Removing and Physico-chemical Characterization of Lignin from Ultrasound-assisted Extractions of Fast-growing Poplar Wood through Organic Solvents and Alkaline Solutions
Four organic and three alkaline lignin fractions were isolated by ultrasound-assisted extractions from fast-growing poplar wood. The seven lignin fractions obtained were comparatively studied by carbohydrate content, UV, alkaline nitrobenzene oxidation, GPC, FT-IR, quantitative 13C and 2D HSQC NMR spectroscopy as well as TGA. The results showed that the ultrasonic treatments and sequential extractions with three different concentrations of NaOH led to a release of 96.2％ of the original lignin. The four organic lignin preparations were degraded significantly and contained more carbohydrate when compared with the three alkaline lignin preparations. The results from quantitative 13C NMR analyses of the highest yield lignin preparation (L5) demonstrated that it contained ～1.73/Ar of methoxyl groups and ～0.31/Ar of β-O-4’ moieties along with small amounts of β-β’ structures (～0.06/Ar). Furthermore, the HSQC NMR spectra of L5 showed a predominance of β-O-4’ aryl ether linkages (83％ of all side-chains), followed by β-β’ resinol-type (16％) and β-5’ phenylcoumaran-type (1％) linkages. The S/G ratio of L5 was estimated to be 1.5 and 1.8 from the quantitative 13C and HSQC NMR spectra, respectively. The analyses also confirmed that L5 is highly acylated at the γ-carbon of the side-chain preferentially over syringyl units. The percentage of lignin acylation of β-O-4’ linkages was 22％, possibly with acetate and p-coumarate groups, while 40％ of the β-β’ linkages was acylated with p-hydroxybenzoate. The ratio of p-hydroxybenzoate/p-coumarate was calculated to be 2.4.
HSQC Lignin Poplar wood Quantitative 13C NMR Sinapyl p-hydroxybenzoate Thermal stability Ultrasound
Tong-qi YUAN Jing HE Feng XU Run-cang SUN
Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing, 100083,China Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing, 100083,China St
国际会议
南京
英文
860-885
2010-10-22（万方平台首次上网日期，不代表论文的发表时间）