Lignin-first fractionation of softwood lignocellulose using a mild dimethyl carbonate and ethylene glycol organosolv process.

Abstract

Here we report on a mild lignin-first acidolysis process (140 °C, 40 min) that uses the benign solvent dimethyl carbonate (DMC) and ethylene glycol (EG) as stabilization agent/solvent in order to produce high yield of aromatic monophenols directly from softwood lignocellulose (pine, spruce, cedar, and Douglas fir) with a depolymerization efficiency of 77-98%. At optimized conditions (140 °C, 40 min, 400 wt% EG and 2 wt% H2SO4 to pinewood) up to 9 wt% of aromatic monophenol was produced reaching a degree of delignification in pinewood of 77%. Cellulose was also preserved as evidenced by a 85% glucose yield after enzymatic digestion. An in-depth analysis of the depolymerization oil was conducted using GC-MS, HPLC, 2D-NMR and SEC providing structural insights into lignin derived dimers and oligomers and the composition of sugars and derived molecules. Mass balance evaluation was provided.