Fractionation of spent liquor from organosolv-pretreatment using lignin-incompatible extraction

Spent liquor, or liquor in short, is the liquid stream resulting from organosolv pretreatment of lignocellulosic materials. The recovery of GVL, lignin and monosaccharide from the liquor is critical for producing value-added products and reducing operating costs. This work presents a new method, referred to as lignin-incompatible extraction, developed for the simultaneous recovery of GVL, lignin and monosaccharides from liquor. This method involves neutralisation of the liquor with calcium carbonate followed by extraction with toluene. Through the lignin-incompatible extraction, 87.6% of GVL was separated from liquor, 89.4% of lignin was precipitated during extraction, and 93.9% of xylose remained in the aqueous fraction. The lignin-incompatible extraction results correlated with the non-dispersion force parameters of the extracting solvent. The precipitated lignin indicated a lower hydrogen bonding ability and recycled GVL proved to have the same effectiveness in organosolv pretreatment in the first two cycles of operation.