WO1983002125A1 - A method for the delignification of wood and other ligno-cellulosic 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

A METHOD FOR THE DELIGNIFICATION OF WOOD AND

OTHER LIGNO-CT.TiULOSIC PRODUCTS

Field of the invention

The present invention concerns a method for the simultaneous delignification of wood and other ligno-cellulosic -materials and hy- drolysis of the he icellulose coπponent thereof into monαneric su¬ gars in the presence of aqueous acid, phenol or mixtures of phenols or other phenolic materials. The invention also concerns the deve¬ lopment of the chemistry of wood constituents in general and, par¬ ticularly, the efficient separation from each other and recovery of cellulose pulp, the pentoses derived 'from wood and, finally, the phe¬ nols issued from lignin.

This invention relates to iπprovements brought up to a method disclosed in European patent application No. 81810246.9

Description of the Prior Art

It is already known to use phenol and other similar coπpounds with phenolic functions for removing hemicellulose (pentosans) and lignin from wood and for obtaining a cellulose pure enough for the manufacture of paper, for instance. Thus, in this connection, SCHWEERS (Chemtech. 1974, 491; Applied Polymer Symposium 28, 277 (1975)) dis¬ closes the use of one part of sawdust, 4 parts of phenol and 10% of water acidified with 0.05% of HC1 or 2% of oxalic acid and to heat the mixture for 3 hrs at 160°C - 170°C in an autoclave. Under such conditions, and after separating the liquid phase, he reports to ob¬ tain cellulose yields of the order of 40 to 60% relative to the weight of the wood treated, such cellulose having a K (Kappa) index of the order of 40 to 100. The K index, used in the paper industry for de¬ fining the quality of the delignified cellulose, refers, among other

OMPI things, to the lignin content of cellulose after delignification; this content is approxi atively equal to K x 0.15 (TAPPI T - 236 m - 60, 1960) . In this method, one can also use, instead of phenol, the pyrolysis products of "phenol-lignin", the product which forms from phenol and lignin during delignification of wood with phenol (German Pat. Appl. DOS 2.229.673) . Normally, this phenol-lignin, which is found to be mixed with the starting phenol at the end of the de¬ lignification operation, is separated from the delignified cellulo¬ se by draining on a filter and washing with an organic solvent af- ter the delignification operation is terminated.

In addition, other phenolic products, such as various xylenols, cateehol, resorcinol, hydroquinone, naphtols and naphtalenediols ha¬ ve been used for delignifying wood using concentrations of about 2% by weight relative to the latter and heating (in aqueous medium, using a 1/1 wood to water suspension) for 90 min at 175°C, and thereafter extracting with a dioxane-water mixture _.(WAYMAN & LORA, TAPPI 61 (6) , 55 (1978)). In these conditions, yields of cellulose of the order of 60%, with a residual lignin content of 4.6% (use of φ -naphtol) , have been reported. Further, APRIL et al (TAPPI _ 2 (5) , 83 (1979)) reported the heat-

*"_ ing to 205°C of pinewood sawdust in the presence of 15 parts of a 1:1 mixture of phenol and water, such a treatment providing a cel¬ lulose with no more than 3% of lignin. From this reference, yields in purified cellulose are of the order of 40%. The methods of the prior-art described above are undoubtedly of technical interest since they permit avoiding classical deligni¬ fication conditions (Kraft, Sulfite process, etc..) which require the use of sulfur coirpounds which are difficult to recycle and which lead to hard,pollution problems. However, these methods of the prior-art have seme drawbacks, especially regarding the need of hav¬ ing to work at teirperatures above 100°C and under pressure. Thus, such conditions may raise problems related to using pressure resist¬ ing and leakproof reactors. Also, since the hemicellulose component of the vegetal material may undergo hydrolysis into pentoses during the delignification operation, the decomposition of said pentoses into furfural may become significant at the high teπperatures involv¬ ed and resinification of the latter will occur. Also, the reaction

OMPI between phenol and the lignin resulting from delignification to phe¬ nol-lignin is emphasized as well as the reaction of said phenol-li¬ gnin with the products issued from the deccnposition of the pento¬ ses, all this leading to hard resins; thus, recovery and recycling of the phenol solvents involved will becαne difficult or even impos¬ sible.

Thus, one object of the present invention is to provide a sim¬ ple and economical route to the efficient separation in high yields of the constituents of wood or of other ligno-cellulosic materials, e.g. straw, chaff, bark residues, dry leaves and other vegetal re¬ fuses.

Another objective of the invention is to provide a method for delignifying the above mentioned ligno-cellulosic materials and fur¬ nishing a delignified cellulose pulp of excellent grade and purity to the dissolving pulp industry or a feedstock for the production of glucose which is much more easily and efficiently processed than the initial cellulose of the ligno-cellulosic materials.

Still another object of the invention is to provide the indus¬ try with phenols extracted in high yields from wood or other ligno-cel- lulosic materials as well as the pentoses that can be further pro¬ cessed to valuable fuels, chemicals and synthetic resins.

Still another object of the invention, is to provide an efficient way to recover valuable products from wooden scrap or other vegetal refuses which are normally burned in the fields or disposed of in streams or sewers, thus acting as strong pollutants of the environ¬ ment.

Other objects of the invention will become evident from the des¬ cription given hereinafter.

Summary of the invention

The method of the invention meets the above-mentioned objects,

-_» remedies the drawbacks of the prior-art and provides, in addition, other unexpected and surprising advantages as will be seen later. it coπprises heating one part by weight of the ligno-cellulosic ma¬ terial with at least 0.5 parts by weight of diluted aqueous acid, the pH of which is below 1.5, and at least 0.4 parts by weight of J OΕMPI phenol or of one or several other phenolic coπpounds. Phenolic com¬ pounds include the coirpounds mentioned hereinabσve and others to be defined hereinafter. Heating involves temperatures in the range of the reflux teπperatures of the water and phenols mixture under am- bient pressure or slightly above or below ambient pressure, i.e. from, say, about 90 to 110°C. The weight of the ligno-cellulosic material referred to above should be understood as calculated on a dry basis, i.e. after substracting the natural moisture contained in the mate¬ rial. Sufficient agitation or displacement of the liquid around the solid is preferably provided to ensure mutual contact of the reac- tants. A continuous leaching of the solid material by the liquid in order to procure efficient conditions for the dissolving of the li¬ gnin coπponent thereof and the hydrolysis of the hemicellulose is advantageous when using relatively high liquid to solid ratios. In such case, efficient contact is provided by refluxing the suspension of solids in the liquid at the boiling temperature under ambient or slightly lowered or raised pressure. However, depending on the na¬ ture and the structure of the ligno-cellulosic material, when using low liquid solid ratios, i.e. in the range of about 0.5 to about 2 or even 4 parts of aqueous acid or aqueous acid plus dissolved phe¬ nol for 1 part of dry ligno-cellulosic material (or of ligno-cellu¬ losic material plus undissolved phenol) , initial milling or knead¬ ing of the comminuted solid with the liquid {the aqueous acid plus the dissolved phenol) before heating is sufficient for ensuring pro- per contact between the solid and the liquid reactants. Alternati¬ vely to providing liquid motion by simple boiling, the latter can- be continuously brought into contact with the solid in divided form and removed therefrom, for instance by circulating it in a closed circuit with, a puπp. Since, as said above, the reflux temperature of such liquid mixture is around 100°C at ambient pressure (or slight¬ ly above or below said pressure) , it is not necessary to provide a gas tight or pressure resistant autoclave which is an important eco¬ nomical factor.

