Selective production of methanol from syngas over LaTi1−xCuxO3 mixed oxides

Abstract

Carbon monoxide hydrogenation was studied over partially substituted copper-containing LaTi1−xCuxO3 oxides and on copper supported on La2O3. The unsubstituted (x = 0) oxide was weakly active for CO hydrogenation, whereas all the other oxides were more active and exhibited high selectivity to methanol. Particularly, for substitutions x = 0.5–0.6, where the perovskite structure was observed, CO conversions close to 22% and selectivity close to 80% were found. Cu/La2O3 was, however, less active and yielded CO2 and hydrocarbons as the major products. Using X-ray photoelectron spectroscopy it was determined that under reaction conditions copper exists as reduced species. The L3VV X-ray induced Auger transition at 1849.2 eV observed for a representative LaMn0.5Cu0.5O3 catalyst prereduced and used in CO hydrogenation at 573 K, suggests that Cu+ species dominates in spent catalyst. These Cu+ species are believed to be stable under reaction conditions in the perovskite structure, only a slight Cu enrichment occurs on the topmost layer of catalysts.