Role of copper in the characterization of the copper(II)-promoted tin(IV) oxide catalysts for the catalytic oxidation of carbon monoxide
Cu(II)/SnO{sub 2} catalyst materials with Cu:Sn ratios in the range 0.02--0.30 have been prepared by three routes: coprecipitation from aqueous solutions containing Cu{sup 2+} and Sn{sup 4+} ions, sorption of Cu{sup 2+} ions on to tin(IV) oxide gel, and destabilization of choline-stabilized tin(IV) oxide colloidal sols by the addition of aqueous copper(II) nitrate solution, and their constitution after thermal treatment in the temperature range 333--1,273 K has been investigated by powder X-ray diffraction and EXAFS. The mode of operation of the catalysts appears to be synergistic in nature with the principal role of Cu(II) being mainly in electron transfer, i.e., it abstracts the negative surface charges (formed in the oxygen vacancies following desorption of CO{sub 2}) to form Cu(I), which is then oxidized back to Cu(II) by reaction with oxygen. The activity of catalysts deactivated by running under highly reducing conditions can be restored completely by heating in a flow of air at 355 K. Irreversible deactivation occurs on processing at very high temperatures due to sintering and the phase separation of copper(II) oxide.
- Research Organization:
- Univ. of Nottingham (GB)
- OSTI ID:
- 20014840
- Journal Information:
- Chemistry of Materials, Vol. 11, Issue 12; Other Information: PBD: Dec 1999; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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