Lignin adsorption on cellulose fibre surfaces: Effect on surface chemistry, surface morphology and paper strength

The adsorption of lignin on cellulose fibres at neutral pH and the effects of calcium ions and a cationic polyelectrolyte (PDADMAC) on the adsorption have been studied. The surface coverage by lignin was determined by electron spectroscopy for chemical analysis (ESCA). The morphology of the lignin layer was studied by atomic force microscopy (AFM). The effect of adsorbed polyelectrolyte and lignin on the strength properties of the paper was also studied. The adsorbed amount of lignin increased monotonically with lignin concentration. Addition of calcium ions resulted in a very high surface coverage by lignin. PDADMAC did not enhance the adsorption of lignin, but without addition of polyelectrolyte the lignin was very weakly attached to the fibre surface. PDADMAC formed complexes with lignin in solution. At high polymer/lignin concentration ratios the charge of the complex was positive and it adsorbed irreversibly as large blobs. At low ratios the complex was easily washed away from the fibre surface. When PDADMAC was pre-adsorbed on the fibre surface the lignin adsorbed as small granules at all lignin concentrations. Neither PDADMAC nor lignin alone increased the strength of pulp sheets significantly. However, together they increased the bonding between fibres.     

SEPARATION AND PURIFICATION OF LIGNIN BY MEANS OF ION EXCHANGE PROCESS

The effect of resin structure on desalination of lignin solution was investigated,the optimal structure of resin is as follows;cross linking degree as 4%,ratio of cationogen to anionogen is near 1.with such resin the desalination of lignin was produced very well because the resin has both molecule sieving and ion retardation properties.The sulfonation degress of lignin and total salt content of lignin solution were determinred with ion exchange technique,the relative error less than 1%.The salt content of small molecule in the lignin solution was calculated from sulfonation degree of lignin and total salt.Among gel and macroporous resins the best separation of lignin from reducing sugar was achieved with interpenetrating sulfonated resin 2×1.5×1.The separation of lignin with interpenetrating resin was carried out simultaneously with fractionation of lignin,the effect of fractionation with macroporous sulfonated resin is better than that with interpenetrating resin,but the former has a definite sorption of lignin which decreased the recovery of lignin.     

丹参木质素及其单体含量的测定

本文建立了一种准确、快速的检测丹参中木质素及其单体含量的方法.采用Klason法和紫外分光光度法分别对丹参根和茎中酸不溶性木质素(Klason木质素)和酸溶性木质素含量进行了测定;运用硫代酸解法并结合气相色谱-质谱法(GC-MS)分别对丹参根和茎中各木质素单体组成进行了分析.结果显示,总木质素在丹参根和茎中的含量分别为...     

Oxidation of hydrolysis lignin with hydrogen peroxide in acid solutions

Optimal conditions were determined for oxidation of hydrolysis lignin and other insoluble lignin samples with hydrogen peroxide in acid solutions, ensuring solubility of lignin in dilute alkali. The correlation was found between the functionalization and solubility of hydrolysis lignin and its oxidation products. A procedure was suggested for determining carboxy groups in lignin.     

Obtainment of chelating agents through the enzymatic oxidation of lignins by phenol oxidase

Oxidation of lignin obtained from acetosolv and ethanol/water pulping of sugarcane bagasse was performed by phenol oxidases: tyrosinase (TYR) and laccase (LAC), to increase the number of carbonyl and hydroxyl groups in lignin, and to improve its chelating capacity. The chelating properties of the original and oxidized lignins were compared by monitoring the amount of Cu²⁺ bound to lignin by gel permeation chromatography. The Acetosolv lignin oxidized with TYR was 16.8% and with LAC 21% higher than that of the original lignin. For ethanol/water lignin oxidized with TYR was 17.2% and with LAC 18% higher than that of the original lignin.     

