FI69129B - EXTENSION OF LABORATORY MATERIAL - Google Patents

Description

ANNOUNCEMENT ISSUE

• SFff ^ 11 UTLÄGGN, NGSSKR, FT Qy \ £ .y • S \ Ö C (45) ratcn radioi: - 'b "' ^ (51) Kv.lk.4 / lnt.Cl.« D 21 C 3 / 20 FINLAND —FINLAND (21) Patent application - Patcntansökning 793678 (22) Filing date - Ansökningsdag 23.11.79 (En) (23) Starting date - Giltighetsdag 23.11.79 (41) Published public - Blivit offentlig 28.05.80

National Board of Patents and Registration Date of publication and publication Publication— q Λ.Ο Or

The patent and registration authorities have been published and published in the UK. UO .05 (32) (33) (31) Privilege claimed — Begärd priority 27.11 .78

Canada (CA) 316951, 22.05.79 Federal Republic of Germany Förbundsrepubliken Tyskland (DE) P 2920731 (71) Bau- und Forschungsgesel1schaft Thermoform A.G., Ryf 50, Murten,

Friborg, Switzerland-Switzerland (CH) (72) Laszlo Paszner, Vancouver, British Columbia, Pei-Ching Chang, Vancouver, British Columbia, Canada (CA) (7 * 0 Oy Jalo Ant-Wuorinen Ab (5 * 0 Method 1 ignocellulosic) for the defibering of material - Förfarande för uppslutning av 1ignocellulosahaltigt material

The present invention relates to a process for treating lignocellulose with a solvent mixture of water and low aliphatic alcohols having up to three carbon atoms and a dissolved proton-producing salt catalyst at elevated temperature at 130-210 ° C to produce a fibrous chemical pulp by best and at least partial depolymerization. lignin and hemicululose substances.

The method is very advantageous in the production of pulps with a low Kappa or Roe number, high fiber strength, leaving the cellulose almost in its natural, non-degradable state. Significantly, the invention is equally effective for wood species belonging to both gymnosperm and angiosperms as well as for lignocellulosic agricultural waste when carefully cooked under the above conditions.

69129 Due to today's scarcity of energy and chemicals, emphasis should be placed on cooking efficiency and the completeness of chemical regeneration. The new fiberization method should be efficient in removing lignin to allow short cooking times and at the same time mild enough to allow near-theoretical fiber yields and quantitative regeneration of dissolved by-products. The removal of lignin should be as complete as possible to avoid low bond strength of the fibers and to reduce the need for bleaching chemicals when fully bleached paper grades are desired. It is further desired from a good cooking method that the release of the fibers be as complete as possible. Thus, the removal of lignin should extend to both the fibrous binder layers (middle lamella) consisting of the lignin-carbohydrate binder, as well as to the cell wall binders containing lignin and hemicellulose in different proportions. Such efficient lignin removal results in low screening waste and the cooked chips require little, if any, mechanical action for complete fiber milling, which preserves manufacturing energy as well as fiber length.

Therefore, in processes where wood is hydrolyzed in aqueous or aqueous organic solvent mixtures containing unbuffered or non-retarded acid catalysts, at 165-210 ° C the cellulose is also broken down so rapidly that before the cell wall lignin and hemicellulose substances have dissolved, the cellulose largely fragmented. Although a relatively weak acid, such as an organic dicarboxylic acid, is used as the catalyst, the fibers, when released, have a lower degree of polymerization of their cellulose than in their natural state, so that paper sheets made from such pulps lack high tear strength, puncture resistance, and breakthrough length. for industrial use.

