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Integration of Salt-Induced Phase Separation with Organosolv Pretreatment for Clean Fractionation of Lignocellulosic Biomass

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journal contribution
posted on 2017-05-17, 00:00 authored by Zhanying Zhang, William O. S. Doherty, Ian M. O’Hara
In this study, salt-induced phase separation was integrated with n-propanol-based pretreatment for clean fractionation of sugar cane bagasse. First, biomass solid residue and pretreatment hydrolysate were separated by filtration following pretreatment. Lignins with high molecular weights (HMWs) were separated through precipitation and filtration after diluting hydrolysate with water. The filtrate was added with (NH4)2SO4 at a saturated concentration, which induced the formation of a biphasic solution: the top layer was n-propanol phase containing sugar degradation products and lignins with low molecular weights (LMWs); the bottom layer was aqueous phase, rich in salt and soluble sugars. The solvent phase was directly reused for pretreatment, while the aqueous phase was distilled to recycle both salt and water. Direct recycling solvent phase for pretreatment four times only led to a slight decrease in glucan digestibility from 100% (fresh solvent) to 96%. Direct reuse of solvent phase also led to a significant increase in furfural concentration from 2.4 g/kg to 15.1 g/kg, while recycling water and salt in aqueous phase by distillation led to a substantial increase in xylose concentration from 3.2 g/kg to 13.5 g/kg after five batches of pretreatments. In addition, the total yield of HMW lignins increased gradually from 38% to 49%.

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