 4-AP through the ultracentrifugation, which shows the retention of more than 60% of catalytic activity of BNNS-AuNP after five repetitions of the of recycling steps.

  4. Substrate-dependent modulation of the enzymatic catalytic activity: reduction of nitrate, chlorate and perchlorate by respiratory nitrate reductase from Marinobacter hydrocarbonoclasticus 617.

    Science.gov (United States)

    Marangon, Jacopo; Paes de Sousa, Patrícia M; Moura, Isabel; Brondino, Carlos D; Moura, José J G; González, Pablo J

    2012-07-01

    The respiratory nitrate reductase complex (NarGHI) from Marinobacter hydrocarbonoclasticus 617 (Mh, formerly Pseudomonas nautica 617) catalyzes the reduction of nitrate to nitrite. This reaction is the first step of the denitrification pathway and is coupled to the quinone pool oxidation and proton translocation to the periplasm, which generates the proton motive force needed for ATP synthesis. The Mh NarGH water-soluble heterodimer has been purified and the kinetic and redox properties have been studied through in-solution enzyme kinetics, protein film voltammetry and spectropotentiometric redox titration. The kinetic parameters of Mh NarGH toward substrates and inhibitors are consistent with those reported for other respiratory nitrate reductases. Protein film voltammetry showed that at least two catalytically distinct forms of the enzyme, which depend on the applied potential, are responsible for substrate reduction. These two forms are affected differentially by the oxidizing substrate, as well as by pH and inhibitors. A new model for the potential dependence of the catalytic efficiency of Nars is proposed. PMID:22561116

  5. 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.

  6. 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

  7. 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...

  8. 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

  9. 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.

  10. 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

  11. 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).

  12. Structural Analysis of Potential Active Sites in Metallo-zeolites for Selective Catalytic Reduction of NOx. An Attempt for the Structure versus Activity Relatioship

    Czech Academy of Sciences Publication Activity Database

    Wichterlová, Blanka

    2004-01-01

    Roč. 28, 1/4 (2004), s. 131-140. ISSN 1022-5528 R&D Projects: GA MŠk 1P04OCD15.20 Institutional research plan: CEZ:AV0Z4040901 Keywords : SCR -NOx * Co-zeolites * Fe-zeolites Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.493, year: 2004

  13. Remarkably enhanced density and specific activity of active sites in Al-rich Cu-, Fe- and Co-beta zeolites for selective catalytic reduction of NOx

    Czech Academy of Sciences Publication Activity Database

    Sazama, Petr; Pilař, Radim; Mokrzycki, Lukasz; Vondrová, Alena; Kaucký, Dalibor; Plšek, Jan; Sklenák, Štěpán; Šťastný, Petr; Klein, Petr

    2016-01-01

    Roč. 189, JUL 2016 (2016), s. 65-74. ISSN 0926-3373 R&D Projects: GA TA ČR(CZ) TH01021259 Institutional support: RVO:61388955 Keywords : SCR -NOx * Al-rich beta zeolite (*BEA) * Cobalt Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.435, year: 2014

  14. Formation of palladium concave nanocrystals via auto-catalytic tip overgrowth by interplay of reduction kinetics, concentration gradient and surface diffusion

    Science.gov (United States)

    Su, Na; Chen, Xueying; Yue, Bin; He, Heyong

    2016-04-01

    A clear understanding of the growth mechanism involved in the shape-controlled synthesis of noble-metal nanocrystals with concave surfaces can provide useful information for the rational design of novel anisotropic nanostructures with controllable properties. In this paper, we conducted a systematic study of the detailed growth mechanism of the Pd arrow-headed tripods and revealed how the formation of the concave Pd nanocrystals was collectively controlled by the reduction kinetics, concentration gradient of Pd precursors, and surface diffusion of atoms. The formation of the arrow-headed tripods can be attributed to an auto-catalytic tip overgrowth process, where the Pd triangular nanoplate seeds formed under a suitably slow reduction rate can auto-catalyze the dehydrogenation of benzyl alcohol to generate hydrogen atoms [H]. The presence of [H] further dramatically accelerates the reduction of Pd(acac)2, which introduces a concentration gradient of Pd precursors in our non-stirring synthesis system and facilitates the kinetically-controlled tip overgrowth under a concentration gradient to form tripods with troughs on the arms. The final shapes of the concave nanocrystals depend on the relative rate of atom deposition and surface diffusion of atoms, which can be tuned by manipulating the reaction conditions such as the reaction temperature and the stirring conditions. This study presents a new possibility for the rational synthesis of various Pd nanostructures by manipulating the auto-catalytic process and tuning the relative rate of atom deposition and surface diffusion of atoms, which provides useful information for understanding the growth mechanism and the design of other anisotropic noble-metal nanostructures.

  15. 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...

