Hydrotropic Solutions Enable Homogeneous Fenton Treatment of Lignin

In biorefineries, renewable resources are converted to value-added chemicals. However, lignin is often only thermally valorized. In this work, we propose an integrated process where lignin is extracted from beech wood by a thermal autoclave pretreatment in a hydrotropic solution. With increasing pretreatment temperature, we find a rising lignin recovery of close to 90% at 200 °C. Subsequently, the hydrotropic solution enables a homogeneous Fenton process as lignin can be dissolved at acidic pH values. While lignin is degraded, we demonstrate a feasible in situ extraction of low-molecular-weight aromatics such as p-cumenol. The proposed process proves to be a viable source for valuable compounds, with up to 30% yield of organic acids based on the initial lignin concentration. Consequently, the integrated process described herein encompasses resource efficiency, as only one solvent is used for pretreatment and degradation, and raw material efficiency with a lignin extraction yield close to 90%.