CS260307B1 - A method of delignifying lignocellulosic materials in a kraft cooking process - Google Patents

Abstract

The purpose of the method of delignification of lignocellulosic materials in the kraft pulping process is to increase the pulp yield. The stated purpose is achieved by adding 1 to 3 wt. %, based on the lignocellulosic material, of oxidized lignin to the pulping solution. The method of delignification of lignocellulosic materials in the kraft pulping process is used in the pulp and paper industry.

Description

The present invention relates to a process for delignifying lignocellulosic materials in the process of kraft cooking.

The sulphate brewing process is the most commonly used technological process for preparing chemical pulps. The alkaline environment at the last stage of the preparation increases the strength properties of the pulp, but at the same time, which is disadvantageous, reduces its yields. To stabilize polysaccharides. in a kraft batch, anthraquinone or derivatives thereof are currently added to the boiling solution, which stabilizes the polysaccharides and at the same time speeds up the delignirination. When 1 kg per tonne of wood is applied, the yield is increased by approximately 1 to 2% by weight. %. The disadvantage of using anthraquinone and its derivatives as stabilizer and polysaccharides is their high cost, deficiency and regeneration problems. Approximately the same increase in pulp yield by 1 to 2 wt. % Can be achieved by using a 30 wt. % sulphide, which does not affect delignification, but oxidizes the polysaccharide end groups, making it necessary to use a higher alkali content than the normal sulphate batch [I. Palenius, O. Pekkala: Zellstoff and Paper 5, 184 (1984); McJonough, T.J., Van Drumen, JJ: Tappi 63, 83 (1980)].

The essence of the delignification of lignocellulosic materials consists in adding 1 to 3 wt. %, Based on the lignocellulosic material, of oxidized lignin.

The advantage of the proposed process is that the addition of oxidized lignin preparations increases the yield by 1 to 3 wt. % at the same lignin content. The oxidized lignin preparations used can be prepared from readily available waste products in the pulp and paper industry to produce kraft pulp. Technological preparation of oxidized lignin preparations as additive compounds is simple, undemanding for chemicals and equipment. The oxidized lignin preparation increases the calorific value of the extract.

The oxidized lignin used in Examples 3 to 6 is prepared in a manner known per se (P.T. Perumal, V. V. Blíatt: Tetrah. Lett. 33, 3099 (1979)):

Example 1

To the dried and ground industrial waste condensate resulting from beech wood prehydrolysis in the process of kraft pulp production (10 g, composition: 98 wt% dry matter; 12.52 wt% methoxy groups; 56.98 wt% carbon; 5.38 wt% 100 ml of 30 vol% sulfuric acid is added. While stirring, 100 ml of 30 wt. % hydrogen peroxide and the temperature was maintained below 50 ° C. It is then filtered on a glass frit and washed with distilled water to pH 7 and dried at 105 ° C. The yield was 6.5 g of oxidized lignin, composition: 51.79 wt. % carbon ·; 4.45 ^: wt. percent hydrogen; 8.90 wt. % of methoxy groups. Content quinone structures from infrared spectra expressed as the ratio of absorbance at 1,660 cm ^-1 and 1,720 cm ^-1 to absorbaincii at 1515 cm ^_1 1.20 and 1.64 [HL Hergert: Infrared Spectra of Κ. V. Sarkanen, CH Ludwig: Lignims, Occurence, Formation, Structure and Reaction, Ed. Wiley-Interscience, New York-London-Toronto 267 (1972)].

Example 2

The procedure is as in Example 1 except that dried industrial waste lignin is used (composition: 97% by weight of dry matter; 10.40% by weight of methoxy groups; 58.57% by weight of carbon; 4.76 and that, when hydrogen peroxide is added, the temperature of the reaction mixture is maintained at 80 ° C. The yield of oxidized lignin is 8.1 g, composition: 53.09 wt. % carbon; 411 wt. % hydrogen; 5.95 wt. % of the methoxy groups, the absorbance ratio at 1660 cm ⁴ and 1720 cm ^-1 to 1515 cm ^-1 is 1.20 and 1.49, respectively.

Example 3

Beech labels (100 gj) are heated in a 750 ml autoclave with 450 ml of boiling solution at a maximum temperature of 170 ° C for 15 minutes with 16 wt% active alkali and 25 wt% sulphide added. The pulp is obtained in a yield of 56.3% with a lignin content of 4.1% by weight.

Example 4

The procedure is as in Example 3 except that the beech chips are heated for 30 minutes in the presence of 3 wt. % oxidized condensate. The pulp is obtained in a yield of 55.5 wt. % with a lignin content of 2.9 wt. %.

Example 5

The procedure was as in Example 3 except that the beech stick was heated for 90 minutes in the presence of 1 wt. % oxidized sulfate lignin. The pulp was obtained in a yield of 52.3 wt. % with a lignin content of 2.1 wt. %.

Example 6

The procedure is as in Example 3 except that the spruce chips are heated for 120 minutes in the presence of 3 wt. % oxidized condensate. The pulp is obtained in a yield of 60.2% by weight, with a lignin content of 5.4% by weight. ° / o.

To compare the catalytic effect of a lignin preparation containing quinone structures with the hitherto used sulphate delignification of lignocellulosic materials, the following examples are given: Example 7

Beech chips (100 g) are heated in a 750 ml autoclave with 400 ml of boiling solution at a maximum temperature of 170 ° C for 15 minutes with the addition of 16 wt. percent and a sulfidity of 25 wt. %. The pulp is obtained in a yield of 53.8 wt. % with a lignin content of 3.5 wt. %.

Example 8

The procedure is as in Example 7 except that the beech chips are heated for 30 minutes. The pulp was obtained in a yield of 52.5 wt. % with a lignin content of 2.7 wt. percent.

Example 9

The procedure is as in Example 7 except that the beech chips are heated for 90 minutes. The pulp was obtained in a yield of 50.4 wt. % With a lignin content of 2.1 wt. percent.

Example 10

The procedure is as in Example 7 except that the spruce chips are heated for 120 minutes. The pulp was obtained in a yield of 49.0 wt. % with a lignin content of 5.3 wt. ° / o.

The invention may find use in the pulp and paper industry in pulp production.

Claims (1)

SUBJECT Process for delignification of lignocellulosic materials in the process of sulphate cooking, characterized in that 1 to 3 wt. %, based on the lignocellulosic material, of oxidized lignin.