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Sample records for catalytic ammonia decomposition

  1. Catalytic Ammonia Decomposition Over Ruthenium Nanoparticles Supported on Nano-Titanates

    DEFF Research Database (Denmark)

    Klerke, Asbjørn; Klitgaard, Søren Kegnæs; Fehrmann, Rasmus

    2009-01-01

    Nanosized Na2Ti3O7, K2Ti6O13 and Cs2Ti6O13 materials were prepared and used as supports of ruthenium nanoparticles for catalytic ammonia decomposition. It is shown that these catalysts exhibit higher catalytic activity than ruthenium supported on TiO2 nanoparticles promoted with cesium. The diffe...

  2. Influence of Preparation Conditions on the Catalytic Performance of MoNx/SBA-15 for Ammonia Decomposition

    Institute of Scientific and Technical Information of China (English)

    Hongchao Liu; Hua Wang; Jianghan Shen; Ying Sun; Zhongmin Liu

    2006-01-01

    The influence of preparation conditions (e.g. H2-N2 ratios, final nitriding temperatures) on the performance of MoNx/SBA-15 catalysts for ammonia decomposition was investigated. The variation of catalytic activity with H2-N2 ratios may be attributed to the variation of surface compositions and particle sizes of the active components. The variation of nitriding temperatures leads to the formation of molybdenum nitride domains of varying compositions, which are responsible for the difference in their catalytic performance with respect to ammonia decomposition. At 923 K, ammonia could be completely decomof ammonia.

  3. Catalytic Ammonia Decomposition over High-Performance Ru/Graphene Nanocomposites for Efficient COx-Free Hydrogen Production

    Directory of Open Access Journals (Sweden)

    Gang Li

    2017-01-01

    Full Text Available Highly-dispersed Ru nanoparticles were grown on graphene nanosheets by simultaneously reducing graphene oxide and Ru ions using ethylene glycol (EG, and the resultant Ru/graphene nanocomposites were applied as a catalyst to ammonia decomposition for COx-free hydrogen production. Tuning the microstructures of Ru/graphene nanocomposites was easily accomplished in terms of Ru particle size, morphology, and loading by adjusting the preparation conditions. This was the key to excellent catalytic activity, because ammonia decomposition over Ru catalysts is structure-sensitive. Our results demonstrated that Ru/graphene prepared using water as a co-solvent greatly enhanced the catalytic performance for ammonia decomposition, due to the significantly improved nano architectures of the composites. The long-term stability of Ru/graphene catalysts was evaluated for COx-free hydrogen production from ammonia at high temperatures, and the structural evolution of the catalysts was investigated during the catalytic reactions. Although there were no obvious changes in the catalytic activities at 450 °C over a duration of 80 h, an aggregation of the Ru nanoparticles was still observed in the nanocomposites, which was ascribed mainly to a sintering effect. However, the performance of the Ru/graphene catalyst was decreased gradually at 500 °C within 20 h, which was ascribed mainly to both the effect of the methanation of the graphene nanosheet under a H2 atmosphere and to enhanced sintering under high temperatures.

  4. Catalytic decomposition of ammonia in a fuel gas at high temperature and pressure

    Energy Technology Data Exchange (ETDEWEB)

    Mojtahedi, W.; Abbasian, J. [Enviropower Inc., Espoo (Finland)

    1995-11-01

    In connection with the purification of fuel gas for gas turbines in the IGCC process to meet NO{sub x} standards and maintain the thermal efficiency of the process, tests were carried out with a 7.5 cm pressurized reactor to decompose ammonia at high temperature (700-900{degree}C) and pressure (2 MPa) using Ni-based catalysts. The effects of temperature, pressure, ammonia concentration and gas residence time were determined. The simulated coal gas composition was varied to allow assessment of the effect of contaminants (sulfur compounds and tars) on the ammonia decomposition efficiency of five catalysts under otherwise identical operating conditions. The results show that two of the catalysts tested are capable of efficiently reducing the concentration of ammonia in the gas. 12 refs., 13 figs.

  5. Synthesis of Ru nanoparticles confined in magnesium oxide-modified mesoporous alumina and their enhanced catalytic performance during ammonia decomposition

    KAUST Repository

    Tan, Hua

    2012-09-01

    In this work, Ru nanoparticles confined in the channels of ordered mesoporous alumina (MA) and magnesium oxide-modified ordered MA are prepared for the first time via a two-solvent technique, combined with the amorphous citrate route. Structural characterizations reveal that uniform 2-3 nm Ru nanoparticles are highly dispersed in the blockage-free channels of mesoporous supports. The Ru nanoparticles confined in MA modified with 20% molar ratio magnesium oxide exhibited a high catalytic activity and stability during ammonia decomposition due to the optimized particle size, basic support, lack of chlorine, and confined space provided by the channels of the mesoporous supports. © 2012 Elsevier B.V. All rights reserved.

  6. Catalytic decomposition of ammonia in fuel gas produced in pilot-scale pressurized fluidized-bed gasifier

    Energy Technology Data Exchange (ETDEWEB)

    Mojtahedi, W.; Ylitalo, M.; Maunula, T.; Abbasian, J. [Enviropower Inc., Tampere (Finland)

    1995-12-01

    Integrated Gasification Combined Cycle (IGCC) process, incorporating pressurized gasification of solid fuels (coal, peat, biomass) and hot gas cleanup, is being developed worldwide to generate power with high efficiency and in an environmentally acceptable manner. The gasifier product gas contains, among others, ammonia and to a lesser extent hydrogen cyanide (HCN) which are converted to oxides of nitrogen (NO{sub x}) when the gas is combusted in the gas turbine. Several nickel-based catalysts were developed and evaluated for decomposition of ammonia present in the gasifier product gas, at Enviropower`s 15 MW{sub th} pilot plant in coal- and biomass-gasification tests. Up to 75% of ammonia in the product gas was decomposed at 800-900{degree}C temperature range and 12-22 bar pressure. 11 refs., 12 figs., 4 tabs.

  7. Hydrogen peroxide catalytic decomposition

    Science.gov (United States)

    Parrish, Clyde F. (Inventor)

    2010-01-01

    Nitric oxide in a gaseous stream is converted to nitrogen dioxide using oxidizing species generated through the use of concentrated hydrogen peroxide fed as a monopropellant into a catalyzed thruster assembly. The hydrogen peroxide is preferably stored at stable concentration levels, i.e., approximately 50%-70% by volume, and may be increased in concentration in a continuous process preceding decomposition in the thruster assembly. The exhaust of the thruster assembly, rich in hydroxyl and/or hydroperoxy radicals, may be fed into a stream containing oxidizable components, such as nitric oxide, to facilitate their oxidation.

  8. Modeling and simulation of ammonia removal from purge gases of ammonia plants using a catalytic Pd-Ag membrane reactor.

    Science.gov (United States)

    Rahimpour, M R; Asgari, A

    2008-05-01

    In this work, the removal of ammonia from synthesis purge gas of an ammonia plant has been investigated. Since the ammonia decomposition is thermodynamically limited, a membrane reactor is used for complete decomposition. A double pipe catalytic membrane reactor is used to remove ammonia from purge gas. The purge gas is flowing in the reaction side and is converted to hydrogen and nitrogen over nickel-alumina catalyst. The hydrogen is transferred through the Pd-Ag membrane of tube side to the shell side. A mathematical model including conservation of mass in the tube and shell side of reactor is proposed. The proposed model was solved numerically and the effects of different parameters on the rector performance were investigated. The effects of pressure, temperature, flow rate (sweep ratio), membrane thickness and reactor diameter have been investigated in the present study. Increasing ammonia conversion was observed by raising the temperature, sweep ratio and reducing membrane thickness. When the pressure increases, the decomposition is gone toward completion but, at low pressure the ammonia conversion in the outset of reactor is higher than other pressures, but complete destruction of the ammonia cannot be achieved. The proposed model can be used for design of an industrial catalytic membrane reactor for removal of ammonia from ammonia plant and reducing NO(x) emissions.

  9. Selective catalytic oxidation of ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Leppaelahti, J.; Koljonen, T. [VTT Energy, Espoo (Finland)

    1996-12-31

    In the combustion of fossil fuels, the principal source of nitrogen oxides is nitrogen bound in the fuel structure. In gasification, a large part of fuel nitrogen forms NH{sub 3}, which may form nitrogen oxides during gas combustion. If NH{sub 3} and other nitrogen species could be removed from hot gas, the NO emission could be considerably reduced. However, relatively little attention has been paid to finding new means of removing nitrogen compounds from the hot gasification gas. The possibility of selectively oxidizing NH{sub 3} to N{sub 2} in the hot gasification has been studied at VTT Energy. The largest NH{sub 3} reductions have been achieved by catalytic oxidation on aluminium oxides. (author) (4 refs.)

  10. Effect of H{sub 2}S on the catalytic decomposition of tar and ammonia with dolomite and sintered iron ore in synthetic gasification gas

    Energy Technology Data Exchange (ETDEWEB)

    Hepola, J. [VTT Energy, Espoo (Finland)

    1996-12-31

    The toluene-decomposing activity of calcined dolomite was not affected by the H{sub 2}S content of synthetic gasification gas. Iron was active with respect to toluene and ammonia at metallic state. The increase of the H{sub 2}S content of synthetic gasification gas (0 - 500 ppmv) decreased the tar-decomposing activity but not the ammonia- decomposing activity of sintered iron ore. (author) (12 refs.)

  11. Catalytic synthesis of ammonia using vibrationally excited nitrogen molecules

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Henriksen, Niels Engholm; Billing, Gert D.

    1992-01-01

    The dissociation of nitrogen is the rate-limiting step in the catalytic synthesis of ammonia. Theoretical calculations have shown that the dissociative sticking probability of molecular nitrogen on catalytic active metal surfaces is enhanced by orders of magnitude when the molecules...

  12. Catalytic activity of carbons for methane decomposition reaction

    Energy Technology Data Exchange (ETDEWEB)

    Muradov, Nazim; Smith, Franklyn; T-Raissi, Ali [Florida Solar Energy Center, University of Central Florida, 1679 Clearlake Road, Cocoa, FL 32922 (United States)

    2005-05-15

    Catalytic decomposition of methane is an environmentally attractive approach to CO{sub 2}-free production of hydrogen. The objective of this work is to evaluate catalytic activity of a wide range of carbon materials for methane decomposition reaction and determine major factors governing their activity. It was demonstrated that the catalytic activity of carbon materials for methane decomposition is mostly determined by their structural and surface properties. Kinetics of methane decomposition reaction over disordered (amorphous) carbons such as carbon black and activated carbon were determined. The mechanism of carbon-catalyzed methane decomposition reaction and the nature of active sites on the carbon surface are discussed in this paper.

  13. Removal of ammonia solutions used in catalytic wet oxidation processes.

    Science.gov (United States)

    Hung, Chang Mao; Lou, Jie Chung; Lin, Chia Hua

    2003-08-01

    Ammonia (NH(3)) is an important product used in the chemical industry, and is common place in industrial wastewater. Industrial wastewater containing ammonia is generally either toxic or has concentrations or temperatures such that direct biological treatment is unfeasible. This investigation used aqueous solutions containing more of ammonia for catalytic liquid-phase oxidation in a trickle-bed reactor (TBR) based on Cu/La/Ce composite catalysts, prepared by co-precipitation of Cu(NO(3))(2), La(NO(3))(2), and Ce(NO(3))(3) at 7:2:1 molar concentrations. The experimental results indicated that the ammonia conversion of the wet oxidation in the presence of the Cu/La/Ce composite catalysts was determined by the Cu/La/Ce catalyst. Minimal ammonia was removed from the solution by the wet oxidation in the absence of any catalyst, while approximately 91% ammonia removal was achieved by wet oxidation over the Cu/La/Ce catalyst at 230 degrees C with oxygen partial pressure of 2.0 MPa. Furthermore, the effluent streams were conducted at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes, and a reaction pathway was found linking the oxidizing ammonia to nitric oxide, nitrogen and water. The solution contained by-products, including nitrates and nitrites. Nitrite selectivity was minimized and ammonia removal maximized when the feed ammonia solution had a pH of around 12.0.

  14. Catalytic synthesis of ammonia using vibrationally excited nitrogen

    DEFF Research Database (Denmark)

    Henriksen, Niels Engholm; Billing, Gert D.; Hansen, Flemming Yssing

    1992-01-01

    In a previous study we have considered the catalytic synthesis of ammonia in the presence of vibrationally excited nitrogen. The distribution over vibrational states was assumed to be maintained during the reaction, and it was shown that the yield of ammonia increased considerably compared...... to that from conventional synthesis. In the present study the nitrogen molecules are only excited at the inlet of a plug flow reactor, and the importance of vibrational relaxation is investigated. We show that vibrational excitation can give an enhanced yield of ammonia also in the situation where vibrational...

  15. Assessing the reliability of calculated catalytic ammonia synthesis rates

    DEFF Research Database (Denmark)

    Medford, Andrew James; Wellendorff, Jess; Vojvodic, Aleksandra

    2014-01-01

    We introduce a general method for estimating the uncertainty in calculated materials properties based on density functional theory calculations. We illustrate the approach for a calculation of the catalytic rate of ammonia synthesis over a range of transition-metal catalysts. The correlation...

  16. Trends in catalytic NO decomposition over transition metal surfaces

    DEFF Research Database (Denmark)

    Falsig, Hanne; Bligaard, Thomas; Rass-Hansen, Jeppe

    2007-01-01

    The formation of NOx from combustion of fossil and renewable fuels continues to be a dominant environmental issue. We take one step towards rationalizing trends in catalytic activity of transition metal catalysts for NO decomposition by combining microkinetic modelling with density functional...... theory calculations. We show specifically why the key problem in using transition metal surfaces to catalyze direct NO decomposition is their significant relative overbinding of atomic oxygen compared to atomic nitrogen....

  17. Ammonia synthesis and decomposition on a Ru-based catalyst modeled by first-principles

    DEFF Research Database (Denmark)

    Hellman, A.; Honkala, Johanna Karoliina; Remediakis, Ioannis

    2009-01-01

    A recently published first-principles model for the ammonia synthesis on an unpromoted Ru-based catalyst is extended to also describe ammonia decomposition. In addition, further analysis concerning trends in ammonia productivity, surface conditions during the reaction, and macro......-properties, such as apparent activation energies and reaction orders are provided. All observed trends in activity are captured by the model and the absolute value of ammonia synthesis/decomposition productivity is predicted to within a factor of 1-100 depending on the experimental conditions. Moreover it is shown: (i...

  18. Ammonia Decomposition over Bimetallic Nitrides Supported on γ-Al2O3

    Institute of Scientific and Technical Information of China (English)

    Chun Shan LU; Xiao Nian LI; Yi Feng ZHU; Hua Zhang LIU; Chun Hui ZHOU

    2004-01-01

    A series of monometallic nitrides and bimetallic nitrides were prepared by temperature-programmed reaction with NH3. The effects of Co, Ni and Fe additives and the synergic action between Fe, Co, Ni and Mo on the ammonia decomposition activity were investigated. TPR-MS, XRD were also carried out to obtain better insight into the structure of the bimetallic nitride. The results of ammonia decomposition activity show that bimetallic nitrides are more active than monometallic nitrides or bimetallic oxides.

  19. KINETIC ANALYSIS OF THE CATALYTIC DECOMPOSITION OF HYDRAZINE

    Directory of Open Access Journals (Sweden)

    J.E. de MEDEIROS

    1998-06-01

    Full Text Available The bond-order conservation method was used to study the catalytic decomposition of N2H4. Variation in the activation energy, E, of the most relevant steps was calculated as a function of the enthalpy of adsorption of N, QN, between 0 and 1250 kJmol-1. Results suggest that below QN = 520 kJmol-1 the catalytic decomposition of N2H4 produces mostly N2 and H2. Above QN = 520 kJmol-1, NH3 and N2 are the main products. Near QN = 520 kJmol-1 N2, H2 and NH3 are obtained, in agreement with experimental results on different metals.

  20. Thermodynamics behind carbon nanotube growth via endothermic catalytic decomposition reaction.

    Science.gov (United States)

    Harutyunyan, Avetik R; Kuznetsov, Oleg A; Brooks, Christopher J; Mora, Elena; Chen, Gugang

    2009-02-24

    Carbon filaments can be grown using hydrocarbons with either exothermic or endothermic catalytic decomposition enthalpies. By in situ monitoring the evolution of the reaction enthalpy during nanotube synthesis via methane gas, we found that although the decomposition reaction of methane is endothermic an exothermic process is superimposed which accompanies the nanotube growth. Analysis shows that the main contributor in this liberated heat is the radiative heat transfer from the surroundings, along with dehydrogenation reaction of in situ formed secondary hydrocarbons on the catalyst surface and the carbon hydrogenation/oxidation processes. This finding implies that nanotube growth process enthalpy is exothermic, and particularly, it extends the commonly accepted temperature gradient driven growth mechanism to the growth via hydrocarbons with endothermic decomposition enthalpy.

  1. Catalytic Methane Decomposition over Fe-Al2O3

    KAUST Repository

    Zhou, Lu

    2016-05-09

    The presence of a Fe-FeAl2O4 structure over an Fe-Al2O3 catalysts is demonstrated to be vital for the catalytic methane decomposition (CMD) activity. After H2 reduction at 750°C, Fe-Al2O3 prepared by means of a fusion method, containing 86.5wt% FeAl2O4 and 13.5wt% Fe0, showed a stable CMD activity at 750°C for as long as 10h. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Monnte Carlo Simulation of Kinetics of Ammonia Oxidative Decomposition over the Commercial Propylene Ammoxidation Catalyst(Mo-Bi)

    Institute of Scientific and Technical Information of China (English)

    罗正鸿; 詹晓力; 等

    2003-01-01

    Monte Carlo method is applied to investigate the kinetics of ammonia oxidative decomposition over the commercial propylene ammoxidation catalyst(Mo-Bi).The simulation is quite in agreement with experimetal results.Monte Carlo simulation proves that the process of ammonia oxidation decomposition is a two-step reaction.

  3. New insight in the microscopic mechanism of the catalytic synthesis of ammonia

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Henriksen, Niels Engholm; Billing, Gert D.

    1995-01-01

    Theoretical quantum calculations and molecular beam experiments of the dissociative chemisorption of N-2 molecules on catalytic active metal surfaces have given new insight in the fundamental process of the ammonia synthesis. This new approach to the study of catalytic process supplements...... to dissociation. Our analysis of the dissociation process suggests that it is not possible to define, in some well specified way, a precursor state at typical temperatures in the technical ammonia synthesis. The kinetic scheme for the complete ammonia synthesis without the precursor state can still account...... for the observed conversion to ammonia. We have constructed an empirical potential energy surface for N-2/Fe(111) which has barriers to dissociation even larger than for the previously studied N-2/Re system. It is shown that the presence of barriers is consistent with the observation that the activation energy...

  4. 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.

  5. Catalytic spectrophotometric determination of iodine in coal by pyrohydrolysis decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Wu Daishe [School of Environmental Science and Engineering, Nanchang University, Nanchang 330031 (China); Institute of Geographic Sciences and Resources Research, CAS, Beijing 100101 (China)], E-mail: dswu@ncu.edu.cn; Deng Haiwen [School of Environmental Science and Engineering, Nanchang University, Nanchang 330031 (China); Wang Wuyi [Institute of Geographic Sciences and Resources Research, CAS, Beijing 100101 (China); Xiao Huayun [School of Environmental Science and Engineering, Nanchang University, Nanchang 330031 (China)

    2007-10-10

    A method for the determination of iodine in coal using pyrohydrolysis for sample decomposition was proposed. A pyrohydrolysis apparatus system was constructed, and the procedure was designed to burn and hydrolyse coal steadily and completely. The parameters of pyrohydrolysis were optimized through the orthogonal experimental design. Iodine in the absorption solution was evaluated by the catalytic spectrophotometric method, and the absorbance at 420 nm was measured by a double-beam UV-visible spectrophotometer. The limit of detection and quantification of the proposed method were 0.09 {mu}g g{sup -1} and 0.29 {mu}g g{sup -1}, respectively. After analysing some Chinese soil reference materials (SRMs), a reasonable agreement was found between the measured values and the certified values. The accuracy of this approach was confirmed by the analysis of eight coals spiked with SRMs with an indexed recovery from 94.97 to 109.56%, whose mean value was 102.58%. Six repeated tests were conducted for eight coal samples, including high sulfur coal and high fluorine coal. A good repeatability was obtained with a relative standard deviation value from 2.88 to 9.52%, averaging 5.87%. With such benefits as simplicity, precision, accuracy and economy, this approach can meet the requirements of the limits of detection and quantification for analysing iodine in coal, and hence it is highly suitable for routine analysis.

  6. 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

  7. A Novel Cu-Mo/ZSM-5 Catalyst for NOx Catalytic Reduction with Ammonia

    Institute of Scientific and Technical Information of China (English)

    Zhe Li; Dang Li; Wei Huang; Kechang Xie

    2005-01-01

    The Cu-Mo/ZSM-5 catalysts with different Cu/Mo ratios were prepared by wet impregnation method, and their catalytic performance for selective catalytic reduction of NOx was studied. The results showed that Cu-Mo/ZSM-5 is a very effective catalyst for NOx catalytic reduction with ammonia, especially when Cu/Mo molar ratio is about 1.5. It not only exhibited the extremely high catalytic activity, but also showed good stability for O2. The bulk phase structure of Cu-Mo/ZSM-5 catalysts was determined by XRD technique, and the results indicated that there is a maximum dispersion for Cu species when Cu/Mo molar ratio is 1.5, and an interaction between Cu and Mo along with HZSM-5 may be present in Cu-Mo/ZSM-5, which may possibly result in a special structure favorable for the catalytic reduction of NOx over Cu-Mo/ZSM-5 catalyst.

  8. Thermally Stable Hierarchical Nanostructures of Ultrathin MoS2 Nanosheet-Coated CeO2 Hollow Spheres as Catalyst for Ammonia Decomposition.

    Science.gov (United States)

    Gong, Xueyun; Gu, Ying-Qiu; Li, Na; Zhao, Hongyang; Jia, Chun-Jiang; Du, Yaping

    2016-04-18

    MoS2 ultrathin nanosheet-coated CeO2 hollow sphere (CeO2@MoS2) hybrid nanostructures with a 3D hierarchical configuration were successfully constructed from a facile two-step wet chemistry strategy: first, CeO2 formed on a silica core which served as a template and was subsequently removed by NaOH solution to attain hollow spheres, and then few-layered ultrathin MoS2 nanosheets were deposited on the CeO2 hollow spheres through a hydrothermal process. As a proof of concept application, the as-prepared CeO2@MoS2 hybrid nanostructures were used as catalytic material, which exhibited enhanced catalytic activity in ammonia decomposition for H2 production at high temperature. It was demonstrated that, even with a structural transformation from MoS2 to MoNx under harsh conditions of ammonia decomposition at high temperature (700 °C), the 3D hierarchical nanostructures of the CeO2@MoNx were well kept, indicating the important role of the CeO2 support.

  9. Study on the Carbon-Methanation and Catalytic Activity of Ru/AC for Ammonia Synthesis

    Institute of Scientific and Technical Information of China (English)

    祝一锋; 李小年; 季德春; 刘化章

    2004-01-01

    The effects of promoters K, Ba, Sm on the resistance to carbon-methanation and catalytic activity of ruthenium supported on active carbon (Ru/AC) for ammonia synthesis have been studied by means of TG-DTG (thermalgravity-differential thermalgravity), temperature-programmed desorption, and activity test. Promoters Ba,K, and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly. Much higher activity can be reached for Ru/AC catalyst with bi- or tri-promoters. Indeed, the triply promoted catalyst showed the highest activity, coupled to a surprisingly high resistance to methanation. The ability of resistance of promoter to methanation of Ru/AC catalyst is dependent on the adsorption intensity of hydrogen. The strong adsorption of hydrogen would enhance methanation and impact the adsorption of nitrogen, which results in the decrease of catalytic activity.

  10. Conversion of the refractory ammonia and acetic acid in catalytic wet air oxidation of animal byproducts.

    Science.gov (United States)

    Fontanier, Virginie; Zalouk, Sofiane; Barbati, Stéphane

    2011-01-01

    Wet air oxidation (WAO) and catalytic wet air oxidation (CWAO) of slaughtered animal byproducts (ABPs) were investigated. Two step experiment was carried out consisting of a non-catalysed WAO run followed by a CWAO run at 170-275 degrees C, 20 MPa, and reaction time 180 min. The WAO (1st step) of sample (5 g/L total organic carbon (TOC)) yielded (82.0 +/- 4)% TOC removal and (78.4 +/- 13.2)% conversion of the initial organic-N into NH4(+)-N. Four metal catalysts (Pd, Pt, Rh, Ru) supported over alumina have been tested in catalytic WAO (2nd step) at elevated pH to enhance ammonia conversion and organic matter removal, particularly acetic acid. It was found that the catalysts Ru, Pt, and Rh had significant effects on the TOC removal (95.1%, 99.5% and 96.7%, respectively) and on the abatement of ammonia (93.4%, 96.7% and 96.3%, respectively) with high nitrogen selectivity. The catalyst Pd was found to have the less activity while Pt had the best performance. The X-Ray diffraction analysis showed that the support of catalyst was not stable under the experimental conditions since it reacted with phosphate present in solution. Nitrite and nitrate ions were monitored during the oxidation reaction and it was concluded that CWAO of ammonia in real waste treatment framework was in good agreement with the results obtained from the literature for ideal solutions of ammonia.

  11. Kinetics Study of the Effect of Oxygen on Ammonia Decomposition on Ru%Ru上有氧条件下氨分解的动力学研究

    Institute of Scientific and Technical Information of China (English)

    李忠来; 梁长海; 王德峥; 李灿

    2004-01-01

    @@ It has been shown that Ru is valid for the synthesis and decomposition of ammonia[1,2]. Further study of ammonia adsorption and its decomposition products desorption on Ru will be important. Previous studies of ammonia adsorption on Ru mainly focused on the ammonia synthesis and hydrogen production in the absence of oxygen[3], only a few investigations on ammonia decomposition in the presence of oxygen have been reported[4,5], and the effect of adsorbed oxygen on the rates of ammonia decomposition and product formation on Ru are still not well understood. In this paper, NH3 decomposition on Ru/SiO2 was investigated in the presence of oxygen using a temporal analysis of products (TAP) reactor.

  12. Catalytic decomposition of low level ozone with gold nanoparticles supported on activated carbon

    Institute of Scientific and Technical Information of China (English)

    Pengyi ZHANG; Bo ZHANG; Rui SHI

    2009-01-01

    Highly dispersed gold nanoparticles were supported on coal-based activated carbon (AC) by a sol immobilization method and were used to investigate their catalytic activity for low-level ozone decomposition at ambient temperature. Nitrogen adsorption-desorption,scanning electron microscope (SEM), and X-ray photo-electron spectroscopy (XPS) were used to characterize the catalysts before and after ozone decomposition. The results showed that the supported gold nanoparticles prepared with microwave heating were much smaller and more uniformly dispersed on the activated carbon than those prepared with traditional conduction heating, exhibiting higher catalytic activity for ozone decomposition. The pH values of gold precursor solution significantly influenced the catalytic activity of supported gold for ozone decomposition, and the best pH value was 8. In the case of space velocity of 120000 h-1, inlet ozone concentration of 50mg/m3, and relative humidity of 45%, the Au/AC catalyst maintained the ozone removal ratio at 90.7% after 2500 min. After being used for ozone decomposition, the surface carbon of the catalyst was partly oxidized and the oxygen content increased accordingly, while its specific surface area and pore volume only decreased a little.Ozone was mainly catalytically decomposed by the gold nanoparticles supported on the activated carbon.

  13. Macrophyte decomposition in a surface-flow ammonia-dominated constructed wetland: Rates associated with environmental and biotic variables

    Science.gov (United States)

    Thullen, J.S.; Nelson, S.M.; Cade, B.S.; Sartoris, J.J.

    2008-01-01

    Decomposition of senesced culm material of two bulrush species was studied in a surface-flow ammonia-dominated treatment wetland in southern California. Decomposition of the submerged culm material during summer months was relatively rapid (k = 0.037 day-1), but slowed under extended submergence (up to 245 days) and during fall and spring sampling periods (k = 0.009-0.014 day-1). Stepwise regression of seasonal data indicated that final water temperature and abundance of the culm-mining midge, Glyptotendipes, were significantly associated with culm decomposition. Glyptotendipes abundance, in turn, was correlated with water quality parameters such as conductivity and dissolved oxygen and ammonia concentrations. No differences were detected in decomposition rates between the bulrush species, Schoenoplectus californicus and Schoenoplectus acutus.

  14. Energy Diagram for the Catalytic Decomposition of Hydrogen Peroxide

    Science.gov (United States)

    Tatsuoka, Tomoyuki; Koga, Nobuyoshi

    2013-01-01

    Drawing a schematic energy diagram for the decomposition of H[subscript 2]O[subscript 2] catalyzed by MnO[subscript 2] through a simple thermometric measurement outlined in this study is intended to integrate students' understanding of thermochemistry and kinetics of chemical reactions. The reaction enthalpy, delta[subscript r]H, is…

  15. Conversion of the refractory ammonia and acetic acid in catalytic wet air oxidation of animal byproducts

    Institute of Scientific and Technical Information of China (English)

    Virginie Fontanier; Sofiane Zalouk; Stéphane Barbati

    2011-01-01

    Wet air oxidation (WAO) and catalytic wet air oxidation (CWAO) of slaughtered animal byproducts (ABPs) were investigated.Two step experiment was carried out consisting ofa non-catalysed WAO run followed by a CWAO run at 170-275℃, 20 MPa, and reaction time 180 min.The WAO (1st step) of sample (5 g/L total organic carbon (TOC)) yielded (82.0 ± 4)% TOC removal and (78.4 ± 13.2)%conversion of the initial organic-N into NH4+-N.Four metal catalysts (Pd, Pt, Rh, Ru) supported over alumina have been tested in catalytic WAO (2nd step) at elevated pH to enhance ammonia conversion and organic matter removal, particularly acetic acid.It was found that the catalysts Ru, Pt, and Rh had significant effects on the TOC removal (95.1%, 99.5% and 96.7%, respectively) and on the abatement of ammonia (93.4%, 96.7% and 96.3%, respectively) with high nitrogen selectivity.The catalyst Pd was found to have the less activity while Pt had the best performance.The X-Ray diffraction analysis showed that the support of catalyst was not stable under the experimental conditions since it reacted with phosphate present in solution.Nitrite and nitrate ions were monitored during the oxidation reaction and it was concluded that CWAO of ammonia in real waste treatment framework was in good agreement with the results obtained from the literature for ideal solutions of ammonia.

  16. The roles of active site residues in the catalytic mechanism of methylaspartate ammonia-lyase.

    Science.gov (United States)

    Raj, Hans; Poelarends, Gerrit J

    2013-01-01

    Methylaspartate ammonia-lyase (MAL; EC 4.3.1.2) catalyzes the reversible addition of ammonia to mesaconate to yield l-threo-(2S,3S)-3-methylaspartate and l-erythro-(2S,3R)-3-methylaspartate as products. In the proposed minimal mechanism for MAL of Clostridium tetanomorphum, Lys-331 acts as the (S)-specific base catalyst and abstracts the 3S-proton from l-threo-3-methylaspartate, resulting in an enolate anion intermediate. This enolic intermediate is stabilized by coordination to the essential active site Mg(2+) ion and hydrogen bonding to the Gln-329 residue. Collapse of this intermediate results in the release of ammonia and the formation of mesaconate. His-194 likely acts as the (R)-specific base catalyst and abstracts the 3R-proton from the l-erythro isomer of 3-methylaspartate, yielding the enolic intermediate. In the present study, we have investigated the importance of the residues Gln-73, Phe-170, Gln-172, Tyr-356, Thr-360, Cys-361 and Leu-384 for the catalytic activity of C. tetanomorphum MAL. These residues, which are part of the enzyme surface lining the substrate binding pocket, were subjected to site-directed mutagenesis and the mutant enzymes were characterized for their structural integrity, ability to catalyze the amination of mesaconate, and regio- and diastereoselectivity. Based on the observed properties of the mutant enzymes, combined with previous structural studies and protein engineering work, we propose a detailed catalytic mechanism for the MAL-catalyzed reaction, in which the side chains of Gln-73, Gln-172, Tyr-356, Thr-360, and Leu-384 provide favorable interactions with the substrate, which are important for substrate binding and activation. This detailed knowledge of the catalytic mechanism of MAL can serve as a guide for future protein engineering experiments.

  17. Catalytic decomposition of hydrogen peroxide on anthraquinonecyanine and phthalocyanine metal complexes in acid and alkaline electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Pobedinskiy, S.N.; Trofimenko, A.A.; Zharnikova, M.A.

    1985-12-01

    A study of octaoxyanthraquinonecyanines (OOATsM) and phthalocyanines (FTs) of cobalt, iron, and manganese determined their catalytic activity in the hydrogen peroxide decomposition reaction. Hydrogen peroxide decomposition on OOATsM and FTs of the metals studied follows the kinetic mechanisms of a reaction of the first order regardless of the central ion of the metal. Complexes with a central atom of iron are most active in decomposition of hydrogen peroxide. Catalytic activity of FTsFe exceeds that of FTsCo more than 10-fold. FTs are 10-fold greater than OOATsM in catalytic activity. Change from an acid to an alkali medium did not affect the kinetic mechanisms of the decomposition reaction but the reaction rate on both a carrier and on metal complexes is higher in an alkaline medium than in an acid medium. The affect of an alkaline medium on the hydrogen peroxide decomposition rate is greater for FTS complexes than for anthraquinone-cyanines. 5 references, 2 figures.

  18. Catalytic non-thermal plasma reactor for the decomposition of a mixture of volatile organic compounds

    Indian Academy of Sciences (India)

    B Rama Raju; E Linga Reddy; J Karuppiah; P Manoj Kumar Reddy; Ch Subrahmanyam

    2013-05-01

    The decomposition of mixture of selected volatile organic compounds (VOCs) has been studied in a catalytic non-thermal plasma dielectric barrier discharge reactor. The VOCs mixture consisting n-hexane, cyclo-hexane and -xylene was chosen for the present study. The decomposition characteristics of mixture of VOCs by the DBD reactor with inner electrode modified with metal oxides of Mn and Co was studied. The results indicated that the order of the removal efficiency of VOCs followed as -xylene > cyclo-hexane > -hexane. Among the catalytic study, MnOx/SMF (manganese oxide on sintered metal fibres electrode) shows better performance, probably due to the formation of active oxygen species by in situ decomposition of ozone on the catalyst surface. Water vapour further enhanced the performance due to the in situ formation of OH radicals.

  19. 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

    2011-01-01

    Cu/TiO2, Fe/TiO2 and heteropoly acid promoted Cu/TiO2, Fe/TiO2 catalysts were prepared and characterized by N2 physisorption, XRPD, NH3-TPD, H2-TPR and EPR. The catalysts exhibited only crystalline TiO2 phases with the active metals and promoters in highly dispersed state. The acidic properties...... 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...... 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...

  20. Assessment of the Vapor Phase Catalytic Ammonia Removal (VPCAR) Technology at the MSFC ECLS Test Facility

    Science.gov (United States)

    Tomes, Kristin; Long, David; Carter, Layne; Flynn, Michael

    2007-01-01

    The Vapor Phase Catalytic Ammonia. Removal (VPCAR) technology has been previously discussed as a viable option for. the Exploration Water Recovery System. This technology integrates a phase change process with catalytic oxidation in the vapor phase to produce potable water from exploration mission wastewaters. A developmental prototype VPCAR was designed, built and tested under funding provided by a National Research. Announcement (NRA) project. The core technology, a Wiped Film Rotating Device (WFRD) was provided by Water Reuse Technologies under the NRA, whereas Hamilton Sundstrand Space Systems International performed the hardware integration and acceptance test. of the system. Personnel at the-Ames Research Center performed initial systems test of the VPCAR using ersatz solutions. To assess the viability of this hardware for Exploration. Life Support (ELS) applications, the hardware has been modified and tested at the MSFC ECLS Test facility. This paper summarizes the hardware modifications and test results and provides an assessment of this technology for the ELS application.

  1. Electrochemical and catalytic properties of Ni/BaCe0.75Y0.25O3-δ anode for direct ammonia-fueled solid oxide fuel cells.

    Science.gov (United States)

    Yang, Jun; Molouk, Ahmed Fathi Salem; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

    2015-04-01

    In this study, Ni/BaCe0.75Y0.25O3-δ (Ni/BCY25) was investigated as an anode for direct ammonia-fueled solid oxide fuel cells. The catalytic activity of Ni/BCY25 for ammonia decomposition was found to be remarkably higher than Ni/8 mol % Y2O3-ZrO2 and Ni/Ce0.90Gd0.10O1.95. The poisoning effect of water and hydrogen on ammonia decomposition reaction over Ni/BCY25 was evaluated. In addition, an electrolyte-supported SOFC employing BaCe0.90Y0.10O3-δ (BCY10) electrolyte and Ni/BCY25 anode was fabricated, and its electrochemical performance was investigated at 550-650 °C with supply of ammonia and hydrogen fuel gases. The effect of water content in anode gas on the cell performance was also studied. Based on these results, it was concluded that Ni/BCY25 was a promising anode for direct ammonia-fueled SOFCs. An anode-supported single cell denoted as Ni/BCY25|BCY10|Sm0.5Sr0.5CoO3-δ was also fabricated, and maximum powder density of 216 and 165 mW cm(-2) was achieved at 650 and 600 °C, for ammonia fuel, respectively.

  2. IN SITU INFRARED STUDY OF CATALYTIC DECOMPOSITION OF NITRIC OXIDE (NO)

    Energy Technology Data Exchange (ETDEWEB)

    Unknown

    1999-12-31

    The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccessful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst. The authors have investigated the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. The silanation approach failed to stabilize Cu-ZSM-5 activity under hydrothermal condition. Silanation blocked the oxygen migration and inhibited oxygen desorption. Oxygen spillover was found to be an effective approach for promoting NO decomposition activity on Pt-based catalysts. Detailed mechanistic study revealed the oxygen inhibition in NO decomposition and reduction as the most critical issue in developing an effective catalytic approach for controlling NO emission.

  3. 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.

  4. The catalytic removal of ammonia and nitrogen oxides from spacecabin atmospheres

    Science.gov (United States)

    Gully, A. J.; Graham, R. R.; Halligan, J. E.; Bentsen, P. C.

    1973-01-01

    Investigations were made on methods for the removal of ammonia and to a lesser extent nitrogen oxides in low concentrations from air. The catalytic oxidation of ammonia was studied over a temperature range of 250 F to 600 F and a concentration range 20 ppm to 500 ppm. Of the catalysts studied, 0.5 percent ruthenium supported on alumina was found to be superior. This material is active at temperatures as low as 250 F and was found to produce much less nitrous oxide than the other two active catalysts, platinum on alumina and Hopcalite. A quantitative design model was developed which will permit the performance of an oxidizer to be calculated. The ruthenium was found to be relatively insensitive to low concentrations of water and to oxygen concentration between 21 percent and 100 percent. Hydrogen sulfide was found to be a poison when injected in relatively large quantities. The adsorption of ammonia by copper sulfate treated silica gel was investigated at temperatures of 72 F and 100 F. A quantitative model was developed for predicting adsorption bed behavior.

  5. Nitrated graphene oxide and its catalytic activity in thermal decomposition of ammonium perchlorate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wenwen; Luo, Qingping; Duan, Xiaohui [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Zhou, Yong [Eco-materials and Renewable Energy Research Center (ERERC), School of Physics, National Lab of Solid State Microstructure, ERERC, Nanjing University, Nanjing 210093 (China); Pei, Chonghua, E-mail: peichonghua@swust.edu.cn [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China)

    2014-02-01

    Highlights: • The NGO was synthesized by nitrifying homemade GO. • The N content of resulted NGO is up to 1.45 wt.%. • The NGO can facilitate the decomposition of AP and release much heat. - Abstract: Nitrated graphene oxide (NGO) was synthesized by nitrifying homemade GO with nitro-sulfuric acid. Fourier transform infrared spectroscopy (FTIR), laser Raman spectroscopy, CP/MAS {sup 13}C NMR spectra and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure of NGO. The thickness and the compositions of GO and NGO were analyzed by atomic force microscopy (AFM) and elemental analysis (EA), respectively. The catalytic effect of the NGO for the thermal decomposition of ammonium perchlorate (AP) was investigated by differential scanning calorimetry (DSC). Adding 10% of NGO to AP decreases the decomposition temperature by 106 °C and increases the apparent decomposition heat from 875 to 3236 J/g.

  6. Catalytic effects of inorganic acids on the decomposition of ammonium nitrate.

    Science.gov (United States)

    Sun, Jinhua; Sun, Zhanhui; Wang, Qingsong; Ding, Hui; Wang, Tong; Jiang, Chuansheng

    2005-12-09

    In order to evaluate the catalytic effects of inorganic acids on the decomposition of ammonium nitrate (AN), the heat releases of decomposition or reaction of pure AN and its mixtures with inorganic acids were analyzed by a heat flux calorimeter C80. Through the experiments, the different reaction mechanisms of AN and its mixtures were analyzed. The chemical reaction kinetic parameters such as reaction order, activation energy and frequency factor were calculated with the C80 experimental results for different samples. Based on these parameters and the thermal runaway models (Semenov and Frank-Kamenestkii model), the self-accelerating decomposition temperatures (SADTs) of AN and its mixtures were calculated and compared. The results show that the mixtures of AN with acid are more unsteady than pure AN. The AN decomposition reaction is catalyzed by acid. The calculated SADTs of AN mixtures with acid are much lower than that of pure AN.

  7. 双分子水和氨气催化CF3OH分子裂解的理论研究%Theoretical Study on Decomposition of CF3OH Catalyzed by Water Dimer and Ammonia

    Institute of Scientific and Technical Information of China (English)

    龙波; 谭兴凤; 隆正文; 任达森; 张为俊

    2011-01-01

    The G3 and CBS-QB3 theoretical methods are employed to study the decomposition of CF3OH into FCFO and HF by water, water dimmer, and ammonia. The decomposition of CF3OH into FCFO and HF is unlikely to occur in the atmosphere due to the high activated energy of 88.7 k J/mol at the G3 level of theory. However, the computed results predict that the barrier for unimolecular decomposition of CF3OH is decreased to 25.1 k J/mol from 188.7 k J/mol with the aid of NH3 at the G3 level of theory, which shows that the ammonia play a strong catalytic effect on the split of CF3OH. In addition, the calculated rate constants show that the decomposition of CF3OH by NH3 is faster than those of H2Oand the water dimmer by 109 and 105 times respectively. The rate constants combined with the corresponding concentrations of these species demonstrate that the reaction CF3 OH with NH3 via TS4 is of great importance for the decomposition of CF3OH in the atmosphere.

  8. Ammonia for hydrogen storage: challenges and opportunities

    DEFF Research Database (Denmark)

    Klerke, Asbjørn; Christensen, Claus H.; Nørskov, Jens Kehlet

    2008-01-01

    The possibility of using ammonia as a hydrogen carrier is discussed. Compared to other hydrogen storage materials, ammonia has the advantages of a high hydrogen density, a well-developed technology for synthesis and distribution, and easy catalytic decomposition. Compared to hydrocarbons...... and alcohols, it has the advantage that there is no CO2 emission at the end user. The drawbacks are mainly the toxicity of liquid ammonia and the problems related to trace amounts of ammonia in the hydrogen after decomposition. Storage of ammonia in metal ammine salts is discussed, and it is shown...... that this maintains the high volumetric hydrogen density while alleviating the problems of handling the ammonia. Some of the remaining challenges for research in ammonia as a hydrogen carrier are outlined....

  9. Solar production of catalytic filamentous carbon by thermal decomposition of hydrocarbons and carbon monoxide

    Energy Technology Data Exchange (ETDEWEB)

    Kirillov, V.A.; Kuvshinov, G.G.; Mogilnykh, Yu.I. [Boreskov Institute of Catalysis, Novosibirsk (Russian Federation); Reller, A. [University of Hamburg (Germany); Steinfeld, A.; Weidenkaff, A.; Meier, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Concentrated solar radiation was used as the clean source of process heat for the production of Catalytic Filamentous Carbon (CFC) by thermal decomposition of gaseous hydrocarbons and by CO disproportionation in the presence of small metal catalyst particles. Depending on the catalyst, two different types of CFC, namely nano tubes and nano fibers, were obtained in solar experiments at the PSI solar furnace. (author) 2 figs., 1 tab., 7 refs.

  10. Investigation of the degradation mechanism of catalytic wires during oxidation of ammonia process

    Science.gov (United States)

    Pura, Jarosław; Wieciński, Piotr; Kwaśniak, Piotr; Zwolińska, Marta; Garbacz, Halina; Zdunek, Joanna; Laskowski, Zbigniew; Gierej, Maciej

    2016-12-01

    The most common catalysts for the ammonia oxidation process are 80 μm diameter platinum-rhodium wires knitted or woven into the form of a gauze. In an aggressive environment and under extreme conditions (temperature 800-900 °C, intensive gas flow, high pressure) precious elements are drained from the surface of the wires. Part of this separated material quickly decomposes on the surface in the form of characteristic "cauliflower-shape protrusions". The rest of the platinum is captured by palladium-nickel catalytic-capture gauzes located beneath. In our investigation we focused on the effects of the degradation of gauzes from one industrial catalytic system. The aim of the study was to compare the degree and the mechanism of degradation of gauzes from a different part of the reactor. The study covered PtRh7 catalytic and PdNi5 catalytic-capture gauzes. X-ray computer microtomography investigation revealed that despite strong differences in morphology, each Pt-Rh wire has a similar specific surface area. This indicates that the oxidation process and morphological changes of the wires occur in a self-regulating balance, resulting in the value of the specific surface area of the catalyst. Microtomography analysis of Pd-Ni wires revealed strong redevelopment of the wires' surface, which is related to the platinum capture phenomenon. Scanning electron microscope observations also revealed the nanostructure in the cauliflower-shape protrusions and large grains in the wires' preserved cores. The high temperature in the reactor and the long-term nature of the process do not favor the occurrence of the nanostructure in this type of material. Further and detailed analysis of this phenomena will provide a better understanding of the precious metals etching and deposition processes during oxidation.

  11. Promoted Ru on high-surface area graphite for efficient miniaturized production of hydrogen from ammonia

    DEFF Research Database (Denmark)

    Sørensen, Rasmus Zink; Klerke, Asbjørn; Quaade, Ulrich

    2006-01-01

    Promoted Ru/C catalysts for decomposition of ammonia are incorporated into micro-fabricated reactors for the first time. With the reported preparation technique, the performance is increased more than two orders of magnitude compared to previously known micro-fabricated reactors for ammonia decom...... studies of both ammonia synthesis and decomposition, and it is shown how proper promotion can facilitate ammonia decomposition at temperatures below 500 K.......Promoted Ru/C catalysts for decomposition of ammonia are incorporated into micro-fabricated reactors for the first time. With the reported preparation technique, the performance is increased more than two orders of magnitude compared to previously known micro-fabricated reactors for ammonia...... decomposition. The catalytic activities for production of hydrogen from ammonia are determined for different promoters and promoter levels on graphite supported ruthenium catalysts. The reactivity trends of the Ru/C catalysts promoted with Cs and Ba are in excellent agreement with those known from earlier...

  12. Selective catalytic oxidation of ammonia over copper-cerium composite catalyst.

    Science.gov (United States)

    Lou, Jie-Chung; Hung, Chang-Mao; Yang, Sheng-Fu

    2004-01-01

    This work considers the oxidation of ammonia (NH3) by selective catalytic oxidation (SCO) over a copper (Cu)-cerium (Ce) composite catalyst at temperatures between 150 and 400 degrees C. A Cu-Ce composite catalyst was prepared by coprecipitation of copper nitrate and cerium nitrate at various molar concentrations. This study also considers how the concentration of influent NH3 (500-1000 ppm), the space velocity (72,000-110,000 hr(-1)), the relative humidity (12-18%) and the concentration of oxygen (4-20%) affect the operational stability and the capacity for removing NH3. The effects of the O2 and NH3 content of the carrier gas on the catalyst's reaction rate also are considered. The experimental results show that the extent of conversion of NH3 by SCO in the presence of the Cu-Ce composite catalyst was a function of the molar ratio. The NH3 was removed by oxidation in the absence of Cu-Ce composite catalyst, and approximately 99.2% NH3 reduction was achieved during catalytic oxidation over the Cu-Ce (6:4, molar/molar) catalyst at 400 degrees C with an O2 content of 4%. Moreover, the effect of the initial concentration and reaction temperature on the removal of NH3 in the gaseous phase was also monitored at a gas hourly space velocity of less than 92,000 hr(-1).

  13. Highly active metastable ruthenium nanoparticles for hydrogen production through the catalytic hydrolysis of ammonia borane.

    Science.gov (United States)

    Abo-Hamed, Enass K; Pennycook, Timothy; Vaynzof, Yana; Toprakcioglu, Chris; Koutsioubas, Alexandros; Scherman, Oren A

    2014-08-13

    Late transition metal nanoparticles (NPs) with a favorably high surface area to volume ratio have garnered much interest for catalytic applications. Yet, these NPs are prone to aggregation in solution, which has been mitigated through attachment of surface ligands, additives or supports; unfortunately, protective ligands can severely reduce the effective surface area on the NPs available for catalyzing chemical transformations. The preparation of 'metastable' NPs can readily address these challenges. We report herein the first synthesis of monodisperse metastable ruthenium nanoparticles (RuNPs), having sub 5 nm size and an fcc structure, in aqueous media at room temperature, which can be stored for a period of at least 8 months. The RuNPs can subsequently be used for the catalytic, quantitative hydrolysis of ammonia-borane (AB) yielding hydrogen gas with 21.8 turnovers per min at 25 °C. The high surface area available for hydrolysis of AB on the metastable RuNPs translated to an Ea of 27.5 kJ mol(-1) , which is notably lower than previously reported values for RuNP based catalysts.

  14. Catalytic on-board hydrogen production from methanol and ammonia for mobile application

    Energy Technology Data Exchange (ETDEWEB)

    Soerijanto, H.

    2008-08-15

    unfavourable for energetic and economic reasons, it is reasonable to investigate another reaction system, which is free of carbon. At the last part of this study the catalytic production of hydrogen from ammonia cracking was investigated. Ammonia is an interesting alternative: it has a high hydrogen density, it is available and cheap. Since the Pt electrode is sensitive to reactive substances, it must be ensured, that for example no hydrazine is produced during the ammonia cracking. A new type of ammonia cracking catalyst was investigated in this study, which unlike the conventional catalyst is not based on metal. Four different zirconium oxynitrides: ss' ZrON, ss'' ZrON, Zr{sub 2}ON{sub 2} and Zr{sub 0.88}Y{sub 0.12}O{sub 1.72}N{sub 0.15} (Y{sub 2}O{sub 3} doped ZrON) were prepared by various methods and subsequently tested for their activity in ammonia cracking. A long-term study was carried out on the best catalyst and no hydrazine was detected. On the basis of the data from the accomplished investigations a reaction mechanism is proposed. The result provides a basis for the further improvement of the catalyst. (orig.)

  15. In situ infrared study of catalytic decomposition of NO. Second semiannual report, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Chuang, S.S.; Tan, Cher-Dip

    1997-04-01

    The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccessful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst. Research is proposed to study the reactivity of adsorbates for the direct NO decomposition and to investigate the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. An innovative infrared reactor system will be used to observe and determine the dynamic behavior and the reactivity of adsorbates during NO decomposition, oxygen spillover, and silanation. A series of experiment including X-ray diffraction, temperature programmed desorption, temperature programmed reaction, X-ray photoelectron spectroscopy will be used to characterize the catalysts. The information obtained from this study will provide a scientific basis for developing an effective catalyst for the NO decomposition under practical flue gas conditions.

  16. Decomposition Pathway of Ammonia Borane on the Surface of nano-BN

    Energy Technology Data Exchange (ETDEWEB)

    Neiner, Doinita; Luedtke, Avery T; Karkamkar, Abhijeet J; Shaw, Wendy J; Wang, Julia; Browning, Nigel; Autrey, Thomas; Kauzlarich, Susan M

    2010-08-19

    Ammonia borane (AB) is under significant investigation as a possible hydrogen storage material. While many chemical additives have been demonstrated to have a significant positive effect on hydrogen release from ammonia borane, many provide additional complications in the regeneration cycle. Mechanically alloyed hexagonal BN (nano-BN) has been shown to facilitate the release of hydrogen from AB at lower temperature, with minimal induction time, less exothermically, and inert nano-BN may be easily removed during any regeneration of the spent AB. The samples were prepared by mechanically alloying AB with nano-BN. Raman spectroscopy indicates that the AB:nano-BN samples are physical mixtures of AB and h-BN. The release of hydrogen from AB:nano-BN mixtures as well as the decomposition products were characterized by 11B magic angle spinning (MAS) solid state NMR, TGA/DSC/MS with 15N labeled AB, and solution 11B NMR spectroscopy. The 11B MAS solid state NMR spectrum shows that diammonate of diborane (DADB) is present in the mechanically alloyed mixture, which drastically shortens the induction period for hydrogen release from AB. Analysis of the TGA/DSC/MS spectra using 15N labeled AB shows that all the borazine (BZ) produced in the reaction comes from AB and that increasing nano-BN surface area results in increased amounts of BZ. However, under high temperature, 150°C, isothermal conditions, the amount of BZ released was the same as for neat AB. High resolution transmission electron microscopy (HRTEM), selected area diffraction (SAD), and electron energy loss spectroscopy (EELS) of the initial and final nano-BN additive provide evidence for crystallinity loss but not significant chemical changes. The higher concentration of BZ observed for low temperature dehydrogenation of AB:nano-BN mixtures versus neat AB is attributed to a surface interaction that favors the formation of precursors which ultimately result in BZ

  17. Comparative study on ammonia oxidation over Ni-based cermet anodes for solid oxide fuel cells

    Science.gov (United States)

    Molouk, Ahmed Fathi Salem; Yang, Jun; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

    2016-02-01

    In the current work, we investigate the performance of solid oxide fuel cells (SOFCs) with Ni‒yttria-stabilized zirconia (Ni-YSZ) and Ni‒gadolinia-dope ceria (Ni-GDC) cermet anodes fueled with H2 or NH3 in terms of the catalytic activity of ammonia decomposition. The cermet of Ni-GDC shows higher catalytic activity for ammonia decomposition than Ni-YSZ. In response to this, the performance of direct NH3-fueled SOFC improved by using Ni-GDC anode. Moreover, we observe further enhancement in the cell performance and the catalytic activity for ammonia decomposition with applying Ni-GDC anode synthesised by the glycine-nitrate combustion process. These results reveal that the high performance of Ni-GDC anode for the direct NH3-fueled SOFC results from its mixed ionic-electronic conductivity as well as high catalytic activity for ammonia decomposition.

  18. A study on the photo catalytic decomposition reactions of organics dissolved in water (II)

    Energy Technology Data Exchange (ETDEWEB)

    Sung, K.W.; Na, J. W.; Cho, Y. H.; Chung, H. H

    2000-01-01

    Experiments on aqueous TiO{sub 2} photo catalytic reaction of nitrogen containing organic compounds such as ethylamine, phenylhydrazine, pyridine, urea and EDTA were carried out. Based on the values calculated for the distribution of ionic species and atomic charge, the characteristics of their photo catalytic decomposition were estimated. It was shown that the decomposition characteristics was linearly proportional to nitrogen atomic charge value. On the other hand, the effects of aqueous pH, oxygen content and concentration on the TiO{sub 2} photo catalytic characteristics of EDTA, EDTA-Cu(II) and EDTA-Fe(III) were experimentally investigated. All EDTA systems were decomposed better in the pH range of 2.5-3.0 and with more dissolved oxygen. These results could be applied to construction of a process for removal of organic impurities dissolved in a source of system water, or for treatment of EDTA-containing liquid waste produced by a chemical cleaning in the domestic NPPs. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Sun, MIn; Perry, Kevin L.

    2015-11-20

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

  20. Removal of ammonia from aqueous solutions by catalytic oxidation with copper-based rare earth composite metal materials: catalytic performance, characterization, and cytotoxicity evaluation

    Institute of Scientific and Technical Information of China (English)

    Chang-Mao Hung

    2011-01-01

    Ammonia (NH3) has an important use in the chemical industry and is widely found in industrial wastewater.For this investigation of copper-based rare earth composite metal materials,aqueous solutions containing 400 mg/L of ammonia were oxidized in a batch-bed reactor with a catalyst prepared by the co-precipitation of copper nitrate,lanthanum nitrate and cerium nitrate.Barely any of the dissolved ammonia was removed by wet oxidation without a catalyst,but about 88% of the ammonia was reduced during wet oxidation over the catalysts at 423 K with an oxygen partial pressure of 4.0 MPa.The catalytic redox behavior was determined by cyclic voltammetry (CV).Furthermore,the catalysts were characterized using thermogravimetric analyzer (TGA) and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX),which showed that the catalytic behavior was related to the metal oxide properties of the catalyst.In addition,the copper-lanthanum-cerium composite-induced cytotoxicity in the human lung MRC-5 cell line was tested,and the percentage cell survival was determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetra-zolium (MTS) analysis in vitro.No apparent cytotoxicity was observed when the human lung cells were exposed to the copper-lanthanum-cerium composite.

  1. Synthesis and characterization of Fe–Ni/ɣ-Al2O3 egg-shell catalyst for H2 generation by ammonia decomposition

    DEFF Research Database (Denmark)

    Silva, Hugo José Lopes; Nielsen, Morten Godtfred; Fiordaliso, Elisabetta Maria

    2015-01-01

    of the active phase should match with the type of reaction. In this work, a novel synthesis route was developed for the preparation of a Fe–Ni/ɣ-Al2O3 egg-shell catalyst. Egg-shell is a preferred profile considering the highly endothermic nature of ammonia decomposition reaction. The high viscosity of glycerol......The Fe–Ni alloyed nanoparticles are a promising alternative to expensive ruthenium-based catalysts for a real-scale application of hydrogen generation by ammonia decomposition. In practical applications, millimeter-sized extrudates are used as catalyst supports, where the spatial distribution....... The outer-shell region showed the presence of Fe and Ni alloyed nanoparticles with a size of approximately 5nm.. The egg-shell catalyst showed significant higher activity in ammonia decomposition by converting 3 times more ammonia to equilibrium conversion than either egg-white or catalyst with uniform...

  2. Development of Catalytic Tar Decomposition in an Internally Circulating Fluidized-Bed Gasifier

    Science.gov (United States)

    Xiao, Xianbin; Le, Due Dung; Morishita, Kayoko; Li, Liuyun; Takarada, Takayuki

    Biomass gasification in an Internally Circulating Fluidized-bed Gasifier (ICFG) using Ni/Ah03 as tar cracking catalyst is studied at low temperature. Reaction conditions of the catalyst bed are discussed, including catalytic temperature and steam ratio. High energy efficiency and hydrogen-rich, low-tar product gas can be achieved in a properly designed multi-stage gasification process, together with high-performance catalyst. In addition, considering the economical feasibility, a newly-developed Ni-loaded brown coal char is developed and evaluated as catalyst in a lab-scale fluidized bed gasifier with catalyst fixed bed. The new catalyst shows a good ability and a hopeful prospect oftar decomposition, gas quality improvement and catalytic stability.

  3. High catalytic activity of anatase titanium dioxide for decomposition of electrolyte solution in lithium ion battery

    Science.gov (United States)

    Liu, Ming; He, Yan-Bing; Lv, Wei; Zhang, Chen; Du, Hongda; Li, Baohua; Yang, Quan-Hong; Kang, Feiyu

    2014-12-01

    It has been indicated that anatase TiO2 is a promising anode material for lithium ion power battery from many previous researches. Whereas, in this work, we find that the anatase TiO2, when used as an anode for lithium ion battery, has high catalytic activity to initiate the decarboxylation reaction of electrolyte solution, resulting in the large generation of sole gaseous component, CO2. The ROLi species and the new phase of flake-like Li2TiF6 material are the main reaction products between anatase TiO2 and LiPF6 based electrolyte solution. This work provides important and urgent information that the surface chemistry of anatase TiO2 used as the anode material of lithium ion battery must be modified to suppress its catalytic activity for the decomposition of solvents.

  4. Production of High Purity Multi-Walled Carbon Nanotubes from Catalytic Decomposition of Methane

    Institute of Scientific and Technical Information of China (English)

    Kong Bee Hong; Aidawati Azlin Binti Ismail; Mohamed Ezzaham Bin Mohd Mahayuddin; Abdul Rahman Mohamed; Sharif Hussein Sharif Zein

    2006-01-01

    Acid-based purification process of multi-walled carbon nanotubes (MWNTs) produced via catalytic decomposition of methane with NiO/TiO2 as a catalyst is described. By combining the oxidation in air and the acid refluxes, the impurities, such as amorphous carbon, carbon nanoparticles, and the NiO/TiO2 catalyst, are eliminated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirm the removal of the impurities. The percentage of the carbon nanotubes purity was analyzed using thermal gravimetric analysis (TGA). Using this process, 99.9 wt% purity of MWNTs was obtained.

