AU756976B2 - Method for separating lignocellulose-containing biomass - Google Patents

Abstract

The invention relates to a method for separating lignocellulose-containing biomass, especially wood, into the essential components in the form of lignin, hemicellulose and cellulose, with the following steps: a) pre-hydrolyzing the lignocellulose-containing biomass by treating it with water or steam; b) extracting the hydrolyzed hemicellulose obtained by pre-hydrolyzation with an aqueous medium; c) extracting the process-modified lignin that remains in the residue with an alkanolamine, isolating the lignin, recovering the alkanolamine, whereby the alkanolamine is not substituted by alkyl groups at the nitrogen atom, and d) obtaining a cellulose raw material. The inventive method is characterized in that hemicelluloses and lignin can be specifically separated from the cellulose in two different process steps. For this purpose, simple and commercially available system components can be used that facilitate an economical operation also with small installations.

Description

Translation Method for Separating Lignocellulose-Containing Biomass.

The present invention relates to a method for separating lignocellulose-containing biomass, especially wood or straw from cereal plants, into the essential components in the form of lignin, hemicellulose and cellulose.

The drawbacks with respect to classical cellulose processes are principally high water demand, high contents of organic substances in the waste water and the relatively high operating costs.

These latter are caused, last not least, by the ancillary operations for processing the brine and the waste water flows and/or residue by-product flows. Without application of sulfur-containing compounds, conventional methods do not succeed in separating the lignin; this involves noxious odors. The classical wood decomposition methods (sulfate, sulfite, milox) are some of the methods which chemically split the lignin and mainly dissolve the cleavage products (ligninsulfonic acid).

From an economic aspect, plants operating according to the conventional methods are only feasible with annual capacities of more than 200 000 tons. Overall, production of chemical cellulose occupies only a minor percentage of approximately 4% of capacity. On the other hand, every processor of chemical cellulose is desirous of obtaining custom-made cellulose grades tailored to his particular requirements and to obtain same, if possible, in different grade classifications.

With respect to the more recent methods, the "Formacell"-method constitutes a method which mainly dissolves the lignin and does very little to decompose same. ASAM and Organocell are combination methods. The ASAM-method in particular requires a complicated chemical recovery system.

A method which dissolves the lignin would have the advantage of being able to readily separate the lignin and other by-products.

Different from the paper cellulose (paper, cardboard, fluff), with respect to the chemical conversion pulp, the chemical properties of the cellulose fibers are setting the standard and not the physical properties, since the structure of the fibers is broken down during chemical cellulose processing. The following criteria play a role in this process: degree and distribution of polymerization, degree of brightness and solubility in NaOH.

One drawback of large-scale introduced cellulose methods is, no doubt, the loss in reactivity due to drying. So-called never-dried pulp (after cleavage and bleaching, not below 30% humid dried cellulose) is, on the other hand, highly reactive. Transportation of the cellulose requires formation of foil on a paper machine and drying. Significant technical costs are expended to that end, which is counter-productive, at least for processing the cellulose into derivatives, inasmuch as high costs are incurred in this step for the reactivation of the chemical conversion pulp. For further chemical processing, the existing fiber shape after cleavage undried would be much more suitable.

With respect to steam-explosion methods, according to the state of the art, pressures of 20 bar are customary for exceeding the softening temperatures of the lignin and polysaccharoses. The high steam temperatures of more than 200 0 C connected with these high pressures cause, on the one hand, high chain degradation of the cellulose, and they result, on the other hand, in condensation of the lignin with poor extractability as a consequence. Penetration of steam in crystalline regions of the ligno-cellulose structure is improbable; to that extent, modifications are not possible there.

The state of the art with respect to Steam Explosion is recorded in a multitude of patents, which relate primarily to the technical design and to the basic process methods. The majority of studies was performed with wood as raw material. In most of the cases, the focus was on optimizing the severity-factor (integral of the product of steam temperature and time of reaction).

One drawback in the utilization of steam is that additives cannot be introduced in the steam or introduced only with significant technical effort. Instead, the biomass must be brought into contact with the to be applied substances prior to the steam explosion, which is generally related §T or distribution and/or higher dosage. Similarly, this also applies with respect to the steam-refining process (steam cleavage method with subsequent mechanical fiber separation), which operates with lower steam pressure (10 15 bar) and employs mechnical devices for fiber separation).

The only fully continuously operable, large-scale cellulose cleavage method is steam-explosion of small chips or other biomass by means of the Stake System II of Stake-Tech Stake Technology.

Removal of the lignin presents the greatest challenge in all wood refining methods. Already at the end of the 19th Century, papers were published for alcoholic extraction of lignin from wood.

At that time, the objective was different from today's for the development of environmentally friendly wood refining methods. Growing criticism of the effects of traditional wood refining method upon the environment, stricter legal provisions concerning waste water discharge, air emissions and handling of waste materials, and also efforts towards better utilization of the wood substance can be viewed as the principal reasons for the increase in effort during the past years to develop new, environmentally friendly wood refining methods. Since chemical cellulose plays a subordinated role (percentage of global cellulose production only approximately the focus of research and development is concentrated on wood refining methods for the manufacture of paper cellulose. However, with chemical cellulose material, the quantitative removal of the lignin plays a greater role than with paper cellulose.

High lignin portions are present to greater extent in the center-lamella of the wood. This causes the rigidity of the wood. The maximum permissible lignin contents, after cellulose cleavage and prior to introduction of large scale bleaching, is cited as a figure of Of particular interest as raw material is also the straw from cereal plants, since there is an annual yield of 125 million tons of wheat straw in the USA and in Europe even higher -170 million tons.

In many countries mainly in Asia (for example China) and in Africa, there is a lack of wood as raw material for the production of cellulose, so that one is dependent upon the utilization of straw. Known refining methods are, for example, steam explosion or soda pulping (cellulose refining) of straw. The former method represents a relatively costly mechanical construction and does not solve the problem of clean separation of cellulose and lignin. The fiber separation is never totally complete, which necessitates subsequent refiners, mainly, however, high dilution of fiber suspension down to For the separation of lignin it is necessary, as in the past, to employ soda lye. The latter method represents a high environmental burden as a result of "straw pulp" mills and/or high costs of waste water processing with alkali-delignification.

Frequently, the technological effort is not expended with "non-woody"-mills, as what has, in the meantime, become state of the art with wood cellulose cleavage methods. With wood cleavage, one operates today with almost closed loops and effective recovery of boiling chemicals. With cleavage of "non-woody" fibers, such as straw, however, the facilities are frequently too small in order to apply the same high technological effort. Even if the size of the facility would economically justify recovery of the boiling chemicals, problems do exist, since it is difficult for the classic cleavage methods to cope with the high silicon contents. As a makeshift solution, a large portion of the utilized cleavage chemicals is simply discharged into the environment. Thus, cellulose factories on straw basis recover only 60% of the boiling chemicals.

In connection with pulping (cleavage of cellulose) two different applications of ammonia are state of the art: Fiber separation of lignocellulose material using ammonia for plastification at higher temperature by means of an explosion-like pressure tension release J. O'Connor Tappi 55(3), (1972) 353-358) and plastification of small chips in an Asplund-Refiner under pressure with ammonia: fiber separation requires a significantly lower amount of energy C. Peterson and R. W. Strauss J. Polymer Sci. C 36 (1971) 241-250). In both cases it was largely impossible to remove the lignin.

