SE436899B - SET UP TO ENCOURAGE LIGNOCELLULOSALLY VEGETABLE MATERIAL - Google Patents

Description

45 20 25 EQ 55 40 7909674-9 2 or unmodified acid catalysts, the cellulose is also attacked so fast that before lignin and the hemicellulose constituents in the cell walls have dissolved, the cellulose has also been greatly degraded.

Even when using relatively weak catalysts acids, such as organic dicarboxylic acids, the fibers then have released a degree of polymerization of the cellulose below that which occurs in the fibers under natural conditions, through the sheets of paper made from such pulp lacks high tear control burst strength and wear resistance that are desirable for technical turn. g ' Although known methods have the advantages of very short cooking times and gives a soluble lignin and dissolved sugars of essential value, there is a desire that when releasing cellular the los fibers could maintain almost the entire polyglucan fraction and the natural strength of the cellulose fibers since acceptance bare lignin content in the pulp was achieved. Another purpose of the The present invention is the preparation in high yields of pulp with low lignin residue, this to provide improved fiber bonding and uniformity in the paper web and reduction of the required give the amount of bleaching chemicals, when it is desired to produce one completely bleached paper. Another wish is to avoid damage. cellulose by attack by acids and in particular those water-miscible organic solvent used in the method of the present invention, which method shows significant consistency with regard to specificity in nification and lack of attack on carbohydrates. Another important improvement made possible by the present invention stems from the choice of affordable and mild-acting salt catalysts. tors, which exhibit the unique property of forming weakly acidic solutions in aqueous alcohols, contribute to the one of acidic protons to the system by cation exchange with functional groups in the lignin and carbohydrates and protects the ceklülosan gene against attacks by acidic protons at high temperatures. The significantly reduced passivity further eliminates the need of highly acid-resistant boilers.

Another object of the present invention is a method pulp cooking, * in the implementation of which essentially no pollution of water or air is caused.

Other objects of the invention will become apparent from the following description. lO 15 20 25 30 35 7909674-9 Processes for boiling pulp in aqueous solutions agents are described, for example, in U.S. Pat 3,585,184 and most recently in U.S. Patent 4,100,016.

The present invention obviates the essential shortcomings of these known methods by a manner which exhibits and distinguishes of the measures specified in claim 1. The way essentially persists in the treatment of lignocellulosic material with a solvent mixture in an amount of at least 4 times the amount by weight of the lignocellulose and consisting of methanol, ethanol or n-propanol or a mixture thereof and water, the solvent water ratio is selected between 20:80 and 80:20, which mixture contains between 0.001 and 1.0 M of a metal salt soluble in water and alcohol namely a chloride or a nitrate of magnesium, calcium or barium or magnesium sulphate or mixtures thereof, at a temperature between 130 and 210, preferably between 170 and 200 and most preferably between 195 and 20,000, for a time that is generally between 15 and about 90 minutes.

Reconciliation nucleocellular materials, which are generally difficult to salts, and salts with low catalytic power, as is the case with magnesium sulphate, a much improved degenerative degree without significant effect of the polymerization of the recovered cellulose. dispersion, if one mixes a strong acid, which preferably has the corresponding anion, in such an amount that the solution becomes 0.0005- 0.008 normal with respect to the strong acid in said solution in addition to the salt catalyst used in it. It is thus written procedure has high specificity with regard to lignification and recovery of high-polymer cellulose fibers degree of merisation and high glucan content.

The process is particularly effective when the salt is magnesium or calcium chloride or nitrate with a molar concentration between 0.02 and 0.05, the volume ratio of water: methanol in solution the mixture is about 50:70 and the cooking is carried out at a temperature between 490 and 20,000. When applying the new the method of the present invention and boiling softwood, for example no wood, a mass is obtained which retains essential amounts of hemicellulose but still have low residual lignin content and higher degree of polymerization than most pulps obtainable in the production of kraft pulp. The cooking time only needs to be 30-45 minutes to obtain a mass with a Kappa number of 55, TAPPI viscosity of 0.5 g of 20 cP or a polymerization degree of 4520. The cooked chips are divided into individual fibers 40 45 20 25 EO 7909674-9 4 already at slurry j_ water and the mass thus obtained can be easily bleached from the brightness of 50% GE, which the pulp has when it has just been cooked, to the desired brightness 80%, and higher brightness ~ than in softwood pulp with comparable residual lignin content and much lower original brightness, namely gene in typical fail 55 GE.

