EP3080190A1

EP3080190A1 - Process for producing nylon-6,6

Info

Publication number: EP3080190A1
Application number: EP14811899.5A
Authority: EP
Inventors: Christoph Müller; Martin Bock; Marion DA SILVA; Rolf-Hartmuth Fischer; Benoit BLANK; Alois Kindler; Johann-Peter Melder; Bernhard Otto; Mathias SCHELWIES; Andreas Henninger
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: JP2017502128A; US20160347908A1; WO2015086821A1

Abstract

The present invention relates to a process for producing nylon-6,6 by a) providing a muconic acid starting material selected from muconic acid, esters of muconic acid, lactones of muconic acid and mixtures thereof, b) subjecting the muconic acid starting material provided in step a) at least to some extent to a reaction with hydrogen in the presence of at least one hydrogenation catalyst Hb) to give adipic acid, c1) subjecting the muconic acid starting material provided in step a) to some extent to a reaction with hydrogen in the presence of at least one hydrogenation catalyst Hc1) to give 1,6-hexanediol, or c2) subjecting the adipic acid obtained in step b) to some extent to a reaction with hydrogen in the presence of at least one hydrogenation catalyst Hc2) to give 1,6-hexanediol, d) subjecting the 1,6-hexanediol obtained in step c1) or c2) to amination in the presence of an amination catalyst to obtain hexamethylenediamine, e) subjecting the hexamethylenediamine obtained in step d) and at least a portion of the adipic acid obtained in step b) to polycondensation to obtain nylon-6,6.

Description

Process for the preparation of polyamide 66

BACKGROUND OF THE INVENTION The present invention relates to a process for producing polyamide 66 from muconic acid and / or one of its esters and / or one of its lactones. The present invention further relates to polyamide 66, which can be produced by means of this process. STATE OF THE ART

Polyamides are among the world's most widely produced polymers and serve in addition to the main application areas of films, fibers and materials of a variety of other uses. Among the polyamides, polyamide 66 (nylon, polyhexamethylene adipamide) is one of the most widely prepared polymers. The production of polyamide 66 is carried out predominantly by polycondensation of so-called AH salt solutions, d. H. 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.

All industrially used processes for the preparation of hexamethylenediamine (HMD) proceed via adiponitrile (ADN) as an intermediate, which is converted into hexamethylenediamine by catalytic hydrogenation. The greatest economic importance in this case have the ADN synthesis starting from butadiene and hydrogen cyanide and the Elektrodimerisierung of acrylonitrile, prepared by ammoxidation of propene.

DE 198 00 698 A1 describes biodegradable polyesteramides with block-structured polyester and polyamide segments. The polyamide blocks are produced in a classical manner from petrochemical raw materials such as caprolactam or AH salt.

It is known to produce hexamethylenediamine by aminating hydrogenation of 1,6-hexanediol. According to such a method, until 1981, hexamethylenediamine was manufactured by Celanese in a plant with a capacity of about 30,000 tons per year. The amination was carried out at 200 ° C and 23 MPa with ammonia in the presence of Raney nickel. This HMD yields of about 90% were achieved. By-products were hexamethyleneimine (azepane) and 1,6-aminohexanol. A disadvantage of the economy of the Celanese process was that the 1, 6-hexanediol was elaborately prepared by the reaction of cyclohexanone with peracetic acid to caprolactone and subsequent catalytic hydrogenation of the caprolactone.

The US 3,215,742 also describes a process for the preparation of alkylenediamines, such as. For example, hexamethylenediamine, by reaction of the corresponding diols with ammonia. It is taught that hexamethyleneimine formed as an undesirable by-product can be recycled to the amination hydrogenation stage and further converted to hexamethylene diamine. The hexamethyleneimine can simultaneously serve as a solvent for the amination reaction.

US 3,520,933 uses cobalt, nickel and / or copper-containing catalysts for the aminating hydrogenation.

WO 2012/1 19929 describes inter alia the homogeneously catalyzed hydrogenating 1, 6-hexanediol amination to hexamethylenediamine.

It is known to use muconic acid for the production of alkanedicarboxylic acids and ε-caprolactam. WO 2012/141997 describes a process for the preparation of ε-caprolactam in which muconic acid is reacted with ammonia and hydrogen in the presence of a catalyst. It is also described that this reaction can proceed via an adipic acid intermediate and that the resulting caprolactam can be used to produce polyamide 6. The production of polyamide 6.6 from muconic acid is not described in this document.

WO 2010/085712 A2 describes a process for the preparation of dodecanedicarboxylic acid in which muconic acid is reduced to hexenedicarboxylic acid and the hexenedicarboxylic acid is reacted with an unsaturated fatty acid in a metathesis reaction.

According to H.-J. Arpe, Industrielle Organische Chemie, 6th edition (2007), Wiley-VCH-Verlag, pages 267 and 270, 1, 6-hexanediol can be prepared by hydrogenation of adipic acid or adipic diesters in the presence of Cu, Co or Mn catalysts. The synthesis is carried out at a temperature of 170 to 240 ° C and a pressure of 5 to 30 MPa. 1, 6-hexanediol can also be obtained by catalytic hydrogenation of caprolactone.

WO 99/25672 describes a process for preparing 1,6-hexanediol and 6-hydroxycaproic acid or their esters by catalytic hydrogenation of adipic acid. Re, adipic acid monoesters or adipic diesters, wherein the obtained in the distillation of the hydrogenation after separation of the hexanediol and hydroxycaproic acid bottom product, which contains substantially oligomeric esters of 6-hydroxy caproic acid, in the hydrogenation.

From EP 883 590 B1 it is known to use a carboxylic acid mixture (DCL) instead of pure adipic acid or adipic acid esters prepared from pure adipic acid. This is obtained as a by-product in the oxidation of cyclohexane with oxygen or oxygen-containing gases and by water extraction of the reaction mixture. The extract contains adipic acid and 6-hydroxycaproic acid as the main products and besides a variety of mono- and dicarboxylic acids. The carboxylic acids are esterified with a lower alcohol. Adipic diesters are separated by distillation from the esterification mixture and hydrogenated catalytically to 1, 6-hexanediol.

It is advantageous that the waste product DCL is very inexpensive compared to pure adipic acid. On the other hand, a considerable distillative effort has to be made to produce pure 1,6-hexanediol. The distillative separation of the 1,4-cyclohexanediols which are by-products is particularly difficult.

Adipic acid is conventionally synthesized by oxidation of cyclohexanol or cyclohexanone starting from benzene. But it can also be obtained in an environmentally friendly manner from biogenic sources.

US 4,968,612 describes a fermentation process for the preparation of muconic acid and the hydrogenation of the resulting muconic acid 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.

KM Draths and JW 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 Muconsäuresalzen. For the production of hexamethylenediamine and polyamide 6.6 nothing is said in this document.

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.

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

J.A. 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.

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 supported on titanium dioxide in solvents selected from methanol, ethanol, Butanol, acetone, toluene and water. The hydrogenations are carried out exclusively at an elevated temperature of 120 ° C. 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.

