Applied Catalysis B: Environmental, Vol.220, 251-263, 2018
Efficient bimetallic NiCu-SiO2 catalysts for selective hydrogenolysis of xylitol to ethylene glycol and propylene glycol
The selective hydrogenolysis of biomass-derived xylitol to ethylene glycol and propylene glycol was carried out over non-noble Ni-decorated Cu-SiO2 nanocatalysts with a wide range of Cu/Ni mass ratios and metal loadings in the presence of Ca(OH)(2). The NiCu-SiO2 bimetallic catalysts showed much superior activities and selectivities to the target glycols relative to the monometallic Cu-SiO2 and Ni-SiO2 catalysts. Among them, 10Ni80Cu-SiO2 catalyst (10/80 refers to the mass ratio of NiO and CuO) prepared by co-precipitation-gel method presented the highest activity and target glycols selectivity, and up to 81.0% combined glycol yield was attained at 473 K and 8 MPa H-2. Moreover, this catalyst exhibited greatly enhanced stability in repeated runs. Characterization of these catalysts by XRD, XPS, BET, N2O-chemisorption, H-2-TPR and TEM showed that the decoration of suitable amount of Ni into Cu-SiO2 catalysts had favorable effects on Cu dispersion, catalyst reducibility and the formation of highly active Ni surface-enriched Cu-Ni alloy sites. The notably enhanced performances of the NiCu-SiO2 bimetallic catalysts could be ascribed to their significantly promoted C-OH dehydrogenation and C=O hydrogenation activities and high resistance to sintering of the active sites, imposed by the structural and electronic effects of Ni. Clearly, these findings provide useful guidance for the design of more efficient and stable non-noble bimetallic nanocatalysts for upgrading biomass-derived platform compounds particularly via hydrogenation/hydrogenolysis reactions. (C) 2017 Elsevier B.V. All rights reserved.