EP2714650A1

EP2714650A1 - Process for preparing polyisocyanates from biomass

Info

Publication number: EP2714650A1
Application number: EP12723181.9A
Authority: EP
Inventors: Eckhard Stroefer; Otto Machhammer; Stefan Bitterlich; Roman Prochazka; Mario Emmeluth; Emmanouil Pantouflas; Julia Leschinski; Dirk Klingler; Stephan Deuerlein; Stephan Schunk; Jochem Henkelmann; Dieter Stützer
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2011-05-24
Filing date: 2012-05-23
Publication date: 2014-04-09
Also published as: KR20140037139A; CN103649044A; JP2014520086A; WO2012160072A1; BR112013029665A2

Abstract

The present invention relates to a process for preparing polyisocyanates from natural raw material sources by starting from a biomass material and preparing a composition which comprises low molecular mass aromatics that contain per molecule at least one hydroxyl group or at least one alkoxy group (oxyaromatics), reacting these oxyaromatics to form the corresponding aromatic amines, and, optionally after condensation with formaldehyde, carrying out further reaction with phosgene to form compounds containing isocyanate groups.

Description

Process for the preparation of polyisocyanates from biomass

BACKGROUND OF THE INVENTION The present invention relates to a process for the production of polyisocyanates from natural raw material sources, which comprises, starting from a biomass material, preparing a composition containing low molecular weight aromatics having at least one hydroxy group or at least one alkoxy group per molecule (oxyaromatics), reacting these oxyaromatics to the corresponding aromatic amines and, optionally after condensation with formaldehyde, further reacting with phosgene to form isocyanate-containing compounds.

PRIOR ART Polyisocyanates (hereinafter, according to general practice, the compounds having more than 2 NCO groups per molecule are also referred to as "diisocyanates") are valuable precursors for the preparation of polyurethanes. Polyurethanes are considered to be the class of plastics with the highest application width in various applications. Accordingly, the global markets for polyisocyanates and polyurethanes have been showing high growth rates for years. The most important diisocyanates are MDI (methylene diphenyl diisocyanate) and TDI (tolylene diisocyanate).

On the one hand, MDI is marketed as a mixture of oligomers and isomers, which is referred to as polymeric MDI (PMDI, polymethylene polyphenylene polyisocyanate). On the other hand, MDI is marketed in the form of the lowest oligomer, the so-called 2-ring MDI, which contains only two aromatic rings in the molecule and is also referred to as monomeric MDI (MMDI). The MMDI is sold either in pure isomeric form or as a mixture of different isomers. The oligomer and isomer composition of the PMDI is determined by the manufacturing process, its operating conditions and the process. PMDI is thus a typical example of a product that can best be characterized by its manufacturing process. From the crude product of the process (the crude MDI mixture), the MMDI can be separated by a separation step. On an industrial scale, this separation step is usually a distillation or crystallization.

In the process for the preparation of TDI, a crude TDI mixture is initially obtained, which consists predominantly of isomers of TDI and of oligomers which are crosslinked via urea and diisocyanate groups. The composition of the oligo- It is also determined by the manufacturing process. The pure isomers or certain isomer mixtures can be obtained from the crude TDI mixture by separation, which generally comprises a distillative separation step. As a precursor for the production of MDI, the corresponding MDA (methylenediphenyldiamine) can be condensed with formaldehyde in an acid-catalyzed manner by customary processes. This process can be carried out both continuously and discontinuously (eg DD 295628 and DD 238042). It is also known to produce diisocyanates from corresponding amines and phosgene. The reaction is carried out either discontinuously or continuously, depending on the nature of the amines, either in the gas phase or in the liquid phase. The continuous production of organic diisocyanates by reactions of primary organic amines and phosgene is widely described and practiced on an industrial scale.

Today's large-scale syntheses of the above-mentioned diisocyanates are almost exclusively continuous. In general, the continuous embodiment of the method is multi-stage. In the first stage of phosgenation, the amine is reacted with phosgene to give the corresponding carbamoyl chloride and hydrogen chloride and to amine hydro chlorides. The primary reaction between amines and phosgene is very fast and exothermic. In order to minimize the formation of by-products and solids, amine and phosgene, both optionally dissolved in an organic solvent, e.g. B. be mixed quickly. The next stage of phosgenation involves both the decomposition of the carbamoyl chloride to the desired diisocyanate and hydrogen chloride, as well as the phosgenation of the amine hydrochloride to the carbamoyl chloride.

Liquid phase phosgenations are described, for example, in EP-A-1 616 857, WO 2004/056756, WO 2006/130405, EP-A-1 509 496, EP-A-1 270 544 and US Pat

DE-A-199 61 973.

To avoid the formation of undesired intermediates of the amine hydrochlorides, the phosgenation can also be conducted as gas phase phosgenation at high temperatures. Such methods are described by way of example in EP-A-593 334, WO 2003/045900, WO 2008/086922 and WO 2008006775 (aerosol phosgenation).

Furthermore, the phosgenation can be carried out in supercritical solvents (WO 2008/049783). Further, as a solvent, the isocyanates themselves (EP-A-1 401 802, US 6,683,204) or ionic liquids (WO 06048141,

WO 2006048171) can be used.

An important problem to be solved lies in the cost-effective and sustainable provision of suitable amines, which account for between 40 and 80% of the production costs of the polyisocyanates and whose availability on the world market is limited. This problem is particularly significant for the provision of aromatic amines. Aromatic amines are conventionally from the corresponding aromatics such. B. benzene or toluene according to the prior art by a nitration step with subsequent hydrogenation of the nitro group to the corresponding amine. For the preparation of nitroaromatics, a wide variety of batch and continuous processes are known. The nitrating agent is usually either a mixture of nitric acid and sulfuric acid or nitric acid alone. After the aromatic compound has been functionalized by nitration, it still has to be hydrogenated to obtain the corresponding amine. The hydrogenation is usually carried out in the presence of a catalyst, wherein water is obtained as a by-product. It can be done technically in various technical configurations such as fluidized beds or fixed beds or in liquid or gaseous phase.

The preparation of polyisocyanates according to the prior art thus has the following technical disadvantages:

The nitriding step as well as the hydrogenation step produce wastewater which requires special treatment.

Since nitro compounds are high-energy substances with very high decomposition energies (> 1000 J / g), the processes make costly safety measures necessary.

The functionalization of the aromatic body to provide the amine for the production of TDI or MDI, requires a complex multi-stage

Method.

There is therefore a need for an alternative way of providing suitable amines for polyisocyanate production.

The large quantities of biomass constantly produced by nature are so far only used to a limited extent as renewable raw materials for material use or for energy production. In order to conserve raw material resources, processes are needed to replace fossil raw materials with biomass feedstock. lien. The aim is to achieve a high efficiency as complete as possible use of biomass material once provided.

It is known to subject streams of various digestion processes of lignin or lignocellulosic materials to aftertreatment for the production of valuable substances.

US 2,057,117 discloses a process for producing vanillin which comprises heating a starting material selected from lignocellulose, a crude lignin extract and lignosulfonic acid with an aqueous alkali metal hydroxide solution under elevated pressure and adding sulfuric acid to the resulting reaction mixture to form organic To precipitate components and convert the vanillin into a soluble form. WO 99/10450 describes a process for converting lignin into a hydrocarbon fuel. Lignin undergoes base-catalyzed depolymerization and subsequent hydroprocessing. This hydroprocessing involves hydrodeoxygenation and mild hydrocracking. The latter is carried out under conditions in which a partial hydrogenation of the aromatic rings takes place.

WO 2008/027699 A2 describes a process in which lignin originating from a pyrolysis of biomass is decarboxylated and hydrodeoxygenated after separation of water-soluble constituents and the organic products from this process step are subsequently subjected to hydrocracking.

WO 2010/026244 describes an integrated process for the production of pulp and of at least one low molecular weight valuable material in which

a) providing a lignocellulose-containing starting material and subjecting it to digestion with a treatment medium,

b) isolating from the digested material a cellulose-enriched fraction and at least one cellulose-depleted fraction, the cellulose-depleted fraction comprising at least part of the treatment medium from step a),

c) subjecting the cellulose-depleted fraction to a treatment to obtain at least one low molecular weight valuable substance, and

d) isolated from the treatment product obtained in step c) the valuable material (s). WO 2009/108601 describes a process for producing a starting material for biorefinery processes for producing a biofuel from a lignin-containing starting material. Lignin from a black liquor of the pulping process or the black liquor itself is subjected to hydroprocessing in the presence of a hydrogen-containing gas and a catalyst on an amorphous or crystalline oxidic support.

WO 2009/108599 has a disclosure content comparable to WO 2009/108601 with a focus on papermaking.

M. Stoecker describes in the Angew. Chem. 2008, 120, 9340 - 9351, the catalytic conversion of lignocellulose-rich biomass for the recovery of BTL (biomass-to-liquid) fuels in biorefineries. US 2009/0227823 describes a process for preparing at least one liquid hydrocarbon product from a solid hydrocarbon feedstock (eg, a lignocellulosic material) by subjecting the feedstock to catalytic pyrolysis and subjecting the pyrolysis products to a catalyzed follow-up reaction to give liquid products.

G.W. Huber et al. describe in Chem. Rev. 2006, 106, 4044-4098, the synthesis of fuels from biomass. According to this, lignocellulosic materials can in principle be converted to three routes into liquid fuels, which differ in their primary step: gasification to syngas, pyrolysis to bio-oil, hydrolysis with the production of sugars and lignin. The bio-oils obtained in the pyrolysis can then be subjected to hydrodeoxygenation in the presence of hydrogen or steam reforming.

The unpublished European patent applications 10162255.3, 10162256.1 and 10162259.5 describe the production of organic recyclables from the digestion of lignocellulose-containing starting materials. Unpublished European Patent Application 10171278.4 describes a composition containing lignin and at least one catalyst dispersed throughout the composition, a process for making such a catalyst and lignin composition, and their use for the preparation of an aromatic composition.

None of the aforementioned biorefinery documents suggest that a biomass feedstock for the integrated production of aromatic polyisocyanates from the corresponding aromatic amines and other value-added products.

Surprisingly, the problem of providing suitable amines for polyisocyanate production has been solved by using a by-product of the treatment of a biological base product into a valuable product to provide aromatic amines. This is specifically to the implementation of lignin, which in the processing of lignocellulosic substances such. As wood or bagasse, for example in papermaking, and can be obtained from the aromatic by the inventive process amines, which are particularly advantageous for polyisocyanate production.

An essential aspect of the present invention is the economically and ecologically improved provision of aromatic amines by utilizing the functionalization of aromatic compounds as produced by nature.

SUMMARY OF THE INVENTION

Surprisingly, it has been found that an advantageous preparation of polyisocyanates with aromatic rings from a biomass starting material is possible.

A first object of the invention is therefore a process for the preparation of poly isocyanates, which comprises using a biomass raw material for preparing a composition of aromatic amines which comprises a C ¹⁴ to C ¹² -lsotopenverhältnis in the range of 0.5 x 10 ^"12 having up to 5 x 10 ^"12, and the composition of aromatic amines of phosgenation is subjected.

With regard to suitable and preferred embodiments for phosgenation, reference is made in full to the following statements on step g).

Preferably, the biomass starting material for preparing the aromatic amine composition is subjected to at least one reaction comprising a digestion to obtain an aromatic composition containing aromatics having at least one hydroxyl group and / or alkoxy group per molecule ("oxyaromatic composition "), and subjected the oxyaromatic to an amination. The oxyaromatic composition preferably contains at least 75% by weight, particularly preferably at least 90% by weight, in particular at least 95% by weight, of mononuclear aromatics, based on the total weight. A further subject of the invention is a process for the preparation of polyisocyanates in which a biomass starting material is subjected to a reaction which comprises a digestion to obtain an aroma composition which contains aromatics which contain at least one molecule per molecule Hydroxyl group and / or at least one alkoxy group ("oxyaromatic composition"), which subjects the oxyaromatic composition to amination, optionally subjecting the amination product to condensation with a formaldehyde source, the amination product or (if the amination product is subjected to condensation with a formaldehyde source) the product of the condensation subjected to a phosgenation with a formaldehyde source.

With regard to suitable and preferred embodiments for digesting the biomass starting material, reference is made in full to the following statements on step b).

With regard to further reaction and / or work-up steps to which the (digested) biomass starting material can be subjected, the following comments on steps c) and d) are referred to in their entirety. With regard to suitable and preferred embodiments for the amination, reference is made in full to the following statements on step e). Preferably, ammonia is used for the amination.

