LU83990A1 - PROCESS FOR TREATING LIGNO-CELLULOSIC MATERIALS - Google Patents

Description

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The present invention relates to a process for the preparation of substituted cellulose or glucose from lignocellulosic materials.

It is known to prepare glucose from cellulose by hydrolysis.

Such methods are for example described - - in American patents 3,642,580 and 4,097,333, as well as in the published German patent application - 29 08 1991.

These known methods have the disadvantage, however, that the treated cellulose must be present in a relatively pure state and in a finely divided state (US Patent 3,642,580). In another method, a preliminary treatment with ethylene of the cellulosic materials has been proposed (American patent 4,097,333). Yet another method consists in dissolving the cellulosic material in Cadoxen after elimination of the hemicelluloses, which then, after separation of the lignin, is reprecipitated (German patent application published 29 08 1991).

The object of the invention is to propose a relatively simple and very economical process; putting to increase the reactivity of the cellulose! "* contained in lignocellulosic materials, so as to make cellulose accessible to degradation, hydrolytic degradation, on the one hand, and to reagents for manufacturing substituted derivatives of cellulose, d On the other hand, without the need to subject the lignocellulosic materials to a long, costly or energy-consuming pretreatment, as in the methods which are the subject of the publications cited above. J / 3 For this purpose, according to the invention, the lignocellulosic materials are first subjected to a selective degradation of lignin and hemicelluloses and then the cellulose thus made accessible is subjected to hydrolysis, in particular for form glucose, or be a substitution reaction, to form substituted cellulose.

Advantageously, according to the invention, the lignocellulosic materials are subjected to the aforementioned selective degradation in an oxidizing solvent so as to at least partially degrade the lignin and the hemicelluloses into soluble compounds, while maintaining the cellulose thus rendered accessible in solid state.

According to a preferred embodiment of the subject of the invention, a halogenated oxidizing solution, in particular a solution of hypochlorite and preferably of sodium hypochlorite, is used for the selective degradation.

20 Other details and particularities of the invention will emerge from the description given below,. By way of non-limiting examples, of some particular embodiments of the object of ‘the invention.

The process according to the invention relates to a treatment for controlled degradation of the lignin of cellulosic materials which makes it possible to make the cellulosic fraction accessible to chemical or biochemical reagents, so as to subject this cellulose to hydrolysis or substitution with a yield. high reaction without the need to subject these materials / lignocellulosigues beforehand to long, costly * / energy consuming pre-treatments. uf 1-; 4 ί

These lignocellulosic materials treated according to the invention have a lignin content which is generally between 10 and 50% by weight relative to the starting dry weight of these materials.

Thus, these ligno-cellulosic materials can be formed by particles of wood, "* straw, bagasse, ears of corn and / or industrial ligno-cellulosic waste.

These materials are advantageously in the form of solid particles whose dimensions are such that the cellulose remains protected by a lignin network and that the cellulose made accessible. After the above-mentioned selective degradation, exhibits properties limited swelling.

This makes it possible to use, for subsequent reactions, in particular hydrolysis or substitution, relatively large concentrations of the cellulose made accessible, which can vary between 2 and 20% by weight and preferably between 20 and 25% by weight. relative to the reaction volume used.

These crude lignocellulose materials are subjected to selective degradation of lignin I and hemicelluloses in an oxidizing solvent, so as to at least partially degrade lignin and hemicelluloses into soluble compounds, while maintaining the cellulose made accessible in solid state.

The fact that the particles used pre-sense an average thickness of between 0.01 mm to 10 mm allows a progressive attack of the lignin by the oxidizing agent. fJ / I '' \ 5

In this way, the lignin not yet attacked or partially attacked in fact plays a moderating role for the oxidizing agent with respect to the cellulose made accessible, so that the latter 5 undergoes practically no deterioration by the oxidizing agent. .

It therefore seems to be useful for obtaining maximum selectivity in the degradation of the lignin network not to eliminate, during this degradation treatment, partially guiding the degraded products originating from lignin.

The lignin network thus degraded can be extracted almost quantitatively in soluble form in aqueous solution. Slightly alkaline, between 50 15 and 100 ° C.

According to the invention, it has been found that alkaline hypochlorite and in particular sodium hypochlorite gives excellent results for the selective degradation of the lignin network, which protects 2o the cellulose fraction of ligno-cellulosic materials.

