EP3080062A1

EP3080062A1 - Method of producing adipic acid or at least a resultant product thereof

Info

Publication number: EP3080062A1
Application number: EP14809901.3A
Authority: EP
Inventors: Rolf Pinkos; Martin Bock
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2013-12-13
Filing date: 2014-12-12
Publication date: 2016-10-19
Also published as: JP2017504594A; US20160311746A1; EP2883857A1; WO2015086827A1

Abstract

The present invention relates to a method for the production of adipic acid or at least a resultant product thereof. According to said method, muconic acid is hydrogenated with hydrogen in a reaction zone in the presence of at least one transition metal catalyst (K) and a water-containing liquid (A), the muconic acid being at least partially insoluble in the liquid (A) under the hydrogenation conditions.

Description

Process for the preparation of adipic acid or at least one secondary product thereof

BACKGROUND OF THE INVENTION The present invention relates to a process for producing adipic acid or at least a secondary product thereof by catalytic hydrogenation of muconic acid.

PRIOR ART Adipic acid is an industrially important raw material and is used in particular for the production of polyamide 66, which is also referred to as nylon. The preparation of polyamide 66 by dehydrating polycondensation of adipic acid with hexamethylenediamine has long been known. The adipic acid used in the production of polyamide 66 is industrially produced mainly by oxidation of cyclohexanol or cyclohexanol / cyclohexanone mixtures, which are also referred to as anolone, with concentrated nitric acid. Anolone is accessible by oxidation of cyclohexane with atmospheric oxygen.

Another known starting material for the production of adipic acid is muconic acid. Muconic acid, systematic name 2,4-hexadiene dicarboxylic acid, may be in the cis, cis, cis, trans, or trans, trans conformation. Muconic acid can be obtained, for example, by biochemical processes from renewable raw materials such as glucose or lignin. Complete hydrogenation of the carbon-carbon double bonds in the muconic acid gives adipic acid.

Muconic acid is distinguished in contrast to adipic acid by a pronounced poor solubility in common solvents such as water and ethanol. For example, cis, cis-muconic acid at about 47 ° C shows a solubility in water of about 1 g per 100 g of water. Therefore, the implementation of muconic acid on an industrial scale, for example, adipic acid, generally associated with increased effort. For this reason, different approaches are found in the literature in order to convert the muconic acid into a more soluble form prior to its further reaction, for example to adipic acid. These include, for example, esterification with short-chain alkanols and neutralization with bases in order to obtain soluble muconic acid salts.

EH Farmer and LA Hughes, J. Chem. Soc. 1934, 1929-1938, describe the preparation of adipic acid starting from the disodium salt of muconic acid in an aqueous medium with hydrogenation catalysts based on nickel or platinum. JA Elvidge et al., J. Chem. Soc. 1950, 2235-2241, describe the preparation of cis, trans-muconic acid and their hydrogenation to adipic acid in ethanol in the presence of a platinum catalyst. Information on the amount of the solvent used and the catalyst are not made.

US 4,968,612 describes a fermentation process for the preparation of muconic acid from toluene and the hydrogenation of the muconic acid thus obtained to adipic acid. Concretely, the muconic acid is reacted as a 40% by weight slurry in acetic acid and in the presence of a palladium catalyst on carbon. The water content of the acetic acid used is not specified. A disadvantage of this reaction is the use of corrosive acetic acid, which requires the use of high-quality corrosion-resistant reactors. A disadvantage of this method is further that serves as a starting material toluene, which does not come from renewable sources.

K.M. Draths and J.W. Frost, J. Am. Chem. Soc. 1994, 16, 399-400 and W. Niu et al., Biotechnol. Prog. 2002, 18, 201 -21 1 describe the production of cis, cis-muconic acid from glucose by biocatalyzed synthesis with subsequent hydrogenation of the cis, cis-muconic acid with the aid of a platinum catalyst to adipic acid. In both cases, the pH of the fermentation mixture is adjusted to above 6.3 or to a value of 7.0 before the hydrogenation. This results in a solution of muconic acid salts. Since in both cases, the fermentation broth is first centrifuged and only the supernatant is used for hydrogenation, this according to the procedure of Niu et al. additionally mixed with activated charcoal twice before the hydrogenation and filtered, it can be assumed that the hydrogenation mixture contains no solid muconic acid.

Another process for the production of muconic acid from renewable sources is described, for example, in WO 2010/148080 A2. According to Example 4 in paragraphs [0065] and [0066] of this document, 15 g of cis, cis-muconic acid and 150 ml of water are heated for 15 minutes under reflux of the water. After cooling to room temperature, filtration and drying, 10.4 g (69%) of cis-trans-muconic acid are obtained. The mother liquor (4.2 g = 28% by weight, based on cis, cis-muconic acid) no longer consists of muconic acid. It contains lactones and other unknown reaction products.

JM Thomas et al., Chem. Commun. 2003, 1 126-1 127, describe the hydrogenation of muconic acid to adipic acid with the aid of bimetallic nanocatalysts by special anchor groups are incorporated in the pores of a mesoporous silica, in pure ethanol.

WO 2010/141499 describes the oxidation of lignin to vanillic acid, their decarboxylation to 2-methoxyphenol and further conversion to catechol and finally oxidation to muconic acid and the hydrogenation of muconic acid thus obtained with various transition metal catalysts to adipic acid. The solvent used for the hydrogenation is not specified. WO 2012/170060 describes a process for the preparation of nitrogen-containing compounds, in particular hexamethylenediamine. The starting products are diammonium adipate-containing fermentation broths. For their preparation, in a suitable embodiment, D-glucose can be converted to cis, cis-muconic acid salts by fermentation. The pH is kept below 7 by the addition of ammonia. Subsequently, the cis, cis-muconate is hydrogenated at room temperature in the presence of 10% platinum on carbon at a hydrogen pressure of 50 psi (3,4474 bar). The low temperature is necessary because at higher temperatures ammonia in the sense of a Michael addition would add to the muconic acid or its salts. The resulting hydrogenated fermentation broth contains diammonium adipate (DAA) and optionally monoammonium adipate (MAA) and / or adipic acid (AA). A disadvantage of the process described in WO 2012/170060 is that the DAA and MAA are converted into AA before the further reaction, ie the ammonia has to be separated off. This is done by distillation in two steps, wherein in the first step aqueous DDA solution is distilled so that overhead ammonia and water are separated. The bottom product of the distillation is cooled and the resulting solid, which consists of MAA, separated. In the second step, an aqueous MAA solution is heated with addition of water and ammonia-containing water vapor is separated off. The solid obtained after cooling consists of adipic acid. The adipic acid thus obtained is hydrogenated to 1,6-hexanediol and the 1,6-hexanediol is aminated with ammonia to hexamethylenediamine. Under what conditions and in the presence of which catalysts the hydrogenation of MAA and AA to hexanediol and the amination of hexanediol to hexamethylenediamine takes place is not stated. The only note on this are the formula schemes in Figures 3, 4 and 5. X. She et al., ChemSus Chem 201 1, 4, 1071-1073, describe the hydrogenation of trans, trans-muconic acid to adipic acid with rhenium catalysts on one Titanium dioxide carrier in solvents selected from methanol, ethanol, 1-butanol, acetone, toluene and water. The results summarized in FIG. 1 of this document show the conversion and the distribution of the hydrogenation of trans, trans-muconic acid obtained in methanol dimethyl ester 1 (adipic acid dimethyl ester), 2 (2-hexenediacetic acid dimethyl ester) and 3 (2,4-Hexadiendicarbonsäuredimethylester). The best result was achieved with a Re / TiO 2 catalyst. However, this reaction is not a process for the production of adipic acid by hydrogenation of muconic acid, since in each case the ester formation proceeds as an essential reaction step. The supplementary information for this document also describes the hydrogenation of trans, trans-muconic acid with a Re / TiO 2 catalyst at 120 ° C. and a hydrogen pressure of 1000 psi (68.95 bar) in water as solvent. Because of the low solubility, the muconic acid concentration in the water used as solvent was only 50 mg / ml (5% by weight). With the catalyst used, only a low selectivity with respect to the adipic acid is achieved in water, the main product being the dihydromuconic acid. Thus, after 5 hours of reaction time, the selectivity to adipic acid was only about 10% and to dihydromuconic acid about 90%. The authors therefore explicitly advise against the use of water as a solvent for the hydrogenation reaction. Thus, it says on page 4, lines 1 - 2 of the supplementary information: "Water is a poor reaction media towards the formation of (I) (= adipic acid).

The processes known from the prior art for the preparation of adipic acid from muconic acid have numerous disadvantages. If the muconic acid is used as a salt, it must first be prepared in an additional step. Furthermore, the use of Muconsäuresalzen leads to the unwanted accumulation of salt in the product mixture, which must be separated consuming. The hydrogenation of muconic acid in alcoholic solvents, eg. As methanol or ethanol, leads to by-products such as the monoesters and diesters of muconic acid, dihydromuconic acid and adipic acid with the aforementioned alcohols. Thus, the yield of adipic acid is reduced and the isolation of adipic acid difficult. The use of corrosive solvents such as acetic acid requires expensive, corrosion-resistant reaction vessels. In many solvents such. As ethanol can be obtained only Muconsäurelösungen low concentration, which in the case that only these solutions and no suspensions are used for hydrogenation, low space-time yields result. In many cases, expensive catalysts, for example based on platinum, are used. The organic solvents used are often flammable and / or their use is undesirable for health and environmental aspects. The yields of adipic acid in the processes described in the prior art are often inadequate.

