EP0082116A1 - Method for the delignification of wood and other lignocellulosic products - Google Patents

Abstract

A method for delignifying ligno-cellulosic materials and efficiently separate from each other the constituents thereof. Said materials which optionally may be prehydrolized are heated in an aqueous acid medium in the presence of phenol compounds whereby the ratio by weight of liquid to solid is at least 0,5. In the case of low liquid solid ratios i.e. below about 4:1 further aqueous liquid is added to the reaction mass after pulping to aid filtration and draining. After isolating the purified solid cellulose pulp, the liquid phase separates into two layers: an aqueous layer rich with pentoses and an organic layer rich with phenols and lignin, the latter providing, by distillation and pyrolysis of the residue, a quantity of phenols at least equal to that of the phenols used in the delignification stage.

Description

Technical area

The present invention relates to a process for delignifying wood and other lignocellulosic materials and, simultaneously, hydrolyzing the hemicellulose thereof to monomeric sugars in the presence of aqueous acid, of phenol or mixtures of phenols or other phenolic products. This invention relates to improvements made to a similar process which is the subject of a previously filed application, in particular European application No. 81810246.9. The present invention also relates to improvements in the field of the chemistry of wood constituents in general and, more particularly, the efficient separation and isolation of cellulose pulp, wood pentoses and lignin phenols.

Prior art

The use of phenol and other similar compounds comprising phenolic functions for extracting lignin from wood and thus obtaining cellulose which is sufficiently pure for the manufacture of paper for example, is already known. Thus, SCHWEERS (Chemtech 1974, 491; Applied Polymer Synposium 28, 277 (1975)) describes the use of a mixture of one part of sawdust, four parts of phenol, and 10% water acidified with 0.05 % HCl or 2% oxalic acid, this mixture being heated for 3 h at 160 - 170 ° C in an autoclave. Under these conditions, and after separation of the liquid phase, cellulose yields of the order of 40 to 60% are obtained relative to the weight of treated wood, this cellulose having a K index (Kappa) of the order of 40 to 100. This K index, used in the paper industry to define the quality of delignified cellulose, relates inter alia to the content of cellulose in lignin after delignification; this content is approximately equal to K x 0.15 (TAPPI T - 236 m - 60, 1960). In this method, it is also possible to use, instead of phenol, the pyrolysis product of phenol-lignin, the latter being the product which is formed by reaction of phenol with lignin during the delignification of wood by phenol ( German patent application DOS 2,229,673). This phenol-lignin, which is found mixed with a part of the starting phenol, is normally separated from the delignified cellulose by wringing and washing the latter with an organic solvent at the end of the delignification operation.

Furthermore, other phenolic products, such as the various xylenols, catechol, resorcinol, hydroquinone, naphthols and naphthalene-diols were used to delignify the wood at a rate of 2% relative to the latter. and heating (in aqueous medium, wood / water suspension 1/1) '90 min at 175 ° C, all followed by extraction with a dioxane-water mixture (WAYMAN and LORA, TAPPI 61 (6), 55 (1978) )). Under these conditions, cellulose yields of the order of 60% with a residual lignin level of 4.6% (use of β-naphthol) have been observed.

In addition, APRIL et al (TAPPI 62 (5), 83 (1979)) mention the heating to 205 ° C of sawdust from pine wood in the presence of 15 parts of a 1: 1 mixture of phenol-water, such treatment leading to a cellulose containing no more than 3% lignin. According to this reference, the yields of purified cellulose are of the order of 40%.

The processes forming part of the state of the art described above are, of course, technically interesting in the sense that they make it possible to get rid of the conventional conditions of delignification (Kraft process, sulfite process, etc.). which use sulfur compounds which are difficult to recycle after use and which are the source of serious sanitation problems. However, they are not free from certain defects, in particular the obligation to work at temperatures above 100 ° C and under pressure. Thus, such conditions can cause sealing and pressure maintenance problems in the reactors. In addition, as the hemicellulose of the plant can hydrolyze into pentoses during delignification, there may be decomposition of the pentoses released by the hydrolysis of hemicellulose into furfural and resinification thereof. There may also be a reaction between phenol and the lignin produced by delignification and the decomposition products of pentoses with the formation of solid resins, hence difficulties in recovering and recycling the phenolic solvents involved.

Also, an object of the present invention consists of a simple and economical means for separating with excellent yields the constituents of wood and other lignocellulosic materials, in particular, straw, bale, bark, dry leaves and other plant residues.

Another object of the invention is a process for delignifying the above-mentioned materials and providing an excellent quality cellulose pulp for the manufacture of cellulose solutions or a starting material for the production of glucose.

Another object of the invention is to produce industrially wood phenols with excellent yields and pentoses which can then be transformed into synthetic resins, fuels or other chemicals.

Another object of the invention is an effective means of recovering useful products from plant waste or wood which are normally burned or thrown in the sewer, which leads to undesirable pollution.

Other objects will appear during the rest of this description.

Statement of the invention

The method of the invention makes it possible to achieve the above aims, remedies the above-mentioned shortcomings and also provides other unexpected and surprising advantages as will be seen below. It is characterized by the fact that one part by weight of the lignocellulosic material is heated with at least 0.5 parts by weight of dilute aqueous acid whose pH does not exceed 1.5 and at least 0.4 part phenol or one or more other phenolic compounds. These phenolic compounds are those mentioned above and others to be defined below. The heating temperatures are in the range of reflux temperatures of the phenolic aqueous mixture at ordinary pressure or slightly below or beyond it, for example between about 90 and 110 ° C. The weight of the lignocellulosic material is counted on the basis of the dry matter, that is to say by subtracting the weight of natural moisture. Preferably, the liquid is stirred or moved so as to ensure good contact between it and the solid to be treated. When using relatively high liquid / solid ratios, it is advantageous to continuously percolate the liquid in the solid, which allows effective dissolution of the lignin and hydrolysis of the hemicellulose. In this case, the reflux effect of the liquid will provide the desired degree of contact. However, depending on the nature of the lignocellulosic material and when rather low liquid / solid ratios are used, for example in the range of 0.5 to about 2 or 4 parts of aqueous acid or aqueous acid and phenol dissolved by part of dry lignocellulosic material (or lignocellulosic material and undissolved phenol), good contact between the solid and liquid reagents can be ensured by kneading or preliminary kneading of them before heating them. Instead of putting the liquid in motion by boiling, it can be circulated in contact with the divided solid, for example by means of a closed-circuit pump. In addition, we work at reflux temperatures close to 100 ° at ordinary pressure (or slightly above or below), it is not necessary to have a pressure-resistant autoclave which, to the point of economic view is important.

The nature of the aqueous acid used is not critical, as long as it is a strong acid. Thus, mineral acids such as H ₂ SO ₄ , HCl, H ₃ PO ₄ are suitable, but sulfuric and hydrochloric acids are preferred. Strong organic acids can also be used if desired, such as, for example, oxalic, benzene sulfonic acids and other aromatic sulfonic acids, trichloroacetic acid, etc., i.e. general, highly water-soluble acids whose pH is less than 2. Preferably, HCl is used with a concentration of between 0.5 and 5%, preferably between 1 and 3%.

