A comparative study of oxidation of methanol on γ-Al2O3 supported group IB metal catalysts

Results are presented concerning the behavior of alumina supported Cu, Ag and Au (M) catalysts and the effect of addition of Li2O and CeOxon the dehydrogenation and oxidation of methanol. The γ-Al2O3 used is able to dehydrogenate methanol to formaldehyde and the addition of a metal to the support increases the CO production. A two-step reaction mechanism is proposed: in the first step, CH3OH is dehydrogenated on alumina to formaldehyde; in the second step, the formaldehyde reacts on M to CO or CO2. Another mechanism is proposed for good oxidizing catalysts: methanol reacts directly on M and is oxidized to CO2. The addition of the co-catalyst CeOx to the catalysts has a beneficial effect on the oxidation of methanol to CO2 because of its ability to provide oxygen. We suggest that Li2O blocks the adsorption site for methanol on alumina, and hence, decreasing the formation of formaldehyde.