有机-无机溶剂连续抽提巨龙竹木质素及其结构表征

为了分析巨龙竹木质素的结构特征,采用有机-无机溶剂连续抽提的方式将木质素和半纤维素进行分离,脱蜡竹粉依次用80%二氧六环、80%二氧六环-0.5% NaOH、2% NaOH、5% NaOH和8% NaOH连续抽提后,得5个木质素样品L₁~L₅,计算了木质素得率,并对抽提所得的木质素样品进行了红外光谱(FT-IR)、紫外光谱(UV)、核磁共振碳谱(¹³C NMR)和二维核磁共振(2D HSQC)分析。结果表明:在二氧六环和不同浓度碱性水溶液的连续抽提下,最终从巨龙竹原料中分离得到70.6%的原本木质素,其中木质素样品L₂的纯度最高,表明该方法是一种较为有效的竹材木质素组分分离方法。木质素的苯环骨架结构在分离过程中没有被破坏,但碱浓度的增加导致木质素中部分酯键发生断裂。巨龙竹木质素大分子主要由愈创木基单元(G)、紫丁香基单元(S)、对羟基苯基单元(H)组成,木质素大分子基本单元之间的联接键主要是β-O-4'醚键,除此之外还有β-β'、β-5'和β-1'联接。     

定量^13C—NMR谱表征蔗糖渣碱木素结构

从蔗渣纸浆黑液中制出纯蔗渣碱木素，然后测定其定量＾１３Ｃ－ＮＭＲ谱。图谱分析表明，蔗渣碱木素主要由紫丁香基，愈创木基和对羟苯基三种丙烷结构单元组成，其中未缩合的紫丁香基，愈创木基和羟苯基含量比为２．２：１．０：１．４。蔗糖碱木素结构单元间主要以β－Ｏ－４烷基芳基醚链连接，也有一定量的非环状α－醚键存在，蔗渣碱木素中，相当部分香豆酸类结构并通过酯键而是通过醚键或碳碳双键连接于芳核上。     

定量~(13)C-NMR谱表征蔗渣碱木素结构

从蔗渣纸浆黑液中制出纯蔗渣碱木素，然后测定其定量13C-NMR谱．图谱分析表明，蔗渣碱木素主要由紫丁香基，愈创木基和对羟苯基三种丙烷结构单元组成，其中未绩合的紫丁香基、愈创木基和对羟羊基含量比为2.2：1．0：1．4．蔗渣碱术素结构单元间主要以β-O－4烷基芳基醚键连接，也有一定量的非环状α-醚键存在．蔗渣碱木素中，相当部分对香豆酸类结构并非通过酯键而是通过醚键或碳双键连接于芳核上．     

巨龙竹有机溶剂木质素提取及结构表征

为表征巨龙竹木质素化学结构,在温和条件下连续采用二氧六环和二甲基亚砜抽提竹材原料,得到竹材木质素组分。红外光谱、凝胶色谱和核磁共振分析结果表明,巨龙竹木质素属于典型的禾草类木质素,其大分子由对羟基苯丙烷(H)、愈创木基丙烷(G)和紫丁香基丙烷(S)三种基本结构单元组成;巨龙竹木质素大分子的主要联接键为β-O-4'醚键、β-β'和β-5'碳-碳键;在巨龙竹木质素大分子中,苯丙烷结构单元侧链γ位碳与对香豆酸存在化学键联接,形成对香豆酸酯。     

阔叶木碱法造纸黑液提取物成分的研究

应用裂解-气相色谱-质谱、红外色谱、凝胶色谱、元素分析仪研究了阔叶木碱法造纸黑液提取物的成分.结果表明:黑液中含有木质素、有机酸等物质.其中,阔叶木木质素属愈创木-紫丁香(GS)型木质素,木质素分子中存在少量的α-β碳碳双键,紫丁香基结构单元的质量分数高于愈创木基结构单元,二者质量分数比为2.27;木质素的结构经验式为...     

