EP1483230A1

EP1483230A1 - Method for producing ethyldimethylamine and triethylamine

Info

Publication number: EP1483230A1
Application number: EP03711916A
Authority: EP
Inventors: Ralf Böhling; Ulrich Steinbrenner; Frank Funke; Günter Müller; Günter Gaus; Christoph Benisch
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2002-03-04
Filing date: 2003-03-03
Publication date: 2004-12-08
Also published as: US20050154235A1; ZA200407045B; WO2003074468A1; JP4201715B2; CN1649825A; DE10209528A1; BR0308205A; CA2478189A1; MY135723A; EA200401151A1; JP2005526743A; CN1308285C; MXPA04008531A; AU2003218681A1; EA009067B1; US7253322B2; KR20040095260A; UA79271C2

Abstract

The invention relates to a method for producing ethyldimethylamine and triethylamine, comprising the steps of (i) reacting a mixture from diethylamine and dimethylamine with ethylene in the presence of a catalyst from the group of the alkalimetal dimethylamides, alkalimetal diethylamides and alkalimetal hydrides, (ii) removing the catalyst, (iii) separating by distillation the obtained mixture into triethylamine and ethyldimethylamine and optionally diethylamine and dimethylamine, (iv) optionally returning the catalyst and the educt amines to the reaction. The inventive method allows the coupled production of ethyldimethylamine and diethylamine in a simple process.

Description

Process for the preparation of ethyldimethylamine and triethylamine

The present application relates to a process for the preparation of ethyldimethylamine and triethylamine.

Triethylamine is used as a raw material for the production of surfactants, textile and flotation aids, bactericides, corrosion and foam inhibitors, additives for pharmaceuticals and as antioxidants for fats and oils. The amine mentioned can be prepared by the hydrogenation of corresponding nitriles or nitro compounds, by the reductive amination of corresponding aldehydes and ketones and by the amination of corresponding alcohols. In particular, it is produced on an industrial scale by the amination of the corresponding alcohol or the corresponding carbonyl compound over metal catalysts, which are optionally supported, under hydrogenating conditions.

Ethyldimethylamine is also an important large-scale product. It is mainly used in the foundry industry, in the so-called cold box ner driving. Small amounts are used in the pharmaceutical industry.

The use of aldehydes, ketones and nitriles and also of alcohols, in this case ethanol, as the starting material for the production of alkylamines is in principle uneconomical compared to the use of the corresponding olefin, i.e. ethene, due to the prices of the starting materials.

An alternative to the production of the amines mentioned is the addition of NH ₃ or amines to ethylene in the presence of acidic catalysts such as zeolites, basic catalysts such as metal amides, in particular alkali and alkaline earth amides, amides of subgroup IV, alkali metal alcoholates, or transition metal complex compounds ,

This so-called hydroamination of olefes, however, has a number of difficulties which frequently prevent the reaction from being used on an industrial scale. Examples are listed below. So are in the NaNH - or KNH ₂ -catalyzed addition of NH to olefins, such as. B. BW Howk et al., J. Am. Chem. Soc. 76 (1954), 1899-1902 and RD Closson et al., US-A-2,750,417, the space-time yields of desired alkylamines are very low even at high temperatures and olefin pressures due to the low activity and solubility of the metal amide. US-A-4,336,162 and US-A-4,302,603 describe an approach to this problem by switching to the Rb and Cs amides or by using a eutectic of NaNH ₂ and KNH ₂ . In the first case, the technical implementation is forbidden because of the extremely high catalyst price, in the second case the space-time yields of the desired alkylamines are still too small.

The hydroamination of olefins with secondary amines in the presence of acidic catalysts in general proceeds in poorer yields and with poorer selectivities than the corresponding hydroamination with ammonia or primary amines.

The object of the present invention is to provide a process with which ethyldimethylamine and trimethylamine can be produced in one process, the desired amounts of ethyldimethylamine and triethylamine being able to be controlled.

