Cu-Based Catalysts with Enhanced Thermal Stability for Cyclohexyl Acetate Hydrogenation: Studies on Cu+ and Cu0 Sites at Different Reduction Temperatures

Abstract

Cyclohexene esterification–hydrogenation for the efficient production of cyclohexanol will be commercialized for the first time. Cu/MgO/Al2O3 catalysts with layered double hydroxides as precursors were developed, and the effect of altering the reduction temperature on the catalytic activity was explored. Fresh and spent Cu/MgO/Al2O3 catalysts exhibited excellent catalytic performance after thermal treatment during the hydrogenation of cyclohexyl acetate to cyclohexanol. STEM images showed that the Cu particles grew slightly, without obvious aggregation. Based on the results of XAES and in situ FTIR of the adsorbed CO method, optimal performance (conversion rate of 99.59% with 98.94% selectivity) was achieved, which was attributed to the synergistic effect on the surface-active Cu0 and Cu+ sites with Cu0/(Cu0 + Cu+) of around 0.70, and the ratios could be maintained at temperatures of 513–553 K. The morphology of Cu/MgO/Al2O3 catalysts was well preserved during the hydrogenation of cyclohexyl acetate, indicating potential industrial applications. The well-dispersed Cu/MgO/Al2O3 catalyst with a stable microstructure possesses an adjustable valence state and thermal stability during the hydrogenation of cyclohexyl acetate, giving it industrial application prospects.