Production of liquid alkanes by controlling reactivity of sorbitol hydrogenation with a Ni/HZSM-5 catalyst in water

Abstract

Liquid fuels derived from renewable biomass are of great importance on the potential substitution for diminishing fossil fuels. The conversion of sorbitol (a product of biomass-derived glucose hydrogenation) into liquid alkanes such as pentane and hexane over the Ni/HZSM-5 catalysts with or without MCM-41 addition was investigated in the presence of hydrogen in water medium. The production distribution of sorbitol hydrogenation can be controlled by adjusting the acidity of the catalyst. The scission of C–C bond in the sorbitol molecule into light C1–C4 alkanes was mainly carried out over Ni/HZSM-5 containing strong Brønsted acid sites, while C–O bond scission into heavier alkanes was dominated over the catalysts added by MCM-41 containing weak Lewis acid sites. The sorbitol conversion and total liquid alkanes selectivity were found to be 67.1% and 98.7% over 2%Ni/HZSM-5 modified by 40wt% of MCM-41, whereas the corresponding value was 40% and 35.6% over 2%Ni/HZSM-5 in the absence of MCM-41. The effect of MCM-41 on the structure, acidity, and reducibility of Ni/HZSM-5 was investigated by using XRD, Py-IR, IR, and H2-TPR. Meanwhile, the resistance of carbon deposition over the catalyst modified by MCM-41 was studied by using TG–DSC technique. MCM-41 was found to have a positive interaction with HZSM-5 on the modulation of its structure properties and acidity, accompanying by the improvement on the reducibility of the catalyst. In addition, MCM-41 can distinctly decrease carbon deposition on the catalyst surface. These roles can favor the selective hydrodeoxygenation of C–O bond in the sorbitol molecule to generate liquid alkanes.