有机-无机溶剂连续抽提巨龙竹木质素及其结构表征北大核心

为了分析巨龙竹木质素的结构特征,采用有机-无机溶剂连续抽提的方式将木质素和半纤维素进行分离,脱蜡竹粉依次用80%二氧六环、80%二氧六环-0.5%NaOH、2%NaOH、5%NaOH和8%NaOH连续抽提后,得5个木质素样品L1~L5,计算了木质素得率,并对抽提所得的木质素样品进行了红外光谱(FT-IR)、紫外光谱(UV)、核磁共振碳谱(^(13)C NMR)和二维核磁共振(2D HSQC)分析。结果表明:在二氧六环和不同浓度碱性水溶液的连续抽提下,最终从巨龙竹原料中分离得到70.6%的原本木质素,其中木质素样品L_2的纯度最高,表明该方法是一种较为有效的竹材木质素组分分离方法。木质素的苯环骨架结构在分离过程中没有被破坏,但碱浓度的增加导致木质素中部分酯键发生断裂。巨龙竹木质素大分子主要由愈创木基单元(G)、紫丁香基单元(S)、对羟基苯基单元(H)组成,木质素大分子基本单元之间的联接键主要是β-O-4'醚键,除此之外还有β-β'、β-5'和β-1'联接。     

杏壳木质素的结构表征及其热解特性研究

为研究杏壳木质素的结构、热解特性及其产物的生成规律,通过硫酸脱除法从杏壳中分离出杏壳木质素,并通过红外光谱(FT-IR)和核磁共振(NMR)对其结构组成进行表征,利用热重及热重-红外联用分析研究其热解产物生成特性。研究结果表明：硫酸脱除法得到的杏壳木质素得率为30.42%,红外光谱图显示有较强的紫丁香基峰,还有一定量的愈创木基,二维核磁共振图谱表明杏壳木质素中有紫丁香基(S)、愈创木基(G)和对羟基苯基(H)3种木质素结构单元,属于SGH型木质素。热重及热重-红外联用分析表明杏壳木质素热解过程主要分为3个阶段,主要热解阶段发生在150~650 ℃之间的较宽温度范围内,360 ℃时热失重速率最大,热解产物主要为H₂O、CO、CO₂、CH₄以及醇、醛、酚、酸等。杏壳木质素中苯丙烷侧链上醚键和苯环间醚键断裂及挥发分二次裂解使CO的析出温度范围较宽,在200~700 ℃之间;羧基和羰基等官能团不稳定易断裂和重整,使CO₂的析出温度范围较窄,在250~650 ℃之间;苯丙烷侧链的断裂和苯环上甲氧基官能团的去甲基化反应,以及芳香环的深度断裂,使CH₄的析出在400和600 ℃时呈现2个峰值。     

有机溶剂法纯化蔗渣木质素

采用有机溶剂法对甲酸预处理蔗渣后的蔗渣木质素进行纯化并进行结构表征。纯化后木质素的纯度为92.1%,收率为76.1%。红外图谱分析、热重和核磁共振氢谱分析表明,提纯前后木质素均含有愈创木基和紫丁香基两种结构,其中紫丁香基单元为主要单元。扫描电镜分析表明,纯化后的木质素由1⁵μm的球体颗粒组成,表面结构松散,颗粒产生粘连现象,有利于其在水凝胶、高分子树脂等方面的应用。     

探头式超声辅助碱性H2O2处理对蔗渣纤维素影响

采用探头式超声辅助碱性H₂O₂处理蔗渣,探讨NaOH质量分数、H₂O₂质量分数、反应时间及反应温度对蔗渣纤维素含量和结晶度影响,同时用SEM、FTIR和固体核磁分析处理后蔗渣微观形态结构,并用HPLC测定纤维素、半纤维素和木质素含量。结果表明,NaOH质量分数10%,H₂O₂质量分数0.9%,反应时间80 min,反应温度200℃,超声功率200 W及超声时间20 min处理蔗渣,纤维素含量(91.63±3.03)%,结晶度(73.08±0.72)%,分别提高45.19%和18.2%;SEM表明蔗渣表面出现沟壑;FTIR表明纤维素特征峰增强,木质素和半纤维素特征峰和固体核磁信号峰减弱。说明探头式超声辅助碱性H₂O₂较完全降解蔗渣木质素和半纤维素,提高纤维素含量,增加其有效接触面积。     

