(85c) One-Pot Conversion of Biomass in Aprotic Solvent for Chemicals and Quality Lignin Based on Plasma Electrolysis

Plasma electrolysis can occur when high-voltage electricity is applied to a solution. Due to the combined effect of joule heating and active species generated, plasma electrolysis of biomass demonstrates unique advantages in comparison to conventional thermal-based conversion. In this study, plasma electrolysis was employed as a novel method to convert red oak in γ-Valerolactone (GVL) and diluted sulfuric acid. It was observed that during the plasma electrolysis, the solution temperature could increase to 165 °C without external heating. Biomass was completely liquified by plasma electrolysis to produce liquid products containing furfural, levoglucosenone (LGO), levulinic acid (LA) and 1,4:3,6-dianhydro-α-D-glucopyranose (DGP). The monomer yields were affected by acid concentration, biomass mass loading, water co-solvent, electricity power parameters, as well as reaction time. With 4% biomass mass loading, LGO yield up to 40.6 mol% per cellulose fraction and furfural yield of 98.1 mol% per hemicellulose fraction were obtained in a GVL solution with 10.5 mM acid. With a lower biomass mass loading of 1.3%, the maximum LGO yield of 45.2 mol% was obtained using only 3.5 mM acid. A comparison study showed that thermally converting red oak at a 165 °C GVL with 10.5 Mm acid can only produce up to 13.1 mol% LGO and 84.7 mol% furfural using much longer reaction times. During plasma electrolysis, lignin dissolution in the solution was followed by dehydration of hemicellulose to furfural, and finally dehydration of cellulose to LGO, LA and DGP. In this study, the solubilized lignin was precipitated and pyrolyzed. As a result, up to 18.71% phenolic monomers were obtained from the plasma-derived lignin, compared to 6.32% from organosolv lignin, and 8.61% from milled lignin. The 2D-NMR analysis showed that ɑ-carbons in β-O-4 and β-5 linkages were absent in the plasm-derived lignin.