The kind of aqueous acid used is not critical as long as it is a strong acid. Thus, mineral acids such as H-SO^, HCl, H₃0, and the like are suitable but hydrochloric acid and sulfuriσ acid are pre¬ ferred. One can also use strong organic acids if desired such as, E4 Ol for instance, oxalic, benzene-sulfonic and other aromatic sulfonic acids, trichloroacetic acid, etc. i.e. in general, good water-solu¬ ble acids with a pK below 2. Preferably, one uses HCl with a concen¬ tration of between 0.5 and 5%, preferably 1 to 3% by weight. If sul- furic acid is used, concentrations in the range of 3 to 6% by weight in water are preferably used.

It should be noted at this stage that the use of aqueous phe¬ nol in the presence of acid catalysts for effecting the delignifi¬ cation of wood and other vegetal materials is mentioned in old re- ferences dating 1919 (German Patents Nos EΞ - 326'705 and - 328'783, ]_-AP3_ uTH) . It is said in these references that catalysts which are convenient include certain mineral and organic acids and other com¬ pounds providing acids under operational conditions such as A1CU, CuCl₂, SnCl₄, TiCl₃, nitrophenol, chlorophenol, etc.. The quantities of these catalysts are given to be "more or less" in reference No. 328'783 without any further specification, whereas in reference No. 326*705, there is indicated that the catalyst consists of a 0.01% HCl solution. Yet, the present inventors have established that with such a diluted acid solution (pH above 2) as a catalyst, it was not possible (at 100°C under ordinary pressure) to correctly delignify ligno-cellulosic materials as will be seen later in the experiment¬ al part of the present disclosure. Moreover, it is never indicated in the above references that by operating under the directions gi¬ ven therein it was possible to effect a substantially complete hy- drolysis of the hemicellulose component and to separate, from the delignified cellulose, on one hand the sugars from hydrolysis of the hemi-cellulose fraction of the starting material and, on another hand, the phenols arising from the decomposition of the lignin. Indeed, the references rather report that, after recovery of the initial phe- nol reactant by distillation of the liquid phase, there remains a residue that will turn out into a hard resin. This disclosure is the¬ refore strong evidence that furfural has formed and has reacted with the lignin decomposition products, the avoiding of such detriment¬ al factor being precisely one of the objects of the present inven- tion. Thus, in contrast, in the invention, the desired separation of the components can be achieved under excellent conditions, as will be seen hereinafter. There is^' also a. reference (UK Patent _3pplica-

OMPI tion 2,036,826 A) which discloses the simultaneous delignification and conversion into sugars of ligno-cellulosic materials by an acid-ca¬ talyzed reaction in the presence of organic solvents. However, this method involves using high temperatures and pressure and it thus re- quires high investment equipment.

It should be also mentioned that, in the present invention, HCl concentrations significantly above 5% by weight in the water phase are either useless or even harmful; thus, for instance, if the react¬ ion is performed with more concentrated acid, say, about 10% HCl, undesirable reactions may happen such as partial decomposition of the products with resinification and yield losses. Evidently, such conditions will be avoided in general except in cases where special effects are wanted. With acids other than HCl, higher concentrations in proportion to higher molecular weights of such acids are possi- ble. For instance with HJO,, concentrations of up to 10% are still admissible.

Description of the preferred embodiments

As the phenol and other phenolic compounds, the following com¬ pounds can be used in the invention in addition to hydroxybenzene and most of the commercially available phenols: p-cresol and o-cre- sol (the cresols have the further advctiitage of being precipitable at the end of the reaction from the reaction mixture by adding Ca^*5-*^" ions), guaiacol, 4-ethylphenol, 2,4-xylenol, 4-methylguaiacol, 4-ethyl- guaiacol, 2-ethylguaiacol, 4-vinylguaiacol, 4-propylguaiacol, euge- nol, 1,3-dimethoxypyrogallol, vanillin, l,3-dimethoxy-5-methy__pyro- gallol, trans-isoeugenol, catechol, phloroglucinol, pyrocatechol, hcxnocatechol, etc... and any mixtures of such phenols or, also, mixt- ures of the phenolic products generated by the pyrolysis of phenol-li¬ gnin, the latter being the product provided, as already mentioned before, by the reaction of phenol (or the other phenolic compounds) with the degraded and dissolved lignin produced in the course of the delignification of ligno-cellulosic materials in the presence of phe- nol (or the mixture of phenols) . Furthermore, within the present me¬ thod, the whole or part of the phenolic reagent material can consist of the phenol-lignin itself (provided it has not been too much de-

O PI graded and converted into a resin by its reaction with the products from the thermal decomposition of the pentoses provided by the hy¬ drolysis of hemicellulose, e.g. furfural) . Yet, (and this is one of the unexpected advantages of the invention) at the relatively mode- rate temperatures used,, the hydrolysis of the pentoses of wood in diluted acid in the presence of phenol takes place under optimal con¬ ditions with an exceptionally high yield and the pentoses thus pro¬ vided only undergo a minimum of decomposition to furfural or other products. As a result, the level of resinification of the phenol-li- gnin is low and the latter can be reused several times, from cycle to cycle, without losing much of its delignification efficiency. This feature is a considerable advantage relative to the prior-art in which, because of the actually implemented temperatures of the or¬ der of 160°C or more, phenol-lignin hardens rapidly and thus loses its desirable properties of being a delignification solvent. It should be understood that when phenol lignin is used in the present inven¬ tion, it is preferably used in admixture with the aforesaid phenol or other phenolic compounds.

Besides, working under conditions preventing the decomposition of pentoses is another advantage since they can be recovered there¬ after for further use as will be seen later in this disclosure.

Moreover, and this is one of the most significant and unexpect¬ ed advantages of this invention, when a liquid to solid ratio of 4 to 1 or more is used, it is not necessary, after separating the pu- rified cellulose by draining at the end of a reaction cycle, to dis¬ til the ligno-phenolic phase for recovering the phenol mixture to be reused in the delignification of a new lot of wooden material. It is enough to isolate by filtration, on one hand the solid deli- gnified ^"cellulose and, on the other hand, the combined aqueous and organic phase, the latter containing the still unreacted phenol and the phenol-lignin; this liquid combination is then directly reusa¬ ble, after addition of a fresh portion of vegetal material, for the next delignification operation. This recycling can continue until the aqueous phase becomes highly loaded with pentoses (up to about 200 g/1) . At this stage, it is evident that the aqueous solution must be put aside for recovering^' the dissolved pentoses; also, at this stage, the -phenol-lignin phase mixed -with the phenols must be set

O aside too, since it has lost part of its efficiency as a delignifi¬ cation solvent because of overconcentration and contamination with the degradation and polymerization products derived from the pento¬ ses. However, and here is still another advantage of the invention, this ligno-phenolic phase can then provide, by distillation and py¬ rolysis, an excellent yield of wood-phenols (a mixture that is suit¬ able for carrying out the present process) which makes the invention self-independent from outside phenol supplies and even produces an excess of phenol and other -phenolic compounds. The invention enables thus to produce, under exceptionally eco¬ nomical conditions and with excellent yields, a cellulose of high degree of purity (even from ligno-cellulosic products with a high percent of lignin) , pentoses that can be easily separated and are usable for various purposes, and phenols part of which is natural- ly recycled in the process and an excess that can be processed ac¬ cording to usual means (distillation, extraction, etc..) for sepa¬ rating the various components thereof for future use.

