木质素在聚氨酯领域中的应用

木质素是植物界中仅次于纤维素的第二大可再生资源,含有多种官能团,如醇羟基、酚羟基、羰基、甲氧基、羧基等,因此木质素被广泛用于环氧树脂、聚氨酯、酚醛树脂等高分子材料中。聚氨酯领域是木质素应用的一个重要领域,重点综述了木质素在聚氨酯薄膜、聚氨酯弹性体、聚氨酯泡沫、聚氨酯胶黏剂方面的国内外学者的研究成果。     

农作物废弃物在工业废水处理方面的研究应用

农作物废弃物中含有丰富的纤维素和木质素.纤维素作为自然界中储量最大的天然高分子材料,具有价廉易得、易被微生物降解、不会给环境带来第二次污染等特点,长期以来对其开发利用一直是科技工作者研究的热点,而利用天然吸附材料处理含重金属废水是目前最有前途的方法之一.作者主要从生物吸附的概念和对废水中污染物的吸附机理方面,综述了以纤维素、木质素为主要成分的农作物废弃物作为吸附材料或用来制备絮凝剂的研究情况以及存在的问题,探索了今后的研究方向.     

秸秆中木质素对其超低酸水解过程的影响

以湖北稻草秸秆为研究对象,研究了超低酸水解木质纤维素的适宜条件,测定了适宜条件下的超低酸法水解15种不同种类秸秆的纤维素及半纤维素的转化率、还原糖得率及结晶度的变化。实验结果表明:秸秆投料量3 g、硫酸投料量45 mL(硫酸质量分数0.05%)、搅拌转速500 r/min、反应温度210 ℃、反应时间10 min为适宜的水解条件。对15种不同种类秸秆的水解结果统计得到,随着秸秆中木质素含量的增大,纤维素和半纤维素的转化率都逐渐降低,还原糖得率逐渐降低;通过SEM和X衍射分析水解前后的木质纤维素结构,得到了木质素影响水解过程的方式:1)木质素含量越大,纤维素的结晶度越大,纤维素的非晶化越困难,从而影响了纤维素的水解;2)原木质素不溶于反应体系且在酸性条件下相对稳定,富木质素层的木质素阻碍反应物与产物扩散,使富木质素层内的纤维素、半纤维素水解速率降低;3)木质素含量越高,木质纤维素的富木质素层越厚、强度越大,水解时难以从颗粒表面脱落,进一步降低水解速率。     

天然高分子基载体对农药控制释放作用的研究进展

本文综述了天然高分子基载体对农药的控制释放作用。纤维素、木质素、淀粉等天然高分子来源丰富且降解性好，作为农药载体，可有效控制活性成分的释放，提高农药利用率、减轻其污染。采用单组分天然高分子载体时，制剂颗粒的大小和交联度是影响活性成分释放速率的主要因素，天然高分子自身在释放过程中的溶解或溶胀将加速活性成分的释放，进而改变...     

木质素磺化的研究

木质素磺酸盐是一种具有广泛用途的高分子物质,开发利用木质素磺酸盐具有很广阔的前途。对造纸黑液及酸析木质素的磺化进行了研究,得出了黑液及酸析木质素磺化的工艺条件。     

木质素基吸附剂制备及应用研究进展

木质素是自然界中储量仅次于纤维素的芳香族天然高分子，具有生产量大、成本低、易于改性加工等优点，在废水处理中具有广阔的应用前景。综述了木质素基微球的制备方法，包括溶剂挥发自组装法、乳液溶剂蒸发法和反相悬浮共聚法；木质素基水凝胶的制备方法，包括氧化还原法和高压均质法；木质素基炭材料吸附剂的制备方法，包括碳化法，静电纺丝法和模板法。综述了木质素基吸附剂在有机染料、重金属和抗生素等吸附领域中的应用，并对木质素基吸附剂目前存在的问题以及发展前景进行了总结和展望。     

木质素及其衍生物对重金属离子吸附性能研究进展

木质素是一种有机高分子,大量存在于木材、竹材、秸秆、草类及其它植物材料中。但由于其结构复杂,导致应用受到很大的限制。有效利用好木质素这种可再生资源已成为科研工作者研究的出发点。木质素吸附剂是近年来木质素高值化利用研究的热点。文章在简要介绍木质素的化学结构及其分子修饰基础上,对木质素及其衍生物近年来在重金属离子的吸附研究进行了综述。     

木质素与合成高分子共混的研究进展

根据文献资料,对木质素与不同合成高分子共混体系的性能、相容性和共混物分子间的氢键作用以及对相容性的影响进行了综述。根据木质素本身的特点,分析了木质素/合成高分子共混体系中的结晶性能、热稳定和光稳定性能以及抗氧化性能的变化。通过对文献的理解和数据的比较,对不同官能团、不同化学环境对木质素/高分子共混体系相容性的影响以及木质素在其晶区所起的作用作了深入的分析,并且对相容性较差体系中木质素种类、分子量和分子量分布对相容性及其它性能的影响进行了评述。     

