Michaelis-Menten kinetics have long been used by biochemists and organic chemists to compare enzymatic and molecular catalysts; however, this model is not typically applied to heterogeneous catalysts.  In this talk, we discuss the application of Michelis-Menten kinetics in terms of an “active site” model to describe heterogeneous catalysts.  In particular, we focus on the utility of this model in ascertaining the role of water in Au catalyzed oxidations, and in understanding the differences between various catalysts. <br/> <br/>Our discussion will primarily focus on CO and benzyl alcohol oxidation over titania and alumina supported Au catalysts.  In CO oxidation, mechanistic (kinetic measurements, isotopic labeling, and in situ IR spectroscopy) studies, as well as parallel DFT modeling indicated that water is a co-catalyst in the reaction.  In this role, water serves both to activate O2 and to assist in the rate-determining decomposition of Au-COOH.  In benzyl alcohol oxidation, the effects of adsorbed water are more subtle, consistent with a mechanism in which O2 is activated after the rate determining C-H activation step.

Using “active site” kinetics models to understand the role of water in Au catalyzed oxidations

251st National Meeting (2016)

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