In the method of the present invention, the amount of acidified water used relative to the milled or comminuted ligno-cellulosic ma- terials (wooden chips or dust, chopped straw from grain crops, ri- ce and various cereals, husked corn cobs and, in general, all green or dry ligno-cellulosic materials) is not particularly critical pro¬ vided that efficient contact of said aqueous acid and the ligno-cei- lulose to be delignified is provided and that the amount of water required to hydrolyze the hemicellulose is stoichicmetrically suf¬ ficient. Thus, in case the liquid to solid ratio is rather high, i.e. about 2 to 1 or more, an efficient mixing action leading to a good contact, continuously renewed, between the solid to be delignified and the- delignification solution can be provided by the refluxing agitation or the percolating effect at the acid water phenol boil¬ ing temperature. To enable easy agitation or refluxing, it is enough to have about 2 to 4 parts by weight or more of aqueous liquid for one part by weight of the suspended solid, but operating with more liquid is possible if desired, for instance with 5 to 50 parts of liquid; however, to use very large volumes of liquid may cause pro¬ blems related to the large size of the equipment needed for handl¬ ing. It should be remembered also that a good contact between the

O PI solid and the liquid can be ensured by agitation of the latter with an agitator or by circulating it continuously by means of a pump through a bed of the comminuted solid material. If the liquid to so¬ lid ratio is rather low, i.e. below about 2 or 3 to 1, it is usual- ly sufficient to mix the aqueous acid plus phenols and the comminut¬ ed vegetal material by kneading for instance with a paddle kneader or, more simply, by simultaneously admitting the solid and the li¬ quids into a heated tubular reactor by means of a screw and slowly conveying the mixed solid and liquids along the heated area of said reactor. Then the solid-liquid mixture will progressively react, con¬ tract in size and aquire sufficient fluidity to be extracted at bot¬ tom of the reactor by other conveying means.

Regarding now the quantity of phenol or phenols required for the delignification operation, again this is not critical provided there is used enough thereof for ensuring a good delignification of the wood. Thus, if 4 parts of phenol or of the mixture of phenols are in general sufficient for 10 parts of comminuted ligno-cellulos¬ ic materials, one can use more phenol if desired, i.e. 10, 20 or even 50 parts of phenol for 10 parts of ligno-cellulosic material. To use much phenol and much aqueous phase relative to the dry comminuted solid may seem at first to be attractive because, in case recycling is contemplated, exaustion of the liquid reagents will be slower and it will be possible to recycle the liquid phase a greater number of times before having to set it aside for the extraction of useful pen- toses and phenols therefrom. However, such technique has the disad¬ vantage that, if the ratio of the solid material to the total volu¬ me of the reaction medium is very small, the yield in each cycle is also small and the overall yield based on the total amount of react- ants used after a number of cycles will not be practically modified. In the general practice of the invention, there will preferab¬ ly be used for one part of comminuted ligno-cellulosic materials 1 to 6 parts by weight of phenol and 1 to 10 parts by weight of dilut¬ ed aqueous acid, for instance 1.5 - 2% HCl or 3 to 6% aqueous H-SO^. It is also preferred that the weight ratio water/phenol be above 1 and, adantageously, of the order of 3:2 or 2.

For practically carrying out the present invention when using liquid to solid ratios of the order of- about 2 to 1 or to 4 to 1 or RE more, the solid and liquid ingredients, i.e. the vegetal ligno-cel¬ lulosic material in comminuted form (wood cuttings, chips, shavings, sawdust, chopped straw or bagasse, etc.. for instance) , the aqueous acid and the phenol or mixture of phenols are charged in a contain- er (glass flask or tube in the laboratory or industrial reactors in a plant) and the mixture is heated for 1 to 8 hrs to the boil. How¬ ever, more sophisticated industrial equipment can be used also as will be seen hereinafter. In general, 2 - 4 hrs of heating are enough which is one further advantage of the invention relative to the prior- art in which the heating periods (under pressure) are much longer. Once the heating period is discontinued, the residual solid is fil¬ tered and drained, which is constituted by very pure cellulose (K being of the order of 30 to 100) , with a yield of approximately 80-90% relative to theory (a 100% yield refers to the theoretical total amount of cellulose present in the sample) , and it is washed with some warm water, possibly made alkaline with NaOH or KQH, and/or a water compatible solvent (e.g. acetone or methanol) for removing all the phenol remnants trapped therein. Then, the liquid phase (dilut¬ ed acid plus the starting phenol plus the phenol-lignin just produo- ed by the sample delignification) may be taken again and recycled with a fresh portion of wooαen dust. This cycle can be repeated at least four times, the delignification efficiency and the purity of the obtained cellulose decreasing only slowly.

After a number of cycles, the aqueous phase loaded with p>ento- ses is separated from the ligno-phenolic phase by simple decantation.• The pentoses are then extracted from the aqueous solution by usual means or, if desired, the solution can be directly heat-treated for converting the pentoses into furane derivatives. This aqueous solu¬ tion can also, be subjected to fermentation (preparation of the pro- teins, alcohol, etc.), the phenol dissolved in this aqueous phase being removed beforehand (for instance, by extraction and distilla¬ tion).-

In regard to the organic phase, the latter is first distilled which enables to recover an important quantity of pure phenol and a mixture of the phenols issued from the lignin; then the undistil- lable residue is pyrolyzed which provides further phenols and a po¬ rous carbonaceous residue usable as a fuel or as adsorbent carbon - li ¬

as well as volatile substances (gases) which can also be burned.

It should be added that at the end of the delignification of a charge of ligno-cellulosic material, it is possible, after sepa¬ rating by cooling and decanting the phenol phase from the water pha- se, to recontact the latter after heating with the drained deligni¬ fied pulp so as to amplify the extraction therefrom of the remain¬ ing phenolic substances still adsorbed thereon. After such further hot "rinsing" of the delignified cellulose by means of the aqueous phase, the latter is observed to reform, after cooling, a new phe- nol containing organic layer that can be again separated by decan- tation. Such a "rinsing" operation can still be repeated once or mo¬ re if desired. It is thus possible by this expedient to further de¬ crease the total amount of solvent (or alkaline water) used for wash¬ ing the cellulose at the end of the reaction and, for this reason, increase the degree of recovery of the phenols from the aqueous pha¬ se.

The technical variations just described hereinabove are prima¬ rily applicable, as already said, when in the present method the ra¬ tio of liquid to solid exceeds a certain value (in the approximate range of 2:1 to about 4:1) above which the solid is easily disper- sible in the liquid and, after the reaction is completed, the liquid can be easily drained from the solid by usual means, e.g. filtration under suction or filter presses. In cases where this ratio liquid to solid is below said value (actually this value is not a strick- ly defined limit since it may naturally vary depending on the natu¬ re of the ligno-cellulosic material, the comminuting^' techniques and the size and surface state of the particles) , i.e. when the quanti¬ ty of liquid relative to that of the solid is below the level at which the solid can be freely dispersed in the liquid and when said liquid is rather in the "adsorbed state" within the solid particulate ma¬ terial, other handling techniques are preferably used. Thus, in such cases, the dry comminuted solid, the aqueous acid and the phenol or phenols are initialy thoroughly mixed or kneaded together by any clas¬ sical means, for instance a slow rotating agitator, a kneader or the like and the kneaded mix is introduced in a container in which the heating operation can be undertaken. Such container can be a clos- ed tube or a reactor. On the industrial scale, a screw-type feed de- vice connected to a vertical tubular, reactor is conveniently used. The solid comminuted, material is introduced in the hopper of the feed screw and the liquids are injected sidewise in the feed screw duct whereby efficient mixing during conveying of the materials to the reactor is obtained. Then the material is progressively packed con¬ tinuously in the reactor from the top thereof and the mixture the¬ rein is subjected to heating for the required overall time i.e. from about i to 2 hrs in all, whereby contraction (by hydrolysis and de¬ lignification) and partial fluidization occur and the pasty viscous product accumulates at the bottom of the reactor wherefrcm it is re¬ moved fcy other classical means, e.g. another screw conveyor.