It is an object of the present invention to provide a process which comprises the hydrogenation of muconic acid to adipic acid in high yield and selectivity. did. The disadvantages of the prior art described above should be avoided. In particular, it should be possible to use the muconic acid itself and not a muconic acid salt for the hydrogenation. Specifically, the process should be simple, inexpensive and be carried out in an environmentally friendly reaction medium, without the need for a costly separation of by-products.

It has now surprisingly been found that these objects are achieved by hydrogenating Muconsaure, which is at least partially in solid form, with hydrogen in a water-containing liquid in the presence of a transition metal catalyst.

SUMMARY OF THE INVENTION The invention therefore relates to a process for the preparation of adipic acid or at least one secondary product thereof selected from 1,6-hexanediol, hexamethylenediamine and polyamide 66 which comprises, in a reaction zone, muconic acid with hydrogen in the presence of at least one heterogeneous transition metal catalyst K. and a hydrous liquid A, wherein the muconic acid in the liquid A is at least partially insoluble under the hydrogenation conditions, and wherein the transition metal catalyst K has at least one transition metal selected from Ru, Co, Rh, Ir, Ni, Fe, Pd , Pt, Cu and Au.

In a specific embodiment, the muconic acid is used in the form of a suspension for hydrogenation. The muconic acid is present as a particulate dispersed phase in the aqueous liquid.

In a further specific embodiment, the liquid A consists only of water.

A further specific embodiment is a process for the preparation of adipic acid or at least one secondary product thereof in which hydrogenated in a reaction zone muconic acid with hydrogen in the presence of at least one transition metal catalyst K and a water-containing liquid A, wherein the muconic acid in the liquid A under the hydrogenation conditions at least is partially insoluble, and wherein the liquid A has a water content in the range of 95 to 100 wt .-%, based on the total weight of the liquid A, the transition metal catalyst K contains metallic nickel, metallic cobalt, metallic rhodium or a mixture of at least two of these metals, and removing at least a portion of the reaction mixture from the reaction zone, the withdrawn reaction mixture separating into an adipic acid enriched fraction and an adipic acid depleted fraction subjects the adipic acid depleted fraction at least partially back to the reaction zone.

Another object of the invention is a process for the preparation of

1,6-hexanediol in which a) muconic acid is hydrogenated with hydrogen in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K, as defined hereinbefore and hereinafter to give adipic acid, b) which in step a) adipic acid subjected to a reaction with hydrogen in the presence of at least one hydrogenation catalyst.

The invention further provides a process for the preparation of hexamethylenediamine in which a) muconic acid is hydrogenated with hydrogen in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K, as defined above and hereinafter, to obtain adipic acid b) the adipic acid obtained in step a) is subjected to a reaction with hydrogen in the presence of at least one hydrogenation catalyst to 1,6-hexanediol, obtained in step b) 1, 6-hexanediol of an amination with ammonia in the presence of an amination catalyst to obtain Undergoes hexamethylenediamine.

Another object of the invention is a process for the preparation of polyamide 66, wherein a) Muconsäure a hydrogenation with hydrogen in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K, as defined above and hereinafter, adipic acid is obtained, b) the adipic acid obtained in step a) of a reaction with hydrogen in the presence at least c) the 1,6-hexanediol obtained in step b) is subjected to amination with ammonia in the presence of an amination catalyst to give hexamethylenediamine, d) the hexamethylenediamine obtained in step c) is subjected to a polycondensation with Adi - To subject acid to obtain polyamide 66.

In a specific embodiment, the adipic acid used in step d) is also at least partially derived from the hydrogenation of muconic acid according to the invention. Specifically, in the aforementioned methods, the muconic acid used in step a) is not in salt form.

In a specific embodiment of the aforementioned processes, the hydrogenation of the muconic acid is carried out continuously.

EMBODIMENTS OF THE INVENTION

More specifically, the invention includes the following preferred embodiments: FIG. A process for the preparation of adipic acid or at least a secondary product thereof, which comprises hydrogenating hydrogen in the presence of at least one transition metal catalyst K and a water-containing liquid A in a reaction zone, wherein the muconic acid in the liquid A is at least partially insoluble under the hydrogenation conditions.

2. The method of embodiment 1, wherein the reaction mixture in a

Minimum content of 50 wt .-% water, based on the total weight of the reaction mixture, at 60 ° C has a pH in the range of 1 to 6, preferably 1 to 5, particularly preferably 1 to 4, having. Method according to one of the preceding embodiments, wherein the liquid A has a water content in the range of 5 to 100 wt .-%, preferably 30 to 100 wt .-%, particularly preferably 50 to 100 wt .-%, in particular 65 to 100 wt. %, especially 95 to 100 wt .-%, based on the total weight of the liquid A having.

Method according to one of the preceding embodiments, wherein the muconic acid under the hydrogenation conditions has a solubility in the liquid A of at most 50 g / L.

Method according to one of the preceding embodiments, wherein the muconic acid in the hydrogenation is at least partially in the form of suspended in the liquid A particles.

Method according to one of the preceding embodiments, wherein for the hydrogenation, a liquid A is used, in which adipic acid under the reaction conditions has a solubility of at least 100 g / L, preferably at least 200 g / L.

Method of one of the preceding embodiments, wherein the Muconsaure originates from renewable sources, wherein their preparation is preferably carried out by biocatalytic synthesis of at least one renewable raw material.

Method according to one of the preceding embodiments being used Muconsaure, the ^"12 to ^5x10" has a ¹⁴ C to ¹² C-lsotopenverhältnis in the range of 0.5x 10 ^12th

Method according to one of the preceding embodiments, wherein the transition metal catalyst K is a heterogeneous catalyst.

Method according to one of the preceding embodiments, wherein the transition metal catalyst K at least one transition metal of groups 7, 8, 9, 10 and 1 1 of the Periodic Table (IUPAC), preferably selected from Re, Fe, Ru, Co, Rh, Ir, Ni , Pd, Pt, Cu and Au, in particular selected from Re, Ru, Co, Rh, Ir, Ni, especially selected from Ni, Co and Rh. 1 1. Method according to one of the preceding embodiments, wherein the transition metal catalyst K contains metallic nickel, metallic cobalt, metallic rhodium or a mixture of at least two of these metals.

12. The method according to any one of the preceding embodiments, wherein the transition metal catalyst K is selected from Raney nickel, Raney cobalt, rhodium on a support material and mixtures thereof.

Process according to one of the preceding embodiments, wherein at least part of the reaction mixture is removed from the reaction zone, the removed reaction mixture is subjected to separation into an adipic acid-enriched fraction and an adipic acid-depleted fraction and optionally at least partially recirculates the adipic acid-depleted fraction into the reaction zone ,

A process according to embodiment 13, wherein the reaction mixture is subjected to a crystallization of the adipic acid and at least a portion of the mother liquor is returned to the reaction zone.

A process for the preparation of adipic acid or at least a secondary product thereof comprising hydrogenating in a reaction zone muconic acid with hydrogen in the presence of at least one transition metal catalyst K and a hydrous liquid A, wherein the muconic acid in the liquid A is at least partially insoluble under the hydrogenation conditions, and wherein the liquid A has a water content in the range of 95 to 100 wt .-%, based on the total weight of the liquid A, the transition metal catalyst K contains metallic nickel, metallic cobalt, metallic rhodium or a mixture of at least two of these metals, and at least removing a portion of the reaction mixture from the reaction zone, the withdrawn reaction mixture separating into an adipic acid enriched fraction, and a fraction depleted of adipic acid at least partially subject the adipic acid depleted fraction to the reaction zone returns. 16. The method according to any one of the preceding embodiments, wherein the hydrogenation at a temperature in the range of 20 ° C to 250 ° C, preferably 40 ° C to 150 ° C, is carried out. 17. The method according to any one of the preceding embodiments, wherein the reaction at an absolute hydrogen pressure in the range of 1 to 300 bar, preferably 2 to 100 bar, performs.

18. The method according to any one of the preceding embodiments, wherein the hydrogenation is carried out continuously.

19. The method according to any one of the preceding embodiments, wherein the hydrogenation is carried out in n successive hydrogenation reactors, wherein n is an integer of at least two.

20. The method according to embodiment 19, wherein the 1. to (n-1). Reactor has a guided in an external circuit current from the reaction zone.

21. Process according to one of the embodiments 19 or 20, wherein the hydrogenation is carried out adiabatically in the nth reactor.

22. A process for the preparation of 1,6-hexanediol in which a) muconic acid is hydrogenated with hydrogen in the presence of a water-containing liquid A and in the presence of at least one transition metal catalyst K, as defined in any of embodiments 1 to 21, wherein Adipic acid is obtained; b) subjecting the adipic acid obtained in step a) to a reaction with hydrogen in the presence of at least one hydrogenation catalyst.