  5. Methane catalytic decomposition over ordered mesoporous carbons: A promising route for hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Botas, J.A.; Serrano, D.P. [Department of Chemical and Environmental Technology, ESCET, Rey Juan Carlos University, c/ Tulipan s/n, 28933 Mostoles, Madrid (Spain); IMDEA Energia, c/Tulipan s/n, 28933 Mostoles, Madrid (Spain); Guil-Lopez, R.; Pizarro, P.; Gomez, G. [Department of Chemical and Environmental Technology, ESCET, Rey Juan Carlos University, c/ Tulipan s/n, 28933 Mostoles, Madrid (Spain)

    2010-09-15

    Methane decomposition offers an interesting route for the CO{sub 2}-free hydrogen production. The use of carbon catalysts, in addition to lowering the reaction temperature, presents a number of advantages, such as low cost, possibility of operating under autocatalytic conditions and feasibility of using the produced carbons in non-energy applications. In this work, a novel class of carbonaceous materials, having an ordered mesoporous structure (CMK-3 and CMK-5), has been checked as catalysts for methane decomposition, the results obtained being compared to those corresponding to a carbon black sample (CB-bp) and two activated carbons, presenting micro- (AC-mic) and mesoporosity (AC-mes), respectively. Ordered mesoporous carbons, and especially CMK-5, possess a remarkable activity and stability for the hydrogen production through that reaction. Under both temperature programmed and isothermal experiments, CMK-5 has shown to be a superior catalyst for methane decomposition than the AC-mic and CB-bp materials. Likewise, the catalytic activity of CMK-5 is superior to that of AC-mes in spite of the presence of mesoporosity and a high surface area in the latter. The remarkable stability of the CMK-5 catalyst is demonstrated by the high amount of carbon deposits that can be formed on this sample. This result has been assigned to the growth of the carbon deposits from methane decomposition towards the outer part of the catalyst particles, avoiding the blockage of the uniform mesopores present in CMK-5. Thus, up to 25 g of carbon deposits have been formed per gram of CMK-5, while the latter still retains a significant catalytic activity. (author)

  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. Catalytic wet oxidation of ammonia solution: activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst.

    Science.gov (United States)

    Hung, Chang-Mao

    2009-04-15

    Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H(2)PtCl(6), Pd(NO(3))(3) and Rh(NO(3))(3). Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes.

  8. Application of microscopy technology in thermo-catalytic methane decomposition to hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Irene Lock Sow, E-mail: irene.sowmei@gmail.com; Lock, S. S. M., E-mail: serenelock168@gmail.com; Abdullah, Bawadi, E-mail: bawadi-abdullah@petronas.com.my [Chemical Engineering Department, Universiti Teknologi PETRONAS, Bandar Sri Iskandar, 31750, Perak (Malaysia)

    2015-07-22

    Hydrogen production from the direct thermo-catalytic decomposition of methane is a promising alternative for clean fuel production because it produces pure hydrogen without any CO{sub x} emissions. However, thermal decomposition of methane can hardly be of any practical and empirical interest in the industry unless highly efficient and effective catalysts, in terms of both specific activity and operational lifetime have been developed. In this work, bimetallic Ni-Pd on gamma alumina support have been developed for methane cracking process by using co-precipitation and incipient wetness impregnation method. The calcined catalysts were characterized to determine their morphologies and physico-chemical properties by using Brunauer-Emmett-Teller method, Field Emission Scanning Electron Microscopy, Energy-dispersive X-ray spectroscopy and Thermogravimetric Analysis. The results suggested that that the catalyst which is prepared by the co-precipitation method exhibits homogeneous morphology, higher surface area, have uniform nickel and palladium dispersion and higher thermal stability as compared to the catalyst which is prepared by wet impregnation method. This characteristics are significant to avoid deactivation of the catalysts due to sintering and carbon deposition during methane cracking process.

  9. The roles of active site residues in the catalytic mechanism of methylaspartate ammonia-lyase

    NARCIS (Netherlands)

    Raj, Hans; Poelarends, Gerrit J

    2013-01-01

    Methylaspartate ammonia-lyase (MAL; EC 4.3.1.2) catalyzes the reversible addition of ammonia to mesaconate to yield l-threo-(2S,3S)-3-methylaspartate and l-erythro-(2S,3R)-3-methylaspartate as products. In the proposed minimal mechanism for MAL of Clostridium tetanomorphum, Lys-331 acts as the (S)-s

  10. Numerical modeling of hydrogen production from ammonia decomposition for fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Chein, Rei-Yu.; Chang, Chia-San [Department of Mechanical Engineering, National Chung-Hsing University, Taichung City 402 (China); Chen, Yen-Cho [Department of Energy and Resources, National United University, Miaoli City 360 (China); Chung, J.N. [Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611-6300 (United States)

    2010-01-15

    The hydrogen production from NH{sub 3} decomposition for fuel cell applications using packed Ni-Pt/Al{sub 2}O{sub 3} particles as the catalyst is theoretically and numerically predicted. The results show that by adopting the chemical reaction model for a packed-bed reactor used in the methanol-steam reforming with ZnO/Al{sub 2}O{sub 3} as the catalyst, the numerical model predicted satisfactory results on the NH{sub 3} decomposition efficiency as compared with the experimental data. For various catalyst bed porosities and particle sizes, the numerical results indicated that porosity and permeability of the catalyst bed produce an insignificant effect on the NH{sub 3} decomposition. Based on this finding, a one-dimensional plug flow model is developed and the predicted species molar fraction variations and NH{sub 3} decomposition efficiency are found in good agreement with the numerical simulations. From the numerical and theoretical results, it is found that the NH{sub 3} volumetric flow rate fed into the reactor is an important factor that determines the reaction temperature and decomposition efficiency in addition to the catalyst. Because of a longer NH{sub 3} residence time inside the reactor, lower reaction temperature can be employed for a high decomposition efficiency when the NH{sub 3} flow rate is low. (author)

  11. Electronic factors in catalysis: the volcano curve and the effect of promotion in catalytic ammonia synthesis

    DEFF Research Database (Denmark)

    Dahl, Søren; Logadottir, Ashildur; Jacobsen, C.J.H.

    2001-01-01

    to calculate how these two factors affect the energies of the intermediates and transition states in the ammonia synthesis reaction. We show that a linear relationship exists between the activation energy for N-2 dissociation and the binding energy of adsorbed nitrogen. The ammonia synthesis activity under...... promoted transition metals. We conclude that promotion is most effective for the best non-promoted catalysts and that promotion will always be essential for obtaining an optimal ammonia synthesis catalyst. Analysis of the micro-kinetic model show that the best catalysts are those with the lowest apparent...

  12. Effect of rare earth and other cationic promoters on properties of CoMoNx/CNTs catalysts for ammonia decomposition

    Institute of Scientific and Technical Information of China (English)

    ZHAO Zhaohui; ZOU Hanbo; LIN Weiming

    2013-01-01

    Carbon nanotubes (CNTs) supported Co-Mo nitride catalysts were prepared by incipient-wetness impregnation method and temperature-programmed reaction in N2-H2 mixed gases.The effects of cationic promoters (K,Ba,La,Ce and Zr) on the catalytic performance and surface properties were investigated.All samples were characterized by N2 physical adsorption,X-ray diffraction,and temperature-programmed reduction of H2.The results showed that the addition of promoters reduced the crystallite size of Mo2N and Co3Mo3N species and increased their surface area and dispersion.Among the catalysts,the La promoted CoMoNx/CNTs catalyst had the highest ammonia conversion which could reach 97.63% at 600 ℃.

  13. Evaluation of denitrification decomposition model for estimating ammonia fluxes from chemical fertilizer application

    Science.gov (United States)

    DeNitrification DeComposition (DNDC) model predictions of NH3 fluxes following chemical fertilizer application were evaluated by comparison to relaxed eddy accumulation (REA) measurements, in Central Illinois, United States, over the 2014 growing season of corn. Practical issues for evaluating closu...

  14. Mesoporous Silica Supported Pd-MnOx Catalysts with Excellent Catalytic Activity in Room-Temperature Formic Acid Decomposition

    Science.gov (United States)

    Jin, Min-Ho; Oh, Duckkyu; Park, Ju-Hyoung; Lee, Chun-Boo; Lee, Sung-Wook; Park, Jong-Soo; Lee, Kwan-Young; Lee, Dong-Wook

    2016-09-01

    For the application of formic acid as a liquid organic hydrogen carrier, development of efficient catalysts for dehydrogenation of formic acid is a challenging topic, and most studies have so far focused on the composition of metals and supports, the size effect of metal nanoparticles, and surface chemistry of supports. Another influential factor is highly desired to overcome the current limitation of heterogeneous catalysis for formic acid decomposition. Here, we first investigated the effect of support pore structure on formic acid decomposition performance at room temperature by using mesoporous silica materials with different pore structures such as KIE-6, MCM-41, and SBA-15, and achieved the excellent catalytic activity (TOF: 593 h-1) by only controlling the pore structure of mesoporous silica supports. In addition, we demonstrated that 3D interconnected pore structure of mesoporous silica supports is more favorable to the mass transfer than 2D cylindrical mesopore structure, and the better mass transfer provides higher catalytic activity in formic acid decomposition. If the pore morphology of catalytic supports such as 3D wormhole or 2D cylinder is identical, large pore size combined with high pore volume is a crucial factor to achieve high catalytic performance.

  15. Mesoporous Silica Supported Pd-MnOx Catalysts with Excellent Catalytic Activity in Room-Temperature Formic Acid Decomposition

    Science.gov (United States)

    Jin, Min-Ho; Oh, Duckkyu; Park, Ju-Hyoung; Lee, Chun-Boo; Lee, Sung-Wook; Park, Jong-Soo; Lee, Kwan-Young; Lee, Dong-Wook

    2016-01-01

    For the application of formic acid as a liquid organic hydrogen carrier, development of efficient catalysts for dehydrogenation of formic acid is a challenging topic, and most studies have so far focused on the composition of metals and supports, the size effect of metal nanoparticles, and surface chemistry of supports. Another influential factor is highly desired to overcome the current limitation of heterogeneous catalysis for formic acid decomposition. Here, we first investigated the effect of support pore structure on formic acid decomposition performance at room temperature by using mesoporous silica materials with different pore structures such as KIE-6, MCM-41, and SBA-15, and achieved the excellent catalytic activity (TOF: 593 h−1) by only controlling the pore structure of mesoporous silica supports. In addition, we demonstrated that 3D interconnected pore structure of mesoporous silica supports is more favorable to the mass transfer than 2D cylindrical mesopore structure, and the better mass transfer provides higher catalytic activity in formic acid decomposition. If the pore morphology of catalytic supports such as 3D wormhole or 2D cylinder is identical, large pore size combined with high pore volume is a crucial factor to achieve high catalytic performance. PMID:27666280

  16. Catalytic Hydrolysis of Ammonia Borane by Cobalt Nickel Nanoparticles Supported on Reduced Graphene Oxide for Hydrogen Generation

    Directory of Open Access Journals (Sweden)

    Yuwen Yang

    2014-01-01

    Full Text Available Well dispersed magnetically recyclable bimetallic CoNi nanoparticles (NPs supported on the reduced graphene oxide (RGO were synthesized by one-step in situ coreduction of aqueous solution of cobalt(II chloride, nickel (II chloride, and graphite oxide (GO with ammonia borane (AB as the reducing agent under ambient condition. The CoNi/RGO NPs exhibits excellent catalytic activity with a total turnover frequency (TOF value of 19.54 mol H2 mol catalyst−1 min−1 and a low activation energy value of 39.89 kJ mol−1 at room temperature. Additionally, the RGO supported CoNi NPs exhibit much higher catalytic activity than the monometallic and RGO-free CoNi counterparts. Moreover, the as-prepared catalysts exert satisfying durable stability and magnetically recyclability for the hydrolytic dehydrogenation of AB, which make the practical reusing application of the catalysts more convenient. The usage of the low-cost, easy-getting catalyst to realize the production of hydrogen under mild condition gives more confidence for the application of ammonia borane as a hydrogen storage material. Hence, this general method indicates that AB can be used as both a potential hydrogen storage material and an efficient reducing agent, and can be easily extended to facile preparation of other RGO-based metallic systems.

  17. Structural and catalytic properties of the four phenylalanine ammonia-lyase isoenzymes from parsley (Petroselinum crispum Nym.).

    Science.gov (United States)

    Appert, C; Logemann, E; Hahlbrock, K; Schmid, J; Amrhein, N

    1994-10-01

    Near-full-length cDNAs for the four phenylalanine ammonia-lyase (PAL) isoenzymes in parsley (Petroselium crispum Nym.) were cloned and the complete amino acid sequences deduced. Fusion proteins with glutathione S-transferase were expressed in Escherichia coli, purified and cleaved. All of the resulting phenylalanine ammonia-lyase proteins, as well as the fusion proteins, were catalytically active. The turnover number of one selected isoenzyme, PAL-1, was estimated to be around 22 s-1 for each active site. In contrast to a certain degree of differential expression in various parts of parsley plants, the four phenylalanine ammonia-lyase isoenzymes exhibited very similar apparent Km values for L-phenylalanine (15-24.5 microM) as well as identical temperature (58 degrees C) and pH (8.5) optima. All of them were competitively inhibited by (E)-cinnamate with similar efficiency (Ki values: 9.1-21.5 microM), lacked cooperative behaviour, and accepted L-tyrosine as a substrate with low affinity (Km values: 2.6-7.8 mM). These results suggest that the occurrence of multiple gene copies has a function other than encoding isoenzymes with different enzyme kinetic properties.

  18. Characterization and performance of Cu/ZnO/Al2O3 catalysts prepared via decomposition of M(Cu,Zn)-ammonia complexes under sub-atmospheric pressure for methanol synthesis from H2 and CO2

    Institute of Scientific and Technical Information of China (English)

    Danjun Wang; Jun Zhao; Huanling Song; Lingjun Chou

    2011-01-01

    Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M(Cu,Zn)-ammonia complexes (DMAC) at various temperatures.The catalysts were characterized in detail,including X-ray diffraction,N2 adsorption-desorption,N2O chemisorption,temperature-programmed reduction and evolved gas analyses.The influences of DMAC temperature,reaction temperature and specific Cu surface area on catalytic performance are investigated.It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts.The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol (212 g/(Lcat·h); T =513 K,p =3 MPa,S V =12000 h-1).

  19. Co-production of hydrogen and carbon nanotubes on nickel foam via methane catalytic decomposition

    Science.gov (United States)

    Ping, Dan; Wang, Chaoxian; Dong, Xinfa; Dong, Yingchao

    2016-04-01

    The co-production of COx-free hydrogen and carbon nanotubes (CNTs) was achieved on 3-dimensional (3D) macroporous nickel foam (NF) via methane catalytic decomposition (MCD) over nano-Ni catalysts using chemical vapor deposition (CVD) technique. By a simple coating of a NiO-Al2O3 binary mixture sol followed by a drying-calcination-reduction treatment, NF supported composite catalysts (denoted as NiyAlOx/NF) with Al2O3 transition-layer incorporated with well-dispersed nano-Ni catalysts were successfully prepared. The effects of Ni loading, calcination temperature and reaction temperature on the performance for simultaneous production of COx-free hydrogen and CNTs were investigated in detail. Catalysts before and after MCD were characterized by XRD, TPR, SEM, TEM, TG and Raman spectroscopy technology. Results show that increasing Ni loading, lowering calcination temperature and optimizing MCD reaction temperature resulted in high production efficiency of COx-free H2 and carbon, but broader diameter distribution of CNTs. Through detailed parameter optimization, the catalyst with a Ni/Al molar ratio of 0.1, calcination temperature of 550 °C and MCD temperature of 650 °C was favorable to simultaneously produce COx-free hydrogen with a growth rate as high as 10.3% and CNTs with uniform size on NF.

  20. Study on the catalytic effect of NiO nanoparticles on the thermal decomposition of TEGDN/NC propellant.

    Science.gov (United States)

    Wei, Wenxian; Jiang, Xiaohong; Lu, Lude; Yang, Xujie; Wang, Xin

    2009-09-15

    The catalytic effect of NiO nanoparticles on the thermal decomposition of double-base propellant composed of nitrocellulose (NC) and triethylene glycol dinitrate (TEGDN) has been investigated by thermogravimetry-mass spectrometry (TG-MS) coupling technique. It was shown that adding 2% of NiO nanoparticles to TEGDN/NC propellant can accelerate the thermal decomposition process after around 188 degrees C TG-MS analysis indicated that NiO nanoparticles have resulted in the increase in intensity (peak area) of m/z=27, 28, and 29 MS signals, but the decrease in the intensity of m/z=18, 30, 44 and 46 (peak 2) MS signals during the thermal decompsition. The catalytic mechanism was also discussed in this paper.

  1. The effect of antimony-tin and indium-tin oxide supports on the catalytic activity of Pt nanoparticles for ammonia electro-oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Júlio César M. [Department of Chemical & Biological Engineering, Centre for Catalysis Research and Innovation (CCRI), University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada); Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, Av. Prof. Lineu Prestes, 2242 Cidade Universitária, CEP 05508-900, São Paulo, SP (Brazil); Piasentin, Ricardo M.; Spinacé, Estevam V.; Neto, Almir O. [Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, Av. Prof. Lineu Prestes, 2242 Cidade Universitária, CEP 05508-900, São Paulo, SP (Brazil); Baranova, Elena A., E-mail: elena.baranova@uottawa.ca [Department of Chemical & Biological Engineering, Centre for Catalysis Research and Innovation (CCRI), University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada)

    2016-09-01

    Platinum nanoparticles supported on carbon (Pt/C) and carbon with addition of ITO (Pt/C-ITO (In{sub 2}O{sub 3}){sub 9}·(SnO{sub 2}){sub 1}) and ATO (Pt/C-ATO (SnO{sub 2}){sub 9}·(Sb{sub 2}O{sub 5}){sub 1}) oxides were prepared by sodium borohydride reduction method and used for ammonia electro-oxidation reaction (AmER) in alkaline media. The effect of the supports on the catalytic activity of Pt for AmER was investigated using electrochemical (cyclic voltammetry and chronoamperometry) and direct ammonia fuel cell (DAFC) experiments. X-ray diffraction (XRD) showed Pt peaks attributed to the face-centered cubic (fcc) structure, as well as peaks characteristic of In{sub 2}O{sub 3} in ITO support and cassiterite SnO{sub 2} phase of ATO support. According to transmission electron micrographs the mean particles sizes of Pt over carbon were 5.4, 4.9 and 4.7 nm for Pt/C, Pt/C-ATO and Pt/C-ITO, respectively. Pt/C-ITO catalysts showed the highest catalytic activity for ammonia electrooxidation in both electrochemical and fuel cell experiments. We attributed this to the presence of In{sub 2}O{sub 3} phase in ITO, which provides oxygenated or hydroxide species at lower potentials resulting in the removal of poisonous intermediate, i.e., atomic nitrogen (N{sub ads}) and promotion of ammonia electro-oxidation. - Highlights: • Oxide support effect on the catalytic activity of Pt towards ammonia electro-oxidation. • Direct ammonia fuel cell (DAFC) performance using Pt over different supports as anode. • Pt/C-ITO shows better catalytic activity for ammonia oxidation than Pt/C and Pt/C-ATO.

  2. Fabrication of ammonium perchlorate/copper-chromium oxides core-shell nanocomposites for catalytic thermal decomposition of ammonium perchlorate

    Energy Technology Data Exchange (ETDEWEB)

    Eslami, Abbas, E-mail: eslami@umz.ac.ir [Department of Inorganic Chemistry, Faculty of Chemistry, University of Mazandaran, P.O.Box 47416-95447, Babolsar (Iran, Islamic Republic of); Juibari, Nafise Modanlou [Department of Inorganic Chemistry, Faculty of Chemistry, University of Mazandaran, P.O.Box 47416-95447, Babolsar (Iran, Islamic Republic of); Hosseini, Seyed Ghorban [Department of Chemistry, Malek Ashtar University of Technology, P.O. Box 16765-3454, Tehran (Iran, Islamic Republic of)

    2016-09-15

    The ammonium perchlorate/Cu(II)-Cr(III)-oxides(AP/Cu-Cr-O) core-shell nanocomposites were in-situ prepared by deposition of copper and chromium oxides on suspended ammonium perchlorate particles in ethyl acetate as solvent. The results of differential scanning calorimetery (DSC) and thermal gravimetric analysis (TGA) experiments showed that the nanocomposites have excellent catalytic effect on the thermal decomposition of AP, so that the released heat increases up to about 3-fold over initial values, changing from 450 J/g for pure AP to 1510 J/g for most appropriate mixture. For better comparison, single metal oxide/AP core-shell nanocomposite have also been prepared and the results showed that they have less catalytic effect respect to mixed metal oxides system. Scanning electron microscopy (SEM) results revealed homogenous deposition of nanoparticles on the surface of AP and fabrication of core-shell structures. The kinetic parameters of thermal decomposition of both pure AP and AP/Cu-Cr-O samples have been calculated by Kissinger method and the results showed that the values of pre-exponential factor and activation energy are higher for AP/Cu-Cr-O nanocomposite. The better catalytic effect of Cu-Cr-O nanocomposites is probably attributed to the synergistic effect between Cu{sup 2+} and Cr{sup 3+} in the nanocomposites, smaller particle size and more crystal defect. - Highlights: • The Cu-Cr-O nanoparticles were synthesized by chemical liquid deposition method. • Then, the AP/Cu-Cr-O core-shell nanocomposites were prepared. • The core-shell samples showed high catalytic activity for AP decomposition. • Thermal decomposition of samples occurs at lower temperature range.

  3. 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. ...

  4. Synthesis of chrysalis-like CuO nanocrystals and their catalytic activity in the thermal decomposition of ammonium perchlorate

    Indian Academy of Sciences (India)

    Jun Wang; Shanshan He; Zhanshuang Li; Xiaoyan Jing; Milin Zhang; Zhaohua Jiang

    2009-11-01

    Chrysalis-like morphologies of CuO have been synthesized in large-quantity via a simple chemical deposition method without the use of any complex instruments and reagents. CuO nanocrystals showed a different morphology at three different temperatures, 25, 60 and 100°C. The particle size, morphology and crystal structure of the samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectra. The catalytic effect of CuO nanoparticles on the decomposition of ammonium perchlorate (AP) was investigated by STA 409 PC thermal analyzer at a heating rate of 10°C min-1 from 35 to 500°C. Compared with the thermal decomposition of pure AP, the addition of CuO nanoparticles decreased the decomposition temperature of AP by about 85°C.

  5. Catalytic hydrolysis of urea with fly ash for generation of ammonia in a batch reactor for flue gas conditioning and NOx reduction

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, J.N.; Gangadharan, P.; Patwardhan, A.V.; Meikap, B.C. [Indian Institute of Technology, Kharagpur (India). Dept. of Chemical Engineering

    2009-01-15

    Ammonia is a highly volatile noxious material with adverse physiological effects, which become intolerable even at very low concentrations and present substantial environmental and operating hazards and risk. Yet ammonia has long been known to be used for feedstock of flue gas conditioning and NOx reduction. Urea as the source of ammonia for the production of ammonia has the obvious advantages that no ammonia shipping, handling, and storage is required. The process of this invention minimizes the risks and hazards associated with the transport, storage, and use of anhydrous and aqueous ammonia. Yet no such rapid urea conversion process is available as per requirement of high conversion in shorter time, so here we study the catalytic hydrolysis of urea for fast conversion in a batch reactor. The catalyst used in this study is fly ash, a waste material originating in great amounts in combustion processes. A number of experiments were carried out in a batch reactor at different catalytic doses, temperatures, times, and at a constant concentration of urea solution 10% by weight, and equilibrium and kinetic studies have been made.

  6. Thermo-Catalytic Methane Decomposition for Hydrogen Production: Effect of Palladium Promoter on Ni-based Catalysts

    Directory of Open Access Journals (Sweden)

    Irene Lock Sow Mei

    2016-08-01

    Full Text Available Hydrogen production from the direct thermo-catalytic decomposition of methane is a promising alternative for clean fuel production. However, thermal decomposition of methane can hardly be of any practical and empirical interest in the industry unless highly efficient and effective catalysts, in terms of both catalytic activity and operational lifetime have been developed. In this study, the effect of palladium (Pd as a promoter onto Ni supported on alumina catalyst has been investigated by using co-precipitation technique. The introduction of Pd promotes better catalytic activity, operational lifetime and thermal stability of the catalyst. As expected, highest methane conversion was achieved at reaction temperature of 800 °C while the bimetallic catalyst (1 wt.% Ni -1wt.% Pd/Al2O3 gave the highest methane conversion of 70% over 15 min of time-on-stream (TOS. Interestingly, the introduction of Pd as promoter onto Ni-based catalyst also has a positive effect on the operational lifetime and thermal stability of the catalyst as the methane conversion has improved significantly over 240 min of TOS. Copyright © 2016 BCREC GROUP. All rights reserved Received: 21st January 2016; Revised: 6th February 2016; Accepted: 6th March 2016 How to Cite: Mei, I.L.S., Lock, S.S.M., Vo, D.V.N., Abdullah, B. (2016. Thermo-Catalytic Methane Decomposition for Hydrogen Production: Effect of Palladium Promoter on Ni-based Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (2: 191-199 (doi:10.9767/bcrec.11.2.550.191-199 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.2.550.191-199

  7. In-situ catalytic synthesis of ammonia from urea in a semi-batch reactor for safe utilization in thermal power plant

    Energy Technology Data Exchange (ETDEWEB)

    J.N. Sahu; A.V. Patwardhan; B.C. Meikap [Indian Institute of Technology (IIT), Kharagpur (India). Department of Chemical Engineering

    2010-05-15

    Urea as the source of ammonia for the flue gas conditioning/NOx reduction system in thermal power plant has the obvious advantages that no ammonia shipping, handling and storage is required. The process of this invention minimizes the risks and hazards associated with the transport, storage and use of anhydrous and aqueous ammonia, as ammonia is a highly volatile noxious material. But no such rapid urea conversion process is available as per requirement of high conversion in shorter time, so here we study the catalytic hydrolysis of urea for fast conversion in a semi-batch reactors. The catalysts used in this study are: TiO{sub 2}, fly ash, mixture of Ni and Fe and Al{sub 2}O{sub 3}.A number of experiments was carried out in a semi-batch reactor at different catalyst doses, temperatures and concentration of urea solution from 10 to 30% by weight and equilibrium study has been made.

  8. 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

  9. Treatment of Low-concentration Ammonia Nitrogen Wastewater by Catalytic Ozonation Process with Activated Carbon%活性炭催化臭氧氧化处理低浓度氨氮废水

    Institute of Scientific and Technical Information of China (English)

    尚会建; 周艳丽; 赵彦; 张高; 郑学明

    2012-01-01

    Low-concentration ammonia nitrogen wastewater was treated by catalytic ozonation process with activated carbon. The factors affecting the treatment effect were studied. The experimental results show that: Activated carbon has a significant catalytic effect on ozonation and can improve the utilization of ozone; Under the condition of high pH, OH- can improve the decomposition of ozone and the generation of o OH, which is in favor of ammonia nitrogen removal with strong oxidation property and fast reaction rate; The increasing of ozone flow can weaken the resistance in the gas-liquid mass-transfer process and increase the removal rate of ammonia nitrogen; Under the conditions of initial ammonia nitrogen mass concentration 35 mg/L, activated carbon dosage 10.0 g/L, ozone flow 30 mg/min, simulated wastewater pH 11.0 and reaction time 90 min, the removal rate of ammonia nitrogen can reach 97.6%, which' is much higher than those by activated carbon adsorption or ozonation.%采用活性炭催化臭氧氧化法处理低浓度氨氮废水,考察了模拟废水pH、活性炭加入量、臭氧流量等因素对处理效果的影响.实验结果表明:活性炭对臭氧有明显的催化作用,并可提高臭氧的利用率;在高pH条件下,OH-能促进臭氧分解生成·OH,·OH氧化性强且反应速率快,有利于氨氮的去除;增大臭氧流量可减小气液传质过程中的阻力,使氨氮去除率增加;在初始氨氮质量浓度为35 mg/L、活性炭加入量为10.0 g/L、臭氧流量为30 mg/min、模拟废水pH为11.0的条件下,反应90 min后,氨氮去除率可达97.6%,相对于单独活性炭吸附和臭氧氧化过程,氨氮去除率有了显著提高.

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

    Energy Technology Data Exchange (ETDEWEB)

    Moreno-Tost, Ramon; Santamaria-Gonzalez, Jose; Rodriguez-Castellon, Enrique; Jimenez-Lopez, Antonio [Departamento de Quimica Inorganica, Cristalografia y Mineralogia, Facultad de Ciencias, Unidad Asociada del Instituto de Catalisis y Petroleoquimica, CSIC, Universidad de Malaga, Campus de Teatinos, 29071 Malaga (Spain); Autie, Miguel A.; Glacial, Marisol Carreras [Centro Nacional de Investigaciones Cientificas, Ciudad de la Habana, La Habana (Cuba); Gonzalez, Edel [Instituto Superior Pedagogico ' Enrique Jose Varona' , La Habana (Cuba); Pozas, Carlos De las [Centro de Gerencia de Programas y Proyectos Priorizados, La Habana (Cuba)

    2004-07-15

    The catalytic selective reduction of NO over Cu-exchanged natural zeolites (mordenite (MP) and clinoptilolite (HC)) from Cuba using NH{sub 3} 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 N{sub 2} at low temperatures, and exhibiting good water tolerance. The chemical state of the Cu(II) in exchanged zeolites was characterized by H{sub 2}-TPR and XPS. Cu(II)-exchanged clinoptilolite underwent a severe deactivation in the presence of SO{sub 2}. 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 SO{sub 2}.

  11. Catalyst for Ammonia Oxidation

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a bimetallic catalyst for ammonia oxidation, a method for producing a bimetallic catalyst for ammonia oxidation and a method for tuning the catalytic activity of a transition metal. By depositing an overlayer of less catalytic active metal onto a more catalytic...

  12. 浮石催化水中臭氧分解研究%Catalytic ozone aqueous decomposition promoted by pumice

    Institute of Scientific and Technical Information of China (English)

    袁磊; 沈吉敏; 陈忠林

    2012-01-01

    To investigate the influences of pumice chemical surface properties on catalytic ozonation,the decomposition rate of ozone in water was measured over pumice and the mechanism of ozone catalytic decomposition was discussed.The results showed that the pseudo-first order rate of ozone decomposition increased by 37.4 % for pumice catalysts.When t-BuOH was added,the rate constant decreased by 45.2 % for pumice catalysts,suggesting that the decomposition of ozone followed the mechanism of hydroxyl radical(·OH).The removal of ozone increased with the increasing of surface hydroxyl groups.High initial pH presented a positive effect in the ozone alone and ozone/pumice system.The pumice surface at nearly zero charged point was favorable for the decomposition of ozone in aqueous solution.Ozone aqueous decomposition in the presence of pumice takes place mainly on the natural material surface.The presence of metal oxides in pumice might catalyse ozone decomposition into more active radicals.%为考察浮石表面化学性质对水中臭氧分解的影响,测定了浮石催化水中臭氧分解的速率常数并探讨催化臭氧分解的途径.结果表明:浮石促进水中臭氧一级分解速率常数提高了37.4%;利用叔丁醇捕获生成的羟基自由基,催化臭氧分解速率常数降低了45.2%,浮石催化臭氧分解生成了羟基自由基;浮石表面羟基密度与催化臭氧分解率成正相关;随着溶液初始pH值增大,单独臭氧分解和浮石催化臭氧分解率均增加;由浮石pHpzc决定的表面电荷状态与催化臭氧分解效果有关,表面接近电中性时对催化臭氧分解有利.水中臭氧分解主要发生在浮石表面,浮石表面的金属氧化物可能是催化水中臭氧分解的活性物质。

  13. Effect of ammonia on catalytic properties of an AShNTs-3 catalyst containing zeolite in alkylation of phenols with styrene

    Energy Technology Data Exchange (ETDEWEB)

    Kolesnichenko, N.V. (A.V. Topchiyev Inst. of Petrochemical Synthesis, USSR); Kurashev, M.V.; Romanovskii, B.V.; Menyailov, A.A.

    1981-01-01

    A study was made of the effect of previous treatment with an ammonia mixture with a small proportion of steam on catalytic properties of AShNTs-3. Preliminary treatment of the catalyst with a mixture of ammonia and steam at 250/sup 0/C for 2 hr increases considerably the yield of methylbenzylphenols, particularly 2-(..cap alpha..-methylbenzyl)phenol. Highest yield of methylbenzylphenols is achieved at a temperature of 250/sup 0/C, a molar ratio of phenol : styrene of 4 : 1 and a space velocity of 5.5 hr/sup -1/.

  14. The role of oxygen and water on molybdenum nanoclusters for electro catalytic ammonia production

    DEFF Research Database (Denmark)

    Howalt, Jakob Geelmuyden; Vegge, Tejs

    2014-01-01

    . In this study, we present theoretical investigations of the influence of oxygen adsorption and reduction on pure and nitrogen covered molybdenum nanocluster electro catalysts for electrochemical reduction of N2 to NH3 with the purpose of understanding oxygen and water poisoning of the catalyst. Density...... functional theory calculations are used in combination with the computational hydrogen electrode approach to calculate the free energy profile for electrochemical protonation of O and N2 species on cuboctahedral Mo13 nanoclusters. The calculations show that the molybdenum nanocluster will preferentially bind...... are -0.72 V or lower for all oxygen coverages studied, and it is thus possible to (re)activate (partially) oxidized nanoclusters for electrochemical ammonia production, e.g., using a dry proton conductor or an aqueous electrolyte. At lower oxygen coverages, nitrogen molecules can adsorb to the surface...

  15. Wax: A benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition.

    Science.gov (United States)

    Gonzalez-Cortes, S; Slocombe, D R; Xiao, T; Aldawsari, A; Yao, B; Kuznetsov, V L; Liberti, E; Kirkland, A I; Alkinani, M S; Al-Megren, H A; Thomas, J M; Edwards, P P

    2016-10-19

    Hydrogen is often described as the fuel of the future, especially for application in hydrogen powered fuel-cell vehicles (HFCV's). However, its widespread implementation in this role has been thwarted by the lack of a lightweight, safe, on-board hydrogen storage material. Here we show that benign, readily-available hydrocarbon wax is capable of rapidly releasing large amounts of hydrogen through microwave-assisted catalytic decomposition. This discovery offers a new material and system for safe and efficient hydrogen storage and could facilitate its application in a HFCV. Importantly, hydrogen storage materials made of wax can be manufactured through completely sustainable processes utilizing biomass or other renewable feedstocks.

  16. Catalytic hydrogen peroxide decomposition on La1-xSrxCo03-d perovskite oxides

    NARCIS (Netherlands)

    Dam, Van-Ahn. T.; Olthuis, W.; Bergveld, P.; Berg, van den A.

    2005-01-01

    Lanthanide perovskite oxides are mentioned as material for hydrogen peroxide sensor because they can catalytically decompose hydrogen peroxide in an aqueous medium. The catalytic properties of these perovskite oxides to hydrogen peroxide are suggested due to their oxygen vacancies influenced by the

  17. Treatment of ammonia by catalytic wet oxidation process over platinum-rhodium bimetallic catalyst in a trickle-bed reactor: effect of pH.

    Science.gov (United States)

    Hung, Chang-Mao; Lin, Wei-Bang; Ho, Ching-Lin; Shen, Yun-Hwei; Hsia, Shao-Yi

    2010-08-01

    This work adopted aqueous solutions of ammonia for use in catalytic liquid-phase reduction in a trickle-bed reactor with a platinum-rhodium bimetallic catalyst, prepared by the co-precipitation of chloroplatinic acid (H2PtCl6) and rhodium nitrate [Rh(NO3)3]. The experimental results demonstrated that a minimal amount of ammonia was removed from the solution by wet oxidation in the absence of any catalyst, while approximately 97.0% of the ammonia was removed by wet oxidation over the platinum-rhodium bimetallic catalyst at 230 degrees C with an oxygen partial pressure of 2.0 MPa. The oxidation of ammonia has been studied as a function of pH, and the main reaction products were determined. A synergistic effect is manifest in the platinum-rhodium bimetallic structure, in which the material has the greatest capacity to reduce ammonia. The reaction pathway linked the oxidizing ammonia to nitric oxide, nitrogen, and water.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-07-01

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

  19. Ammonia-treated Ordered Mesoporous Carbons as Catalytic Materials for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiqing; Lee, Je Seung; Zhu, Qing; Liu, Jun; Wang, Yong; Dai, Sheng

    2010-04-13

    Polymer electrolyte membrane fuel cells (PEMFCs) have been considered as promising alternative power sources for many mobile and stationary applications. Compared to the fast hydrogen oxidation at the anode, the sluggish oxygen reduction reaction (ORR) at the cathode requires high-performance catalysts. Currently, platium (Pt) nanoparticles supported on high surface area carbons remain the best catalysts for ORR. However, both instability and high cost of Pt-based catalysts represent two main obstacles limiting the commercial applications of PEMFCs. The instability of supported Pt catalysts is mainly due to the corrosion of carbon support under operation conditions and the agglomation and detachment of Pt particles, leading to a decrease in catalytic surface areas. Development of corrosion resistant supports and enhancement of the interactions between Pt and supports are two strategies to improve the cathode long-term activity.

  20. Preparation of Nano-MnFe2O4 and Its Catalytic Performance of Thermal Decomposition of Ammonium Perchlorate

    Institute of Scientific and Technical Information of China (English)

    韩爱军; 廖娟娟; 叶明泉; 李燕; 彭新华

    2011-01-01

    Nano-MnFe2O4 particles were synthesized by co-precipitation phase inversion method and low-temperature combustion method respectively, using MnCl2, FeCl3, Mn(NO3)2, Fe(NO3)3, NaOH and C6H8O7. X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravim-etry-differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC) were used to characterize the structure, morphology, thermal stability of MnFe2O4 and its catalytic performance to ammonium perchlorate. Results showed that single-phased and uniform spinel MnFe2O4 was obtained. The average particle size was about 30 and 20 nm. The infrared absorption peaks appeared at about 420 and 574 cm-1, and the particles were stable below 524 ℃. Using the two prepared catalysts, the higher thermal decomposition temperature of ammonium perchlorate was decreased by 77.3 and 84.9 ℃ respectively, while the apparent decomposition heat was increased by 482.5 and 574.3 J?g?1. The catalytic mechanism could be explained by the favorable electron transfer space provided by outer d orbit of transition metal ions and the high specific surface absorption effect of MnFe2O4 particles.

  1. Catalytic decomposition of N₂O over CeO₂ supported Co₃O₄ catalysts

    Indian Academy of Sciences (India)

    S K MAHAMMADUNNISA; T AKANKSHA; K KRUSHNAMURTY; CH SUBRAHMANYAM

    2016-11-01

    This work was aimed to design efficient catalysts for N₂O decomposition at low temperatures. Cobalt oxide (Co₃O₄) was prepared by hydrothermal, precipitation and combustion methods and tested for N₂O decomposition. It was found that the catalysts prepared by solution combustion synthesis were most active for this reaction. Subsequently, a series of ceria (CeO₂) supported Co₃O₄ catalysts (xCeCo) were prepared by solution combustion method and used them for N₂O decomposition. All the catalysts were characterized by analytical methods like XRD, TEM, BET, XPS, UV-Vis, Raman and H2-TPR. It was found that 10 and 20 wt..% loading of CeO₂ on Co₃O₄ promoted the activity of Co₃O₄ towards N₂O decomposition, whereas, higher loading of CeO₂ reduced the activity. Typical results indicated that addition of CeO₂ increases the surface area of Co₃O₄ , and improves the reduction of Co³⁺ to Co²⁺ by facilitating the desorption of adsorbed oxygen species, which is the rate-determining step for the N₂O decomposition over Co₃O₄ spinel catalysts. Optimal CeO₂ loading can increase both dispersion and surface area of Co₃O₄ catalysts and weaken the Co–O bond strength to promote N₂O decomposition.

  2. 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.

  3. Reaction mechanism for the highly efficient catalytic decomposition of peroxynitrite by the amphipolar iron(III) corrole 1-Fe.

    Science.gov (United States)

    Avidan-Shlomovich, Shlomit; Gross, Zeev

    2015-07-21

    The amphipolar iron(III) corrole 1-Fe is one of the most efficient catalysts for the decomposition of peroxynitrite, the toxin involved in numerous diseases. This research focused on the mechanism of that reaction at physiological pH, where peroxynitrite is in equilibrium with its much more reactive conjugated acid, by focusing on the elementary steps involved in the catalytic cycle. Kinetic investigations uncovered the formation of a reaction intermediate in a process that is complete within a few milliseconds (k1 ∼ 3 × 10(7) M(-1) s(-1) at 5 °C, about 7 orders of magnitude larger than the first order rate constant for the non-catalyzed process). Multiple evidence points towards iron-catalyzed homolytic O-O bond cleavage to form nitrogen dioxide and hydroxo- or oxo-iron(iv) corrole. The iron(iv) intermediate was found to decay via multiple pathways that proceed at similar rates (k2 about 10(6) M(-1) s(-1)): reaction with nitrogen dioxide to form nitrate, nitration of the corrole macrocyclic, and dimerization to binuclear iron(iv) corrole. Catalysis in the presence of substrates affects the decay of the iron intermediate by either oxidative nitration (phenolic substrates) or reduction (ascorbate). A large enough excess of ascorbate accelerates the catalytic decomposition of PN by 1-Fe by orders of magnitude, prevents other decay routes of the iron intermediate, and eliminates nitration products as well. This suggests that the beneficial effect of the iron corrole under the reducing conditions present in most biological media might be even larger than in the purely chemical system. The acquired mechanistic insight is of prime importance for the design of optimally acting catalysts for the fast and safe decomposition of reactive oxygen and nitrogen species.

  4. 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

    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...... are required in the reduction, and, nally, oxidation by NO + O2 or NO2 leads to the same state of the catalyst. These points are shown experimentally for a Cu-CHA catalyst, by combining in situ X-ray absorption spectrosocpy (XAS), electron paramagnetic resonance (EPR), and Fourier transform infrared...... for standard SCR. Finally, the role of a nitrate/nitrite equilibrium and the possible in uence of Cu dimers and Brønsted sites are discussed, and an explanation is offered as to how a catalyst can be effective for SCR, while being a poor catalyst for NO oxidation to NO2....

  5. Thermo catalytic decomposition of methane over Pd/AC and Pd/CB catalysts for hydrogen production and carbon nanofibers formation

    Directory of Open Access Journals (Sweden)

    K. Srilatha

    2014-09-01

    Full Text Available Hydrogen production studies have been carried using Thermo Catalytic Decomposition (TCD Unit. Thermo catalytic decomposition of methane is an attractive route for COx free production of hydrogen required in fuel cells. Although metal based catalysts produce hydrogen at low temperatures, carbon formed during methane decomposition reaction rapidly deactivates the catalyst. The present work compares the results of 10 wt% Pd supported on commercially available activated carbon and carbon black catalysts (samples coded as Pd10/AC and Pd10/CB respectively for methane decomposition reaction. Hydrogen has been produced by thermo catalytic decomposition of methane at 1123K and Volume Hourly Space Velocity (VHSV of 1.62 L/h g on the activity of both the catalysts has been studied. XRD of the above catalysts revealed, moderately crystalline peaks of Pd which may be responsible for the increase in catalytic life and formation of carbon fibers. Also during life studies (850°C and 54 sccm of methane it has been observed that the activity of carbon black is sustainable for a longer time compared to that of activated carbon.

  6. Synthesis, Characterization and Catalytic Properties of Attapulgite/CeO2 Nanocomposite Films for Decomposition of Rhodamine B.

    Science.gov (United States)

    Lu, Xiaowang; Li, Xiazhang; Qian, Junchao; Chen, Feng; Chen, Zhigang

    2015-08-01

    ATP(attapulgite)/CeO2 nanocomposite films were prepared on the glass substrates via a sol-gel and dip-coating route. The ATP/CeO2 nanocomposite films were characterized by Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), atomic force microscopy (AFM) and fourier transform infrared spectroscopy (FT-IR). The results showed that the ATP/CeO2 nanocomposite films were free from cracks and the nanoparticles were attached onto the surface of attapulgite. The ATP/CeO2 nanocomposite films displayed excellent catalytic activity for decomposition of Rhodamine B. The COD (chemical oxygen demand) removal rate of rhodamine B using ATP/CeO2 nanocomposite films as catalyst reached as high as 94% when the weight ratio of ATP to CeO2 was 2:1.

  7. Hydrogen production by catalytic decomposition of methane using a Fe-based catalyst in a fluidized bed reactor

    Institute of Scientific and Technical Information of China (English)

    D.Torres; S.de Llobet; J.L.Pinilla; M.J.Lázaro; I.Suelves; R.Moliner

    2012-01-01

    Catalytic decomposition of methane using a Fe-based catalyst for hydrogen production has been studied in this work.A Fe/Al2O3 catalyst previously developed by our research group has been tested in a fluidized bed reactor (FBR).A parametric study of the effects of some process variables,including reaction temperature and space velocity,is undertaken.The operating conditions strongly affect the catalyst performance.Methane conversion was increased by increasing the temperature and lowering the space velocity.Using temperatures between 700 and 900 ℃ and space velocities between 3 and 6 LN/(gcat·h),a methane conversion in the range of 25%-40% for the gas exiting the reactor could be obtained during a 6 h run.In addition,carbon was deposited in the form of nanofilaments (chain like nanofibers and multiwall nanotubes) with similar properties to those obtained in a fixed bed reactor.

  8. Wax: A benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition

    Science.gov (United States)

    Gonzalez-Cortes, S.; Slocombe, D. R.; Xiao, T.; Aldawsari, A.; Yao, B.; Kuznetsov, V. L.; Liberti, E.; Kirkland, A. I.; Alkinani, M. S.; Al-Megren, H. A.; Thomas, J. M.; Edwards, P. P.

    2016-01-01

    Hydrogen is often described as the fuel of the future, especially for application in hydrogen powered fuel-cell vehicles (HFCV’s). However, its widespread implementation in this role has been thwarted by the lack of a lightweight, safe, on-board hydrogen storage material. Here we show that benign, readily-available hydrocarbon wax is capable of rapidly releasing large amounts of hydrogen through microwave-assisted catalytic decomposition. This discovery offers a new material and system for safe and efficient hydrogen storage and could facilitate its application in a HFCV. Importantly, hydrogen storage materials made of wax can be manufactured through completely sustainable processes utilizing biomass or other renewable feedstocks. PMID:27759014

  9. Catalytic decomposition of methane to COx-free hydrogen and carbon nanotubes over Co–W/MgO catalysts

    Directory of Open Access Journals (Sweden)

    Ahmed E. Awadallah

    2015-09-01

    Full Text Available Bimetallic catalysts containing a series of Co/W at 40/10, 30/20, 20/30 and 10/40 wt% supported on MgO with a total metal content of 50 wt% were prepared and used for the catalytic decomposition of methane to COx-free hydrogen and multi-walled carbon nanotubes (MWCNTs. The solid fresh and exhausted catalysts were characterized structurally and chemically through XRD, TPR, BET, TGA, TEM and Raman spectroscopy. The 40%Co–10%W/MgO catalyst exhibited the highest activity for the production of both hydrogen and MWCNTs. The formation of a large amount of non-interacted Co3O4 species is considered as the main reason for the catalyst superiority in its activity. On the contrary, catalysts formulations of 20%Co–30%W and 10%Co–40%W demonstrated the formation of a large amount of hardly reducible CoWO4 and MgWO4 particles causing lower activity of these catalysts toward methane decomposition as evidenced through the XRD and TPR results.

  10. Catalytic decomposition of tar derived from wood waste pyrolysis using Indonesian low grade iron ore as catalyst

    Science.gov (United States)

    Wicakso, Doni Rahmat; Sutijan, Rochmadi, Budiman, Arief

    2016-06-01

    Low grade iron ore can be used as an alternative catalyst for bio-tar decomposition. Compared to other catalysts, such as Ni, Rd, Ru, Pd and Pt, iron ore is cheaper. The objective of this research was to investigate the effect of using low grade iron ore as catalyst for tar catalytic decomposition in fixed bed reactor. Tar used in this experiment was pyrolysis product of wood waste while the catalyst was Indonesian low grade iron ore. The variables studied were temperatures between 500 - 600 °C and catalyst weight between 0 - 40 gram. The first step, tar was evaporated at 450 °C to produce tar vapor. Then, tar vapor was flowed to fixed bed reactor filled low grade iron ore. Gas and tar vapor from reactor was cooled, then the liquid and uncondensable gas were analyzed by GC/MS. The catalyst, after experiment, was weighed to calculate total carbon deposited into catalyst pores. The results showed that the tar components that were heavy and light hydrocarbon were decomposed and cracked within the iron ore pores to from gases, light hydrocarbon (bio-oil) and carbon, thus decreasing content tar in bio-oil and increasing the total gas product. In conclusion, the more low grade iron ore used as catalyst, the tar content in the liquid decrease, the H2 productivity increased and calorimetric value of bio-oil increased.

  11. Synthesis of polycrystalline Co{sub 3}O{sub 4} nanowires with excellent ammonium perchlorate catalytic decomposition property

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Hai [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Lv, Baoliang, E-mail: lbl604@sxicc.ac.cn [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Wu, Dong; Xu, Yao [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)

    2014-12-15

    Graphical abstract: Co{sub 3}O{sub 4} nanowires with excellent ammonium perchlorate catalytic decomposition property were synthesized via a methanamide-assisted hydrolysis and subsequent dissolution–recrystallization process in the presence of methanamide. - Abstract: Co{sub 3}O{sub 4} nanowires, with the length of tens of micrometers and the width of several hundred nanometers, were produced by a hydrothermal treatment and a post-anneal process. X-ray diffraction (XRD) result showed that the Co{sub 3}O{sub 4} nanowires belong to cubic crystal system. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) analysis indicated that the Co{sub 3}O{sub 4} nanowires, composed by single crystalline nanoparticles, were of polycrystalline nature. On the basis of time-dependent experiments, methanamide-assisted hydrolysis and subsequent dissolution–recrystallization process were used to explain the precursors' formation process of the polycrystalline Co{sub 3}O{sub 4} nanowires. The TGA experiments showed that the as-obtained Co{sub 3}O{sub 4} nanowires can catalyze the thermal decomposition of ammonium perchlorate (AP) effectively.

  12. Photochemical fabrication of size-controllable gold nanoparticles on chitosan and their application on catalytic decomposition of acetaldehyde

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Chung-Chin [Department of Environmental Engineering, Vanung University, 1, Van Nung Road, Shuei-Wei Li, Chung-Li City, Taiwan (China); Nano Materials Applications R and D Center, Vanung University, 1, Van Nung Road, Shuei-Wei Li, Chung-Li City, Taiwan (China); Yang, Kuang-Hsuan, E-mail: khy@mail.vnu.edu.tw [Department of Chemical and Materials Engineering, Vanung University, 1, Van Nung Road, Shuei-Wei Li, Chung-Li City, Taiwan (China); Nano Materials Applications R and D Center, Vanung University, 1, Van Nung Road, Shuei-Wei Li, Chung-Li City, Taiwan (China); Liu, Yu-Chuan [Department of Chemical and Materials Engineering, Vanung University, 1, Van Nung Road, Shuei-Wei Li, Chung-Li City, Taiwan (China); Nano Materials Applications R and D Center, Vanung University, 1, Van Nung Road, Shuei-Wei Li, Chung-Li City, Taiwan (China); Chen, Bo-Chuen [Department of Chemical and Materials Engineering, Vanung University, 1, Van Nung Road, Shuei-Wei Li, Chung-Li City, Taiwan (China)

    2010-07-15

    In this work, we report a new pathway to prepare size-controllable gold nanoparticles (NPs) on chitosan (Ch) in aqueous solutions for improving catalytic decomposition of acetaldehyde by pure gold NPs at room temperature. First, Au substrates were cycled in deoxygenated aqueous solutions containing 0.1N NaCl and 1 g/L Ch from -0.28 to +1.22 V vs Ag/AgCl at 500 mV/s for 200 scans. Then the solutions were irradiated with UV lights of different wavelengths to prepare size-controllable Au NPs on Ch. Experimental results indicate that the particle sizes of prepared NPs are increased when UV lights with longer wavelengths were employed. The particle sizes of resulted Au NPs can be controlled from 10 to 50 nm. Moreover, the decomposition of acetaldehydes in wines can be significantly enhanced by ca. 190% of magnitude due to the contribution of the adsorption of Au NPs on Ch.

  13. Pyrolysis of aseptic packages (tetrapak) in a laboratory screw type reactor and secondary thermal/catalytic tar decomposition.

    Science.gov (United States)

    Haydary, J; Susa, D; Dudáš, J

    2013-05-01

    Pyrolysis of aseptic packages (tetrapak cartons) in a laboratory apparatus using a flow screw type reactor and a secondary catalytic reactor for tar cracking was studied. The pyrolysis experiments were realized at temperatures ranging from 650 °C to 850 °C aimed at maximizing of the amount of the gas product and reducing its tar content. Distribution of tetrapak into the product yields at different conditions was obtained. The presence of H2, CO, CH4, CO2 and light hydrocarbons, HCx, in the gas product was observed. The Aluminum foil was easily separated from the solid product. The rest part of char was characterized by proximate and elemental analysis and calorimetric measurements. The total organic carbon in the tar product was estimated by elemental analysis of tars. Two types of catalysts (dolomite and red clay marked AFRC) were used for catalytic thermal tar decomposition. Three series of experiments (without catalyst in a secondary cracking reactor, with dolomite and with AFRC) at temperatures of 650, 700, 750, 800 and 850 °C were carried out. Both types of catalysts have significantly affected the content of tars and other components in pyrolytic gases. The effect of catalyst on the tetrapack distribution into the product yield on the composition of gas and on the total organic carbon in the tar product is presented in this work.

  14. Sol–gel method to prepare graphene/Fe{sub 2}O{sub 3} aerogel and its catalytic application for the thermal decomposition of ammonium perchlorate

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Yuanfei; Li, Xiaoyu; Li, Guoping; Luo, Yunjun, E-mail: yjluo@bit.edu.cn [Beijing Institute of Technology, School of Materials Science and Engineering (China)

    2015-10-15

    Graphene/Fe{sub 2}O{sub 3} (Gr/Fe{sub 2}O{sub 3}) aerogel was synthesized by a simple sol–gel method and supercritical carbon dioxide drying technique. In this study, the morphology and structure were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and nitrogen sorption tests. The catalytic performance of the as-synthesized Gr/Fe{sub 2}O{sub 3} aerogel on the thermal decomposition of ammonium perchlorate (AP) was investigated by thermogravimetric and differential scanning calorimeter. The experimental results showed that Fe{sub 2}O{sub 3} with particle sizes in the nanometer range was anchored on the Gr sheets and Gr/Fe{sub 2}O{sub 3} aerogel exhibits promising catalytic effects for the thermal decomposition of AP. The decomposition temperature of AP was obviously decreased and the total heat release increased as well.

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

    Directory of Open Access Journals (Sweden)

    M. Nahavandi

    2015-12-01

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

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

    Science.gov (United States)

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

    2012-03-16

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

  17. 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.

  18. Mo-Bi系丙烯氨氧化催化剂上氨分解反应动力学的Monte Carlo模拟%Monte Carlo Simulation of Kinetics of Ammonia Oxidative Decomposition over the Commercial Propylene Ammoxidation Catalyst (Mo-Bi)

    Institute of Scientific and Technical Information of China (English)

    罗正鸿; 詹晓力; 陈丰秋; 阳永荣

    2003-01-01

    Monte Carlo method is applied to investigate the kinetics of ammonia oxidative decomposition overthe commercial propylene ammoxidation catalyst(Mo-Bi). The simulation is quite in agreement with experimentalresults. Monte Carlo simulation proves that the process of ammonia oxidation decomposition is a two-step reaction.

  19. Structural and kinetic changes to small-pore Cu-zeolites after hydrothermal aging treatments and selective catalytic reduction of NO_x with ammonia

    OpenAIRE

    Albarracin-Caballero, Jonatan D.; Khurana, Ishant; Di Iorio, John R.; Shih, Arthur J.; Schmidt, Joel E.; Dusselier, Michiel; Davis, Mark E.; Yezerets, Aleksey; Miller, Jeffrey T.; Ribeiro, Fabio H.; Gounder, Rajamani

    2016-01-01

    Three small-pore, eight-membered ring (8-MR) zeolites of different cage-based topology (CHA, AEI, RTH), in their proton- and copper-exchanged forms, were first exposed to high temperature hydrothermal aging treatments (1073 K, 16 h, 10% (v/v) H_2O) and then to reaction conditions for low temperature (473 K) standard selective catalytic reduction (SCR) of NO_x with ammonia, in order to study the effect of zeolite topology on the structural and kinetic changes that occur to Cu-zeolites used in ...

  20. Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

    Institute of Scientific and Technical Information of China (English)

    Wei Jiang; Ying Li; Wenfeng Han; Yaping Zhou; Haodong Tang; Huazhang Liu

    2014-01-01

    A series of high surface area graphitic carbon materials (HSGCs) were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x (x is the ball-milling time in hour) catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.

  1. Formation of {open_quotes}metal wool{close_quotes} structures and dynamics of catalytic etching of platinum surfaces during ammonia oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Lyubovsky, M.R.; Barelko, V.V. [Institute of Chemical Physics in Chernogolovka, Moscow (Russian Federation)

    1994-09-01

    Reconstruction of a clean surface of a platinum catalyst and a platinum surface covered with gold during ammonia oxidation was studied by SEM observations. It was found that the process of catalytic etching had two sequential stages in which different crystal structures with different rates of growth formed on the surface. The first stage was the formation of parallel facets, and the second stage was the formation of individual microcrystals with perfect crystal faces. It was also found that the second state had a threshold character, beginning after some delay from the start of the reaction. A structure resembling metal wool and consisting of interlaced platinum filaments was found to form on the surface of gold-covered platinum catalysts. Characteristic features of this structure`s development are reported. The growth of filaments is attributed to the vapor-liquid-solid mechanism of whisker growth. On the basis of the observed platinum whisker formation and behavior during ammonia oxidation, a mechanism of catalyst surface reconstruction that explains observed characteristic features of the process of catalytic etching is proposed. 25 refs., 8 figs.

  2. Red mud as an efficient, stable, and costfree catalyst for COx-free hydrogen production from ammonia

    OpenAIRE

    Uzun, Alper; Kurtoğlu, Samira Fatma

    2016-01-01

    Red mud, one of the mostly produced industrial wastes, was converted into a catalyst with exceptionally high and stable performance for hydrogen production from ammonia. Results showed that iron species produced after reduction of the HCl digested red mud were converted into epsilon-Fe2N during the induction period of ammonia decomposition reaction at 700 degrees C. The catalytic performance measurements indicated that the modified red mud catalyst provides a record high hydrogen production r...

  3. Synthesis of carbon nanotubes by catalytic vapor decomposition (CVD) method: Optimization of various parameters for the maximum yield

    Indian Academy of Sciences (India)

    Kanchan M Samant; Santosh K Haram; Sudhir Kapoor

    2007-01-01

    This paper describes an effect of flow rate, carrier gas (H2, N2 and Ar) composition, and amount of benzene on the quality and the yield of carbon nanotubes (CNTs) formed by catalytical vapour decomposition (CVD) method. The flow and mass control of gases and precursor vapors respectively were found to be interdependent and therefore crucial in deciding the quality and yield of CNTs. We have achieved this by modified soap bubble flowmeter, which controlled the flow rates of two gases, simultaneously. With the help of this set-up, CNTs could be prepared in any common laboratory. Raman spectroscopy indicated the possibilities of formation of single-walled carbon nanotubes (SWNTs). From scanning electron microscopy (SEM) measurements, an average diameter of the tube/bundle was estimated to be about 70 nm. The elemental analysis using energy dispersion spectrum (EDS) suggested 96 at.wt.% carbon along with ca. 4 at.wt. % iron in the as-prepared sample. Maximum yield and best quality CNTs were obtained using H2 as the carrier gas.

  4. Alloyed Ni-Fe nanoparticles as catalysts for NH3 decomposition

    DEFF Research Database (Denmark)

    Simonsen, Søren Bredmose; Chakraborty, Debasish; Chorkendorff, Ib;

    2012-01-01

    A rational design approach was used to develop an alloyed Ni-Fe/Al2O3 catalyst for decomposition of ammonia. The dependence of the catalytic activity is tested as a function of the Ni-to-Fe ratio, the type of Ni-Fe alloy phase, the metal loading and the type of oxide support. In the tests with high...

  5. Catalytic decomposition of CH4 over Ni-Al2O3-SiO2 catalysts:Influence of pretreatment conditions for the production of H2

    Institute of Scientific and Technical Information of China (English)

    Jangam Ashok; Gangadhara Raju; Padigapati Shiva Reddy; Machiraju Subrahmanyam; Akula Venugopal

    2008-01-01

    This article reports the production of COx free hydrogen and carbon nanofibers by the catalytic decomposition of methane over Ni-Al2O3-SiO2 catalysts. The influence of reaction temperature, pretreatment temperature, and effect of reductive pretreatment on the decomposition of methane activity is investigated. The physico-chemical characteristics of fresh and deactivated samples were characterized using BET-SA, XRD, TPR, SEM/TEM, CHNS analyses and correlated with the methane decomposition results obtained. The Ni-Al-Si (4 : 0.5 : 1.5) catalyst reduced with hydrazine hydrate produced better H2 yields of ca. 1815 mol H2/mol Ni than the catalyst reduced with 5% H2/N2.

