Direct oxidation of methane to methanol over proton conductor/metal mixed catalysts

The intermediate-temperature and low-pressure production of methanol from methane in a one-pass process was investigated using a micro- or nanosized electrocatalyst system. The powdered catalyst was prepared by mixing proton-conducting Sn0.9In0.1P2O7 particles with high-activity Pd–Au–Cu/C particles to provide numerous electrolyte–electrode interfaces as reaction sites for methane oxidation. For a feed mixture of H2O, O2, and methane, a local electrochemical cell can be formed at the electrode–electrolyte interface: H2O → 1/2O2 + 2H+ + 2e− at the anode site; O2 + CH4 + 2H+ + 2e− → CH3OH + H2O at the cathode site. In addition, the electrode also functions as a lead wire that short-circuits the cell. Therefore, the overall reaction can be expected to be CH4 + 1/2O2 → CH3OH. The series of reactions successfully resulted in reduction in the temperature for initiation of methane oxidation to 250 °C and increased the methanol yield while maintaining a very high selectivity toward methanol for temperatures up to 400 °C.