23. The method of embodiment 22, wherein the hydrogenation catalyst used in step b) based on the total weight of the reduced catalyst contains at least 50 wt .-% of elements selected from rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel and copper ,

24. A process for the preparation of hexamethylenediamine, in which a) subjecting muconic acid to hydrogenation with hydrogen in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K, as defined in any of embodiments 9 to 12, to obtain adipic acid, b) the adipic acid obtained in step a) is reacted with hydrogen in the presence of at least one hydrogenation catalyst to 1, 6-hexanediol, c) the obtained in step b) 1, 6-hexanediol of an amination with ammonia in

Subjecting an amination catalyst to hexamethylenediamine,

25. A process for the preparation of polyamide 66 comprising: a) subjecting hydrogen fluoride to hydrogenation in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K as defined in any one of embodiments 9 to 12 to obtain adipic acid, b ) the adipic acid obtained in step a) subjected to a reaction with hydrogen in the presence of at least one hydrogenation catalyst to 1,6-hexanediol, c) the obtained in step b) 1, 6-hexanediol of an amination with ammonia in

Subjecting an amination catalyst to hexamethylenediamine, d) subjecting the hexamethylenediamine obtained in step c) to polycondensation with adipic acid to give polyamide 66.

26. The method of embodiment 25, wherein the adipic acid used in step d) is at least partially prepared by the method according to any one of embodiments 1 to 21.

DESCRIPTION OF THE INVENTION

The process according to the invention is characterized by the following advantages: Muconic acid produced from renewable raw materials is generally obtained in aqueous solutions. Hydrogenation without a solvent change is possible by the process according to the invention. - A preferred industrial processing method is the recrystallization, so that no solvent change is required here.

The aqueous adipic acid-containing mother liquors obtained in the workup can be recycled to the hydrogenation.

adipic acid

In the hydrogenation process according to the invention, preference is given to using a muconic acid feedstock which consists essentially of muconic acid. With particular preference, the muconic acid starting material used in the process according to the invention comprises at least 90% by weight, very particularly preferably at least 95% by weight, in each case based on the total weight of the muconic acid feed, of muconic acid. The muconic acid which can be used in the process according to the invention can come from renewable sources, with which natural sources such as sugars, e.g. As starch, cellulose and glucose, or lignin are meant. The production of, for example, muconic acid from z. As starch, cellulose, glucose or lignin can be done in all known to the expert types, eg. B. biocatalytically. The biocatalytic production of cis, cis-muconic acid by fermentation processes is described, for example, for glucose in the cited prior art. The muconic acid which can be used in the process according to the invention can also be derived from non-renewable sources. In principle, all muconic acids are suitable for the process according to the invention, regardless of which renewable or non-renewable source they originate from and by what route of synthesis they were prepared. The muconic acid which can be used according to the invention preferably comes from renewable sources. Renewable compounds, such as muconic acid, have a different ¹⁴ C to ¹² C isotope ratio than compounds derived from fossil sources such as petroleum. The preferably used, derived from renewable sources muconic acid accordingly preferably has a ¹⁴ C to ¹² C isotope ratio in the range of

0,5x10- ¹² to 5 × 10 ^12.

The term "muconic acid" in the context of the invention encompasses the different isomers of the muconic acid, namely cis, cis-muconic acid, cis, trans-muconic acid and trans, trans- Muconic acid in any composition. Suitable starting materials for the process according to the invention are all isomers of muconic acid. The muconic acid used in the process according to the invention preferably comprises at least 80% by weight, particularly preferably at least 90% by weight, of cis, cis-muconic acid, based on the total weight of all the muconic acid isomers contained in the muconic acid used.

In the context of the invention, the term "muconic acid" denotes a feedstock which consists essentially of completely protonated, non-derivatized muconic acid. The muconic acid used for the hydrogenation preferably comprises at least 80% by weight, preferably at least 95% by weight, in particular at least 99% by weight, of completely protonated, non-derivatized muconic acid.

In the hydrogenation of muconic acid according to the invention, intermediates and by-products may result. Intermediates are the hydrogenation still accessible partially hydrogenated Dihydromuconsäuren. By-products can result, for example, by addition of water to one or both double bonds of the muconic acid used and optionally subsequent lactone formation. The adipic acid obtained by the process according to the invention can thus contain at least one intermediate or by-product selected from the isomers of dihydromic acid, in particular 2-hexene dicarboxylic acid and 3-hexene dicarboxylic acid, the saturated and unsaturated mono- and dilactones (III), ( IV) and (V) of the muconic acid and mixtures containing several of these intermediate or by-product.

The hydrogenation product obtained by the process according to the invention preferably contains at most 5% by weight, more preferably at most 2% by weight, of lactones of the formulas III to V, based on the total weight of the hydrogenation product. The hydrous liquid A is a substance or mixture of substances which forms a liquid phase under the hydrogenation conditions. The liquid A behaves substantially inert under the hydrogenation conditions, ie it is essentially not hydrogenated. Accordingly, the water-containing liquid A preferably has no ethylenically unsaturated double bonds.

The liquid A is preferably chosen such that the resulting process product adipic acid in the liquid A under the hydrogenation conditions in a proportion of at least 1 wt .-%, preferably at least 10 wt .-%, particularly preferably at least 20 wt .-%, based on the total weight of the liquid A, dissolves.

According to the invention, the liquid A comprises water or the liquid A consists of water. The liquid A preferably has a water content in the range from 1 to 100% by weight, particularly preferably 10 to 100% by weight, in particular 50 to 100% by weight, in each case based on the total weight of the liquid A. Most preferably, the liquid A consists exclusively of water, accordingly, the liquid A most preferably has a water content in the range of 95 to 100 wt .-%, based on the total weight of the liquid A on.

The water-containing liquid A is particularly preferably exclusively water. However, the water-containing liquid A may also contain at least one organic solvent which is liquid under the hydrogenation conditions. Preferably, the organic solvents are at least partially miscible with water. The organic solvent is preferably selected from C 1 -C 6 -carboxylic acids, linear and cyclic, aliphatic and aromatic ethers and mixtures thereof. Examples of preferred C 1 -C 6 -carboxylic acids are formic acid, acetic acid, propionic acid, butyric acid, valeric acid and mixtures thereof. Examples of preferred ether-containing solvents are mono- and di-C 2 -C 4 -alkylene glycol-C 1 -C 4 -alkyl ethers and C 4 -C 8 -cycloalkyl ethers, eg. For example, unsubstituted or C 1 -C 4 -alkyl-substituted tetrahydrofuran. Particularly preferred ethers are ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether (diglyme), diethylene glycol diethyl ether, 1,3-propanediol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, diphenyl ether, dioxane and mixtures thereof.

If the water-containing liquid A contains at least one organic solvent, the proportion of the organic solvent is preferably 1 to 99 wt .-%, preferably 1 to 90 wt .-%, particularly preferably 1 to 50 wt .-%, based on the total weight of Liquid A. In a preferred embodiment of the invention According to the invention, the proportion of organic solvent in the liquid A is less than 10% by weight, more preferably less than 5% by weight, in particular less than 1% by weight, based on the total weight of the liquid A. The muconic acid is under the hydrogenation conditions in the liquid A at least partially insoluble. Preferably, the mixture of muconic acid and liquid A is a suspension of the muconic acid in the liquid A.

Preferably, the reaction mixture at a minimum content of 50 wt .-% water, based on the total weight of the reaction mixture, at 60 ° C, a pH in the range of 1 to 6, preferably 1 to 5, particularly preferably 1 to 4, on.

Preferably, the liquid A has a water content in the range of 5 to

100 wt .-%, preferably 30 to 100 wt .-%, particularly preferably 50 to 100 wt .-%, in particular 65 to 100 wt .-%, especially 95 to 100 wt .-%, based on the total weight of the liquid A. , on.

Preferably, the muconic acid under the hydrogenation conditions, a solubility in the liquid A of preferably at most 80 g / L, more preferably at most 50 g / L.

Preference is given to using a suspension of the muconic acid in which the solids content of the muconic acid is at least 1% by weight, preferably at least 10% by weight, particularly preferably at least 20% by weight, based on the total weight of liquid A and muconic acid. The solubility of the muconic acid under the hydrogenation conditions in the liquid A can be determined by the person skilled in the art from literature data and, if appropriate, by simple experiments.

Preferably, the adipic acid obtained in the hydrogenation of the muconic acid is discharged together with the liquid A from the reaction zone. For this purpose, it is advantageous if the adipic acid has a certain solubility in the liquid A. Preferably, in the process according to the invention, a liquid A is used in which adipic acid has a solubility of at least 50 g / L, preferably at least 100 g / L, under reaction conditions.

