Process for the preparation of triethylenediamine (TEDA)

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DESCRIPTION

Procedure to obtain trimethylenediamine (TEDA).

The present invention relates to a process for obtaining triethylenediamine (TEDA) by reacting ethylenediamine (EDA) in the presence of a zeolite catalyst.

Triethylenediamine (TEDA = DABCO® = 1,4-diazabicyclo- [2,2,2] -octane) is an important chemical raw material and finds application, among other things, in the manufacture of pharmaceutical products and synthetic materials. , especially as a catalyst in the manufacture of polyurethanes.

The known processes for obtaining TEDA differ fundamentally in the type of starting materials and catalysts. In principle, it is advantageous to use suitable basic chemicals as starting materials, such as, for example, lamonoethanolamine (MEOA) or ethylenediamine (1,2-diaminoethane, EDA). However, traditional procedures have proven not very selective, especially with regard to the EDA educt. Furthermore, the separation of the impurities that are formed during the cyclization reaction is difficult, so that these processes cannot be carried out on an industrial scale.

The procedure described in US publication 3,285,920 (HG Muhlbauer et al., Jefferson Chemical Co.) for the simultaneous preparation of TEDA and piperazine (hereinafter called PIP), is a 2-step process, according to which EDA is reacted first. , ethanolamine and / or its oligomers, in the presence of ammonia and hydrogen to give a mixture formed by piperazine and N- (beta-aminoethyl) -piperazine in a reduction amination process with the application of hydrogenation catalysts of the metal oxide type and the remaining residue is cyclized -after removal of the piperazine- in the presence of catalysts for cyclization such as phosphate salts and aluminosilicates. Returns on TEDA are approximately 25%, returns on PIP are approximately 12%.

Publication US-A-2,937,176 (Houdry Process Corp.) refers to obtaining TEDA by reaction in the gas phase of an alkylenepolyamine or an alkanolamine in the presence of a solid acid catalyst, such as silica-alumina, at temperatures from 300 to 500 ° C. Purification of TEDA is carried out by crystallization from hydrocarbons, preferably from pentane.

The publication DE-A-24 34 913 (Shunan Petrochemicals) (equivalent: US-A-3, 956,329) describes the use of pentasilzeolites for the synthesis of TEDA from amines such as N-aminoethylpiperazine, PIP or EDA by reaction of type A, X and Y zeolites of the general formula a (M_{2 / n}O) (Al₂OR₃) m (SiO₂) with M = alkali metal, alkaline earth metal, element of the zinc group, II 'or NH₄+; n = valence of the cation; a = 1.0 ± 0.5; n = 2-12. The zeolites are treated, for their transformation into the desired form, with an aqueous solution of hydrochloric acid to give an ion exchanger with hydrogen cations or with metal halides to give ion exchangers with the desired metal cations.

Publication EP-A-158 319 (Union Carbide Corp.) refers to the preparation of 1-aza-bicyclo [2.2.2] octane and 1,4-diaza-bicyclo [2.2.2] octanes from amines acyclic or heterocyclic in the presence of a "high-silica zeolite" catalyst ("high-silica zeolite").

From the publications EP-A-313 753 (equivalent: DE-A1-37 35 212) and EP-A-312 734 (equivalent: DEA1-37 35 214) (both Hüls AG) a process for obtaining a PIP / TEDA mixture by reacting ethanolamines and / or ethylenediamine in the presence of a zeolite of the pentasyl type. According to the procedure, the reaction product is passed at 280 to 380 ° C, with a LHSV (liquid hourly space velocity) of 0.1 to 10 h¹ and at an absolute pressure of 0.1 to 10 bar, in gaseous form, through a solid bed catalyst. It has also been proposed to use the starting compounds together with a diluent, such as for example water. Selectivities are reached in TEDA of a maximum of 46%.

According to the publication EP-A-382 055 (equivalent: DE-A-39 03 622, BASF AG), 1,2-diaminoethane (EDA) and from 0 to 200 mol% of piperazine are reacted on silicate silicate zeolites. aluminum, boron, gallium and / or iron under the following preferred reaction conditions, in the case of a reaction in liquid phase, to give TEDA: reaction temperature from 100 to 300 ° C, pressure from 1 to 5 bars and WHSV from 1 to 10 h ¹. Preferably, the reaction is carried out in the gas phase at a reaction temperature of 200 to 400 ° C, at a pressure of 0.5 to 5 bar and with a WHSV of 1 to 10 h.^-1. A solvent or diluent can be added, such as water. In the preferred form of work, in the gas phase, yields in TEDA of up to 70% are obtained. As a preferred form of preparation, after the zeolite has been molded, a treatment with aqueous hydrochloric acid and then calcination at 400 to 500 ° C is described.

Publication EP-A-423 526 (equivalent: DE-A-39 34 459, Bayer AG) describes a process for obtaining TEDA and PIP by reacting EDA on pentasyl-type zeolites with weakened acidity. Such zeolites would be obtained, according to this application, by exchanging at least 50% of all the exchangeable cations for alkali cations or they are those, in which the aluminum of the zeolite structure has been replaced in an isomorphic way by iron. According to this application, the ZSM-5 catalysts that have not been treated according to this procedure have been found to be less suitable. The conversion is carried out at a temperature from

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300 up to 400 ° C and with a catalyst load from 0.03 to 2.0 kg (EDA) / kg (zeolite) / h, using EDA / water mixtures with 2 to 25 moles, preferably with 5 to 15 moles of water per mole of EDA. Selectivities are reached, in relation to the TEDA, of up to 65%.