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.

EP 01 17048 A2 describes a process for the preparation of nylon 6,6-salt, in which toluene is converted to muconic acid by fermentation in the presence of hexamethylenediamine, to obtain a fermentation medium containing hexamethylenediamine. contains conat. From this fermentation medium, the microorganisms are separated and the Hexamethylendiaminmuconat hydrogenated to Hexamethylendiaminadipat. The resulting nylon 6,6 salt can be used to prepare polyamide 6,6. A disadvantage of this process is that the starting material is toluene, which does not come from renewable sources. It is also an essential feature of this process that a salt of the muconic acid with the diamine used for amide formation is used for the hydrogenation. The hydrogenation of free muconic acid or a muconic acid ester to adipic acid is not described in this document. US 2012/0196339 describes the preparation of industrially relevant compounds from prokaryotic organisms. Thus, starting from dehydroshikimate, the cis, cis-muconic acid can be prepared and further converted to adipic acid. Only in the context of drawing 1 A, the further implementation of nylon 6,6 is shown. However, this document contains not the slightest indication that the second component of nylon 6,6 production, the hexamethylenediamine, is also produced from a renewable raw material. In particular, therefore, any reference to how to integrate the production of adipic acid and of hexamethylenediamine into a single process starting from muconic acid is also lacking. Also with regard to the hydrogenation of cis, cis-muconic acid to adipic acid and their isolation and / or purification, the teaching of this document is completely unclear. Thus, in paragraph [0150] on page 17 of US 2012/0196339, the hydrogenation of muconic acid to adipic acid is mentioned as a general rule. However, neither a suitable solvent for the hydrogenation reaction nor for any purification of the adipic acid by recrystallization is mentioned. WO 2012/141993 A1 describes the preparation of hexamethylenediamine (HMDA) from muconic diesters, wherein the muconic diesters are amidated in a first step and then directly reduced to HMDA (Route 1) or dehydrated after the amidation to nitriles and then hydrogenated to HMDA (Route 2 ) or hydrogenated to adipamide after amidation, dehydrated to adiponitrile and then hydrogenated to HMDA (Route 3). This method has several disadvantages. Thus, the amidation with ammonia must be carried out at room temperature, takes 4 to 14 hours, the diamide is obtained only in moderate yield. A further disadvantage is that adjuvants such as POC and P2O5 are necessary for the elimination of water. These disadvantages could be overcome by the process according to the invention, according to which hexamethylenediamine is prepared by hydrogenation of muconic acid or adipic acid to 1, 6-hexanediol and its catalytic amination. Moreover, in the process described in WO 2012/141993 A1, only the hexamethylenediamine, but not the adipic acid, is produced from renewable raw materials. The present invention has for its object to provide an economical process for the production of polyamide 66. In particular, this process should not start from petrochemical C6 building blocks but from C6 building blocks that can be produced from renewable raw materials. The aim is to make the polyamide 66 available in high yield and purity.

It has now surprisingly been found that this object is achieved by subjecting a muconic acid starting material which is selected from muconic acid, esters of muconic acid, lactones of muconic acid and mixtures thereof, a reaction to adipic acid on the one hand and to hexamethylenediamine on the other hand. The lactones of muconic acid are especially suitable for the preparation of 1,6-hexanediol which, according to the invention, can serve as an important intermediate for the preparation of the hexamethylenediamine. In particular, the muconic acid used is derived from renewable (biogenic) sources.

SUMMARY OF THE INVENTION

A first aspect of the invention is a process for preparing polyamide 66 comprising: a) providing a muconic acid starting material selected from muconic acid, esters of muconic acid, lactones of muconic acid and mixtures thereof; b) at least the muconic acid starting material provided in step a) partially reacting with hydrogen in the presence of at least one hydrogenation catalyst Hb) to adipic acid, c1) the muconic acid starting material provided in step a) partially reacting with hydrogen in the presence of at least one hydrogenation catalyst

Hc1) to 1, 6-hexanediol, or c2) subjecting the adipic acid obtained in step b) partially to a reaction with hydrogen in the presence of at least one hydrogenation catalyst Hc2) to 1, 6-hexanediol, d) subjecting the 1,6-hexanediol obtained in step c1) or c2 to an amination in the presence of an amination catalyst to give hexamethylenediamine, e) at least part of the adipic acid obtained in step b) and the hexamethylenediamine obtained in step d) of a polycondensation subject to polyamide 66.

Another object of the invention is a polyamide 66 having a C ¹⁴ / C ¹² isotope ratio in the range of 0.5 x 10 ^"12 to 5 x 10 ^{" 12} .

A further subject of the invention is polyamide 66, which can be prepared starting from muconic acid synthesized from at least one renewable raw material. Specifically, the muconic acid starting material provided in step a) contains no salts of the muconic acid.

In a specific embodiment, the hydrogenation takes place in at least one of the steps b) and / or c1) and / or c2) in the liquid phase in the presence of water as solvent. In a more specific embodiment, the hydrogenation is carried out in at least one of steps b) and / or c1) and / or c2) in the liquid phase in the presence of water as the sole solvent.

It has surprisingly been found that the muconic acid can be hydrogenated in aqueous solvents and especially in water as the sole solvent in high yields to adipic acid and to 1, 6-hexanediol. Especially the high adipic acid yields are surprising, since in the light of the prior art was expected to significantly lower yields. Thus, it is known from Example 4 of WO 2010/148080 that on heating muconic acid in the presence of water, ie conditions such as also exist in the hydrogenation of cis, cis-muconic acid (but without hydrogen and catalyst), an isomerization to cis, trans-muconic acid (yield 69%) and its further reaction to an internal lactone (yield 25%) and its hydrolysis and decarboxylation to levulinic acid (yield 3%). In view of these results, the achievement of such a high adipic acid yield was not to be expected in the process according to the invention.

Muconic acid (2,4-hexadiene dicarboxylic acid) exists in three stereoisomeric forms, the ice, cis, cis, trans and trans, trans forms, which may be present as a mixture. All three forms are crystalline compounds with high melting points (decomposition), see, for. B. Römpp Chemie Lexikon, 9th edition, Volume 4, page 2867). It has been found that hydrogenation of Muconsäureschmelzen technically is hardly possible, since the most preferred hydrogenation temperatures are well below the melting points. Therefore, an inert solvent with the highest possible solubility for muconic acid would be desirable for the hydrogenation. At first glance, water as a solvent is unsuitable for the person skilled in the art, since muconic acid, in contrast to adipic acid, is poorly soluble in the temperature range from 20 to 100 ° C. As described above, WO 2010/148080 teaches that upon heating cis, cis-muconic acid in water under reflux and subsequent crystallization, cis-trans-muconic acid is obtained in only 69% yield. The remaining mother liquor no longer consists of muconic acid but contains lactones and other unknown reaction products. From these results, those skilled in the art would have expected substantially lower adipic acid yields in the hydrogenation of water-suspended muconic acid, according to a preferred embodiment of the present invention.

