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Selective saccharification of cellulose into glucose is a critical step for utilization of lignocellulosic biomass. Molten salt hydrates (MSHs) have shown promising performance in selectively converting cellulose into glucose because of the high solubility of cellulose in the solvent. However, the separation of formed glucose from the MSHs is still a grand challenge. To address this issue, we developed a two-step process, where crystalline cellulose is hydrolyzed into short-chain glucan oligomers in MSHs followed by separation and subsequent hydrolysis of the formed oligomers into glucose under mild conditions. The two-step method provides an easy separation for glucan oligomers from the MSHs without sacrificing the selectivity to glucose. Application of the method for crystalline cellulose is, however, limited to a relatively low concentration, 26.2 mg/mL, because of the formation of byproducts in the MSH that facilitate oligomers degradation. In this work, reactive adsorption was employed to in situ remove the byproducts formed during cellulose hydrolysis in the MSH. It was found that hyper-cross-linked polymer (HCP) made from the polymerization of 4-vinylbenzyl chloride and divinylbenzene can selectively adsorb 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) while showing negligible sugar adsorption in both water and the MSH. With the reactive adsorption approach, byproducts including 5-HMF and LA were removed from the reaction media under reaction conditions, and their negative effects on oligomer degradation were inhibited. In the presence of the HCP, the obtained glucan oligomer concentration was enhanced from less than 54.2 to 247.1 mg mL-1 when the weight ratio of cellulose was increased to MSH from 1:60 to 1:4, exhibiting an oligomer yield of 69.5%. The HCP can be effectively separated from the reaction media by filtration and regenerated by oxidation with hydrogen peroxide. Application of reactive adsorption with HCP for cellulose hydrolysis in the MSH provides a promising method to produce glucan oligomers and glucose with an improved yield and efficiency.

Molten salt hydrates (MSHs) are remarkable in breaking through the recalcitrant structure of microcrystalline cellulose and raw biomass. After being pretreated in 60 wt% LiBr at 130 °C for 2 h, cellulose crystallinity as well as degree of polymerization (DP) decreased. It was found that 91.3% yield of pretreated cellulose was removed from MSHs by filteration followed by being hydrolyzed into glucose with a high yield of 75.3% by dilute acid under mild reaction conditions. The pretreatment process also works on raw corn stover hydrolysis. After being pretreated at 100 °C for 5 h, 88.4% yield of cellulose in biomass was recovered and can be hydrolyzed into 54.9% yield of glucose with dilute acid. It was found that the cellulose in corn stover can be easier degraded compared with microcrystalline cellulose during MSHs pretreatment, which dues to the formation of acetic acid from hemicellulose hydrolysis. The proposed pretreatment technique presents a promising potential for glucose production from biomass in a commercial way.