Publication US-A-4,966,969 (Idemitsu Kosan) describes a method for obtaining TEDA from compounds, containing amine, such as, for example, monoethanolamine, ethylenediamine, piperazine or piperazine derivatives, on metal silicates of the pentasyl type with ratios between SiO₂/To the₂OR₃ greater than 12, which have been calcined at 400 to 600 ° C, at reaction temperatures from 100 to 500 ° C and at pressures from 3 bars.

In US-A-5,041,548 (Idemitsu Kosan Ltd.) it is proposed, among other things, to use pentasyl zeolites (SiO₂/ M₂OR₃: for example H-ZSM5, SiO₂/To the₂OR₃ = 45-90), which have been obtained in the presence of an organic model, such as tetraalkylammonium compounds, in the reaction of amine-containing compounds, such as, for example, monoethanolamine, ethylenediamine or piperazine, to obtain the TEDA. In the reaction of EDA / water mixtures, TEDA yields of 45% are achieved at 400 ° C. The zeolites of the pentasyl type, which have been prepared without an organic model, present in the reactions of the compounds containing amine, at 350-400 ° C, significantly worse yields in TEDA.

The publications EP-A-831 096, EP-A-842 936 and EP-A-952 152 (Air Products and Chemicals Inc.) describe processes for obtaining TEDA from EDA or monoethanolamine using of specially modified pentasyl zeolites:

According to the publication EP-A-831 096 (equivalent: US-A-5,731,449) it can be achieved by means of a bleach treatment of a pentasyl zeolite (Na-ZSM5, SiO₂/To the₂OR₃ = 160), which was then transformed with NH solution₄NOT₃ and calcination, in the H + form (H-ZSM5, SiO₂/To the₂OR₃ = 153), an increase in selectivity relative to TEDA from 23 to 56% and in storage stability up to 32 hours without visible deactivation in the reaction of an EDA / water mixture at 340 ° C, versus zeolites that have not been treated. The effect is explained by the passivation of the active centers (hydroxyl groups, analysis with IR spectroscopy) on the most extreme external surfaces.

According to the publication EP-A-842 936 (equivalent: US-A-5,741,906) the outer surface can also be passivated, further away from the pentasyl zeolites (H-ZSM5, SiO₂/To the₂OR₃ = 180), by pretreatment with a dealumination reagent (chelating for the removal of aluminum, for example oxalic acid) and thus an improved selectivity is achieved in the synthesis of TEDA from monoethanolamine, from piperazine and water, at 350 ° C, up to 30%, compared to zeolites that have not been treated.

According to the publication EP-A-952 152 (equivalent: US-A-6,084,096) a surface passivation of the pentasyl zeolites can also be achieved by means of treatment with a silicon compound and then calcination. By treating a very finely crystallized pentasyl zeolite (H-ZSM5, SiO₂/To the₂OR₃ = 90, crystallite size: 0.07 μιη) with a solution of tetraethoxysilane in ethanol and subsequent calcination could be increased, for example, with a slight loss of activity, for the reaction of a EDA / water mixture, at 340 ° C, selectivity with respect to TEDA and PIP from 81% to 89% against untreated material.

Publication EP-A-842 935 (equivalent: US-A-5,756,741) (Air Products and Chemicals Inc.) describes a two-step process, in which, first, a piperazine-rich intermediate is prepared from of an amino compound by cyclization reaction, which is then transformed, with the addition of, for example, EDA on a pentasyl zeolite, to give TEDA. This special two-step procedure would minimize or even eliminate the need for a recycle of the PIP to the TEDA synthesis.

Publication EP-A-1 041 073 (Tosoh Corp.) refers to a process for obtaining triethylenediamines and piperazines by contacting certain compounds with an aminoethyl group with a crystalline aluminosilicate, the silica / alumina ratio being at least 12. The molded aluminosilicate is calcined at a temperature of from 500 to 950 ° C, preferably from 550 to 850 ° C for at least one hour (preferably 3). After calcination, an acid treatment with an aqueous inorganic acid is carried out at 50 to 80 ° C for 3 to 50 hours.

Publication US-A-4,289,881 (Bayer AG; equivalent: EP-A-10 671) describes the preparation of TEDA from certain piperazine derivatives in the presence of a SiO catalyst₂.

The publication DD-A-206 896 (VEB Leuna-Werke) refers to a process for obtaining TEDA by reacting N- (beta-aminoethyl) piperazine and / or N- (beta-hydroxyethyl) piperazine to starting from a porous SiO catalyst₂/To the₂OR₃ in the presence of NH₃.

The publication Derwent Abstract Nr. 1997-371381 (RU-A-20 71 475 (AS Sibe Catalysis Inst.)) Describes the preparation of triethylenediamines from monoethanolamine on a pentasyl zeolite, which has been treated with an aqueous solution of a complex builder.

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In the publication RU-C1-21 14 849 (Institut für Technologie und Konstruktion von Katalyse- und AdsorptionsProzessen mit Zeolith "Tseosit" SORAN) (Derwent Abstract Nr. 2000-036595) procedures for obtaining the TEDA from a mixture of monoethanolamine (MEOA), EDA and PIP on pentasyl zeolites with a modulus (molar ratio of SiO₂/To the₂OR₃) from 40 to 300. The zeolites used are dealuminated by treatment with an aluminum chelate complexer (EDTA, sulfosalicylic acid, TMAOH). The patent refers especially to the reaction of mixtures of MEOA / EDA, MEOA / PIP, EDA / PIP and EDA / MEOA / PiP with NH₃or with water as diluent (1: 3-10) on zeolites treated correspondingly at 350 to 450 ° C. The reactor discharge is separated into boiling ranges by rectification. The range from 160 to 180 ° C is then cooled and crystallized out. The mother liquors are used again as starting material.

