Soda Cooking Research Articles

Xylanase pretreatment leads to enhanced soda pulping of wheat straw

Wheat straw was treated with a crude enzyme containing mainly xylanase prior to soda cooking. The enzyme was prepared from the culture filtration of Aspergillus niger strain An-76. The suitable conditions of pretreatment were xylanase dosage of 4 IU/g (on oven dry wheat straw), 48°C, 6–8 h, and pH 5.0, pretreated wheat straw was thorough washed after pretreatment. Xylanase pretreatment can improve pulpability of wheat straw effectively, and produce the pulps with lower kappa number (about 2 units lower), lower rejects and similar yields of screened-pulps under identical pulping conditions. The residual active alkali consistency of black liquor was increased by xylanase pretreatment. The brightness of bleached pulps from the xylanase pretreated wheat straw was about 3%ISO higher than that of the controls using identical bleaching sequence and conditions. The pulps, including unbleached pulps and bleached pulps, from the xylanase pretreated wheat straw had a higher tear index, a lower tensile index, and a lower burst index as compared to the control. The changes in the chemical components of wheat straw, crystallizability degree of cellulose, fiber average length and fines contents in the pulps were investigated in order to interpret differences of pulping results from the xylanase pretreated wheat straw and the controls.

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.

Cleavage of syringylglycerol ß-syringyl ethers during soda cooking

The degradation of model compounds of the syringylglycerol β-syringyl ether type [2-(2,6-dimethoxyphenoxy)-1-(4-hydroxy-3,5-dimethoxyphenyl)-1, 3-propanediol and 2-(2,6-dimethoxy-4-methylphenoxy)-1 ...

Characteristics of Bagasse Ligninin Situand in Alkaline Delignification

The structural features of depithed bagasse lignin and its changes in soda cooking have been characterized in situ by the nitrobenzene oxidation, phenyl nucleus exchange and periodate oxidation methods. The bulk of bagasse lignin (∼ 75%) can be readily delignified in alkali below 100°C, and does not appear to be resulted from the cleavage of β-aryl ether structures. Concerning the reactivity of uncondensed structures, the p-hydroxyphenyl units were most labile to alkaline treatments, whereas the guaiacyl and syringyl units were removed nearly at the same rate. The residual lignin appears to be rather condensed and to contain an appreciable amount of guaiacyl diphenylmethane-like structures.

A 13C CP/MAS NMR evaluation of the structural changes in wheat straw subjected to different chemical and biological pulping conditions

Wheat straw pulps prepared by chemical (soda) and biological (enzymatic or fungal) treatments were analyzed by 13C CP/MAS NMR spectrometry under quantitative acquisition conditions. The most significant changes reflected in the spectra as a result of soda cooking correspond to: (i) decrease of methoxyl content of the residual lignin (56, 153, 147 and 135 ppm), and (ii) deacetylation of hemicellulose fractions and saponification of cinnamyl esters concomitant to the release of alkali-soluble fractions (21 and 172 ppm). Reaction time was the factor with the greatest bearing on the former process, whereas soda concentration and temperature play an additional role in the latter. The decrease of the methoxyl/aryl ratio both after chemical and biological pulping suggests preferential removal of S-type lignin units. The comparison between quality parameters of the pulps and the 13C NMR integration data suggests that the linkage breakdown between straw macromolecules has a greater influence on paperboard properties than the neat extent of the chemical and biological removal of lignin fractions.

Delignification Kinetics of Soda Pulping of Kenaf

ABTRACT Kenaf (Hibiscus Cannabihus) is an alternative, non wood fiber source for pulping and papennaking. Delignification kinetics of extractive free samples from three fractions of kenaf procured from Mississippi State University, U.S.A have been studied. The extractive free samples were cooked at three different temperatures: 140° C, 155° C, and 170° C with soda cooking liquor. The results indicate that the activation energies for the bark, core, and whole kenaf are 68 kJ/mole, 91 kJ/mole, and 75 kJ/mole respectively. These are significantly lower than the reported values for the conifers. The delignification selectivity for the three samples was also investigated.

