枫香树材硫酸盐制浆工艺技术研究

通过对枫香树材硫酸盐蒸煮的用碱量、硫化度、温度和保温时间四因素三水平方差分析工艺技术研究发现,在所选的四因素三水平内,用碱量对浆料得率和卡伯值的影响最大,硫化度对浆料得率和卡伯值的影响最小。枫香树材硫酸盐蒸煮较为适宜的工艺条件为:用碱量17%(Na2O计),硫化度20%,温度165℃,保温时间60 min,液比1∶6。另外,在枫香树材硫酸盐蒸煮过程中添加AQ,对提高蒸煮脱木素选择性具有明显的效果。     

麦草低温氧碱蒸煮浆料性质的研究

麦草碱法蒸煮后,浆料不经洗涤,直接通入氧气进行处理。对麦草氧碱蒸煮段用碱量、氧压、温度和时间四因素三水平方差分析表明,用碱量对得率的影响最大,时间对其影响最小;浆料黏度下降并不明显;用碱量对浆料卡伯值的影响最大,氧压对其影响最小。在较适宜的工艺条件下氧碱蒸煮结果为:浆料得率52.6%;浆料黏度为1 042 mL/g,比单段碱法蒸煮后浆料黏度(1 099 mL/g)降低5.2%;浆料卡伯值17.9,比单段碱法蒸煮后浆料卡伯值(20.3)降低11.8%;黑液黏度为3.4 mPa.s,比单段碱法蒸煮黑液黏度(5.1 mPa.s)降低33.3%。     

Kraft pulping of Eucalyptus nitens wood chips biotreated by Ceriporiopsis subvermispora

Eucalyptus nitens and E. globulus are wood species used in kraft pulping in Chile and Australia. Although E. nitens adapts very well to cold regions it requires more severe cooking conditions to produce bleachable kraft pulps. An attempt was made to find out whether a pre‐treatment with Ceriporiopsis subvermispora would improve its performance during kraft pulping and the pulp properties. The biotreatment of the chips carried out for a period of 15 days resulted in 13.3% lignin loss and a limited glucan degradation (2%). The pulping of biotreated samples required lower active alkali charge to reach the target kappa number compared to the control untreated sample and exhibited better pulping selectivity. The pulp yield increased by 3% and 1.5% for the pulps of 22 and 16 kappa numbers, respectively. The biotreated pulp's strength properties were improved and were similar to those of E. globulus reference pulp. Copyright © 2006 Society of Chemical Industry     

Assessment of potential approaches to improve Eucalyptus globulus kraft pulping yield

The main goal of this work is to study the potential approaches to improve polysaccharides retention during Eucalyptus globulus kraft pulping. The addition of anthraquinone to kraft pulping leads to the highest pulp yield while the addition of urea promotes lower depolymerization of polysaccharides (higher pulp viscosity), but does not have a significant effect on yield. The early interruption of kraft cooking followed by oxygen delignification is a reliable approach to increase pulp yield, particularly when pulping is interrupted at the end of the faster and more selective kinetic regime (bulk phase). Yield loss during oxygen delignification is considerably lower than that incurred in the last phase of kraft pulping. Pulping with OH^?/HS^? charge profiling, carried out with liquor injection in three different phases leads to a yield increase. However, this increase results from a lower total alkali charge applied when profiling pulping is compared to standard pulping conditions, rather than to alkali profiling. Standard kraft pulping with different active alkali (AA) charges demonstrated that this operational variable is determinant for pulp yield and viscosity. Pulping experiences with lower AA (14%) resulted in a higher and almost constant pulp viscosity and in a higher pulp yield, assigned to improved retention of both cellulose and xylan. During the last stage of pulping, cellulose content decreases, this being mainly responsible for the decrease of pulp yield, while xylan content is almost constant, a feature attributed to the peculiar structure of this E. globulus's hemicellulose. Copyright © 2007 Society of Chemical Industry     

Delignification and Bleaching Response of Earlywood and Latewood

Abstract

The delignification response in cooking and the impact of bleaching on earlywood and latewood were studied. Spruce earlywood and latewood chips were pulped by the kraft process and subsequently treated with one bleaching chemical at a time. In cooking, latewood required a higher alkali charge to reach the same kappa number. No difference in the light absorption coefficient between the different fiber types was observed. After oxygen delignification the earlywood fibers had a higher light absorption coefficient at the same kappa number. The difference in light absorbing material was maintained when bleaching was performed with chlorine dioxide, ozone, and peracetic acid. Hydrogen peroxide decreased the light absorbing structures in the earlywood to the same level as for latewood. The earlywood pulp had a higher brightness at a given kappa number than the latewood. The higher brightness remained through all bleaching operations and was primarily due to a higher light scattering ability.     

