WO2011138355A2

WO2011138355A2 - Method for producing pulp and at least one organic liquid or liquefiable valuable material with exhaust gas recycling

Info

Publication number: WO2011138355A2
Application number: PCT/EP2011/057098
Authority: WO
Inventors: Roman Prochazka; Stefan Bitterlich; Stephan Deuerlein; Otto Machhammer; Dirk Klingler; Emmanouil Pantouflas
Original assignee: Basf Se
Priority date: 2010-05-07
Filing date: 2011-05-04
Publication date: 2011-11-10
Also published as: WO2011138355A3

Abstract

The present invention relates to an integrated method for producing pulp and at least one organic liquid or liquefiable valuable material, in which a) a lignocellulosic starting material is prepared and subjected to disruption with an aqueous-alkaline treatment medium, b) from the disrupted material a cellulose-enriched fraction and a cellulose-depleted black liquor are isolated, c) the black liquor is subjected to a treatment with at least one organic liquid or liquefiable valuable material and at least one exhaust gas stream being obtained, d) at least one of the exhaust gas streams of step c) is recirculated to the method for producing pulp and utilized.

Description

Process for the production of pulp and at least one organic liquid or liquefiable recyclable material with exhaust gas recirculation

description

The present invention relates to a process for the production of pulp and at least one organic liquid or liquefiable recyclable material, wherein a waste gas stream obtained during the production of the valuable material is recycled to the pulp process and utilized therein.

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 protect raw material resources, processes are needed that enable the replacement of fossil raw materials with biomass raw materials. The aim is to achieve a high efficiency as complete as possible use of biomass material once provided.

With a share of approximately 700 billion tonnes of the estimated biomass supply of 1.5 trillion tonnes on earth, cellulose is the most important representative in the group of organic biopolymers and a very versatile raw material. In the biomass available as a source of raw materials, however, cellulose hardly ever occurs in pure or sufficiently enriched form, but essentially as a constituent of lignocellulose. The chemical digestion of lignocellulose results in a pulp called pulp, which consists mainly of cellulose. Pulp is the basis for making wood-free paper that has the property of not yellowing. The pulp for paper is mainly made from wood chips (wood chips), but other vegetable fibers are used.

There are two main types of pulp processes which are dominant in the market: the acid sulphite (after Mitscherlich) and the alkaline sulphate process. Today, mainly the sulphate process, which is also called Kraft process, is used worldwide. It is named after the Na2S0 ₄ added as a make-up chemical in the recovery of the pulping chemicals. The active substances are caustic soda and sodium sulfide.

There is still a need for a pulping process in which the lignin contained in the lignocellulosic feedstock is efficiently supplied to high quality use. With regard to the material cycles of the process chemicals and solvents used, the lignin recovery and processing as well as possible in the pulp production process.

It is known to produce low molecular weight aromatic compounds and especially phenolic compounds from lignin-containing starting materials. Such low molecular weight aromatic compounds and especially phenolic compounds have found wide use as intermediates and valuable products. They serve z. For example, as a precursor for various resins, surface-active compounds, specialty chemicals, etc. However, there is still a need for a simple, inexpensive process that allows the provision of a variety of different aromatics products for various applications. It is advantageous if, in addition to the desired aromatics products recovered more valuable materials and possible in the process for aromatics or a process coupled thereto, for. As a method for pulp production, can be used again.

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

WO 2006/031 175 describes a process for the isolation of lignin from a black liquor, in which they are acidified and dewatered to precipitate the lignin. 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 the vanillin in 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) isolated from the digested material, a cellulose-enriched fraction and at least one cellulose-depleted fraction, wherein the

Cellulose-depleted fraction comprises 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 material, and

d) isolated from the treatment product obtained in step c) the valuable material (s).

In one embodiment of the process, a cellulose-enriched fraction and a fraction enriched in lignin are isolated from the digested material, the lignin-enriched fraction is subjected to depolymerization, and an aromatic compound is isolated from the polymerization product.

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 is extracted from a black liquor of the pulping

Process or even the black liquor itself subjected to a hydroprocessing in the presence of a hydrogen-containing gas and a catalyst on an amorphous or crystalline oxide support. Specifically, a heterogeneous molybdenum sulfide catalyst is used. When using black liquor, the hydroprocessing can also be carried out in two stages. The process can be carried out either at a refinery site to which lignin or black liquor is being transported, or directly at the site of a paper mill. The subsequent to the hydroprocessing biorefinery process is not described in detail.

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 production of BTL (biomass-to- liquid) fuels in biorefineries. In this case, the use of a lignin material obtained from the biomass in a pyrolysis to bio-oil and a further work-up to phenolic resins, synthesis gas, etc. are also shown schematically. 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.

Surprisingly, it has been found that the production of further organic liquid or liquefiable recyclables from the resulting black liquor can be advantageously integrated into the kraft process (sulfate process) for pulp production. In the production of other recyclable materials can also win a waste gas stream, which in turn can be returned to the process for the production of pulp and recycled in this.

The invention relates to an integrated process for the production of pulp and at least one organic liquid or liquefiable recyclable material, in which one provides a lignocellulose-containing starting material and subjected to digestion with an aqueous-alkaline treatment medium from the digested material, a cellulose-enriched fraction and an Cellulose-depleted black liquor which comprises at least part of the treatment medium from step a), c) the black liquor is subjected to a treatment to obtain at least one organic liquid or liquefiable valuable material and at least one exhaust gas stream, d) at least one of the exhaust gas streams obtained in step c) is recycled and utilized in the process for producing pulp. An organic liquid or liquefiable recyclable material is understood as meaning an organic compound or a composition of at least two organic compounds which are liquid under normal conditions (0 ° C., 1013 mbar) or liquefiable without decomposition. Liquefaction refers to the transition from the solid to the liquid state of matter in the sense of melting and not solubilization with the addition of a solvent.

The organic liquid or liquefiable recyclable material is z. B. selected from unfunctionalized and functionalized aliphatic, cycloaliphatic and aromatic hydrocarbons. These include, in particular, alkanes (such as pentane, hexane, etc.), alkenes, alkadienes, alkanols (such as methanol, ethanol, etc.), aliphatic aldehydes (such as acetaldehyde, etc.), cyloalkanes, cycloalkenes, cycloalkadienes, cycloalkanols, cycloalkadienols , Cycloalkanpolyole with more than two OH groups and unfunctionalized and functionalized aromatic hydrocarbons. The organic liquid or liquefiable recyclable material is preferably selected from unfunctionalized and functionalized aromatic hydrocarbons. Functionalized aromatic hydrocarbons preferably have at least one substituent selected from C 1 -C 4 -alkyl, OH, C 1 -C 4 -alkoxy, formyl, C 1 -C 4 -acyl and combinations thereof. The organic liquid or liquefiable recyclable material is in particular selected from benzene, alkylated benzenes (for example toluene and xylenes), higher condensed aromatic hydrocarbons, mono-, di- and polyalkylated higher-condensed aromatics, phenol, mono-, di- and polyalkylated Phenols, more highly condensed aromatics having one, two or more than two OH groups, mono-, di- or higher alkylated, more highly condensed aromatics having one, two or more than two OH groups, alkoxylated derivatives of the aforementioned aromatic alcohols and Mixtures thereof.

In a specific embodiment, the organic liquid or liquefiable valuable material produced according to the invention is an aromatic compound with a high content of mononuclear, low or unalkylated aromatics. An aromatics composition with a high content of mononuclear, low or non-alkylated aromatics is understood to mean a composition which, based on its total weight, contains at least 50% by weight of mononuclear aromatic compounds. The salary of non-alkylated and monoalkylated aromatics, based on their total weight, at least 50 wt .-%.

The organic liquid or liquefiable recyclable material produced according to the invention preferably contains at least 70% by weight, more preferably at least

80 wt .-%, in particular at least 90 wt .-%, based on the total amount of mononuclear aromatic.

In the context of the invention, "black liquor" means a cellulose-depleted fraction from the aqueous-alkaline digestion of a lignocellulose-containing starting material by the kraft process (sulfate process) for producing pulp.

