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

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 C-1-C-4 alkanes was mainly carried out over Ni/HZSM-5 containing strong Bronsted 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 40 wt% 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 H-2-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. (C) 2013 Elsevier Ltd. All rights reserved