Activity control by structural design of multicomponent scheelite-type molybdate catalysts for the selective oxidation of propene

Control of the catalytic selective oxidation of propene to acrolein was ach ieved by designing multicomponent metal oxide catalysts to have the multifu nctions required for the reaction, such as activation of allylic hydrogen o f propene, oxygen insertion, reduction-oxidation coupling, lattice oxygen m obility, and activation of molecular oxygen. Scheelite-type Na0.5-3xLa0.5+x MoO4 oxides having lattice oxide ion mobility were chosen as a basic cataly tic material and used as a support for bismuth molybdate and cerium oxide l oadings. The catalytic activity was primarily controlled by the introductio n of lanthanum into the Na0.5-3xLa0.5+xMoO4 lattice, and the selectivity to acrolein was attained separately by loading bismuth molybdates on the surf ace of the support. It was found that the catalytic activity of Bi2Mo3O12/N a0.5-3xLa0.5+xMoO4 is strongly governed by the value of x irrespective of t he loading of Bi2Mo3O12. It was also demonstrated that high activities exce eding the primary activity were achieved by designedly introducing cerium b oth into the surface bismuth molybdate phase and in the vicinity of the sur face of the scheelite support. (C) 1999 Academic Press.