The concentration of sodium hypochlorite _2 used is generally between 10 and 4 M, and preferably between 0.3 and 0.5 M. (molar).

Advantageously, the pH of the medium, during the aforementioned selective degradation, is maintained at a value between 2 and 12 and preferably between 7 and 9, in particular of the order of 8.

The reaction temperature can be taken from 0 to 90 ° C and is generally room temperature, while the reaction time is generally between 5 and 500 minutes and / is preferably of the order of 30 to 60 minutes. / d 1- 6

In order to increase the homogeneity of the degradation, one can advantageously proceed in two successive stages, one of diffusion under conditions of low reactivity, eg low temperature and or extreme pH or pH 5, in particular pH lower than 3 or higher. at 11, the other attack step comprising an abrupt variation - of temperature or pH to make the medium reactive within the materials to be treated.

In order to minimize the consumption of oxidizing agent, this can be recycled after having separated the treated material.

Furthermore, the cellulose made accessible and separated from the oxidizing agent is in turn subjected to hydrolytic degradation by a bio-chemical or chemical agent, until in particular glucose is obtained.

This hydrolytic degradation in fact constitutes a process known per se. the biochemical agent used may for example be an immobilized or non-immobilized enzymatic complex, and in particular a cellololytic complex originating from a microorganism, such as for example trichoderma-viride, while, if a chemical agent is used, this can be an acid, a base or an oxidant.

Likewise, for the preparation of substituted cellulose derivatives from this cellulose made accessible by the process described above, use may also be made of known processes, such as the formation of ethers or 'esters, depending on the nature of the desired substitute.

The process according to the invention will be illustrated in a more concrete manner by the examples given below. /

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Example 1: Glucose formation from straw and wood by enzymatic hydrolysis.

1.5 g of a substrate formed by broken straw 5 are treated for 1 h, at ordinary temperature, in 25 ml of an aqueous solution of hypochlorite „_ and sodium chloride (" Bleach ") , at the approximate concentration of 6.10 ^ molar in hypochlorite.

Then, the remaining solid part of the substrate is subjected to two successive washes with water (50 ml), then is dried at 60 ° C.

In the next stage, 250 mg of the dried substrate, containing the cellulose made accessible, is subjected to enzymatic hydrolysis in a solution maintained at 45 ° C. and containing, as buffer, 10 ml of citrate. at a pH of 4.8, and 0.5 filtered paper units, (u pf), per ml of trichoderma-viride cellulase "onozuka".

This same treatment is then carried out on 1.5 g of substrate formed by sawdust ("soft wood", white fir).

The results obtained after 24 h and 72 h hydrolysis are given in the table below in which a comparison is made with straw and wood substrates which have not undergone prior selective degradation by means of the j qn hypochlorite solution. /) /,% 8 24 h 72 h glucose glucose -1, -1

g L g L

| straw 1 1.6 d 5 straw + hypccMatite 4.9 9.5 wood 1 1.5 wood + hypocKkxite 3.5 6.0 cellulose * 5.3 9.0 10 £ The last row of the table gives, for comparison, the yields in glucose obtained under the same hydrolysis conditions from pure cellu-j (not treated with hypochlorite).

15 Considering that the treated substrate has lost mainly lignin and / or hemicellu- | lose, it therefore contains + 60%, for a wood substrate, and + 65% for a straw, cellulose substrate, which would give a theoretical hydrolysis yield I, after selective degradation treatment , with respect to cellulose, the following results J: The theoretical yield of hydrolysis of the cellulose contained fj '* 25 in the sample.

| 24 h 72 h straw + hypochlorite + 33% + 64%! - j wood + hypochlorite + 25% + 45% i "pure cellulose" + 26% + 35% / \ - Ί / i 9

Example 2: Formation of a cellulose ester by the basic route starting from wood and straw.

1.5 g of straw were treated with 25 ml of an aqueous solution of hypochlorite and commercial sodium chloride ("bleach") for 1 h at ordinary tempecatize. The substrate thus treated was then filtered so as to retain, as solid product, a cellulosic material made accessible.

Then 5 ml of 18% NaOH was added which was allowed to react for 1 h at room temperature.

In a next stage, 0.8 ml of CS 4 was added and this reagent was allowed to react at ordinary temperature for about 16 h.

25 ml of water and 25 ml of 3% NaOH were then added so as to dissolve the xanthate obtained practically completely.