With regard to suitable and preferred embodiments for condensation with a formaldehyde source, reference is made in full to the following statements on step f).

With regard to suitable and preferred embodiments for phosgenation, reference is made in full to the following statements on step g). A further subject of the invention is a process for the preparation of polyisocyanates in which a) a biomass starting material is provided, b) the biomass starting material is subjected to digestion, c) optionally the decomposed material obtained in step b) at least one aromatics-enriched fraction C1) and at least one aromatics-depleted fraction C2), d) optionally the digestion product from step b) or the aromatics-enriched fraction C1) from step c) fed into a Dealkylierungszone and in the presence of Reacting hydrogen and / or steam, discharging the dealkylation zone, and optionally subjecting the dealkylation zone discharge to at least one dealkylated aromatic enriched stream D1) and at least one more volatile component enriched stream D2), e ) the digestion product from step b) or the aromatic enriched fraction C1) from step c) or the discharge of the dealkylation zone from step d) or the stream D1) enriched in dealkylated aromatics in an amination zone undergoes an amination by reaction with ammonia, f) optionally the amination product from step e g) subjecting the amination product from step e) or the product of the condensation with a formaldehyde source from step f) to a phosgenation. Another object of the invention is a polyisocyanate composition, wherein the C ¹⁴ to C ¹² isotope ratio in the range of 0.4 x 10 ^"12 to 4.5 x 10 ^{" 12} .

A further subject of the invention is a polyisocyanate composition obtainable by a process as described above and below. The polyisocyanate composition according to the invention preferably has an NCO number of at least 30. DESCRIPTION OF THE INVENTION

In the context of the present application, "biomass" refers to a plant material of non-fossil origin. Biomass also includes dead plants and parts of plants, such as deadwood, straw, leaves, etc. The term biomass also includes products in which a vegetable material of non-fossil origin has undergone a chemical and / or physical treatment. These include, in particular, the products of the digestion and fractionation of lignocellulose, such as lignin. In particular, biomass does not include coal, oil, natural gas, peat and their performance products, such as coke.

In the context of the invention, the term "oxyaromatics" denotes aromatics which have at least one hydroxyl group and / or at least one alkoxy group per molecule Accordingly, an "oxyaromatic composition" denotes a composition which contains oxyaromatics Preferred as oxyaromatics are monochromatic aromatics or are compositions with Preferably, the oxyaromatic composition used in the process according to the invention contains, based on the total weight, at least 75% by weight, preferably at least 90% by weight, in particular at least 95% by weight, of mononuclear aromatics.

The mononuclear oxyaromatics are preferably selected from compounds of the general formula (I)

in which the radicals R ¹ independently of one another are hydrogen or C 1 -C 6 -alkyl, the radicals R ² are selected independently of one another from C 1 -C 6 -alkyl, C 1 -C 6 -hydroxyalkyl, C 1 -C 6 -alkoxy-C 1 -C 6 -alkyl, Formyl, C 2 -C 6 -acyl, C 1 -C 6 -alkoxycarbonyl and C 1 -C 6 -alkylcarbonyloxy, m is 1, 2 or 3, n is 0, 1, 2, 3 or 4, and the sum of m and n is an integer from 1 to 6.

In particular, the process of the invention makes it possible to provide an oxyaromatic composition containing monomeric oxyaromatics selected from phenol, phenol ethers, cresols, xylenols, gujacols, veratrols, resorcinol, catechol, hydroquinone and mixtures thereof.

In a specific embodiment, the method according to the invention comprises the provision of an oxyaromatic composition with a high content of mononuclear aromatic compounds from a biomass starting material. Mononuclear aromatics are also referred to in the context of the invention as "monomeric aromatics". Polynuclear aromatics having from 2 to 15 aromatic rings are also referred to as "oligomeric aromatics".

If, for the preparation of the composition of aromatic amines, a biomass starting material is subjected to at least one digestion, the primary digestion product obtained is an aroma composition which, based on the total weight, is at least 1% by weight, more preferably at least 2% by weight .-% of mononuclear oxyaromatic compounds. By further reaction and / or work-up steps, as described below, the proportion of mononuclear oxyaromatics can be significantly increased. The resulting additional components can be recycled in an advantageous manner in the process of the invention or work up to further product of value or recover energy. In a specific embodiment, the reaction of the biomass starting material to provide the oxyaromatic composition comprises at least one dealkylation. The dealkylation products obtained in this way have a markedly increased content of mononuclear dealkylated aromatics compared to the aromatic composition used. Such an oxyaromatic composition is particularly advantageous for further conversion to polyisocyanates.

In the context of the invention, "dealkylation" refers to a reaction of the substituted and / or polynuclear aromatic compounds present in an aromatic composition in the presence of hydrogen and / or water vapor, wherein these are at least partially converted so that substituents are replaced by hydrogen and / or several compounds containing aromatic nuclei are cleaved to compounds with a smaller number of nuclei. The substituents replaced by hydrogen are here selected from alkyl groups, hydroxyl groups, alkoxy groups, aryloxy groups, etc. In the context of the invention, the term "dealkylation" also encompasses various reactions which are associated with a reduction in molecular weight, such as dehydroxylation, dealkoxylation or aromatic cleavage. Aromatea cleavage refers to a reaction in which essentially the number of aromatic nuclei per molecule is reduced without the aromatic nuclei themselves being destroyed. However, according to the invention, the dealkylated oxyaromatics obtained by dealkylation always have at least one hydroxyl group and / or at least one alkoxy group per molecule per molecule. Provision of biomass feedstock (step a)

Preferably, in step a) of the method according to the invention, a lignin-containing material is provided as biomass starting material. Suitable lignin-containing starting materials are pure lignin and lignin-containing compositions. In this case, the lignin content of the compositions is not critical over a wide range, only if the lignin contents are too low can the process no longer be operated economically. Preferably, in step a), a lignin-containing starting material is provided which contains at least 10% by weight, preferably at least 15% by weight, based on the dry matter of the material, of lignin. Preferably suitable are lignin-containing compositions containing 10 to 100 wt .-%, particularly preferably 15 to 95 wt .-%, based on the dry matter of the material, lignin. In the context of this invention, the term dry matter is understood in the sense of the standard ISO 1 1465.

Lignocellulose-containing materials are also suitable for providing a lignin-containing starting material for use in the process according to the invention. Lignocellulose forms the structural framework of the plant cell wall and contains lignin, hemicelluloses and cellulose as main constituents. Other components of the plant cell wall and thus obtained lignocellulose-containing materials are, for. As silicates, extractable low molecular weight organic compounds (so-called extractives such as terpenes, resins, fats), polymers such as proteins, nucleic acids and gum (so-called exudate), etc. Lignin is a biopolymer whose basic unit is essentially phenylpropane, which, depending on the natural source, may be substituted with one or more methoxy groups on the phenyl rings and with a hydroxy group on the propylene units. Therefore, typical structural units of lignin are p-hydroxyphenylpropane, guaiacylpropane and syringylpropane, which are linked by ether bonds and carbon-carbon bonds.

Suitable biomass starting materials for the process according to the invention are both lignocellulose-containing materials which are used without further chemical treatment in natural composition, such. As wood or straw, as well as lignocellulosic streams from the processing of lignocellulose, z. B. from processes for cellulose production (pulp process). The lignocellulosic materials which can be used according to the invention are e.g. B. from wood and vegetable fibers available as starting material. Preferred lignocellulosic materials are those of wood and residues of the woodworking industry. These include z. B. the various types of wood, ie hardwoods, such as maple, birch, pear, oak, alder, ash, eucalyptus, hornbeam, cherry, linden, walnut, poplar, willow, etc. and conifers such as Douglas fir, spruce, yew, hemlock, Pine, larch fir, cedar, etc. Wood can be distinguished not only in deciduous and conifers, but also in so-called "hardwoods" and "softwoods", which is not synonymous with the terms deciduous or coniferous wood. Soft wood, in contrast to hardwood, means lighter wood (ie wood with a density of less than 0.55 g / cm ³ , such as willow, cardboard, linden and almost all softwoods). In principle, all hardwoods and all softwoods are suitable for use in the process according to the invention. The wood used in the process according to the invention can also be used in ready-made form, for. In the form of pellets. Suitable residues in the woodworking industry are in addition to wood waste and sawdust, parquet sanding dust, etc. Suitable lignocellulosic materials are still natural fibers, such as flax, hemp, sisal, jute, straw, coconut fibers, switchgrass (Panicum virgatum) and other natural fibers. Suitable lignocellulosic materials also fall as a residue in agriculture, z. As in the harvest of cereals (wheat straw, corn straw, etc.), corn, sugar cane (bagasse), etc. Suitable lignocellulosic materials also fall as a residue in the forest industry, z. In the form of branches, barks, woodchips, etc. A good source of lignocellulosic materials are also short rotation crops, which enable high biomass production in a relatively small area. In step a), a lignocellulosic stream from the digestion of a lignocellulosic material for producing cellulose (pulp), preferably a black liquor, in particular a black liquor from the power digestion (sulfate digestion), is preferably provided as the biomass feedstock.

In a preferred embodiment, to provide the biomass starting material, a lignocellulose-containing material is subjected to digestion and from the digested material a cellulose-enriched fraction and a lignin-enriched (and simultaneously depleted in cellulose) fraction is isolated. The latter then serves, if appropriate after further workup, as biomass starting material for the process according to the invention. In this embodiment, a lignocellulose-containing material is thus subjected to a first digestion in step a) of the process according to the invention, from which a lignin-enriched material is isolated and subsequently subjected to a second digestion in step b).

Processes for the digestion of lignocellulose-containing materials for the production of cellulose are known in principle. In principle, lignin-containing streams are suitable for use as biomass starting material from all the digestion processes known to those skilled in the art. In principle, these processes can be classified with regard to the treatment medium used in aqueous-alkaline processes, aqueous-acidic processes and organic processes. An overview of these methods and the digestion conditions can be found z. In WO 2010/026244.

The treatment medium used to digest the lignocellulosic materials is capable of solubilizing at least a portion of the lignin. By contrast, the cellulose contained in the lignocellulose-containing material is generally not or only partially solubilized in the treatment medium. Preferably, the separation of a cellulose-enriched fraction is then carried out by filtration or centrifugation.

Preferably, a lignin-containing (cellulose-depleted) fraction is isolated from the digested material, which contains in addition to lignin at least one further component which is for example selected from hemicellulose, cellulose, degradation products of the aforementioned components, digestion chemicals and mixtures thereof.

In many cases, it is not critical for the digestion in step b) if the biomass starting material used is a lignin-containing starting material which contains at least one further component in addition to lignin. If a lignin-containing fraction which contains at least one further component in addition to lignin is used to provide the lignin-containing starting material, at least some of the compounds other than lignin can be removed before the digestion in step b). The components removed from the lignin-containing fraction (organic components and / or inorganic process chemicals) are preferably fed to a further work-up and / or thermal utilization, preferably in the course of the cellulose production process from which the lignin-containing fraction was obtained.

To remove at least a portion of the compounds other than lignin, the pH of the lignin-containing fraction may first be adjusted to a suitable value. Lignin-containing fractions from aqueous-alkaline processes (such as the Kraft process) can be mixed with an acid to adjust the pH. Suitable acids are, for. As CO2, mineral acids such as hydrochloric acid, sulfuric acid and phosphoric acid. Particularly preferred acid is CO2 (or the resulting carbon dioxide with water). Preferably, CO2 is used from an exhaust gas stream of the process according to the invention or a pulp process coupled to the process according to the invention. Suitable is z. As the exhaust from a black liquor combustion (recovery boiler) or a lime kiln. In this case, the exhaust gas can be introduced into the lignin-containing fraction either directly or after separation from the other components (eg by means of a washing process, such as a Benfield wash). As a rule, the carbonates and / or bicarbonates resulting from the addition of CU2 can be easily recycled into the coupled pulp process, eg. B. in a previously taken to Ligningewinnung black liquor. The use of CO2 to adjust the pH of the lignin-containing fraction is therefore associated with lower costs than with the use of other acids and also generally allows a good integration into a pulp process. Lignin-containing fractions from aqueous-acidic processes can be mixed with a base to adjust the pH. Suitable bases are, for. As alkali metal bases, such as sodium hydroxide or potassium hydroxide, alkali metal carbonates, such as soda or potassium carbonate, alkali metal bicarbonates, such as sodium bicarbonate or potassium bicarbonate and alkaline earth metal bases, such as calcium hydroxide, calcium oxide, magnesium hydroxide or magnesium carbonate, and ammonia or amines.