This object is achieved by a process for the preparation of ethyldimethylamine and triethylamine with the following steps:

(i) reacting a mixture of diethylamine and dimethylamine with ethylene in the presence of a catalyst from the group of alkali metal dimethylamides, alkali metal diethylamides and alkali metal hydrides

(ii) separating the catalyst

(iii) separating the mixture obtained by distillation into triethylamine and ethyldimethylamine and, if appropriate, diethylamine and dimethylamine

iv) optionally recycling the catalyst and the starting amines into the reaction.

The inventive method allows the production of ethyldimethylamine and triethylamine in a process in which a co-production of ethyldimethylamine and triethylamine is carried out, it being possible to produce these amines in a single process using simple process steps. Since ethyldimethylamine and triethylamine can easily be separated from one another and from diethylamine or a diethylamine / dimethylamine mixture by distillation, the process according to the invention is advantageous over the separate production of the two amines. Diethylamine and dimethylamine are used as starting materials for the reaction.

The applicants DE 100 30 619.5 and DE 100 41 676.4 describe a general process for the preparation of amines by hydroamination of olefins. In the first stage, an olefin is used

a) with a primary amine or with a secondary amine in the presence of a metal monoalkyl amide or metal dialkyl amide as a catalyst or

b) with ammonia or a primary amine in the presence of an inorganic solid acid as a catalyst or

c) with ammonia, a primary amine or a secondary amine in the presence of a transition metal complex compound as a catalyst

implemented and then the hydroamination products obtained in the second process stage, either in the presence of a transalkylation catalyst or in the presence of hydrogen and a transalkylation hydrogenation or dehydrogenation catalyst at from 80 to 400 ° C.

It is not disclosed in these applications to use ethylene with diethylamine and dimethylamine together in one process for the preparation of the corresponding ethyl- and methyl-containing amines.

The method according to the invention is described in more detail below.

In the first stage of the process, ethylene is reacted with diethylamine and dimethylamine under hydroaminating conditions. The addition of ethylene to the respective amine produces triethylamine and ethyldimethylamine. The relative amount of ethylene (partial pressure) and the amount of amines allow the distribution of the resulting products to be controlled.

Dimethylamine reacts with ethylene to a more stable product than diethylamine. In the presence of a mixture of diethylamine and dimethylamine, the amount of dimethylamine present then completely or almost completely reacts with ethylene before triethylamine is formed. The product composition of the mixture obtained can thus be controlled in a simple manner via the composition of the starting material mixture, a deficit in ethylene causing an incomplete conversion of diethylamine.

If the process according to the invention is intended to produce product mixtures which, in addition to the products ethyldimethylamine and triethylamine and any by-products which may be present, no longer contain diethylamine, an excess of ethylene is used in the hydroamination reaction. If a certain proportion of diethylamine is to be retained, a substoichiometric amount of ethylene is used.

In general, the hydroamination according to the present invention is carried out in such a way that the amine from which the preferred alkylamine is produced is used in excess over the other starting material. Since there is generally a greater need for triethylamine, the starting materials diethylamine and dimethylamine are preferably used in a ratio of (8 to 15): 1, in particular in a ratio of 10: 1, so that triethylamine and ethyldimethylamine are also obtained in such a ratio , This usually corresponds to market demand. The ratios of diethylamine and diethylamine to be used can, however, be flexibly adapted to the needs of the respective products, which is a further advantage of the process according to the invention.

A significant excess of ethylene is preferably also added.

The hydroamination according to the invention using diethylamine and dimethylamine is preferably carried out in one reaction step, the product distribution being set as set out above using the starting materials.

The hydroamination according to the invention is carried out using an alkali metal hydride or amides of the alkali metals as a catalyst. The hydrides and amides which can be used are salts of Li, Na, K, Rb or Cs, preferably of Li, Na or K, in particular of Na. The most preferred hydride is NaH.

The amides used according to the invention are diethylamide, dimethylamide and or ethylmethylamide. Diethylamide or dimethylamide or a mixture of the two is preferably used in any desired ratio. Na-diethylamide, Na-dimethylamide or mixtures thereof are particularly preferred.

The metal amides can be used as such, for example in the form of a solution, in the reaction according to the invention, it being possible for the metal amides to come from any source.

