title: Molecular characteristics of Kraft-AQ pulping lignin fractionated by sequential organic solvent extraction.
abstract: Kraft-AQ pulping lignin was sequentially fractionated by organic solvent extractions and the molecular properties of each fraction were characterized by chemical degradation, GPC, UV, FT-IR, (13)C-NMR and thermal analysis. The average molecular weight and polydispersity of each lignin fraction increased with its hydrogen-bonding capacity (Hildebrand solubility parameter). In addition, the ratio of the non-condensed guaiacyl/syringyl units and the content of β-O-4 linkages increased with the increment of the lignin fractions extracted successively with hexane, diethylether, methylene chloride, methanol, and dioxane. Furthermore, the presence of the condensation reaction products was contributed to the higher thermal stability of the larger molecules.
authors.affiliation: Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing 100083, China; E-Mails: wangkun@bjfu.edu.cn (K.W.); xfx315@bjfu.edu.cn (F.X.).
authors.forename: Kun
authors.initials: K
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
authors.forename: Runcang
authors.initials: R
authors.lastname: Sun
mesh_terms: D002850:Chromatography, Gel; D008031:Lignin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy
chemical_list: C076151:Kraft lignin; D008031:Lignin