Preferably, in step a) the removal of at least a portion of the lignin-different compounds from the lignin-containing fraction) by filtration, centrifuging, extraction, precipitation, distillation, stripping or a combination thereof. Of the One skilled in the art can control the composition of the lignin-containing fraction and thus of the lignin-containing starting material for the digestion in step b) via the separation process. The at least partial separation of the components other than lignin can be carried out in one or more stages. Usual filtration methods are z. Cake and depth filtration (eg, described in A. Rushton, AS Ward, RG Holdich: Solid-Liquid Filtration and Separation Technology, VCH Verlagsgesellschaft, Weinheim 1996, pages 177ff., KJ Ives, in A. Rushton (A. Hg.): Mathematical Models and Design Methods in Solid-Liquid Separation, NATO ASI Series E No. 88, Martinus Nijhoff, Dordrecht 1985, pages 90ff.) And crossflow filtrations (eg described in J. Med. Altmann, S. Ripperger, J. Membrane Sci. 124 (1997), pages 1 19-128). Usual centrifugation methods are z. See, for example, G. Hultsch, H. Wilkesmann, "Filtering Centrifuges," DB Purchas, Solid-Liquid Separation, Upland Press, Croydon 1977, pp. 493-559; and H. Trawinski, The Equivalent Clarifying Surface of Centrifuges, Chem. Ztg. 83 (1959), pages 606-612. For extraction z. As a non-miscible with the treatment medium from pulp production solvent or at least one miscibility-exhibiting solvent can be used in the lignin and optionally other desired components in a sufficient amount is soluble. The separation of components which can be decomposed without decomposition from the lignin-containing fraction can be carried out by customary distillation processes known to the person skilled in the art. Suitable apparatus for working up by distillation include distillation columns, such as tray columns, which may be equipped with bells, sieve plates, sieve trays, packings, random packings, valves, side draws, etc., evaporators, such as thin film evaporators, falling film evaporators, forced circulation evaporators, Sambay evaporators, etc., and combinations from that.

In a specific embodiment, a lignin-containing stream from the digestion of a lignocellulosic material which comprises at least part of the liquid treatment medium from the digestion is used to provide the lignin-containing starting material in step a). Preferably, the lignin-containing stream is then subjected to precipitation of a lignin-containing fraction, followed by partial or complete removal of the liquid components, to provide the lignin-containing starting material for digestion in step b).

Preferably, the lignin-containing starting material is provided in the context of a process for the production of cellulose (pulp) into which the synthesis of synthesis gas according to the invention and at least one organic liquid or liquefiable recyclable material is integrated. In a specific embodiment, the removal of at least a portion of the liquid compounds then takes place in the context of the process for the production of pulp. Thus, to provide the lignin-containing starting material z. For example, a black liquor can be used which is taken before or during the course of the individual evaporation steps of the underlying pulp process.

Preferably, to provide the biomass starting material in step a), a lignin-containing stream from the digestion of a lignocellulosic material with an alkaline treatment medium is used. Particular preference is given to using a black liquor, in particular a black liquor from the sulphate digestion (power digestion). To provide a lignin-containing material, a black liquor from the Kraft digestion can first be acidified to precipitate at least a portion of the lignin contained and then the precipitated lignin can be isolated. For acidification, the aforementioned acids are suitable. In particular, CO2 is used. Preferably, the pH of the black liquor is lowered to a value of at most 10.5. The isolation of the precipitated lignin is preferably carried out by a filtration process. Suitable filtration methods are those mentioned above. If desired, the isolated lignin may be subjected to at least one further work-up step. This includes z. B. a further cleaning, preferably a wash with a suitable washing medium. Suitable washing media are for. For example, mineral acids such as sulfuric acid, preferably in aqueous solution. In a special embodiment, to prepare a lignin-containing material, a black liquor from the kraft digestion is first acidified with CO 2 to precipitate at least part of the lignin contained, then the precipitated lignin is isolated by filtration and the filtrate is subjected to scrubbing with sulfuric acid.

A process for the isolation of lignin from a black liquor by precipitation with CO2 is described in WO 2008/079072, to which reference is hereby made. Particularly suitable is also the so-called lignoboost process, which in the

WO 2006/038863 (EP 1797236 A1) and WO 2006/031 175 (EP 1794363 A1), to which reference is also made.

Digestion (step b) In step b) of the process according to the invention, the biomass starting material is subjected to digestion to obtain a digestion product which contains components whose average molecular weight is significantly below the average molecular weight of the components contained in the biomass starting material. In a specific embodiment, a lignin-containing starting material is used for the digestion in step b). According to this embodiment, the digestion product obtained in step b) predominantly comprises components having a molecular weight of at most 500 g / mol, more preferably of at most 400 g / mol, in particular of at most 300 g / mol.

The digestion in step b) can in principle take place according to two variants, which are described in detail below. The first variant comprises a pyrolysis and leads accordingly to a pyrolysis product. The second variant comprises an implementation in the presence of a liquid digestion medium and accordingly leads to a product of the liquid digestion.

1 . Variant: pyrolysis In a first variant of the process according to the invention, the biomass starting material, especially the lignin-containing starting material, is subjected to pyrolysis in step b). In the context of the invention, pyrolysis is understood as meaning a thermal treatment of the biomass starting material, molecular oxygen being not or only to a small amount being supplied. A small amount is to be understood as an amount that is significantly less than the amount necessary for a complete oxidation of the carbon contained in the biomass starting material to CO2. Preferably, the amount of molecular oxygen fed in the pyrolysis is at least 50 mol%, more preferably at least 75 mol%, in particular at least 90 mol%, below the amount necessary for complete oxidation of the carbon contained in the biomass starting material to CO2 is necessary. Pyrolysis is generally endothermic. In this variant of the method according to the invention, the digestion product is at least partially gaseous. The pyrolysis can be carried out batchwise or continuously. Continuous pyrolysis is preferred.

The pyrolysis takes place in at least one pyrolysis zone. The biomass starting material, especially the lignin-containing starting material, by means of suitable transport devices, such. B. screw conveyor or pneumatic conveying, are registered in a pyrolysis zone.

For pyrolysis, the biomass starting material, especially the lignin-containing starting material, is preferably used in predominantly solid form. Predominantly solid Form means in the context of the invention that the starting material used for pyrolysis under normal conditions (20 ° C, 1013 mbar) has a liquid content of at most 70 wt .-%, more preferably of at most 50 wt .-%, based on the total weight of the starting material , For pyrolysis, the biomass starting material, especially the lignin-containing starting material, then z. B. used as a moist or predried solid.

The pyrolysis zone may be designed in various embodiments, for. B. as a rotary kiln or fluidized bed. Both stationary and circulating fluidized beds are suitable. In the execution of the pyrolysis zone as a fluidized bed, a fluidizing gas (preferably water vapor or a gas mixture from one of the subsequent process steps) and as a fluidized material under the given conditions inert granular additive is supplied. Particularly suitable as an additive is quartz sand. Such a fluidized bed process is z. For example, in US 4,409,416 A described. In an alternative embodiment, the pyrolysis zone comprises at least one fixed bed. The fixed beds may comprise at least one inert fixed bed and / or at least one catalytically active fixed bed. If the process according to the invention is operated with at least one fixed bed as the pyrolysis zone, then an interval operation may be advantageous in which a pyrolysis phase is followed by a combustion phase in order to remove low-volatility components from the fixed bed.

For pyrolysis, a fluidizing gas can be fed into the pyrolysis zone. Preferred fluidizing gases are water vapor, carbon dioxide, nitrogen, etc., or mixtures of these gases.

In a first preferred embodiment, the pyrolysis is not carried out with the addition of hydrogen. In this embodiment, the hydrogenating reaction takes place essentially in the dealkylation step d), if this is provided. In a second preferred embodiment, the pyrolysis with the addition of

Hydrogen performed. This embodiment of the pyrolysis can also be referred to as hydrocracking. In hydrocracking, the biomass feedstock, specifically lignin, is split by the action of hydrogen into small-molecule fragments. The pyrolysis with the addition of hydrogen is preferably carried out in suspension. It is furthermore preferably carried out using a catalyst and / or under high pressure. Such a method is z. In US 4,420,644 and in HL Churn et al., Adv. Solar Energy, Vol.4 (1988), 91 et seq. In a further preferred embodiment, a vaporized black liquor from the kraft process is used for pyrolysis. Such a method is z. As described in US 3,375,283. The black liquor is predominantly in solid form. Also in this process variant falls as a product to a pyrolysis gas stream. The also incurred solid residue can, for. B. be returned to the pulping process.

In a specific embodiment, pyrolysis is carried out using a black liquor material which under normal conditions (20 ° C., 1013 mbar) has a liquid content of at most 70% by weight, particularly preferably at most 50% by weight, based on the total weight of the black liquor material having.

If desired, the pyrolysis in step b) can be carried out in the presence of at least one pyrolysis catalyst. As pyrolysis z. For example, silica, alumina, aluminosilicates, layered aluminosilicates and zeolites such as mordenite, faujasite, zeolite X, zeolite-Y and ZSM-5, zirconia or titania.

The temperature in the pyrolysis is preferably in a range of 200 to 1500 ° C, more preferably 250 to 1000 ° C, especially 300 to 800 ° C.

The pressure in the pyrolysis is preferably in a range of 0.5 to 250 bar (absolute), preferably 1, 0 to 40 bar (absolute).

The residence time at the pyrolysis temperature can be a few seconds to several days. In a specific embodiment, the residence time at the pyrolysis temperature is 0.5 second to 5 minutes, more specifically 2 seconds to 3 minutes. The residence time, especially in the case of a fluidized-bed reactor, results from the quotient of the total volume of the reactor to the volume flow of the fluidizing gas under the pyrolysis conditions.

Suitable processes for the catalyzed or uncatalyzed pyrolysis of lignin are e.g. Also described in WO 96/09350 (Midwest Research Institute, 1996) or US 4,409,416 (Hydrocarbon Research Institute, 1983), which is incorporated herein by reference.

In the pyrolysis zone, the biomass starting material, especially the lignin, is converted to a pyrolysis product which is at least partly gaseous ("pyrolysis gas") under the conditions of pyrolysis. Furthermore, during pyrolysis, a pyro- lyseprodukt that are partially liquid and / or solid under the conditions of pyrolysis.

The composition of the digestion product obtained in step b) (= pyrolysis product) may vary depending on the biomass used.

In any case, the digestion product obtained in the pyrolysis in step b) contains oxyaromatics in the context of the invention. In addition to oxyaromatics, the digestion product may contain other aromatics and other components selected from water vapor, inert gas (eg nitrogen), non-aromatic hydrocarbons, H, CO, CO2, sulfur-containing compounds, such as e.g. As H2S, etc. and mixtures thereof. The non-aromatic hydrocarbons are preferably degradation products, such as methane. The separation and further treatment of the digestion product obtained in the pyrolysis in step b) is described in more detail in step c).

2nd Variant: Digestion in the Liquid Phase In a second variant of the process according to the invention, the biomass starting material, especially the lignin-containing starting material, is subjected to digestion in the presence of a liquid digestion medium in step b). In this variant, the digestion product falls at least partially in the liquid phase. The digestion in the liquid phase is possible by a variety of methods, which differ mainly with regard to the digestion medium. The biomass starting material, in particular the lignin-containing starting material, is preferably subjected to digestion in the presence of an aqueous-alkaline, aqueous-acidic or organic disintegration medium in step b).

For digestion in the presence of a liquid digestion medium in step b), at least one cellulose-depleted fraction from a pulp process is preferably used. One particular embodiment is a cellulose-depleted fraction from a pulp process which still contains at least a portion of the liquid treatment medium from pulping the lignocellulosic material for pulping.

