Using γ-valerolactone and toluenesulfonic acid to extract lignin efficiently with a combined hydrolysis factor and structure characteristics analysis of lignin

A method for isolating components of lignocellulose in hybrid poplar by using an organic solvent (γ-valerolactone) in combination with a solid organic acid (p-toluenesulfonic acid) is studied here. The combined hydrolysis factor (CHF) was used to measure the severity of the pretreatment conditions and to find the optimal reaction conditions (CHF = 54.99) by judging enzymatic saccharification and characterization of lignin residual. At this pretreatment strength, 91.67% hemicellulose and 86.14% lignin in lignocellulose were effectively removed, and the enzymatic hydrolysis of cellulose residue reached 84.84%. Hemicellulose was hydrolyzed to 4.39 g L−1 of xylose, and a portion was converted to 2.95 g L−1 of furfural and 3.59 g L−1 of acetic acid. The molecular weight, polydispersities and phenolic hydroxyl groups content of the isolated lignin were 1587 g mol−1, 1.04 and 3.64 mmol g−1 respectively, which indicated that the lignin had the potential to be a phenolic resin material and wood polyurethane foam. In summary, this method effectively separated three components of lignocellulose and obtained high purity cellulose and lignin.