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Catalytic Reduction (catalytic + reduction)
Kinds of Catalytic Reduction Selected AbstractsElectropolymerized Pyrrole-Substituted Manganese Phthalocyanine Films for the Electroassisted Biomimetic Catalytic Reduction of Molecular OxygenELECTROANALYSIS, Issue 2 2005Nazaré, Pereira Rodrigues Abstract We report for the first time on the electroassisted biomimetic activation of molecular oxygen by a newly prepared electropolymerized polypyrrole-manganese phthalocyanine film. The prepared films and their intervention in the electroassisted catalytic reduction of molecular oxygen were analyzed by cyclic voltammetry and UV-visible spectrophotometry on optically transparent electrodes. The obtained results demonstrate the probable existence of the key-steps responsible for the suggested formation of the highly reactive manganese oxo intermediate. [source] The Role of Amine,B(C6F5)3 Adducts in the Catalytic Reduction of Imines with H2: A Computational StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2009Timofei Privalov Abstract This study thoroughly examines the potential energy surfaces (PESs) of two possible mechanisms for reduction of imines by B(C6F5)3 and H2. The key reaction steps of the first catalytic mechanism, which is the focus of our study, are: (i) the uptake of H2 by a thermally activated amine,B(C6F5)3 species; (ii) proton transfer from the NH2+ moiety of [RNH2CH2R,]+[HB(C6F5)3], to the imine; (iii) nucleophillic attack of the C-center of the iminium ion by the BH, group. The potential energy barriers of the latter, as determined by calculating the evolution of the H-bonded complex of an imine and [RNH2CH2R,]+[HB(C6F5)3], in toluene, are around 10 kcal,mol,1 each. In the second mechanism, only imines serve as basic partners of B(C6F5)3 in the H2 activation, which affords an [RN(H)CHR,]+[HB(C6F5)3], ion pair; direct reduction then proceeds via nucleophilic attack of the C-center by the BH, in [RN(H)CHR,]+[HB(C6F5)3],. This route becomes catalytic when the product amine is released into the solvent and B(C6F5)3 is re-used for H2 activation. Upon taking into account the association energy of an amine,B(C6F5)3 adduct [,9.5 kcal,mol,1 for tBuN(H)CH2Ph and B(C6F5)3 in toluene], the potential energy barrier for H2 uptake by an imine and B(C6F5)3 increases to 14.5 kcal,mol,1. We report a somewhat lower potential energy barrier for H2 uptake by thermally activated amine,B(C6F5)3 adducts [12.7 kcal,mol,1 for the B-N adduct of tBuN(H)CH2Ph and B(C6F5)3 in toluene], although the difference between the two H2 activationbarriers is within the expected error of the computational method. Two catalytic routes are compared based on B3LYP-computed PESs in solvent (toluene).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] A Nanoreactor Framework of a Au@SiO2 Yolk/Shell Structure for Catalytic Reduction of p -Nitrophenol,ADVANCED MATERIALS, Issue 8 2008Joongoo Lee A nanoreactor system comprising gold cores and silica hollow shells with empty inner space demonstrated. The Au@SiO2 yolk/shell nanoreactor is synthesized by selective etching of the gold cores in Au@SiO2 core/shell particles (see figure). This nanoreactor framework catalyzes the reduction of p -nitrophenol, exhibiting interesting size-dependent reaction property. [source] An Environmentally Benign, Highly Efficient Catalytic Reduction of p -Nitrophenol using a Nano-Sized Nickel Catalyst Supported on Silica-AluminaADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2010Islam Hamdy Abd El Maksod Abstract A green and effective method is reported for the reduction of p -nitrophenol to p -aminophenol using a nano-sized nickel catalyst supported on silica-alumina in the presence of hydrazine hydrate as an alternative source of hydrogen. It was found that nickel loaded on a silica-alumina support is a very effective catalyst in the hydrogenation of p -nitrophenol to p -aminophenol. Thus it attained 100% conversion in only 69 seconds instead of 260 seconds for commercial Raney nickel. In addition, the possibility to reuse it more than one time with great efficiency gives it another advantage over commercial Rainey nickel which cannot be used more than once. This economical and environmentally friendly method provides a potentially new approach for the synthesis of the intermediate product of paracetamol in industry, which overcomes the