Biorefinery Lignin to Renewable Chemicals via Sequential Fractionation and Depolymerization

Abstract

Switchgrass-based, lignin-rich residues from cellulosic ethanol production were valorized into green chemicals via sequential methanol fractionation and hydrogenolysis depolymerization. The biomass residues were relatively purified by removing some structural carbohydrates and water soluble compounds. Methanol fractionation solubilized 14 % lignin from the above purified biomass residue, of which 95 % was klason lignin. The subsequent hydrogenolysis was catalyzed by Raney nickel with formic acid as hydrogen donors. Methanol soluble lignin fraction gave 58.11 % bio-oil yield, which was more than five times that from other fractions. The oxidation using hydrogen peroxide altered functional groups in lignin fractions but did not enhance the bio-oil yields. The GC–MS results revealed that bio-oil from all fractions except methanol soluble fraction contained more guaiacyl derivatives than syringyl derivatives. Sugar derivatives were generated at significant amounts from the depolymerization of the fractions that contained structural carbohydrates. Most of the generated monomers are renewable chemicals with wide industrial applications.