The "black liquor" used in step c) can also be a lignin-containing material in which at least part of the compounds other than lignin is removed from the black liquor isolated in step b) before further treatment in step c) , The fraction obtained from the black liquor by removing at least part of the compounds other than lignin is also referred to below as the "lignin-enriched fraction". Suitable lignin-containing materials for use in step c) are pure lignin and lignin-containing black liquor compositions. In this case, the lignin content is not critical in many areas, only if the lignin content is too low can the process no longer be operated economically. Under "pyrolysis" is in the context of the invention, a thermal treatment of

Black liquor or a lignin-enriched fraction obtained from the black liquor understood, wherein molecular oxygen is not or only in small quantities supplied. A small amount is to be understood as meaning an amount which is significantly less than the amount necessary for a complete oxidation of the carbon contained in the material used for the pyrolysis to CO2. The amount of molecular oxygen fed in the pyrolysis is preferably 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 material used for the pyrolysis contained carbon to CO2 is necessary. Pyrolysis is generally endothermic.

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 among alkyl groups, hydroxy 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, aromatics. tenspaltung. 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.

In the context of the invention, the term "offgas stream" designates gas streams of different composition, such as are obtained in the treatment of the black liquor for the production of the organic liquid or liquefiable recyclable material.

"Normal conditions" are within the scope of the invention 0 ° C and 1013 mbar (according to DIN 1343).

In a first embodiment, the black liquor or a lignin-enriched fraction obtainable from the black liquor is subjected to pyrolysis for the digestion. This usually results in organic components that are not volatile under the pyrolysis. These remain z. B. in the catalyst bed or are located on the inert granular aggregate of a fluidized bed reactor. Combustion of these non-volatile components results in a burn-off gas that is suitable for recirculation as an exhaust gas stream. In this first embodiment, the exhaust gas stream contains at least one of the following components CO2, CO, H2O, O2, SO2 and mixtures thereof.

In a second embodiment, the black liquor or a lignin-enriched fraction obtainable from the black liquor is subjected to pyrolysis to digest. The resulting digestion products are a separation step, such. As condensation or absorption subjected. In this case, under the process conditions gaseous, secured to organic liquid or liquefiable recyclables fraction result, which is suitable for recycling as exhaust gas flow. In an alternative embodiment, a liquid or solid fraction may also result as the effluent stream suitable for recycle to the process of producing pulp, such as an exhaust gas stream. A liquid or solid fraction may be obtained, for example, when the (originally gaseous) digestion products are subjected to an additional separation into at least two fractions in which the substance is subjected to flow in liquid form. siger or solid form. Such a fuel stream then constitutes an exhaust gas stream in the sense of the invention. (All streams which are originally gaseous in the process can be exhaust gas streams in the sense of the invention). In a third embodiment, the black liquor or lignin-enriched fraction obtainable from the black liquor is subjected to digestion to obtain a digestion product which is subsequently separated and subjected to dealkylation. The dealkylation product is subjected to separation whereby at least one organic liquid or liquefiable recyclable material and at least one stream enriched in components which are more volatile than the organic valuable material are obtained. The enriched in lighter than the organic material volatile components stream is suitable as an exhaust gas stream. In this third embodiment, the exhaust gas stream contains H, H2O, CO, CO2, volatile organic components, such as methane, H2S, etc.

In a fourth embodiment, the black liquor or a lignin-enriched fraction obtainable from the black liquor is subjected to digestion, whereby a digestion product is obtained and then the resulting digestive material is subjected to a dealkylation. The dealkylation product is subjected to separation to give a stream E1) enriched in mononuclear, low or unalkylated aromatics and stream E2) enriched in low or non dealkylated aromatics. The enriched in low or non-dealkylated aromatics stream E2) is suitable as an exhaust gas stream. In this embodiment, the exhaust stream contains one or more components selected from mono-, di-, and polyalkylated phenols; Alkoxyphenols, such as methoxyphenols; polyalkylated benzenes; Compounds containing two or more aromatic rings and mixtures thereof. These components are referred to below as "low or non dealkylated aromatics". Stream E2) may be subjected to further separation to yield a fraction enriched in compounds which are substantially non-dealkylatable under the process conditions.

In a fifth embodiment, the exhaust gas stream comprises the composition of synthesis gas. The term synthesis gas is explained below.

In a specific embodiment, the exhaust gas stream contains at least one sulfur compound, in particular H2S. The term "synthesis gas" in the context of the invention refers to a carbon monoxide and hydrogen-containing gas mixture. This gas mixture may additionally contain other gases, such as CO 2, CH 4, etc. Advantageously, the process according to the invention makes it possible to produce synthesis gas with a high content of carbon monoxide and hydrogen.

Digestion after the force process (step a))

According to the invention, a lignocellulose-containing starting material (lignocellulosic material) is provided in step a) of the process and subjected to digestion by the kraft process (sulfate process). The digestion allows at least partial separation of the lignocellulose-containing starting material into cellulose and cellulose impurities. The cellulose impurities include lignin, hemicelluloses, 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. These cellulose accompanying substances are in usually components of the isolated in step b) black liquor.

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.

The usable in step a) lignocellulosic materials are, for. B. from wood and vegetable fibers as starting material is available. 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 coniferous wood, 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 willows, poplars, lime trees 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 In addition to wood waste, sawdust, parquet sanding dust, etc. are also suitable. Suitable lignocellulosic materials continue to be natural fiber materials 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. B. in the harvest of grain (wheat straw, corn straw, etc.), corn, sugar cane (bagasse), etc. Suitable lignocellulosic materials are also available as a residue in forestry, 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.

According to the invention, in step a) a lignocellulose-containing material is subjected to digestion in an aqueous-alkaline treatment medium by the kraft process (sulfate process). It may be advantageous to subject the lignocellulose-containing starting material to at least one pretreatment step before digestion. This includes z. As a mechanical comminution of cellulose-containing starting material, eg. B. by shredding (shredding) and / or grinding. Due to their material properties, fiber-containing materials are preferably not subjected to pressure-shear comminution but to impact crushing. Suitable grinding devices are hammer mills, grinders operating on the principle of jet milling and beater wheel mills. The latter are especially suitable for high throughputs.

It may be advantageous to treat the lignocellulose-containing starting material with mineral acid and / or water vapor prior to digestion with the aqueous-alkaline treatment medium. Suitable mineral acids are, for. As hydrochloric acid and especially sulfuric acid. The treatment with steam is preferably carried out at a temperature in the range of about 1 10 to 300 ° C, particularly preferably 120 to 250 ° C. Treatment of the lignocellulose-containing starting material with mineral acid and / or steam prior to digestion with an aqueous-alkaline treatment medium causes at least partial hydrolysis of the hemicelluloses contained in the lignocellulosic material. In the case of coniferous woods, prehydrolysis usually involves dissolving 10 to 15% by weight of the lignocellulosic material, based on the total weight, in solution. In the case of deciduous trees, 15 to 20% by weight of the lignocellulosic material, based on the total weight, generally dissolve in solution. The digestion in step a) is carried out by the kraft process (sulfate process). The treatment medium used in step a) then contains as main components at least one base and at least one alkali metal sulfide in an aqueous medium. 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 Erdalkalime- tallhydrogencarbonate, z. For example, sodium bicarbonate, potassium bicarbonate, calcium bicarbonate or magnesium bicarbonate, alkali metal and alkaline earth metal carbonates, eg. For example, sodium carbonate, potassium carbonate, calcium carbonate or magnesium carbonate, alkaline earth metal oxides such as calcium oxide or magnesium oxide, and mixtures thereof. Preferred bases are sodium hydroxide, potassium hydroxide and mixtures thereof. Particularly preferred as the base is sodium hydroxide.

Preferably, the treatment medium used in step a) contains NaOH and at least one sulfur-containing compound, preferably Na 2 S and / or NaHS, in an aqueous medium.

In a specific embodiment, the treatment medium used in step a) contains NaOH, Na 2 S and / or NaHS, Na 2 CC "3 and Na ₂ SO ₄ in an aqueous medium.