Although the known methods have the advantage of requiring very short cooking times and producing soluble lignin and dissolved sugars of considerable value, it is desirable that the release of cellulose fibers protect almost the entire polyglucon fraction and the initial strength of the cellulose fibers to an acceptable low lignin strength. Another object of the invention is to produce a high yielding pulp with a low residual lignin content to improve fiber binding and shape in the paper web and to reduce the need for bleaching chemicals in the production of fully bleached grades. Another desirable goal is to avoid damage to cellulose by mixing with acids and especially water. due to the organic solvents used in this invention which show a clear uniformity in their lignin removal property and do not degrade carbohydrates. One major improvement of the invention is due to the selection of inexpensive, mild salt catalysts with the unique property of forming weakly acidic solutions in aqueous alcohols, promoting the production of acidic protons in the system by cation exchange with functional groups of lysine and carbohydrates temperature. Substantially reduced acidity further eliminates the need to obtain highly acid-resistant cookware.

It is an object of the invention to provide a process for cooking cellulose which is substantially free of water and air pollution.

Other objects of the invention will become apparent from the following description, which describes the method in more detail.

Aqueous solvent cooking methods are described in U.S. Pat. 3,585,184 and most recently in U.S. Pat. 4,100,016. The invention avoids the major drawbacks of these and other known chemical cooking methods by using a method which essentially consists in treating lignocellulosic substances with a solvent mixture of at least four times the weight of the lignocellulosic material to be cooked and the solvent consisting of methanol, ethanol or n-propanol or a mixture thereof. 20 to 80% of a mixture in water and containing 0.005 to 1.0 moles of a metal salt soluble in water and an alcohol selected from magnesium chlorides, sulphates or nitrates of magnesium, calcium or barium or mixtures thereof. The temperature is 130-210 ° C, preferably 170-200 ° C and especially about 195-200 ° C, and the reaction time is generally 15 to about 90 minutes. For lignocellulosic substances, which are generally difficult to remove lignin, and for salts with low catalytic activity, such as magnesium sulphate, small amounts of a strong acid with the corresponding preferred anion are added to bring the solution to 0.0CO5 -0.008 N strong acid. in addition to the salt catalyst used in said solution, significantly improves the degree of lignin removal without adversely affecting the polydispersity of the regenerated cellulose. The disclosed method provides high lignin removal specificity and produces cellulosic fibers with very high polymerization and high glucone content. The process is very effective when the 69129 salt is magnesium or calcium chloride or nitrate and the molar concentration is 0.02 to 0.05 moles and the volume ratio of water to solvent mixture methanol is 35:70, and the boiling is carried out at 190-200 ° C: in. When coniferous trees, such as spruce, are cooked by the new method, a pulp is obtained which retains considerable amounts of hemicellulose, but which nevertheless has a low residual lignin content and a higher degree of polymerization (DP) than most pulps obtained by kraft paper methods. The cooking time only needs to be 30 to 45 minutes to produce a pulp with a Kappa number of 33, a 0.5 g TAPPI viscosity of 20 centipoise or a degree of polymerization of 1320. The cooked chips are separated into individual fibers only by slurrying them in water and the resulting pulp can be easily bleached. from 50% GE to the desired 80% and whiter than power-perch spruce with a corresponding residual lignin content with a much lower initial whiteness, usually 35% GE.

The current cooking methods still have the disadvantage that the regeneration of the by-product greatly interferes with the regeneration of the cooking chemicals, making such efforts less economically attractive. Furthermore, in the kraft paper process, for example, dissolved sugars are largely converted to saccharic acid salts, which have only limited use as industrial chemicals. Similarly, lignin is converted to sulfur derivatives to achieve the required degree of solubility to isolate a low lignin fiber, a fact that otherwise converts partially solvent-soluble lignin to one that can only be dispersed in alkali. In contrast to these above-mentioned difficulties in regenerating a by-product from the cooking of lignocellulosic materials, this process of the invention requires regeneration of dissolved lignin and sugar as they normally separate in cooking solvent regeneration by expansion evaporation, leaving relatively concentrated aqueous sugar solutions with other concentrated sugar solutions. Separation of lignin from sugars takes place by centrifugation or simple filtration.

