人工神经网络在纸浆卡伯值光学定量分析中的应用

卡伯值 (硬度 )是纸浆的重要质量指标 ,是制浆过程控制的关键参数 .目前的测量方法包括化学分析法和光学分析法两大类型 ,国内大多数的制浆造纸厂采用离线的传统化学分析法来测定纸浆的卡伯值 ,需要比较长的时间 .而光学分析法因具有实时性好、精度和可靠性高等优点 ,已逐步用于卡伯值的在线测量和控制 .研究 [1] 发现 ,在 460～ 580 nm的可见光谱范围内 ,蒸煮液吸光度的变化可以表征纸浆中木素含量的变化 .本文将可见分光光谱技术应用于蒸煮液中木素含量的在线测量 ,根据蒸煮液在所选波段的吸光度来预测纸浆的卡伯值 ,建立纸浆卡伯值与蒸煮…     

主成分-BP算法在近红外光谱法纸浆卡伯值测量中的应用研究

提出采用主成分-BP算法建立纸浆卡伯值近红外光谱法在线测量模型。结果表明,这种算法由于既考虑到了近红外光谱响应的非线性因素,又可防止BP算法在建模时出现“过拟合”的现象,利用该算法建立的纸浆卡伯值测量模型与一元回归,多元回归和主成分回归等线性方法相比,具有更高的预测精度。     

硫酸盐纸浆浓度对纸浆反射光谱影响的定性研究

提出了采用反射光谱测量纸浆卡伯值的新方法。就硫酸盐纸浆浓度对纸浆反射光谱的影响进行了研究。结果表明：在指定波段内纸浆的光反射率受到疏酸盐纸浆水分含量(纸浆浓度)的影响,随着纸浆水分的增加,纸浆的光反射率下降,在长波长处的光反射率降幅大于短波长处;使用该方法时为了有良好的测量分辨率．硫酸盐纸浆浓度应大于2％．     

甘蔗渣乙醇法制浆——添加剂对脱木素作用的影响

研究了甘蔗渣乙醇法制浆及添加剂对这一制浆过程脱木素作用的影响。结果表明,不加添加剂的乙醇制浆脱木素极不充分,添加酸性添加剂反而使脱木素的效果变劣,添加碱性添加剂则可以大大促进乙醇溶剂的脱木素作用。讨论了酸性和碱性添加剂脱木素作用的两种绝然不同影响的原因,主要是脱木素的缩聚问题所造成。碱性添加剂能有效地抑制蒸煮过程中木素的缩聚反应,从而能使木素得到有效的脱除。碱性添加剂的加入量以控制介质蒸煮终了时的pH值在7—10的范围为宜,最好控制在pH=9—10,此时成浆的硬度可以降到卡伯值17—20范围,粗浆得率为54—57％。     

~(19)F-NMR法测定聚醚多元醇中伯羟基的相对含量

<正> 聚醚多元醇是聚氨酯材料的主要原料之一.多元醇中伯羟基含量的多少对反应活性有着直接的影响,因此,准确地测定伯羟基含量已成为许多研究者关心的课题,并已报道了不少测定方法,其中主要包括化学动力学方法、~1H-核磁共振(NMR)法和~(19)F-NMR法,~1H-NMR法系利用不同的酰化剂,将聚醚多元醇酰化后测其酰化物的~1H-NMR谱,从伯、仲羟基相应的酯基氢的积分比例来计算伯羟基的相对含量,但由于体系中存在其它含氢基因,且是大量的,使测量困难或应用受到限制.~(19)F-NMR法测伯羟     

用超滤法从纸浆废液中分离浓缩木素

<正> 绪言工业废水是发展工业过程中必须解决的环境保护问题。制浆造纸工业是排放废水量最大的行业之一,在纸浆废液中含有大量的木素和多糖等宝贵的物质,弃之则污染环境,用之则变废为宝。近年来,关于木素的结构性能及其利用的研究受到愈来愈大的重视,并取得了一定     

基于氧化淀粉的新型Pickering苯丙乳液表面施胶剂的合成

以苯乙烯、丙烯酸丁酯为单体,过硫酸铵为引发剂,氧化淀粉作固体粒子乳化剂,采用无皂乳液聚合的方法来制备Pickering苯丙聚合物乳液,考察了不同含量的氧化淀粉对乳液固含量、转化率、卡伯值以及稳定性的影响,并对制备的Pickering苯丙聚合物乳液进行了粒径、红外光谱表征,当氧化淀粉的含量为2%时,制备的Pickering苯丙聚合物乳液转化率为96%,粒径为264.4nm,卡伯值为71.4g/m~2,抗水性和稳定性较好.     