Preferably, the digestion of the lignocellulose-containing starting material with at least one aqueous-alkaline treatment medium in step a) at a temperature in a range of 50 to 300 ° C., more preferably from 70 to 250 ° C.

In a specific embodiment, the temperature in the course of the digestion in step a) is increased successively or continuously until the desired final temperature is reached. This can z. B. the digestion in a first stage at a temperature in the range of about 50 to 130 ° C and in a second stage in a range of about 130 to 250 ° C. The duration of the first stage is z. B. 5 to 50%, based on the total digestion time. The heating takes place with customary devices, for. B. by heat exchangers, heat baths, gas burners, etc. Also possible is the use of heat obtained in other areas of the process according to the invention, for. B. from the combustion of the resulting in the production of organic liquid or liquefiable recyclable waste gas stream. The pressure during the digestion in step a) is generally in the range from 0.1 bar to 100 bar, preferably 1 bar to 10 bar. In a special version, working at ambient pressure. The duration of the digestion in step a) is generally 0.5 minutes to 7 days, preferably 5 minutes to 96 hours.

The digestion in step a) can take place in one or more stages. In the simplest case, the digestion in step a) takes place in one stage. In a suitable embodiment of a two-stage digestion z. B. a subsequent stage at an elevated temperature and / or an elevated pressure than the previous stage. In a multi-stage digestion, the digested material from only one of the stages or from several stages for further processing in step b) can be used. The condition for this, however, is that the material used for further processing in step b) is a black liquor.

The treatment medium used in step a) is capable of solubilizing at least part of the cellulose impurities of the lignocellulose-containing starting material under the pulping conditions specified below. In particular, at least a partial, preferably substantially complete, solubilization of the ligin contained in the lignocellulose-containing starting material takes place. By this is meant that preferably at least 50% by weight, more preferably at least 75% by weight, based on the total weight of the lignin contained in the lignocellulose-containing starting material, are solubilized. The cellulose contained in the lignocellulose-containing starting material is not or only partially solubilized in the treatment medium. This means that preferably at most 20% by weight, particularly preferably at most 10% by weight, based on the total weight of the cellulose contained in the lignocellulose-containing starting material, are solubilized.

In the context of the invention, the term "solubilization" refers to the conversion into a liquid state and comprises the generation of solutions of the cellulase accompanying substances (especially of lignin-containing solutions) as well as the conversion into a different solubilized state. When a lignocellulosic component is converted to a solubilized state, the individual molecules, e.g. B. polymer molecules, not necessarily completely surrounded by a solvation shell. It is essential that the lignocellulosic component changes to a liquid state as a result of the solubilization. Solubilisates according to the invention are thus also colloidal solutions, microdispersions, gels, etc. Isolation of cellulose and black liquor (step b))

In step b), a cellulose-enriched fraction and a cellulose-depleted black liquor are isolated from the digested material.

Preferably, in step b) the isolation of the cellulose-enriched fraction and the cellulose-depleted fraction (s) is carried out by filtration, centrifugation, extraction, precipitation, distillation, stripping or a combination thereof. The person skilled in the art can control the composition of the cellulose-depleted black liquor via the isolation process. Preferably, in step b), the isolation of the cellulose-enriched fraction and the black liquor by filtration or centrifugation. 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. Altmann, S. Ripperger, J. Membrane Sci. 124 (1997), pages 1 19-128). Usual centrifugation methods are z. See G. Hultsch, H. Wilkesmann, "Filtering Centrifuges," DB Purchas, Solid-Liquid Separation, Upland Press, Croydon 1977, pp. 493-559, and H. Trawinski, The Equivalent Purification Plane 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 methods 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, the removal of at least a portion of the liquid components from the black liquor already takes place in the context of the process for the production of pulp, ie in step b). Thus, for treatment in step c) z. Legs Black liquor are used, which is taken before or during the individual evaporation steps of the underlying pulp process.

The black liquor obtained in step b) contains lignin as one of its essential components. Furthermore, the black liquor isolated in step b) contains at least part of the treatment medium from step a).

In general, the black liquor isolated in step b) contains the following components:

Lignin;

hemicellulose;

optional cellulose;

optionally of lignin, hemicellulose and cellulose various organic components;

- Optional inorganic constituents from the lignocellulose-containing starting material;

at least one inorganic pulping chemical.

The organic components other than lignin, hemicellulose and cellulose are selected, for example, from decomposition products of lignin, hemicellulose and / or cellulose, extractable low molecular weight organic compounds (so-called extract substances, such as terpenes, resins, fats), polymers, such as proteins, nucleic acids and vegetable gums ( so-called exudate). The inorganic constituents from the lignocellulose-containing starting material include silicates.

The inorganic pulping chemicals are selected from those previously mentioned in step a). Specifically, the inorganic digestion chemicals are selected from NaOH, Na ₂ S, Na ₂ CO ₃ and Na ₂ SO ₄ .

The black liquor has, for example, a solids content in the range of about 10 to 70 wt .-%. The black liquor isolated in step b) preferably has a lignin content of from 1 to 50% by weight, particularly preferably from 3 to 30% by weight, based on the solids content of the black liquor. The black liquor isolated in step b) preferably has a sulfur content of from 0 to 20% by weight, particularly preferably from 0.4 to 4% by weight, based on elemental sulfur and the solids content of the black liquor. Production of a valuable substance and an exhaust gas stream from the black liquor (step c))

In many cases, it is uncritical for the recovery of at least one organic liquid or liquefiable recyclable material from the lignin-containing black liquor isolated in step b) if the material used for the further treatment contains at least one further component in addition to lignin.

In a specific embodiment, before the further treatment in step c), at least part of the compounds other than lignin are removed from the black liquor. (The fraction obtained from the black liquor by removing at least part of the compounds other than lignin is also referred to as "lignin-enriched fraction" hereinafter). The components removed from the black liquor are preferably fed to a further work-up and / or thermal utilization, preferably within the scope of the cellulose production process from which the black liquor was obtained. The components which are at least partially removed from the black liquor are preferably selected from organic components and / or inorganic process chemicals.

To remove at least a portion of the compounds other than lignin, the pH of the black liquor may first be adjusted to a suitable value. For this purpose, the black liquor can be added to adjust the pH with an acid or an acid-forming component. Suitable acids and acid-forming components are, for. As CO2, mineral acids such as hydrochloric acid, sulfuric acid and phosphoric acid. Particularly preferred is CO2 (or the resulting carbon dioxide with water). Preferably, CO2 is used from an exhaust gas stream of the production of the liquid or liquefiable organic valuable material or from the integrated pulp process. 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 (for example by means of a washing process, such as a Benfield wash). Because of the process-related nature of CO2 in the pulp process, the use of CO2 to adjust the pH of black liquor is associated with lower costs than the use of other acids and, as a rule, also allows good integration into the pulp process. 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 can 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, a black liquor from the Kraft digestion is first acidified to CO2 to precipitate at least a portion of the lignin contained, then the precipitated lignin is isolated by filtration and the filtrate subjected to a wash 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 the so-called lignoboost process, which is used in the

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

In step c), the black liquor or the lignin-enriched fraction is preferably subjected to treatment for treatment. Preferably, the digested material obtained in the digestion of the black liquor or lignin-enriched fraction is subjected to dealkylation for further treatment.

A specific embodiment is a process in which, in step c): c1), if appropriate, removing from the black liquor at least a portion of the compounds other than lignin to obtain a lignin-enriched fraction, c2) the black liquor or the lignin-enriched product obtained in step c1) Subjecting the fraction to a digestion, optionally separating the digested material obtained in step c2) into at least one aromatics-enriched fraction C1) and at least one aromatics-depleted fraction C2), c4) the digestion product from step c2) or the aromatic-enriched fraction C1) from step c3) into a dealkylation zone and reacting in the presence of hydrogen and / or water vapor, c5) takes a discharge from the dealkylation zone and subjects it to a separation, whereby at least one organic liquid or liquefiable recyclable material and at least one stream enriched in more easily than the organic valuable material is obtained.

information

In the digestion in step c) of the process according to the invention a final product is obtained which contains components whose average molecular weight is significantly below the average molecular weight of the components contained in the lignocellulose-containing starting material.