Valorization of Rice Straw via Hydrotropic Lignin Extraction and Its Characterization

Rice straw hydrotropic lignin was extracted from p-Toluene sulfonic acid (p-TsOH) fractionation with a different combined delignification factor (CDF). Hydrotropic lignin characterization was systematically investigated, and alkaline lignin was also studied for the contrast. Results showed that the hydrotropic rice straw lignin particle was in nanometer scopes. Compared with alkaline lignin, the hydrotropic lignin had greater molecular weight. NMR analysis showed that β-aryl ether linkage was well preserved at low severities, and the unsaturation in the side chain of hydrotropic lignin was high. H units and G units were preferentially degraded and subsequently condensed at high severity. High severity also resulted in the cleavage of part β-aryl ether linkage. ³¹P-NMR showed the decrease in aliphatic hydroxyl groups and the increasing carboxyl group content at high severity. The maximum weight loss temperature of the hydrotropic lignin was in the range of 330–350 °C, higher than the alkaline lignin, and the glass conversion temperature (T_g) of the hydrotropic lignin was in the range of 107–125 °C, lower than that of the alkaline lignin. The hydrotropic lignin has high β-aryl ether linkage content, high activity, nanoscale particle size, and low T_g, which is beneficial for its further valorization.     

Factors affecting lignin solubility

The solubility of lignin in aqueous NaOH solutions was studied in relation to the lignin molecular weight, temperature, liquid to solid ratio, and ionic strength. A new procedure for determining the content of phenolic hydroxyls in lignin was developed. A formula was suggested for calculating the lignin solubility in aqueous alkali solutions.     

羟甲基化木质素磺酸盐添加剂对钻井液性能的影响

为了进一步优化木质素磺酸盐作为钻井液处理剂的效能,利用其与甲醛的羟甲基化反应制备了羟甲基化木质素磺酸盐;采用红外光谱仪、X射线粉末衍射仪、扫描电镜等分析了其结构;测定了改性前后的木质素磺酸盐对钻井液流变性、降滤失性、黏土水化膨胀抑制性等性能的影响.结果显示,改性后的羟甲基化木质素磺酸盐的整体结构变化不大,但羟基数量增加,与水的相溶性增强.与木质素磺酸盐相比,羟甲基化木质素磺酸盐在室温下对基浆有较强的提黏作用,经180℃高温老化后降黏、降滤失作用有所增强,形成的泥饼厚度降低,对黏土水化膨胀的抑制作用增强.     

Graphite from hydrolysis lignin: Preparation procedure,structure, properties,and application

The possibility of preparing graphite from hydrolysis lignin using pyrolysis and graphitization processes was considered. The influence of lignin milling on the granulometric composition of the graphite obtained was studied. The structure of graphite prepared from lignin was confirmed by X-ray diffraction analysis. Prospects for using graphite materials prepared from lignin in electrochemical and other technologies are demonstrated.     

萝卜木质素的提取及其抗自由基活性

以浓度为80%的乙二醇水溶液为溶剂,采用高沸醇溶剂法(HBS)从萝卜中提取萝卜木质素,采用红外光谱、紫外光谱和~1H NMR等方法对其结构进行了表征.结果表明,所提取的萝卜木质素具有木质素类化合物的典型结构特征.采用可见光分光光度法研究了萝卜木质素对DPPH·自由基和HO·自由基的抑制效率.结果表明萝卜木质素对两种自由基均具有较高的抑制率,其对两种自由基的抑制率最高分别为90%和68.3%.     

The oxidative destruction of lignin in the ozonation of wood

The oxidative destruction of lignin in the ozonation of aspen wood was studied. The kinetic curves of ozone consumption for samples with different contents of water were obtained. The consumption of ozone increased as the content of water grew. The second derivatives of the UV absorption spectra of lignin were obtained to show that the principal direction of lignin transformations under the action of ozone was the destruction of its aromatic constituents with the formation of carboxyl- and carbonyl-containing compounds. Measurements of the UV diffuse reflectance and EPR spectra of wood showed that the ozonation of wood caused the destruction of lignin quinoid structures. Part of lignin remained unchanged under the action of ozone. A key role in the destruction of wood lignin was played by ozone dissolved in water. Varying the content of water in wood samples allows various lignin transformation products to be obtained through ozonation.     