In principle, all transition metal catalysts known to those skilled in the art for hydrogenating carbon-carbon double bonds can be used as transition metal catalysts K in the process according to the invention. In general, the transition metal catalyst K comprises at least one transition metal of groups 7, 8, 9, 10 and 1 1 of the periodic table according to IUPAC. Preferably, the transition metal catalyst K has at least one transition metal selected from the group consisting of Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu and Au. The transition metal catalyst K particularly preferably has at least one transition metal selected from the group consisting of Re, Ru, Co, Rh, Ir and Ni. Most preferably, the transition metal catalyst K has at least one transition metal from the group Ni, Co and Rh. The transition metal catalysts K comprise the transition metals mentioned, in particular the transition metals which are mentioned as being preferred, generally as such, supported on a support, as precipitation catalysts, as Raney catalysts or as mixtures thereof. Specifically, the transition metal catalyst K is selected from Raney nickel, Raney cobalt, rhodium on a support material, e.g. As rhodium on carbon, and mixtures thereof.

As an inert support material for the transition metal catalysts K according to the invention, virtually all support materials of the prior art, such as are advantageously used in the preparation of supported catalysts, for example carbon, S1O2 (quartz), porcelain, magnesium oxide, tin dioxide, silicon carbide, T1O2 (rutile, Anatas ), Al 2 O 3 (alumina), aluminum silicate, steatite (magnesium silicate), zirconium silicate, cerium silicate or mixtures of these support materials. Preferred support materials are carbon, alumina and silica. A particularly preferred carrier material is carbon. Silica materials of different origin and production, eg. As pyrogenic silicas or wet-chemically prepared silicas, such as silica gels, aerogels or precipitated silicas, are used for catalyst preparation (for the preparation of various SiO 2 starting materials see: W. Buchner, R. Schliebs, G. Winter, KH Büchel: Industrial Inorganic Chemistry, 2nd ed., P. 532-533, VCH Verlagsgesellschaft, Weinheim 1986).

The transition metal catalysts K can be used as shaped bodies, for. B. in the form of spheres, rings, cylinders, cubes, cuboids or other geometric bodies. Unsupported catalysts can be formed by conventional methods, e.g. By extruding, tableting, etc. The shape of supported catalysts is determined by the shape of the support. Alternatively, the support may be subjected to a molding process before or after application of the catalytically active component (s). The transition metal catalysts K can, for. In the form of compressed cylinders, tablets, pastilles, carriage wheels, rings, stars or extrudates such as solid strands, polylobal strands, hollow strands and honeycomb bodies or other geometric bodies. The catalyst particles generally have an average of the (largest) diameter of 0.5 to 20 mm, preferably 1 to 10 mm. These include z. B. transition metal catalysts K in the form of tablets, for. B. with a diameter of 1 to 7 mm, preferably 2 to 6 mm and a height of 3 to 5 mm, in the form of rings with z. B. 4 to 7 mm, preferably 5 to 7 mm outer diameter, 2 to 5 mm in height and 2 to 3 mm hole diameter, or in the form of strands of different lengths with a diameter of z. B. 1, 0 to 5 mm. Such forms can be obtained in a manner known per se by tableting, extrusion or extrusion. For this purpose, the catalyst composition customary auxiliaries, for. As lubricants such as graphite, polyethylene oxide, cellulose or fatty acids (such as stearic acid) and / or molding aids and reinforcing agents, such as fibers of glass, asbestos or silicon carbide, are added.

The transition metal catalyst K can be present under the hydrogenation conditions both as a homogeneous and as a heterogeneous catalyst. The transition metal catalyst K is preferably present under the hydrogenation conditions as a heterogeneous catalyst. If a heterogeneous transition metal catalyst K is used, this may be applied, for example, on a reticulated carrier. Alternatively or additionally, the heterogeneous transition metal catalyst K can be applied to the inner wall of a tubular support, wherein the tubular support is flowed through by the reaction mixture. As the muconic acid in the liquid A is substantially as a solid, embodiments of the transition metal catalyst K and / or the carrier on which the transition metal catalyst K is applied are preferred which are not clogged and / or damaged by the particles of the muconic acid. Alternatively or additionally, the transition metal catalyst K can be used as a particulate solid. In a preferred embodiment, the transition metal catalyst K is present in the form of a suspension in the liquid A. If a liquid reaction discharge is taken out of the reaction zone, the suspended transition metal catalyst K can be kept in the reaction zone by means of retention processes known to those skilled in the art. These retention methods preferably comprise a cross-flow filtration, a gravity filtration and / or a filtration by means of at least one filter candle z. B. as metal sintered frit.

Preferably, the hydrogenation is carried out at a temperature in the range of 20 ° C to 250 ° C, more preferably at a temperature in the range of 30 ° C to 200 ° C, most preferably in the range of 40 ° C to 150 ° C. The hydrogenation according to the invention is preferably carried out at an absolute hydrogen pressure in the range from 1 to 300 bar, particularly preferably in the range from 1.5 to 200 bar, very particularly preferably in the range from 2 to 100 bar. The hydrogen used for hydrogenation may contain one or more inert diluent gases, e.g. As nitrogen and / or argon. The hydrogen used for the hydrogenation is preferably employed essentially in pure form, ie the hydrogen used for the hydrogenation generally contains less than 10% by weight, preferably less than 5% by weight, based on the total weight of the gas used for the hydrogenation , on gases other than hydrogen.

The average residence time of the reaction mixture in the reaction zone is generally in the range of 0.1 hours to 48 hours, preferably in the range of 0.2 hours to 24 hours, more preferably in the range of 0.3 hours to 10 hours.

Depending on the production quantity, the process according to the invention may usefully be carried out as a batch process, semi-batch process or as a continuous process. In the production of technical quantities (> 100 t), the continuous execution of the method according to the invention is preferred.

If the process according to the invention is carried out as a batch process, the procedure is generally such that muconic acid, liquid A and transition metal catalyst K are initially introduced in a reaction vessel and hydrogen is pressed once. If the process according to the invention is carried out as a semi-batch process, the procedure will generally be such that muconic acid, liquid A and transition metal catalyst K are initially introduced in a reaction vessel and hydrogen is continuously fed. After the reaction has taken place, the adipic acid solution obtained is generally discharged from the reaction vessel and, if appropriate, subjected to a work-up, preferably the same work-up as that of the reaction zone removed from the reaction mixture in a continuous process. If appropriate, the transition metal catalyst K can be separated off by the abovementioned retention devices and / or retention methods and can preferably be employed in at least one further batch or semi-batch process according to the invention. The process according to the invention is preferably carried out as a continuous process. In this case, the reaction zone is continuously muconic acid, liquid A, hydrogen and optionally transition metal catalyst K supplied and continuously removed at least a portion of the adipic acid-containing reaction mixture. The muconic acid is the reaction zone preferably without added solvent as Solid or fed as a suspension. It is understood that the supply of muiconic acid, if it is to be introduced without solvent as a solid in the reaction zone, spatially and / or temporally separated from the supply of the liquid A in the reaction zone. If the muconic acid is to be introduced as a suspension into the reaction zone, the reaction zone is preferably preceded by at least one vessel in which the suspension of the muconic acid, preferably the liquid A, is prepared, for example with stirring or pumping. If the transition metal catalyst K is used in suspended form, the production of the transition metal catalyst suspension can be carried out together with the preparation of the suspension of the muconic acid in the at least one upstream reaction vessel.

In a preferred embodiment of the process according to the invention, at least part of the reaction mixture is taken from the reaction zone and subjecting the withdrawn reaction mixture to separation into an adipic acid-enriched fraction and a fraction depleted in adipic acid. Suitable fraction for fractionation into an adipic acid-enriched fraction and an adipic acid-depleted fraction are the separation methods which are known to those skilled in the art, preferably selected from crystallization processes, distillative processes, adsorption processes, ion exchange processes, membrane separation processes, extraction processes or a combination of two or more of these processes. Particularly preferably, the separation into a fraction enriched in adipic acid and a fraction depleted of adipic acid comprises a one-stage or multistage process for the at least partial crystallization of adipic acid. The crystallization is preferably carried out at temperatures of 10 to 80 ° C.

Preferably, the adipic acid-depleted fraction is at least partially recycled to the reaction zone. In a preferred embodiment, the reaction mixture withdrawn from the reaction zone is at least partially subjected to crystallization of the adipic acid and at least part of the adipic acid-depleted supernatant (the mother liquor) is returned to the reaction zone. The crystallization of adipic acid can also be carried out in several stages. In order to avoid the accumulation of impurities, a part of the mother liquor can be discharged. In a further embodiment, a homogeneous, that is essentially dissolved in the liquid, transition metal catalyst K is used, which is at least partially recycled together with the mother liquor in the reaction zone. In a further embodiment of this embodiment, the homogeneous transition metal catalyst K from the withdrawn from the reaction zone part of the reaction mixture recovered by the expert in principle known extraction method. The recovered portion of the homogeneous transition metal catalyst K may optionally be recycled to the reaction zone. Preferably, the muconic acid used comes from renewable sources. Depending on the degree of purity of the muconic acid used, it may also contain substances which act as catalyst poison for the transition metal catalyst K. These may be, for example, compounds containing sulfur, phosphorus, nitrogen and / or halogens. There may therefore be a need to continuously replace the spent transition metal catalyst K with fresh, still reactive transition metal catalyst K. If the transition metal catalyst K is to be replaced continuously by unused, still reactive transition metal catalyst K, transition metal catalysts K which are present in the liquid A as a suspension are preferred in the process according to the invention. If a suspended transition metal catalyst K is used, and the process is carried out as a continuous process, embodiments of the process according to the invention are accordingly particularly preferred in which continuously at least a portion of the suspended transition metal catalyst K is removed from the reaction zone, for. B. by filtration or partial or complete depletion of a removed from the reaction zone part of the reaction mixture with o- without recycling the depleted transition metal catalyst K portion of the removed reaction mixture, and in which continuously reactive transition metal catalyst K is fed to the reaction zone. The continuous supply of transition metal catalyst K to the reaction zone can take place in the form of a solid or in the form of a suspension, preferably a suspension in the liquid A.