N1923从碱性氰化液中萃取金(Ⅰ)的研究

采用放射性同位素198Au示踪法研究了伯胺N1923和TBP从碱性氰化液中萃取金(Ⅰ),考察了酸化率、水相pH值、萃取剂浓度等对萃取率的影响,以及NaOH对载金有机相的反萃作用。结果表明,TBP含量大于20％,酸化的N1923与KAu(CN)2摩尔比值在11时,金能够完全被萃取。载金有机相可采用0.1mol·L-1的NaOH溶液定量反萃。机理研究表明,伯胺和TBP萃取Au(CN)2-,符合BC类协同萃取机理。当金浓度大于10g·L-1时,在萃取有机相中形成纳米级的聚集体。     

碳数规律中((e)A)/((e)(1/r))、( B')/((e)(1/r))值与固定液极性的关系

采用n-烷烃在不同极性的固定液中,在不同色谱柱温下试验的大量数据表明,碳数规律中A、B'值与柱温倒数(1/T)的关系中,(e)A/(e)(1/T)值随固定液极性增加而增大;(e)B'/(e)(1/T)值随固定液极性增加而减小,即(e)A/(e)(1/T)值与Mertynolder常数成正比;(e)B'/(e)(1/T)值与Mertynolder常数成反比.     

碳数规律中值与固定液极性的关系

采用n-烷烃在不同极性的固定液中,在不同色谱柱温下试验的大量数据表明,碳数规律中A、B'值与柱温倒数(1/T)的关系中,(e)A/(e)(1/T)值随固定液极性增加而增大;(e)B'/(e)(1/T)值随固定液极性增加而减小,即(e)A/(e)(1/T)值与Mertynolder常数成正比;(e)B'/(e)(1/T)值与Mertynolder常数成反比.     

Dissolution of ionisable groups and lignocellulosic components during low-temperature kraft pulping of pinus radiata

A wide range of kraft pulps from radiata pine produced by low-temperature kraft pulping in flow-through reactors was assessed for carboxyl and hexenuronic acid (HexA) contents using the conductometric titrations and UV spectrophotometer, respectively. The Kappa number of pulps varied from 20.8 to 84.7 when using a cooking liquor of 1 M effective alkali as Na₂O, 25% sulfidity, and cooking time of 100–250 min. The experimental results showed that the carboxyl groups (including HexA) and HexA groups dissolved and their residual values in the pulp samples correlate linearly with Kappa number and pulp yield. The dissolving rate of all carboxyl groups is much faster than the loss of HexA. The HexA/lignin ratio decreased non-linearly with Kappa number.     

Pyrolysis-GC/MS and TG/MS study of mediated laccase biodelignification of Eucalyptus globulus kraft pulp

Biobleaching studies using laccase mediator system (LMS) were carried out, under optimized conditions, on two unbleached Eucalyptus globulus kraft pulps, one produced by conventional way, with kappa number of 16.1, and another with kappa number of 14.5, obtained by modified kraft procedure with a high liquor/wood ratio and with black liquor replacement in the middle of the cooking. The pulp properties before and after LMS and alkaline extraction were evaluated in terms of kappa number, hexeneuronic acid content, viscosity, brightness and acid insoluble lignin content.The original milled wood sample and the kraft pulps were characterized by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry/mass spectrometry (TG/MS). Eucalypt wood lignin produces guaiacol and syringol derivatives during pyrolysis. These lignin products can be detected with high sensitivity using the selected ion chromatograms even in the bleached pulp of low lignin content (about 0.5%). Py-GC/MS revealed that the lignin moieties were similarly altered during biobleaching as during pulping, which is exemplified by the preferential removal of aldehyde groups from the alkyl side groups. Semi-quantitative analysis of the pyrograms indicates that the lignin content of the biobleached pulps is reduced by about half in comparison with the unbleached pulps. The TG/MS results show that the hemicellulose content of wood was strongly modified during pulping resulting in higher thermal stability.     