In a preferred embodiment of the present invention, the metal amide is used from the corresponding amine, ie dimethylamine, before use in the reaction

Ethylmethylamine or diethylamine. The production of the metal amides is carried out using methods known from the literature. These are described, for example, in Houben-Weyl,

Methods of Organic Chemistry, 4th Edition, Volume XI / 2, Thieme Verlag, Stuttgart,

Pages 182ff US 4,595,779, WO-A 93/14061, DE-A 21 17 970, German Reich Patent 615,468, GB-A 742 790, DE-A 26 13 113, US 2,750,417, J. Wollensak, Org. Synth. 43

(1963), pages 45ff, and C.A. Brown, J. Am. Chem. Soc. 95 (1973), pages 982ff.

Generally, the preparation of the amide is carried out either by reacting one

Alkali metal with the corresponding amine in the presence of an unsaturated compound such as butadiene, isoprene, naphthalene, pyridine or styrene as an electron transfer, by reacting a metal amide or hydride with the corresponding amine or reacting an organometallic compound, for example n-BuLi, MeLi, PhNa, Et ₂ Mg or EttZr, with the corresponding amine.

In the production from amine and alkali metal, generally technical quality alkali metal is used which is contaminated by up to 10% by weight of oxides, hydroxides, calcium and the other alkali metals. Other elements can be present in traces (> 1% by weight), but these generally do not interfere even at higher concentrations. It is of course also possible to use pre-cleaned alkali metal which does not contain the impurities mentioned or only in traces. However, technical alkali metal is generally preferred for reasons of cost. All alkali metals can be used, preferably Li, Na or K are used, more preferred are Na or K, especially Na. If appropriate, mixtures of the alkali metals can also be used.

In one embodiment of the present invention, the alkali metal is dispersed in a suitable inert solvent before the addition of the amine. Saturated hydrocarbons are preferably used as inert solvents, preferably low-boiling paraffins, such as n-butane, i-butane, pentanes and hexanes, cyclohexane and mixtures thereof, or high-boiling paraffins which may contain branched and saturated cycloparaffins, for example white oil.

The solvents mentioned are generally of technical origin and can also contain acidic impurities such as water, aldehydes, ketones, amides, nitriles or alcohols in small amounts.

The dispersion can be carried out above the melting temperature of the alkali metal using, for example, a suitable stirrer, a nozzle, a reaction mixing pump or a pump and a static mixer. The alkali metal can also be injected into cold solvent or sprayed onto cold solvent from the gas phase. Spraying in cold gas with subsequent redispersion is also possible.

Further possibilities are to disperse the alkali metal in a mixture of inert solvent and eductamine or to disperse the alkali metal in the solvent or solvents and to add the corresponding eductamine. Another possibility is finally to disperse the alkali metal in the product amine or amines and to add the corresponding amine. If necessary, a separate device is used for the dispersion process, for example a stirred tank, a nozzle or a reaction mixing pump.

When producing the amide, the alkali metal is generally introduced in the form of fine particles. In the case of sodium, these particles preferably have a size distribution such that 50% by weight of the particles have a size of <1000 μm, more preferably <300 μm, in particular <100 μm.

In one embodiment of the present invention, the alkali metal is dispersed in a paraffin and at least a large part of this paraffin is decanted off before the alkali metal is used in the reaction and replaced by trialkylamine and / or dialkylamine. An electron transfer agent, in particular 1,3-butadiene, is then metered in either alone or in a mixture with the educt dialkylamine. Alternatively, a simultaneous addition of the electron carrier and the dialkylamine is also possible.

Salt formation to the amide thus takes place in the presence of a suitable unsaturated compound, for example butadiene, isoprene, naphthalene, pyridine or styrene. In a preferred embodiment of the present invention, butadiene or isoprene are used as the unsaturated compound, particularly preferably 1,3-butadiene.

In the production of the amide catalyst from elemental metal, preferably Na, a temperature of 0 to 150 ° C, preferably 20 to 90 ° C, in particular 30 to 70 ° C and a pressure of 1 to 200 bar, preferably 1 to 100 bar, in particular 3 to 50 bar. The amide preparation can be carried out batchwise, semi-continuously or continuously.