  6. Cis-and Trans-Cinnamic Acids Have Different Effects on the Catalytic Properties of Arabidopsis Phenylalanine Ammonia Lyases PAL1, PAL2, PAL4

    Institute of Scientific and Technical Information of China (English)

    Ming-Jie CHEN; Veerappan VIJAYKUMAR; Bing-Wen LU; Bing XIA; Ning LI

    2005-01-01

    Cis-cinnamic acid (CA) is a naturally occurring compound, presumably converted from transCA in higher plants. To investigate the effect of cis-CA on the activity of Arabidopsis phenylalanine ammonia lyase (PAL), AtPAL1, AtPAL2, and AtPAL4 genes were isolated using reverse transcription polymerase chain reaction. These genes were fused to a glutathione S-transferase gene and overexpressed in a heterologous prokaryotic system of Escherichia coli. The purified PAL1, PAL2 and PAL4 enzymes were characterized biochemically to determine the effects of cis-CA on the kinetic parameter Km. The results showed that cis-CA is a competitive inhibitor for PAL1, but not PAL2 and PAL4, whereas trans-CA acts as a competitive inhibitor for all three PAL isomers, suggesting that cis- and trans-CA have different effects on the catalytic activity of PAL.

  7. pH dependent catalytic activities of platinum nanoparticles with respect to the decomposition of hydrogen peroxide and scavenging of superoxide and singlet oxygen

    Science.gov (United States)

    Liu, Yi; Wu, Haohao; Li, Meng; Yin, Jun-Jie; Nie, Zhihong

    2014-09-01

    Recently, platinum (Pt) nanoparticles (NPs) have received increasing attention in the field of catalysis and medicine due to their excellent catalytic activity. To rationally design Pt NPs for these applications, it is crucial to understand the mechanisms underlying their catalytic and biological activities. This article describes a systematic study on the Pt NP-catalyzed decomposition of hydrogen peroxide (H2O2) and scavenging of superoxide (O2&z.rad;-) and singlet oxygen (1O2) over a physiologically relevant pH range of 1.12-10.96. We demonstrated that the catalytic activities of Pt NPs can be modulated by the pH value of the environment. Our results suggest that Pt NPs possess peroxidase-like activity of decomposing H2O2 into &z.rad;OH under acidic conditions, but catalase-like activity of producing H2O and O2 under neutral and alkaline conditions. In addition, Pt NPs exhibit significant superoxide dismutase-like activity of scavenging O2&z.rad;- under neutral conditions, but not under acidic conditions. The 1O2 scavenging ability of Pt NPs increases with the increase in the pH of the environment. The study will provide useful guidance for designing Pt NPs with desired catalytic and biological properties.Recently, platinum (Pt) nanoparticles (NPs) have received increasing attention in the field of catalysis and medicine due to their excellent catalytic activity. To rationally design Pt NPs for these applications, it is crucial to understand the mechanisms underlying their catalytic and biological activities. This article describes a systematic study on the Pt NP-catalyzed decomposition of hydrogen peroxide (H2O2) and scavenging of superoxide (O2&z.rad;-) and singlet oxygen (1O2) over a physiologically relevant pH range of 1.12-10.96. We demonstrated that the catalytic activities of Pt NPs can be modulated by the pH value of the environment. Our results suggest that Pt NPs possess peroxidase-like activity of decomposing H2O2 into &z.rad;OH under acidic conditions

  8. Pure CuCr2O4 nanoparticles: Synthesis, characterization and their morphological and size effects on the catalytic thermal decomposition of ammonium perchlorate

    Science.gov (United States)

    Hosseini, Seyed Ghorban; Abazari, Reza; Gavi, Azam

    2014-11-01

    In the present paper a pure phase of the copper chromite spinel nanoparticles (CuCr2O4 SNPs) were synthesized via the sol-gel route using citric acid as a complexing agent. Then, the CuCr2O4 SNPs has been characterized by field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In the next step, with the addition of Cu-Cr-O nanoparticles (NPs), the effects of different parameters such as Cu-Cr-O particle size and the Cu/Cr molar ratios on the thermal behavior of Cu-Cr-O NPs + AP (ammonium perchlorate) mixtures were investigated. As such, the catalytic effect of the Cu-Cr-O NPs for thermal decomposition of AP was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA/DSC results showed that the samples with different morphologies exhibited different catalytic activity in different stages of thermal decomposition of AP. Also, in the presence of Cu-Cr-O nanocatalysts, all of the exothermic peaks of AP shifted to a lower temperature, indicating the thermal decomposition of AP was enhanced. Moreover, the heat released (ΔH) in the presence of Cu-Cr-O nanocatalysts was increased to 1490 J g-1.

  9. Hydrothermal preparation of Fe{sub 2}O{sub 3}/graphene nanocomposite and its enhanced catalytic activity on the thermal decomposition of ammonium perchlorate

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Yuan [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China); Jiang, Wei, E-mail: smallyuan1234@163.com [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China); Wang, Yujiao; Shen, Ping; Li, Fengsheng; Li, Pingyun [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China); Zhao, Fengqi; Gao, Hongxu [Xi’an Modern Chemistry Research Institute, Xi’an 710065 (China)

    2014-06-01

    Fe{sub 2}O{sub 3}/graphene nanocomposite was prepared by a facile hydrothermal method, during which graphene oxides (GOs) were reduced to graphene with hydrazine and Fe{sub 2}O{sub 3} nanoparticles were simultaneously anchored on graphene sheets. The morphology of the obtained Fe{sub 2}O{sub 3}/graphene nanocomposite was investigated by scanning electron microscopy (SEM) and transmission electron microscope (TEM). It was revealed by TEM images that Fe{sub 2}O{sub 3} nanoparticles grew well on the surfaces of graphene. As much as I know, this new nanocomposite has not been investigated as a catalyst on the thermal decomposition of AP yet. In this work, the catalytic performance of the synthesized material on the thermal decomposition of ammonium perchlorate (AP) was investigated creatively by differential scanning calorimetry (DSC). The results of DSC indicated that graphene obviously improved the catalytic activity of Fe{sub 2}O{sub 3} on the thermal decomposition of AP due to its high specific area.

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

    DEFF Research Database (Denmark)

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

    2007-01-01

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

  11. Ru-N-C Hybrid Nanocomposite for Ammonia Dehydrogenation: Influence of N-doping on Catalytic Activity

    Directory of Open Access Journals (Sweden)

    Nguyen Thi Bich Hien

    2015-06-01

    Full Text Available For application to ammonia dehydrogenation, novel Ru-based heterogeneous catalysts, Ru-N-C and Ru-C, were synthesized via simple pyrolysis of a mixture of RuCl3·6H2O and carbon black with or without dicyandiamide as a nitrogen-containing precursor at 550 °C. Characterization of the prepared Ru-N-C and Ru-C catalysts via scanning transmission electron microscopy, in conjunction with energy dispersive X-ray spectroscopy, indicated the formation of hollow nanocomposites in which the average sizes of the Ru nanoparticles were 1.3 nm and 5.1 nm, respectively. Compared to Ru-C, the Ru-N-C nanocomposites not only proved to be highly active for ammonia dehydrogenation, giving rise to a NH3 conversion of >99% at 550 °C, but also exhibited high durability. X-ray photoelectron spectroscopy revealed that the Ru active sites in Ru-N-C were electronically perturbed by the incorporated nitrogen atoms, which increased the Ru electron density and ultimately enhanced the catalyst activity.

  12. Experimental investigation of the catalytic decomposition and combustion characteristics of a non-toxic ammonium dinitramide (ADN)-based monopropellant thruster

    Science.gov (United States)

    Chen, Jun; Li, Guoxiu; Zhang, Tao; Wang, Meng; Yu, Yusong

    2016-12-01

    Low toxicity ammonium dinitramide (ADN)-based aerospace propulsion systems currently show promise with regard to applications such as controlling satellite attitude. In the present work, the decomposition and combustion processes of an ADN-based monopropellant thruster were systematically studied, using a thermally stable catalyst to promote the decomposition reaction. The performance of the ADN propulsion system was investigated using a ground test system under vacuum, and the physical properties of the ADN-based propellant were also examined. Using this system, the effects of the preheating temperature and feed pressure on the combustion characteristics and thruster performance during steady state operation were observed. The results indicate that the propellant and catalyst employed during this work, as well as the design and manufacture of the thruster, met performance requirements. Moreover, the 1 N ADN thruster generated a specific impulse of 223 s, demonstrating the efficacy of the new catalyst. The thruster operational parameters (specifically, the preheating temperature and feed pressure) were found to have a significant effect on the decomposition and combustion processes within the thruster, and the performance of the thruster was demonstrated to improve at higher feed pressures and elevated preheating temperatures. A lower temperature of 140 °C was determined to activate the catalytic decomposition and combustion processes more effectively compared with the results obtained using other conditions. The data obtained in this study should be beneficial to future systematic and in-depth investigations of the combustion mechanism and characteristics within an ADN thruster.

  13. Purification of Carbon Nanotubes Synthesized by Catalytic Decomposition of Methane using Bimetallic Fe-Co Catalysts Supported on MgO

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Beh Hoe; Ramli, Irmawati [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia 43400 UPM Serdang, Selangor (Malaysia); Yahya, Noorhana [Fundamental and Applied Science Department Universiti Teknologi Petronas, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Pah, Lim Kean, E-mail: irmawati@science.upm.edu.my [Physics department, Faculty of Science, Universiti Putra Malaysia 43400 UPM Serdang, Selangor (Malaysia)

    2011-02-15

    This work reports the synthesis of carbon nanotubes by catalytic decomposition of methane using bimetallic Fe-Co catalysts supported on MgO. Transmission electron microscopy (TEM) results show the as-prepared carbon nanotubes are multi-walled carbon nanotubes (MWCNTs) with diameter in the range of 15nm to 45nm. Purification of as-prepared MWCNTs was carried out by acid and heat treatment method. EDX results show the Fe, Co and MgO catalysts were successfully removed by refluxing the as-prepared MWCNTs in 3M H{sub 2}SO{sub 4}.

  14. Purification of Carbon Nanotubes Synthesized by Catalytic Decomposition of Methane using Bimetallic Fe-Co Catalysts Supported on MgO

    Science.gov (United States)

    Guan, Beh Hoe; Ramli, Irmawati; Yahya, Noorhana; Kean Pah, Lim

    2011-02-01

    This work reports the synthesis of carbon nanotubes by catalytic decomposition of methane using bimetallic Fe-Co catalysts supported on MgO. Transmission electron microscopy (TEM) results show the as-prepared carbon nanotubes are multi-walled carbon nanotubes (MWCNTs) with diameter in the range of 15nm to 45nm. Purification of as-prepared MWCNTs was carried out by acid and heat treatment method. EDX results show the Fe, Co and MgO catalysts were successfully removed by refluxing the as-prepared MWCNTs in 3M H2SO4.

  15. Catalytic Decomposition of Cellulose in Cooperative Ionic Liquids%复合离子液体中纤维素的催化分解

    Institute of Scientific and Technical Information of China (English)

    龙金星; 郭斌; 李雪辉; 王芙蓉; 王乐夫

    2011-01-01

    通过将酸性功能化离子液体与对纤维素具有溶解作用的离子液体进行复合,构建了一类新型的高效催化纤维素分解的体系,并采用热重(TG)分析方法,研究了复合离子液体中纤维素的分解行为.结果表明:复合离子液体中纤维素的分解温度明显降低,溶于离子液体中的纤维素可被酸性离子液体原位催化分解.纤维素的分解温度受离子液体催化剂的酸性及纤维素在复合离子液体中的溶解度影响明显:酸性越强,溶解度越大,纤维素的分解温度越低.%Cellulose, the abundant and cost-ineffective resource, is considered to be a perfect alternative for the alleviation of energy crisis and environmental pollution. However, most processes for the treatment of cellulose are rigor currently as it is insoluble in water and conventional organic solvents due to its strong intra and inter-molecular hydrogen bonds, where the phase problem hampers its utilization widely. Here, we built a novel and efficient cooperative ionic liquid pairs system for the low temperature catalytic conversion of cellulose, which was constructed through the combination of an acidic ionic liquid catalyst and a cellulose soluble ionic liquid solvent. The catalytic decomposition behavior of microcrystal cellulose in this vigorous catalytic system was studied intensively by thermogravimetry (TG). Results show that the decomposition temperature of cellulose decreases greatly in all cooperative ionic liquid pairs, cellulose dissolved in ionic liquid solvents can be in situ catalytic decomposed by acidic ionic liquids. Furthermore, the decomposition temperature is dependent on the acidic strength of the ionic liquid catalysts, stronger acidity results in a lower decomposition temperature of the cellulose. Moreover, we found that cellulose can be decomposed at lower temperature when the ionic liquid with higher solubility of cellulose is used.

  16. TiO2纳米管阵列光电催化氧化处理氨氮废水%Photo-electro Catalytic Oxidation of Ammonia Nitrogen Wastewater on TiO2 Nanotube Arrays

    Institute of Scientific and Technical Information of China (English)

    李丹丹; 刘中清; 颜欣; 郑剑; 刘旭

    2011-01-01

    用电化学阳极氧化法制备了高度有序的钛基二氧化钛纳米管阵列薄膜.用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)表征样品的形貌与晶型特征.以二氧化钛纳米管阵列为光阳极,石墨为对电极,测试了不同pH值和外加偏压条件下的光电流响应和光电催化氧化降解NH4CI水溶液(以N计,100 mg·L-1)的效率.结果表明:所制备的Ti02纳米管阵列具有锐钛矿和金红石的混晶结构,且主要晶型为锐钛矿.光电流响应的强弱与光电催化氧化效率的高低相对应,降解氨氮废水的最佳条件为pH=11,偏压为1.0 V.%Highly ordered TiO2 nanotube arrays on titanium substrate were prepared by electrochemical anodization. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were used to characterize the morphology and crystal form of the samples. Photo current response and photo-electro catalytic oxidation efficiency of ammonium chloride aqueous solution were evaluated with nitrogen content of 100 mg· L-1 at various pH values and applied voltages, using TiO2 nanotube arrays as a photo anode and graphite as a counter electrode. The results show that the as-prepared TiO2 nanotube arrays possess co-crystal structure with rutile and anatase phases, mainly anatase phase. Strong photo current response corresponds to high photo-electro catalytic oxidation efficiency, and weak response to low efficiency. The optimum conditions for ammonia nitrogen wastewater decomposition are pH value of 11 and applied voltage of 1.0 V.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2004-07-01

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

  18. Preparation of Coaxial-Line and Hollow Mn2O3 Nanofibers by Single-Nozzle Electrospinning and Their Catalytic Performances for Thermal Decomposition of Ammonium Perchlorate.

    Science.gov (United States)

    Liang, Jiyuan; Yang, Jie; Cao, Weiguo; Guo, Xiangke; Guo, Xuefeng; Ding, Weiping

    2015-09-01

    Coaxial-line and hollow Mn2O3 nanofibers have been synthesized by a simple single-nozzle electrospinning method without using a complicated coaxial jet head, combined with final calcination. The crystal structure and morphology of the Mn2O3 nanofibers were investigated by using the X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results indicate that the electrospinning distance has important influence on the morphology and structure of the obtained Mn2O3 nanofibers, which changes from hollow fibers for short electrospinning distance to coaxial-line structure for long electrospinning distance after calcination in the air. The formation mechanisms of different structured Mn2O3 fibers are discussed in detail. This facile and effective method is easy to scale up and may be versatile for constructing coaxial-line and hollow fibers of other metal oxides. The catalytic activity of the obtained Mn2O3 nanofibers on thermal decomposition of ammonium perchlorate (AP) was studied by differential scanning calorimetry (DSC). The results show that the hollow Mn2O3 nanofibers have good catalytic activity to promote the thermal decomposition of AP.

  19. Study on the carbon-methanation and catalytic activity of Ru/AC for ammonia synthesis%抑制碳负载钌基氨合成催化剂甲烷化的研究

    Institute of Scientific and Technical Information of China (English)

    祝一锋; 李小年; 季德春; 刘化章

    2004-01-01

    The effects of promoters K,Ba,Sm on the resistance to carbon-methanation and catalytic activity of ruthenium supported on active carbon(Ru/AC)for ammonia synthesis have been studied by means of TG-DTG(thermalgravity-differential thermalgravity),temperature-programmed desorption,and activity test.Promoters Ba,K,and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly.Much higher activity can be reached for Ru/AC catalyst with bi- or tri-promoters.Indeed,the triply promoted catalyst showed the highest activity,coupled to a surprisingly high resistance to methanation.The ability of resistance of promoter to methanation of Ru/AC catalyst is dependent on the adsorption intensity of hydrogen.The strong adsorption of hydrogen would enhance methanation and impact the adsorption of nitrogen,which results in the decrease of catalytic activity.

  20. 催化分解臭氧的方法及催化剂性能概述%Review of Ozone Catalytic Decomposition

    Institute of Scientific and Technical Information of China (English)

    傅嘉媛; 冯易君; 钟兵; 杨庆良

    2001-01-01

    臭氧作为一种有毒物质广泛存在于人们生活环境中,当 其浓度超过0.06mg/m3时,对人体就有害了。因此对臭氧的分解十分必要。本文介绍了多 种分解臭氧的方法,并着重介绍催化分解法。对各种臭氧分解催化剂的组成、制备方法及活 性作一综述。%Ozone is a toxic substance commonly found or gener a ted in human environments.When its concentration is up to 0.06mg/m3,it is d angerous to people.So ozone decomposition is necessary.This review provides man y methods of ozone decomposition,mainly provides catalytic ozone decomposition including catalyst composition,catalyst preparation,and performance.

  1. Synthesis of Co Nanoparticles and Their Catalytic Effect on the Decomposition of Ammonium Perchlorate%纳米金属钴粒子的制备及对高氯酸铵热分解的影响

    Institute of Scientific and Technical Information of China (English)

    段红珍; 蔺向阳; 刘冠鹏; 徐磊; 李凤生

    2008-01-01

    The monodispersed Co nanoparticles were successfully prepared by means of hydrogen plasma method in inert atmosphere. The particle size, specific surface area, crystal structure and morphology of the samples were characterized by transmission electron microscopy (TEM), BET equation, X-ray diffraction (XRD), and the corre- sponding selected area electron diffraction (SAED). The catalytic effect of Co nanoparticles on the decomposition of ammonium perchlorate (AP) was investigated by differential thermal analyzer (DTA). Compared with the ther- mal decomposition of pure AP, the addition of Co nanoparticles (2%-10%, by mass) decreases the decomposition temperature of AP by 145.01-155.72℃. Compared with Co3O4 nanoparticles and microsized Co particles, the catalytic effect of Co nanoparticles for AP is stronger. Such effect is attributed to the large specific surface area and its interaction of Co with decomposition intermediate gases. The present work provides useful information for the application of Co nanoparticles in the AP-based propellant.

  2. Synthesis and kinetics investigation of meso-microporous Cu-SAPO-34 catalysts for the selective catalytic reduction of NO with ammonia.

    Science.gov (United States)

    Liu, Jixing; Yu, Fuhong; Liu, Jian; Cui, Lifeng; Zhao, Zhen; Wei, Yuechang; Sun, Qianyao

    2016-10-01

    A series of meso-microporous Cu-SAPO-34 catalysts were successfully synthesized by a one-pot hydrothermal crystallization method, and these catalysts exhibited excellent NH3-SCR performance at low temperature. Their structure and physic chemical properties were characterized by means of X-ray diffraction patterns (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), N2 sorption-desorption, nuclear magnetic resonance (NMR), Inductively Coupled Plasma-Atomic Emission spectrometer (ICP-AES), X-ray absorption spectroscopy (XPS), Temperature-programmed desorption of ammonia (NH3-TPD), Ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS) and Temperature programmed reduction (TPR). The analysis results indicate that the high activities of Cu-SAPO-34 catalysts could be attributed to the enhancement of redox property, the formation of mesopores and the more acid sites. Furthermore, the kinetic results verify that the formation of mesopores remarkably reduces diffusion resistance and then improves the accessibility of reactants to catalytically active sites. The 1.0-Cu-SAPO-34 catalyst exhibited the high NO conversion (>90%) among the wide activity temperature window in the range of 150-425°C.

  3. Modification of Cu/ZSM-5 catalyst with CeO2for selective catalytic reduction of NOxwith ammonia

    Institute of Scientific and Technical Information of China (English)

    刘雪松; 吴晓东; 翁端; 石磊

    2016-01-01

    Cu/ZSM-5 and CeO2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO2was found to enhance the NOxselective catalytic reduction (SCR) activity of the catalyst atlow temperatures, but the high-temperature activitywas weakened. The catalysts were characterized by X-ray diffraction (XRD), nitrogen physisorption, induc-tively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), H2temperature-programmed reduction (TPR) and NH3temperature-programmed desorption (TPD). The results showedthat more CuO clusters instead of isolated Cu2+specieswere obtained on the modified catalyst. These active CuO clusters, as well as the Cu-Ce synergistic effect, improvedthe redox property of the catalyst and low-temperatures SCR activity via promoting the oxidation of NO to NO2and fast SCR reaction. The loss in high-temperatures activitywas attributedto the enhanced competitive ox-idation of NH3by O2and decreased surface acidity of the catalyst.

  4. 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.

  5. Understanding Catalytic Activity Trends for NO Decomposition and CO Oxidation using Density Functional Theory and Microkinetic Modeling

    DEFF Research Database (Denmark)

    Falsig, Hanne

    -relations between transition energies and adsorption energies. We establish a simple kinetic framework within the Sabatier analysis and obtain trends in catalytic activity based on the descriptors EO and ECO. We show that gold nanoparticles are optimal catalysts for low temperature CO oxidation and Pt closed packed...

  6. Hydrogen production from catalytic decomposition of methane; Produccion de hidrogeno a partir de la descomposicion termica catalitica del biogas de digestion anaerobia

    Energy Technology Data Exchange (ETDEWEB)

    Belsue Echevarria, M.; Etxebeste Juarez, O.; Perez Gil, S.

    2002-07-01

    The need of substitution of part of the energy obtained from fossil fuels instead of energy from renewable sources, together with the minimal emissions of CO{sub ''} and CO that are expected with these technologies, make renewable sources a very attractive predecessor for the production of hydrogen. In this situation, a usable source for hydrogen production is the biogas achieved by means of technologies like the anaerobic digestion of different kinds of biomass (MSW, sewage sludge, stc.). In this article we suggest the Thermal Catalytic Decomposition of the methane contained in this biogas, after separation of pollutants like CO{sub ''}, H{sub 2}S. steam. This technology will give hydrogen, usable in fuel cells, and nanoestructured carbon as products. (Author) 7 refs.

  7. Catalytic Decomposition of CFC-12 over Heteropolyacids%杂多酸催化分解氟里昂-12

    Institute of Scientific and Technical Information of China (English)

    马臻; 华伟明; 唐颐; 高滋

    2000-01-01

    @@ Chlorine atoms from chlorofluorocarbons (CFCs) deplete stratospheric ozone and CFCs are green-house gases too. Owing to these environmental problems, many kinds of CFCs have been banned since the Montreal Protocol and two kinds of cleaning techniques have been developed. One is the synthesis of CFCs alternatives[1,2] and the other is the decomposition of banned CFCs in existing equipments[3,4].

  8. Effect of surface structure on the catalytic behavior of Ni:Cu/Al and Ni:Cu:K/Al catalysts for methane decomposition

    Institute of Scientific and Technical Information of China (English)

    S.Tajammul Hussain; Sheraz Gul; Muhammed Mazhar; Dalaver H.Anjum; Faical Larachi

    2008-01-01

    Methane decomposition using nickel, copper, and aluminum (Ni:Cu/Al) and nickel, copper, potassium, and alu-minum (Ni:Cu:K/Al) modified nano catalysts has been investigated for carbon fibers, hydrogen and hydrocarbon production. X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectrometry (SSIMS), thermal gravimetric analysis (TGA),Fourier transform infrared (FT-IR), secondary electron microscopy/X-ray energy dispersive (SEM-EDX), and temperature pro-grammed desorption (TPD) were used to depict the chemistry of the catalytic results. These techniques revealed the changes in surface morphology and structure of Ni, Cu, Al, and K, and formation of bimetallic and trimetallic surface cationic sites with sifferent cationic species, which resulted in the production of graphitic form of pure carbon on Ni:Cu/Al catalyst. The addition of K has a marked effect on the product selectivity and reactivity of the catalyst system. K addition restricts the formation of carbon on the surface and increases the production of hydrogen and C2, C3 hydrocarbons during the catalytic reaction whereas no hydrocarbons are produced on the sample without K. This study completely maps the modified surface structure and its re-lationship with the catalytic behavior of both systems. The process provides a flexible route for the production of carbon fibers and hydrogen on Ni:Cu/Al catalyst and hydrogen along with hydrocarbons on Ni:Cu:K/Al catalyst. The produced carbon fibers are imaged using a transmission electron microscope (TEM) for diameter size and wall structure determination. Hydrogen produced is COx free, which can be used directly in the fuel cell system. The effect of the addition of Cu and its transformation and interaction with Ni and K is responsible for the production of CO/CO2 free hydrogen, thus producing an environmental friendly clean energy.

  9. Study on Carbon Nanotubes Prepared from Catalytic Decomposition of CH4 over Lanthanum Containing Ni-Base Catalysts

    Institute of Scientific and Technical Information of China (English)

    Wang Minwei; Li Fengyi

    2004-01-01

    A series of lanthanum containing Ni-base catalysts were prepared by citric acid complex method.Carbon nanotubes (CNT) were synthesized bY catalytic decomposing CH4 over these catalysts and characterized by XRD, TEM and TGA.It is found that the addition of lanthanum can not increase the yield of carbon nanotube, but can make the diameter of carbon nanotube thinner and even.The more the lanthanum addsr, the thinner the diameter of CNTs becomes.With the CNTs prepared on Ni-Mg catalyst, the CNTs prepared on Ni-La-Mg catalyst has better crystallinity and thermal stability.

  10. A novel ammonia-assisted method for the direct synthesis of Mn3O4 nanoparticles at room temperature and their catalytic activity during the rapid degradation of azo dyes

    Science.gov (United States)

    Mansournia, Mohammadreza; Azizi, Fatemeh; Rakhshan, Narges

    2015-05-01

    In this study, we prepared trimanganese tetroxide nanoparticles from MnCl2 solution in an ammonia atmosphere using a new surfactant-free method at room temperature. We analyzed and characterized the effects of different processing conditions, such as the concentrations of manganese and the ammonia source, as well as the reaction time, on the structure, purity, and morphology of the products using powder X-ray diffraction (XRD), scanning electron microscopy, and Fourier transformation infrared spectroscopy (FTIR) techniques. The XRD and FTIR analyses confirmed that the prepared products comprised single phase Mn3O4. At room temperature, the paramagnetic characteristics were also verified by vibrating sample magnetometry. Furthermore, we tested the catalytic activity of the nanoparticles during the degradation of methyl orange and Congo red, which are organic pollutants. Our experiments demonstrated the rapid color removal and reduction in the chemical oxygen demand (>70% and >50% within 10 min, respectively) using aqueous solutions of azo dyes.

  11. 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).

  12. Structure–acidity correlation of supported tungsten(VI)-oxo-species: FT-IR and TPD studies of adsorbed pyridine and catalytic decomposition of 2-propanol

    Energy Technology Data Exchange (ETDEWEB)

    Zaki, M.I., E-mail: mizaki@mu.edu.eg; Mekhemer, G.A.H.; Fouad, N.E.; Rabee, A.I.M.

    2014-07-01

    The amount of 10 wt%-WO{sub 3} was supported on alumina, titania or silica by impregnation with aqueous solution of ammonium paratungstate and subsequent calcination at 500 °C for 10 h. Tungstate-related chemical and physical changes in the calcination products were resolved by ex-situ infrared (IR) spectroscopy. Nature of exposed surface acid sites were probed by in-situ IR spectroscopy of adsorbed pyridine (Py) molecules at room temperature (RT). The relative strength of the acid sites thus probed was gauged by combining results of temperature-programmed desorption (TPD) measurements of the RT-adsorbed Py with those communicated by in-situ IR spectra of residual Py on the surface after a brief thermoevacuation at high temperatures (100–300 °C). Reactivity of the surface acid sites was tested toward 2-propanal catalytic decomposition, and observed by in-situ IR gas phase spectra. Results obtained were correlated with predominant structures assumed by the supported tungstate species. Accordingly, polymerization of the supported tungstate into 2-/3-dimensional structures, was found to be relatively most advanced on favorable locations of titania surfaces as compared to the case on alumina or silica surfaces. Consequently, the Lewis acidity was strengthened, and strong Bronsted acidity was evolved, leading to a 2-propanol dehydration catalyst (tungstate/titania) of optimal activity and selectivity. Strong tungstate/support interfacial interactions were found to hamper the formation of the strongly acidic and catalytically active polymeric structures of the supported tungstate (i.e., the case on alumina or silica).

  13. Catalytic Decomposition of Nitric Oxide over Nano-sized PbTiO3 Supported Cupric Oxide%纳米晶PbTiO3负载CuO催化NO分解

    Institute of Scientific and Technical Information of China (English)

    邢丽; 薛念华; 陈向科; 郭学锋; 丁维平; 陈懿

    2005-01-01

    A large specific surface area perovskite-type mixed oxide PbTiO3 supported cupric oxide was synthesized as a catalyst for NO decomposition and characterized by techniques such as XPS, XRD,H2-TPR before and after NO deconlposition reactions. The catalytic properties were tested with a fix-bed micro-reactor. The results showed that the PbTiO3 was inactive for the reactions, but 1wt % Cu/PbTiO3 catalyst gave fairly good activities for NO decomposition at temperature as low as 473K. Copper species were found well-dispersed but weakly interacted with the support before NO decomposition, and the NO decomposition caused significant change in the environment of the copper species, which became Cu(Ⅰ) and most probably incorporated into surface crystal lattice of the nano-sized PbTiO3. In NO reaction, a large amount of oxygen atoms from the decomposition of NO penetrated into the nano-sized PbTiO3 support and caused small expansion of crystal lattice. The transport of oxygen between the copper species and the catalyst support may be helpful to speed up the kinetic regeneration of active metal sites from oxygen occupancy and resulted in good catalytic performance.

  14. [Study on mechanism of ceramic honeycomb-catalytic ozonation for the decomposition of trace nitrobenzene in aqueous solution].

    Science.gov (United States)

    Zhao, Lei; Ma, Jun; Sun, Zhi-Zhong; Liu, Zheng-Qian; Yang, Yi-Xin; Lu, Wei

    2007-02-01

    The experiment investigated effects of the presence of hydroxyl radical inhibitor on degradation efficiency of trace nitrobenzene in aqueous solution in the processes of ozonation alone and ceramic honeycomb-catalyzed ozonation, including HCO3-, CO3(2-), HPO4(2-), H2PO4- and tert-butanol, and studied preliminarily on their mechanism. The results indicated that degradation rate of the two processes both increased firstly and decreased subsequently with the increase of the concentration of HCO3- (0 - 200 mg x L(-1)), and reached the climax at the concentration of bicarbonate ion 50 mg x L(-1) under the same experimental condition. The degradation rates of ozonation alone and ozonation/ ceramic honeycomb both declined by 16.57% and 27.52% with the increase of the concentration of CO3(2-) (0 - 20 mg x L(-1)), respectively, and decreased by 13.61% and 17.52% with the addition of the concentration of HPO4(2-) (0 - 12 mg x L(-1)), and reduced by 6.61% and 12.52% with the enhancement of the concentration of H2PO4- (0 - 120 mg x L(-1)), and dropped by 30.06% and 46.09% with the increasing of the concentration of tert-butanol (0 - 10 mg x L(-1)). The experimental results indicated that decomposition of nitrobenzene in both processes all followed the mechanism of oxidization by OH free radical, and tert-butanol is a more suitable indicator for the radical type reaction. The removal rate of ozonation alone rose with the increase of the concentration of pH (3.02 - 10.96), but that of ozonation/ceramic honeycomb process reached the maximum at pH = 9.23.

  15. Liquid-phase chemical hydrogen storage: catalytic hydrogen generation under ambient conditions.

    Science.gov (United States)

    Jiang, Hai-Long; Singh, Sanjay Kumar; Yan, Jun-Min; Zhang, Xin-Bo; Xu, Qiang

    2010-05-25

    There is a demand for a sufficient and sustainable energy supply. Hence, the search for applicable hydrogen storage materials is extremely important owing to the diversified merits of hydrogen energy. Lithium and sodium borohydride, ammonia borane, hydrazine, and formic acid have been extensively investigated as promising hydrogen storage materials based on their relatively high hydrogen content. Significant advances, such as hydrogen generation temperatures and reaction kinetics, have been made in the catalytic hydrolysis of aqueous lithium and sodium borohydride and ammonia borane as well as in the catalytic decomposition of hydrous hydrazine and formic acid. In this Minireview we briefly survey the research progresses in catalytic hydrogen generation from these liquid-phase chemical hydrogen storage materials.

  16. 超临界氨合成%AMMONIA SYNTHESIS AT SUPERCRITICAL CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    刘化章; 唐浩东; 李小年

    2004-01-01

    Ammonia synthesis at supercritical conditions was first studied over iron and active carbonsupported ruthenium catalysts in a fixed-bed reactor. The influences of 15 kinds of different supercritical media, such as alkanes of C7-C13, 1, 2, 3, 4-tetrahydronaphthalene, cis-decalin, o-xylene,ethylbenzene, quinolin, n-hexane and aniline etc. and reaction conditions (catalyst, temperature, space velocity, particial pressure of media) on ammonia at supercritical condition were investigated.Supercritical medium was decomposed under reaction conditions over Fe and Ru/AC catalysts. The decomposition products deactivated the catalysts. Alkane decomposed the least, and the rate of deactivation was the slowest. Therefore alklane was a relatively good medium. The decomposion of supercritical medium was the key for the deactivation of catalysts. Another important reason for the decrease of ammonia concentration was that the effective pressure of syngas decreased because of the presence of supercritical media. The active temperature of catalyst was the decisive factor in supercritical ammonia synthesis. Supercritical catalytic reaction was viable only at a lower temperature. Ammonia ynthesis at supercritical conditions is possible if a catalyst with active temperature lower than 573 K could e developed and the decomposition of supercritical media could be prevented.

  17. Preparation of fibrous porous cobalt powders by thermal decomposition of cobalt oxalate complex with ammonia%热分解含氨草酸钴复盐制备纤维状多孔钴粉

    Institute of Scientific and Technical Information of China (English)

    湛菁; 周涤非; 张传福; 贺跃辉; 岳建峰

    2011-01-01

    以氨为配位剂,通过配位沉淀法制备纤维状钴粉复杂前驱体,并采用XRD,IR,SEM和TGA/DTA研究前驱体粉末的物相、成分与形貌,系统考察前驱体粉末热分解过程中热分解条件如热分解气氛、热分解温度、热分解时间和升温速率对金属钻粉形貌、粒度和比表面积的影响.研究结果表明:在Co(Ⅱ)-C2042——NH3-NH4+-H2O反应体系中得到的前驱体为含氨草酸钴复盐,形貌为纤维状,氨与钴离子配合并生成含氨草酸钴复盐是纤维状形貌形成的内在机制,它是通过含NH3基配合物以链状结构连接[(NH3)M-OX-M(NH3)]2+生长基元以轴向取向连生形成一维形貌;在弱还原性气氛、热分解时间为30~60 min、升温速率为15~20 K/min、热分解温度为623~723 K条件下,热分解含氨草酸钴复盐粉末可以制备比表面积为10.44 m2·g-1的纤维状多孔金属钴粉,其孔结构为两端开放的管状毛细孔且多为中孔.%A novel precursor of fibrous cobalt powders was synthesized by coordination-precipitation process using ammonia as complex agent. The phase, composition and morphology of the novel precursor were characterized by XRD,IR, DTA/TGA and SEM analysis. The influences of various conditions in pyrolysis, such as decomposition atmosphere,decomposition temperature, decomposition time and heating rate, on the morphology, average size and specific surface area of the cobalt powders were investigated. The results show that the precursors obtained in reaction system Co(Ⅱ )-C2O42--NH3-NH4+-H2O is ammoniacal complex of cobalt oxalate and the morphology is fibrous. The formation of the complex of oxalate cobalt with ammonia precipitated by coordination of ammonia and cobalt reacting with oxalate is quite essential to form fibrous morphology for the precursor, which may be formed through [(NH3)M-OX-M(NH3)] 2+growth units along the axial direction. The fibrous cobalt powders with 10.44 m2·g-1 for specific surface area are

  18. Synthesis of Nano-sized Yttria via a Sol-Gel Process Based on Hydrated Yttrium Nitrate and Ethylene Glycol and Its Catalytic Performance for Thermal Decomposition of NH4 ClO4

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination temperature on crystallite size of the products were studied. The catalytic performance of the as-prepared yttria for the ammonium perchlorate (AP) decomposition was investigated by differential scanning calorimetry (DSC). The results indicate that the nano-sized cubic yttria particles with less than 20 nm in average crystallite size can be obtained after 2 h reflux at 70 ℃, dried at 90 ℃, forming xerogel, and followed by annealing of xerogel for 2 h, and that the addition of the nano-sized yttria to AP incorporates two small exothermic peaks of AP in the temperature ranges of 310 ~ 350 ℃ and 400 ~ 470 ℃ into a strong exothermic peak of AP and increases the apparent decomposition heat from 515 to over 1110 J·g-1. It is also clear that the temperature of AP decomposition exothermic peak decreases and the apparent decomposition heat of AP increases with the increase of the amount of nano-sized yttria. The fact that the addition of the 5 % nano-sized yttria to AP decreases the temperature of AP exothermic peak to 337.7 ℃ by reduction of 114.6 ℃ and increases the apparent decomposition heat from 515 to 1240 J·g-1, reveals that nano-sized yttria shows strong catalytic property for AP thermal decomposition.

  19. Electroreduction of N2 to ammonia at ambient conditions on mononitrides of Zr, Nb, Cr, and V – A DFT guide for experiments

    DEFF Research Database (Denmark)

    Abghoui, Younes; Garden, Anna L.; Howalt, Jakob Geelmuyden

    2016-01-01

    with only a -0.5 V overpotential, thereby avoiding decomposition. We suggest that this is a promising step towards the development of a method for synthesizing ammonia cheaply, to prepare high-value-added nitrogenous compounds directly from air, water and electricity at ambient conditions. An additional......A rapid and facile reduction of nitrogen to achieve a sustainable and energy efficient production of ammonia is critical to its use as a hydrogen storage medium, chemical feedstock and especially for manufacturing inorganic fertilizers. For a decentralization of catalytic ammonia production, small...... of molecular nitrogen to ammonia in aqueous media at ambient conditions with only a low applied bias. The most promising catalysts are VN, ZrN, NbN and CrN, which are identified among a range of transition metal nitride surfaces through a comprehensive density functional theory based analysis. All four...

  20. Ammonia as efficient fuel for SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Fuerte, A.; Valenzuela, R.X.; Escudero, M.J. [CIEMAT, Departamento de Energia, Av. Complutense 22, 28040 Madrid (Spain); Daza, L. [CIEMAT, Departamento de Energia, Av. Complutense 22, 28040 Madrid (Spain); Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain)

    2009-07-01

    Ammonia is a possible candidate as the fuel for SOFCs. In this work, the influence on the performance of a tubular SOFC running on ammonia is studied. Analysis of open circuit voltages (OCVs) on the cell indicated the oxidation of ammonia within a SOFC is a two-stage process: decomposition of the inlet ammonia into nitrogen and hydrogen, followed by oxidation of hydrogen to water. For comparison, cell was also tested with hydrogen as the fuel and air as oxidant at different temperatures showing a similar behaviour. The performance of the cell tested under various conditions shows the high potential of ammonia as fuel for SOFCs. (author)

  1. Plasma Catalysis of Methane Decomposition in Pulse Microwave Discharge

    Science.gov (United States)

    Potapkin, B.; Rusanov, V.; Jivotov, V.; Babaritski, A.; Potechin, S.; Etievant, C.

    1997-10-01

    Investigation of plasma catalysis effects in various chemical reactions, such as SO2 and hydrocarbons oxidation, ammonia and nitrogen oxides synthesis, has been of interest for many decades. Present work describes the first experimental observation and theoretical analysis of plasma catalysis effects in the case of endothermic methane decomposition into molecular hydrogen and carbon black. Process energy requirements are coverd mainly by low potential gas thermal energy while plasma is used for acceleration of chemical reactions via active species generation. The experiments were done as follows: (i) methane was preheated in a conventional heat exchanger up to about 40-65 ^oC where thermal methane decomposition is limited by process kinetics, (ii) methane was passed through a non-equilibrium pulse microwave discharge (9.04 GHz, pulse duration 1 μs). Experiments have shown a strong catalytic effect of plasma on methane decomposition. The degree of conversion after discharge increased drastically, despite gas cooling, because of heat absorption in the methane decomposition reaction. Theoretical analysis of process kinetics and energy balance gave clear evidence of the catalytic effect of plasma under experimental conditions. The estimated chain length was about 300. The possible mechanism of plasma catalysis, the ion-molecular chain Winchester mechanism, is proposed and described.

  2. Ammonia synthesis at low temperatures

    DEFF Research Database (Denmark)

    Rod, Thomas Holm; Logadottir, Ashildur; Nørskov, Jens Kehlet

    2000-01-01

    Density functional theory (DFT) calculations of reaction paths and energies for the industrial and the biological catalytic ammonia synthesis processes are compared. The industrial catalyst is modeled by a ruthenium surface, while the active part of the enzyme is modeled by a MoFe6S9 complex...... have been carried out to evaluate its feasibility. The calculations suggest that it might be possible to catalytically produce ammonia from molecular nitrogen at low temperatures and pressures, in particular if energy is fed into the process electrochemically. (C) 2000 American Institute of Physics....

  3. 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.

  4. Catalytic hot gas cleaning of gasification gas

    Energy Technology Data Exchange (ETDEWEB)

    Simell, P. [VTT Energy, Espoo (Finland). Energy Production Technologies

    1997-12-31

    The aim of this work was to study the catalytic cleaning of gasification gas from tars and ammonia. In addition, factors influencing catalytic activity in industrial applications were studied, as well as the effects of different operation conditions and limits. Also the catalytic reactions of tar and ammonia with gasification gas components were studied. The activities of different catalyst materials were measured with laboratory-scale reactors fed by slip streams taken from updraft and fluid bed gasifiers. Carbonate rocks and nickel catalysts proved to be active tar decomposing catalysts. Ammonia decomposition was in turn facilitated by nickel catalysts and iron materials like iron sinter and iron dolomite. Temperatures over 850 deg C were required at 2000{sup -1} space velocity at ambient pressure to achieve almost complete conversions. During catalytic reactions H{sub 2} and CO were formed and H{sub 2}O was consumed in addition to decomposing hydrocarbons and ammonia. Equilibrium gas composition was almost achieved with nickel catalysts at 900 deg C. No deactivation by H{sub 2}S or carbon took place in these conditions. Catalyst blocking by particulates was avoided by using a monolith type of catalyst. The apparent first order kinetic parameters were determined for the most active materials. The activities of dolomite, nickel catalyst and reference materials were measured in different gas atmospheres using laboratory apparatus. This consisted of nitrogen carrier, toluene as tar model compound, ammonia and one of the components H{sub 2}, H{sub 2}O, CO, CO{sub 2}, CO{sub 2}+H{sub 2}O or CO+CO{sub 2}. Also synthetic gasification gas was used. With the dolomite and nickel catalyst the highest toluene decomposition rates were measured with CO{sub 2} and H{sub 2}O. In gasification gas, however, the rate was retarded due to inhibition by reaction products (CO, H{sub 2}, CO{sub 2}). Tar decomposition over dolomite was modelled by benzene reactions with CO{sub 2}, H

  5. Cs(x)H(3.0-x)PW12O40 (X = 2.0-3.0) heteropolyacid nano-catalysts for catalytic decomposition of 2,3-dihydrobenzofuran to aromatics.

    Science.gov (United States)

    Kim, Jeong Kwon; Park, Hai Woong; Hong, Ung Gi; Choi, Jung Ho; Song, In Kyu

    2014-11-01

    Cesium-exchanged Cs(x)H(3.0-x)PW12O40 (X = 2.0, 2.3, 2.5, 2.8, and 3.0) heteropolyacid nanocatalysts were prepared, and they were applied to the catalytic decomposition of lignin model compound to aromatics. Successful formation of cesium-exchanged Cs(x)H(3.0-x)PW12O40 (X = 2.0-3.0) catalysts was confirmed by FT-IR, ICP-AES, and XRD measurements. 2,3-Dihydrobenzofuran was employed as a lignin model compound for representing β-5 bond in lignin. Phenol, ethylbenzene, and 2-ethylphenol were mainly produced by the catalytic decomposition of 2,3-dihydrobenzofuran. Conversion of 2,3-dihydrobenzofuran and total yield for main products (phenol, ethylbenzene, and 2-ethylphenol) were closely related to the surface acidity of Cs(x)H(3.0-x)PW12O40 (X = 2.0-3.0) catalysts. Conversion of 2,3-dihydrobenzofuran and total yield for main products increased with increasing surface acidity of the catalysts. Among the catalysts tested, Cs2.5H0.5PW12O40 with the largest surface acidity showed the highest conversion of 2,3-dihydrobenzofuran and the highest total yield for main products. These results indicate that surface acidity of Cs(x)H(3.0-x)PW12O40 (X = 2.0-3.0) catalysts served as an important factor determining the catalytic performance in the decomposition of 2,3-dihydrobenzofuran to aromatics.

  6. 超重力氨法制备超细氧化锌%Preparation of Ultra-Fine Zinc Oxide by Ammonia Decomposition Method in High Gravity Field

    Institute of Scientific and Technical Information of China (English)

    焦纬洲; 刘有智; 祁贵生; 杨森; 李孟委

    2012-01-01

    在旋转填料床反应器中,以锌氨络合物与蒸汽为原料制得氧化锌前驱体,经煅烧后得到超细氧化锌产品.考察了超重力因子、气液比、蒸汽流量和温度等操作参数对产品收率的影响.结果表明,在超重力因子167.2,气液比1.14 kg/L,蒸汽流量 30 L/h和蒸汽温度135℃的条件下,沉锌率较高,可达96.7%.氧化锌产品的透射电镜(TEM)表征结果表明,其形貌为近球状,平均粒径为45 nm.%In the high gravity rotating packed bed reactor, the zinc-ammonia complex solution reacted with steam to precipitate the precursor of zinc oxide, which was then calcinated into ultra-fine zinc oxide. The effects of gravity factor, gas-liquid ratio, steam flow rate and temperature on the efficiency of zinc precipitation were investigated. The results showed that the zinc precipitation could reach up to 96.7% under the conditions of gravity factor of 167.2, gas-liquid ratio of 1.14 kg/L, steam flow rate of 30 L/h and steam temperature of 135℃. Transmission electron microscope (TEM) results showed that the product had a near spherical morphology with an average particle size of 45 nm.

  7. Synthesis, characterization, and catalytic activity of Zirconium oxide nitrides supported on high-surface SiO{sub 2}; Praeparation und Charakterisierung von SiO{sub 2}-getraegerten Zirconiumoxidnitriden mit hoher Oberflaeche und Untersuchung ihrer katalytischen Aktivitaet bei der Ammoniakzersetzung

    Energy Technology Data Exchange (ETDEWEB)

    Frenzel, Nancy; Otremba, Thorsten; Schomaecker, Reinhard; Ressler, Thorsten; Lerch, Martin [Technische Univ. Berlin (Germany). Inst. fuer Chemie

    2011-02-15

    Zirconium oxide nitrides are active ammonia decomposition catalysts for the production of hydrogen. We present a route to zirconium oxide nitrides with high surface area. The precursor used consisted of a high-surface-area silica material coated with zirconium alkoxide. Subsequent hydrolysis and calcination resulted in ZrO{sub 2} supported on SiO{sub 2}. The high surface area of the material could be maintained in the following ammonolysis procedure leading to the corresponding zirconium oxide nitride. In contrast to the as-prepared ZrO{sub 2}, the zirconium oxide nitrides exhibited a significant catalytic activity in ammonia decomposition, but compared to an iron oxide-based reference material, the new oxide nitrides showed a rather low activity. Nevertheless, zirconium oxide nitrides constitute suitable model systems for elucidating the effect of nitrogen in the anion substructure on the activity and selectivity of oxide-based ammonia decomposition catalysts. (orig.)

  8. OPTIMAL OPERATION CONDITIONS OF AMMONIA SYNTHESIS AND CATALYTIC ACTIVITY FOR A301 CATALYST%A301氨合成催化剂最佳操作条件与催化活性的关系

    Institute of Scientific and Technical Information of China (English)

    刘化章; 李小年; 胡樟能; 岑亚青; 傅冠平

    2001-01-01

    用高压氨合成催化剂性能评价装置,研究了反应温度、压力、空速、惰性气体含量、氢氮比和催化剂粒度对A301催化剂活性的影响。A301催化剂在15 MPa下的最适反应温度在430~480℃,在7 MPa下在376~450℃,比A110-2低15~35℃。A301催化剂的最佳H2,N2摩尔比nm在450℃时为2.55~3.0,在400℃时为2.23~2.55,在350℃时为1.76~2.22, 并可用nm =1.50+1.49(cNH3/c*NH3)来表示。惰性气体含量会使催化剂活性大幅度降低,每当惰性气体含量增加1%,出口氨浓度(氨净值)平均降低0.2%~0.35%。颗粒大小对活性或反应速率有严重的影响,其内表面利用率受反应温度和催化效率两个因素的影响,对于高活性的A301催化剂,催化效率的因素起主要作用。根据实验结果和合成氨反应的基本理论,讨论并提出了A301催化剂在合成氨生产中的最佳操作工艺条件。%The influences of temperature, pressure, space velocity, concentration of inert gas, ratio of hydrogen to nitrogen and particle size on the activity of A301 catalyst were investigated. The optimal reaction temperatures for A301 catalyst are in the range of 430~480℃ at 15MPa of pressure and 376~450℃ at 7MPa of pressure, 15~35℃ lower than A110-2 catalyst. The optimal ratios of hydrogen to nitrogen nm for A301 catalyst are 2.55~3.0, 2.23~2.55 and 1.76~2.22 at temperature of 450, 400 and 350℃ respectively, and may be expressed by equation of nm =1.50+1.49(cNH3/cNH3*). The more the content of inert gas (CH4+Ar), the lower the outlet ammonia concentration. When the content of inert gas increased by one percent, the outlet ammonia concentration lowered 0.2%~0.35%. The use ratio of inner face of a catalyst is not only related to the particle size but also to temperature and catalytic efficiency. But the catalytic efficiency acts mainly for high active A301 catalyst. According to the experiment results and the

  9. 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 activity of the mesoporous samples in NO SCR with NH3 is significantly higher than for conventional samples. Such a difference in the activity is probably related with the better diffusion of reactants and products in the mesopores and better dispersion of the iron particles in the mesoporous zeolite...

  10. Novel ultrasonic-modified MnOx/TiO2 for low-temperature selective catalytic reduction (SCR) of NO with ammonia.

    Science.gov (United States)

    Zhang, Yaping; Zhao, Xiaoyuan; Xu, Haitao; Shen, Kai; Zhou, Changcheng; Jin, Baosheng; Sun, Keqin

    2011-09-01

    A novel ultrasonic-modified MnO(x)/TiO(2) catalyst was prepared and compared with two different kinds of MnO(x)/TiO(2) catalysts in the process of low-temperature selective catalytic reduction of NO with NH(3). The physicochemical properties of the catalysts were studied by using various characterization techniques, such as Brunauer-Emmett-Teller (BET) surface measurement, X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and in situ Fourier transform infrared spectroscopy (in situ FT-IR). The ultrasonic-modified process introduced ultrasound in the solution impregnation step of traditional impregnation method for MnO(x)/TiO(2) catalyst preparation. In this study, ultrasonic process significantly improved the dispersion behavior and surface acid property of manganese oxide on TiO(2) as well as the catalytic activity, especially at temperature below 120°C. The NO conversion could reach 90% at 100°C. For the novel ultrasonic-modified catalyst, the combination analysis of XRD and HRTEM confirmed that manganese oxide was in a highly dispersed state and Ti and Mn had strong interaction. Furthermore, in situ FT-IR studies revealed that there were significant amounts of Lewis acidity and high Mn atom concentration on the surface of the novel catalysts.

  11. Catalytic behaviors of CoB and CoB/SiO2 in thermal decomposition of ammonium perchlorate%CoB和CoB/SiO2对AP热分解的催化活性研究

    Institute of Scientific and Technical Information of China (English)

    李茸; 刘祥萱; 王煊军

    2011-01-01

    Silicon-supported cobalt-boron(CoB/SiO2) and cobalt-boron (CoB) nano-sized catalysts were synthesized via chemical deposition method. Their catalytic behavior in the thermal decomposition of ammonium perchlorate( AP) was briefly studied by thermo-gravimetric and differential thermal analysis (TG-DTA). Results show that both CoB/SiO2 and CoB have catalytic effects on the thermal decomposition of AP. CoB/SiO2 is more effective. The high-temperature thermal decomposition temperature of AP was decreased by 166. 2 ℃ with the addition of 5% CoB/SiO2. This effect is mainly attributed to its higher thermodynamic stability compared with CoB,whch is favorable for catalysis.%采用化学沉积方法,制备了纳米尺度CoB和SiO2·负载的CoB/SiO2催化剂.通过热重-差热分析(TG-DTA)实验,研究了催化剂在AP热分解过程中的催化性能.结果表明,CoB和CoB/SiO2对AP热分解均表现出催化活性,CoB/SiO2的活性更强;质量分数5%的CoB/SiO2,可将AP高温热分解峰的峰温降低166.2℃;CoB/SiO2较好的催化效果,归因于其相对CoB更高的热力学稳定性;负载型催化剂的较高热力学稳定性,更有利于其催化活性的履行.

  12. Effect of ammonia concentration on the catalytic activity of Pd-Cu supported on attapulgite clay prepared by ammonia evaporation in CO oxidation at room temperature%氨浓度对氨蒸发法制备Pd-Cu/凹凸棒土催化剂常温CO氧化性能的影响

    Institute of Scientific and Technical Information of China (English)

    王永钊; 范莉渊; 武瑞芳; 石晶; 李潇; 赵永祥

    2015-01-01

    With attapulgite clay ( APT ) as support, the Pd-Cu/APT catalysts were prepared by an ammonia evaporation method and characterized by N2-physisorption, XRD, FT-IR, TEM and H2-TPR. The effect of ammonia concentration on the catalytic performance of Pd-Cu/APT in CO oxidation at room temperature was investigated in a fixed-bed continuous flow microreactor. The results showed that CuO appears as the main Cu species in the Pd-Cu/APT catalysts prepared with over low or over high ammonia concentration, whereas the quantity of Cu2(OH)3Cl phase is much less. However, a proper concentration of ammonia is of benefits to forming stable Cu2( OH) 3 Cl species in Pd-Cu/APT;owing to its high dispersion, nano-platelet morphology and strong interaction with Pd species, the presence of stable Cu2 ( OH ) 3 Cl can significantly promote the catalytic performance of Pd-Cu/APT in CO oxidation. Under a gas hourly space velocity ( GHSV) of 6 000 h-1 for a feed stream containing 1. 5% CO and 3. 3% water, the Pd-Cu/APT catalyst exhibits excellent activity and stability in CO oxidation even at room temperature.%以凹凸棒土( APT)作载体,采用氨蒸发法制备了Pd-Cu/APT催化剂,以CO氧化为探针反应,在连续流动微反应装置上,考察了初始氨浓度对催化剂CO常温催化氧化性能的影响。通过N2-physisorption、XRD、FT-IR、TEM和H2-TPR等手段对催化剂的结构和性质进行了表征。结果表明,在较低或过高氨浓度条件下,制备的Pd-Cu/APT中Cu物种均主要以CuO为主,仅有少量Cu2(OH)3Cl;适宜的氨浓度有利于稳定Cu2(OH)3Cl物相的形成,其薄片状的形貌特征、良好的分散状态以及与Pd物种间较强的相互作用,显著提高了CO催化氧化性能。在空速6000 h-1、CO体积分数1.5%、水蒸气体积分数3.3%的反应条件下,Pd-Cu/APT催化剂表现出优异的CO室温催化氧化活性和稳定性。

  13. Numerical Simulation for Uniform Mixing of Flue Gas and Ammonia in the Selective Catalytic Reduction Denitration Reacto%SCR脱硝反应器内烟气与氨均混的数值模拟

    Institute of Scientific and Technical Information of China (English)

    彭慧; 姜昌伟; 陈冬林; 刘小波; 冯延林; 曾昭良

    2011-01-01

    为了改善选择性催化还原(SCR)脱硝反应器内烟气与氨气的混合效果,提出3种导流板布置方案,应用数值模拟方法分析了导流板布置方式对SCR反应器内烟气流场与氨浓度分布的影响。分析结果表明:不同的导流板布置方式对烟气与氨气混合效果具有重要影响,采用3块导流板不均匀布置的方案具有最佳的混合效果。%In order to improve the mixing effect of the flue gas and ammonia in SCR( selective catalytic reduc- tion) denitration reactor, three layout methods for deflectors are proposed. A numerical simulation has been applied for the study on the field of flue ga

  14. 氨铜比对蒸氨法Cu/SiO2催化剂活性组分演变及二氧化碳加氢性能的影响%Effect of ammonia-copper ratio on the structural evolution and catalytic activity of Cu/SiO2 catalysts prepared by ammonia evaporation method in CO2 hydrogenation reaction

    Institute of Scientific and Technical Information of China (English)

    李静; 靳博晗; 岳海荣; 应建康

    2016-01-01

    铜催化剂表面铜活性物种的性质与分散度是影响CO2加氢性能的关键因素。以硅溶胶为载体、铜氨络合物为铜源,采用蒸氨法制备了Cu/SiO2催化剂,考察了氨铜比对Cu/SiO2催化剂表面铜活性物种的形成和CO2加氢制甲醇反应性能的影响。通过N2-physisorption、TEM、XRD、IR和BET等技术对催化剂的结构和性质进行了表征。结果显示,铜氨溶液中适当的氨浓度,有利于铜氨配体的形成和蒸氨过程中铜活性组分的均匀分布,有利于层状硅酸铜和氧化铜双活性组分的形成。在反应温度523 K,反应压力2.5 MPa,进气比V(CO2)∶V(H2)∶V(N2)=10∶30∶4,反应空速1800 mLSTP/( g· h)的条件下,氨铜比为4的Cu/SiO2-N4催化剂获得较优CO2加氢催化性能,CO2的转化率31%,CH3 OH的选择性54.8%,CH3 OH的收率17%。%The nature and distribution of surface copper active species on the copper based catalysts are crucial for the catalytic hydrogenation of CO 2 to methanol .Silica supported copper catalyst Cu /SiO2 was pre-pared by ammonia evaporation ( AE) method with different ammonia-copper molar ratio and characterized by N2-physisorption ,TEM,XRD,IR and BET techniques .Performance of the Cu/SiO2 catalysts on the hy-drogenation of CO2 reaction was also evaluated with a feed gas ratio of V(CO2)∶V(H2)∶V(N2)=10∶30∶4 under 523 K,2.5 MPa.The results indicated that the ammonia-copper molar ratio in the AE method exerted profound effects on the copper loading ,texture properties and surface composition of the Cu /SiO2 catalysts. Catalysts with the proper copper loading ,smaller copper particle size ,larger metallic copper surface area and good dispersion of copper species could be obtained by using a proper ammonia -copper molar ratio .The Cu/SiO2-N4 catalyst with an optimal ratio of ammonia to copper of 4 can achieve CO 2 conversion of 31%,CH3 OH selectivity of 54.8%and CH3 OH

  15. 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.

  16. 不同方法制备的Cu/HZSM-5催化剂上NO的催化分解反应%Catalytic decomposition of nitrogen oxide over Cu/HZSM-5 catalysts prepared by different methods

    Institute of Scientific and Technical Information of China (English)

    阳鹏飞; 周继承; 任文明

    2011-01-01

    采用离子交换法、固相分散法和微波固相法等不同方法制备了Cu/HZSM-5催化剂,以BET、XRD和XPS等手段对催化剂样品进行了表征.结果表明,不同方法制备的Cu/HZSM-5催化剂上Cu物种的落位分布状态不同,离子交换法制备的催化剂Cu物种更多地落位于分子筛孔道内,微波固相法和固相分散法制备的催化剂Cu物种较多地落位分布在分子筛外表面.固相分散法制备的样品未能使铜物种完全分散于分子筛表面,在13.1°、16.8°、35.5°和38.0°等处仍存在CuO的晶相衍射峰.催化分解NO反应的活性考察结果表明,用微波固相法制备的催化剂催化分解NO的活性及稳定性明显超过另两种方法所制备的催化剂,在无氧条件下NO最初转化率高达89.2%,经反应25h后,转化率仍维持在70%以上;在富氧气氛下催化分解NO活性降低速率低于由离子交换法制备的催化剂.结合表征结果可以得出,落位于分子筛外表面以离子交换态形式存在的Cu物种对催化分解NO反应更为有利,而且催化稳定性更好.%Cu/HZSM-5 catalysts were prepared by different methods of ion exchange, solid-state dispersion and solid-state microwave irradiation. The obtained Cu/HZSM-5 catalysts were characterized by means of BET,XRD and XPS. Experimental results exhibited that the location of Cu species was strongly dependent on the preparation method. Cu species on the external surface of the zeolite prepared by solid-state microwave irradiation and solid-state dispersion are more than ion exchange. And the crystalline diffraction peaks of CuO species can be found in the samples prepared by solid-state dispersion. In addition, the catalytic performance of the catalyst for NO catalytic decomposition was investigated. Compared with the other two methods, the catalysts prepared by solide-state microwave irradiation showed higher catalytic activity and stability for NO catalytic decomposition. Under anaerobic

  17. An operando optical fiber UV–vis spectroscopic study of the catalytic decomposition of NO and N2O over Cu-ZSM-5

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Groothaert, M.H.; Lievens, K.; Leeman, H.; Schoonheydt, R.A.