Effect of Alkaline Hemicellulose Extraction on Kraft Pulp Fibers from Eucalyptus Grandis

Abstract

The alkaline extraction of hemicelluloses from hardwoods prior to pulping, for further conversion to value-added products, seems to be a promising pathway for paper mills to increase profit and improve sustainability. However, the amount of hemicellulose extracted will be limited by the requirement to maintain pulp quality and pulp yield in comparison to existing pulping processes. The effects of NaOH concentration, temperature, and time on hemicellulose extraction of Eucalyptus grandis were studied using a statistical experimental design. Extracted wood chips were subjected to kraft pulping to evaluate the effect of the extraction on cooking chemicals, pulp quality, and handsheet paper strengths. The selective xylan recovery (12.4% dry mass) from E. grandis combined with low-cooking, active alkali charge, and less cooking time advantaged the xylan extraction and subsequent modified kraft pulping process under the studied conditions. Pulp viscosity, breaking strength, and tensile index of handsheets were slightly improved.     

脱氢二香草醇的合成及LCC的形成机理(Ⅰ)

合成了一种缩合型木素模型化合物——脱氢二香草醇,并利用红外光谱、核磁共振谱(1H-NMR)对其进行了分析和确认。在此基础上,模拟硫酸盐法蒸煮过程,将合成的木素模型物和典型的半纤维素组成部分(木聚糖)进行蒸煮,然后利用酸析沉淀木素、乙酸乙酯抽提的方法将蒸煮后的产物分级,并利用FT-IR、13C-NMR对分级后的各个部分进行分析,探讨传统硫酸盐法制浆过程中木素-碳水化合物复合体(LCC)的形成机理。研究发现脱氢二香草醇在硫酸盐法蒸煮过程中非常稳定,残留的脱氢二香草醇以及新形成的LCC主要存在于酸不溶物、乙酸乙酯抽提物中,大部分未降解的木聚糖存在于酸不溶物中,碱不溶物和酸可溶物内都不存在新形成的LCC结构。     

Delignification of Pinus taeda wood chips treated with Ceriporiopsis subvermispora for preparing high‐yield kraft pulps

Pinus taeda wood chips were treated with the white‐rot fungus Ceriporiopsis subvermispora in 20‐dm³ bioreactors for periods varying from 15 to 90 days. Decayed samples, non‐inoculated controls and extractive‐free wood samples were submitted to kraft pulping using 25% of sulfidity and different active alkali concentrations in the cooking liquor. Cooking reactions were carried out isothermally at 170 °C. Residual lignin contents of pulps prepared from biotreated wood chips were lower than those observed in pulps from the undecayed control. Delignification kinetic studies showed that the initial delignification phase was accelerated and shortened by the fungal pretreatment. At a cooking time fixed before the end of the bulk delignification phase, the fungal pretreatment provided pulps with significantly lower kappa numbers or pulps with a fixed kappa number were obtained by reducing the amount of active alkali added to the liquor. Pulps of kappa 80 were obtained both from the undecayed control cooked with 20.8% of active alkali and from the 15‐day‐biotreated sample cooked with only 15% of active alkali. The biopulping benefits were neither proportional to the extent of the biodelignification nor to the biological removal of some specific wood component. DFRC‐determination (derivatization followed by reductive cleavage) of the amount of aryl–ether linkages in residual lignins of biotreated samples indicated an extensive depolymerization during the initial stages of biodegradation, which suggested that bio‐depolymerized lignin was easily released during the first stages of cooking, resulting in a faster and shorter initial delignification phase. © 2002 Society of Chemical Industry     

Laser-Induced Fluoresence of Lignins with Excitation from 457 to 621 Nanometers

Laser-induced fluorescence has been used to examine changes in lignin and black liquor during the course of kraft pulping. When excited with a laser at 457 and 488 nm, lignin samples isolated during the course of pulping, purified, and redissolved in alkali exhibited increasing fluorescent emission intensity. This may be explained by changes in lignin structure during pulping. At higher excitation wavelengths, differences between samples diminished. Black liquors showed decreasing fluorescent intensity with increasing pulping. We attribute this behavior to the increase in optical density of the liquors as cooking time proceeds. The optical density increases with cooking time proceeds. The optical density increases with cooking time because greater amounts of lignin and other materials dissolve from the wood and enter the black liquor.     