drawbacks of the known reduction methods. The prepared catalysts were fully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and electron spin resonance (ESR) tehniques. [source] Enhanced NH3 Selective Catalytic Reduction for NOx AbatementANGEWANDTE CHEMIE, Issue 44 2009Pio Forzatti Prof. Eine beschleunigte NO-Reduktion wird beobachtet, wenn NO mit Ammoniak und einer wässrigen NH4NO3 -Lösung in Abwesenheit von NO2 bei niedrigen Temperaturen (200,300,°C) an kommerziellen vanadium- und eisendotierten Zeolithkatalysatoren reagiert. Die Reduktionseffizienz kommt der einer schnellen selektiven katalytischen Reduktion (SCR) mit NH3 nahe (siehe Diagramm). [source] High Activity of Pt/AlPO4 Catalyst for Selective Catalytic Reduction of Nitrogen Monoxide by Propene in Excess Oxygen.CHEMINFORM, Issue 47 2003Ryuta Fujii Abstract For Abstract see ChemInform Abstract in Full Text. [source] Using Acetylene for Selective Catalytic Reduction of NO in Excess OxygenCHINESE JOURNAL OF CHEMISTRY, Issue 5 2006Shan-Shan Yu Abstract Acetylene as a reducing agent for selective catalytic reduction of NO (C2H2 -SCR) was investigated over a series of metal exchanged HY catalysts, in the reaction system of 0.16% NO, 0.08% C2H2, and 9.95% O2 (volume percent) in He. 75% of NO conversion to N2 with hydrocarbon efficiency about 1.5 was achieved over a Ce-HY catalyst around 300 °C. The NO removal level was comparable with that of selective catalytic reduction of NOx by C3H6 reported in literatures, although only one third of the reducing agent in carbon moles was used in the C2H2 -SCR of NO. The protons in zeolite were crucial to the C2H2 -SCR of NO, and the performance of HY in the reaction was significantly promoted by cerium incorporation into the zeolite. NO2 was proposed to be the intermediate of NO reduction to N2, and the oxidation of NO to NO2 was rate-determining step of the C2H2 -SCR of NO over Ce-HY. The suggestion was well supported by the results of the NO oxidation with O2, and the C2H2 consumption under the conditions in the presence or absence of NO. [source] Synthesis of tritium labelled delta sleep-inducing peptideJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 7 2001Matthieu Giraud Abstract The ,,, -dehydro precursor of the delta sleep-inducing peptide (DSIP) for tritiation was prepared prior to tritiation using a 3+6 fragment coupling strategy on a solid support. The first fragment, ,,, -dehydrotripeptide, was prepared in solution in five steps in 79% overall yield while the second fragment was obtained by a step by step peptide synthesis on a Wang resin using an Fmoc strategy. The ,,, -dehydrotripeptide was coupled to the fragment linked to the resin, followed by a deprotection/cleavage step to yield the ,,, -dehydro-DSIP, 7. Catalytic reduction of unsaturated DSIP using tritium gas and palladium oxide as catalyst gave [3H]DSIP having a specific activity of 1.184 TBq/mmol(32 Ci/mmol). Copyright © 2001 John Wiley & Sons, Ltd. [source] Rosiglitazone maleate (BRL 49653-C); the preparation of [14C] and [3H] isotopomersJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 5 2001Tabassum Kirefu Abstract The glitazone insulin sensitisers are an important class of pharmaceuticals for the treatment of Type 2 diabetes. Syntheses of [methyl - 14C] and [3H]rosiglitazone maleate (BRL 49653-C), marketed by SmithKline Beecham Pharmaceuticals as Avandia® are described. [Methyl - 14C]BRL 49653-C was prepared in 5 steps in 12.6% overall radiochemical yield from K[14C]CN. Catalytic reduction with tritium gas of a dibromo derivative gave [3H]rosiglitazone with a specific activity of 58Ci/mmol. Copyright © 2001 John Wiley & Sons, Ltd. [source] Electropolymerized Pyrrole-Substituted Manganese Phthalocyanine Films for the Electroassisted Biomimetic Catalytic Reduction of Molecular OxygenELECTROANALYSIS, Issue 2 2005Nazaré, Pereira Rodrigues Abstract We report for the first time on the electroassisted biomimetic activation of molecular oxygen by a newly prepared electropolymerized polypyrrole-manganese phthalocyanine film. The prepared films and their intervention in the electroassisted catalytic reduction of molecular oxygen were analyzed by cyclic voltammetry and UV-visible spectrophotometry on optically transparent electrodes. The obtained results demonstrate the probable existence of the key-steps responsible for the suggested formation of the highly reactive manganese