At the outset of the reactor, the pasty mass is subjected to treatments for physically separating the components of the ligno-cel¬ lulosic material (i.e. the cellulose, the sugar monomers and the phe- nolic compounds) which are still mixed together but potentially split frαn each other (in the chemical sense) by the above process. Such treatments involve washing steps quite alike the aforesaid disclos¬ ed rinsing steps of the drained delignified cellulose crops. Thus, the pasty mass can be taken with a suitable aqueous solvent that will entrain the liquid or water entrainable component of the mixture and effect separation from the solid delignified cellulose. Such a sol¬ vent is conveniently warm phenol-saturated water. Indeed, if the mass is taken with such a solvent and the whole is drained on a filter for instance, the phenolic phase, the acid and the hydrolyzed pen- toses will be removed in the liquid phase that will ultimately se¬ parate into the expected organic (phenol) and water phases (sugar solution) which can be then decanted and further processed separa¬ tely as described previously. Of course, in the aforesaid mention¬ ed cases -where the liquid to solid ratio is on the low side, satur- ration of the phenol solvent with the phenol lignin will occur qui¬ te soon (normally already after one cycle) and recycling of the phe¬ nol plus phenol-lignin needs not be contemplated. Thus, such cases rather refer to a continuous process in which the material to be treat¬ ed is fed continuously to the delignification equipment together with the other required reagents and the products are directly gathered and subjected to further purification treatments.

Summarizing- briefly,, the present method has the following ad- vantages relative to the teaching of the prior-art: a) Moderate reaction temperature that enables to operate with untightly sealed reactors, i.e. containers operating under atmospher¬ ic pressure or in conditions only slightly above or below ambient pressure. b) Excellent efficiency for dissolving pentosans in the aque¬ ous phase (yields can attain 98%) and the ready possibility of re¬ covering and further using the resulting pentoses. c) Minimized formation of reaction products between phenol and dissolved lignin and also iniimum degradation of the pentoses at the temperatures considered and, consequently, minimal formation of re¬ sins from the phenols reacting with said degradation products, whe¬ reby said phenols can be easily recovered and an excess of such phe¬ nols relative to the initial added quantity is even recoverable. d) Easy separation of the three key phases involved in the me¬ thod: solid phase, i.e. cellulose of a high degree of purity; aque¬ ous phase with a high concentration of pentoses; and organic ligno-phe- nolic phase the distillation and further pyrolysis of which provi¬ des a considerable quantity of useful products. e) Full profitability from the wood constituents, losses being kept to a minimum. With classical methods, the pentoses, lignin and part of the phenol are lost or decomposed to a much larger extent. f) High cellulose quality and excellent purification yields. g) Independence of the method relative to the starting reagents. After the initial addition of phenol, the operations can be conti¬ nued with the recovered phenols without the need of additional ex¬ ternal phenols. Further, energywise, the use of the recovered car¬ bonaceous residue and the volatile gases gives autonomy to the me¬ thod which does not comprise evaporating steps or the concentration of large volumes of water. h) In the case where relatively high liquid to solid ratios are used, repeated recycling of the liquid phase for the successive de¬ lignification of several portions of ligno-cellulosic materials will provide, after several cycles, an aqueous phase the sugar concentra- tion of -which is very high. i) The unpyrolyzed lignin can be used directly as a fuel (lit¬ tle pollution because it is free from sulfur and minerals except for a -small amount of ashes) , as a source of phenols or as starting ma¬ terial for making polymeric resins. j) Possibility of using a large variety of ligno-cellulosic was¬ tes (wood, hardwoods and softwoods, grassy products, leaves, pulp>- 5 ing wastes, bagasse, straws, barks, etc..) in the green or in the dry state, the water needed for reaction being easily adapted depend¬ ing on the moisture already present in the starting material. Thus, for instance, sugar-cane stalks freshly extracted (green bagasse) can be used as well as dry stalks (dry bagasse) , the amount of wa-

10 ter in the reactor being larger in the second case than in the first.

The existence of further references the subject matter of which is somewhat related to the present invention will still be mention¬ ed as the general background to the art; thus, USP No. 3,776,897 con¬ cerns the addition to a previously acidified sulfite liquor for the

15 delignification of wood of an organic solvent that will first cau¬ se hemicellulose to separate followed by the separation of an aque¬ ous phase containing dissolved sugars and an organic phase contain¬ ing lignin. Although there is some possible analogies between the operations involved in this separation process and the practical un-

20 dertaking of the present invention, it is evident that the teaching of the reference does not make the present invention obvious. Indeed, in the chemical industry, the selective extraction of components by causing a solution to separate into two non miscible liquid phases is well known per se and, with regard to the present invention, the

25 reference discloses no more than any practical text-book on experi¬ mental chemistry. The general field of the reference, i.e. the al- caline sulfite liquor to be acidified and the practically negligi¬ ble hydrolysis extent of the pentosanes, etc., does not provide a teaching usable by men skilled^' in the art to achieve the present in-

30 vention.

Another reference, French Patent No. 1.430.458 provides a dis¬ closure very similar to that of the above OS Patent and does not ei¬ ther enable people skilled in the art to achieve the invention. Mo¬ reover, a third reference, GB Patent No. 341.861, concerns the dis-

35 tillaticn at 300°C of the residues resulting from the evaporation of the alkaline digestion solutions of ligno-cellulosic materials.

---. Such residues, rich with pentosanes and lean of lignin (see page 1,

lines 60 - 85) provide by distillation mixtures of acids, hydrocar¬ bons, phenols, furfural and various gases which result does not seem much different from that of simply distilling wood (except for me- thanol). Finally, a last reference (TAPPI 52, 486 - 488 (1969)) con¬ cerns the conversion into furfural of the residual pentoses from a sulfite liquor for the delignification of wood. In essence, this re¬ ference does not seem to teach anything that can be used, by analo¬ gy, to achieve the present invention.

The following Examples illustrate the invention in more detail.

Example 1

In a 250 ml pyrex flask provided with a reflux condenser, the¬ re were charged the following ingredients: 10 g of beech-wood saw- dust with 10% moisture (composition: 17.25% of pentosanes, 53.6% of cellulose, 27.4% of lignin and 1.2% of ashes) , 40 g of phenol and 60 ml of 1.85% HCl (pH 0.3). The mixture was refluxed for 4 hrs af¬ ter which the solid was drained on a B chner funnel and washed with warm water and acetone. Yield 4 g, 78%; K (Kappa) = 40; lignin con- tent = 6% (Analysis by the Standard method TAPPI T-122 OS-74) .

After cooling, the liquid phase resulting from the filtration of the cellulose split into two phases which were separated by de- cantation in a separatory funnel. The upper aqueous phase was ana¬ lyzed according to LISOV & ΪAROTSKII (Izvest. Akad. Nauk SSSR, Ser. Khim (4) , 877-88 (1974) and was shown to contain 1.47 g of pentoses (85% of theory) and 0.43 g of hexose (8% of theoretical glucose) to¬ gether with a small quantity of dissolved phenol. The organic pha¬ se (42 g) contained the main part of the delignification phenol and, dissolved therein, the phenol-lignin resulting from delignification of the wood. Significant amounts of phenol were also recovered from the washings of the cellulose.

Example 2

In a 21 flask fitted as described in Example 1, there were plac¬ ed 100 g of beech-wood sawdust (see composition in Example 1) , 400 g of phenol and 600 ml of 1.85%- aqueous HCl. -After boiling for 4 hrs.

the solid was drained on a Biichner funnel and washed with warm 1.85% HCl until having a total filtrate of 1000 g. An aliquot of this li¬ quid was taken for analysis after which the liquid was recycled for delignifying a fresh portion of 100 g of sawdust. Thereafter, the same full- cycle was repeated two more times each with a new portion of 100 g of sawdust and the filtrate from the previous cycle. Each time, an aliquot of the liquid was taken for analysis. The results are gathered in Table I below together with the results of analysis of the obtained cellulose fractions.

TABLE I

Cycle Obtained cellulose Yield of sugar monomers

No. fibers

Weight Lignin K number Pentoses Hexoses

⁽g⁾ (%) (C5%) (C6%>

1 45.7 6.9 46 80.7 8.2

2 47.1 7.25 48.3 82.5 7.2

3 49.1 9.85 65.7 82 5.8

4 54.5 18.2 ^' 121.3 100 2.4

After the fourth cycle, the liquid was separated as in Example 1 into an aqueous phase and an organic phase. T"he aqueous phase was first counter-current extracted with toluene and the toluene extract was added, after removal of the solvent, to the organic phase. The purified aqueous phase contained, dissolved, about 60 g of pentoses. This fraction was steam distilled whereby the furfural (produced by heat from the pentoses) was separated.