The utilization of alkanolamines for removal of lignin from ligno-cellulose was described, for the first time, by Elton Fisher and R.S. Bower Am. Chem. Soc. 63 (1941) 1881 1883). In the Seventieth, monoethanolamine was worked as additive to soda lye for pulping purposes (key words: alkaline pulping in aqueous alcohols and amines, acceleration of soda delignification, sulfur free delignification). Said method was to facilitate the reduction or even substitution of sulfur-containing chemicals.

One problem poses the conversion of the cleavage chemicals soda lye and ethanolamine and the separation of the lignin. Customarily, lignin is obtained from soda lye by precipitation under addition of acid. The lignin extraction from the solution of soda lye/alkanolamine by this method surely would not have made easier the conversion and recovery of the cleavage chemicals. The traditional combustion of lignin in the NaOH after concentration as the first step of the NaOH recovery would, in addition, lead to the loss of the alkanolamine, which would be connected with significant costs.

For that reason, presumably, the employment of monoethanolamine was given up as additive to the NaOH for the manufacture of high yield substances. In no case was the target the production of chemical cellulose. Monoethanolamine was applied, in all cases, to fresh wood, mostly wood from coniferous trees. Boiling took place in pressure vessels in batch operation.

Also described is the utilization of very little monoethanolamine as additive to aqueous ammonia solution (Patents: CA 1232109 Kauppi, Peter K. "Alkanolamine and NH O H in High-Yield Pulping" and also EP 149 753 Gordy, John "Nonsulfur Chemo-chemical Pulping") When treating small chips at temperatures of 120 0 C and higher, the monoethanolamine acts as plastification agent in these diluted aqueous ammonia-alkali solutions, which makes easier the subsequent mechanical fiber separation of the wood for production of cardboard- and/or paper.

According to the disclosure of US 2 192 202, a method is described for cellulose cleavage of raw ligno-cellulose materials, especially for extraction of alpha-cellulose and other valuable product, with utilization of at least 70% by weight of alkylolamine as treatment agent. The treatment is done by boiling under pressure between ambient temperature and 200 0 C for a period from 4 to 20 hours. NaOH can optionally be employed. Subsequently, the treatment medium is separated, the obtained cellulose is washed and bleached with diluted inorganic acid. The thereby achieved separation of the cellulose into the individual components is, however, completely inadequate and the obtained quality is unsatisfactory.

Accordingly, the invention is based on the object of making available a method for fractionation of lignocellulose-containing biomass, for which the addressed drawbacks of the state of the art have largely been eliminated. The wood components: hemicellulose, lignin and cellulose are to be extracted separately from each other, with the lowest possible impurity contents, in order to be able, in this fashion, to make these raw materials available to refiners, the objective being to make available a sulfur- and chlorine-free wood conversion method, which additionally works without soda lye and thus making superfluous costly recovery, exhaust air- and waste water R ion methods. In particular, the extraction of chemical cellulose is to be performed in a small, decentralized unit, in a manner which will save time, chemicals and energy. Cellulose is to be further processed as never-dried pulp, i.e. with high accessibility, directly into cellulose derivatives. With said method, manufacture of custom-tailored cellulose materials according to the criteria of the individual chemical cellulose processors shall be made possible in a costeffective manner and, in addition, in a state of highest reactivity, comprising an integrated processing sequence from wood to the cellulose derivative.

The above object is solved according to the invention by means of a process for separation of lignocellulose-containing biomass, especially wood, into the essential components in form of lignin, hemi-cellulose and cellulose, with the following steps: a) pre-hydrolizing of the lignocellulose-containing biomass by treatment with water or steam; b) extraction of hydrolized hemi-cellulose obtained by pre-hydrolization, with an aqueous medium; c) extracting the process-modified lignin that remains in the residue with an alkanolamine, isolating the lignin, recovering the alkanolamine, whereby the alkanolamine is not substituted by alkyl groups at the nitrogen atom, and d) obtaining a cellulose raw material.

The inventive method makes possible that ligno-cellulose is converted and separated into ist components, in that they are first subjected to pre-hydrolizing by treatment with water or steam, subsequently the formed hydrolyzed hemi-cellulose components are extracted with aqueous media and then the residue is subjected to extraction with alkanolamine, while recovering a cellulose raw material.

All types of ligno-cellulose can be employed with respect to the inventive teaching, i.e.

fractionation into the essential components cellulose, polysaccharoses and lignin. Suitable as lignocellulose-containing biomass are plant growth materials of the most diverse kind, such as wood, hulls of rye, stalks of corn and cereal, bagasse, straw of any kind, such as wheat straw, rice &w and rye straw. With wood it is customary to employ round wood or rest pieces of industrial wood, preferably in comminuted form, such as small wood chip. For fibrous raw materials, such as annuals, fibers are suitable that have been reduced by means of cutting.

Preferred use is made of comminuted or shredded wood in form of foliage tree wood, beech tree wood or wood from coniferous trees.

The water contents of the lignocellulose containing biomass may range between approximately by mass for the freshly harvested ligno-cellulose, especially 50% by mass, and, after intensive drying it may also be close to 0%.

The introductory step of the inventive method comprises pre-hydrolysis of the lignocellulosecontaining biomass by treatment with water or steam. Preferred mass ratio setting is a ratio of steam to biomass (based on dry substance) of approximately 1:1 to 3:1, of water to biomass of approximately 3:1 to 10:1, especially approximately 6:1. The biomass can hereby be subjected to a so-called steam-explosion method, and application of the steam-refining method is also possible. It is preferable to execute the pre-hydrolysis under gentle conditions, whereby the objective of said method step is to decompose the hemi-cellulose to such an extent that their subsequent separation as oligosaccharides with aqueous media can take place without any problem, like washing with water. Pre-hydrolysis is a known process step in the cellulose industry, which does not need to be explained in more detail here. Cellulose and lignin shall be affected as little as possible during this step.

According to the invention, the total decomposition of the hemi-cellulose can take place during the first step of the process, i.e. the pre-hydrolysis, since the alkanolamine will attack neither the cellulose nor the hemi-cellulose during the extraction step, but rather stabilize same. The prehydrolysis according to step a) can, however, also be performed at low scale. Pre-hydrolysis is then done to the extent that the acids attached to the hemi-cellulose, can be split off and, according to step b) the split-off acids are washed out. This plays a role especially with respect to the manufacture of high yield cellulose. Excess acid would react with the subsequently introduced alkanolamine and thus lead to losses. Consequently, a minimum pre-hydrolysis may already suffice.

In order to improve the effectiveness of the pre-hydrolysis, it is possible to also perform a twostage pre-hydrolysis at the same temperature and same boiling conditions, but with greater effectiveness, i.e. first steam and then hot water.

