Liquefaction of Softwoods and Hardwoods in Supercritical Methanol: A Novel Approach to Bio-Oil Production

Abstract

The production of consistent renewable-based hydrocarbons from woody biomass involves the efficient conversion into stable product streams. Supercritical methanol treatment is a new approach to efficiently convert woody biomass into bio-oil at modest processing temperatures (> 238 °C) and pressures (> 8.1 MPa). The conversion of common Alaskan tree species namely, Alaskan birch and Sitka spruce, was evaluated using the supercritical methanol liquefaction process to yield bio-oil and biochar fractions. Results show that liquefaction of softwoods and hardwoods can be achieved in excess of 90 wt%. The biochar was characterized by Fourier transform infrared spectroscopy and showed that this was lignin derived. The volatile components from the resultant bio-oil were chemically characterized (composition) by gas chromatography-mass spectrometry. The resulting bio-oil was comprised of partially methylated lignin-derived monomers and sugar derivatives which results in a stable and consistent product platform that can be followed by catalytic upgrading into a drop-in-fuel. The broader implications of this novel approach to obtain sustainable bioenergy and biofuel infrastructure are discussed.