蔗渣硫酸盐木质素的分级分离与表征
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摘要
从蔗渣制浆黑液中提取纯化硫酸盐木质素(KL),将KL溶解在甲醇/丙酮混合溶液后,通过有机溶剂(乙酸乙酯、乙酸乙酯/石油醚和石油醚)沉降分级分离木质素得到F1、F2、F3和F4这4个组分,再利用红外光谱、元素分析、凝胶渗透色谱、热重和核磁共振波谱等手段对原料以及F1、F2和F3组分进行表征。实验结果表明:F1、F2、F3和F4分别占硫酸盐木质素质量的59.6%、28.4%、10.8%和1.2%;与原料相比,F1相对分子质量(M_r)较高、均一性较好,F2~F4的M_r及分散系数均小于原料;从F1、F2到F3,甲氧基含量、羟基(醇羟基与酚羟基)含量以及结构单元间连接键比例均随木质素M_r的变化而变化,β-O-4'结构比例随M_r降低而减小,β-5'结构比例随M_r降低而增加。
Kraft lignin( KL) of sugarcane bagasse extracted from bagasse pulping black liquor was successively fractionated into four fractions( e.g. F1,F2,F3 and F4) by various organic solvents( ethyl acetate,ethyl acetate/petroleum ether,and petroleum ether) according to their solubility. Kraft lignin and its three fractions( F1,F2 and F3) were comprehensively characterized by elemental composition analysis,gel permeation chromatography,Fourier transform infrared spectroscopy,and nuclear magnetic resonance including ~(31) P,~(13) C,and ~1 H-~(13) C HSQC NMR,respectively. The results indicated that F1,F2,F3 and F4 were respectively accounting for 59. 6%,28. 4%,10. 8% and 1. 2% of kraft lignin. Compared with the original kraft lignin,the molecular weight of F1 was higher and the homogeneity was better. The molecular weight and dispersity of lignin fractions F2 to F4 were smaller than those of original kraft lignin. Furthermore,the contents of methoxyl group,hydroxyl group,and inter-unit linkages,as well as the thermal properties of fractions( F1,F2,and F3),were varied with their molecular weights. The proportion of β-O-4' structure decreases with the decrease of molecular weight,and the proportion of β-5' increases with the decrease of molecular weight.
Kraft lignin( KL) of sugarcane bagasse extracted from bagasse pulping black liquor was successively fractionated into four fractions( e.g. F1,F2,F3 and F4) by various organic solvents( ethyl acetate,ethyl acetate/petroleum ether,and petroleum ether) according to their solubility. Kraft lignin and its three fractions( F1,F2 and F3) were comprehensively characterized by elemental composition analysis,gel permeation chromatography,Fourier transform infrared spectroscopy,and nuclear magnetic resonance including ~(31) P,~(13) C,and ~1 H-~(13) C HSQC NMR,respectively. The results indicated that F1,F2,F3 and F4 were respectively accounting for 59. 6%,28. 4%,10. 8% and 1. 2% of kraft lignin. Compared with the original kraft lignin,the molecular weight of F1 was higher and the homogeneity was better. The molecular weight and dispersity of lignin fractions F2 to F4 were smaller than those of original kraft lignin. Furthermore,the contents of methoxyl group,hydroxyl group,and inter-unit linkages,as well as the thermal properties of fractions( F1,F2,and F3),were varied with their molecular weights. The proportion of β-O-4' structure decreases with the decrease of molecular weight,and the proportion of β-5' increases with the decrease of molecular weight.
引文
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[22]LI Q,SEREM W K,DAI W,et al. Molecular weight and uniformity define the mechanical performance of lignin-based carbon fiber[J]. Journal of Materials Chemistry A,2017,5(25):12740-12746.
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[3]GARRISON M D,HARVEY B G. Bio-based hydrophobic epoxy-amine networks derived from renewable terpenoids[J/OL]. Journal of Applied Polymer Science,2016,133(45):1-12[2016-03-11]. https:∥onlinelibrary. wiley. com/doi/pdf/10. 1002/app. 43621.