    2003-01-01

    The role of the bis(μ-oxo)dicopper core, i.e., [Cu2(μ-O)2]2+, in the decomposition of NO and N2O by the Cu-ZSM-5 zeolite has been studied with combined operando UV–vis monitoring of the catalyst and on-line GC analysis. An optical fiber was mounted on the outer surface of the quartz wall of the plug

  18. Comparison of the Effects of Fluidized-Bed and Fixed-Bed Reactors in Microwave-Assisted Catalytic Decomposition of TCE by Hydrogen

    Directory of Open Access Journals (Sweden)

    Lili Ren

    2012-01-01

    Full Text Available Trichloroethylene (TCE decomposition by hydrogen with microwave heating under different reaction systems was investigated. The activities of a series of catalysts for microwave-assisted TCE hydrodechlorination were tested through the fixed-bed and the fluidized-bed reactor systems. This study found that the different reaction system is suitable for different catalyst type. And there is an interactive relationship between the catalyst type and the reaction bed type.

  19. FY 1998 annual report on the decomposition/removal of harmful compounds in the gaseous phase by porous membrane provided with a catalytic function; 1998 nendo shokubai kinotsuki fuyo takomaku ni yoru kisochu yugai busshitsu no bunkai jokyo chosa hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-03-01

    Harmful compounds, e.g., dioxins and nitrogen oxides, released into the air are causing severer environmental problems on a global scale. In order to solve these problems, it is necessary to efficiently remove the released compounds in the vicinity of the living environments, while preventing, as far as possible, their formation at the sources. An attempt has been made to develop porous membranes impregnated with composites of a variety of metallic oxides showing activities as photocatalysts and for dark reactions by the ion engineering method, in order to drastically solve the above problems. Described herein are the FY 1998 results. Thin films of various titanium oxide crystals (anatase, rutile, and their combinations) are formed on Si substrates by the ion engineering method, as the photocatalysts for decomposition of aldehyde and water (for hydrogen production), to validate the optimum crystalline structures for the photocatalysis. Porous bodies of Ni and carbon are also impregnated with anatase TiO{sub 2} for decomposition of harmful gaseous compounds and water, to validate the effects of the porous membranes provided with catalytic functions. (NEDO)

  20. Synthesis of CuO porous nanorods and their catalytic activity in the decomposition of potassium chlorate and peroxide%孔状氧化铜纳米棒的制备及其催化性能研究

    Institute of Scientific and Technical Information of China (English)

    徐惠; 黄剑; 陈泳

    2011-01-01

    Copper monoxide (CUO) porous nanorods of 100-200nm in diameter and 2-3μm in length were successfully synthesized using a hydrothermal reaction method in the presence of urea. The products were characterized by SEM., TEM, FT-IR, XRD and TG analysis techniques. The results of catalytic activity indicate that CuO nanocrystal promoted potassium chlorate and peroxide decomposition. When the ratio of H2O2 to CuP is 5 to 1,the decomposition of peroxide is perfect.%以硝酸铜为铜源,采用尿素矿化剂,通过水热法制得纳米氧化铜前驱体,高温煅烧后得到长21μm,直径200nm的氧化铜多孔纳米捧,所得产品尺寸均一,微孔分布均匀,排列整齐.通过IR、XRD、SEM以及TEM对其结构和形貌进行了表征.研究表明,所制备的纳米氧化铜多孔棒无需任何制样处理对氯酸钾和过氧化氢具有较高的催化活性,当n(H2O2):n(CuO)=5:1时,过氧化氢的分解速率最快.

  1. Preparation of nanometer NiO/MgO and its catalytic performance for thermal decomposition of ammonium perchlorate%纳米NiO/MgO的制备及其对AP热分解催化性能影响

    Institute of Scientific and Technical Information of China (English)

    谈玲华; 李勤华; 杭祖圣; 潘仁明; 姜炜; 李凤生

    2011-01-01

    采用浸渍法制备出纳米NiO/MgO复合氧化物粒子,运用X射线衍射(XRD)、X射线能谱仪(EDS)等对产物的物相和组成进行了表征,并研究了单一纳米粒子(NiO、MgO)、纳米NiO+MgO混合粒子及纳米NiO/MgO复合氧化物粒子对AP热分解的催化性能.结果表明,所制备的纳米NiO/MgO复合氧化物粒子中NiO粒子高度分散于MgO载体中.纳米NiO/MgO复合氧化物粒子可使AP的高温分解峰温降低92.2℃,高低温分解峰温差减小到10.6℃,表现出较强的催化性能,其催化性能优于单一纳米粒子(NiO、MgO)、纳米NiO+MgO混合粒子.纳米MgO的载体支撑作用,可防止NiO纳米粒子的团聚,增加反应活性中心,从而提高催化效果.%The nanometer NiO/MgO composite particles were prepared via impregnation method. The phase and morphology of NiO/MgO composites were characterized by X-ray diffraction, transmission electron microscopy and energy dispersive X-Ray spectroscopy. The catalysis of nanometer particles ( NiO, MgO), NiO + MgO mixture particles and NiO/MgO composite particles the thermal decomposition of ammonium perchlorate (AP) was investigated by DSC. The Results show that NiO particles are highly dispersed on the MgO support. Catalytic performance of the obtained nanometer NiO/MgO composite particles is superior to that of corresponding single ingredient and NiO + MgO mixture particles. Nanometer NiO/MgO can make the high-temperature decomposition peak value of AP decrease by 92.2 ℃ and the temperature difference value between the low and high temperature decomposition peak reduce up to 10. 6 ℃, which indicates good catalytic performance. The supporting effect of the nanometer MgO can effectively prevent the aggregation of NiO particles and increase the active sites.

  2. Decomposição catalítica de óxidos de nitrogênio Catalytic decomposition of nitrogen oxides

    Directory of Open Access Journals (Sweden)

    Julia María Díaz Cónsul

    2004-06-01

    Full Text Available Contaminant gases in the atmosphere constitute an important problem to be solved in the world. The NOx gases produced as a consequence of engine high temperatures are deleterious to environment and human health, as they promote acid rain and can act in the same way as freons in the destruction of the ozone layer in the stratosphere. In this review, three way and selective reduction catalysts for decomposition of these contaminant gases are described. Details about conditions and problems, such as catalyst poisoning, and the search for new catalysts are shown.

  3. Characterization and catalytic behavior of MoO3/V2O5/Nb2 O5 systems in isopropanol decomposition

    Directory of Open Access Journals (Sweden)

    J. B. de Paiva Jr

    2006-12-01

    Full Text Available The influence of molybdenum oxide as a promoter on the V2O5/Nb2O5 system was investigated. A series of MoO3/V2O5/Nb2 O5 catalysts, with MoO3 loading ranging from 1 to 3 wt% MoO3 and fixed V2O5 content (21 wt%, were prepared by impregnation of the Nb2O5 support with an aqueous solution of ammonium metavanadate and ammonium molybdate. The acid-base properties of the catalysts were investigated to determine of the selectivity of the isopropanol decomposition reaction. The X-ray diffraction results showed the presence of the beta-(Nb,V2O5 phase. The temperature-programmed reduction profiles showed that the reducibility of vanadium was affected by the presence of molybdenum oxide. Activity results for isopropanol decomposition revealed that the acid-base properties of V2O5/Nb2O5 catalysts are affected upon incorporation of MoO3, specifically for loadings of 3 wt %. For this catalyst composition both propylene and acetone formation rates decreased.

  4. Microwave-assisted synthesis of carbon-supported carbides catalysts for hydrous hydrazine decomposition

    Science.gov (United States)

    Mnatsakanyan, Raman; Zhurnachyan, Alina R.; Matyshak, Valery A.; Manukyan, Khachatur V.; Mukasyan, Alexander S.

    2016-09-01

    Microwave-assisted synthesis of carbon-supported Mo2C and WC nanomaterials was studied. Two different routes were utilized to prepare MoO3 (WO3) - C precursors that were then subjected to microwave irradiation in an inert atmosphere. The effect of synthesis conditions, such as irradiation time and gas environment, was investigated. The structure and formation mechanism of the carbide phases were explored. As-synthesized nanomaterials exhibited catalytic activity for hydrous hydrazine (N2H4·H2O) decomposition at 30-70 °C. It was shown that the catalyst activity significantly increases if microwave irradiation is applied during the decomposition process. Such conditions permit complete conversion of hydrazine to ammonia and nitrogen within minutes. This effect can be attributed to the unique nanostructure of the catalysts that includes microwave absorbing carbon and active carbide constituents.

  5. Red Mud as an Efficient, Stable, and Cost-Free Catalyst for COx-Free Hydrogen Production from Ammonia

    Science.gov (United States)

    Kurtoğlu, Samira Fatma; Uzun, Alper

    2016-08-01

    Red mud, one of the mostly produced industrial wastes, was converted into a catalyst with exceptionally high and stable performance for hydrogen production from ammonia. Results showed that iron species produced after reduction of the HCl digested red mud were converted into ɛ-Fe2N during the induction period of ammonia decomposition reaction at 700 °C. The catalytic performance measurements indicated that the modified red mud catalyst provides a record high hydrogen production rate for a non-noble metal catalyst at this temperature. For instance, stable hydrogen production rates were measured as 72 and 196 mmol H2 min-1 gcat-1 for the corresponding space velocities of 72 000 and 240 000 cm3 NH3 h-1 gcat-1, respectively, at 700 °C. These results offer opportunities to utilize one of the key hazardous industrial wastes as an eco-friendly, efficient, stable, and almost cost-free catalyst for COx-free hydrogen production from ammonia decomposition.

  6. Involvement of metals in enzymatic and nonenzymatic decomposition of C-terminal alpha-hydroxyglycine to amide: an implication for the catalytic role of enzyme-bound zinc in the peptidylamidoglycolate lyase reaction.

    Science.gov (United States)

    Takahashi, Kenichi; Harada, Saori; Higashimoto, Yuichiro; Shimokawa, Chizu; Sato, Hideaki; Sugishima, Masakazu; Kaida, Yasuhiko; Noguchi, Masato

    2009-02-24

    The peptide C-terminal amide group essential for the full biological activity of many peptide hormones is produced by consecutive actions of peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidylamidoglycolate lyase (PAL); PHM catalyzes the hydroxylation of C-terminal glycine, and PAL decomposes the peptidyl-alpha-hydroxyglycine to an amidated peptide and glyoxylate. PAL contains 1 mol of zinc, but its role, catalytic or structural, has not yet been clarified. In this study, we found that a series of transition metals, Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), and Cd(2+), catalyze the nonenzymatic decomposition of the hydroxyglycine intermediate in a concentration-dependent manner. The second-order rate constant of the metal catalysis increased with elevation of pH, indicating that the hydrated metal acts as a general base. Extensive removal of the enzyme-bound metals remarkably diminished the PAL activity; k(cat) of the metal-depleted enzyme retaining 0.1 mol of zinc decreased to 3.2 s(-1) from 25.7 s(-1) of the wild-type enzyme. Among a series of divalent metals tested, Zn(2+), Co(2+), and Cd(2+) could fully restore the PAL activity of the metal-depleted enzyme. Especially, Zn substitution reproduced the steady-state parameters of the wild-type enzyme. On the other hand, Co and Cd substitution largely altered the kinetic parameters; the k(cat) increased 3- and 5-fold and the K(m) for the substrate increased 2.5- and 4-fold, respectively. These observations support that the enzyme-bound zinc plays a catalytic role, rather than a structural role, in the PAL reaction through the action of zinc-bound water as a general base.

  7. Removal of nitrogen compounds from gasification gas by selective catalytic or non-catalytic oxidation; Typpiyhdisteiden poisto kaasutuskaasusta selektiivisellae katalyyttisellae ja ei-katalyyttisellae hapetuksella

    Energy Technology Data Exchange (ETDEWEB)

    Leppaelahti, J.; Koljonen, T. [VTT Energy, Espoo (Finland)

    1996-12-01

    In gasification reactive nitrogenous compounds are formed from fuel nitrogen, which may form nitrogen oxides in gas combustion. In fluidized bed gasification the most important nitrogenous compound is ammonia (NH{sub 3}). If ammonia could be decomposed to N{sub 2} already before combustion, the emissions if nitrogen oxides could be reduced significantly. One way of increasing the decomposition rate of NH{sub 3} could be the addition of suitable reactants to the gas, which would react with NH{sub 3} and produce N{sub 2}. The aim of this research is to create basic information, which can be used to develop a new method for removal of nitrogen compounds from gasification gas. The reactions of nitrogen compounds and added reactants are studied in reductive atmosphere in order to find conditions, in which nitrogen compounds can be oxidized selectively to N{sub 2}. The project consists of following subtasks: (1) Selective non-catalytic oxidation (SNCO): Reactions of nitrogen compounds and oxidizers in the gas phase, (2) Selective catalytic oxidation (SCO): Reactions of nitrogen compounds and oxidizers on catalytically active surfaces, (3) Kinetic modelling of experimental results in co-operation with the Combustion Chemistry Research Group of Aabo Akademi University. The most important finding has been that NH{sub 3} can be made to react selectively with the oxidizers even in the presence of large amounts of CO and H{sub 2}. Aluminium oxides were found to be the most effective materials promoting selectivity. (author)

  8. Characteristics of La-modified Ni-Al2O3 and Ni-SiO2 catalysts for COx-free hydrogen production by catalytic decomposition of methane

    Institute of Scientific and Technical Information of China (English)

    Chatla; Anjaneyulu; Velisoju; Vijay; Kumar; Suresh; K.Bhargava; Akula; Venugopal

    2013-01-01

    Hydrotalcite precursors of La modified Ni-Al2O3 and Ni-SiO2 catalysts prepared by co-precipitation method and the catalytic activities were examined for the production of COx-free H2 by CH4 decomposition. Physico-chemical characteristics of fresh, reduced and used catalysts were evaluated by XRD, TPR and O2 pulse chemisorptions, TEM and BET-SA techniques. XRD studies showed phases due to hydrotalcite-like precursors in oven dried form produced dispersed NiO species upon calcination in static air above 450 C. Raman spectra of deactivated samples revealed the presence of both ordered and disordered forms of carbon. Ni-La-Al2O3catalyst with a mole ratio of Ni : La : Al = 2 : 0.1 : 0.9 exhibited tremendously high longevity with a hydrogen production rate of 1300 molH2 mol 1 Ni. A direct relationship between Ni metal surface area and hydrogen yields was established.

  9. 氨基甲酸酯裂解制HDI热力学分析%Thermodynamic analysis of catalytic decomposition of dimethyl-hexane-1,6-dicarbamate to hexamethylene-1,6-diisocyanate

    Institute of Scientific and Technical Information of China (English)

    孙大雷; 黄振荣; 黄宇嘉; 邓剑如; 晁自胜

    2013-01-01

    The catalytic decomposition of dimethyl-hexane-1,6-dicarbamate (HDU) to hexamethylene-1,6-diisocyanate (HDI) was a complex reaction system.The reaction heat,Gibbs free energy change and equilibrium constant of the reactions were calculated by methods of group contribution.The estimated data were compared with the literature and experimental data,and the results showed that they are reliable,which could be used to guide the laboratory research and industrial production.%由六亚甲基二氨基二甲酸甲酯(HDU)裂解合成六亚甲基-1,6-二异氰酸酯(HDI)为一复合反应体系.用基团贡献法计算了该反应体系的反应热、吉布斯自由能变化、化学反应平衡常数.计算数据与文献值及实验结果比较,表明计算结果可靠,对实验室研究及工业化生产都有重要的指导意义.

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

    Science.gov (United States)

    Kröcher, Oliver; Elsener, Martin

    2007-03-01

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

  11. Ozone Decomposition on the Surface of Metal Oxide Catalyst

    Directory of Open Access Journals (Sweden)

    Batakliev Todor Todorov

    2014-12-01

    Full Text Available The catalytic decomposition of ozone to molecular oxygen over catalytic mixture containing manganese, copper and nickel oxides was investigated in the present work. The catalytic activity was evaluated on the basis of the decomposition coefficient which is proportional to ozone decomposition rate, and it has been already used in other studies for catalytic activity estimation. The reaction was studied in the presence of thermally modified catalytic samples operating at different temperatures and ozone flow rates. The catalyst changes were followed by kinetic methods, surface measurements, temperature programmed reduction and IR-spectroscopy. The phase composition of the metal oxide catalyst was determined by X-ray diffraction. The catalyst mixture has shown high activity in ozone decomposition at wet and dry O3/O2 gas mixtures. The mechanism of catalytic ozone degradation was suggested.

  12. Preparation of Nanometer ZnTiO_3 Powder and Its Catalytic Performance for Thermal Decomposition of Ammoniam Perchlorate%钛酸锌的制备及其对高氯酸铵热分解的催化性能

    Institute of Scientific and Technical Information of China (English)

    杨行浩; 张景林; 王作山

    2009-01-01

    @@ 从20世纪60年代开始.钛酸锌(ZnO-TiO_2)体系相图及特性的基础研究工作就开展起来了[1].钙钛矿型氧化物结构的ZnTiO_3及基于ZnTiO_3的一些ABO_3型陶瓷固溶体材料,由于在超导体、催化剂、微波介电陶瓷以及电磁材料等领域有着重要用途,近年来已引起越来越多的关注[2~9].%ZnTiO_3 nanocrystals were prepared by sol-gel method, using Zn(NO_3)_2 and Ti(C_4H_9O)_4 in the topic. The as-prepared ZnTiO_3 nanocrystals were characterized by XRD, FTIR and TEM, and the catalytic performance of ZnTiO_3 nanocrystals of different contents for the ammonium perchlorate (AP)decomposition was investigated by thermal analysis. The results indicate that ZnTiO_3 with pure cube structure can be synthesized at 600 ℃ by this procedure,which was spheroid with particle size of about 60~100 nm. The results expressed that the low temperature decomposition peaks of AP is advanced by 17 ℃ and the high temperature decomposition peaks of AP is advanced by 24 ℃ when adding 5% nanoparticle ZnTiO_3 powder. The catalytic effects of ZnTiO_3 powders on the high temperature decomposition of AP are less than that of nanometer metal powders, but all the micron metal powders decrease the low decomposition temperature of AP.

  13. Catalytic hot gas cleaning

    Energy Technology Data Exchange (ETDEWEB)

    Simell, P. [VTT Energy, Espoo (Finland)

    1996-12-31

    Gasification gas that contains particulates can be purified from tars and ammonia by using nickel monolith catalysts. Temperatures over 900 deg C are required at 20 bar pressure to avoid deactivation by H{sub 2}S and carbon. Dolomites and limestones are effective tar decomposing catalysts only when calcined. Tar decomposition in gasification conditions can take place by steam or dry (CO{sub 2}) reforming reactions. These reactions follow apparent first order kinetics with respect to hydrocarbons in gasification conditions. (author) (16 refs.)

  14. Unsteady catalytic processes and sorption-catalytic technologies

    Energy Technology Data Exchange (ETDEWEB)

    Zagoruiko, A N [G.K. Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2007-07-31

    Catalytic processes that occur under conditions of the targeted unsteady state of the catalyst are considered. The highest efficiency of catalytic processes was found to be ensured by a controlled combination of thermal non-stationarity and unsteady composition of the catalyst surface. The processes based on this principle are analysed, in particular, catalytic selective reduction of nitrogen oxides, deep oxidation of volatile organic impurities, production of sulfur by the Claus process and by hydrogen sulfide decomposition, oxidation of sulfur dioxide, methane steam reforming and anaerobic combustion, selective oxidation of hydrocarbons, etc.

  15. Development of catalytic gas cleaning in gasification

    Energy Technology Data Exchange (ETDEWEB)

    Simell, P.; Kurkela, E.; Staahlberg, P.; Hepola, J. [VTT Energy, Espoo (Finland)

    1996-12-31

    Gasification gas containing dust can be efficiently purified from tars and ammonia with a nickel monolith catalyst. Temperatures of >900 deg C and a residence time of about 1 s (SV 2 500 1/h) were needed at 5 bar pressure to achieve complete tar decomposition and 80 % ammonia conversion. Catalyst deactivation was not observed during test runs of 100 h. At lower pressures dolomites and limestones can also be applied for tar removal at about 900 deg C temperatures. (orig.) 12 refs.

  16. 不同方法制备碳载金催化剂对臭氧的催化分解%Catalytic Activity of Au Supported on Activated Carbon Catalyst Preparing with Different Methods for Ozone Decomposition

    Institute of Scientific and Technical Information of China (English)

    张博; 徐九华; 李宏煦; 史蕊

    2011-01-01

    采用浸渍法和溶胶负载法制备以改性活性碳为载体以纳米金为活性组分的催化剂,通过BET,SEM和XPS表征制备方法对催化剂比表面积、孔隙结构、表面形貌及表面元素组成的影响,测试催化剂在室温下对低浓度臭氧的催化分解性能.结果显示,在室温,相对湿度为45±5%,空速为96000h(-1).臭氧初始浓度为50mg/m3,气体与催化剂的接触时间为0.04s的条件下,在1200min时采用浸渍法制备的催化剂对臭氧的分解率为85%,而溶胶负载法制备的催化剂此时对臭氧的分解效率仍在94%以上.采用溶胶负载法制备的催化剂纳米金颗粒粒径更小、更均匀,在催化剂表面的覆盖率更大是其催化活性更高的主要原因.%The catalysts of nano-particle Au supported by modified activated carbon are prepared with the methods of impregnation and sol-immobilized, and characterized by BET, SEM and XPS to consider the influence of preparation method to its specific surface area, pore structure, surface topography and composition.The catalytic activity for low-level ozone decomposition at ambient temperature of the catalysts is evaluated.The results show that under the condition of 50mg/m3 ozone in air, space velocity 96000 h-1, relative humidity 45 ±5% , contact time 0.04s and ambient temperature, the ozone removal ratio with the catalyst prepared by impregnation method is at 85% within 1200min, however, the ozone removal ratio with the catalyst by sol-immobilized method could be maintained above 94%.This is due to the reason that the supported gold nanoparticles in the catalyst prepared with sol-immobilized method are much smaller and more uniformly dispersed on the activated carbon, exhibit the higher fraction of coverage.

  17. Ammonia-Free NOx Control System

    Energy Technology Data Exchange (ETDEWEB)

    Song Wu; Zhen Fan; Andrew H. Seltzer; Richard G. Herman

    2005-03-31

    Research is being conducted under United States Department of Energy (DOE) Contract DE-FC26-03NT41865 to develop a new technology to achieve very low levels of NOx emissions from pulverized coal fired boiler systems by employing a novel system level integration between the PC combustion process and the catalytic NOx reduction with CO present in the combustion flue gas. The combustor design and operating conditions will be optimized to achieve atypical flue gas conditions. This approach will not only suppress NOx generation during combustion but also further reduce NOx over a downstream catalytic reactor that does not require addition of an external reductant, such as ammonia.

  18. Exhaust purification with on-board ammonia production

    Science.gov (United States)

    Robel, Wade J.; Driscoll, James Joshua; Coleman, Gerald N.

    2008-05-13

    A system of ammonia production for a selective catalytic reduction system is provided. The system includes producing an exhaust gas stream within a cylinder group, wherein the first exhaust gas stream includes NOx. The exhaust gas stream may be supplied to an exhaust passage and cooled to a predetermined temperature range, and at least a portion of the NOx within the exhaust gas stream may be converted into ammonia.

  19. Growth of organic microspherules in sugar-ammonia reactions.

    Science.gov (United States)

    Weber, Arthur L

    2005-12-01

    Reaction of small sugars of less than four carbons with ammonia in water yielded organic microspherules generally less than ten microns in size. The time course of microspherule growth was examined for the D-erythrose-ammonia reaction that yielded microspherules attached to the glass walls of containers. Measurements were made of the elemental composition and infrared spectrum of the microspherule material. These viscose semi-solid microspherules are viewed as possible containers for prebiotic catalytic processes relevant to the origin of life.

  20. Liquid composition having ammonia borane and decomposing to form hydrogen and liquid reaction product

    Science.gov (United States)

    Davis, Benjamin L; Rekken, Brian D

    2014-04-01

    Liquid compositions of ammonia borane and a suitably chosen amine borane material were prepared and subjected to conditions suitable for their thermal decomposition in a closed system that resulted in hydrogen and a liquid reaction product.

  1. Catalytic Effect of NdCoO_3 Nanoparticles on the Thermal Decomposition of Ammonium Perchlorate by DSC/TG-MS%纳米NdCoO_3催化高氯酸铵热分解的DSC/TG-MS研究

    Institute of Scientific and Technical Information of China (English)

    余宗学; 江晓红; 陆路德; 汪信

    2009-01-01

    Cubic structural perovskite NdCoO_3 nanocrystals were prepared by microemulsion method. The catalytic effect of the NdCoO_3 for thermal decomposition of ammonium perchlorate (AP) was investigated by DSC and TG-MS. The results revealed that the NdCoO_3 nanoparticles had effective catalysis on the thermal decomposition of AP. Adding 2% of NdCoO_3 nanoparticles to AP decreased the temperature of thermal decomposition by 113 ℃ and increased the heat of decomposition from 655 J·g~(-1) to 1 363 J·g~(-1). Gaseous products of thermal decomposition of AP were NH_3, H_2O, O_2, HCl, N_2O, NO, NO_2 and Cl_2. The mechanism of catalytic action was based on the presence of superoxide ion (O_2~-) and oxygenic ion (O~-, O~(2-)) on the surface of NdCoO_3, and the difference of thermal decomposition of AP with 2% of NdCoO_3 and pure AP was mainly caused by the different extent of oxidation of ammonium.%采用微乳液法制备了立方晶系的NdCoO_3纳米晶.利用DSC/TG-MS研究了NdCoO_3对AP热分解的催化作用.结果表明,在NdCoO_3的催化作用下,AP的热分解反应峰值温度下降了113℃,表观分解反应热从655 J·g~(-1)增加到1 363 J·g~(-1),分解的气相产物主要有NH3,H_2O,O_2,HCl,N_2O,NO,NO_2和Cl_2.在金属氧化物表面吸附生成超氧化离子(O_2~-)和氧离子(O~-,O~(2-)),这是加速AP分解反应的主要原因.加入NdCoO_3催化AP热分解,由于对氨的氧化深度不同而导致分解放热量的增加.

  2. Nickel ferrite spinel as catalyst precursor in the dry reforming of methane:Synthesis, characterization and catalytic properties

    Institute of Scientific and Technical Information of China (English)

    Rafik Benrabaa; Hamza Boukhlouf; Axel L(o)fberg; Annick Rubbens; Rose-N(o)elle Vannier; Elisabeth Bordes-Richard; Akila Barama

    2012-01-01

    Dry reforming of methane by CO2 using nickel ferrite as precursor of catalysts was investigated.Nickel ferrite crystalline particles were prepared by coprecipitation of nitrates with NaOH or ammonia followed by calcination,or by hydrothermal synthesis without calcination step.The textural and structural properties were determined by a number of analysis methods,including X-ray diffraction (XRD),Raman spectroscopy and X-ray photoelectron spectroscopy (XPS),among which X-ray diffraction (XRD) was at room and variable temperatures.All synthesized oxides showed the presence of micro or nanoparticles of NiFe2O4 inverse spinel,but Fe2O3 (hematite) was also present when ammonia was used for coprecipitation.The reducibility by hydrogen was studied by temperature-programmed reduction (TPR) and in situ XRD,which showed the influence of the preparation method.The surface area (BET),particle size (Rietveld refinement),as well as surface Ni/Fe atomic ratio (XPS) and the behavior upon reduction varied according to the synthesis method.The catalytic reactivity was investigated using isopropanol decomposition to determine the acid/base properties.The catalytic performance of methane reforming with CO2 was measured with and without the pre-treatment of catalysts under H2 in 650-800 ℃ range.The catalytic conversions of methane and CO2 were quite low but they increased when the catalysts were pre-reduced.A significant contribution of reverse water gas shift reaction accounted for the low values of H2/CO ratio.No coking was observed as shown by the reoxidation step performed after the catalytic reactions.The possible formation of nickel-iron alloy observed during the study of reducibility by hydrogen was invoked to account for the catalytic behavior.

  3. Ferrocene Covalently Functionalized Graphene Oxide: Preparation,Characterization and Catalytic Performance for Thermal Decomposition of Ammonium Perchlorate%二茂铁功能化石墨烯氧化物的制备、表征及对高氯酸铵热分解的催化性能

    Institute of Scientific and Technical Information of China (English)

    周磊; 王立; 俞豪杰; 高敬民; 丁文兵; 高浩其

    2013-01-01

    A new ferrocene modified graphene oxide nano-material (GO-EDA-Fc) was synthesized via a new synthesis route.The GO-EDA-Fc was characterized by Fourier transform infrared spectra,and its morphology was observed under scanning electron microscopy.The graphene oxide was covalently decorated by ferrocene.The catalytic performance of GO-EDA-Fc in the thermal decomposition of ammonium perchlorate(AP) was investigated by thermogravimetric analysis (TGA).The results showed that GO-EDA-Fc exhibited high catalytic activity.When 4wt% of GO-EDA-Fc was added,the peak temperature of the high-temperature decomposition peak of AP had a decrease of 60℃ and the peak of the low-temperature decomposition was shifted to lower as well.The more GO-EDA-Fc was added,the better catalytic performance would be achieved.Notably,the ferrocene functionalized graphenc oxide had shown a synergistic catalytic effect.The mechanism of promote action was also investigated.%本文通过一种新的合成路线合成了二茂铁功能化的氧化石墨烯(GO-EDA-Fc).利用傅里叶变换红外光谱和扫描电子显微镜对其结构和形貌进行了表征.通过热重分析(TGA)研究了其对高氯酸铵(AP)热分解的催化性能,结果表明,氧化石墨烯和二茂铁表现出很好的协同催化效果,对AP热分解具有高的催化活性.催化效果随着GO-EDA-Fc加入量的增加而增强,当加入4wt%的GO-EDA-Fc时,AP的高温分解峰的峰值温度下降了60℃,低温分解峰的峰值也有降低.文中还对催化机制进行了研究.

  4. 纳米SiO2负载的过渡金属硼化物对AP热分解的催化作用%Catalytic Activity of Nano-silica Supported Transition-metal Borides on the Thermal Decomposition of Ammonium Perchlorate

    Institute of Scientific and Technical Information of China (English)

    李茸; 刘祥萱; 王煊军

    2012-01-01

    采用化学还原法制备纳米NiB/SiO2、CoB/SiO2、MoB/SiO2催化剂,通过热重-差热分析(TG-DTA)研究了其对AP热分解过程的催化作用.结果表明,负载过渡金属硼化物催化剂对AP分解的催化活性顺序为:CoB/SiO2>NiB/SiO2> MoB/SiO2;加入质量分数5%的CoB/SiO2使AP高温热分解峰温度降低166.2℃;SiO2载体将CoB晶型转化推迟了 110℃左右,改善了催化剂的热稳定性.%The nano-silica supported transition metal catalysts NiB/SiO2 , CoB/SiO2 , MoB/SiO2 were prepared by chemical reduction method. Their catalytic activity on the thermal decomposition of ammonium perchlorate (AP) was studied by TG-DTA. Results show that catalytic activity of nano-silica supported transition metal borides for the thermal decomposition of AP decreases in the order: CoB/SiO2 > NiB/SiO2 >MoB/SiO2. The CoB/SiO2 (mass ration of 5%) catalyst makes the high-temperature thermal decomposition temperature of AP decrease by 166. 2℃. The SiO2 carrier makes the crystal transformation temperature delay about 110℃, revealling the improvement of thermal stability of the catalyst.

  5. Photocatalytic catalytic oxidation of ammonia in aqueous solutions by Cu/La-codoped TiO2%Cu/La共掺杂TiO2光催化氧化水中的氨氮

    Institute of Scientific and Technical Information of China (English)

    刘佳; 龙天渝; 陈前林; 杜坤

    2013-01-01

    The Cu/La-codoped TiO2 nanoparticles were prepared by hydrolysis-precipitation method. The nano-TiO2 was characterized by X-ray diffractometer (XRD) , X-ray photoelectron spectra (XPS) , and the BET surface areas. The photocatalytic degradation of ammonia in aqueous solutions by doped TiO2 powders under UV irradiation was studied. Results of structural characterization indicate that the catalyst has the better anatase phase, the pore size rang is 4 ~ 8 ntn and the incorporation of La as La3+ and Cu as Cu + ,Cu exist in Cu/La-codoped TiO2 nanoparticles. Experimental results show that the treatment of ammonia and coking wastewater exhibit high photocatalytic activity by modified TiO2 catalyst.%采用水解-沉淀法制备了Cu/La共掺杂纳米TiO2催化剂,利用XRD、XPS和BET技术对其进行表征,并考察了在紫外灯下,共掺杂TiO2对氨氮的光催化氧化工艺条件.物相结构和比表面积测试结果表明,共掺杂催化剂具有较好的锐钛矿晶型,孔径分布为4 ~8 nm,Cu/La共掺杂TiO2La以La3,Cu是以Cu2+、Cu+的形式掺杂进入TiO2的晶格.光催化实验表明:所得改性光催化剂对氨氮的去除及焦化废水的处理均具有较高的催化活性.

  6. Surface modification of multi-walled carbon nanotubes by ammonia and catalytic degradation of oxalic acid by ozonation%多壁碳纳米管的氨表面改性及其臭氧催化降解草酸

    Institute of Scientific and Technical Information of China (English)

    何志桥; 姜哲; 姜理英; 杨樟保; 陈建孟; 宋爽

    2012-01-01

    采用水热方法制备了一系列用浓氨水改性的多壁碳纳米管催化剂,该催化剂的活性通过非均相催化臭氧化降解水溶液中的草酸来进行评价.降解过程符合零级反应动力学模型,且催化剂的表观动力学常数与其表面碱性基团数量以及零电位pH值(pHpzc)呈正相关.为此,可断定用浓氨在水热条件下处理多壁碳纳米管能明显提高催化臭氧降解草酸能力是因为提高了催化剂的表面碱性基团数量和pHpzc.%A series of ammonia-modified multi-walled carbon nanotubes was prepared via hydrothermal method. Their catalytic activity was evaluated by oxalic acid degradation in aqueous solution in the presence of ozone. It was found that the reaction process can be fitted to zero-order reaction kinetics. The apparent zero-order rate constant had a positive relation with the basic groups and pH value at zero charge point (pHpzc) of the catalysts. On this basis, it can be concluded that the significant enhancement of oxalic acid degradation is achieved by hydrothermal treatment with ammonia. The reason could be that the method promotes formation of basic groups and increase of pHPZC.

  7. Techniques for measuring ammonia in fly ash, mortar, and concrete

    Energy Technology Data Exchange (ETDEWEB)

    Rathbone, R.F. [Kentucky Univ., Lexington, KY (United States). Center for Applied Energy Reseach; Majors, R.K. [Boral Material Technologies, Inc., San Antonio, TX (United States). Engineered Materials

    2003-12-01

    The presence of ammonia in fly ash that is to be used in mortar and concrete is of increasing concern in the U.S., mainly due to the installation of selective catalytic reduction (SCR) DeNOx systems. When the SCR catalyst is new, contamination of the fly ash with ammonia is generally not a concern. However, as the catalyst in the SCR ages and becomes less efficient, the ammonia slip increases and results in a greater amount of ammonium salt being precipitated on the fly ash. The increase in ammonia concentration is compounded by variability that can occur on a day-to-day basis. When marketing ammonia-laden fly ash for use in mortar and concrete it is imperative that the concentration of ammonia is known. However, there currently is no widely accepted or ''standard'' method for ammonia measurement in fly ash. This paper describes two methods that have been developed and used by the University of Kentucky Center for Applied Energy Research and Boral Material Technologies, Inc. One of the methods uses gas detection tubes and can provide an accurate determination within five to ten minutes. Thus it is suitable as a rapid field technique. The other method employs a gas-sensing electrode and requires a longer period of time to complete the measurement. However, this second method can also be used to determine the quantity of ammonia in fresh mortar and concrete. (orig.)

  8. Assessing Ammonia Treatment Options

    Science.gov (United States)

    This is the second of three articles to help water system operators understand ammonia and how to monitor and control its effects at the plant and in the distribution system. The first article (Opflow, April 2012) provided an overview of ammonia's chemistry, origins, and water sy...

  9. Method for forming ammonia

    Science.gov (United States)

    Kong, Peter C.; Pink, Robert J.; Zuck, Larry D.

    2008-08-19

    A method for forming ammonia is disclosed and which includes the steps of forming a plasma; providing a source of metal particles, and supplying the metal particles to the plasma to form metal nitride particles; and providing a substance, and reacting the metal nitride particles with the substance to produce ammonia, and an oxide byproduct.

  10. 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

  11. Including lateral interactions into microkinetic models of catalytic reactions

    DEFF Research Database (Denmark)

    Hellman, Anders; Honkala, Johanna Karoliina

    2007-01-01

    In many catalytic reactions lateral interactions between adsorbates are believed to have a strong influence on the reaction rates. We apply a microkinetic model to explore the effect of lateral interactions and how to efficiently take them into account in a simple catalytic reaction. Three differ...... different approximations are investigated: site, mean-field, and quasichemical approximations. The obtained results are compared to accurate Monte Carlo numbers. In the end, we apply the approximations to a real catalytic reaction, namely, ammonia synthesis....

  12. 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.

  13. Predicting catalysis: Understanding ammonia synthesis from first-principles calculations

    DEFF Research Database (Denmark)

    Hellmann, A.; Baerends, E.J.; Biczysko, M.

    2006-01-01

    . Furthermore, our studies provide new insight into several related fields, for instance, gas-phase and electrochemical ammonia synthesis. The success of predicting the outcome of a catalytic reaction from first-principles calculations supports our point of view that, in the future, theory will be a fully......Here, we give a full account of a large collaborative effort toward an atomic-scale understanding of modern industrial ammonia production over ruthenium catalysts. We show that overall rates of ammonia production can be determined by applying various levels of theory (including transition state...... for any given point along an industrial reactor, and the kinetic results can be integrated over the catalyst bed to determine the industrial reactor yield. We find that, given the present uncertainties, the rate of ammonia production is well-determined directly from our atomic-scale calculations...

  14. System and method for determining an ammonia generation rate in a three-way catalyst

    Science.gov (United States)

    Sun, Min; Perry, Kevin L; Kim, Chang H

    2014-12-30

    A system according to the principles of the present disclosure includes a rate determination module, a storage level determination module, and an air/fuel ratio control module. The rate determination module determines an ammonia generation rate in a three-way catalyst based on a reaction efficiency and a reactant level. The storage level determination module determines an ammonia storage level in a selective catalytic reduction (SCR) catalyst positioned downstream from the three-way catalyst based on the ammonia generation rate. The air/fuel ratio control module controls an air/fuel ratio of an engine based on the ammonia storage level.

  15. Reactor for removing ammonia

    Science.gov (United States)

    Luo, Weifang; Stewart, Kenneth D.

    2009-11-17

    Disclosed is a device for removing trace amounts of ammonia from a stream of gas, particularly hydrogen gas, prepared by a reformation apparatus. The apparatus is used to prevent PEM "poisoning" in a fuel cell receiving the incoming hydrogen stream.

  16. Ammonia-Free NOx Control System

    Energy Technology Data Exchange (ETDEWEB)

    S. Wu; Z. Fan; R. Herman

    2004-03-31

    Research is being conducted under United States Department of Energy (DOE) Contract DEFC26-03NT41865 to develop a new technology to achieve very low levels of NOx emissions from pulverized coal fired boiler systems by employing a novel system level integration between the PC combustion process and the catalytic NOx reduction with CO present in the combustion flue gas. The combustor design and operating conditions will be optimized to achieve atypical flue gas conditions. This approach will not only suppress NOx generation during combustion but also further reduce NOx over a downstream catalytic reactor that does not require addition of an external reductant, such as ammonia. This report describes the work performed during the January 1 to March 31, 2004 time period.

  17. Ammonia-Free NOx Control System

    Energy Technology Data Exchange (ETDEWEB)

    S. Wu

    2003-12-31

    Research is being conducted under United States Department of Energy (DOE) Contract DEFC26-03NT41865 to develop a new technology to achieve very low levels of NOx emissions from pulverized coal fired boiler systems by employing a novel system level integration between the PC combustion process and the catalytic NOx reduction with CO present in the combustion flue gas. The combustor design and operating conditions will be optimized to achieve atypical flue gas conditions. This approach will not only suppress NOx generation during combustion but also further reduce NOx over a downstream catalytic reactor that does not require addition of an external reductant, such as ammonia. This report describes the work performed during the October 1 to December 31, 2003 time period.

  18. Catalytic Synthesis of Nitriles in Continuous Flow

    DEFF Research Database (Denmark)

    Nordvang, Emily Catherine

    , alternative path to acetonitrile from ethanol via the oxidative dehydrogenation of ethylamine. The catalytic activity and product ratios of the batch and continuous flow reactions are compared and the effect of reaction conditions on the reaction is investigated. The effects of ammonia in the reaction...... dehydrogenation of ethylamine and post-reaction purging.Chapter 4 outlines the application of RuO2/Al2O3 catalysts to the oxidative dehydrogenation of benzylamine in air, utilizing a new reaction setup. Again, batch and continuous flow reactions are compared and the effects of reaction conditions, ammonia...

  19. Lanthanum-Promoted Ru/Sepiolite in Ammonia Synthesis

    Institute of Scientific and Technical Information of China (English)

    Le Zhiping; Lin Jianxin; Yu Xiujin; Huang Yueyu; Wei Kemei

    2005-01-01

    A new kind of Ru supported on sepiolite catalyst with La as promoter for ammonia synthesis was prepared. The effects of reaction conditions on catalytic activity were discussed. The result shows that La is an effective promoter for sepiolite-supported Ru based catalyst. When the load of Ru is 5% (mass fraction), and the molar ratio of La/Ru is 1.5, under the condition of 10 MPa 450 ℃ 20000 h-1, the ammonia synthesis rate is 38.5 mmol NH3·g-1·h-1.

  20. STUDY ON CATALYTIC DECOMPOSITION OF RICE HULL GASIFICATION TAR WITH PALYGORSKITE CLAY%凹凸棒石粘土催化裂解生物质气化炉焦油初探

    Institute of Scientific and Technical Information of China (English)

    刘海波; 陈天虎; 谢晶晶; 常冬寅; 庆承松; 李金虎

    2011-01-01

    Tar derived from biomass gasification restricts the development of biomass gasification system. The catalytic cracking of rice hull gasification derived tar over a nature palygorskite catalyst was investigated, and the reaction mechanism was also discussed. Catalyst' s activity was evaluated under varied temperature and purity of palygorskite. Results showed that the catalytic activity of tar cracking increases with the rising in temperature and purity of palygorskite. Synergy between palygorskite and dolomite was found to promote the catalytic cracking of tar. Compared with other mineral materials (calcium oxide, olivine, stilbite) , palygorskite was the most active one for catalytic cracking of tar, though it has the highest level of carbon deposition.%研究了凹凸棒石粘土对稻壳气化焦油的催化裂解性能,分析了不同温度和不同凹凸棒石粘土/白云石比值下催化剂催化脱焦油活性.结果表明:随着催化裂解温度增加,各种催化剂对生物质气化炉焦油的去除率均有不同程度的提高,且随凹凸棒石粘土/白云石比值的增加,焦油的去除率有所增加.凹凸棒石粘土与白云石之间存在协同作用,这种协同作用提高了焦油催化裂解活性.与其他几种常用的矿物材料催化剂(氧化钙、橄榄石、辉沸石)相比,尽管凹凸棒石粘土催化裂解焦油后积炭量最大,但还是显示出对焦油裂解反应最好的催化活性.

  1. Characterization and catalytic behavior of MoO{sub 3}/V{sub 2}O{sub 5}/Nb{sub 2} O{sub 5} systems in isopropanol decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Paiva Junior, J.B. de; Cortez, G.G. [Universidade de Sao Paulo, Lorena, SP (Brazil). Escola de Engenharia. Lab. de Catalise II]. E-mail: cortez@dequi.faenquil.br; Monteiro, W.R.; Zacharias, M.A.; Rodrigues, J.A.J. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Combustao e Propulsao]. E-mail: jajr@lcp.inpe.br

    2006-10-15

    The influence of molybdenum oxide as a promoter on the V{sub 2}O{sub 5}/Nb{sub 2}O{sub 5} system was investigated. A series of MoO{sub 3}/V{sub 2}O{sub 5}/Nb{sub 2}O{sub 5} catalysts, with MoO{sub 3} loading ranging from 1 to 3 wt% MoO{sub 3} and fixed V{sub 2}O{sub 5} content (21 wt%), were prepared by impregnation of the Nb{sub 2}O{sub 5} support with an aqueous solution of ammonium metavanadate and ammonium molybdate. The acid-base properties of the catalysts were investigated to determine of the selectivity of the isopropanol decomposition reaction. The X-ray diffraction results showed the presence of the {beta}-(Nb,V){sub 2}O{sub 5} phase. The temperature-programmed reduction profiles showed that the reducibility of vanadium was affected by the presence of molybdenum oxide. Activity results for isopropanol decomposition revealed that the acid-base properties of V{sub 2}O{sub 5}/Nb{sub 2}O{sub 5} catalysts are affected upon incorporation of MoO{sub 3}, specifically for loadings of 3 wt %. For this catalyst composition both propylene and acetone formation rates decreased. (author)

  2. Electro Decomposition of Ammonia into Hydrogen for Fuel Cell Use

    Science.gov (United States)

    2012-01-01

    hexamethylenetetramine (HMT) with 100 mL of water. This mixture was allowed to react in a sealed Teflon vessel at 90 °C for 24 hrs. A green precipitate...Development Center FC flow control (valve) FT-IR Fourier transform infrared (spectroscopy) HMT hexamethylenetetramine HQUSACE Headquarters, U.S. Army

  3. Structural properties of cyanase. Denaturation, renaturation, and role of sulfhydryls and oligomeric structure in catalytic activity.

    Science.gov (United States)

    Little, R M; Anderson, P M

    1987-07-25

    Cyanase is an inducible enzyme in Escherichia coli that catalyzes bicarbonate-dependent decomposition of cyanate to give ammonia and bicarbonate. The enzyme is composed of 8-10 identical subunits (Mr = 17,008). The objective of this study was to clarify some of the structural properties of cyanase for the purpose of understanding the relationship between oligomeric structure and catalytic activity. Circular dichroism studies showed that cyanase has a significant amount of alpha-helix and beta-sheet structure. The one sulfhydryl group per subunit does not react with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) unless cyanase is denatured. Denaturation is apparently complete in 10 M urea or 6 M guanidine hydrochloride, but is significantly reduced in 10 M urea by the presence of azide (analog of cyanate) and is incomplete in 8 M urea. Denatured cyanase could be renatured and reactivated (greater than 85%) by removal of denaturants. Reactivation was greatly facilitated by the presence of certain anions, particularly bicarbonate, and by high ionic strength and protein concentration. The catalytic activity of renatured cyanase was associated only with oligomer. Cyanase that had been denatured in the presence of DTNB to give a cyanase-DTNB derivative could also be renatured at 26 degrees C to give active cyanase-DTNB oligomer. The active oligomeric form of the cyanase-DTNB derivative could be converted reversibly to inactive dimer by lowering the temperature to 4 degrees C or by reduction of the ionic strength and removal of monoanions. These results provide evidence that free sulfhydryl groups are not required for catalytic activity and that catalytic activity may be dependent upon oligomeric structure.

  4. Catalytic Performance of Fe/H-beta Catalyst Modified by Mn for NOx Decomposition at Low Temperature%Mn改性Fe/H-beta催化剂的低温催化分解NOx的研究

    Institute of Scientific and Technical Information of China (English)

    潘华; 宋华丰

    2012-01-01

    通过Mn改性制备了Fe和Mn的质量比为1且Fe和Mn的质量分数均为5% (5%Fe-5%Mn/H-beta)的催化剂,通过氢气程序升温还原(H2-TPR)比较分析了Fe-Mn/H-beta、Fe/H-beta和Mn/H-beta催化剂中Fe和Mn的化学形态,考察了O2、SO2和H2O等反应条件对Fe-Mn/H-beta催化剂低温催化分解NOx的影响.结果表明,相比Fe/H-beta和Mn/H-beta,Fe-Mn/H-beta 催化剂在富氧和低温条件下具有较好的催化活性,其中623 K下催化剂的活性最高,NOx的转化率达到45%左右.Fe-Mn/H-beta催化剂中Fe和Mn的共存提高了Fe2O3和MnO2的含量.氧的存在促进了NOx催化分解,水蒸气和SO2对NOx催化分解有一定的抑制作用.%Direct decomposition of NOX was investigated with 5% Fe-5% Mn/H-beta catalysts with equal weight of Mn and Fe. The chemical states of Fe and Mn in Fe-Mn/H-beta, Fe/H-be-ta, and Mn/H-beta catalysts were characterized by H2-TPR. The effects of O2, SO2 and H20 on decomposition of NOX at low temperature with 5 %Fe-5% Mn/H-beta catalysts were examined. The results indicate that the activity of Fe-Mn/H-beta is higher than that of Fe/H-beta or Mn/H-beta at rich oxygen and low temperature from 573 K to 673 K. The maximum NO* conversion is about 45% with 5 %Fe-5%Mn/H-beta at 623 K. The presence of Fe in Fe-Mn/H-beta enhances the transformation of Mn3+ ions into Mn4+ ions, and the addition of Mn increases the amount of Fe2O3 in Fe-Mn/H-beta. In addition, O2 inhibition is not observed in NOX decomposition with Fe-Mn/H-beta while the presence of H2O and SO2 inhibits the activity of Fe-Mn/H-beta.

  5. Cu、Co交换改性蒙脱土的制备及其对N2O分解的催化活性%PREPARATION OF Cu,Co-EXCHANGED Al-PILLARED MONTMORILLONITE AND ITS CATALYTIC ACTIVITY FOR N2O DECOMPOSITION

    Institute of Scientific and Technical Information of China (English)

    徐秀峰; 索掌怀; 魏玉萍; 宫宝安; 安立敦

    2001-01-01

    用Al交联剂对天然蒙脱土改性,制得Al交联(支撑)蒙脱土。用Cu2+、Co2+离子交换蒙脱土层间阳离子,制备Cu、Co交换蒙脱土,经高温焙烧,得到实验用催化剂,考察它们对N2O分解的催化活性。结果表明:用Al/土比为10 mmol/g的Al交联蒙脱土作载体,通过优化制备条件制得的Cu交换蒙脱土,催化活性与CuY 相近;而Co-蒙脱土的催化活性甚至高于 CoY。%Nitrous oxide(N2O) is now considered as a greenhouse gas and contributes to catalytic stratospheric-ozone destruction. Therefore, the catalytic decomposition of N2O has become one of the urgent environmental issues. In this paper, raw montmorillonite was pillared by oligomeric hydroxyl aluminum cation with changing Al/clay ratio to make Al cross-linked montmorillonite (Al-CLM). The basal spacing(d001) of Al-CLM measured by X-ray diffraction is 1.80?nm, while that of raw montmorillonite 1.53?nm. The thermal stability of modified CLM was improved by Al pillar. Cu, Co-exchanged Al-CLM catalysts were prepared by changing preparation parameters and used to catalytically decompose N2O. The results show that the catalytic activity of Cu-exchanged clay with Al/clay ratio 10 mmol/g, calcined at 500 ℃, is equivalent to that of CuY, while Co-clay even higher than CoY for 3% N2O and 1% CH4 feed gas at space velocity 5000 h-1.

  6. Life cycle assessment of selective non-catalytic reduction (SNCR) of nitrous oxides in a full-scale municipal solid waste incinerator

    DEFF Research Database (Denmark)

    Møller, Jacob; Munk, Bjarne; Crillesen, Kim

    2011-01-01

    Selective non-catalytic reduction (SNCR) of nitrous oxides in a full-scale municipal solid waste incinerator was investigated using LCA. The relationship between NOx-cleaning and ammonia dosage was measured at the plant. Un-reacted ammonia – the ammonia slip – leaving the flue-gas cleaning system......-removal in flue-gas cleaning from waste incineration....

  7. Ammonia emissions in Europe

    DEFF Research Database (Denmark)

    Jacobsen, Brian H.

    2012-01-01

    The NEC (National Emission Ceiling) directive has set targets for the 2010 ammonia emissions from a number of European countries. The target will be reached by most EU-countries and the total emission for EU-27 has been reduced by 22% from 1990 to 2007. Denmark is one of the countries with the la......The NEC (National Emission Ceiling) directive has set targets for the 2010 ammonia emissions from a number of European countries. The target will be reached by most EU-countries and the total emission for EU-27 has been reduced by 22% from 1990 to 2007. Denmark is one of the countries...

  8. Respiratory ammonia output and blood ammonia concentration during incremental exercise

    NARCIS (Netherlands)

    Ament, W; Huizenga, [No Value; Kort, E; van der Mark, TW; Grevink, RG; Verkerke, GJ

    1999-01-01

    The aim of this study was to investigate whether the increase of ammonia concentration and lactate concentration in blood was accompanied by an increased expiration of ammonia during graded exercise. Eleven healthy subjects performed an incremental cycle ergometer test. Blood ammonia, blood lactate

  9. AMMONIA-FREE NOx CONTROL SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Song Wu; Zhen Fan; Andrew H. Seltzer; Richard G. Herman

    2006-06-01

    This report describes a novel NOx control system that has the potential to drastically reduce cost, and enhance performance, operation and safety of power plant NOx control. The new system optimizes the burner and the furnace to achieve very low NOx levels and to provide an adequate amount of CO, and uses the CO for reducing NO both in-furnace and over a downstream AFSCR (ammonia-free selective catalytic reduction) reactor. The AF-SCR combines the advantages of the highly successful SCR technology for power plants and the TWC (three-way catalytic converter) widely used on automobiles. Like the SCR, it works in oxidizing environment of combustion flue gas and uses only base metal catalysts. Like the TWC, the AF-SCR removes NO and excess CO simultaneously without using any external reagent, such as ammonia. This new process has been studied in a development program jointed funded by the US Department of Energy and Foster Wheeler. The report outlines the experimental catalyst work performed on a bench-scale reactor, including test procedure, operating conditions, and results of various catalyst formulations. Several candidate catalysts, prepared with readily available transition metal oxides and common substrate materials, have shown over 80-90% removal for both NO and CO in oxidizing gas mixtures and at elevated temperatures. A detailed combustion study of a 400 MWe coal-fired boiler, applying computational fluid dynamics techniques to model boiler and burner design, has been carried out to investigate ways to optimize the combustion process for the lowest NOx formation and optimum CO/NO ratios. Results of this boiler and burner optimization work are reported. The paper further discusses catalyst scale-up considerations and the conceptual design of a 400 MWe size AF-SCR reactor, as well as economics analysis indicating large cost savings of the ammonia-free NOx control process over the current SCR technology.

  10. Hydroaminomethylation in supercritical ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Martin, A.; Kant, M. [Leibniz-Institute for Catalysis, Berlin (Germany); Klein, H.; Jackstell, R.; Beller, M. [Leibniz-Institute for Catalysis, Rostock (Germany)

    2006-07-01

    Thermodynamic measurements were carried in the reaction system of hydroaminomethylation of olefins. Mixtures of ammonia, olefins, co-solvents, syngas and products such as nonylamine used as model and water were studied. In dependence on the reaction conditions and the mixtures selected opalescence points in a region from 92-290 bar and 120-172 C were found. (orig.)

  11. Enhancement of Alkene Epoxidation Activity of Titanosilicates by Gas-Phase Ammonia Modification

    Institute of Scientific and Technical Information of China (English)

    张里艳; 徐乐; 孙晶晶; 蒋金刚; 刘月明; 吴海虹; 吴鹏

    2012-01-01

    Novel ammonia-treated titanosilicates have been prepared by heating the samples of Ti-MWW, TS-l and Ti-Beta under pure ammonia gas flow at 673 K for a period of time. The ammonia modification improved their catalytic performance in liquid-phase oxidations. Especially, the catalytic activities of ammonified Ti-MWW, N-Ti-MWW, were enhanced greatly in the epoxidation of 1-hexene with H2O2. The reason that the ammonia treat- ment played such an important role in post-modification of titanosilicate was investigated in details. In comparison to the parent Ti-MWW catalyst, N-Ti-MMW was more robust and produced less coke in oxidation reactions.

  12. Preparation of nanometer FeCuP alloy and its application in decomposition of PH3

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new ternary Fe-based alloy catalyst FeCuP applied to decompose PH3 was prepared with low-cost material by chemical reduction deposition method. The properties of it were characterized by XRD, ICP and SEM. Its catalytic activity on the decomposition of PH3 and the decomposition conditions were studied. FeCuP alloy exhibits high thermal stabilities and high catalytic activity. Using it as catalyst, the decomposition temperature of phosphine decreases from over 800 ℃ to 400-500 ℃. The decomposition rate of phosphine achieved 100%.

  13. 溶剂热合成Cu2O微球及其对高氯酸铵热分解的催化作用%Solvo-Thermal Synthesis of Cu2O Micro-Spheres and Their Catalytic Performance for Thermal Decomposition of Ammonium Perchlorate

    Institute of Scientific and Technical Information of China (English)

    罗小林; 韩银凤; 杨德锁; 陈亚芍

    2012-01-01

    以聚乙烯吡咯烷酮(PVP)为添加剂,利用溶剂热法合成了Cu2O微球.考察了PVP用量以及反应温度对产物形貌的影响,并在反应时间为2.5与4.5 h时分别合成了直径为100-200 nm和1 μm的Cu2O微球.同时,利用差热分析(DTA)技术考察了不同直径的Cu2O微球对高氯酸铵(AP)热分解的催化效果,结果表明:添加2%(w)的直径为100-200 nm和1μm的Cu2O微球使得AP的高温分解温度分别降低了116和118℃,AP在低温阶段的分解量也明显提高.%Cu2O micro-spheres were fabricated by a solvothermal method using poly vinylpyrrolidone (PVP) as an additive. The influences of PVP dosage and reaction temperature on the morphologies of the products were investigated. CuzO micro-spheres with diameters of 100-200 nm and about 1 um were synthesized with reaction time of 2.5 and 4.5 h, respectively. Meanwhile, differential thermal analysis (OTA) was used to determine the catalytic performance of these Cu2O micro-spheres with different diameters for thermal decomposition of ammonium perchlorate (AP). Adding 2% (w) CujO micro-spheres with diameters of 100-200 nm and about 1 um into AP decreased the maximum temperature of AP decomposition by 116 and 118 °C, respectively, and increased the amount of AP decomposed at lower temperature.

  14. Catalytic Thermal Decomposition of Ammonium Perchlorate by Cu/Co/Fe Mixed Oxides Derived from Layered Double Hydroxides%Cu/Co/Fe水滑石衍生的复合氧化物催化高氯酸铵热分解的研究

    Institute of Scientific and Technical Information of China (English)

    刘洪博; 黄志勇; 郭冰之; 矫庆泽

    2013-01-01

    Cu/Co/Fe mixed oxides (Cu/Co/Fe-MOs) were prepared by calcining the precursors of Cu/Co/Fe layered double hydroxides (Cu/Co/Fe-LDHs),and were used as new catalysts for the thermal decomposition of ammonium perchlorate (AP).The catalytic activity was investigated using differential thermal analysis (DTA) and thermal gravimetric analyzer coupled with an online mass spectrometer (TG-MS).The results reveal that Cu/Co/Fe-MOs exhibit CuFe2O4 and (CoFe2)O4 phase with high specific surface area of 70~110 m2·g-1.The Cu/Co/Fe-MOs have homogenous particles with crystallite size of 20~30 nm.The thermal decomposition temperature of AP can be lowered by 139 ℃ with 4wt% of Cu/Co/Fe-MOs calcined at 400 ℃.The improvement in thermal decomposition of AP by Cu/Co/Fe-MOs catalysts is achieved via the superoxide ion (O2-) adsorbed on the surface of Cu/Co/Fe-MOs.%以Cu/Co/Fe水滑石(Cu/Co/Fe-LDHs)为前驱体经过焙烧制备了Cu/Co/Fe复合氧化物(Cu/Co/Fe-MOs).利用DTA和TG-MS研究了Cu/Co/Fe-MOs作为新型催化剂对高氯酸铵热分解的催化性能.结果表明,Cu/Co/Fe-MOs呈现为CuFe2O4和(CoFe2)O4晶相,具有70~110 m2·g-1的比表面积.晶粒大小均匀,尺寸在20~30 nm.添加4wt%的400℃焙烧得到的Cu/Co/Fe-MOs催化剂使高氯酸铵热分解反应的温度降低了139℃.Cu/Co/Fe-MOs是通过吸附在金属氧化物表面的超氧离子(O2-)来加速高氯酸铵热分解的.

