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1.
The purpose of this study was to investigate the behavior of lignin and carbohydrates in kraft pulps during sulfuric acid bleaching. Beech kraft pulp and red pine kraft pulp were bleached with dilute sulfuric acid at pH 1.3 with addition of sodium nitrate and sodium nitrite at 100°C for 1 h. The pulps were then extracted with aqueous sodium hydroxide solution at 70°C for 1 h. Lignin and carbohydrates in the acid effluents and the alkali effluents were analyzed. The carbohydrate compositions of unbleached and bleached kraft pulps were also determined. The residual lignin in kraft pulp was degraded to a molecular size similar to that of milled wood lignin during sulfuric acid bleaching without additives, and it was further degraded to a much smaller molecular size during sulfuric acid bleaching with additives. It was found that the amount of carbohydrate dissolved in the bleach effluents were only about 1 of the dry weight of the kraft pulp under these bleaching conditions. The carbohydrates dissolved during bleaching were mostly of hemicellulose origin.Part of this report was presented at the 8th International Symposium on Wood and Pulping Chemistry, Helsinki, July 1995  相似文献   

2.
To investigate the bleaching mechanism, a lignincarbohydrate complex (LCC) model compound, a vinyl ether-type lignin model dimer, and a hexeneuronic acid model compound were treated with dilute sulfuric acid of different pHs. Beech kraft pulp and red pine kraft pulp were also treated with dilute sulfuric acid and then extracted with aqueous alkali. The amount of hexeneuronic acid degradation products in acid effluents and lignin dissolved in alkali effluents were determined. It was found that the benzyl ether-type LCC bond and the vinyl ether bond in lignin were effectively cleaved under the pH where sulfuric acid bleaching of kraft pulp was effective. Hexeneuronic acid group was also effectively degraded during sulfuric acid bleaching. In beech kraft pulp bleaching, both lignin removal and hexeneuronic acid removal contributed to the kappa number reduction. In red pine bleaching, the contribution of hexeneuronic acid removal was negligible, and most of the kappa number reduction was achieved by the lignin removal.Part of this report was presented at the 9th International Symposium on Wood and Pulping Chemistry, Montreal, July 1997  相似文献   

3.
The progress of lignin oxidation during oxygenalkali bleaching of pulp was evaluated by the method based on the difference between permanganate consumption of original pulp and that of the mixture of pulp and effluent after oxygen-alkali bleaching. By low-consistency oxygen bleaching of softwood kraft pulp, the permanganate consumption decreased very little. When the kappa number of the pulp was halved (from 25.4 to 13.4), the decrease in permanganate consumption of 1 g pulp was only 1.22ml of 0.02mol/l potassium permanganate. This value was smaller than that obtained for the oxygen-alkali treatment of a corresponding amount of isolated residual lignin, 6.40ml. This was not due to the slow oxidation of lignin in pulp but to the formation of permanganate-consuming substances from carbohydrates. Those newly formed substances cannot be oxidized by oxygen-alkali treatment. Taking these facts into account, lignin originally present in pulp was found to be oxidized well. Reduction of carbonyl groups in carbohydrates prevented the formation of such substances.Part of this paper was presented at the 10th ISWPC, Yokohama, June 1999; and at the 43rd Lignin Symposium, Fuchu, October 1998  相似文献   

4.
对氧碱漂白过程中木质素氧化进行定量分析,分析方法是基于氧化前后高锰酸钾消耗量的变化。该方法对溶出残余木质素的氧化结果分析发现其呈明显3个阶段：第一段木质素氧化的当量电荷数约4～5／木质素单元;木质素总氧化电荷数大约为9／木质素单元。这些数据以及甲氧基的脱除（75％）均表明：木质素的氧化不仅发生在酚型木质素单元,同时也发生在非酚型结构单元上。只有第一阶段氧化反应是木质素与氧气直接反应,而在第二、三阶段主要是协同氧化作用,氧化反应过程中产生的活性氧基团扮演了一定角色。通过对低浓度针叶材硫酸盐浆的氧漂研究发现：当卡伯值下降一半（25．4至13．4）时平均每个木质素单元氧化3当量电子,氧漂后的纸浆中仍然有大量未被氧化的残余木质素。定量地证明了在氧漂过程中木质素氧化是脱木质素反应的实质。  相似文献   

5.
Unbleached and oxygen-bleached hardwood kraft pulp (UKP and OKP), respectively, were bleached with a culture filtrate containing manganese peroxidase (MnP) and lignin peroxidase (LiP) fromPhanerochaete chrysosporium Burds. The brightness increases of UKP upon biobleaching with the culture filtrate with and without MnSO4 were the same. The brightness increase of OKP with MnSO4 decreased to about half that seen without MnSO4. Changes in the brightness of UKP and OKP by treatment with the culture filtrate were determined. The brightness increased sharply by about eight points during the first 3h. The 3-h treatment was repeated seven times. The brightness increased linearly with the bleaching of UKP. On bleaching of OKP, the brightness increased slowly and stopped at about 78%.Part of this report was presented at the 62nd Pulp and Paper Research Conference of the Japan Tappi, Tokyo, June 1995  相似文献   