  16. Prediction of Optimum parameters for NO/sub x/ reduction utilizing selective non-catalytic reduction (sncr) technique (thermal DeNO/sub x/ process)

    International Nuclear Information System (INIS)

    In this paper thermal DeNO/sub x/ process for Selective Non-Catalytic removal (SNCR) of nitric oxide from engine exhaust gases has been discussed and optimum parameters i.e optimum temperature, optimum residence time, and optimum molar ratio has been calculated by using CHEMKIN-II software. To run the code exhaust emission data has been obtained from reciprocating engine power plant operating on duel fuel system (40% Natural gas and 60% HFO). Finally it is concluded that if the conditions prescribed as predicted results are met in the exhaust stream, then with ammonia injection a substantial decrease in NO/sub x/ (about 96%) can be achieved. Sources of NO/sub x/ formation and different NO/sub x/ control techniques are also discussed in the paper. (author)

  17. Catalytic reduction of U(VI) to U(IV) using hydrogen with platinum loaded on alumina and silica

    International Nuclear Information System (INIS)

    During the reprocessing of spent nuclear fuel, uranium (U) and plutonium (Pu) are together extracted by employing tri-n-butyl phosphate (TBP)/dodecane mixture and their partitioning is achieved by adding uranous nitrate. The partitioning agent, uranous is conventionally produced by the electrolytic reduction of uranyl nitrate. An alternate route for the reduction of U from (VI) to (IV) using hydrogen (H2) as reductant was developed using platinum (Pt) based catalyst. Improvements in the development of the catalyst have been carried out in order to reduce the requirement of Pt without affecting the reduction performance. Experiments using 2 wt% Pt loaded on alumina beads and alumina powder have been performed and results are discussed. As the catalyst supported on alumina was found to be unstable in acidic environment, Pt loaded on silica powder has also been developed. Pt loaded on alumina and silica substrates have been tried to envisage the reduction behaviour using H2 as reductant in presence of hydrazine nitrate which acts as U(IV) stabiliser as well as reductant. Parametric studies have been carried out to optimise the process parameters namely pressure, temperature, U concentration, free acidity, hydrazine concentration and catalyst to U (C/U) ratio. 2 wt% Pt loaded on silica has been selected for further scale up studies for making uranous. (author)

  18. Formal verification of functional properties of a SCR-style software requirements specification using PVS

    International Nuclear Information System (INIS)

    Industrial software companies developing safety-critical systems are required to use rigorous safety analysis techniques to demonstrate compliance to regulatory bodies. In this paper, we describe an approach to formal verification of functional properties of requirements for an embedded real-time software written in software cost reduction (SCR)-style language using PVS specification and verification system. Key contributions of the paper include development of an automated method of translating SCR-style requirements into PVS input language as well as identification of property templates often needed in verification. Using specification for a nuclear power plant system, currently in operation, we demonstrate how safety demonstration on requirements can be accomplished while taking advantage of assurance provided by formal methods

  19. 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.

  20. Method and system for SCR optimization

    Science.gov (United States)

    Lefebvre, Wesley Curt; Kohn, Daniel W.

    2009-03-10

    Methods and systems are provided for controlling SCR performance in a boiler. The boiler includes one or more generally cross sectional areas. Each cross sectional area can be characterized by one or more profiles of one or more conditions affecting SCR performance and be associated with one or more adjustable desired profiles of the one or more conditions during the operation of the boiler. The performance of the boiler can be characterized by boiler performance parameters. A system in accordance with one or more embodiments of the invention can include a controller input for receiving a performance goal for the boiler corresponding to at least one of the boiler performance parameters and for receiving data values corresponding to boiler control variables and to the boiler performance parameters. The boiler control variables include one or more current profiles of the one or more conditions. The system also includes a system model that relates one or more profiles of the one or more conditions in the boiler to the boiler performance parameters. The system also includes an indirect controller that determines one or more desired profiles of the one or more conditions to satisfy the performance goal for the boiler. The indirect controller uses the system model, the received data values and the received performance goal to determine the one or more desired profiles of the one or more conditions. The system model also includes a controller output that outputs the one or more desired profiles of the one or more conditions.

  1. 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

  2. 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

  3. Size-dependent catalytic performance of CuO on γ-Al2O3: NO reduction versus NH3 oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Ja Hun; Tonkyn, Russell G.; Tran, Diana N.; Mei, Donghai; Cho, Sung June; Kovarik, Libor; Lee, Jong H.; Peden, Charles HF; Szanyi, Janos

