Efficient selective oxidation of benzyl alcohol with oxygen in a continuous fixed bed reactor over NiGa hydrotalcite derived catalyst

Abstract

A series of NiGa catalysts have been prepared by calcining Ni5Ga-LDH under different temperatures, detailedly characterized, and investigated in the aerobic oxidation of benzyl alcohol to benzaldehyde in a fixed-bed reactor. The results indicated that calcination has a key effect on the composition of the catalyst and the catalytic performance, and the NiGa hydrotalcite calcined at 250 ℃ (Ni5Ga-LDH-250) exhibited the highest activity, which probably was due to the highest amount of surface basic site and the composition of Ni species. Under the optimized conditions, an excellent 91.5 % yield of benzaldehyde could be continuously obtained. Moreover, the catalytic performance kept almost steady in 170 h, and the catalyst could be regenerated and reused with slight reduction of the catalytic performance. According to the analysis of structure-activity relationship and the results of controlled experiments, possible reaction pathways for the aerobic oxidation of benzyl alcohol over Ni5Ga-LDH-250 are proposed.