Publication WO-A-89/05810 refers to processes for obtaining TEDA and / or one or more cyclic or acyclic amines in the presence of molecular sieves of the zeolite type.

Publication US-A-5,741,906 describes a process for obtaining TEDA in the presence of a ZSM-5 zeolite that has been previously treated with a chelating agent.

The processes of the state of the art have in common a low selectivity with regard to the formation of TEDA, a very high proportion of water and, therefore, if necessary uneconomical, as a diluent or as a solvent in the feed. to the reactor, insufficient catalyst life, for example as a result of deactivation, and, if necessary, also costly manufacture and / or modification of the catalyst.

The task of the present invention was to find a process for obtaining economically improved TEDA, compared to the state of the art, from easily accessible starting compounds, which could be carried out in a simple way, which had a high yield, selectivity and life of the catalyst and a low mandatory formation of piperazine and that the TEDA with high purity is formed, according to said procedure, color stability (i.e. low color number, for example APHA color number according to DIN ISO 6271, which remains low even during long storage times, for example 6.12 or more months) and quality with regard to odor [i.e. a unique odor of TEDA as far as possible and no odor of saturated 5-membered ring-membered N-heterocycles or other cyclic 6-membered N-heterocycles, saturated (eg PIP, N-ethyl-piperazine) and / or aromatic 5- or 6-membered ring-membered heterocycles].

Thus, a procedure was found to obtain triethylenediamine (TEDA) by reacting ethylenediamine (EDA) in the presence of a zeolite catalyst, characterized in that EDA is reacted, with 17 to 250% by weight of PIP and with 33 to 250% by weight of water, referred respectively to the EDA, the zeolite catalyst having one or more metals M at oxidation level III, chosen from the group consisting of B, Fe, Co, Ni, V , Mo, Mn, As, Sb, Bi, La, Ga, In, Y, Sc and Cr, in the form of oxides, for M = metal at oxidation level III or M = two or more metals at oxidation level III, a molar proportion of SiO₂/ M₂OR₃greater than 100: 1 and the reaction temperature is between 250 and 500 ° C.

The process according to the invention can be carried out batchwise or, preferably, continuously.

The reaction according to the invention can be carried out in the liquid phase or, preferably, in the gas phase.

The reaction is preferably carried out in the presence of a solvent or diluent.

Suitable solvents or diluents are, for example, acyclic or cyclic ethers with 2 to 12 carbon atoms, such as dimethyl ether, diethyl ether, di-n-propyl ether or their isomers, MTBE, THF, pyran or lactones, such as gamma-butyrolactone, polyethers, such as monoglyms, diglymes, etc., aromatic or aliphatic hydrocarbons, such as benzene, toluene, xylene, pentane, cyclopentane, hexane, and Petroleum ether, or their mixtures and especially also N-methylpyrrolidone (NMP). Furthermore, ammonia is suitable as a solvent or as a diluent.

Also suitable as diluents for carrying out the reaction in the gas phase are inert gases such as nitrogen (for example above saturation of the feed to the reactor) or argon. The reaction is preferably carried out in the gas phase in the presence of ammonia.

For example, the reaction is carried out in the presence of 2 to 1,200% by weight, preferably 12 to 1,200% by weight, especially 14 to 300% by weight, very particularly preferably from 23 up to 300% by weight of solvent or diluent, relative to the EDA used.

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For example, the starting mixture used in the process or the reactor discharge (= starting stream in the case in which it is operated continuously) contains from 5 to 80% by weight, especially from 10 to 80% by weight, particularly preferably from 20 to 70% by weight, very particularly preferably from 20 to 65% by weight of EDA and from 20 to 60% by weight, preferably from 10 to 60% by weight, particularly preferably from 15 to 60% by weight, in particular from 20 to 50% by weight of the solvent (s) and diluents.

In a preferred embodiment of the process according to the invention, the EDA and one or more amino compounds are reacted, each having a 2-aminoethyl group, -HN-CH₂-CH₂-.

Such amino compounds are preferably ethanolamines (such as for example: monoethanolamine (MEOA), diethanolamine (DEOA), triethanolamine (TEOA), diethylenetriamine (DETA), triethylenetetraamine (TETA), tri (2-aminoethyl) ) amine, N- (2-aminoethyl) ethanolamine (AEEA) and piperazine derivatives, such as for example N- (2-hydroxyethyl) -piperazine (HEP) and N- (2-aminoethyl) -piperazine (AEPIP).

The content of these amino compounds in the reactor discharge amounts, in this special embodiment (in total) generally from 1 to 1000% by weight, preferably from 3 to 250% by weight, in particular from 7 to 250% by weight, respectively referred to the EDA used.

For example, the starting mixture, used in the process or the reactor discharge (= starting stream when working continuously) (in total) from 0.5 to 50% by weight, preferably from 2 to 50% by weight, especially from 5 to 50% by weight, of these amino compounds.

Since it has also been found that in this special embodiment the MEOA can lead, when used in the discharge mixture or in the reactor feed, to the formation of secondary products that are difficult to separate from the reactor discharge (= product in the case of continuous work), the content in the discharge mixture or in the reactor feed will be, in the case of this amino compound, preferably from 1 to 50% by weight, based on the EDA used.