  15. Experimental and modelling evaluation of an ammonia-fuelled microchannel reactor for hydrogen generation / Steven Chiuta

    OpenAIRE

    Chiuta, Steven

    2015-01-01

    In this thesis, ammonia (NH3) decomposition was assessed as a fuel processing technology for producing on-demand hydrogen (H2) for portable and distributed fuel cell applications. This study was motivated by the present lack of infrastructure to generate H2 for proton exchange membrane (PEM) fuel cells. An overview of past and recent worldwide research activities in the development of reactor technologies for portable and distributed hydrogen generation via NH3 decomposition wa...

  16. Study on ammonia slip detection in the harsh combustion environments using diode laser spectroscopy

    Science.gov (United States)

    You, Kun; Zhang, Yu-jun; Li, Hong-bin; He, Yin; Gao, Yan-wei; Wang, Li-ming; Liu, Wen-qing

    2016-10-01

    The emissions of NOX from Cement plant or Coal-fired power plant have serious pollution to the environment. In recent years, Selective Catalytic Reduction (SCR) is an effective means of reducing the emissions of NOX by injecting ammonia into the combustion flue gas, which ideally reacts with the NOX to produce harmless components (H2O and N2). The efficiency of SCR is determined by monitoring the ammonia slip of the flue exhaust outlet, excess ammonia injection can cause ammonia slip, which not only destroy the plant, but also increase the operating costs. In addition, ammonia is also pollution gases as NOX. The flue gas at the measurement point is high temperature, vibrate and high particle density processes in Cement plant primarily, such harsh conditions coupled with the highly reactive nature of ammonia, so it is difficult to reliable extractive low level analysis. The paper describes an in-situ Tunable Diode Laser analyzer for measuring ammonia slip in the combustion flue gas after SCR in Cement Plant or Coal-fired power plant. A correlation filtering algorithm is developed to select high-quality spectral absorption signal, which improve the accuracy of concentration inversion of analyzer. The paper also includes field test data on an actual Cement plant all day, and we compare the ammonia slip and NOX emissions of flue gas during actual production process, the results indicate that the measured values of the ammonia slip and NOX emissions present a good correlation and comply with the principle of SCR.

  17. Me-OMS-1s分子筛催化叔丁基过氧化氢分解制备叔丁醇%Catalytic decomposition oftert-butyl hydroperoxide intotert-butyl alcohol over Me-OMS-1s molecular sieves

    Institute of Scientific and Technical Information of China (English)

    冯利利; 卢书培; 齐兴义; 韩晓

    2015-01-01

    A series of Me-OMS-1s (Me=Mg, Co, Ni, Cu) molecular sieves wassynthesized by the static hydrothermal method. The as-synthesized Me-OMS-1s were characterized by means of XRD and AES-ICP. The effects of reaction temperature (318—338 K), reaction time (0.5—6 h) and formal catalyst concentration (1.67—8.33 mg·ml−1) were investigated in detail on catalytic decomposition of tert-butyl hydroperoxide intotert-butyl alcohol over the as-synthesized Me-OMS-1s. The results showed that the synthetic Me-OMS-1s belonged to todorokite-type manganese oxides. All the Me-OMS-1 catalysts bore the activity for the catalytic disproportionation decomposition oftert-butyl hydroperoxide under the selected heterogeneous catalytic reaction conditions. The conversion of the reactanttert-butyl hydroperoxide under various reaction conditions was found to be high and the selectivity towards the producttert-butyl alcohol was 100%. The activity of Me-OMS-1s followed the order of: Cu-OMS-1 > Mg-OMS-1 > Ni-OMS-1 > Co-OMS-1. The conversion level oftert-butyl hydroperoxide was markedly enhanced with increasing reaction temperature, contact time and formal Me-OMS-1 concentration.%采用静态水热法合成了Me-OMS-1s(Me=Mg,Co,Ni,Cu)分子筛催化剂,对合成的分子筛进行了X射线衍射和电感耦合等离子体发射光谱表征,并系统考察了反应温度(318~338 K)、反应时间(0.5~6 h)和催化剂用量(1.67~8.33 mg·ml−1)对Me-OMS-1s催化叔丁基过氧化氢分解制备叔丁醇反应性能的影响。研究结果表明,合成的分子筛均为钡镁锰矿型(todorokite)氧化锰;在选择的多相催化反应条件下,Me-OMS-1s均有催化叔丁基过氧化氢歧化分解的反应活性,反应物叔丁基过氧化氢具有较高的转化率,产物叔丁醇的选择性均为100%。Me-OMS-1s催化叔丁基过氧化氢歧化分解的反应活性顺序为:Cu-OMS-1> Mg-OMS-1> Ni-OMS-1> Co-OMS-1。叔丁基过氧化氢的转

  18. 热分解法制备Pd-Sn催化剂的结构与性能%Structure and catalytic property of Pd-Sn catalyst prepared by thermal decomposition

    Institute of Scientific and Technical Information of China (English)

    李文良; 唐电; 张腾

    2015-01-01

    Nanoscale Ti/Pd2 Sn+PdO and Ti/Pd electrodes are prepared by a thermal decomposition method .The catalysts are characterized by high resolution transmission electron microscopy , energy dispersive spectrometer and selected area electron diffraction method .The activity and stability of the prepared catalysts were studied using cyclic voltammetry and chronoamperometry methods .The results show that Ti/Pd2Sn+PdO electrode has much higher activity toward formic acid oxidation than that of Ti /Pd catalyst (about 2.4 times).In addition, the combination of Pd 2 Sn and PdO results in the high stability of Ti/Pd2 Sn+PdO electrode , which exhibits only 25%degradation of current density after being maintained at 0.3 V (vs SCE) for 500 s.The significant improvement in the stability as well as activity of Ti /Pd2Sn+PdO electrode provides a promising solution for the instability of Pd-based catalysts for direct formic acid fuel cell application .%用热分解法制备Ti/Pd2 Sn+PdO和Ti/Pd电极. 采用高分辨率透射电子显微镜、能量散射谱仪、选区电子衍射对催化剂进行表征. 利用循环伏安法和计时电流法研究了所制备催化剂的催化活性和稳定性. 结果表明,Ti/Pd2 Sn+PdO电极比Ti/Pd电极具有更高的甲酸催化活性(约2.4倍). Ti/Pd2Sn+PdO电极在0.3 V(vs SCE)下测试500 s后电流密度仅衰减25%,具有比Ti/Pd电极更好的稳定性. Ti/Pd2 Sn+PdO电极显著提高了催化活性和稳定性,为Pd基直接甲酸燃料电池催化剂的应用提供可行方案.

  19. Combustion driven ammonia generation strategies for passive ammonia SCR system

    Energy Technology Data Exchange (ETDEWEB)

    Toner, Joel G.; Narayanaswamy, Kushal; Szekely, Jr., Gerald A.; Najt, Paul M.

    2016-12-06

    A method for controlling ammonia generation in an exhaust gas feedstream output from an internal combustion engine equipped with an exhaust aftertreatment system including a first aftertreatment device includes executing an ammonia generation cycle to generate ammonia on the first aftertreatment device. A desired air-fuel ratio output from the engine and entering the exhaust aftertreatment system conducive for generating ammonia on the first aftertreatment device is determined. Operation of a selected combination of a plurality of cylinders of the engine is selectively altered to achieve the desired air-fuel ratio entering the exhaust aftertreatment system.

  20. Ammonia emissions from seabird colonies

    Science.gov (United States)

    Blackall, Trevor D.; Wilson, Linda J.; Theobald, Mark R.; Milford, Celia; Nemitz, Eiko; Bull, Jennifer; Bacon, Philip J.; Hamer, Keith C.; Wanless, Sarah; Sutton, Mark A.

    2007-05-01

    Ammonia emissions were measured from two entire seabird colonies with contrasting species assemblages, to ascertain the ammonia volatilisation potentials among seabird species in relation to their nesting behaviour. Emissions were calculated from downwind plume measurements of ammonia concentration using both inverse dispersion and tracer ratio methods. Measured colony emissions ranged 1-90 kg NH3 hour-1, and equated to 16 and 36% volatilization of excreted nitrogen for colonies dominated by ground/burrow nesting and bare rock nesting birds, respectively. The results were applied in a bioenergetics model with a global seabird database. Seabird colonies are found to represent the largest point sources of ammonia globally (up to ~6 Gg NH3 colony-1 year-1). Moreover the largest emissions occur mainly in remote environments with otherwise low NH3 emissions. These ammonia ``hot spots'' explain significant perturbations of the nitrogen cycle in these regions and add ~20% to oceanic ammonia emissions south of latitude 45°S.

  1. Heterogeneous Catalytic Ozonization of Sulfosalicylic Acid

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper describes the potential of heterogeneous catalytic ozonization of sulfo-salicylic acid (SSal). It was found that catalytic ozonization in the presence of Mn-Zr-O (a modified manganese dioxide supported on silica gel) had significantly enhanced the removal rate (72%) of total organic carbon (TOC) compared with that of ozonization alone (19%). The efficient removal rate of TOC was probably due to increasing the adsorption ability of catalyst and accelerating decomposition of ozone to produce more powerful oxidants than ozone.

  2. Copper Containing SBA-15 Prepared through pH Modification Method and Its Catalytic Activity for N_2 O Decomposition%铜掺杂SBA-15的pH调节法直接合成及其在N_2O分解反应中的催化性能

    Institute of Scientific and Technical Information of China (English)

    Mohd Haizal Mohd Husin; Mohd Ridzuan Nordin; 李金林; 刘光荣; Chin Sim Yee

    2012-01-01

    Copper-substituted SBA-15(Cu/SBA-15) mesoporous materials were directly synthesized under acidic conditions by a "pH modification method" using hexamethylenetetramine(HMTA) as an internal pH-modifier.The synthesized material has been characterized by XRD,SEM-EDX,TEM and FT-IR.The results showed that the resultant materials exhibit highly ordered hexagonal mesoporous structures.In addition,the HMTA also strongly affected the incorporation of copper in the silica framework.During hydrothermal process the HMTA dissociates to release NH3 and increases the internal pH value and helps to introduce more copper into SBA-15 framework.Catalytic screenings reveal that Cu/SBA-15 materials can be used as potential catalyst for the decomposition of N2O.The Cu/SBA-15(110) have good catalytic activity causing 50% of N2O to decomposed at 600°C.%酸性条件下,用环六亚甲基四胺作为pH调节剂,采用pH调节法直接合成了铜同构替代掺杂的SBA-15中孔分子筛(Cu/SBA-15).采用X-射线衍射(XRD)、扫描电子显微镜-能量色散X射线光谱(SEM-EDX)、透射电子显微镜(TEM)以及傅立叶变换红外光谱(FT-IR)等技术对目标材料进行了表征.结果表明:该材料具有六方中孔有序结构,且环六亚甲基四胺显著影响了铜和SBA-15硅骨架的结合,在水热合成过程中,环六亚甲基四胺分解释放出氨气,增加了体系的pH值,有助于更多的铜进入到分子筛的骨架中.该材料可用于N2O分解反应的催化剂,其中Cu/SBA-15(110)在600℃下具有优异的催化活性,可分解50%N2O.

  3. Spectral Decomposition Algorithm (SDA)

    Data.gov (United States)

    National Aeronautics and Space Administration — Spectral Decomposition Algorithm (SDA) is an unsupervised feature extraction technique similar to PCA that was developed to better distinguish spectral features in...

  4. Alteration of the Diastereoselectivity of 3-Methylaspartate Ammonia Lyase by Using Structure-Based Mutagenesis

    NARCIS (Netherlands)

    Raj, Hans; Weiner, Barbara; Puthan Veetil, Vinod; Reis, Carlos R.; Quax, Wim J.; Janssen, Dick B.; Feringa, Ben L.; Poelarends, Gerrit J.

    2009-01-01

    3-Methylaspartate ammonia-lyase (MAL) catalyzes the reversible amination of mesaconate to give both (2S,3S)-3-methylaspartic acid and (2S,3R)-3-methylaspartic acid as products. The deamination mechanism of MAL is likely to involve general base catalysis, in which a catalytic base abstracts the C3 pr

  5. A DECOMPOSITION METHOD OF STRUCTURAL DECOMPOSITION ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    LI Jinghua

    2005-01-01

    Over the past two decades,structural decomposition analysis(SDA)has developed into a major analytical tool in the field of input-output(IO)techniques,but the method was found to suffer from one or more of the following problems.The decomposition forms,which are used to measure the contribution of a specific determinant,are not unique due to the existence of a multitude of equivalent forms,irrational due to the weights of different determinants not matching,inexact due to the existence of large interaction terms.In this paper,a decomposition method is derived to overcome these deficiencies,and we prove that the result of this approach is equal to the Shapley value in cooperative games,and so some properties of the method are obtained.Beyond that,the two approaches that have been used predominantly in the literature have been proved to be the approximate solutions of the method.

  6. Theoretical models for NO decomposition in Cu-exchanged zeolites

    CERN Document Server

    Tsekov, R

    2015-01-01

    A unified description of the catalytic effect of Cu-exchanged zeolites is proposed for the decomposition of NO. A general expression for the rate constant of NO decomposition is obtained by assuming that the rate-determining step consists of the transferring of a single atom associated with breaking of the N-O bond. The analysis is performed on the base of the generalized Langevin equation and takes into account both the potential interactions in the system and the memory effects due to the zeolite vibrations. Two different mechanisms corresponding to monomolecular and bimolecular NO decomposition are discussed. The catalytic effect in the monomolecular mechanism is related to both the Cu+ ions and zeolite O-vacancies, while in the case of the bimolecular mechanism the zeolite contributes through dissipation only. The comparison of the theoretically calculated rate constants with experimental results reveals additional information about the geometric and energetic characteristics of the active centers and con...

  7. Multiresolution signal decomposition schemes

    NARCIS (Netherlands)

    Goutsias, J.; Heijmans, H.J.A.M.

    1998-01-01

    [PNA-R9810] Interest in multiresolution techniques for signal processing and analysis is increasing steadily. An important instance of such a technique is the so-called pyramid decomposition scheme. This report proposes a general axiomatic pyramid decomposition scheme for signal analysis and synthes

  8. Predicting catalysis: understanding ammonia synthesis from first-principles calculations.

    Science.gov (United States)

    Hellman, A; Baerends, E J; Biczysko, M; Bligaard, T; Christensen, C H; Clary, D C; Dahl, S; van Harrevelt, R; Honkala, K; Jonsson, H; Kroes, G J; Luppi, M; Manthe, U; Nørskov, J K; Olsen, R A; Rossmeisl, J; Skúlason, E; Tautermann, C S; Varandas, A J C; Vincent, J K

    2006-09-14

    Here, we give a full account of a large collaborative effort toward an atomic-scale understanding of modern industrial ammonia production over ruthenium catalysts. We show that overall rates of ammonia production can be determined by applying various levels of theory (including transition state theory with or without tunneling corrections, and quantum dynamics) to a range of relevant elementary reaction steps, such as N(2) dissociation, H(2) dissociation, and hydrogenation of the intermediate reactants. A complete kinetic model based on the most relevant elementary steps can be established for any given point along an industrial reactor, and the kinetic results can be integrated over the catalyst bed to determine the industrial reactor yield. We find that, given the present uncertainties, the rate of ammonia production is well-determined directly from our atomic-scale calculations. Furthermore, our studies provide new insight into several related fields, for instance, gas-phase and electrochemical ammonia synthesis. The success of predicting the outcome of a catalytic reaction from first-principles calculations supports our point of view that, in the future, theory will be a fully integrated tool in the search for the next generation of catalysts.

  9. A comparative kinetic study of SNCR process using ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Javed, M. Tayyeb; Ahmed, Z.; Ibrahim, M. Asim; Irfan, N.

    2008-07-01

    The paper presents comparative kinetic modelling of nitrogen oxides (NOx) removal from flue gases by selective non-catalytic reduction process using ammonia as reducing agent. The computer code SENKIN is used in this study with the three published chemical kinetic mechanisms; Zanoelo, Kilpinen and Skreiberg. Kinetic modeling was performed for an isothermal plug flow reactor at atmospheric pressure so as to compare it with the experimental results. A 500 ppm NOx background in the flue gas is considered and kept constant throughout the investigation. The ammonia performance was modeled in the range of 750 to 1250{sup o}C using the molar ratios NH{sub 3}/NOx from 0.25 to 3.0 and residence times up to 1.5 seconds. The modeling using all the mechanisms exhibits and confirms a temperature window of NOx reduction with ammonia. It was observed that 80% of NOx reduction efficiency could be achieved if the flue gas is given 300 msec to react with ammonia, while it is passing through a section within a temperature range of 910 to 1060{sup o}C (Kilpinen mechanism) or within a temperature range of 925 to 1030{sup o}C (Zanoelo mechanism) or within a temperature range of 890 to 1090{sup o}C (Skreiberg mechanism). 20 refs., 6 figs.

  10. Low-temperature synthesis of Mn-based mixed metal oxides with novel fluffy structures as efficient catalysts for selective reduction of nitrogen oxides by ammonia.

    Science.gov (United States)

    Meng, Bo; Zhao, Zongbin; Chen, Yongsheng; Wang, Xuzhen; Li, Yong; Qiu, Jieshan

    2014-10-21

    A series of Mn-based mixed metal oxide catalysts (Co-Mn-O, Fe-Mn-O, Ni-Mn-O) with high surface areas were prepared via low temperature crystal splitting and exhibited extremely high catalytic activity for the low-temperature selective catalytic reduction of nitrogen oxides with ammonia.

  11. [Pathway of aqueous ferric hydroxide catalyzed ozone decomposition and ozonation of trace nitrobenzene].

    Science.gov (United States)

    Ma, Jun; Zhang, Tao; Chen, Zhong-lin; Sui, Ming-hao; Li, Xue-yan

    2005-03-01

    In this paper, the decomposition rate of ozone in water was measured over GAC and ferric hydroxide/GAC (FeOOH/GAC) catalyst and the mechanism of ozone catalytic decomposition was discussed. The catalytic ozonation activity of trace nitrobenzene in water was determined on several metal oxides and correlated with their surface density of hydroxyl groups and pHzpc,(pH of zero point of charge). The results show that: 1) The pseudo-first order rate of ozone decomposition increased by 68 and 108 percent for GAC and FeOOH/GAC catalysts respectively; 2) When t-butanol was added, the rate constant decreased by 9 % for GAC and 20% for FeOOH/GAC; 3) There was no direct correlation between surface density of hydroxyl groups and the activity of catalytic ozonation of nitrobenzene; 4) The oxide surface at nearly zero charged point was favorable for the catalytic ozonation of nitrobenzene.

  12. Sustainable Ammonia Synthesis – Exploring the scientific challenges associated with discovering alternative, sustainable processes for ammonia production

    Energy Technology Data Exchange (ETDEWEB)

    Nørskov, Jens [Stanford Univ., CA (United States); ; SLAC National Accelerator Lab., Menlo Park, CA (United States); Chen, Jingguang [Columbia Univ., New York, NY (United States); Brookhaven National Lab. (BNL), Upton, NY (United States); Miranda, Raul [Dept. of Energy (DOE), Washington DC (United States). Office of Science; Fitzsimmons, Tim [Dept. of Energy (DOE), Washington DC (United States). Office of Science; Stack, Robert [Dept. of Energy (DOE), Washington DC (United States). Office of Science

    2016-02-18

    Ammonia (NH3) is essential to all life on our planet. Until about 100 years ago, NH3 produced by reduction of dinitrogen (N2) in air came almost exclusively from bacteria containing the enzyme nitrogenase.. DOE convened a roundtable of experts on February 18, 2016. Participants in the Roundtable discussions concluded that the scientific basis for sustainable processes for ammonia synthesis is currently lacking, and it needs to be enhanced substantially before it can form the foundation for alternative processes. The Roundtable Panel identified an overarching grand challenge and several additional scientific grand challenges and research opportunities: -Discovery of active, selective, scalable, long-lived catalysts for sustainable ammonia synthesis. -Development of relatively low pressure (<10 atm) and relatively low temperature (<200 C) thermal processes. -Integration of knowledge from nature (enzyme catalysis), molecular/homogeneous and heterogeneous catalysis. -Development of electrochemical and photochemical routes for N2 reduction based on proton and electron transfer -Development of biochemical routes to N2 reduction -Development of chemical looping (solar thermochemical) approaches -Identification of descriptors of catalytic activity using a combination of theory and experiments -Characterization of surface adsorbates and catalyst structures (chemical, physical and electronic) under conditions relevant to ammonia synthesis.

  13. Synthesis and catalytic properties of metal clusters encapsulated within small-pore (SOD, GIS, ANA) zeolites.

    Science.gov (United States)

    Goel, Sarika; Wu, Zhijie; Zones, Stacey I; Iglesia, Enrique

    2012-10-24

    The synthesis protocols for encapsulation of metal clusters reported here expand the diversity in catalytic chemistries made possible by the ability of microporous solids to select reactants, transition states, and products on the basis of their molecular size. We report a synthesis strategy for the encapsulation of noble metals and their oxides within SOD (Sodalite, 0.28 nm × 0.28 nm), GIS (Gismondine, 0.45 nm × 0.31 nm), and ANA (Analcime, 0.42 nm × 0.16 nm) zeolites. Encapsulation was achieved via direct hydrothermal synthesis for SOD and GIS using metal precursors stabilized by ammonia or organic amine ligands, which prevent their decomposition or precipitation as colloidal hydroxides at the conditions of hydrothermal synthesis (12), thereby causing precipitation of even ligand-stabilized metal precursors as hydroxides. As a result, encapsulation was achieved by the recrystallization of metal clusters containing GIS into ANA, which retained these metal clusters within voids throughout the GIS-ANA transformation.

  14. 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

  15. Heterogeneous Photocatalytic Degradation Kinetic of Gaseous Ammonia Over Nano-TiO2 Supported on Latex Paint Film

    Institute of Scientific and Technical Information of China (English)

    QI-JIN GENG; XI-KUI WANG; SHAN-FANG TANG

    2008-01-01

    Objective To investigate the photoeatalytic degradation of gaseous ammonia in static state by using nano-TiO2 as photocatalyst supported on latex paint film under UV-irradiation.Methods Experiments were conducted to study the relationship between the initial concentration of ammonia and the degradation products competing to be adsorbed on catalyst surface.Degradation of ammonia and its products were detected by spectrophotometry and catalytic kinetic spectrophotometry,respectively.Results On the one hand,TiO2 catalyst was excellent for degradation of ammonia,and the crystal phase of TiO2,anatase or rutile,had little effect on degradation of ammonia,but the conversion of ammonia grew with the increase of catalyst content.On the other hand,apparent rate constant and conversion of anmaoma decreased with the increase of initial concentration of ammonia,and the photocatalytic degradation reaction followed a pseudo-first-order expression due to the evidence of linear correlation between-lnC/Co vs.irradiation time t, but the relationship between initial concentration and the degradation products Was not linear in low initial concentration.Conclusion Whether the photocatalytic degradation of ammonia in static state follows a first-order reaction depends on the initial ammonia concentration due to competition in adsorption between reactant and the degradation products.

  16. Dominant modal decomposition method

    Science.gov (United States)

    Dombovari, Zoltan

    2017-03-01

    The paper deals with the automatic decomposition of experimental frequency response functions (FRF's) of mechanical structures. The decomposition of FRF's is based on the Green function representation of free vibratory systems. After the determination of the impulse dynamic subspace, the system matrix is formulated and the poles are calculated directly. By means of the corresponding eigenvectors, the contribution of each element of the impulse dynamic subspace is determined and the sufficient decomposition of the corresponding FRF is carried out. With the presented dominant modal decomposition (DMD) method, the mode shapes, the modal participation vectors and the modal scaling factors are identified using the decomposed FRF's. Analytical example is presented along with experimental case studies taken from machine tool industry.

  17. Spectral proper orthogonal decomposition

    CERN Document Server

    Sieber, Moritz; Paschereit, Christian Oliver

    2015-01-01

    The identification of coherent structures from experimental or numerical data is an essential task when conducting research in fluid dynamics. This typically involves the construction of an empirical mode base that appropriately captures the dominant flow structures. The most prominent candidates are the energy-ranked proper orthogonal decomposition (POD) and the frequency ranked Fourier decomposition and dynamic mode decomposition (DMD). However, these methods fail when the relevant coherent structures occur at low energies or at multiple frequencies, which is often the case. To overcome the deficit of these "rigid" approaches, we propose a new method termed Spectral Proper Orthogonal Decomposition (SPOD). It is based on classical POD and it can be applied to spatially and temporally resolved data. The new method involves an additional temporal constraint that enables a clear separation of phenomena that occur at multiple frequencies and energies. SPOD allows for a continuous shifting from the energetically ...

  18. Decomposition of Polynomials

    CERN Document Server

    Blankertz, Raoul

    2011-01-01

    This diploma thesis is concerned with functional decomposition $f = g \\circ h$ of polynomials. First an algorithm is described which computes decompositions in polynomial time. This algorithm was originally proposed by Zippel (1991). A bound for the number of minimal collisions is derived. Finally a proof of a conjecture in von zur Gathen, Giesbrecht & Ziegler (2010) is given, which states a classification for a special class of decomposable polynomials.

  19. Catalytic abatement of nitrous oxide from nitric and production

    NARCIS (Netherlands)

    Oonk, J.

    1998-01-01

    Nitric acid production is identified as a main source of nitrous oxide. Options for emission reduction however are not available. TNO and Hydro Agri studied the technological and economic feasibility of catalytic decomposition of nitrous oxide in nitric acid tail-gases. Although in literature promis

  20. Progresses in synthesis of phenol and cyclohexanone by catalytic oxidation-decomposition of cyclohexylbenzeneⅠ. Hydroalkylation of benzene to cyclohexylbenzene%环己基苯氧化-分解联产苯酚和环己酮技术的研究进展Ⅰ.苯加氢烷基化制备环己基苯

    Institute of Scientific and Technical Information of China (English)

    纪刚; 温朗友; 夏玥穜; 郜亮; 慕旭宏; 宗保宁

    2016-01-01

    A new process has come up recently for the co-production of phenol and cyclohexanone through three steps:the hydroalkylation of benzene,the peroxidation of cyclohexylbenzene and the decomposition of the resulting hydroperoxide products. Compared with the oxidation of cumene,this process produce cyclohexanone with high added-value and solve the acute problem of acetone over-capacity production. A thorough summarization on the methods of cyclohexylbenzene preparation was reported,including the hydroalkylation of benzene,the Friedel-Crafts alkylation of benzene and cyclohexene,and the selective hydrogenation of biphenyl. Thereinto,the relative chemical reactions,catalytic mechanism,preparation of bi-functional catalysts and process flow for the hydroalkylation of benzene were discussed in detail. Meanwhile,challenges and further development strategies were covered too.%苯通过加氢烷基化反应制备环己基苯,再经氧化-分解反应可同时得到苯酚和环己酮2种重要化工原料,是近些年发展起来的生产苯酚和环已酮的新途径;该工艺与传统异丙苯氧化生产苯酚方法相比,副产了高附加值的环己酮,解决了丙酮生产过剩的问题。比较了苯加氢烷基化、环己烯与苯烷基化和联苯选择加氢制备环己基苯3种方法,重点对苯加氢烷基化所涉及的化学反应、催化机理、双功能催化剂、反应工艺及流程的研究进展进行概述。并指出了该技术存在的问题,对其今后的发展提出了建议。

  1. Crystal structure and characterization of a novel L-serine ammonia-lyase from Rhizomucor miehei.

    Science.gov (United States)

    Qin, Zhen; Yan, Qiaojuan; Ma, Qingjun; Jiang, Zhengqiang

    2015-10-23

    L-serine ammonia-lyase, as a member of the β-family of pyridoxal-5'-phosphate (PLP) dependent enzymes, catalyzes the conversion of L-serine (L-threonine) to pyruvate (α-ketobutyrate) and ammonia. The crystal structure of L-serine ammonia-lyase from Rhizomucor miehei (RmSDH) was solved at 1.76 Å resolution by X-ray diffraction method. The overall structure of RmSDH had the characteristic β-family PLP dependent enzyme fold. It consisted of two distinct domains, both of which show the typical open twisted α/β structure. A PLP cofactor was located in the crevice between the two domains, which was attached to Lys52 by a Schiff-base linkage. Unique residue substitutions (Gly78, Pro79, Ser146, Ser147 and Thr312) were discovered at the catalytic site of RmSDH by comparison of structures of RmSDH and other reported eukaryotic L-serine ammonia-lyases. Optimal pH and temperature of the purified RmSDH were 7.5 and 40 °C, respectively. It was stable in the pH range of 7.0-9.0 and at temperatures below 40 °C. This is the first crystal structure of a fungal L-serine ammonia-lyase. It will be useful to study the catalytic mechanism of β-elimination enzymes and will provide a basis for further enzyme engineering.

  2. Catalytic pyrolysis of Pubescens to phenols over Ni/C catalyst

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The pyrolysis of Pubescens over Ni/C catalyst was studied at 350°C in H2 flow.The presence of Ni/C catalyst efficiently improved the degradation of raw materials,and produced bio-oil with high content of phenols but low contents of acetic acid,furfural and water.In the reaction,Ni/C catalyst plays the role of catalytic decomposition and catalytic hydrogenation.The existence of the carbon carrier favors the formation of active Ni in small sizes with more defects,which results in high catalytic activity of Ni in biomass decomposition and selective production of phenols.

  3. Global Seabird Ammonia Emissions

    Science.gov (United States)

    Riddick, S. N.; Blackall, T. D.; Dragosits, U.; Daunt, F. H.; Braban, C. F.; Tang, Y. S.; Trathan, P.; Wanless, S.; Sutton, M. A.

    2010-12-01

    Seabird colonies represent a major source of atmospheric ammonia (NH3) in remote coastal and marine systems in temperate, tropical and polar regions. Previous studies have shown that NH3 emissions from Scottish seabird colonies were substantial - of similar magnitude to the most intensive agricultural point source emissions. The UK data were used to model global seabird NH3 emissions and suggested that penguins are a major source of emissions on and around the Antarctic continent. The largest seabird colonies are in the order of millions of seabirds. Due to the isolation of these colonies from anthropogenic nitrogen sources, they may play a major role in the nitrogen cycle within these ecosystems. A global seabird database was constructed and used in conjunction with a species-specific seabird bioenergetics model to map the locations of NH3 emissions from seabird colonies. The accuracy of the modelled emissions was validated with field data of NH3 emissions measured at key seabird colonies in different climatic regions of the world: temperate (Isle of May, Scotland), tropical (Ascension Island) and polar (Signy Island, South Georgia). The field data indicated good agreement between modelled and measured NH3 emissions. The measured NH3 emissions also showed the variability of emission with climate. Climate dependence of seabird NH3 emissions may have further implications under a changing global climate. Seabird colonies represent NH3 emission ‘hotspots’, often far from anthropogenic sources, and are likely to be the major source of nitrogen input to these remote coastal ecosystems. The direct manuring by seabirds at colony locations may strongly influence species richness and biodiversity. The subsequent volatilisation and deposition of NH3 increases the spatial extent of seabird influence on nitrogen cycling in their local ecosystem. As many seabird populations are fluctuating due to changing food supply, climate change or anthropogenic pressures, these factors

  4. MEASUREMENT OF AMMONIA RELEASE FROM SALTSTONE

    Energy Technology Data Exchange (ETDEWEB)

    Zamecnik, J; Alex Cozzi, A

    2009-01-15

    SRNL was requested by WSRC Waste Solidification Engineering to characterize the release of ammonia from saltstone curing at 95 C by performing experimental testing. These tests were performed with an MCU-type Tank 50H salt simulant containing 0, 50, and 200 mg/L ammonia. The testing program showed that above saltstone made from the 200 mg/L ammonia simulant, the vapor space ammonia concentration was about 2.7 mg/L vapor at 95 C. An upper 95% confidence value for this concentration was found to be 3.9 mg/L. Testing also showed that ammonia was chemically generated from curing saltstone at 95 C; the amount of ammonia generated was estimated to be equivalent to 121 mg/L additional ammonia in the salt solution feed. Even with chemical generation, the ammonia release from saltstone was found to be lower than its release from salt solution only with 200 mg/L ammonia.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2002-03-01

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

  6. Manure-DNDC: a biogeochemical process model for quantifying greenhouse gas and ammonia emissions from livestock manure systems

    Science.gov (United States)

    From the point of view of biogeochemistry, manure is a complex of organic matter containing minor minerals. When manure is excreted by animals, it undergoes a series of reactions such as decomposition, hydrolysis, ammonia volatilization, nitrification, denitrification, and fermentation from which ca...

  7. Ammonia Volatilization from Urea Applied to Acid Paddy Soil in Southern China and Its Control

    Institute of Scientific and Technical Information of China (English)

    CAIGUI-XIN; PENGGUANG-HAO; 等

    1992-01-01

    Results showed that ammonia loss from urea broadcast into floodwater and incorporated into soil at transplanting was as high as 40% of applied N,and the corresponding total nitrogen (N) loss was 56%.Ammonia loss was measured with simplified micrometeorological method (ammonia sampler),and total N loss was concurrently measured using 15N balance technique.The experiment was conducted under strong sunshine conditions on acid paddy soil derived from Quaternary red clay.The ammonia loss in this particular condition was much greater than those obtained from previous studies when urea was also applied to acid paddy soil but under cloudy conditions.It is concluded that the strong sunshine conditions with high temperature and shallow floodwater during the period of present experiment favoured ammonia volatilization.Application of stearyl alcohol on the surface of the floodwater reduced ammonia loss to 23% of applied N.However,the effect of stearyl alcohol was short-lived,probably due to the microbiological decomposition.

  8. Decomposing Nekrasov decomposition

    Science.gov (United States)

    Morozov, A.; Zenkevich, Y.

    2016-02-01

    AGT relations imply that the four-point conformal block admits a decomposition into a sum over pairs of Young diagrams of essentially rational Nekrasov functions — this is immediately seen when conformal block is represented in the form of a matrix model. However, the q-deformation of the same block has a deeper decomposition — into a sum over a quadruple of Young diagrams of a product of four topological vertices. We analyze the interplay between these two decompositions, their properties and their generalization to multi-point conformal blocks. In the latter case we explain how Dotsenko-Fateev all-with-all (star) pair "interaction" is reduced to the quiver model nearest-neighbor (chain) one. We give new identities for q-Selberg averages of pairs of generalized Macdonald polynomials. We also translate the slicing invariance of refined topological strings into the language of conformal blocks and interpret it as abelianization of generalized Macdonald polynomials.

  9. Symmetric tensor decomposition

    CERN Document Server

    Brachat, Jerome; Mourrain, Bernard; Tsigaridas, Elias

    2009-01-01

    We present an algorithm for decomposing a symmetric tensor, of dimension n and order d as a sum of rank-1 symmetric tensors, extending the algorithm of Sylvester devised in 1886 for binary forms. We recall the correspondence between the decomposition of a homogeneous polynomial in n variables of total degree d as a sum of powers of linear forms (Waring's problem), incidence properties on secant varieties of the Veronese Variety and the representation of linear forms as a linear combination of evaluations at distinct points. Then we reformulate Sylvester's approach from the dual point of view. Exploiting this duality, we propose necessary and sufficient conditions for the existence of such a decomposition of a given rank, using the properties of Hankel (and quasi-Hankel) matrices, derived from multivariate polynomials and normal form computations. This leads to the resolution of polynomial equations of small degree in non-generic cases. We propose a new algorithm for symmetric tensor decomposition, based on th...

  10. Decomposing Nekrasov Decomposition

    CERN Document Server

    Morozov, A

    2015-01-01

    AGT relations imply that the four-point conformal block admits a decomposition into a sum over pairs of Young diagrams of essentially rational Nekrasov functions - this is immediately seen when conformal block is represented in the form of a matrix model. However, the q-deformation of the same block has a deeper decomposition - into a sum over a quadruple of Young diagrams of a product of four topological vertices. We analyze the interplay between these two decompositions, their properties and their generalization to multi-point conformal blocks. In the latter case we explain how Dotsenko-Fateev all-with-all (star) pair "interaction" is reduced to the quiver model nearest-neighbor (chain) one. We give new identities for q-Selberg averages of pairs of generalized Macdonald polynomials. We also translate the slicing invariance of refined topological strings into the language of conformal blocks and interpret it as abelianization of generalized Macdonald polynomials.

  11. Catalytic Activation of Small Molecules. Development and Characterisation of Ruthenium Complexes for Application in Catalysis

    OpenAIRE

    Choi, Jong-Hoo

    2016-01-01

    In this work, the synthesis, characterisation and catalytic application of ruthenium pincer complexes is presented. In this context, new synthetic strategies are discussed to obtain novel ruthenium pincer dihydrogen complexes. Furthermore, the reactivity of the complexes towards small molecules (e.g. alcohols, boranes, ammonia, amines, nitriles and hydrogen) was observed, delivering fundamental insights into catalytic applications. With the reactivity testing, new borylated B-H-σ-complexes we...

  12. Characterization of La/Fe/TiO2 and Its Photocatalytic Performance in Ammonia Nitrogen Wastewater

    Directory of Open Access Journals (Sweden)

    Xianping Luo

    2015-11-01

    Full Text Available La/Fe/TiO2 composite photocatalysts were synthesized by Sol-Gel method and well characterized by powder X-ray diffraction (XRD, scanning electron microscopy (SEM, nitrogen-physical adsorption, and UV-Vis diffuse reflectance spectra (UV-Vis DRS. It is interesting that the doped catalysts were in anatase phase while the pure TiO2 was in rutile phase. In addition, the composites possessed better physical chemical properties in photocatalytic activity than pure TiO2: stronger visible-light-response ability, larger specific surface area, and more regular shape in morphology. The photodegradation results of ammonia nitrogen indicate that: the La/Fe/TiO2 had higher catalytic activity to ammonia nitrogen waste water compared pure TiO2 and the other single metal-doped TiO2. pH 10 and 2 mmol/L H2O2 were all beneficial to the removal of ammonia nitrogen by La/Fe/TiO2. However, the common inorganic ions of Cl−, NO3−, SO42−, HCO3−/CO32−, Na+, K+, Ca2+ and Mg2+ in water all inhibited the degradation of ammonia nitrogen. By balance calculation, at least 20% of ammonia nitrogen was converted to N2 during the 64.6% removal efficiency of ammonia nitrogen.

  13. Characterization of La/Fe/TiO₂ and Its Photocatalytic Performance in Ammonia Nitrogen Wastewater.

    Science.gov (United States)

    Luo, Xianping; Chen, Chunfei; Yang, Jing; Wang, Junyu; Yan, Qun; Shi, Huquan; Wang, Chunying

    2015-11-01

    La/Fe/TiO₂ composite photocatalysts were synthesized by Sol-Gel method and well characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen-physical adsorption, and UV-Vis diffuse reflectance spectra (UV-Vis DRS). It is interesting that the doped catalysts were in anatase phase while the pure TiO₂ was in rutile phase. In addition, the composites possessed better physical chemical properties in photocatalytic activity than pure TiO₂: stronger visible-light-response ability, larger specific surface area, and more regular shape in morphology. The photodegradation results of ammonia nitrogen indicate that: the La/Fe/TiO₂ had higher catalytic activity to ammonia nitrogen waste water compared pure TiO₂ and the other single metal-doped TiO₂. pH 10 and 2 mmol/L H₂O₂ were all beneficial to the removal of ammonia nitrogen by La/Fe/TiO₂. However, the common inorganic ions of Cl(-), NO₃(-), SO₄(2-), HCO₃(-)/CO₃²(-), Na⁺, K⁺, Ca(2+) and Mg(2+) in water all inhibited the degradation of ammonia nitrogen. By balance calculation, at least 20% of ammonia nitrogen was converted to N₂ during the 64.6% removal efficiency of ammonia nitrogen.

  14. Characterization of La/Fe/TiO2 and Its Photocatalytic Performance in Ammonia Nitrogen Wastewater

    Science.gov (United States)

    Luo, Xianping; Chen, Chunfei; Yang, Jing; Wang, Junyu; Yan, Qun; Shi, Huquan; Wang, Chunying

    2015-01-01

    La/Fe/TiO2 composite photocatalysts were synthesized by Sol-Gel method and well characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen-physical adsorption, and UV-Vis diffuse reflectance spectra (UV-Vis DRS). It is interesting that the doped catalysts were in anatase phase while the pure TiO2 was in rutile phase. In addition, the composites possessed better physical chemical properties in photocatalytic activity than pure TiO2: stronger visible-light-response ability, larger specific surface area, and more regular shape in morphology. The photodegradation results of ammonia nitrogen indicate that: the La/Fe/TiO2 had higher catalytic activity to ammonia nitrogen waste water compared pure TiO2 and the other single metal-doped TiO2. pH 10 and 2 mmol/L H2O2 were all beneficial to the removal of ammonia nitrogen by La/Fe/TiO2. However, the common inorganic ions of Cl−, NO3−, SO42−, HCO3−/CO32−, Na+, K+, Ca2+ and Mg2+ in water all inhibited the degradation of ammonia nitrogen. By balance calculation, at least 20% of ammonia nitrogen was converted to N2 during the 64.6% removal efficiency of ammonia nitrogen. PMID:26593929

  15. Abiotic nitrogen fixation on terrestrial planets: reduction of NO to ammonia by FeS.

    Science.gov (United States)

    Summers, David P; Basa, Ranor C B; Khare, Bishun; Rodoni, David

    2012-02-01

    Understanding the abiotic fixation of nitrogen and how such fixation can be a supply of prebiotic nitrogen is critical for understanding both the planetary evolution of, and the potential origin of life on, terrestrial planets. As nitrogen is a biochemically essential element, sources of biochemically accessible nitrogen, especially reduced nitrogen, are critical to prebiotic chemistry and the origin of life. Loss of atmospheric nitrogen can result in loss of the ability to sustain liquid water on a planetary surface, which would impact planetary habitability and hydrological processes that shape the surface. It is known that NO can be photochemically converted through a chain of reactions to form nitrate and nitrite, which can be subsequently reduced to ammonia. Here, we show that NO can also be directly reduced, by FeS, to ammonia. In addition to removing nitrogen from the atmosphere, this reaction is particularly important as a source of reduced nitrogen on an early terrestrial planet. By converting NO directly to ammonia in a single step, ammonia is formed with a higher product yield (~50%) than would be possible through the formation of nitrate/nitrite and subsequent conversion to ammonia. In conjunction with the reduction of NO, there is also a catalytic disproportionation at the mineral surface that converts NO to NO₂ and N₂O. The NO₂ is then converted to ammonia, while the N₂O is released back in the gas phase, which provides an abiotic source of nitrous oxide.

  16. Decomposition of residue currents

    OpenAIRE

    Andersson, Mats; Wulcan, Elizabeth

    2007-01-01

    Given a submodule $J\\subset \\mathcal O_0^{\\oplus r}$ and a free resolution of $J$ one can define a certain vector valued residue current whose annihilator is $J$. We make a decomposition of the current with respect to Ass$(J)$ that correspond to a primary decomposition of $J$. As a tool we introduce a class of currents that includes usual residue and principal value currents; in particular these currents admit a certain type of restriction to analytic varieties and more generally to construct...

  17. Ammonia abatement by slurry acidification

    DEFF Research Database (Denmark)

    Petersen, Søren O.; Hutchings, Nicholas John; Hafner, Sasha

    2016-01-01

    Livestock production systems can be major sources of trace gases including ammonia (NH3), the greenhouse gases methane (CH4) and nitrous oxide (N2O), and odorous compounds such as hydrogen sulphide (H2S). Short-term campaigns have indicated that acidification of livestock slurry during in...... sections with 30-32 pigs with or without daily adjustment of slurry pH to below 6. Ammonia losses from reference sections with untreated slurry were between 9.5 and 12.4% of N excreted, and from sections with acidified slurry between 3.1 and 6.2%. Acidification reduced total emissions of NH3 by 66 and 71...

  18. Nitrocarburizing in ammonia-hydrocarbon gas mixtures

    DEFF Research Database (Denmark)

    Pedersen, Hanne; Christiansen, Thomas; Somers, Marcel A. J.

    2011-01-01

    The present work investigates the possibility of nitrocarburising in ammonia-acetylene-hydrogen and ammonia-propene-hydrogen gas mixtures, where unsaturated hydrocarbon gas is the carbon source during nitrocarburising. Consequently, nitrocarburising is carried out in a reducing atmosphere...

  19. Enrichment of high ammonia tolerant methanogenic culture

    DEFF Research Database (Denmark)

    Fotidis, Ioannis; Karakashev, Dimitar Borisov; Proietti, Nicolas

    Ammonia is the major toxicant in full scale anaerobic digesters of animal wastes which are rich in proteins and/or urea, such as pig or poultry wastes. Ammonia inhibition decreases methane production rates, increases volatile fatty acids concentration and leads to economic losses for the biogas...... plants. The methods used today to counteract ammonia inhibition are slow and costexpensive. A new biological approach to avoid or counteract ammonia inhibition by using ammonia tolerant methanogens, could provide a sustainable solution for cost-effective digestion of abundant ammonia-rich wastes. The aim...... of the current study was to isolate and identify methanogenic cultures tolerant to high ammonia concentrations. A mixed methanogenic population was stepwise exposed to ammonia concentrations (1 to 9.26 g NH4+-N L-1) during an enrichment process with successive batch cultivations. The methanogenic population...

  20. RESULTS OF INITIAL AMMONIA OXIDATION TESTING

    Energy Technology Data Exchange (ETDEWEB)

    Nash, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Fowley, M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-12-30

    This memo presents an experimental survey of aqueous phase chemical processes to remove aqueous ammonia from waste process streams. Ammonia is generated in both the current Hanford waste flowsheet and in future waste processing. Much ammonia will be generated in the Low Activity Waste (LAW) melters.i Testing with simulants in glass melters at Catholic University has demonstrated the significant ammonia production.ii The primary reaction there is the reducing action of sugar on nitrate in the melter cold cap. Ammonia has been found to be a problem in secondary waste stabilization. Ammonia vapors are noxious and destruction of ammonia could reduce hazards to waste treatment process personnel. It is easily evolved especially when ammonia-bearing solutions are adjusted to high pH.

  1. DETERMINATION OF AMMONIA IN EAR-LOBE CAPILLARY BLOOD IS AN ALTERNATIVE TO ARTERIAL BLOOD AMMONIA

    NARCIS (Netherlands)

    HUIZENGA, [No Value; GIPS, CH; CONN, HO; JANSEN, PLM

    1995-01-01

    Blood ammonia determination is a laboratory test to diagnose hepatic encephalopathy. Arterial blood is superior to peripheral venous blood ammonia because of ammonia metabolism in muscle. We have compared capillary with arterial whole blood ammonia as capillary sampling is an attractive alternative.

  2. Final Report, "Molecular Design of Hydrocarbon Oxidation Catalytic Processes"

    Energy Technology Data Exchange (ETDEWEB)

    Professor Francisco Zaera

    2007-08-09

    production of small amounts of ethylene and water, most likely via the concerted decomposition or disproportionation of the adsorbed molecular species. The bulk of the 2-iodoethanol decomposes at about 150 K via an initial carbon-iodine scission to form –O(H)CH2CH2– (~80%) and 2-hydroxyethyl (~20%) intermediates. Two competing reactions are involved with the subsequent conversion of the 2-hydroxyethyl species around 160 K, a reductive elimination with surface hydrogen to yield ethanol, and a β-H elimination to surface vinyl alcohol. The –O(H)CH2CH2–, on the other hand, dehydrogenates to a –OCH2CH2– oxametallacycle species about the same temperature. Both 2-hydroxyethyl and oxametallacycle species tautomerize to acetaldehyde, around 210 K and above 250 K, respectively, and some of that acetaldehyde desorbs while the rest decomposes to hydrogen and carbon monoxide. We contend that a better understanding of the surface chemistry of oxygen-containing surfaces can lead to better selectivities in catalysis. This is arguably the most important issue in the field of catalysis in the near future, and one that impacts several technologies of interest to DOE such as the manufacturing of speciality chemicals and the control and removal of pollutants. Additional work was performed on the characterization of the chemistry of methyl and methylene adsorbed species on oxygen-treated nickel surfaces. Complex chemistry was observed involving not only hydrogenation and dehydrogenation steps, but also C-C couplings and methylene insertions to produce heavier hydrocarbons, and oxygen insertion reactions that yield oxygenates. Finally, a dual titration technique employing xenon and a chemically sensitive probe was developed to identify minority catalytic sites on oxide surfaces. In the case of oxygen-treated Ni(110) single crystals, it was found that both hydrogen transfer with adsorbed water or ammonia and certain hydrocarbon hydrogenation reactions take place at the end of the

  3. Clustering via Kernel Decomposition

    DEFF Research Database (Denmark)

    Have, Anna Szynkowiak; Girolami, Mark A.; Larsen, Jan

    2006-01-01

    Methods for spectral clustering have been proposed recently which rely on the eigenvalue decomposition of an affinity matrix. In this work it is proposed that the affinity matrix is created based on the elements of a non-parametric density estimator. This matrix is then decomposed to obtain poste...

  4. 46 CFR 154.1760 - Liquid ammonia.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Liquid ammonia. 154.1760 Section 154.1760 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SAFETY STANDARDS FOR....1760 Liquid ammonia. The master shall ensure that no person sprays liquid ammonia into a cargo...

  5. 27 CFR 21.96 - Ammonia, aqueous.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Ammonia, aqueous. 21.96 Section 21.96 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT... Ammonia, aqueous. (a) Alkalinity. Strongly alkaline to litmus. (b) Ammonia content. 27 to 30 percent...

  6. Parameter Optimization on Experimental Study to Reduce Ammonia Escape in CO2 Absorption by Ammonia Scrubbing

    Institute of Scientific and Technical Information of China (English)

    Hao Leng; Jianmin Gao; Mingyue He; Min Xie; Qian Du; Rui Sun; Shaohua Wu

    2016-01-01

    In order to research ammonia escape in CO2 absorption by ammonia scrubbing, ammonia escape was studied in CO2 absorption process using the bubbling reactor in different conditions as gas flow rate, CO2 ratio, absorbent temperature and ammonia concentration and quantity of escaped ammonia was measured by chemical titration. The results indicated that, the amount of ammonia escape can be around 20% of original amount in 90 min and the escaped amount will increase with the rise of gas flow rate, absorbent temperature, concentration of ammonia while decrease as CO2 ratio goes up. Through the analysis of the law of ammonia escape, at the same time, combined with ammonia escape and the influence of the relationship between the CO2 absorption efficiency, reducing ammonia escape working condition parameter optimization is given.

  7. Hydrogen production using ammonia borane

    Science.gov (United States)

    Hamilton, Charles W; Baker, R. Thomas; Semelsberger, Troy A; Shrestha, Roshan P

    2013-12-24

    Hydrogen ("H.sub.2") is produced when ammonia borane reacts with a catalyst complex of the formula L.sub.nM-X wherein M is a base metal such as iron, X is an anionic nitrogen- or phosphorus-based ligand or hydride, and L is a neutral ancillary ligand that is a neutral monodentate or polydentate ligand.

  8. Ammonia in power plant emission

    Science.gov (United States)

    Hammerich, Mads; Henningsen, J. O.; Olafsson, Ari

    1990-08-01

    Ammonia monitoring is needed in most schemes for denitrification of power plant emission. In the PALAMON system we use a 500 MHz tunable, single mode, single line, CO2 laser as light source for a low pressure, high temperature, photoacoustic cell. With this cell we can resolve the sR(5,O) line of the ammonia spectrum, and suppress the interfering C02(9R30) absorption line down to a lppm NH3 detection limit. The validity of the measured ammonia concentrations is strongly dependent on details of the sampling system and on the reliability of the calibration routines. In particular calibration with certified mixtures of NH3:N2 has proved insufficient due to the multiple and long time constants caused by adsorption of ammonia to different materials in the system. Presence of water vapor in the gas greatly reduces these time constants. Therefore a number of methods for simple production of moist calibration gases from macroscopic amounts of NH3 are applied. The calibrations are translated to response from an easily managable absorber in order to allow automated recalibration of the photoacoustic response. Data from a field test of the system, and calibration data will be presented.

  9. Ceramic Membranes for Ammonia Recovery

    Energy Technology Data Exchange (ETDEWEB)

    Camus, O.; Perera, S.; Crittenden, B. [Department of Chemical Engineering, University of Bath, Bath, BA2 7AY (United Kingdom); Van Delft, Y.C.; Meyer, D.F.; Pex, P.P.A.C. [ECN Solar Energy, Westerduinweg 3, P.O. Box 1, 1755 ZG Petten (Netherlands); Kumakiri, I.; Miachon, S.; Dalmon, J.A. [CNRS-Institut de Recherches sur la Catalyse 2, av. A. Einstein, 69626 Villeurbanne (France); Tennison, S. [MAST Carbon, Ltd., Henley Park, Guildford, Surrey, GU3 2AF (United Kingdom); Chanaud, P. [Pall-Exekia, BP1, Usine a Bazet (France); Groensmit, E. [Kemira GrowHow SA/NV, Avenue Einstein 11, B-1300 Wavre (Belgium); Nobel, W. [Continental Engineers BV, Rustenburg 114, 1506 AZ Zaandam (Netherlands)

    2008-12-15

    An extensive screening program has been performed to find a suitable membrane configuration and operating conditions for the effective recovery of ammonia from the syngas loop. All the experiments have been performed at steady state. MFI zeolite membranes in tubular and multi-channel fiber configurations have been tested along with tubular silica membranes. At 80C, a high ammonia permeance (2.1 x 10{sup -7} mol.m{sup -2}.s{sup -1}.Pa{sup -1}), and a selectivity of about 10 were found with the tubular zeolite membrane, whereas for the silica membrane an even higher ammonia permeance was measured (7.6 x 10{sup -7} mol.m{sup -2}.s{sup -1}.Pa{sup -1}) with a selectivity of about 7. For both silica and zeolite membranes, the selectivity was found to increase with increasing temperature up to 80C. This is a combined effect of weaker adsorption of ammonia and increased diffusion at higher temperature. The results have been modeled using both the well-mixed reactor and the log mean pressure difference approaches. To overcome their limitations in addressing changes in feed concentration along the membrane surface, a segmental model has been used to obtain suitable operating conditions and membrane areas required for an industrial application.

  10. Inhibiting Wet Oxidation of Ammonia

    Science.gov (United States)

    Onisko, D. B. L.

    1985-01-01

    Simple modification of wet-oxidation process for treating organicwaste reduces loss of fixed nitrogen, potentially valuable byproduct of process. Addition of sufficient sulfuric acid to maintain reaction pH below 3 greatly reduces oxidation of ammonia to free nitrogen. No equipment modification required.

  11. Reducing ammonia emissions in Europe

    DEFF Research Database (Denmark)

    Jacobsen, Brian H.

    2011-01-01

    The NEC directive has set targets for the 2010 ammonia emissions from a number of European countries. The target will be reached by most EU-countries and the total emission for EU-27 has been reduced by 22% from 1990 to 2007. Denmark is one of the countries with the largest reductions since 1990...

  12. Forthcoming Oversupply for Synthetic Ammonia

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhantong

    2007-01-01

    @@ Stable output increase The total capacity of synthetic ammonia in China is 52.0 million t/a today.There are around 540 producers mainly located in Shandong, Shanxi, Hebei,Henan, Jiangsu and Sichuan provinces.The cumulative capacity in Shandong province ranks the highest, accounting for 14.6% of the national total.

  13. Effect of samarium on methanation resistance of activated carbon supported ruthenium catalyst for ammonia synthesis

    Institute of Scientific and Technical Information of China (English)

    周春晖; 祝一锋; 刘化章

    2010-01-01

    The effects of samarium(Sm) on carbon-methanation and catalytic activity of the Ba-Ru-K/AC (active carbon) catalyst for ammonia synthesis were investigated. The addition of samarium improved significantly the activity and stability of the catalyst. The results of temperature-programmed desorption (H2-TPD) and in-situ-TPSR FTIR indicated that samarium impeded the adsorption of hydrogen on the catalyst surface, thus leading to the high catalytic activity and resistance to carbon-methanation. XRD patterns reve...

  14. [Influence of ammonia on leaching behaviors of incineration fly ash and its geochemical modeling].

    Science.gov (United States)

    Guan, Zhen-Zhen; Chen, De-Zhen; Thomas, Astrup

    2013-06-01

    Incineration fly ash could be contaminated with NH3 that was slipped from the ammonia-based selective non-catalytic reduction(SNCR) process and from evaporation of municipal solid wastes' leachate involved in the wastes. This research was conducted to investigate the impacts of ammonia on leaching of dissolved organic carbon (DOC) and metals from incineration fly ash in the pH range of 3.66-12.44 with an active ammonia spike. A geochemical modeling software Visual MINTEQ was adopted to calculate the chemical speciation of metals under the leaching conditions to reveal the mechanism behind the impacts. It was proved that at pH > 9, the leaching of DOC increased significantly in the presence of high concentrations of ammonia (> or = 1 357 mg x L(-1)), but there was little effect when the ammonia level in eluates was not higher than 537 mg x L(-1). At pH or = 3 253 mg x L(-1)) mobilized Cd, Cu, Ni and Zn significantly due to the formation of soluble metal-ammonia complexes, and the leaching rates reached their peaks at pH around 9; however, ammonia had little impacts on Al and Pb leaching within this pH range. At pH > 12, for Cd, Cu, Ni and Zn, their leaching species were predominantly in the form of hydroxide complexes. Under the ammonia concentration of 3253 mg x L(-1), the Visual MINTEQ modeling results were compared with the experimental data, and it was proved that the leaching of Al, Pb and Zn was mainly controlled by precipitation/dissolution modeling, while Cd, Cu and Ni were controlled by precipitation/dissolution and surface complexation/precipitation processes; Visual MINTEQ modeling could well describe the leaching behaviors of Al, Cu, Pb and Zn from incineration fly ash.

  15. Nitrate reduction to nitrite, nitric oxide and ammonia by gut bacteria under physiological conditions.

    Science.gov (United States)

    Tiso, Mauro; Schechter, Alan N

    2015-01-01

    The biological nitrogen cycle involves step-wise reduction of nitrogen oxides to ammonium salts and oxidation of ammonia back to nitrites and nitrates by plants and bacteria. Neither process has been thought to have relevance to mammalian physiology; however in recent years the salivary bacterial reduction of nitrate to nitrite has been recognized as an important metabolic conversion in humans. Several enteric bacteria have also shown the ability of catalytic reduction of nitrate to ammonia via nitrite during dissimilatory respiration; however, the importance of this pathway in bacterial species colonizing the human intestine has been little studied. We measured nitrite, nitric oxide (NO) and ammonia formation in cultures of Escherichia coli, Lactobacillus and Bifidobacterium species grown at different sodium nitrate concentrations and oxygen levels. We found that the presence of 5 mM nitrate provided a growth benefit and induced both nitrite and ammonia generation in E.coli and L.plantarum bacteria grown at oxygen concentrations compatible with the content in the gastrointestinal tract. Nitrite and ammonia accumulated in the growth medium when at least 2.5 mM nitrate was present. Time-course curves suggest that nitrate is first converted to nitrite and subsequently to ammonia. Strains of L.rhamnosus, L.acidophilus and B.longum infantis grown with nitrate produced minor changes in nitrite or ammonia levels in the cultures. However, when supplied with exogenous nitrite, NO gas was readily produced independently of added nitrate. Bacterial production of lactic acid causes medium acidification that in turn generates NO by non-enzymatic nitrite reduction. In contrast, nitrite was converted to NO by E.coli cultures even at neutral pH. We suggest that the bacterial nitrate reduction to ammonia, as well as the related NO formation in the gut, could be an important aspect of the overall mammalian nitrate/nitrite/NO metabolism and is yet another way in which the microbiome

  16. Adsorption and decomposition of monopropellant molecule HAN on Pd(100) and Ir(100) surfaces: A DFT study

    Science.gov (United States)

    Banerjee, Sourav; Shetty, Sharath A.; Gowrav, M. N.; Oommen, Charlie; Bhattacharya, Atanu

    2016-11-01

    We have performed density functional theory calculations with the generalized gradient approximation to investigate the catalytic decomposition reactions of one of the most promising monopropellants, hydroxylammonium nitrate (HAN), on two catalytically active single crystal Pd(100) and Ir(100) surfaces, aiming at exploring different reaction pathways and reactivities of these two surfaces towards the catalytic decomposition of HAN. We find that the HAN molecule binds both the Pd(100) and Ir(100) surfaces molecularly in different orientations with respect to the surface. The HONO elimination is found to possess the lowest activation energy on the Pd(100) surface; whereas, NO2 elimination is predicted to show the lowest activation energy on the Ir(100) surface. Exothermicities associated with different reaction steps are also discussed. This is the first theoretical report on the catalytic decomposition reactions of the HAN molecule on the single crystal Pd(100) and the Ir(100) surfaces using the periodic DFT calculations.

