Microwave-assisted Lignin Depolymerization for Bio-oil and Phenolic Monomer Production

Abstract

The population expansion, industrial development and environmental deterioration drive a shift from petroleum-refinery to biorefinery. Lignin, is an abundantly available bioresource that can be valorized to produce a wide array of bio-based products. However, depolymerization of this macropolymer is costly and technically difficult. This research evaluated a microwave-assisted depolymerization of lignin in the presence of formic acid to produce bio-oil and phenolic monomers. The amount of formic acid was identified as the most critical factor influencing product yields. Depolymerization conditions for alkaline and de-alkaline were optimized. An “in-house” downstream processing protocol was developed, and demonstrated efficient to recover high-quality bio-oil. Acidic condition favored the product recovery than neutral or basic conditions. In terms of reaction medium, ethanol was better than water. This work provided a feasible route to depolymerize lignin under mild condition (temperature of 230°C) using renewable reagents (formic acid and ethanol) and energy-efficient heating source (microwave irradiation).