Supercritical methanol depolymerization and hydrodeoxygenation of pyrolytic lignin over reduced copper porous metal oxides.

Supercritical methanol depolymerization and hydrodeoxygenation (SCM-DHDO) is a process to produce fuel from biomass with supercritical methanol and CuMgAlOx catalyst. Previous research has shown that SCM-DHDO can convert cellulose, lignin and whole biomass feedstock in a single reaction step. In this paper, we show that SCM-DHDO can convert pyrolytic lignin derived from pyrolysis oil at approximately 50% carbon yield to an upgraded oil product. The upgraded oil mainly contains lignin monomers and dimers while an additional 50% of the carbon was converted into undesired products including methanol, insoluble pyrolytic lignin and coke. We demonstrated that after a 4 h SCM-DHDO reaction the pyrolytic lignin molecular weight did not significantly change, but the ketones, acids and aldehydes in the pyrolytic lignin were completely converted. Increasing the reaction time of SCM-DHDO reaction from 2 to 10 h increased the lignin monomer and dimer yield. The reduced CuAlMgOx catalyst hydrogenated 57.4% of the aromatic carbons to aliphatic carbons and removed 64% of the oxygen. However, the product oil could still not be distilled because of the thermal instability of the upgraded pyrolytic lignin. [ABSTRACT FROM AUTHOR]