The regenerated sugar solution has been found to be rich in xylan and other hemicellulose substances, as well as relatively low glucone yields. Most of the sugars exist as dimers and low molecular weight oligomers, which can be easily reduced to simple sugars by post-hydrolysis as an almost quantitative product. The fact that the sugars are present as low molecular weight sugar polymers protects them from dehydration at high temperature, i.e. during cooking, and allows for better dissolved sugar regenerations.

ti 5,691 29

The precipitated lignin resulting from the removal of the solvent retains its solvent solubility, a property that is highly desirable when aiming for chemical production. The molecular weight of such solvent-soluble lignin was determined to be 300 to 12,000 by gel permeation chromatography and high pressure liquid chromatography, and the average molecular weight was calculated to be about 3,000 to 3,000. The lignin thus obtained can be easily purified by redissolving it in acetone, filtering the acetone solution to remove insoluble matter by repeated reprecipitation into water or a non-polar solvent such as diethyl ether, benzene and n-hexane. Other solvents such as dichloromethane can also be used as a precipitant, while tetrahydrofuran, dimethyl sulfoxide, furfural, methylcellulose, dioxane, ethanol and acrylonitrile are excellent solvents for lignin. The most interesting energy saving technique for the regeneration of precipitated lignin takes place by spray drying from acetone solutions at a temperature below 65 ° C. The lignin thus obtained is generally pale in color and in the form of a free-flowing powder.

Fully cooked chips are easily separated into free fibers by slurrying them in a good lignin solvent, which removes large amounts of lignin from the fiber. In general, a simple wash with hot methanol / water or acetone is sufficient to remove the dissolved lignin mass attached to the fibers. Subsequent washing with water has no adverse effect on the bleachability of the fibers. One feature of the fibers thus prepared is that a fat content, which is normally desirable for papermaking pulp, can be achieved with a substantially less energy milling process. The initial fat content obtained with spruce pulp requires only kOOO revolutions with a PFi cholester to achieve 300 fat content compared to kraft pulps with the same initial fat content and requiring 7000 to 9000 revolutions to achieve the same fat content, normally 300.

The invention will be explained in more detail by means of the following examples and claims of the preferred forms for carrying out said method.

Example I

A study of lignin removal and polydispersity of cellulose was performed using 0.16 mole CaCl 2 concentrations in 30:70 mixtures of water and methanol, ethanol or n-propanol. The decoctions were performed in a laboratory-scale, 6 69129 stainless steel pressure vessel about 20 cm high and 8 cm in diameter. Air-dried wood chips with a moisture content of 8% and made of spruce were mixed in a cooking pot in 10 g portions together with the previously prepared cooking solution, which in each case was 100 .mu.g. The sealed vessels were heated to 200 ° C and kept at the cooking temperature for a specified time. The cooking time was chosen so as to obtain a free mass after the cooked chips had been slurried in 500 ml of acetone and the solution stirred at less than 800 rpm. At the end of cooking, the dishes were cooled and the solution was decanted. The mass was washed with acetone and water and air dried until a constant weight was obtained. Samples were taken to determine the Kappa number and viscosity, and the final moisture content of the ice mass was determined to allow the mass yield to be calculated. TAPPI standard test methods were used for all analyzes. All test results from these cooking cycles are shown in Table I. The values clearly indicate the excellent selectivity of methanol as a lignin scavenger, as seen from the high viscosity of the isolated cellulose pulp.

TABLE I

COOKING SOLUTION CaCl2 COOKING TEMPERATURE KAPPA- TAPS- - CATALYST TIME STATUS YIELD FIGURE VISC0SI-

K00STUMUS VOL. RATIO MOLIA MIN. ° C% TEETTE

0.5 g δ: 20 0.16 30 200 58 63 18 70:30 0.16 30 200 53 55 20.5

MeOH: HO -—-- 2 6θ: 4θ 0.16 30 200 51 44 14 80:20 0.16 30 200 54 66 12.5

EtOH: H 2 O 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-propanol 70:30 0.10 35 200 48 48 6 H2 ° 70:30 0.10 45 200 46 32 5 il 7

