Chemical recovery of γ -valerolactone/water-based biorefinery

Biorefinery, employing biomass as renewable resource, emerges as basis for a sustainable bio-economy. Forest biomass consists of valuable biopolymers which can fulfill the needs for materials, chemicals, and energy. We recently introduced a novel organosolv fractionation process where wood is treated at elevated temperature in aqueous γ-valerolactone (GVL) solution for effective deconstruction into its principal components: cellulose, hemicellulose and lignin, which can be further processed to products such as textile fibers, chemicals, fuels or energy. In order to assess the commercial feasibility of the process, we studied different methods for recovery of GVL and other extracted components in the spent liquor. We hereby present the two promising methods of 2-stage distillation at reduced pressure and near-critical CO2 extraction.
The spent liquor was produced from the uncatalyzed fractionation of Eucalyptus globulus wood chips in GVL aqueous solution under selected operational conditions. In distillation experiment, the spent liquor was initially diluted with water in order to partly precipitate the extracted lignin. The diluted liquid was subjected to distillation at reduced pressure to obtain an aqueous distillate containing the volatile compounds and an organic one rich in GVL. The residual liquid, rich in GVL and extracted components, was subjected to another dilution-lignin precipitation-distillation cycle. This method recovered ca. 91% GVL and 90% of the lignin in wood. Besides, inspired by previous pioneering research, we tested and confirmed that near-critical CO2 extraction enables an efficient separation of GVL from its aqueous solution.
Henceforth, we investigate the conversion of batch-wise distillation to continuous mode for improving the recovery rate, and simultaneously construct the extraction unit employing near-critical CO2 to separate GVL from the spent liquor.