It should be noted that old references (German patents Nos DE-326.705 and 328.783 (1919)) mention the delignification of wood and other plants by phenol in the presence of acid catalysts. It is said in these references that such catalysts include mineral and organic acids and other acid reaction compounds under operating conditions such as AlCl ₃ , CuCl ₂ , SnCl ₄ , TiCl ₃ , nitrophenol, chlorophenol, etc. The quantities to be used of these catalysts are qualified as "more or less" in reference 328.783 without further information; in reference 326.705, it is said that the catalyst is a 0.01% HCl solution. On this subject, the present inventors have found that with an acid as diluted (pH greater than 2), it is not possible to effectively delignify a lignocellulosic material (at 100 ° C. and under ordinary pressure), as will see it later in the experimental part of this request. In addition, nowhere does it indicate in the references in question that it is possible, by working according to the recommended indications, to carry out the practically complete hydrolysis of the hemicellulose and to separate, from the delignified cellulose, a on the one hand, the sugars resulting from the hydrolysis of the hemicellulose of the starting product and, on the other hand, the phenols resulting from the decanposition of lignin. In fact, the references say rather than after recovery of the phenol involved by distillation of the liquid phase, there remains a residue which turns into infusible resin. This strongly demonstrates that furfural has formed and that it has reacted with the decomposition products of lignin, which is precisely to be avoided in the process of the present invention. Thus, on the contrary, a separation of these components is possible according to the invention under excellent cam conditions, as will be seen below.

There is also a reference (British patent application No. 2,036,826 A) which describes the delignification of lignocellulosic materials and their simultaneous conversion to sugars by hydrolysis in an acid catalyzed reaction and in the presence of organic solvents. However, this method requires high temperatures and pressures and, therefore, expensive equipment.

It should also be mentioned that, in the present invention, the use of HCl concentrations clearly greater than 5% by weight in the aqueous phase is either unnecessary or even harmful. Thus, if the reaction is carried out with more concentrated acid, for example at 10% HCl, undesirable effects may occur, such as partial decompositions, resinifications and yield losses. Also, such conditions will generally be avoided unless certain special effects are desired. With acids other than HC1, higher proportions are possible (due, for example, to a higher molecular weight). For example in the case of H ₃ PO ₄ , we can still admit a concentration of 10%.

As phenol and other phenolic compounds, it is possible to use, in addition to hydroxybenzene and most of the commercially available phenols, in particular the following compounds: p-cresol, o-cresol, guaiacol, 4-ethylphenol, 2,4-xylenol, 4-methylguaiacol , 4-ethylguaiacol, 2-ethylguaiacol, 4-vinylguaiacol, 4-prcpylguaiacol, eugenol, 1,3-dimethoxy-pyrogallol, vanillin, 1,3-dimethoxy-5-methylpyrogallol, trans-isoeugenol, catechol, phloroglucinol , homocatechol, etc. and any mixtures of these phenols where, also, mixtures of phenolic products resulting from the pyrolysis of phenolignin, the latter being, as already indicated above, the product of reaction between phenol (or other phenolic compounds) with degraded and dissolved lignin during the delignification of wood in the presence of phenol (or other phenols). In addition, it is advantageous to use, within the framework of the present process, in all or part of the phenolic materials, the phenol-lignin itself (provided that it is not too resinified by reaction with the thermal decomposition products of the pentoses from the hydrolysis of hemicellulose, for example, furfural). However, this is one of the unexpected advantages of the invention: at relatively low reflux temperatures, the hydrolysis of wood pentoses in dilute acid in the presence of phenol takes place with an exceptionally high yield and the pentoses which from it undergo only a minimum of decomposition into furfural or other products. It follows that the resinification of phenol-lignin is not very pronounced and that it can be reused several times, from cycle to cycle, without the efficiency of delignification being significantly reduced. This factor constitutes a considerable advantage compared to the prior art where, precisely, at the temperatures used, of the order of 160 ° C. or more, the phenol-lignin rapidly resins and thus loses its qualities of solvent. delignification. Note that when using phenol-lignin, we has the advantage of mixing it with phenol or other phenolic compounds.

Furthermore, the fact that the pentoses practically do not decompose is another advantage since, afterwards, they can be recovered for later use as will be seen below.

Finally, and therein lies one of the most striking and unexpected advantages of the invention, when we are dealing with a liquid / solid ratio of 4: 1 or more, it is in no way necessary, after separation of the purified cellulose by spinning at the end of a cycle, distilling the ligno-phenolic phase in order to recover the mixture of phenols to be used for the delignification of a new portion of sawdust; according to the present process, it suffices to isolate, on the one hand, the delignified cellulose by wringing and, on the other hand, all of the aqueous phase and the phenol-lignin containing the unreacted phenol, this set being directly reusable, after addition of a new portion of sawdust, for the following delignification operation: this sequence can continue until the aqueous phase reaches a high concentration of pentoses (up to values of the order of 200 g / 1). At this stage, it is obvious that the aqueous solution must be discarded in order to recover the dissolved pentoses; similarly, at this stage, the phenol-lignin phase mixed with the phenols is also to be ruled out, having lost its effectiveness as a delignification solvent by over-concentration and by contamination with the resinification products of the pentoses. However, and this is again one of the advantages of the invention, this ligno-phenolic phase can then provide, by distillation and pyrolysis, an exceptional yield of wood phenols (a mixture which is perfectly suitable for the use of the present process) which makes the invention autonomous, and even excess, in phenol and other phenolic compounds.

The invention therefore makes it possible to produce, under exceptional economic conditions and with excellent yields: cellulose of high degree of purity (even from lignocellulosic products with a high percentage of lignin), easily separable pentoses and usable for other purposes, and phenols, part of which is naturally recycled in the process and the rest can be treated by the usual means (distillation, extraction, etc.) to separate the various components for later use.

In the process of the present invention, the amount of acidulated water that is used relative to the lignocellulosic materials ground or in powder (wood in shavings or in sawdust, straws of wheat, rice, various chopped cereals, ears corn but ginned and, in general, all lignocellulosic vegetable matter dry or fresh) is not particularly critical provided that a good liquid / solid contact is ensured and that the quantity of water present is stoichiometrically sufficient to hydrolyze the pentosanes.

Thus, if the liquid / solid ratio is rather high, for example 2: 1 or more, the stirring or percolation effect provided by the boiling of the water-phenol mixture is sufficient to ensure good contact, continuously renewed , between solid and liquid. Thus, to guarantee good reflux, the proportion of water relative to the solid must be sufficient to provide a fluid medium, that is to say a suspension of said solid in water and acid. Generally 4 parts of aqueous liquid for one part of solid in suspension (by weight) is sufficient, but one can operate with more liquid if desired, for example from 5 to 50 parts of liquid; however, using very large volumes of liquid is impractical due to space issues.