    2012-05-25

    Catalytic reaction pathways of NH{sub 3} on CuO/{gamma}-Al{sub 2}O{sub 3} catalysts during NH{sub 3} SCR reactions were investigated under oxygen-rich conditions. On 10 wt % CuO/{gamma}-Al{sub 2}O{sub 3}, NH{sub 3} reacted with oxygen to produce NO{sub x}. In contrast, on the 0.5 wt % CuO/{gamma}-Al{sub 2}O{sub 3} catalyst NH{sub 3} reacted primarily with NO to form N{sub 2} with conversion efficiency of {approx}80% at 450 C. H{sub 2}-TPR results show that Cu species present in 10 wt % CuO/{gamma}-Al{sub 2}O{sub 3} can be easily reduced at {approx}160 C, which suggests the formation of large CuO clusters on the alumina surface. On the other hand, the TPR spectrum obtained from the 0.5 wt % CuO/{gamma}-Al{sub 2}O{sub 3} catalyst does not show any measurable H{sub 2} consumption up to 700 C, which suggests the presence of non-reducible isolated Cu species in this catalyst. STEM images collected from 10 wt % CuO/{gamma}-Al{sub 2}O{sub 3} show nano-sized CuO clusters, while no evidence of cluster formation is seen in the images recorded from the 0.5 wt % CuO/{gamma}-Al{sub 2}O{sub 3} sample, due to the intrinsic limitation of low Z contrast between highly dispersed Cu (atomic weight = 63.5) species and the alumina support (atomic weight of Al = 27). EXAFS data indicates the presence of Cu-Cu (Al) second shell at 0.35 nm only in the 10% CuO/{gamma}-Al{sub 2}O{sub 3} catalyst, and an estimated coordination number of {approx}1.7. The XANES and EXAFS results suggest the formation of relatively highly dispersed Cu oxide nanoclusters even at 10 wt % Cu loading. However, FT-IR spectra collected after CO adsorption on the CuO/{gamma}-Al{sub 2}O{sub 3} catalysts demonstrate the existence of different Cu species at Cu loadings of 0.5 and 10 wt %. Density functional theory (DFT) results show that supported CuO clusters, represented by a two-dimensional (2D) CuO monolayer, can effectively dissociate adsorbed NO and O2 to produce atomic oxygen species. These reactive atomic oxygen

  4. 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

  5. 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).

  6. Structure Investigation of Ti(IV)BODOLates Involved in the Catalytic Asymmetric Reduction of Ketones Using Catecholborane

    DEFF Research Database (Denmark)

    Sarvary, Ian; Norrby, Per-Ola; Frejd, Torbjörn

    2004-01-01

    The complexes formed on mixing Ti(OiPr)4 and bicyclo-octanediols (BODOLs) 1 and 2 (1:1) are useful as chiral catalysts in asymmetric reductions and were investigated by 1HNMR-spectroscopy and by computational methods. A consistent picture emerged of head-to-tail dimers being kept together via a Ti...

  7. Immobilized redox mediator on metal-oxides nanoparticles and its catalytic effect in a reductive decolorization process.

    Science.gov (United States)

    Alvarez, L H; Perez-Cruz, M A; Rangel-Mendez, J R; Cervantes, F J

    2010-12-15

    Different metal-oxides nanoparticles (MONP) including α-Al(2)O(3), ZnO and Al(OH)(3), were utilized as adsorbents to immobilize anthraquinone-2,6-disulfonate (AQDS). Immobilized AQDS was subsequently tested as a solid-phase redox mediator (RMs) for the reductive decolorization of the azo dye, reactive red 2 (RR2), by anaerobic sludge. The highest adsorption capacity of AQDS was achieved on Al(OH)(3) nanoparticles, which was ∼0.16 mmol g(-1) at pH 4. Immobilized AQDS increased up to 7.5-fold the rate of decolorization of RR2 by anaerobic sludge as compared with sludge incubations lacking AQDS. Sterile controls including immobilized AQDS did not show significant (<3.5%) RR2 decolorization, suggesting that physical-chemical processes (e.g. adsorption or chemical reduction) were not responsible for the enhanced decolorization achieved. Immobilization of AQDS on MONP was very stable under the applied experimental conditions and spectrophotometric screening did not detect any detachment of AQDS during the reductive decolorization of RR2, confirming that immobilized AQDS served as an effective RMs. The present study constitutes the first demonstration that immobilized quinones on MONP can serve as effective RMs in the reductive decolorization of an azo dye. The immobilizing technique developed could be applied in anaerobic wastewater treatment systems to accelerate the redox biotransformation of recalcitrant pollutants. PMID:20813453

  8. 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.

  9. Evolution of nanoporous Pt-Fe alloy nanowires by dealloying and their catalytic property for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Shui, Jiang-Lan; Chen, Chen; Li, James C.M. [Material Science Program, University of Rochester, Rochester, NY (United States)

    2011-09-09

    The short life and high cost of carbon-supported Pt nanoparticle catalysts (Pt/C) are two main problems with proton exchange membrane fuel cells. Porous Pt alloy nanowires have more durability and catalytic activity than Pt/C. Dealloying is a facile way to make nanoporous Pt. However, the process of porosity formation is difficult to control. In this paper, electrospinning and chemical dealloying techniques are used to make long, thin and yet nanoporous Pt-Fe alloy nanowires. The evolution of nanoporosity is observed and studied. It is found that non-uniform composition in the precursor PtFe{sub 5} alloy nanowires helps the formation of nanoporous structure. The overall wire diameter is about 10-20 nm and the ligament diameter only 2-3 nm. These porous long nanowires interweave to form a self-supporting network with a high specific activity, 2.3 times that of conventional Pt/C catalysts, and also have better durability. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. 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.

  11. 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; Gabrielsson, Pär; Skoglundh, Magnus

    2013-01-01

    A global kinetic model which describes H2-assisted NH3-SCR over an Ag/Al2O3 monolith catalyst has been developed. The intention is that the model can be applied for dosing NH3 and H2 to an Ag/Al2O3 catalyst in a real automotive application as well as contribute to an increased understanding of the...

