Activity Control by Structural Design of Multicomponent Scheelite-Type Molybdate Catalysts for the Selective Oxidation of Propene

Abstract

Control of the catalytic selective oxidation of propene to acrolein was achieved by designing multicomponent metal oxide catalysts to have the multifunctions required for the reaction, such as activation of allylic hydrogen of propene, oxygen insertion, reduction–oxidation coupling, lattice oxygen mobility, and activation of molecular oxygen. Scheelite-type Na0.5−3xLa0.5+xMoO4 oxides having lattice oxide ion mobility were chosen as a basic catalytic material and used as a support for bismuth molybdate and cerium oxide loadings. The catalytic activity was primarily controlled by the introduction of lanthanum into the Na0.5−3xLa0.5+xMoO4 lattice, and the selectivity to acrolein was attained separately by loading bismuth molybdates on the surface of the support. It was found that the catalytic activity of Bi2Mo3O12/Na0.5−3xLa0.5+xMoO4 is strongly governed by the value of x irrespective of the loading of Bi2Mo3O12. It was also demonstrated that high activities exceeding the primary activity were achieved by designedly introducing cerium both into the surface bismuth molybdate phase and in the vicinity of the surface of the scheelite support.