Production, bleaching, and characterization of pulp from Stipa tenacissima

Alfa grass pulping was successfully performed in hydro-organic acid medium under mild conditions (107°C, atmospheric pressure, cooking time: 3 h). Use of an acetic acid/formic acid/water mixture as pulping liquor was perfectly suitable for selective isolation of pulp, lignin, and hemicelluloses. The unbleached pulp obtained in good yield was first delignified by peroxyacids in organic acid medium and then bleached with hydrogen peroxide in a basic medium to give pulp offering good physico-chemical and mechanical characteristics.     

Infra-red spectroscopic study of lignins

Infra-red spectra from 200–4000cm⁻¹ of lignin precipitated from black liquor produced from different pulping processes of bagasse, e.g. soda, kraft, sulfite, peroxyacid and butanol, have been characterized. Peroxyacid lignins are more degraded than other lignins. However, peroxyacid lignin has a higher intensity band at 1720cm⁻¹ than other types of lignins. At the same time, the aromatic ring of lignin produced from peroxyacid pulping of bagasse undergoes severe degradation. Syringyl type of lignin is predominant in all isolated lignins. Peroxyacid and butanol lignins have lower quantities of syringyl lignin shown by the lower ratio of relative absorbance of band intensity at 1500cm⁻¹ to the band at 1600cm⁻¹ than other lignins. Kraft lignin has a broad weak band at about 630cm⁻¹ that is probably due to a C---S bond. A sharp band at 655cm⁻¹, which is due to SO₃H, is characteristic of lignosulfonate, which is precipitated from black liquor produced from sulfite pulping process of bagasse. Generally, degradation of different lignins during pulping of bagasse with different processes has the following sequence: peroxyformic > peroxyacetic > butanol-water > butanol-alkali > kraft > sulfite > soda.     

Analysis of precipitated lignin on kraft pulp fibers using atomic force microscopy

A method is presented which enables analysis of lignin precipitated on the surface of kraft pulp fibers. As experimental input, high-resolution atomic force microscopy phase images of the fiber surfaces have been recorded in tapping mode. A digital image analysis procedure—based on the watershed algorithm—is applied to distinguish between cellulose fibrils and the precipitated lignin. In this way, size distributions for the diameter of lignin precipitates on pulp fiber surfaces can be obtained. In an initial application of the method, three softwood kraft pulps were analyzed: a black liquor cook with a very high content of precipitated lignin, a bleached pulp where nearly no precipitated lignin is visible and an unbleached industrial pulp. The proposed method is suggested as an appropriate tool to investigate the kinetics of lignin precipitation and the structure of lignin precipitates in pulping and bleaching.     

Estimation of the Effect of Diffusion and Transformation of Lignosulfonates on the Mechanism of Delignification in Sulfite Cooking of Spruce Wood

The contribution of diffusion and transformation of macromolecules to the mechanism of delignification of cell wall in sulfite cooking of spruce wood was quantitatively estimated from variation of the parameters of the Kolmogorov-Erofeev-Avrami equation and hydrodynamic radii of lignosulfonate macromolecules found in the cooking liquor.     

Improvement of the technology for reprocessing black liquors from kraft pulp production

A way to improve the kraft pulp production process via acid–base treatment of black liquor was suggested. Data on the process for kraft lignin production by the sulfuric acid procedure were substantiated.     

Cellulose Depolymerisation and Paper Properties in E. Globulus Kraft Pulps

The aim of this work was to study the impact of cellulose depolymerisation on the beating potential and handsheet properties of the portuguese E. globulus kraft pulp. A homogeneous sample of eucalypt wood chips was cooked using different kraft pulping conditions (cooking temperatures and times, and sodium hydroxide and sodium sulphide concentrations) in order to obtain a wide variation for intrinsic viscosity of the pulps. In the range of industrial cooking conditions, this property was found to be linearly dependent on the effective alkali charge, for a given cooking time and temperature. Unbeaten and beaten (at 2000 rev. PFI) pulp properties were evaluated and the results confirm that the higher the pulp intrinsic viscosity the better the pulp beatability and the paper properties. However, the differences in the latter cannot be exclusively explained by the differences in viscosity, since pulps with the same viscosity may exhibit distinct papermaking potentials. It was then necessary to scan other pulp chemical characteristics that could also influence the development of paper properties such as lignin, pentosan content and polysaccharides relative composition.