Pyrolysis characteristics and volatiles formation rule of organic solvent fractionized kraft lignin

• Published in: Fuel (Guildford) 2020-06, Vol.270, p.117520, Article 117520
• Main Authors: Chen, Sijia, Cheng, Hao, Wu, Shubin
• Format: Article
• Language: English
• Subjects: Chromatography; Depolymerization; Fourier transforms; Fraction; Fractionation; Functional groups; Gas chromatography; Headspace; Hydroxyl groups; Infrared analysis; Infrared spectroscopy; Kraft lignin; Lignin; Linkages; Liquid chromatography; Molecular weight; Monomers; NMR; Nuclear magnetic resonance; Phenolic compounds; Phenols; Pyrolysis; Pyrolysis characteristics; Selectivity; Solvents; Thermochemical properties; Volatiles; Volatiles formation
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.117520

•Different lignin fractions were obtained by organic solvent fractionation.•Organic solvent fractionation had significant influence on lignin structure.•Pyrolysis properties of different lignin fractions were studied.•Low-molecule lignin fractions were more conducive to depolymerize.•Fractionation had great effect on the yield of pyrolysis products. In this paper, kraft lignin (KL) was fractionated by organic solvent method, and different lignin fractions were characterized by Gel permeation chromatography (GPC) and 1H–13C HSQC NMR. The active functional groups content was analyzed by 31P NMR and headspace gas chromatography (HS-GC). The results showed that fractionation could efficiently separate different molecular weight lignin fractions and the linkage bonds of lignin fractions F1 to F3 changed as follows: non-condensed linkages (β-O-4) and condensed linkages (β-5 and β-β) both decreased. Moreover, some active functional groups such as phenolic hydroxyl groups and methoxy groups increased by fractionation. The thermochemical properties and volatiles formation rule of fractionized kraft lignin during pyrolysis were studied by thermogravimetric (TG), kinetics analysis, in situ Fourier-transform infrared spectroscopy (FT-IR) and U-type tube closed system pyrolysis experiment. The result showed that low-molecule lignin fractions were easier to depolymerize than that with high-molecule. Low-molecule lignin fractions had better selectivity of S-type monomer products while high-molecule fractions had better selectivity of G-type monomer products, and pyrolysis conducted at a relatively higher temperature was beneficial to the generation of G-type monomer products.