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 th e reduction of nitric oxide by carbon monoxide was performed. In sol-g el 'sintered/reduced' catalysts' a redispersion of the metal phase and higher resistance to sintering was observed. On the other hand, in th e impregnated 'sintered/reduced catalysts', an important sintering eff ect was observed. The sol-gel 'reduced catalysts' and 'sintered/reduce d 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 re sistance to sintering on sol-gel 'sintered/reduced catalysts' was inte rpreted as a surface migration effect of the metal particles buried in alumina and titania gels. (C) 1998 Elsevier Science B.V.