Vapor-Phase Dehydrocoupling of Methanol to Methyl Formate over CuAl2O4

Abstract

CuO–Al2O3systems with different Cu/Al ratios were prepared by the amorphous citrate process, and their catalytic activities for the dehydrocoupling of methanol to methyl formate were examined. In the CuO–Al2O3systems, CuAl2O4samples calcined at temperatures below 1000°C were partially reduced during the reaction at 310°C and decreased the selectivity to methyl formate (MF) with increasing Cu(0) content. Cu(0) species catalyzed the dehydrocoupling reaction without decomposition of methyl formate at temperatures below 210°C, whereas Cu(0) decomposed methyl formate into methanol and CO above 210°C. On the other hand, CuAl2O4calcined at 1100°C showed the highest activity of the formation of methyl formate at a reaction temperature of 310°C. Since the CuAl2O4sample was not reduced even at 310°C, Cu(II) species in the CuAl2O4were found to be effective sites for the dehydrocoupling at temperatures above 250°C. In addition, Cu(I) species in CuAlO2was also found to be active with keeping high MF selectivity up to 290°C.