Separation of short-chain glucan oligomers from molten salt hydrate and hydrolysis to glucose

Abstract

Selective production of glucose from hydrolysis of cellulose is the key step for efficient utilization of lignocellulose biomass. Crystalline cellulose can be dissolved and hydrolyzed into glucose with a high...

Enhanced production and separation of short-chain glucan oligomers from corn stover in an unacidified LiBr molten salt hydrate via pre-extraction of hemicellulose

“…The produced sugars, MSH and methanol can be readily separated and recycled in commercial ways. 17 It was found that after being treated using this stepwise method, the yield of glucan oligomers produced from corn stover hydrolysis remarkably increased from 59.9% to 79.5% and the separation efficiency also increased from 54.2% to 80.6%, suggesting potential applications in lignocellulose valorization as the value-added chemical in healthcare 29,30 and agriculture. 31,32 Crystalline cellulose (99%), glucose (99.9%), xylose (99.9%), 5-hydroxymethylfurfural (5-HMF, 99%), levulinic acid (99.9%), tetrahydrofuran (TOF, 99%) and anhydrous pyridine (99.8%) were bought from Aladdin Chemical Co., Ltd, China.…”

“…11 The formed glucan oligomers can be readily separated from the MSHs via adsorption using amorphous carbon 11 or anti-solvent precipitation. 17 The separated glucan oligomer can be selectively hydrolyzed into glucose with a high yield under mild conditions. Under optimized conditions, a 90.4% yield of glucan oligomers can be obtained from cellulose in 60 wt% LiBr at 130 °C for 5 h without catalysts, 11 and the formed products can be precipitated out of the MSH using methanol as an anti-solvent with a high efficiency of 90.3%, 17 which is much more efficient than the separation of glucose from the MSH.…”

“…However, our previous work indicated that only 69.2% yield of glucan oligomers was obtained from cotton stalk hydrolysis at 130 °C for 4 h, and the precipitation efficiency is as low as 26.2%, much lower than using cellulose as the substrate. 17 The reduced oligomer yield and low separation efficiency are likely due to the formation of acetic acid derived from the hydrolysis of the acetoxy group in hemicellulose (Scheme 1). 22 It has been known that acetic acid shows a slight enhancement in crystalline cellulose hydrolysis in the aqueous phase due to its limited accessibility to glycosidic bonds.…”

Adsorption-Enhanced Glucan Oligomer Production from Cellulose Hydrolysis over Hyper-Cross-Linked Polymer in Molten Salt Hydrate

“…The selectivity to oligomer, however, decreases to 44.0% when the cellulose concentration increases to 188.2 mg mL –1 . The reduced selectivity to oligomer is likely due to the formation of byproducts including 5-hydroxymethylfurfural (5-HMF), levulinic acid (LA), and formic acid (FA). − The formation of byproducts not only decreases the yield to the glucan oligomers but also catalyzes other nonselective reactions to form humins.…”

“…In our previous study, we have shown that the oligomers can be separated by cyclic temperature swing adsorption− desorption processes using amorphous carbon. 17 Moreover, glucan oligomers can be separated by precipitation using antisolvent 18 and a nanofiltration method.…”