Structure and reactivity of Zn-Cr mixed oxides. Role of non-stoichiometry in the catalytic synthesis of methanol

Abstract

The catalytic behaviour of Zn/Cr mixed oxides with different compositions was investigated as a function of the bulk and surface properties. It was observed that non-stoichiometric spinel-type phases were stable also in the reaction conditions, in which zinc-surface enrichment did not occur. The maximum productivity in methanol was observed for monophasic non-stoichiometric spinel-type samples with a Zn/Cr ratio near to one, whereas the samples richest in zinc, for which a side phase, ZnO also was detected, showed a strong decrease in activity. The catalytic data support the hypothesis that non-stoichiometric spinel is the active phase for the synthesis of methanol on coprecipitated Zn-Cr catalysts.