Conversion of lignocellulosic biomass is believed as one of the most promising pathways to tackle the emerging fossil fuels shortage and environmental issues caused by their combustion. Within the bio-refining supply chain, pretreatment is a critical step fractionating cellulose, hemicellulose and lignin for downstream utilization. It normally accounts for 20% to 30% of the total cost of biofuel production due to the large amount of chemicals and energy used in traditional pretreatment technologies. Combing the interests in cost reduction and approaching more environmentally friendly pretreatment, advanced organosolv pretreatment using non-toxic/low-toxic biobased green solvents have attracted increasing attentions for realizing sustainable biorefinery, such as methanol, ethanol and butanol. Despite the pretreatment effect of alcohol organosolv is excellent, the process suffers from maintaining the negative pressure environment due to low boiling point, which would contribute to extensive degradation of lignin and energy consumption. In this work, a biomass-derived green solvent, Dimethyl isosorbide (DMI) was applied to pretreat lignocellulosic biomass for the first time to our best knowledge, to obtain high quality cellulose and lignin streams. Results showed that DMI/H2O cosolvent has high potential as a green pretreatment solvent in terms of lignin removal, resulting cellulose rich pulp for relatively easy defibrillation and efficient enzymatic hydrolysis, which are comparable to those of previously reported γ-valerolactone and tetrahydrofuran based cosolvent systems. Under the mild condition (120 °C, 60 min), the removal efficiencies of lignin and xylan could achieve over 90% and 96%, respectively. High sugar yield at over 95% was obtained after 72 h of enzyme hydrolysis, and the pretreated biomass become easier to be defibrillated than bleached raw eucalyptus. The mechanism of this pretreatment method was assessed by investigating the structural characteristics of pretreated biomass and characteristics of recovered lignin. We also find that with the increase of water content of cosolvent, the lignin condensation was reduced with around 60% β-O-4 links preserved. This successful application demonstrates that DMI/H2O coslovent pretreatment could contribute to developing a closed-loop green biorefinery process.

Dimethyl isosorbide for sustainable biomass pretreatment

ACS Spring 2022

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