CS222679B2 - Method of batching lignocellulosic materials - Google Patents

Abstract

A method for brewing lignocellulosic materials, in which the lignocellulosic material is boiled in a mixture of water and 1 to 4 volumes of an aliphatic alcohol with a maximum of 3 carbon atoms per 1 volume of water containing a metal salt and optionally a small amount of an acidic reacting substance at a temperature of 130 to 210 °C for a maximum of two hours, using 4 parts by weight of cooking liquor per one part by weight of lignocellulosic material, the loosened cellulose fibers are then separated from the binding liquor, the alcohol is evaporated from the cooking liquor and lignin and sugars are separated from the remaining cooking liquor, which is characterized in that the aqueous alcohol solution contains 0.001 to 1.0 moles of magnesium, calcium or barium chloride or nitrate or magnesium sulfate or a mixture thereof and a strong mineral acid in a 0.000 5 to 0.008 normal concentration.

Description

The invention relates to a method of batching lignocellulosic materials.

The subject of the invention is a method for brewing lignocellulosic materials, in which the lignocellulosic material is boiled in a mixture of water and 1 to 4 volumes of an aliphatic alcohol with a maximum of 3 carbon atoms per 1 volume of water containing a metal salt and optionally a small amount of an acidic reacting substance at a temperature of 130 to 210 °C for a maximum of two hours, using 4 parts by weight of cooking liquor per one part by weight of lignocellulosic material, the loosened cellulose fiber is then separated from the cooking liquor, the alcohol is evaporated from the cooking liquor and lignin and sugars are separated from the remaining cooking liquor, which is characterized in that the aqueous solution of alcohol used as cooking liquor contains 0.001 to 1.0 moles of magnesium, calcium or barium chloride or nitrate or magnesium sulfate or mixtures thereof and a strong mineral acid in 0.000 5 to 0.008 normal concentration.

The process is particularly suitable for the production of pulp with a low Kappa or Roe number, with high fiber strength and with cellulose in an almost native, undegraded state. It is significant that the process according to the invention is equally suitable for gymnosperm and angiosperm wood, as well as for lignocellulosic agricultural wastes when carefully cooked under the above conditions.

With the current shortage of energy and chemicals, the emphasis is on batch efficiency and perfect recovery of chemicals. New batching methods should be efficient with regard to lignin removal, so that the batch can be shortened, while the batch should be mild enough to achieve near-theoretical fiber yield and quantitative recovery of dissolved by-products. Delignification must be as perfect as possible to prevent low fiber bond strengths and to reduce the amount of bleaching chemicals needed in cases where fully white paper is to be produced. A good batch also requires as perfect a disintegration of the fibers as possible. Delignification must therefore affect both the cementing layers of the fibers - the middle lamellae - consisting of a lignin-carbohydrate matrix, and the cell walls of the matrix containing lignin and hemicellulose in varying proportions.

Such efficient delignification results in a low screen retention and the cooking chips require little, if any, mechanical agitation for full disintegration, thereby saving operating energy as well as fiber length.

-· In the hydrolysis processes of wood in aqueous mixtures or in aqueous-organic solvent mixtures containing unbuffered or unmoderated acid catalysts at temperatures of 165 to 210 °C, cellulose is attacked so rapidly that significant degradation of cellulose occurs before the lignin and hemicellulose components of the cell walls are dissolved. Even when relatively weak acids such as dicarboxylic organic acids are used as catalysts, the disintegrated fibers have a lower degree of polymerization of cellulose than in the native state, so that paper sheets made from these pulps have insufficient tear strength, compression strength and have insufficient breaking length for industrial purposes.

The advantages of the well-known processes include very short batch times and high yields of soluble lignin and dissolved sugars, but the requirement for the known processes remains to break down the cellulose fibers while retaining almost all of the polyglucan fraction while maintaining the strength of the native cellulose fibers at an acceptably low lignin content in the pulp.