It will be remembered that good solid / liquid contact can also be ensured by agitating the latter with an agitator or by circulating it continuously by a pump through a bed of divided solid material. If the liquid / solid ratio is rather low, i.e. less than 2: 1 or 3: 1, it is generally sufficient to mix the aqueous acid and the phenols with the plant material divided by kneading, for example in a paddle kneader or, more simply, by simultaneously penetrating the solid and the liquid into a tubular reactor by means of a screw and by slowly moving the intimate mixture of the solid and the liquid in the heating zone of the reactor. The solid / liquid mixture gradually reacts, contracts and acquires sufficient fluidity so that it can be extracted at the opposite end of the reactor by other means of displacement.

As regards the quantity of phenol or phenols for delignification, again this is not critical provided that enough is used to ensure good delignification of the wood. Thus, if 4 parts of phenol or the mixture of phenols are generally sufficient for 10 parts of divided lignocellulosic materials, more phenol can be used, if desired, i.e., 10, 20 or even 50 parts of phenol. Using a lot of phenol and a lot of acidic aqueous phase may, at first, seem advantageous because, then, we can recycle the liquid phase a greater number of times before removing it to extract the pentoses and useful phenols; however, this advantage is, in fact, quite illusory because, then, the quantity of solid matter relative to the total volume of the reaction medium being lower, the yield of each cycle will be all the more reduced and the overall yield useful after a certain number of cycles will not be essentially changed.

Consequently, in the general practice of the invention, it is preferred to use, for one part of the cellulosic materials in the divided state, from 1 to 6 parts of phenol and from 1 to 10 parts of dilute acid, for example HCl at 1.5 - 2% or aqueous H ₂ S0 ₄ at 3 - 6% by weight. It is also preferred that the water / phenol weight ratio is greater than 1 and, advantageously, of the order of 3: 2 or 2: 1.

In general, to implement the invention with liquid / solid ratios of the order of 2: 1 to 4: 1 or more, the mixture is mixed in a container (laboratory flask, glass or stainless steel reactor in industry) lignocellulosic material in divided form (for example, chips, shavings or sawdust) with dilute acid and phenol or mixture of phenols and the mixture is brought to the boil from 1 to 8 h. If desired, more sophisticated equipment can also be used as will be seen below. In general, 2 to 4 h of reflux are sufficient, which again constitutes an advantage of the invention compared to the prior art where the heating times (under pressure) are much longer. Once the reflux period has ended. the residual solid which is constituted by very pure cellulose (K being of the order of 30 to 100) is drained with a yield of the order of 80 to 90% relative to the theoretical yield of the sample of corrected cellulose like 100% and we have it wash with a little hot water, possibly alkalized with NaOH or KOH and / or a water-soluble solvent (for example, acetone or methanol) in order to remove practically all the phenol. Then we resume the liquid phase (dilute acid plus phenol plus phenol-lignin produced by delignification) and we recycle it with a new portion of sawdust. This recycling can then be repeated at least four times, the efficiency of delignification and the purity of the cellulose produced decreasing only slowly.

After a certain number of cycles, the aqueous phase rich in pentoses is separated from the lignophenolic phase by simple decantation. The pentoses are then extracted from the aqueous solution by the usual means or, if desired, this solution can be directly treated with heat, so as to transform the pentoses into furan carposés. This aqueous solution can also be subjected to fermentation (preparation of protein substances, alcohol, etc.), the phenol dissolved in this aqueous phase also being able to be recovered therefrom (for example by extraction and by distillation).

As for the liquid organic phase, it is first distilled, which makes it possible to recover a large quantity of pure phenol and a mixture of lignin phenols; then the indistinguishable residue is pyrolysed, which again provides phenols and a porous carbonaceous residue usable as fuel or as adsorbent carbon as well as volatile materials (gases) also combustible.

It should be mentioned that, at the end of the delignification operation of a charge of lignocellulosic material and after separation by decantation of the phenolic phase from the aqueous phase, bring the latter back into contact, hot, with cellulosic pulp delignified in order to complete the elimination of the rest of the phenols still adsorbed thereon. After such rinsing of the cellulose delignified by the aqueous phase, it is noted that the latter separates again upon cooling into two phases which can be isolated by decantation. Consequently, this "rinsing" can be repeated one or more times if desired each time with the aqueous phase from which part of the phenol has been removed. By this means, it is possible to reduce the total volume of solvents (or alkaline water) necessary for washing the cellulose at the end of the reaction and thus to increase the recovery rate of the phenols from the aqueous phase.

The modifications described above are mainly applicable when, according to the present process, the liquid / solid ratio exceeds a certain value (of the order of 2: 1 to approximately 4: 1) at which the solid disperses easily in the liquid and at which, when the reaction is finished, the liquid easily separates from the solid by the usual means, for example vacuum filtration or use of filter presses. When the liquid / solid ratio is less than such a value (in fact this value is not strictly fixed since it can naturally depend on factors such as the nature of the lignocellulosic material, the chopping techniques and the size and the surface condition of the particles), that is to say when the liquid / solid ratio is lower than that at which the solid disperses freely in the liquid and in the case where the liquid is rather in the " adsorbed "on the solid in particular, other handling techniques are preferably used. Thus, in such cases, the solid in particular is kneaded or kneaded together, the aqueous acid and the phenol (or phenols) by any usual means, for example a slow-running agitator, a kneader or the like and the pasty mass kneaded in a device suitable for the heating operation. Such a device can be a closed tube or a reactor. On an industrial scale, a screw device advantageously connected to a vertical tubular reactor is advantageously used. The material is introduced in divided form into the hopper of the screw device and the liquids are injected laterally into the conduit of the screw device, which allows an effective liquid / solid mixture during the movement of the materials towards the reactor. These materials are then gradually introduced continuously into the reactor through its upper end and the mixture is heated in the latter for the required time, for example from 0.5 to 2 hours in all, which causes its contraction and its partial fluidization. (by hydrolysis and delignification), the pasty mass collects at the bottom of the reactor from which it is removed by other usual means, for example a second screw conveyor.

On leaving the reactor, the pasty mass is subjected to treatments for separating the components of the lignocellulosic material (that is to say, cellulose, the monomeric sugars and the phenolic compounds) which are still mixed together but potential Lately split from each other (in the chemical sense) by the process described above. Such treatments include washes similar to the rinsing steps already described with regard to the portions of delignified cellulose. The pasty mass can be taken up with a suitable aqueous solvent to entrain soluble contaminants and separate them from the delignified cellulose. Cane such solvent, hot water saturated with phenol is suitable. Indeed, if the mass is treated with such a solvent and then spun on a filter for example, the liquid phase entails the phenolic constituents, the acid and the hydrolysis pentoses, this liquid phase then separating out an organic layer (phenol) and an aqueous layer (sugar solution) which can be decanted and which can then be processed. ted separately as described above. Of course, in cases where the liquid / solid ratio is rather low, the saturation of the phenolic solvent with phenol-lignin will occur rapidly (already after a normal operating cycle} and there is no need to provide for the restoration. direct play of the phenol-phenol-lignin mixture. Therefore, such cases relate rather to a continuous process according to which the material to be delignified as well as the other reagents are continuously introduced into the apparatus to be delignified, and harvested directly. the products formed with a view to their further purification.