ワラ類の化学パルプ化 （ＩＩ） 稲ワラ・ソーダ蒸解黒液リグニンから分散剤の調製

Soda lignin from rice straw was sulfomethylated, and the dispersion ability of sulfomethylated lignin was compared with that of commercial softwood lignosulfonate. The results are summarized as follows : (1) Black liquor from soda cooking of rice straw was adjusted to pH 8.2 with aq. sulfurous acid. Same mole of formaldehyde as sodium sulfite formed in black liquor was added, and then dissolved lignin was directly sulfomethylated (SML I). Sulfomethylated black liquor was separated by gel filtration method (SML II : 0.18 S/C6-C3).(2) SML I shows the similar standard dispersion number (SDN), regardless of max. temperature of soda cooking and reaction time of sulfomethylation.SDN of sulfomethylated liquor including SWL I, however, is inferior to that of lignosulfonate. This may be due to the low content of sulfonic acid group and low purity of SML I. In order to utilize straw soda lignin as dispersant, it is necessary to isolate soda lignin from black liquor and to sulfomethylate the isolated soda lignin.(3) The setting time of mortar with SML II show the relatively similar results to that of commercial lignosulfonate. SML I, however, requires a long period of the setting time. The utilization of SML I as the dispersant is impractical in mortar manufacture.(4) The dispersion effect with SML II was compared by the use of various types of additives. Among seventeen additives tested here, citric acid, gluconic acid, glucuronic acid and K, H-glucarate show the excellent SDN. Very high SDN shown by K, H-glucarate is worth noting.

アミン添加ソーダ蒸解の研究

アミン添加ソーダ蒸解の研究

Fast growing poplar and Miscanthus sinensis—future raw materials for pulping in Central Europe

To evaluate the pulping properties of Miscanthus sinensis, the neutral sulfite process with anthraquinone addition (NS/AQ) was applied and important pulping conditions were optimized. The results are compared with soda cooking references, as well as with data obtained in former investigations with fast growing poplar, which is a competing raw material, when an alternative utilization of farmland is proposed. The results confirm that Miscanthus sinensis is well suited for pulp production. Using moderate conditions in NS/AQ pulping, the raw material could be delignified to low residual lignin contents. In bleaching, high brightness can be achieved with three chlorine free stages. The fully bleached pulp yield is remarkably high. Compared to soda cooking the NS/AQ process gives much better results and the pulp quality is nearly as good as that of poplar pulps produced with the ASAM process.

Effect of temperature on the soda and kraft cooking of corn stalks

AbstractThis study included soda and kraft process of corn stalks at constant active alkali, the kraft liquor having 25% sulfidity. Five cookings were made at different temperatures, 80, 120, 140, 160, and 180°C, each for 1 h. Under the condition of the study the following temperature effects were noted: (1) Delignification could be approximated by a first‐order reaction. (2) The kraft process exhibited twice the rate of lignin removal as the soda of the same digestion temperature. (3) The rate of removal of carbohydrates in the kraft process is faster than soda process due to presence of sulfide ion. (4) The carbon content of thiolignin increased hydrogen and oxygen content decreased while in soda lignin the opposite occurs. (5) The amount of phenolic OH increased with increasing the cooking temperature and was more noticeable in thiolignins than in soda lignins. (6) Demethoxylation occurs in kraft cooking at elevated temperature rather than soda cooking.

クラフト蒸解に関する化学工学的基礎研究 ＩＩ クラフト蒸解反応における化学量論的解析

This report concerns the experimental results to clarify the stoichiometry between the consumption of alkali or sulfur, and the dissolution of wood components (carbohydrate, lignin, etc.) during alkali cooking of two wood species, Buna (Fagus crenata Blume) and Akamatsu (Pinus densi flora S. et Z.).From the results, the different manner of the carbohydrate dissolution was observed between kraft and soda cooking of Buna, but no difference in the case of Akamatsu. The most part of lignin in both woods was dissolved on the bulk delignification stage. NaOH was guantitatively consumed by dissolution of carbohydrate, but no Na2S was consumed by it. A small part of Na2S was consumed during the delignification reaction.

じん皮繊維原料のしゅう酸アンモニウム蒸解 ＩＩＩ コウゾ属じん皮の化学組成およびその蒸解

The bast fibers of paper mulberry (Kozo Broussonetia Kazinoki SIEB. and Kazinoki : B. papyritera VENT.) were subjected to the chemical analysis and pulping test by means of ammonium oxalate solution cooking comparing with those by the conventional caustic soda cooking. The extractive contents (water, 1 % NaOH and alcohol-benzene) in six varieties of bast fibers are generally higher than those in woody materials, as well as the content of ash (Table 1). The large quantities of pectin material are also characteristic of the bast fibers while very few content of lignin are observed.The ratio of pectin/lignin content reached at around 6.1 in average of six samples tested (Table 2). The pulping yields by ammonium oxalate cooking were always higher than those by caustic soda cooking at similar chemical concentration of cooking liquor (Fig. 1). The strengths of pulp obtained by ammonium oxalate cooking were also remarkably higher than those obtained by caustic soda cooking (Fig. 3 & 4). The results of cooking test on temperature in ammonium oxalate solution show that the highest strength of pulp is given at 85°C (Fig. 6 & 7). The relation between the pulping yield and the strength of pulp indicates the beneficial effect of ammonium oxalate as the pulping agent for paper mulberry bast fibers (Fig. 8).Thus, it is suggested that the removal of pectin material located mainly in interfiber zone of bast fibers is so effectively done by the ammonium oxalate solution under neutral or weak acidic condition (Fig. 1), that the defiberizing to individual fiber will be easily done with few damage of fiber structure.