The catalyst systems described above which are suitable for carrying out the reaction according to the invention can be used in solution, as a suspension or applied to a support.

Diethylamine and dimethylamine are used after the catalyst is provided

Ethylene implemented. This creates a mixture of ethyldimethylamine and triethylamine.

The relative amount of the organylamines formed can be controlled by the amount of starting material.

After the hydroamination has taken place, the amine mixture obtained is separated as described below.

In the hydroamination, ethene is hydroaminated with diethylamine and dimethylamine in the presence of catalytic amounts of an alkali metal diethyl or dimethyl amide or a mixture thereof or an alkali metal hydride. The streams fed to the reactor contain 0 to 1% by weight, preferably <0.1% by weight ammonia, 0 to 5% by weight, preferably <1% by weight monoethylamine and monomethylamine, 20 to 80% by weight. %, preferably 40 to 70% by weight, (diethylamine + dimethylamine), 0 to 50% by weight, preferably <40% by weight triethylamine, 5 to 50% by weight, preferably 10 to 30% by weight ethylene , 0.01 to 20% by weight, preferably 0.1 to 2% by weight of the catalyst and 0 to 20% by weight of a solvent for the catalyst. O

In the case of a batch process, these current data correspond to the starting concentrations in the reactor.

The reaction can be carried out in various reactors e.g. B. in a bubble column (preferably cascaded), a stirred tank, a jet loop reactor or a reactor cascade. The reaction is carried out at 40 to 150 ° C and 1 to 100 bar, in particular at 70 to 120 ° C and 5 to 40 bar. The catalyst is preferably in homogeneous solution in the liquid phase. In principle, if the solubility of the catalyst is exceeded, the reactor can also be operated in the suspension mode.

The reaction discharge is worked up using the methods known to the person skilled in the art, preferably by distillation, in such a way that the low boilers (ethene, dimethylamine), the high boilers (catalyst, triethylamine) and diethylamine are separated off from the reaction discharge and returned to the reactor. The products obtained as medium boilers (triethylamine, ethyldimethylamine) are separated and removed from the process.

In the case of a batchwise design of the process, the addition products formed are preferably distilled off directly from the reactor. As long as it has sufficient activity, the catalyst can remain in the reactor and can thus be used for further reactions.

In the continuous design of the process, the adducts formed (triethylamine, ethyldimethylamine) can be removed from the reaction mixture, for example by stripping with unreacted ethene. However, the reaction mixture is preferably fed to flash evaporation or directly to a distillation. The catalyst, which is preferably dissolved in a high-boiling solvent (> 50% by weight) or in trialkylamine (> 50% by weight) and is obtained at the bottom of the column or in the liquid phase of the flash, is in a preferred embodiment in returned the reactor. A partial stream is disposed of for high boiler and catalyst exclusion. As an alternative to the thermal work-up of the reaction discharge, a filtration can be used for catalyst recovery or retention. The low and medium boilers are worked up in a manner known to the person skilled in the art suitable distillation sequence, with ethene, dimethylamine and diethylamine being returned to the reactor.

Parts of the ethene dissolved in the reaction discharge can preferably first be separated from the reaction discharge in a flash evaporation and returned directly to the reactor via a compression. The remaining reaction discharge is carried out as described above.

In the hydroamination reactions, inert alkylamines or saturated hydrocarbons can be present in the reactor. However, since they make it difficult to separate the product mixture by distillation, the presence of these compounds is not preferred.

In a preferred embodiment of the present invention, the preparation of the amide and the hydroamination are carried out in a single process step.

In this embodiment, one of the amines to be alkylated, or a mixture of these amines in the desired ratio, is advantageously first reacted with the amount of Na required to form the necessary amount of amide in the presence of an electron-transferring compound, preferably butadiene. The formation of the amide occurs spontaneously due to the presence of the electron carrier. The excess of the amine or amines, which is not reacted with the Na to the amide, reacts with ethylene to the desired product.

The amount of Na used in the production of the amide is chosen so that a molar ratio of Na to the total amount of ethylene is from 1: 5 to 500, preferably from 1:10 to 1: 200, in particular from 1:50 to 1: 150 is present.

