Fractionation of Degraded Lignin by Using a Water/1-Butanol Mixture with a Solid-Acid Catalyst: A Potential Source of Phenolic Compounds

Fractionation of a lignin-derived liquid using a water/1-butanol mixture was investigated with the aim of developing a source of phenols. The effect of various phases on lignin depolymerization by using a water/1-butanol mixture with a solid acid catalyst was investigated. The water/1-butanol solvent was confirmed to be heterogeneous under the reaction conditions, and the liquid phase was essential for effective depolymerization of lignin. To make optimum use of the depolymerized lignin and to understand its chemical structure, solvent fractionation was performed by using a water/tetrahydrofuran solution, ethyl acetate, and n-hexane as solvents. Catalytic cracking of the n-hexane soluble fraction was performed over an iron oxide catalyst by using a high-pressure fixed-bed flow reactor at 673 K. The production of phenol was confirmed, and the demethoxylation reaction was examined by using model compounds. In addition, as the heavy components were extracted during the solvent fractionation, as confirmed by analysis of the molecular structures of the fractionated components, the formation of solid products could be suppressed to a level below 2.5 mol(C)% based on lignin.