Pretreatment of Birch With Nitric Oxide and Oxygen Before Soda Cooking

Abstract During treatment of birch meal with nitric oxide and oxygen methanol was produced at high rate even when only 2% of the added nitric oxide was present as nitrogen dioxide and nitric oxide. This confirms that nitrogen dioxide was regenerated in a reaction cycle. A high temperature and a large addition of nitric oxide favored the regeneration. Soda cooking of pretreated birch chips showed that an increased regeneration led to an improved delignification reflected in an enhanced yield and pulp viscosity provided that a severe depolymerization of the carbohydrates during the pretreatment was avoided.

Soda Cooking of Wood Meal Pretreated with Nitrogen Dioxide

Abstract An increasing dry content during NO2/O2 Pretreatment of wood meal led to an improved delignification during a subsequent soda cooking, both with and without addition of anthraquinone, and to an increased depolymerization of the carbohydrates during the pretreatment. The carbohydrates were stabilized towards alkaline peeling. The highest viscosity and yield compared at a given kappa number of the alkali-cooked pulp were obtained at an intermediate dry content. A pretreatment of birch meal gave rise to an enhanced yield compared at a given kappa number, while for aspen a loss was obtained. An alkaline extraction after the pretreatment led to a decreased yield of final pulp.

Quinones As Additives During Soda Cooking

Abstract Anthraquinone-1-acetic acid is a less effective delignification catalyst than anthraquinone but it gives an enhanced carbohydrate stabilization by converting reducing sugar end groups more effectively to aldonic acid end groups. This reaction produces the hydroquinone form of the additive which is then easily oxidized by oxygen at 80°C. Oxygen treatment favors the end group stabilization. Depolymerization of the cellulose is suppressed by the presence of magnesium hydroxide but cannot be avoided completely.

アルカリメタノール蒸解 ＩＶ リグニンおよび炭水化物の挙動に関するモデル実験

In the earlier report13, 6) of this series, it was shown that pulp yield by alkali-methanol cooking is 25% higher than that by kraft cooking and both pulps are similar in sheet strength. It was also elucidated that the rapid delignification during alkali-methanol cooking is due to the prevention of condensation through methylation of active benzylalcohol groups in lignin molecule. Recovery of methanol in spent liquor was also discussed2) .The present paper is concerned with the behaviors of lignin and carbohydrate during alkalimethanol cooking. Model experiments were carried out by the use of guaiacylglycerol-β-guaiacyl ether as a lignin model substance, and by the use of hydrocellulose and cellobiose as carbohydrate model substances. Each model substance was cooked in alkali-methanol [(40 g NaOH+400 g MeOH) /l ] and soda [40 g NaOH/l] cooking liquors under various cooking conditions. Results obtained are as follows : a) The yield of guaiacyl produced by the clavage of β-ether linkage of guaiacylglycerol β-guaiacyl ether was lower in alkali-methanol cooking than in soda cooking (Table 1). It is noteworthy that the kraft-like rapid delignification can be attained in alkali methanol cooking, although the rate of, β-ether cleavage is slower than soda cooking.b) Guaiacylglycerol-β-guaiacyl ether was methylated at the α-position of side chain. A methylated compound was isolated and identified by mass spectrum and 13C-NMR of it (Fig. 13). The mechanism of methylation was discussed by the analysis of 13C-NMR and assumed to follow the SN 2 (Fig. 4).c) Residual hydrocellulose after alkali-methanol cooking was 12% higher than soda cooking (Table 2). Corresponding to this result, the yield of gluco-isosaccharinic acid produced by peeling-off reaction was lower in alkali-methanol cooking than in soda cooking.d) Residual cellobiose depends on the concentration of methanol in alkali-methanol cooking liquor (Fig. 5). It was shown that the higher the concentration of methanol, the more the residual cellobiose.e) It can be concluded from the above-mentioned results that the peeling-off reaction was suppressed in alkali-methanol cooking. This may suggest that the isomerization rate of a glucose end group to a fructose end group is slower in alkali-methanol cooking liquor than in soda cooking liquor.