The invention also relates to a method for producing high-yield pulp with low residual lignin content to improve fiber bonding and arrangement in the paper sheet and to reduce the consumption of bleaching chemicals in the production of fully bleached papers.

It is further desirable to prevent damage to cellulose by the water-miscible organic solvents used in the process of the invention, which are effective in delignification and do not attack carbohydrates.

Another significant improvement of the process according to the invention results from the choice of an inexpensive mild catalyst, which is a salt having the unique property of forming slightly acidic solutions in aqueous alcohols, contributing to the release of acidic protons into the system by cation exchange with the functional groups of lignin and carbohydrates and protecting the cellulose from attack by acidic protons at high temperatures. The substantially reduced acidity further eliminates the need to use highly acid-resistant digesters.

The invention also relates to a method of producing pulp which substantially does not pollute water or air.

One known method, which also does not pollute the environment, is the Kleinert batch process. It is described, for example, in US Patent Nos. 1,856,567 and 3,585,04 and in German Patent Application DAS No. 2,644,55. The only chemicals used in this method are alcohol, which can be regenerated and recycled, and small amounts of acidic or basic substances. However, its disadvantage is that the pH of the cooking liquor must be adjusted to at least 8, so that the pH of the waste liquor is 4 to 7, in order to prevent the cellulose obtained from being damaged by organic acids released from the lignocellulosic material during the batch. However, at these pH values, delignification proceeds relatively slowly. In addition, the rapid evaporation of alcohol from the spent cooking liquor leads to the separation of dissolved lignin in the form of a non-aqueous, dark brown, as if molten, highly plastic mass, which is not easily removed from the digester and which has no industrial use.

In contrast, the method of delignification or batching of cellulosic material according to the invention with the addition of at least one soluble alkaline earth metal salt is substantially shortened and the rapid evaporation of alcohol from the spent cooking liquor leads to the precipitation of dissolved lignin in powder form; the lignin is then easily separated by filtration or centrifugation and can be used, optionally after recrystallization, as a fuel or as a starting material for, for example, the production of vanillin and other products.

Rapid evaporation recovers the majority of the used alcohol from the cooking waste liquor and this alcohol can then be recycled. Since the waste liquor is withdrawn from the high temperature digester, little energy is required for this evaporation.

The method according to the invention therefore eliminates the shortcomings of the Kleinert method and other similar methods, described for example in US Patent Nos. 3,585,184 and 4,100,016, by treating lignocellulosic materials with a solvent mixture in an amount of at least four times the weight of the material to be spun, the solvent being methanol, ethanol or n-propanol or a mixture thereof in an amount of 20 to 80% to 80 to 20% water, the mixture of alcohol and water containing 0.005 to 1.0 moles of a metal salt soluble in water and alcohol, selected from the group comprising chlorides, sulfates or nitrates of magnesium, calcium or barium or mixtures thereof, and the treatment is carried out at a temperature of .30 to 210 °C, preferably .70 to 200 °C and especially at a temperature of .95 to 800 °C for a period of generally 15 to 90 minutes.

In the case of lignocellulosic materials which are difficult to delignify and in the case of the use of salts which have a low catalytic effect, such as magnesium sulphate, the degree of delignification is considerably improved without appreciably affecting the polydispersity of the cellulose by the addition of a small amount of strong acid, preferably with an anion corresponding to the salt used, until a 0.005 to 0.008 N solution is obtained containing, in addition to the salt, a strong acid as a catalyst. Such a process is then highly specific with regard to delignification and ^cellulose fibres with a high degree of polymerization and a high glucan content are obtained.

The method according to the invention is particularly effective if magnesium or calcium chloride or nitrate is used as the salt in a molar concentration of 0.02 to 0.05 and a volume ratio of water to methanol in the solvent mixture of 30 to 70, with the batch being carried out at a temperature of 190 to 200°C.