Synthesis of polyurea nanocomposite from industrial waste lignin: Classical curing of isocyanate by lignin-polyamine

Polyurea is an important class of polymer obtained through curing of the isocyanate and polyamine. Here lignin amine processed successive three-step reactions for the synthesis of nanostructure polyurea composite. Further the competence nature is found out by combining different lignin-polyamine with various di-isocyanate. In the first step, lignin was reacted with tosyl-chloride which modified the hydroxy function of lignin as a good leaving group. This reaction for tosylated lignin (Lignin-OTs) has 80% yield. Further lignin-OTs was reacted with four different polyamines replaced tosyl functional group by amine gives aminated lignin. Eventually, a classical reaction of aminated lignin and three different di-isocyanate yield a polyurea composite. A series of changes from lignin to its tosylation eventually to polyurea composite was pursued by the change in the functional group of lignin. The tosylated lignin was confirmed by IR absorption of the C-O peak at 1190 and 1365 cm^?1 and invisible peak absorption at 3500 cm^?1. The aminated lignin was confirmed by IR absorption at 3120 and 3430 cm^?1 for –NH. Thermal gravimetric analysis (TGA) and differential scanning colorimetry (DSC) were used to determine the product's thermal characteristics. Complete structural morphology of nanostructure lignin-polyurea composite was investigated by X-ray diffraction, FE-SEM and EDX.     

Lignin derived oils from the fast pyrolysis of poplar wood

A pyrolysis oil obtained from the fast pyrolysis of poplar wood was subjected to mild hydrolysis and an aqueous and a non-aqueous fraction recovered. The non-aqueous fraction (pyrolytic lignin), a brown powder, was 23% of the oil, or 16% of the wood, corresponding to about 80% volatilization of the lignin content. Nuclear magnetic resonance spectra of this pyrolytic lignin were obtained, and its structure appears to be very similar to that of steam exploded poplar lignin. Methoxy content is relatively high and syringyl units appear to predominate over guaiacyl units. The pyrolytic lignin appears to be somewhat more degraded than steam exploded lignin and is probably lower in molecular weight.     

Effects of lignin on the ionic-liquid assisted catalytic hydrolysis of cellulose: chemical inhibition by lignin

The production of cellulose-derived biofuels and biochemicals, such as bioalcohols and bioplastics, from lignocellulose requires the isolation of cellulose by lignin removal or delignification processes. While the remaining lignin and its phenolic fragments have been reported to inhibit the biological conversion of cellulose, we observed that the catalytic hydrolysis of cellulose also can be inhibited most likely because of an associative interaction between cellulose and lignin. The associative interaction between cellulose and the functional groups of lignin was proven by gel-permeation-chromatography measurement of regenerated mixtures of lignin and cellulose which simulate the lignocellulose-derived cellulose containing lignin as an impurity. Chemical bonds between cellulose and lignin were hypothesized using lignin model compounds containing known functionalities such as hydroxyl, methoxy, phenyl, allyl, and carboxyl groups in order to explain the effects of lignin on the hydrolysis of cellulose. The yield of glucose from cellulose dropped when carboxylic and hydroxyl groups were present possibly because of the formation of ether and ester bonds between the lignin and cellulose. These observations may help develop the chemical processes and therefore convert the inedible biomass resource of lignocellulose-based cellulose containing lignin and its derivatives to the valuable fuels and chemicals.     

Selective Utilization of the Methoxy Group in Lignin to Produce Acetic Acid

Selective transformation of lignin into a valuable chemical is of great importance and challenge owing to its complex structure. Herein, we propose a strategy for the transformation of methoxy group (‐OCH₃) which is abundant in lignin into pure highly valuable chemicals. As an example to apply this strategy, a route to produce acetic acid with high selectivity by conversion of methoxy group of lignin was developed. It was demonstrated that the methoxy group in lignin could react with CO and water to generate acetic acid over RhCl₃ in the presence of a promoter. The conversions of methoxy group in the kraft lignin and organosolv lignin reached 87.5 % and 80.4 %, respectively, and no by‐product was generated. This work opens the way to produce pure chemicals using lignin as the feedstock.     