Preferably, the digestion product obtained in the digestion in step c) (especially in step c2)) 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 c) (especially in step c2)) 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 a reaction in the presence of a liquid digestion medium and leads accordingly to a product of the liquid digestion. 1 . Variant: pyrolysis

In a first variant of the process according to the invention, the black liquor or the lignin-enriched fraction in step c) (especially in step c2)) is subjected to pyrolysis. In this variant of the method according to the invention, the final 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 black liquor or the lignin-enriched fraction can by means of suitable transport facilities, such as. B. screw conveyor or pneumatic conveying, are registered in a pyrolysis zone. For pyrolysis, the black liquor, especially the lignin-enriched fraction, is preferably used in predominantly solid form. Predominantly solid form in the context of the invention means that the substance is known to those skilled in the method for solid support (see, for example, Perry's chemical engineers' handbook, published by Robert H. Perry, Don W. Green, Issue 8, published by McGraw-Hill, 2008) is accessible. For pyrolysis, the black liquor, especially the lignin-enriched fraction, 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 fluidized bed, a fluidizing gas (preferably water vapor, carbon dioxide, nitrogen or a gas mixture from one of the subsequent process steps) and a granular additive inert under the given conditions are also 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.

In a first preferred embodiment, the pyrolysis is not carried out with the addition of hydrogen. In this embodiment, the hydrogenating reaction essentially takes place in the dealkylation step (especially in step c4)).

In a second preferred embodiment, the pyrolysis is carried out with the addition of hydrogen. This embodiment of the pyrolysis can also be referred to as hydrocracking. In hydrocracking, the lignin content of the black liquor or of the lignin-enriched fraction is completely or partially split into low-molecular fractions by the action of hydrogen. 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 H. L. 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 in front. 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. The pyrolysis in step c) (especially in step c2)) can, if desired, be carried out in the presence of at least one pyrolysis catalyst. As pyrolysis z. Silicic acid, 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. In WO 96/09350 (Midwest Research Institute, 1996) or US 4,409,416 (Hydrocarbon Research Institute, 1983), to which reference is hereby made.

In the pyrolysis zone, the black liquor or the lignin-enriched fraction is converted to a pyrolysis product which is at least partly gaseous ("pyrolysis gas") under the conditions of pyrolysis. Furthermore, during the pyrolysis, a pyrolysis product may result that is partially liquid and / or solid under the conditions of pyrolysis.

The composition of the pyrolysis product may vary depending on the black liquor or the lignin-enriched fraction.

In any case, the digestion product obtained during pyrolysis in step c) (especially in step c2) contains substituted aromatics and / or polynuclear aromatics. The digestion product may contain, in addition to aromatics, other components which are selected from water vapor, inert gas (eg., Nitrogen), non-aromatic hydrocarbons, H2, CO, CO2, sulfur-containing compounds, such as. B. H2S, SO2, 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 below (especially in step c3)). According to the invention, an exhaust gas stream is obtained in step c) of the process, which is subsequently recycled (in step d)) into the process for the production of pulp and utilized therein. If step c) comprises pyrolysis, organic components generally result which can not be vaporized under the pyrolysis conditions. These remain z. B. in the catalyst bed or are located on the inert granular aggregate of a fluidized bed reactor. Combustion of these non-volatile components results in a burn-off gas that is suitable for recirculation as an exhaust gas stream. In this embodiment, the exhaust gas stream contains at least one of the following components CO2, CO, H2O, O2, SO2 and mixtures thereof.

In order to obtain the exhaust gas stream, a discharge from the pyrolysis zone containing non-volatile or low-volatile components may be brought into contact with an oxygen-containing gas at elevated temperatures after separation from the pyrolysis gas in a suitable device (eg cyclone).

Alternatively, to recover the exhaust stream, pyrolysis of the black liquor or lignin enriched fraction may be discontinued and the pyrolysis zone itself contacted with an oxygen-containing gas at elevated temperatures to remove non-volatile or low-volatility components.

Preferably, air is used as the oxygen-containing gas. The temperature for obtaining the exhaust gas stream is preferably in the range from 400 to 2000 ° C., particularly preferably from 600 to 1500 ° C., in particular from 700 to 1300 ° C. Upon burning off the nonvolatile or poorly volatile components produced during the pyrolysis, the offgas stream is obtained. The burning off can take place in the pyrolysis zone itself or in a separate combustion zone. If the process according to the invention is operated with at least one fixed bed as pyrolysis zone, the burnup is preferably carried out in a separate burnup zone. By means of a suitable separation device or in the pyrolysis zone itself (embodiment eg as fluidized bed), the aggregate is then separated from the resulting effluent and returned to the pyrolysis zone by a suitable conveying device. However, the burnup can also take place at intervals, with a burnup interval in each case following a pyrolysis interval. In the combustion interval, low-volatility components are removed from the fixed bed and the exhaust gas flow is thereby obtained.

2nd variant: digestion in the liquid phase

In a second variant of the process according to the invention, the black liquor or the lignin-enriched fraction in step c) (especially in step c2)) is subjected to digestion in the presence of a liquid digestion medium. In this variant, the digestion product falls at least partially in the liquid phase.

The digestion in the liquid phase is in principle possible by a variety of methods, which differ mainly in terms of the digestion medium. The black liquor or the lignin-enriched fraction is preferably subjected to digestion in the presence of an aqueous-alkaline digestion medium. Specifically, it is the digestion medium from step a) of the process according to the invention. The corresponding statements under step a) are hereby fully incorporated by reference.

Preferably, the digestion in the liquid phase in step c) (especially in step c2)) 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 special embodiment, the temperature is initially increased successively or continuously during the course of the treatment until the desired final temperature is reached.

The liquid phase digestion in step c) (especially in step c2)) may be at reduced pressure, at ambient pressure or above 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 c) (especially in step c2)) is generally 0.5 minutes to 7 days, preferably 5 minutes to 96 hours. Preferably, the digestion is carried out in close proximity to the site 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 c) (especially in step c2)) contains substituted aromatics and / or polynuclear aromatics. The separation and further treatment of the digestion product obtained in the presence of a liquid digestion medium in step c) (especially in step c2)) will be described in more detail below (especially in step c3)).

In the case of digestion by pyrolysis, it is possible to use the decomposition product obtained in the digestion of the black liquor or a lignin-enriched fraction without further separation and / or treatment for a dealkylation. Specifically, the digestion product obtained in step c2) can be used without further separation and / or treatment for dealkylation in step c4). In another embodiment of the process according to the invention, the digestion product obtained by digesting the black liquor or a lignin-enriched fraction is subjected to a dealkylation of a separation and / or treatment before it is used. Specifically, the digestion product obtained in step c2) is subjected to separation and / or treatment in step c3) before it is used in the dealkylation in step c4).

Separation / treatment of the digestion product (step c3))

Preferably, in step c3) the digested material obtained in step c2) is separated into at least one aromatic-enriched fraction C1) and at least one aromatic-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 event that the digestion in step c2) takes place in the liquid phase, the separation in step c3) is preferably carried out by means of distillation and / or extraction. In a first specific embodiment of the process according to the invention, the black liquor or a lignin-enriched fraction thereof is subjected to liquid phase digestion in step c2) and comprises, in step c3), separation into at least one aromatics enriched fraction C1) and at least one aromatics-depleted fraction C2) an extraction and / or distillation.