Example II 6 9 ”1 2 9

The method shows high tolerance to a large variation in the molar concentration of the light metal salt used, otherwise under constant cooking conditions. Deciduous trees can generally be boiled at the lowest salt concentrations of any of the preferred salt catalysts than conifers. For example, aspen is boiled with calcium or magnesium chloride or nitrate in less than 30 minutes at salt concentrations of 0.0025 to 0.10 moles, while the same concentration of magnesium sulfate is required for * + 5 minutes. Conifers, such as spruce, generally require a higher salt concentration of 0.05 to 0.20 moles, and in some cases improved fiber separation can be achieved at concentrations of 0.5 mole or greater. The preferred salts are magnesium and calcium chlorides. which have the advantages of the lowest cost and the fact that they are well suited to fermentation processes to which an aqueous sugar residue can be fed to convert sugar into ethyl alcohol, yeast or other fermentation product. Magnesium sulfate is sparingly soluble in alcohols and therefore the salt concentration that can be incorporated into the solution can often be limited. To compensate for the lower salt concentration of MgSO 4, longer cooking times are required than those considered acceptable.

Table II shows illustrative data on the mass yield and properties of one hardwood, aspen, and one softwood, spruce, when boiled with aqueous methanol at 200 ° C with a constant ratio of wood to solution of 1:10 (water: methanol is 50:20).

TABLE II

CATALYTIC PAPER OF CATALYTIC SALT Μηηττφ TIME YIELD VISKOSI- D.P.

M00LIT MIN. % CHAPTER ORDED

_0.5 g_

MgCl 2 0.01 30 62 27 20 1320

MgSO 4 0.05 60 69 35 23 1910

CaCl- 0.01 30 63 30 21 1360 <d _____% CaCl 0.10 25 61 16 18.7 1280 w -----—-——--

MgCl 2 0.10 25 59 15 19 1300

BaCl2 0.01 30 69 96 weak fiber separation 8 TABLE II (cont. ♦) 691 2 9 CATALYTIC PAPER WOOD OF CATALYTIC SALT IKAηηττφ TIME YIELD VISCOSE D.P.

M00LIT MIN. % CHAPTER ORDED

0.5 g

MgCl 2 0.05 30 59 51 17 1200

MgCl 2 0.10 30 5 * + 29 18 1270

MgSO 4 0.05 60 78 95 weak fiber separation 3 CaCl 0.05 30 66 60 20 1320: = »-------- ---------------— - ------- 1 1 ------- '- * CaCl 2 0.10 30 5 ^ 35 η9 1300

Mg (NO3) 2, i0_if5_57 55_23_1 ^ 10

Ca (NO 2) 2.10 _ * + 5_58_62_29_1570

In Table II, DP values are derived from TAPPI standard viscosity measurements and using a nomogram published by Rydholm (p. 1120).

Example III

Additional cooking was performed according to the wood and solution stains shown in the previous example. The solution consisted of a mixture of 70:30 water and methanol and contained 0.10 moles of CaCl 2 as a catalyst. Both cooking time and temperature were varied as shown in Table III.

TABLE III

COOKING TEMPERATURE KAPPA-TAPPI-VISKOSI-TYPE TIME STATE YIELD TTTI ^ TT TEA (0.5 g) D.P.

MIN. ° C% NUMBER cP

15 200 72 103 no fiber separation 25 200 62 63 28 155Ο 35 200 56 ^ 6 18 1275 SIX ---------- i + 5 200 52 k2 15 1160

50 190 63 61 28 I5OO

80 190 56 ^ 0 23 1M0 tl 9 TABLE III (, -jtk.) 6 912 9 COOKING TEMPERATURE KAPPA- TAPPI-VISKOSI-T. TT TIME STATUS YIELD TI1I.TT TEA (0.5 g) D.P.

