Catalytic reduction of nitric oxide on Pt and Rh catalysts supported on alumina and titania synthesized by the sol-gel method

Platinum and rhodium supported on alumina and titania were synthesized by the sol-gel method. Characterization and catalytic activity for the reduction of nitric oxide by carbon monoxide was performed. In sol-gel 'sintered/reduced' catalysts' a redispersion of the metal phase and higher resistance to sintering was observed. On the other hand, in the impregnated 'sintered/reduced catalysts', an important sintering effect was observed. The sol-gel 'reduced catalysts' and 'sintered/reduced catalysts' showed higher activity than that of impregnated reference catalysts, mainly when the titania is the support. Moreover, sol-gel preparations are more selective to N-2, whereas impregnated reference catalysts are selective to N2O. The increase in dispersion and high resistance to sintering on sol-gel 'sintered/reduced catalysts' was interpreted as a surface migration effect of the metal particles buried in alumina and titania gels. (C) 1998 Elsevier Science B.V.