When softwood, such as spruce, is cooked by the method of the invention, a pulp is obtained which retains a significant amount of hemicelluloses but has a low residual lignin content and a higher degree of polymerization than most pulps obtainable by the kraft cooking process; the cooking time need only be 30 to 45 minutes to obtain a pulp with a Kappa number of 33, a TAPPI viscosity of 0.5 g 20 m Pa.s, or a degree of polymerization of 1,320. The cooked chips are separated into individual fibers by simply suspending them in water and the resulting pulp is more easily bleached from its brightness of 50-25 GE to the desired brightness of 80% and possibly higher than spruce pulp obtained by the kraft cooking process, which has a comparable residual lignin content but a much lower initial brightness, typically 35% GE.

A further disadvantage of current pulp production processes is that the by-products of the batch significantly interfere with the regeneration of the cooking chemicals, making this regeneration economically unattractive. In addition, in the kraft batch process, for example, dissolved sugars are largely converted to saccharic acid salts, which are of limited importance as industrial chemicals. Similarly, lignin is converted to sulfur derivatives in order to obtain the necessary degree of solubility for the production of low-lignin fibers, which means that the otherwise partially solvent-soluble lignin is converted to a form that can only be dispersed in alkalis. In contrast to these inconveniences in obtaining by-products from a lignocellulose batch, the process according to the invention obtains dissolved lignin and sugars, which are separated during the batch in the solvent by rapid evaporation, thereby obtaining relatively concentrated aqueous sugar solutions in which the otherwise solvent-soluble lignin is in the form of a powdery precipitate. The lignin is then separated from the sugars by centrifugation or simple filtration.

The sugar solution obtained is rich in xylan and other hemicelluloses and contains relatively little glucan. Most of the sugars are in the form of dimers and low molecular weight oligomers, which can be readily degraded to simple sugars by secondary hydrolysis in almost quantitative yield. The fact that the sugars are in the form of polymers of low molecular weight sugars protects them from dehydration during high temperature brewing and allows for the recovery of more soluble sugars.

The lignin precipitated after removal of the solvent retains its solubility in solvents, a highly desirable property for the further chemical processing contemplated. The molecular weight of such solvent-soluble lignin is determined by gel permeation chromatography and high-performance liquid chromatography and is 300 to 12,000, with an average calculated molecular weight of about 3,000.

The lignin thus obtained is easily purified by redissolving in acetone, filtering the acetone solution to remove undissolved matter, and repeatedly precipitating into water or a nonpolar solvent such as diethyl ether, benzene, and n-hexane. Other solvents such as dichloromethane can also be used as precipitating solvents, while tetrahydrofuran, dimethyl sulfoxide, furfural, methyl cellosolve, dioxane, ethanol, and acrylonitrile are excellent solvents for lignin.

From the point of view of energy saving, the most advantageous method of obtaining precipitated lignin appears to be spray drying of its acetone solution at a temperature of 65 ° C. The lignin obtained in this way is usually light in color and in the form of a free-flowing powder.

Fully opened chips are easily separated into loose fibers by suspension in a good lignin solvent, which removes a large amount of lignin from the fibers. A simple wash with methanol/water or acetone is usually sufficient to remove most of the dissolved lignin that is embedded between the fibers. Subsequent washing with water has no adverse effect on the bleachability of the fibers.

Another characteristic of the fibers produced in this way is the possibility of achieving the dewatering normally desired in paper pulps with considerably less energy input during milling. The dewatering rate of the spruce pulp obtained at 750 requires only 4,000 revolutions on the PPI mill to obtain a dewatering rate of 300, compared to pulp produced by the kraft process with the same initial dewatering rate, which requires 7,000 to 9,000 revolutions to achieve the same dewatering rate, preferably a dewatering rate of 300.

The invention is further illustrated in the following examples. Percentages are by weight unless otherwise stated.

Example 1

The delignification and polydispersity of cellulose were studied using 0.16 molar concentration of calcium chloride in a mixture of water with methanol, ethanol or n-propanol in the ratio 30:70. The batch was carried out in a laboratory pressure vessel made of stainless steel with a height of 20 cm and a diameter of 8 cm.

