Direct methanol steam reforming to hydrogen over CuZnGaO_x catalysts without CO post-treatment: mechanistic considerations

Utilization of hydrogen gas (and carbon dioxide) from methanol steam reforming reaction directly without CO post-treatment to supply proton exchange membrane fuel cells for mobile applications is an attractive option. CuZnGaO_x based mixed oxides prepared by co-precipitation are found to be active as catalysts for the reforming reaction. It is also found that the use of lower temperature and a faster substrate flow rate with a shorter contact time with the catalyst bed can significantly reduce the CO level in the product gas stream. At 150 °C this class of oxides gives a decent methanol conversion but can also totally suppress the CO production at a short contact time, which is in a sharp contrast with conventional CuZnO_x based catalysts that give a significant degree of CO formation. Characterization using Diffuse Reflectance Infrared Fourier Transform (DRIFT) analysis presented in this work clearly suggests the importance of the interface between copper metal-defective oxides for the catalysis. Mechanistic aspects of this reaction are therefore discussed in this paper.