Preferably, prior to the separation in step c3), the pH of the discharge from a liquid phase digestion in step c2) is adjusted to a desired value. According to the invention, a digestion product which has been obtained by digestion in the presence of an alkaline digestion medium from the kraft process is used in step c3). 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 the pulp process coupled with 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 use of CO2 to adjust the pH is thus 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 c2) 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 c2) from the digestion in the liquid phase can be carried out by customary methods known to the person skilled in the art, an aromatics-enriched distillate being obtained. In this procedure, one uses the water vapor volatility (heteroazeotropy) of the aromatic fragments obtained in the digestion in step c2) 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 evaporation in another stage. The distillation product obtained is enriched in aromatics with respect to the digestion product used and is suitable, if appropriate after removal of the aqueous phase, as feedstock for the dealkylation in step c4). The separation of the product obtained in step c2) 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 c2) is separated, while the remaining residue (low-aromatic organic components, inorganic process chemicals, etc.) further processing and / or thermal utilization, preferably in the context of the inventive method or a coupled integrated process to the pulp process can be supplied.

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 c2), 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. Preferably, the extractant has a boiling point under normal conditions that is at least 10 K below the boiling point under normal conditions of that aromatic component which boils lowest of the components formed to any appreciable extent in step c2).

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, with the residue separated from the extraction agent phase in each case being brought into contact with a fresh portion of extraction agent and / or the extractant being passed in countercurrent. For discontinuous implementation brings under mechanical movement, for. By stirring, the digestion product and the extractant in a suitable vessel, the mixture is allowed to rest for phase separation and one of the phases is removed 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 to suitable apparatus in an analogous manner 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 c3) comprises the following substeps: c31) extraction of the digestion product obtained in step c2) to obtain an aromatic c32) optionally separating the extract into an extractant-enriched (and aromatics-depleted) fraction and an aromatic-enriched (and depleted-in) fraction, c33) feeding the feedstock obtained in step c31) to the resulting extract and aromatics; obtained in aromatics enriched extract or obtained in step c32), aromatic-enriched fraction in step c4).

Before the extraction, the pH of the digestion product obtained in step c2) can be adjusted by adding at least one acid or at least one base. The pH is then preferably adjusted to a value of not more than 9, particularly preferably not more than 8, before the separation of the digestion product by the addition of acid. 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 (raffinate) 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. Preferably, CO2 is used from a fuel stream of the process according to the invention or the pulp process coupled with the process according to the invention. Suitable is z. As the fuel from a black liquor combustion (recovery boiler) or a lime kiln. In this case, the waste can be introduced into the digestion product either directly or after separation from the other components (for example by means of a washing process, such as a Benfield wash). 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.

The separation of the extract in step c32) 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 c32) can be carried out by customary methods known to the person skilled in the art. Suitable processes are described in: K. Sattler, Thermal Separation Methods, Wiley-VCH, Third Essentially Revised and Extended Edition, July 2001. Suitable distillative separation equipment 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 a second specific embodiment of the process according to the invention, the black liquor or a lignin-enriched fraction thereof is subjected to pyrolysis in step c2) and comprises the separation in step c3) into at least one aromatics-enriched fraction C1) and at least one aromatic-depleted fraction C2) Absorption.

The discharged from the pyrolysis discharge can in addition to the pyrolysis gases may 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 pyrolysis in step c2), the discharge from the pyrolysis zone may also contain fractions of the aggregate. These solid and / or liquid components may, if desired, in step c3) by means of a suitable device, for. As a cyclone, are separated from the pyrolysis gas. Separate solid additives are preferably recycled to the pyrolysis zone. From aggregates different separated components are recycled. This includes, as described above, z. B. combustion to obtain a process according to the invention in the pulp recirculated exhaust gas stream. It is also possible, a discharge from the pyrolysis zone, which contains at least one additive and under the pyrolysis low-volatile components in a spatially separated from the pyrolysis zone Ab- fire zone with an oxygen-containing gas, preferably air, bringing into contact, resulting in the burning of resulting in the pyrolysis low volatility components ("coke"). By a suitable separator, the aggregate is then separated from the resulting fuel gas and passed through a suitable conveyor in the pyrolysis zone. The fuel gas is at least partially recycled as exhaust gas flow in the pulp process.

If desired, condensable pyrolysis products (i.e., products which are present under normal conditions as liquids or solids) are separated from the effluent from the pyrolysis (optionally after separation of solids and / or liquids). This can be accomplished by means of suitable separation processes known to those skilled in the art, such as condensation, absorption, adsorption, membrane separation processes, etc. A preferred variant is an absorption, wherein the discharge from the pyrolysis, preferably after a cooling step in which a condensation of high-boiling components can take place, in a suitable apparatus (eg column) with a stream D1), which is a suitable solvent contains, is brought into contact. The contact apparatus emanates a liquid stream D2) which contains the absorbent and aromatic pyrolysis products and a gaseous stream D3), which is depleted compared to the discharge from the pyrolysis of aromatic pyrolysis products. Stream D2) is, preferably by distillation, fractionated into a fraction D4) enriched in aromatic pyrolysis products relative to D2) and a fraction D5 depleted in aromatic pyrolysis products relative to D2). D4), if necessary after further work-up, as stream C1) in the subsequent Dealkylierungsschritt and D5), after further cooling, led back into the absorption, d. H. D5) is the main component of D1). Another ingredient 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. 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. Particularly preferably, the solvent tel a boiling point, which is at least 10 K below the boiling point of the phenol under identical conditions. 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 gas stream D3 leaving the absorption 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 D3) leaving the absorption is then subjected to at least partial removal of the solvent contained. Preferably, the separation of the solvent from the gas stream D3) takes place in the form of a water wash. Here, a good water solubility of the solvent used for absorption is particularly advantageous. The washed 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 c2) can be subjected to at least one further treatment step in step c3) 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 c2) or the fraction C1) isolated therefrom in step c3) 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 c3) is used at least partially to recover the exhaust gas stream.

In a specific embodiment of the process according to the invention, the aromatics-depleted fraction C2) isolated in step c3) is used at least partly for the production of synthesis gas.

Dealkylation (step c4)) In the dealkylation, the aromatic decomposition products formed during the pyrolysis in step c2) and optionally isolated in step c3) as fraction C1) are at least partially converted by the action of hydrogen and / or water vapor so that substituents are replaced by hydrogen and / or several aromatic hydrocarbons Cores containing nuclei are cleaved to compounds with fewer nuclei. Thus, as previously stated, "dealkylation" also refers to reactions in which no alkyl substituent is replaced by hydrogen, such as dehydroxylation, dealkoxylation, aromatic cleavage, etc. The hydrogen-substituted substituents are preferably selected from alkyl groups, hydroxy groups, and alkoxy groups.

Dealkylation processes suitable for use in step c4) include hydrodekylation, vapor dealkylation or mixtures thereof. In the case of a pure hydrodealkylation according to the invention, molecular hydrogen is fed into the dealkylation zone in addition to the pyrolysis gas stream, but no water. In the case of a pure steam dealkylation according to the invention, water is fed into the dealkylation zone in addition to the pyrolysis gas stream, but no molecular hydrogen. The dealkylation process in step c4) 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. The person skilled in the art is able with this information to design suitable and preferred process parameters for a mixed form of hydrodealkylation and

Determine 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 from about 40:60 to 60:40. The hydrogen required for the reaction is formed in the case of Dampfdealkylierung in situ by reaction of water with (mainly organic) components, either in the educt mixture of Dampfdealkylierung are included or arise in the course of Dampfdealkylierung. 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, particularly preferably from 1 to 20 bar, in particular from 1 to 10 bar.

In a first preferred embodiment, the pyrolysis gas stream is subjected to a hydrodealkylation in step c4). For this purpose, the reaction in step c4) takes place in the presence of hydrogen.

The temperature in the dealkylation zone for the hydrodealkylation is preferably in the range from 500 to 900 ° C., particularly preferably from 600 to 800 ° C.

The absolute pressure in the dealkylation zone for the hydrodealkylation is preferably in a range from 1 to 100 bar, particularly preferably from 1 to 20 bar.

For the hydrodealkylation, the feed ratio of H 2 to H 2 (stoichiometric) is preferably in a range from 0.02 to 50, more 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. For the hydrodealkylation, the residence time in the dealkylation zone is preferably in the range from 0.1 to 500 s, more preferably from 0.5 to 200 s.

