(143b) The Fate of Oxygen during Light Alkane Reforming, Oxidative Dehydrogenation, and Combustion

Catalytic transformation of light alkanes (C1-C3) is of industrially importance. The light alkanes undergo catalytic conversion, by reacting with O₂, CO₂, H₂O oxidants that increase their carbon oxidation state in partial oxidation, combustion, reforming, or oxidative dehydrogenation reactions, which may occur sequentially or concomitantly, as routes for producing syngas, olefin, or energy. Through kinetic, isotopic, spectroscopic, and density functional theory studies, we probe the active site requirements for activating the strong C-H bonds in these alkanes and their sequential reactions on first-row transition metal and metal oxide catalysts. Although these reactions occur at seemingly different oxygen and carbon chemical potential ranges, their catalytic requirements remain identical, i.e., initial activation of the C-H bond, kinetically coupled with the removal of the carbonaceous intermediates with reactive oxygen species. We probe the type of the reactive oxygen species present on first row transition metals (Ni, Co, Fe) and metal oxides (MoO_x) and connect their reactivities in oxidizing the carbonaceous intermediates to the rate dependences and also to the catalyst life. We address the catalytic requirements that lead to retaining the C-C bonds and thus to the formation of olefins and then establish the relationship between the reactivities of reverse water-gas shift to the stability of the catalysts against coke deposition.