• a) Tenpérature réactionnelle modérée, ce qui permet de travailler dans des récipients non scellés et pouvant fonctionner à la pression atmosphérique où légèrement en dessous et au-dessus de celle-ci.
• b) Excellente efficacité de dissolution des pentosanes dans la phase aqueuse (rendements de l'ordre de 98%) et possibilité inmédia- te de récupérer et utiliser les pentoses ainsi formés.
• c) Minime formation de produits de réaction phénol-lignine dissoute et dégradation très limitée des pentoses aux températures de travail et, partant, formation minimum de résines entre les phénols et ces produits de dégradation, d'où récupération aisée des phénols et même formation d'un excédent de ceux-ci.
• d) Séparation aisée des trois phases clé du procédé: phase solide, cellulose d'un haut degré de pureté; phase aqueuse riche en pentoses et phase ligno-phénolique dont, par distillation d'abord puis pyrolyse ensuite, on récupère une portion considérable de produits utiles.
• e) Mise en valeur complète des constituants du bois, les pertes étant maintenues à un minimum. Dans les procédés classiques, la lignine et les pentoses sont plus ou moins perdus.
• f) Qualité de la cellulose obtenue et excellent rendement de purification.
• g) Autonomie du procédé relativement aux matières premières. Après une première addition de phénol, la fabrication peut se poursuivre au moyen des phénols récupérés sans apport extérieur. De plus, énergétiquement parlant, le résidu charbonneux combustible ainsi que les volatils récupérés rend le procédé autonome qui ne comprend aucune étape d'évaporation et de concentration de grands volumes aqueux.
• h) Lorsqu'on utilise des rapports liquide/solide relativement élevés, le recyclage répété de la phase liquide pour délignifier plusieurs portions successives de matières ligno-cellulosiques fournit, après plusieurs cycles, une phase aqueuse dont la concentration en sucres est très élevée.
• i) La lignine non pyrolisée peut être utilisée directement can- me combustible (peu polluant car ne contenant ni soufre, ni minéraux), comme source de phénols ou comme matière première de résines poly- mériques.
• j) Possibilité de mettre en jeu une variété étendue de déchets ligno-cellulosiques (bois de qualités et d'essences diverses, matières herbacées, feuilles déchets de papeterie, bagasse, pailles, écorces, etc..) à l'état vert ou sec, l'eau nécessaire à la réaction étant facilement mesurée selon le degré d'humidité de la matière de départ. Ainsi, on peut utiliser aussi bien des cannes à sucre fraîchement extraites (bagasse verte) que des cannes à sucre après séchage (bagasse sèche), la quantité d'eau à ajouter dans le réacteur étant plus forte dans le second cas.

In summary, the present process has the following advantages over the state of the art:

• a) Moderate reaction temperature, which makes it possible to work in unsealed containers which can operate at atmospheric pressure or slightly below and above it.
• b) Excellent efficiency of dissolution of the pentosans in the aqueous phase (yields of the order of 98%) and immediate possibility of recovering and using the pentoses thus formed.
• c) Minimal formation of dissolved phenol-lignin reaction products and very limited degradation of pentoses at working temperatures and, consequently, minimum formation of resins between phenols and these degradation products, hence easy recovery of phenols and even formation of 'a surplus of these.
• d) Easy separation of the three key phases of the process: solid phase, cellulose of a high degree of purity; aqueous phase rich in pentoses and ligno-phenolic phase from which, by distillation first and then pyrolysis, a considerable portion of useful products is recovered.
• e) Complete development of wood constituents, losses being kept to a minimum. In conventional processes, lignin and pentoses are more or less lost.
• f) Quality of the cellulose obtained and excellent purification yield.
• g) Autonomy of the process relative to raw materials. After a first addition of phenol, the production can continue using the phenols recovered without external input. In addition, energetically speaking, the combustible carbon residue as well as the volatiles recovered makes the process autonomous which does not include any stage of evaporation and concentration of large aqueous volumes.
• h) When relatively high liquid / solid ratios are used, the repeated recycling of the liquid phase to delignify several successive portions of lignocellulosic materials provides, after several cycles, an aqueous phase whose sugar concentration is very high.
• i) Non-pyrolized lignin can be used directly as a fuel (low polluting because it contains no sulfur or minerals), as a source of phenols or as a raw material for polymer resins.
• j) Possibility of bringing into play a wide variety of lignocellulosic waste (wood of various qualities and essences, herbaceous materials, leaves stationery waste, bagasse, straw, bark, etc.) in a green or dry state , the water necessary for the reaction being easily measured according to the degree of humidity of the starting material. Thus, it is possible to use both freshly extracted sugar canes (green bagasse) as well as sugar canes after drying (dry bagasse), the amount of water to be added to the reactor being greater in the second case.

We will also mention, as a general context, certain references whose object is more or less related to the invention. Patent USP 3,776,897 relates to the addition of an organic solvent to a sulphite liquor for the delignification of wood after acidification thereof; it results first from the separation of

hemicellulose and then the separation of an aqueous solution ¹ e sugars and an organic phase containing lignin. Although we can see certain analogies between this separation process and the implementation of the present invention, this prior art cannot make the invention obvious. Indeed, the selective extraction of the components of a mixture by an operation of separation into two immiscible liquids is generally known in the chemical industry and, in this context, the reference teaches nothing more than a textbook of experimental chemistry. Thus, the general field to which the reference relates, that is to say that of alkaline sulfite liquors which must be acidified beforehand and the negligible degree of hydrolysis of pentosans, etc., does not provide specialists with the information likely to lead to the present invention.

French patent No. 1,430,458 provides a teaching very close to that of the US patent mentioned above and does not allow either to carry out the process of the invention. There is also a third reference, the British patent GB 341,861 according to which the evaporation residues of alkaline digestion solutions of lignocellulose are distilled at 300 ° C. Such residues, rich in pentosans and poor in lignin (see page 1, lines 60 - 85) provide, by distillation, mixtures of acids, hydrocarbons, phenols, furfural and various gases, such a result not appearing not much different from that of dry distillation of wood (except methanol). Finally, a last reference (TAPPI 52, 486 - 488 (1969)) deals with the conversion to furfural of the residual pentoses drawn from a sulphite liquor for the delignification of wood. It does not seem that one can find in this reference any information usable by analogy to carry out the present invention.

The following examples illustrate the invention in detail.