The catalyst loading in continuous operation is preferably 0.01 to 100 kg, particularly preferably 0.1 to 50 kg of muconic acid to be hydrogenated per kg of transition metal catalyst K and hour.

The molar ratio of hydrogen to muconic acid compound is preferably from 2: 1 to 20: 1, more preferably from 2: 1 to 3: 1. In a specific embodiment of the process according to the invention, the hydrogenation is carried out in n hydrogenation reactors connected in series (in series), where n is a integer of at least 2 stands. Suitable values for n are 2, 3, 4, 5, 6, 7, 8, 9 and 10. Preferably, n is 2 to 6 and in particular 2 or 3. In this embodiment, the hydrogenation is preferably carried out continuously. The reactors used for the hydrogenation may independently have one or more reaction zones within the reactor. The reactors may be the same or different reactors. These can be z. B. each have the same or different mixing characteristics and / or be subdivided by internals one or more times.

Suitable pressure-resistant reactors for the hydrogenation are known to the person skilled in the art. These include the commonly used reactors for gas-liquid reactions, such as. B. tube reactors, tube bundle reactors, gas circulation reactors, bubble columns, loop apparatus, stirred tank (which can also be designed as stirred tank cascades), air-lift reactors, etc.

The process according to the invention using heterogeneous transition metal catalysts K can be carried out in a fixed bed or suspension mode. The fixed bed mode can be z. B. in sump or in trickle run. The transition metal catalysts K are preferably used as shaped bodies, as described above, for. B. in the form of pressed cylinders, tablets, pastilles, carriage wheels, rings, stars or extrudates, such as solid strands, polylobären strands, hollow strands, honeycomb bodies, etc.

For the hydrogenation of solids-containing mixtures, such as. For example, of muconic acid suspensions, fixed bed reactors are not suitable. However, they can in the process according to the invention z. B. can be used as secondary reactors, in which a homogeneous liquid phase is fed ge.

In the suspension mode heterogeneous catalysts are also used. The heterogeneous catalysts are usually used in a finely divided state and are finely suspended in the reaction medium before.

Suitable heterogeneous catalysts and processes for their preparation are those described above.

In the hydrogenation on a fixed bed, a reactor is used, in the interior of which the fixed bed is arranged, through which the reaction medium flows. The fixed bed can be formed from a single or multiple beds. Each bed may have one or more zones, wherein at least one of the zones contains a material active as a hydrogenation catalyst. Each zone can have one or more different catalytically active materials and / or one or more have several different inert materials. Different zones may each have the same or different compositions. It is also possible to provide a plurality of catalytically active zones, which are separated from each other, for example, by inert beds. The individual zones may also have different catalytic activity. For this purpose, various catalytically active materials can be used and / or at least one of the zones an inert material can be added. According to the invention, the reaction medium which flows through the fixed bed contains at least one liquid phase, namely the inert liquid A. The reaction medium may additionally contain a gaseous phase.

As reactors in the hydrogenation in suspension are in particular loop apparatuses, such as jet loops or propeller loops, stirred tank, which can also be configured as Rührkesselkaskaden, bubble columns or air-lift reactors are used.

If desired, in a hydrogenation apparatus of n reactors, at least two of the reactors (i.e., 2 to n of the reactors) may have a different temperature from each other. In a specific embodiment, each downstream reactor is operated at a higher temperature than the previous reactor. In addition, each of the reactors may have two or more different temperature reaction zones. Thus, for example, in a second reaction zone another, preferably a higher, temperature than in the first reaction zone or in each subsequent reaction zone can be set to a higher temperature than in a preceding reaction zone, for. B. to achieve the fullest possible conversion in the hydrogenation.

If desired, in a hydrogenator of n reactors, at least two of the reactors (i.e., 2 to n of the reactors) may have a different pressure from each other. In a specific embodiment, each downstream reactor is operated at a higher pressure than the previous reactor.

The feeding of the hydrogen required for the hydrogenation can be carried out in the first and optionally additionally in at least one further reactor. Preferably, the feed of hydrogen takes place only in the first reactor. The amount of hydrogen fed to the reactors results from the amount of hydrogen consumed in the hydrogenation reaction and the amount of hydrogen optionally discharged with the exhaust gas. The adjustment of the amount of muconic acid reacted in the respective reactor can be determined, for example, by B. on the reactor volume and / or the residence time in the reactor. The conversion in the first reactor, based on muconic acid, is preferably at least 60%, more preferably at least 70%. The total conversion in the hydrogenation of the muconic acid, based on the muconic acid, is preferably at least 97%, particularly preferably at least 98%, in particular at least 99%.

To remove the heat of reaction arising during the exothermic hydrogenation, one or more of the reactors may be provided with at least one cooling device. In a specific embodiment, at least the first reactor is provided with a cooling device. The heat of reaction can be removed by cooling an external recycle stream or by internal cooling in at least one of the reactors. For internal cooling, the customary devices, generally hollow body modules, such as field pipes, pipe coils, heat exchanger plates, etc. can be used. Alternatively, the reaction can also be carried out in a cooled tube bundle reactor.

The hydrogenation is preferably carried out in n hydrogenation reactors connected in series, where n is an integer of at least two, and where at least one reactor has an external circulation stream from the reaction zone (external recycle stream, liquid recycle, loop mode). Preferably, n stands for two or three.

The hydrogenation is preferably carried out in n hydrogenation reactors connected in series, where n is preferably two or three, and the first to (n-1). Reactor has a guided in an external circuit current from the reaction zone.

The hydrogenation is preferably carried out in n hydrogenation reactors connected in series, n preferably being two or three, and the reaction being carried out adiabatically in the nth reactor (the last reactor through which the reaction mixture to be hydrogenated is passed).

Preferably, the hydrogenation is carried out in n series-connected hydrogenation reactors, where n is preferably two or three, and wherein the n. Reactor is operated in a straight pass.

If a reactor is operated "in straight pass", it should be understood here and below that a reactor is operated without recycling the reaction product in the sense of the loop procedure. The mode of operation in the straight In this case, passageway does not exclude backmixing internals and / or stirring devices in the reactor.

If the reaction mixture hydrogenated in one of the reactors downstream of the first reactor (ie the 2nd to nth reactor) has only such small amounts of hydrogenatable muconic acid or intermediates that the heat of reaction occurring in the reaction is insufficient, the desired temperature in the reactor is too high It may also be necessary to heat the reactor (or individual reaction zones of the second reactor). This can be carried out analogously to the previously described removal of the heat of reaction by heating an external circulating flow or by internal heating. In a suitable embodiment, the heat of reaction from at least one of the previous reactors can be used to control the temperature of a reactor. Furthermore, the heat of reaction removed from the reaction mixture can be used to heat the feed streams of the reactors. This can z. B. the feed stream of muconic acid in the first reactor at least partially mixed with an external recycle stream of this reactor and the combined streams are then fed into the first reactor. Furthermore, when m = 2 to n reactors, the feed stream from the (m-1) -th reactor in the mth reactor can be mixed with a recycle stream from the mth reactor and the combined streams then into the mth reactor be guided. Furthermore, the feed stream of the muconic acid and / or another feed stream can be heated by means of a heat exchanger which is operated with deprived hydrogenation heat.

In a special embodiment of the process, a reactor cascade of n reactors connected in series is used, the reaction being carried out adiabatically in the nth (nth) reactor. This term is understood in the context of the present invention in the technical and not in the physico-chemical sense. As a result, the reaction mixture generally experiences an increase in temperature when it flows through the second reactor due to the exothermic hydrogenation reaction. Adiabatic reaction is understood to mean a procedure in which the amount of heat liberated during the hydrogenation is taken up by the reaction mixture in the reactor and no cooling by cooling devices is used. Thus, the heat of reaction with the reaction mixture is discharged from the second reactor, except for a residual portion, which is discharged by natural heat conduction and heat radiation from the reactor to the environment. Preferably, the nth reactor is operated in a straight pass. In a preferred embodiment, a two-stage reactor cascade is used for the hydrogenation, wherein the first hydrogenation reactor has a current conducted in an external circuit from the reaction zone. In a special embodiment of the process, a reactor cascade of two reactors connected in series is used, the reaction being carried out adiabatically in the third reactor.