麦草木质素在甘油蒸煮过程中结构的变化

主要对麦草经过甘油蒸煮后分离得到的木质素进行化学结构分析,并将其和麦草中原有的木质素进行对比。可知,两种木质素均是由愈创木基、紫丁香木基和对羟苯基木基3种基本结构单元组成,其中愈创木基单元为主要单元。麦草在蒸煮过程中,连接木质素苯丙烷单体的醚键在蒸煮过程中遭到不同程度的破坏,生成新的酚羟基和醇羟基,从而造成甘油木质素的紫外吸收峰较二氧六环木质素的紫外吸收峰向长波方向移动(红移)。由两种木质素的凝胶色谱可知,二氧六环木质素和甘油木质素的数均相对分子质量分别为3172和2241,重均相对分子质量分别为6601和2361,多分散系数分别为2.08和1.05。甘油木质素较二氧六环木质素相对分子质量更小更均匀,这种较窄的分子量分布有利于其更广泛的应用。     

甘蔗渣原料磨木素和磺化甘蔗渣磨木素的研究

在甘蔗渣碱性亚硫酸钠化学机械法制浆研究的基础上,采用化学分析方法和仪器测试技术,研究了甘蔗渣原料磨木素和磺化处理后甘蔗渣磨木素的化学结构及其变化情况。在化学预处理过程中,甘蔗渣木素中的酯键和烷基芳基醚键等连接形式在一定程度上断裂,愈创木基结构单元发生较多的磺化和溶出,对羟苯基结构单元也有一定数量的溶出,因而使得留存于浆料木素中的紫丁香基结构单元相对增加。经过磺化处理后,甘蔗渣木素的平均分子量和多分散性减小,基于化学机械浆的预处理条件,木素大分子的碎解和溶出是有限度的。除了溶出的一部分磺化木素之外,残留于甘蔗渣的木素中仍有相当含量的磺酸基(达到0.15HSO_3/C_9),甲氧基含量明显增加(从1.00OCH_(?)/C_9增至1.22OCH_3/C_9),酚羟基含量有所增加(从0.29Ph-OH/C_9增至0.33Ph—OH/C_9),而醇羟基含量减少(从1.50Alc-OH/C_9减至0.79AlC-OH/C_9)。     

Extraction and characterization of lignins from maize stem and sugarcane bagasse

Lignins were isolated from maize stem and sugarcane bagasse by using mild dioxane or acidic dioxane solution. The result of nitrobenzene oxidation of the isolated lignins shows that there is a high proportion of p‐hydroxyphenyl alcohol in the lignins of maize stem and sugarcane bagasse. The lignins isolated from maize stem and sugarcane bagasse have relatively same value of the weight‐average (M _w = 3405–3868 g mol⁻¹) and number‐average (M _n = 1411–1612 g mol⁻¹) molecular weights, and polydispersity (M _w/M _n = 2.24–2.51). Acidic dioxane treatment did attack the β‐aryl ether structures in lignins, in particular for β‐aryl syringyl ethers, and broke the ester bonds between arabinose and ferulic acid that etherified to lignins, and it also cleaved lots of bonds in hemicellulosic polymer. The proportion of β‐O‐4 (threo) guaiacyl units is higher than that of β‐O‐4 (erthreo) guaiacyl units. The phenyl glycoside and benzyl ether linkages between lignin and hemicelluloses are also demonstrated in NMR analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Physicochemical characterization of lignin fractions sequentially isolated from bamboo (Dendrocalamus brandisii) with hot water and alkaline ethanol solution

