Two series of the Ce-Mo oxide catalysts for the partial oxidation of toluen
e to benzaldehyde have been prepared, respectively, by the sol-gel and copr
ecipitation methods and characterized by using various techniques. The resu
lts have shown that the catalytic reactivity is strongly composition relate
d; and ultrafine Ce-Mo oxide particles prepared by the sol-gel process are
apparently a better catalyst than large Ce-Mo oxide particles with a same c
omposition but prepared by the coprecipitation method. The highest yield of
benzaldehyde is obtained when the composition of the ultrafine particles r
eaches the vicinity of Ce/(Ce + Mo) = 0.50, corresponding to a catalyst con
sists of both CeO2 and Ce-2(MoO4)(3). The reaction mechanism and the promot
ion effect of the excess CeO2 in the ultrafine Ce-Mo oxide are discussed to
explain why ultrafine Ce-Mo oxide particles prepared by the sol-gel method
are good for the partial oxidation of toluene. (C) 2001 Elsevier Science B
.V. All rights reserved.