If, for example, straw is used as biomass, it is possible to forego the pre-hydrolysis according to step a) and b) and extraction may be performed directly according to step c) with increased temperature below approximately 170 0 C, preferably below approximately 160'C, specifically at approximately 115 to 135 0 C, in order to obtain paper cellulose. Alternatively, it is also possible to pre-hydrolyze the straw at approximately 150 0 C to 190 0 C, in particular approximately 170 0

C

and to subsequently perform an extraction according to step c) at higher temperature, below approximately 170 0 C, preferably below approximately 160 0 C, in particular approximately 115 to 135 0 C, in order to obtain chemical cellulose. Extraction of sugars is obtained by concentration of the pre-hydrolyzed substance, subsequent to which there may follow appropriate further processing. Depending upon desired cellulose quality, the appropriate variation can be chosen.

If appropriate, stabilizers may be added in order to avoid condensation of the lignin components.

Moreover, prior to performing step i.e. the pre-hydrolysis, the lignocellulose containing biomass can be subjected to acid or alkaline pre-treatment. This means further increase in yield of the desired products.

After the utilized steam-explosion- and/or the steam-refining method, for example, it is possible to treat the already well separated raw fiber material with hot water in order to dissolve and separate the major portion of the decomposed hemicellulose. The pre-hydrolyzed and softened biomass is thus freed from the developed hydrolyzed hemicellulose by extraction with an aqueous medium. To that end, excess water is preferably pressed-off and hot water wash applied.

This may be followed by a mechanical fiber separation of the biomass, for example diminution in a refiner to the desired degree of separation, which may be of significant importance, depending upon specific quality.

Then may follow an optional treatment with ammonia. This may be done at any appropriate location, after washing according to step with aqueous ammonia solution, with ammonia gas or with liquid ammonia.

The mass ratio of the liquid ammonia relative to the mass to be treated (based on dry substance) is set at a range between approximately 0.1 1 to 4: 1.

This is followed by an extraction of the biomass already freed from the hemi-cellulose of the process-modified lignin that remains in the residue with an alkalomine, while obtaining a cellulose raw material. Given consideration as alkanolamine are especially all alkanolamines which are not substituted by alkyl groups at the nitrogen atom. Thus are eliminated, for example: N-methyl-monoethanolamine and N,N-dimethyl-monoethanolamine, since these do not show any effect during extraction of the lignin from the wood.

The extraction medium monoethanolamine is preferably utilized which can be applied in preheated form, especially at approximately 80 0 C. It has been demonstrated that the extraction effect clearly increases in the series of untreated biomass via pre-hydrolyzed biomass to biomass pretreated with ammonia. Subject to the same treatment conditions, the lignin contents of the ammonia treated biomass extract is approximately by 60% higher than for the pre-hydrolyzed only biomass.

The extraction according to the invention preferably takes place under pressure, i.e. in an appropriate autoclave or a continuous extractor. With extraction under atmospheric pressure, it is possible to obtain equally good results, for example with straw.

For batch operation, i.e. in an autoclave, the biomass which has been washed clean from hemicellulose, comminuted and pre-treated in appropriate fashion with ammonia, is heated up including water contained therein, and extraction agent for at least 1 hour approximately, to a temperature ranging between 80 and 220 0 C. Solvents for the developing lignin decomposition components may also be already present.

Preferred vis-a-vis a batch operating mode is a continuous extraction. Same can be performed in that the biomass, which is filled into a pressure vessel, is being permeated by the preheated extraction agent or in that the to be extracted product, the biomass, is transported, in counter-flow to the extraction agent. Both variations have the benefit vis-a-vis the autoclave, i.e. the stationary operation, that side reactions are largely excluded as a result of the decomposition products being carried away with the extraction agent. In addition, it is possible to operate with a lower float ratio of extraction agent to small chips and at lower temperature, achieving equal extraction effect. The solubility of organosolv-Lignin in monoethanolamine is relatively high (250 g/liter).

In a specific preferred inventive embodiment, the extraction is performed by multi-stages, i.e. in at least two successive extractions with alkanolamine. In this procedure, the identical total volume of alkanolamine is preferably employed as that of a single-stage extraction. In this procedure, a counter-flow extraction can take place in effective manner, inasmuch as the shortest extraction times are hereby realized.

If, for example a two-stage pre-hydrolysis is performed, then this can very well be combined with the known technologies for the production of chemo-mechanical pulp [chemical mechanical pulp cmp], if the steam treatment of the optimally additionally with diluted acetic acid impregnated small chips is executed in a so-called "inclined screw reactor" (pre-hydrolysis proper) and then performs, under separation of fibers, the extraction of sugars according to the counter-flow principle. Monoethanolamine (hereinafter abbreviated as: MEA) as extraction agent presents various benefits. During the pulping process, MEA prevents lignin condensation and grafting onto cellulose it protects the cellulose from DP degradation, improves the delignification and reduces the demand for bleaching chemicals.

The alkanolamine extraction can be performed at lower temperatures (approximately 100 to 120 0 C) if pre-treatment with ammonia is undertaken. In spite of the low temperatures, low kappa numbers are then obtained. In addition, side reactions are greatly cut back.

After the extraction phase, the cellulose raw material is obtained. To that end, the deeply brown to black colored lignin extract is separated, in appropriate fashion, from the raw cellulose fibers and segregated according to the customary methods for solid/liquid separation. If complete removal of the remaining residues of process-modified lignin in the raw cellulose is desired, said ligning can be extracted with a suitable solvent by means of washing or by counter-flow washing.

The solvent employed in said procedure can subsequently be separated from the lignin and the extraction medium by distillation and recovered in this manner and is thus again available.

The residue, after the solvent has been distilled off, can, furthermore, be combined with the extract separated from the fibers. Separated from same by means of distillation, preferably by means of vacuum distillation, is the water and the alkanolamine serving as extraction agent.

Other separation processes are appropriate here as well, which, according to specification, lead to condensation of the lignin extract in border line situation up to dry mass. There is also successful separation of the lignin in that a non-solvent is added to the lignin solution in alkanolamine. The lignin then precipitates in the form of solid particles and can be separated from the extraction agent alkanolamine by an appropriate solid/liquid separation process, such as filtration, centrifugal extraction, thin layer evaporation or membrane separation method.

Separation of lignin can take place, for example, after the alkanolamine extraction, by introduction of CO 2 into the with water diluted or better with washing-water diluted and, if appropriate, concentrated lignin/alkanolamine extract. As a result of concentration by means of thin layer evaporation or a suitable other distillation method, a large portion of the alkanolamine is recovered in pure form. The remainder of the alkanolamine is distilled, after distilling likewise in vacuum, the water from the precipitation liquid following separation of lignin.

The lignin precipitation is thus accomplished by introduction of CO 2 and by centrifuging. The addition compound Alkanolamine*CO 2 developing with the CO 2 can again be fully decomposed into alkanolamine and CO 2 by application of heat or by injection of steam. The residue consists of lignin which has been highly reduced in its molar mass, but remains chemically essentially unchanged. Same can therefore be further used as a chemical raw material, for example for the manufacture of pressure setting plastics or polyurethanes.

The decomposed hemi-cellulose is present in aqueous solution or suspension and may likewise be used for other applications.

The raw cellulose has a kappa number of maximum approximately 20, preferably below approximately 10. This corresponds to a lignin contents of 3 or 1.5 mass-% and constitutes beneficial entry into the bleach.