EMBODIMENTS OF THE INVENTION

More specifically, the invention includes the following preferred embodiments: FIG. A process for preparing polyamide 66 comprising: a) providing a muconic acid starting material selected from muconic acid, esters of muconic acid, lactones of muconic acid and mixtures thereof; b) the muconic acid starting material provided in step a) at least partially reacting with hydrogen in the presence at least one hydrogenation catalyst Hb) is subjected to adipic acid, d) the muconic acid starting material provided in step a) partially undergoes a reaction with hydrogen in the presence of at least one hydrogenation catalyst Hc1) to give 1,6-hexanediol, or c2) the adipic acid obtained in step b) is partially replaced by one Reacting with hydrogen in the presence of at least one hydrogenation catalyst Hc2) to give 1,6-hexanediol, the 1,6-hexanediol obtained in step c1) or c2) undergoes an amination in the presence of an amination catalyst to give hexamethylenediamine, e) at least part of the adipic acid obtained in step b) and the hexamethylenediamine obtained in step d) of a polycondensation subject to polyamide 66.

Process according to embodiment 1, wherein in step a) a muconic acid starting material is provided in which the muconic acid originates from a renewable source, the preparation of which is preferably carried out by biocatalytic synthesis from at least one renewable raw material.

The method of embodiment 1 or 2, wherein the Muconsaure used in step a) comprises a ¹⁴ C to ¹² C-lsotopenverhältnis in the range of 0.5x10 ^"12-5 ^χ 10- ^12th

Method according to one of embodiments 1 to 3, wherein the hydrogenation in step b) and / or in step c1) a muconic acid starting material is used, which is selected from muconic acid, Muconsäuremonoestern, Muconsäu- rediester, poly (muconic acid esters) and mixtures thereof.

Method according to one of embodiments 1 to 3, wherein for the hydrogenation in step c1) a muconic acid starting material is used which is selected from lactones (III), (IV) and (V) and mixtures thereof:

(III) (IV) The process according to any one of embodiments 1 to 5, wherein the hydrogenation catalyst Hb) is selected from Raney cobalt, Raney nickel and Raney copper. Method according to one of embodiments 1 to 6, wherein the hydrogenation in step b) takes place at a temperature which is in the range of 50 to 160 ° C. Method according to one of embodiments 1 to 7, wherein the hydrogenation in

Step c1) takes place in the liquid phase in the presence of a solvent which is selected from water, aliphatic C 1 to C 8 alcohols, aliphatic C 2 to C 6 diols, ethers and mixtures thereof.

Process according to one of embodiments 1 to 7, wherein the hydrogenation in step c1) takes place in the liquid phase in the presence of water as sole solvent. Process according to one of the embodiments 1 to 7, wherein for the hydrogenation in step c1) a muconic diester is used, which is selected from compounds of the general formula (II)

R ¹ OOC-CH = CH-CH = CH-COOR ² (II) in which the radicals R ¹ and R ² independently of one another represent straight-chain or branched C ¹ -C 8 -alkyl, the hydrogenation in step c1) being in the gas phase he follows. Method according to one of the preceding embodiments, wherein as the hydrogenation catalyst Hc1) in step c1) a homogeneous or heterogeneous transition metal catalyst is used, preferably a heterogeneous transition metal catalyst. Method according to one of embodiments 1 to 1 1, wherein in step c1) a muconic acid starting material is used, which is selected from muconic acid, Muconsäuremonoestern, lactones of the muconic acid and mixtures thereof and the hydrogenation catalyst Hc1) at least 50 wt .-% cobalt , Ruthenium or rhenium based on the total weight of the reduced catalyst. Method according to one of embodiments 1 to 1 1, wherein in step c1) a muconic acid starting material is used which is selected from muconic acid diesters, poly (muconic acid esters) and mixtures thereof and the hydrogenation catalyst Hc1) at least 50 wt .-% of copper on the total weight of the reduced catalyst.

Process according to one of the preceding embodiments, in which the hydrogenation catalyst Hc2) used in step c2) contains at least 50% by weight, based on the total weight of the reduced catalyst, of elements which are selected from rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel and copper.

Method according to one of the preceding embodiments, wherein the hydrogenation in step c2) takes place at a temperature which is in the range of 160 to 240 ° C. Method according to one of the preceding embodiments, wherein adipate-containing water, which is obtained in an isolation of the hydrogenation catalyst Hc2) after completion of step c2), is used as solvent in step b). Process according to one of the preceding embodiments, wherein the hydrogenation in step b) and / or the hydrogenation in step c1) and / or the hydrogenation in step c2) are carried out in n series-connected hydrogenation reactors, n being an integer of at least two stands. Method according to embodiment 17, wherein the 1. to (n-1). Reactor has a guided in an external circuit current from the reaction zone. Method according to one of the embodiments 17 or 18, wherein the hydrogenation is carried out adiabatically in the nth reactor. Process according to one of the preceding embodiments, wherein the 1,6-hexanediol obtained in step c1) or in step c2) is reacted with ammonia in step d) to form hexamethylenediamine in the presence of the amination catalyst. Method according to one of the preceding embodiments, wherein the amination in step d) is carried out with or without supply of hydrogen. A process according to any one of the preceding embodiments, wherein the reaction effluent of the amination in step d) is subjected to a separation to give a hexamethyleneimine-enriched fraction and a hexamethylenediamine-depleted fraction.

The process of embodiment 22, wherein the hexamethyleneimine enriched fraction is recycled to the amination in step d). 24. The method according to any one of the preceding embodiments, wherein in step d) hexamethyleneimine is used as the sole solvent.

Polyamide 66, characterized in that it comprises a C ¹⁴ / C ¹² -lsotopenverhältnis range of 0.5 x 10 ^"12 to 5 × ^{10." 12}

26. polyamide 66, characterized in that it can be prepared from biocatalytically at least one renewable raw material synthesized Muconsaure.

DETAILED DESCRIPTION OF THE INVENTION

In the context of the present invention, esters of the muconic acid are the esters with a separate (external) alcohol component. As lactones of muconic acid, the compounds (III) and (IV) obtainable by intramolecular Michael addition and the product (V) of the hydrogenation of the compound (III) are understood as meaning:

The lactone (V) can also be formed by intramolecular Michael addition of dihydromuconic acid.

Step a) The muconic acid provided in step a) of the process according to the invention preferably originates from renewable sources. For the purposes of the invention, this includes natural (biogenic) sources and non-fossil sources, such as crude oil, natural gas or coal. Preferably, the compound obtained in step a) of the invention driving provided muconic acid from carbohydrates, eg. As starch, cellulose and sugars, or lignin. 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 muconic acid used in step a) accordingly has preferably a C ^{^14-to-12} C lsotopenverhältnis in the range of 0.5 * 10 ¹² to 5x10 ^"12.

