Coproduction of Hydrogen and Methanol from Methane by Chemical Looping Reforming

Coproduction of hydrogen and methanol from methane by chemical looping reforming is a novel approach to transform natural gas. Compared with conventional reforming processes, the mole ratio of methane to water fed to a chemical looping reactor can be the stoichiometric ratio without concerns over coking. In this work, the redox scheme was experimentally and numerically investigated, where a SrFeO3−δ perovskite acted as the oxygen transfer agent. To improve its redox performance, SrFeO3−δ was dispersed into three oxides: CaO, MnO, and CaO·MnO. Among them, CaO·MnO enhances the reforming performance best. Specifically, SrFeO3−δ/CaO·MnO composites exhibit 6.9% coke selectivity, 66.2% maximum instantaneous methane conversion, and 91.5% syngas (H2/CO ≈ 2) selectivity in the methane partial oxidation step and up to 90% H2O to H2 conversion in the water splitting step at a redox temperature of 900 °C. Further studies suggest that the low coke selectivity stems from the reaction between manganese oxide and coke or its precursor, which becomes more favorable at high temperatures. To evaluate the process of solar fuel production by chemical looping technology, an economic analysis of the coproduction of the hydrogen and methanol process was carried out and compared with conventional methanol synthesis. Compared with thermally driven methanol synthesis, the solar-driven coproduction scheme demonstrates 14% exergy efficiency improvement, 63% CO2 emission reduction, and 1.9 times more net income than the former. Our findings demonstrate that solar-driven chemical looping reforming is a very promising option for solar fuel production.