In a further preferred embodiment, a three-stage reactor cascade is used for the hydrogenation, wherein the first and the second hydrogenation reactor have a current conducted in an external circuit from the reaction zone. In a specific embodiment of the process, a reactor cascade of three reactors connected in series is used, the reaction being carried out adiabatically in the third reactor. Adiabatic reaction is understood to mean a procedure in which the amount of heat liberated in the hydrogenation is taken up by the reaction mixture in the reactor and no cooling by cooling devices is used.

In one embodiment, additional mixing can take place in at least one of the reactors used. Additional mixing is particularly advantageous if the hydrogenation takes place at high residence times of the reaction mixture. For mixing z. B. the currents introduced into the reactors are used by introducing them via suitable mixing devices, such as nozzles, in the respective reactors. For mixing, it is also possible to use streams in an external circuit from the respective reactor. To complete the hydrogenation, the first to (n-1) -th reactor is removed from a discharge which still contains hydrogenatable muconic acid and / or intermediates and fed into the respective downstream hydrogenation reactor. In a specific embodiment, the discharge is separated into a first and a second partial stream, wherein the first partial stream is recycled as a circular stream to the reactor to which it was taken and the second partial stream is fed to the subsequent reactor. The discharge may contain dissolved or gaseous portions of hydrogen. In a specific embodiment, the discharge from the first to (n-1) -th reactor is fed to a phase separation vessel, separated into a liquid and into a gaseous phase, the liquid phase separated into the first and the second partial stream and the gas phase at least partially fed separately downstream reactor. In an alternative embodiment, the discharge from the first to (n-1) -th reactor is fed to a phase separation vessel and separated into a first liquid hydrogen-depleted substream and a second hydrogen-enriched substream. The first partial flow is then returned to the reactor as a circular flow, he was removed and the second partial stream to the subsequent reactor (as Muconsäureverbindung-M and hydrogen-containing feed) is supplied. In a further alternative embodiment, the feed of the second to nth reactor with hydrogen is not carried out via a hydrogen-containing feed taken from the upstream reactor, but with fresh hydrogen via a separate feed line.

The process variant described above is particularly advantageous for controlling the reaction temperature and the heat transfer between the reaction medium, limiting apparatus walls and environment. Another way to control the heat balance is to control the inlet temperature of the muconic acid feed. Thus, a lower temperature of the incoming feed usually leads to an improved removal of the heat of hydrogenation. As the catalyst activity decreases, the inlet temperature may be set higher to achieve a higher reaction rate and thus to compensate for the decreasing catalyst activity. Advantageously, the service life of the transition metal catalyst K used can thus generally be extended.

1, 6-hexanediol The invention further relates to a process for the preparation of 1, 6-hexanediol, in which a) subjecting a hydrogenone to hydrogenation with hydrogen in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K, as defined above Adipic acid is obtained; b) the adipic acid obtained in step a) of a hydrogenation in the presence of a

Hydrogenation catalyst to obtain 1, 6-hexanediol. The inventive method is particularly suitable for the production of 1, 6-hexanediol from natural sources of raw materials. A completely natural raw material sources produced 1, 6-hexane diol typically has a ¹⁴ ^C-to-12 C lsotopenverhältnis in the range of 0.5 x 10 ^"12 to 5 × ^{10" 12.} The hydrogenation of adipic acid to 1,6-hexanediol is known in principle. It is preferably carried out in the liquid phase. The hydrogenation can be carried out without the addition of an external solvent or in the presence of an external solvent. Suitable external solvents are preferably selected from water, aliphatic

C 1 -C 8 -alcohols (in particular selected from methanol, ethanol, n-propanol, i-propanol, n-butanol, sec-butanol, i-butanol and tert-butanol), aliphatic C 2 -C 6 -α, ω-diols (ie, ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1 , 5-pentanediol or 1,6-hexanediol), ethers (in particular selected from tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether and methyl tert-butyl ether) and mixtures thereof. Aliphatic Ci-Cs alcohols, water and mixtures of these solvents are preferred. Particularly preferred are methanol, n-butanol, isobutanol, water and mixtures of these solvents. Furthermore, it is preferred to use the target product 1, 6-hexanediol as a solvent. In this case, 1, 6-hexanediol can be used alone or in admixture with alcohols and / or water.

It is preferred that for the catalytic hydrogenation in step b) a solution is used which contains 10 to 60 wt .-%, particularly preferably 20 to 50 wt .-%, most preferably 30 to 50 wt .-% adipic acid. Preferably, the hydrogenation catalyst used in step b) based on the total weight of the reduced catalyst contains at least 50 wt .-% of elements selected from rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel and copper. Catalysts which contain at least 50% by weight of cobalt and at least 0.1% by weight of ruthenium and / or at least 0.1% by weight of rhenium, based on the total weight of the reduced, are preferably used for the hydrogenation according to the invention in step b) Catalyst, included. Catalysts containing at least 50% by weight of cobalt may furthermore contain in particular phosphoric acid and further transition metals such as copper, manganese and / or molybdenum.

The preparation of a suitable co-catalyst precursor is known from DE 2 321 101. This contains in the unreduced, calcined state 40 to 60 wt .-% cobalt (calculated as Co), 13 to 17 wt .-% copper (calculated as Cu), 3 to 8 wt% manganese (calculated as Mn), 0.1 to 5 wt .-% of phosphates (calculated as H3PO4) and 0.5 to 5 wt .-% molybdenum (calculated as M0O3). EP 636 409 B1 describes the preparation of further suitable cobalt catalyst precursors containing from 55 to 98% by weight of cobalt, from 0.2 to 15% by weight of phosphorus, to from 0.2 to 15% by weight. % of manganese and 0.2 to 15 wt .-% of alkali metals (calculated as oxide) exist. Such catalyst precursors can be reduced to the active, metallic cobalt-containing catalysts by treatment with hydrogen or mixtures of hydrogen and inert gases such as nitrogen. These catalysts are full contacts, which are predominantly made of metal and contain no catalyst support. Suitable catalysts are in principle all suitable for the hydrogenation of carbonyl homogeneous and heterogeneous catalysts such as metals, metal oxides, metal compounds or mixtures thereof into consideration. Examples of homogeneous catalysts are, for example, in Houben-Weyl, Methods of Organic Chemistry, Volume IV / 1 c, Georg Thieme Verlag Stuttgart, 1980, pp 45-67 and examples of heterogeneous catalysts are, for example in Houben-Weyl, methods of organic chemistry , Volume IV / 1 c, pp 16 to 26 described. Preference is given to using catalysts which contain one or more of the elements from groups 3 and 6 to 11 of the Periodic Table of the Elements (IUPAC), preferably copper, chromium, molybdenum, manganese, rhenium, ruthenium, cobalt, nickel or palladium, particularly preferably copper , Cobalt or rhenium. The catalysts may consist solely of active components or their active components may be supported. Suitable support materials are in particular Cr 2 O 3, Al 2 O 3, SiO 2 and ZrO 2 or mixtures thereof.

Particular preference is given to catalysts, as described in EP 0 552 463 A1. These are catalysts which in the oxidic form the composition

CUaAlbZrcMn _d Ox, where a> 0, b> 0, c a 0, d> 0, a> b / 2, b> a / 4, a> c and a> d and x are to preserve the electron neutrality per Formula unit called required number of oxygen ions. The preparation of these catalysts can be carried out, for example, according to the specifications of EP 552 463 A1 by precipitation of sparingly soluble compounds from solutions containing the corresponding metal ions in the form of their salts. Suitable salts are, for example, halides, sulfates and nitrates. Suitable precipitants are all agents which lead to the formation of such insoluble intermediates which can be converted into the oxides by thermal treatment. Particularly suitable intermediates are the hydroxides and carbonates or bicarbonates, so that alkali metal carbonates or ammonium carbonate are used as particularly preferred precipitants. There is a thermal treatment of the intermediate stages at temperatures in the range of 500 ° C to 1000 ° C. The BET surface area of such catalysts is between 10 and 150 m ² / g. Furthermore, catalysts are suitable which have a BET surface area of 50 to 120 m ² / g, wholly or partially contain crystals with spinel structure and copper in the form of copper oxide. WO 2004/085 356 A1 also describes copper catalysts suitable for the process according to the invention, the copper oxide, aluminum oxide and at least one of the oxides of lanthanum, tungsten, molybdenum, titanium or zirconium and additionally pulverulent metallic copper, copper flakes, pulverulent cement, Containing graphite or a mixture thereof.

The hydrogenation of adipic acid to 1, 6-hexanediol in step b) is preferably carried out at a temperature which is in the range of 160 to 240 ° C, more preferably 170 to 230 ° C, most preferably 170 to 220 ° C. In a preferred embodiment of the process according to the invention for preparing 1,6-hexanediol from muconic acid, the hydrogenation of muconic acid in step a) takes place in a first loop reactor and the hydrogenation of the adipic acid obtained in step a) in step b) in a second loop reactor. Preferably, the hydrogenation product obtained in step b) is post-hydrogenated in a subsequent tube reactor which is operated in a straight pass.

