Oxidative dehydrogenation of ethylbenzene on nanocarbon: Kinetics and reaction mechanism

Abstract

Active site titration, kinetic analysis, isotope and temperature programmed surface reaction experiments have been applied to reveal the nature of nanocarbon catalyzed alkane oxidative dehydrogenation reactions. The catalytic reaction involves the redox cycle of ketonic carbonyl-hydroxyl pairs on nanocarbon materials, during which the substrate of ethylbenzene (EB) dehydrogenates to product styrene, and the molecular oxygen re-oxidizes the catalysts yielding water. The rate equation based on the mechanistic interpretations of the catalytic reactions provides intrinsic rate or equilibrium constants, which have their specific physicochemical meanings and could be directly linked to the catalytic process. The proposed rate equation could also accurately describe the effects of reactant (EB or O2) pressures and isotopomers (deuterated-EB or 18O2) on rate data, and provide a quantitative analysis on the evolution and content of surface intermediates on carbon catalysts, which is a reliable descriptor of the intrinsic reactivity and essential to establish the structure-function relations for carbon catalyzed redox reactions.