After the reaction, the products formed are isolated from the reaction discharge by customary methods, for example by distillation and / or rectification; unconverted starting materials can be recycled to reaction.

In this way, the PIP formed in the reaction discharge of the process according to the invention can be separated, for example by distillation, and can be recycled to the reaction.

A special advantage of the process is that intermediate fractions obtained during the work-up of the reaction discharge, which contain both TEDA and piperazine, and fractions containing, for example, N- (2- hydroxyethyl) -piperazine (HEP), N- (2-aminoethyl) -piperazine (AEPIP), diethylenetriamine (DETA), triethylenetetraamine (TETA), tri (2-aminoethyl) amine and / or N- (2-aminoethyl) ethanolamine ( AEEA).

Furthermore, the residues, which are compulsorily formed, of other amino compounds originating from other amino cyclization / condensation reactions, can be fed to the reaction according to the invention, without significantly impairing the yields of TEDA.

In a particularly preferred embodiment, the process according to the invention should be conducted in such a way that, especially in the case of continuous operation (steady state), the EDA is reacted and from 110 to 185% by weight of water and from 25 to 100% by weight of PIP, based respectively on the EDA.

In this embodiment, the proportion of PIP or EDA can also be reduced or increased by an amount from 0.01 to 20% by weight, for example from 0.01 to 10% by weight, in favor of of the one and to the detriment of the other.

For example, the starting mixture used in the process or the reactor discharge contains in this particularly preferred embodiment from 10 to 60% by weight of water, from 20 to 70% of EDA and from 5 to 50% by weight of PIP, preferably from 15 to 60% by weight of water, from 20 to 65% by weight of EDA and from 5 to 50% by weight of PIP, so particularly preferred from 20 to 50% by weight of water, from 20 to 60% by weight of EDA and from 10 to 50% by weight of PIP, very particularly preferably from 45 to 55% by weight of water, from 30 to 40% by weight of EDA and from 10 to 30% by weight of PIP,

ES 2 249 652 T3, it being possible to reduce or increase the proportion of PIP or EDA also by an amount as described above in favor of one and to the detriment of the other.

In this particularly preferred embodiment of the process, the reactor discharge contains, in addition to the EDA, the PIP and water in the quantitative proportions or in the amounts indicated above, preferably less than 10% by weight, preferably less than 5% by weight, especially less than 2% by weight, of other components.

In this particularly preferred embodiment, it has been found that, with the quantitative proportions or with the amounts indicated above of the raw materials, the reaction can be conducted, especially in the case in which the continuous operation (at steady state) is carried out in such a way. so that the EDA is almost completely converted (i.e. conversion greater than 95%, especially greater than 97%) to give the TEDA and PIP with a selectivity greater than 90%, especially greater than 95%.

The process will be carried out according to the invention preferably by adjusting a corresponding EDA / PIP ratio in the reactor feed (= current of the starting material when operating continuously) in the aforementioned intervals in such a way that the consumption in PIP tends towards zero in the total balance by separating the PIP from the reaction discharge and recycling to the reactor feed (for example from 0 to 30 kg, especially from 0 to 15 kg, very particularly preferably from 0 to 10 kg, per 100 kg of TEDA in the reactor discharge), being especially zero, and at the same time the EDA used is completely converted (> 95% , especially> 97%, especially preferably> 99%). In other words, as a result, during the continuous mode of operation, no additional PIP is fed to the process according to the invention.

Since in a reaction line of this type, according to the invention, the amount of EDA discharged tends towards zero, the separation of the discharge from the reactor is particularly simple, for example by distillation and / or rectification, in accordance with this variant of the procedure.

The reaction temperature in the process according to the invention is preferably between 300 and 400 ° C, particularly preferably between 310 and 390 ° C.

Advantageously, the components of the educt or the feed to the reactor are previously tempered.

In addition, the following reaction conditions have proven to be suitable for carrying out the process according to the invention :

- a WHSV (weight hourly space velocity) referred to the amine used in the reaction, from 0.05 to 6 h ¹, preferably 0.1 to 1 h ¹, particularly preferably from 0.3 to 1 h ¹, Y

- a pressure (absolute) from 0.01 to 40 bars, especially from 0.1 to 10 bars, preferably from 0.8 to 2 bars.

Suitable reactors in which the process according to the invention can be carried out are stirred vessels, especially tube reactors and tube bundle reactors.

The zeolite catalyst is preferably arranged in the form of a fixed bed in the reactor.

The reaction in the liquid phase is carried out, for example, in a suspension way, in the form of fine rain or by flooding.

The preferred reaction in the gas phase can be carried out in a fluidized bed of the catalyst or, preferably, in a solid bed of the catalyst.

In the following paragraph, the way in which the method according to the invention can be carried out will also be described by way of example:

The feed to the reactor (composition: as described above) is transformed into the gaseous phase at a temperature of 250 to 500 ° C in an evaporator, which, if appropriate, can be an integral part of the reactor itself and is conducted over the catalyst. The reaction discharge, which is obtained in the gaseous state at the outlet of the reactor, is tempered at temperatures of 20 to 100 ° C, preferably at 80 ° C by means of the discharge of the liquefied reaction, pumped in a closed circuit. This discharge from the liquefied reaction is processed as follows: in a first distillation stage, low-boiling products such as acetaldehyde, ethylamine, ammonia and water are separated as well as heterocyclic compounds, which are formed as by-products in synthesis. In a second distillation stage, the piperazine reaction discharge is released, which is fed back to the reactor feed. The separated piperazine stream may in this case contain up to 20% by weight of TEDA. (Alternatively, the simultaneous separation of water and piperazine is also possible, which can be recycled together to the reactor feed). In a third distillation stage the product is obtained

ES 2 249 652 T3 made up of the TEDA by distillation from the reaction discharge and, if necessary, further processed for example in a subsequent crystallization step (for example as described below).