6.
Summary The methoxyl loss from softwood kraft pulp during chlorine dioxide treatment can be accounted for by methanol and the methoxyl content of dissolved organic material in the bleach filtrate. This was established by a methoxyl group mass balance made at different bleaching times. It was found that ClO2 rather than the in-situ generated hypochlorous acid is mainly responsible for the methanol formation. It was shown that fully methylated pulp is hardly demethylated by ClO2 under industrial ClO2 bleaching conditions when hypochlorous acid is effectively captured. Furthermore, the rates of formation of methanol and methoxyl group containing dissolved organic material are proportional to each other. The experimental evidence suggest that demethylation and delignification are closely related during ClO2 treatment of softwood kraft pulp.  相似文献   

7.
A new method is applied to evaluate the progress of the oxidation reaction of lignin during oxygen-alkali treatment. This method employs the difference in permanganate consumption of the sample before and after the oxygen-alkali treatment as an indication for the lignin oxidation. When kraft lignin and residual lignin isolated from unbleached softwood kraft pulp were subjected to oxygen-alkali treatment up to 6000min, the progress of the oxidation expressed by this method was separated into clearly distinguished three phases. During the first and second phases, the progress of oxidation was well correlated to the loss of methoxyl group and to the decrease in the yield of nitrobenzene oxidation products. The addition of Mn+ to the oxygen-alkali treatment depressed oxidation during the second phase partly and that during the third phase almost completely. Calculations based on the change in the permanganate consumption revealed that the oxidation during the first phase corresponded to 4.2 electrons abstracted from one lignin structural unit on average. The oxidation process by oxygen-alkali treatment was hypothetically attributed to the direct reaction between molecular oxygen and the phenolic unit of lignin, which mainly took place during the first phase, and to the autooxidation-type oxidation during the second and third phases.Part of this paper was presented at the 9th ISWPC, Montreal, June 1997; and at the 42nd Lignin Symposium, Sapporo, October 1997  相似文献   

8.
Chloroform formation, balance, and discharge were estimated in a kraft pulp mill that used an elemental chlorine-free (ECF) bleaching line with chlorine dioxide as well as an effluent treatment process. This was achieved by collecting and analyzing discharge water and air samples that contained measurable levels of chloroform. Chloroform formation in ECF bleaching of hardwood oxygen-delignified kraft pulp (LOKP) was estimated to be 2.07–5.34g/pulp air-dried ton (adt), and approximately 30% of the chloroform produced was discharged to bleaching effluents. Chloroform in the effluents was not decomposed by activated sludge, and more than 97% was emitted to the air by volatilization. It is suggested that chloroform formation in Japanese LOKP bleaching mills can be decreased to 16–42t/year with a production of 8 million adt pulp by introducing ECF bleaching into all mills. This is a considerable fall from the chloroform discharge from ECF and chlorine bleaching mills in Japan that was estimated to be approximately 1000t for the 1999 fiscal year.  相似文献   

9.
Microcrystalline cellulose with minimal surface charge was prepared from softwood kraft pulp via hydrolysis by 4N hydrochloric acid instead of sulfuric acid. To this material, sulfate ester groups as surface charge were introduced by treating with 55% (w/w) sulfuric acid. A treatment at 60°C for 2h gave nearly the same level of surface charge as that of the H2SO4 -hydrolyzed microcrystal. The number of sulfate groups were controlled by changing the H2SO4 treatment conditions. Although the microscopic size and shape of the microcrystalline particles were the same irrespective of the preparation method, the introduction of surface charge drastically reduced the viscosity and removed its time dependence. These changes in viscosity behavior are considered to result from charge-induced dispersion of loose aggregates existing in the initial charge-free microcrystals prepared by HCl hydrolysis.Part of this report was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998  相似文献   

