Crystal plane effect of ceria on supported copper catalyst for liquid-phase hydrogenation of unsaturated aldehyde

Ceria has been widely used as catalyst support displaying a size- or shape-dependent catalytic performance due to the strong metal-support interaction (SMSI) effect with active metal. Almost all the studies on the SMSI effect of ceria-supported metal catalysts are involved generally in gas-phase reaction, but rarely in the liquid-phase reaction system. In this work, Cu/CeO₂-P (copper loaded on nano-polyhedral CeO₂ with (111) terminated surface) was investigated its catalytic performance on liquid-phase hydrogenation and studied the SMSI effect by comparing with the catalysts supported on nano-rod and nano-cube CeO₂. It was found that Cu was highly dispersed on the external surface of ceria in the Cu/CeO₂-P catalyst via a moderate SMSI effect. Furthermore, the degree of the interaction showed great influence on the chemical state of Cu species, and the ratio of (Cu⁺+Cu⁰)/Cu²⁺ in Cu/CeO₂-P was higher than Cu/CeO₂-R (Cu loaded on nano-rod CeO₂ with (110) plane) and Cu/CeO₂-C (Cu loaded on nano-cube CeO₂ with (100) facet). As a result, the Cu/CeO₂-P catalyst showed the best catalytic performance among three types of catalysts. Based on series of catalytic investigations, the catalytic performance in liquid-phase hydrogenation was intrinsically relevant to the crystal plane effect and reduced Cu proportion induced by an appropriate SMSI effect, which was completely different from gas-phase hydrogenation.