Towards a Lignincellulosic Biorefinery: Direct One-Step Conversion of Lignin to Hydrogen-Enriched Biofuel

TLDR

The study introduces a one‑step liquefaction process that depolymerizes lignin into low‑oxygen bio‑oil suitable for blending with fossil fuels and is designed to integrate with ethanol production in a lignocellulosic biorefinery. The liquefaction is performed in formic acid, where depolymerization and oxygen removal occur simultaneously, an alcohol cosolvent can improve yields and H/C ratios, and the method is intended to be coupled with ethanol production from lignocellulosic carbohydrates. The process produces low‑coke (5%) bio‑oil that separates into a lighter phase rich in low‑molecular‑weight alkylphenols and C8–C10 aliphatics, making it suitable for fuel blending.

Abstract

This paper reports a novel liquefaction process that is capable of depolymerizing the natural biopolymer lignin into a liquid bio-oil with a very low oxygen content, suitable as a blending component to be combined with conventional fossil fuels for motor fuel applications. During the conversion, both depolymerization and removal of oxygen by formation of water occur in a single step. Formic acid serves as both the hydrogen donor and reaction medium in the pyrolysis/solvolysis process. Using an alcohol as cosolvent can improve the liquid yields and H/C ratios. Very little coke (5%) is produced. The liquids produced comprise two easily separable phases, where the lighter organic phase consists mainly of low molecular weight alkylphenols and C8−C10 aliphatics. The process is developed to be combined with ethanol production from lignocellulosic carbohydrates in a biorefinery concept aimed at converting all fractions of the wood into renewably sourced liquid fuels.