The combined organic phase (about 490 g) was distilled (73°/13 Torr) which provided 323 g of phenol (about 67%) , the undistillable residue was, as shown by NMR analysis, a mixture of phenols deriv¬ ed from wood and partially-degraded lignin. This residue was pyro- lyzed under nitrogen at 450°C ^**Aιich provided 111.6 g (68% of the re- sidue) of an anhydrous mixture of ordinary phenol (62.4%) and other phenolic compounds (37.6%) which were subjected to vapor phase chro- matography (see SCHWEERS & RBCHY, PAPIER 26 (10a) , 585 (1972)) . This enabled to identify some typical phenols resulting from the degra- dation of wood, i.e. guaiacol, the cresols, etc The residue from pyrolysis (51.3 g, 30.7%) consisted in a porous carbonaceous resi¬ due (plus ashes) and the difference in weight from theory was due to the evolution of non condensable volatile gases.

Example 3

The same procedure as in the previous Examples was followed by using 5 g of sawdust, 30 ml of aqueous 1.85% HCl and 20 g of the phe¬ nol mixture as obtained after pyrolysis in Example 2. There was thus obtained 2 g of cellulose K = 33; lignin content 5%. The aqueous pha¬ se contained 0.85 g, 98.6% of the theoretical amount of pentoses (cal¬ culated on the hemicellulose content of the sawdust used), 0.24 g, 9% of hexoses and 1 g of phenol. The organic phase (21 g) gave 8.3 of phenol by distillation. For comparison purposes a test was undertaken by subjecting 10 g of sawdust to 4 hrs of cooking with 100 ml of 1.85% aqueous HCl with¬ out phenol. In this case, the yield in pentoses was only about 70%. This shows, and this is there an unexpected and surprising effect of the invention, that the phenols promote the hydrolysis of the he- micellulose component of ligno-cellulosic substances simultaneous¬ ly with the delignification thereof.

Example 4

In a 500 ml flask provided with a condenser and a stirrer, the¬ re were introduced 100 g of the mixture of phenols, such as that ob¬ tained, by pyrolysis according to Example 2, and 123 g of formalde¬ hyde as the standard 37% aqueous solution. There were still added 4.7 g of Ba(OH)₂.8H₂0 and the mixture was agitated for 2 hrs at 70°C. The mixture was neutralized to pH 6 - 7 with 10% H₂S0₄ and it was concentrated under reduced pressure below 70°C until a viscous mass was obtained. This mass constitutes a "stage A" prehardened "RESOL"

type resin. It can be used for instance for the manufacture of la¬ minated panels, as 'an adhesive for agglomerated wood panels and for thermosetting coating compositions according to usual means.

5 Example 5

Investigation of operational parameters

With the objective of better knowing the importance of operation-

10 al parameters such as temperature, reaction time, acid strength, phe¬ nol to solid ratio, etc., a series of delignification experiments were carried out with samples of 30 g (1 part) of dry bagasse (ave¬ rage composition: cellulose 40.2%; hemicellulose 25.6%; lignin 22.2%; extractibles 7.24%; ashes 4.76%) which were treated with various mixt-

15 ures of phenol and acidified water at various temperatures and for various lengths of time. Then, the delignified pulp was separated by filtration and it was extracted with 5% sodium hydroxide solution in order to remove all the adsorbed phenol in the form of alkali phe- nolate (the solution of phenolate was thereafter acidified in order

20 to cause the phenol to separate and this second crop of phenol was added to the first crop from the above filtration). Moreover, in ad¬ dition to the weighing of the purified pulp and the analysis of the residual lignin content therein, the amunts of - sugars (pentoset.) and Cg sugars (hexoses) were determined in the aqueous reaction pha-

25 se.

The analytical methods used were as follows: For the phenol in water, conversion into tribrcsrophenol by bromine at pH around 0 to 1 was used followed by back titration of the excess of bromine with KI + thiosulfate. According to another route, a VPC analysis was car-

30 ried out (column DC 550, silicone oil; temperature of column: 147°C; temperature of injector: 190°C; carrier gas: nitrogen at 60 ml/friin; detector: by flame ionization. There was also used a HPIC analysis method (High Performance liquid Chromatography) (column C-18 RP-WA- TERS-Bondapack 10 u; solvent acetone/water 40/60 at 1 ml/min; detec-

35 tion at ^ = 254 πju; internal standard: acetophenone) .

The sugars resulting from hydrolysis were analyzed in the aque-

^*■- - ous phase -and in the pulp washing water fractions by the o-toluidi- ne method. The total, of these sugar values is recorded in the yield figures of the Tables below.

The operating parameters used for the above described operations and the obtained results are summarized in Tables II to IV herein- after.

In the Tables, the heading ^'"separated solids" concerns the to-, tal weight of isolated pulp, plus the undissolved lignin, plus the ashes, plus other insoluble impurities. The weight % of lignin in said solids (pulp) is given in the next column. The data concerning the sugars liberated by hydrolysis are given in % relative to the theoretical amount of said sugars derived from the total original content of the sample in cellulose and hemicellulose.

TABLE II

(Effect of reaction time at various reacting temperatures for the reaction of 1 part of bagasse, 4 parts of phenol and 6 parts of aqueous HCl at 1.85% by weight)

Experiment Temp. Reaction Separated Residual Recovered

No. °C Time(hrs) Solids(ppw) lignin in pento- hexo- pulp (%) ses(%) ses(%)

B-14 90 1 0.59 11.4 68 10

B-12 90 2 0.42 10 84.3 —

B-13 90 3 0.52 7.14 91 3

B- 7 90 4 0.52 5.5 85 —

B- 9 ^■ 100 1 0.44 6.4 85 17

B-10 100 2 0.45 4.4 89 13

B-ll 100 3 0.43 4.1 91 16

B- 8 100 4 0.43 3 95 11

The data of the above TABLE II show that the general trend with increasing reaction time is to improve the dissolution of lignin and the hydrolysis of the pentosanes. There is not much change in the amount of dissolved C_g sugars. Operating at 100°C gives better re- JRE ^ suits than at 90°C.

' TABLE HI

(The effect of changing the amount of phenol relative to the aqueous acid (1.85% for 1 part of bagasse reacted for 4 hrs at 100°C))

Experiment Acidic Phenol Separated Lignin Recovered No. solution (ppw) solids(ppw) in pulp pento- hexo- (ppw) (%) ses(%) ses(%)

B-19 8 2 0.44 5.1 91 12

B-18 7 3 0.42 4 93 16

B- 8 6 4 0.435 3 95 11

B-20 5 5 0.42 3.6 93 16

B-8^{, , f} 9 6 0.41 3 95 16

The data of TABIE III show that, except for a slight improve¬ ment in the amount -of lignin contaminating the separated pulp, the decrease in the total of phenol used for delignification has not much influence.

TABLE IV

(The effect of changing the acid concentration of the water pha¬ se in the case of reacting 1 part of bagasse with 4 parts of phenol and 6 part of aqueous solution at 100° for 4 hrs) . Experiment HCL Separated Lignin Recovered Recovered No. cone, solids in pulp pentoses hexoses phenols (%) (ppw) (%) (%) (%) (%)

B-23 0.01 0.91 13.2 16.6 4.2 ,

B-21 0.5 0.50 7.6 83.3 12.5

B-22 1.0 0.433 7.9 83.7 —

B- 8 1.85 0.435_. 3 95 11 99.13%

B-36 10.0 0.34 2.22 6 16 96.25%

The data of TABLE IV show that low concentration of acid such as disclosed by HARTMUTH (DEC - 326.705) are totally unsuitable for achieving the invention in the prevailing conditions, i.e. reflux at ordinary pressure. Too much acid is also detrimental, both for pentoses and phenol recovery.