In a second preferred embodiment, the pyrolysis gas stream is subjected to steam dealkylation in step c4). For this purpose, the reaction takes place in step c4) in the presence of steam.

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. Preferably, for vapor dealkylation, the molar ratio of H to ChU in the dealkylation zone is in a range of <50: 1, more 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 dealkylation zone 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.

For the steam dealkylation, WHSV is preferably in a range from 0.05 to 10 kg / (L ^* h), particularly 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. The

US Pat. No. 3,775,504 describes that steam dealkylation actually consists of a combination of steam dealkylation and hydrodealkylation, since at least part of the hydrogen produced is inherently reacted again at the same time. In the dealkylation step c4), at least one low molecular weight aromatic valuable substance is formed as the target product of the process according to the invention. The low molecular weight aromatic valuable substances are preferably selected from benzene and phenolic compounds, such as phenol and / or dihydroxybenzenes. In particular, they have lower proportions of the following components than the pyrolysis effluent before being fed into the dealkylation step c4): 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 (step c5))

The dealkylation zone is removed from a discharge and subjected to separation. In this case, at least one organic liquid or liquefiable recyclable material is obtained as the first desired product and at least one stream, which is enriched in components which are more volatile than the organic valuable material, is obtained as second valuable product. It is preferred to obtain, as the first desired product, an aromatic compound with a high content of mononuclear, low or non-alkylated aromatics.

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

E1) a stream enriched in mononuclear, slightly or non-alkylated aromatics,

E2) an enriched in low or non dealkylated aromatics stream,

E3) enriched in lighter than E1) and E2) volatile 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. Stream E1) is the first value product produced in the process according to the invention. E1) is preferably an aromatics composition with a high content of mononuclear, low or unalkylated aromatics. In addition, stream E1) can be subjected to a further workup to obtain the aroma composition prepared according to the invention.

The stream E1) contains, based on the total amount of E1), preferably at least 70 wt .-%, particularly preferably at least 80 wt .-%, in particular at least 90 wt .-%, of mononuclear aromatic.

The stream E1), based on the total amount of E1), preferably at most 30 wt .-%, particularly preferably at most 20 wt .-%, in particular at most 10 wt .-%, of low or non dealkylated aromatics. As mentioned above, in the context of the invention "dealkylation" also refers to the replacement of substituents other than alkyl groups (such as alkoxy groups, aryloxy groups, hydroxy groups, etc.) by hydrogen. Depending on the composition of the aromatics used for dealkylation, stream E1) then also has a high content of aromatics in which a substituent other than alkyl groups has been replaced by hydrogen. Specifically, stream E1) has a high content of low alkoxylated or non-alkoxylated aromatics.

The stream E2), based on the total amount of E2), preferably at least 70 wt .-%, more preferably at least 80 wt .-%, in particular at least 90 wt .-%, of low or non-dealkylated aromatics.

Stream E2) may be subjected to further separation to yield a fraction enriched in compounds which are substantially non-dealkylatable under the process conditions. Preferably, then, this fraction enriched in dealkylation-resistant compounds is recirculated as waste gas stream into the pulp process.

The stream E3) contains components that z. B. are selected from non-aromatic see hydrocarbons, especially methane, hydrogen, carbon monoxide, carbon dioxide and mixtures thereof. In addition, the stream E3) usually contains sulfur-containing by-products from the kraft process. This includes especially F S.

Preferably, the stream E3) is at least partially recycled as waste gas stream in the pulp process. In a specific embodiment, the stream E3) is used at least partially for the production of synthesis gas. The synthesis gas obtained in this way or a hydrogen-rich gas stream produced therefrom can, for its part, be recycled at least partially as an offgas stream into the pulp process. 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 c5) preferably comprises an absorption. In the absorption, the gaseous discharge from the dealkylation zone is brought into contact 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, laden: absorbate) is preferably used for absorption, in which the aromatics obtained in the dealkylation are soluble in a sufficient amount and the volatile by-products other than these are substantially 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 absorbate laden with aromatics. The aromatic components contained in the absorbate correspond in their composition to the sum of the aromatics in the streams E1) and E2) plus any aromatics optionally present in the absorption medium. The components contained in the remaining gas stream correspond in their composition to the stream E3). If desired, the gas stream may be subjected to an additional 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 c5) comprises the following substeps: c51) contacting the discharge from the dealkylation zone with an absorbent to obtain an aromatics-enriched absorbate and an aromatics-depleted gas stream E3), c52 ) Separation of the absorbate into a stream E1) enriched in mononuclear, slightly or non-alkylated aromatics, stream E2) enriched in slightly or non-dealkylated aromatics and optionally in a stream containing the absorbent, c53) if present, recycle of the absorbent containing Stream into step c51), c54) optionally recycling at least a portion of the stream E2) into the dealkylation zone of step c4).

Preferably, the absorbent has a boiling point which is above the components of the stream E1. If the dealkylation is operated in such a way that predominantly benzene is formed, the boiling point at atmospheric pressure of the absorption medium is preferably at least 85 ° C .; if the dealkylation is operated so that at least partially phenol is formed, the boiling point at normal pressure of the absorbent is preferably at least 187 ° C.

In a first suitable embodiment, an absorbent is used, which is different from the components of the streams E1) and E2). Preferably, the absorbent has a boiling point which is above the components of stream D1. Further preferably, the absorbent has a high dissolving power for the aromatics formed in the dealkylation step. Suitable solvents are, for. As aliphatic, cycloaliphatic and aromatic hydrocarbons, aliphatic, cycloaliphatic and aromatic alcohols, amides such as N-methylpyrrolidone or dimethylformamide. Aliphatic, cycloaliphatic and aromatic hydrocarbons preferably have a carbon atom number of at least 6. Aliphatic, cycloaliphatic and aromatic alcohols preferably have a carbon atom number of at least 4.

If an absorbent is used which is different from the components of the streams E1) and E2), the separation of the discharge from the dealkylation zone in step c5) preferably comprises the following substeps: c51) contacting the discharge from the dealkylation zone with an absorbent to obtain an aromatics-enriched absorbate and an aromatics-depleted gas stream (or a gas stream E3 enriched in by-products which are more volatile than E1 and E2), c52) separating the absorbate into a stream E1 enriched in mononuclear, low or non-alkylated aromatics ), a stream E2) enriched in slightly or non-dealkylated aromatics and a stream containing the absorbent, c53) recycling the stream containing the absorbent into step e1), c54) optionally recycling at least a portion of the stream E2) into the dealkylation zone of step c4).

In a particularly preferred variant, the absorbent used is an aromatic compound which can be obtained 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 particularly preferred variant, the absorbent used is an aromatic composition whose composition largely corresponds to the stream E2 or a mixture of E1 and E2.

If an absorbent is used whose composition largely or completely corresponds to stream E2 or a mixture of E1 and E2, the separation of the discharge from the dealkylation zone in step c5) preferably comprises the following substeps: c51) contacting the discharge from the dealkylation zone c52) separating the absorbate into a stream E1) enriched in mononuclear, slightly or non-alkylated aromatics, and stream E2 enriched in slightly or non-dealkylated aromatics) with an absorbent to obtain an aromatics-enriched absorbate and an aromatics-depleted gas stream E3) , c54) optionally recycling at least a portion of the stream E2) into the dealkylation zone of step c4).

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 see between said partial condensation and the absorption to switch another partial condensation, in particular water is condensed out. In this variant as well, together with the absorption of desired product, at least partial absorption of the aromatics which are not reacted or not fully converted takes place. Ie. In this variant too, the aromatic components contained in the absorbate correspond in composition to the sum of the aromatics of the streams E1) and E2).

In step c52), 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 c51)). The aromatics are processed further as before and described below.

Preferably, in step c52), the aromatics-enriched absorbate is 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 separation by distillation in step c52), 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 top product obtained in the distillation in step c52) contains the target product of the process according to the invention. It can either be withdrawn directly as stream E1) or subjected to further work-up. Water contained in the overhead product can be separated off by known processes. For this purpose, the overhead product, after condensation of the vapors from the distillation, can be fed to a phase separator for the removal of water. The resulting water is discharged as another stream from the process. The organic phase from the phase separator can either be at least partially withdrawn as stream E1) 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 work-up. This is preferably used for the removal of water still contained and / or undesirable organic components.