The production of muconic acid from renewable sources can be carried out by all methods known to those skilled in the art, preferably biocatalytically. The biocatalytic production of muconic acid from at least one renewable raw material is described, for example, in the following documents: US Pat. No. 4,968,612, US Pat.

WO 2010/148063 A2, WO 2010/148080 A2 and K. M. Draths and J. W. Frost, J. Am. Chem. Soc. 1994, 16, 339-400 and W. Niu et al., Biotechnol. Prog. 2002, 18, 201 - 21 1.

As stated previously, muconic acid (2,4-hexadiene dicarboxylic acid) exists in three isomeric forms, the cis, cis, cis, trans and trans, trans forms, which may be present as a mixture. For the purposes of the invention, the term "muconic acid" encompasses the different conformers of the muconic acid in any desired composition. [Sind Als] As starting materials for the reaction with hydrogen in step b) and / or in step c1) of the process according to the invention, all conformers of the muconic acid and / or or their esters and any mixtures thereof.

In a preferred embodiment, in step a) of the process according to the invention, a muconic acid starting material is provided which is enriched in cis, trans-muconic acid and / or its esters or which consists of cis, trans-muconic acid and / or their esters. Thus, cis, trans-muconic acid and their esters have a higher solubility in water and in organic media than cis, cis-muconic acid and trans, trans-muconic acid. If, in step a) of the process according to the invention, a muconic acid starting material is provided which comprises at least one component selected from cis, cis-muconic acid, trans, trans-muconic acid and / or their esters, this muconic acid starting material can be present before or during the hydrogenation in step b) or step c1) an isomerization to cis, trans-muconic acid or their esters are subjected. The isomerization of cis, cis-muconic acid to cis, trans-muconic acid is shown in the following scheme:

HO

OOH Suitable catalysts are, in particular, inorganic or organic acids, hydrogenation catalysts, iodine or UV radiation. Suitable hydrogenation catalysts are those described below. The isomerization can be carried out, for example, according to the method described in WO 201 1/08531 1 A1.

Preferably, the starting material for the reaction with hydrogen in step b) and / or in step c1) to at least 80 wt .-%, particularly preferably at least 90 wt .-% of cis, trans-muconic acid and / or their esters, based on the total weight of all muconic acid and Muconsäureester- conformers contained in the feedstock.

For the hydrogenation in step b) and / or in step c1), preference is given to using a muconic acid starting material which is selected from muconic acid, muconic acid monoesters, muconic diesters, poly (muconic acid esters) and mixtures thereof. For the hydrogenation in step b) it is also possible to use lactones of muconic acid. In the context of the present invention, the term muconic acid polyester also denotes oligomeric muconic acid esters which have at least one repeating unit derived from the muconic acid or the diol used for ester formation and at least two repeating units which are complementary thereto via carboxylic acid ester groups.

Preferably, the muconic acid monoester used is at least one compound of the general formula (I)

R OOC-CH = CH-CH = CH-COOH (I) used, wherein the radicals R ¹ independently of one another represent straight-chain or branched Ci-Cs-alkyl. As muconic acid diester, preference is given to at least one compound of the general formula (II)

R ¹ OOC-CH = CH-CH = CH-COOR ² (II) used, wherein the radicals R ¹ and R ² independently of one another represent straight-chain or branched Ci-Cs-alkyl.

Preferred as poly (muconic acid ester) is at least one compound of the general formula (VI)

(VI) used, in which x is an integer from 2 to 6, n is an integer from 1 to 100,

R ^{3 is} H, straight-chain or branched C 1 -C 5 -alkyl or a group HO- (CH 2) _x -

R ^{4 is} H or a group -C (= O) -CH = CH-CH = CH-COOR ⁵ , in which R ^{5 is} H or straight-chain or branched C 1 -C 8 -alkyl, with the proviso that for n = 1 either R ^{3 is} H and R ^{4 is} -C (= O) -CH = CH-CH = CHCOOROR ⁵ or R ^{3 is} a group HO- (CH ₂ ) x- and R ^{4 is} H.

In the context of the invention, the degree of polymerization of the poly (muconic acid ester) denotes the sum of repeating units which formally derive from muconic acid and repeating units which formally derive from diols HO- (CH 2) x -OH.

In a first preferred embodiment, for the hydrogenation in step b) and / or in step c1) a muconic acid starting material is used which is selected from muconic acid, muconic acid monoesters, muconic diesters, poly (muconic acid esters) and mixtures thereof.

In a second preferred embodiment, the hydrogenation in step b) uses a muconic acid starting material selected from lactones (III), (IV and (V) and mixtures thereof:

(III) (IV)

(V) In a first preferred embodiment, for the hydrogenation in step b) and / or in step c1) a muconic acid starting material is used which is selected from muconic acid, muconic acid monoesters, muconic diesters, poly (muconic acid esters) and mixtures thereof and the hydrogenation is carried out in the liquid phase.

Hydrogenation steps b), c1) and c2)

In a first embodiment of the process according to the invention, the hydrogenation takes place in step b) and / or in step c1) and / or in step c2) in the liquid phase in the presence of a solvent which is selected from water, aliphatic Ci- to Cs- Alcohols, C2 to C6 aliphatic diols, ethers and mixtures thereof. The solvent is preferably selected from water, methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol and tert-butanol, ethylene glycol, 1, 3-propanediol, 1, 4- Butanediol, 1, 5-pentanediol, 1, 6-hexanediol, tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, methyl tert-butyl ether and mixtures thereof. Aliphatic C to 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 hydrogenation in the liquid phase in step b) and / or in step c1) a solution is used which comprises 10 to 60% by weight of muconic acid or one of its esters, more preferably 20 to 50% by weight .-%, most preferably 30 to 50 wt .-%, contains.

In a second preferred embodiment, for the hydrogenation in step b) and / or c1) at least one muconic acid diester of the general formula (II)

R ¹ OOC-CH = CH-CH = CH-COOR ² (II) used, wherein the radicals R ¹ and R ^{2 are} independently straight-chain or branched Ci-Cs-alkyl and wherein the hydrogenation is carried out in the gas phase.

Suitable hydrogenation catalysts for the reaction in steps b), c1) and c2) are in principle the transition metal catalysts known to those skilled in the art for hydrogenating carbon-carbon double bonds. In general, the catalyst comprises at least one transition metal of groups 7, 8, 9, 10 and 1 1 of the period Systems according to IUPAC. Preferably, the catalyst comprises at least one transition metal selected from the group consisting of Mn, Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu and Au. Particularly preferably, the catalyst has at least one transition metal from the group Co, Ni, Cu, Re, Fe, Ru, Rh, Ir. The hydrogenation catalysts consist of the mentioned transition metals as such or comprise the said transition metals supported, as precipitation catalysts, as Raney catalysts or as mixtures thereof.

