Depolymerization and Hydrodeoxygenation of Switchgrass Lignin with Formic Acid

Abstract

Organosolv switchgrass lignin is depolymerized and hydrodeoxygenated with a formic acid hydrogen source, 20 wt % Pt/C catalyst, and ethanol solvent. The combination of formic acid and Pt/C is found to promote production of higher fractions of lower molecular weight compounds in the liquid products. After 4 h of reaction, all of the switchgrass lignin is solubilized and 21 wt % of the biomass is shown to be converted into seven prominent molecular species that are identified and quantified. Reaction time is shown to be an important variable in affecting changes in product distributions and bulk liquid product properties. At 20 h of reaction, the lignin is significantly depolymerized to form liquid products with a 76 % reduction in the weighted average molecular weight. Elemental analysis also shows that the resultant liquid products have a 50 % reduction in O/C and 10 % increase in H/C molar ratios compared to the switchgrass lignin after 20 h.