The treatment medium used for the digestion in step b) comprises at least one compound which is liquid under normal conditions (20 ° C. and 1013 mbar). This is preferably selected from water, acids, bases, organic solvents and mixtures thereof. Under normal conditions, liquid acids and bases or liquid mixtures containing acids or bases may be selected by one skilled in the art from those listed below. The organic solvents are preferably selected from alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol or phenol, diols and polyols, such as ethanediol and propanediol, aminoalcohols, such as ethanolamine, diethanolamine or triethanolamine, aromatic hydrocarbons, such as benzene, toluene, ethylbenzene or xylenes, halogenated solvents, such as dichloromethane, chloroform, carbon tetrachloride, dichloroethane or chlorobenzene, aliphatic solvents, such as pentane, hexane, heptane, octane, ligroin, petroleum ether, cyclohexane or decalin, ethers, such as tetrahydrofuran , Diethyl ether, methyl tert-butyl ether or diethylene glycol monomethyl ether, ketones such as acetone or methyl ethyl ketone, esters such as ethyl acetate, formamide, dimethylformamide (DMF), dimethylacetamide, dimethyl sulfoxide (DMSO), acetonitrile and mixtures thereof.

Preferably, the liquid compound is selected from water, water-miscible organic solvents and mixtures thereof. Particularly preferably, the liquid compound is selected from water, alcohols and mixtures thereof. Thus, as the liquid compound, water, methanol, ethanol, a mixture of water with methanol and / or ethanol or a mixture of methanol and ethanol can be used.

The liquid digestion medium used in step b) may comprise at least one base. Suitable bases are alkali and alkaline earth metal hydroxides, e.g. For example, sodium hydroxide, potassium hydroxide, calcium hydroxide or magnesium hydroxide, alkali metal and Erd- alkali metal bicarbonates, z. For example, sodium bicarbonate, potassium hydrogen carbonate, calcium bicarbonate or magnesium hydrogen carbonate, alkali metal and Erd- alkali metal carbonates, eg. Sodium carbonate, potassium carbonate, calcium carbonate or magnesium carbonate, alkaline earth metal oxides such as calcium oxide or magnesium oxide, and mixtures thereof.

The liquid digestion medium used in step b) may comprise at least one acid. In principle, Brönsted acids or Lewis acids are suitable. Suitable Brönsted acids are inorganic acids, their acid salts and anhydrides. These include, for example, mineral acids, such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or amidosulfonic acid, but also ammonium salts, such as ammonium fluoride, ammonium chloride, ammonium bromide or ammonium sulfate. Also suitable are hydrogen sulfates, such as sodium hydrogen sulfate, potassium hydrogen sulfate, calcium umhydrogen sulfate or magnesium hydrogen sulfate. Also suitable are hydrogen sulfites, such as sodium hydrogen sulfite, potassium hydrogen sulfite, calcium hydrogen sulfite or magnesium hydrogen sulfite. Also suitable are hydrogen phosphates and dihydrogen phosphates, such as sodium hydrogen phosphate, sodium dihydrogen phosphate, potassium hydrogen phosphate or potassium dihydrogen phosphate. Also suitable are SO2, SO3 and C0 ₂ .

Suitable Bronsted acids are also organic acids and their anhydrides, such as formic acid, acetic acid, methanesulfonic acid, trifluoroacetic acid or p-toluenesulfonic acid.

Suitable Lewis acids are any metal or semimetallic halides in which the metal or metalloid has an electron pair gap. Examples of these are BF ₃ , BCl ₃ , BBr ₃ , AIF ₃ , AICI ₃ , AIBr ₃ , ethylaluminum dichloride, diethylaluminum chloride, TiF ₄ , TiCl ₄ , TiBr ₄ , VCIs, FeF ₃ , FeCl ₃ , FeBr ₃ , ZnF ₂ , ZnCl ₂ , ZnBr ₂ , Cu ( l) F, Cu (I) Cl, Cu (I) Br,

Cu (II) F ₂ , Cu (II) Cl ₂ , Cu (II) Br ₂ , Sb (II) F ₃ , Sb (V) F ₅ , Sb (III) Cl ₃ , Sb (V) Cl ₅ , Nb (V) ₅ CI, Sn (II) F _2, Sn (II) Cl _2, Sn (II) Br _2, Sn (IV) F _4, Sn (IV) Cl _4, and Sn (IV) Br. ₄

The liquid digestion medium used in step b) may comprise at least one salt other than the abovementioned compounds. The salts are preferably selected from salts of the abovementioned acids and bases and also their oxidation or reduction products. Suitable salts are, for. For example, ammonium, alkali metal or alkaline earth metal sulfates, such as sodium sulfate, potassium sulfate, calcium sulfate or magnesium sulfate. Also suitable are ammonium, alkali metal or alkaline earth metal sulfites, such as sodium sulfite, potassium sulfite, calcium sulfite or magnesium sulfite.

Also suitable are ammonium, alkali metal or alkaline earth metal sulfides, such as sodium sulfide, potassium sulfide, calcium sulfide or magnesium sulfide. Also suitable are alkali metal hydrogen sulfides, such as sodium hydrogen sulfide or potassium hydrogen sulfide. The liquid digestion medium used in step b) may contain other compounds which are different from the abovementioned compounds. These are in particular the customary process chemicals known to the person skilled in the art for the various digestion processes for the production of pulp from a lignocellulose-containing starting material. Such processes and the process chemicals used therein are known to the person skilled in the art.

In a first particularly preferred embodiment, an alkaline digestion medium is used in step b). Specifically, for digestion in step b) at least one cellulose-depleted fraction from a pulp process is used, which at least partially comprises the alkaline digestion medium from the previous pulp process.

For digestion in step b), a cellulose-depleted fraction from the kraft process (sulfate process) is then preferably used. The digestion medium used in step b) then contains NaOH and Na 2 S in an aqueous medium. In a specific embodiment, the treatment medium used in step a) contains NaOH, Na 2 S, Na 2 CO 3 and Na ₂ SO ₄ in an aqueous medium. For digestion in step b), in particular, a black liquor obtained during pulp production after the kraft process is used. Either the weak liquor ("weak black liquor") arising directly after the separation of the pulp fibers or a more concentrated quality resulting from evaporation can be used for this purpose. Particularly advantageous is the digestion in alkaline aqueous phase, as described by Clark and Green in Tappi, 51 (1), 1968, 44 ff.

For digestion in step b), a cellulose-depleted fraction from the soda process (soda process) can also be used. The treatment medium used in step b) then contains as the main component NaOH in an aqueous medium which is essentially free of sulfur-containing compounds.

For the digestion in step b), a cellulose-depleted fraction from the alkali-oxygen digestion can also be used. For the digestion in step b), a cellulose-depleted fraction from the alkali peroxide digestion can also be used.

For the digestion in step b), it is also possible to use a cellulose-depleted fraction from the digestion in the presence of anthraquinone.

For the digestion in step b), a cellulose-depleted fraction from the digestion of the lignocellulosic material with organic solvents (also referred to as organosolv process) can be used. Suitable organic solvents are those mentioned above. Specifically, an organic solvent is used, which is selected from C 1 -C ₄ -alkanols, mixtures of C 1 -C ₄ -alkanols and mixtures of at least one C 1 -C ₄ -alkanol with water. The C 1 -C ₄ -alkanols are preferably selected from methanol, ethanol, n-propanol, isopropanol and n-butanol. Preferred are methanol, ethanol and mixtures thereof. Mixtures of at least one C 1 -C ₄ -alkanol with water preferably contain 10 to 99% by weight. %, particularly preferably 20 to 95 wt .-%, of at least one Ci-C4-alkanol, based on the total weight of the mixture. The digestion medium used in step b) can then additionally contain an additive from the underlying pulp process. These include z. Alkali metal hydroxides, such as sodium hydroxide; Ammonium hydrogen sulfite and alkali and alkaline earth metal hydrogen sulfites, such as sodium hydrogen sulfite and magnesium hydrogen sulfite. These also include mineral acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or amidosulfonic acid and their ammonium, alkali metal and alkaline earth metal salts. Also suitable as additives are organic acids, such as oxalic acid, formic acid or acetic acid. Also suitable are peracids, such as persulfuric acid or peracetic acid.

Also suitable for use in step b) of the process according to the invention are the cellulose-depleted fractions which contain at least part of the liquid treatment medium from one of the following commercially used organosolv processes:

Alcell method: ethanol / water mixture as treatment medium.

ASAM method: Alkaline sulfite-anthraquinone-methanol treatment medium. Organocell method: Two-stage process with an organic medium in the first stage and an alkaline medium in the second stage, eg. B. digestion with methanol and / or ethanol in the first stage and with methanol and / or ethanol, NaOH, and optionally anthraquinone in the second stage.

Acetosolv process: acetic acid / hydrochloric acid mixture as treatment medium. The digestion in the presence of a liquid digestion medium in step b) can be carried out in one or more stages. In the simplest case, the digestion in step b) takes place in one stage.

The digestion in step b) preferably takes place above the ambient temperature. The temperature is preferably in a range of about 40 to 300 ° C, more preferably 50 to 250 ° C. In a specific embodiment, the temperature is initially increased successively or continuously in the course of treatment until the desired final temperature is reached. The digestion in step b) can be carried out at reduced pressure, at ambient pressure or above the ambient pressure. The pressure in step a) is generally in a range of 0.01 bar to 300 bar, preferably 0.1 bar to 100 bar. The duration of the digestion in step b) is generally 0.5 minutes to 7 days, preferably 5 minutes to 96 hours.

If a cellulose-depleted fraction from the pulp process is used for digestion in step b), the digestion is advantageously carried out in close proximity to the location of pulp production, in order to minimize the transport costs for the cellulose-depleted fraction, especially a black liquor , The transport preferably takes place via pipeline. In any case, the digestion product obtained in the digestion in the presence of a liquid digestion medium in step b) contains oxyaromatics according to the invention.

The separation and further treatment of the digestion product obtained in the presence of a liquid digestion medium in step b) is described in more detail in step c).

It is in principle possible to use the digestion product obtained in step b) without further separation and / or treatment for dealkylation in step d) or for the amination in step e). If the digestion product obtained in step b) is obtained in the liquid phase, this is preferably subjected to evaporation before the feed in step d) or in step e). A preferred embodiment of the evaporation is depicted in FIG. 1 and described below.

In another embodiment of the process according to the invention, the digestion product obtained in step b) is subjected to separation and / or treatment (step c) before it is used in the dealkylation (step d) or the amination (step e).

Separation / treatment of the digestion product (step c)

Preferably, in step c) the digested material obtained in step b) is separated into at least one aromatics enriched fraction C1) and at least one aromatics depleted fraction C2). The separation is preferably carried out by distillation, extraction, absorption, membrane processes or a combination thereof. The separation is particularly preferably carried out by distillation, extraction or a combination thereof. In the case that the digestion in step b) takes place in the liquid phase, the separation in step c) preferably takes place by means of distillation and / or extraction.

In a first specific embodiment of the process according to the invention, the biomass starting material provided in step a) is subjected to digestion in the liquid phase in step b) and comprises in step c) the separation into at least one aromatics-enriched fraction C1) and at least one Aromatic fraction C2), an extraction and / or a distillation. Preferably, prior to the separation in step c), the pH of the discharge from a digestion in the liquid phase in step b) is set to a desired value. In a specific embodiment, a digestion product obtained by digestion in the presence of an alkaline digestion medium is used in step c). In particular, for the digestion, at least one cellulose-degraded fraction from a pulp process, in particular a black liquor from the kraft process, was used. Preference is then given to adjusting the pH of the digestion product by addition of acid to a value of at most 9, more preferably of at most 8. Suitable acids are, for. For example, mineral acids such as hydrochloric acid, sulfuric acid and phosphoric acid and acid-forming compounds such as CO2 and H2S. Preferably, CO2 is used from an exhaust gas stream of the process according to the invention or a pulp process coupled to the process according to the invention. Suitable is z. As the exhaust from a black liquor combustion (recovery boiler) or a lime kiln. In this case, the exhaust gas can be introduced into the digestion product either directly or after separation from the other components (eg by means of a washing process, such as a Benfield wash). The resulting by CÜ2 addition carbonates and / or bicarbonates can be easily z. B. in a coupled to the pulping process pulp process, z. B. in a previously extracted for Ligninge- winning black liquor. The use of CO2 to adjust the pH value is therefore associated with lower costs than with the use of other acids and also generally allows a good integration into a pulp process. The hydroxyaromatics obtained in the digestion in step b) are virtually completely present as salts (phenolates) at pH values above about 9. By previously lowering the pH to a value <9, preferably <8, effective separation by distillation and / or extraction is facilitated.