The current procedures for cooking pulp also has the disadvantage of extracting by-products greatly interferes with the recovery of the cooking chemicals, which makes such recovery less attractive from the nomic point of view. When boiling kraft pulp is also converted read sugars largely to the corresponding acid salts as has only limited utility as industrial chemicals.

Likewise, lignin is converted to sulfur derivatives to achieve the degree of solubility required for the extraction of fibers with low lignin content, whereby it is otherwise in solvent partially soluble lignin is converted to one which can only be dispersed ras and alkali. In contrast, recovered according to the present invention the soluble lignin and the sugars therein expansion evaporator normally applied for recovery of the solvent used as the boiling liquid, thereby obtaining maintains a relatively concentrated aqueous solution of sugar, i which is otherwise the lignin soluble in the solvent in the form of a powdery precipitate. The lignin can be separated from the sugar by centrifugation or simply by filtration The extracted sugar solution has been shown to be rich in xylan and other hemicelluloses and relatively poor in glucan.

Most sugars appear as dimers and low molecular weight oligomers, which can be easily degraded to simple sugars by a second hydrolysis in almost quantitative yield.Gen0m that the sugars occur in the form of low molecular weight sugars polymers, they are protected from dehydration during cooking at high temperature and more far-reaching recovery is achieved of loose sugar.

After the solvent is removed, it retains precipitate lignin its solubility, that is, a highly desirable property when referring to chemical processing. The molecular weight of such soluble lignin was determined by gel permeation chromatography and high pressure liquid chromatography at a value between 500 and 12,000; whereby the average molecular weight was calculated to be about 5000. \. 'l '10 20 40 7909674-9 The lignin thus obtained can be easily purified by redissolution in acetone, filtration of the acetone solution to remove insoluble constituents and repeated precipitation in water or in a non-polar solvent such as diethyl ether, benzene or n- hexane. Other solvents, such as dichloromethane, may also be used. used as a precipitating agent, whereas tetrahydrofuran, di- methyl sulfoxide, furfural, methylcellosolv, dioxane, ethanol and Acrylonitrile are excellent solvents for lignin. The most attractive, energy-saving technology for extracting the precipitated lignin is to spray dry an acetone solution at a temperature below 6500. The lignin thus obtained is usually light in color and obtained in the form of a free sprinkleable powder.

The fully cooked chips are easily divided into free fibers when slurried in a solvent suitable for lignin, whereby large amounts of lignin are removed from the fibers. Usually a simple wash with a hot mixture is sufficient of methanol and water or with acetone to remove the bulk of the dissolved lignin deposited in the fibers.

Subsequent washing with water has no adverse effect. can on the possibility of bleaching the fibersAnother characteristic of the fibers so produced are that the drainage capacity that is normally desirable in pulp intended for papermaking can be achieved with significantly less energy consumption during ningen. The initial drainage capacity of 750 ml obtained kept with spruce pulp only needs to be ground with 4000 turns in one PFI grinder to achieve a drainage capacity of 300 ml.

This is to be compared with mass with the same original torque capacity, which requires about 7000-9000 rpm to achieve those of the same drainage capacity, which is typically 500 ml.

The invention will be described in more detail in the following exemplary preferred embodiments.