Air-dried wood chips with a moisture content of 8% from spruce wood are placed in a quantity of 10 g in a cooker next to 100 g of a previously prepared cooking solution. The sealed container is heated to 200 °C in an oil bath and maintained at the cooking temperature for a predetermined time. The cooking time is chosen so that a loose pulp is obtained after suspending the cooked chips in 500 ml of acetone and after stirring the solution at a speed of 800 rpm. At the end of the cooking, the container is cooled rapidly and the solution is decanted.

The pulp is washed with acetone and then water and air dried to constant weight. Samples are taken for Kappa number and viscosity determination and the final moisture content of the remaining pulp is determined for determination by pulp yield calculation. TAPPI standard methods are used for all tests.

All test results from this batch series are listed in Table I. The values clearly show the higher selectivity of methanol as a delignifying agent, which results from the high viscosity of the isolated cellulose pulp.

Table 1

Boiling solution CaClg as catalyst moles Conditions of brewing Pulp Yield % Number Kappa Viscosity TAPPI 0.5 g m Pa.s . composition Volume ratio time min and the temperature 80:20 0.16 - 30 200 58 63 18 MeOHzHjO 70:30 0.16 30 200 53 55 20.5 60:40 0.16 30 200 51 44 14 80:20 0.16 30 200 54 66 12.5 EtOH:HgO 70:30 0.16 30 200 50 59 8 60:40 0.16 30 200 46 27 5 70:30 0.10 25 200 52 75 8 n~propane xHgO 70:30 0.10 35 200 48 48 6 70:30 0.10 45 200 46 32 5

Example 2

The process allows for wide variations in the molar concentration of the metal salt used under otherwise constant batch conditions. Hardwoods can generally be boiled at lower salt concentrations of any catalyst than softwoods; for example, boiling aspen wood with calcium or magnesium chloride or nitrate for less than 30 minutes requires 0.005 to 0.10 molar salt concentrations, while boiling the same concentration of magnesium sulfate for 45 minutes requires 45 minutes. Softwoods, such as spruce, generally require higher salt concentrations, such as 0.05 to 0.20 molar, and in certain cases improved fiber separation is achieved at 0.5 molar or higher concentrations. Preferred salts are magnesium and calcium chlorides, which are advantageous both for their low cost and because they do not interfere with fermentation processes in which the aqueous sugar residues are converted to ethyl alcohol, yeast, or other fermentable products. Magnesium sulfate has limited solubility in alcohols, and therefore the concentration of salt that can enter the solution is often limited. To compensate for the low concentration of salt, magnesium sulfate, a longer brew time is required than is considered acceptable.

Table 2 shows the characteristic pulp yield values and properties of pulp from hard aspen wood and soft spruce wood when cooked in aqueous methanol at a temperature of 200 °C at a constant wood to cooking liquor ratio of 1:10 (with a water to methanol ratio of 30170).

Table 2

Wood Catalyst Brewing time min Pulp Yield % Number Kappa TAPPI Viscosity 0.5 g m Pa.s Polymerization degree composition moths aspen MgCl 0.01 30 62 27 20 1,320 MgSO ₄ 0.05 60 64 35 23 1,410 CaCl ₂ 0.01 30 63 30 21 1,360 CsCl^ 0.10 25 61 16 »8.7 1,280 MgCl ₂ 0.10 25 59 15 19 1,300 BaClg 0.01 30 69 46 poor fiber separation spruce MgCl 0.05 30 59 51 17 1,200 MgCl ₂ 0.10 30 54 29 18 1,270 MgSO ₄ 0.05 60 78 95 poor fiber separation CeClg 0.05 30 66 60 20 1,320 CeClg 0.10 30 54 35 19 1,300 Mg(NO ₃ ) ₂ 0.10 45 57 55 23 1,410 Ca(NO ₃ ) ₂ 0.10 45 58 62 29 1,570

In Table 2, the values of the degree of polymerization are derived from viscosity measurements according to the TAPPI standard and using the nomogram published by Eydholm on page 1,120.

