Structure and properties of graphitic carbons for oxidative dehydrogenation of isobutane

The use of carbons as alternatives for conventional metal-based catalysts has increased continuously in recent years for oxidative dehydrogenation (ODH) reactions of industrial relevance. So far, studies have been focused mainly on the surface functionality effect on ODH reaction. Due to the diverse nature of the structure and functionalities in different carbon materials, the precise mechanism of the ODH reaction over carbon surface remains a controversial topic. In this work, we have explored the effects of surface oxygenates and defective sites of mesoporous graphitic carbon catalysts on ODH reaction performance. For this purpose, carbons with controlled burn-off values varying from 13% to 70% have been prepared. The relationship between the catalytic activity and the physical and chemical structure of the carbon materials was investigated by comparison of the ratios of defective/graphitic sites and the amounts of surface oxygenates before and after reaction. The surface oxygenates appear to form on defective edge sites and they provide the oxygen species for ODH reaction. Further analyses of the rate constants for isobutane dehydrogenation and the deep oxidation of isobutane and isobutene suggest that different oxygen species are required for dehydrogenation and deep oxidation, respectively.