Highly Efficient SiC-Supported Ni-Based Catalysts with Enhanced Recycle Stability for One-Pot Cellobiose Hydrolytic Hydrogenation to Hexitols

In this contribution, SiC material was applied as the catalyst support in the aqueous-phase reaction of one-pot cellobiose hydrolytic hydrogenation to hexitols, with the less costly transition metal Ni. Even with its neutral nature, more than 50% hexitol yield was achieved with Ni contents as low as 3 wt % supporting on SiC, and further improved to near 70% hexitol yield with Ni loadings increased to 5 wt %. The catalytic performances were superior to the others supported with different carriers (Al2O3, carbon nanotube (CNT), and AC). DFT simulation results indicate that the H-2 dissociation energy on the Ni-4/SiC(111) slab is at -26.9 kcal/mol, which is substantially lower than those on the Ni-4/Al2O3(100) slab (-34.1 kcal/mol) and Ni-4/graphene slab (-32.5 kcal/mol, taken graphene as a local structure of CNT). The hexitol yield on SiC-supported Ni catalyst was further improved to 75.7% with Ir promoter, more importantly, with a much enhanced recycle stability. Hexitol yield could be maintained around 60% even after five cycles on Ir-promoted catalyst, compared to 12% after only three cycles on Ni monometallic catalyst. ICP-OES results revealed that the leaching of Ni was greatly inhibited with the assistance of Ir. The results of the H-2-TPR analysis suggest an easier H-2 activation ability observed on the surface of Ir-promoted catalyst due to the synergetic effects between Ni and Ir. The findings would shed light on SiC for further applications in biomass conversion.