Study of ternary-component bismuth molybdate catalysts by 18O 2 tracer in the oxidation of propylene to acrolein

Abstract

Participation of lattice oxide ions of ternary-component bismuth molybdate catalysts MBiMo O (M = Ni, Co, Mg, Mn, Ca, Sr, Ba, and Pb) was investigated using the 18O 2 tracer in the selective oxidation of propylene to acrolein. The participation of the lattice oxide ions in the oxidation is prominent on every catalyst but the extent of the participation varies significantly depending on the structure of the catalyst. Only lattice oxide ions in the bismuth molybdate phase are incorporated into the oxidized products on the catalysts (M = Ni, Co, Mg, and Mn) where M have smaller ionic radius than Bi 3+; catalyst particles are composed of a shell of bismuth molybdates and a core of MMoO 4. On the other hand, whole oxide ions in the active particles are involved in the oxidation on catalysts having a scheelite-type structure (M = Ca, Sr, Ba, and Pb) where M has a comparable ionic radius to Bi 3+.