In actual operation, a so-called "inclined screw reactor" can be employed for the pre-hydrolysis, followed by in the production of "CMP" (see above) customary fiber separation and ablution.

Preferred, for example, is the use of an inclined screw reactor for the pre-treatment with

NH

4 OH/alkanolamine, after that the above mentioned fiber separation for full lignin extraction in form of counter-flow extraction. These two steps result in the first instance in a low lignincontaining, water-rich fraction, which can be employed several times, with lignin concentration being undertaken, and in the second instance, in a high lignin-containing and alkanolamine-rich fraction. The combination of the two fractions at a ratio 'water-rich/alkanolamine-rich' of approximately 2/1 facilitates precipitation of the lignin by CO 2 at increased temperature. Only little water needs to be distilled from the alkanolamine-rich and water-poor fraction in order to then be able to recover, for example, the major portion of alkanolamine by means of thin layer evaporation and to concurrently thereby increase the lignin concentration by more than In order to better explain the inventive method, various variations are depicted in the attached Figures 1 and 2, in form of process diagrams of the method for separation of lignocellulosecontaining biomass. Figure 1 depicts the so-called pre-hydrolysis, for example in the form of the steam-explosion or the steam-refining method, which results after extraction in an aqueous medium for separation of the hemicellulose. Subsequently thereto, a fiber separation in a refiner is performed, which influences the execution of the further process course. This is then followed, optionally, by a treatment with ammonia. This may involve, for example, a so-called ammonia explosion. After that, there may take place another fiber separation in a refiner, leading subsequently to an extraction with an alkanolamine, especially a monoethanolamine, in batch- or continuous operating mode, for the separation of lignin and cellulose. Execution of an ammonia treatment is not necessarily required, it is possible, following pre-hydrolysis or following a steam explosion or a steam refining process, to directly follow-up with an alkanolamine extraction.

A variation of the alkanolamine extraction is shown in detail in Figure 2. A return circuit is shown here which represents the recovery of the employed solvent or of the employed extraction agent. Said variation permits an extraordinarily cost-effective operating mode.

A multitude of benefits are attached to the invention. One benefit lies, firstly, in that no sulfurcontaining chemicals are utilized for the wood pulping. Additionally, no chlorine containing chemicals need to be involved for the bleaching.

With respect to the pure steam treatment (steam refining, steam explosion) it is necessary, in contrast to the present invention, to select the so-called severity factor the integral from steam temperature and reaction period) so high so that both, the hemicellulose as well as the lignin can be successfully degraded, but under such drastic conditions, the molar mass of the cellulose also strongly decreases and the lignin fragments have a tendency toward condensation.

The advantages of said one-step processes result in a compromise with the quality of the fractionated components.

One of the benefits of the inventive method lies also in the fact that hemicellulose and lignin are separated from the cellulose in two different process steps by respectively appropriate and targeted measures. This has the result that the molar mass of the cellulose will not decrease quite as much and the lignin contents before bleaching is clearly lower than in the above cited methods and also in the industrially introduced processes (sulfate and sulfite methods).

In addition, the steam utilized for pre-hydrolysis of the hemicellulose can serve for preheating of the extractor. Thus it enjoys dual utilization. The energy which must be expended for fiber separation is likewise very low due to the substantial softening of the biomass after extraction.

Fiber separation occurs mainly after pre-hydrolysis, in some instances after the extraction step, without having to put up with significant charge in mechanical energy.

Another benefit lies in avoidance of soda lye as extraction means for lignin, as is customary after the steam explosion or steam refining method. It is precisely the utilization of soda lye which occasions the construction and operation of the so-called recovery facilities in the cellulose plants. Their size is predicated upon the rational operation of these ancillary fixtures which makes sense only from a cost-effective aspect in a certain order of magnitude.

If cereal straw is used as starting material, then the multi-step and expensive traditional recovery with NaOH is eliminated or the wet oxidation. With alkanolamine, the recovery consists of simple vacuum distillation. The addition compound Alkanolamine*CO 2 forming with the CO 2 can again be fully decomposed into alkanolamine and CO 2 by means of heat or injection of steam. The need for recovery of sodium salts is eliminated. As a result of simple pre-hydrolysis with water, the alkanolamine extraction becomes so effective that the raw cellulose already presents an ISO brightness of approximately 50%. Given the low water contents of the straw, alkanolamine extraction can be performed without pressure, which permits utilization of simple apparatuses.

The so-called "white liquor" in other words, the mixture of at least 20% soda lye and sodium sulfide in the sulfate (power) process is employed using a relatively high float ratio of 10:1 with respect to the biomass (for example in form of small chips) The biomass must, furthermore, be uniform in size (within relatively narrow limits) inasmuch as otherwise during separation for example, larger chips will not be adequately permeated with white liquor during the boiling time.

In contrast thereto, the invention permits extraction with an alkanolamine with substantially lower float ratio (approximately 3:1) especially with continuous operation. This has a positive effect upon the consumption of steam during extraction and recovery.

In the method according to the invention, after the pre-hydrolysis with steam, the biomass is also beneficially reduced to small chips in appropriate refining and defibrating vessels, using low mechanical energy, so that during the subsequent extraction with alkanolamine, diffusion processes will have no effect upon effective duration.

Small, decentralized production units of chemical cellulose cannot be operated at cost-effective conditions if there is the need for recovery of soda lye. The utilization of alkanolamines as extraction means is thus beneficial from two points of view: recovery by means of distillation does not require much energy, given the evaporation temperatures of these materials. The separation of the lignin can take place without use of acids, which likewise avoids costly processing steps and is beneficial for the environment.

Additives for preventing condensation of lignin are not required, which saves costs. Since there is no need for prior treatment with chemicals as is required for exclusive use of the steam explosion and steam refining method there are no problems with respect to their distribution.

Consequently the inventive methods has a very low reject rate (coarse wood components which, due to insufficient distribution have not been adequately separated into fibers).

In addition, after the extraction with alkanolamine, the cellulose material shows increased decrystallization in comparison with other processes. This, no doubt, is extremely favorable for the use of chemical cellulose, inasmuch as this affords uniform accessibility with respect to chemicals for the manufacture of cellulose derivatives. The possibility of using ammonia in clearly lower volume than with pure ammonia explosion of wood, likewise has a beneficial effect upon the operating costs. Expensive recovery of liquid ammonia is eliminated.

Since, naturally, the expenditure for bleaching is lower with lower kappa-numbers (lignin contents) after extraction, there likewise exist beneficial conditions in the inventive method. As a result of a totally continuous operation, the specific investments are, consequently, low and spatial/time exploitation is high. Simple plant components can be used which are commercially available. This permits economical operation already with small plant sizes (smaller by a factor of 10 than presently operated facilities). Furthermore, the alkanolamine recovery can be done with closed circuit. As a result, there is lower expenditure during concentration, lower water consumption and lower energy cost during distillation.

According to the invention, the pre-hydrolysis can be used either for full degradation or for degradation to a lesser extent, which provides for an additional variation possibility. If a multistage alkanolamine extraction is selected with respect to the inventive method instead of a single phase, then said alternative offers additional benefits with regard to efficiency and productive performance of process control. The inventive method also achieves improvement in the sugar separation by fiber separation before and/or after the pre-hydrolysis. Moreover, in order to improve the effectiveness of the pre-hydrolysis, it is possible to execute a two-stage prehydrolysis. Short dwelling times and effective extraction result, in addition, to lower furfural formation.