If the amide preparation and the hydroamination are carried out as described above, this takes place at temperatures from 0 to 150 ° C., preferably 20 to 90 ° C., in particular 30 to 70 ° C., and pressures from 1 to 200 bar, preferably 1 to 100 bar , in particular 3 to 50 bar.

In most cases, the main product desired will be triethylamine. In these cases, an excess of diethylamine, based on dimethylamine, is used. The excess of dietliylamine and possibly also the amount of ethylene is preferably adjusted so that triethylamine is formed in an 8- to 15-fold excess, in particular in a 10-fold excess, over dimethylethylamine.

The hydroamination of ethylene described above is carried out at temperatures from 30 to 180 ° C., preferably 50 to 100 ° C. and pressures from 1 to 200 bar, preferably 20 to 200 bar, in particular 30 to 50 bar.

In all the reaction variants described above, the reaction of the olefin with the amine is carried out in the presence of the amide in a manner known to the person skilled in the art. The description of preferred implementation variants can be found in GP Pez et al., Pure and Applied Chemistry 57 (1985), pages 1917-26, RD Closson et al., J. Org. Chem. 22 (1957), pages 646-9, US 2,501,556, D. Steinborn et al., Z. Chem. 29 (1989), pages 333 -4, D. Steinborn et al., Z. Chem. 26 (1986), pages 349 -59 and H. Lehmkuhl et al ., J. Organomet. Chem. 55 (1973), pages 215-20. The reaction of the olefin with the amine in the presence of the metal alkyl amide can also be carried out in the presence of smaller amounts of ammonia, generally <1 mol%, based on the amines used, as described, for example, in DE-A 21 17 970.

The metal alkyl amide can be converted into metal hydride during the reaction by β-elimination or the action of H ₂ as described in DE-A 26 13 113, an imine being formed in the case of β-elimination. This hydride can under the action of a primary or secondary amine according to DE-A 26 13 113, CA Brown, J. Am. Chem. Soc. 95 (3) (1973), 982ff or CA Brown, Synthesis (1978), 754ff, are converted back into metal alkyl amide and H ₂ , so that the metal hydride can be regarded as a kind of "resting form" of the metal alkyl amide. For the purposes of the present invention, it is therefore equivalent to the metal alkyl amide.

In a preferred embodiment of the present invention, a cocatalyst is used which has an acidity of <35 on the McEven-Streitwieser-Appleguest-Dessy scale, preferably from 20 to 35, particularly preferably from 25 to 35, very particularly preferably from 30 to 35 , having. The scale from McEven-Streitwieser-Appleguest-Dessy is in DJ. Cram, Fundamentals of Carbanion Chemistry 1965, Acad. Press, NY, Chapter 1 released. Unsaturated nitrogen compounds are preferably used as cocatalysts. These can be imine or tautomeric enamine compounds. These can be cyclic or open chain.

Open-chain nitrogen compounds used with preference are selected from open-chain imine or the tautomeric enamine compounds of the general formula (I) or (Ia)

(I) (la)

wherein the radicals R ¹ to R ⁶ independently of one another denote hydrogen or alkyl radicals which can be branched or unbranched and / or can be interrupted by one or more nitrogen atoms. R ¹ to R ^{6 are} preferably C 1 -C ₂ -alkyl radicals, particularly preferably C 1 -C 6 -alkyl radicals. Suitable alkyl radicals are, for example, methyl, ethyl, n- or isopropyl, n- or iso- or tert-butyl.

R ¹ to R ⁶ can also be, independently of one another, cycloalkyl radicals which can be substituted by the above-mentioned functional groups or by alkyl, alkenyl or alkynyl groups and / or interrupted by one or more nitrogen atoms. Cycloalkyl radicals which are preferably used have 3 to 12 carbon atoms - optionally partially replaced by nitrogen atoms - in their ring, particularly preferably 5 or 6 carbon atoms. The cycloalkyl radicals are very particularly preferably unsubstituted. Particularly suitable cycloalkyl radicals are, for example, cyclopentyl and cyclohexyl.