木质素在聚氨酯合成中的研究进展

木质素是木质纤维类生物质的第二大组分,木质素的高效、低成本转化是木质纤维素类生物质转化工艺实用化的技术关键。本文综述了利用木质素代替部分多元醇制备聚氨酯材料的两种主要途径：直接添加与改性添加。直接添加木质素包括碱木质素、木质素磺酸盐、硫酸盐木质素、溶剂型木质素等;改性添加木质素包括羟基化改性木质素、木质素硝化反应。最后指出了木质素基聚氨酯材料存在的不足和今后的发展方向。     

木质素在塑料中的应用研究进展

木质素是一种含量丰富的、天然的、可再生的资源,随着石油资源的减少,木质素在高分子合成与应用中起着越来越大的作用。综述了国内外木质素与石化有机小分子单体合成高分子树脂,以及天然高分子材料的接枝共聚、共混在塑料中的应用,并对其存在问题、技术的发展趋势进行了分析。     

Coliquefaction of coal and black liquor

Black liquor from the Kraft pulping process to produce cellulose pulp contains lignin and sodium hydroxide, which are known to enhance the dissolution of coal. But no work has so far been done on the depolymerization of coals using black liquor as an additive. The addition of black liquor enhanced the coal conversion yield about 38.6% in this experiment. But the extent of the enhancement was lower than expected values from separate NaOH/coal and lignin/coal experiments.     

Investigation of liquefied wood residues based on cellulose,hemicellulose, and lignin

Chinese eucalyptus was subjected to a liquefaction process using glycerol/ethylene glycol (EG) as liquefaction solvent. The effects of various liquefaction conditions, including reaction time, liquefaction temperature, acid concentration, and liquor ratio on the chemical composition of liquefied wood residues were studied. The results showed that the whole liquefaction process took place in two stages, the liquefaction yield of wood depended on the reaction temperature, acid concentration and liquor ratio. With increased acid concentration the liquefaction yield, acid‐insoluble lignin, and hemicellulose content of the residues were increased, and the relative content of cellulose was decreased. Fourier transform infrared (FT‐IR) analyses of the residues showed that hemicellulose and lignin were almost decomposed at the initial stages of reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

木质素的综合利用

木质素是结构复杂的天然高分子材料。木素可降解为小分子利用，也可以大分子形式直接用于建筑工程、热固型树脂、分散剂和表面活性剂、制备皮革鞣剂等领域。为充分利用木素应加快木素分子结构、化学修饰、生化降解等基础性研究。     

Investigation and Characterization of Lignin Precipitation in the LignoBoost Process

Lignin of high purity can be separated from black liquor using the LignoBoost process, of which the overall efficiency is largely dependent on the precipitation yield of lignin, which depends on the properties of black liquor and process conditions. In this paper, the influences of process conditions on the precipitation yield of lignin from mixed hardwood/softwood black liquor were investigated. The Klason and standard UV method were used to determine lignin concentration. The chemical and structural properties of lignin were also analyzed. The results showed that the precipitation yield of lignin increased along with a decrease in pH and temperature, or with an increase in the ion strength of black liquor, and the yield was lower when mixed softwood/hardwood black liquor was used. It also showed that at a higher precipitation yield the precipitated lignin had a lower average molecular weight but had higher methoxyl and phenolic hydroxyl content.     

Systematic Isolation and Utilization of Lignocellulosic Components from Sugarcane Bagasse

Lignocellulosic constituents as renewable feedstock can be utilized for various applications. A systematic procedure for separation of cellulose and lignin followed by hydrolysis of hemicelluloses was proposed in this study. Sugarcane bagasse was first subjected to alkaline hydrolysis to remove lignin and hemicelluloses. Then cellulose was separated from the alkali pretreatment residue and further purified. Meanwhile, the obtained pre-hydrolysis liquor (PHL) was acidified to precipitate lignin, and the filtrate was hydrolyzed with 1-methylimidazolium hydrogen sulfate ([Hmim]HSO₄) to prepare furfural. Response surface methodology (RSM) was employed to determine optimal conditions for isolation of cellulose. The sequential treatments resulted in a total release of over 77.3% of the original cellulose and 84.5% of the original lignin. In particular, 7.5% yield of furfural was obtained. The structures of the isolated cellulose and lignin were elucidated with Fourier transform infrared spectroscopy (FT-IR).     