Nine lignin fractions from bamboo (Dendrocalamus brandisii) were sequentially isolated with hot water at 80, 100, and 120°C for 3 h and 60% aqueous ethanol containing 0.25, 0.5, 1.0, 2.0, 3.0, and 5.0% NaOH at 80°C for 3 h. Molecular weight and purity analysis revealed that the lignin fractions isolated by hot water (L₁, L₂, and L₃) had lower weight-average molecular weights (between 1350 and 1490 g mol⁻¹) and contained much higher amounts of associated hemicelluloses (between 9.26 and 22.29%), while the lignin fractions isolated by alkaline aqueous ethanol (L₄, L₅, L₆, L₇, L₈, and L₉) had higher weight-average molecular weights (between 2830 and 3170 g mol⁻¹) and contained lower amounts of associated hemicelluloses (between 0.63 and 1.66%). Spectroscopy (UV, FTIR, ¹³C-NMR, and HSQC) analysis showed that the bamboo (Dendrocalamus brandisii) lignin was typical grass lignin, consisting of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units. The major interunit linkages presented in the alkaline aqueous ethanol extractable bamboo lignin were β-O-4′ aryl ether linkages (about 74.3%), followed by β-β′ resinol-type linkages and β-1′ spirodienone-type linkages (both for 7.8%), together with small amounts of β-5′ phenylcoumaran (6.8%) and p-hydroxycinnamyl alcohols end groups (3.1%). In addition, a small percentage (1.0%) of the lignin side-chain was found to be acetylated at the γ-carbon, predominantly over syringyl units. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Determination of Sugarcane Bagasse Lignin S/G/H Ratio by Pyrolysis GC/MS

Abstract

In this work, analytical pyrolysis (Py-GC-MS) was employed to identify lignin markers derived from H, S, and G phenylpropanoid units in sugarcane bagasse. Temperatures of 450 and 500°C allowed the detection of key products that were informative on the bagasse lignin composition. The method was validated by comparing the S/G ratio as determined by the nitrobenzene oxidation (NBO) standard method for five sugarcane varieties. The S/G ratio as determined by Py-GC-MS, taking into consideration all known lignin markers in the analysis, resulted in a correlation coefficient of 0.85 with a linear regression coefficient of 0.74. When a group of selected markers (M2) was used, the correlation coefficient between methods was improved to 0.95 and the linear regression coefficient was adjusted to 0.92. M2 markers consisted of five syringyl markers (syringol, 4-methylsyringol, 4-ethylsyringol, 4-vinylsyringol, and trans-4-propenylsyringol) and four guaiacyl markers (guaiacol, 4-vinylguaiacol, 4-methylguaiacol, and vanillin). Importantly, Py-GC-MS allowed for the study of lignin composition in sugarcane bagasse without the need to remove the extractives, minimizing the work with sample preparations.     

Separation and Structural Characterization of Lignin from Hybrid Poplar Based on Complete Dissolution in DMSO/LiCl

In this paper, the physicochemical properties and structural features of six lignin preparations separated with a total dissolution of ball-milled wood in dimethyl sulfoxide and lithium chloride (DMSO/LiCl) followed by extraction with ethanol/water were investigated. These isolated lignin fractions were characterized using wet chemical analysis, FT-IR, and ¹H and¹³C-NMR techniques. Experimental results showed that separated lignin preparations were relatively free of associated polysaccharides. These lignin fractions were classified as guaiacyl-syringyl lignin type: mainly composed of guaiacyl units with noticeable amounts of syringyl units and fewer p-hydroxyphenyl units. The molar ratio of non-condensed guaiacyl units to syringyl units (G/S) decreased as the ratio of LiCl to poplar weight increased. The results also showed that these lignin preparations consisted mainly of β-O-4 ether bonds combined with small quantities of β-β′ and β-5 carbon-carbon linkages. Furthermore, considerable amounts of esterified p-hydroxybenzoic acids and minor amounts of esterified p-coumaric acid were also detected in these lignin fractions.     