A loop reactor is to be understood as meaning a reactor in which the reactor contents are circulated. The feed can be cooled after passing through the reactor in a cooling device such as a heat exchanger, a partial stream of the cooled stream returned to the reactor and the residual stream are passed to the next stage of the process. It can be an internal or an external cycle. Preferably, the external circuit may be cooled in a cooling device, such as a heat exchanger. As a heat exchanger plate, tube bundle or double jacket heat exchangers are preferred. By dissipating the heat of reaction, the temperature rise in the reactor can be well controlled in the exothermic hydrogenation. The average residence time in the loop reactor is preferably 0.1 to 10 h, more preferably 0.2 to 4 h.

In a further preferred embodiment of the process according to the invention, steps a) and b) take place in the same loop reactor, wherein in this

Loop reactor two reaction zones are present at different temperatures. In this embodiment, a tubular reactor operated in a straight pass preferably follows, in which the hydrogenation product obtained in step b) is post-hydrogenated. The hydrogenations in the loop reactors preferably take place in a sump or trickle mode. The reaction product obtained in the hydrogenation of adipic acid in water as solvent represents an aqueous 1,6-hexanediol solution. After cooling and venting of the hydrogenation product, the water is generally removed by distillation, and 1,6-hexanediol can be dissolved in high purity (> 97%) can be obtained. hexamethylenediamine

The invention further relates to a process for the preparation of hexamethylenediamine comprising: a) subjecting hydrogenuric acid to hydrogenation in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K as defined above and hereinafter to give adipic acid; b) subjecting the adipic acid obtained in step a) to 1, 6-hexanediol in the presence of at least one hydrogenation catalyst; c) the 1,6-hexanediol obtained in step b) of an amination with ammonia in the presence of an amination catalyst to obtain Subject hexamethylenediamine,

With regard to method steps a) and b), reference is made in full to the previous comments on these steps. The 1,6-hexanediol obtained in step b) is preferably reacted with ammonia in step c) to form hexamethylenediamine in the presence of an amination catalyst.

The hexamethylenediamine synthesized in the process according to the invention generally has a ¹⁴ C to ¹² C isotope ratio in the range from 0.5 ^χ 10 ^"12 to 5 ^χ 10 ^{" 12} .

The amination according to the invention can be carried out without the supply of hydrogen, but preferably with the supply of hydrogen. The catalysts used in one embodiment of the invention are preferably predominantly cobalt, silver, nickel, copper or ruthenium or mixtures of these metals. By "predominantly" it is to be understood that one of these metals contains more than 50% by weight in the catalyst (calculated without carrier) The catalysts can be used as unsupported catalysts, ie without a catalyst carrier or as carrier catalysts The supports used are preferably SiO 2, Al 2 O 3, T 2 O 2, ZrO 2, activated carbon, silicates and / or zeolites The catalysts mentioned are preferably used as fixed bed catalysts It is also possible to use cobalt, nickel and / or copper in the form of Raney suspension catalysts Type.

In one embodiment of the invention, the amination of the 1,6-hexanediol is carried out in a homogeneous phase and the catalyst is a complex catalyst which contains at least one element selected from groups 8, 9 and 10 of the Periodic Table (IUPAC) and at least one donor ligand. Such catalysts are known, for example, from WO 2012/1 19929 A1.

The amination is preferably carried out at temperatures of 100 to 250 ° C, more preferably 120 to 230 ° C, most preferably 100 to 210 ° C.

The total pressure is preferably in the range of 5 to 30 MPa, more preferably 7 to 27 MPa, most preferably 10 to 25 MPa.

The molar ratio of 1,6-hexanediol to ammonia is preferably 1 to 30, more preferably 1 to 25, most preferably 1 to 20.

The amination can be carried out solvent-free. However, it is preferably carried out in the presence of at least one solvent. Preferred solvents are water, ethers or mixtures of these solvents, with ethers being particularly preferably selected from dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, dibutyl ether and methyl tert-butyl ether.

In a preferred embodiment of the process according to the invention, the aqueous 1,6-hexanediol solutions obtained in the hydrogenation of muconic acid are used without work-up in the amination step.

In a particularly preferred embodiment, the amination is carried out in the presence of hexamethyleneimine as solvent or hexamethyleneimine / water mixtures. The amount of solvent is preferably such that 5 to 80, preferably 10 to 70, particularly preferably 15 to 60 wt .-% strength 1, 6-hexanediol solutions. Per mole of 1,6-hexanediol, preferably 10 to 150 liters, more preferably 10 to 100 liters of hydrogen are fed.

The hydrogen partial pressure is preferably in the range of 1 to 40 MPa, more preferably 5 to 30 MPa, most preferably 10 to 25 MPa.

In one embodiment of the invention, the amination of 1,6-hexanediol with ammonia takes place in a first substep c1) to give a mixture of 1-amino-6-hydroxyhexane and hexamethylenediamine which contains more than 50% by weight of 1-amino Contains 6-hydroxyhexane. This is separated in a partial step c2) together with hexamethylenediamine from unreacted 1, 6-hexanediol and reacted in a sub-step c3) with further ammonia to hexamethylenediamine.

The amination can be carried out batchwise or continuously, in the liquid or gas phase, preference being given to a continuous process.

The workup of the still 1-amino-6-hydroxyhexane-containing target product hexamethylenediamine is preferably carried out by distillation. Since 1-amino-6-hydroxyhexane and hexamethylenediamine have very similar vapor pressures, pure hexamethylenediamine is discharged. Mixtures of 1-amino-6-hydroxyhexane and hexamethylenediamine are recycled to the distillation stage.

Polyamide 66

The invention also relates to a process for the preparation of polyamide 66 comprising: a) subjecting hydrogenuric acid to hydrogenation in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K as defined above and hereinafter to give adipic acid, b ) the adipic acid obtained in step a) is subjected to a reaction with hydrogen in the presence of at least one hydrogenation catalyst to give 1,6-hexanediol, c) subjecting the 1,6-hexanediol obtained in step b) to amination with ammonia in the presence of an amination catalyst to give hexamethylenediamine, d) subjecting the hexamethylenediamine obtained in step c) to a polycondensation with adipic acid to give polyamide 66.

Methods for producing polyamide 66 (nylon, polyhexamethylene adipamide) are known in principle to the person skilled in the art. The production of polyamide 66 is carried out predominantly by polycondensation of so-called AH salt solutions, d. H. of aqueous solutions containing adipic acid and 1,6-diaminohexane (hexamethylenediamine) in stoichiometric amounts. Conventional production methods for polyamide 66 are z. B. in Kunststoffhandbuch, 3/4 Engineering thermoplastics: polyamides, Carl Hanser Verlag, 1998, Munich, pp 42-71, described. In particular, it is also possible to work according to a protocol known from Hans-Georg Elias, Makromolekule, 4th edition, pages 796 to 797, Hüthig-Verlag (1981). The aforementioned documents are hereby incorporated by reference in their entirety.

The preparation of polyamide 66 according to the invention preferably comprises: d1) reacting adipic acid and hexamethylenediamine in a molar ratio of about 1: 1 to hexamethylenediammonium adipate (AH salt), and

d2) Reaction of the hexamethylenediammonium adipate to polyamide 66. The hexamethylenediammonium adipate is converted to polyamide 66 in step d2), in particular in the presence of water at a maximum temperature of 280 ° C., more preferably of not more than 275 ° C.

The process according to the invention is particularly suitable for the partial or complete production of polyamide 66 from natural raw material sources. An essential aspect of the present invention is thus the ecologically and economically improved provision of adipic acid, hexamethylenediamine and polyamide 66 prepared therefrom from natural muconic acid sources. A fully made of natural resources polyamide 66 typically has a ¹⁴ ^C-to-12 C lsotopenverhältnis in the loading range from 0.5 x 10 ^"12 to 5 × ^{10" 12.}

In a preferred embodiment for the production of polyamide 66, a preparation prepared by the process according to the invention comprising steps a) to c) is used. xamethylenediamine is polycondensed with an adipic acid prepared according to steps a) of the process according to the invention to polyamide 66.

The following examples serve to illustrate the invention and are not intended to be limiting.