Example 3

Further batches are carried out with the same types of wood and with the same doses of cooking liquor as in Example 2. The cooking liquor consists of a mixture of water and methanol in a ratio of 70:30 and contains 0.10 mol of calcium chloride as a catalyst. The batch time and cooking liquor temperature are given in the following table 3.

Table 3

Wood species Batch Pulp Yield % Number Kappa Viscosity TAPPI 0.5 g m Pa.s Polymerization degree time minutes teglota Spruce 15 200 72 103 there will be no separation fibers 25 200 62 63 28 1,550 35 200 56 46 ,8 1,275 45 200 52 42 15 - 1,160 50 190 63 61 28 1,500 80 190 56 40 23 1,410 Aspen 10 200 90 99 no fiber separation 15 200 73 61 25 1,450 20 200 63 22 21 1,360 25 200 6, 16 19 1,300 40 .80 63 48 4, 1,750 40 .90 57 9 2, 1,360

Since each lignocellulosic material has a different composition and character of its lignin-carbohydrate matrix due to the natural growth of the plant material, it is necessary to carry out several tests with a given material in the process according to the invention in order to obtain pulp with optimal properties. Some guidance can be given in Table 4, which shows the analytical values of seven different types of raw materials, all of which yield high quality pulps. The pulps are produced under the conditions described above. These conditions should be considered practical rather than optimal. The table includes the properties of a test sheet of hand paper after pulping to a drainage rate of 300 according to the Canadian standard, the hand paper sheet tests being carried out in the manner described in the TAPPI standard. The pulps are tested only after washing with acetone to remove dissolved lignin and are suspended in water before being sieved and processed into a paper sheet.

The results of the analysis of sugars, lignin and wood pulp for aspen and spruce wood are presented in Table 4 and Table 5.

Properties of pulp from a batch of wood in a mixture of wood and methanol in the ratio 3:7, Properties of handmade paper from washed unbleached pulp, mle at a ratio of wood to cooking liquor of 1:10, at variable temperature and con- at a drainage rate of 300 according to the Canadian standard centration of calcium chloride i ť

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Table 5

Type of wood Substrate Pulp yield Residual viscosity of lignin TAPPX gluc. Carbohydrate compounds xyl.gal. Arab. man gla. sugars » % V,5 B d Pa. a % % % % % % % aspen wood 77.4’ 19.7 ² 22 ³ 57.9 13 0.5 0.2 3.4 1.0 76.0 pulp 6, ,0 2.1 19 53.1 3 0.1 foot 2.2 0.06 58.26 lye - 16.3 - 0.4 7 0.5 foot 0.8 0.2 9.1 spruce wood 72.3 26.5 21 49.9 6 ?,8 1.1 11.9 0.8 7’,5 pulp 52 2.9 19 43.1 2 - 2.5 footprints 47.6 lye - 23.0 - 1.7 1, 4 1 0.6 4.7 0.1 8.9

¹ holocellulose (lignin-free), ² Klason lignin, ³ FeTNa viscosity according to Jayma

The high glucose content in the pulp indicates that little, if any, damage to the wood cellulose has occurred.

Example 4

Since salts tend to react by cation exchange with wood, it was expected that the pulp would contain some salt. Therefore, pulps were prepared according to Example 3 and subjected to a strong oxidizing agent boil, after which the samples were diluted with demineralized water. Calcium and magnesium ions were determined in the resulting solutions by atomic absorption spectrophotometry. The results are given in Table 6.

Table 6

Type of cation % in wood % in pulp Wood magnesium 0.021 5 0.010 7 aspen calcium 0.108 6 0.000 9 magnesium 0.005 2 0.007 7 calcium 0.065 1 0.001 2 spruce magnesium 0.015 1 0.001 5 calcium 0.071 2 0.045 3 birch

All batches were run with 70:30 methanol/water containing 0.05 M magnesium chloride or calcium chloride under heat for 30 minutes. The pulps were washed once with acetone and two 500 ml portions of distilled water before drying for analysis.