Fractional Separation and Structural Characterization of Chlorophyll and Lignin from Perennial Ryegrass (L. perenne) and Cocksfoot Grass (D. glomerata)

Abstract

One chlorophyll rich fraction and two lignin preparations were separated from perennial grass and cocksfoot grass by sequential three‐stage treatments with 80% ethanol containing 0.2% NaOH, 2.5% H₂O₂?0.2% EDTA containing 1.5% NaOH, and 2.5% H₂O₂?0.2% TAED containing 1.0% NaOH at 75°C for 3 h, respectively, which released 4.6 and 3.6% chlorophyll rich fraction, 2.3 and 5.8%, and 0.9 and 1.0% lignin preparations, except for releasing 8.0 and 10.4%, 79.1 and 77.0%, and 12.9 and 12.5% of the original hemicelluloses, respectively. The lignin fractions obtained from the two different grasses had very similar molecular weights and structural composition. The NMR spectra of the lignin preparations revealed the presence of p‐hydroxyphenyl, guaiacyl, and syringyl structures, and the lignin in chlorophyll rich fraction contained more guaiacyl and syringyl units than p‐hydroxyphenyl unit, whereas the reverse trend was found in the two lignin preparations. The lignin preparations are distinguished with straw and wood lignins by relatively higher contents of p‐hydroxyphenyl unit and lower amounts of condensed units (β‐5 and 5‐5′) and resinol units (β‐β). This difference in distribution of structural units indicated some structural heterogeneity between grass and straw/or wood lignin.     

Fractionation of Lignocellulosic Materials for the Biorefinery: Separation and Characterization of Lignin from Calamagrostis angustifolia Kom

Dewaxed Calamagrostis angustifolia Kom was pretreated with hot water at 60 and 90°C for 3 h, and then the residue obtained was successively treated with 70% ethanol, and 70% ethanol containing 0.2%, 1.0%, 2.0%, 4.0%, and 8.0% NaOH at 80°C for 3 h. The dissolved components were subjected to further separation to get eight lignin fractions, which were characterized by gel permeation chromatography, Fourier transform infrared, and sugar analysis. All the lignin fractions had small weight-average molecular weights between 810 and 2580 g/mol. Two typical lignins, L₃ (prepared with 70% ethanol) and L₅ (prepared with 70% ethanol containing 1.0% NaOH), were further analyzed using ¹H, ¹³C NMR and HSQC spectroscopy. Signals from guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H) units observed in aromatic/olefinic region of HSQC spectra indicated that the lignin from Calamagrostis angustifolia Kom could be classified as “GSH” lignin. In aliphatic-oxygenated region, β-O-4′ together with small amounts of β-5′, β-β′, and p-hydroxycinnamyl alcohol end group were the main interunit linkages observed. Aqueous ethanol, which could avoid the cleavage of ether bonds in lignin at neutral condition, was more effective than water on lignin extraction.     

氢氧化钠预处理对甘蔗渣酶解和发酵性能的影响

采用氢氧化钠预处理甘蔗渣,通过单因素和正交试验考察了不同预处理条件对甘蔗渣酶解和发酵性能的影响,并进一步分析了比表面积和木质素含量对酶解性能的影响。结果表明：预处理温度、氢氧化钠质量分数及预处理时间对酶解和发酵效率影响较为显著,最佳的预处理条件为：温度85℃、时间11 h、NaOH质量分数4.5%,在此优化条件下预处理的甘蔗渣,含纤维素56.46%,与原料相比提高了46.16%;半纤维素20.30%、Klason木质素5.79%,与原料相比分别降低了15.77%和72.87%,酶解36 h的还原糖得率为0.69 g/g（以甘蔗渣质量计）。经过氢氧化钠预处理后的甘蔗渣比表面积显著增加（由原料的0.07 m²/g最大可增加到1.07 m²/g）,木质素显著降低,有利于提高酶解和发酵效率。当比表面积超过0.30 m²/g时,酶解初始速率和酶解效率达到平衡;当木质素低于11%时,酶解效率达到平衡。