oxo intermediate. [source] Multilayer Assemblies Consisting of Tri-Vanadium-Substituted Heteropolyanions and Its Electrocatalytic PropertiesELECTROANALYSIS, Issue 14 2003Shengyong Zhai Abstract We describe the controlled fabrication of ultrathin multilayer films consisting of tri-vanadium- substituted heteropolytungstate anions (denoted as P2W15V3) and a cationic polymer of quaternized poly (4-vinylpyridine) partially complexed with osmium bis(2,2,-bipyridine) (denoted as QPVP-Os) on the 4-aminobenzoic acid (4-ABA) modified glassy carbon electrode (GCE) surface based on layer-by-layer assembly. Cyclic voltammetry and UV-vis absorption spectrometry have been used to easily monitor the thickness and uniformity of thus-formed multilayer films. The V-centered redox reaction of P2W15V3 in the multilayer films can effectively catalyze the reduction of BrO and NO. The resulting P2W15V3/QPVP-Os multilayer film modified electrode behaves as a much promising electrochemical sensor because of the low overpotential for the catalytic reduction of BrO and NO, and the catalytic oxidation of ascorbic acid. [source] Materials Issues Related to Catalysts for Treatment of Diesel ExhaustINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2005Chaitanya K. Narula The driver for lean NOx treatment is the need to meet regulatory standards for diesel engines and gasoline direct injection spark-ignited engines that offer better fuel economy. Efforts over the last decade have been focused toward finding an active lean NOx catalyst that can reduce NOx under oxidizing conditions or strategies such as selective catalytic reduction (SCR), plasma-catalysis, plasma catalyst SCR, and lean NOx traps with varying degrees of success. At present, it appears that SCR with urea and lean NOx traps are the leading contender technologies for commercial deployment. Key issues that remain to be resolved for these two technologies include byproduct formation, dosing control, and durability. In this review, we summarize material-related issues that are unique to each of these technologies, and point out the improvements necessary to facilitate their deployment. [source] Bioprocesses for the removal of nitrogen oxides from polluted airJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2005Yaomin Jin Abstract Nitrogen oxides (NOx) of environmental concern are nitrogen monoxide (NO) and nitrogen dioxide (NO2). They are hazardous air pollutants that lead to the formation of acid rain and tropospheric ozone. Both pollutants are usually present simultaneously and are, therefore, called NOx. Another compound is N2O which is found in the stratosphere where it plays a role in the greenhouse effect. Concern for environmental and health issues coupled with stringent NOx emission standards generates a need for the development of efficient low-cost NOx abatement technologies. Under such circumstances, it becomes mandatory for each NOx-emitting industry or facility to opt for proper NOx control measures. Several techniques are available to control NOx emissions: selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), adsorption, scrubbing, and biological methods. Each process offers specific advantages and limitations. Since bioprocesses present many advantages over conventional technologies for flue gas cleaning, a lot of interest has recently been shown for these processes. This article reviews the major characteristics of conventional non-biological technologies and recent advances in the biological removal of NOx from flue gases based on the catalytic activity of either eucaryotes or procaryotes, ie nitrification, denitrification, the use of microalgae, and a combined physicochemical and biological process (BioDeNOx). Relatively uncomplicated design and simple operation and maintenance requirements make biological removal a good option for the control of NOx emissions in stationary sources. Copyright © 2005 Society of Chemical Industry [source] Comprehensive process design study for layered-NOX -control in a tangentially coal fired boilerAICHE JOURNAL, Issue 3 2010Wei Zhou Abstract As emissions regulations for coal-fired power plants become stricter worldwide, layering combustion modification and post-combustion NOX control technologies can be an attractive option for efficient and cost-effective NOX control in comparison to selective catalytic reduction (SCR) technology. The layered control