This was precipitated in sulfuric acid, washed three times in succession and dried.

2o This example was repeated with a substrate formed from sawdust.

The weight of regenerated cellulose obtained from the straw substrate was of the order of 42% and, from a wood substrate, of the order of 50% of the weight of the dry substrate before treatment.

Quantitative saccharifications have shown that it was a compound containing more than 95% of reducing sugars, of which more than 90% in the form of glucose. / y 10

Example 3: Formation of a cellulose ester by acid starting from wood and straw.

2 g of straw were treated with 30 ml of an aqueous solution of industrial hypochlorite ("bleach") for 1 h at ordinary temperature.

-, The solid residue was then filtered and rinsed with 50 ml of water.

Two experiments were carried out in parallel; in the first (A) the substrate thus treated was used as it is, in the second (B) the lignin was extracted for 1 h at 80 ° C. with 30 ml of NaOH 0 solution, 1 molar,. the substrate then being filtered and then rinsed with 50 ml of Ή20.

The substrates (A) and (B) were then activated 3 times by stirring in the presence of 20 ml of glacial acetic acid followed by filtration on a Büchner filter.

18 ml of glacial acetigue acid and 0.1 ml of concentrated 30 ^ 30 ^ were then added and the mixture was stirred for 1 hour. * 5 ml of acetigue anhydride were then added with vigorous stirring; allowed to react for 30 minutes.

v. "0.75 ml of H 2 O and 1.75 ml of acetic acid were then added and stirred for 30 minutes.

Then diluted with 30 ml of acetic acid used for activation.

It was reprecipitated dropwise in 2 l of vigorously stirred water, it was filtered and washed twice with 500 ml of water: the precipitate was taken up in 500 ml and it was neutralized until the color of the phenophta- / leine with dilute sodium carbonate. / Vf 11

The product was then filtered, dried and dissolved in 100 ml of a dichloromethane-methanol mixture (90-10 / W / W).

It was filtered again and in case (A) 5 it was observed that the formation of a gel which slowed down the filtration.

On the other hand, in case (B), almost all of the product. ^ was soluble and instantly filtered.

The solvent was evaporated on a rotary evaporator and dried in vacuo.

10 This example was repeated with the same amount of sawdust (white fir).

The weights recovered were 15 cases (A) case (B) straw 1.15 g 1.3 g wood 1.06 g 1.37 g 20

The maximum recovery, taking into account the amount of cellulose, present in the starting materials, and what the number of acetylation would be. ^ ‘Of the order of 2.8 to 3 per unit of glucose, which should be about 1.3 g for straw and 1.4 g for- / - -U. ^ 12

Example 4: Formation of a cellulose ether from straw and wood.

2 g of a sawdust substrate were reacted in 30 ml of an aqueous solution of industrial hypochlorite (“Bleach”) for 1 hour at ordinary temperature.

The solid reaction product obtained was then separated by filtration.

Then 7 ml of 18% NaOH was added and stirred for 1 h. at room temperature.

25 ml of isopropanol and 1 g of chloroacetric acid were then added.

The whole was brought to reflux for 3 h.

It was filtered and the precipitate was taken up in water and left for 30 minutes at 100 ° C.

Finally, by filtration, the carboxymethyl cellulose which was swollen was separated in the form of a colorless gel, the colored residues being eliminated in water.

The amount of carboxymethylcellulose obtained was 900 mg.

This example was repeated with the same amount of straw, which made it possible to obtain 650 mg of carboxymethylcellulose.

It is understood that the invention is not limited to the embodiments described and that many variants can be envisaged without departing from the scope of this patent.

/ 13 Thus the lignocellulosic materials used according to the invention can be very variable in nature.

