Subcritical liquefaction of lignocellulose for the production of bio-oils in ethanol/water system

Lignocellulose (20-40 mesh) was converted into bio-oils in ethanol with different concentrations (0, 20%, 40%, 60%, 80%, and 100%). The products were separated to obtain solid residues, heavy and light oils, and they were comprehensively characterized with a series of both chemical and spectral methods. Results indicated that the addition of ethanol enhanced the penetration of solvent into the rigid structure of lignocellulose. The highest bio-oil yield of 36.62% was obtained when the lignocellulose was liquified with 60% ethanol. The higher heating value of heavy oil decreased whereas that of light oil increased when more ethanol was used. H-1 NMR analysis revealed that the addition of ethanol resulted in a high proportion of alcohols, ethers and esters, together with less aldehydes in the heavy oil. Meanwhile, the proportions of aldehydes in the light oil decreased with the increase of ethanol concentration. (C) 2019 Elsevier Ltd. All rights reserved.