Ethanol dehydrogenation to acetaldehyde over a Cuδ+-based Cu-MFI catalyst

Copper catalysts have been extensively investigated for the dehydrogenation of ethanol to acetaldehyde. However, identifying the essential active sites for this reaction is difficult because of the complex coordination structure and variable valences of the Cu species during the reaction. The stability of the Cu catalysts in the reaction also needs to be substantially improved. In this study, Cu-MFI, a well-defined Cu-based Lewis acid catalyst, was prepared using a post-acid treatment method for ethanol dehydrogenation. Different from the widely reported Cu+ and Cu0 species accounting for the activity of Cu catalysts, conditional experiments and in situ characterizations revealed that the highly dispersed Cuδ+ (1 < δ < 2) species on the MFI support are the essential active sites for ethanol dehydrogenation. Due to the strong interaction between Cu and silica via the Cu–O–Si linkage, the Cuδ+ species were very stable in the reaction and played the role of a Lewis acid catalyst in promoting ethanol activation and dehydrogenation. Over the optimal catalyst 5%Cu-MFI-deCu, 95% selectivity of acetaldehyde and approximately 87% ethanol conversion were obtained at 250 °C and a weight hourly space velocity of 0.64 h−1 in 120 h time on stream.