In situ studies of hydrocarbon oxidation by bismuth molybdate and vanadyl pyrophosphate catalysts
Conference Paper
Overview
Identity
View All
Overview
abstract
Conventional wisdom is that metal oxide-catalyzed selective oxidations follow the Mars-van Krevelen mechanism. Our studies of butane oxidation by vanadyl pyrophosphate catalysts have quantitatively determined the kinetics of catalyst reduction and reoxidation, and have shown that oxygen removal from the lattice is too slow to account for the steady-state reaction rate. In contrast, bismuth molybdate catalysts for propene oxidation utilize lattice oxygen to a much greater extent. We have synthesized bismuth molybdates and novel bismuth vanadomolybdate materials derived from the structure of the highly selective beta-Bi2Mo2O9. We have quantified the relative contribution of the redox mechanism to the overall oxidation reaction in the bismuth molybdates and vanadomolybdates. All propylene oxidation takes place by redox reactions involving the lattice, in accordance with the Mars van Krevelen mechanism. Addition of a limited amount of vanadium to the structure of beta-Bi2Mo2O9 increases activity by enhancing the interaction of gas-phase oxygen with the surface.
