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P J Millington - One of the best experts on this subject based on the ideXlab platform.
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Selective Reduction of nitrogen oxides by hydrocarbons under lean burn conditions using supported platinum group metal catalysts
Catalysis Today, 1995Co-Authors: R Burch, P J MillingtonAbstract:The performance of supported platinum-group metals (Pt, Pd, Rh, Ir and Ru) for the Selective Reduction of nitrogen oxides by hydrocarbons under oxidising conditions is reviewed. Kinetic and mechanistic studies on these catalysts are assessed. Many of the factors influencing de-NOx behavior are considered. These include the choice of metal, the metal loading and the metal particle size, the carbon number and hydrocarbon type of the reductant used and the type of support material. It is found that highest de-NOx activity is obtained with platinum-based catalysts although large quantities of nitrous oxide are formed in addition to nitrogen. Rhodium also exhibits a significant but lower activity although much less N2O is produced. It is seen that NOx Reduction is coincident with hydrocarbon combustion. Although metal particle size has little effect on overall de-NOx activity, large particles have higher turnover frequencies. For a given carbon number, it is found that the de-NOx efficiency increases in the order i-paraffins < aromatics < n-paraffins < olefins ≈ alcohols and that, in general, activity increases with increasing carbon number. When using olefins as the reductant, varying the support material has little effect on activity although large differences can be seen when using saturated hydrocarbons. Mechanistic studies, including FT-IR and TAP experiments, are reviewed and the various mechanisms that have been proposed for this reaction are discussed.
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mechanism of the Selective Reduction of nitrogen monoxide on platinum based catalysts in the presence of excess oxygen
Applied Catalysis B-environmental, 1994Co-Authors: R Burch, P J Millington, Andrew Peter WalkerAbstract:Abstract A range of alumina-supported platinum catalysts have been prepared and investigated for the Selective Reduction of nitrogen monoxide in the presence of a large excess of oxygen. Steady-state microreactor experiments have demonstrated that these catalysts are very active and Selective for the Reduction of nitrogen monoxide by propene at temperatures as low as 200°C. There does not appear to be a simple correlation between the activity for nitrogen monoxide Reduction and the platinum surface area. Instead it is found that there is a very good inverse correlation between the maximum nitrogen monoxide Reduction activity and the temperature. The most active catalysts for Selective nitrogen monoxide Reduction are those that generate activity at the lowest temperature. The technique of temporal analysis of products (TAP) has been used to obtain detailed mechanistic data about the Selective nitrogen monoxide Reduction reaction on an alumina-supported platinum catalyst. Using carbon monoxide, hydrogen or propene as reductant it has been demonstrated that the predominant mechanism for Selective nitrogen monoxide Reduction involves the decomposition of nitrogen monoxide on reduced platinum metal sites, followed by the regeneration of the active platinum sites by the reductant. In the decomposition step it has been shown that oxygen from nitrogen monoxide is retained on the surface of the platinum and blocks the surface for further adsorption/reaction of nitrogen monoxide; it has been observed that oxidised platinum catalysts are not active for the nitrogen monoxide Reduction reaction. Under typical operating conditions, propene is a far more efficient reductant than either carbon monoxide or hydrogen. The greater efficiency of propene as a reductant is explained on the basis of the additional reducing power of the propene molecule, which can react with as many as nine adsorbed oxygen atoms, ensuring that 'patches' of reduced platinum are available for nitrogen monoxide adsorption/reaction. A small additional activity of reduced platinum in the presence of propene, which is not observed when carbon monoxide or hydrogen is used as reductant, has been explained on the basis of a second mechanism involving the carbon-assisted decomposition of nitrogen monoxide at sites on the reduced platinum adjacent to adsorbed carbon-containing moieties, believed to be fragments from adsorbed propene molecules. A model for the Selective Reduction of nitrogen monoxide on alumina-supported platinum catalysts is presented which is capable of explaining all the results obtained in this work and in the published literature on this subject.