Impact of effective alkali and sulfide profiling on Eucalyptus globulus kraft pulping. Selectivity of the impregnation phase and its effect on final pulping results

BACKGROUND: Eucalyptus globulus is an important wood source for paper production and, in the last few years, great efforts have been made to assess its chemical specificities and improve the kraft pulping efficiency. Despite the existence of several works concerning mostly the kinetics of E. globulus kraft pulping there is a lack of systematic studies on the initial phase of pulping as well as on the impact of effective alkali (EA) charge profiling on the kraft pulping performance of this species. The aim of the present work is to assess the effect of initial effective alkali and sulfide charges on the lignin and carbohydrates removal on the impregnation phase and to investigate the effect of EA splitting charge on the whole E. globulus pulping process efficiency. RESULTS: When the EA charge at impregnation phase increases, the amount of dissolved wood increases until it reaches a constant value of about 20%. Maximum polysaccharide removal at impregnation phase was about 10% of total wood weight. Glucose removal during impregnation was attributed to the degradation and/or dissolution of E. globulus glucans. For EA charges at impregnation phase higher than ～15%, xylan retention on wood was roughly constant. Despite the differences found at impregnation phase on the amount of dissolved wood and lignin removal, it was demonstrated that these differences are almost completely attenuated until the end of the kraft pulping process. CONCLUSION: In the case of E. globulus, for a constant effective alkali charge, alkali profiling does not affect the whole kraft pulping performance. Copyright © 2007 Society of Chemical Industry     

PEG-BASED AQUEOUS BIPHASIC SYSTEMS AS IMPROVEMENT FOR KRAFT HARDWOOD PULPING PROCESS

Aqueous biphasic systems (ABS) represent wholly aqueous systems that are safe, nontoxic, nonflammable, and relatively environmentally benign as extraction media. We have studied detailed phase diagrams and partitioning data currently used in wholly aqueous solvent extraction or reactive extraction processes that may be applicable to the delignification of cellulosic materials at elevated temperature. The study results indicate that increasing the concentration of salt improves the degree of phase divergence. The partitioning results of different lignin species in PEG/salt ABS show that lignin prefers the polymer-rich phase of ABS. Four complete time-at-temperature (130-160°C) batch-cooking experiments were made using a Kraft pulping solution with and without PEG. The results for wood chips composed of a mixture of southern hardwood indicate that the use of PEG results in a pulp with lower Kappa number, lower lignin content, higher residual pulp yield, and reduced alkali consumption.     

稻草碱性亚硫酸钾清洁制浆工艺研究

研究了稻草碱性K₂SO₃-AQ体系蒸煮优化工艺,结果表明最佳蒸煮条件为:10% 总碱量,0.8的碱比, 0.2% AQ,最高温度 160℃ 和保温时间 120 min。所制得纸浆的卡伯值14.5,粗浆得率 53.8%,细浆得率 42.5%,本体系较传统钠基盐蒸煮的优势是其经济的回收系统,一种新型的生态循环将在农作物和造纸厂之间形成。     

Removal of residual lignin of ethanol‐based organosolv pulp by an alkali extraction process

Organosolv pulps usually have high kappa number. This research investigated an alkaline extraction method prior to bleaching for reducing the kappa number of organosolv pulp. Ethanol wheat straw pulp with a kappa number of 58.2 was extracted with 1% NaOH solution. The results show that the ethanol pulp has a large amount of lignin particles on the fiber surface. After 1 min alkali extraction, the kappa number of the ethanol pulp is reduced by 60%, to 22.2, and both the number and the size of the lignin particles on the fiber surface are significantly reduced. In comparison with a further ethanol washing/extraction, the alkali extraction is much more effective in terms of lignin removal. X‐ray photoelectron spectroscopy results show that a thin layer of lignin remained on the fiber surface after alkli extraction, but this did not reduce the internal bond strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Ethanol-water pulping: Cooking variables optimization

The ethanol-based pulping of Eucalyptus globulus by the ALCELL® process was studied to determine the optimum cooking conditions. In the first set of experiments the influence of chip size, chip impregnation, liquor-to-wood ratio and cooking additives was studied. Once the more convenient values for these variables were established according to kappa number, yield and viscosity, a surface response method was used to determine the influence of cooking temperature, cooking time and ethanol concentration on autocatalyzed pulping process. The developed models indicate that a high screened pulp yield (56%) and acceptable kappa number (23) and viscosity (1030 mL/g) can be obtained when cooking conditions are around 185°C, 110 min and 50% of ethanol.     

不同预处理对剑麻纤维组分和结构的影响

采用机械破碎、酸法蒸煮、氢氧化钠溶液碱法蒸煮、氨水处理和蒸汽爆破等五种不同物理和化学方法对剑麻纤维进行处理。通过化学分析、扫描电镜(SEM)及红外光谱(IR)等手段表征了处理前后剑麻纤维组分和结构的变化。结果表明,不同预处理方法均使剑麻纤维组分分离,杂质含量降低,纤维素含量提高。其表面形态和聚集态结构根据不同的处理方法而发生不同变化。在五种方法中以碱煮和蒸汽爆破处理效果较佳。     