It is furthermore possible for the radicals R to R to be, independently of one another, alkenyl radicals or alkynyl radicals which have one or more multiple bonds, preferably 1 to 4 multiple bonds. The alkenyl or alkynyl radicals can be substituted in accordance with the alkyl radicals or interrupted by one or more nitrogen atoms.

It is also possible that two of the radicals R ¹ to R ⁶ together form a ring which in turn can be substituted by alkyl, alkenyl or alkynyl groups. The radicals R to R are particularly preferably independently of one another hydrogen, methyl or ethyl, the radicals R ¹ to R ^{6 being} very particularly preferably each hydrogen.

Both cyclic enamines and N-heterocyclic compounds in the form of imines or enamines are suitable as cyclic unsaturated nitrogen compounds. Cyclic enamines which are preferably used have a C to C ₈ carbon junction, particularly preferably a C to C ₈ carbon junction. This carbon ring is at least monounsaturated and carries at least one amino group which has at least one hydrogen atom. Depending on the ring size, the carbon ring can also carry two or more double bonds. Cyclic enamines which are not further conjugated are preferably used. The carbon ring can be substituted by one or - depending on the ring size - several residues in addition to the amino group. Suitable radicals correspond to those already mentioned above for R ¹ to R ⁶ , with the exception of hydrogen (in the context of the substitution of this carbon ring with radicals, a substitution with hydrogen is not regarded as a radical). Preferred radicals are alkyl radicals which can be branched or unbranched and have 1 to 6, particularly preferably 1 to 4, carbon atoms. The number of residues depends on the ring size, with no to 3 residues being preferred and the carbon ring particularly preferably carrying no or, very particularly preferably, no residue.

Suitable cyclic unsaturated nitrogen compounds are for example:

such as

Double bond isomers therein R ⁷ to R ^{12 are} hydrogen or one of the radicals mentioned for R ¹ to R ⁶ . R ⁷ to R ¹² are preferably hydrogen, methyl or ethyl radicals, very particularly preferably hydrogen or ethyl radicals.

R 'can represent a single or more substituents on the carbon ring, the maximum number of radicals R' corresponding to the number of hydrogen atoms of the ring carbon atoms. The number of radicals R 'is preferably 0 to 3, particularly preferably 0 to 1, very particularly preferably 0, that is to say all carbon atoms of the carbon ring are substituted with hydrogen, with the exception of one carbon atom which bears the amino group. Suitable radicals R 'are, independently of one another, alkyl radicals which can be branched or unbranched and / or interrupted by one or more nitrogen atoms. The radicals R 'are preferably Cj - C _u alkyl, more preferably Ci - C ₄ alkyl radicals. Suitable alkyl radicals are, for example, methyl, ethyl, n- or isopropyl, n- or iso- or tert-butyl.

The radicals R 'can also be, independently of one another, cycloalkyl radicals which can be substituted by the functional groups mentioned above or by alkyl, alkenyl or alkynyl groups and / or interrupted by one or more nitrogen atoms. Cycloalkyl radicals which are preferably used have 3 to 12 carbon atoms - optionally partially replaced by nitrogen atoms - in their ring, particularly preferably 5 or 6 carbon atoms. The cycloalkyl radicals are very particularly preferably unsubstituted. Particularly suitable cycloalkyl radicals are, for example, cyclopentyl and cyclohexyl.

It is furthermore possible for the radicals R 'to be, independently of one another, alkenyl radicals or alkynyl radicals which have one or more multiple bonds, preferably 1 to 4 multiple bonds. The alkenyl or alkynyl radicals can be substituted in accordance with the alkyl radicals or interrupted by one or more nitrogen atoms.

It is also possible that two of the radicals R 'together form a ring which in turn can be substituted by alkyl, alkenyl or alkynyl groups.

The radicals R 'are particularly preferably independently of one another methyl, ethyl or n- or isopropyl. From the listed compounds, no further conjugated enamines are selected from

very particularly preferred.