The distillative separation of the product obtained in step b) from the digestion in the liquid phase can be carried out by customary methods known to the person skilled in the art. Preference is given to a steam distillation, wherein an aromatics enriched Distillate is obtained. In this procedure, one uses the water vapor volatility of the obtained in the digestion in step b) aromatic fragments to separate them from the digestion product. Preference is given to a multi-stage process in which the heat of condensation of the vapors of at least one stage is used for vaporization in another stage. The distillation product obtained is enriched in aromatics with respect to the digestion product used and, if appropriate after separation of the aqueous phase, is suitable as feedstock for the optional dealkylation in step d) or the amination in step e). The separation of the product obtained in step b) from the digestion in the liquid phase is also preferably carried out by extraction. In this case, at least part of the aromatics obtained in the digestion in step b) is separated off, while the remaining residue (low-aromatics organic components, inorganic process chemicals, etc.) further processing and / or thermal utilization, preferably in the context of the inventive method or a coupled integrated pulp production process.

For extraction, a solvent (extractant) can be used in which the aromatics obtained in the digestion are soluble in a sufficient amount and otherwise forms a miscibility gap with the digestion product. The extractant is then intimately contacted with the digestion product obtained in step b), followed by phase separation. The extraction can be configured in one or more stages. Suitable extractants are organic compounds such as aromatic or non-aromatic hydrocarbons, alcohols, aldehydes, ketones, amides, amines and mixtures thereof. These include z. B. benzene, toluene, ethylbenzene, xylenes, pentane, hexane, heptane, octane, ligroin, petroleum ether, cyclohexane, decalin, n-butanol, sec-butanol, tert-butanol, 1-pentanol, 1 -hexanol, 1 - Heptanol, 1-octanol, methyl ethyl ketone and mixtures thereof.

Extraction may be discontinuous or continuous as described in: K. Sattler, Thermal Separation Methods, Wiley-VCH, Third Essentially Redesigned and Extended Edition, July 2001. Several discontinuous separation operations can be carried out in cascade succession, wherein the separated from the extractant phase residue is in each case brought into contact with a fresh portion of extractant and / or the extractant is passed in countercurrent. For discontinuous implementation brings under mechanical movement, for. B. by stirring, the digestion product and the extractant in a suitable Vessel, allowing the mixture to rest for phase separation and removing one of the phases by conveniently drawing off the heavier phase at the bottom of the vessel. To carry out the extraction continuously, the extractant and the digestion product are continuously added in a suitable apparatus in a manner analogous to the discontinuous variant.

The extraction takes place z. B. in at least one mixer-separator combination or at least one extraction column. Suitable mixers are both dynamic and static mixers.

In a preferred embodiment, the separation into at least one aromatics-enriched fraction C1) and at least one aromatic-depleted fraction C2) in step c) comprises the following substeps: c1) extraction of the digestion product obtained in step b) to obtain an aromatic compound enriched extract and an aromatics-depleted residue, optionally separating the extract into an extractant-enriched (and aromatics-depleted) fraction, and an aromatics-enriched (and depleted-in) fraction;

Feeding the aromatics-enriched extract obtained in step c1) or the aromatic-enriched fraction obtained in step c2) into step d) and / or e).

Before the extraction, the pH of the digestion product obtained in step b) can be adjusted by adding at least one acid or at least one base. Furthermore, in the case of a multistage extraction, the pH of the digestion product used in the first stage and the pH of the residue separated from the extractant phase at the respective stage can be adjusted by adding at least one acid or acid-forming compound or at least one base. Suitable acids are, for. For example, mineral acids such as hydrochloric acid, sulfuric acid and phosphoric acid, or acid-forming compounds such as CO2 and H2S. Suitable bases are, for. Example, alkali metal bases, such as sodium hydroxide or potassium hydroxide, alkali metal carbonates, such as soda or potassium carbonate, alkali metal bicarbonates, such as sodium bicarbonate or potassium bicarbonate and alkaline earth metal bases, such as calcium hydroxide, calcium oxide, magnesium hydroxide or magnesium carbonate and ammonia or amines. The separation of the extract in step c2) into an extractant-enriched fraction and an aromatic-enriched fraction C1) is preferably carried out by distillation.

The distillative separation of the extract in step c2) can be carried out by customary methods known to the person skilled in the art. Suitable methods are described in: K. Sattler, Thermal Separation Methods, Wiley-VCH, Third Essentially Revised and Extended Edition, July 2001. Suitable apparatus for distillative separation include distillation columns, such as tray columns containing bells, sieve plates, sieve trays, packing , Internals, valves, side vents, etc. may be provided. Especially suitable are dividing wall columns, which can be provided with side draws, returns, etc. For distillation, a combination of two or more than two distillation columns can be used. Also suitable are evaporators, such as thin film evaporators, falling film evaporators, Sambay evaporators, etc., and combinations thereof.

In the case that the digestion in step b) comprises pyrolysis, the separation in step c) is preferably carried out by absorption.

In a second embodiment of the process according to the invention, the biomass starting material provided in step a) is subjected to pyrolysis for digestion in step b) and comprises the separation in step c) into at least one aromatics-enriched fraction C1) and at least one aromatic-depleted fraction C2) an absorption.

The discharged from the pyrolysis discharge can in addition to the pyrolysis still contain fractions of solid and / or liquid components. These are z. For example, low-volatility components (eg coke) formed during pyrolysis. If at least one solid aggregate is used for the pyrolysis in step b), the discharge from the pyrolysis zone may also contain fractions of the aggregate. These solid and / or liquid components may, if desired, in step c) by means of a suitable device, for. As a cyclone, are separated from the pyrolysis gas. Separated solid additives are preferably recycled to the pyrolysis zone. From aggregates different separated components are supplied to another utilization, eg. As a combustion for heat recovery, which is preferably used again in the method according to the invention or an integrated method. The resulting exhaust gas, which contains mainly CO2 and water and optionally O2, can also be recycled become. It is also possible, a discharge from the pyrolysis zone containing at least one additive and under the pyrolysis low-volatile components, in a spatially separate from the pyrolysis zone combustion zone with an oxygen-containing gas, preferably air, in contact, resulting in burning of low-volatility components ("coke") produced during pyrolysis. By a suitable separator, the aggregate is then separated from the resulting exhaust gas and passed through a suitable conveyor in the pyrolysis zone. In a suitable embodiment, the discharge from the pyrolysis can be conducted directly, ie without separation of condensable components, into an optionally following dealkylation zone. In this embodiment, however, components of the discharge from the pyrolysis zone, which are difficult to volatilize under the conditions of pyrolysis in step b) and are not gaseous in the discharge from the pyrolysis zone, but solid or liquid, can be separated before entry into the dealkylation zone. In a particular embodiment, however, from the discharge from the pyrolysis (after separation of solid / liquid) condensable pyrolysis products (ie products that are present under normal conditions as liquids or solids) are separated. This can be accomplished by means of suitable separation processes known to the person skilled in the art, such as condensation, absorption, adsorption, membrane separation processes, etc.

A particularly preferred variant is absorption. In this case, the discharge from the pyrolysis zone is brought into contact with a stream Ab1) which contains a suitable solvent. The contacting is preferably carried out after a cooling step in which a condensation of high-boiling components can take place. The contacting takes place in a suitable device (eg a column). The contact device emanates a liquid stream Ab2), which contains the absorbent and aromatic pyrolysis products and a gaseous stream Ab3), which is depleted compared to the discharge from the pyrolysis of aromatic pyrolysis products. Stream Ab2) is separated, preferably by distillation, into a fraction Ab4) enriched in aromatic pyrolysis products in comparison with Ab2) and a fraction Ab5) depleted in comparison with Ab2) to aromatic pyrolysis products. Ab4) is, if necessary, after further work-up, as stream C1) in the optional subsequent Dealky- lierungsschritt d) or the amination step e) out and Ab5), after further cooling, led back into the absorption, ie Ab5 is the main component of Ab1 ). Another component is a solvent portion, which is added to compensate for solvent losses. Solvents suitable as absorbents are organic compounds such as aromatic or non-aromatic hydrocarbons, alcohols, aldehydes, ketones, amides, amines and mixtures thereof. These include z. B. benzene, toluene, ethylbenzene, xylenes, pentane, hexane, heptane, octane, ligroin, petroleum ether, cyclohexane, decalin, methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert. butanol,

1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, acetaldehyde, acetone, methyl ethyl ketone, N-methylpyrrolidone, dimethylformamide, dimethylacetamide and mixtures thereof.

The solvent preferably has a boiling point which, under identical conditions, is below that of the phenol. The solvent particularly preferably has a boiling point which, under identical conditions, is at least 10 K below that of the phenol. The solvent additionally preferably has a high solubility in water. These include z. As methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol and tert-butanol.

Many of the solvents used as absorbents have a vapor pressure under the conditions of absorption, which leads to a loading of the absorption gas stream Ab3) with the absorbent. This is especially true for the preferred solvents used having a boiling point below the boiling point of phenol. Preferably, the gas stream Ab3) emerging from the absorption is then subjected to at least partial removal of the solvent contained. Preferably, the separation of the solvent from the gas stream Ab3) takes place in the form of a water wash. Here, a good water solubility of the solvent used for absorption is particularly advantageous. The loaded with solvent and optionally aromatics wash water stream may, for. B. be worked up by distillation. The thereby separated absorbent is returned (optionally together with the aromatics) in the absorption step.

The digestion product obtained in step b) can be subjected to at least one further treatment step in step c) in addition to the separation described above. Additional treatment steps can be carried out before, during or after the separation.

Preferably, the digestion product obtained in step b) or the fraction C1) isolated therefrom in step c) predominantly comprises components having a molecular weight of at most 500 g / mol, more preferably of at most 400 g / mol, in particular of at most 300 g / mol , In a specific embodiment of the process according to the invention, the aromatics-depleted fraction C2) isolated in step c) is used at least partially for the production of synthesis gas. Dealkylation (step d)

If appropriate, the digestion product from step b) or the aromatics-enriched fraction C1) from step c) is fed into a dealkylation zone and reacted in the presence of hydrogen and / or water vapor. In the dealkylation, the products formed in the pyrolysis in step b) and optionally in step c) as

Fraction C1) isolated aromatic degradation products by the action of hydrogen and / or water vapor are at least partially converted so that substituents are replaced by hydrogen and / or more aromatic nuclei containing compounds are cleaved to compounds with a smaller number of nuclei. Thus, as previously stated, "dealkylation" also refers to reactions in which no alkyl substituent is replaced by hydrogen, such as dehydroxyation, dealkoxylation, aromatic cleavage, etc. The hydrogen-substituted substituents are preferably selected from alkyl groups. Suitable dealkylation processes for use in step d) include hydrodealkylation, steam dealkylation or mixtures thereof. In the case of pure hydrodealkylation according to the invention, in addition to the pyrolysis gas stream, molecular hydrogen is fed into the dealkylation zone (in pure form or mixed with other components, such as CO), but no water. In the case of a pure steam dealkylation according to the invention, water (in pure form or in a mixture with other components) is fed into the dealkylation zone in addition to the pyrolysis gas stream, but no molecular hydrogen. The dealkylation process in step d) can also be designed as a mixed form of hydrodealkylation and steam dealkylation. Then, in addition to the pyrolysis gas stream, both water and molecular hydrogen are fed into the dealkylation zone. In the following, suitable and preferred process parameters are given in part for the hydrodealkylation and the steam dealkylation. With this information, the person skilled in the art is able to determine suitable and preferred process parameters for a mixed form of hydrodealkylation and steam dealkylation. Preferably, the reaction gas used for dealkylation of H2 and H2O then has a mixing ratio of H2 to H2O in the range of about 0.1: 99.9 to 99.9: 0.1. A particularly suitable mixing ratio of H2 to H2O is in the range of about 40:60 to 60:40. The hydrogen required for the reaction is formed in situ in the case of steam dealkylation by reaction of water with (mainly organic) components which are either present in the educt mixture of the steam dealkylation or are formed during steam dealkylation. As an example, the formation of hydrogen from methane and water can be named according to the equation CH ₄ + H2O - CO + 3 H2.

Preferably, the temperature in the dealkylation zone is in a range from 400 to 900 ° C, more preferably from 500 to 800 ° C.

The absolute pressure in the dealkylation zone is preferably in the range from 1 to 100 bar, more preferably from 1 to 20 bar.

In a first preferred embodiment, the digestion product from step b) or the aromatic-enriched fraction C1) is subjected to a hydrodealkylation. For this purpose, the reaction in step d) takes place in the presence of hydrogen.

Preferably, the temperature in the dealkylation zone for the hydrodealkylation is in a range of 500 to 900 ° C, more preferably 600 to 800 ° C.