It is clearly evident from Table 6 that the pulps contain even fewer cations than were present in the original wood.

222679 ^{1 0}

Example 5

It is known that for rapid complete delignification in an acid-catalyzed aqueous organic solvent mixture, a relatively large increase in proton concentration is required to achieve rapid delignification. It appears that the metal salt catalysts of the invention are not capable of generating such a high proton concentration in situ. A moderate decrease in pH from 5.8 for a 70:30 methanol/water mixture containing 0.05 moles of calcium chloride to 4.2 was observed only when a cooking solution was added to wood chips. The development of such a weak acidic character in salt solutions added to wood chips is well known from the literature.

In some cases, especially in gymnosperm pulping, delignification may be too slow and not sufficiently selective, making it difficult to produce pulps with low residual lignin content. In such cases, it has been found that the initial proton concentration can be favorably influenced by a small concentration of mineral acid, which usually has the same ion as the salt. Such an acid addition usually affects the overall delignification and hydrolysis of hemicelluloses at a time when the cellulose is still well protected from protons by the encrusted lignin, because in its native structural arrangement, cellulose is less accessible to acids if the swelling by solvent is limited by the lignin-hemicellulose matrix.

The catalytic activity of the metal salt does not change from that expected in the absence of mineral acid, i.e. the metal salt acts as a proton donor and as an important protective agent for the cellulose, especially in the later stages of the batch, protecting it against hydrolytic solvolysis. Such a synergistic effect is clearly evident from Table 7. Higher acid concentrations are much more effective in reducing the residual lignin content in the pulp. This occurs at the expense of a slight reduction in pulp yield without a significant decrease in cellulose viscosity.

Thus, air-dried spruce wood chips are boiled at a wood to boiling solution ratio of 1:10 of a 70:30 methanol/water mixture containing the indicated amounts of acid and salt as catalyst. The temperature during the boil is 200°C and the heating time to this temperature is 7 minutes for each boil and is included in the indicated boil time.

Table 7

Catalyst Acid salt N U Brewing time min Pulp Yield % number Kappa Viscosity TA.PPI 0.5 g m Pa.s Polymerization degree th ₂ sat ₄ 0.003 75 40 45.8 39 3.7 460 MgSO ₄ 0.05 60 78 105 no splitting into fibers _{H2SO4 / MgSO4} 40 51 36 9.5 9.0 HC1 0.002 40 ⁷⁰ no threads division CeClg 0.05 40 54 44 20 1,320 HCl/CaCl ₂ 40 56 58 30 1,600 HCl 0.002/CaCl ₂ 35 58 57 24 1,440 HCl 0.004/CaCl ₂ 40 53 37 23 1,420 HCl 0.00/MgSO ₄ 40 56 51 19.2 1 3.0 HNOj 0.004 45 48 50 4.0 470 Ca/NOj/g 0.10 45 58 62 29 1,570 HNOj 0.004/Ca/NOj/g 45 55 37 23 1,420

continuation of table 7

Catalyst N

Acid M salt

Batch time min

Yield number Viscosity of pulp Kappa TAPPI 0.5 g % o Pa.s

Polymerization degree

HNO ₃ 0.002/Mg/N0 ₃ / ₂ 45

HCl 0.002/CaCl, 0.05 aspen wood 25

39 25

450

20 25

450

The description and examples fully explain the method according to the invention and facilitate its use by those skilled in the art. The scope of the invention also includes variations and modifications of the above-described methods according to the appended claims. The advantages of the method according to the invention in comparison with the methods known from the prior art are also illustrated by the following comparative example.

Comparative example

The comparative example demonstrates the increase in delignification rate when using alkaline earth metal salts compared to the Kleinert batch method. All batches were carried out stationary. The batch at .90 °C was carried out for .7 minutes, the batch at 200 °C was carried out for 13 minutes.