Preferred N-heterocyclic compounds in the form of imines or enamines are cyclic compounds with a total of 3 to 20 atoms, preferably 5 to 12 atoms, particularly preferably 5 to 7 atoms. In addition to the necessary nitrogen atom, the N-heterocyclic compound can contain further heteroatoms, preferably nitrogen atoms. The number of further heteroatoms depends on the ring size. The N-heterocyclic compounds preferably contain from one ring size of 5 atoms no to 2 further heteroatoms, particularly preferably no or 1 further heteroatom. The carbon atoms of the N-heterocyclic compound can carry further radicals. Suitable radicals are the same as those already listed as radicals R 'of the carbon rings of the cyclic enamines mentioned above. In the case of N-heterocyclic compounds which, in addition to the N atom, contain further heteroatoms, preferably nitrogen atoms, in addition to the carbon atoms, the heteroatoms, apart from one nitrogen atom, can also carry further radicals R '. In addition to the imine or enamine double bond, the N-heterocyclic compounds can have further double bonds which can be conjugated or non-conjugated to the imine or enamine double bond. N-heterocyclic compounds which have no conjugated double bonds are preferably used.

Suitable N-heterocyclic compounds are, for example:

Therein the radical R 'has the same meaning as the radical R' mentioned in connection with the preferred cyclic enamines. R 'is preferably 0 to the number of ring atoms minus 1, particularly preferably all ring atoms of the N-heterocyclic compounds carry hydrogen atoms or a radical R, where at least one nitrogen atom of the N-heterocyclic ring carries a hydrogen atom.

Among the listed compounds, N-heterocyclic compounds which have no conjugated double bonds are selected from

particularly preferred. Compounds of the following formula are very particularly preferred:

where R has the meaning given above.

The cocatalyst is particularly preferably an imine or tautomeric enamine compound which is formed during the dehydrogenation of the reactant and / or product amines or a decay or secondary product of the corresponding imine or tautomeric enamine compound. The cocatalyst is very particularly preferably an imine or tautomeric enamine compound which is formed during the dehydrogenation of the eductamine or a decomposition or secondary product of the imine or tautomeric enamine compound.

It is possible to produce the desired cocatalyst and add it separately to the starting products. However, it is also possible to produce the cocatalyst in situ before or during the reaction (hydroamination reaction). In a preferred embodiment, the cocatalyst is formed by reacting the hydride used as the catalyst or the metal used to prepare the catalyst with the mono- or dialkylamine (or optionally mono- or diarylamine or alkylarylamine) selected as the starting material before the reaction with the alkene. reacted and the hydrogen formed is removed from the reaction mixture. The mixture is preferably distilled and then separated into a gas phase, a low boiler fraction containing the starting material and the cocatalyst and a bottom fraction containing the hydride or the metal. The low boiler fraction is then added to the bottom fraction, the procedure described is optionally repeated and the hydroamination is started by adding alkene and optionally further eductamine.

It is also possible to form the desired cocatalyst during the reaction. The cocatalyst is formed during the reaction by reacting diethylamine with ethylene in the presence of a metal hydride or metal as catalyst, the reaction mixture obtained preferably being separated by distillation into a gas phase (a) which contains hydrogen and unreacted ethylene, a low boiler fraction ( b) which contains unreacted starting amine and the cocatalyst, a middle boiler fraction (c), which contains product amine, and a bottom action (d), which contains the catalyst. Fraction (b) is supplemented with fresh starting material and ethylene and returned to the bottom fraction which contains the catalyst. It is also possible to isolate the unreacted ethylene from the gas phase (a) and together with the low boiler fraction (b) to the bottom fraction

In a preferred embodiment, the process according to the invention is carried out in such a way that hydrogen formed during the reaction is removed from the reaction mixture. This can preferably be done by distillation or stripping. It must be taken into account here that the remaining substances separated off during the distillation are returned in whole or in part to the process.

Without being bound by theory, a possible mechanism which leads to the formation of the cocatalyst in the in-situ formation of the cocatalyst in the reaction of sodium hydride and diethylamine is described below. The proposed mechanism applies both to the use of metal hydrides and to the use of alkali metals for the preparation of the catalysts.

Minor amounts of NaNEt _{2 are} formed by the reaction of sodium hydride with diethylamine. This probably decays according to the following scheme:

NaH + NHEt ₂ - = ^ = NaNEt ₂ + H ₂

The resulting enamine / imine has sufficient acidity, which is sufficient to enable protonation of the sodium hydride or oxidation of the metal to a high degree.

