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Effects of precursor and support variation in the performance of uranium oxide catalysts for CO oxidation and selective reduction of NO

Effects of precursor and support variation in the performance of uranium oxide catalysts for CO oxidation and selective reduction of NO
Effects of precursor and support variation in the performance of uranium oxide catalysts for CO oxidation and selective reduction of NO
Uranium oxide catalysts supported upon gamma-Al2O3 and amorphous and mesoporous silica have been tested for CO/O-2 and NO/CO conversions. Pre-calcination is deleterious to catalysts on a mesoporous support due to extrusion of the active uranium phase into poorly dispersed uranium oxide particles. Developing the catalysts under CO/O-2/He or CO/NO/He avoids extrusion and results in superior mesoporous catalysts (from uranyl nitrate precursor) which are comparable to Pt/Al2O3 catalysts. Chloride is found generally to be deleterious to catalyst performance. The exception to this in UCl4/gamma-Al2O3 calcined at 873 K for CO/O-2. In this system, the total activity is correlated to the level of chlorine retention and average uranium phase crystallite size within the catalyst. The net rate expression for selective reduction of NO by CO over the best mesoporous catalyst is zero order in NO and proportional to [CO](1,4) in contrast to bulk U3O8 where the net rate depends upon [NO]. The activation energy (E(,)) and pre-exponential factors (v) are highly correlated both to each other and the net dispersion of the UO2.2 phase recovered after catalysis; the most active systems are highly dispersed where the E(,) values are more than compensated for by higher values of v.
62-68
Campbell, T.
33dfe406-da80-4386-b7f9-cd1724025000
Newton, M.A.
cf7f71a3-7c53-46f4-bf2d-9c02e0f2eda0
Boyd, V.
966272b5-2837-4a7e-8534-bdfa62440d61
Lee, D.F.
ee1df4c9-475a-49f9-9c53-e258e3fc1bdb
Evans, J.
05890433-0155-49fe-a65d-38c90ea25c69
Campbell, T.
33dfe406-da80-4386-b7f9-cd1724025000
Newton, M.A.
cf7f71a3-7c53-46f4-bf2d-9c02e0f2eda0
Boyd, V.
966272b5-2837-4a7e-8534-bdfa62440d61
Lee, D.F.
ee1df4c9-475a-49f9-9c53-e258e3fc1bdb
Evans, J.
05890433-0155-49fe-a65d-38c90ea25c69

Campbell, T., Newton, M.A., Boyd, V., Lee, D.F. and Evans, J. (2006) Effects of precursor and support variation in the performance of uranium oxide catalysts for CO oxidation and selective reduction of NO. Journal of Molecular Catalysis A: Chemical, 245 (1-2), 62-68. (doi:10.1016/j.molcata.2005.09.030).

Record type: Article

Abstract

Uranium oxide catalysts supported upon gamma-Al2O3 and amorphous and mesoporous silica have been tested for CO/O-2 and NO/CO conversions. Pre-calcination is deleterious to catalysts on a mesoporous support due to extrusion of the active uranium phase into poorly dispersed uranium oxide particles. Developing the catalysts under CO/O-2/He or CO/NO/He avoids extrusion and results in superior mesoporous catalysts (from uranyl nitrate precursor) which are comparable to Pt/Al2O3 catalysts. Chloride is found generally to be deleterious to catalyst performance. The exception to this in UCl4/gamma-Al2O3 calcined at 873 K for CO/O-2. In this system, the total activity is correlated to the level of chlorine retention and average uranium phase crystallite size within the catalyst. The net rate expression for selective reduction of NO by CO over the best mesoporous catalyst is zero order in NO and proportional to [CO](1,4) in contrast to bulk U3O8 where the net rate depends upon [NO]. The activation energy (E(,)) and pre-exponential factors (v) are highly correlated both to each other and the net dispersion of the UO2.2 phase recovered after catalysis; the most active systems are highly dispersed where the E(,) values are more than compensated for by higher values of v.

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Published date: 2006

Identifiers

Local EPrints ID: 44400
URI: http://eprints.soton.ac.uk/id/eprint/44400
PURE UUID: 0b07696a-08a7-4d3c-9a06-67bdc4f332a7

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Date deposited: 06 Mar 2007
Last modified: 15 Mar 2024 09:03

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Contributors

Author: T. Campbell
Author: M.A. Newton
Author: V. Boyd
Author: D.F. Lee
Author: J. Evans

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