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

In this paper, kraft lignin (KL) was fractionated by organic solvent method, and different lignin fractions were characterized by Gel permeation chromatography (GPC) and H-1-C-13 HSQC NMR. The active functional groups content was analyzed by P-31 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 (beta-O-4) and condensed linkages (beta-5 and beta-beta) 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 siw Fourier-transform infrared spectroscopy (FT-IR) and U-type tube closed system pyrolysis experiment. The result showed that lowmolecule 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.