Phase Equilibria Aided Optimization of Levoglucosan Extraction during Condensation of Fast Pyrolysis Bio-Oils

The production of levoglucosan (LG) from biomass has gained considerable attention, as it represents a major precursor for the production of monomeric sugars such as glucose and subsequently biofuels such as bioethanol. This study investigated the efficiency of applying a novel recovery method of LG from fast pyrolysis vapors during condensation. The method employed quenching the hot pyrolysis volatiles with water in a single-step condensation process such that the condensed organic-rich condensate (ORC) fraction of the fast pyrolysis bio-oil is recovered together with the spent water quench on a single stage. Of the two-phase products recovered, 100% LG ended up in the spent water quench phase. Compared to the liquid–liquid (solvent) extraction of LG from an already condensed ORC, this technique demonstrated to be highly efficient for LG extraction from fast pyrolysis bio-oils (FPBOs), as it requires a significantly lower solvent-to-feed ratio for optimum LG recovery and it eradicates the need for downstream liquid–liquid extraction setups. Interestingly, the aqueous pyrolysis condensate (aqueous condensate), a side-stream product that is usually recovered during fractional condensation of hot pyrolysis vapors, has shown promising characteristics over freshwater in its utilization as a solvent for LG extraction from the ORC, which proves to be a favorable addition toward attaining a sustainable pyrolysis biorefinery. Model predictions of both techniques also showed that the modified UNIFAC Dortmund model in addition to its huge prospects in predicting vapor–liquid equilibrium behavior of fast pyrolysis vapors also has huge capabilities in accurately handling liquid–liquid equilibrium behavior of water and FPBOs.