  12. The effect of the gas composition on hydrogen-assisted NH3-SCR over Ag/Al2O3

    DEFF Research Database (Denmark)

    Tamm, Stefanie; Fogel, Sebastian; Gabrielsson, Pär;

    2013-01-01

    In addition to high activity in hydrocarbon-SCR, Ag/Al2O3 catalysts show excellent activity for NOx reduction for H2-assisted NH3-SCR already at 200°C. Here, we study the influence of different gas compositions on the activity of a pre-sulfated 6wt% Ag/Al2O3 catalyst for NOx reduction...... at constant temperature, the concentration of NO reaches steady state fast, whereas it takes longer time for NH3 due to accumulated surface species, probably on the alumina. The oxidation of NO to NO2 is sensitive to the H2 concentration in similarity to the SCR reaction, while higher amounts of H2 suppress...... the oxidation of NH3. Moreover, the dependency on the O2 concentration is much higher for the NO and NH3 oxidation than for the SCR reaction. To explain all these features a reaction mechanism is proposed in which the role of H2 is to free silver from single oxygen atoms. Ammonia and nitric oxygen can adsorb...

  13. 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.

  14. 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.

  15. 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

  16. Benefit evaluation of replacement strategies for SCR catalyst in thermal power plants%火电厂 SCR 催化剂更新策略分析及效益评估

    Institute of Scientific and Technical Information of China (English)

    谢新华; 陆继东; 黄秋雄; 邓柱

    2016-01-01

    A new replacement strategy for selective catalytic reduction (SCR) catalyst in coal‐fired power plants was put forward based on the analysis of the variation in deactivation rate of different catalyst layer .T he life ,replacement cycle for catalysts and running costs of SCR system w ere ana‐lyzed and compared between three replacement strategies through simulation method ,including a tra‐ditional approach ,a regeneration strategy and the new strategy .The simulation results show that the proposed strategy can extend the catalyst life by 21% and extend the replacement cycle by 50% com‐paring with the traditional approach .Further cost‐benefit analysis show that the new strategy can save 7 .87% ~19 .63% of running costs w hen the price of SCR catalyst varies in the range of 1 × 104 ~5 × 104 RMB/m3 .The new strategy has obvious benefits in lowering average deactivation rate ,extending the catalyst life and reducing operational cost .%在分析现有催化剂更新方法和各层催化剂失活速率差异的基础上,提出了一种新的燃煤电厂选择性催化还原(SCR)催化剂再生‐调换更新策略,并采用催化剂更新策略模拟方法对比分析了三种催化剂更新策略下的催化剂寿命、更新周期和脱硝装置运行成本.结果显示:此再生‐调换更新策略可延长催化剂理论寿命21%,从而使催化剂更新周期延长50%.进一步对比脱硝装置运行成本发现:当催化剂价格为1×104~5×104元/m3时,采用此更新策略较普遍采用的催化剂更换策略可节约运行成本7.87%~19.63%.新的催化剂更新策略可显著降低催化剂在燃煤电厂服役过程中的整体失活速率、延长催化剂使用寿命和节约脱硝系统运行成本.

  17. Multiphase catalysts for selective reduction of NOx with hydrocarbons

    International Nuclear Information System (INIS)

    Among the existing proposed solutions to reduce emission of NOx there is a promising alternative, the so-called (HC-SCR) selective catalytic reduction of NOx using hydrocarbons as reductant. This thesis is part of a worldwide effort devoted to gain knowledge on the selective catalytic reduction of NOx with hydrocarbons with the final goal to contribute to the development of suitable catalysts for the above mentioned process. Chapter 2 describes the details of the experimental set-up and of the analytical methods employed. Among the catalyst for HC-SCR, Co-based catalyst are known to be active and selective, thus, a study on a series of Co-based catalysts, supported on zeolites, was undertaken and the results are presented in Chapter 3. Correlation between catalytic characteristics and kinetic results are employed to understand the working catalyst and this is used as a basis for catalyst optimization. With the intention to prepare a multi-functional catalyst that will preserve the desired characteristics of the individual components, minimizing their negative aspects, catalysts based on Co-Pt, supported on ZSM-5, were investigated. In Chapter 4 the results of this study are discussed. A bimetallic Co-Pt/ZSM-5 catalysts with low Pt contents (0.1 wt %) showed a synergistic effect by combining high stability and activity of Pt catalysts with the high N2 selectivity of Co catalysts. Furthermore, it was found to be sulfur- and water-tolerant. Its positive qualities brought us to study the mechanism that takes place over this catalyst during HC-SCR. The results of an in-situ i.r mechanistic study over this catalyst is reported in Chapter 5. From the results presented in Chapter 5 a mechanism operating over the Co-Pt/ZSM-5 catalyst is proposed. The modification of Co catalyst with Pt improved the catalysts. However, further improvement was found to be hindered by high selectivity to N2O. Since Rh catalysts are generally less selective to N2O, the modification of Co

  18. Modified SCR for optically actuated triggering

    International Nuclear Information System (INIS)

    A simple inexpensive, optically actuated triggering device (optical trigger) has been developed for synchronizing pulsed lasers with signal gathering instrumentation. The heart of this device is a commercially available SCR that has been modified for light activated operation. The optical trigger delivers, into a 50-Ω load, a pulse of either 84 V with a 8.3-ns rise time and 3.5-μs width, or 42 V with a 6.2-ns rise time and 7-μs width. The device is sensitive throughout the visible and near-visible spectrum. It has a transit time of only 2.2 ns and less than 1-ns jitter. The performance of this optical trigger is examined in terms of the criteria of an ''ideal'' optical trigger and the effects of circuit and input parameters on output pulse characteristics are discussed

  19. TRIAC/SCR proportional control circuit

    Science.gov (United States)

    Hughes, W.J.