Example 1: A study of delignification and cellulose polydispersity was performed using a 0.46 ~ molar in a solvent consisting of a mixture ethanol or solution of CaCl2 in the ratio 50270 of water and methanol, n-propanol. The cooking was carried out in stainless steel pressure vessels steel (laboratory scale, height about 20 cm and diameter about 8 cm). 40 grams of air-dried spruce chips with a moisture content of 8% were invested in each of the pressure vessels together with 100 grams previously \ Y1 10 fx) UI 40 7909674-9 prepared cooking solution. The pressure vessels were closed and heated tiB.200 ° G in an oil bath and kept at the boiling temperature for designated time. The cooking time was chosen so that free mass was obtained afterwards slurry the cooked chips -in 500 ml of acetone and stirring of the solution at less than 800 rpm. At the boiling point finally the vessels were cooled and the liquid was decanted off. Hassan wash- was added with acetone and then with water and air dried constant weight. Samples were taken to determine Kappa numbers and viscosity, whereupon the final moisture content of the remaining the mass was determined to calculate the mass yield. For all analyzes, standard samples were applied according to TAPPI. All test data in this cooking series are summarized in Table 1, These data clearly show that methanol is superior with respect to selectivity in the demlignification, as indicated by the iso- the high viscosity of the cellulose pulp.

Table I Kokvätska šâëâšyä K ° kníng Massa- Kappa- vis- a * _ "'__" "'“ "_ '_ cacia, tid, temp., äšte tai ïgâl together- Vclymy mol min OC W 3 acc setting ratio "" ' l lande @APPI LO, 5 a) * _ 80 20 0.46 50 200 58 65 4s Ne ° ¿'h2 ° 70 50 0.46 50 200 55 55 20.5 60:40 0.46 50 200 54 44 44 neon H, 0 so 20 0.46 50 200 54 66 42.5 70:50 0.46 50 200 50 59 a 60 40 0.46 50 200 46 27 5 n_prOpa_ 70 = 50 0.40 25 200 52 75 a nßlå O _ 70 50 0.40 55 200 48 48 6 ^ 2 70 50 0.40 45 200 46 52 5 Example 2: The process shows high tolerance to large variations in the molar concentration of the metal salt used during 10 15 20 25 55 40 7 and 7909674-9 otherwise constant cooking conditions. Hardwood can in general boiled with lower levels of those preferred as catalysts na salts than softwood. Thus, for example, you can boil aspen with calcium or magnesium chloride or nitrate of less than 50 minutes at molar salt concentrations of 0.025 - 0.40. However required when using magnesium sulphate with the same concentration tion 45 minutes boiling. Coniferous wood, such as spruce, generally requires generally higher salt concentration, namely a molar concentration which is between 0.05 and 0.20, and in some cases can be achieved improved fiber separation with molar concentrations goes to 0.5 or higher. Preferred salts are chlorides of gastric nesium and calcium. These have the advantage of being affordable and is also well tolerated by the possible fermentation, at the aqueous sugar residue is converted into ethyl alcohol, yeast or other fermentable products. Magnesium sulphate has limited solubility in alcohols and consequently is often the amount salt that can be introduced into the solution limited. To compensate the low concentration of MgSO 4 requires longer cooking times than that deemed appropriate.

Table II has compiled representative data on found mass yield and properties of a hardwood (aspen) and a softwood (spruce) after boiling with aqueous methanol at 20,000 'and a constant proportion of wood: cooking liquid of 4:10. Amount- the water-methanol ratio was 50:70.

Table II vad fïâïâíï '§g§§§g¿ §§g; g¿ §g§PA- ïåškêšíï Éïššïšïåäa " sdt, m fl. % ° TMWI 0.5 grams Mgcig o, o1 50 62 27 eo '152o Mgsoq o, o5 eo 61+ 55 i 25 1410 cacig o, o1 50 65 50 21 1560 E? caciz o, 1o 25 61 16 18.7 12ao rxgcia o, 1o 25 ^ 59 15 19 15oo 351012 o, o1 50 69 _ de gâšågcfibersepara- \ ï'l 40 45 20 50 55 7909674-9 I 8 cont. Table II At salt, ”mo1 minutes uëbyte, number 0 TAPPI tions degree 0.5 grams NQCl 2 0.05 30 59 54 47 _4200 MgCl 2 0.40 50 54 29 48 4270 MgSO4 0.05 60 78 95 poor fiber separation ä 03012 0.05 50 66 60 20 aaao and CaCl2 0.40 EO §4 55 49 4500 Hg (No¿) 2.4o 45 5? 55 25 4440 ca (N0¿) 2.40 45 56 62 5 29 4570 The values for the degree of polymerization given in Table II has been determined by the WAPPT Standard and the ~ reversal of the nomogram published by Rydholm on page 4420.