Continuous operation of the method also has benefits: Displacement of one process liquid by another liquid is eliminated, as it is required with respect to the classical pulping technology in boilers. The exchange and washing processes in boilers are less effective and last for a relatively long time. In addition, in actual practice, the defined sharpness in separation during displacement is such that there are frequently unwelcome mixings or unclear transitions, so that additional expenditure becomes necessary for recovery. In a continuous process it is possible to employ equipment which need not be designed for high pressures.

There is no necessity which exists with conventional boilers of expelling the air from the chip by means of water/steam, as otherwise there is danger that the prehydrolysis will not be homogeneous and uniform); because homogenous conditions exist in fiber separation according to the invention, such as employing, for example, the customary technologies during the e of "cmp". Also there is no risk with respect to fiber separation performed within the scope of the invention of acid residues remaining in the chips after the prehydrolysis and washing (which is unavoidable with traditional methods).

Drying can be eliminated for cost-effective operation of small decentralized units. This is possible with the method according to the invention. This then clearly reduces the specific investment and the operating costs. The inventive method provides, in addition, higher yields than other chemical cellulose processes; cold-alkali-extraction for attainment of low hemicellulose contents is likewise not required.

Bleaching of obtained product is possible, for example, with peracetic acid, which allows a directly following acetylation without change of solvents and constitutes high savings in cost. In the following, a detailed description is given of the invention, making use of examples, which are not intended to limit the inventive teaching. To the expert, additional specific exemplary embodiments will be obvious within the scope of the inventive disclosure.

Examples The following analytical methods were employed in the examples: a. Determination of Kappa Figure Lignin Contents Determination was made pursuant to "Code of Practice" IV/37/80 according to Zellcheming.

Volumetric analysis is done with 0.ln potassium permanganate solution (3.161/1). The number of ml per gram during titration consumed cellulose is equal to the kappa-number. Lignin contents can be estimated from the kappa-number by multiplication with 0.15.

b. Optical Density of the MEA Extract as Measurement for Lignin Concentration The measurement was taken concerning maximum adsorption of lignin, in a 1mm crystal bulb, involving extract that had been diluted by a factor of 100 with MEA, at a wave length of X 281 nm (compare Fengel, Wegener "Wood" page 159, table 6-5 Extinction coefficients of lignin: for organosolvlignin applies E 24 26[1/g*cm].

From our own measurements of UV spectra (concentration series with organosolvlignin in monoethanolamine) we ascertained the extinction coefficient for e 26 [1 g*cm] from the optical density at X 281 nm. Said extinction coefficient served for calculating the concentration of lignin extracted by MEA.

c. DP-Determination The DP determination was done with the known Cuoxam Method.

The following course of action was taken: 1. Prehydrolysis: Without addition of acid: The chopped-up chips were heated with steam in a boiler to 160 0 C, then left at 160 0 C for one hour. The condensate had a pH-value of 4.6.

With addition of acid: The pre-comminuted, chopped-up chips were heated up in a 10-liter autoclave under addition of sulfuric acid or hydrochloric acid, during a time period of 20 to 30 minutes, to reach final prehydrolysis temperature. The mass ratio of steam to chips (having 50% mass-% humidity) ranged between 1 1 and 3 1. Final temperature was between 120 0 C and 180 0 C. Dwelling times were maximally at 60 minutes.

2. Pre-treatment with Ammonia The pre-comminuted chips were treated for several minutes, under pressure, in a pressure-proof reactor with liquid ammonia, in proportion to a mass ratio in the range from 0.1 1 to 4 1, at temperatures from 80 T 125 0 C. After that, the contents of the pressurized reactor was discharged, at all once in one fell swoop, by opening a ball cock. The chips which still contained ammonia were subsequently subjected to further extractive treatment.

In an alternative treatment, the pre-comminuted chips were soaked at room temperature with ammonia in the form of commercially available ammonia water (25 mass-%) the ammonia water was then filtered off and extracted.

Example 1 (Comparison Example Comminuted and pre-hydrolyzed (160 0 C, 1 hour) chips (40 g) were treated with liquid ammonia, removed from the pressurized reactor by blow-like discharge and then beaten into single fibers with a kitchen mixer. The kappa-figure as ascertained at 142. Following an alkaline extraction (8 mass-% NaOH relative to chips, calculated on "oven-dry" basis) at 90 0 C for one hour, subject to thorough washing with roughly 50-time volume of distilled water and centrifuging in a wash drum, determination of solid matter contents at 30 40% and kappa-number at 131.

Example 2 (Comparison Example) Comminuted and pre-hydrolyzed chips (160 0 C, 1 hour) (40 g) were boiled in a mixture comprising liquid ammonia, monoethanolamine and water (80 g 40 g 20 g) in the pressure reactor at 140 0 C, then discharged, in one fell swoop, from the reactor, washed, and dried. The kappa-number amounted to 143 after the alkaline extraction of Example 1, the kappa-number stood at 129.

Example 3: Influence exerted of pressure during extraction with Monoethanolamine g of comminuted, pre-hydrolyzed and ammonia-exploded chips were respectively extracted with 110 ml MEA over two hours, on the one side under atmospheric conditions (boiling under return flow) and, on the other side, under pressure of 3 bar resulting in the autoclave at 180 0

C.

The optical densities (measured at 281 nm) amounted to 0.25 or 0.55. This indicates that pressure constitutes an important parameter with respect to extraction.

Example 4: Influence exerted by volume of extraction agent Monoethanolamine g of comminuted and pre-hydrolyzed chips were extracted with the below indicated quantities of MEA over a time span of three hours under pressures resulting in the autoclave at 155 0

C.

Results are represented in Figure 3. These results show that the-extracted lignin amount does not depend, within wide bounds, upon the employed amount of monoethanolamine relative to 10 g chopped-up chips of natural humidity (50 mass-%).

Example Influence of Temperature g of comminuted and pre-hydrolyzed chips were extracted with respectively 110 ml MEA over a time span of two hours under pressures resulting in the autoclave, at various temperatures.

Table 1 Temperature Pressure Optical Density 0 c] [bar] 155 3 0,48 180 6 0,83 198 9 0,62 Temperatures far in excess of the boiling point of MEA (170 0 C) obviously do not produce an additional increase in lignin extraction; this is possibly related to the decomposition of MEA in acetaldehyde and ammonia, which sets in above the boiling point.

Example 6: Influence of Extraction Duration g of comminuted and pre-hydrolyzed chips are extracted with respectively 110 ml of MEA for the duration of the mentioned time spans under the resulting pressures in the autoclave, at 155 0

C.

A time span of two hours extraction in the autoclave at 155 0 C appears to be required in order to achieve stable conditions.

Table 2 Duration (Hours) Optical Density 0,154 0,33 0,48 0,47 Example 7: Extraction with Derivatives of Monoethanolamine.

N-Methylmonoethanolamine and N,N-dimethylmonoethanolamine show no effect during extraction since Nitrogen is substituted by alkyl-groups.