    1999-04-06

    A power controller device is disclosed which uses a voltage-to-frequency converter in conjunction with a zero crossing detector to linearly and proportionally control AC power being supplied to a load. The output of the voltage-to frequency converter controls the ``reset`` input of a R-S flip flop, while an ``0`` crossing detector controls the ``set`` input. The output of the flip flop triggers a monostable multivibrator controlling the SCR or TRIAC firing circuit connected to the load. Logic gates prevent the direct triggering of the multivibrator in the rare instance where the ``reset`` and ``set`` inputs of the flip flop are in coincidence. The control circuit can be supplemented with a control loop, providing compensation for line voltage variations. 9 figs.

  20. An SCR inverter for electric vehicles

    Science.gov (United States)

    Latos, T.; Bosack, D.; Ehrlich, R.; Jahns, T.; Mezera, J.; Thimmesch, D.

    1980-01-01

    An inverter for an electric vehicle propulsion application has been designed and constructed to excite a polyphase induction motor from a fixed propulsion battery source. The inverter, rated at 35kW peak power, is fully regenerative and permits vehicle operation in both the forward and reverse directions. Thyristors are employed as the power switching devices arranged in a dc bus commutated topology. This paper describes the major role the controller plays in generating the motor excitation voltage and frequency to deliver performance similar to dc systems. Motoring efficiency test data for the controller are presented. It is concluded that an SCR inverter in conjunction with an ac induction motor is a viable alternative to present dc vehicle propulsion systems on the basis of performance and size criteria.

  1. The Hamiltonian structure of soliton equations and deformed scr(W)-algebras

    International Nuclear Information System (INIS)

    The Poisson bracket algebra corresponding to the second Hamiltonian structure of a large class of generalized KdV and mKdV integrable hierarchies is carefully analysed. These algebras are known to have conformal properties and their relation to scr(W)-algebras has been previously investigated in some particular cases. The class of equations that is considered includes practically all the generalizations of the Drinfel close-quote d endash Sokolov hierarchies constructed in the literature. In particular, it has been recently shown that it includes matrix generalizations of the Gelfand endash Dickey and the constrained KP hierarchies. Therefore, our results provide a unified description of the relation between the Hamiltonian structure of soliton equations and scr(W)-algebras, and it comprises almost all the results formerly obtained by other authors. The main result of this paper is an explicit general equation showing that the second Poisson bracket algebra is a deformation of the Dirac bracket algebra corresponding to the scr(W)-algebras obtained through Hamiltonian reduction. copyright 1997 Academic Press, Inc

  2. 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.

  3. 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. PMID:24121703

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. Compact SCR trigger circuit for ignitron switch operates efficiently

    Science.gov (United States)

    Foster, L. E.

    1965-01-01

    Trigger circuit with two series-connected SCR triggers an ignitron switch used to discharge high-energy capacitor banks. It does not require a warmup period and operates at relatively high efficiency.

  9. Dynamic flow control strategies of vehicle SCR Urea Dosing System

    Science.gov (United States)

    Lin, Wei; Zhang, Youtong; Asif, Malik

    2015-03-01

    Selective Catalyst Reduction(SCR) Urea Dosing System(UDS) directly affects the system accuracy and the dynamic response performance of a vehicle. However, the UDS dynamic response is hard to keep up with the changes of the engine's operating conditions. That will lead to low NO X conversion efficiency or NH3 slip. In order to optimize the injection accuracy and the response speed of the UDS in dynamic conditions, an advanced control strategy based on an air-assisted volumetric UDS is presented. It covers the methods of flow compensation and switching working conditions. The strategy is authenticated on an UDS and tested in different dynamic conditions. The result shows that the control strategy discussed results in higher dynamic accuracy and faster dynamic response speed of UDS. The inject deviation range is improved from being between -8% and 10% to -4% and 2% and became more stable than before, and the dynamic response time was shortened from 200 ms to 150 ms. The ETC cycle result shows that after using the new strategy the NH3 emission is reduced by 60%, and the NO X emission remains almost unchanged. The trade-off between NO X conversion efficiency and NH3 slip is mitigated. The studied flow compensation and switching working conditions can improve the dynamic performance of the UDS significantly and make the UDS dynamic response keep up with the changes of the engine's operating conditions quickly.