Furthermore, any treatment of 5-ligno-cellulosic materials having undergone selective degradation according to the invention, even without. to go through a glucose isolation phase, involves a hydrolysis of cellulose, remains within the scope of this patent; this includes in particular the production of bacterial proteins; alcoholic or acetonbutyl fermentation, or the production by microorganisms of other molecules, such as amino acids, nucleic acids or organic acids. //

Claims (23)

1. Process for preparing substituted cellulose or glucose from lignocellulosic materials, characterized in that the materials are first subjected to a selective degradation of lignin and hemicelluloses and then subjected the cellulose thus made accessible to a - - hydrolyset in particular to form glucose, or to a substitution reaction, to form substituted cellulose. 2. Method according to claim 1, i characterized in that lignocellulosic materials are treated whose lignin content is between 10 and 50% by weight relative to the dry weight '' starting of these materials. 3. Method according to either of Claims 1 and 2, characterized in that lignocellulosic materials which are present are treated | in the form of solid particles, the dimensions of which are such that the cellulose is protected by a lignin network and that the cellulose made accessible after the above-mentioned selective degradation has limited swelling properties, i 4. Method according to any one of claims 1 to 3, characterized in that I treat lignocellulosic materials formed by: coarse particles of straw wood, bagasse, j: corn on the cob and / or lignocellulosic waste ,, / | industrial. ^ / ^ / i i; t 'i |; 5. Method according to any one of claims 1 to 4, characterized in that the lignocellulosic materials are subjected to the aforementioned selective degradation without prior physical, chemical or biochemical treatment. 6. Method according to any one * 4 of claims 1 to 5, characterized in that the lignocellulosic materials are subjected to a “selective degradation of lignin and hemi-j_q celluloses in an oxidizing solvent so as to at least partially degrade lignin and hemicelluloses into soluble compounds, while keeping the cellulose made accessible in the solid state. 7. Method according to claim 6, characterized in that a solution of an oxidizing halogen compound is used for selective degradation. 8. Method according to claim 7, characterized in that as the halogen compound 2o oxidizing hypochlorite, preferably sodium hypochlorite. 9. Method according to any one of claims 1 to 8, characterized in that * ^ * degrades at a temperature where the reagent remains liquid and preferably at ordinary temperature. 10. Method according to claim 8, characterized in that a concentration -2 / of hypochlorite between 10 and 4 molar, / 2q and preferably between 0.3 and 0.6 molar is used. / 1 / L'f 11. Method according to any one of claims 7 to 10, characterized in that one works, during the selective degradation, at a pH of between 12 and 2, and preferably between 9 and 7. 12. Method according to claim 11, characterized in that the pH is maintained at a value of the order of 8. -5 " 13. Method according to any one of the preceding claims, characterized in that the materials are subjected to selective degradation for a period of between 5 and 500 minutes, and preferably of the order of 30 to 60 minutes. : 14. Method according to any one of claims 6 to 13, characterized in that gu'on 15 recycles the oxidizing solvent after having separated the treated substrate. 15. Method according to any one of claims 1 to 13, characterized in that the lignin is extracted in water-soluble form guasi guantitati- vely in a weak alkaline aqueous medium between 50 and 100 ° C. 16. Process according to any one of Claims 1 to 15, characterized in that the [cellulose made accessible is subjected to the hydrolysis treatment at a concentration of between 2 and 30% by weight relative to the volume of the hydrolysis treatment solution. 17. A method according to any one of claims 1 to 16, characterized in that the cellu-lose made accessible is subjected to hydrolytic degradation by a biological, biocnamic or / chemical agent, until glucose is obtained. 5 * f 18. A method according to any one of claims 1 to 15, characterized in that the cellulose made accessible is subjected to a substitution reaction by the basic route: esterification or etherification, or by the acid route: esterification. 19. Method according to any one of claims 1 to 18, characterized in that one proceeds in at least two successive stages, one of diffusion, under conditions of low reactivity, in particular at ambient temperature and a pH value less than 3 or greater than 11, the other attack step comprising an abrupt change in temperature and / or pH to make · the reaction medium within the materials to be treated. 20. Process for the preparation of substituted cellulose or glucose from lignocellulosic materials, as described above. 21. Process for making cellulose from lignocellulosic materials accessible, characterized in that these materials are subjected to selective degradation of lignin and hemicelluloses in an oxidizing solvent, in particular halogen, such as hypo -sodium chlorite, so as to at least partially degrade the lignin and hemicelluloses into soluble compounds, while maintaining the cellulose thus made accessible in the solid state. 22 Method according to any one of claims 1 to 21, characterized in that, after the above-mentioned selective degradation, the lignin is extracted in soluble form in slightly alkaline aqueous solution. 23. Process for making cellulose of lrign materials accessible, such as described above. ______ / l'J- pcgOc cent _Λ ........ r-ç? card ..... 43, ...... r '' '~ description ... k ... - - - c ··; claims ...... GiEcriptif '! . ! -g d; ', / Λ