Example 1

In a 250 ml pyrex flask equipped with a condenser, 10 g of beech sawdust at 10% humidity (containing 17.25% of pentosans, 53.6% of cellulose, 27.4% of lignin and 1.2% ash), 40 g of phenol and 60 ml of 1.85% aqueous HCl (pH 0.3). We boiled for 4 h at reflux after which the solid fibers were wrung on büchner and washed with hot water and acetone on büchner; yield 4 g, 78%, Kappa = 40; lignin level = 6% (analysis by TAPPI T 122 OS-74 method).

After cooling, the liquid phase originating from the filtration of the cellulose separated into two phases which were isolated by decantation by means of a tap funnel. The upper aqueous phase, analyzed by the method of LISOV & YAROTSKII (IZVEST. AKAD NAUK SSSR, Ser, Khim. (4), 877-88 (1974) contained 1.47 g (85%) of pentoses and 0.43 g (8%) of hexoses accompanied by a small amount of dissolved phenol. The heavier organic phase (42 g) contained the bulk of the phenol, and in solution therein, the phenol-lignin produced by the wood delignification. A significant amount of phenol was also recovered in the cellulose washing waters.

Example 2

In a 2 liter flask equipped as described in Example 1, 100 g of beech sawdust (see composition in Example 1), 400 g of phenol and 600 ml of 1.85% aqueous HCl were placed. After 4 h of boiling, it was drained on a büchner and washed with hot 1.85% HCl until a filtrate weighing a total of 1000 g was obtained. A sample of this filtrate was taken for analysis, then the above procedure was repeated using again 100 g of sawdust and the 1000 g of filtrate mentioned above. The above operation was then repeated twice more, still with fresh portions of 100 g of sawdust and, as in the liquid phase, the filtrate from the previous operation. Samples were taken for analysis each time. The results are recorded in Table I below with, including, the results of analysis of the portions of delignified cellulose obtained.

After the last operation, the liquid was separated as in Example 1 into its aqueous phase and its organic phase. The aqueous phase was extracted with toluene against the current and the extracts, after evaporation of the solvent, added to the organic layer. The aqueous phase contained about 60 g of pentoses. By steam distillation of this aqueous phase, these pentoses were transformed into furfural.

The combined organic phases (approximately 490 g) were distilled (73 ° C / 13 Torr) which provided 323 g of phenol (approximately 67%), the remainder consisting of a mixture of wood phenols and partially degraded lignin which was shown by NMR analysis.

The undistilled residue was then pyrolyzed under nitrogen at 450 ° C. which provided 111.6 g (68% of the residue) of an anhydrous mixture of phenol (62.4%) and phenolic compounds (37.6% ) which was subjected to gas phase chranatography (see SCHWEERS & RECHY, PAPIER, 26 (10a), 585 (1972)) which made it possible to identify a certain number of typical phenols resulting from the degradation of lignin wood, for example, guaiacol, cresols, methyl- and ethyl- guaiacols, etc.

The residue from the pyrolysis (51.3 g, 30.7%) consisted of porous carbon residue and the difference to make 100% was due to the departure of non-condensable gases.

Example 3

We proceeded exactly as in the previous Examples using 5 g of sawdust, 30 ml of 1.85% aqueous HCl and 20 g of the mixture of phenols obtained by pyrolysis in Example 2. We thus obtained 2 g cellulose, K = 33; 5% lignin. The aqueous phase contained 0.85 g, 98.6% of the theoretical amount of pentoses based on the hemicellulose content of the sawdust used, 0.24 g, 9% hexoses and 1 g of phenol. The organic phase (21 g) contained 8.3 g of phenol separated by distillation.

A comparative test was carried out by subjecting 10 g of sawdust to 4 h of hydrolysis in 100 ml of HCl at 1.85% but without phenol. In this case, the yield of pentoses was only about 70%, which shows, and this is a surprising and unexpected effect, that the phenols promote the hydrolysis of hemicellulose in lignocellulosic materials at the same time. time they carry out the delignification of these.

Example 4

100 g of the mixture of phenols as obtained by pyrolysis in Example 2 and 123 g of formaldehyde in 37% aqueous solution were introduced into a 500 ml flask equipped with a condenser and a stirrer. An additional 4.7 g of Ba (OH) ₂ .8H ₂ O was added and the mixture was stirred for 2 h at 70 ° C. Was then acidified to pH 6-7 with 10% H ₂ SO ₄ and concentrated under reduced pressure at a temperature not exceeding 70 ° C until a viscous mass was obtained. This mass constitutes a “RESOL” type resin at the “A” stage of polymerization. It is used, for example, for the manufacture of laminates, adhesives for agglomerates and thermosetting varnishes according to the usual means.

Example 5 Study of operational parameters

In order to better understand the influence of operational parameters such as temperature, reaction time, acid concentration, phenol / solid ratio, we undertook a series of tests with samples of 30 g (1 part) of dry bagasse (average composition: cellulose 40.2%; hemicellulose 25.6%; lignin 22.2%; extractable 7.24%; ash 4.76%) which have been treated with different mixtures of phenol and acidified water , at different temperatures and for different times. Then the delignified paste was separated by wringing and extracted with 5% aqueous caustic soda so as to remove all of the phenol adsorbed in the form of alkaline phenolate (then the phenolate was acidified so that the phenol separated and this second crop of phenol was added to the first crop obtained in the wringing liquid). In addition to determining the weight of the purified cellulose pulp and its residual lignin content, the content of the aqueous phase in Ce and C ₆ sugars (pentoses and hexoses) was measured.

For the analyzes, the procedure was as follows: for phenol in water, it was converted into tribromophenol by bromine at pH 0-1 followed by reverse titration of the excess bromine by thiosulfate in the presence of KI. The analysis was also carried out by VPC (DC 550 column, silicone oil; column temperature: 147 ° C; flame ionization detector; injector temperatures: 190 ° C; carrier gas: nitrogen at the rate 60 ml / min). HPLC (High Performance Liquid Chranatography) analysis was also used (column C-18 RP-WATERS-Bondapack 10 u; solvent: acetone / water 40/60 at 1 ml / min; detection at À = 254 mu; internal standard: acetcphenone).

The sugars from hydrolysis in the aqueous phase and the washing fractions were analyzed by the o-toluidine method. The results of these analyzes are given in the Tables which follow.

The operating parameters used in the tests described as well as the results are shown in Tables II to IV below. In these Tables, the column entitled "separate solids" (parts in weight) refers to the sum of the isolated cellulose, undissolved lignin, ash and other insoluble impurities. The% by weight of the lignin of this cellulose is in the following column. The figures concerning the sugars released by hydrolysis are given in% compared to the theoretical value (100%) represented by the cellulose and hemicellulose content of the initial sample.

The figures in Table II indicate that an extension of the reaction time improves the dissolution of lignin and the hydrolysis of pentosans. The amount of dissolved C ₆ sugars hardly changes. The results at 100 ° C are better than at 90 ° C.