Example §: Further cooking was carried out with the same wood and fluid rates indicated in the previous example. The liquid consisted of a mixture of water and methanol containing 50:70 0.40 mol of GaCl2 as catalyst. Both cooking time and temperature were varied as shown in Table III.

Table III At K ° knïng ïëâsâg KAPPA- viskasi- Polymerisa- time, temp.,% y ° tal tet acc. degree of tions minutes oc 'TAPPI (0.5 6) cP 45 200 72 40š no fiber separation 25 200 62 65 26 4550 É 55 200 56 46 46 4275 H) 05 200 52 42 45 4460 50 490 65 64 28 4500 80 490 56 40 25 4440 MW 10 15 cont. Table III 7909674-9 K kn 'H - _. _.

Ved I o ing uëâšëe KAPPA- V1skos1 ~ Polymerisa- tid, temp., 'tal tet enl. degree of tions minutes oc% TAPPI (0.5 s) cP 40 200 90 99 no fiber separation 15 200 75 61 2§ 1450 g 20 200 65 22 21 1560 m 25 i zoo 61 16 19 1500 40 180 65 48 41 1750 ao 190 57 9 21 1560 All lignocellulosic materials have different compositions and character of the lignin-carbohydrate matrix as such occurs in natural plant material, in practical application carrying out the invention carry out some experiments with a given material for obtaining optimal pulp properties. Some management can be achieved by means of Table IV, in which the mass analyzes for seven different raw materials, all of which provided high quality 718588.

Table IV see page 10 IQ 7909674-9 _ Qmnw ommv m.om mm mm om oom ov.o mm fi muoo Moo fi ëwm owmv vw om mm om oom mo.o qnmowma omwmv om mm oow.ov ooo.m omm oomv mv mm mm om oom ov.o ammo oomwv Nm vm oom.ov oow + v omm oomv vw om mm om omv ov.o xnm fl m omoom mm mo ooo.m omm om: mwmv m.vm mv mm mm omv ov, o a fi mn @ »w> xnmo oovmv om mo ooo.w oom.v oom ommv m.mm o.mv om om omv mo.o <lnmxoownmm ooowv mo mm oow.w oom.m mvm owmv vw v.m mm om omk ov.o mw < fi o . - Am oo . oonw Hmmqa HB .mm sm fl o fi v .Hmm ammo . mä. Hmvm fi> nm> awanmw vmw um »1onmux«> name mxnmuw ømhmm, umømH .wnwn nmwn fl n | fl nmS u fl mox Hmß .wßhn .QHS oo fl oä fo | w = mnow 1> fi m | p fl Hw IHM: -mamma | h fl om wm fi> | mmmm fl wmnm whmu l fl mpm nm fi ummmov Ha oom mmmëumwmm flfl nm fl : mao H fifl p o fi ms mmmmë om @ vw> p uxæ fl ßo mom mnnommxmnmmm .nommmm naowmøømm ovnmHo fi nm> .ovuv u .ßnm Honmuoalowm w > H flfl wnma .Hm @ HmA | mHowo noo Hspmnwmswu «Xmpm> Mo @ om» wonm fifl monooowmmz wø fi nMoxwm> @ fl> Hmmmxmuwwm wnmmmmä 45 GG 40 7909674-9 44 The pulps were prepared under the conditions described above.