technology approach designed in this article consists of separate overfire air (SOFA), reburn, and selective noncatalytic reduction (SNCR). The combined system can achieve up to 75% NOX reduction. The work presented in this article successfully applied this technology to NRG Somerset Unit 6, a 120-MW tangential coal-fired utility boiler, to reduce NOX emissions to 0.11 lb/MMBtu (130 mg/Nm3), well under the US EPA SIP Call target of 0.15 lb/MMBtu. The article reviews an integrated design study for the layered system at Somerset and evaluates the performance of different layered-NOX -control scenarios including standalone SNCR (baseline), separated overfire air (SOFA) with SNCR, and gas reburn with SNCR. Isothermal physical flow modeling and computational fluid dynamics simulation (CFD) were applied to understand the boiler flow patterns, the combustible distributions and the impact of combustion modifications on boiler operation and SNCR performance. The modeling results were compared with field data for model validation and verification. The study demonstrates that a comprehensive process design using advanced engineering tools is beneficial to the success of a layered low NOX system. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Experimental investigation on evaporation of urea-water-solution droplet for SCR applicationsAICHE JOURNAL, Issue 12 2009Tae Joong Wang Abstract The evaporation behavior of urea-water-solution (UWS) droplet was investigated for application to urea-selective catalytic reduction (SCR) systems. A number of experiments were performed with single UWS droplet suspended on the tip of a fine quartz fiber. To cover the temperature range of real-world diesel exhausts, droplet ambient temperature was regulated from 373 to 873 K using an electrical furnace. As a result of this study, UWS droplet revealed different evaporation characteristics depending on its ambient temperature. At high temperatures, it showed quite complicated behaviors such as bubble formation, distortion, and partial rupture after a linear D2 -law period. However, as temperature decreases, these phenomena became weak and finally disappeared. Also, droplet diminishment coefficients were extracted from transient evaporation histories for various ambient temperatures, which yields a quantitative evaluation on evaporation characteristics of UWS droplet as well as provides valuable empirical data required for modeling or simulation works on urea-SCR systems. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Synthesis and properties of fluorinated polyimides based on 1,4-bis(4-amino-2-trifluoromethylphenoxy)-2,5-di- tert -butylbenzene and various aromatic dianhydridesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2004Chin-Ping Yang Abstract A novel fluorinated diamine monomer, 1,4-bis(4-amino-2-trifluoromethylphenoxy)-2,5-di- tert -butylbenzene (2), was prepared through the nucleophilic substitution reaction of 2-chloro-5-nitrobenzotrifluoride and 2,5-di- tert -butylhydroquinone in the presence of potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C. Fluorinated polyimides (5a,5f) were synthesized from diamine 2 and various aromatic dianhydrides (3a,3f) via thermal or chemical imidization. These polymers had inherent viscosities of 0.77,1.01 dL/g. The 5 series polyimides were soluble in N -methyl-2-pyrrolidone, N,N -dimethylacetamide, and N,N -dimethylformamide and were even soluble in dioxane, tetrahydrofuran, and dichloromethane. 5(C) showed cutoff wavelengths between 363 and 404 nm and yellowness index (b*) values of 6.5,40.2. The polyimide films had tensile strengths of 93,114 MPa, elongations to break of 9,12%, and initial moduli of 1.7,2.1 GPa. The glass-transition temperatures were 255,288 °C. The temperatures of 10% weight loss were all above 460 °C in air or nitrogen atmospheres. In comparison with a nonfluorinated polyimide series based on 1,4-bis(4-aminophenoxy)-2,5-di- tert -butylbenzene, the 5 series showed better solubility and lower color intensity, dielectric constants, and moisture absorption. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2272,2284, 2004 [source] Synthesis and characterization of novel soluble triphenylamine-containing aromatic polyamides based on N,N,-bis(4-aminophenyl)- N,N,-diphenyl-1,4-phenylenediamineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2002Guey-Sheng Liou Abstract A new triphenylamine-containing aromatic diamine, N, N,-bis(4-aminophenyl)- N, N,-diphenyl-1,4-phenylenediamine, was prepared by the condensation of N,N,-diphenyl-1,4-phenylenediamine with 4-fluoronitrobenzene, followed by catalytic reduction. A series of novel aromatic polyamides with triphenylamine units were prepared from the diamine and various aromatic dicarboxylic acids or their diacid chlorides via the direct phosphorylation polycondensation or low-temperature solution polycondensation. All the polyamides were amorphous and readily soluble in many organic solvents such as N, N -dimethylacetamide and N -methyl-2-pyrrolidone. These polymers could be solution cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with relatively high glass-transition temperatures (257,287 °C), 10% weight-loss temperatures in excess of 550 °C, and char yields at 800 °C in nitrogen higher than 72%. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2810,2818, 2002 [source] Polyimides based on 2,5-bis(4-aminophenoxy)biphenylJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2002Chin-Ping Yang Abstract A diamine monomer II, 2,5-bis(4-aminophenoxy)biphenyl, was prepared through a nucleophilic substitution reaction of phenylhydroquinone and p -chloronitrobenzene in the presence of potassium carbonate in N,N -dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. A series of all-aromatic, organosoluble polyimides bearing pendent phenyl groups were synthesized from the diamine with six kinds of commercial dianhydrides via a conventional two-stage process. For improving solubility of polypyromellitimide, copolypyromellitimides with arbitrary solubilities were prepared from II and a pair of dianhydrides, which were mixed at certain molar ratios. These polymers showed good solubilities in N -methyl-2-pyrrolidone and m -cresol. The softening temperatures of these polyimides were recorded between 206 and 269 °C. Polymers had glass-transition temperatures at 230,286 °C and 10% weight-loss temperatures above 521 °C in air or nitrogen atmospheres. Their films had high tensile moduli and strengths. Excellent properties of these polyimides are attributed to the incorporation of the pendent phenyl group in diamine II. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 429,438, 2002; DOI 10.1002/pola.10116 [source] An appraisal of methods for measurement of pesticide transformation in the groundwater zone,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 4 2001Minze Leistra Abstract Laboratory and field studies show that pesticides may be transformed in the groundwater zone. Possible reaction mechanisms are chemical hydrolysis, catalytic reduction and aerobic or anaerobic microbial transformation. Transformation in the groundwater zone can be an important element in the advanced evaluation of the potential risk arising from a pesticide in the public drinking water supply. However, rate and pathway of transformation can show large differences, depending on the bio-geochemical conditions in the groundwater zone. Knowledge of the reaction mechanisms and the effect of aquifer conditions would allow vulnerable and low-vulnerable application areas for a pesticide to be delimited. An outline is given of possible approaches to quantifying these transformation processes and using the results in registration procedures, especially in the EU and its member states. Furthermore, areas where there is need for continued research and better understanding are highlighted. © 2001 Society of Chemical Industry [source] A novel continuous reactor for catalytic reduction of NOx,fixed bed simulationsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2008Terris T. Yang Abstract A novel dual-zone fluidized bed reactor was proposed for the continuous adsorption and reduction of NOx from combustion flue gases. The adsorption and reaction behaviour of such a reactor has been simulated in a fixed bed reactor using Fe/ZSM-5 catalyst and propylene reductant with model flue gases. Fe/ZSM-5 exhibited acceptable activity at T,=,350°C and GHSV,=,5000 h,1 when O2 concentration was controlled at levels lower than 1% with a HC to NO molar ratio of about 2:1. XPS and BET surface area measurement revealed the nature of the deactivation of the catalyst. Those performance data demonstrated the feasibility of a continuous dual-zone fluidized bed reactor for catalytic reduction of NOx under lean operating conditions. Un nouveau réacteur