The absolute pressure in the dealkylation zone for the hydrodealkylation is preferably in the range from 1 to 100 bar, particularly preferably from 1 to 20 bar, in particular from 1 to 10 bar. For the hydrodealkylation, the feed ratio of H 2 to H 2 (stoichiometric) is preferably in a range from 0.02 to 50, particularly preferably from 0.2 to 10. H 2 (stoichiometric) stands for the amount H 2, which theoretically is just the complete one Reaction of the supplied into the Dealkylierungszone aromatics to benzene is required, assuming that per mole of substituent 1 mole of H2 reacted.

The residence time in the dealkylation zone is preferably in the range from 0.1 to 500 s, particularly preferably from 0.5 to 200 s, for the hydrodealkylation.

In a second preferred embodiment, the digestion product from step b) or the aromatics-enriched fraction C1) from step c) is subjected to a steam dealkylation. For this purpose, the reaction in step d) takes place in the presence of water vapor. The temperature in the dealkylation zone for the vapor dealkylation is preferably in the range from 400 to 800 ° C., particularly preferably from 475 to 600 ° C., in particular from 525 to 600 ° C. The absolute pressure in the dealkylation zone for the vapor dealkylation is preferably in a range from 1 to 100 bar, particularly preferably from 1 to 20 bar, in particular from 1 to 10 bar.

For the steam dealkylation, the amount ratio of H 2 O to C ^{* is} preferably in a range from 0.1 to 20 mol / mol, particularly preferably from 0.5 to

2 mol / mol. C ^* stands for the molar amount of carbon, determined by carbon-based balancing of the pyrolysis or by determining the amounts of the product exhausts from the steam dealkylation by methods known to the person skilled in the art. For steam dealkylation, the molar ratio of H2 to CH4 in the dealkylation zone is preferably in a range of <50: 1, particularly preferably <25: 1.

Preferably, for a steam dealkylation in the absence of Dealkylierungskata- lysators the molar ratio of OR (where R = H, alkyl) to C _ge including in the Dealkylierungszo- ne in a range of> 0.05: 1, more preferably from 0.1: 1 to 0.2: 1.

Preferably, for steam dealkylation in the absence of a dealkylation catalyst, the ratio of OR (with R = H, alkyl) to Cabs in the dealkylation zone is in the range of> 0.5: 1, more preferably from 1: 1 to 10: 1 , in particular from 1: 1 to 2: 1.

Preferably, for the steam dealkylation WHSV is in a range of 0.05 to 10 kg / L ^* h, more preferably from 0.1 to 2 kg / L ^* h. The steam dealkylation can be carried out in the presence or absence of a catalyst. In a specific embodiment, steam dealkylation is carried out in the absence of a catalyst. A catalyzed process for steam dealkylation is in

WO 2008/148807 A1. Reference is made in its entirety to this document and the references cited therein to suitable catalysts. Further information on catalyst types and process steps of steam dealkylation can be found in WO 2007/051852 A1, WO 2007/051851 A1, WO 2007/051855 A2, WO 2007/051856 A1, WO 2008/135581 A1 and WO 2008/135582 A1

(EP 2008055585), without thereby limiting. US 3,775,504 describes that steam dealkylation actually consists of a combination tion of steam dealkylation and hydrodealkylation, since systemically inherent at least a portion of the hydrogen produced is reacted again immediately.

In the dealkylation step d) at least one oxyaromatic composition is obtained, which generally has lower proportions of the following components than the digestion product from step b) or the aromatic-enriched fraction C1) from step c): mono-, di-, and polyalkylated phenols; Alkoxyphenols, such as methoxyphenols; polyalkylated benzenes; Compounds containing two or more aromatic rings. These components are referred to below as "low or non dealkylated aromatics".

Separation of the discharge from the dealkylation zone

The discharge from the dealkylation zone can be fed directly to the amination in step e).

In an alternative embodiment, a discharge is taken from the dealkylation zone and subjected to separation prior to use for the amination in step e). At least one stream D1) enriched in dealkylated oxyaromatics and at least one stream D2) enriched in volatile components are obtained. Preferred product D1) is an oxyaromatic composition having a high content of mononuclear, low or non-alkylated oxyaromatics.

Preferably, the effluent from the dealkylation zone is subjected to separation to give the following three streams:

D1) an enriched in mononuclear, low or non-alkylated oxyaromatic stream, D2) an enriched in low or non-dealkylated aromatics stream,

D3) an enriched lighter than D1) and D2) by-products stream. Optionally, the effluent from the dealkylation zone may be subjected to separation to yield additional streams, such as e.g. B. a hydrous stream.

The stream D1) is advantageously suitable for use in the amination step e). The stream D1) preferably contains at least 70% by weight, more preferably at least 80% by weight, in particular at least 90% by weight, based on the total amount of D1) of mononuclear aromatic compounds. The stream D1) preferably contains at most 30% by weight, particularly preferably at most 20% by weight, in particular at most 10% by weight, based on the total amount of D1) of aromatics which are not dealkylated.

The stream D2) preferably contains at least 70% by weight, particularly preferably at least 80% by weight, in particular at least 90% by weight, based on the total amount of D2) of aromatics which are not dealkylated or are not dealkylated.

The stream D3) contains components that z. B. are selected from non-aromatic hydrocarbons, especially methane, hydrogen, carbon monoxide, carbon dioxide and mixtures thereof. Depending on the lignin-containing starting material provided in step a), the stream D3) may contain further components. When using a lignin-containing starting material from the kraft process to include sulfur-containing by-products, especially h S. Preferably, a gaseous discharge is removed from the Dealkylierungszone and then subjected to a separation.

As a method of separation, the well-known thermal separation methods can be used.

The separation of the discharge from the dealkylation zone in step d) preferably comprises an absorption. In the absorption, the gaseous effluent from the dealkylation zone is contacted with a solvent (absorbent), whereby a part of the components contained in the gas stream is absorbed and thus separated.

The absorption is carried out in a suitable apparatus, e.g. B. a countercurrent column, bubble column, etc. Preferably, the absorption is carried out in a countercurrent column.

The absorption can be configured in one or more stages.

A solvent (unloaded: absorbent, loaded: sorbate) is preferably used for absorption, in which the aromatics obtained in the dealkylation are used in a reaching soluble amount and the various volatile by-products are essentially insoluble. In this case, together with the mononuclear, low or non-alkylated aromatics (= target product) and the low or non-dealkylated at least partially absorbed.

The absorption thus contains on the one hand an aromatics-laden absorbate. The aromatic components contained in the absorbate correspond in composition to the sum of the aromatics in the streams D1) and D2) plus any aromatics optionally present in the absorbent. The components contained in the remaining gas stream correspond in their composition to stream D3). If desired, the gas stream may be subjected to an additional aromatic aromatics removal step. These can then be combined again with the aromatics contained in the separated solvent for joint workup. In general, however, such isolation of aromatics from the separated gas stream is not required.

In a preferred embodiment, the separation of the discharge from the dealkylation zone in step d) comprises the following substeps:

Contacting the discharge from the dealkylation zone with an absorbent to give an absorbate enriched in aromatic main products of the dealkylation and a gas stream D3 depleted in aromatic main products of dealkylation, d2) separating the absorbate into a stream enriched in mononuclear, low or non-alkylated oxyaromatics D1) d2) enriched in low or non-dealkylated aromatics, and optionally a stream containing the absorbent, d3) if present, recycle the absorbent-containing stream to step d1), d4) optionally recycle at least a portion of stream D2) into the stream Dealkylation zone of step d).

Preferably, the absorbent has a boiling point which is above the boiling point of the highest boiling components of stream D1. In a first suitable embodiment, an absorbent is used, which is different from the components of the streams D1) and D2). Suitable absorbents for this embodiment are non-aromatic hydrocarbons, non-aromatic alcohols, non-aromatic aldehydes, ketones, amides, amines and mixtures thereof. Preferably, the absorbent for this embodiment is selected from pentane, hexane, heptane, octane, ligroin, petroleum ether, cyclohexane, decalin, methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, 1 Pentanol, 1-hexanol, 1-heptanol, 1-octanol, acetaldehyde, acetone, methyl ethyl ketone, N-methylpyrrolidone, dimethylformamide, dimethylacetamide and mixtures thereof.

Suitable absorbents are further from the components of the streams D1) and D2) different aromatic hydrocarbons. These aromatic hydrocarbons are preferably selected from optionally substituted acetophenones, optionally substituted benzophenones, optionally substituted biphenyls, optionally substituted terphenyls, optionally substituted diphenyl ethers and mixtures thereof. If the absorption medium used is a component which is also present in the streams D1) or D2) as by-product, measurements and control measures known to the person skilled in the art can be used to ensure that this component is continuously present in the amount in which it is obtained. is led out of the process.

If an absorbent is used which is different from the components of the streams D1) and D2), the separation of the discharge from the dealkylation zone in step d) preferably comprises the following substeps: d1) contacting the discharge from the dealkylation zone with an absorbent to obtain an absorbate enriched in aromatic main products of dealkylation and a gas stream D3 depleted in aromatic main products of dealkylation (or a gas stream D3 enriched in by-products which are more volatile than D1 and D2),

Separation of the absorbate into a stream D1) enriched in mononuclear, slightly or non-alkylated oxyaromatic compounds, a stream D2) enriched in slightly or non-dealkylated aromatics and a stream containing the absorbent, d3) recycling the stream containing the absorbent to step d1 ) d4) optionally recycling at least a portion of the stream D2) into the dealkylation zone of step d).

In a special variant, the absorption medium used is an aroma composition obtainable by the process according to the invention. This is specifically a mixture of aromatics that are not or not fully converted in the dealkylation. In a preferred variant, the absorbent used is an aromatic composition whose composition corresponds, in part or in full, to stream D2 or to a mixture of D1 and D2. Optionally, the stream D2 or the mixture of D1 and D2 may be subjected to at least one work-up step prior to use as an absorbent.

If an absorption medium is used whose composition largely or completely corresponds to stream D2 or a mixture of D1 and D2, the separation of the discharge from the dealkylation zone in step d) preferably comprises the following substeps:

Contacting the discharge from the dealkylation zone with an absorbent to give an absorbate enriched in aromatic main products of dealkylation and a gas stream D3 depleted in aromatic main products of dealkylation,

Separation of the absorbate into a stream D1) enriched in mononuclear, slightly or non-alkylated oxyaromatic compounds and a stream D2) enriched in aromatics which are sparingly or not dealkyated, if appropriate recycling at least part of the stream D2)

Dealkylation zone of step d). In this variant, the solvent can be obtained by partial condensation of the stream from the dealkylation or a gas stream from a downstream of the dealkylation high boiler pre-separation. Here, it may be advantageous to switch between the said partial condensation and the absorption of a further partial condensation in which in particular water is condensed out. In this variant as well, together with the absorption of desired product, at least partial absorption of the unreacted or incompletely reacted aromatics takes place. Ie. also in this variant, the aromatic components contained in the absorbate of their composition correspond to the sum of the aromatics of the streams D1) and D2). In step d2), the aromatics-enriched absorbate is preferably separated by distillation. The thereby recovered solvent is, optionally after separation of absorbed water, returned to the absorption (step d1). The aromatics are processed further as before and described below.

In step d2), the aromatics-enriched absorbate is preferably separated by distillation in at least one column ("regeneration column"). The distillation conditions are preferably selected so that substantially low or non-alkylated aromatics and, if present, water and, as the bottom product, substantially low or non-dealkylated aromatics are obtained as top product.

It is understood that in the distillative separation in step d2), the bottom temperature is chosen so low that undesirable side reactions of the bottom product are substantially avoided. This can be achieved in particular by setting a suitable column pressure and / or the low boiler content in the bottoms (the low boiler content can be further reduced by a downstream stripping). The overhead product obtained in the distillation in step d2) can be withdrawn directly as stream D1) and used for the amination in step e).

Alternatively, the top product obtained in the distillation in step d2) can be subjected to a further work-up.

Water contained in the top product can be separated by known methods. For this, the top product can be fed to a phase separator for water separation after condensation of the vapors from the distillation. The resulting water is discharged as another stream from the process. The organic phase from the phase separator can be either at least partially withdrawn as stream D1) or subjected to further work-up. The organic phase from the phase separator can be partly recycled as reflux to the column and / or subjected to a further distillative workup. This is preferably used for the removal of water still contained and / or undesirable organic components.