In the Kleinert process, a preferred lye is used, which is a mixture of ethanol and water in a volume ratio of 50:50 with an initial pH of 6.0 to 6.5 (see U.S. Patent No. 3,585,04, column 6, line 4 et seq.).

In the brewing process according to the invention, a mixture of methanol, the most preferred alcohol for brewing, and water in a volume ratio of 80:20 and calcium chloride in a concentration of 0.05 m is used as the cooking liquor.

All pulps with Kappa numbers above 65 are treated with chlorite for 5 minutes at 50°C and then their viscosity is determined.

The results are shown in the following table.

Table 8

Method Wood species Brew temperature °C Time min Pulp yield Spit TAPPI Kappa number 0.5% ¹ Alpha-Cellulose % after alkaline extraction weight viscosity Pa.s ^-3 Kleinert's aspen 190 60 70.4 - uncooked 90 64.4 58.4 10.1 66 21 - - 120 63.0 53.0 2.3 36 17 - - .50 58.7 48.7 1.5 33 ,8 40.1 24 According to the invention aspen 190 25 68.8 - 3.2 37 42 - - 35 63.6 - 0.4 21 38 47.2 38 40 6, ,0 - - 14 32 - - 50 60.4 - - 10 27 - - 65 58.5 - - 8.6 24 46.5 28

continuation of table 8

Wood Batch Time Pulp mill yield TAPPI number Alpha-cellulose ^ZpŮ8 ° ^b type ^te P ^lota min ^PO e;^i ^ké Kappa 0.5 gyield viscosity ^C . ^Z ' 5S Pa.s ^-3

Klelnert spruce 200 30 82.8 - uncooked 60 70.3 - is not running out : to department fiber 90 64.1 53.4 33.7 150 - - - 120 59.9 53.0 24.2 110 15 - - 180 56.5 49.1 , 13.1 86 13 - - 210 52.3 46.3 6.9 71 11 39 18 260 51.2 44.8 4.5 65 9.7 - - According to the invention of Smrk 200 20 75.2 4.6 102 38 25 66.8 - 2.9 94 43 - - 35 63.5 - 3.0 87 48 - - 50 61.0 - 1.3 60 42 - - 60 58.6 - 1.0 51 36 44 37 65 57.2 - 0.8 43 35 - - 70 55.1 - - 32 32 - - 80 54.4 . - - 25 28.7 - -

The values in the table show that when using the cooking liquor according to the invention, the lignin dissolves significantly faster than when using the cooking liquor which Kleinert considers to be advantageous. Furthermore, it can be concluded from the alpha-cellulose yield values and the viscosity values achieved in the brewing according to the invention that the cellulose is not damaged during the brewing by the organic acids which are released during the brewing.

Claims (3)

SUBJECT OF THE INVENTION ,. Process for batching lignocellulosic materials, wherein the lignocellulosic material is boiled from a mixture of water and 1-4 volumes of aliphatic alcohol of at most 3 carbon atoms per volume of water containing a metal salt and optionally a small amount of acidic reagent at a temperature of 130 to 210 ° C. two hours using 4 parts by weight of cooking liquor per part by weight of Ugnocellulose material, the loose cellulose pulp is then separated from the cooking liquor, the alcohol is evaporated from the cooking liquor and lignin and sugars are separated from the remaining cooking liquor, characterized in that The alcoholic solution used as boiling liquor contains 0.001 to 1.0 moles of magnesium, calcium or barium chloride or nitrate or magnesium sulphate or mixtures thereof and a strong mineral acid at 0.0005 and 0.008 normal concentration. 2. A process according to claim 1, wherein the alcohol used in the cooking liquor is methanol or methanol. ethanol. 3. A process according to claim 1, wherein the strong mineral acid in the cooking liquor is hydrochloric, sulfuric, phosphoric or nitric acid. Severography, n. P., MOST