  10. 尿素水溶液浸渍对柴油机 NH3-SCR后处理铜基分子筛催化剂性能的影响%Impact of diesel emission fluid soaking on the performance of Cu-zeolite catalysts for diesel NH3-SCR systems

    Institute of Scientific and Technical Information of China (English)

    Dong-wei YAO; Feng WU; Xin-lei WANG

    2016-01-01

    ) soaking and urea deposits on selective catalytic reduction (SCR) catalysts are critical issues for real diesel engine NH3-SCR systems. To investigate the impact of DEF soaking and urea deposits on SCR catalyst performance, fresh Cu-zeolite catalyst samples were drilled from a full-size SCR catalyst. Those samples were impregnated with DEF solutions and subsequently hydrothermally treated to simulate DEF soaking and urea deposits on real SCR catalysts during diesel engine operations. Their SCR performance was then evaluated in a flow reactor with a four-step test protocol. Test results show that the DEF soaking leached some Cu from the SCR catalysts and slightly reduced their Cu loadings. The loss of Cu and associated metal sites on the catalysts weakened their catalytic oxidation abilities and caused lower NO/NH3 oxidation and lower high-temperature N2O selectivity. Lower Cu loading also made the catalysts less active to the decomposition of surface ammonium nitrates and decreased low-temperature N2O selectivity. Cu loss during DEF impregnation released more acid sites on the surface of the catalysts and increased their acidities, and more NH3 was able to be adsorbed and involved in SCR reactions at medium and high temperatures. Due to lower NH3 oxidation and higher NH3 storage, the DEF-impregnated SCR catalyst samples showed higher NOx conversion above 400 °C compared with the non-soaked one. The negative impact of urea deposits during DEF im-pregnation was not clearly observed, because the high-temperature hydrothermal treatment helped to remove the urea deposits.

  11. In situ Synthesis of Cu-SSZ-13/Cordierite Monolithic Catalyst for the Selective Catalytic Reduction of NO with NH3%Cu-SSZ-13/堇青石整体式催化剂的原位合成及其NH3选择性催化还原NO性能

    Institute of Scientific and Technical Information of China (English)

    张宇; 王红宁; 陈若愚

    2015-01-01

    采用水热合成技术,在堇青石蜂窝陶瓷载体上原位合成了SSZ-13分子筛,并借助X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)等手段对其进行表征.在此基础上,研究了合成时间对催化剂结构和机械性能的影响.另外,使用固定床反应器测试了离子交换度为50%的Cu-SSZ-13/堇青石催化剂和Cu-SSZ-13催化剂水热老化前后的氨气选择性催化还原(NH3-SCR) NO性能.结果表明,通过原位合成法制备的Cu-SSZ-13/堇青石催化剂在200-500° C的窗口温度内能达到80%以上的转化率,并在300° C时达到96.4%的转化率.在850°C水热老化12 h后, Cu-SSZ-13催化剂完全丧失了催化性能,而Cu-SSZ-13/堇青石催化剂在300°C时仍然保持91%的转化率.使用XRD和固体27Al核磁共振(27Al NMR)的方法,研究了水热老化前后两种催化剂结构的变化,结果表明,当水热老化12 h后, Cu-SSZ-13基本丧失了SSZ-13结构特征峰,而Cu-SSZ-13/堇青石仍然保持了一定的SSZ-13骨架结构.证明了通过原位合成法制备的Cu-SSZ-13/堇青石催化剂具有较好的抗水热老化性能.%SSZ-13 molecular sieves were synthesized in situ on the surface of a honeycomb-shaped cordierite support using a hydrothermal method, and the resulting material was characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). The process for preparing SSZ-13/cordierite was optimized in detail. Furthermore, the ion exchange levels of the 50%Cu-SSZ-13/cordierite and Cu-SSZ-13 catalysts were tested in the ammonia-selective catalytic reduction (NH3-SCR) of NO both before and after the hydrothermal treatment process using a fixed-bed reactor. The results of these experiments showed that the Cu-SSZ-13/cordierite prepared in situ by hydrothermal synthesis had good catalytic activity, and gave an NO conversion of more than 80%at temperatures in the range of 200-500 °C, with the highest NO conversion of

  12. Selective catalytic reduction of NOx in lean-burn engine exhaust over a Pt/V/MCM-41 catalyst

    International Nuclear Information System (INIS)

    The activities of Pt supported on various metal-substituted MCM-41 (V-, Ti-, Fe-, Al-, Ga-, La-, Co-, Mo-, Ce-, and Zr-MCM-41) and V-impregnated MCM-41 were investigated for the reduction of NO by C3H6. Among these catalysts, Pt supported on V-impregnated MCM-41 showed the best activity. The maximum conversion of NO into N2+N2O over this Pt/V/MCM-41 catalyst (Pt=1wt.%, V=3.8wt.%) was 73%, and this maximum conversion was sustained over a temperature range of 70C from 270 to 340C. The high activity of Pt/V/MCM-41 over a broad temperature range resulted from two additional reactions besides the reaction occurring on usual supported Pt, the reaction of NO with surface carbonaceous materials, and the reaction of NO occurring on support V-impregnated MCM-41. The former additional reaction showed an oscillation characteristic, a phenomenon in which the concentrations of parts of reactant and product gases oscillate continuously. At low temperature, some water vapor injected into the reactant gas mixture promoted the reaction occurring on usual supported Pt, whereas at high temperature, it suppressed the additional reaction related to carbonaceous materials. Five-hundred parts per million of SO2 added to the reactant gas mixture only slightly decreased the NO conversion of Pt/V/MCM-41