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role of propene in the Selective Reduction of nitrogen monoxide in copper exchanged zeolites
Applied Catalysis B-environmental, 1993Co-Authors: R Burch, P J MillingtonAbstract:Abstract Gas switching experiments, examining the first few minutes of reaction, have been used to study the Selective Reduction of nitrogen monoxide by propene on a Cu-ZSM-5 catalyst in an oxygen-rich gas mixture. It has been found that the conversion of nitrogen monoxide to nitrogen reaches a steady-state activity in a very short period of time. It is concluded that carbon deposition is not responsible for the conversion of nitrogen monoxide into nitrogen. It is proposed instead that the hydrocarbon and oxygen act to maintain the active copper sites in an oxidation state suitable for direct nitrogen monoxide decomposition.
R Burch - One of the best experts on this subject based on the ideXlab platform.
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Selective Reduction of nitrogen oxides by hydrocarbons under lean burn conditions using supported platinum group metal catalysts
Catalysis Today, 1995Co-Authors: R Burch, P J MillingtonAbstract:The performance of supported platinum-group metals (Pt, Pd, Rh, Ir and Ru) for the Selective Reduction of nitrogen oxides by hydrocarbons under oxidising conditions is reviewed. Kinetic and mechanistic studies on these catalysts are assessed. Many of the factors influencing de-NOx behavior are considered. These include the choice of metal, the metal loading and the metal particle size, the carbon number and hydrocarbon type of the reductant used and the type of support material. It is found that highest de-NOx activity is obtained with platinum-based catalysts although large quantities of nitrous oxide are formed in addition to nitrogen. Rhodium also exhibits a significant but lower activity although much less N2O is produced. It is seen that NOx Reduction is coincident with hydrocarbon combustion. Although metal particle size has little effect on overall de-NOx activity, large particles have higher turnover frequencies. For a given carbon number, it is found that the de-NOx efficiency increases in the order i-paraffins < aromatics < n-paraffins < olefins ≈ alcohols and that, in general, activity increases with increasing carbon number. When using olefins as the reductant, varying the support material has little effect on activity although large differences can be seen when using saturated hydrocarbons. Mechanistic studies, including FT-IR and TAP experiments, are reviewed and the various mechanisms that have been proposed for this reaction are discussed.
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mechanism of the Selective Reduction of nitrogen monoxide on platinum based catalysts in the presence of excess oxygen
Applied Catalysis B-environmental, 1994Co-Authors: R Burch, P J Millington, Andrew Peter WalkerAbstract:Abstract A range of alumina-supported platinum catalysts have been prepared and investigated for the Selective Reduction of nitrogen monoxide in the presence of a large excess of oxygen. Steady-state microreactor experiments have demonstrated that these catalysts are very active and Selective for the Reduction of nitrogen monoxide by propene at temperatures as low as 200°C. There does not appear to be a simple correlation between the activity for nitrogen monoxide Reduction and the platinum surface area. Instead it is found that there is a very good inverse correlation between the maximum nitrogen monoxide Reduction activity and the temperature. The most active catalysts for Selective nitrogen monoxide Reduction are those that generate activity at the lowest temperature. The technique of temporal analysis of products (TAP) has been used to obtain detailed mechanistic data about the Selective nitrogen monoxide Reduction reaction on an alumina-supported platinum catalyst. Using carbon monoxide, hydrogen or propene as reductant it has been demonstrated that the predominant mechanism for Selective nitrogen monoxide Reduction involves the decomposition of nitrogen monoxide on reduced platinum metal sites, followed by the regeneration of the active platinum sites by the reductant. In the decomposition step it has been shown that oxygen from nitrogen monoxide is retained on the surface of the platinum and blocks the surface for further adsorption/reaction of nitrogen monoxide; it has been observed that oxidised platinum catalysts are not active for the nitrogen monoxide Reduction reaction. Under typical operating conditions, propene is a far more efficient reductant than either carbon monoxide or hydrogen. The greater efficiency of propene as a reductant is explained on the basis of the additional reducing power of the propene molecule, which can react with as many as nine adsorbed oxygen atoms, ensuring that 'patches' of reduced platinum are available for nitrogen monoxide adsorption/reaction. A small additional activity of reduced platinum in the presence of propene, which is not observed when carbon monoxide or hydrogen is used as reductant, has been explained on the basis of a second mechanism involving the carbon-assisted decomposition of nitrogen monoxide at sites on the reduced platinum adjacent to adsorbed carbon-containing moieties, believed to be fragments from adsorbed propene molecules. A model for the Selective Reduction of nitrogen monoxide on alumina-supported platinum catalysts is presented which is capable of explaining all the results obtained in this work and in the published literature on this subject.
