Porous carbon-encapsulated Ni nanocatalysts for selective catalytic hydrogenation of cinnamaldehyde to hydrocinnamaldehyde

Hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) or hydrocinnamaldehyde (HCAL) with high selectivity has important industrial value. Previous studies have shown that nickel-based catalysts are highly active and favor the selectivity to HCAL. However, Ni in metallic state is so active that most of nickel-based catalysts need to be pre-reduced before use. In this paper, a stable Ni–C catalyst was prepared by simple pyrolysis of Ni-BTC and systematically characterized. The results showed that metallic Ni nanoparticles were uniformly dispersed and encapsulated in the carbon layer, which protects the metallic Ni from oxidation. Therefore, the Ni–C catalyst can be directly used in CAL hydrogenation without pre-reduction. The catalyst Ni-C-600 achieved 92.5% selectivity to HCAL at 96.2% conversion of CAL at 120 °C under 2 MPa H 2 for 6 h with a poor reusability in isopropanol (IPA), while the catalytic performance and reusability were evidently enhanced (HCAL selectivity ~ 94%, CAL conversion ~ 99% in five consecutive runs for 4 h) in a solvent containing water and IPA. This study provides a facile and low-cost method to prepare effective Ni-based catalysts displaying excellent catalytic activity with high HCAL selectivity and stable reusability in CAL hydrogenation. Graphical abstract