10.
Summary Ozonation of kraft pulp and oxygen-delignified kraft pulp in acetic acid/water mixtures has been studied at different pulp consistencies with and without an inhibitor to obtain information about the limitations of the selectivity of the ozone treatment. The experiments have been performed according to a full factorial design and data have been analysed by stepwise regression analysis. The results show that a better delignification selectivity can be achieved when ozone is applied in acetic acid media instead of conventional aqueous media. By combining conventional oxygen delignification and ozonation in acetic acid, pulps with equal strength properties and better optical properties compared to those of conventional O(DC)E prebleached pulps can be obtained. This study has also revealed that the reagent is utilized far more efficiently in ozonation at high pulp consistency (35%) than in ozonation at low consistency (1%), and that a similar selectivity can be achieved in both types of ozonation by choosing appropriate conditions. The greater selectivity of ozonation in acetic acid than in water is interpreted in terms of different stabilities of the oxidant in these reaction media. The relation between the formation of hydroxyl radicals and the extent and selectivity of delignification during ozonation has been investigated. The final bleaching of pulps prebleached with ozone in acetic acid medium has been studied. Two final bleaching sequences are presented, by which pulps with ISO brightness levels of 79% and 90% can be produced.The authors are indebted to the Swedish National Board for Technical Development (Styrelsen för Teknisk Utveckling) for financial support for this work and to STORA Technology for pulp tests and analyses  相似文献   

11.
From among 419 wood-rotting fungi 10 were selected by the Poly R decolorization test, and their ability to bleach hardwood kraft pulp was assayed. Of the 10 selected, 6 fungi (i.e.,Phanerochaete crassa WD1694 and F150;Pleurotus pulmonarius PSC-H, PSC-M, and PSC-T;and Pleurotus species A119) showed much higher bleaching ability thanPhanerochaete chrysosponum BKMF1767 orTrametes versicolor WD1670, both of which are well-known high ligninolytic fungi.P. crassa WD1694 had the highest bleaching ability among the selected strains, and it increased the pulp brightness from 28 to 54, with a corresponding decrease in kappa number from 16 to 6 after 10 days of cultivation and alkali extraction. MnP was a predominant ligninolytic enzyme ofP. crassa WD1694 during the biobleaching.This research was presented in part at the 46th Annual Meeting of the Japan Wood Research Society, Kumamoto, April 1996  相似文献   

12.
Methanol liberation and methoxyl loss during chlorine bleaching of softwood kraft pulp were quantitatively investigated to estimate the degree of structural modification of lignin aromatics. An increase in the chlorine multiple led to enhanced methoxyl loss from lignin. Our result, using pH-adjusted chlorine water (pH 5.7), by which chlorination under oxidation-favorable conditions was achieved, strongly supported the importance of the oxidation reaction by chlorine during delignification and lignin degradation. It was also suggested that methanol can be produced not only via catalytic hydrolysis by chlorine but via oxidative cleavage of the ether bond as well. The infrared spectrum of chlorolignins suggested that chlorine oxidation can open aromatic rings to muconic acid derivatives without cleaving ether bonding of the methoxyl group. No straight relation between the methoxyl content and the kappa number of chlorinated pulps was shown. The methoxyl content of bleached kraft pulps subjected to successive chlorination and alkali extraction showed a good relation with the kappa number. This means that almost all the portions of the oxidatively modified lignin structure were successfully removed during these treatments, and the aromatic structures of residual lignin in chlorinated and alkali-extracted pulps were thought to remain intact.Part of this paper was presented at the 46th Annual Meeting of the Japan Wood Research Society, Kumamoto, April 1996; the 10th International Symposium on Wood and Pulping Chemistry, Yokohama, June 1999; and the 67th Pulp and Paper Research Conference, Tokyo, June 2000  相似文献   

13.
Due to the complexity of delignification, it is still not accurate enough to describe the whole chlorine dioxide delignification system with mechanistic models such as kinetic studies. The simple aim of predicting and optimizing the process requires the use of economical empirical models, few of which are in the literature. In this study, principal component analysis was used to classify various bleaching response variables, including end pH, kappa number, viscosity, and optical properties such as brightness, into different categories. Statistical methods, including factorial design, multiple regression, and response surface methodology, were then used successfully to screen the importance of bleaching factors and their interactions. Models to control, predicate, and optimize the bleaching responses were established. In most cases, the results of empirical modeling coincided well with those from conventional research methods, but the empirical methodology was more economic or less laborious. The empirical models are robust enough to predicate and optimize the bleaching responses to chlorine dioxide delignification of oxygen-delignified hardwood kraft pulp.  相似文献   

14.
In this investigation, the sorption of kraft lignin (KL) from spent liquors, membrane filtrated and model KL liquors on fully bleached softwood kraft pulp fibres, was studied. The time, temperature and alkalinity during the sorption experiments were chosen to reflect the conditions of black liquor impregnation of chips before the cooking operation. The amount of sorbed KL was estimated by brightness and kappa number measurements. A linear correlation between the k value and the kappa number was found. Among the parameters investigated, the concentration of metal non-process elements was found the most crucial for the sorption of KL on pulp fibres under black liquor impregnation. The influences of KL concentration, metal ion profile and KL molecular weight distribution on the KL sorption behaviour under black liquor impregnation are discussed.  相似文献   