The figures in Table III indicate that, apart from a slight variation in the level of lignin in cellulose, the decrease in the level of phenol used for delignification is of little importance.

The data in Table IV show that low concentrations of acid, such as those disclosed by HARTMUTH (German patent 326,705) are not suitable for carrying out the invention under the chosen conditions, i.e. boiling at ordinary pressure . Too much acid is also harmful both for the production of pentoses and phenol.

Example 6

This exenple will be better understood if reference is made to the appended drawing which schematically represents a pilot apparatus for the delignification of chopped plant products according to the invention.

The apparatus shown comprises a reactor 1 filled with particulate plant material up to the level of a screen 2 for retaining the solid but which lets the delignification liquid pass. Via a valve 3, the bottom of the reactor communicates with a tank 4 of the delignification solution. By means of a pump 7, this solution is circulated from the bottom of the tank 4 to the upper part of the reactor 1 by means of the valves 5 and 6. From there, the liquid comes into contact with the particles of the plant material thus effecting continuous leaching of these. The reactor 1 comprises a reflux condenser 8 and the reservoir 4 comprises a condenser 9. The apparatus also comprises two heating mantles 10 and 11 with circulation of liquid for the reactor and the reservoir, respectively; the heating liquid (oil or any liquid) is circulated by a pump and heated by a heating element 13 thermostatically controlled. A bypass valve 14 is placed between the pump 7 and the valve 6 to allow the flow rate of the delignification liquid to be controlled so as to maintain the liquid at gentle boiling in the reactor 1.

• 1er lavage: On a remis 500 ml d'eau dans le circuit et on l'a mis en circulation 2,5 h à 100°C. Puis on a évacué cette eau sous léger vide et on l'a mise en réserve aux fins d'analyse.
• 2ème lavage (à l'alcali): On a fait circuler à nouveau 2 h à travers le lit de fibres une solution de 10 g d'hydroxyde de sodium dans 500 ml d'eau à 40° (température maximum). On a évacué cette solution sous pression légèrement réduite et on l'a acidifiée à pH 5 avec du HCl. On a soumis cette solution à l'analyse du phénol.
• 3ème lavage (à l'acide): Q1 a retiré la pâte cellulosique du réacteur et, sur un entonnoir de büchner, on l'a lavée par petites portions d'eau acidulée à pH 4 de manière à éliminer toute trace d'alcalinité (total de la solution de lavage: 2 1). On a essoré la pâte de cellulose par centrifugation dans un panier jusqu'à un taux d'humidité résiduelle de 50 - 60%. On a prélevé un aliquot de cette fibre et on l'a séchée pour déterminer le rendement total: trouvé 29 g de fibre de bagasse.

The operation of the device goes without saying for the skilled person from the above description and the drawing. Other comments are therefore superfluous and it suffices to give the operating parameters of the present Example: in a reactor 1 whose double jacket 10 has an inside diameter of 40 mm and a length of 370 mm, 67 g of chopped bagasse have been packed at 10% humidity (60.3 g dry bagasse). This reactor is connected at the top to a water-cooled refrigerant 8. The bottom of the column was connected to the thermostatically controlled tank 4 containing the required quantity of acidified aqueous phenol for delignification, ie 400 g of phenol (purity 99.5%) and 600 ml of 1.85% aqueous HCl. The aqueous phenol was heated to 100 °, the temperature at which the dissolution of phenol in water is complete and the phase is homogeneous. This phase was put into circulation by means of the Teflon recirculation ponpone 7. The flow of liquid was adjusted so as to maintain the level at an adequate value above the fixed bed of bagasse by means of the valve. bypass 14; by this, the liquid circulating in the circuit has also been made homogeneous. The circulating liquid was kept for 3 hours after equilibration of the temperature at 100 ° C. In the fixed bagasse bed, the liquid was kept slightly boiling by raising the temperature of the thermostatically controlled heating oil to 120 ° C. After the end of the reaction, the pump was stopped and the liquid was drained by gravity during cooling. The liquid was collected and cooled in the tank 4. Then the organic layer (main organic phase) was separated from the aqueous layer by decantation. The aqueous layer, after separation of the first jet of organic substances, was recirculated for 3 hours at 100 ° through the bed of bagasse dough. By this treatment, an excess of phenol which was retained by the fiber was separated. The liquid phase (main aqueous phase) was cooled to room temperature so that it again separated into two layers. The new organic layer was decanted again (second stream of phenol) from the aqueous layer and combined with the first stream. Then the cellulose remaining in the reactor was washed 1 carme follows:

• 1st wash: 500 ml of water were put back into the circuit and it was put into circulation for 2.5 h at 100 ° C. This water was then removed under slight vacuum and placed in reserve for analysis.
• 2nd wash (with alkali): A solution of 10 g of sodium hydroxide in 500 ml of water at 40 ° (maximum temperature) was circulated again for 2 hours through the fiber bed. This solution was drained under slightly reduced pressure and acidified to pH 5 with HCl. This solution was subjected to phenol analysis.
• 3rd wash (with acid): Q1 removed the cellulose pulp from the reactor and, on a büchner funnel, it was washed with small portions of acidulated water at pH 4 so as to remove all traces of alkalinity ( total washing solution: 2 1). The cellulose pulp was drained by centrifugation in a basket to a residual moisture level of 50-60%. An aliquot of this fiber was removed and dried to determine the total yield: found 29 g of bagasse fiber.

In the reaction, 67 g of bagasse (60.3 g in the dry state), 400 g of phenol, 600 ml of 1.85% aqueous HCl were therefore used. The total of the components is therefore approximately 1067 g.

After the reaction and before recirculation, 472 g of main aqueous phase, 294.5 g of main organic phase and approximately 300 g of wet paste were recovered, which, in total, corresponds closely to the above values. After the 3 h of recirculation, re-extraction of the fiber and the union of the organic layers, the respective weights were: main aqueous phase 377.5 g (analysis, 7.2% of phenol = 27.2 g of phenol); combined organic phases: 424 g (analysis, 71.6% = 303.94 g of phenol); first wash water: 466.3 g (analysis, 7.45 = 34.74 g of phenol); second alkaline wash: 611 g (analysis, 4.65 = 28.4 g of phenol); third acid wash: 2006 g (analysis, negligible phenol content). Thus, the total of the phenol in these various fractions is 393 g, which corresponds to almost all of the phenol involved.

The fiber recovered (29 g = 48% of the dry bagasse) had a number K = 13, which corresponds to 2.7% of residual lignin. Aliquots of this fiber were hydrolyzed in 40% HCl and, by analysis of the resulting dilute solutions, the sample was found to contain 78.75% cellulose (by analysis of C ₆ sugars) and 3.5% hemicellulose (from analysis of C ₅ sugars). The difference, 17.75%, is due to residual lignin, ash and other insoluble components.

