Highly Efficient Fractionation of Cornstalk into Noncondensed Lignin, Xylose, and Cellulose in Formic Acid

Abstract

Traditional pretreatment of lignocellulose is usually conducted under higher acidic and high temperature conditions, which leads to both the degradation of sugar and the condensation of lignin, hindering the subsequent conversion. An effective approach to fractionate lignocellulose into 93.9% of noncondensed lignin, 99.4% of cellulose, 17.8% of xylose, and 66.7% of xylooligosaccharides under mild conditions was developed using the formic acid solution at 80 °C for 100 min. The β-O-4 bond content of lignin fractionated with formic acid (54.6 per 100 C9 units) was higher than dioxasolv lignin (48.4 per 100 C9 units), indicating that formic acid pretreatment well protected the ether bonds in lignin. Therefore, the hydrogenolysis of fractionated lignin contributed to 28.0% of aromatic monomer yield, which was comparable to dioxasolv lignin. As cellulose possesses a large amount of porosity because lignin was separated from lignocellulose, the hydrolysis of fractionated cellulose by molten salt hydrates gave a 96.4% of glucose yield.

Sulfonic Acid-Functionalized Molecular Sieve as a Solid Acid Catalyst for Transformation of Agricultural Residues to Furfural

“…Due to the high concentration of formic acid, the solubility of lignin is high, and the condensation between the oligomer formed by lignin degradation and the oligosaccharides hydrolyzed by hemicellulose leads to low furfural yield . The addition of water to formic acid can not only hydrolyze the dissolved oligosaccharides into xylose but also effectively separate the acid soluble lignin oligomers from formic acid solution . When the concentration of formic acid was 90% (V/V), the yields of furfural and HMF reached 30.6 and 7.8%, respectively.…”

“…47 The addition of water to formic acid can not only hydrolyze the dissolved oligosaccharides into xylose but also effectively separate the acid soluble lignin oligomers from formic acid solution. 48 When the concentration of formic acid was 90% (V/V), the yields of furfural and HMF reached 30.6 and 7.8%, respectively. However, excessive water content reduces the concentration of formic acid and weakens the destruction of lignocellulose, resulting in weakened hydrolysis.…”

Cascade fractionation of birch into xylose, glucan oligomers, and noncondensed lignin improved using microwave assistance and molten salt hydrates

“…Therefore, the fractionation of raw lignocellulose into noncondensed lignin is still paramount to promoting the value-added application of lignocellulose. 7 The critical requirement in noncondensed lignin production depends on the mild fractionation conditions employed, such as using weak alkalis (e.g., anhydrous ammonia 8 ) or organic acids (e.g., formic acid 9 and p-toluenesulfonic acid 10,11 ) at low temperatures. Moreover, ligninsoluble solvents, such as alcohols, ionic liquids, and deep eutectic solvents, are generally used to improve fractionation efficiency.…”

“…, anhydrous ammonia 8 ) or organic acids ( e.g. , formic acid 9 and p -toluenesulfonic acid 10,11 ) at low temperatures. Moreover, lignin-soluble solvents, such as alcohols, ionic liquids, and deep eutectic solvents, are generally used to improve fractionation efficiency.…”