[4]SALMEN L,BERGNOR E,OLSSON A M,et al. Extrusion of softwood Kraft lignins as precursors for carbon fibres[J]. Bioresources,2015,10(4):7544-7554.
[5]王晓红,马玉花,刘静,等.木素的胺化改性[J].中国造纸,2010,29(6):42-45.WANG X H,MA Y H,LIU J,et al. Amination modification of lignin[J]. China Pulp&Paper,2010,29(6):42-45.
[6]HUANG H J,RAMASWAY S,TSCHIMER U W,et al. A review of separation technologies in current and future biorefineries[J]. Separation and Purification Technology,2008,62(1):1-21.
[7]CUI C Z,SUN R K,ARGYROPOULOS D S. Fractional precipitation of softwood Kraft lignin:Isolation of narrow fractions common to a variety of lignins[J]. ACS Sustainable Chemistry&Engineering,2014,2(4):959-968.
[8]WANG G H,CHEN H Z. Fractionation of alkali-extracted lignin from steam-exploded stalk by gradient acid precipitation[J]. Separation and Purification Technology,2013,105:98-105.
[9]JONSSON A S,NORDIN A K,WALLBERG O. Concentration and purification of lignin in hardwood kraft pulping liquor by ultrafiltration and nanofiltration[J]. Chemical Engineering Research and Design,2008,86(11):1271-1280.
[10]WANG G H,CHEN H Z. Fractionation and characterization of lignin from steam-exploded corn stalk by sequential dissolution in ethanol-water solvent[J]. Separation and Purification Technology,2013,120:402-409.
[11]BJORKMAN A. Studies of finely divided wood. Part 1:Extraction of lignin with neutral solvents[J]. Svensk Papperstidning,1956,59(13):477-485.
[12]LI H L,CHAI X S,LIU M R,et al. Novel method for the determination of the methoxyl content in lignin by headspace gas chromatography[J].Journal of Agricultural and Food Chemistry,2012,60(21):5307-5310.
[13]蒋晓.硫酸盐木质素的分级分离与性能表征[D].南京:南京林业大学硕士学位论文,2015.JIANG X. Fractionation and characterization of Kraft lignin[D]. Nanjing:Master Degree Thesis of Nanjing Forestry University,2015.
[14]GRANATA A,ARGYROPOUOLS D S. 2-Chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphosp-holane,a reagent for the accurate determination of the uncondensed and condensed phenolic moieties in lignins[J]. Journal of Agricultural and Food Chemistry,1995,43(6):1538-1544.
[15]HU Z J,DU X Y,LIU J,et al. Structural characterization of pine Kraft lignin:Biochoice lignin vs indulin AT[J]. Journal of Wood Chemistry&Technology,2016,36(6):432-446.
[16]ZHAO X B,DAI L M,LIU D H. Characterization and comparison of acetosolv and Milox lignin isolated from crofton weed stem[J]. Journal of Applied Polymer Science,2009,114(2):1295-1302.
[17]SHUKRY N,FADEL S M,AGBLEVOR F A,et al. Some physical properties of acetosolv lignins from bagasse[J]. Journal of Applied Polymer Science,2008,109(1):434-444.
[18]BRODIN I,SJCHOLM E,GELLERSTEDT G. Kraft lignin as feedstock for chemical products:The effects of membrane filtration[J].Holzforschung,2009,63(3):290-297.
[19]MARTINEZ A T,RENCORET J,MARQUES G,et al. Monolignol acylation and lignin structure in some nonwoody plants:A 2D NMR study[J]. Phytochemistry,2008,69(16):2831-2843.
[20]RENCORET J,MARQUES G,GUTIERREZ A,et al. Isolation and structural characterization of the milled-wood lignin from Paulownia fortunei wood[J]. Industrial Crops and Products,2009,30(1):137-143.
[21]RENCORET J,MARQUES G,GUTIERREZ A,et al. Structural characterization of milled wood lignins from different eucalypt species[J].Holzforschung,2008,62(5):514-526.
[22]LI Q,SEREM W K,DAI W,et al. Molecular weight and uniformity define the mechanical performance of lignin-based carbon fiber[J]. Journal of Materials Chemistry A,2017,5(25):12740-12746.