NaBH4/I2催化加氢还原碱木质素的研究

从麦草碱法制浆黑液中提取木质素,精制后,以苯乙酮为木质素的模型化合物,对催化剂组成及溶剂进行了考察.在此基础上,以NaBH4/I2为催化剂,无水乙醇为溶剂,对木质素进行加氢还原裂解反应研究.考察了温度和时间对木质素催化加氢效果的影响,采用红外光谱(FTIR)、元素分析及凝胶渗透色谱分析(GPC),表征木质素反应前后结构的变化.凝胶渗透色谱分析表明,加氢还原后木质素的分子量明显降低.采用自动电位滴定法测定反应前后木质素中总羟基含量,反应后木质素中总羟基含量为10.19%.得到了NaBH4/I2催化木质素加氢还原反应的最优条件:以1,2-二氯乙烷和乙醇(2∶1,v/v)作溶剂,m(NaBH4)∶m(I2)=1∶1,温度175℃,反应时间15 h.     

Quaternized lignin-based dye dispersant: Characterization and performance research

Lignin-based dye dispersants have aroused an increasing interest due to their environment-friendly properties. In this research, the quaternized lignin-based dye dispersant (QLD) was prepared using alkali lignin from masson pine sulfate pulping liquor as raw materials by chemical modification, that is, sulfonation and quaternization. The structure and performance characterization of alkali lignin and QLD were studied. The analyses indicated that the structural unit of alkali lignin contained more G type and S type. Additionally, it was also proved that QLD contained quaternary ammonium group, amine group, and sulfonic group, which could improve the dispersion performance and thermostability of QLD. The results of thermogravimetric (TG) concluded that the dispersion performance and thermostability of QLD prevailed over alkali lignin. Compared with the contact angle of water, alkali lignin, and QLD with dye, the contact angle of QLD was much better than water and alkali lignin, indicating that the hydrophilicity and dispersion performance of QLD were superior to water and alkali lignin in Vat Olive T.     

两种β-O-4型木素高聚模型物的合成

本文从4-羟基苯乙酮和4-羟基-3-甲氧基苯乙酮出发,经由CuBr2溴化、碱催化氧负离子亲核加成形成聚合物,再由NaBH4还原,合成了愈创木基型(G)和对羟苯基型(H)的木质素高聚模型物。高聚模型物经核磁共振氢谱和碳谱(1H-NMR、13C-NMR)、红外光谱(IR)、基质辅助激光解析串联飞行时间质谱(MALDI-TOF/TOF MS)和凝胶渗透色谱(GPC)表征,结果表明高聚物是含有β-O-4连接、无γ-C及γ羟基的直链聚合物,重复单元式量为136.16n+2。这类木质素模型物具有与分离木素类似的结构与性质,可溶于木质素常用溶剂,两种聚合物的重均分子量均在5000以上,与工业木质素分子量相近,其多分散度分别为1.26-1.76。该木质素高聚模型物的合成为进一步考察木素大分子在不同热化学环境下的热解特性提供了又一新的研究方法。     

Studies on thermal characterization of lignin

Thermal properties of control phenol formaldehyde (cpf) adhesive and lignin substituted phenol formaldehyde (lpf) adhesives have been investigated in detail. The effect of varying lignin mass percent of phenol and source of lignin like bagasse, eucalyptus bark, coconut coirpith and coffee bean shell on the thermal stability have been studied using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). 50 mass% of lignin loading in cpf adhesive shows better bond strength, whereas lignin incorporation up to 25 mass% yields a resin of thermal stability comparable to cpf. Loading of lignin in cpf delays the first thermal transition event. The mass loss in this event was found to increase with increasing lignin content. Lignin source has significant effect on the thermal stability of lpf resins. Rate of curing is enhanced by incorporation of lignin into cpf.     

Polymerization of lignin model compounds with formaldehyde in acidic aqueous medium

The reaction of formaldehyde with lignin model compounds in acidic medium was shown to give fast crosslinking of alkyl-substituted phenolic and etherified phenolic lignin model compounds at positions meta to the aromatic hydroxy groups. This reaction differs from the reaction of formaldehyde with phenolic lignin model compounds in alkaline conditions, where the reaction with formaldehyde always occurs at positions ortho/para to the aromatic hydroxy group., The reaction of formaldehyde with lignin in acidic medium have considerable potential for the crosslinking of lignin, particularly heavily condensed alkali lignin, for use in polymeric products.