Production of water-soluble sugar from cellulose and corn stover via molten salt hydrate impregnation and separation
2022
Zhou, Liang | Liu, Qiyu | Ma, Qiaozhi | Guan, Mingzhao | Ouyang, Xinping | Qiu, Xueqing
Saccharification of cellulose into glucose is a key step for the utilization of lignocellulose. Molten salt hydrate (MSH) is unique in selective hydrolysis of cellulose into glucose but the separation of formed glucose from MSH is challenging due to the high solubility of glucose in MSH. To address this issue, this work developed a method where a small dosage of MSH was applied to impregnate cellulose and convert it into water-soluble sugar with the degree of polymerization (DP) lower than 6, which can be readily hydrolyzed into glucose under mild conditions without sacrificing selectivity. Under the optimized impregnation condition at 110 °C for 2 h, cellulose was selectively converted into water-soluble sugar with a yield of 87.5%. Then the MSH can be efficiently dissolved and removed by anti-solvent isolation with n-butanol, resulting in a sugar recovery of 84.3%. We showed that the separation efficiency was influenced by anti-solvent polarity and oligosaccharides chain-length. Moreover, the production and separation of water-soluble sugar from corn stover was also investigated. 88.9% yield of water-soluble sugar was obtained from the impregnation of corn stover under the optimized reaction conditions. With the addition of n-butanol as an anti-solvent, the water-soluble sugar can be recovered from MSH with a selectivity of 86.7%.
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