As inert carrier material for the hydrogenation catalysts used according to the invention in step b), c1) and c2), virtually all support materials of the prior art can be used

Technique which are advantageously used in the preparation of supported catalysts, for example carbon, S1O2 (quartz), porcelain, magnesium oxide, tin dioxide, silicon carbide, T1O2 (rutile, anatase), Al2O3 (alumina), aluminum silicate, steatite (magnesium silicate), zirconium silicate , Cersilikat or mixtures of these carrier materials, are used. Preferred support materials are carbon, alumina and silica. A particularly preferred carrier material is carbon. As the silica support material can silica materials of different origin and production, for. B. 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 S1O2 starting materials see: W. Büchner, R. Schliebs, G. Winter, KH Büchel: Industrial Inorganic Chemistry, 2nd ed., P. 532-533, VCH Verlagsgesellschaft, Weinheim 1986). The hydrogenation catalysts 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. B. in the form of pressed cylinders, tablets, pastilles, carriage wheels, rings, stars or extrudates, such as solid strands, polylobären strands, hollow strands and honeycomb bodies or other geometric bodies are used.

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, 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 strands of different lengths of 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 can mass customary tools, z. For example, lubricants such as graphite, polyethylene oxide, celluloses or fatty acids (such as stearic acid) and / or molding aids and reinforcing agents, such as glass fibers, asbestos or silicon carbide, are added.

The catalyst can be present under the hydrogenation conditions both as a homogeneous and as a heterogeneous catalyst. Preferably, the catalyst is present under the hydrogenation conditions as a heterogeneous catalyst. Specifically, the catalyst is present under the hydrogenation conditions in at least one of steps b) and / or c1) and / or c2) as a heterogeneous catalyst. More specifically, the catalyst is present under the hydrogenation conditions in each of steps b) and / or c1) and / or c2) as a heterogeneous catalyst.

If a heterogeneous catalyst is used, this can be applied, for example, to a reticulated carrier. Alternatively or additionally, the heterogeneous catalyst can be applied to the inner wall of a tubular support, wherein the tubular support is flowed through by the reaction mixture. Alternatively or additionally, the catalyst can be used as a particulate solid.

In a preferred embodiment, the hydrogenation takes place in at least one of steps b), c1) and c2) in the liquid phase and the catalyst is in the form of a suspension. In a specific embodiment, the hydrogenation in each of steps b), c1) and c2) takes place in the liquid phase and the catalyst is in the form of a suspension. If a liquid reaction product is removed from the reaction zone, the suspended catalyst can be kept in the reaction zone by retention methods known to those skilled in the art. These retention methods preferably comprise cross-flow filtration, gravity filtration and / or filtration by means of at least one filter candle.

In a specific embodiment of the process according to the invention, the hydrogenation takes place in at least one of steps b), c1) and c2) in n hydrogenation reactors connected in series (in series), where n is an integer of at least 2. Suitable values for n are 2, 3, 4, 5, 6, 7, 8, 9 and 10. Preferably, n is 3 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. tubular reactors, tube bundle reactors, gas circulation reactors, bubble columns, loop apparatuses, stirred tank (which can also be configured as Rührkesselkaskaden), air-lift reactors, etc.

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

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 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 can contain an inert material. be mixed. The reaction medium flowing through the fixed bed contains at least one liquid phase. The reaction medium may also contain a gaseous phase in addition. 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. Preferably, the continuous hydrogenation is carried out in at least one of the steps b), c1) and / or c2) in at least two fixed bed reactors connected in series (in series). The reactors are preferably operated in direct current. The feeding of the feed streams can be done both from above and from below. If desired, in a hydrogenation apparatus of n reactors, at least two of the reactors (ie, 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 setting of the reacted in the respective reactor portion of compound to be hydrogenated can, for. B. on the reactor volume and / or the residence time in the reactor. For removing 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. Preferably, the hydrogenation is carried out in n series-connected hydrogenation reactors, where n is an integer of at least two, and wherein at least one reactor has a guided in an external circuit stream from the reaction zone (external recycle stream, liquid circulation, 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 straight-through operation basically excludes backmixing internals and / or stirring devices in the reactor. If the hydrogenated reaction mixture in one of the reactors downstream of the first reactor (ie the 2nd to nth reactor) has only small amounts of hydrogenatable muconic acid, then the heat of reaction occurring during the reaction is insufficient to maintain the desired temperature in the reactor. it may also be necessary to heat the reactor (or individual reaction zones of the second reactor). This can be done analogously to the previously described removal of the heat of reaction by heating an external circulation stream 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 the compound to be hydrogenated 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 of the mth reactor and the combined streams then fed to the mth reactor , Furthermore, the feed stream of the compound to be hydrogenated and / or another feed stream can be heated by means of a heat exchanger which is operated with withdrawn 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. Thus, the reaction mixture as it flows through the second reactor generally undergoes a temperature increase 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 is a reactor cascade of two reactors connected in series, wherein the reaction is carried out adiabatically in the second 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.

In one embodiment, additional mixing can take place in at least one of the reactors used. An additional mixing is particularly advantageous if the hydrogenation takes place at high residence times of the reaction mixture. For mixing z. For example, the streams introduced into the reactors can be used by introducing them into the respective reactors via suitable mixing devices, such as nozzles. For mixing, it is also possible to use streams in an external circuit from the respective reactor.

In order to complete the hydrogenation, the first (n-1) th reactor is each discharged from an outlet which still contains hydrogenatable components and is 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 the subsequent Reactor fed separately. 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 recycled as a circulating stream to the reactor, to which it has been removed and the second partial flow fed to the subsequent reactor. 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 possibility for controlling the heat balance is to control the inlet temperature of the inlet of the compound to be hydrogenated. 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 hydrogenation catalyst used can thus be extended as a rule.

Hydrogenation step b)

In step b) of the process according to the invention, the muconic acid starting material provided in step a) is at least partially subjected to a reaction with hydrogen in the presence of at least one hydrogenation catalyst Hb) to give adipic acid.

Preferably, the hydrogenation catalyst Hb) is selected from Raney cobalt, Raney nickel and Raney copper.

The hydrogenation in step b) is preferably carried out at a temperature in the range from 50 to 160.degree. C., more preferably from 60 to 150.degree. C., very particularly preferably from 70 to 140.degree. Step b) can be carried out, for example, using at least one loop reactor. In a specific embodiment, a combination of at least one loop reactor and at least one subsequent tubular reactor is used for the reaction in step b). But it is also possible to get along with a loop reactor. According to this embodiment, it is preferred if two temperature zones are provided in the loop reactor. Also in this embodiment, a run in a straight passage tubular reactor can connect. The hydrogenation in step b) is preferably carried out in bottom or trickle mode.

Hydrogenation step c1)

Hydrogenation of muconic acid, muconic acid monoesters and lactones In a first process variant, a muconic acid starting material is used for the hydrogenation in step c1), which is selected from muconic acid, muconic monoesters, lactones of muconic acid and mixtures thereof. According to this process variant, the hydrogenation in step c1) is preferably carried out using a hydrogenation catalyst which contains at least 50% by weight of cobalt, ruthenium or rhenium, based on the total weight of the reduced catalyst.