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role of propene in the Selective Reduction of nitrogen monoxide in copper exchanged zeolites
Applied Catalysis B-environmental, 1993Co-Authors: R Burch, P J MillingtonAbstract:Abstract Gas switching experiments, examining the first few minutes of reaction, have been used to study the Selective Reduction of nitrogen monoxide by propene on a Cu-ZSM-5 catalyst in an oxygen-rich gas mixture. It has been found that the conversion of nitrogen monoxide to nitrogen reaches a steady-state activity in a very short period of time. It is concluded that carbon deposition is not responsible for the conversion of nitrogen monoxide into nitrogen. It is proposed instead that the hydrocarbon and oxygen act to maintain the active copper sites in an oxidation state suitable for direct nitrogen monoxide decomposition.
Yoshiaki Kintaichi - One of the best experts on this subject based on the ideXlab platform.
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remarkable promoting effect of rhodium on the catalytic performance of ag al2o3 for the Selective Reduction of no with decane
Applied Catalysis B-environmental, 2003Co-Authors: Kazuhito Sato, Yoshiaki Kintaichi, Tomohiro Yoshinari, Masaaki Haneda, Hideaki HamadaAbstract:Abstract The addition of small amounts of rhodium enhanced the activity of Ag/Al2O3 catalyst for the Selective Reduction of NO with decane at low temperatures. The Rh-promoted Ag/Al2O3 showed its high performance even in the presence of low concentrations of SO2. Based on the catalytic activity for elementary reactions, it was suggested that the role of added rhodium is to enhance the reaction between NOx and decane-derived species, leading to NO Reduction. Catalyst characterization by UV-Vis spectroscopy indicated that the major silver species on Rh-promoted Ag/Al2O3 is Agnδ+ clusters, which would be responsible for the high activity. FT-IR measurements revealed that the formation rate of isocyanate species, which is a major reaction intermediate, is higher on Rh-promoted Ag/Al2O3.
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role of oxygen in Selective Reduction of nitrogen monoxide by propane over zeolite and alumina based catalysts
Catalysis Letters, 1992Co-Authors: Motoi Sasaki, Hideaki Hamada, Yoshiaki KintaichiAbstract:The role of coexisting oxygen in the Selective Reduction of nitrogen monoxide by propane on H-zeolites, alumina, Cu-ZSM-5 zeolite and Pt/Al2O3 catalysts was investigated. In the case of H-zeolites and alumina, oxidation of NO to NO2 played an important role for the overall Selective Reduction of NO. On the other hand, the initial reaction step was considered to be partial oxidation of propane over Cu-ZSM-5 and Pt/Al2O3.
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transition metal promoted silica and alumina catalysts for the Selective Reduction of nitrogen monoxide with propane
Applied Catalysis, 1991Co-Authors: Hideaki Hamada, Yoshiaki Kintaichi, Motoi Sasaki, Mitsunori TabataAbstract:Abstract The effect of transition metal additives on the catalytic performances of silica and alumina was investigated for the Selective Reduction of nitrogen monoxide with propane in the presence of high concentrations of oxygen. Some metal-silica catalysts showed the activity although silica was quite inactive. Most of the transition metals were found to promote the catalytic activity of alumina, although the performances were dependent on the preparation conditions. In particular, metal-alumina catalysts containing metal aluminate showed excellent activity at low temperatures and under high space velocity conditions.
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Selective Reduction of nitrogen monoxide with propane over alumina and hzsm 5 zeolite effect of oxygen and nitrogen dioxide intermediate
Applied Catalysis, 1991Co-Authors: Hideaki Hamada, Yoshiaki Kintaichi, Motoi Sasaki, Mitsunori TabataAbstract:In this study we investigated the Reduction of nitric oxide with propane over alumina or HZSM-5 zeolite under various reaction conditions and found that the presence of oxygen is essential for Selective Reduction to occur. It was also found that the Reduction of nitrogen dioxide takes place more effectively than that of nitric oxide. Thus we think that the oxidation of nitric oxide to nitrogen dioxide is an important step. This paper deals with the reaction mechanism of the new reaction
Amarnath Natarajan - One of the best experts on this subject based on the ideXlab platform.