  13. Study of the catalytic reduction or uranyl nitrate by hydrogen. Sizing of a three-phase reactor

    International Nuclear Information System (INIS)

    As solutions generated by nuclear fuel processing plants contain a mixing of uranium VI (uranyl nitrate) and of plutonium IV, and as uranous nitrate can be used to reduce plutonium to its valence III, this last reduction reaction raises many problems, and the first objective of this research thesis is to better understand and control the various phenomena involved in this reaction. Thus, a first part addresses the reaction chemistry and kinetics. It is based on tests performed in a closed reactor, and aims at clarifying problems of re-oxidation and at devising a kinetic model. A specific attention is paid to matter transfers between the different gaseous, liquid and solid phases. In the second part, the author reports the study of the hydrodynamic behaviour of an airlift-type reactor. Such an apparatus displays indeed interesting benefits to implement the reaction. It notably allows temperature to be well controlled, and the catalyst to be easier handled. Based on these kinetic and hydrodynamic studies, the third part proposes a reactor model, and reports the calculation of its performance by simulation

  14. Demonstration of SCR technology for the control of NOx emissions from high-sulfur coal-fired utility boilers

    Energy Technology Data Exchange (ETDEWEB)

    Hinton, W.S. [W.S. Hinton and Associates, Cantonment, FL (United States); Maxwell, J.D.; Healy, E.C.; Hardman, R.R. [Southern Company Services, Inc., Birmingham, AL (United States); Baldwin, A.L. [Dept. of Energy, Pittsburgh, PA (United States)

    1997-12-31

    This paper describes the completed Innovative Clean Coal Technology project which demonstrated SCR technology for reduction of flue gas NO{sub x} emissions from a utility boiler burning US high-sulfur coal. The project was sponsored by the US Department of Energy, managed and co-funded by Southern Company Services, Inc. on behalf of the Southern Company, and also co-funded by the Electric Power Research Institute and Ontario Hydro. The project was located at Gulf Power Company`s Plant Crist Unit 5 (a 75 MW tangentially-fired boiler burning US coals that had a sulfur content ranging from 2.5--2.9%), near Pensacola, Florida. The test program was conducted for approximately two years to evaluate catalyst deactivation and other SCR operational effects. The SCR test facility had nine reactors: three 2.5 MW (5,000 scfm), and operated on low-dust flue gas. The reactors operated in parallel with commercially available SCR catalysts obtained from suppliers throughout the world. Long-term performance testing began in July 1993 and was completed in July 1995. A brief test facility description and the results of the project are presented in this paper.

  15. An in situ UV-vis and FTIR spectroscopy study of the effect of H.sub.2./sub. and CO during the selective catalytic reduction of nitrogen oxides over a silver alumina catalyst

    Czech Academy of Sciences Publication Activity Database

    Wichterlová, Blanka; Sazama, Petr; Breen, J. P.; Burch, R.; Hill, C. J.; Čapek, Libor; Sobalík, Zdeněk

    2005-01-01

    Roč. 235, č. 1 (2005), s. 195-200. ISSN 0021-9517 R&D Projects: GA AV ČR 1ET400400413 Institutional research plan: CEZ:AV0Z40400503 Keywords : SCR -NOx * Ag/alumina * Ag clusters * H2 effect in SCR -NOx Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.780, year: 2005

  16. Green synthesis of Pd/CuO nanoparticles by Theobroma cacao L. seeds extract and their catalytic performance for the reduction of 4-nitrophenol and phosphine-free Heck coupling reaction under aerobic conditions.

    Science.gov (United States)

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad; Rostami-Vartooni, Akbar; Bagherzadeh, Mojtaba

    2015-06-15

    We report the green synthesis of palladium/CuO nanoparticles (Pd/CuO NPs) using Theobroma cacao L. seeds extract and their catalytic activity for the reduction of 4-nitrophenol and Heck coupling reaction under aerobic conditions. The catalyst was characterized using the powder XRD, TEM, EDS, UV-vis and FT-IR. This method has the advantages of high yields, elimination of surfactant, ligand and homogeneous catalysts, simple methodology and easy work up. The catalyst can be recovered from the reaction mixture and reused several times without any significant loss of catalytic activity. PMID:25721860

  17. Preparation of zeolite supported TiO2, ZnO and ZrO2 and the study on their catalytic activity in NOx reduction and 1-pentanol dehydration

    Science.gov (United States)

    Fatimah, Is

    2016-03-01

    Preparation of zeolite supported TiO2, ZnO and ZrO2 and their catalytic activity was studied. Activated natural zeolite from Indonesia was utilized for the preparation and catalytic activity test on NOx reduction by NH3 and also 1-pentanol dehydration were examined. Physicochemical characterization of materials was studied by x-ray diffraction (XRD) measurement, scanning electron microscope, solid acidity determination and also gas sorption analysis. The results confirmed that the preparation gives some improvements on physicochemical characters suitable for catalysis mechanism in those reactions. Solid acidity and specific surface area contributed significantly to the activity.