If catalysts which contain at least 50% by weight of cobalt are used for the hydrogenation, they may furthermore contain, in particular, phosphoric acid and / or further transition metals, preferably copper, manganese and / or molybdenum.

The preparation of a suitable catalyst precursor is known from DE 2321 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.

Hydrogenation of muconic diesters and muconic acid polyesters

In a first process variant, a muconic acid starting material is used for the hydrogenation in step c1), which is selected from muconic diesters, poly (muconic acid esters) and mixtures thereof.

According to this process variant, the hydrogenation in step c1) is preferably carried out using a hydrogenation catalyst which contains at least 50% by weight of copper, based on the total weight of the reduced catalyst. Such catalysts are preferably used for the hydrogenation of Muconsäureestern.

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 subgroups I and VI. to VIII. of the Periodic Table of the Elements, preferably copper, chromium, molybdenum, manganese, rhenium, ruthenium, cobalt, nickel or palladium, particularly preferably copper, cobalt or rhenium.

The cobalt, ruthenium or rhenium-containing catalysts mentioned above can also be used in the hydrogenation of the muconic acid diesters, oligoesters and polyesters. However, it is preferred to use at least 50% by weight of copper (based on the total weight of the reduced catalyst) containing catalysts instead of these catalysts.

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, ZrO 2, ZnO, BaO and MgO 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 by thermal treatment in the oxides. 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 intermediates 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. Further suitable as catalysts having 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 contained. 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. These catalysts are particularly suitable for all the ester hydrogenations mentioned.

The hydrogenation in step c1) can be carried out batchwise or continuously, with continuous hydrogenation being preferred. The hydrogenation in step c1) can be carried out in the gas phase or in the liquid phase.

In a specific embodiment, the hydrogenation in step c1) uses a hydrogenation device comprising at least 2 reactors or at least one reactor having at least two reaction zones. Then, the hydrogenation is carried out initially in a temperature range of 50 to 160 ° C and then in a temperature range of 160 to 240 ° C.

The catalyst loading in continuous operation is preferably 0.1 to 2 kg, more preferably 0.5 to 1 kg of starting material to be hydrogenated per kg of hydrogenation catalyst and hour.

The molar ratio of hydrogen to muconic acid starting material is preferably from 50: 1 to 10: 1, more preferably from 30: 1 to 20: 1. According to the invention, the muconic acid starting material is selected from muconic acid, esters of muconic acid, lactones of muconic acid and mixtures thereof.

If, for the hydrogenation in step c1), a muconic acid starting material is used which is selected from at least two of the abovementioned compounds, the amount of hydrogen used, depending on the proportion of the compounds to be hydrogenated, is selected according to the abovementioned design rule.

The conversion in the first reactor, based on adipic acid or adipic acid ester formed, is preferably at least 70%, more preferably at least 80%. The total conversion in the hydrogenation, based on hydrogenatable starting material, is preferably at least 97%, particularly preferably at least 98%, in particular at least 99%. The selectivity in the hydrogenation, based on formed 1,6-hexanediol, is preferably at least 97%, particularly preferably at least 98%, in particular at least 99%.

Hydrogenation step c2)

In step c2), the adipic acid obtained in step b) is partially subjected to a reaction with hydrogen in the presence of at least one hydrogenation catalyst Hc2) to 1, 6-hexanediol. Preferably, the hydrogenation catalyst used in step c2) Hc2) 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. For hydrogenating adipic acid, adipic acid monoesters and adipic diesters, it is particularly preferred that the catalyst Hc2) contains at least 50% by weight of elements selected from the group consisting of rhenium, ruthenium and cobalt. For hydrogenating an adipic acid oligoester or polyester, it is particularly preferred that the catalyst c2) contains at least 50% by weight of copper.

The hydrogenation in step c2) is preferably carried out at a temperature which is in the range from 160 to 240 ° C., particularly preferably from 170 to 230 ° C., very particularly preferably from 170 to 220 ° C. Step c2) can be carried out, for example, using at least one loop reactor. In a specific embodiment, a combination of at least one loop reactor and at least one subsequent tubular reactor is used for the reaction in step c2). But it is also possible to get along with a loop reactor. According to this embodiment, it is preferred if two temperature zones are provided in the loop reactor. Also in this embodiment, a run in a straight passage tubular reactor can connect. The hydrogenation in step c2) is preferably carried out in bottom or trickle mode. Working up of 1,6-hexanediol from step c1) or c2)

In a preferred embodiment of the process according to the invention, the discharge from the hydrogenation in step c1) or c2) is subjected to a distillative separation to obtain a fraction enriched in 1,6-hexanediol and the fraction enriched in 1,6-hexanediol for the amination in step d ) used.

In a hydrogenation variant after step c1), muconic acid in water is used as solvent for the hydrogenation. The reaction product obtained in the hydrogenation of muconic acid in step c1) in water as solvent provides an aqueous 1, 6

Hexanediol solution. After cooling and relaxing the hydrogenation, the water is preferably removed by distillation and 1, 6-hexanediol can be obtained in high purity (> 97%). If the muconic acid hydrogenation is carried out in a hydrogenation variant after step c1), for example in methanol as solvent, a part of the muconic acid is converted in situ into the muconic acid monomethyl and muconic acid dimethylester. The hydrogenation is a solution of 1, 6-hexanediol in a mixture of methanol and water. By distillation, methanol and water are separated from 1, 6-hexanediol. Methanol is preferably separated from water and recycled to the hydrogenation. Water is discharged.

If n-butanol or isobutanol is used as the solvent in the hydrogenation of the mucous acid, a liquid two-phase mixture is obtained after cooling and venting of the hydrogenation effluent. The aqueous phase is separated from the organic phase by phase separation. The organic phase is distilled. Butanol is separated off as the top product and is preferably recycled to the muconic acid hydrogenation. 1, 6-hexanediol can, if necessary, be further purified by distillation. If muconic acid diesters are used for the hydrogenation, largely anhydrous solutions of 1,6-hexanediol are obtained, which can be worked up by distillation to give pure 1,6-hexanediol. The resulting alcohols are preferably recycled to the esterification step. In the hydrogenation of muconic acid oligo- and polyesters containing 1,6-hexanediol as the diol component, a predominantly composed of 1,6-hexanediol precipitates

Hydrogenation on. Step d)

In step d) of the process according to the invention, the 1,6-hexanediol obtained in step c1) or c2) is subjected to an amination in the presence of an amination catalyst to obtain hexamethylenediamine.

The 1,6-hexanediol is preferably reacted with ammonia in step d) to form hexamethylenediamine in the presence of the amination catalyst. 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 is more than 50% by weight in the catalyst (calculated without carrier) The catalysts can be used as unsupported catalysts, ie without catalyst carrier or as carrier catalysts. The supports used are preferably S1O2, Al2O3, T1O2, ZrO2, 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 type suspension catalysts use.

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 containing 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, 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.