15.
Kraft pulp bleaching effluent supplemented with glucose was decolorized by a newly isolated fungusGeotrichum candidum Dec 1 (Dec 1) that showed a wide decolorizing spectrum to synthetic dyes. When the glucose concentration in the effluent was 30 g/l, the color removal and the reduction of absorbable organic halogens were 78% and 43% after 7 days culture, respectively. The average molecular weight of colored substances measured by gel filtration chromatography was lowered to less than 3000 from 5600 after 7 days culture. As the contribution of extracellular enzymes such as peroxidase (DyP), manganese peroxidase, and laccase to the decolorization of the kraft pulp bleaching effluent was small, Dec 1 appears to have a different mechanism of decolorizing kraft pulp bleaching effluent when compared with enzymes used to decolorize synthetic dyes.  相似文献   

16.
Summary The prolysis of cellulose, hemicelluloses, lignin preparations, and wood was studied by differential calorimetric analysis (DCA) for the range of 25° to 800° C. The test samples included powdered and filter paper celluloses; hardwood xylan; softwood galactoglucomannans, compression wood galactan, and arabinogalactan; a synthetic (DHP), sulfuric acid, Björkman, Brownell, and cellulase lignins; and unextracted and extracted hardwoods and softwoods. Heats of reaction were determined from the DCA thermal transition areas. Distinct differences were found between the thermograms of each hemicellulose and lignin sample. Although wood species could not be separated thermally, hardwood and softwood thermograms differed because of the hemicellulose degradation pattern.Trade names and company names are included for the benefit of the reader and do not imply any endorsement or preferential treatment of the product by the U.S. Department of Agriculture.Formerly Research Technologist, Forest Products Laboratory, Forest Service, U.S. Department of Agriculture. The Laboratory is maintained at Madison, Wis. 53705, in cooperation with the University of Wisconsin. Present address: The Pennsylvania State University, University Park, Pennsylvania 16802.  相似文献   

17.
Change in the oxidation state of manganese atoms in unbleached hardwood kraft pulp (UKP) during the biological bleaching of UKP withPhanerochaete sordida YK-624 was determined by the electron spin resonance (ESR) method. The spectrum of Mn(II), which reveals hyperfine splitting, was not observed in the ESR analysis of UKP, but the spectrum for manganese dioxide was observed. After fungal treatment of UKP withP. sordida YK-624, the spectrum of Mn(II) was detected. The reduction of manganese dioxide was triggered by the increase in NADPH-dependent ferrireductase activity. It is concluded that the manganese dioxide dominant in UKP was reduced byP. sordida YK-624 to Mn(II), which stimulates the production and function of manganese peroxidase.  相似文献   

18.
竹子作为造纸原料的性能和潜力   总被引：22，自引：0，他引：22  
竹子的纤维形态及化学组成表现出较好的制浆性能。从制浆性能及纸浆强度来评价，竹子是较好的造纸原料，仅次于针叶木，接近于阔叶木。随着造纸工业的发展，采用连续蒸煮和以氧及过氧化氢等无污染漂白新方法、新技术代替传统的竹子间歇蒸煮及常规含氯漂白的制浆技术是现代竹浆厂的目标。以竹代木，以减轻造纸工业对木材原料需求的压力，适应生态环境保护的要求为竹浆造纸提供了一个广阔的发展良机。  相似文献   

19.
 The diffuse-reflectance laser-flash photolysis method together with ground state diffuse reflectance spectroscopy have been used to study the effect of pH and temperature of the hydrogen peroxide treatment on oxygen delignified softwood kraft pulp. Received 20 December 1999  相似文献   

20.
Lignin Characterization of Triploid Clones of Populus tomentosa Carr.   总被引：2，自引：0，他引：2  
In order to understand the structural characteristics of lignin in triploid clones ofPopulus tomentosa and its changes in the processes of pulping and bleaching, milled wood lignin （MWL）, lignin carbohydrate complex （LCC） and the residual lignin from kraft pulp （KP） and sulfite pulp （SP） were isolated and analyzed by Fourier transform infrared （FTIR） spectrum and ^13C nuclear magnetic resonance （NMR）. The most diagnostic peaks were assigned and the differences were discussed. The spectral patterns reveal that triploid P tomentosa shows the specific features of hardwood from temperate areas, but in the spectrum of FTIR, the strength ratio orAl270 cm^-1 to A1226 cm^-1 is 0.88, higher than the average of hardwood from temperate areas, which will make the lignin delignification more difficult during pulping and bleaching. The LCC from triploid P tomentosa is mainly composed of xyloglucan and glucuronic acid, and other glucides have much lower ratio. In LCC FTIR, there are three peaks at 1 427, 1 329 and 1 046 cm^-1, indicating that both semi-cellulose and cellulose could exist in LCC, and that there might be relationships between cellulose and lignin. Compared with the residual lignin from KP and SP, the condensed structure in KP is more than that in SP.  相似文献   

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