TYPE MIN. ° C% NUMBER cP

10 200 90 99 no separation of fibers 15 200 73 61 25 1 ^ + 50 20 200 63 22 21 1360 ASAP 25 200 16 19 1300 40 180 63 48 41 1750 40 190 57 9 21 1360 10

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ti 11 69129

Since each lignocellulosic component exhibits a different composition and property of its lignin carbohydrate binder, as occurs in naturally growing plant materials, the practice of the invention necessarily requires some experimentation with the putative material to achieve optimal pulp properties. Some guidance is provided in Table IV, which explains the mass analyzes for seven different species, all of which produced benign pulp. The pulp was prepared under the conditions described above. It is clear that these conditions are examples of good practical performance rather than optimal conditions. The table contains the interesting properties of the test sheet after the pulp has been ground to a Canadian Standard Freeness value of 300, at which time the sheet was tested according to the TAPPI standard. The pulps were treated with acetone wash only to wash away the dissolved lignin and suspended in water before screening and forming a test sheet.

A summary analysis for sugars, lignin, and wood pulp was performed for aspen and spruce soups, the results of which are explained in Table IV and shown in Table V.

TABLE V

LAS SUBSTRATE MASS RESIDUE- PIN Carbohydrate COMPOSITION SIZE.

RETURN LIGN. Viskos. GLUC.XYL.GAL.ARAB.MANN.GLAC SUGAR 11% cP %%%%%%% WOOD 77.1 + 1 19.72 225 57.9 13 0.5 0.2 3.4 1.0 76.0 § MASS 61.0 2.1 19 53.1 3 0.1 pi®ni. 2.2 0.06 58.26 <maara <c m - - ----- 1 ........... - 1—1. 1 solution - 16.3 - o, 4 7 0.5 0.8 0.2 9.1 'amount WOOD 72.3 26.5 21 49.9 6 1.8 1.1 11.9 0.8 71 .5 H MASS 52 2.9 19 43.1 2 - 2.5 P?! ^ Ni47.6 w ',' maara '' '* SOLUTION - 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 Jayme.

The high glucose content in the pulp indicates a slight deterioration, if any, in the wood pulp.

12 69129

Example VI

Because the salts were assumed to be associated with the cation exchange type series. reaction to wood, it was expected that some salt would remain in the pulp fibers. For this reason, the pulps were prepared according to Example III and decomposed in a strong oxidizing agent, after which they were dissolved in desalted water. The resulting solutions were then analyzed for Ca ++ and Mg: ++ ions by atomic absorption spectrophotometry. The results are shown in Table VI.

TABLE VI

CATION SPECIES% IN WOOD% BY MASS SPECIES

Mg + + 0.0215 0.0107

- HAAPA

Ca ++ 0.1086 0.0009

Mg ++ 0.0052 0.0077

- SIX

Ca ++ 0.0651 0.0012

Mg ++ 0.0151 0.0015

- BIRCH

Ca ++ 0.0712 0.0 ^ 53

All decoctions were performed in a ratio of 70:30 in methanol and water and contained 0.05 moles of MgCl 2 or CaCl 2 and the temperature was maintained for 30 min. The pulps were washed once with acetone and with two portions of 500 ml of distilled water before being air-dried and analyzed.

It is quite clear from Table VI that the pulps contained much less cations than were originally present in the corresponding trees.

Example V

It is known that for the rapid removal of lignin mass in acid-catalyzed aqueous organic solvent mixtures, relatively high initial proton concentrations are required to achieve rapid lignin removal. The metal salt catalysts disclosed herein appear to be incapable of producing such high proton concentrations at the site 11 13 691 29. On average, a decrease in pH from 5.8 to 70:30 for methanol: water mixtures containing 0.05 moles of CaCl 2 to h, 2 was observed only when the broth was added to the wood chips. The development of such a weak acid property in cooking solutions when added to wood chips is well known in the literature. Sometimes, especially in the case of gymno sperm, the rate of lignin removal can be too slow and sufficiently non-selective, so that pulps with a low residual lignin content are difficult to produce. In such cases, it was found that the initial proton concentration can be effectively accelerated by low mineral acid concentrations, which usually have the same anion type as in the metal salt. Such acid additions normally increase the mass removal of lignin and the hydrolysis of hemicellulose materials while the cellulose is still well protected by proton-coated lignin because in its original structural environment the cellulose is less susceptible to acids, solvent expansion with limited binder-hellin. The function and effects of the metal salt catalysts remain unchanged from what has been experienced in the absence of mineral acid, i. the metal salt acts both as a proton-producing substance and provides important protection for cellulose, especially in the later stages of cooking against subsequent hydrolytic solvolysis. Evidence for such an enhancing effect is shown in Table VI ±. Higher acid concentrations have been found to be more effective in reducing residual lignin in the pulp. This has been achieved at the expense of a small reduction in pulp yield without a significant reduction in the viscosity of the cellulose.