Examples:

Uses used: cis, cis-muconic acid (Aldrich)

water

hydrogen

Raney nickel

Raney cobalt

2% rhodium on carbon

Experimental Example for Examples 1 to 3:

Table 1

A suspension of 24 g of cis, cis-muconic acid, 56 g of water and 1 g of the transition metal catalyst K indicated in Table 1 was prepared and the suspension was charged into a 300 mL stirred autoclave made of stainless steel 1 .4571. It was pressed 30 bar hydrogen, turned on the stirrer (700 rev / min) and heated the mixture over a period of 20 minutes at 80 ° C. After the mixture was heated to 80 ° C, the hydrogen pressure was increased to 100 bar and kept this hydrogen pressure by metered addition of hydrogen during the reaction time constant. After 12 hours reaction time, the reaction mixture was cooled to about 60 ° C, the pressure reduced to atmospheric pressure and the reaction mixture filtered from the catalyst. The filtrate was analyzed by ¹ H NMR spectroscopy. By means of ¹ H-NMR The yields of adipic acid, the amounts of unreacted cis, cis-muconic acid and the amounts of by-products formed (compounds of the formulas III, IV and V) were determined by spectroscopy. Example 4:

15 g of 2% Rh / C catalyst was suspended in 150 ml of water and the suspension was placed in a 250 mL reactor. The suspension was stirred (700 rpm) and heated to 80 ° C. (internal temperature of the reactor). This temperature was kept constant during the reaction period by a tempering device attached to the reactor. 30 g / hour of a 33% strength by weight suspension of cis, cis-muconic acid in water and 50 standard liters / hour of hydrogen gas were continuously introduced into the reactor. At the same time, liquid and excess gas were continuously withdrawn from the reactor, keeping the volume of liquid and the pressure (about 50 bar) in the reactor constant. The reactor had, before the discharge opening, a metal sintered frit (pore diameter 5 micrometers) through which the suspended catalyst particles and muconic acid particles were kept in the reactor. Behind the Austragsoffnung was the discharge. The discharge line had a valve through which the mixture of discharged reaction mixture and discharged gas at 80 ° C to ambient pressure relaxed. The pH of the reaction solution, measured at 60 ° C., was about 3. In total, about 5 kg of the cis, cis-muconic acid suspension were reacted in the reactor. The discharged liquid was analyzed by ¹ H-NMR spectroscopy. According to ¹ H-NMR analysis, the discharged liquid contained, after removal of the water, 96 wt .-% adipic acid, 0.5 wt .-% muconic acid, 2 wt .-% dihydromuconic acid and 1 wt .-% lactone I. Subsequently purified the discharged liquid by crystallization or carried out a post-hydrogenation followed by crystallization.

crystallization:

The discharged from the reactor liquid was purified by crystallization. For this purpose, 1 kg of the discharged liquid was slowly cooled from 60 ° C. to 20 ° C., whereby adipic acid crystallized out. The crystals were filtered off and dried. About 300 g of adipic acid having a purity of 99.85% were obtained. The adipic acid thus obtained was dissolved in 600 g of water, the solution was heated to 80 ° C. and the solution was slowly cooled to 20 ° C., the adipic acid crystallizing out. The crystals were filtered off and dried. About 270 g of adipic acid having a purity of 99.92% were obtained. The mother liquors were each recycled to the hydrogenation. Post-hydrogenation and crystallization

The discharged from the reactor liquid was post-hydrogenated and purified by crystallization. 4 kg of the discharged liquid were subsequently hydrogenated in a trickle bed reactor at 50 bar hydrogen pressure to 200 mg 2% Rh / C at 150 ° C. In this case, 50 g / hour of the discharged liquid and 20 standard liters of hydrogen gas / hour were fed to the trickle bed reactor. In the reaction effluent from the trickle bed reactor no ethylenically unsaturated compounds could be detected by ¹ H-NMR analysis. The liquid discharged from the trickle bed reactor was heated to 80 ° C. and the liquid was slowly cooled to 20 ° C., with adipic acid crystallizing out. The crystals were filtered off and dried. This gave about 310 g of adipic acid with a purity of 99.95%.

Claims

claims:

A process for the preparation of adipic acid or at least one secondary product thereof, selected from 1,6-hexanediol, hexamethylenediamine and polyamide 66 which comprises hydrogenating in a reaction zone muconic acid with hydrogen in the presence of at least one heterogeneous transition metal catalyst K and a hydrous liquid A, the muconic acid is at least partially insoluble in the liquid A under the hydrogenation conditions, and wherein the transition metal catalyst K has at least one transition metal selected from Ru, Co, Rh, Ir, Ni, Fe, Pd, Pt, Cu and Au.

A process according to claim 1, wherein the reaction mixture at a minimum content of 50% by weight of water, based on the total weight of the reaction mixture, at 60 ° C has a pH in the range of 1 to 6, preferably 1 to 5, particularly preferably 1 to 4, has.

Method according to one of the preceding claims, wherein the liquid A has a water content in the range of 5 to 100 wt .-%, preferably 30 to

100 wt .-%, particularly preferably 50 to 100 wt .-%, in particular 65 to 100 wt .-%, especially 95 to 100 wt .-%, based on the total weight of the liquid A having.

Method according to one of the preceding embodiments, wherein the hydrogenation is carried out continuously.

A process according to any one of the preceding claims, wherein the muconic acid has a solubility in the liquid A of at most 50 g / L under the hydrogenation conditions.

Method according to one of the preceding claims, wherein the muconic acid in the hydrogenation at least partially in the form of suspended in the liquid A particles.

Method according to one of the preceding claims, wherein for hydrogenation, a liquid A is used, in which adipic acid under the reaction conditions has a solubility of at least 100 g / L, preferably at least 200 g / L.

8. The method any of the preceding claims, wherein the muconic acid is derived from renewable sources, the preparation thereof is preferably carried out by biocatalytic synthesis of at least one renewable raw material.

A process according to any one of the preceding claims wherein muconic acid having a ¹⁴ C to ¹² C isotope ratio in the range 0.5x10 ^-12 to

5 ^χ 10- ¹² .

10. The method according to any one of the preceding claims, wherein the transition metal catalyst K K at least one transition metal selected from Re, Fe,

Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu and Au, especially selected from Ru, Co, Rh, Ir, Ni, especially selected from Ni, Co and Rh.

1 1. Method according to one of the preceding claims, wherein the transition metal catalyst K contains metallic nickel, metallic cobalt, metallic rhodium or a mixture of at least two of these metals.

12. The method according to any one of the preceding claims, wherein the transition metal catalyst K is selected from Raney nickel, Raney cobalt, rhodium on a support material and mixtures thereof.

13. The method according to any one of the preceding claims, wherein removing at least a portion of the reaction mixture from the reaction zone, subjected to the removed reaction mixture separation into an adipic acid enriched fraction and a fraction depleted of adipic acid and optionally at least partially depleted in the adipic acid fraction in the Reaction zone leads back.

A process according to claim 13 wherein the reaction mixture withdrawn from the reaction zone is subjected to crystallization of adipic acid and at least a portion of the mother liquor is recycled to the reaction zone.

A process for the preparation of adipic acid or at least one secondary product thereof, selected from 1,6-hexanediol, hexamethylenediamine and polyamide 66 which comprises hydrogenating in a reaction zone muconic acid with hydrogen in the presence of at least one heterogeneous transition metal catalyst K and a hydrous liquid A, the muconic acid is at least partially insoluble in the liquid A under the hydrogenation conditions, and wherein the liquid A has a water content in the range of 95 to 100 wt .-%, based on the total weight of the liquid A, the transition metal catalyst K contains metallic nickel, metallic cobalt, metallic rhodium or a mixture of at least two of these metals, and at least removing a portion of the reaction mixture from the reaction zone, subjecting the removed reaction mixture to separation into an adipic acid-enriched fraction and a fraction depleted of adipic acid, at least partially recirculating the adipic acid-depleted fraction into the reaction zone.

Process according to one of the preceding embodiments, wherein the hydrogenation is carried out at a temperature in the range from 20 ° C to 250 ° C, preferably 40 ° C to 150 ° C.

Method according to one of the preceding embodiments, wherein the reaction is carried out at an absolute hydrogen pressure in the range of 1 to 300 bar, preferably 2 to 100 bar.

A process according to any one of the preceding claims, wherein the hydrogenation is carried out in n hydrogenation reactors connected in series, where n is an integer of at least two, and wherein 1 to (n-1). Reactor has a guided in an external circuit current from the reaction zone and the adiabatic hydrogenation in the n. Reactor is performed.

19. A process for the preparation of 1, 6-hexanediol, in which

Subjecting muconic acid to hydrogenation with hydrogen in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K as defined in any of claims 1, 10, 11 or 12 to give adipic acid; subjecting the adipic acid obtained in step a) to a reaction with hydrogen of at least one hydrogenation catalyst.

20. The method of claim 19, wherein the hydrogenation catalyst used in step b) based on the total weight of the reduced catalyst at least Contains 50% by weight of elements selected from rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel and copper.

21. A process for the preparation of hexamethylenediamine comprising: a) subjecting hydrogenuric acid to hydrogenation in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K as defined in any one of claims 1, 10, 11 or 12 to give adipic acid c) the 1, 6-hexanediol obtained in step b) of an amination with ammonia in the presence of an amination catalyst to obtain hexamethylenediamine subjects,

22. A process for the preparation of polyamide 66 which comprises: a) subjecting hydrogen fluoride to hydrogenation in the presence of a hydrous liquid A and in the presence of at least one transition metal catalyst K as defined in any of claims 1, 10, 11 or 12, wherein Adipic acid is obtained, b) the adipic acid obtained in step a) subjected to a reaction with hydrogen in the presence of at least one hydrogenation catalyst to 1, 6-hexanediol, c) the obtained in step b) 1, 6-hexanediol of an amination with ammonia in

Subjecting the amination catalyst to hexamethylenediamine, d) subjecting the hexamethylenediamine obtained in step c) to a polycondensation with adipic acid to give polyamide 66.

23. The method of claim 22, wherein the adipic acid used in step d) is at least partially prepared by the method according to any one of claims 1 to 18.