It may be advantageous to completely or partially dehydrate part of the aqueous 1,6-hexanediol obtained in step c1) or c2). In the case of partial dehydration, it is possible, for example, to remove 50%, preferably 70%, particularly preferably 90%, of the water present in the crude 1,6-hexanediol. This can be z. B. by evaporation of the water at 50 to 90 ° C at reduced pressure (eg., On a rotary evaporator) or by distillation.

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.

In one embodiment of the invention, the amination of 1,6-hexanediol with ammonia takes place in a first substep d1) 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 d2) together with hexamethylenediamine from unreacted 1, 6-hexanediol and reacted in a partial step d3) 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 He- xamethylenediamine have very similar vapor pressures, pure hexamethylenediamine is discharged. Mixtures of 1-amino-6-hydroxyhexane and hexamethylenediamine are recycled to the distillation stage. In a further, particularly preferred embodiment, the hexamethyleneimine formed in the amination of 1,6-hexanediol is separated by distillation from the amination discharge and recycled to the amination stage. If the recycled hexamethyleneimine amount is 34% by weight (based on the total weight of 1,6-hexanediol and hexamethyleneimine), then advantageously no additional hexamethyleneimine is formed. Hexamethyleneimine can be separated by distillation as an azeotrope with water.

The resulting hexamethylenediamine may be subjected to further purification. This preferably comprises at least one distillation step. In a specific embodiment, the obtained hexamethylenediamine is brought to "fiber quality" by fractional distillation (i.e., a hexamethylenediamine content of at least 99.9%). If the compounds containing 2-aminomethylcyclopentylamine (AMCPA) and / or 1,2-diaminocyclohexane (DACH) are by-produced with hexamethylenediamine, these can be prepared according to US Pat. No. 6,251,229 B1 at pressures of from 1 to 300 mbar using pressure-loss-poor Separate distillation columns.

Step e) In the process of this invention can be synthesized polyamide 66 having a C ¹⁴ / C ¹² -lsotopenverhältnis in the range of 0.5 x 10 ^"12 to 5 × ^{10." 12}

In one embodiment of the invention, adipic acid prepared in step b) is polycondensed with the hexamethylenediamine prepared in step d) to form polyamide 66. This is preferably carried out in the following substeps: e1) reacting adipic acid and hexamethylenediamine in a molar ratio of essentially 1: 1 to hexamethylenediammonium adipate (AH salt), and e2) reacting the hexamethylenediammonium adipate to polyamide 66 at a temperature of not more than 275 ° C.

In order to achieve high molar masses of the polyamide 66, adipic acid and hexamethylenediamine should in this case be combined as exactly as possible in a molar ratio of 1: 1. In particular, it is possible to work in accordance with a rule which consists of Hans-Georg Elias, Macromolecules, 4th edition, pages 796 to 797, Hüthig-Verlag (1981) is known.

In another embodiment of the invention, muconic acid prepared in step a) is polycondensed with the hexamethylenediamine prepared in step d) to give polyamide 66 (see EP 1 17048 A2). This is preferably carried out in the following substeps: e1.1) reacting muconic acid and hexamethylenediamine in a molar ratio of essentially 1: 1 to hexamethylenediammonium muconate,

e1.2) hydrogenating the hexamethylenediammonium muconate to hexamethylenediammonium adipate, and

e2) Reaction of the hexamethylenediammonium adipate to polyamide 66. In order to achieve high molar masses of the polyamide 66, muconic acid and hexamethylenediamine should in this case be combined as accurately as possible in a molar ratio of 1: 1.

The reaction of the hexamethylenediammonium adipate to give polyamide 66 takes place in particular in the presence of water at a temperature of not more than 280 ° C., more preferably of not more than 275 ° C.

The invention will be further illustrated by the following non-limiting examples.

Examples Example 1:

Preparation of muconic acid cis, cis-muconic acid was prepared according to the procedure in K.M. Draths, J.W. Frost, J. Am. Chem. Soc., 1 16 (1994), pages 399-400 by means of the Escherichia coli mutant

AB2834 / pKD136 / pKD8.243A / pKD8.292 biocatalytically produced from D-glucose. Example 2:

Representation of adipic acid

A suspension of 24 g of the cis, cis-muconic acid and 1 g of Raney Ni in 56 g of water was introduced into a 250 ml stirring autoclave, 3 MPa of hydrogen were pressed in and heated to 80 ° C. After reaching the temperature of 80 ° C, the pressure was increased to 10 MPa and replenished so much hydrogen that the pressure remained constant. After 12 h reaction time was cooled to a temperature of 60 ° C, depressurized to atmospheric pressure and the solution was filtered from the catalyst. It was then slowly cooled to 20 ° C and thereby crystallized adipic acid as a white solid. In addition to adipic acid, lactone (V) could be detected in the solution. The yield of adipic acid was 95% and of lactone (V) 5%. The adipic acid and lactone (V) containing mother liquor is recycled to the hydrogenation stage. Example 3:

Preparation of 1, 6-hexanediol

15 g / h of a mixture of 33% of adipic acid and 67% of water, at a feed temperature of 70 ° C in a 30 ml tube reactor in which 20 ml of catalyst (66% CoO, 20% CuO, 7.3% Mn ₃ 0 ₄ , 3.6% Mo0 ₃ , 0.1% Na ₂ 0, 3% H ₃ P0 ₄ , preparation according to DE 23 21 101 A, 4 mm strands, activation with hydrogen up to 300 ° C) were, in trickle mode hydrogenated at a temperature of 230 ° C and a pressure of 25 MPa. The reactor effluent was separated in a separator of excess hydrogen (amount of flue gas 2 l / h) and reached on the one hand via a pump as recycle stream back to the head of the reactor, where it is combined with the feed stream (inlet: circulation = 1:10), and on the other hand in a discharge vessel. The discharges were analyzed by gas chromatography (% by weight, method with internal standard). The yield of 1, 6-hexanediol was 94%, the conversion of adipic acid was 98.5%. Other products that were found were 3% 6-hydroxycaproic acid, 1% 6-hydroxycaproic acid 1,6-hexanediol ester and 1% hexanol.

Preparation of hexamethylenediamine:

The preparation of hexamethylenediamine from 1,6-hexanediol based on muconic acid was carried out analogously to US Pat. No. 3,215,742, Examples 1 and 2.

Example 4:

Amination of 1,6-hexanediol

The water content of the crude 1,6-hexanediol prepared according to Example 3 of this application was lowered to 5% by weight by evaporation at 70 ° C. and water-jet vacuum.

193 g of crude 1,6-hexanediol were reacted with the amounts of dioxane, Raney nickel and liquid ammonia described in Example 1 in an autoclave at 200 ° C. for 5 hours and stirred 200 bar. Then the autoclave was cooled and relaxed. Gas chromatographic analysis of the reaction showed that 55% of the 1,6-hexanediol had been converted into a mixture consisting of 65% hexamethylenediamine and 35% hexamethylimine.