à lit fluidisé à double zone est proposé pour l'adsorption et la réduction en continu de NOx à partir de gaz de carneau de combustion. Le comportement d'adsorption et de réaction d'un tel réacteur a été simulé dans un réacteur à lit fixe utilisant un catalyseur Fe/ZSM-5 et un agent réducteur avec des gaz de carneau modèle. Le Fe/ZSM-5 montre une activité acceptable à T,=,350°C et GHSV,=,5000 h,1 lorsque la concentration d'O2 est contrôlée à des niveaux inférieurs à 1% avec un rapport molaire HC,NO d'environ 2:1. La mesure de surface par XPS et BET a permis de caractériser la désactivation du catalyseur. Ces données de performance illustre la faisabilité du réacteur à lit fluidisé à double zone Fe/ZSM-5 pour la réduction catalytique de NOx dans des conditions opératoires pauvres. [source] Kinetic Reaction Models for the Selective Reduction of NO by Methane over Multifunctional Zeolite-based Redox CatalystsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2004T. Sowade Abstract Kinetic measurements of the selective catalytic reduction (SCR) of NO by methane were performed over CeO2/H-ZSM-5, In-ZSM-5, and CeO2/In-ZSM-5 catalysts. The parameter space covered NO, CH4, and O2 concentrations varying from 250 to 1000 ppm, from 500 to 2000 ppm, and from 0.5 to 10,vol.-%, respectively, space velocities between 5000 and 90000 h,1 and temperatures between 573 and 873 K depending on the catalyst activities. With CeO2/In-ZSM-5 an additional series of measurements was performed with moistened feed gas (0.5,10,vol.-% H2O). On the basis of a pseudo-homogeneous, one-dimensional fixed-bed reactor model, the data were fitted to a kinetic model that includes power rate laws for the reduction of NO and for the unselective total oxidation of methane. From analyses of isothermal data sets, almost all reaction orders were found to vary significantly with changing temperature, which indicates that the simple kinetic model cannot reflect the complex reaction mechanism correctly. Nevertheless, the data measured with In-ZSM-5 could be modeled with good accuracy over a wide range of reaction temperatures (150 K) while the accuracy was less satisfactory with the remaining data sets, in particular for data with the moist feed over CeO2/In-ZSM-5. With the latter catalyst it was not possible to represent the data measured in dry and in moist feed in a single model even upon confinement to fixed reaction temperatures. A comparison of the separate models established showed strong changes in the reaction orders in the presence of water, which occur apparently already at a very low water content (,,0.5,vol.-%). The kinetic parameters found are in agreement with earlier conclusions about the reaction mechanisms. With In-ZSM-5, both reaction orders and the activation energy show a rate-limiting influence of NO oxidation on the NO reduction path which is removed by the presence of the CeO2 promoter. A difference in the reaction mechanism over CeO2/In-ZSM-5 and CeO2/H-ZSM-5 is reflected in different kinetic parameters. The differences of the kinetic parameters between dry-feed and moist-feed models for CeO2/In-ZSM-5 reflect adsorption competition between the reactants and water. [source] Using Acetylene for Selective Catalytic Reduction of NO in Excess OxygenCHINESE JOURNAL OF CHEMISTRY, Issue 5 2006Shan-Shan Yu Abstract Acetylene as a reducing agent for selective catalytic reduction of NO (C2H2 -SCR) was investigated over a series of metal exchanged HY catalysts, in the reaction system of 0.16% NO, 0.08% C2H2, and 9.95% O2 (volume percent) in He. 75% of NO conversion to N2 with hydrocarbon efficiency about 1.5 was achieved over a Ce-HY catalyst around 300 °C. The NO removal level was comparable with that of selective catalytic reduction of NOx by C3H6 reported in literatures, although only one third of the reducing agent in carbon moles was used in the C2H2 -SCR of NO. The protons in zeolite were crucial to the C2H2 -SCR of NO, and the performance of HY in the reaction was significantly promoted by cerium incorporation into the zeolite. NO2 was proposed to be the intermediate of NO reduction to N2, and the oxidation of NO to NO2 was rate-determining step of the C2H2 -SCR of NO over Ce-HY. The suggestion was well supported by the results of the NO oxidation with O2, and the C2H2 consumption under the conditions in the presence or absence of NO. [source] | ||||||||||||||||||||||||||||