CHEMICAL AND SODA PULPING PROPERTIES OF KENAF AS A FUNCTION OF GROWTH

Kenaf (Hibiscus canabinus)is a promising non-wood source of fibre for pulping and papermaking. Because the chemical and physical composition of the plant changes as the plant develops, research is needed to determine its pulping properties at various stages of growth in order to establish the optimum harvesting time. In the present work, the chemical composition and pulping properties of kenaf as a function of growth have been studied. Kenaf plants were harvested at the end of 90, 120, 150, and 200 days (maturity). Extractive-free ground samples of the stem were cooked at three different temperatures, 140, 155, and 170°C, using soda cooking liquor of 32 g/L NaOH, with an active alkali charge of 15% as Na₂O, and a liquor-to-wood ratio of 6:1. The differences in the holocellulose and lignin content for 90, 120, and 150-day old kenaf were not significant, while 200-day-old kenaf was significantly different from others. Pulping of kenaf at various stages of growth indicated that soda pulping properties were not significant. In comparing the yields of kenaf pulps, it is observed that; over the whole range of cooking times and temperatures studied, the average yield for 150-day-old kenaf is highest at 60.4%. Kenaf can be harvested at the end of 150-day growth period, based on the results of chemical analyses to achieve higher yield, with lower lignin content.     

SO2-Ethanol-Water (SEW) Pulping: II. Kinetics for Spruce,Beech, and Wheat Straw

Abstract

SO₂-ethanol-water (SEW) delignification kinetics for spruce, beech, and wheat straw are presented. All these species produce pulps using SEW cooking liquor and follow first order delignification kinetics at similar bulk delignification rates. However, residual delignification is much slower for beech than for spruce.

The hemicelluloses retention (135°C) and cellulose degradation kinetics are also characterized for beech SEW pulping. Xylan and glucomannan are removed from the pulp following first-order kinetics with a higher rate constant for xylan. Cellulose is retained in the fibers until kappa number 9, after which it starts to dissolve in the liquor. The yield also drops significantly in the region of kappa numbers 9–7.

Cellulose degradation is followed by intrinsic viscosity measurements and is found to be zero order in cellulose. The rates are higher at 135 and 145°C for beech SEW pulping than for spruce.     

A new softening agent for melt spinning of softwood kraft lignin

Kraft lignin obtained from the pulping of wood is an interesting new precursor material for carbon fiber production because of its high carbon content and ready availability. However, continuous spinning of softwood kraft lignin (SKL) has been impossible because of its insufficient softening characteristics and neat hardwood kraft lignin (HKL) has required extensive pretreatments to enable fiber formation. Softwood kraft lignin permeate (SKLP) and hardwood kraft lignin permeate (HKLP), fractionated by membrane filtration, were continuously melt spun into fibers. To improve the spinnability of SKL and HKL, HKLP was added as a softening agent. SKL‐ and HKL‐based fibers were obtained by adding 3–98 wt % HKLP. A suitable temperature range for spinning was 20–85°C above the T_g of the lignin samples, and this range gave a flawless appearance according to the SEM analysis. Smooth, homogeneous fibers of SKLP, HKLP, and SKL with HKLP were successfully processed into solid carbon fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanistic Differences Between Kraft and Soda/AQ Pulping. Part 1: Results from Wood Chips and Pulps

Abstract

Soda pulping catalyzed by anthraquinone (AQ) or 2-methylanthraquinone (MAQ) can produce hardwood chemical pulps similar to kraft pulps in all respect but for bleachability. Results accumulated in our laboratory suggest that the residual lignin in pulps from anthraquinone catalyzed processes is less reactive toward bleaching chemicals than that in kraft pulps. Analyses of pulps by periodate and permanganate oxidations suggest that the residual lignin from the non-sulfur processes contained more condensed structures than kraft residual lignin. The low reactivity of these structures is believed to be responsible for the lower brightness of bleached soda-AQ (SAQ) pulps. Pulping and bleaching trials with hardwood chips demonstrated that shortening of the cooking time and/or increasing the alkalinity is one strategy for improving bleachability of SAQ pulps. When sugar maple (Acer saccharum) chips were SAQ cooked for 1.0 and 2.0 h at 165°C, the higher kappa number pulp produced after 1.0 h of cooking bleached to a significantly higher brightness with a small increase in the chlorine dioxide application.     

Methanol-based pulping of eucalyptus globulus

The autocatalyzed pulping of Eucalyptus globulus wood with methanol-water mixtures was studied. A surface response design was employed to develop mathematical models describing the pulp properties as a function of cooking time, cooking temperature and methanol concentration. The ranges studied for these variables were 40–120 min, 170-200°C and 30-70% (w/w), respectively. The pulp properties modeled were kappa number, total yield, screenings content, screened yield and viscosity. Under the optimum cooking conditions pulps with low kappa number and acceptable viscosity can be obtained with a high yield.