Example 8: Influence of Pre-Treatment of Chips g of comminuted chips are extracted following varied pre-treatment, under pressure resulting in the autoclave, at 155 0 C. It has been demonstrated that pre-treatment exerts a significant influence on the extraction result.

a) with 110 ml MEA, duration 3 hours Table 3 Pre-Treatment Optical Density without pre-hydrolysis with pre-hydrolysis 0.43 0.47 0.73 pre-hydrolysis NH 3 -Explosion b) with 30 ml MEA and 3 hours duration Table 4 Pre-Treatment Optical Density with pre-hydrolysis with pre-hydrolysis NH 3 -Explosion with pre-hydrolysis NH -Explosion with MEA c) with 110 ml MEA, duration 1 hour Table Pre-Treatment with pre-hydrolysis with pre-hydrolysis NH 3 -Explosion with pre-hydrolysis NH 3 -Explosion with MEA 1.50 2.07 1.31 Optical Density 0.33 0.55 0.30 Accordingly, lignin extraction is considerably improved if an ammonia explosion has taken place. On the other hand, the addition of MEA with the ammonia to the comminuted chips, prior to the explosion, produces no positive effect vis-a-vis the NH 3 -explosion without MEA-addition.

Example 9: Influence of multiple extraction treatments of the same specimen.

This is to demonstrate the efficiency of the extraction treatment. 10 g of comminuted and prehydrolyzed chips were extracted under pressure resulting in the autoclave, at 155 0

C.

Through-put First extraction Second extraction Duration [h] 2 2 Table 6 MEA [ml] 110 60 Chips [g] 10 5.5 Optical Density 0.48 0.083 Already with the first through-put, the chips had largely lost the lignin.

Through-put First extraction Second extraction Duration [h] 3 2 Table 7 MEA [ml] 30 30 Chips [g] 10 10 Optical Density 0.419 0.036 It is possible with only a small amount of MEA to reduce already with the first through-put the lignin contents to less than 10% of the original percentage (compare optical densities).

Through-put Du first extraction 45 second extraction 45 third extraction 45 ration [min] Table 8 MEA [ml] 30 30 30 Chips [g] 10 10 10 Optical Density 0.266 0.189 0.066 Even with an extraction time of only 45 minutes and a small quantity of monoethanolamine, it is possible to successively lower the lignin contents.

Example Continuous Extraction The results of continuous extraction are explained by means of Figure 4.

Recorded are the cumulative extracted lignin amounts, stated in of absolute lignin contents, for series 1 (100 0 series 2 (140 0 C) and series 3 (170 0 Extraction velocity amounted to approximately 45 ml per hour. Comminuted and pre-hydrolyzed chips (40 g) were used. The employed equipment is a pressure-proof chromatography column which was filled with the chips. Said column was brought by electrical heating strips to the stated temperatures; temperatures were kept constant by means of an electronic control. The monoethanolamine was pumped, by means of a high-pressure pump (HPLC), in pre-heated condition, through the chips.

Fractions of 25 ml each were collected, the optical density of which was measured, after having been diluted by a factor of 100.

Fig. 4 registers on the ordinate, the relative percentage rate of lignin extracted from the wood.

100% of extracted lignin corresponds in this analysis to the lignin amount originally contained in the wood.

With use of 40g of wood having 50% humidity by mass, the percentage of wood is 20 g. With a typical lignin contents of 22 mass-% for beech wood, the contents accordingly is 4.4 g of lignin.

These 4.4 grams of lignin correspond to the value of the ordinate of 100 in Fig. 4, in other words, the entire lignin contents contained in the wood was extracted. The same is now true for lesser ordinate values.

Table 9 Extracted Lignin in of originally in wood contained Lignin Lignin still remaining in wood Kappa-Number Quantity in g Quantity in 0.44 0.88 1.32 3.52 3.96 0 2.2 4.4 6.6 17.6 19.8 22 0 14.7 29.3 44 117.3 132 146.7 absolute percentage of lignin contained in wood the kappa-number is a quantity which is traditionally used in the wood pulp industry; it is calculated from the absolute lignin contents in that the lignin contents value is divided by 0.15.

For example, with respect to series 2 in Figure 4, in other words the dark column, the results show that with the 4th fraction, the dark column attains nearly 80%. Since the amount of extracted lignin is indicated on the ordinate in percent of rate originally contained in the wood, it can be concluded that after the 4th fraction only 20% of the originally in the wood contained lignin had not as yet been extracted. Since the extraction process takes place at an extraction velocity of 45 ml per hour and since each fraction totals 25 ml, it is estimated that after 4 fractions 100 ml of extract, extraction time stood at somewhat over 2 hours.

Example 11: The inventive method was executed with Eucalyptus Urograndis. The following determinants were carried out: a) cellulose yield and xylose contents of Eucalyptus Urograndis: Wood Pulp Highly pure Solucell* Wood Pulp with low Xylose content (according to invention) H. Sixta, A. B Table Cellulose Yield 95.9 97.55 Xylose Contents orgards "Paper" 4 (1999) page 220 ff.

b) Xylose contents and DP for Eucalyptus Urograndis: Wood Pulp Highly Pure Solucell Wood Pulp with low Xylose-contents (according to invention) Cellulose Contents 95.9 98.7 Table 11 Xylose Contents DP 1.9 620 1.2 750 c) Acetic Acid Retention Capability: Table 12 Wood Pulp Acetic Acid Retention Capability Acetylated wood pulp (commercial grade) 38 Acetylated wood pulp, (commercial grade) treated with liquid

NH

3 then NH3 exchanged for water and, lastly water exchanged 77 for anhydrous vinegar Wood Pulp, never-dried (according to invention) 105 Wood Pulp, dried, lh at 105 0 C (accord. to invention) 54 d) the obtained X-ray diffraction diagram is apparent from Figure 5. Ascertained peaks were as follows: Peak 02- old B old INT old 0 20new B new INT new INT(F) 1 16.110 4.803 353.2 15.540 3.885 303.6 11793.8 2 21.000 7.000 250.0 20.901 7.808 203.6 15900.8 3 22.610 4.070 859.7 22.266 2.418 706.8 17088.5 4 34.300 1.000 30.0 34.372 2.668 72.1 1923.7 Substratum 47.7 2.61020 Table 14 Peak 1: 20 15.540 3 3.8850 INT= 304 c/s 69% Peak 2: 20 =20.901 13 7.8080 INT= 204 c/s 93% Peak 3: 20 22.266 13 2.4180 INT 707 c/s 100% Peak 4: 20 34.372 B 2.6680 INT 72 c/s 11% 11-0 AI '?0 Example 12: Pre-Hydrolysis of Eucalyptus A pre-hydrolysis of Eucalyptus was performed with the inventive method. The following Table depicts mass results, taking into consideration the effect of comminution by a disc refiner: Table Carbohydrates in mass% relative to dry mass Original chips Chips[Eucalyptus] Pre-hydrol.

with nonreduced chips Pre-hydr with reduced chips Nonreduced chips after wash phase Reduced chips after wash phase Raw Pulp from non reduced chips Raw Pulp from reduced chips Galactose Glucose Xylose Mannose 0.47 54.5 4.5 0.63 0.58 56.8 5.1 0.64 61.5 3.1 0.65 65.2 60.9 2.4 63.3 95.5 2.3 monosaccharide total 57.7 96.2 not detectable below detection limit (0.3 mg/100 mg) Example 13: Effect of pre-treatment with ammonia water a) for pretreatment at room temperature over a time space of 30 minutes, 25% ammonia water was used in such quantity so that for 30 grams of reduced beech chips having a water contents of 70 by mass, 7 grams of pure NH 3 was employed. Extraction of lignin from reduced chips impregnated with ammonia water was done with 60 grams MEA at 140 0 C over the course of two hours. A kappa-figure of 10 was obtained with this procedure.

b) A comparison test (without impregnation) resulted, under otherwise equal test conditions, in a kappa-figure of 18.

