Hydrogenolysis of glycerol without external H2 over Nb-doped Ni catalysts supported on ordered mesoporous alumina

The correlation between the physico-chemical properties of Nb-doped nickel supported on ordered mesoporous alumina catalysts and product distribution during hydrogenolysis of glycerol with in situ produced hydrogen in continuous was investigated. The synthesis of alumina was carried out by the evaporation induced self-assembly (EISA) method. To achieve different interaction strengths among Ni, Nb and Al, the catalysts were prepared by co-impregnation of Ni and Nb on alumina, successive impregnation on alumina, and Ni impregnation on Nbmodified alumina using a Ni/Nb atom ratio of 2. Catalytic runs were performed at 235 degrees C/ 45 bar for 30 h TOS, at 12.2 h- 1 WHSV. All the catalysts showed high carbon yields to liquid products, mainly 1,2-propylene glycol and hydroxyacetone. The NiNb-SI catalyst, prepared through sequential impregnation of Nb and Ni, demonstrated the highest initial glycerol conversion rate (69.3%) and stability over 30 h TOS. Furthermore, it produced the highest carbon selectivity for propylene glycol at 56.7%. The catalytic performance of NiNb-SISi was also assessed under the same conditions with the addition of hydrogen, resulting in an enhanced capacity for dehydration- hydrogenation. However, glycerol conversion decreased. Post-reaction characterization revealed that catalyst deactivation was primarily caused by leaching, sintering and oxidation of Ni.