The adsorption of NO and NH3 on V205/Ti02 catalysts has been studied by ESR and XPS at temperatures and pressures close to those used for industrial tail gas cleanup from power plants and HNO, plants, using NO reduction with ammonia. The paper extends and confirms earlier studies on pure V20s and Ti02 samples.' The reduction of the vanadia sites by adsorbed NH3 occurs over the whole range of temperatures studied while NO adsorption is observed on the titania support. Reduction of NO to N2 occurs on the reduced vanadia sites, which are reoxidized in the process. The reduced vanadia sites, however, are blocked by chemisorbed NH,, preventing the reduction of NO which causes a drop in the NO molar conversion. The presence of oxygen (or water) in the reaction mixture plays a major role in the selectivity of the vanadium oxide catalyst since it interacts with NH, at the reduced vanadia sites, resulting in the elimination of the NH3 poisoning of the reduced surface sites at temperatures above 550 K. 1989, 55, 15 1. (14) Inomata, M.; Miyamoto, A.; Murakami, Y. J . C a r d 1980, 62, 40. (15) Odenbrand, C U. I.; Lundin, S. T.; Anderson, L. A. H. Appl. Carol.
ChemInform Abstract Auger electron spectroscopy (AES) and thermal desorption spectroscopy (TDS) are used to study the adsorption of NH3 and NO on the title supports at pressures and temp. close to those used in industry for the NO reduction with NH3 over V2O5/TiO2 catalysts ( 25 torr, 20-675 K). NH3 adsorption occurs over the whole range of temp. and on all surfaces studied, while NO adsorption takes place only on TiO2 and on reduced V2O5, but not on oxidized V2O5 surfaces. NH3 reduces the V2O5 surface resulting in the production of N2O. The presence of N2O, NO, and O2 leads to the reoxidation of the vanadium surface and formation of N2. No evidence for the NO/NH3 reaction is obtained on the TiO2 surface. However, NO adsorption on TiO2 appears to be a main factor for the catalytic effectiveness in V2O5/TiO2 samples.
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