The influence of temperature on lignin extract, utilizing MEA, either with or without pretreatment with ammonia water is apparent from Figure 6. It becomes quite clear that at equal extraction temperature it is possible to reduce the kappa-figure, after a preceding treatment with ammonia water. For attaining a given kappa-figure, subject to appropriate pre-treatment, it is possible to operate with a lower extraction temperature (lower by approximately 15 to 20 0 It becomes evident from extrapolation of curves kappa f (extraction temperature) to lower temperatures that it is quite possible, as a result of impregnation with ammonia water, that the extraction temperature can be reduced to 100 110 0 C. Low extraction temperature has the effect that fewer side reactions will take place. The relationship of activation energies of extraction, with/without pretreatment with/without ammonia water can be determined from the inclination of the straight line In(kappa) vs. 1/T to 0.87.

Example 14: Effect of a multi-stage extraction When using an overall equal amount of monoethanolamine for lignin extraction, there is a greater drop in the kappa-figure if the employed amount of monoethanolamine is distributed over two succeeding extractions. This is demonstrated in Figure 7, in which the kappa-figure of eucalyptus pulp is shown after a single-step and dual step extraction with monoethanolamine 1 boiler; T 160 0 C; tI step 90 minutes, t 2 step 120 minutes.

Example Influence of prevailing pressure during extraction: This influence is shown in Figure 8. The kappa-figure is represented for eucalyptus pulp following two-step extraction with monoethanolamine (parameters: with and without pressure, laboratory autoclave, T 160 0 C, t 2 x 60 min.).

Example 16: Influence of water contents during MEA extraction of Lignin: With a mass ratio of MEA/Water 4.9/1 and a wood moisture of 50% (total water contents in the system during extraction approx. 17%) no difference is found with respect to extraction conditions of 2 hours at 160 0 C and an extraction of said reduced chips with pure MEA (total water contents in the system during extraction, approx. However, extractive effect diminishes if the mass ratio of MEA/Water is 2.6/1 (Total water contents in the system during extraction, approximately 26%).

Example 17: Influence of hemi-cellulose contents upon extractability of lignin With previously employed substances for the MEA extraction, the pre-hydrolysis degree varied significantly. Accordingly, residual hemi-cellulose contents varied from 1.5 to 16 mass-%. Any significant influence on extractability oflignin by monoethanolamine could not be ascertained.

Example 18: The yield when following the process steps of "Pre-hydrolysis washing MEA-extraction washing" when using the same type of wood is clearly greater than with conventional pulping methods and is also greater with more recent pulping methods. Eucalyptus pulping with lower Xylose-contents (acetate grade) can be obtained with much higher yield than with a modem prehydrolysis-sulfate method. A tabulated overview is shown in Table 16: Table 16 Cellulose Tests (at applicant) 20 1 Autoclave (at applicant) Invention Modem Prehydrolysis-sulfate method** Solucell Very pi vise. Solucel Test X XI VII-EO 1 59X 4.5:1 ure 11 Liqid/solid ratio 3:1 in pre-hydrolysis.

Aid Conc. 0 Heating Time 30 (min) Pre-Hyd. 170 Temp. °C Pre-Hydr. (min) 120 DP 460 Glucose* 97.4 Xylose* 1.9 Mannose* 0.75 Yield/Cellulose 44.6 Relative Yield 86 Wood 3.55 Requirement in m 3 f. 1 ADMT Cellulose Composition cellulose, 20 for example: 4.75%AcOH 30 5%AcOH 18 1.7 AcOH 120 0.2%AcOH 170 90 750 97.9 1.7 0.3 45.5 88 90 680 97.2 2.2 0.7 45.3 87 3.5 170 90 970 98.7 1.2 0.1 49.1 94 3.2 1215 92.2 6.9 0.9 48.6 93.5 3.3 550 93.8 3.6 0.5 38.5 74 620 95.9 1.9 0.2 34.5 66.3 3.5 4.1 4.6 of Eucalyptus Kordsachia, R. Pan, H. Sixta "Paper 2" (1999) 96:52% glucuronoxylate, 2% glucomannose and 23% lignin Bacell Process Sixta, A. Borgards "Paper 4" (1999) pages 220 ff.) Example 19: Variations of the Pre-hydrolysis Conditions.

Depending upon the type of wood involved, the pre-hydrolysis (heating time, duration, temperature, type of acid and concentration) can be adapted in order to attain the desired hemicellulose content. The following table indicates the attained state with respect to test in the laboratory autoclave (heating time approximately 30 minutes): Table 17 Test Liquid T C Dwell Time Cellulose Xylose distined as glucose Mannose VH-27 0.6% 3:1 160 60 98.0 1.7 0.3 Beech

H

2 S0 4 VF-4 0.3% 4:1 150 60 93.9 2.7 3.4 Pine

H

2 S0 4 VH-P-M1 Water 6.5:1 160 180 93.7 6.1 0.2 Straw VE-4 0.3% 4.5:1 150 60 98.8 1.0 0.2 Eucalyptus H 2 S0 4 Acetic acid is not sufficient for complete pre-hydrolysis of hemi-cellulose in beech wood. A hemi-cellulose contents of approx. 3 mass-% is attainable for reduced beech wood chips without addition of acid in pre-hydrolysis. Under these conditions, the mannose contents is Thus, the a-cellulose contents is 96%, which is adequate for chemical cellulose except for acetylate cellulose. It was, however, possible to attain the required low xylose contents 2 mass-% in beech wood under more stringently delineated separation conditions and in Eucalyptus wood with less stringently delineated conditions. No deterioration of target values was ascertained with change-over to chips in original size. The results were even better in larger autoclaves.

Example A pre-hydrolysis was performed with modified hydrolysis temperature, as indicated in Figure 9.

It is apparent from Fig. 9 that with increasing concentration of sulfuric acid, it is clearly possible to reduce the residual xylose contents.

Example 21: Straw as biomass Straw was coarsely reduced with scissors and pre-hydrolyzed with water at a float ratio of 10:1, in a small laboratory autoclave (holding capacity 300 ml), at a temperature of 170 0 C and a pressure of approximately 7 bar. This procedure was undertaken with a heating time of approximately 30 minutes and a dwell time of 120 minutes. After removal of the pre-hydrolysate and after a water rinse, the pre-hydrolyzed moist straw was reacted with MEA at a ratio of 1:6.5.

It was reheated to 1600 C for 30 minutes and held at that temperature and at a pressure of 3 bar for three hours.

