Vapor-phase dehydrocoupling of methanol to methyl formate over CuAl2O4

CuO-Al2O3 systems 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-Al2O3 systems, CuAl2O4 samples calcined at temperatures below 1000 degrees C were partially reduced during the reaction at 310 degrees 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 degrees C, whereas Cu(0) decomposed methyl formate into methanol and CO above 210 degrees C. On the other hand, CuAl2O4 calcined at 1100 degrees C showed the highest activity of the formation of methyl formate at a reaction temperature of 310 degrees C. Since the CuAl2O4 sample was not reduced even at 310 degrees C, Cu(II) species in the CuAl2O4 were found to be effective sites for the dehydrocoupling at temperatures above 250 degrees C. In addition, Cu(I) species in CuAlO2 was also found to be active with keeping high MF selectivity up to 290 degrees C. (C) 1997 Academic Press.