The bottom product obtained in the distillation in step c52) contains the aromatics which are not or not sufficiently converted during dealkylation, ie it is enriched in aromatics which are sparingly or not dealkylated. It can either be withdrawn directly as stream E2) or subjected to further work-up. The bottom product obtained in the distillation in step c52) is preferably divided into at least two partial streams. Preferably, a first substream in step e) of the sorptiven separation of the discharge from the Dealkylierungszone is returned as an absorbent. For this purpose, this partial stream, if necessary, cooled to a suitable temperature. A second partial stream is withdrawn as stream E2). The current E2) may be subjected to separation of constituents other than stream D2) prior to recycling to the dealkylation zone of step c4). This is z. B. advantageous if an absorption solvent is used which is not obtained as an intermediate of the process according to the invention. It is also advantageous at this point of stream E2) deduct a purge stream and z. B. in a combustion device to reduce the accumulation of under the conditions of dealkylation not or slowly reacting components.

The stream E2) is preferably subjected to evaporation before it is fed into the dealkylation. A preferred variant is shown in FIG. 2 and explained in the associated description of the figures.

Synthesis gas production In the process according to the invention, synthesis gas can be produced as another desired product. In a specific embodiment of the process according to the invention, the fraction C2) isolated in step c) (especially in step c3)) is used at least partly for the production of synthesis gas. It is also possible to use an offgas stream from the digestion (especially from step c2)) and / or dealkylation (especially from step c4)) in synthesis gas 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 F / 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, article "Gas Production", DOI: 10.1002 / 14356007.a12_169.pub2.

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 fully or partially used in at least one process comprising hydrogen, CO or Mixtures of both consumed used. These include z. As a hydrogenation, hydroformylation, carbonylation, methanol synthesis, synthesis of hydrocarbons according to Fischer-Tropsch, etc. In a preferred embodiment of the method according to the invention generated in the process synthesis gas-containing stream or produced from the synthesis gas, hydrogen-enriched stream in the digestion (especially in step c2) and / or in the dealkylation (especially in step c4)) fed. An enrichment of the synthesis gas to hydrogen, 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 to the dealkylation in step c4). The particular advantage of this variant is that the proportion of phenol (s) in the products of the dealkylation is higher than in the case of the pure

Steam dealkylation, d. H. without hydrogen supply. This advantage results overall in dealkylation in the presence of hydrogen. The higher phenol formation represents an economic advantage, since phenol is a higher value material than oxygen-free aromatics, such as benzene. In addition, hydrogen, which is not produced in the process according to the invention, is more costly and in many cases not available or only at great expense, especially if the dealkylation is to be carried out away from a chemical composite site.

Recycling and utilization of the exhaust gas flow (step d))

The aim of the pulp process is the complete recovery of the process chemicals and the fullest possible thermal utilization of the non-recoverable in the production of other organic recyclables organic components. In pulp production, the combustion of the black liquor serves to generate electricity and process heat, which cover a considerable part of the energy demand in pulp and paper production.

The invention provides an advantageous integrated method in which exhaust gas streams obtained during the production of organic valuable materials are guided into a device of the pulp process and utilized therein. This is preferably a thermal utilization in the context of combustion. For this purpose, at least one exhaust gas stream is preferably conducted into the waste liquor combustion (recovery boiler). In this case, preferably the recovery of the organic liquid or liquefiable recyclable material in local proximity to the location of pulp production. Before- zugt find the recovery of the organic liquid or liquefiable recyclable material and the pulp process at a distance of at most 10 km, more preferably at most 5 km, in particular at most 1 km instead. Thus, the cost of transporting the exhaust gas stream (preferably via a pipeline) is kept low. This embodiment has the advantage that no additional facilities for the treatment or utilization of the exhaust gases are needed, namely for the combustion (applies especially for lighter than the organic valuable volatile components from the Dealkylie- tion and the synthesis gas), the steam or Electricity generation and flue gas desulphurisation. The latter is particularly significant because the Kraft lignin contains up to 5 percent sulfur, based on the solids content, which, chemically bound, is produced in the exhaust gas streams.

DESCRIPTION OF THE FIGURES A preferred embodiment of the treatment of the black liquor by the process according to the invention is shown in FIG.

A black liquor starting material (1), especially a lignin-enriched fraction from the black liquor (1), is subjected to digestion.

An accumulating exhaust gas stream (2) is optionally supplied to the pulp process, preferably the recovery boiler.

The digestion product (3) is optionally subjected to separation and / or treatment, whereby an aromatics-enriched stream (6) and a stream (4) enriched in aromatics are obtained. Optionally, the aromatics-depleted stream (4) is at least partially recycled as waste gas stream (5) in the pulp process. Furthermore, the stream (4) can be at least partially fed to a reforming / conversion for synthesis gas production.

The digestion product (3) or the aromatics-enriched stream (6) obtained therefrom is fed into a dealkylation unit together with a stream of hydrogenating gas (7). The discharge from the dealkylation zone (8) is subjected to separation into the following 3 streams:

- value product (stream (9)), a substance or mixture of substances which has arisen through the above-mentioned dealings,

not or incompletely dealkylated product (stream (10)), this contains substances that have not been dealkylated or to a lesser extent than the desired product; Electricity (1 1) containing volatile by-products. These are selected from methane and other hydrocarbons, H2O, CO, CO2 and sulfur-containing by-products, especially H2S. Optionally, a water stream (water) is separated off and discharged during the separation.

Stream (9) is withdrawn, optionally after further work-up, as a product stream.

The enriched in only slightly or non-dealkylated aromatics stream (10) is returned via an evaporation of the dealkylation. A preferred embodiment of the evaporation is depicted in FIG. 2 and described below. Alternatively, the stream (10) can be at least partially recycled as waste gas in the pulp process. For this purpose, the stream (10) can be subjected to a further separation, whereby a fraction is obtained which is enriched in compounds which can not be substantially dealkylated (not shown).

The stream (11) containing the volatile by-products from the separation is at least partially recycled as an offgas stream into the pulp process. Preferably, the stream (1 1) is fed to a combustion in the context of the pulp process. This includes in particular the waste liquor combustion (recovery boiler). This design has the advantage that no additional apparatus for steam or electricity generation or flue gas desulfurization are needed. In another variant, the combustion is desulfurized, eg. B. in the form of a hydrogen sulfide removing gas scrubber, followed by a conversion of the H 2 S in elemental sulfur (eg Claus process) upstream.

Alternatively, the stream (11) or a partial stream (12) diverted therefrom can be fed to reforming / conversion for the production of synthesis gas. In this case, optionally with the introduction of a stream containing water or oxygen (optional stream (13)), the organic components contained in stream (11) are converted to a synthesis gas (14) containing CO and H2. When the dealkylation is a hydrodealkylation, a hydrogen-containing stream (15) obtained from synthesis gas production can be passed into the dealkylation. If hydrogen is used for the digestion, a hydrogen-containing stream (16) obtained from synthesis gas production can be passed into the digestion.

It is also possible to recycle otherwise unneeded syngas as the exhaust stream into the pulp process.

Figure 2 shows the evaporation of an aromatics-containing stream, as z. B. in the absorptive and distillative separation of the discharge from the Dealkylierungszone as stream E2) (in Figure 1 with (10)) is obtained. Stream (10) is preferably subjected to evaporation prior to recycling to the dealkylation, as shown in FIG.

The Aromatenstrom (10) is preheated in apparatus A to a temperature at which no significant decomposition takes place in the liquid phase. This preheated stream (stream 100) is combined in an apparatus B with a gaseous stream 200 whose amount, temperature and composition are chosen so that the stream 100 is partially or completely evaporated. Stream 200 contains dealkylation reactants, i. H. in the case of steam dealkylation, water vapor and in the case of hydrodealkylation a hydrogen-containing gas (stream (5) in FIG. 1). The amounts of streams 100 and 200 are adjusted so that stream 300 leaving in apparatus B gives a composition favorable for the type of dealkylation chosen.