Example 6

This Example will be better understood with reference to the annexed drawing which represents schematically a small semi-works equipment for carrying out the delignification of comminuted vege¬ tal materials according to the invention. The apparatus represented on the drawing comprises a reactor 1 filled with comminuted vegetal material down to a retaining filt¬ er screen 2 which retains the solid in the reactor but allows cir¬ culation of the delignification liquid. The bottom of reactor 1 is connected by a cock 3 to a tank 4 containing the supply of deligni- fication solution. This solution is circulated from the bottom of tank 4, through valves 5 and 6, by a pump 7 to the upper part of react¬ or 1 wherefrom it penetrates the vegetal particles thus effecting a continuous leaching^' of said particles. Reactor 1 is further equip¬ ped with a reflux condenser 8 and tank 4 is also equipped with a re- flux condenser 9. The apparatus further comprises two heating man¬ tles 10 and 11 for the reactor and the tank, respectively, in which • a heating liquid (oil or -any heating fluid) is circulated by a pump 12 and heated in a thermostat controlled heater element 13. A by-pass valve 14 exists between pump 7 and valve 6 for ensuring easy control of the flow rate of the circulating delignification liquid in order that gentle boiling be maintained in reactor 1. The operation of the equipment is self evident to skilled per¬ sons from the above description and the drawing and needs not be de- velopped any further. Suffice to give the operating parameters of the present Example: 67 g of bagasse containing 10% H₂O (i.e. 60.3 g dry bagasse) were packed in the reactor 1 with the double-envelope 10 having an internal diameter of 40 mm and a length of 370 m . The top of the column was connected to the condenser 8 cooled with wa¬ ter. The bottom of the column was connected to the thermostated tank 4 which contained the required amount of aqueous phenol mixture for the delignification operation, i.e. 400 g of phenol (purity: 99.5%) and 600 ml of 1.85% HCl solution. The aqueous phenol phase was heat¬ ed to near 100°C by means of the circulating oil; at this tempera¬ ture it provided a homogeneous solution, i.e. the phenol was enti¬ rely dissolved in the water. This phase was pumped using the teflon recirculating pump 7. The liquid flow was regulated in order to main- tain a correct level of liquid above the bagasse fixed bed using the by-pass valve 14 and this was also for homcgeneizing the circulat¬ ing liquid phase in the circuit. The liquid circulation was maintain¬ ed for 3 hours after equilibration of the temperature of the liquid to 100°C. In the fixed bagasse bed a slight, boiling of liquid was maintained by raising the temperature of the thermostating oil to about 120°C. After reaction completion, the pump was stopped and the liquid was drained off by gravity during cooling. The liquid solu¬ tion was collected and cooled in flask 4. The organic layer (main organic-phase) was then separated from the aqueous layer by decan- tation. The aqueous phase, after separation of the first crop of or- ganics, was heated again and recirculated for 3 hours at 100°C through the fixed bagasse pulp bed. During this treatment some additional phenol retained previously in the pulp fibres was removed. This li¬ quid phase (main aqueous phase) was again cooled to room temperatu- re which caused the separation of another organic layer (second crop of phenol) . This phenol was decanted and added to the main organic phase. The cellulose in-reactor 1 was then washed as follows: 1st washing

500 ml of clean water was then added to the circuit heated to 100°C and circulated through the pulp fixed bed for 2.5 hours. Then, after cooling the pulp was drained under slightly reduced pressure and the washing water was recovered for phenol analysis.

2nd washing (with alkali)

500 ml of water containing 10 g of sodium hydroxide was intro¬ duced into the circuit and circulated through the pulp bed for 2 hours at 40°C (maximum) . Then the pulp was again drained under reduced pres¬ sure. The washing with alkali was then acidified to pH 5 with hydro¬ chloric acid. The second washing was then analysed for its phenol content.

3rd washing (with acidified water)

The pulp was removed from reactor 1 and placed on a buchner fun- nel and washed with about 2 liters (in small fractions) of acidified water (pH 4) to remove the residual alkalinity. After centrifugation in a basket, the final pulp had a 50 - 60% residual E O content. The cellulose yield in the pulp was determined after the drying of an aliquot. 29 g of pulped bagasse were recovered. . in the reaction there were used 67 g of bagasse (60.3 g dry) , plus 400 g of phenol, plus 600 ml of 1.85% aqueous HCl. Total is ap¬ proximately 1067 g.

There were recovered, after the reaction and before the recir- culation, 472 g of main aqueous phase, 294.5 g of main organic pha- se and about 300 g of wet pulp the total of which is approximately the same as above. After the three hours of recirculation, reextrac- tion of the pulp and completion of the organic phase, the respecti¬ ve weight had become: main aqueous phase: 377.5 g (analysis, 7.2% phenol = 27.2 g of phenol); main organic phase: 424 g (analysis, 71.6% ^~ 303.94 g of phenol); first washing water: 466.3 g (analysis, 7.45%. = 34.74 g of phenol); second alkaline washing: 611 g (analysis, 4.65% = 28.4 g of phenol); third washing: 2006 g (analysis, phenol content not significant) . Ihus the total of phenol in the various fractions was 393 g which accounts for nearly all of the phenol at the start.

Ωie recovered pulp (29 g = 48% of the dry bagasse) had a K num¬ ber of 13-which corresponds to 2.7% of residual lignin. Aliquots of this pulp were hydrolyzed with 40% HCl and analysis of the diluted solutions indicated that the sample contained 78.75% of cellulose (ascertained by the C_g sugars content) and 3.5% of hemi-cellulose (from the C₅ content) . The difference of 17.75% was due to the re¬ sidual lignin, the ashes and other insoluble components. One hundred gram of the organic phase (containing, in princi¬ ple 28.3 g of material other than free phenol) were distilled under reduced pressure which gave about 97 g of moist phenols plus a re¬ sidue of 3 g of moist lignin. After drying this lignin residue, it was calculated (with reference to the total organic phase) that the total lignin in the organic phase was 10.6 g.

Example 7

Wood delignification with oxalic acid as catalyst instead of HCl

There were used:

20 g dry birch sawdust (22.2 g wet), 80 g of phenol, 100 ml of an aqueous oxalic acid solution at 0.5 N (22.5 g/1 or 2.25 g/d), 100 ml E-O) . Heating was carried out 4.5 hours at 100°C.

After cooling and filtration of the liquid the pulp was wash¬ ed on the filter with several portions of hot water. The total aque¬ ous phase recovered was 2 litres. The organic phase was 0.055 1. The yield of sugar monomers recovered in the liquid was: Pentoses (C- ): 31.55%, Hexoses (C_g ): 15.12%.

The washed -pulp after drying weighed 15.5 g. The K number of this pulp was 87.45 corresponding to a residual lignin content of 13.11% (2.03 g) . The initial lignin present in the raw material was 4 g, therefore 50% of the lignin had been dissolved. Example 8

Twenty grams of dry bagasse were refluxed 4 hrs at 100°C with 80 g of vanillin and 120 g of 1.85% aqueous HCl. The mass was hot filtered on a Biichner funnel and washed with 600 ml of hot water (by portion) and 200 ml of 1% aqueous NaOH, then again with water to neu¬ trality. The yield of delignified pulp was 8.9 g (dry); K = 20 (3% lignin) . The combined liquid phases were allowed to stand, after which the organic phase was separated from the water phase and distilled upon which the vanillin was recovered. The aqueous phase contained 92% of the theoretical pentoses and 12% of hexoses (from hydrolysis of the cellulose) .