The method according to the invention achieves, among others, the following advantages:

- The procedure makes it possible to replace the EDA, used as starting material, depending on price and availability, by one or more amino compounds, respectively having a 2-aminoethyl group, —HN-CH₂CH₂-, (see above), or add these amino compounds further to the reactor feed.

- piperazine, which is essentially the only by-product, can be reintroduced into the process when conducting the reaction properly, as described above and in this case can be converted to TEDA. Also mixtures of unconverted piperazine and TEDA can be sent back to the catalyst, since TEDA has been found to be stable under the reaction conditions.

- By properly choosing the EDA / PIP ratio in the reactor feed, as described above, the PIP consumption tends towards zero in the total balance, since when the PIP is recycled, contained in the discharge of the reaction, a constant PIP current is obtained in terms of its quantity in the reactor feed and, in this way, it only has to be fed from the outside continuously to the reaction, in the total balance, EDA exclusively as a single amine.

- high selectivity and high conversion are achieved, relative to the reaction of EDA to give TEDA.

- due to the zeolite catalysts used according to the invention, a smaller amount of by-products is formed during the EDA reaction and, if necessary, of the aforementioned amino compounds, which leads to a simplification of the production of the TEDA obtained according to the procedure to achieve the required conditions of the product (purity, color index, odor).

The zeolite, which is used as a catalyst in the process according to the invention, to obtain TEDA, has a basic structure, which is essentially made up of silicon dioxide (SiO2).

For M = metal at oxidation level III or M = two or more metals at oxidation level III, the zeolite catalysts preferably used in the process according to the invention have a molar proportion of SiO₂/ M₂OR₃ (modulus) from more than 100 to 40,000: 1, especially from more than 200 to 5,000: 1.

The zeolite catalyst used in the process according to the invention is preferably of the pentasyl type.

The upper limit of the modulus (40,000) is limited only by the purity of the starting substances (residual traces of M or M compounds) and by the cleanliness and chemical stability of the apparatus used for the synthesis of zeolite. .

With a modulus below the indicated limits, the density of the Bronsted and Lewis acidity (density of the acidity: acid centers / total catalyst surface) of the zeolites clearly increases, clearly decreasing the yield and selectivity achievable in TEDA and the life time of the catalyst and clearly increasing the cost for the purification of the TEDA.

Surprisingly, it has been found that, by drastically reducing the acidity within the zeolite crystal in the process according to the invention that is generated due to the incorporation of trivalent metals in the form of metal oxides in the crystal lattice, in the normal case, During hydrothermal synthesis, the advantages according to the invention are achieved, for example a clear improvement in selectivity with respect to TEDA.

For the zeolite catalyst, preferably of the pentasyl type, with modules such as those given above, there are no additional requirements as regards the material of the zeolite as such or as regards the process according to which it can be obtained. the same.

The zeolite catalyst, used in the process according to the invention, which contains, in addition to SiO2, one or more metals M at oxidation level III in the form of oxide, metal M at oxidation level III will preferably be chosen from the group formed by B, Fe, Co, Ni, V, Mo, Mn, As, Sb, Bi, La, Ga, In, Y, Sc and Cr or mixtures thereof.

Zeolites in which M stands for gallium, iron or boron are preferred. Those in which M stands for iron and boron are especially preferred.

Suitable zeolite catalysts of the pentasyl type to be used according to the invention are, for example, the following types: ZSM-5 (as disclosed for example in US-A-3,702,886), ZSM-11 (as

ES 2 249 652 T3 has been disclosed for example in the publication US-A-3,709,979), ZSM-23, ZSM-53, NU-87, ZSM-35, ZSM-48 and mixed structures consisting of at least two of the zeolites previously mentioned, especially ZSM-5 and ZSM11 as well as their mixed structures.

Particularly preferred for the process according to the invention are zeolites with an MFI, MEL structure, with a mixed MEL / MfI or MFI / MEL structure.

The zeolites used according to the invention are crystalline metal silicates with a channel-shaped structure and an ordered cage-shaped structure, which have micropores. The crystal lattice of such zeolites is made up of SiO tetrahedra₄ and from M_{2 / z}O (z = 3), which are linked through common oxygen bridges. A compilation of known structures can be found, for example, in the publication of WM Meier, DH Olsen und Ch. Baerlocher in "Atlas of Zeolite Structure Types", Elsevier, 4^to edition, London 1996.

Furthermore, according to the invention, zeolites that do not contain aluminum (M = Al) and in which Si (IV) is partially replaced in the zeolite crystal lattice by a metal M (III), such as B, Fe, can be used according to the invention. Co, Ni, V, Mo, Mn, As, Sb, Bi, La, Ga, In, Y, Sc and Cr.

(III = oxidation level 3, IV = oxidation level 4).