  17. Photocatalytic Activity for Water Decomposition to Hydrogen over Nitrogen-doped TiO2 Nanoparticle

    Institute of Scientific and Technical Information of China (English)

    LI,Xiao-Bo; JIANG,Xiao-Ying; HUANG,Jian-Hua; WANG,Xue-Jing

    2008-01-01

    Nitrogen-doped TiO2 nanoparticle photocatalysts were obtained by an annealing method with gaseous ammonia and nitrogen. The influence of dopant N on the crystal structure was characterized by XRD, XPS, BET, TEM and UV-Vis spectra. The results of XRD indicate that, the crystal phase transforms from anatase to rutile structure gradually with increase of annealing temperature from 300 to 700 ℃. XPS studies indicate that the nitrogen atom enters the TiO2 lattice and occupies the position of oxygen atom. Agglomeration of particles is found in TEM im-ages after annealing. BET results show that the specific surface areas of N-doped samples from 44.61 to 38.27 m2/g are smaller than that of Degussa TiO2. UV-Vis spectra indicate that the absorption threshold shifts gradually with increase of annealing temperature, which shows absorption in the visible region. The influence of annealing condi-tion on the photocatalytic property has been researched over water decomposition to hydrogen, indicating that ni-trogen raises the photocatalytic activity for hydrogen evolution, and the modified TiO2 annealed for 2 h at 400 ℃ under gas of NH3/N2 (V/V= 1/2) mixture shows better efficiency of hydrogen evolution. Furthermore, the N-doped TiO2 nanoparticle catalysts have obvious visible light activity, evidenced by hydrogen evolution under visible light (λ>400 nm) irradiation. However, the catalytic activity under visible light irradiation is absent for Degussa as ref-erence and the N-doped TiO2 annealed at 700 ℃.

  18. Modeling N2O Reduction and Decomposition in a Circulating Fluidized bed Boiler

    DEFF Research Database (Denmark)

    Johnsson, Jan Erik; Åmand, Lars-Erik; Dam-Johansen, Kim;

    1996-01-01

    The N2O concentration was measured in a circulating fluidized bed boiler of commercial size. Kinetics for N2O reduction by char and catalytic reduction and decomposition over bed material from the combustor were determined in a laboratory fixed bed reactor. The destruction rate of N2O in the comb......The N2O concentration was measured in a circulating fluidized bed boiler of commercial size. Kinetics for N2O reduction by char and catalytic reduction and decomposition over bed material from the combustor were determined in a laboratory fixed bed reactor. The destruction rate of N2O...

  19. Transcriptional Response of the Archaeal Ammonia Oxidizer Nitrosopumilus maritimus to Low and Environmentally Relevant Ammonia Concentrations

    OpenAIRE

    Nakagawa, Tatsunori; Stahl, David A.

    2013-01-01

    The ability of chemoautotrophic ammonia-oxidizing archaea to compete for ammonia among marine microorganisms at low ambient concentrations has been in part attributed to their extremely high affinity for ammonia, but as yet there is no mechanistic understanding of supporting metabolism. We examined transcription of selected genes for anabolic functions (CO2 fixation, ammonia transport, and cell wall synthesis) and a central catabolic function (ammonia oxidation) in the thaumarchaeon Nitrosopu...

  20. Transcriptional response of the archaeal ammonia oxidizer Nitrosopumilus maritimus to low and environmentally relevant ammonia concentrations.

    Science.gov (United States)

    Nakagawa, Tatsunori; Stahl, David A

    2013-11-01

    The ability of chemoautotrophic ammonia-oxidizing archaea to compete for ammonia among marine microorganisms at low ambient concentrations has been in part attributed to their extremely high affinity for ammonia, but as yet there is no mechanistic understanding of supporting metabolism. We examined transcription of selected genes for anabolic functions (CO2 fixation, ammonia transport, and cell wall synthesis) and a central catabolic function (ammonia oxidation) in the thaumarchaeon Nitrosopumilus maritimus SCM1 growing at two ammonia concentrations, as measured by combined ammonia and ammonium, one well above the Km for ammonia oxidation (∼500 μM) and the other well below the Km (ammonia-replete to ammonia-limiting conditions. Transcript levels for ammonia oxidation, CO2 fixation, and one of the ammonia transport genes were approximately the same at high and low ammonia availability. Transcripts for all analyzed genes decreased with time in the complete absence of ammonia, but with various rates of decay. The new steady-state mRNA levels established are presumably more reflective of the natural physiological state of ammonia-oxidizing archaea and offer a reference for interpreting message abundance patterns in the natural environment.

  1. Autonomous micromotor based on catalytically pneumatic behavior of balloon-like MnO(x)-graphene crumples.

    Science.gov (United States)

    Chen, Xueli; Wu, Guan; Lan, Tian; Chen, Wei

    2014-07-11

    A novel autonomous micromotor, based on catalytically pneumatic behaviour of balloon-like MnOx-graphene crumples, has been synthesized via an ultrasonic spray pyrolysis method. Through catalytic decomposition of H2O2 into O2, the gas accumulated in a confined space and was released to generate a strong force to push the micromotor.

  2. Production of filamentous carbon and H{sub 2} by solarthermal catalytic cracking of CH{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Kirillov, V.; Kuvshinov, G. [Boreskov Inst. of Catalysis (Russian Federation); Reller, A. [Hamburg Univ., Hamburg (Germany); Steinfeld, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The catalytic thermal decomposition of methane has been experimentally studied using high-temperature solar process heat. Nickel catalyst particles, fluidized in methane, were directly irradiated at the PSI solar furnace. Carbon deposition consisted of randomly interlaced filaments that grew as fibers and hollow nanotubes (of approx. 30 nm diameter) originating at each catalytic particle. (author) 4 figs., 7 refs.

  3. 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...

  4. 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...

  5. Catalytic combustor for hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Mercea, J.; Grecu, E.; Fodor, T.; Kreibik, S.

    1982-01-01

    The performance of catalytic combustors for hydrogen using platinum-supported catalysts is described. Catalytic plates of different sizes were constructed using fibrous and ceramic supports. The temperature distribution as well as the reaction efficiency as a function of the fuel input rate was determined, and a comparison between the performances of different plates is discussed.

  6. Decomposition of semigroup algebras

    CERN Document Server

    Boehm, Janko; Nitsche, Max Joachim

    2011-01-01

    Let A \\subseteq B be cancellative abelian semigroups, and let R be an integral domain. We show that the semigroup ring R[B] can be decomposed, as an R[A]-module, into a direct sum of R[A]-submodules of the quotient ring of R[A]. In the case of a finite extension of positive affine semigroup rings we obtain an algorithm computing the decomposition. When R[A] is a polynomial ring over a field we explain how to compute many ring-theoretic properties of R[B] in terms of this decomposition. In particular we obtain a fast algorithm to compute the Castelnuovo-Mumford regularity of homogeneous semigroup rings. As an application we confirm the Eisenbud-Goto conjecture in a range of new cases. Our algorithms are implemented in the Macaulay2 package MonomialAlgebras.

  7. Ruthenium-Catalyzed Ammonia Borane Dehydrogenation: Mechanism and Utility.

    Science.gov (United States)

    Zhang, Xingyue; Kam, Lisa; Trerise, Ryan; Williams, Travis J

    2017-01-17

    One of the greatest challenges in using H2 as a fuel source is finding a safe, efficient, and inexpensive method for its storage. Ammonia borane (AB) is a solid hydrogen storage material that has garnered attention for its high hydrogen weight density (19.6 wt %) and ease of handling and transport. Hydrogen release from ammonia borane is mediated by either hydrolysis, thus giving borate products that are difficult to rereduce, or direct dehydrogenation. Catalytic AB dehydrogenation has thus been a popular topic in recent years, motivated both by applications in hydrogen storage and main group synthetic chemistry. This Account is a complete description of work from our laboratory in ruthenium-catalyzed ammonia borane dehydrogenation over the last 6 years, beginning with the Shvo catalyst and resulting ultimately in the development of optimized, leading catalysts for efficient hydrogen release. We have studied AB dehydrogenation with Shvo's catalyst extensively and generated a detailed understanding of the role that borazine, a dehydrogenation product, plays in the reaction: it is a poison for both Shvo's catalyst and PEM fuel cells. Through independent syntheses of Shvo derivatives, we found a protective mechanism wherein catalyst deactivation by borazine is prevented by coordination of a ligand that might otherwise be a catalytic poison. These studies showed how a bidentate N-N ligand can transform the Shvo into a more reactive species for AB dehydrogenation that minimizes accumulation of borazine. Simultaneously, we designed novel ruthenium catalysts that contain a Lewis acidic boron to replace the Shvo -OH proton, thus offering more flexibility to optimize hydrogen release and take on more general problems in hydride abstraction. Our scorpionate-ligated ruthenium species (12) is a best-of-class catalyst for homogeneous dehydrogenation of ammonia borane in terms of its extent of hydrogen release (4.6 wt %), air tolerance, and reusability. Moreover, a synthetically

  8. Ammonia Production, Excretion, Toxicity, and Defense in Fish: A Review

    OpenAIRE

    Yuen K Ip; Chew, Shit F.

    2010-01-01

    Many fishes are ammonotelic but some species can detoxify ammonia to glutamine or urea. Certain fish species can accumulate high levels of ammonia in the brain or defense against ammonia toxicity by enhancing the effectiveness of ammonia excretion through active NH 4 + transport, manipulation of ambient pH, or reduction in ammonia permeability through the branchial and cutaneous epithelia. Recent reports on ammonia toxicity in mammalian brain reveal the importance of permeation of ammonia thr...

  9. Study of catalytic upgrading of biomass tars using Indonesian iron ore

    Science.gov (United States)

    Wicakso, Doni Rahmat; Sutijan, Rochmadi, Budiman, Arief

    2017-03-01

    Catalytic decomposition is a promising way for chemical upgrading process of low quality oil such as biomass tars. In this experiment, catalytic decomposition of biomass tars was performed over Indonesian low grade iron ore catalyst. This process is carried out in a fixed bedreactor which is equipped with preheater to convert the tars into vapor form. The reaction was studied at the temperature range of 500 - 700°C. The kinetic study of catalytic decomposition of biomass tars is represented using first order reaction. The results show that value of constant of chemical reaction is in range 0.2514 - 0.9642 cm3.gr-1.min-1 with value of the frequency factor (A) and the activation energy (E) are 48.98 min-1 and 5724.94 cal.mol-1, respectively.

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

    Institute of Scientific and Technical Information of China (English)

    YiangChen CHOU; Young KU

    2012-01-01

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

  11. Ammonia Process by Pressure Swing Adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Dr Felix Jegede

    2010-12-27

    The overall objective of the project is to design, develop and demonstrate a technically feasible and commercially viable system to produce ammonia along with recovery of the products by adsorption separation methods and significantly decrease the energy requirement in ammonia production. This is achieved through a significantly more efficient ammonia psa recovery system. The new ammonia recovery system receives the reactor effluents and achieves complete ammonia recovery, (which completely eliminates the energy intensive refrigeration and condensation system currently used in ammonia production). It also recovers the unused reactants and recycles them back to the reactor, free of potential reactor contaminants, and without the need for re-compression and re-heat of recycle stream thereby further saving more energy. The result is a significantly lower energy consumption, along with capital cost savings.

  12. Adaptive Integrand Decomposition

    CERN Document Server

    Mastrolia, Pierpaolo; Primo, Amedeo; Bobadilla, William J Torres

    2016-01-01

    We present a simplified variant of the integrand reduction algorithm for multiloop scattering amplitudes in $d = 4 - 2\\epsilon$ dimensions, which exploits the decomposition of the integration momenta in parallel and orthogonal subspaces, $d=d_\\parallel+d_\\perp$, where $d_\\parallel$ is the dimension of the space spanned by the legs of the diagrams. We discuss the advantages of a lighter polynomial division algorithm and how the orthogonality relations for Gegenbauer polynomilas can be suitably used for carrying out the integration of the irreducible monomials, which eliminates spurious integrals. Applications to one- and two-loop integrals, for arbitrary kinematics, are discussed.

  13. Mode decomposition evolution equations.

    Science.gov (United States)

    Wang, Yang; Wei, Guo-Wei; Yang, Siyang

    2012-03-01

    Partial differential equation (PDE) based methods have become some of the most powerful tools for exploring the fundamental problems in signal processing, image processing, computer vision, machine vision and artificial intelligence in the past two decades. The advantages of PDE based approaches are that they can be made fully automatic, robust for the analysis of images, videos and high dimensional data. A fundamental question is whether one can use PDEs to perform all the basic tasks in the image processing. If one can devise PDEs to perform full-scale mode decomposition for signals and images, the modes thus generated would be very useful for secondary processing to meet the needs in various types of signal and image processing. Despite of great progress in PDE based image analysis in the past two decades, the basic roles of PDEs in image/signal analysis are only limited to PDE based low-pass filters, and their applications to noise removal, edge detection, segmentation, etc. At present, it is not clear how to construct PDE based methods for full-scale mode decomposition. The above-mentioned limitation of most current PDE based image/signal processing methods is addressed in the proposed work, in which we introduce a family of mode decomposition evolution equations (MoDEEs) for a vast variety of applications. The MoDEEs are constructed as an extension of a PDE based high-pass filter (Europhys. Lett., 59(6): 814, 2002) by using arbitrarily high order PDE based low-pass filters introduced by Wei (IEEE Signal Process. Lett., 6(7): 165, 1999). The use of arbitrarily high order PDEs is essential to the frequency localization in the mode decomposition. Similar to the wavelet transform, the present MoDEEs have a controllable time-frequency localization and allow a perfect reconstruction of the original function. Therefore, the MoDEE operation is also called a PDE transform. However, modes generated from the present approach are in the spatial or time domain and can be

  14. Symmetric Tensor Decomposition

    DEFF Research Database (Denmark)

    Brachat, Jerome; Comon, Pierre; Mourrain, Bernard;

    2010-01-01

    of polynomial equations of small degree in non-generic cases. We propose a new algorithm for symmetric tensor decomposition, based on this characterization and on linear algebra computations with Hankel matrices. The impact of this contribution is two-fold. First it permits an efficient computation...... of total degree d as a sum of powers of linear forms (Waring’s problem), incidence properties on secant varieties of the Veronese variety and the representation of linear forms as a linear combination of evaluations at distinct points. Then we reformulate Sylvester’s approach from the dual point of view...

  15. Catalytic NiO Filter Supported on Carbon Fiber for Oxidation of Volatile Organic Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Sim, Jong Ki; Seo, Hyun Ook; Jeong, Myunggeun; Kim, Kwangdae; Kim, Young Dok [Sungkyunkwan Univ., Suwon (Korea, Republic of); Lim, Dong Chan [Korea Institute of Materials Science, Changwon (Korea, Republic of)

    2013-07-15

    Carbon-fiber-supported NiO catalytic filters for oxidation of volatile organic compounds were prepared by electroless Ni-P plating and subsequent annealing processes. Surface structure and crystallinity of NiO film on carbon fiber could be modified by post-annealing at different temperatures (500 and 650 .deg. C). Catalytic thermal decompositions of toluene over these catalytic filters were investigated. 500 .deg. C-annealed sample showed a higher catalytic reactivity toward toluene decomposition than 650 .deg. C-annealed one under same conditions, despite of its lower surface area and toluene adsorption capacity. X-ray diffraction and X-ray photoelectron spectroscopy studies suggest that amorphous structures of NiO on 500 .deg. C-annealed catalyst caused the higher reactivity for oxidation of toluene than that of 650 .deg. C-annealed sample with a higher crystallinity.

  16. Ammonia emission from crop residues : quantification of ammonia volatilization based on crop residue properties

    NARCIS (Netherlands)

    Ruijter, de F.J.; Huijsmans, J.F.M.

    2012-01-01

    This paper gives an overview of available literature data on ammonia volatilization from crop residues. From these data, a relation is derived for the ammonia emission depending on the N-content of crop residue.

  17. Catalytic Functions of Standards

    NARCIS (Netherlands)

    K. Blind (Knut)

    2009-01-01

    textabstractThe three different areas and the examples have illustrated several catalytic functions of standards for innovation. First, the standardisation process reduces the time to market of inventions, research results and innovative technologies. Second, standards themselves promote the diffusi

  18. Catalytic Synthesis Lactobionic Acid

    Directory of Open Access Journals (Sweden)

    V.G. Borodina

    2014-07-01

    Full Text Available Gold nanoparticles are obtained, characterized and deposited on the carrier. Conducted catalytic synthesis of lactobionic acid from lactose. Received lactobionic acid identify on the IR spectrum.

  19. Catalytic distillation process

    Science.gov (United States)

    Smith, Jr., Lawrence A.

    1982-01-01

    A method for conducting chemical reactions and fractionation of the reaction mixture comprising feeding reactants to a distillation column reactor into a feed zone and concurrently contacting the reactants with a fixed bed catalytic packing to concurrently carry out the reaction and fractionate the reaction mixture. For example, a method for preparing methyl tertiary butyl ether in high purity from a mixed feed stream of isobutene and normal butene comprising feeding the mixed feed stream to a distillation column reactor into a feed zone at the lower end of a distillation reaction zone, and methanol into the upper end of said distillation reaction zone, which is packed with a properly supported cationic ion exchange resin, contacting the C.sub.4 feed and methanol with the catalytic distillation packing to react methanol and isobutene, and concurrently fractionating the ether from the column below the catalytic zone and removing normal butene overhead above the catalytic zone.

  20. Catalytic distillation process

    Science.gov (United States)

    Smith, L.A. Jr.

    1982-06-22

    A method is described for conducting chemical reactions and fractionation of the reaction mixture comprising feeding reactants to a distillation column reactor into a feed zone and concurrently contacting the reactants with a fixed bed catalytic packing to concurrently carry out the reaction and fractionate the reaction mixture. For example, a method for preparing methyl tertiary butyl ether in high purity from a mixed feed stream of isobutene and normal butene comprising feeding the mixed feed stream to a distillation column reactor into a feed zone at the lower end of a distillation reaction zone, and methanol into the upper end of said distillation reaction zone, which is packed with a properly supported cationic ion exchange resin, contacting the C[sub 4] feed and methanol with the catalytic distillation packing to react methanol and isobutene, and concurrently fractionating the ether from the column below the catalytic zone and removing normal butene overhead above the catalytic zone.

  1. Decomposition and reduction of N2O on CaS (100) surface: A theoretical account

    Science.gov (United States)

    Wu, Lingnan; Qin, Wu; Hu, Xiaoying; Ju, Shaoda; Dong, Changqing; Yang, Yongping

    2015-02-01

    The catalytic effect of CaS on N2O decomposition and reduction was investigated using density functional theory calculations. N2O approached the CaS (100) surface and crossed an energy barrier of 1.228 eV, decomposing into a free N2 molecule and an adsorbed O atom. The generated adsorbed O atom could be removed through two reaction pathways: binding with a neighboring adsorbed O atom into O2 with the barrier energy of 1.877 eV or reacting with another N2O molecule generating an adsorbed O2 with the barrier of 1.863 eV. The removal of the surface adsorbed O atom is the rate-determining step of the catalytic decomposition of N2O. In comparison with the homogeneous reaction between N2O and CO, CO accelerated the removal of the adsorbed O atom, hence improving the reduction of N2O on CaS (100). Furthermore, while compared with the CaO-catalytic removal of N2O, CaS is not as active as CaO for the decomposition and reduction of N2O. Our study is the first attempt to theoretically reveal the mechanism of CaS-catalytic decomposition and reduction of N2O, which provides a better understanding of the nitrogen chemistry in the reducing atmosphere zone of circulating fluidized bed boilers.

  2. Decomposition and reduction of N2O over Limestone under FBC Conditions

    DEFF Research Database (Denmark)

    Johnsson, Jan Erik; Jensen, Anker; Vaaben, Rikke;

    1997-01-01

    The addition of limestone for sulfur retention in FBC has in many cases been observed to influence the emission of N2O. The catalytic activity of N2O over calcined Stevns Chalk for decomposition of N2O in a laboratory fixed bed quartz reactor was measured. It was found that calcined Stevns Chalk ...

  3. Decomposition and Reduction of N2O over Limestone under FBC Conditions

    DEFF Research Database (Denmark)

    Johnsson, Jan Erik; Jensen, Anker; Vaaben, Rikke;

    1997-01-01

    The addition of limestone for sulfur retention in fluidized bed combustion (FBC) has in many cases been observed to influence the emission of N2O. The catalytic activity of N2O over calcined Stevns Chalk for decomposition of N2O in a laboratory fixed bed quartz reactor was measured. It was found...

  4. Recovery and removal of nutrients from swine wastewater by using a novel integrated reactor for struvite decomposition and recycling.

    Science.gov (United States)

    Huang, Haiming; Xiao, Dean; Liu, Jiahui; Hou, Li; Ding, Li

    2015-05-11

    In the present study, struvite decomposition was performed by air stripping for ammonia release and a novel integrated reactor was designed for the simultaneous removal and recovery of total ammonia-nitrogen (TAN) and total orthophosphate (PT) from swine wastewater by internal struvite recycling. Decomposition of struvite by air stripping was found to be feasible. Without supplementation with additional magnesium and phosphate sources, the removal ratio of TAN from synthetic wastewater was maintained at >80% by recycling of the struvite decomposition product formed under optimal conditions, six times. Continuous operation of the integrated reactor indicated that approximately 91% TAN and 97% PT in the swine wastewater could be removed and recovered by the proposed recycling process with the supplementation of bittern. Economic evaluation of the proposed system showed that struvite precipitation cost can be saved by approximately 54% by adopting the proposed recycling process in comparison with no recycling method.

  5. Catalytic distillation structure

    Science.gov (United States)

    Smith, L.A. Jr.

    1984-04-17

    Catalytic distillation structure is described for use in reaction distillation columns, and provides reaction sites and distillation structure consisting of a catalyst component and a resilient component intimately associated therewith. The resilient component has at least about 70 volume % open space and is present with the catalyst component in an amount such that the catalytic distillation structure consists of at least 10 volume % open space. 10 figs.

  6. A STUDY OF THE EFFECTS OF POST-COMBUSTION AMMONIA INJECTION ON FLY ASH QUALITY: CHARACTERIZATION OF AMMONIA RELEASE FROM CONCRETE AND MORTARS CONTAINING FLY ASH AS A POZZOLANIC ADMIXTURE

    Energy Technology Data Exchange (ETDEWEB)

    Robert F. Rathbone; Thomas L. Robl

    2002-10-30

    The Clean Air Act Amendments of 1990 require large reductions in emissions of NO{sub x} from coal-fired electric utility boilers. This will necessitate the use of ammonia injection, such as in selective catalytic reduction (SCR), in many power plants, resulting in the deposition of ammonia on the fly ash. The presence of ammonia could create a major barrier to fly ash utilization in concrete because of odor concerns. Although there have been limited studies of ammonia emission from concrete, little is known about the quantity of ammonia emitted during mixing and curing, and the kinetics of ammonia release. This is manifested as widely varying opinions within the concrete and ash marketing industry regarding the maximum acceptable levels of ammonia in fly ash. Therefore, practical guidelines for using ammoniated fly ash are needed in advance of the installation of many more SCR systems. The goal of this project was to develop practical guidelines for the handling and utilization of ammoniated fly ash in concrete, in order to prevent a decrease in the use of fly ash for this application. The objective was to determine the amount of ammonia that is released, over the short- and long-term, from concrete that contains ammoniated fly ash. The technical approach in this project was to measure the release of ammonia from mortar and concrete during mixing, placement, and curing. Work initially focused on laboratory mortar experiments to develop fundamental data on ammonia diffusion characteristics. Larger-scale laboratory experiments were then conducted to study the emission of ammonia from concrete containing ammoniated fly ash. The final phase comprised monitoring ammonia emissions from large concrete slabs. The data indicated that, on average, 15% of the initial ammonia was lost from concrete during 40 minutes of mixing, depending on the mix proportions and batch size. Long-term experiments indicated that ammonia diffusion from concrete was relatively slow, with greater

  7. Tetraammineplatinum(II dichloride ammonia tetrasolvate

    Directory of Open Access Journals (Sweden)

    Tobias Grassl

    2014-07-01

    Full Text Available The title compound, [Pt(NH34]Cl2·4NH3, was crystallized in liquid ammonia from the salt PtCl2. The platinum cation is coordinated by four ammonia molecules, forming a square-planar complex. The chloride anions are surrounded by nine ammonia molecules, either bound within the platinum complex or solvent molecules. The solvent ammonia molecules are packed in such a way that an extended network of N—H...N and N—H...Cl hydrogen bonds is formed. The structure is isotypic with [Pd(NH34]Cl2·4NH3 [Grassl & Korber (2014. Acta Cryst. E70, i32].

  8. Reducing ammonia emissions in Europe

    DEFF Research Database (Denmark)

    Jacobsen, Brian H.

    2011-01-01

    The NEC directive has set targets for the 2010 ammonia emissions from a number of European countries. The target will be reached by most EU-countries and the total emission for EU-27 has been reduced by 22% from 1990 to 2007. Denmark is one of the countries with the largest reductions since 1990...... to the high expectations at the outset. Despite this, the paper concludes that Denmark is likely to reduce emission by 50% from 1990 to 2020 and reach the likely 2020 NEC ceiling....

  9. Ammonia Synthesis using Ti and Nb Nitride Nano-particles Prepared by Mesoporous Graphitic C3N4

    KAUST Repository

    Kumagai, Hiromu

    2015-01-22

    TiN and NbN nanoparticles were synthesized from mesoporous graphitic C3N4 (mpg-C3N4) as a reactive template and used as the catalyst for ammonia synthesis. The obtained TiN and NbN nanoparticles possess high surface areas of 299 and 275 m2 g-1, respectively, making them attractive in the use of catalysis and support. Although most of the TiN and NbN particles show no measurable activity for ammonia formation, the nanoparticles enabled an ammonia synthesis rate of 31 μmol h-1 g-cat-1 at 673 K and 0.1 MPa of synthesis gas (N2 + 3H2) for both TiN and NbN catalysts. It is evident that the formation of nanoparticles with high nitride surface area is essential for the materials to function as catalysts in ammonia synthesis. The addition of Fe to TiN enhanced the ammonia synthesis activity, whereas it had detrimental effects on the catalytic activity of NbN. The properties of these catalysts in ammonia synthesis are discussed.

  10. Dihydrogen Phosphate Stabilized Ruthenium(0 Nanoparticles: Efficient Nanocatalyst for The Hydrolysis of Ammonia-Borane at Room Temperature

    Directory of Open Access Journals (Sweden)

    Feyyaz Durap

    2015-07-01

    Full Text Available Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution under mild conditions in the presence of a suitable catalyst. Herein, we report the synthesis of ruthenium(0 nanoparticles stabilized by dihydrogenphosphate anions with an average particle size of 2.9 ± 0.9 nm acting as a water-dispersible nanocatalyst in the hydrolysis of ammonia-borane. They provide an initial turnover frequency (TOF value of 80 min−1 in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. Moreover, the high stability of these ruthenium(0 nanoparticles makes them long-lived and reusable nanocatalysts for the hydrolysis of ammonia-borane. They provide 56,800 total turnovers and retain ~80% of their initial activity even at the fifth catalytic run in the hydrolysis of ammonia-borane at room temperature.

  11. Erbium hydride decomposition kinetics.

    Energy Technology Data Exchange (ETDEWEB)

    Ferrizz, Robert Matthew

    2006-11-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report are analyzed quantitatively using Redhead's method to yield kinetic parameters (E{sub A} {approx} 54.2 kcal/mol), which are then utilized to predict hydrogen outgassing in vacuum for a variety of thermal treatments. Interestingly, it was found that the activation energy for desorption can vary by more than 7 kcal/mol (0.30 eV) for seemingly similar samples. In addition, small amounts of less-stable hydrogen were observed for all erbium dihydride films. A detailed explanation of several approaches for analyzing thermal desorption spectra to obtain kinetic information is included as an appendix.

  12. Differentially Private Spatial Decompositions

    CERN Document Server

    Cormode, Graham; Shen, Entong; Srivastava, Divesh; Yu, Ting

    2011-01-01

    Differential privacy has recently emerged as the de facto standard for private data release. This makes it possible to provide strong theoretical guarantees on the privacy and utility of released data. While it is well-known how to release data based on counts and simple functions under this guarantee, it remains to provide general purpose techniques to release different kinds of data. In this paper, we focus on spatial data such as locations and more generally any data that can be indexed by a tree structure. Directly applying existing differential privacy methods to this type of data simply generates noise. Instead, we introduce a new class of "private spatial decompositions": these adapt standard spatial indexing methods such as quadtrees and kd-trees to provide a private description of the data distribution. Equipping such structures with differential privacy requires several steps to ensure that they provide meaningful privacy guarantees. Various primitives, such as choosing splitting points and describi...

  13. Autonomous Gaussian Decomposition

    CERN Document Server

    Lindner, Robert R; Murray, Claire E; Stanimirović, Snežana; Babler, Brian L; Heiles, Carl; Hennebelle, Patrick; Goss, W M; Dickey, John

    2014-01-01

    We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21cm absorption spectra from the 21cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the HI line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the up...

  14. Bioaugmentation of syntrophic acetate-oxidizing culture in biogas reactors exposed to increasing levels of ammonia.

    Science.gov (United States)

    Westerholm, Maria; Levén, Lotta; Schnürer, Anna

    2012-11-01

    The importance of syntrophic acetate oxidation for process stability in methanogenic systems operating at high ammonia concentrations has previously been emphasized. In this study we investigated bioaugmentation of syntrophic acetate-oxidizing (SAO) cultures as a possible method for decreasing the adaptation period of biogas reactors operating at gradually increased ammonia concentrations (1.5 to 11 g NH(4)(+)-N/liter). Whole stillage and cattle manure were codigested semicontinuously for about 460 days in four mesophilic anaerobic laboratory-scale reactors, and a fixed volume of SAO culture was added daily to two of the reactors. Reactor performance was evaluated in terms of biogas productivity, methane content, pH, alkalinity, and volatile fatty acid (VFA) content. The decomposition pathway of acetate was analyzed by isotopic tracer experiments, and population dynamics were monitored by quantitative PCR analyses. A shift in dominance from aceticlastic methanogenesis to SAO occurred simultaneously in all reactors, indicating no influence by bioaugmentation on the prevailing pathway. Higher abundances of Clostridium ultunense and Tepidanaerobacter acetatoxydans were associated with bioaugmentation, but no influence on Syntrophaceticus schinkii or the methanogenic population was distinguished. Overloading or accumulation of VFA did not cause notable dynamic effects on the population. Instead, the ammonia concentration had a substantial impact on the abundance level of the microorganisms surveyed. The addition of SAO culture did not affect process performance or stability against ammonia inhibition, and all four reactors deteriorated at high ammonia concentrations. Consequently, these findings further demonstrate the strong influence of ammonia on the methane-producing consortia and on the representative methanization pathway in mesophilic biogas reactors.

  15. Regeneration of ammonia borane from polyborazylene

    Science.gov (United States)

    Sutton, Andrew; Gordon, John C; Ott, Kevin C; Burrell, Anthony K

    2013-02-05

    Method of producing ammonia borane, comprising providing a reagent comprising a dehydrogenated material in a suitable solvent; and combining the reagent with a reducing agent comprising hydrazine, a hydrazine derivative, or combinations thereof, in a reaction which produces a mixture comprising ammonia borane.

  16. Method for releasing hydrogen from ammonia borane

    Science.gov (United States)

    Varma, Arvind; Diwan, Moiz; Shafirovich, Evgeny; Hwang, Hyun-Tae; Al-Kukhun, Ahmad

    2013-02-19

    A method of releasing hydrogen from ammonia borane is disclosed. The method comprises heating an aqueous ammonia borane solution to between about 80-135.degree. C. at between about 14.7 and 200 pounds per square inch absolute (psia) to release hydrogen by hydrothermolysis.

  17. Ammonia Sensor Using Wavelength Modulation Spectroscopy

    KAUST Repository

    Farooq, Aamir

    2015-09-01

    An ammonia sensor can include a laser detector configured to provide stable sample readings. The sensor can implement a method including processing the recorded intensity of the laser beam to determine a first harmonic component and a second harmonic component and the amount of ammonia in the sample.

  18. Oxidative and nitrosative stress in ammonia neurotoxicity.

    Science.gov (United States)

    Skowrońska, Marta; Albrecht, Jan

    2013-04-01

    Increased ammonia accumulation in the brain due to liver dysfunction is a major contributor to the pathogenesis of hepatic encephalopathy (HE). Fatal outcome of rapidly progressing (acute) HE is mainly related to cytotoxic brain edema associated with astrocytic swelling. An increase of brain ammonia in experimental animals or treatment of cultured astrocytes with ammonia generates reactive oxygen and nitrogen species in the target tissues, leading to oxidative/nitrosative stress (ONS). In cultured astrocytes, ammonia-induced ONS is invariably associated with the increase of the astrocytic cell volume. Interrelated mechanisms underlying this response include increased nitric oxide (NO) synthesis which is partly coupled to the activation of NMDA receptors and increased generation of reactive oxygen species by NADPH oxidase. ONS and astrocytic swelling are further augmented by excessive synthesis of glutamine (Gln) which impairs mitochondrial function following its accumulation in there and degradation back to ammonia ("the Trojan horse" hypothesis). Ammonia also induces ONS in other cell types of the CNS: neurons, microglia and the brain capillary endothelial cells (BCEC). ONS in microglia contributes to the central inflammatory response, while its metabolic and pathophysiological consequences in the BCEC evolve to the vasogenic brain edema associated with HE. Ammonia-induced ONS results in the oxidation of mRNA and nitration/nitrosylation of proteins which impact intracellular metabolism and potentiate the neurotoxic effects. Simultaneously, ammonia facilitates the antioxidant response of the brain, by activating astrocytic transport and export of glutathione, in this way increasing the availability of precursors of neuronal glutathione synthesis.

  19. Ammonia sensors and their applications - a review

    NARCIS (Netherlands)

    Timmer, Björn; Olthuis, Wouter; Berg, van den Albert

    2005-01-01

    Many scientific papers have been written concerning gas sensors for different sensor applications using several sensing principles. This review focuses on sensors and sensor systems for gaseous ammonia. Apart from its natural origin, there are many sources of ammonia, like the chemical industry or i

  20. Ammonia and hydrogen sulfide removal using biochar

    Science.gov (United States)

    Reducing ammonia and hydrogen sulfide emissions from livestock facilities is an important issue for many communities and livestock producers. Ammonia has been regarded as odorous, precursor for particulate matter (PM), and contributed to livestock mortality. Hydrogen sulfide is highly toxic at elev...

  1. Chilled Ammonia Process for CO2 Capture

    DEFF Research Database (Denmark)

    Darde, Victor Camille Alfred; Thomsen, Kaj; Well, Willy J.M. van

    2010-01-01

    The chilled ammonia process absorbs the CO2 at low temperature (2–10°C). The heat of absorption of carbon dioxide by ammonia is significantly lower than for amines. In addition, degradation problems can be avoided and a high carbon dioxide capacity is achieved. Hence, this process shows good...

  2. Chilled ammonia process for CO2 capture

    DEFF Research Database (Denmark)

    Darde, Victor Camille Alfred; Thomsen, Kaj; van Well, Willy J. M

    2009-01-01

    The chilled ammonia process absorbs the CO2 at low temperature (2-10 degrees C). The heat of absorption of carbon dioxide by ammonia is significantly lower than for amines. In addition, degradation problems can be avoided and a high carbon dioxide capacity is achieved. Hence, this process shows...

  3. Catalytic fast pyrolysis of lignocellulosic biomass

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Changjun; Wang, Huamin; Karim, Ayman M.; Sun, Junming; Wang, Yong

    2014-11-21

    Increasing energy demand, especially in the transportation sector, and soaring CO2 emissions necessitate the exploitation of renewable sources of energy. Despite the large variety of new energy Q3 carriers, liquid hydrocarbon still appears to be the most attractive and feasible form of transportation fuel taking into account the energy density, stability and existing infrastructure. Biomass is an abundant, renewable source of energy; however, utilizing it in a cost-effective way is still a substantial challenge. Lignocellulose is composed of three major biopolymers, namely cellulose, hemicellulose and lignin. Fast pyrolysis of biomass is recognized as an efficient and feasible process to selectively convert lignocellulose into a liquid fuel—bio-oil. However bio-oil from fast pyrolysis contains a large amount of oxygen, distributed in hundreds of oxygenates. These oxygenates are the cause of many negative properties, such as low heating values, high corrosiveness, high viscosity, and instability; they also greatly Q4 limit the application of bio-oil particularly as transportation fuel. Hydrocarbons derived from biomass are most attractive because of their high energy density and compatibility with the existing infrastructure. Thus, converting lignocellulose into transportation fuels via catalytic fast pyrolysis has attracted much attention. Many studies related to catalytic fast pyrolysis of biomass have been published. The main challenge of this process is the development of active and stable catalysts that can deal with a large variety of decomposition intermediates from lignocellulose. This review starts with the current understanding of the chemistry in fast pyrolysis of lignocellulose and focuses on the development of catalysts in catalytic fast pyrolysis. Recent progress in the experimental studies on catalytic fast pyrolysis of biomass is also summarized with the emphasis on bio-oil yields and quality.

  4. Ammonia tolerant enriched methanogenic cultures as bioaugmentation inocula to alleviate ammonia inhibition in continuous anaerobic reactors

    DEFF Research Database (Denmark)

    Fotidis, Ioannis; Wang, Han; Angelidaki, Irini

    Ammonia is the most common inhibitor of anaerobic digestion (AD) process, resulting in suboptimal exploitation of the biogas potential of the feedstocks, causing significant economic losses to the biogas plants. Ammonia is mainly inhibiting the aceticlastic methanogens, while the hydrogenotrophic...... of ammonia-rich organic waste in full-scale continuous reactors.......Ammonia is the most common inhibitor of anaerobic digestion (AD) process, resulting in suboptimal exploitation of the biogas potential of the feedstocks, causing significant economic losses to the biogas plants. Ammonia is mainly inhibiting the aceticlastic methanogens, while the hydrogenotrophic...... methanogens are more robust to ammonia toxicity effect. It has been shown that bioaugmentation of a pure strain of a hydrogenotrophic methanogen (i.e. Methanoculleus bourgensis) in an ammonia inhibited continuous anaerobic reactor can improve methane production more than 30%. Nevertheless, cultivation...

  5. Clinical utility of breath ammonia for evaluation of ammonia physiology in healthy and cirrhotic adults.

    Science.gov (United States)

    Spacek, Lisa A; Mudalel, Matthew; Tittel, Frank; Risby, Terence H; Solga, Steven F

    2015-12-01

    Blood ammonia is routinely used in clinical settings to assess systemic ammonia in hepatic encephalopathy and urea cycle disorders. Despite its drawbacks, blood measurement is often used as a comparator in breath studies because it is a standard clinical test. We sought to evaluate sources of measurement error and potential clinical utility of breath ammonia compared to blood ammonia. We measured breath ammonia in real time by quartz enhanced photoacoustic spectrometry and blood ammonia in 10 healthy and 10 cirrhotic participants. Each participant contributed 5 breath samples and blood for ammonia measurement within 1 h. We calculated the coefficient of variation (CV) for 5 breath ammonia values, reported medians of healthy and cirrhotic participants, and used scatterplots to display breath and blood ammonia. For healthy participants, mean age was 22 years (±4), 70% were men, and body mass index (BMI) was 27 (±5). For cirrhotic participants, mean age was 61 years (±8), 60% were men, and BMI was 31 (±7). Median blood ammonia for healthy participants was within normal range, 10 μmol L(-1) (interquartile range (IQR), 3-18) versus 46 μmol L(-1) (IQR, 23-66) for cirrhotic participants. Median breath ammonia was 379 pmol mL(-1) CO2 (IQR, 265-765) for healthy versus 350 pmol mL(-1) CO2 (IQR, 180-1013) for cirrhotic participants. CV was 17  ±  6%. There remains an important unmet need in the evaluation of systemic ammonia, and breath measurement continues to demonstrate promise to fulfill this need. Given the many differences between breath and blood ammonia measurement, we examined biological explanations for our findings in healthy and cirrhotic participants. We conclude that based upon these preliminary data breath may offer clinically important information this is not provided by blood ammonia.

  6. Catalytic synthesis of long-chained alcohols from syngas

    DEFF Research Database (Denmark)

    Christensen, Jakob Munkholt

    This work has been an investigation of the catalytic conversion of syngas into mixed alcohols with Mo-based catalysts. The primary focus has been on the use of alkali promoted cobalt-molybdenum sulfide as a catalyst for the alcohol synthesis. The alcohol synthesis is a possibility...... the user to employ a less thorough and therefore less costly syngas cleaning. To evaluate, to which extent a removal of other components in the raw syngas is necessary, the influence of NH3 and H2O in the feed has also been investigated. Ammonia (741 ppmv) in the feed is observed to cause a general...

  7. Catalytic hydrotreating process

    Science.gov (United States)

    Karr, Jr., Clarence; McCaskill, Kenneth B.

    1978-01-01

    Carbonaceous liquids boiling above about 300.degree. C such as tars, petroleum residuals, shale oils and coal-derived liquids are catalytically hydrotreated by introducing the carbonaceous liquid into a reaction zone at a temperature in the range of 300.degree. to 450.degree. C and a pressure in the range of 300 to 4000 psig for effecting contact between the carbonaceous liquid and a catalytic transition metal sulfide in the reaction zone as a layer on a hydrogen permeable transition metal substrate and then introducing hydrogen into the reaction zone by diffusing the hydrogen through the substrate to effect the hydrogenation of the carbonaceous liquid in the presence of the catalytic sulfide layer.

  8. Enhancing Biogas Production from Anaerobically Digested Wheat Straw Through Ammonia Pretreatment

    Institute of Scientific and Technical Information of China (English)

    杨懂艳; 庞云芝; 袁海荣; 陈树林; 马晶伟; 郁亮; 李秀金

    2014-01-01

    Aqueous ammonia was used to pretreat wheat straw to improve biodegradability and provide nitrogen source for enhancing biogas production. Three doses of ammonia (2%, 4%, and 6%, dry matter) and three moisture contents (30%, 60%, and 80%, dry matter) were applied to pretreat wheat straw for 7 days. The pretreated wheat straws were anaerobically digested at three loading rates (50, 65, and 80 g·L-1) to produce biogas. The results indi-cated that the wheat straw pretreated with 80%moisture content and 4%ammonia achieved the highest methane yield of 199.7 ml·g-1 (based on per unit volatile solids loaded), with shorter digestion time (T80) of 25 days at the loading rate of 65 g·L-1 compared to untreated one. The main chemical compositions of wheat straw were also ana-lyzed. The cellulose and hemicellulose contents were decomposed by 2%-20%and 26%-42%, respectively, while the lignin content was hardly removed, cold-water and hot-water extracts were increased by 4%-44%, and 12%-52%, respectively, for the ammonia-pretreated wheat straws at different moisture contents. The appropriate C/N ratio and decomposition of original chemical compositions into relatively readily biodegradable substances will improve the biodegradability and biogas yield.

  9. Gas Turbine Combustion and Ammonia Removal Technology of Gasified Fuels

    Directory of Open Access Journals (Sweden)

    Takeharu Hasegawa

    2010-03-01

    Full Text Available From the viewpoints of securing a stable supply of energy and protecting our global environment in the future, the integrated gasification combined cycle (IGCC power generation of various gasifying methods has been introduced in the world. Gasified fuels are chiefly characterized by the gasifying agents and the synthetic gas cleanup methods and can be divided into four types. The calorific value of the gasified fuel varies according to the gasifying agents and feedstocks of various resources, and ammonia originating from nitrogenous compounds in the feedstocks depends on the synthetic gas clean-up methods. In particular, air-blown gasified fuels provide low calorific fuel of 4 MJ/m3 and it is necessary to stabilize combustion. In contrast, the flame temperature of oxygen-blown gasified fuel of medium calorie between approximately 9–13 MJ/m3 is much higher, so control of thermal-NOx emissions is necessary. Moreover, to improve the thermal efficiency of IGCC, hot/dry type synthetic gas clean-up is needed. However, ammonia in the fuel is not removed and is supplied into the gas turbine where fuel-NOx is formed in the combustor. For these reasons, suitable combustion technology for each gasified fuel is important. This paper outlines combustion technologies and combustor designs of the high temperature gas turbine for various IGCCs. Additionally, this paper confirms that further decreases in fuel-NOx emissions can be achieved by removing ammonia from gasified fuels through the application of selective, non-catalytic denitration. From these basic considerations, the performance of specifically designed combustors for each IGCC proved the proposed methods to be sufficiently effective. The combustors were able to achieve strong results, decreasing thermal-NOx emissions to 10 ppm (corrected at 16% oxygen or less, and fuel-NOx emissions by 60% or more, under conditions where ammonia concentration per fuel heating value in unit volume was 2.4 × 102 ppm

  10. 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

  11. Ambient pressure proton transfer mass spectrometry: detection of amines and ammonia.

    Science.gov (United States)

    Hanson, D R; McMurry, P H; Jiang, J; Tanner, D; Huey, L G

    2011-10-15

    An instrument to detect gaseous amines and ammonia is described, and representative data from an urban site and a laboratory setting are presented. The instrument, an Ambient pressure Proton transfer Mass Spectrometer (AmPMS), consists of a chemical ionization and drift region at atmospheric pressure coupled to a standard quadrupole mass spectrometer. Calibrations show that AmPMS sensitivity is good for amines, and AmPMS backgrounds were suitably determined by diverting sampled air through a catalytic converter. In urban air at a site in Atlanta, amines were detected at subpptv levels for methyl and dimethyl amine which were generally at a low abundance of ammonia were high, and data are very limited for these species. Improvements in detecting amines and ammonia from a smog chamber were evident due to improvements in AmPMS background determination; notably dimethyl amine and its OH oxidation products were followed along with impurity ammonia and other species. Future work will focus on accurate calibration standards and on improving the sample gas inlet.

  12. Influence of alumina binder content on catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone.

    Directory of Open Access Journals (Sweden)

    Xiangjin Kong

    Full Text Available The influence of the amount of alumina binders on the catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone was investigated in a fixed-bed reactor. N2 sorption, X-ray diffraction, H2-chemisorption and temperature-programmed desorption of ammonia were used to characterize the catalysts. It can be observed that the Ni/HZSM-5 catalyst bound with 30 wt.% alumina binder exhibited the best catalytic performance. The high catalytic performance may be due to relatively good Ni metal dispersion, moderate mesoporosity, and proper acidity of the catalyst.

  13. Influence of alumina binder content on catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone.

    Science.gov (United States)

    Kong, Xiangjin; Liu, Junhai

    2014-01-01

    The influence of the amount of alumina binders on the catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone was investigated in a fixed-bed reactor. N2 sorption, X-ray diffraction, H2-chemisorption and temperature-programmed desorption of ammonia were used to characterize the catalysts. It can be observed that the Ni/HZSM-5 catalyst bound with 30 wt.% alumina binder exhibited the best catalytic performance. The high catalytic performance may be due to relatively good Ni metal dispersion, moderate mesoporosity, and proper acidity of the catalyst.

  14. The Influence of Magnesium Hydride on the Thermal Decomposition Properties of Nitrocellulose

    Science.gov (United States)

    Jin, Limei; Du, Ping; Yao, Miao

    2014-05-01

    Magnesium hydride is a kind of attractive hydrogen storage material. In this article, the thermal decomposition characteristic of the pure nitrocellulose and the mixture of nitrocellulose with 5% MgH2 was investigated using an accelerating rate calorimeter. The kinetic parameters such as activation energy, Ea; preexponential factor, A; and self-accelerating decomposition temperature, TSADT, were also calculated. We easily showed that the decomposition reaction could be accelerated by adding MgH2, which indicated that MgH2 has an obvious catalytic influence on the decomposition of nitrocellulose. On the other hand, the calculated values of Ea and TSADT showed a decrease in thermal sensitivity with the addition of MgH2. These results were in accordance with our objectives. Therefore, MgH2 is very likely to be an important additive in propellants.

  15. Thermal decomposition of lutetium propionate

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude

    2010-01-01

    The thermal decomposition of lutetium(III) propionate monohydrate (Lu(C2H5CO2)3·H2O) in argon was studied by means of thermogravimetry, differential thermal analysis, IR-spectroscopy and X-ray diffraction. Dehydration takes place around 90 °C. It is followed by the decomposition of the anhydrous ...... of the oxycarbonate to the rare-earth oxide proceeds in a different way, which is here reminiscent of the thermal decomposition path of Lu(C3H5O2)·2CO(NH2)2·2H2O...

  16. Ammonia gas permeability of meat packaging materials.

    Science.gov (United States)

    Karim, Faris; Hijaz, Faraj; Kastner, Curtis L; Smith, J Scott

    2011-03-01

    Meat products are packaged in polymer films designed to protect the product from exterior contaminants such as light, humidity, and harmful chemicals. Unfortunately, there is almost no data on ammonia permeability of packaging films. We investigated ammonia permeability of common meat packaging films: low-density polyethylene (LDPE; 2.2 mil), multilayer polyolefin (MLP; 3 mil), and vacuum (V-PA/PE; 3 mil, 0.6 mil polyamide/2.4 mil polyethylene). The films were fabricated into 10 × 5 cm pouches and filled with 50 mL deionized water. Pouches were placed in a plexiglass enclosure in a freezer and exposed to 50, 100, 250, or 500 ppm ammonia gas for 6, 12, 24, and 48 h at -17 ± 3 °C and 21 ± 3 °C. At freezing temperatures, no ammonia residues were detected and no differences in pH were found in the water. At room temperature, ammonia levels and pH of the water increased significantly (P packaging materials have low ammonia permeability and protect meat products exposed to ammonia leaks during frozen storage.

  17. Low-cost anodes for ammonia electrooxidation

    Science.gov (United States)

    Selverston, Steven M.

    This research focused on the development of low-cost electrodes for the electrochemical oxidation of ammonia to nitrogen, a reaction that has possible applications in hydrogen generation, direct ammonia fuel cells, water treatment, and sensors. Statistical design of experiments was used to help develop an efficient and scalable process for electrodeposition of platinum with a specific electrochemical surface area of over 25 m2 /g. Catalyst surface area and activity were evaluated using cyclic voltammetry, and the material microstructure and morphology were investigated using x-ray diffraction and scanning electron microscopy. The synthesized electrodes were found to be active toward the ammonia electrooxidation reaction, particularly when supporting electrolyte was added. However, supporting electrolyte was not required in order to oxidize the ammonia. As proof of concept, a homemade direct ammonia fuel cell employing a commercial anion exchange membrane was tested at room temperature with gravity-fed fuel and without supporting electrolyte. At room temperature, with passive reactant supply and using dissolved oxygen at the cathode, the cell produced about one quarter the power of a direct methanol fuel cell that used active transport of humidified oxygen and preheated (50 °C) methanol. With continued development of the membrane, cathode and membrane electrode assembly, the passive direct ammonia fuel cell using anion exchange membrane could have performance similar to the equivalent direct methanol fuel cell, and it could benefit from many advantages of ammonia over methanol such as lower cost, higher energy density, and reduced greenhouse gas emissions.

  18. Ammonia distribution and excretion in fish.

    Science.gov (United States)

    Randall, D J; Wright, P A

    1987-05-01

    This paper reviews the literature concerning ammonia production, storage and excretion in fish. Ammonia is the end product of protein catabolism and is stored in the body of fish in high concentrations relative to basal excretion rates. Ammonia, if allowed to accumulate, is toxic and is converted to less toxic compounds or excreted. Like other weak acids and bases, ammonia is distributed between tissue compartments in relation to transmembrane pH gradients. NH3 is generally equilibrated between compartments but NH4 (+) is distributed according to pH. Ammonia is eliminated from the blood upon passage through the gills. The mechanisms of branchial ammonia excretion vary between different species of fish and different environments, and primarily involves NH3 passive diffusion and NH4 (+)/Na(+) exchange. Water chemistry near the gill surface may also be important to ammonia excretion, but a more accurate measurement of the NH3 gradient across the gill epithelium is required before a more detailed analysis of NH3 and NH4 (+) excretion can be made.

  19. Resveratrol prevents ammonia toxicity in astroglial cells.

    Directory of Open Access Journals (Sweden)

    Larissa Daniele Bobermin

    Full Text Available Ammonia is implicated as a neurotoxin in brain metabolic disorders associated with hyperammonemia. Acute ammonia toxicity can be mediated by an excitotoxic mechanism, oxidative stress and nitric oxide (NO production. Astrocytes interact with neurons, providing metabolic support and protecting against oxidative stress and excitotoxicity. Astrocytes also convert excess ammonia and glutamate into glutamine via glutamine synthetase (GS. Resveratrol, a polyphenol found in grapes and red wines, exhibits antioxidant and anti-inflammatory properties and modulates glial functions, such as glutamate metabolism. We investigated the effect of resveratrol on the production of reactive oxygen species (ROS, GS activity, S100B secretion, TNF-α, IL-1β and IL-6 levels in astroglial cells exposed to ammonia. Ammonia induced oxidative stress, decreased GS activity and increased cytokines release, probably by a mechanism dependent on protein kinase A (PKA and extracellular signal-regulated kinase (ERK pathways. Resveratrol prevented ammonia toxicity by modulating oxidative stress, glial and inflammatory responses. The ERK and nuclear factor-κB (NF-κB are involved in the protective effect of resveratrol on cytokines proinflammatory release. In contrast, other antioxidants (e.g., ascorbic acid and trolox were not effective against hyperammonemia. Thus, resveratrol could be used to protect against ammonia-induced neurotoxicity.

  20. WOOD COLOR CHANGES BY AMMONIA FUMING

    Directory of Open Access Journals (Sweden)

    Josip Miklečić,

    2012-06-01

    Full Text Available This paper studies the influence of ammonia gas on wood color changes in response to an increasing demand for dark colored wood specimens. The darker wood color in ammonia fuming is accomplished through chemical reactions between ammonia gas and wood compounds. We exposed oak, maple, spruce, and larch wood samples to ammonia gas for 16 days. During fuming, the color changes were studied using CIE L*a*b* parameters. After fuming, the changes in extractives content, tannin, and nitrogen content were analyzed. The chemical changes of wood and residues of wood extractives after fuming were analyzed by FTIR spectroscopy. Oak wood reacted intensively with ammonia gas in a very short time, and the darkening was prominent for all the investigated wood species. It was established that tannin had no major influence on color changes of maple and larch wood in the ammonia-fuming process. The FTIR spectra of fumed wood indicated involvement of carbonyl groups, and the FTIR spectra of wood extractives indicated involvement of carbonyl, aromatic, and alcohol groups in reaction with ammonia gas.

  1. AUTONOMOUS GAUSSIAN DECOMPOSITION

    Energy Technology Data Exchange (ETDEWEB)

    Lindner, Robert R.; Vera-Ciro, Carlos; Murray, Claire E.; Stanimirović, Snežana; Babler, Brian [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Heiles, Carl [Radio Astronomy Lab, UC Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); Hennebelle, Patrick [Laboratoire AIM, Paris-Saclay, CEA/IRFU/SAp-CNRS-Université Paris Diderot, F-91191 Gif-sur Yvette Cedex (France); Goss, W. M. [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville, Socorro, NM 87801 (United States); Dickey, John, E-mail: rlindner@astro.wisc.edu [University of Tasmania, School of Maths and Physics, Private Bag 37, Hobart, TAS 7001 (Australia)

    2015-04-15

    We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21 cm absorption spectra from the 21 cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the H i line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the upcoming Square Kilometer Array and pathfinder telescopes.

  2. Catalytically driven assembly of trisegmented metallic nanorods and polystyrene tracer particles.

    Science.gov (United States)

    Jewell, Erik L; Wang, Wei; Mallouk, Thomas E

    2016-03-07

    Trisegmented Au-Ru-Au and Ru-Au-Ru nanorods catalyze the decomposition of hydrogen peroxide, pumping fluid along their axis as "pullers" and "pushers" respectively. Numerical simulations and experiments with passive tracer particles show that catalytically generated hydrodynamic and electrostatic forces both contribute to pairwise and collective particle assembly.

  3. Catalytic efficiency of designed catalytic proteins.

    Science.gov (United States)

    Korendovych, Ivan V; DeGrado, William F

    2014-08-01

    The de novo design of catalysts that mimic the affinity and specificity of natural enzymes remains one of the Holy Grails of chemistry. Despite decades of concerted effort we are still unable to design catalysts as efficient as enzymes. Here we critically evaluate approaches to (re)design of novel catalytic function in proteins using two test cases: Kemp elimination and ester hydrolysis. We show that the degree of success thus far has been modest when the rate enhancements seen for the designed proteins are compared with the rate enhancements by small molecule catalysts in solvents with properties similar to the active site. Nevertheless, there are reasons for optimism: the design methods are ever improving and the resulting catalyst can be efficiently improved using directed evolution.

  4. Catalytic Phosphination and Arsination

    Institute of Scientific and Technical Information of China (English)

    Kwong Fuk Yee; Chan Kin Shing

    2004-01-01

    The catalytic, user-friendly phosphination and arsination of aryl halides and triflates by triphenylphosphine and triphenylarsine using palladium catalysts have provided a facile synthesis of functionalized aryl phosphines and arsines in neutral media. Modification of the cynaoarisne yielded optically active N, As ligands which will be screened in various asymmetric catalysis.

  5. Impact of Support and Potassium-Poisoning on the V2O5-WO3/ZrO2 Catalyst Performance in Ammonia Oxidation

    DEFF Research Database (Denmark)

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

    2009-01-01

    A series of WO3-promoted zirconia supports were synthesized and calcined between 400 and 800C. Subsequently vanadium oxide was introduced to obtain 3.5 wt% V2O5. The influence of the calcination temperature and potassium-poisoning (K/V = 0.2, molar ratio) on the catalytic activity in the selective...... catalytic reduction (SCR) of NO with NH3 was previously studied. Here, we focus on the influence of these parameters on the catalytic activity for the undesirable oxidation of ammonia, which decrease the N2 selectivity of the SCR process. It is found that potassium doping of the catalysts results...... in a considerable decrease in the overall ammonia conversion while selectivity to NO increases....

  6. A low energy aqueous ammonia CO2 capture process

    DEFF Research Database (Denmark)

    Gaspar, Jozsef; Waseem Arshad, Muhammad; Blaker, Eirik Ask

    2014-01-01

    with existing aqueous ammonia CO2 capture processes. Moreover, the thermal reactor can operate at 1 bar and 86 °C, therefore the NH3 regeneration temperature is reduced by approximately 50 qC. The integration of low- and mid- temperature waste heat becomes possible which can greatly improve the economics...... based CO2 capture with a thermal decomposition reactor. The overall energy penalty is reduced at the expense of introducing a solid handling section which consists of a saturation reactor, a crystallizer and a belt filter. The feasibility of the present approach is demonstrated by simulation. Flow...

  7. Poisoning of bubble propelled catalytic micromotors: the chemical environment matters

    Science.gov (United States)

    Zhao, Guanjia; Sanchez, Samuel; Schmidt, Oliver G.; Pumera, Martin

    2013-03-01

    Self-propelled catalytic microjets have attracted considerable attention in recent years and these devices have exhibited the ability to move in complex media. The mechanism of propulsion is via the Pt catalysed decomposition of H2O2 and it is understood that the Pt surface is highly susceptible to poisoning by sulphur-containing molecules. Here, we show that important extracellular thiols as well as basic organic molecules can significantly hamper the motion of catalytic microjet engines. This is due to two different mechanisms: (i) molecules such as dimethyl sulfoxide can quench the hydroxyl radicals produced at Pt surfaces and reduce the amount of oxygen gas generated and (ii) molecules containing -SH, -SSR, and -SCH3 moieties can poison the catalytically active platinum surface, inhibiting the motion of the jet engines. It is essential that the presence of such molecules in the environment be taken into consideration for future design and operation of catalytic microjet engines. We show this effect on catalytic micromotors prepared by both rolled-up and electrodeposition approaches, demonstrating that such poisoning is universal for Pt catalyzed micromotors. We believe that our findings will contribute significantly to this field to develop alternative systems or catalysts for self-propulsion when practical applications in the real environment are considered.

  8. Decomposition methods for unsupervised learning

    DEFF Research Database (Denmark)

    Mørup, Morten

    2008-01-01

    This thesis presents the application and development of decomposition methods for Unsupervised Learning. It covers topics from classical factor analysis based decomposition and its variants such as Independent Component Analysis, Non-negative Matrix Factorization and Sparse Coding to their genera...... to the analysis of social network data.......This thesis presents the application and development of decomposition methods for Unsupervised Learning. It covers topics from classical factor analysis based decomposition and its variants such as Independent Component Analysis, Non-negative Matrix Factorization and Sparse Coding...... methods and clustering problems is derived both in terms of classical point clustering but also in terms of community detection in complex networks. A guiding principle throughout this thesis is the principle of parsimony. Hence, the goal of Unsupervised Learning is here posed as striving for simplicity...