Example 5:

Amination of mixtures of crude 1, 6-hexanediol and hexamethyleneimine

17 g of partially dehydrated crude 1,6-hexanediol and 54 g of hexamethyleneimine were dissolved in 50 g of dioxane. This solution was stirred in an autoclave together with 540 g of liquid ammonia and 72 g of Raney nickel at 180 to 183 ° C for six hours. The autoclave was cooled and relaxed. Gas chromatographic analysis revealed that the 1,6-hexanediol conversion was 35%. The Hexamethylendiamin- yield was 98%, based on reacted 1,6-hexanediol.

Claims

Patent claims

Process for producing polyamide 66, in which a) a muconic acid starting material is provided which is selected from muconic acid, esters of muconic acid, lactones of muconic acid and mixtures thereof, b) the muconic acid starting material provided in step a) is at least partially reacted with hydrogen in the presence of at least one hydrogenation catalyst Hb) to give adipic acid, c1) the muconic acid starting material provided in step a) is partially subjected to a reaction with hydrogen in the presence of at least one hydrogenation catalyst Hc1) to give 1,6-hexanediol, or c2) the adipic acid obtained in step b). partially subjected to a reaction with hydrogen in the presence of at least one hydrogenation catalyst Hc2) to give 1,6-hexanediol, d) subjecting the 1,6-hexanediol obtained in step c1) or c2) to an amination in the presence of an amination catalyst to obtain hexamethylenediamine, e) subjecting at least part of the adipic acid obtained in step b) and the hexamethylenediamine obtained in step d) to a polycondensation to obtain polyamide 66.

Method according to claim 1, wherein in step a) a muconic acid starting material is provided, in which the muconic acid comes from a renewable source, the production of which is preferably carried out by biocatalytic synthesis from at least one renewable raw material.

The method according to claim 1 or 2, wherein the muconic acid used in step a) has a ¹⁴ C to ¹² C isotope ratio in the range of 0.5x 10 ^"12 to 5x10 ^"12 .

4. The method according to any one of claims 1 to 3, wherein for the hydrogenation in step b) and / or in step c1) a muconic acid starting material is used, which is selected from muconic acid, muconic acid monoesters, muconic diesters, poly (muconic acid esters) and mixtures thereof.

5. The method according to any one of claims 1 to 3, wherein for the hydrogenation in step c1) a muconic acid starting material is used which is selected from the lactones (III), (IV) and (V) and mixtures thereof:

6. The method according to any one of claims 1 to 5, wherein the hydrogenation catalyst Hb) has at least one transition metal selected from the group Co, Ni, Cu, Re, Fe, Ru, Rh, Ir.

7. The method according to any one of claims 1 to 6, wherein the hydrogenation catalyst Hb) is selected from Raney cobalt, Raney nickel and Raney copper.

8. The method according to any one of claims 1 to 7, wherein the hydrogenation in step b) takes place at a temperature which is in the range from 50 to 160 ° C.

9. The method according to any one of the preceding claims, wherein the hydrogenation in at least one of steps b) and / or c1) and / or c2) takes place in the liquid phase in the presence of water as a solvent.

10. The method according to any one of the preceding claims, wherein the hydrogenation in at least one of steps b) and / or c1) and / or c2) takes place in the liquid phase in the presence of water as the sole solvent.

1 1 . Process according to one of the preceding claims, wherein the catalyst is present as a heterogeneous catalyst under the hydrogenation conditions in at least one of steps b) and/or c1) and/or c2).

12. The method according to any one of the preceding claims, wherein the hydrogenation in at least one of steps b), c1) and c2) takes place in the liquid phase and the catalyst is in the form of a suspension.

Process according to one of claims 1 to 12, wherein the hydrogenation in step c1) takes place in the liquid phase in the presence of a solvent selected from water, aliphatic d- to Cs-alcohols, aliphatic C2- to C6-diols, ethers and mixtures from it.

14. The method according to any one of claims 1 to 12, wherein the hydrogenation in step c1) takes place in the liquid phase in the presence of water as the sole solvent. 15. The method according to any one of claims 1 to 7, wherein for the hydrogenation in step c1) a muconic acid diester is used which is selected from compounds of the general formula (II)

R ¹ OOC-CH=CH-CH=CH-COOR ² (II) in which the radicals R ¹ and R ² independently represent straight-chain or branched Ci-Cs-alkyl, the hydrogenation in step c1) taking place in the gas phase.

Method according to one of the preceding claims, wherein a heterogeneous transition metal catalyst is used as the hydrogenation catalyst Hc1) in step c1).

Method according to one of the preceding claims, wherein in step c1) a muconic acid starting material is used which is selected from muconic acid, muconic acid monoesters, lactones of muconic acid and mixtures thereof and a heterogeneous hydrogenation catalyst Hc1) which has at least 50% by weight is used. % cobalt, ruthenium or rhenium based on the total weight of the reduced catalyst, or in step c1) a muconic acid starting material is used which is selected from muconic diesters, poly(muconic acid esters) and mixtures thereof and a heterogeneous hydrogenation catalyst Hc1) is used , which contains at least 50% by weight of copper based on the total weight of the reduced catalyst.

18. The method according to any one of the preceding claims, wherein the hydrogenation catalyst Hc2) used in step c2) contains at least 50% by weight of elements selected from rhenium, iron, ruthenium, cobalt, rhodium, iridium, based on the total weight of the reduced catalyst , nickel and copper.

19. The method according to any one of the preceding claims, wherein the hydrogenation in step c2) takes place at a temperature which is in the range from 160 to 240 ° C.

Method according to one of the preceding claims, wherein water containing adipic acid, which is obtained during isolation of the hydrogenation catalyst Hc2) after completion of step c2), is used as a solvent in step b).

Method according to one of the preceding claims, wherein the hydrogenation in step b) and/or the hydrogenation in step c1) and/or the hydrogenation in step c2) is carried out in n hydrogenation reactors connected in series, where n represents an integer of at least two and where the 1st to (n-1 ). Reactor has a stream from the reaction zone carried in an external circuit and the hydrogenation is carried out adiabatically in the nth reactor.

Method according to one of the preceding claims, wherein the 1,6-hexanediol obtained in step c1) or in step c2) is reacted in step d) with ammonia in the presence of the amination catalyst to give hexamethylenediamine.

Method according to one of the preceding claims, wherein the amination in step d) is carried out without or with the addition of hydrogen.

24. The method according to any one of the preceding claims, wherein the reaction product of the amination in step d) undergoes a separation to obtain a hexamethyleneimine enriched and a hexamethylenediamine depleted

Fraction is subjected and the fraction enriched in hexamethyleneimine is returned to the amination in step d).

25. The method according to any one of the preceding claims, wherein in step d) hexamethyleneimine is used as the only solvent.

26. Polyamide 66, characterized in that it has a C ¹⁴ /C ¹² isotope ratio in the range of 0.5 x 10 ^"12 to 5 x 10 ^"12 .

27. Polyamide 66, characterized in that it can be produced starting from muconic acid synthesized biocatalytically from at least one renewable raw material.