Effective low-temperature hydrogenolysis of lignin using carbon-supported ruthenium and formic acid as reducing agent

Abstract

Herein, we report that re-condensation of lignin fragments after high temperature and hydrogen partial pressure treatment of lignin could be effectively avoided if the Cα-OH in the lignin are pre-oxidized to Cα = O. The pre-oxidized lignin was depolymerized into bio-oil through formylation-elimination-hydrogenolysis using carbon-supported ruthenium as a catalyst, and formic acid (FA) as an in-situ hydrogen source in methanol. Bio-oil of 41 wt% with a low average molecular weight of 690 Da, including 8.24 wt% monomers, was obtained at 110 °C after 24 h of reaction. In contrast to lignin, the hydrogen content in the obtained bio-oil significant increased and the oxygen content reduced, leading to a higher heating value (HHV) of 31 MJ/kg.