An IR study of methanol steam reforming over ex-hydrotalcite Cu Zn Al catalysts

A Cu-ZnO-Al2O3 catalyst prepared via hydrotalcite-like hydroxycarbonate precursor, has been tested in the oxidative steam reforming of methanol (MOSR) to produce hydrogen and CO2 with poor CO content in a flow reactor. The conversion of methanol over oxidized, reduced and hydrated catalyst has been investigated by IR spectroscopy. The reactions of CO over hydrated and reduced surfaces and of the CO2 + H2 mixture has also been investigated by IR in the range 200-400 °C. It has been concluded that during methanol steam reforming the catalyst works in a partially oxidized state. Methoxy and formate groups are intermediates in the reaction. The key step for low CO concentration in the products is the fast oxidation of adsorbed CO to CO2. Pure methanol decomposition to CO and hydrogen, instead, occurs over highly reduced catalyst. The mechanism of the water gas shift reaction has also been discussed.