The effects of water tolerant Lewis acids on the hydrothermal liquefaction of lignocellulosic biomass

Abstract

The objective of this study was to investigate the effects of water tolerant Lewis acids (i.e., In(OTf)3, Yb(OTf)3 and InCl3) on bio-oil and solid residue yields. For this purpose, poplar wood was liquefied at 300 °C with a residence time of 10 min without and with water tolerant Lewis acids in various concentrations from 0.5 to 10 wt% under hydrothermal conditions. The use of water tolerant Lewis acids had negative effects on bio-oil yields. The bio-oil from the run without a catalyst had a value of 17.50 wt% at 300 °C, 10 min. The highest bio-oil yields under identical conditions were the following: 14.27 wt%, 13.37 wt% and 12.42 wt% for Yb(OTf)3 (with a concentration of 0.5 wt% of the raw material), In(OTf)3 and InCl3 (with concentrations of 1 wt% of the raw material). The concentrations of catalysts used in the experiments had significant effects on both bio-oil and solid residue yields. An increase of catalyst concentrations resulted in a decrease in bio-oil yields. The catalysts changed neither the molecular nor the elemental compositions of bio-oils and solid residues significantly. The prominent compounds in bio-oils from all runs including the run without a catalyst were phenol, 2,6-dimethoxyphenol, and 2-methoxyphenol.