Example 9

The procedure of Example 8 was repeated but using 100 g of a 1:1:1 mixture of the o-,p- and -cresols and 150 ml of 1.85% HCl. After washing as above, the water /phase gave 96% of Cr sugars and 15% of Cg sugars whereas the cresols were recovered by distillation of the organic phase. Pyrolysis of the residue gave a further crop of wood phenols. The yield of dry pulp was 8.1 g; K = 18.7 (2.8% li¬ gnin) .

Example 10

Sixty grams of comminuted bagasse (weight calculated on the ba¬ sis of dehydrated material) , 84 g of phenol and 126 g of 1.85% aque¬ ous HCl were kneaded together until full impregnation was achieved. Then the moist material was divided into 4 lots and each lot was in- troduced into a 100 ml glass tube which was closed with a stopper. The tubes were heated for periods of times (shown below) without agit¬ ation, then they were cooled and the reacted product was treated as described in the previous Examples for separating the constituents. ^* The results concerning the yield of delignified cellulose and the residual lignin of said cellulose are shown in TABLE V. The Experi^¬ ments were actually carried out twice, the results shown being the average of the two experiments. TABLE V

Sample Heating time Pulp yield Residual lignin in pulp

(hrs) (%) after NaOH washing (%)

_

1 1 40.5 4.18

2 2 40.5 4.4

3 3 40 3.5

4 4 41 3.5

The above results show that prolonged heating time do not bring much significant improvements.

Example 11

One hundred and eleven grams of dry bagasse (i.e. 100 g of com¬ pletely dehydrated material) were placed in a horizontally rotating flask equipped with a reflux condenser (ROTAVAPOR) and 160 g of phe¬ nol and 240 g of 1.85% aqueous HCl were added. The flask was rotat¬ ed for 30 minutes at room temperature to ensure proper mixing of the ingredients after which rotation was continued under heating to re¬ flux temperature (bath at 105°C) for periods of times. After cool- ing, the mixture was treated as usual and gave the results shown in TABLE VI. TABLE VI

Sample Reaction time pulp yield Residual Yield of sugars(%) 5 (hrs) (%) lignin in pentoses hexoses pulp (%)