The bottom product obtained during the distillation in step d2) contains the aromatics which are not or not sufficiently converted in the case of dealkylation, ie it is enriched in aromatics which are sparingly or not dealkylated. It can be either directly as Stream D2) withdrawn or subjected to further work-up. The bottom product obtained in the distillation in step d2) is preferably divided into at least two partial streams. Preferably, a first partial stream is returned in step d) of the absorptive separation of the discharge from the dealkylation zone as an absorbent. For this purpose, this partial stream, if necessary, cooled to a suitable temperature. A second partial stream is withdrawn as stream D2). Stream D2 may be subjected to separation of non-stream D2 components prior to recycling to the dealkylation zone of step d). This is z. B. advantageous if an absorption solvent is used, which is not obtained as an intermediate product of the process according to the invention. It is also advantageous at this point of stream D2) deduct a purge and z. B. in a combustion device to reduce the accumulation of under the conditions of dealkylation not or slowly reacting components. The stream D2) is preferably subjected to evaporation before it is fed into the dealkylation. A preferred variant is shown in FIG. 1 and explained in the associated description of the figures.

In a specific embodiment, the stream D3) obtained in step d), which is depleted in aromatics and enriched in readily volatile by-products, is used at least partially for the production of synthesis gas. If, according to the preferred embodiment of the process according to the invention described above, the separation of the discharge from the dealkylation zone in step d) comprises an absorption, the gas stream leaving the absorption device (stream D3), optionally after a removal step for removing absorbent and / or aromatics , at least partially used for the production of synthesis gas.

The stream D3) obtained in step d) can be partly supplied to various other uses in addition to synthesis gas production. This includes on the one hand the combustion. When the process according to the invention is spatially close to a pulp process, it may be advantageous to feed stream D3) into an apparatus of the pulp process. Particularly preferably, the stream D3) is fed into the waste liquor combustion (recovery boiler). This embodiment has the advantage that no additional devices for the steam or power generation or the flue gas desulfurization in the combustion of the stream D3) are required. In another variant, the combustion of the stream D3) is a desulfurization, z. B. in the form of a hydrogen sulfide removing gas scrubber, followed by a conversion of the formed H2S in elemental sulfur, upstream. The formation of sulfur can be prepared by known methods, for. As the Claus process done. The combustion can instead be followed by a desulfurization unit.

Optionally, for synthesis gas production in addition to electricity E3) at least one further stream can be used, the z. B. water vapor and / or oxygen.

In a specific embodiment of the process according to the invention, the aromatic-depleted fraction C2) isolated in step c) is used at least partly for the production of synthesis gas. It is also possible to remove an exhaust gas stream from the

Use in step b) and / or the optional dealkylation in step d) in the syngas production. It may be z. B. to act as a combustion gas from the combustion of volatile components. By feeding such an exhaust gas stream, the h / CO ratio of the synthesis gas can be reduced.

The synthesis gas production preferably comprises the following stages:

a reforming stage,

a conversion stage (in which, if necessary, additional water is conducted), in which the water gas shift reaction (CO + H ₂ 0 H ₂ + C0 ₂ ) takes place, optionally a stage for the partial separation of acid gases, such as. B. C0 ₂ .

The execution of the syngas generation corresponds to the prior art, as he z. In Ullmann's Encyclopedia of Industrial Chemistry, "Gas Production", DOI: 10.1002 / 14356007.a12_169. pub2, is described.

In a preferred variant, the synthesis gas produced in the process according to the invention (if necessary after further purification steps known per se for the removal of water, sulfur-containing components, CO2, etc.) is completely or partially used in at least one process comprising hydrogen, CO or mixtures both consumed, used. These include z. As a hydrogenation, hydroformylation, carbonylation, methanol synthesis, synthesis of hydrocarbons Fischer-Tropsch, etc.

In a preferred embodiment of the process according to the invention, a synthesis gas-containing stream produced in the process or a hydrogen-enriched stream prepared from the synthesis gas is fed into the digestion in step b) and / or into the optional dealkylation in step d). An enrichment of the Synthesis gas to hydrogen can, as described above, carried out by water gas shift reaction.

Preferably, a synthesis gas-containing stream produced in the process or a hydrogen-enriched stream prepared from the synthesis gas is fed into the dealkylation in step d). The particular advantage of this variant is that the proportion of phenol (s) in the products of dealkylation is higher than in pure steam dealkylation, ie. H. without hydrogen supply. The higher phenol formation represents an important advantage for the polyisocyanate preparation according to the invention.

Amination (step e)

The oxyaromatic composition obtained from the biomass starting material by digestion and optionally further reaction and / or work-up steps is subjected to an amination in step g). The oxyaromatic compound is preferably reacted in an amination zone with an ammonia source to give the corresponding aromatic amines.

Preference is given in step e) to the digestion product from step b) or the aromatics-enriched fraction C1) from step c) or the discharge of the dealkylation zone from step d) or the dealkylated aromatic enriched stream D1) from step d) of an amination by reaction subjected to an ammonia source.

The reaction with an ammonia source can be carried out by customary methods known to the person skilled in the art, as described, for example, in US Pat. in DE-AS-1 289 530, US 3,578,714,

US 5,214,210 and EP-A-0 321 275 are described. The disclosure of these documents is hereby incorporated by reference.

For amination, ammonia or an ammonia source capable of forming ammonia under the reaction conditions can be used. These include z. B. compounds which form ammonia upon thermal decomposition, such as ammonium carbonate and ammonium sulfate. Alternatively, an organic amine can also be used for the amination, preferably selected from methylamine, ethylamine, n-propylamine, dimethylamine, diethylamine, dipropylamine, methylethylamine, cyclohexylamine, aminopyridines, aniline, methylaniline, ethylaniline, n-propylaniline, isopropylaniline, dimethylaniline, Diethylaniline, dipropylaniline, methylethylaniline and methylpropylaniline. Preferably, ammonia is used for the amination. The amination is preferably carried out in the presence of a suitable catalyst. Preferably, a catalyst based on at least one Al oxide or Si-Al oxide is used. If necessary, the educts may be subjected to a preheating prior to the amination, which may be associated with evaporation.

The temperature in the amination zone is preferably in the range from 100 to 600 ° C., more preferably from 200 to 450 ° C.

The absolute pressure in the amination zone is preferably in the range from 1 to 100 bar, more preferably from 1 to 30 bar.

As reactors for the amination, preference is given to using fixed beds or fluidized beds.

For the amination, the molar ratio of ammonia to oxyaromatic is preferably in the range from 5: 1 to 30: 1. The gas leaving the amination zone preferably contains a larger molar proportion of amines than of oxyaromatics.

For workup, the discharge removed from the amination zone is preferably subjected to separation. The discharge from the amination zone is usually gaseous. In a preferred embodiment, the discharged from the amination zone discharge is cooled and fed to a first distillation column to separate contained excess ammonia. This is preferably recycled to the amination zone. At the bottom of the first distillation column, the amines formed are obtained as a mixture with water and optionally small amounts of by-products. The bottoms product of the first distillation column is fed to a second distillation column to separate the water. The further separation preferably takes place in at least one further distillation column. In this case, at least one enriched in aromatic amines stream E1) and at least one enriched in oxyaromatic stream E2). Using the split-column technology, it is also possible to combine several columns in a column provided with one or more side draws. Suitable columns with side draws that are thermally coupled in a specific embodiment and dividing wall columns are known in the art. The stream E1) enriched in aromatic amines is fed to the phosgenation (step g). The oxyaromatic enriched stream E2) is preferably recycled to the amination zone. If desired, the aromatic amine-enriched stream E1) may be subjected to further separation. Further separation occurs in a specific embodiment when the aromatic amines-enriched stream E1) is monoamines (ie, Nh-group-containing amines) and polyamines (ie, amines having more than one Nh-group, eg, two, three or more) four Nh groups). The further separation is preferably carried out by distillation. A stream El m) enriched in aromatic monoamines and a stream E 1 p) enriched in aromatic polyamines are then preferably obtained. In a specific embodiment, the stream En m) enriched in aromatic monoamines is subjected to condensation with a formaldehyde source in step f) before the phosgenation in step g). The stream El p) enriched in aromatic polyamines can either be subjected to condensation with a formaldehyde source in step f) before the phosgenation in step g) or used directly for the phosgenation in step g).

In a specific embodiment, at least one amine which has not been obtained from biomass (hereinafter "conventional amines") is added to the amination product from step e) before the reaction in step f) and / or g). As stated above, "biomass" in the context of the invention refers to a plant material of non-fossil origin. The added amines are preferably derived from a source of fossil resources selected from coal, petroleum, natural gas and their performance products, such as coke.

The amines used for the reaction in step f) and / or g) preferably contain at least 50% by weight, more preferably at least 75% by weight, in particular at least 90% by weight, especially at least 99% by weight, of amines prepared according to the invention from a biomass starting material, based on the total amount of amines used for the reaction in step f) and / or g). Conventional Amines Suitable conventional aromatic amines can be prepared from the corresponding aromatics such. B. benzene or toluene can be prepared by methods known in the art. This includes in particular the nitration with subsequent hydrogenation of the nitro group to the corresponding amine. Nitroaromatics can be prepared by batch or continuous processes. The nitrating agent is preferably either a mixture of nitric acid and sulfuric acid or nitric acid alone. Suitable processes for continuous preparation in the liquid phase z. By Meissner et al., Continuous production of nitrotoluenes, Ind. Eng. Chem., 46 4 (1954), 718-24 and in US 2,773,911. Nitrogenation with nitric acid alone is described in US Pat. No. 2,739,174 and gas phase nitration of hydrocarbons in GB 586732. A summary of a suitable technical process is z. In Leslie A. Carmichael, Aromatic Amines, SRI Stanford Research Institute, 1972. The

EP-A-748 788 and EP-A-059 7361 describe the adiabatic and continuous liquid-phase nitriding for the production of nitrotoluene. US 5,302,763 describes the sulfuric acid-free nitration with nitric acid. EP-A-1 350 787 describes a process for the heterogeneous catalytic nitration of toluene over acidic zeolites to increase the selectivity. EP-A-0 184 569 describes a process for heterogeneously catalyzed nitration of mixed oxides in the gas phase. A review of dinitrotoluene preparation can be found in Hermann et al., Industrial nitration of toluene to dinitrotoluene, ACS Symp. Series 623 (nitration), 234-249

EP-A-1 880 989 describes fine technical embodiments of the method. The isothermal process procedure in the liquid phase is described in WO 2005/075407 and

EP-A-0 903 336. Details of the wastewater treatment are described in DE 10329303 and the integration into a larger composite in EP-A-1 132 347 and EP-A-0 976 718. CN 18541 14 teaches nitration with the addition of metal salts. The significance of the concentration of the sulfuric acid used is described in DE-A-4230099. The comments on dinitrotoluene as precursor of TDI apply analogously to mononitrobenzene as precursor of MDA / MDI. Descriptions of suitable continuous processes in the liquid phase can be found in US 2,849,497 and US 2,773,911. As reactors come z. B. stirred boiler with heat exchangers or flow tubes in question. The adiabatic reaction in the flow tube is described in BE 724918, DE 4428460 and DE 4428461. In this case, the nitrating acid absorbs the heat of reaction of the nitration reaction. The stored heat can be used to separate the by-product water from the reaction mixture by relaxing. A particular embodiment of the adiabatic flow tube for carrying out the reaction in the liquid phase in the nitration of aromatics can be found in DE 10223483, EP 0 489 21 1 and WO 01/64333. The adiabatic reaction in the liquid phase is particularly preferred in the preparation of mononitrobenzene over that of nitrotoluene, since selectivities with respect to the formation of isomers need not be considered. The safe monitoring and management of nitriding processes is described in EP-A-1 445 246. Quadros et al., Ind. Eng.

Chem. Res. 2004, 43, 4438 - 4445 are dedicated to the problem of wastewater. To the Of- The disclosure of the aforementioned documents is hereby incorporated by reference in its entirety.