The resulting analysis provided the following composition: Cellulose (as glucose) Xylose Mannose 93.7% 6.1% 0.2% Yield came to 40% degree of whiteness: Example 22: Example 21 was repeated, but no pre-hydrolysis was performed.

whiteness came to 22%.

The attained degree of Example 23: A test was made with autoclave open to the atmosphere. Straw, which had been reduced in size, was directly subjected to an MEA extraction. The conditions were: 160 0 C, float ratio 10:1 MEA/Straw and 180 minutes boiling time. Contrary to expectations, no unpleasant odor developed during boiling of the not pre-hydrolyzed straw with MEA, nor did any steam exit from the autoclave. The degree of whiteness was 29%.

Example 24: The obtained products from the preceding examples were each tested for accumulated byproducts of monoethanolamine. Findings showed that the by-products of monoethanolamine, such as N-methyl-monoethanolamine, N,N-dimethyl-monoethanolamine, N-acetylmonoethanolamine and N-formyl-monoethanolamine did not occur, or, in one instance when using N-methyl-monoethanolamine, were present at a rate of 0.3% only (in proportion to the analyzed MEA-lignin extract). The employed analytical method for this purpose was the socalled Space-gas-chromatography.

Claims (25)

1. Method for separating lignocellulose-containing biomass, into the essential components in the form of lignin, hemicellulose and cellulose, with the following steps: a) pre-hydrolyzing the lignocellulose-containing biomass by treating it with water or steam; b) extracting the hydrolyzed hemicellulose obtained by pre-hydrolyzation, with an aqueous medium; c) extracting the process-modified lignin residue with an alkanolamine, isolating the lignin, recovering the alkanolamine, wherein the alkanolamine is not substituted by alkyl groups at the nitrogen atom, and d) obtaining a cellulose raw material. washed out. S:3. Method according to Claim 1 or 2, characterized in that comminuted or S..shredded wood, is used as lignocellulose-containing biomass.

4. Method according to claim 3 wherein said comminuted or shredded wood comprises foliage tree wood, beech tree wood or pine tree wood. Method according to Claim 1 or Claim 2, characterized in that cereal plant straw is utilized as biomass.

6. A method for separating lignocellulose-containing biomass comprising cereal plant straw to recover a cellulose material comprising extracting the biomass with an alkanolamine, isolating lignin, recovering the alkanolamine, wherein the alkanolamine is not substituted by alkyl groups at the nitrogen atom, and obtaining a cellulose material, with the proviso that subsequently no enzymatic hydrolysis with cellulose is

7. Method according to Claim 6 wherein said step of extracting the biomass with an alkanolamine is performed at a temperature below approximately 160'C.

8. Method according to Claim 6 wherein said extracting step is performed at approximately 115 to 135 0 C.

9. Method according to Claim 4, characterized in that pre-hydrolysis is performed at approximately 150 to 190 0 C and thereafter extraction is performed according to step at increased temperature, below approximately 170 0 C in order to obtain chemical cellulose. Method according to Claim 9 characterised in that pre-hydrolysis is performed at approximately 170C.

11. Method according to Claim 9 or Claim 10 wherein extraction is performed according to step below approximately 160'C.

12. Method according to Claim 11 wherein extracting is performed according to step at a temperature of from approximately 115'C to approximately 135 0 C.

13. Method according to any one of claims 1-5 or 9-12, characterized in that the pre-hydrolyzed, lignocellulose-containing biomass is mechanically separated, prior to o• •performing step a a i 14. Method according to any one of claims 1-5 or 9-13, characterized in that prior to steam treatment of step additionally an acid or alkaline pre-treatment is undertaken. Method according to any one of claims 1-5 or 9-14, characterized in that the pre-hydrolysis according to step is performed in the form of a steam-explosion or steam-refining method.

16. Method according to any one of claims 1-5 or 9-15, characterized in that, according to step a solvent or solvents is/are added for lignin.

17. A Method according to any one of claims 1-5 or 9-16 characterized in that the Sbiomass is treated with water in step and the ratio of water to biomass (related to dry substance) in step is adjusted to approximately 3:1 as 10:118. Method according to claim 17 wherein the mass ratio of water to biomass is approximately 6:1.

19. A method according to any one of claims 1-5 or 9-16 in which the biomass is treated with steam in step and the mass ratio of steam to biomass (related to a dry substance) in step is adjusted to approximately 1:1 to 3:1. Method according to any one of claims 1-5 or 9-18, characterized in that the water prior to step is pressed out of the obtained mass and same is subsequently mechanically separated into fibers.

21. Method according to claim 20, characterized in that the fiber-separated mass is additionally washed with hot water.

22. Method according to any one of claims 1-5 or 9-21, characterized in that according to step a treatment is additionally performed with aqueous ammonia solution, with ammonia gas or with liquid ammonia. oo

23. Method according to claim 22, characterized in that it is worked with liquid ammonia at higher initial pressure as compared with atmospheric pressure. oooo.

24. Method according to claim 23, characterized in that the obtained mass is still hot from the preceding steam treatment and washing, and the available volume of the mass to be treated with ammonia, and stripped of hemi-cellulose, is enlarged, in explosion-like fashion, while dropping the pressure by at least 5 bar. Method according to Claim 24, characterized in that the mass ratio of liquid ammonia to mass to be treated (referring to dry substance) is adjusted to approximately 0.1:1 to 4:1.

26. Method according to any one of claims 1-5 or 9-25, characterized in that in Sstep at least two succeeding extractions with alkanolamine are performed. 37

27. Method according to any one of the preceding claims, characterized in that extraction takes place for at least one hour approximately, at a temperature of approximately 80 to 220 0 C.

28. Method according to any one of the preceding claims, characterized in that the extraction medium is preheated.

29. Method according to claim 28 wherein the extraction medium in step is preheated to at least approximately Method according to any one of the preceding claims, characterized in that monoethanolamine is employed as extraction medium.

31. Method according to any one of the preceding claims, characterized in that after extraction, residues of the process-modified are dissolved in the alkanolamine and the residues are adhering to the raw cellulose, and wherein the residues are removed from the raw cellulose by a solvent.

32. Method according to claim 31, characterized in that the residues adhereing to the raw cellulose are removed with the solvents via washing or counter-flow washing and, subsequently, the solvent is separated from the lignin and the extraction medium °alkanolamine by distillation and reclaimed for renewed application. S33. Method according to claim 31 wherein the solvent is separated from the lignin S* and the extraction medium alkanolamine by distillation and said solvent is recovered for renewed use. °°oo

34. Method according to any one of the preceding claims, characterized in that removal from the raw cellulose of the alkanolamine with the therein dissolved process-modified lignin takes place by means of squeezing or centrifuging. Method according to any one of the preceding claims, characterized in that the process-modified lignin is precipitated from the alkanolamine by addition of a non- solvent and separated by solid/liquid separation processes. Method according to claim 35, characterized in that the precipitated lignin is 4 z, 38 separated from the alkanolamine by filtering or centrifuging.

37. Method according to claim 35, characterized in that the process-modified lignin is separated from the alkanolamine in a thin layer evaporator or a membrane process.

38. Method according to claim 1 substantially as hereinbefore described with reference to the accompanying drawings.