The aforementioned zeolites are usually manufactured by reacting a mixture consisting of a SiO2 source as well as a metal source (for example B, Fe, Co, Ni, V, Mo, Mn, As, Sb, Bi, La, Ga , In, Y, Sc and Cr, at the oxidation level as described above) and a model nitrogen base ("template compound"), such as, for example, tetraalkylammonium salt, optionally additionally with the aid of basic compounds (for example alkaline lyes), in a pressure vessel under elevated temperature over a period of time of several hours or a few days, forming a crystalline product. This is separated (eg filtered off, spray dried or precipitated), washed, dried and calcined at elevated temperature to remove organic nitrogen bases (see below). By choice, modelless synthesis is also possible, as long as the formation of the zeolite is ensured. In the powder thus obtained, the metal (for example M = B, Fe, Co, Ni, V, Mo, Mn, As, Sb, Bi, La, Ga, In, Y, Sc and Cr, in the oxidation level as described above) occurs at least in part within the zeolite lattice in varying proportions with a quadruple, quintuple or sixfold coordination).

The zeolites, used according to the invention, can be manufactured according to the described process and / or can be purchased commercially.

When the zeolite catalyst to be used according to the invention, preferably of the pentasyl type, is not present, due to the type of production, at least partially in the preferred acid form II 'and / or in the NH form₄+, but if it is present, for example, in the Na + form (or in another arbitrary form of the metal), it can be transformed at least partially into the preferred H + form and / or into the NH form₄+ according to the state of the art, by ion exchange, for example with ammonium ions and then calcination (see below). In the same way, the treatment, also known in the literature, with dilute protonic acids, for example mineral acids, can be practiced for the transformation of the zeolite, at least in part in the H + form. All protonic acids are suitable here, such as, for example, hydrochloric acid or sulfuric acid (see below).

It is then possible to transform the zeolite catalyst, exchanged in this way, by ion exchange with a corresponding solution of metal salt (Me = alkali metal, alkaline earth metal, transition metal) into a desired Me + form, still containing H + and / or NH₄+.

In order to achieve as high a selectivity as possible, a high conversion as well as a particularly long catalyst life, it may be advantageous to modify the zeolite catalysts according to requirements.

A suitable modification of zeolite catalysts consists, as described in the publication of J. Weitkamp et al., Catalysis and Zeolites, chapter 3: Modification of Zeolites, Springer Verlag, 1999 ', in that the -moulded zeolitic material or not molded- undergoes a treatment, according to the known state of the art (EPA-382 055, page 4, line 2 and following + line 20 and following; DE-C2-24 34 913, page 3 line 23 and following ; US-A-5,041,548, page 4, line 27 and following), with concentrated or dilute protonic acids - such as, for example, hydrochloric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, a carboxylic acid, dicarboxylic acids or polycarboxylic acids- and / or complexing agents -such as acetylacetonate (acac), nitrilotriacetic acid, sulfosalicylic acid, ethylenediaminetetraacetic acid (EDTA) -, for example according to publications EP-A-842 936 and RU-C1-21 14 849, and / or steam.

In a preferred embodiment, a doping of the zeolite used in the process according to the invention can be carried out therein by applying transition metals of secondary groups I to VIII, preferably secondary groups I, II, IV and VIII, especially preferably Zn, Ti, Zr, Fe, Co, Ni, Cr, V.

ES 2 249 652 T3

The application can be achieved by impregnation of the zeolite, used in the process according to the invention, in aqueous solutions of metal salts, by overspray of the corresponding solutions of metal salts on the zeolite or by other suitable procedures, known in the state of the art. . Suitable metal salts for the preparation of metal salt solutions are nitrates, nitrosylnitrates, halides, carbonates, carboxylates, acetylacetonates, chlorine complexes, nitro complexes or amino complexes of the corresponding metals. nitrates and nitrosylnitrates being preferred. In the case of zeolites, which are doped with several metals, the metallic salts or the solutions of the metallic salts may be applied simultaneously or successively.

The zeolites coated or impregnated with the solutions of the metal salts are then dried, preferably at temperatures between 60 and 150 ° C and calcined, optionally, at temperatures between 200 and 950 ° C, preferably between 400 and 750 ° C. C. In the case of a separate impregnation, the catalyst will be dried after each impregnation stage and optionally calcined as indicated above. The order in which the transition metals are surface-impregnated can be freely chosen in this case. The coated and dried zeolites, as well as, if desired, calcined, are then optionally activated by treatment in a gaseous stream containing free hydrogen at temperatures between 30 and approximately 600 ° C, preferably between 150 and approximately , 450 ° C. The gaseous stream preferably consists of 50 to 100% by volume of hydrogen and of 0 to 50% by volume of nitrogen.

The solutions of the transition metals are applied to the zeolite in an amount such that the total content of transition metal, respectively referred to the total weight of the catalyst, is approximately from 0.01 to approximately 10% by weight. preferably from about 0.01 to 5% by weight, more preferably from about 0.01 to about 2% by weight, and especially from about 0.05 to 1% by weight.

In this case, the surface area of ​​the transition metals on the catalyst is preferably about 0.01 to about 10 µm in total.²/ g, more preferably 0.05 to 5 m²/ g and especially from about 0.05 to 3 m²/ g (m² per g of catalyst). The surface of the metals is determined by means of the chemisorption procedure described by J. LeMaitre et al. in "Characterization of Heterogeneous Catalysts," editor Francis Delanny, Marcel Dekker, New York 1984, pages 310-324. To increase the strength, the zeolites used according to the invention can be placed on supports, for example on cellulose materials, clays, polymers, metals, graphite, binders or metal oxides such as clays, aluminum oxide, silicon dioxide. Furthermore, it is possible to use them in the form of granules, in the form of balls or applied to glass or other bodies such as, for example, fabrics (especially metallic fabrics) of any type.