The aromatic nitro compounds obtained by nitration are converted by hydrogenation into the corresponding amines. The by-product of the hydrogenation is water. The hydrogenation is preferably carried out in the presence of a catalyst. It can be done technically in various technical configurations such as fluidized beds or fixed beds or in liquid or gaseous phase. Advantageously, the high heat of reaction is used to generate energy and / or coupled into a heat network (see EP-A-1 137 623, US 7,064,237, EP-A-0 696 573, EP-A-0 748 789). The reaction in coated microchannels is described in DE-A-10 2006 01 1 497. The disclosure of the aforementioned documents is hereby incorporated by reference. - nuclear hydrogenation

The amination product obtained in step e) (especially the stream El p enriched in aromatic polyamines) may be subjected to a core hydrogenation before an optional condensation with a formaldehyde source in step f) or before the phosgenation in step g). Thus, economically and ecologically favorable aliphatic polyisocyanates can be obtained. Suitable processes for nuclear hydrogenation are described, for example, in US Pat. No. 6,429,338, WO 2006/066762 and EP-A-799 817. The disclosure of these documents is hereby incorporated by reference. Condensation with a formaldehyde source (step f)

In order to obtain polyisocyanates with high NCO numbers, the amination product obtained in step e) can be partially or completely subjected to condensation with formaldehyde before the phosgenation in step g). Furthermore, it is possible to mix condensed amines with non-condensed amines for the phosgenation in step g).

With regard to suitable processes for the condensation of the aromatic amines with formaldehyde, reference is made to DE-A-19961973, DD 295628 and DD 238042.

Suitable formaldehyde sources for the reaction in step f) are formalin solutions, formaldehyde oligomers, eg. Trioxane, and polymers of formaldehyde, such as paraformyl maldehyd. Preference is given to using paraformaldehyde or formalin solution. Of course you can also use gaseous formaldehyde.

The molar ratio of the amines used to formaldehyde is preferably from 1, 5: 1 to 10: 1, in particular 2: 1 to 6: 1.

The condensation reaction is preferably carried out with the addition of acidic catalysts. Acid catalysts which can be used are the catalysts generally known for this reaction, for example mineral acids such as phosphoric acid, sulfuric acid and hydrochloric acid. Hydrochloric acid is preferably used as the catalyst for the condensation in step f).

The molar ratio of catalyst to amines is preferably 0.01 to 1, in particular 0.1 to 0.5.

The condensation reaction is usually carried out at temperatures of 20 to 150 ° C, preferably 20 to 130 ° C. In a preferred variant, aniline and the acidic catalyst are initially charged and formaldehyde is added. The acid amine mixture of the condensation can be worked up by conventional methods such as neutralization, phase separation and distillation.

Phosgenation (step g) The phosgenation of the amine product obtained in step e) (especially the stream El p enriched in aromatic polyamines) or the condensation product obtained in step f) can be carried out by customary methods known to the person skilled in the art.

Liquid phase phosgenations suitable for the phosgenation in step g) are described, for example, in EP-A-1 616 857, WO 2004/056756, WO 2006/130405, EP-A-1 509 496, EP-A-1 270 544 and DE-A A-199 61 973. The disclosure of these documents is hereby incorporated by reference.

Alternatively, the phosgenation in step g) can be carried out as gas phase phosgenation. One advantage of high temperature phosgenation in the gas phase is that the formation of undesirable intermediates of the amine hydrochlorides can usually be avoided. Such processes are described in EP-A-593 334, WO 2003/045900, WO 2008/086922 and WO 2008/006775 (aerosol phosgenation), to which reference is also hereby made in their entirety. Furthermore, the phosgenation in step g) can be carried out in supercritical solvents (WO 2008/049783). Further, as solvents, the isocyanates themselves (EP-A-1 401 802, US 6,683,204) or ionic liquids

(WO 2006/048141 BASF, WO 2006/048171 BASF) can be used.

In a suitable embodiment, the phosgenation in step g) is carried out in a solvent which is inert under the conditions of phosgenation. Suitable solvents are, for. As aromatics, such as toluene, mono- or dichlorobenzene. The phosgenation in step g) can be carried out in customary reactors, for example stirred kettles or columns.

The temperature in the phosgenation is preferably in a range of 50 to 150 ° C, particularly preferably 70 to 100 ° C.

The pressure in the phosgenation is preferably in a range of 0.5 to 10 bar, more preferably 0.8 to 5 bar.

The crude isocyanate obtained in the phosgenation in step g) can be purified by conventional methods, for example distillation. As apparatuses for falling film or thin film evaporators or packed columns can be used. This cleaning can be done in two steps. At a temperature of 50 to 150 ° C, phosgene, HCl and solvent are first separated by stripping, optionally under vacuum or by feeding inert gas, from the crude isocyanate. Subsequently, at a temperature of 150 to 190 ° C, again by stripping or vacuum, the residual solvent and any chlorine-containing compounds are removed.

Claims

claims

A process for the preparation of polyisocyanates, which comprises using a biomass raw material for preparing a composition of aromatic amines having a C ¹⁴ to C ¹² -lsotopenverhältnis in the range of 0.5 x 10 ^"12 to 5 × ^{10" 12,} and the The composition of aromatic amines undergoes phosgenation.

Process according to claim 1, in which the biomass starting material for the preparation of the aromatic amines composition is subjected to at least one reaction comprising digestion to obtain an aromatic composition containing aromatics containing at least one hydroxy group per molecule and / or at least one hydroxy group have an alkoxy group ("Oxyaromatenzusammensetzung"), and the Oxyaromatenzusammensetzung subjected to an amination.

A process according to claim 2, wherein the oxyaromatic composition contains, based on the total weight, at least 75% by weight, preferably at least 90% by weight, in particular at least 95% by weight, of mononuclear aromatics.

4. A process for the preparation of polyisocyanates in which a biomass starting material is provided (step a) and subjected to a reaction which comprises a digestion (step b), to obtain an aromatics composition which contains aromatics per molecule at least one hydroxy group and / or at least one alkoxy group ("oxyaromatic compound") subjecting the oxyaromatic composition to amination (step e), optionally subjecting the amination product to condensation with a formaldehyde source (step f), the amination product or the product of condensation with a formaldehyde source subjected to phosgenation (step g).

Process for the preparation of polyisocyanates, comprising: a) providing a biomass starting material, optionally subjecting the biomass starting material to digestion, optionally separating the digested material obtained in step b) into at least one aromatics-enriched fraction C1) and at least one aromatics-depleted fraction C2), optionally the digestion product from step b) or the aromatic-enriched fraction C1) from step c) feeds into a dealkylation zone and reacts in the presence of hydrogen and / or steam, discharges the dealkylation zone, and optionally subject the discharge of the dealkylation zone to a separation, at least one stream enriched in dealkylated oxyaromatics D1) and at least one light volatile component enriched stream D2), the digestion product from step b) or the aromatics enriched fraction C1) from step c) or the discharge of the dealkylation zone from step d) or the dealkylated aromatic enriched stream D1) in egg subjecting the amination product from step e) to a condensation with a formaldehyde source; g) subjecting the amination product from step e) or the product of the condensation with a formaldehyde source from step f) to phosgenation.

Method according to one of the preceding claims, wherein a lignin-containing material is provided as biomass starting material.

Method according to one of the preceding claims, wherein as biomass starting material, a lignocellulosic material or a digestion product of a lignocellulosic material is provided.

Method according to one of the preceding claims, wherein the biomass starting material used is a lignin-containing stream from the digestion of a lignocellulosic material. losematerials for the production of cellulose (pulp), preferably a black liquor, in particular a black liquor from the Kraft digestion (sulfate digestion) is provided.

Method according to one of claims 2 to 8, wherein the provided biomass starting material for the digestion in step b) is subjected to a pyrolysis.

10. The method of claim 9, wherein the pyrolysis is not carried out with the addition of hydrogen compounds.

1 1. Process according to claim 9, wherein the pyrolysis is carried out with the addition of hydrogen (hydrocracking). 12. The method according to any one of claims 9 to 1 1, wherein a black liquor material is used for the pyrolysis, which under normal conditions (20 ° C, 1013 mbar) has a liquid content of at most 70 wt .-%, preferably of at most 50 wt .-%, based on the total weight of the black liquor material.

13. The method according to any one of claims 2 to 8, wherein the provided biomass starting material in step b) is subjected to a digestion in the liquid phase. 14. The method of claim 13, wherein the biomass starting material, preferably a lignin-containing starting material, in step b) is subjected to a digestion in the presence of an aqueous-alkaline, aqueous-acidic or organic digestion medium. 15. The method according to any one of claims 13 or 14, wherein for digestion at least one cellulose-depleted fraction from a pulp process, in particular a black liquor from the kraft process, is used.

16. The method according to any one of claims 5 to 15, wherein in step c) the separation into at least one aromatics enriched fraction C1) and at least one aromatics depleted fraction C2) by distillation, extraction, absorption, membrane processes or a combination thereof , preferably by distillation, extraction, absorption or a combination thereof.

17. The method according to any one of claims 9 to 12, wherein the provided in step a) biomass starting material for digestion in step b) is subjected to pyrolysis and in step c) the separation into at least one aromatics enriched fraction C1) and at least one aromatic-depleted fraction C2) comprises an absorption.

The method according to any one of claims 13 to 15, wherein the biomass starting material provided in step a) is subjected to liquid phase digestion in step b) and the separation into at least one aromatics enriched fraction C1) and at least one in step c) Aromatics depleted fraction C2) comprises an extraction and / or a distillation.

A process according to claim 18, wherein the separation into at least one aromatic-enriched fraction C1) and at least one aromatic-depleted fraction C2) in step c) comprises the following substeps:

Extraction of the digestion product obtained in step b) to obtain an aromatics-enriched extract and an aromatic-depleted residue, optionally separating the extract into an extractant-enriched and aromatics-depleted fraction, and an aromatics-enriched and depleted extractant fraction,

A process according to any one of the preceding claims, wherein the reaction step d) comprises a hydrodealkylation or a vapor dealkylation or a mixed form thereof.

A process according to any one of the preceding claims, wherein the temperature in the dealkylation zone is in a range of from 400 to 900 ° C, preferably from 500 to 800 ° C.

22. The method according to any one of the preceding claims, wherein the absolute pressure in the dealkylation zone in a range of 1 to 100 bar, more preferably from 1 to 20 bar, in particular from 1 to 10 bar, is located. A process according to any one of claims 5 to 22, wherein the discharge from the dealkylation zone in step d) is subjected to separation to give the following three streams:

D1) a mononuclear, low or non-alkylated oxyaromatic enriched stream,

D2) an enriched in low or non dealkylated aromatics stream,

D3) an enriched lighter than D1) and D2) by-products stream.

Method according to one of claims 4 to 23, wherein for the amination in step e) ammonia is used.

A process according to any one of claims 4 to 24, wherein the discharge from the amination zone in step e) is subjected to separation to obtain at least one stream E1) enriched in aromatic amines and at least one stream E2) enriched in oxyaromatics.

A process according to any one of claims 25, wherein the separation to obtain at least one aromatic amines enriched stream E1) and at least one oxygenated enriched stream E2) comprises the following substeps: e1) distillative separation of the discharge from the amination zone to give ammonia enriched E2) optionally distillative removal of water from the ammonia-depleted fraction from step e1), e3) distillative separation into at least one stream enriched in aromatic amines E1) and at least one stream enriched in oxygenated aromatics E2).

27. The method according to any one of claims 25 or 26, wherein the aromatic amines enriched stream E1) is at least partially subjected to a condensation with a formaldehyde source (step h). 28. The method according to any one of claims 25 to 27, wherein the stream enriched in aromatic amines E1) is at least partially used without prior condensation with a formaldehyde source for phosgenation (step g).

29. The method according to any one of claims 25 to 28, wherein the stream enriched in aromatic amines E1) is subjected to a further separation to obtain a stream enriched in aromatic monoamines El m) and an enriched in aromatic polyamines stream El p).

30. The process according to claim 29, wherein the stream enriched in aromatic monoamines El m) is subjected to a condensation with a formaldehyde source in step f) before the phosgenation in step g).

31. A process according to any one of claims 29 or 30, wherein the aromatic polyamine-enriched stream El p) is subjected to condensation with a formaldehyde source in step f) prior to phosgenation in step g), or directly to

Phosgenation in step g) is used.

32. A process according to any one of claims 25 to 31, wherein the oxygen-aromatic enriched stream E2) is recycled to the amination zone in step e).

33. The process as claimed in any of claims 4 to 32, wherein at least one amine which has not been obtained from biomass is added to the amination product from step e) before the reaction in step f) and / or g). 34. Polyisocyanate composition, wherein the C ¹⁴ to C ¹² is -lsotopenverhältnis in the range of 0.4 x 10 ^"12 to 4.5 x ^{10" 12th}

35. A polyisocyanate composition obtainable by a process as defined in any of claims 1 to 33.

36. A polyisocyanate composition according to claim 34 or 35 having an NCO number of at least 30.