  18. [Synthesis of Fe/nitrogen-doped Carbon Nanotube/Nanoparticle Composite and Its Catalytic Performance in Oxygen Reduction].

    Science.gov (United States)

    Yang, Ting-ting; Zhu, Neng-wu; Lu, Yu; Wu, Ping-xiao

    2016-01-15

    The cathode catalyst plays an important role in the electricity generation of microbial fuel cells (MFCs). In order to achieve the large-scale application of MFCs, cathode catalyst with low cost and high oxygen reduction reaction (ORR) has great sense to substitute the precious catalyst of Pt/C. Here chemical vapor deposition (CVD) method was utilized accompanied with melamine as a nitrogen and carbon precursor, oxidized carbon powder (Black Pearls 2000 or Acetylene Black) as carbon precursor and iron acetate as an iron precursor so as to synthesize two kinds of Fe and nitrogen doped carbon nanotube/nanoparticle composites (FeNCB and FeNCC) as MFCs cathode catalysts. The cyclic voltammetry and rotating ring-disk electrode were applied to analyze the ORR activity discrepancies of FeNCB, FeNCC, and Pt/C (20%), which was confirmed by MFC operation. The results showed that the ORR performance of FeNCB was slightly better than Pt/C and dramatically better than FeNCC. Moreover, the catalysis of ORR by FeNCB was through a four-electron transfer pathway. Besides, the performance of MFC-FeNCB was higher than MFC-Pt/C and observably higher than MFC-FeNCC which was a contribute to promote the scale of MFC. MFC-FeNCB achieved the maximum power output density of 1212.8 mW x m(-2), an open circuit potential of 0.875 V, and a stabilized voltage of (0.500 +/- 0.025) V. Further analysis via X-ray diffraction, X ray photoelectron spectroscopy, and Raman exhibited that the diameter of carbon nanotube, the types of N and Fe as well as the concentration of nitrogen, iron and oxygen was the reason for the discrepancies of ORR characteristics for the prepared catalysts. PMID:27078977

  19. Optimization of the fluid catalytic cracking unit performance by application of a high motor Octane catalyst and reduction of gasoline vapour pressure

    International Nuclear Information System (INIS)

    Full text: The fluid catalytic cracking (FCC) gasoline is the main contributor to the refinery gasoline pool in the LUKOIL Neftohim Burgas (LNB) refinery. Next in quantity contributor in the refinery gasoline pool is the reformate. The FCC gasoline sensitivity (MON-RON) is about 12 points. The reformer gasoline sensitivity is 11 points. The high sensitivity of the main contributors to the LNB refinery gasoline pool leads to a shortage in the motor octane number. For that reason a selection of an FCC catalyst that is capable of increasing the motor octane number of the FCC gasoline was performed. The application of this catalyst in the LNB FCC unit has led to an increase of the motor octane number of the FCC gasoline by 0.5 points, which enabled the refinery to increase the production of automotive gasolines by 1.3 % and to increase the share of premium automotive gasoline by 5 %. This had an effect of improvement of the refinery economics by a six figure number of US $ per year. The optimization of the FCC gasoline Reid Vapor Pressure (RVP) during the winter season, consisting in a reduction of the RVP from 60 to 50 kPa and an increase of the FCC C4 olefins yield, has led to an augmentation of high motor octane number alkylate production. As a result the refinery economics was improved by a five figure number of US $ per year. key words: FCC gasoline motor octane number, gasoline RVP, FCC operation profitability

  20. Interaction Induced High Catalytic Activities of CoO Nanoparticles Grown on Nitrogen-Doped Hollow Graphene Microspheres for Oxygen Reduction and Evolution Reactions

    Science.gov (United States)

    Jiang, Zhong-Jie; Jiang, Zhongqing

    2016-06-01

    Nitrogen doped graphene hollow microspheres (NGHSs) have been used as the supports for the growth of the CoO nanoparticles. The nitrogen doped structure favors the nucleation and growth of the CoO nanoparticles and the CoO nanoparticles are mostly anchored on the quaternary nitrogen doped sites of the NGHSs with good monodispersity since the higher electron density of the quaternary nitrogen favors the nucleation and growth of the CoO nanoparticles through its coordination and electrostatic interactions with the Co2+ ions. The resulting NGHSs supported CoO nanoparticles (CoO/NGHSs) are highly active for the oxygen reduction reaction (ORR) with activity and stability higher than the Pt/C and for the oxygen evolution reaction (OER) with activity and stability comparable to the most efficient catalysts reported to date. This indicates that the CoO/NGHSs could be used as efficient bi-functional catalysts for ORR and OER. Systematic analysis shows that the superior catalytic activities of the CoO/NGHSs for ORR and OER mainly originate from the nitrogen doped structure of the NGHSs, the small size of the CoO nanoparticles, the higher specific and electroactive surface area of the CoO/NGHSs, the good electric conductivity of the CoO/NGHSs, the strong interaction between the CoO nanoparticles and the NGHSs, etc.