High-Temperature Conversion of CH4 to C2-Hydrocarbons and H2 Using a Redox System of Metal Oxide

Abstract

A high-temperature thermochemical process using a redox system of metal oxide is proposed for converting CH4 to C2-hydrocarbons (C2-HCs) and H2. Reactions were performed in a two-step redox cycle. In the first high-temperature and endothermic step, methane is reacted with metal oxide to produce C2-HCs and the reduced metal oxide. The reduced metal oxide is reoxidized with water to generate H2 at a low temperature in the second step. A thermodynamic analysis showed that redox systems of Fe3O4/FeO, SnO2/SnO, and WO3/WO2 are promising for the two-step process. The redox system of Fe3O4 was experimentally examined. Highly selective conversion could be repeated with SiO2-supported Fe3O4 (Fe3O4/SiO2) to produce C2-HCs (mainly C2H4) and H2 alternately in the different steps at temperatures from 1123 to 1173 K; evolution of COx and deposition of bulk carbon were scarcely observed. Experimental studies using unsupported Fe3O4 showed that the formation of C2-HCs in the first high-temperature step occurred favorably...