COMPARISON OF SILICA-SUPPORTED MOO3 AND V2O5 CATALYSTS IN THE SELECTIVE PARTIAL OXIDATION OF METHANE

Silica-supported molybdenum oxide and vanadium oxide catalysts have be en prepared with a wide range of surface metal loadings (0.3-3.5 metal atom/nm(2)), Isolated surface metal oxide species are dominant at sur face metal loadings on silica below ca. 1 metal atom/nm(2) while at hi gher loadings, the metal oxide species tend to aggregate into crystall ine MoO3 and V2O5 particles. Both catalyst series have been tested in the selective oxidation of methane with molecular oxygen at atmospheri c pressure. The reactivity for methane conversion appears to be essent ially related to dispersed isolated surface metal oxide species, with the surface vanadium oxide species being more reactive than molybdenum oxide species. The higher reactivity of the surface vanadium oxide si tes may be related to the different nature of the interaction of the o xides with oxygen, Silica-supported vanadium oxide catalysts, despite their higher activity, result in lower yields to HCHO than silica-supp orted molybdenum oxide catalysts. (C) 1996 Academic Press, Inc.