100 g of the organic phase were distilled under reduced pressure (containing, in principle, 28.3 g of substances other than free phenol), which gave 97 g of wet phenol plus a residue of 3 g wet lignin. It has been deduced therefrom (referring to the total of the organic phase) that the total lignin content thereof is 10.6 g.

Example 7 Delignification of wood with oxalic acid in place of HC1.

We used: 20 g of birch sawdust (22.2 g in the wet state), 80 g of phenol, 100 ml of a 0.5 N solution of oxalic acid (22.5 g / 1), 100 ml of water. 4.5 hours were heated to 100 ° C.

After cooling and filtering off the liquid, the fiber was washed on the filter with several portions of hot water. A total of 2 L of aqueous phase was recovered. The organic phase was 0.055 1. The yield of monomeric sugars in the liquid was: pentoses (C ₅ ): 31.55%, hexoses (C ₆ ): 15.12%.

The washed and dried fiber weighed 15.5 g. Its K index was 87.45, which corresponds to a residual lignin level of 13.11% (2.03 g). The weight of lignin initially present was 4 g; as a result, 50% of this starting lignin has been dissolved.

Example 8

20 g of dry bagasse were boiled for 4 h at 100 ° with 80 g of vanillin and 120 g of 1.85% aqueous HCl. It was filtered hot on a buchner and the solid was washed with 600 ml of boiling water (in portions) and 200 ml of 1% aqueous NaOH solution and then again with water until neutral. The yield of delignified fiber was 8.9 g (dry); K = 20 (3% lignin). After standing, the liquid separated into two layers; the organic phase was removed and distilled so as to recover the vanillin. In the aqueous phase were found 92% of pentoses compared to the theory and 12% of hexoses (coming from the hydrolysis of cellulose).

Example 9

The procedure of Example 8 was repeated but using 100 g of a 1: 1: 1 mixture of o-, p- and m-cresols and 150 ml of 1.85% aqueous HCl. After washing as above, the aqueous phase gave 96% of C ₅ sugars and 15% of C ₆ sugars; the cresols were recovered by distillation of the organic phase. Pyrolysis of the residue produced a crop of wood phenols. Dry fiber yield 8.1 g; K = 18.7 (2.8% lignin).

Example 10

60 g of chopped bagasse (weight calculated on the basis of the dry product), 84 g of phenol and 126 g of 1.85% aqueous HCl were kneaded together until the solid was completely impregnated with. the liquid. Then the wet material was divided into 4 parts, each of which was introduced into a 100 ml glass tube closed with a stopper. These tubes were heated for different times (see below) without stirring, then after cooling, the reaction mass was treated as in the previous examples in order to separate the constituents. The results concerning the yields of delignified cellulose and the residual lignin thereof appear in Table V. The tests were carried out twice and the results are an average.

The above results show that prolonged heating does not provide a noticeable improvement.

Example 11

111 g (100 g completely dry) of dehumidified bagasse were placed in a rotary evaporator (ROTAVAPOR) with 160 g of phenol and 240 g of 1.85% aqueous HCl. The evaporator was run 30 min at room temperature to ensure good mixing, then heated to reflux (105 ° bath). 4 independent tests were carried out summarized in Table VI below.

Example 12

Tests similar to those of Example 10 were carried out using 42.5 g of birch chips (38.25 g dry), 53.55 g of phenol and 80.32 g of 1.85 aqueous HCl %. Four samples were heated for different times. The results are reported in Table VII.

Example 13

Four tests identical to those of Example 11 were carried out using 110 g portions of birch chips with the addition of 80 g of phenol and 120 g of 1.85% aqueous HCl (sample A) or addition of 160 g of phenol and 240 g of 1.85% HCl (sample B). The heating periods were: 20 min of preheating until reflux, then 2 and 4 h at reflux. After cooling, the fiber was washed with boiling water, hot dilute NaOH and water again.

The results are shown in Table VIII.

These results show no significant differences except with regard to the quantity of cellulose transformed into hexoses which increases with the proportions of acid and of phenol used.

Example 14

A mixture of 111 g of chopped bagasse (100 g in a perfectly dry state), 160 g of phenol and 240 g of 1N aqueous sulfuric acid (4.625% by weight) was brought to reflux in a rotary evaporator for 1 hour. Then filtered and drained, which gave a liquid which separated into two layers (80 ml of organic layer and 75 ml of aqueous layer). The fiber was washed on the filter with several portions of boiling water and then with a 1N NaOH solution. The washing waters were combined with the aqueous phase (75 ml). The solid, dried, weighed 42.9 g.

• Fractions aqueuses combinées: C₅, 60%; C6, 9%; lignine, -.
• Phase organique: C₅, 20%; C₆, 1%; lignine, 88%.
• Fibre sèche: C₅, 20%; C₆, 90%; lignine, 12%.

The lignin and the sugars were analyzed in the above fractions and the following results were obtained (the distribution of the sugars is given in% of the theoretical amount contained in the bagasse):

• Combined aqueous fractions: C ₅ , 60%; C6.9%; lignin, -.
• Organic phase: C ₅ , 20%; C _6.1 %; lignin, 88%.
• Dry fiber: C ₅ , 20%; C ₆ , 90%; lignin, 12%.

The 80 ml of the organic phase were boiled for 1 hour with 80 ml of the combined washing water fraction and, after cooling and separation of the phases, it was found by analysis that 80% of sugars originally retained in the organic phase had passed in aqueous solution. Thus, the yield of pentoses (dissolved in the aqueous phase) was 76%. The other analytical results showed that 88% of the lignin in the sample had been dissolved, the level of residual lignin in the fiber being 6.3%.

Example 15

Was refluxed for 1 hour, with 160 g of phenol and 240 g of 1.85% aqueous HCl, 110 g of raw bagasse (100 g in the perfectly dry state) having the following composition in% by weight: pentosanes 25.6; cellulose 40.2; lignin 25.8; SiO ₂ plus extractable in water and extractable by organic solvents 12. It was filtered on a filter, which provided a mass C of fibers and a filtrate separating into two layers at rest: an aqueous phase and a phase organic AP. The aqueous phase was decanted and the solid C was washed on the filter with it; then the C fiber was strongly pressed and, after standing, the total of the liquids expelled again separated into an aqueous phase BW and an organic phase BP which was added to AP. Then we washed again C with hot water and wrung well by pressing. Wash liquid D was collected and analyzed for its content of phenol, sugars, acid and other dissolved substances. Similar analyzes were made on the other fractions: BW, AP + BP and fiber C. The results are shown in Table IX.

Example 16

The same type of tests was carried out as those of Example 15 using 150 g of birch chips (135.6 g dry, having the following composition in% by weight: pentosans 23.4 (potential pentoses 26, 6); cellulose 40.0 (potential hexoses 44.44); lignin 20.33; uronic acids 8.98; acetyl groups 3.6; extractable in water and in organic medium 3.6); 217 g of phenol and 325 g of 1.85% HCl. We carried 4 hours at reflux instead of one hour as in Example 15, all the other working conditions being the same as in this Example. Details and results are shown in Table X.