Fractionation and concentration of kraft black liquor lignin with ultrafiltration

Kraft black liquor lignin is a biofuel that is separated from the cellulose during kraft pulping. Improved technology and energy integration in paper mills have led to an energy surplus at many mills. It is therefore of great interest to extract the lignin from the pulp mill and sell it as fuel to replace fossil fuel in other furnaces. The fractionation of kraft black liquor with a total dry matter content of about 15 wt% has been studied using ultrafiltration. The flux for three polymeric membranes with different cut-offs was investigated as well as their retention of lignin and other process specific substances. The retention of lignin for the three membranes with cut-offs of 4,8 and 20 kDa was 80%, 67% and 45%, respectively. The retention of sulphur and sodium was zero for all three membranes. The purity of the final lignin fuel is of importances as the ash content preferably should be as low as possible. The flux and retention during concentration and diafiltration of the black liquor were therefore studied. The dialfiltration operation was conducted in batch and semicontinuous mode. The lignin purity was 36% in the original kraft black liquor and 78% after semi-continuous dialfiltration.     

木糖渣的有机溶剂预处理及酶解性能

木糖渣是玉米芯经稀酸处理提取木糖后的残余物,一般作为燃料焚烧以提供部分热能。由于其含有丰富的纤维素组分,故可通过生物转化来生产多种化工产品,但残渣中大量木素的存在严重抑制了纤维素酶的水解效率。采用一些有机溶剂预处理可将部分木素溶出,因而可改善物料的酶解性能。采用乙醇对木糖渣进行预处理,研究了预处理条件（如温度、时间、固液比等）对木糖渣化学组分和纤维素酶解转化率的影响,并与玉米秸秆和玉米芯等进行了对比。结果表明预处理降低了木糖渣的木素含量,在固液（质量/体积）比1︰8、处理液中乙醇浓度50%（体积）、预处理温度210℃、预处理时间60 min时,木素脱除率为53.26%,预处理后木糖渣在酶解72 h时的纤维素转化率达到84.42%,比预处理前提高 14.58%。研究还发现,与木糖渣相比,有机溶剂乙醇更适合用于玉米芯和玉米秸秆酶解前的预处理。     

Parameters Affecting the Cross-Flow Filtration of Dissolved LignoBoost Kraft Lignin

In the kraft pulping process, the lignin-containing by-product kraft black liquor is currently combusted as an energy source. LignoBoost is a technique that extracts lignin from kraft black liquor, resulting in a lignin-lean black liquor, which is returned to the process, and an extracted kraft lignin. To facilitate the use of the extracted kraft lignin in high-value applications, it can be refined via fractionation to produce a more homogeneous starting raw material. Hence, the aim of this study is to investigate the behavior of dissolved softwood kraft lignin during cross-flow filtration. The effects of the lignin concentration, pH, and ionic strength on the fractionation of the dissolved lignin during cross-flow filtration are investigated. The results indicate that large amounts of low-molecular-weight kraft lignin can be produced from solutions having a low lignin concentration. Furthermore, the effects of pH and ionic strength on the fractionation of low-molecular-weight lignin are identified within the studied ranges.     

Formation of Chlorinated Organic Matter from Carbohydrate During Kraft Pulp Bleaching

Chlorinated organic matter is formed during chlorine bleaching of carbohydrate. After chlorine bleaching of various cellulosic materials, organochlorine is found in the cellulose substrate (e.g., about 490 μg Cl/g substrate for cotton cellulose) as well as in the spent bleaching liquor. Some organochlorine is mineralized by alkali treatment of the cellulose and some is dissolved. Some organochlorine is not removed by exhaustive extraction with organic solvents, i.e., is inextractable. The carbohydrate-originated organochlorine accounts for part of the inextractable organochlorine in fully-bleached chemical pulp (previously ascribed entirely to a lignin origin). Chlorination of unmodified simple sugars results in some organochlorine (17 to 83 μg Cl/g sugar), while chlorination of “kraft-cooked” glucose precipitate results in 6150 μg organochlorine as Cl/g substrate. Household hypochlorite bleaching of cotton fabric also results in formation of inextractable organochlorine.     

Rapid Hydrothermolysis of Poplar Wood: Comparison of Sapwood,Heartwood, Bark,and Isolated Lignin

Abstract

Rapid hydrothermolysis at 350°C of poplar sapwood, heartwood and bark, as well as the lignin extracted from the sapwood and heartwood, gives oil and water soluble fractions whose chemical analysis is correlated with the nature of the feed stock. Results from cellulose and Douglas fir are included, and the poplar bark and heartwood lignin are shown to give an ether soluble oil that consists mainly of guaiacyl units while the sapwood product is mainly syringyl. However, the chloroform soluble oil from both sapwood and heartwood was mainly syringyl with the additional presence of carbohydrate derived material in the heartwood oil. The acetone-only soluble residue from sapwood was shown by pyrolysis mass spectrometry to be mainly cellulose derived while that from heartwood was mainly from lignin. Thus there is a fundamental difference in the behaviour of the poplar sapwood and heartwood that may arise from different distributions of the guaiacyl and syringyl units, and of the binding to the cellulose. The origin of the rapid hydrothermolysis products with respect to the major wood components is discussed. An empirical approach to the calculation of the lignin content based on the rapid hydrothermolysis fractions is presented.