Particle size effects in copper-catalyzed hydrogenation of ethyl acetate

Supported Cu catalysts are widely used in the chemical industry. Here, we discuss the role of the Cu particle size in the hydrogenation of ethyl acetate, as a model reaction for Cu-based hydrogenation catalysis and a crucial step to produce ethanol via synthesis gas. A series of carbon-supported Cu catalysts was prepared with Cu particle sizes tuned between 3 and 14 nm. At temperatures of 180–210 °C and a pressure of 30 bar, the surface-normalized activity increased around 4-fold when increasing the Cu particle size from 3 to 10 nm, while it became constant for Cu particles above 10 nm, hence showing that the Cu-catalyzed hydrogenation reaction is weakly sensitive to the Cu surface structure. The apparent activation energy for the reaction was around 94 kJ mol−1 for all Cu particle sizes, suggesting a size-independent nature of the active sites, whereas the abundance of the active sites increased with increasing Cu particle size below 10 nm. A maximal copper-normalized activity was achieved with Cu particles of around 6 nm, providing an optimal balance between intrinsic activity and available surface area. These findings may guide optimization strategies for reactions where hydrogenation of relatively stable intermediates is the rate-limiting step.