Apparatus B is a liquid-gas contact apparatus known in the art. Apparatus B can, for. Example, be carried out as a container with jet nozzle or column, wherein stream 100 is supplied from above, liquid and gas are passed in cocurrent or countercurrent, in the lower part may optionally a low-volatile residue (stream 250) are deducted. Alternatively, apparatus B can also be designed as a fluidized bed. Via the externally heated fluidized material, additional energy can be efficiently entered into the stream 100.

In a preferred variant, stream 300 is split into streams 400 and 500, with dealkylation (D) stream 400 and stream 500 being recycled via a heat exchanger C in apparatus B. This variant allows limiting the temperatures of the streams 100, 200 and 500 (after heat exchangers) to limit values that result from the availability of the heat sources, the thermal stability of the materials and the stability of the materials. The naturally occurring pressure loss along the streams 300, 400 and 500 can be compensated for by a suitable device for compression. For this purpose, well-known compressor or fans can be used, but it is also possible to perform the apparatus B completely or partially as a liquid jet fan, wherein stream 100 is used as the driving medium. In this case, if the amount of stream 100 is not sufficient for the required compaction performance, liquid can be circulated via apparatus B in the circuit.

Claims

claims

1 . Integrated process for the production of pulp and at least one organic liquid or liquefiable recyclable material in which a) a lignocellulose-containing starting material is prepared and subjected to digestion with an aqueous-alkaline treatment medium, from the digested material a cellulose-enriched fraction and one to cellulose isolated black liquor, the black liquor is subjected to a treatment to obtain at least one organic liquid or liquefiable recyclable material and at least one exhaust gas stream, at least one of the exhaust gas streams from step c) in the process for the production of pulp recycled and recycled.

The method of claim 1, wherein the treatment medium used in step a) contains NaOH and at least one sulfur-containing compound, preferably Na 2 S and / or NaHS, in an aqueous medium.

Process according to one of the preceding claims, wherein in step b) the isolation of the cellulose-enriched fraction and the cellulose-laden black liquor is carried out by filtration, centrifuging, extraction, precipitation, distillation, stripping or a combination thereof.

Method according to one of the preceding claims, wherein in step b) from the digested material, a black liquor is isolated, which contains at least one component which is selected from

Lignin;

hemicellulose;

optional cellulose;

optional of lignin, hemicellulose and cellulose various organic components;

optional inorganic constituents from the lignocellulose-containing starting material;

inorganic digestion chemicals;

and mixtures thereof.

5. The method according to any one of the preceding claims, wherein from the

Black liquor in step c) first removes at least a portion of the compounds other than lignin, whereby a lignin-enriched fraction is obtained.

6. The method according to any one of the preceding claims, wherein subjecting the black liquor or a lignin-enriched fraction obtained therefrom for treatment in step c) a digestion and optionally the resulting digested material of a dealkylation.

A process according to claim 6, wherein the black liquor or the lignin-enriched fraction obtained therefrom is subjected to the digestion of a pyrolysis, and the non-vaporizable components obtained under the pyrolysis conditions are used to obtain the exhaust gas stream.

Method according to one of claims 6 or 7, wherein the black liquor or the lignin-enriched fraction obtained therefrom is subjected to the pyrolysis for digestion and the resulting digestion product is subjected to a separation, resulting in an organic liquid or liquefiable recyclables depleted fraction which at least partially as an exhaust gas stream is used.

A process according to any one of claims 6 to 8, wherein the black liquor or a lignin-enriched fraction obtained therefrom, for treatment in step c) is subjected to digestion and the resulting digested material is dealkylated, the dealkylation zone is discharged and subjected to separation, at least one organic liquid or liquefiable recyclable material and at least one enriched in lighter than the organic material volatile components stream is obtained and this stream is at least partially used as an exhaust gas stream.

Method according to one of the preceding claims, wherein a synthesis gas produced in the process is at least partially used as an exhaust gas stream.

1 1. Method according to one of the preceding claims, wherein in step c): d) if appropriate, removing from the black liquor at least a portion of the compounds other than lignin, a lignin-enriched fraction being obtained, c2) subjecting the black liquor or the lignin-enriched fraction obtained in step c1) to digestion, c3) if appropriate, the fraction obtained in step c2), digested material in at least one aromatics enriched fraction C1) and at least one aromatics depleted fraction C2), c4) the digestion product from step c2) or the aromatic-enriched fraction C1) from step c3) in a Dealkylierungszone feeds and in the presence of C5) removes the discharge from the dealkylation zone and subjects it to a separation, whereby at least one organic liquid or liquefiable valuable material and at least one stream enriched in components which are more volatile than the organic valuable substance are obtained.

The method of claim 1 1, wherein the digestion of the black liquor or a lignin-enriched fraction thereof in step c2) comprises pyrolysis.

13. The method of claim 12, wherein in step c3) the separation into at least one aromatics enriched fraction C1) and at least one aromatics depleted fraction C2) comprises an absorption.

14. The method of claim 1 1, wherein in step c2) the black liquor or a lignin-enriched fraction thereof is subjected to a digestion in the liquid phase.

15. The method of claim 14, wherein in step c3) the separation into at least one aromatics enriched fraction C1) and at least one aromatics depleted fraction C2) comprises an extraction and / or a distillation.

16. The method of claim 15, wherein the separation into at least one aromatic-enriched fraction C1) and at least one aromatic-depleted fraction C2) in step c3) comprises the following substeps: c31) extraction of the digestion product obtained in step c2) to obtain an aromatics-enriched extract and an aromatic-depleted residue, c32) optionally separating the extract into an extractant-enriched and aromatics-depleted fraction and an aromatics-enriched and extractant depleted fraction, c33) feeding the aromatic-enriched extract obtained in step c31) or the aromatic-enriched fraction obtained in step c32) into step c4).

17. The method according to any one of claims 1 1 to 16, wherein the isolated in step c3), aromatics depleted fraction C2) at least partially for the preparation of

Synthesis gas is used.

18. The process according to any one of claims 11 to 17, wherein the reaction in step c4) comprises a hydrodealkylation or a vapor dealkylation or a mixed form thereof.

19. The method according to any one of claims 1 1 to 18, wherein the temperature in the Dealkylierungszone in a range of 400 to 900 ° C, preferably from 500 to 800 ° C, is located. 20. The method according to any one of claims 1 1 to 19, wherein the absolute pressure in the dealkylation zone in a range of 1 to 100 bar, particularly preferably from 1 to 20 bar, is located.

21. A process according to any one of claims 11 to 20, wherein the effluent from the dealkylation zone in step c5) is subjected to separation to obtain the following three

Is subjected to a stream of mononuclear, low or unalkylated aromatics, a stream enriched in low or non-dealkylated aromatics,

E3) an enriched stream of volatile by-products lighter than E1) and E2).

22. The method according to any one of the preceding claims, wherein the separation of the discharge from the Dealkylierungszone in step c5) comprises an absorption. 23. The process according to claim 22, wherein the separation of the discharge from the dealkylation zone in step c5) comprises the following substeps:

Contacting the effluent from the dealkylation zone with an absorbent to obtain an aromatics-enriched absorbate and an aromatics-depleted gas stream E3), c52) separating the absorbate into a mononuclear, low or unalkylated aromatics-enriched stream E1), one at low c53) if present, recirculation of the absorbent-containing stream to step c51), c54) optionally recycling at least a portion of stream E2) into the dealkylation zone of (c) or non-dealkylated aromatic enriched stream E2) Step c4).

Method according to one of claims 21 to 23, wherein the current E3) obtained in step c5) is used at least partially to obtain the exhaust gas flow.

Process according to one of claims 21 to 24, wherein the stream E3) obtained in step c5) is used at least partly for the production of synthesis gas.

Method according to one of the preceding claims, wherein at least partially used for obtaining the exhaust gas flow, a synthesis gas-containing current or a hydrogen-enriched stream produced from the synthesis gas.