The oxidation and ammoxidation of propene produce ~ 10 billion lbs of acrolein and acrylonitrile annually. The catalyst used for these reactions is based on bismuth molybdate, promoted with up to ten other metallic elements. While Bi has long been known to be an essential component of all catalysts, it role has not been fully understood until recently. We will describe recent experimental and theoretical work aimed at developing a clear understanding of the role of Bi. This effort has revealed that Bi3+ cations are stable under reaction conditions and do not undergo redox reactions. Instead, these cations serve two important purposes – one is to adsorb propene, and in the case of ammoxidation, NH3, and the other is to reduce the barrier for the rate-limiting step which involves cleavage of a C-H bond in the methyl group of adsorbed propene. Our work has also revealed that the pathway for the oxidation of alkanes and alkenes over oxides having a scheelite structure similar to a-Bi2Mo3O12 is closely related to the strength of the weakest C-H bond in both the reactant and subsequent intermediates. This concept also helps to explain the formation of byproducts during the ammoxidation of propene

Partial oxidation and ammoxidation of propene over a-Bi2Mo3O12: The special role of Bi

254th National Meeting (2017)

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