Example 17

The process of the present invention was also carried out using pheydrolysed lignocellulosic materials instead of raw lignocellulosic materials. This prehydrolysis is carried out by bringing to the boil a mixture of wood chips or other materials in the divided state and aqueous HCl or H ₂ SO ₄ diluted according to the usual technique. During the prehydrolysis in this dilute acid (for example 1 to 5% by weight in the solution), part of the pentosans is converted into pentoses which dissolve in the prehydrolysis solution. Then, afterwards, the process according to the invention was carried out, either by removing all or part of the prehydrolysis solution and replacing it with the appropriate quantity of dilute acid and phenol according to the conditions described above, or by leaving in the presence of the prehydrolysis solution and adding the required amount of phenol and adjusting the pH (by adding more water or acid depending on the concentration of the prehydrolysis solution) so as to obtain the desired acid ratios and phenol suitable for the present delignification solution. The main advantage of this variant comprising a prehydrolysis preceding the implementation of the invention consists in a better subsequent recovery of the phenol involved; it is also not known exactly why such conditions improve this recovery of phenol. Another advantage is the shortening in certain cases of the time necessary for the delignification of the specimens of pre-hydrolysed lignocellulosic materials. When the prehydrolysis solution is separated beforehand before implementing the method according to the invention, it can either be treated separately to remove the dissolved pentoses, or it can be combined with the aqueous phase resulting from the delignification in order to a global sugar recovery treatment.

100 g (on a dry matter basis) of red oak shavings having the following composition in% by weight were used: pentosans 18 (potential pentoses 20.5); cellulose 39.9 (potential glucose 44.33); lignin 22.2; uronic acids 3.2; acetyl groups 5; ashes, indeterminate substances and substances extractable from water and solvents, organic 11.68. We boiled this material 2 h in 1 1 of H ₂ SO ₄ at 4%. The solid was then separated and boiled for 2 h with a mixture of 240 g of 1.85% aqueous HCl and 160 g of phenol. After cooling, 1 l of acetone was added, filtered and the solid was washed with acetone; then this solid was extracted for several hours in a soxhlet. All the aqueous and acetone liquors were combined and analyzed to determine the amount of phenol recovered. The amount of phenol not recovered amounted to only 3 - 3.5 g (approximately 2%). During a control test (without a prehydrolysis step), the quantity of phenol not recovered was approximately 4%. Furthermore, in the test, the amount of residual lignin in the delignified fiber was only 2.3% by weight, while this figure was 4.8% in the case of the control tests.

Example 18

1.5 h 107 g of wheat straw (100 g dry) were boiled with 240 g of phenol and 360 g of 1.85% HCl. The crude product had the following analysis (% by weight): Pentosanes 24.58; cellulose 41.55: lignin 17.26; uronic acids 0.89; acetyls 5.54; SiO ₂ 2.37; extractable in water and extractable in organic medium 5.65. The subsequent separation steps were carried out exactly as in Examples 15 and 16 and the results are reported in Table XI. The figures are in grams.

Claims (16)

1. Process for delignifying wood or other lignocellulosic materials and simultaneously hydrolyzing the hemicellulose thereof to corresponding pentoses, according to which this wood or other lignocellulosic materials are heated with an aqueous acidic solution of phenol or other phenolic compounds and finally, the delignified cellulose is separated from said aqueous acidic phenol solution, characterized in that 1 part by weight of said lignocellulosic material is used, at least 0.5 part by weight of aqueous acid. diluted to pH less than 1.5, at least 0.4 part by weight of phenol or other phenolic compounds; and heated under ordinary pressure to the reflux temperature of the aqueous mixture. 2. Method according to claim 1, characterized in that the acid is chosen from HCl, H ₂ SO ₄ , H ₃ PO ₄ , strong organic acids, oxalic acid, benzene sulfonic acid, acid trichloroacetic and other alkyl and aryl sulfonic acids and mixtures of these acids. 3. Method according to claim 2, characterized in that the acid is aqueous hydrochloric acid or aqueous sulfuric acid. 4. Method according to claim 3, characterized in that the concentration of HC1 is 1 to 3% by weight and that of H ₂ SO ₄ 3 to 6% by weight. 5. Method according to claim 1, characterized in that the other phenolic compounds consist of a mixture of phenols provided by pyrolytic distillation of the lignin fraction from said delignification. 6. Method according to claim 1, characterized in that the phenolic compounds comprise the phenol-lignin produced during said delignification in mixture with hydroxybenzene and / or the phenols supplied by the pyrolytic distillation of the lignin fraction from delignification. 7. The method of claim 1, wherein the weight ratio liquid reagents / solid reactants is higher than the range of about 2: 1 to 4: 1, characterized in that after o After heating, the delignified cellulose is separated by filtration and spinning, which provides a filtrate which resolves in two distinct phases, that is to say an aqueous phase containing dissolved pentoses resulting from the hydrolysis of hemicellulose from starting material subjected to delignification and an organic phase consisting of the major part of the phenol or other phenolic compounds used and containing dissolved phenol-lignin originating from the delignification, then these two distinct phases are separated. 8. The method of claim 1 wherein the weight ratio liquid reagents / solid reagents is less than the range 2: 1 to 4: 1, characterized in that after heating the reaction mass, a surplus of aqueous liquid thereto so as to improve filtration and spinning, and separating the delignified cellulose from the liquid reagents according to claim 7. 9. Method according to claim 8, characterized in that the excess aqueous liquid is hot water saturated with phenol. 10. Method according to claim 7, characterized in that the pentoses are separated from the aqueous phase by concentration, crystallization and isolation or by heating it to transform these pentoses into furfural and by isolating this furfural. 11. Method according to claim 7, characterized in that the organic phase is distilled, which provides a distillate and a residue and that the residue is pyrolysed, which provides phenolic compounds, a combustible carbon residue and gases combustibles. 12. Method according to claim 7, characterized in that it is made a first implementation then that a second implementation is always carried out according to the method of claim 7 using carme phenolic compounds the organic phase obtained during from the first implementation. 13. Method according to claim 1, characterized in that it is made a first implementation then that a second implementation is always carried out according to the method of claim 1 using, as the aqueous phenol reaction medium acid, the total liquid phase obtained after separation of the cellulose lignified during the first implementation. 14. Method according to claim 7, characterized in that the phenol-lignin and the resulting phenols are then used to manufacture synthetic resins. 15. The method of claim 1, characterized in that the resulting delignified cellulose is used to manufacture, as desired, paper pulp, cellulose derivatives, viscose, cellulose esters and ethers, carboxymethylcellulose and sugars (glucose) derived from cellulose by hydrolysis. 16. The method of claim 1, characterized in that before heating the lignocellulosic material with said mixture of aqueous acid and phenol, this material is subjected to a prehydrolysis step in dilute aqueous acid.

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