As casting processes, reinforcing agents for the zeolites used according to the invention, it is possible in principle to use all methods to achieve a corresponding casting. Procedures in which molding is verified by planking or extrusion will be preferred. Processes in which the molding is carried out by extrusion in customary extruders, for example to give bars with customary dimensions of 1 to 10 mm, especially 2 to 5 mm, are particularly preferred. When binders and / or auxiliary agents are required, extrusion or tableting, a mixing or kneading process will be conveniently previously carried out. If appropriate, a calcination step is additionally carried out after extrusion / planking. If desired, the shaped articles obtained are preferably comminuted into granules or grits with a particle diameter of 0.5 to 5 mm, in particular 0.5 to 2 mm. This granulate or this shot and even the catalyst moldings, generated in another way, practically do not contain parts of finer grain than those with a minimum diameter of the particles of 0.5 mm.

In a preferred embodiment, the molded zeolite to be used according to the invention contains up to 80% by weight of binders, relative to the total weight of the catalyst. Particularly preferred binder contents are from 1 to 60% by weight, especially from 20 to 45% by weight. Suitable binders are, in principle, all compounds used for this type of purpose, with preferred compounds, especially oxides, of silicon, aluminum, boron, phosphorus, zirconium and / or titanium. Silicon dioxide is of special interest as a binder, and SiO can be incorporated₂ also in the form of the silica sol or in the form of tetraalkoxysilanes in the molding process. Magnesium and beryllium oxides as well as clays, for example montmorillonite, kaolins, bentonites, haloisites, diquites, nacrites and anauxites can also be used as binders.

As auxiliary agents for the molding process, according to the invention, mention may be made, for example, of auxiliary agents for the formation of bars for extrusion, methylcellulose being a usual agent for the formation of bars. Such agents are generally completely burned out in a subsequent calcination step.

The calcination of the zeolite catalyst, to be used according to the invention, is carried out at temperatures from 250 to 950 ° C, preferably at 400 to 750 ° C, especially preferably from 450 to 600 ° C, for a time of at least, in general, one hour, preferably from 2 to 5 hours. Calcination is carried out in a gaseous atmosphere, for example nitrogen, air, noble gas atmosphere. As a general rule,

ES 2 249 652 T3 will calcine in an atmosphere containing oxygen, the oxygen content being from 0.1 to 90% by volume, preferably from 0.2 to 22% by volume, particularly preferably from 10 to 22% by volume. However, the use of other oxygen supplying substances is also possible. The above expression of "oxygen supplying substances" encompasses all those substances that are capable of releasing oxygen under the conditions of calcination. Special mention should be made of: nitrogen oxides of the formula N_xOR_Y, where x and y are chosen in such a way that a neutral nitrogen oxide is produced, N₂Or, exhaust gases containing N2O from an adipic acid, NO, NO2, ozone installation or a mixture formed by two or more of them. When CO2 is used as the oxygen supplying substance, temperatures of from 500 ° C to 800 ° C will preferably be set during calcination. In the same way, calcination under a steam atmosphere is possible.

According to the invention, it has also been observed that after the use of the zeolite catalyst, used according to the invention, it can be regenerated regardless of its shape, for example after a decrease in activity and / or selectivity, by means of a process in which regeneration is carried out by specific combustion of the coating responsible for deactivation. In this case, work will preferably be done in an inert gas atmosphere, which contains exactly defined amounts of oxygen supplying substances. A regeneration process of this type has been described, among others, in the publication WO 98/55228 and in the publication DE-A1-19 72 39 49, the disclosure of which forms in this case, in its entirety, also the object of the present application due to the corresponding reference.

After regeneration, the activity and / or selectivity of the catalyst is increased compared to the state immediately prior to regeneration.

The zeolite catalyst to be used according to the invention, which must be regenerated, is heated either in the reaction device (reactor) or in an external furnace, in an atmosphere containing from 0.1 to approximately 20 parts by volume of substances supplying oxygen, especially preferably from 0.1 to about 20 parts by volume of oxygen, up to a temperature in the range from about 250 ° C to 800 ° C, preferably from about 400 to 550 ° C, and especially from about 450 ° C to 500 ° C. In this case, heating will preferably be carried out with a heating rate of about 0.1 ° C / min to about 20 ° C / min, preferably from about 0.3 ° C / min to about 15 ° C / min and especially from 0.5 ° C / min to 10 ° C / min.

During this heating phase, the catalyst is heated to a temperature at which the coatings, in most cases organic, which are in it, begin to decompose, while, at the same time, the temperature is regulated through oxygen content and thus does not increase in such a way that deterioration of the catalyst structure occurs. The slow increase of the temperature or of the residence time at low temperature by adjusting the corresponding oxygen content and the corresponding thermal efficiency is an essential step in the case of highly organic coatings of the catalyst to be regenerated to prevent a local overheating of the catalyst. catalyst.

If the temperature of the gas stream drops at the outlet of the reactor despite the increasing amount of oxygen-supplying substances in the gas stream, the combustion of the organic coating is complete. The duration of the treatment generally amounts to approximately 1 to 30 hours, preferably approximately 2 to approximately 20 hours, and in particular approximately 3 to approximately 10 hours.

During the subsequent cooling of the catalyst, regenerated in this way, it must be taken into account that the cooling does not take place too quickly ("quenching"), since otherwise the mechanical strength of the catalyst may be adversely affected. .

It may be necessary to subject the catalyst, after regeneration by calcination, as described above, to a rinse with water and / or dilute acids, such as, for example, hydrochloric acid to eventually remove the remaining inorganic load from the catalyst due to the impurities of the educt (traces of alkali, etc.). This is followed by a further drying and / or calcination of the catalyst.

