Methane reforming with carbon dioxide on the Co/α-Al2O3 catalyst:: The formation, state, and transformations of surface carbon

The interactions of oxidized and reduced Co/alpha-Al2O3 (4 wt % CoO) with H-2, CH4, CO2, and O-2 and their mixtures are studied in flow and pulse regimes using a setup involving a DSC-111 differential scanning calorimeter and a system for chromatographic analyses. It is shown that treatment with hydrogen at 700degreesC results in the partial reduction of cobalt oxide to Co. Methane poorly reacts with the oxidized catalyst but readily reacts with the reduced catalyst to form H-2 and surface carbon. The initial surface carbon transforms into other forms, which block the cobalt surface to different extents and differ in the heats of reaction with CO2. Carbon dioxide may react with the surface carbon to form CO (rapidly) and with metallic Co to form CO and CoO (slowly). Thus, the main route of methane reforming with carbon dioxide on Co/alpha-Al2O3 is the dissociative adsorption of CH4 to form surface carbon and H-2 and the reaction of surface carbon with CO2 to form CO via the reverse Boudouard reaction.