1 1 40 4.86 85 16

10 2 2 39 4.80 81 21

3 3 41 4.89 85 16

4 4 43 3.99 74 16

~~~ Example 12

Experiments similar to those of Example 10 were carried out using 42.5 g birch shavings (38.25 g anhydrous) , 53.55 g of phenol and 80.32 g of 1.85% aqueous HCl. Four samples were subjected to heat- 0 ing periods and the products were separated and analyzed as usual. The results are shown in TABIE VII.

TABLE VII 5

Sample Heating time Pulp yield Residual Yield of sugars(%)

(hrs) (%) lignin in pentoses hexoses pulp (%) 0

1 1.75 42 7.14 65 20

2 1.75 42 7.56 53 70

3 2.75 41.6 4.76 91 33 5 ^■ 4 2.75 41.7 4.66 64 12

^•^TJRΪX^^*-- The reason why the reproducibility of the results regarding the liberation of the sugars is not good has not been investigated.

Example 13

Experiments identical with those reported in Example 11 were carried out using four 110 g lots of birch-wood chips with either the addition of 80 g of phenol plus 120 g of 1.85% HCl (sample A) or the addition of 160 g of phenol plus 240 g of 1.85% B^l (sample B) . Heating periods were 2 and 4 hrs. Preheating time to refluxing temperature (i.e. to zero time regarding the boiling periods) was 20 min. After cooling the reaction mixture, it was successively wash¬ ed with hot water, warm dilute aqueous NaOH solution and water again. The results are gathered in TABIE VTII.

TABLE VIII

Sample Heating time Pulp yield Residual Yield of sugars(%)

(hrs) (%) lignin in pentoses hexoses pulp (%)

A-l 2 44 7.1 77 6.8

A-2 4- 39 4.2 82 5.8

B-l 2 40 5.6 78 11.4

B-2 4 37 1.9 90 12

These results do not show significant differences except with regard to the amount of cellulose converted to hexoses which is higher when using larger proportions of phenol + acid.

Example 14

A mixture of 111 g of chopped bagasse (100 g on a fully dry ba- sis) , 160 g of phenol and 240 g of a 1 N sulfuric acid solution (4.625% by weight) was rotated in a rotating evaporator under reflux for one hour. -Ihe reaction mixture was put on a filter and drained thus providing a liquid which decanted to two phases (organic, 80 ml and aqueous, 75 ml) . Then the pulp on the filter was washed with se¬ veral portions of hot water then with 1 N NaOH solution. The hot wa¬ ter washing portions were added to the 75 ml of aqueous phase alrea¬ dy separated. The remaining solid was dried and weighed 42.9 g.

Pentose, hexose and lignin analysis were carried out on the va- rious components and the following results were obtained: (distri¬ bution of the sugars in percent of their theoretical amount in the starting bagasse)

Combined aqueous fractions: C_j., 60%; Cg, 9%;_. lignin: —

Organic phase : -, 20%; Cg, 1%; lignin: 88% Dried pulp : C_ς, 20%; Cg, 90%; lignin: 12%

The 80 ml of the organic phase were boiled for one hour .with 80 ml of . the combined washing phase and after cooling and separation of the phases, it was found by analysis that 80% of the sugars ori¬ ginally retained in the organic phase had been extracted and had pas- sed into the aqueous solution. Thus, the overall yield of pentoses (dissolved in the water phase) was 76%. The other analytical results showed that 88% of the lignin originally contained in the sample had been dissolved, the residual lignin content of the pulp being 6.3%.

Example 15

One hundred and ten grams of crude bagasse (100 g dry having the following % by weight composition: pentosans 25.6: cellulose 40.2; Si0₂ plus water and organic extractibles 12) were refluxed for 1 hr with 160 g of phenol and 240 g of 1.85% aqueous HCl. The product was drained on a filter to provide a mass of pulp C and a filt ate which separated into two phases on standing: an aqueous phase, and an orga- nic phase AP. The water phase was decauted and used to wash C on the filter; C was then pressed and the total expelled liquids were allow¬ ed to stand whereby they again separated into a water phase Hϊ and an organic phase BP which was added to AP. The solid pulp C was again washed with a portion of hot water and drained by pressing. Ihe wash¬ ing liquids (D) were collected and analyzed for phenol, sugar, acid and other dissolved materials. Similar analysis were carried out on the other phases: BW, AP + BP and the pulp C. The results are report¬ ed in Table IX below:

TABLE DC (g)

Fraction phenol pentosans pentoses cellulose

C (46,8) 0.1 4.68 33.6

BW (180) 11.3 14.7

D (3300) 28.04 6.54 BP (180) L18.7 —— 2.8

Total 158.14 4.68 24.04 33.6

Fraction glucose lignin SiOg, other extractibles

C (46,8) _ 5.09 3

BW (180) 3.85 4.9

D (3300) 2.5 2.45

BP (180)^" - . 1 20.8 1.7

Total 7.35 25.89 12.05

Example 16

The same type of experiment described in Example 15 was carried out using 150 g of crude birch wood chips (135.6 g dry having the % by weight composition: pentosans 23.4 (26.6 potential pentoses); cellulose 40.0 (44.44 potential hexoses) ; lignin 20.33; uronic acids 8.98; acetyl groups 3.6; other water and organic extractibles 3.6, 217 g of phenol and 325 g of 1.85% HCl. Refluxing was carried out for 4 hrs instead of 1 hr. Other processing conditions were as in Example 15. Details and results are summarized in Table X.

TABLE X

Fraction (g) pphheennooll pentosans pentoses cellulose

Pulp (62.5) 0.17 6.88 48.7

Main water phase (274) 13.29 19.80

Final water phase (3250) 24.83 5.7 Organic phase

(252.8) 175.8 2.88

Fraction (g) gglluuccoossee lignin uronic acetyl others acids n

Pulp (62.5) —— 5.33 4 Main water phase (274) ^• 2.83 8.75 3.5 1.84

Final water phase (3250) 1.6 2.44 0.98 1.03 Organic phase

(252.8) 0.73 22.33 0.98 0.4 2.22

Example 17

The process of the present invention was also carried out using prehydrolyzed lignocellulosic materials instead of raw lignocellu- losic materials. Prehydrolysis was effected by boiling for instance chipped wood or other materials in divided form with dilute aqueous HCl or H₂S0_* according to usual practice. During prehydrolysis in such dilute acids (for instance 1 to 5% by weight solutions) part of the pentosans was converted, to pentoses which dissolved into the prehydrolysis solution. The method according to the invention was carried out afterwards, either by first removing part or all the pre¬ hydrolysis solution and replacing by the appropriate amount of phenol + dilute acid in accord with the conditions set up hereintofore, or 5 not removing the prehydrolysis solution and adding the required amount of phenol and adjusting the pH (by adding more water or acid depend¬ ing on the concentration of the prehydrolysis solution) to arrive at the proper diluted acid and phenol ratios for meeting the present delignification solution. Ωie main advantage of this modification 0 involving prehydrolysis prior to effecting the method of the inven¬ tion is to improve the recovery of the phenol afterwards; the reason for this better phenol recovery is not exactly known. Another advan¬ tage is that the time for delignifying prehydrolyzed lignocellulosic material is shortened in some cases. If the prehydrolysis solution

X5 has been separated from the material to be delignified before under¬ taking the method of the invention, it may either be processed sepa¬ rately for recovery of the pentoses dissolved therein or it may be combined with the water phase resulting from the delignification for total sugar treatment or recovery.

20 One hundred grams (dry basis) of red-oak wood drips (% by weight analysis: pentosans 18 (20.5 potential pentoses)); cellulose 39.9 (44.33 potential glucose; lignin 22.2; uronic acids 3.2; acetyl groups 5; ash undetermined and H₂0 plus organic extractibles 11.68) were boiled for 2 hrs with one liter of 4% aqueous H₂SO.. Then, the solid

25 was separated from the liquid and boiled with a mixture of 240 g of 1.85 aqueous HCl and 160 g of phenol. After cooling, 1 liter of aceto¬ ne was added, the solid was filtered and washed with acetone; then it was extracted ith acetone in a Soxhlet apparatus for several hours. All water and acetone wash liquors were combined and analyzed for

30 total phenol recovery. The amount of unrecovered phenol was only

3-3.5 g (approximately 2%) . In a corresponding control experiment (no prehydrolysis stage) , the amount of unrecovered phenol was appro¬ ximately 4%. Also, in the experiments, the amounts of residual lignin in the delignified pulp was only 2.3% by weight whereas it was 4.8%

35 in the case of the controls. Example 18

A sample of raw wheat straw (107.8 g; 100 g dry) was refluxed for 1.5 hrs with a mixture of 240 g of phenol and 360 g of 1.85% aque- ous HCl. The crude dry product had the following analysis (% by weight) pentosans 24.58; cellulose 41.55; lignin 17.26; uronic acids 0.89; acetyl 5.54; Si0₂ 2.37; water and organic extractibles 5.65. The further separation steps were carried out exactly as described in Example 15 and 16 and the results are summarized in Table XI. The figures represent grams.

TABLE XI (g)

Fraction (g) phenol pentosans pentoses cellulose

Pulp 0.12 2.32 43.94 Main water phase (270.2) 17.56 : 17 .72

Final water phase (2000) 33.88 4 .0

Organic phase

(289.3) 188.44 3 .55

Fraction (g) glucose lignin uronic acetyl others acids

Pulp ——— 2.29 "*— ¹ '''" 2.4 Main water phase (270.2) 3.42 0.6 3.0 3.48

Final water phase (2000) 2.6 0.29 1.0 2.3

Organic phase

(289.3) 0.6 14.97 0.1 1.54 2.5

Claims

C L A I M S

1. A method for simultaneous delignification of wood and other ligno-cellulosic materials and hydrolysis of the hemicellulose com-_r ponent thereof into corresponding pentoses in which said wood and other lignocellulosic materials are heated with acidic aqueous phenol

5 or other phenolic compounds and -ultimately separating a delignified cellulose from said aqueous acidic phenol, which comprises employ¬ ing one part by weight of said lignocellulosic material; at least 0.5 parts by weight of a diluted aqueous acid of a pH below 1.5; and at least 0.4 parts of phenol or other phenolic compounds; and heat- X0 ing under ambient pressure at reflux temperature of the aqueous mix¬ ture.

2. The method of claim 1, wherein the acid is selected from HCl, H₂S0^, HJPO,, and strong organic acids, oxalic acid, benzenε-sulfonic acid, trichloroacetic acid, and other alkyl and aryl-sulfonic acids

X5 and mixtures of said acids.

3. The method of claim 2, wherein the acid is aqueous hydrochlo¬ ric acid or sulfuric acid.

4. The method of claim 3, wherein the concentration of the HCl is 1 to 3%.by weight and the concentration of H₂S0₄ is.3 to 6% by

20 weight.

5. The method of claim 1, wherein the phenolic compounds are a mixture of phenols provided by a pyrolytic distillation of a lignin fraction from said delignification.

6. The method of claim 1, wherein the phenolic compounds co- 25 prise phenol-lignin produced from said delignification in admixtu¬ re with hydroxybenzene and/or phenols provided by a pyrolytic dis¬ tillation of a lignin fraction from said delignification.

7. The method of claim 1 in which the ratio by weight of liquid reagents to solid reagents is higher than the range of about 2:1 to

30 4:1, which comprises, subsequent to the heating, separating a deli¬ gnified cellulose by filtration and draining to provide a liquid fil¬ trate forming two distinc phases of an aqueous phase containing, dissolved, pentoses resulting frαn hydrolysis of hemicellulose in said material subjected to delignification and of an organic phase constituted by a major part of the employed phenol or other pheno¬ lic compounds and containing, dissolved, phenol-lignin from the deli¬ gnification; and separating the two distinct phases.

8. The method of claim 1 in which the ratio by weight of liquid reagents to solid reagents is below the range of about 2:1 to 4:1 which comprises, subsequent to the heating, adding further aqueous liquid to the reaction mass to aid filtration and draining, and sepa¬ rating the delignified cellulose from the liquid reagents as disclos- ed in claim 7.

9. The method of claim 8 in which said further aqueous liquid is warm water saturated with phenol.

10. The method of claim 7, which comprises separating pentoses from the aqueous phase by concentration, crystallization and isola¬ tion or by heating for converting them into furfural and isolation of the furfural.

11. The method of claim 7, which comprises distilling said orga¬ nic phase to provide a distillate and a residue and pyrolyzing the residue of said distillation to obtain phenolic compounds, a combus¬ tible carbonaceous residue, and combustible gases.

12. The method of claim 7, which comprises first practising the method of claim 7 and, second, practising the method of claim 7 again using as said phenolic compounds the" organic phase^* obtained in sai first practising.

13. The method of claim 1, which comprises first practising the method of claim 1 and, second, practising again the method of claim

1, using as the acidic aqueous phenol reaction medium a total liquid phase obtained after separation o_ς the delignified cellulose from the mixture resulting from said first practising.

14. The method of claim 7, which comprises employing the phenol- lignin and the phenols provided for making synthetic resins.

15. The method of claim.1, which comprises employing the deli¬ gnified cellulose for making paper pulp, cellulose derivatives such as viscose, cellulose esters and ethers, carboxymethyl cellulose, and sugars (glucose) derived from cellulose by hydrolysis.

16. The method of claim 1, wherein the lignocellulosic material is subjected to a prehydrolysis step with dilute aqueous acid prior to its heating with said acqueous acidic phenol. ^--T-pFi—--.