Of course, these conditions are rather illustrative of good practice than optimal. The table includes interesting properties of made paper after the pulp has been ground to a drainage capacity of 500 ml Canadian Standard Freeness. Sheet testing was performed in in accordance with TAPPI Standards. The masses were washed only with acetone for leaching of dissolved lignin and slurried in water before producing sheets of paper by hand on a sieve.

A cumulative analysis for sugar, lignin and pulp carried out was for aspen and spruce. The cooking was carried out in the manner described is from Table IV and the results are summarized in Table V.

Table V Carbohydrate composition what Under- Mass- Rest- Vis- gluk.xyl. al.arab.mann.g1a. Tot. " %% eel e ~%%. laß uåbytes làsnin »% gÉi ~ I _: gck4 TAPPI _ CP šlalt , / 0 ; at 77.4 “49,? 2 225 s?, 9 43 0, fi 0.2 a, 4 4.0 76.0 0.4 Track 2.2 Op658428 ' Q Mass 61.0 2.4 19 55.1 5 liquid - 46.5 - 0.4 7 Ao, 5 spai '0.8 0.2 "9.4 at 72.5 26.5 24 u9.9_ 6 4.8 4.4 44.9 o, s 74.5 É Massa 52 2.9 49 45.4 2 - - 2.5 tracks w in liquid _- 25.0 - 4.7'4, n fz 0.6 4.7 0.4 8.9 1. Holocellulose (lignin-free); 2. Lignin classes; 5. FeTNa- viscosity according to Jayme.

The high glucose content in the masses shows little or no degradation of wood cellulose.

Example 4: One suspects that the salts were bound to the wood through a cat kat exchange type reaction one could expect to some of the salts would be retained in the pulp fibers. Of this For this reason, pulps were prepared according to Example 5 and subjected to digestion in a strong oxidizing agent and then diluted with demineralized water. The solutions thus obtained were analyzed. 7909674-9 42 was then obtained by atomic absorption spectroscopy with respect to those on Ca ++ and Mg ++. The data thus obtained are compiled 1 tabeii vr. Table VI Cation% in wood% in mass' Wood 40 ng ** o, o215 -0,040? aspen ca ** o, 1oss _ o, ooe9 - Mg ** o, oo52 o, oo77 ++ gran ca o, os54 o, oo12 “5 Mg ** o, o454 o, oo15 ++ birch ca o, o712 o, o455 All cooking was performed with a mixture of methanol and water 7o = 5o containing 0, 5 Mgcl, or cacla and temperature EO pure was maintained for 50 minutes. The masses were then washed one with acetone and in two portions of 500 ml each distilled clay water, after which they were air-dried and analyzed.

It is clear from the results compiled in Table VI clear that the masses held much lower levels of cations than the 25 _tive ved.

Example 2: It is known that to achieve fast delignification in the treatment of large quantities of wood with acid catalyzed mixtures of organic solvents must be used turn relatively large initial concentrations of protons. The i The metal salt catalysts listed in the present context appear lack the ability to generate such high proton concentrations in situ concentrations. On average, a pH drop from has been observed 5.8 to 4.2 for methanol-water mixtures containing 70:50 0.05 moles of CaCl9 already when the boiling solution was added to the wood chips. 55 Development of the slightly acidic character in saline solutions when these wood chips, is a well-documented fact in the literature. inch. Sometimes, especially in the treatment of wood from gymnosperms, the de-lignification rate may be too low and so non-selective, that it is difficult to obtain pulp with a low residual content. IN In such cases, it has been found that the initial concentration of ¶O 45 20 »25 50 55 40 7909674-9 45 protons can be effectively raised with small concentrations of mineral acid, usually mineral acid having the same anion as the metal salt tet. Such acid additions usually improve upon treatment of large wood masses the degeneration and hydrolysis of hemicellular the losers at a time when the cellulose is still well protected against the protons by entrapment in lignin, since cellular the solution in its naturally structured environment is less available to acids, when the solvent caused the swelling limited by the matrix of lignin -hemicellulose. Metal salt the function and effect of the catalysts remain unchanged and you get the same function and effect as in the absence of the mineral acid i.e. the metal salt acts both as a proton generating agent and as an important preservative for cellulose, especially during the later stages of cooking, as a result of which hydrolytic solvolysis. Signs of such synergistic effect is found in Table VII. The higher acid concentrations have proven to be the most effective in terms of reduction of residual lignin, in the mass. This is accomplished at the expense of one slight reduction in pulp yield without significant reduction in cello the viscosity of the solution. g Thus, air-dried spruce chips were boiled with a wood liquid holding 1:10 with a mixture of methanol and water 70:50 added with the indicated amount of acid / salt catalyst. Tempera- the temperature was 200 ° C and the heating time, which is included in it specified cooking time, was 7 minutes in each cook.

