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 degrees 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 similar to 94%, CAL conversion similar to 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.

Automated summary

In this study, a stable Ni-C catalyst with high selectivity and reusability in CAL hydrogenation was successfully prepared. By encapsulating metallic Ni nanoparticles in a carbon layer, the catalyst can be directly used in the reaction without pre-reduction.