Hydrogen-Transfer Reductive Catalytic Depolymerization of the Solid Residue from a Demonstration Lignocellulosic Ethanol Plant

In this study, corn stover residue (CSR), rich in lignin, was collected from the outlet waste stream of a lignocellulosic ethanol demonstration plant and was valorized into highly depolymerized bio-oil by hydrogen-transfer reductive catalytic depolymerization (RCD), in which Raney Ni served as a catalyst and 2-PrOH served as a hydrogen donor. The primary reactions involved in the hydrogen-transfer RCD of the CSR were investigated. It showed hydrogenolysis, hydrogenation, hydrodeoxygenation, demethoxylation, decarboxylation, and dealkylation were involved in the RCD of CSR. Results indicated a highest monomeric lignin yield of 8.31 wt % was obtained on conditions of 220 °C, 500 rpm, and 3 h. This work provides a feasible example for exploiting all the chemical compositions in lignocelluloses, by the combination of the traditional but mature “carbohydrate-first” strategy and the emerging but not yet commercialized “lignin-first” strategy.