In another embodiment of the process according to the invention, the deactivated catalyst is washed, at least in part, as a step prior to heating, according to the regeneration process, with a solvent in the conversion reactor or in an external reactor to remove the valuable product still attached. In this case, the washing will be carried out in such a way that the valuable products adhered respectively to the catalyst can be detached, but the temperature and pressure will not be chosen so high that the coatings, in most cases organic, are also detached. . Preferably the catalyst is simply rinsed in this case with a suitable solvent. Therefore, all solvents in which the corresponding reaction product dissolves perfectly are suitable for this washing process. The amount of solvent used as well as the duration of the washing process are not critical. The washing process can be repeated several times and can be carried out at elevated temperature. The use of CO2 above the critical pressure as a solvent is preferred, otherwise the washing process can be carried out under normal pressure or under higher or above critical pressure. Once the washing process is finished, the catalyst dries, in general. Although the drying process is not critical, in general, the temperature for drying should not greatly exceed the

ES 2 249 652 T3 boiling temperature of the solvent used for washing in order to avoid a flash evaporation of the solvent in the pores, especially in the micropores since this can also lead to deterioration of the catalyst.

A preferred form of the production process may consist in that the continuous process according to the invention for the synthesis of TEDA does not have to be interrupted for the regeneration of the catalyst according to the invention in order to increase the process flow rate. This can be achieved by using at least two reactors connected in parallel, which can be operated alternately.

Regeneration of the catalyst can be carried out in such a way that at least one of the reactors, connected in parallel, is decoupled from the corresponding reaction stage and the catalyst contained in this reactor is regenerated, with at least one reactor always being available for the conversion of the EDA in the course of the process in continuous, in each stage.

The TEDA, obtained according to the invention, can be recrystallized to improve its purity in suitable solvents (for example pentane, hexane). However, this is not necessary in most cases, since TEDA can be manufactured according to the process of the invention with a purity greater than 95% by weight, for example greater than 97% by weight.

In a special configuration the process for the manufacture of TEDA according to the invention is combined with the subsequent process of TEDA according to the earlier patent application EP Nr. 00114475.7 dated 07.06.00 (BASF AG).

According to this combination, the TEDA according to the invention is first manufactured. In the subsequent work-up of the TEDA (for example by distillation), which may contain several stages, the TEDA is evaporated, preferably in the last work-up stage (especially distillation stage or rectification stage) and passed TEDA in the vapor state, obtained for example at the top or in a side discharge of the distillation column, which previously had a purity greater than 95% by weight, especially greater than 97% by weight, through a liquid solvent. This passage of the vaporized TEDA directly through a liquid solvent will be referred to below as the TEDA quench.

By subsequent crystallization separation of the TEDA from the solution thus obtained, pure TEDA of high quality will be obtained.

The liquid solvent will generally be chosen from the group of cyclic or acyclic hydrocarbons, of aliphatic and chlorinated hydrocarbons, of aromatic hydrocarbons, of alcohols, of ketones, of aliphatic esters of carboxylic acids, of aliphatic nitriles and ethers.

For the manufacture of a pure TEDA solution according to the above combination of processes, which for example can be used as a catalyst solution in the manufacture of polyurethane foam, preferably an alcohol (for example ethylene glycol, 1,4-butanediol, preferably dipropylene glycol). The color number of a 33% by weight solution of TEDA in dipropylene glycol obtained in this way is less than 150 APHA, especially less than 100 APHA, very particularly preferably less than 50 APHA.

For the production of the pure (crystalline) TEDA according to the preceding process combination, preferably an aliphatic hydrocarbon, in particular a saturated aliphatic hydrocarbon with 5 to 8 carbon atoms (such as, for example, hexane , heptane, preferably pentane). The crystallization of pure TEDA from the TEDA solution manufactured according to the invention can be carried out according to procedures known to those skilled in the art. The TEDA crystals, obtained by subsequent crystallization in several stages, or preferably in a single stage, are of high purity (purity in general of at least 99.5% by weight, especially of at least 99.8% in weight. PIP content less than 0.1% by weight, especially less than 0.05% by weight, N-ethylpiperazine content less than 0.02% by weight, especially less than 0.01% by weight) and the color number of a 33% by weight solution in dipropylene glycol is less than 50 APHA, especially less than 30 APHA.

(All APHA indices according to DIN ISO 6271).

The passage of the TEDA in the vapor state through the liquid solvent is carried out in an apparatus for quenching, preferably in a falling film condenser (thin film condenser, fine rain film condenser or current condenser). descending) or in a nozzle apparatus. In this case, the TEDA can be conducted in the vapor state in a parallel current or countercurrent with respect to the liquid solvent. The introduction of the TEDA in vapor form through the upper part of the tempering apparatus is advantageous. Furthermore, the tangential feeding of the liquid solvent through the head of the falling film condenser or the feeding of the liquid solvent through one or more nozzles to achieve complete wetting of the internal wall of the tempering apparatus is advantageous.

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In general, a temperature in the tempering of the TEDA will be established by tempering the solvent used and / or the tempering apparatus at 20 to 100 ° C, preferably at 30 to 60 ° C. The absolute pressure in the tempering of the TEDA is, in general, from 0.5 to 1.5 bar.

In general, proceed in such a way that, depending on the type of solvent, in the tempering of the TEDA, first, solutions with a TEDA content of approximately 1 to 50% by weight, preferably from 20 to 40%, are obtained. % in weigh.