Table VII Catalyst Cooking time, Massaut -KAPPA- Viscose- Polymeric- '(, _' S ra E min. byte, ß tal ëïëpïnl. degree of tions salt M CP ' 'Granflis HZSO4 0.00575 40 45.8 59 5.7 460 »Gmgsoa 0.05 so 78 jos No fiber separation H2SO4 / MgSO4 40 54 56 9.5 940 H01 0.002 40 70 - No fiber separation CaCl2 0.05 40 54 4% 20 4320 \) '1 10 15 LN íï 7909674 ~ 9 'lll- before fi s. Table vIIl Catalyst Cooking time, Massaut- .KAPPA-_Viskosif _Polymerisa ~ , min. byte,% tal tet enl. degree of tions EXÉÉ E. TÄPPI salt 'H so ggenflis Hcl / Cacla 40 56 53 50 4600 H01 0.002 / CaCl2 55 58 5? 24 44 # O 'H01 0.004 / CaCl2 40 55 57 25 1420 .xclooluozä / Mgsoä ao 56 54 49,2 1540 'HNO5 0.004 45 48 50 4.0 470 Ca (NO5) 2 0, ¶O 45 58 62 29 4570 HN05 0.004 / 45 55 5? 25 1420 w I I : moi 0.002 / 45 56 59 25 4450 J / ïisüliï fl n j í- Agpflis HCl 0.002 / 25 58 20 25 4450 / CaCl 2, 0.05 In the above discussion and examples, they are reproduced so far best embodiments of the present invention. In the aftermath the following claims define the invention, but the invention take equivalents and modifications and the person skilled in the art can without to depart from the inventive idea or exceed the scope of the claims replace parts of the above description and embodiments against other parts and workforces.

Claims (5)

10 15 20 25 30 '5 7909674-9 Patent claims A method of digesting lignocellulosic plant material, wherein the material is boiled for a maximum of two hours at 130-210 ° C with a mixture of water and a low molecular weight aliphatic alcohol having not more than 3 carbon atoms, which mixture contains 1-4 volume units of said alcohol per unit volume of water. , a proton-generating metal salt and optionally a small amount of an acid-reacting substance, using at least 4 parts by weight of said cooking liquid on a part by weight of the lignocellulosic material, separating the cellulosic fibers released during cooking and evaporating the alcohol, then sugar and lignin are recovered from the liquid thus obtained, characterized in that it is used as a cooking liquid, the aqueous alcohol with a chloride or a nitrate of magnesium, calcium or barium, or with magnesium sulphate, or with a soluble mixture. thereof, and possibly as an acid-reacting substance a strong mineral acid, provided that a soluble mixture is thereby maintained. A method according to claim 1, in that methanol is used as the low molecular weight alcohol. 3. A method according to claim 1 or 2, in that hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid are used as strong mineral acid. 4. A method according to any one of the preceding claims, characterized in that an aqueous alcohol is used as the cooking liquid, in which the metal salts are present with a molarity between 0.001 and 1.0 and the strong mineral acid, where applicable, has a normality between 0.0005 and 0.008. 5. A process according to any one of the preceding claims, characterized in that, after separating the cellulose fibers from the remaining solution of lignocellulosic decomposition products, the alcohol is distilled off by expansion evaporation and the known residue is separated from the known - feel - as a powder precipitated lignin.