  9. Some nonlinear space decomposition algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Tai, Xue-Cheng; Espedal, M. [Univ. of Bergen (Norway)

    1996-12-31

    Convergence of a space decomposition method is proved for a general convex programming problem. The space decomposition refers to methods that decompose a space into sums of subspaces, which could be a domain decomposition or a multigrid method for partial differential equations. Two algorithms are proposed. Both can be used for linear as well as nonlinear elliptic problems and they reduce to the standard additive and multiplicative Schwarz methods for linear elliptic problems. Two {open_quotes}hybrid{close_quotes} algorithms are also presented. They converge faster than the additive one and have better parallelism than the multiplicative method. Numerical tests with a two level domain decomposition for linear, nonlinear and interface elliptic problems are presented for the proposed algorithms.

  10. Mitsunobu Reactions Catalytic in Phosphine and a Fully Catalytic System.

    Science.gov (United States)

    Buonomo, Joseph A; Aldrich, Courtney C

    2015-10-26

    The Mitsunobu reaction is renowned for its mild reaction conditions and broad substrate tolerance, but has limited utility in process chemistry and industrial applications due to poor atom economy and the generation of stoichiometric phosphine oxide and hydrazine by-products that complicate purification. A catalytic Mitsunobu reaction using innocuous reagents to recycle these by-products would overcome both of these shortcomings. Herein we report a protocol that is catalytic in phosphine (1-phenylphospholane) employing phenylsilane to recycle the catalyst. Integration of this phosphine catalytic cycle with Taniguchi's azocarboxylate catalytic system provided the first fully catalytic Mitsunobu reaction.

  11. Response of sheep to supplementation of Probio-catalytic in the diets

    Directory of Open Access Journals (Sweden)

    B Haryanto

    2008-12-01

    Full Text Available biotic and catalytic supplement, on the productive performances of sheep fed Pennisetum purpuphoides (King grass. The concentrate was made of rice bran, molasses-coated palm kernel cake, minerals and salt. Probio-catalytic supplements were added either at 0.5% or 1.0% of the concentrate. The probiotic in the probio-catalytic supplements was either Probion (produced by Balitnak and assigned as probio-catalytic supplement A, or a mixture of rumen microbes of buffaloes which was assigned as probio-catalytic B. The catalytic supplement consisted of gelatinized sago, Zn, Co, urea and sulfur. Twenty heads of male young sheep with an average liveweight of 18.8 ± 1.7 kg were divided into 4 groups based on the bodyweight and allocated to 5 feeding treatments. The treatments were (1 Control (without probio-catalytic supplement, (2 R1 addition of probio-catalytic supplement A at 0.5%, (3 R2 addition of probio-catalytic supplement A at 1.0%, (4 R3 addition of probio-catalytic supplement B at 0.5%, and (5 R4 addition of probio-catalytic supplement B at 1.0%. The experiment was carried out by a randomized block design. A four-week adaptation period was then followed by a 12-week feed intake data collection and growth trial. An intake and digestibility study of the feed was carried out for 7 days. Rumen fluids were taken for analysis of pH, ammonia and volatile fatty acids and microbial population. Results indicated a significantly greater weight gain in the group received R1 than that of the other treatments. Feed dry matter intakes were less in the groups supplemented with probio-catalytic resulting in a better feed conversion ratio. The pH and concentration of ammonia of rumen fluid were not significantly different among treatments. While the acetic acid and propionic acid concentrations were not different among treatments, the butyric acid was significantly lower (P<0.05 in the groups received R3 and R4, whereas those received R2 and R3 was not

  12. Decomposition of indwelling EMG signals

    OpenAIRE

    2008-01-01

    Decomposition of indwelling electromyographic (EMG) signals is challenging in view of the complex and often unpredictable behaviors and interactions of the action potential trains of different motor units that constitute the indwelling EMG signal. These phenomena create a myriad of problem situations that a decomposition technique needs to address to attain completeness and accuracy levels required for various scientific and clinical applications. Starting with the maximum a posteriori probab...

  13. Synthesis and Catalytic Activity of Copper(Ⅱ) Resorcylic Acid Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Copper(Ⅱ) resorcylic acid(CuRes) nanoparticles were synthesized by using reactive precipitation method with resorcylic acid and blue copperas as the raw material in a rotating packed bed. The sample obtained was characterized by using X-ray diffraction( XRD), transmission electron microscopy( TEM ), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analyses (TG), and element analysis. In addition, the catalytic activity of CuRes nanoparticles on the thermal decomposition of nitrocellulose-nitroglycerine (NC-NG) was also determined via DSC.The results show that the spherical nanoparticles with a diameter of 20 nm were obtained in ethanol solution. The peak temperature of the thermal decomposition of NC-NG-CuRes decreases by 3 ℃ compared with that of normal CuRes,and the decomposition enthalpy is increased by 735 J/g, and therefore, it is reasonable to assume that CuRes nanoparticles have a better catalytic activity.

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

    OpenAIRE

    TsungYu Lee; Hsunling Bai

    2016-01-01

    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 temper...

  15. TREE DECOMPOSITIONS OF MULTIGRAPHS

    Institute of Scientific and Technical Information of China (English)

    SHI Minyong

    1999-01-01

    For a graph G, ifE(G) can be partitioned into several pairwise disjointsets as { E1, E2,……,El} such thatthe subgraph induced by Ei is a tree of orderki, (i=1,2, ……, l), then G is said to have a {k1,k2,……, kl}-tree-decomposition, denoted by {k1,k2,……, kl}∈G.For k≥1 and l≥0, a collection(G)(k,l) is the setof multigraphs such that G∈(G)(k,l) if and only if ε(G) = k(|G|-1)-l and ε(H)≤max{(k-1)(|H|-1), k(|H|-1)-l} for any subgraph H of G.We prove that (1) If k≥2, 0≤l≤3 and G∈(G)(k,l) of order n≥l+1, then {n,n,……, n-l}∈ G. (2) If k≥2 and G∈(G)(k,2) oforder n≥3, then {n,n,……, n,n-2}∈G and {n,n,……, n,n-1,n-1}∈G. (3) If k3 and G∈(G)(k,3) oforder n≥4, then {n,n,……, n,n-3}∈G ,{ n,n,……, n,n-1,n-2}∈ G and {n,n, ……, n,n-1,n-1,n-1}∈G.

  16. Ammonia-oxidizing archaea have more important role than ammonia-oxidizing bacteria in ammonia oxidation of strongly acidic soils.

    Science.gov (United States)

    Zhang, Li-Mei; Hu, Hang-Wei; Shen, Ju-Pei; He, Ji-Zheng

    2012-05-01

    Increasing evidence demonstrated the involvement of ammonia-oxidizing archaea (AOA) in the global nitrogen cycle, but the relative contributions of AOA and ammonia-oxidizing bacteria (AOB) to ammonia oxidation are still in debate. Previous studies suggest that AOA would be more adapted to ammonia-limited oligotrophic conditions, which seems to be favored by protonation of ammonia, turning into ammonium in low-pH environments. Here, we investigated the autotrophic nitrification activity of AOA and AOB in five strongly acidic soils (pHnitrification inhibitor dicyandiamide (DCD) completely inhibited the nitrification activity and CO(2) fixation by AOA, accompanied by decreasing thaumarchaeal amoA gene abundance. Bacterial amoA gene abundance decreased in all microcosms irrespective of DCD addition, and mostly showed no correlation with nitrate concentrations. Phylogenetic analysis of thaumarchaeal amoA gene and 16S rRNA gene revealed active (13)CO(2)-labeled AOA belonged to groups 1.1a-associated and 1.1b. Taken together, these results provided strong evidence that AOA have a more important role than AOB in autotrophic ammonia oxidation in strongly acidic soils.

  17. Decomposition of indwelling EMG signals.

    Science.gov (United States)

    Nawab, S Hamid; Wotiz, Robert P; De Luca, Carlo J

    2008-08-01

    Decomposition of indwelling electromyographic (EMG) signals is challenging in view of the complex and often unpredictable behaviors and interactions of the action potential trains of different motor units that constitute the indwelling EMG signal. These phenomena create a myriad of problem situations that a decomposition technique needs to address to attain completeness and accuracy levels required for various scientific and clinical applications. Starting with the maximum a posteriori probability classifier adapted from the original precision decomposition system (PD I) of LeFever and De Luca (25, 26), an artificial intelligence approach has been used to develop a multiclassifier system (PD II) for addressing some of the experimentally identified problem situations. On a database of indwelling EMG signals reflecting such conditions, the fully automatic PD II system is found to achieve a decomposition accuracy of 86.0% despite the fact that its results include low-amplitude action potential trains that are not decomposable at all via systems such as PD I. Accuracy was established by comparing the decompositions of indwelling EMG signals obtained from two sensors. At the end of the automatic PD II decomposition procedure, the accuracy may be enhanced to nearly 100% via an interactive editor, a particularly significant fact for the previously indecomposable trains.

  18. Study on Chemisorption and Desorption of Hydrogen and Nitrogen on Ru-based Ammonia Synthesis Catalyst

    Institute of Scientific and Technical Information of China (English)

    祝一锋; 李小年

    2003-01-01

    The effects of promoters K,Ba,Sm,on the chemisorption and desorption of hydrogen and nitrogen,dispersion of metallic Ru and catalytic activity of active carbon(AC) supported ruthenium catalyst for ammonia synthesis have been studied by means of pulse chromatography,temperature-programmed desorption,and activity test,Promoters K,Ba and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly,and particularly,potassium exhibited the best promotion on the activity because of the strong electronic donation to metallic Ru.Much higher activity can be obtained for Ru/AC catalyst with binary or triple promoters.The activity of Ru/AC catalyst is dependent on the adsorption of hydrogen and nitrogen.The high activity of catalyst could be ascribed to strong dissociation of nitrogen on the catalyst surface.Strong adsorption of hydrogen would inhibit the adsorption of nitrogen,resulted in decrease of the catalytic activity.Ru/AC catalyst promoted by Sm2O3 shows the best dispersion of metallic Ru,since the partly reduced SmO2 on the surface modifies the morphology of active sites and favors the dispersion of metallic Ru.The activity of Ru/AC catalysts is in accordance to the corresponding amount of nitrogen chemisorption and the desorption activation enery of nitrogen.The desorption activation energy for nitrogen decreases in the order of Ru>Ru-Ba>Ru-Sm>Ru-Bs-Sm>Ru-K>Ru-K-Bm>Ru-K-Ba>Ru-K-Ba-Sm,just opposite to the order or catalytic activity,suggesting that the ammonia synthesis over Ru-based catalyst is controlled by the step of dissociation of nitrogen.

  19. Ammonia as a Suitable Fuel for Fuel Cells

    OpenAIRE

    Lan, Rong; Tao, Shanwen

    2014-01-01

    Ammonia, an important basic chemical, is produced at a scale of 150 million tons per year. Half of hydrogen produced in chemical industry is used for ammonia production. Ammonia containing 17.5 wt% hydrogen is an ideal carbon-free fuel for fuel cells. Compared to hydrogen, ammonia has many advantages. In this mini-review, the suitability of ammonia as fuel for fuel cells, the development of different types of fuel cells using ammonia as the fuel and the potential applications of ammonia fuel ...

  20. Ammonia transformation in a biotrickling air filter

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter; Nielsen, Marie Louise; Andersen, Mathias;

    2007-01-01

    measurements and model was obtained by using conventional substrate and inhibition kinetics of ammonium and nitrite oxidizing bacteria. Highest rates of ammonia removal were observed in the central section of the filter. Near the air outlet and water inlet the process was ammonia limited, while high nitrous...... acid concentrations almost excluded any biological activity near the air inlet and water outlet. Nitrous acid inhibition also stabilized pH at 6.5-7 all through the filter. Being sensitive to both ammonia and nitrous acid the nitrite oxidation process occurred mainly in the filter sections near the air...... outlet / water inlet, and only 8% of the nitrite was turned into nitrate. Water supply only exceeded evaporation by 20% but modelling indicated that additional watering would have limited effect on filter efficiency. The filter was also robust to varying loading, as a 4-fold increase in ammonia inlet...

  1. Ammonia Affects Astroglial Proliferation in Culture.

    Directory of Open Access Journals (Sweden)

    Guillermo Bodega

    Full Text Available Primary cultures of rat astroglial cells were exposed to 1, 3 and 5 mM NH4Cl for up to 10 days. Dose- and time-dependent reductions in cell numbers were seen, plus an increase in the proportion of cells in the S phase. The DNA content was reduced in the treated cells, and BrdU incorporation diminished. However, neither ammonia nor ammonia plus glutamine had any effect on DNA polymerase activity. iTRAQ analysis showed that exposure to ammonia induced a significant reduction in histone and heterochromatin protein 1 expression. A reduction in cell viability was also noted. The ammonia-induced reduction of proliferative activity in these cultured astroglial cells seems to be due to a delay in the completion of the S phase provoked by the inhibition of chromatin protein synthesis.

  2. 21 CFR 573.180 - Anhydrous ammonia.

    Science.gov (United States)

    2010-04-01

    ... silage. (2)(i) The food additive anhydrous ammonia is applied directly to corn plant material for use in... to corn plant material containing 28 to 38 percent dry matter. (iv) The silage treated with...

  3. Nitrocarburising in ammonia-hydrocarbon gas mixtures

    DEFF Research Database (Denmark)

    Pedersen, Hanne; Christiansen, Thomas; Somers, Marcel A. J.

    2010-01-01

    The present work investigates the possibility of nitrocarburising in ammonia-acetylene-hydrogen and ammoniapropene- hydrogen gas mixtures, where unsaturated hydrocarbon gas is the carbon source during nitrocarburising. Consequently, nitrocarburising is carried out in a reducing atmosphere...

  4. Aqueous Ammonia soaking of digested manure fibers

    DEFF Research Database (Denmark)

    Mirtsou-Xanthopoulou, Chrysoula; Jurado, Esperanza; Skiadas, Ioannis

    2012-01-01

    , their economical profitable operation relies on increasing the methane yield from manure, and especially of its solid fraction which is not so easily degradable. In the present study, Aqueous Ammonia Soaking was successfully applied on digested fibers separated from the effluent of a manure-fed, full......-scale anaerobic digester to enhance their methane productivity. Soaking in six different reagent concentrations in ammonia (5%, 10%, 15%, 20%, 25%, 32%) was applied for 3 days at 22°C. An overall methane yield increase from 85% to 110% was achieved compared to controls (digested manure fibers where AAS...... was not applied). The difference in reagent concentration at the range of 5-25% w/w in ammonia did not affect that much the overall methane yield resulting to an increase of 104-110% compared to the non AAS-treated fibers. Thus, an ammonia concentration as low as 5% is adequate for achieving the same increase...

  5. Ammonia and urea permeability of mammalian aquaporins

    DEFF Research Database (Denmark)

    Litman, Thomas; Søgaard, Rikke; Zeuthen, Thomas

    2009-01-01

    The human aquaporins,AQP3,AQP7, AQP8,AQP9, and possibly AQP10, are permeable to ammonia, and AQP7, AQP9, and possibly AQP3, are permeable to urea. In humans, these aquaporins supplement the ammonia transport of the Rhesus (Rh) proteins and the urea transporters (UTs). The mechanism by which...... ammonium is transported by aquaporins is not fully resolved. A comparison of transport equations, models, and experimental data shows that ammonia is transported in its neutral form, NH(3). In the presence of NH(3), the aquaporin stimulates H(+) transport. Consequently, this transport of H(+) is only...... significant at alkaline pH. It is debated whether the H(+) ion passes via the aquaporin or by some external route; the investigation of this problem requires the aquaporin-expressing cell to be voltage-clamped. The ammonia-permeable aquaporins differ from other aquaporins by having a less restrictive aromatic...

  6. Síntese, caracterização e avaliação catalítica de Vo x/Mg yAlo x na reação de decomposição do isopropanol Synthesis, characterization and catalytic evaluation of Vo x/Mg yAlo x in the decomposition of isopropanol

    Directory of Open Access Journals (Sweden)

    Gilberto G. Cortez

    2008-01-01

    Full Text Available Vanadium oxide supported on hydrotalcite-type precursors was studied in the decomposition of isopropanol. Hydrotalcite-type compounds with different y = Mg+2/Al+3 ratios were synthesized by the method of coprecipitating nitrates of Mg+2 and Al+3 cations with K2CO3 as precipitant. The X-ray diffraction patterns of Al-rich hydrotalcite precursors showed the presence of crystalline phases of brucite and gibbsite. It was shown that chemical composition, texture, acid-base properties of the active sites and also Mg/Al ratio strongly affect the formation of the products in the oxidation of isopropanol. The Al-rich catalysts were much more active than the Mg-rich ones, converting isopropanol mainly to propylene.

  7. Dimension meditated optic and catalytic performance over vanadium pentoxides

    Science.gov (United States)

    Su, Dezhi; Zhao, Yongjie; Zhang, Ruibo; Ning, Mingqiang; Zhao, Yuzhen; Zhou, Heping; Li, Jingbo; Jin, Haibo

    2016-12-01

    Morphologies and sizes of V2O5 had crucial effect on their optic and catalytic performance. Diverse dimensional V2O5 were successfully synthesized by the combination of a hydrothermal and post heat treatment method. The as-obtained samples were characterized by X-ray power diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectra. Moreover, the optic properties of diverse dimensional V2O5 were examined by Fourier transform imaging spectrometer and UV-vis-spectrophotometer. It showed that the IR transmittance of nanowire (at 1019 cm-1 is 85%) and UV absorbance of microflowers (at 480 nm) were high. Furthermore, the catalytic properties of diverse dimensional V2O5 on the thermal decomposition of ammonium perchlorate were evaluated and compared by Thermo-Gravimetric Analysis and Differential Scanning Calorimetry. Moreover, the best catalytic performance was obtained with the morphology of nanowire. It showed the thermal decomposition temperatures of AP with nanowire, microflowers and microsphere were reduced to 373 °C, 382 °C and 376 °C (decreased by 52 °C, 43 °C and 49 °C).

  8. Alcohol amination with ammonia catalyzed by an acridine-based ruthenium pincer complex: a mechanistic study.

    Science.gov (United States)

    Ye, Xuan; Plessow, Philipp N; Brinks, Marion K; Schelwies, Mathias; Schaub, Thomas; Rominger, Frank; Paciello, Rocco; Limbach, Michael; Hofmann, Peter

    2014-04-23

    The mechanistic course of the amination of alcohols with ammonia catalyzed by a structurally modified congener of Milstein's well-defined acridine-based PNP-pincer Ru complex has been investigated both experimentally and by DFT calculations. Several key Ru intermediates have been isolated and characterized. The detailed analysis of a series of possible catalytic pathways (e.g., with and without metal-ligand cooperation, inner- and outer-sphere mechanisms) leads us to conclude that the most favorable pathway for this catalyst does not require metal-ligand cooperation.

  9. Corrosion inhibitor for aqueous ammonia absorption system

    Science.gov (United States)

    Phillips, Benjamin A.; Whitlow, Eugene P.

    1998-09-22

    A method of inhibiting corrosion and the formation of hydrogen and thus improving absorption in an ammonia/water absorption refrigeration, air conditioning or heat pump system by maintaining the hydroxyl ion concentration of the aqueous ammonia working fluid within a selected range under anaerobic conditions at temperatures up to 425.degree. F. This hydroxyl ion concentration is maintained by introducing to the aqueous ammonia working fluid an inhibitor in an amount effective to produce a hydroxyl ion concentration corresponding to a normality of the inhibitor relative to the water content ranging from about 0.015 N to about 0.2 N at 25.degree. C. Also, working fluids for inhibiting the corrosion of carbon steel and resulting hydrogen formation and improving absorption in an ammonia/water absorption system under anaerobic conditions at up to 425.degree. F. The working fluids may be aqueous solutions of ammonia and a strong base or aqueous solutions of ammonia, a strong base, and a specified buffer.

  10. Real interest parity decomposition

    Directory of Open Access Journals (Sweden)

    Alex Luiz Ferreira

    2009-09-01

    Full Text Available The aim of this paper is to investigate the general causes of real interest rate differentials (rids for a sample of emerging markets for the period of January 1996 to August 2007. To this end, two methods are applied. The first consists of breaking the variance of rids down into relative purchasing power pariety and uncovered interest rate parity and shows that inflation differentials are the main source of rids variation; while the second method breaks down the rids and nominal interest rate differentials (nids into nominal and real shocks. Bivariate autoregressive models are estimated under particular identification conditions, having been adequately treated for the identified structural breaks. Impulse response functions and error variance decomposition result in real shocks as being the likely cause of rids.O objetivo deste artigo é investigar as causas gerais dos diferenciais da taxa de juros real (rids para um conjunto de países emergentes, para o período de janeiro de 1996 a agosto de 2007. Para tanto, duas metodologias são aplicadas. A primeira consiste em decompor a variância dos rids entre a paridade do poder de compra relativa e a paridade de juros a descoberto e mostra que os diferenciais de inflação são a fonte predominante da variabilidade dos rids; a segunda decompõe os rids e os diferenciais de juros nominais (nids em choques nominais e reais. Sob certas condições de identificação, modelos autorregressivos bivariados são estimados com tratamento adequado para as quebras estruturais identificadas e as funções de resposta ao impulso e a decomposição da variância dos erros de previsão são obtidas, resultando em evidências favoráveis a que os choques reais são a causa mais provável dos rids.

  11. Cerium and Lanthanum Modified Pd/Al2O3 Catalysts for Methanol Decomposition

    Institute of Scientific and Technical Information of China (English)

    杨成; 任杰; 孙予罕

    2001-01-01

    CeO2 improves the activity and selectivity of Pd/Al2O3 catalyst for methanol decomposition. The interaction between Pd and CeO2 was then proposed to result in the promoting effect. The selectivity of CO and H2 is significantly improved by addition of La2O3 to either Pd/Al2O3 or Pd/CeO2/Al2O3 catalysts. Moreover, a synergistic promotion between CeO2 and La2O3 on γ-Al2O3 supported Pd catalysts was observed for the catalytic activity towards methanol decomposition into CO and H2.

  12. Bis(í-oxo)dicopper in Cu-ZSM-5 and Its Role in the Decomposition of NO: A Combined in Situ XAFS, UV-Vis-Near-IR, and Kinetic Study

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Groothaert, M.H.; Bokhoven, J.A. van; Battiston, A.A.; Schoonheydt, R.A.

    2003-01-01

    In situ XAFS combined with UV-vis-near-IR spectroscopy are used to identify the active site in copper-loaded ZSM-5 responsible for the catalytic decomposition of NO. Cu-ZSM-5 was probed with in situ XAFS (i) after O2 activation and (ii) while catalyzing the direct decomposition of NO into N2 and O2.

  13. Investigation of nitrogen-bearing species in catalytic steam gasification of poultry litter.

    Science.gov (United States)

    Sheth, Atul C; Bagchi, Bratendu

    2005-05-01

    The production of broiler chickens has become one of the largest sectors in U.S. agriculture, and the growing demand for poultry has led to an annual production growth rate of 5%. With increased demand for poultry, litter management has become a major challenge in the agriculture industry. Although the catalytic steam gasification has been accepted as a possible and feasible method for litter management, concern has been expressed about the presence of nitrogen and phosphorus containing species in the fuel gas and/or in the final solid residue. The possible release of phosphorus as phosphine gas in the fuel gas can have an adverse impact on the environment. Similarly, possible release of ammonia from the nitrogen containing species is also not acceptable. Hence, under partial U.S. Department of Agriculture support, a study was conducted to examine the fate and the environmental impact of the nitrogen- and phosphorus-containing species released during catalytic steam gasification of poultry litter. From various preliminary tests, it was concluded that most (approximately 100%) of the phosphorus would remain in the residue, and some (20-70%) of the nitrogen would end up as ammonia in the fuel gas. The effects of temperature, catalyst loading, and type of catalyst on ammonia liberation were studied in a muffled furnace setup at atmospheric pressure. The fraction of nitrogen released as ammonia was found to decrease with an increase in temperature during pyrolysis and steam gasification. It also decreased with an increase in catalyst loading.

  14. Thermal behavior and kinetic study for catalytic co-pyrolysis of biomass with plastics.

    Science.gov (United States)

    Zhang, Xuesong; Lei, Hanwu; Zhu, Lei; Zhu, Xiaolu; Qian, Moriko; Yadavalli, Gayatri; Wu, Joan; Chen, Shulin

    2016-11-01

    The present study aims to investigate the thermal decomposition behaviors and kinetics of biomass (cellulose/Douglas fir sawdust) and plastics (LDPE) in a non-catalytic and catalytic co-pyrolysis over ZSM-5 catalyst by using a thermogravimetric analyzer (TGA). It was found that there was a positive synergistic interaction between biomass and plastics according to the difference of weight loss (ΔW), which could decrease the formation of solid residue at the end of the experiment. The first order reaction model well fitted for both non-catalytic and catalytic co-pyrolysis of biomass with plastics. The activation energy (E) of Cellulose-LDPE-Catalyst and DF-LDPE-Catalyst are only 89.51 and 54.51kJ/mol, respectively. The kinetics analysis showed that adding catalyst doesn't change the decomposition mechanism. As a result, the kinetic study on catalytic co-pyrolysis of biomass with plastics was suggested that the catalytic co-pyrolysis is a promising technique that can significantly reduce the energy input.

  15. Ammonia and hydrazine. Transition-metal-catalyzed hydroamination and metal-free catalyzed functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, Guy [Univ. of California, San Diego, CA (United States)

    2012-06-29

    The efficient and selective preparation of organic molecules is critical for mankind. For the future, it is of paramount importance to find catalysts able to transform abundant and cheap feedstocks into useful compounds. Acyclic and heterocyclic nitrogen-containing derivatives are common components of naturally occurring compounds, agrochemicals, cosmetics, and pharmaceuticals; they are also useful intermediates in a number of industrial processes. One of the most widely used synthetic strategies, allowing the formation of an N-C bond, is the addition of an N-H bond across a carbon-carbon multiple bond, the so-called hydroamination reaction. This chemical transformation fulfills the principle of “green chemistry” since it ideally occurs with 100% atom economy. Various catalysts have been found to promote this reaction, although many limitations remain; one of the most prominent is the lack of methods that permit the use of NH3 and NH2NH2 as the amine partners. In fact, ammonia and hydrazine have rarely succumbed to homogeneous catalytic transformations. Considering the low cost and abundance of ammonia (136 million metric tons produced in 2011) and hydrazine, catalysts able to improve the reactivity and selectivity of the NH3- and NH2NH2-hydroamination reaction, and more broadly speaking the functionalization of these chemicals, are highly desirable. In the last funded period, we discovered the first homogeneous catalysts able to promote the hydroamination of alkynes and allenes with ammonia and the parent hydrazine. The key feature of our catalytic systems is that the formation of catalytically inactive Werner complexes is reversible, in marked contrast to most of the known ammonia and hydrazine transition metal complexes. This is due to the peculiar electronic properties of our neutral ancillary ligands, especially their strong donating capabilities. However, our catalysts currently require

  16. 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

  17. Novel Regenerated Solvent Extraction Processes for the Recovery of Carboxylic Acids or Ammonia from Aqueous Solutions Part II. Recovery of Ammonia from Sour Waters

    Energy Technology Data Exchange (ETDEWEB)

    Poole, L.J.; King, C.J.

    1990-03-01

    Two novel regenerated solvent extraction processes are examined. The first process has the potential to reduce the energy costs inherent in the recovery of low-volatility carboxylic acids from dilute aqueous solutions. The second process has the potential for reducing the energy costs required for separate recovery of ammonia and acid gases (e.g. CO{sub 2} and H{sub 2}S) from industrial sour waters. The recovery of carboxylic acids from dilute aqueous solution can be achieved by extraction with tertiary amines. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle. Experimental work was performed with lactic acid, SUCCiOlC acid, and fumaric acid. Equilibrium data show near-stoichiometric recovery of the carboxylic acids from an organic solution of Alamine 336 into aqueous solutions of trimethylamine. For fumaric and succinic acids, partial evaporation of the aqueous back extract decomposes the carboxylate and yields the acid product in crystalline form. The decomposition of aqueous solutions of trimethylammonium lactates was not carried out to completion, due to the high water solubility of lactic acid and the tendency of the acid to self-associate. The separate recovery of ammonia and acid gases from sour waters can be achieved by combining steam-stripping of the acid gases with simultaneous removal of ammonia by extraction with a liquid cation exchanger. The use of di-2,4,4-trimethylpentyl phosphinic acid as the liquid cation exchanger is explored in this work. Batch extraction experiments were carried out to measure the equilibrium distribution ratio of ammonia between an aqueous buffer solution and an organic solution of the phosphinic acid (0.2N) in Norpar 12. The concentration

  18. Using a Hands-On Hydrogen Peroxide Decomposition Activity to Teach Catalysis Concepts to K-12 Students

    Science.gov (United States)

    Cybulskis, Viktor J.; Ribeiro, Fabio H.; Gounder, Rajamani

    2016-01-01

    A versatile and transportable laboratory apparatus was developed for middle and high school (6th-12th grade) students as part of a hands-on outreach activity to estimate catalytic rates of hydrogen peroxide decomposition from oxygen evolution rates measured by using a volumetric displacement method. The apparatus was constructed with inherent…

  19. Decomposition mechanism of melamine borate in pyrolytic and thermo-oxidative conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hoffendahl, Carmen; Duquesne, Sophie; Fontaine, Gaëlle; Bourbigot, Serge, E-mail: serge.bourbigot@ensc-lille.fr

    2014-08-20

    Highlights: • Decomposition of melamine borate in pyrolytic and thermo-oxidative conditions was investigated. • With increasing temperature, orthoboric acid forms boron oxide releasing water. • Melamine decomposes evolving melamine, ammonia and other fragments. • Boron oxide is transformed into boron nitride and boron nitride-oxide structures through presence of ammonia. - Abstract: Decomposition mechanism of melamine borate (MB) in pyrolytic and thermo-oxidative conditions is investigated in the condensed and gas phases using solid state NMR ({sup 13}C and {sup 11}B), X-ray photoelectron spectroscopy (XPS), pyrolysis-gas chromatography–mass spectrometry (py-GCMS) and thermogravimetric analysis coupled with a Fourier transform infrared spectrometer (TGA–FTIR). It is evidenced that orthoboric acid dehydrates to metaboric and then to boron oxide. The melamine is partially sublimated. At the same time, melamine condensates, i.e., melem and melon are formed. Melon is only formed in thermo-oxidative conditions. At higher temperature, melem and melon decompose releasing ammonia which reacts with the boron oxide to form boron nitride (BN) and BNO structures.

  20. Piecewise-adaptive decomposition methods

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, J.I. [Room I-320-D, E.T.S. Ingenieros Industriales, Universidad de Malaga, Plaza El Ejido, s/n, 29013 Malaga (Spain)], E-mail: jirs@lcc.uma.es

    2009-05-30

    Piecewise-adaptive decomposition methods are developed for the solution of nonlinear ordinary differential equations. These methods are based on some theorems that show that Adomian's decomposition method is a homotopy perturbation technique and coincides with Taylor's series expansions for autonomous ordinary differential equations. Piecewise-decomposition methods provide series solutions in intervals which are subject to continuity conditions at the end points of each interval, and their adaption is based on the use of either a fixed number of approximants and a variable step size, a variable number of approximants and a fixed step size or a variable number of approximants and a variable step size. It is shown that the appearance of noise terms in the decomposition method is related to both the differential equation and the manner in which the homotopy parameter is introduced, especially for the Lane-Emden equation. It is also shown that, in order to avoid the use of numerical quadrature, there is a simple way of introducing the homotopy parameter in the two first-order ordinary differential equations that correspond to the second-order Thomas-Fermi equation. It is also shown that the piecewise homotopy perturbation methods presented here provide more accurate results than a modified Adomian decomposition technique which makes use of Pade approximants and the homotopy analysis method, for the Thomas-Fermi equation.

  1. Ammonia transformations and abundance of ammonia oxidizers in a clay soil underlying a manure pond.

    Science.gov (United States)

    Sher, Yonatan; Baram, Shahar; Dahan, Ofer; Ronen, Zeev; Nejidat, Ali

    2012-07-01

    Unlined manure ponds are constructed on clay soil worldwide to manage farm waste. Seepage of ammonia-rich liquor into underlying soil layers contributes to groundwater contamination by nitrate. To identify the possible processes that lead to the production of nitrate from ammonia in this oxygen-limited environment, we studied the diversity and abundance of ammonia-transforming microorganisms under an unlined manure pond. The numbers of ammonia-oxidizing bacteria and anammox bacteria were most abundant in the top of the soil profile and decreased significantly with depth (0.5 m), correlating with soil pore-water ammonia concentrations and soil ammonia concentrations, respectively. On the other hand, the numbers of ammonia-oxidizing archaea were relatively constant throughout the soil profile (10(7) amoA copies per g(soil)). Nitrite-oxidizing bacteria were detected mainly in the top 0.2 m. The results suggest that nitrate accumulation in the vadose zone under the manure pond could be the result of complete aerobic nitrification (ammonia oxidation to nitrate) and could exist as a byproduct of anammox activity. While the majority of the nitrogen was removed within the 0.5-m soil section, possibly by combined anammox and heterotrophic denitrification, a fraction of the produced nitrate leached into the groundwater.

  2. Adiabatic calorimetric decomposition studies of 50 wt.% hydroxylamine/water.

    Science.gov (United States)

    Cisneros, L O; Rogers, W J; Mannan, M S

    2001-03-19

    Calorimetric data can provide a basis for determining potential hazards in reactions, storage, and transportation of process chemicals. This work provides calorimetric data for the thermal decomposition behavior in air of 50wt.% hydroxylamine/water (HA), both with and without added stabilizers, which was measured in closed cells with an automatic pressure tracking adiabatic calorimeter (APTAC). Among the data provided are onset temperatures, reaction order, activation energies, pressures of noncondensable products, thermal stability at 100 degrees C, and the effect of HA storage time. Discussed also are the catalytic effects of carbon steel, stainless steel, stainless steel with silica coating, inconel, titanium, and titanium with silica coating on the reaction self-heat rates and onset temperatures. In borosilicate glass cells, HA was relatively stable at temperatures up to 133 degrees C, where the HA decomposition self-heat rate reached 0.05 degrees C/min. The added stabilizers appeared to reduce HA decomposition rates in glass cells and at ambient temperatures. The tested metals and metal surfaces coated with silica acted as catalysts to lower the onset temperatures and increase the self-heat rates.

  3. Distributed k-Core Decomposition

    CERN Document Server

    Montresor, Alberto; Miorandi, Daniele

    2011-01-01

    Among the novel metrics used to study the relative importance of nodes in complex networks, k-core decomposition has found a number of applications in areas as diverse as sociology, proteinomics, graph visualization, and distributed system analysis and design. This paper proposes new distributed algorithms for the computation of the k-core decomposition of a network, with the purpose of (i) enabling the run-time computation of k-cores in "live" distributed systems and (ii) allowing the decomposition, over a set of connected machines, of very large graphs, that cannot be hosted in a single machine. Lower bounds on the algorithms complexity are given, and an exhaustive experimental analysis on real-world graphs is provided.

  4. Thermal decomposition of ammonium hexachloroosmate

    DEFF Research Database (Denmark)

    Asanova, T I; Kantor, Innokenty; Asanov, I. P.

    2016-01-01

    Structural changes of (NH4)2[OsCl6] occurring during thermal decomposition in a reduction atmosphere have been studied in situ using combined energy-dispersive X-ray absorption spectroscopy (ED-XAFS) and powder X-ray diffraction (PXRD). According to PXRD, (NH4)2[OsCl6] transforms directly...... to metallic Os without the formation of any crystalline intermediates but through a plateau where no reactions occur. XANES and EXAFS data by means of Multivariate Curve Resolution (MCR) analysis show that thermal decomposition occurs with the formation of an amorphous intermediate {OsCl4}x with a possible...... polymeric structure. Being revealed for the first time the intermediate was subjected to determine the local atomic structure around osmium. The thermal decomposition of hexachloroosmate is much more complex and occurs within a minimum two-step process, which has never been observed before....

  5. The effect of microwave-assisted for photo-catalytic degradation of rhodamine B in aqueous nano TiO2 particles dispersions.

    Science.gov (United States)

    Shin, Hyun-Chung; Park, Sung Hoon; Ahn, Ho-Geun; Chung, Minchul; Kim, Byung Whan; Kim, Sun-Jae; Seo, Seong-Gyu; Jung, Sang-Chul

    2011-02-01

    The photo-catalytic decomposition of rhodamine B was examined in aqueous nano TiO2 particles dispersions to assess effects of the microwave radiation assisted photo-catalytic process driven by UV radiation. The results of photo-catalytic degradation of rhodamine B showed that the decomposition rate increased with the microwave intensity, UV intensity, TiO2 particle dosages and the circulating fluid velocity. Addition of oxygen gas in the photo-catalytic degradation of rhodamine B increased the reaction rate. The effect of addition of H2O2 was not significant when photo-catalysis was used without additional microwave radiation or when microwave was irradiated without the use of photo-catalysts. When H2O2 was added under simultaneous use of photo-catalysis and microwave irradiation, however, considerably higher degradation reaction rates were observed. This study demonstrates that the microwave irradiation can play a very important role in photo-catalytic degradation.

  6. Electron-induced ammonia adsorption on iron

    CERN Document Server

    Narkiewicz, U; Trybuchowicz, A; Arabczyk, W

    2003-01-01

    The adsorption of ammonia on an iron surface at ambient temperature has been investigated using Auger electron spectroscopy (AES). The effect of the electron beam on the process of the ammonia adsorption has been studied. The polycrystalline iron samples precovered with different amounts of oxygen (0.15-1 ML) or sulphur (1 ML) were used. The initial sticking coefficient of ammonia to oxygen precovered iron surface was estimated as s sub 0 approx 5x10 sup - sup 4 (independently on the oxygen coverage) for the adsorption experiments without the effect of the electron beam. The strong inhibiting effect of sulphur precoverage on the ammonia adsorption has been found (s sub 0 approx 6.5x10 sup - sup 6). The electron beam has favourable effect on the adsorption of ammonia, and this effect increases with the oxygen coverage (one monolayer of adsorbed nitrogen atoms at the saturation state and s sub 0 approx 1 for the iron surface precovered with one monolayer of oxygen). The proposed explanation is the favourable ef...

  7. Ammonia/Hydrogen Mixtures in an SI-Engine

    DEFF Research Database (Denmark)

    Mørch, Christian Sandersen; Bjerre, Andreas; Gøttrup, Morten Piil

    2011-01-01

    In recent years there has been increasing focus on using metal ammine complexes for ammonia storage. In this paper a fuel system for ammonia fuelled internal combustion engines using metal ammine complexes as ammonia storage is analyzed. The use of ammonia/hydrogen mixtures as an SI-engine fuel...... is investigated in the same context. Ammonia and hydrogen were introduced into the intake manifold of a CFR-engine. Series of experiments with varying excess air ratio and different ammonia to hydrogen ratios was conducted. This showed that a fuel mixture with 10 vol.% hydrogen performs best with respect...

  8. The effect of outside conditions on anaerobic ammonia oxidation reaction

    Institute of Scientific and Technical Information of China (English)

    YANG Min; WANG Shu-bo

    2016-01-01

    Organic carbon, inorganic carbon, temperature, pH and ORP are all to have a certain influence on the anaerobic ammonia oxidation reaction. We can draw some conclusions on the optimum conditions of anaerobic ammonia oxidation reaction. The optimum temperature of the anaerobic ammonia oxidation reaction is 30-35℃. And the optimum pH of the anaerobic ammonia reaction is 7.5-8.3. The presence of organic matters can affect the anaerobic ammonia reaction, and different organic matters have different influence on it. The concentration of the inorganic carbon also exist great influence on the reaction. High inorganic carbon concentration also can inhibit anaerobic ammonia oxidation reaction.

  9. Nanosized iron and iron–cobalt spinel oxides as catalysts for methanol decomposition

    OpenAIRE

    Manova, Elina; Tsoncheva, Tanya; Estournès, Claude; Paneva, Daniela; Tenchev, K.; Mitov, Ivan; Petrov, L.

    2006-01-01

    Nanosized iron and mixed iron–cobalt oxides supported on activated carbon materials and their bulk analogues prepared by thermal synthesis are studied by X-rays diffraction, Mo¨ssbauer spectroscopy, magnetic measurements and temperature programmed reduction. Their catalytic behavior in methanol decomposition to H2, CO and methane is tested. Phase transformations in the metal oxides affected by the reaction medium are also investigated. Changes in the reaction mechanism of the methanol decompo...

  10. Catalytic oxidation of volatile organic compounds (VOCs) - A review

    Science.gov (United States)

    Kamal, Muhammad Shahzad; Razzak, Shaikh A.; Hossain, Mohammad M.

    2016-09-01

    Emission of volatile organic compounds (VOCs) is one of the major contributors to air pollution. The main sources of VOCs are petroleum refineries, fuel combustions, chemical industries, decomposition in the biosphere and biomass, pharmaceutical plants, automobile industries, textile manufacturers, solvents processes, cleaning products, printing presses, insulating materials, office supplies, printers etc. The most common VOCs are halogenated compounds, aldehydes, alcohols, ketones, aromatic compounds, and ethers. High concentrations of these VOCs can cause irritations, nausea, dizziness, and headaches. Some VOCs are also carcinogenic for both humans and animals. Therefore, it is crucial to minimize the emission of VOCs. Among the available technologies, the catalytic oxidation of VOCs is the most popular because of its versatility of handling a range of organic emissions under mild operating conditions. Due to that fact, there are numerous research initiatives focused on developing advanced technologies for the catalytic destruction of VOCs. This review discusses recent developments in catalytic systems for the destruction of VOCs. Review also describes various VOCs and their sources of emission, mechanisms of catalytic destruction, the causes of catalyst deactivation, and catalyst regeneration methods.

  11. Multi-component removal in flue gas by aqua ammonia

    Science.gov (United States)

    Yeh, James T.; Pennline, Henry W.

    2007-08-14

    A new method for the removal of environmental compounds from gaseous streams, in particular, flue gas streams. The new method involves first oxidizing some or all of the acid anhydrides contained in the gas stream such as sulfur dioxide (SO.sub.2) and nitric oxide (NO) and nitrous oxide (N.sub.2O) to sulfur trioxide (SO.sub.3) and nitrogen dioxide (NO.sub.2). The gas stream is subsequently treated with aqua ammonia or ammonium hydroxide which captures the compounds via chemical absorption through acid-base or neutralization reactions. The products of the reactions can be collected as slurries, dewatered, and dried for use as fertilizers, or once the slurries have been dewatered, used directly as fertilizers. The ammonium hydroxide can be regenerated and recycled for use via thermal decomposition of ammonium bicarbonate, one of the products formed. There are alternative embodiments which entail stoichiometric scrubbing of nitrogen oxides and sulfur oxides with subsequent separate scrubbing of carbon dioxide.

  12. Using advanced electron microscopy for the characterization of catalytic materials

    Science.gov (United States)

    Pyrz, William D.

    -corrected electron microscopy was used to systematically examine, atomic column by atomic column, the effect of elemental substitution on the long-range crystalline order, atomic coordinates, and site occupancies of the various formulations such that trends could be developed linking these properties to catalytic yields. To accomplish this task, an algorithm was developed that enabled the direct extraction of atomic coordinates and site occupancies from high-angle annular dark-field (HAADF) images to within 1% and 15% uncertainty, respectively. Furthermore, this general method could be applied to various crystalline systems and may dramatically improve the quality of initial structural models used in Rietveld refinements. Improvement in the quality of starting models may increase the structural and chemical complexity of inorganic structures that can be solved by using "powder methods" alone. In addition to the development of these trends, HAADF analyses also revealed the presence of coherent compositional miscibility gaps, rotational twin domains, and structural intergrowths in the complex Mo-V-M-O oxide system. Other catalytic systems that are addressed in this dissertation include Pd, Ag, and bimetallic Pd-Ag catalysts for the selective hydrogenation of acetylene in excess ethylene, alkali and alkaline earth promoted Ru catalysts for the production of clean hydrogen through the decomposition of ammonia, the production of Pt nanoparticles using dendrimer templates, and Pt-Re bimetallic catalysts for the conversion of glycerol to hydrocarbons and syn gas. In each of these studies, electron microscopy was used as a complimentary tool to synthetic and reaction studies to better understand interactions between the nanoparticles and the support/template, to determine the effect of adding various promoters, or to understand the nanoscale structural and chemical changes associated with the formation of bimetallic nanoparticles. A final area addressed in this dissertation is the

  13. Hydrazine borane-induced destabilization of ammonia borane, and vice versa

    Energy Technology Data Exchange (ETDEWEB)

    Petit, Jean-Fabien; Moussa, Georges [IEM (Institut Europeen des Membranes), UMR 5635 (CNRS-ENSCM-UM2), Universite Montpellier 2, Place E. Bataillon, F-34095 Montpellier (France); Demirci, Umit B., E-mail: umit.demirci@um2.fr [IEM (Institut Europeen des Membranes), UMR 5635 (CNRS-ENSCM-UM2), Universite Montpellier 2, Place E. Bataillon, F-34095 Montpellier (France); Toche, François; Chiriac, Rodica [Université Lyon 1, CNRS, UMR 5615, Laboratoire des Multimatériaux et Interfaces, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne (France); Miele, Philippe [IEM (Institut Europeen des Membranes), UMR 5635 (CNRS-ENSCM-UM2), Universite Montpellier 2, Place E. Bataillon, F-34095 Montpellier (France)

    2014-08-15

    Graphical abstract: - Highlights: • Hydrazine borane and ammoniaborane (mole ratio 1:1) destabilize each other. • This is characterized by a melting point at ∼30 °C and decomposition into hydrazine. • Also, some hydrogen H{sub 2} is “explosively” liberated at around 90 °C. • The mixture can be however stabilized into a potential hydrogen storage material. • This hydrogen storage material dehydrogenates up to 300 °C to form boron nitride. - Abstract: In the field of solid-state chemical hydrogen storage, ammonia borane NH{sub 3}BH{sub 3} has been widely studied while hydrazine borane N{sub 2}H{sub 4}BH{sub 3} can be considered as a “novel” material. In the present work, we investigated the behaviour of these boranes when mixed together in a mole ratio of 1:1. Hydrazine borane and ammonia borane destabilize each other. Though stable at 20–25 °C, the mixture melts at ∼30 °C and then undergoes significant decomposition, with desorption of hydrogen H{sub 2} and hydrazine N{sub 2}H{sub 4} from 67 °C. This is explained by the fact that the presence of hydrazine borane disrupts the H{sup δ+}⋯H{sup δ−} network of ammonia borane, and vice versa; the mixture is then much less stable than the pristine boranes. The mixture can nevertheless be stabilized (by heat- or vacuum-treatment and thus extraction of evolving hydrogen and hydrazine), making the as-obtained solid a potential chemical hydrogen storage material. Over the range 25–300 °C, it is able to release ca. 11.4 wt% of almost pure H{sub 2}. Furthermore forms boron nitride as the solid residue, at temperatures as low as 300 °C.

  14. Novel Catalytic Membrane Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Stuart Nemser, PhD

    2010-10-01

    There are many industrial catalytic organic reversible reactions with amines or alcohols that have water as one of the products. Many of these reactions are homogeneously catalyzed. In all cases removal of water facilitates the reaction and produces more of the desired chemical product. By shifting the reaction to right we produce more chemical product with little or no additional capital investment. Many of these reactions can also relate to bioprocesses. Given the large number of water-organic compound separations achievable and the ability of the Compact Membrane Systems, Inc. (CMS) perfluoro membranes to withstand these harsh operating conditions, this is an ideal demonstration system for the water-of-reaction removal using a membrane reactor. Enhanced reaction synthesis is consistent with the DOE objective to lower the energy intensity of U.S. industry 25% by 2017 in accord with the Energy Policy Act of 2005 and to improve the United States manufacturing competitiveness. The objective of this program is to develop the platform technology for enhancing homogeneous catalytic chemical syntheses.

  15. Transformation of ammonia i biological airfilters

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter; Sørensen, Karen; Andersen, Mathias;

    2007-01-01

    Ammonia is a major compound in ventilation air from animal houses. In biological filters it is with varying efficiency transformed by physical, biological, and chemical processes and ends up as ammonium, nitrate, and nitrite dissolved in water and as dinitrogen, nitrous oxide and nitric oxide...... emitted to the air. To identify the key regulators of these transformations we have combined data from studies of microbiology and performance in 10 experimental and full scale filters of varying design, loading, and management. Inhibition by nitrite controlled ammonium oxidation and pH, while biological...... nitrite oxidation only appeared in locations with minimal ammonia and nitrite levels. Nitrous oxide emission depended on anoxic microsites, and nitric oxide production was associated with nitrite accumulation. Water and biomass management appear to be the important tools for optimization of ammonia...

  16. A personal ammonia monitor utilizing permeation sampling

    Energy Technology Data Exchange (ETDEWEB)

    Benedict, A.F. (Occupational Safety and Health Administration, Baton Rouge, LA); Reiszner, K.D.; West, P.W.

    1983-01-01

    A method has been developed for the determination of the time-weighted-average personal exposure to ammonia. Sample collection was achieved by permeation through a silicone membrane into a boric acid solution. The trapped ammonia was then determined spectrophotometrically with Nessler's reagent or potentiometrically with an ion selective electrode. The device may be used for sampling periods as short as 5 minutes and was not affected by changes in the environmental parameters normally encountered at industrial locations. The detection limit is 0.4 ppm for an 8 hr sampling period and the monitor responds linearly to at least 150 ppm. The Nessler's method may be utilized in industrial environments containing monoethanol amine in conjunction with ammonia with no significant interference. Although some interference was observed from ethylenediamine with the Nessler's technique, little interference was found with the potentiometric determination.

  17. Modular Decomposition of Boolean Functions

    NARCIS (Netherlands)

    J.C. Bioch (Cor)

    2002-01-01

    textabstractModular decomposition is a thoroughly investigated topic in many areas such as switching theory, reliability theory, game theory and graph theory. Most appli- cations can be formulated in the framework of Boolean functions. In this paper we give a uni_ed treatment of modular decompositio

  18. Stepwise decomposition in controlpath synthesis

    NARCIS (Netherlands)

    Berg, ten A.J.W.M.

    1990-01-01

    A method is presented for the synthesis of the microarchitecture of controlpaths. This method is called stepwise decomposition. It focuses primarily on controlpaths of instruction set processors, however it is also applicable for more general Finite State Machine synthesis. Many of the current contr

  19. The ecology of carrion decomposition

    Science.gov (United States)

    Carrion, or the remains of dead animals, is something that most people would like to avoid. It is visually unpleasant, emits foul odors, and may be the source of numerous pathogens. Decomposition of carrion, however, provides a unique opportunity for scientists to investigate how nutrients cycle t...

  20. Microbial interactions during carrion decomposition

    Science.gov (United States)

    This addresses the microbial ecology of carrion decomposition in the age of metagenomics. It describes what is known about the microbial communities on carrion, including a brief synopsis about the communities on other organic matter sources. It provides a description of studies using state-of-the...

  1. Ammonia emission time profiles based on manure transport data improve ammonia modelling across north western Europe

    Science.gov (United States)

    Hendriks, C.; Kranenburg, R.; Kuenen, J. J. P.; Van den Bril, B.; Verguts, V.; Schaap, M.

    2016-04-01

    Accurate modelling of mitigation measures for nitrogen deposition and secondary inorganic aerosol (SIA) episodes requires a detailed representation of emission patterns from agriculture. In this study the meteorological influence on the temporal variability of ammonia emissions from livestock housing and application of manure and fertilizer are included in the chemistry transport model LOTOS-EUROS. For manure application, manure transport data from Flanders (Belgium) were used as a proxy to derive the emission variability. Using improved ammonia emission variability strongly improves model performance for ammonia, mainly by a better representation of the spring maximum. The impact on model performance for SIA was negligible as explained by the limited, ammonia rich region in which the emission variability was updated. The contribution of Flemish agriculture to modelled annual mean ammonia and SIA concentrations in Flanders were quantified at respectively 7-8 and 1-2 μg/m3. A scenario study was performed to investigate the effects of reducing ammonia emissions from manure application during PM episodes by 75%, yielding a maximum reduction in modelled SIA levels of 1-3 μg/m3 during episodes. Year-to-year emission variability and a soil module to explicitly model the emission process from manure and fertilizer application are needed to further improve the modelling of the ammonia budget.

  2. Production of hydrogen by superadiabatic decomposition of hydrogen sulfide

    Energy Technology Data Exchange (ETDEWEB)

    Slimane, R.B.; Lau, F.S.; Dihu, R. [Gas Technology Inst., Des Plaines, IL (United States); Bingue, J.P.; Saveliev, A.V.; Fridman, A.A.; Kennedy, L.A. [Illinois Univ., Chicago, IL (United States)

    2002-07-01

    It is expected that hydrogen will become the fuel of choice for advanced technologies. Hydrogen is currently used as feedstock in the synthesis of ammonia and methanol, in the desulfurization and hydrocracking at oil refineries, and in the upgrading of hydrocarbon resources such as heavy oil and coal. Hydrogen sulfide (H{sub 2}S) is regarded as a mineral from which both hydrogen and sulfur can be extracted. Since there are large amounts of H{sub 2}S available worldwide, significant research has gone into the development of converting hydrogen sulfide into hydrogen through thermal decomposition. The high temperature required for the reaction, however, makes the approach impractical. This paper presents results of a study using a new approach to overcome the limitations of thermal decomposition. In this newly developed process, operation at very high temperatures is possible and economical through oxidation of part of the H{sub 2}S to provide the energy needed for the decomposition reaction. Partial oxidation is carried out in the presence of an inert, porous, high-capacity medium and the heat exchange results in flame temperatures that exceed the adiabatic flame temperature of the gas mixture. This process is less stringent than the Claus process because of the required feed gas conditioning. SO{sub 2} emissions inevitably form because part of the H{sub 2}S is oxidized to generate heat. However, SO{sub 2} is not expected to form to a significant degree. It was concluded that the product/byproduct separation schemes need to be examined further to have a better idea regarding the cost of hydrogen production from this process. 6 refs., 5 figs.

  3. Deammoniation and ammoniation processes with ammonia complexes

    Directory of Open Access Journals (Sweden)

    Pim Donkers

    2016-12-01

    Full Text Available For selecting the most suitable ammoniate as a heat storage material we have reviewed all the available literature since 1860. This data reveal that we can order the dissociation temperature and the enthalpy of reaction of di erent ammoniates. We show that all data can be represented by a single master curve. This curve shows that ammoniates belonging to the alkali metal periodic group have the lowest energy pro ammonia molecule, whereas transition metals (3d have the highest energy pro ammonia molecule. These trends can be used to select the most suitable ammoniates under certain working conditions.

  4. Enantioselective, iridium-catalyzed monoallylation of ammonia.

    Science.gov (United States)

    Pouy, Mark J; Stanley, Levi M; Hartwig, John F

    2009-08-19

    Highly enantioselective, iridium-catalyzed monoallylations of ammonia are reported. These reactions occur with electron-neutral, -rich, and -poor cinnamyl carbonates, alkyl and trityloxy-substituted allylic carbonates, and dienyl carbonates in moderate to good yields and excellent enantioselectivities. This process is enabled by the use of an iridium catalyst that does not require a Lewis acid for activation and that is stable toward a large excess of ammonia. This selective formation of primary allylic amines allows for one-pot syntheses of heterodiallylamines and allylic amides that are not otherwise accessible via iridium-catalyzed allylic amination without the use of blocking groups and protective group manipulations.

  5. Structure of Ramie Treated by Liquid Ammonia

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The morphology and supermolecular structures of the scoured/bleached ramie and scoured/bleached/liquid ammonia treated ramie were studied by means of scanning electron microscope, X-ray diffractometer, reverse gel permeation chromatography, etc. The results indicate that liquid ammonia treatment of the scoured/bleached ramie leads to a smoother surface, a lower crystallinity, partial crystal transformation from cellulose Ⅰ to cellulose Ⅲ, a decrease in the volume and cumulative surface area of the larger micropores and an increase in those of the smaller ones in the fiber.

  6. Computational Search for Improved Ammonia Storage Materials

    DEFF Research Database (Denmark)

    Jensen, Peter Bjerre; Lysgaard, Steen; Vegge, Tejs

    Metal halide ammines, e.g. Mg(NH3)6Cl2 and Sr(NH3)8Cl2, can reversibly store ammonia, with high volumetric hydrogen storage capacities. The storage in the halide ammines is very safe, and the salts are therefore highly relevant as a carbon-free energy carrier in future transportation infrastructure....... In this project we are searching for improved mixed materials with optimal desorption temperatures and kinetics, optimally releasing all ammonia in one step. We apply Density Functional Theory, DFT, calculations on mixed compounds selected by a Genetic Algorithm (GA), relying on biological principles of natural...

  7. Electrochemical ammonia production on molybdenum nitride nanoclusters

    DEFF Research Database (Denmark)

    Howalt, Jakob Geelmuyden; Vegge, Tejs

    2013-01-01

    Theoretical investigations of electrochemical production of ammonia at ambient temperature and pressure on nitrogen covered molybdenum nanoparticles are presented. Density functional theory calculations are used in combination with the computational hydrogen electrode approach to calculate the free...... energy profile for electrochemical protonation of N2 and N adatoms on cuboctahedral Mo13 nanoparticles. Pathways for electrochemical ammonia production via direct protonation of N adatoms and N2 admolecules with an onset potential as low as -0.5 V and generally lower than -0.8 V on both a nitrogen...

  8. The Effect of Catalyst Support on the Decomposition of Methane to Hydrogen and Carbon

    Directory of Open Access Journals (Sweden)

    Sharif Hussein Sharif Zein Abdul Rahman Mohamed

    2012-10-01

    Full Text Available Decomposition of methane into carbon and hydrogen over Cu/Ni supported catalysts was investigated. The catalytic activities and the lifetimes of the catalysts were studied. Cu/Ni supported on TiO2 showed high activity and long lifetime for the reaction. Transmission electron microscopy (TEM studies revealed the relationship between the catalyst activity and the formation of the filamentous carbon over the catalyst after methane decomposition. While different types of filamentous carbon formed on the various Cu/Ni supported catalysts, an attractive carbon nanotubes was observed in the Cu/Ni supported on TiO2. Key Words:  Methane decomposition, carbon nanotube, Cu/Ni supported catalysts.

  9. Anatase-brookite mixed phase nano TiO2 catalyzed homolytic decomposition of ammonium nitrate.

    Science.gov (United States)

    Vargeese, Anuj A; Muralidharan, Krishnamurthi

    2011-09-15

    Compared to the conventional ammonium perchlorate based solid rocket propellants, burning of ammonium nitrate (AN) based propellants produce environmentally innocuous combustion gases. Application of AN as propellant oxidizer is restricted due to low reactivity and low energetics besides its near room temperature polymorphic phase transition. In the present study, anatase-brookite mixed phase TiO(2) nanoparticles (~ 10 nm) are synthesized and used as catalyst to enhance the reactivity of the environmental friendly propellant oxidizer ammonium nitrate. The activation energy required for the decomposition reactions, computed by differential and non-linear integral isoconversional methods are used to establish the catalytic activity. Presumably, the removal of NH(3) and H(2)O, known inhibitors of ammonium nitrate decomposition reaction, due to the surface reactions on active surface of TiO(2) changes the decomposition pathway and thereby the reactivity.

  10. Catalytic ramifications of steam deactivation of Y zeolites: An analysis using 2-methylhexane cracking

    Energy Technology Data Exchange (ETDEWEB)

    Yaluris, G.; Dumesic, J.A. [Univ. of Wisconsin, Madison, WI (United States); Madon, R.J. [Engelhard Corp., Iselin, NJ (United States)

    1999-08-15

    Kinetic analysis of experimental data for 2-methylhexane cracking demonstrates that trends in activity and selectivity are well simulated by adjusting a single parameter that represents the acid strength of a Y-based FCC catalyst. This acid strength may be modified via steam deactivation, and the authors have experimentally corroborated acidity changes using ammonia microcalorimetry and infrared spectroscopy. Increased severity of steam treatment reduces the number and strength of catalyst acid sites, and it leads to a reduction in the turnover frequency of all surface processes and a decrease in overall site time yield. Streaming of the catalyst does not change the fundamental chemistry involved in catalytic cracking. However, change in acidity caused by steaming alters product selectivity by changing relative rates of various catalytic cycles in the cracking process. For example, steam treatment increases olefin selectivity by favoring catalytic cycles that produce olefins.

  11. Ammonia effect on hydrogenotrophic methanogens and syntrophic acetate oxidizing bacteria

    DEFF Research Database (Denmark)

    Wang, Han; Fotidis, Ioannis; Angelidaki, Irini

    2015-01-01

    Ammonia-rich substrates can cause inhibition on anaerobic digestion process. Syntrophic acetate oxidizing bacteria (SAOB) and hydrogenotrophic methanogens are important for the ammonia inhibitory mechanism on anaerobic digestion. The roles and interactions of SAOB and hydrogenotrophic methanogens...

  12. Study of Ammonia Emissions in a Ventilated Pig Pen

    DEFF Research Database (Denmark)

    Rong, Li

    Pig productions cause a wide emission of odors, such as ammonia (NH3), hydrogen sulfide (H2S), and methane (CH4). Ammonia is one of the most important emissions for evaluating the air quality either in animal buildings or atmospheric environment. In studies of ammonia emission from animal buildings...... solution temperatures. The results show that the diffusive ceiling ventilation system can provide a relative low velocity in the pig pen and decrease ammonia emissions from the pig pen, but this ventilation system causes high ammonia concentration distribution in the animal occupied zone. Further, our...... reported in literature, little effort has been made to investigate the accuracy of current Henry’s law constant for modeling ammonia mass transfer process and study ammonia emissions in a full scale pig pen from fluid dynamics by CFD simulations. This will be the main objectives of this study. The ammonia...

