Oxidative dehydrogenation of isobutane catalyzed by an activated carbon fiber cloth exposed to supercritical fluids

Abstract

Modifications that supercritical fluids promote in the surface chemistry of carbon materials are scarcely investigated. Due to this lack of knowledge, carbon materials exposed to supercritical fluids have not been tested in any catalytic application. Here, we present the oxidative dehydrogenation of isobutane catalyzed by an activated carbon fiber cloth previously exposed to supercritical carbon dioxide, supercritical water and nitric acid. The role of carbonyl quinone groups as active sites is confirmed by their direct correlation with catalytic activity. The ability of the active sites to produce isobutene is hindered by the presence of acidic groups. Supercritical treatments develop microporosity, while removing acidic oxygen surface groups and incorporating carbonyl quinone groups, so they are appropriate methods to develop efficient carbon catalysts for this reaction. Coke deposits formed during reaction modify the surface chemistry and porosity of the catalysts. Samples presenting high surface areas are deactivated by coke deposition more slowly. Thanks to it, fibers exposed to supercritical water showed the best performance.