Kinetic mechanism for the reaction between methanol and water over a Cu-ZnO-Al2O3 catalyst

The steam reforming of methanol over a Cu/ZnO/Al₂O₃ catalyst has been investigated. The reaction yields carbon dioxide and hydrogen in the ratio of one to three, with small amounts of dimethyl ether and carbon monoxide being produced at high conversion. Comparison of the rates of methanol dehydrogenation and of steam reforming over the same catalyst indicate that steam reforming proceeds via dehydrogenation to methyl formate. Methyl formate then hydrolyses to formic acid which decomposes to carbon dioxide and hydrogen. Detailed studies of the kinetics of the reactions show that methanol dehydrogenation controls the rate of steam reforming. Langmuir-Hinshelwood modelling indicates that hydrogen extraction from adsorbed methoxy groups is rate determining to the overall processes.