  13. Radiation decomposition of alcohols and chloro phenols in micellar systems; Descomposicion por irradiacion de alcoholes y clorofenoles en sistemas micelares

    Energy Technology Data Exchange (ETDEWEB)

    Moreno A, J

    1998-12-31

    The effect of surfactants on the radiation decomposition yield of alcohols and chloro phenols has been studied with gamma doses of 2, 3, and 5 KGy. These compounds were used as typical pollutants in waste water, and the effect of the water solubility, chemical structure, and the nature of the surfactant, anionic or cationic, was studied. The results show that anionic surfactant like sodium dodecylsulfate (SDS), improve the radiation decomposition yield of ortho-chloro phenol, while cationic surfactant like cetyl trimethylammonium chloride (CTAC), improve the radiation decomposition yield of butyl alcohol. A similar behavior is expected for those alcohols with water solubility close to the studied ones. Surfactant concentrations below critical micellar concentration (CMC), inhibited radiation decomposition for both types of alcohols. However radiation decomposition yield increased when surfactant concentrations were bigger than the CMC. Aromatic alcohols decomposition was more marked than for linear alcohols decomposition. On a mixture of alcohols and chloro phenols in aqueous solution the radiation decomposition yield decreased with increasing surfactant concentration. Nevertheless, there were competitive reactions between the alcohols, surfactants dimers, hydroxyl radical and other reactive species formed on water radiolysis, producing a catalytic positive effect in the decomposition of alcohols. Chemical structure and the number of carbons were not important factors in the radiation decomposition. When an alcohol like ortho-chloro phenol contained an additional chlorine atom, the decomposition of this compound was almost constant. In conclusion the micellar effect depend on both, the nature of the surfactant (anionic or cationic) and the chemical structure of the alcohols. The results of this study are useful for wastewater treatment plants based on the oxidant effect of the hydroxyl radical, like in advanced oxidation processes, or in combined treatment such as

  14. HYDROGEN TRANSFER IN CATALYTIC CRACKING

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Hydrogen transfer is an important secondary reaction of catalytic cracking reactions, which affects product yield distribution and product quality. It is an exothermic reaction with low activation energy around 43.3 kJ/mol. Catalyst properties and operation parameters in catalytic cracking greatly influence the hydrogen transfer reaction. Satisfactory results are expected through careful selection of proper catalysts and operation conditions.

  15. Gauss decomposition for quantum groups and duality

    CERN Document Server

    Damaskinsky, E V; Lyakhovsky, V D; Sokolov, M A

    1995-01-01

    The Gauss decomposition of quantum groups and supergroups are considered. The main attention is paid to the R-matrix formulation of the Gauss decomposition and its properties as well as its relation to the contraction procedure. Duality aspects of the Gauss decomposition are also touched. For clarity of exposition a few simple examples are considered in some details.

  16. Modelling of ammonia emissions from dairy cow houses

    OpenAIRE

    Monteny, G.J.

    2000-01-01

    Dairy cow husbandry contributes to environmental acidification through the emission of ammonia. In-depth knowledge on the processes and variable factors that play a role in the emission of ammonia from dairy cow houses benefits the production of emission data, the development of low emission housing systems, and evaluation of emission levels in a farming system approach. A mechanistic simulation model for the ammonia emission from dairy cow houses was developed to facilitate this.An ammonia p...

  17. Ammonia production, excretion, toxicity, and defense in fish: A Review

    Directory of Open Access Journals (Sweden)

    Alex Y K Ip

    2010-10-01

    Full Text Available Many fishes are ammonotelic but some species can detoxify ammonia to glutamine or urea. Certain fish species can accumulate high levels of ammonia in the brain or defense against ammonia toxicity by enhancing the effectiveness of ammonia excretion through active NH4+ transport, manipulation of ambient pH, or reduction in ammonia permeability through the branchial and cutaneous epithelia. Recent reports on ammonia toxicity in mammalian brain reveal the importance of permeation of ammonia through the blood-brain barrier and passages of ammonia and water through transporters in the plasmalemma of brain cells. Additionally, brain ammonia toxicity could be related to the passage of glutamine through the mitochondrial membranes into the mitochondrial matrix. On the other hand, recent reports on ammonia excretion in fish confirm the involvement of Rhesus glycoproteins in the branchial and cutaneous epithelia. Therefore, this review focuses on both the earlier literature and the up-to-date information on the problems and mechanisms concerning the permeation of ammonia, as NH3, NH4+ or proton-neutral nitrogenous compounds, across mitochondrial membranes, the blood-brain barrier, the plasmalemma of neurons, and the branchial and cutaneous epithelia of fish. It also addresses how certain fishes with high ammonia tolerance defend against ammonia toxicity through the regulation of the permeation of ammonia and related nitrogenous compounds through various types of membranes. It is hoped that this review would revive the interests in investigations on the passage of ammonia through the mitochondrial membranes and the blood-brain barrier of ammonotelic fishes and fishes with high brain ammonia-tolerance, respectively.

  18. Detection of Ammonia in Liquids Using Millimeter Wave Spectroscopy

    Directory of Open Access Journals (Sweden)

    Hilmi Ozturk

    2012-01-01

    Full Text Available Detection of ammonia plays a vital role for counter-bioterrorism applications. Using millimeter wave absorption measurements, ammonia dissolved in water solution is analyzed and compared to water-only solution. The inversion of ammonia molecule results in split rotational spectral lines and transitions of these lines can be detected. Two-port measurements were carried out with vector network analyzer and measurements revealed that ammonia presence can be identified, especially between 30–35 GHz.

  19. Catalytic quantum error correction

    CERN Document Server

    Brun, T; Hsieh, M H; Brun, Todd; Devetak, Igor; Hsieh, Min-Hsiu

    2006-01-01

    We develop the theory of entanglement-assisted quantum error correcting (EAQEC) codes, a generalization of the stabilizer formalism to the setting in which the sender and receiver have access to pre-shared entanglement. Conventional stabilizer codes are equivalent to dual-containing symplectic codes. In contrast, EAQEC codes do not require the dual-containing condition, which greatly simplifies their construction. We show how any quaternary classical code can be made into a EAQEC code. In particular, efficient modern codes, like LDPC codes, which attain the Shannon capacity, can be made into EAQEC codes attaining the hashing bound. In a quantum computation setting, EAQEC codes give rise to catalytic quantum codes which maintain a region of inherited noiseless qubits. We also give an alternative construction of EAQEC codes by making classical entanglement assisted codes coherent.

  20. Catalytic pyrolysis-gc/ms of spirulina: evaluation of a highly proteinaceous biomass source for production of fuels and chemicals

    Science.gov (United States)

    Pyrolysis of microalgae offers a pathway towards the production of compounds derived from the thermal decomposition of triglycerides, proteins as well as lignocelluloses and their combinations thereof. When catalytically induced, this could lead to the production of fuels and chemicals including aro...

  1. Nonlinear mode decomposition: a noise-robust, adaptive decomposition method.

    Science.gov (United States)

    Iatsenko, Dmytro; McClintock, Peter V E; Stefanovska, Aneta

    2015-09-01

    The signals emanating from complex systems are usually composed of a mixture of different oscillations which, for a reliable analysis, should be separated from each other and from the inevitable background of noise. Here we introduce an adaptive decomposition tool-nonlinear mode decomposition (NMD)-which decomposes a given signal into a set of physically meaningful oscillations for any wave form, simultaneously removing the noise. NMD is based on the powerful combination of time-frequency analysis techniques-which, together with the adaptive choice of their parameters, make it extremely noise robust-and surrogate data tests used to identify interdependent oscillations and to distinguish deterministic from random activity. We illustrate the application of NMD to both simulated and real signals and demonstrate its qualitative and quantitative superiority over other approaches, such as (ensemble) empirical mode decomposition, Karhunen-Loève expansion, and independent component analysis. We point out that NMD is likely to be applicable and useful in many different areas of research, such as geophysics, finance, and the life sciences. The necessary matlab codes for running NMD are freely available for download.

  2. Nonlinear mode decomposition: A noise-robust, adaptive decomposition method

    Science.gov (United States)

    Iatsenko, Dmytro; McClintock, Peter V. E.; Stefanovska, Aneta

    2015-09-01

    The signals emanating from complex systems are usually composed of a mixture of different oscillations which, for a reliable analysis, should be separated from each other and from the inevitable background of noise. Here we introduce an adaptive decomposition tool—nonlinear mode decomposition (NMD)—which decomposes a given signal into a set of physically meaningful oscillations for any wave form, simultaneously removing the noise. NMD is based on the powerful combination of time-frequency analysis techniques—which, together with the adaptive choice of their parameters, make it extremely noise robust—and surrogate data tests used to identify interdependent oscillations and to distinguish deterministic from random activity. We illustrate the application of NMD to both simulated and real signals and demonstrate its qualitative and quantitative superiority over other approaches, such as (ensemble) empirical mode decomposition, Karhunen-Loève expansion, and independent component analysis. We point out that NMD is likely to be applicable and useful in many different areas of research, such as geophysics, finance, and the life sciences. The necessary matlab codes for running NMD are freely available for download.

  3. Catalytic Combustion of Gasified Waste

    Energy Technology Data Exchange (ETDEWEB)

    Kusar, Henrik

    2003-09-01

    This thesis concerns catalytic combustion for gas turbine application using a low heating-value (LHV) gas, derived from gasified waste. The main research in catalytic combustion focuses on methane as fuel, but an increasing interest is directed towards catalytic combustion of LHV fuels. This thesis shows that it is possible to catalytically combust a LHV gas and to oxidize fuel-bound nitrogen (NH{sub 3}) directly into N{sub 2} without forming NO{sub x} The first part of the thesis gives a background to the system. It defines waste, shortly describes gasification and more thoroughly catalytic combustion. The second part of the present thesis, paper I, concerns the development and testing of potential catalysts for catalytic combustion of LHV gases. The objective of this work was to investigate the possibility to use a stable metal oxide instead of noble metals as ignition catalyst and at the same time reduce the formation of NO{sub x} In paper II pilot-scale tests were carried out to prove the potential of catalytic combustion using real gasified waste and to compare with the results obtained in laboratory scale using a synthetic gas simulating gasified waste. In paper III, selective catalytic oxidation for decreasing the NO{sub x} formation from fuel-bound nitrogen was examined using two different approaches: fuel-lean and fuel-rich conditions. Finally, the last part of the thesis deals with deactivation of catalysts. The various deactivation processes which may affect high-temperature catalytic combustion are reviewed in paper IV. In paper V the poisoning effect of low amounts of sulfur was studied; various metal oxides as well as supported palladium and platinum catalysts were used as catalysts for combustion of a synthetic gas. In conclusion, with the results obtained in this thesis it would be possible to compose a working catalytic system for gas turbine application using a LHV gas.

  4. Comparison of ammonia emissions determined using different sampling methods

    Science.gov (United States)

    Dynamic, flow-through flux chambers are sometimes used to estimate ammonia emissions from livestock operations; however, ammonia emissions from the surfaces are affected by many factors which can be affected by the chamber. Ammonia emissions estimated using environmental flow-through chambers may be...

  5. The Ammonia Smoke Fountain: An Interesting Thermodynamic Adventure.

    Science.gov (United States)

    Alexander, M. Dale

    1999-01-01

    Describes a new demonstration that uses an apparatus like the ammonia-fountain apparatus but with modifications designed to produce ammonium-chloride smoke. This demonstration is easy to perform, interesting to observe, and allows demonstration of the solubility of ammonia in water, the basic nature of ammonia, the acidic nature of hydrogen…

  6. Cerebral ammonia uptake and accumulation during prolonged exercise in humans

    DEFF Research Database (Denmark)

    Nybo, Lars; Dalsgaard, Mads K.; Steensberg, Adam

    2005-01-01

    We evaluated whether peripheral ammonia production during prolonged exercise enhances the uptake and subsequent accumulation of ammonia within the brain. Two studies determined the cerebral uptake of ammonia (arterial and jugular venous blood sampling combined with Kety-Schmidt-determined cerebra...

  7. Werkwijze voor het behandelen van ammonia-houdend afvalwater

    NARCIS (Netherlands)

    Loosdrecht, M.C.M.; Jetten, M.S.M.

    1998-01-01

    Treatment of ammonia-comprising waste water comprises: (a) subjecting the waste water to a nitrification treatment using a nitrifying microorganism and adding oxygen, to give a solution comprising an oxidation product of ammonia, and (b) converting the oxidation product of ammonia into nitrogen usin

  8. Catalytic hydrolysis of CFC-12 over solid acid Ti(SO4)2

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The catalytic hydrolysis of dichlorodifluoromethane (CFC-12) was investigated over solid acid Ti(SO4)2. The catalytic activity decreased with the calcination temperature. When space velocity was 6 l h-1 g-cat-1, the CFC-12 conversion at 310oC over Ti(SO4)2 calcined at 350oC remained about 98.5% during 360 h on stream, and the selectivity to by-products remained zero. The findings enlarged the scope of traditional catalyst systems for the CFCs decomposition.

  9. Treatment of nickel-ammonia complex ion-containing ammonia nitrogen wastewater

    Institute of Scientific and Technical Information of China (English)

    MIN Xiao-bo; ZHOU Min; CHAI Li-yuan; WANG Yun-yan; SHU Yu-de

    2009-01-01

    Air stripping was adopted to treat nickel ammonia complex ion-containing wastewater in order to remove nickel and ammonia simultaneously in one technological process. The relationship among pH, the concentration of nickel ammonia complex ion and total ammonia concentration was analyzed theoretically. Influence of pH value, water temperature, airflow rate and time on air stripping was studied in detail by static experiment in laboratory. The results show that at pH 11, temperature of 60 ℃ and airflow rate of 0.12 m~3/h, NH_3 and Ni~(2+) concentrations remained in wastewater are less than 2 and 0.2 mg/L, respectively, after blowing for 75 min, which reaches the standard of the state discharge. When the tail gas is absorbed by 0.5 mol/L H_2SO_4 in order to avoid the secondary pollution, the absorption rate can achieve 70%.

  10. Ammonia tolerant enriched methanogenic cultures as bioaugmentation inocula to alleviate ammonia inhibition in continuous anaerobic reactors

    DEFF Research Database (Denmark)

    Fotidis, Ioannis; Wang, Han; Angelidaki, Irini

    tolerant methanogenic culture as potential bioaugmentation inoculum in a continuous stirred tank reactor (CSTR) operating under “inhibited steady-state”, triggered by high ammonia levels (5 g NH4+-N L-1). The results of the current study established for the first time that bioaugmentation of an enriched...... ammonia tolerant methanogen in a CSTR reactor could completely alleviate the ammonia inhibitory effect. Furthermore, it was found that bioaugmentation with the enriched culture resulted in 25% higher methane production compared to when the bioaugmentation was achieved with pure methanogenic strains....... The bioaugmentation was performed without pausing the continuous operation of the CSTR reactor and without excluding the ammonia-rich substrate from the feedstock. Thus, bioaugmentation with mixed methanogenic cultures could potentially support the development of an efficient and cost-effective biomethanation process...

  11. Adsorption of Ammonia on Regenerable Carbon Sorbents

    Science.gov (United States)

    Wójtowicz, Marek A.; Cosgrove, Jesph E.; Serio, Michael A..; Wilburn, Monique

    2015-01-01

    Results are presented on the development of reversible sorbents for the combined carbon dioxide, moisture, and trace-contaminant (TC) removal for use in Extravehicular Activities (EVAs), and more specifically in the Primary Life Support System (PLSS). The currently available life support systems use separate units for carbon dioxide, trace contaminants, and moisture control, and the long-term objective is to replace the above three modules with a single one. Data on sorption and desorption of ammonia, which is a major TC of concern, are presented in this paper. The current TC-control technology involves the use of a packed bed of acid-impregnated granular charcoal, which is non-regenerable, and the carbon-based sorbent under development in this project can be regenerated by exposure to vacuum at room temperature. In this study, several carbon sorbents were fabricated and tested for ammonia sorption. Ammonia-sorption capacity was related to carbon pore structure characteristics, and the temperature of oxidative carbon-surface treatment was optimized for enhanced ammonia-sorption performance.

  12. USDA-EPA Collaborative Ammonia Research

    Science.gov (United States)

    In 2014, a work group was formed between USDA and EPA to facilitate information exchange on ammonia emissions from agriculture, air quality impacts and emission mitigation options and to identify opportunities for collaboration. This document provides background on the work grou...

  13. Ammonia synthesis from first principles calculations

    DEFF Research Database (Denmark)

    Honkala, Johanna Karoliina; Hellman, Anders; Remediakis, Ioannis

    2005-01-01

    The rate of ammonia synthesis over a nanoparticle ruthenium catalyst can be calculated directly on the basis of a quantum chemical treatment of the problem using density functional theory. We compared the results to measured rates over a ruthenium catalyst supported on magnesium aluminum spinet...

  14. Diversity and abundance of ammonia-oxidizing

    NARCIS (Netherlands)

    Cardoso, J.F.M.F.; van Bleijswijk, J.D.L.; Witte, H.; van Duyl, F.C.

    2013-01-01

    We analysed the diversity and abundance of ammonia-oxidizing Archaea (AOA) and Bacteria (AOB) in the shallow warm-water sponge Halisarca caerulea and the deep cold-water sponges Higginsia thielei and Nodastrella nodastrella. The abundance of AOA and AOB was analysed using catalyzed reporter depositi

  15. Radiation Chemistry in Ammonia-Water Ices

    Science.gov (United States)

    Loeffler, M. J.; Raut, U.; Baragiola, R. A.

    2010-01-01

    We studied the effects of 100 keV proton irradiation on films of ammonia-water mixtures between 20 and 120 K. Irradiation destroys ammonia, leading to the formation and trapping of H2, N2 NO, and N2O, the formation of cavities containing radiolytic gases, and ejection of molecules by sputtering. Using infrared spectroscopy, we show that at all temperatures the destruction of ammonia is substantial, but at higher temperatures (120 K), it is nearly complete (approximately 97% destroyed) after a fluence of 10(exp 16) ions per square centimeter. Using mass spectroscopy and microbalance gravimetry, we measure the sputtering yield of our sample and the main components of the sputtered flux. We find that the sputtering yield depends on fluence. At low temperatures, the yield is very low initially and increases quadratically with fluence, while at 120 K the yield is constant and higher initially. The increase in the sputtering yield with fluence is explained by the formation and trapping of the ammonia decay products, N2 and H2 which are seen to be ejected from the ice at all temperatures.

  16. Footprints on Ammonia Concentrations from Environmental Regulations

    DEFF Research Database (Denmark)

    Skjøth, Carsten Ambelas; Ellermann, Thomas; Hertel, Ole

    2008-01-01

    Releases of ammonia (NH3) to the atmosphere contribute significantly to the desposition of nitrogen to both terrestrial and aquatic ecosystems. This is the background for the national NH3 emission ceilings in Europe. However, in some countries the national legislation aims not only to meet theese...

  17. Fiber Optic Detection of Ammonia Gas

    Directory of Open Access Journals (Sweden)

    L. Kalvoda

    2006-01-01

    Full Text Available Bathochromic shifts accompanying the formation of several bivalent metallic complexes containing 5-(4’-dimethylaminophenylimino quinolin-8-one (L1, and 7-chlore-5(4’-diethylamino-2-methylphenylimino quinolin-8-one (L2 ligands in ethanol solutions were evaluated by VIS-NIR spectroscopy. The [L1-Cu-L1] sulphide complex was selected as a reagent for further tests on optical fibres. Samples of multimode siloxane-clad fused-silica fibre were sensitized by diffusing an ethanol/chloroform solution of the dye into the cladding polymer, and tested by VIS-NIR optical spectroscopy (12 cm long fibre sections, and optical time domain reflectometry (OTDR; 20 ns laser pulses, wavelength 850 nm, 120 m long fibre sensitized within the interval 104–110 m. A well-resolved absorption band of the reagent could be identified in the absorption spectra of the fibres. After exposure to dry ammonia/nitrogen gas with increasing ammonia concentration (0–4000 ppm, the short fibre samples showed subsequent decay of NIR optical absorption; saturation was observed for higher ammonia levels. The concentration resolution r ? 50 ppm and forward response time t90 ? 30 sec were obtained within the interval 0–1000 ppm. The OTDR courses showed an enhancement of the back-scattered light intensity coming from the sensitized region after diffusion of the initial reagent, and decay after exposure to concentrated ammonia/nitrogen gas (10000 ppm.

  18. Serine-202 is the putative precursor of the active site dehydroalanine of phenylalanine ammonia lyase. Site-directed mutagenesis studies on the enzyme from parsley (Petroselinum crispum L.).

    Science.gov (United States)

    Schuster, B; Rétey, J

    1994-08-01

    To investigate the possible role of serine as a precursor of dehydroalanine at the active site of phenylalanine ammonia lyase, two serines, conserved in all known PAL and histidase sequences, were changed to alanine by site-directed mutagenesis. The resulting mutant genes were subcloned into the expression vector pT7.7 and the gene products were assayed for PAL activity. Mutant PALMutS209A showed the same catalytic property as wild-type PAL, whereas mutant PALMutS202A was devoid of catalytic activity, indicating that serine-202 is the most likely precursor of the active site dehydroalanine.

  19. Regulation of the intersubunit ammonia tunnel in Mycobacterium tuberculosis glutamine-dependent NAD[superscript +] synthetase

    Energy Technology Data Exchange (ETDEWEB)

    Chuenchor, Watchalee; Doukov, Tzanko I.; Resto, Melissa; Chang, Andrew; Gerratana, Barbara (SSRL); (Maryland)

    2012-08-31

    Glutamine-dependent NAD{sup +} synthetase is an essential enzyme and a validated drug target in Mycobacterium tuberculosis (mtuNadE). It catalyses the ATP-dependent formation of NAD{sup +} from NaAD{sup +} (nicotinic acid-adenine dinucleotide) at the synthetase active site and glutamine hydrolysis at the glutaminase active site. An ammonia tunnel 40 {angstrom} (1 {angstrom} = 0.1 nm) long allows transfer of ammonia from one active site to the other. The enzyme displays stringent kinetic synergism; however, its regulatory mechanism is unclear. In the present paper, we report the structures of the inactive glutaminase C176A variant in an apo form and in three synthetase-ligand complexes with substrates (NaAD{sup +}/ATP), substrate analogue {l_brace}NaAD{sup +}/AMP-CPP (adenosine 5'-[{alpha},{beta}-methylene]triphosphate){r_brace} and intermediate analogues (NaAD{sup +}/AMP/PPi), as well as the structure of wild-type mtuNadE in a product complex (NAD{sup +}/AMP/PPi/glutamate). This series of structures provides snapshots of the ammonia tunnel during the catalytic cycle supported also by kinetics and mutagenesis studies. Three major constriction sites are observed in the tunnel: (i) at the entrance near the glutaminase active site; (ii) in the middle of the tunnel; and (iii) at the end near the synthetase active site. Variation in the number and radius of the tunnel constrictions is apparent in the crystal structures and is related to ligand binding at the synthetase domain. These results provide new insight into the regulation of ammonia transport in the intermolecular tunnel of mtuNadE.

  20. 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

    are required in the reduction, and, nally, oxidation by NO + O2 or NO2 leads to the same state of the catalyst. These points are shown experimentally for a Cu-CHA catalyst, by combining in situ X-ray absorption spectrosocpy (XAS), electron paramagnetic resonance (EPR), and Fourier transform infrared...

  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......)-TPD. Due to the high-surface area anatase particles, loading of 20 wt% vanadia could be obtained without exceeding monolayer coverage of V(2)O(5). This resulted in unprecedented high deNO(x) SCR activity corresponding to a factor of two compared to an industrial reference and to other V(2)O(5)/TiO(2...

  2. Variance decomposition in stochastic simulators

    KAUST Repository

    Le Maître, O. P.

    2015-06-28

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  3. Variance decomposition in stochastic simulators

    Science.gov (United States)

    Le Maître, O. P.; Knio, O. M.; Moraes, A.

    2015-06-01

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  4. Variance decomposition in stochastic simulators.

    Science.gov (United States)

    Le Maître, O P; Knio, O M; Moraes, A

    2015-06-28

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  5. AMMONIA CONCENTRATION IN SALTSTONE HEADSPACE SUMMARY REPORT

    Energy Technology Data Exchange (ETDEWEB)

    Zamecnik, J; Alex Cozzi, A

    2008-09-26

    The Saltstone Facility Documented Safety Analysis (DSA) is under revision to accommodate changes in the Composite Lower Flammability Limit (CLFL) from the introduction of Isopar into Tank 50. Saltstone samples were prepared with an 'MCU' type salt solution spiked with ammonia. The ammonia released from the saltstone was captured and analyzed. The ammonia concentration found in the headspace of samples maintained at 95 C and 1 atm was, to 95% confidence, less than or equal to 3.9 mg/L. Tank 50 is fed by several influent streams. The salt solution from Tank 50 is pumped to the salt feed tank (SFT) in the Saltstone Production Facility (SPF). The premix materials cement, slag and fly ash are blended together prior to transfer to the grout mixer. The premix is fed to the grout mixer in the SPF and the salt solution is incorporated into the premix in the grout mixer, yielding saltstone slurry. The saltstone slurry drops into a hopper and then is pumped to the vault. The Saltstone Facility Documented Safety Analysis (DSA) is under revision to accommodate changes in the Composite Lower Flammability Limit (CLFL) from the introduction of Isopar{reg_sign} L into Tank 50. Waste Solidification-Engineering requested that the Savannah River National Laboratory (SRNL) perform testing to characterize the release of ammonia in curing saltstone at 95 C. The test temperature represents the maximum allowable temperature in the Saltstone Disposal Facility (SDF). Ammonia may be present in the salt solution and premix materials, or may be produced by chemical reactions when the premix and salt solution are combined. A final report (SRNS-STI-2008-00120, Rev. 0) will be issued that will cover in more depth the information presented in this report.

  6. Ammonia downstream from HH 80 North

    Science.gov (United States)

    Girart, Jose M.; Rodriguez, Luis F.; Anglada, Guillem; Estalella, Robert; Torrelles, Jose, M.; Marti, Josep; Pena, Miriam; Ayala, Sandra; Curiel, Salvador; Noriega-Crespo, Alberto

    1994-01-01

    HH 80-81 are two optically visible Herbig-Haro (HH) objects located about 5 minutes south of their exciting source IRAS 18162-2048. Displaced symmetrically to the north of this luminous IRAS source, a possible HH counterpart was recently detected as a radio continuum source with the very large array (VLA). This radio source, HH 80 North, has been proposed to be a member of the Herbig-Haro class since its centimeter flux density, angular size, spectral index, and morphology are all similar to those of HH 80. However, no object has been detected at optical wavelengths at the position of HH 80 North, possibly because of high extinction, and the confirmation of the radio continuum source as an HH object has not been possible. In the prototypical Herbig-Haro objects HH 1 and 2, ammonia emission has been detected downstream of the flow in both objects. This detection has been intepreted as a result of an enhancement in the ammonia emission produced by the radiation field of the shock associated with the HH object. In this Letter we report the detection of the (1,1) and (2,2) inversion transitions of ammonia downstream HH 80 North. This detection gives strong suppport to the interpretation of HH 80 North as a heavily obscured HH object. In addition, we suggest that ammonia emission may be a tracer of embedded Herbig-Haro objects in other regions of star formation. A 60 micrometer IRAS source could be associated with HH 80 North and with the ammonia condensation. A tentative explanation for the far-infrared emission as arising in dust heated by their optical and UV radiation of the HH object is presented.

  7. Effect of Activated Carbon as a Support on Metal Dispersion and Activity of Ruthenium Catalyst for Ammonia Synthesis

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Ten kinds of activated carbon from different raw materials were used as supports to prepare ruthenium catalysts. N2 physisorption and CO chemisorption were carried out to investigate the pore size distribution and the ruthenium dispersion of the catalysts. It was found that the Ru dispersion of the catalyst was closely related to not only the texture of carbon support but also the purity of activated carbon. The activities of a series of the carbon-supported barium-promoted Ru catalysts for ammonia synthesis were measured at 425 ℃, 10.0 MPa and 10 000 h-1. The result shows that the same raw material activated carbon, with a high purity, high surface area, large pore volume and reasonable pore size distribution might disperse ruthenium and promoter sufficiently, which activated carbon as support, could be used to manufacture ruthenium catalyst with a high activity for ammonia synthesis. The different raw material activated carbon as the support would greatly influence the catalytic properties of the ruthenium catalyst for ammonia synthesis. For example, with coconut shell carbon(AC1) as the support, the ammonia concentration in the effluent was 13.17% over 4%Ru-BaO/AC1 catalyst, while with the desulfurized coal carbon(AC10) as the support, that in the effluent was only 1.37% over 4%Ru-BaO/AC10 catalyst.

  8. Ammonia and ammonium hydroxide sensors for ammonia/water absorption machines: Literature review and data compilation

    Science.gov (United States)

    Anheier, N. C., Jr.; McDonald, C. E.; Cuta, J. M.; Cuta, F. M.; Olsen, K. B.

    1995-05-01

    This report describes an evaluation of various sensing techniques for determining the ammonia concentration in the working fluid of ammonia/water absorption cycle systems. The purpose was to determine if any existing sensor technology or instrumentation could provide an accurate, reliable, and cost-effective continuous measure of ammonia concentration in water. The resulting information will be used for design optimization and cycle control in an ammonia-absorption heat pump. Pacific Northwest Laboratory (PNL) researchers evaluated each sensing technology against a set of general requirements characterizing the potential operating conditions within the absorption cycle. The criteria included the physical constraints for in situ operation, sensor characteristics, and sensor application. PNL performed an extensive literature search, which uncovered several promising sensing technologies that might be applicable to this problem. Sixty-two references were investigated, and 33 commercial vendors were identified as having ammonia sensors. The technologies for ammonia sensing are acoustic wave, refractive index, electrode, thermal, ion-selective field-effect transistor (ISFET), electrical conductivity, pH/colormetric, and optical absorption. Based on information acquired in the literature search, PNL recommends that follow-on activities focus on ISFET devices and a fiber optic evanescent sensor with a colormetric indicator. The ISFET and fiber optic evanescent sensor are inherently microminiature and capable of in situ measurements. Further, both techniques have been demonstrated selective to the ammonium ion (NH4(+)). The primary issue remaining is how to make the sensors sufficiently corrosion-resistant to be useful in practice.

  9. Ammonia and ammonium hydroxide sensors for ammonia/water absorption machines: Literature review and data compilation

    Energy Technology Data Exchange (ETDEWEB)

    Anheier, N.C. Jr.; McDonald, C.E.; Cuta, J.M.; Cuta, F.M.; Olsen, K.B.

    1995-05-01

    This report describes an evaluation of various sensing techniques for determining the ammonia concentration in the working fluid of ammonia/water absorption cycle systems. The purpose of this work was to determine if any existing sensor technology or instrumentation could provide an accurate, reliable, and cost-effective continuous measure of ammonia concentration in water. The resulting information will be used for design optimization and cycle control in an ammonia-absorption heat pump. PNL researchers evaluated each sensing technology against a set of general requirements characterizing the potential operating conditions within the absorption cycle. The criteria included the physical constraints for in situ operation, sensor characteristics, and sensor application. PNL performed an extensive literature search, which uncovered several promising sensing technologies that might be applicable to this problem. Sixty-two references were investigated, and 33 commercial vendors were identified as having ammonia sensors. The technologies for ammonia sensing are acoustic wave, refractive index, electrode, thermal, ion-selective field-effect transistor (ISFET), electrical conductivity, pH/colormetric, and optical absorption. Based on information acquired in the literature search, PNL recommends that follow-on activities focus on ISFET devices and a fiber optic evanescent sensor with a colormetric indicator. The ISFET and fiber optic evanescent sensor are inherently microminiature and capable of in situ measurements. Further, both techniques have been demonstrated selective to the ammonium ion (NH{sub 4}{sup +}). The primary issue remaining is how to make the sensors sufficiently corrosion-resistant to be useful in practice.

  10. Thermal and catalytic cracking of ethylene in presence of CaO, MgO, zeolite and calcined dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Taralas, G.; Sjoestroem, K.; Jaeraas, S.; Bjoernbom, E. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemical Technology

    1993-12-31

    The subject of the present work is to study the effect of catalysts such as calcined dolomite (CaO.MgO), CaO (quicklime), MgO and Zeolite (EKZ-4) on the cracking of ethylene in the presence and absence of steam. N-heptane, toluene, naphthalene, thiophene have been some suitable model compounds for studies of the thermal and catalytic decomposition of tar. Previous results showed that the reaction scheme of the thermal decomposition of n-heptane was consistent with the high yield of ethylene observed in thermal decomposition of n-heptane. The effect of the reactor wall and the ferric impurities in the dolomite are also subjects of the research in this study. The results may also throw some additional light on the nature of the gas-phase thermal and catalytic reactions occurring in the use of dolomite as tar cracking catalysts. 28 refs

  11. Thermal decomposition of natural dolomite

    Indian Academy of Sciences (India)

    S Gunasekaran; G Anbalagan

    2007-08-01

    Thermal decomposition behaviour of dolomite sample has been studied by thermogravimetric (TG) measurements. Differential thermal analysis (DTA) curve of dolomite shows two peaks at 777.8°C and 834°C. The two endothermic peaks observed in dolomite are essentially due to decarbonation of dolomite and calcite, respectively. The TG data of the decomposition steps have also been analysed using various differential, difference-differential and integral methods, viz. Freeman–Carroll, Horowitz–Metzger, Coats–Redfern methods. Values of activation entropy, Arrhenius factor, and order of reaction have been approximated and compared. Measured activation energies vary between 97 and 147 kJ mol-1. The large fluctuation in activation energy is attributed to the presence of impurities such as SiO2, Al2O3, Fe2O3, Cl- etc in the samples. FTIR and XRD analyses confirm the decomposition reaction. SEM observation of the heat-treated samples at 950°C shows cluster of grains, indicating the structural transformation.

  12. A Lagrangian Dynamic Mode Decomposition

    CERN Document Server

    Sesterhenn, Jörn

    2016-01-01

    Temporal or spatial structures are readily extracted from complex data by modal decompositions like POD or DMD. Subspaces of that decompositions serve as reduced order models and define spatial structures in time or temporal structures in space. Convecting phenomena pose a major problem to those decompositions. A structure travelling with a certain group velocity will be perceived as a plethora of modes in time or space respectively. This manifests itself for example in poorly decaying Singular Values when using a POD. The poor decay is very counter-intuitive, since we expect a single structure to be represented by a few modes. The intuition proves to be correct and we show that in a properly chosen reference frame along the characteristic defined by the group velocity, a POD or DMD reduces moving structures to a few modes, as expected. Beyond serving as a reduced model, the re- sulting entity can be used to define a constant or minimally changing structure in turbulent flows. This can be interpreted as an em...

  13. The thermal decomposition of nitrocellulose

    Energy Technology Data Exchange (ETDEWEB)

    Jones, D. E. G.; Turcotte, R.; Acheson, B.; Kwok, Q. S. M.; Vachon, M. [Natural Resources Canada, CANMET Canadian Explosives Research Laboratory, Ottawa, ON (Canada)

    2003-03-01

    In the past, the thermal decomposition of nitrocellulose, the main high-energy component of explosives and solid rocket propellant compositions, was studied using DSC, thermogravimetry and accelerating rate calorimetry. This paper discusses new results obtained by accelerating rate calorimetry (ARC), heat flux calorimetry (HFC), simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) coupled to FTIR and mass spectrometry (MS). Experiments with ARC showed that both the onset temperature and the activation energy for the thermal decomposition depend on sample mass. Evaluating the thermal decomposition of nitrocellulose using HFC at various pressures of argon between ambient and 27 MPa showed that the true onset temperature and the width of the corresponding exotherms are a strong function of the initial pressure. Also presented are the results of investigations conducted using TG-DTA-FTIR-MS in air and in helium. Corresponding to the sharp exotherm observed in helium, many gaseous product species were detected in a narrow band in FTIR and MS spectra. The main species observed by FTIR were carbon dioxide, formic acid, carbon monoxide and trace amounts of formaldehyde, nitrous oxide and water. In comparison, the products detected in air were found to occur in a much wider temperature range. Absorbances of carbon dioxide, nitrogen dioxide and water were observed to have been strongly enhanced in air, while organic species such as formic acid and formaldehyde were significantly depressed. 13 refs., 1 tab., 8 figs.

  14. 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. Quarterly report No. 3, January--March 1991

    Energy Technology Data Exchange (ETDEWEB)

    1991-07-01

    The objective of this project is to demonstrate and evaluate commercially available Selective Catalytic Reduction (SCR) catalysts from US, Japanese and European catalyst suppliers on a high-sulfur US coal-fired boiler. SCR is a post-combustion nitrogen oxide (NOx) 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 NOx to convert it to nitrogen and water vapor.

  15. 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

    Energy Technology Data Exchange (ETDEWEB)

    1991-07-01

    The objective of this project is to demonstrate and evaluate commercially available Selective Catalytic Reduction (SCR) catalysts from US, Japanese and European catalyst suppliers on a high-sulfur US coal-fired boiler. SCR is a post-combustion nitrogen oxide (NOx) 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 NOx to convert it to nitrogen and water vapor.

  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. Technical progress report, third and fourth quarters 1995

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-05-01

    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{sub x}) 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{sub x} to convert it to nitrogen and water vapor.

  17. 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

    Energy Technology Data Exchange (ETDEWEB)

    1991-02-01

    The objective of this project is to demonstrate and evaluate commercially available Selective Catalytic Reduction (SCR) catalysts from US, Japanese and European catalyst suppliers on a high-sulfur US coal-fired boiler. SCR is a post-combustion nitrogen oxide NO{sub x} 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{sub x} to convert it to nitrogen and water vapor.

  18. Innovative Clean Coal Technology (ICCT): Demonstration of Selective Catalytic Reduction (SCR) technology for the control of nitrogen oxide (NO{sub x}) emissions from high-sulfur coal-fired boilers. Quarterly report No. 2, October--December 1990

    Energy Technology Data Exchange (ETDEWEB)

    1991-02-01

    The objective of this project is to demonstrate and evaluate commercially available Selective Catalytic Reduction (SCR) catalysts from US, Japanese and European catalyst suppliers on a high-sulfur US coal-fired boiler. SCR is a post-combustion nitrogen oxide NO{sub x} 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{sub x} to convert it to nitrogen and water vapor.

  19. Catalytic production of biodiesel

    Energy Technology Data Exchange (ETDEWEB)

    Theilgaard Madsen, A.

    2011-07-01

    The focus of this thesis is the catalytic production of diesel from biomass, especially emphasising catalytic conversion of waste vegetable oils and fats. In chapter 1 an introduction to biofuels and a review on different catalytic methods for diesel production from biomass is given. Two of these methods have been used industrially for a number of years already, namely the transesterification (and esterification) of oils and fats with methanol to form fatty acid methyl esters (FAME), and the hydrodeoxygenation (HDO) of fats and oils to form straight-chain alkanes. Other possible routes to diesel include upgrading and deoxygenation of pyrolysis oils or aqueous sludge wastes, condensations and reductions of sugars in aqueous phase (aqueous-phase reforming, APR) for monofunctional hydrocarbons, and gasification of any type of biomass followed by Fischer-Tropsch-synthesis for alkane biofuels. These methods have not yet been industrialised, but may be more promising due to the larger abundance of their potential feedstocks, especially waste feedstocks. Chapter 2 deals with formation of FAME from waste fats and oils. A range of acidic catalysts were tested in a model fat mixture of methanol, lauric acid and trioctanoin. Sulphonic acid-functionalised ionic liquids showed extremely fast convertion of lauric acid to methyl laurate, and trioctanoate was converted to methyl octanoate within 24 h. A catalyst based on a sulphonated carbon-matrix made by pyrolysing (or carbonising) carbohydrates, so-called sulphonated pyrolysed sucrose (SPS), was optimised further. No systematic dependency on pyrolysis and sulphonation conditions could be obtained, however, with respect to esterification activity, but high activity was obtained in the model fat mixture. SPS impregnated on opel-cell Al{sub 2}O{sub 3} and microporous SiO{sub 2} (ISPS) was much less active in the esterification than the original SPS powder due to low loading and thereby low number of strongly acidic sites on the

  20. The effect of microwave-assisted for photo-catalytic reaction in aqueous nano TiO2 particles dispersions.

    Science.gov (United States)

    Chae, Jeong-Seok; Chung, Minchul; Ahn, Ho-Geun; Jung, Sang-Chul

    2010-05-01

    In this study, the photo-catalytic degradation of methylene blue in TiO2 particles-dispersed aqueous solution was carried out by irradiating microwave and UV light simultaneously. The results of photocatalytic degradation of methylene blue showed that the decomposition rate increased with the microwave intensity, UV intensity, TiO2 particle dosages and the circulating fluid velocity. From the result of microwave-assisted photo-catalytic degradation of methylene blue, decomposition rate were shown gradually increased according to the increase of pH. The photo-catalytic degradation rate constant obtained under simultaneous irradiation of microwave and UV light case was about 1.5 times higher than irradiation of UV light only case. This result suggests that there is a synergy effect when the constituent techniques are applied together and that the additional irradiation of microwave can play a very important role in photo-catalysis of organic water pollutants.

  1. Catalytic Hydrothermal Gasification

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, Douglas C.

    2015-05-31

    The term “hydrothermal” used here refers to the processing of biomass in water slurries at elevated temperature and pressure to facilitate the chemical conversion of the organic structures in biomass into useful fuels. The process is meant to provide a means for treating wet biomass materials without drying and to access ionic reaction conditions by maintaining a liquid water processing medium. Typical hydrothermal processing conditions are 523-647K of temperature and operating pressures from 4-22 MPa of pressure. The temperature is sufficient to initiate pyrolytic mechanisms in the biopolymers while the pressure is sufficient to maintain a liquid water processing phase. Hydrothermal gasification is accomplished at the upper end of the process temperature range. It can be considered an extension of the hydrothermal liquefaction mechanisms that begin at the lowest hydrothermal conditions with subsequent decomposition of biopolymer fragments formed in liquefaction to smaller molecules and eventually to gas. Typically, hydrothermal gasification requires an active catalyst to accomplish reasonable rates of gas formation from biomass.

  2. Study of Hydrogen Supply System with Ammonia Fuel

    Science.gov (United States)

    Saika, Takashi; Nakamura, Mitsuhiro; Nohara, Tetsuo; Ishimatsu, Shinji

    Carbon-free fuel is effective in preventing global warming. Hydrogen has no carbon and can be made also from nuclear energy or reproducible energies other than fossil fuels. However, hydrogen lacks portability because of its difficulty in liquefying, but ammonia can easily be liquefied at a room temperature and dissociated into high-content hydrogen and nitrogen using a suitable catalyst. An ammonia dissociation system for fuel cells is proposed in this paper. The residual ammonia by 13ppm or more in the dissociated gas (H2+ N2) causes a decrease in the output of fuel cells. To separate residual ammonia, it should be sent to an ammonia separator and then to an ammonia distiller. In the experiment, the authors examine the concentrations of ammonia after dissociation at various temperatures, pressures and space velocities. The ammonia separator uses the fact that ammonia dissolves well in water. Then the ammonia water is distilled in the distiller. Thereby, the authors have proposed an ammonia circulation system that is a clean energy system.

  3. Establishing relative sensitivities of various toxicity testing organisms to ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Karle, L.M.; Mayhew, H.L.; Barrows, M.E.; Karls, R.K. [Battelle/Marine Sciences Lab., Sequim, WA (United States)

    1994-12-31

    The toxicity of ammonia to various organisms was examined to develop a baseline for mortality in several commonly used testing species. This baseline data will assist in choosing the proper test species and in interpreting results as they pertain to ammonia. Responses for two juvenile fish species, three marine amphipods, and two species of mysid shrimp were compared for their sensitivity to levels of ammonia. All mortality caused by ammonia in the bottom-dwelling Citharichthys stigmaeus occurred within 24 h of exposure, whereas mortality in the silverside, Menidia beryllina, occurred over the entire 96-h test duration. Responses to ammonia varied among the amphipods Rhepoxynius abronius, Ampelisca abdita, and Eohaustorius estuarius. R. abronius and A. abdita showed similar sensitivity to ammonia at lower concentrations; A. abdita appeared more sensitive than R. abronius at levels above 40 mg/L. Concentrations of ammonia required to produce significant mortality in the amphipod E. estuarius were far higher than the other species examined (> 100 mg/L NH{sub 3}). A comparison of ammonia toxicity with two commonly used invertebrates, Holmesimysis sculpts and Mysidopsis bahia, suggest that these two species of mysid have similar sensitivities to ammonia. Further studies with ammonia that examine sensitivity of different organisms should be conducted to assist regulatory and environmental agencies in determining appropriate test species and in interpreting toxicological results as they may be affected by levels of ammonia.

  4. Structured materials for catalytic and sensing applications

    Science.gov (United States)

    Hokenek, Selma

    been synthesized and characterized to establish the effects of nanoparticle size on catalytic activity in methanol decomposition. The physicochemical properties of the synthesized palladium-nickel nanoparticles will be discussed, as a function of the synthesis parameters. The optical characteristics of the Ag and Pd nanoparticles will be determined, with a view toward tuning the response of the nanoparticles for incorporation in sensors. Analysis of the monometallic palladium particles revealed a dependence of syngas production on nanoparticle size. The peak and steady state TOFs increased roughly linearly with the average nanoparticle diameter. The amount of coke deposited on the particle surfaces was found to be independent on the size of the nanoparticles. Shape control of the nickel-palladium nanoparticles with a high selectivity for (100) and (110) facets (≤ 80%) has been demonstrated. The resulting alloy nanoparticles were found to have homogeneous composition throughout their volume and maintain FCC crystal structure. Substitution of Ni atoms in the Pd lattice at a 1:3 molar ratio was found to induce lattice strains of ~1%. The Ag nanocubes synthesized exhibited behavior very similar to literature values, when taken on their own, exhibiting a pair of distinct absorbance peaks at 350 nm and 455 nm. In physical mixtures with the Pd nanoparticles synthesized, their behavior showed that the peak position of the Ag nanocubes' absorbance in UV-Vis could be tuned based on the relative proportions of the Ag and Pd nanoparticles present in the suspension analysed. The Ag polyhedra synthesized for comparison showed a broad doublet peak throughout the majority of the visible range before testing as a component in a physical mixture with the Pd nanoparticles. The addition of Pd nanoparticles to form a physical mixture resulted in some damping of the doublet peak observed as well as a corresponding shift in the baseline absorbance proportional to the amount of Pd added to

  5. Catalytic Membrane Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, T.J.; Brinker, C.J.; Gardner, T.J.; Hughes, R.C.; Sault, A.G.

    1998-12-01

    The proposed "catalytic membrane sensor" (CMS) was developed to generate a device which would selectively identify a specific reagent in a complex mixture of gases. This was to be accomplished by modifying an existing Hz sensor with a series of thin films. Through selectively sieving the desired component from a complex mixture and identifying it by decomposing it into Hz (and other by-products), a Hz sensor could then be used to detect the presence of the select component. The proposed "sandwich-type" modifications involved the deposition of a catalyst layered between two size selective sol-gel layers on a Pd/Ni resistive Hz sensor. The role of the catalyst was to convert organic materials to Hz and organic by-products. The role of the membraneo was to impart both chemical specificity by molecukir sieving of the analyte and converted product streams, as well as controlling access to the underlying Pd/Ni sensor. Ultimately, an array of these CMS elements encompassing different catalysts and membranes were to be developed which would enable improved selectivity and specificity from a compiex mixture of organic gases via pattern recognition methodologies. We have successfully generated a CMS device by a series of spin-coat deposited methods; however, it was determined that the high temperature required to activate the catalyst, destroys the sensor.

  6. Catalytic gasification of biomass

    Science.gov (United States)

    Robertus, R. J.; Mudge, L. K.; Sealock, L. J., Jr.; Mitchell, D. H.; Weber, S. L.

    1981-12-01

    Methane and methanol synthesis gas can be produced by steam gasification of biomass in the presence of appropriate catalysts. This concept is to use catalysts in a fluidized bed reactor which is heated indirectly. The objective is to determine the technical and economic feasibility of the concept. Technically the concept has been demonstrated on a 50 lb per hr scale. Potential advantages over conventional processes include: no oxygen plant is needed, little tar is produced so gas and water treatment are simplified, and yields and efficiencies are greater than obtained by conventional gasification. Economic studies for a plant processing 2000 T/per day dry wood show that the cost of methanol from wood by catalytic gasification is competitive with the current price of methanol. Similar studies show the cost of methane from wood is competitive with projected future costs of synthetic natural gas. When the plant capacity is decreased to 200 T per day dry wood, neither product is very attractive in today's market.

  7. Catalytic cracking of lignites

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, M.; Nowak, S.; Naegler, T.; Zimmermann, J. [Hochschule Merseburg (Germany); Welscher, J.; Schwieger, W. [Erlangen-Nuernberg Univ. (Germany); Hahn, T. [Halle-Wittenberg Univ., Halle (Germany)

    2013-11-01

    A most important factor for the chemical industry is the availability of cheap raw materials. As the oil price of crude oil is rising alternative feedstocks like coal are coming into focus. This work, the catalytic cracking of lignite is part of the alliance ibi (innovative Braunkohlenintegration) to use lignite as a raw material to produce chemicals. With this new one step process without an input of external hydrogen, mostly propylene, butenes and aromatics and char are formed. The product yield depends on manifold process parameters. The use of acid catalysts (zeolites like MFI) shows the highest amount of the desired products. Hydrogen rich lignites with a molar H/C ratio of > 1 are to be favoured. Due to primary cracking and secondary reactions the ratio between catalyst and lignite, temperature and residence time are the most important parameter to control the product distribution. Experiments at 500 C in a discontinuous rotary kiln reactor show yields up to 32 wt-% of hydrocarbons per lignite (maf - moisture and ash free) and 43 wt-% char, which can be gasified. Particularly, the yields of propylene and butenes as main products can be enhanced four times to about 8 wt-% by the use of catalysts while the tar yield decreases. In order to develop this innovative process catalyst systems fixed on beads were developed for an easy separation and regeneration of the used catalyst from the formed char. (orig.)

  8. Spin-state chemistry of deuterated ammonia

    Science.gov (United States)

    Sipilä, O.; Harju, J.; Caselli, P.; Schlemmer, S.

    2015-09-01

    Aims: We aim to develop a chemical model that contains a consistent description of spin-state chemistry in reactions involving chemical species with multiple deuterons. We apply the model to the specific case of deuterated ammonia, to derive values for the various spin-state ratios. Methods: We applied symmetry rules in the context of the complete scrambling assumption to calculate branching ratio tables for reactions between chemical species that include multiple protons and/or deuterons. New reaction sets for both gas-phase and grain-surface chemistry were generated using an automated routine that forms all possible spin-state variants of any given reaction with up to six H/D atoms, using the predetermined branching ratios. Both a single-point and a modified Bonnor-Ebert model were considered to study the density and temperature dependence of ammonia and its isotopologs, and the associated spin-state ratios. Results: We find that the spin-state ratios of the ammonia isotopologs are, at late times, very different from their statistical values. The ratios are rather insensitive to variations in the density, but present strong temperature dependence. We derive high peak values (~0.1) for the deuterium fraction in ammonia, in agreement with previous (gas-phase) models. The deuterium fractionation is strongest at high density, corresponding to a high degree of depletion, and also presents temperature dependence. We find that in the temperature range 5 K to 20 K, the deuterium fractionation peaks at ~15 K, while most of the ortho/para (and meta/para for ND3) ratios present a minimum at 10 K (ortho/para NH2D has instead a maximum at this temperature). Conclusions: Owing to the density and temperature dependence found in the abundances and spin-state ratios of ammonia and its isotopologs, it is evident that observations of ammonia and its deuterated forms can provide important constraints on the physical structure of molecular clouds. Appendix A is available in

  9. Decomposition of toluene in a steady-state atmospheric-pressure glow discharge

    Science.gov (United States)

    Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Yu. S.

    2013-02-01

    Results are presented from experimental studies of decomposition of toluene (C6H5CH3) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C6H5CH3 removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N2: O2: H2O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C6H5CH3 decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C6H5CH3 is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.

  10. Effect of dry torrefaction on kinetics of catalytic pyrolysis of sugarcane bagasse

    Science.gov (United States)

    Daniyanto, Sutijan, Deendarlianto, Budiman, Arief

    2015-12-01

    Decreasing world reserve of fossil resources (i.e. petroleum oil, coal and natural gas) encourage discovery of renewable resources as subtitute for fossil resources. Biomass is one of the main natural renewable resources which is promising resource as alternate resources to meet the world's energy needs and raw material to produce chemical platform. Conversion of biomass, as source of energy, fuel and biochemical, is conducted using thermochemical process such as pyrolysis-gasification process. Pyrolysis step is an important step in the mechanism of pyrolysis - gasification of biomass. The objective of this study is to obtain the kinetic reaction of catalytic pyrolysis of dry torrified sugarcane bagasse which used Ca and Mg as catalysts. The model of kinetic reaction is interpreted using model n-order of single reaction equation of biomass. Rate of catalytic pyrolysis reaction depends on the weight of converted biomass into char and volatile matters. Based on TG/DTA analysis, rate of pyrolysis reaction is influenced by the composition of biomass (i.e. hemicellulose, cellulose and lignin) and inorganic component especially alkali and alkaline earth metallic (AAEM). From this study, it has found two equations rate of reaction of catalytic pyrolysis in sugarcane bagasse using catalysts Ca and Mg. First equation is equation of pyrolysis reaction in rapid zone of decomposition and the second equation is slow zone of decomposition. Value of order reaction for rapid decomposition is n > 1 and for slow decomposition is nConstant and order of reactions for catalytic pyrolysis of dry-torrified sugarcane bagasse with presence of Ca tend to higher than that's of presence of Mg.

  11. Magnetic carbon xerogels for the catalytic wet peroxide oxidation of 4-nitrophenol solutions

    OpenAIRE

    Ribeiro, R.; Silva, Adrián; Faria, Joaquim; Gomes, Helder

    2015-01-01

    Catalytic wet peroxide oxidation (CWPO) is a well-known advanced oxidation process for the removal of organic pollutants from industrial process waters and wastewater. Specifically, CWPO employs hydrogen peroxide (H2O2) as oxidation source and a suitable catalyst to promote its decomposition via formation of hydroxyl radicals (HO•), which exhibit high oxidizing potential and serve as effective species in the destruction of a huge range of organic pollutants

  12. Preparation and Catalytic Properties of Iron-Cerium Phosphates with Sodium Dodecyl Sulfate

    OpenAIRE

    Hiroaki Onoda; Takeshi Sakumura

    2012-01-01

    Iron phosphate was prepared from iron nitrate and phosphoric acid with sodium dodecyl sulfate at various stirring hours. The chemical composition of the obtained samples was estimated from ICP and XRD measurements. Particle shape and size distribution were observed by SEM images and laser diffraction/scattering methods. Further, the catalytic activity was studied with the decomposition of the complex between formaldehyde, ammonium acetate, and acetylacetone. The peaks of FePO4 were observed i...

  13. EFFECTS OF AMMONIA LOADING ON PORCELLIO SCABER: GLUTAMINE AND GLUTAMATE SYNTHESIS, AMMONIA EXCRETION AND TOXICITY

    Science.gov (United States)

    Wright; Donnell; Reichert

    1994-03-01

    The effects of ammonia loading in the terrestrial isopod Porcellio scaber were studied by exposing animals to atmospheres of high PNH3. Isopods show a remarkable tolerance of elevated ambient PNH3, with an LD50 of 89 Pa for a 7-day exposure. However, haemolymph total ammonia concentrations generally remained below 5 mmol l-1 (PNH3=0.37 Pa) over the range of ambient ammonia levels used (6.6­165 Pa). Following a 7-day loading period, whole-animal glutamine (Gln) and glutamate (Glu) levels increased in direct proportion to ambient PNH3, reaching values of 35 µmol g-1 fresh mass for glutamine and 12 µmol g-1 fresh mass for glutamate in 99 Pa PNH3; these correspond to control levels of 7.5 µmol g-1 fresh mass and 5.9 µmol g-1 fresh mass, respectively. Following transfer to ammonia-free chambers, NH3 excretion rates were augmented five- to sixfold relative to non-loaded controls. Ammonia volatilization subsequently declined, approaching control levels after 8­9 days. Levels of Gln and Glu showed a concomitant decline to 13.7 µmol g-1 fresh mass and 9.2 µmol g-1 fresh mass, respectively. The results suggest that these amino acids function in ammonia sequestration and, hence, detoxification. Calculations indicate that mobilization of amino groups by deamination of accumulated Gln and Glu could explain 35 % of the increased ammonia production. Implications of NH3 volatilization for acid­base balance are discussed.

  14. Immigration process in catalytic medium

    Institute of Scientific and Technical Information of China (English)

    洪文明; 王梓坤

    2000-01-01

    The longtime behavior of the immigration process associated with a catalytic super-Brown-ian motion is studied. A large number law is proved in dimension d≤3 and a central limit theorem is proved for dimension d = 3.

  15. Immigration process in catalytic medium

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The longtime behavior of the immigration process associated with a catalytic super-Brownian motion is studied. A large number law is proved in dimension d≤3 and a central limit theorem is proved for dimension d=3.

  16. Operation summary of ammonia synthesis ammonia storage safety%合成氨氨库安全运行总结

    Institute of Scientific and Technical Information of China (English)

    周荷珍; 张志翠

    2014-01-01

    介绍了氨对人体健康的危害及急救措施、氨罐的操作、汽车氨罐卸氨的原理及具体操作、氨吸收塔的操作,指出只有对氨库实行科学管理和精心操作,才能保证氨库的长期安全稳定运行。%The paper introduces damage from ammonia on human health and emergency measures, ammonia tank operation, the principle of car unloading ammonia ammonia tank and the specific operation, ammonia absorption tower operation, points out that only the ammonia base of scientific management and careful operation, in order to ensure the long-term safe and stable operation of ammonia storage.

  17. Modelling of Ammonia Heat Pump Desuperheaters

    DEFF Research Database (Denmark)

    Christensen, Stefan Wuust; Elmegaard, Brian; Markussen, Wiebke Brix

    2015-01-01

    This paper presents a study of modelling desuperheating in ammonia heat pumps. Focus is on the temperature profile of the superheated refrigerant. Typically, the surface area of a heat exchanger is estimated using the Log Mean Temperature Difference (LMTD) method. The assumption of this method...... is that the specific heat is constant throughout the temperature glide of the refrigerant in the heat exchanger. However, considering ammonia as refrigerant, the LMTD method does not give accurate results due to significant variations of the specific heat. By comparing the actual temperature profiles from a one....... The area of the heat exchanger can be increased or the condensation temperature can be raised to achieve the same temperature difference for the discretized model as for the LMTD. This would affect the compressor work, hence the COP of the system. Furthermore, for higher condenser pressure, and thus higher...

  18. 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.

  19. Ammonia volatilization from sows on grassland

    Science.gov (United States)

    Sommer, S. G.; Søgaard, H. T.; Møller, H. B.; Morsing, S.

    According to regulations, sows with piglets on organic farms must graze on pastures. Volatilization of ammonia (NH 3) from urine patches may represent a significant source of nitrogen (N) loss from these farms. Inputs of N are low on organic farms and losses may reduce crop production. This study examined spatial variations in NH 3 volatilization using a movable dynamic chamber, and the pH and total ammoniacal nitrogen (TAN) content in the topsoil of pastures with grazing sows was measured during five periods between June 1998 and May 1999. Gross NH 3 volatilization from the pastures was also measured with an atmospheric mass balance technique during seven periods from September 1997 until June 1999. The dynamic chamber study showed a high variation in NH 3 volatilization because of the distribution of urine; losses were between 0 and 2.8 g NH 3-N m -2 day -1. Volatilization was highest near the feeding area and the huts, where the sows tended to urinate. Ammonia volatilization rate was linearly related to the product of NH 3 concentration in the boundary layer and wind speed. The NH 3 in the boundary layer was in equilibrium with NH 3 in soil solution. Gross NH 3 volatilization was in the range 0.07-2.1 kg NH 3-N ha -1 day -1 from a pasture with 24 sows ha -1. Ammonia volatilization was related to the amount of feed given to the sows, incident solar radiation and air temperature during measuring periods, and also to temperature, incident solar radiation and rain 1-2 days before measurements. Annual ammonia loss was 4.8 kg NH 3-N sow -1.

  20. Fast and Accurate Exhaled Breath Ammonia Measurement

    OpenAIRE

    Solga, Steven F; Mudalel, Matthew L; Spacek, Lisa A.; Risby, Terence H.

    2014-01-01

    This exhaled breath ammonia method uses a fast and highly sensitive spectroscopic method known as quartz enhanced photoacoustic spectroscopy (QEPAS) that uses a quantum cascade based laser. The monitor is coupled to a sampler that measures mouth pressure and carbon dioxide. The system is temperature controlled and specifically designed to address the reactivity of this compound. The sampler provides immediate feedback to the subject and the technician on the quality of the breath effort. Toge...