アルカリ蒸解におけるキノンの反応機構 脱リグニンの促進および炭水化物の安定化

The reaction mechanism of 1, 4, 11, 12-tetrahydroanthraquinone (THAQ) in alkaline cooking has been studied. The results are summarized as follows : (1) The addition of 0.05% THAQ per o. d. wood powder to soda or kraft cooking liquor accelerates the delignification remarkably and increases pulp yield by 2.03.5%. THAQ has such a catalytic effect more remarkably on soda cooking than on kraft cooking.(2) THAQ shows the same level of delignification with and without oxygen in the cooking system.(3) Decrease of DPv of cellulose during cooking is suppressed by the presence of THAQ. THAQ reduces the formation of isosaccharinic acid which comes from reducing end groups of carbohydrates in alkaline cooking. These results shows that THAQ suppresses the peeling reaction by oxidizing the reducing end units of carbohydrates to aldonic acid type units.(4) It is thought that THAQ is reduced mainly by carbohydrate and the reduced one is oxidized mainly by lignin.

アルカリ・メタノール蒸解の経済的評価

Alkali-methanol cooking of mixed hardwood chip has been studied and the results were compared with kraft cooking. A recovery process of methanol which was similar to that of conventional kraft cooking was designed, and the economic evaluation was made. The results are summarized as follows.1) Within the present study, the most adequate condition of cooking was found to be at wood-to-liquor ratio of 1/4, methanol concentration of 40% w/v and active alkali of 16% as Na2O.2) Screened pulp yield by alkali-methanol cooking was about 2% higher than that by kraft cooking in the range of kappa number of 2025.3) The delignification rate of alkali-methanol cooking was slightly slower than that of kraft cooking, but faster than that of soda cooking.4) The strength properties of alkali-methanol pulps were nearly same as kraft pulp, except that the tear factor and elongation were slightly less than that of kraft pulp. The beating of the former was easier than that of the latter. The bleaching property of alkali-methanol pulp was not studied.5) The pulp price of alkali-methanol cooking is 2.5, 6.4 yen/kg a. d. pulp higher than that of kraft cooking. The increase of pulp price is mainly due to the steam cost for methanol recovery. In addition to the high cost of methanol recovery, a closed equipment, prevention of explosion and safety counterplot for operator must be sufficiently achieved to carry out alkali-methanol cooking and recovery.Therefore, the alkali-methanol cooking would not be economically feasible compared with kraft cooking at the present time or even in near future.

アルカリ・メタノール蒸解 ＩＩＩ 蒸解過程におけるリグニンの挙動

The behavior of lignin during alkali-methanol cooking has been studied using the lignin model compounds, vanillylalcohol and veratrylalcohol. The amounts of functional groups and molecular weight distributions of isolated alkali-methanol and soda lignins have been measured.Vanillylalcohol was methylated to vanillylmethylether by treating with alkali-methanol, while vanillylalcohol gave the condensation products with soda cooking liquor. These facts indicate that the mehylation of vanillylalcohol prevents the condensation of it. Vaeratrylmethylether was only slightly produced from veratrylalcohol by alkali-methanol treatment.Comparing the functional groups of both isolated lignins, there are higher amounts of methoxyl groups in alkali-methanol lignin and of phenolic hydroxyl groups in soda lignin. Gel filtration curves of both isolated lignins have revealed that there are less high molecular weight fractions in alkali-methanol lignin than in soda lignin under the same cooking conditions.Summarizing the results mentioned above, it can be concluded that the rapid delignification during alkali-methanol cooking is due to the prevention of condensation through the methylation of active benzylalcohol groups in lignin molecule.

On the Sulfur-Soda Cooking

In some small soda pulp plants which have no equipments to recover sodium hydroxide from the waste liquor, sodium sulfide is added to the soda cooking liquor to speed up the pulping reaction and to obtain a product of improved strength properties. We studied on using of powdered sulfur instead of sodium sulfide in such small plants in order to decrease the cost for pulping chemicals.Wood chips fo P. densifiora were cooked with the sulfur-soda cooking liquors which were prepared by dissolving various amounts of powdered sulfur to the sodium hydroxide solutions, and the pulp yield, the lignin content of pulp, and the strengths of pulp were determined. In the case of using the cooking liquor containing sulfur of about 12% on the weight of sodium hydroxide, the pulping reaction proceeded most rapidly and the pulp obtained was as strong as sulfate pulp.Wood chips were precooked with a solution of lime and sulfur at 100°C, and then cooked with a soda cooking liquor. By this method, the delignification reaction proceeded more easily.