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The conventional fractionation of lignocellulose is generally carried out at high temperatures, high acid or alkali, or using organic solvents due to the rigid matrix of lignocellulose and crystallinity of cellulose, leading to the condensation of lignin and environmental pollution, and hindering the further value-added utilization of lignin. In this work, a rapid fractionation method was proposed, in which hemicellulose and cellulose (holocellulose) were first dissolved and partially hydrolyzed in acidified LiCl molten salt hydrates, followed by a filtration process to isolate the lignin solid with a purity of 88.3%. It was found that the dissolution of holocellulose required the addition of a small amount of acid to break the cellulose chain into short chains. Due to the small amount of acid added and the rapid dissolution, the obtained lignin has as high as 89.5% of β-O-4 bond content close to the theoretical value, suggesting that a promising native lignin structure was preserved. The isolated lignin can be selectively depolymerized into monophenol over Ru/C catalyst with a high yield of 24.2%. In addition, the dissolved holocellulose without containing lignin was selectively hydrolyzed into sugars in acidified LiCl molten salt hydrates, giving 63.1% of xylose, 43.9% of glucose, 29.5% of xylan oligomers, and 48.2% of glucan oligomers, respectively. [Display omitted] • LiCl molten salt hydrates required little acid to dissolve holocellulose. • LiCl-AMSH could quickly dissolve holocellulose and separate noncondensed lignin. • 88.3% purity of noncondensed lignin was fractionated. • 24.2% of monophenol (88.0% to theoretical) was obtained from noncondensed lignin. • 63.1% of xylose, 43.9% of glucose, 29.5% of xylan oligomers, and 48.2% of glucan oligomers were obtained. [ABSTRACT FROM AUTHOR]

High-yield noncondensed lignin and cellulose possessing high enzymatic digestibility can be obtained using p -toluenesulfonic acid in methanol under microwave irradiation. [Display omitted] • 87.9% of noncondensed lignin with ether bonds preserved was obtained. • 42.0% of monophenol (74.9% to theoretical) obtained from noncondensed lignin. • 94.3% of enzymatically digestible cellulose was isolated. • Microwave irradiation facilitated lignin-carbohydrate complex bonds cleavage. • The α-methoxylation by methanol inhibited condensation of extracted lignin. Production of noncondensed lignin via lignocellulose fractionation usually shows limited yield. Promoting reaction conditions benefits lignin production but has negative effect on structural condensation and thus inhibits its value-added applications in depolymerization. To address this issue, a unique fractionation method was proposed using p -TsOH (p -toluenesulfonic acid) in methanol under microwave irradiation to produce high-yield noncondensed lignin. It was found that microwave irradiation efficiently decreased the activation energy of lignin-carbohydrate complex (LCC) bonds cleavage from 102.1 to 63.8 kJ/mol and thereby facilitated lignin exfoliation from carbohydrates. And an effective α-alkoxylation reaction occurred between methanol molecular and C α -OH group in lignin, which protected β -O-4 linkages from condensation. After being fractionated under a relatively mild fractionation condition of 85 ℃ for 30 min, a promising lignin yield of 87.9 % can be obtained from poplar sawdust, with 91.8 % of ether bonds preserved. The obtained lignin can be selectively depolymerized into monophenols with a high yield of 42.0 %, which was 74.9 % to the theoretical yield. Besides, 94.3 % of cellulose was retained in solid part after fractionation, which can be efficiently converted into glucose with a yield of 98.5 % via enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

Selective hydrolysis of crystalline cellulose to cello-oligosaccharides in molten salt hydrates (MSHs) is a promising method for valorization of lignocellulose. However, the by-products derived from cellulose hydrolysis can facilitate cello-oligosaccharide degradation and decrease its selectivity. To address this issue, lignin-based hyper cross-linked polymers (LHCPs) were prepared to in situ adsorb by-products during hydrolysis and thus prevent cello-oligosaccharides from degradation. The synthesized LHCP‐33%, with a high lignin content of 33%, showed a remarkable surface area of 708.7 m2 g−1 and good hydrophilicity, exhibiting a promising adsorption capacity of 340 mg g−1 towards 5-hydroxymethylfurfural (5-HMF), which is supposed to be the major cellulose-derived by-product. We showed that 5-HMF adsorption was driven by the formation of CH-π bonds between 5-HMF and aromatic rings on LHCP. When LHCP‐33% was employed in cellulose hydrolysis, the yield of cello-oligosaccharide can be efficiently enhanced from 39.5% to 78.2%. This work offered a new application of lignin in enhanced cello-oligosaccharide production from cellulose. [Display omitted] • 78.2 % yield of cello-oligosaccharide can be selectively produced from crystalline cellulose saccharification via in situ adsorption of by-products on lignin-based hyper cross-linked polymer (LHCP). • The synthesized LHCP shows a high surface area and good hydrophilcity which is beneficial for by-products adsorption. • The adsorption of hydrolysis-derived 5-hydroxymethylfurfural (5-HMF) on LHCP is driven by the formation of CH-π bonds rather than hydrogen bonds. • This approach provides a new alternative in utilization of lignin for high-valued cello-oligosaccharide production from cellulose. [ABSTRACT FROM AUTHOR]