Hexane-carbon dioxide reaction catalyzed by alkaline earth metal oxides. II. Reaction network

The catalytic properties of alkaline earth metal oxides and the reaction sequences in the hexane-carbon dioxide reaction were investigated at 1173 K and atmospheric pressure. The catalytic activity for the decomposition of hexane to give deposited carbon increased with increase in the surface area of the catalyst, but the order of the activity for gasification of the deposited carbon was not parallel with either that for the decomposition of hexane or that for the hexane-carbon dioxide reaction. The catalytic activity for the hexane-carbon dioxide reaction was determined from the balance between the activity for the decomposition of hexane to produce the intermediate and that for the gasification of the deposited intermediate carbon. An oxygen transfer mechanism was applied to explain the gasification of carbon deposited on the catalyst surface. It was also confirmed that alkaline earth metal oxides catalyze the water-gas shift reaction under the gasification conditions. Based on these results, a network for the hexane-carbon dioxide reaction is proposed in order to understand comprehensively the catalysis of these oxides.