Near-critical water hydrothermal transformation of industrial lignins to high value phenolics

A process for the production of high-value-added phenolics following hydrothermal depolymerization of black liquor lignins after acidification without catalysis was successfully deployed and is described herein. A high yield of liquid products up to 33.3 mg/mL (based on raw black liquor) was recovered at 290 degrees C, 30 min, and pH 6; meanwhile, only 12.6 mg/mL solid residue was obtained. GC-MS analyses of the liquid products confirmed value-added aromatic monomers, among which the yields of phenol, guaiacol, and 2,6-dimethoxy-phenol were high (similar to 60% of the identified compounds). FT-IR of the solid residues indicated that the black liquor lignin was depolymerized through cleavage of ether bonds and decarboxylation. The results suggest that black liquor may be a new resource for aromatic products. (C) 2016 Elsevier B.V. All rights reserved.