Oxidative Catalytic Fractionation and Depolymerization of Lignin in a One-Pot Single-Catalyst System

It has been known that the yield of lignin monomers during lignin depolymerization is limited by the irreversible condensations of lignin in the fractionation and/or depolymerization process. In this study, we report a new oxidative catalytic fractionation (OCF) process with a simple and effective one-pot but two-step approach to depolymerize lignin to lignin-derived chemicals (LDCs) using polyoxometalate (POM) as the only catalyst. First, the POM effectively catalyzed the methoxylation of the active a-OH groups of lignin in a methanol and water mixture at low temperature (100 degrees C), and 96% of the stabilized lignin in the lignocellulose sawdust was extracted to the solution simultaneously. Then the lignin solution was heated to an elevated temperature (140 degrees C) in the same solvent. As a result, 74.0 wt % of the lignin (based on the weight of the Klason lignin in the wood) was converted to LDCs, including 45.9 wt % aromatic monomers.

Automated summary

In this study, a new oxidative catalytic fractionation (OCF) process using polyoxometalate (POM) as the only catalyst was developed to depolymerize lignin to lignin-derived chemicals (LDCs). The process involved methoxylation of lignin followed by heating to convert a significant portion of lignin to LDCs, including a high content of aromatic monomers (45.9%). This provides an efficient and novel method for the utilization of lignin.