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Lignocellulosic materials (LCMs) extracted from waste-wood products are promising sources of renewable chemicals and fuels. Organosolv pretreatment is commonly used for the fractionation of LCMs; however, these methods require high reaction temperatures, which remain problematic. In this study, room temperature ionic liquids (RTILs) and electrochemical conversion were used for LCMs fractionation. This paper presents a modified organosolv pretreatment, termed electro-assisted organosolv pretreatment (EAOP), which utilises gamma-valerolactone and 1-Butyl-3-methylimidazolium acetate as binary solution, in the presence of electrical energy. Importantly, EAOP can selectively fractionate lignin or cellulose at temperatures lower than 80 °C. Cellulose dissolution occurred at 2.4 V whereas lignin dissolution occurred at 4.2 V. A capacitance parameter was established and validated to describe the operating condition and selectively of EAOP. Operations conducted with capacitance less than 2317 F have the potential for cellulose solubilisation, whereas at capacitance exceeding 2317, lignin solubilisation was observed. This study showed that EAOP can overcome organosolv pretreatment shortfalls., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The electro-assisted organosolv pretreatment (EAOP) is a biomass pretreatment method which is viable at room temperature. Previously, it was shown that the electrochemically generated hydroxyl radical (OH*) during EAOP is key to the delignification efficiency when 1-butyl-3-methylimidazolium acetate and gamma-valerolactone (10 wt% [Bmim]OAc/GVL) are used as the solvent. However, the effect of additives and biomass loading on this novel pretreatment process have not previously been investigated. In this study, inorganic salts of NaOH, NaCl, FeCl 3 , with and without added water, were used as additives into [Bmim]OAc/GVL, to determine their effect on OH* formation during EAOP. These inorganic salts were selected as they have been proven effective in the electrochemical conversion of either lignin or cellulose. It was found that [Bmim]OAc/GVL with NaCl/water showed the most rapid and largest amount of OH* formation, being 45% higher than [Bmim]OAc/GVL without additives. The 240-min EAOP with NaCl/water delignified 70.8 wt% of Eucalyptus sawdust and the residual biomass showed 204.4 mg/g total reducing sugar yield. In addition, EAOP with NaCl/water present can be done rapidly (in 30 min) and at high biomass loading (25%). The total reducing sugar (TRS) yield of sawdust from the high-loading rapid EAOP is up to 194.0 mg/g, which is around 10-fold higher than untreated sawdust. The spent solvent from EAOP could be regenerated, with only minor TRS yield decrease (10%) observed after recycling the solvent four times. NaCl and water were added into the electro-assisted organosolv pretreatment as inorganic additives, which enabled EAOP to be completed in 30 min at 25% biomass loading. The residual biomass from EAOP can produce up to 204.4 mg/g reducing sugar (approximately 10-folds higher than untreated biomass) and the regenerated solvent showed only minor decreases (10%) in total reducing sugar yield after four cycles. [Display omitted] • Electro-assisted organosolv pretreatment (EAOP) and different inorganic additives. • Addition of NaCl/water increased the OH* generation by 45% during EAOP • Optimum EAOP fractionation with NaCl/water for 30 min at 25% biomass loading. • RB after EAOP produced reducing sugar 10-folds higher than untreated biomass. • Only 10% decrease in the TRS yield using regenerated solvent after four cycles. [ABSTRACT FROM AUTHOR]