Thus, air-dried spruce chips were boiled in a wood: solution ratio of 1:10 to 70:30 with a methanol: water mixture to which the indicated amount of acid / salt-la-catalyst had been added. The temperature was 200 ° C and the heating time included in the time shown was 7 minutes for each cooking.

69129

TABLE VII

14 CATALYTIC COOKING MASS KAPPA- TAP-- TIME YIELD FIGURE VISAS. D.P.

acid N.

--- Tr min. % cP

salt M

H2SO4 0.00375 ^ 0 ί + 5, δ 39 3.7 ^ 60

MgSO 4 0.05 60 78 105 no fiber separation i ^ SO 2 / MgSO 2 ^ 0 51 36 9.5 910 HCl 0.002 ^ 0 70 - no fiber separation

CaCl2 0.05 k $ kk 20 ”320 HCl / CaCl2 ^ + 0 56 58 30 1600

HCl 0.002 / CaCl 2 35 58 57 2k IkkO

HCl 0.00VCaCl ^ 0 53 37 23 1 ^ 20

HCl 0.0025 / MgSO 4 kO 56 51 19.2 13IO

HNOj 0.004 k <5 k8 50 k, 0 ^ 70

Ca (NO 2) 2 0.10 45 58 62 29 ”> 570 HNO 2 0.00VCa (NO 2) 2 k $ 55 37 23 1 ^ 20 HNO 2 0.002 / Mg (NO 2) 2 ^ 5 56 39 25 1 ^ 50 HOI 0.002 / CaCl2 0.05 25 58 20 25 1 ^ 50

Through the above representations and examples, we seek to explain this invention in the most complete, clear, and concise terms possible so that those skilled in the art can practice it, and since we have explained the best mode for carrying out our invention, we consider it to be stated and clearly claimed. We are aware that the invention may be modified or parts thereof substantially replaced without departing from the scope of the claims of the invention. It is intended that the patent cover what is stated in the claims and any patentable novelty that is included in the invention.

il

Claims (5)

A process for cooking lignocellulose, wherein the lignocellulose is boiled in an aqueous mixture of 1 to 4 parts by volume of a low molecular weight aliphatic alcohol containing up to 3 carbon atoms per volume of water, with a metal salt and optionally a small amount of acid reactive substance for up to two hours at 190 ° C At 200 ° C, using at least 4 parts by weight of cooking solution per part by weight of lignocellulose, the released cellulose fibers are separated from the solution, from which the alcohol is then evaporated, and lignin and sugar are recovered from the residual solution, characterized by adding aqueous alcohol to the cooking solution. chloride, nitrate or magnesium sulphate of magnesium, calcium or barium, or a soluble mixture thereof, and optionally a strong mineral acid as an acid-reactive substance, provided that the mixture remains soluble. 1 5 Claims; 6,912 9 Process according to Claim 1, characterized in that methanol or ethanol is used as the low-molecular-weight alcohol. Process according to Claim 1, characterized in that hydrochloric, sulfuric, nitric or phosphoric acid is used as the strong mineral acid. Process according to Claim 1, characterized in that an aqueous alcohol is used as the cooking solution, in which the concentration of metal salts is 0.001 to 1.0 M and that of the strong mineral acid, if used, is 0.0005 N to 0.008 N. Process according to Claim 1, characterized in that, after separation of the cellulose fibers, the alcohol remaining from the solution containing the lignocellulose degradation products is distilled off by known expansion evaporation and the lignin precipitating as an aqueous residue is separated by filtration or centrifugation.