Mesoporous carbons as metal-free catalysts for propane dehydrogenation: Effect of the pore structure and surface property

Abstract

Nanocarbon materials have been used as important metal-free catalysts for various reactions in-cluding alkane dehydrogenation. However, clarifying the active sites and tuning the nanocarbon structure for direct dehydrogenation have always been significantly challenging owing to the lack of fundamental understanding of the structure and surface properties of carbon materials. Herein, mesoporous carbon materials with different pore ordering and surface properties were synthesized through a soft-templating method with different formaldehyde/resorcinol ratios and carbonization temperatures and used for catalytic dehydrogenation of propane to propylene. The highly ordered mesoporous carbons were found to have higher catalytic activities than disordered and ordered mesoporous carbons, mainly because the highly ordered mesopores favor mass transportation and provide more accessible active sites. Furthermore, mesoporous carbons can provide a large amount of surface active sites owing to their high surface areas, which is favorable for propane dehydroge-nation reaction. To control the surface oxygenated functional groups, highly ordered mesoporous carbons were carbonized at different temperatures (600, 700, and 800 °C). The propylene forma-tion rates exhibit an excellent linear relationship with the number of ketonic C=O groups, suggest-ing that C=O groups are the most possible active sites. Mesoporous carbons with different pore ordering and concentrations of surface oxygenated functional groups were synthesized and used as metal-free catalysts for direct dehydrogenation of propane to propylene.