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face Selective Reduction of the exocyclic double bond in isatin derived spirocyclic lactones
Organic and Biomolecular Chemistry, 2013Co-Authors: Sandeep Rana, Amarnath NatarajanAbstract:We report an unusual face Selective Reduction of the exocyclic double bond in the α-methylene-γ-butyrolactone motif of spiro-oxindole systems. The spiro-oxindoles were assembled by an indium metal mediated Barbier-type reaction followed by an acid catalyzed lactonization.
Hideaki Hamada - One of the best experts on this subject based on the ideXlab platform.
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remarkable promoting effect of rhodium on the catalytic performance of ag al2o3 for the Selective Reduction of no with decane
Applied Catalysis B-environmental, 2003Co-Authors: Kazuhito Sato, Yoshiaki Kintaichi, Tomohiro Yoshinari, Masaaki Haneda, Hideaki HamadaAbstract:Abstract The addition of small amounts of rhodium enhanced the activity of Ag/Al2O3 catalyst for the Selective Reduction of NO with decane at low temperatures. The Rh-promoted Ag/Al2O3 showed its high performance even in the presence of low concentrations of SO2. Based on the catalytic activity for elementary reactions, it was suggested that the role of added rhodium is to enhance the reaction between NOx and decane-derived species, leading to NO Reduction. Catalyst characterization by UV-Vis spectroscopy indicated that the major silver species on Rh-promoted Ag/Al2O3 is Agnδ+ clusters, which would be responsible for the high activity. FT-IR measurements revealed that the formation rate of isocyanate species, which is a major reaction intermediate, is higher on Rh-promoted Ag/Al2O3.
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role of oxygen in Selective Reduction of nitrogen monoxide by propane over zeolite and alumina based catalysts
Catalysis Letters, 1992Co-Authors: Motoi Sasaki, Hideaki Hamada, Yoshiaki KintaichiAbstract:The role of coexisting oxygen in the Selective Reduction of nitrogen monoxide by propane on H-zeolites, alumina, Cu-ZSM-5 zeolite and Pt/Al2O3 catalysts was investigated. In the case of H-zeolites and alumina, oxidation of NO to NO2 played an important role for the overall Selective Reduction of NO. On the other hand, the initial reaction step was considered to be partial oxidation of propane over Cu-ZSM-5 and Pt/Al2O3.
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transition metal promoted silica and alumina catalysts for the Selective Reduction of nitrogen monoxide with propane
Applied Catalysis, 1991Co-Authors: Hideaki Hamada, Yoshiaki Kintaichi, Motoi Sasaki, Mitsunori TabataAbstract:Abstract The effect of transition metal additives on the catalytic performances of silica and alumina was investigated for the Selective Reduction of nitrogen monoxide with propane in the presence of high concentrations of oxygen. Some metal-silica catalysts showed the activity although silica was quite inactive. Most of the transition metals were found to promote the catalytic activity of alumina, although the performances were dependent on the preparation conditions. In particular, metal-alumina catalysts containing metal aluminate showed excellent activity at low temperatures and under high space velocity conditions.
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Selective Reduction of nitrogen monoxide with propane over alumina and hzsm 5 zeolite effect of oxygen and nitrogen dioxide intermediate
Applied Catalysis, 1991Co-Authors: Hideaki Hamada, Yoshiaki Kintaichi, Motoi Sasaki, Mitsunori TabataAbstract:In this study we investigated the Reduction of nitric oxide with propane over alumina or HZSM-5 zeolite under various reaction conditions and found that the presence of oxygen is essential for Selective Reduction to occur. It was also found that the Reduction of nitrogen dioxide takes place more effectively than that of nitric oxide. Thus we think that the oxidation of nitric oxide to nitrogen dioxide is an important step. This paper deals with the reaction mechanism of the new reaction