Alternatively or additionally, the imine can also be prepared by dehydrogenating the eductamine in the presence of a hydrogenation / dehydrogenation catalyst, which is shown below:

[Cat.] = Hydrogenation / dehydrogenation catalyst

All conventional hydrogenation-Z-dehydrogenation catalysts are suitable as hydrogenation-Z-dehydrogenation catalysts. Transition metal catalysts in the form of unsupported or supported catalysts are generally used. Preferred transition metals are selected from groups VHIb and Ib of the Periodic Table of the Elements. Fe, Ru, Co, Ni, Pd, Pt and Cu or alloys of these metals are particularly preferred. Suitable carrier materials are, for example, carbon, SiO ₂ , Al ₂ O, ZrO and TiO ₂ . Furthermore, the hydrogenation / dehydrogenation catalysts can contain promoters / modifiers selected from Sn, Sb, alkali metals, alkaline earth metals, Bi and Pb. Suitable hydrogenation / dehydrogenation catalysts are, for example, Raney-Ni, Raney-Cu, Raney-Co, Pd / γ-Al ₂ O ₃ , Pt / carbon, Ru / SiO ₂ , Pd / Sn / Cs / γ-Al ₂ O ₃ .

The exact compositions of suitable hydrogenation-Z-dehydrogenation catalysts are known to the person skilled in the art.

In a preferred embodiment of the process according to the invention, the hydrogenation / dehydrogenation catalysts are used in one reactor together with the metal hydride or metal amide used as catalyst.

In a preferred embodiment of the process according to the invention, the hydrogen is removed from the system during the reactions described above in order to shift the equilibrium further in the direction of the desired cocatalysts.

The present application thus also relates to a process according to the invention for the preparation of alkylamines (product amines) by reacting ethylene with diethylamine and dimethylamine in the presence of a metal hydride or metal amide as catalyst, the reaction taking place in the presence of a cocatalyst. In this process, the cocatalyst is formed in situ before the diethylamine is reacted with the ethylene (hydroamination) or during the reaction of the diethylamine with the ethylene.

Furthermore, complexing agents can be present as solvents both in the preparation of the catalyst and in the reaction.

So describe e.g. B. J.F. Remenar (J. Am. Chem. Soc. 120 (1988), 4081fr), H. Lehmkuhl et al. (J. Organomet. Chem. 55 (1973), 215ff. And D. Steinborn et al. (Z. Chem. 29 (1989), 333ff. The use of N ^ N'.N'-tetamethylethylenediamine, N, N, N ' , N ", N" - pentamethyldiethylenetriamine, N, N, N ^ N'-tetamethylcyclohexanediamine and tetrahydrofuran as complexing agents.

Furthermore, amines with several amine N atoms per molecule, such as. B. N.NjN'jN'-tetaethylethylenediamine, N-permethylated or N-perethylated triethylene tetramine to N-permethylated or N-perethylated polyimine with molecular weights up to 500,000 daltons, ethers and polyethers, such as. b. Diglyme, triglyme and the corresponding homologues, end-capped polyols - e.g. B. PEG, PPG, poly-THF, and complexing agents with amine N and ethereal O atoms in the molecule, such as. B. 3-methoxyethylamine, 3- (2-methoxyethoxy) propylamine or N, N, N ', N'-tetramethyl-diaminodiethyl ether, the reaction mixture.

The catalyst can be used as a solution, as a suspension or supported on a typical catalyst support such as. B. SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , activated carbon, MgO, MgAl ₂ O ₄ are present. The catalyst is preferably present as a solution or suspension, particularly preferably as a solution.

The hydroamination of ethylene can be carried out batchwise (adding the olefin to the catalyst and amine), semi-continuously (adding the olefin to the reaction mixture) or continuously (adding all components).

A molar ratio of ethylene: secondary amine of 3: 1 to 1:10 is preferred in each case, and 1: 1 to 1: 2 is particularly preferred.

Following the hydroamination reaction, the catalyst is separated from the reaction mixture. This is done by the usual methods, for example Distillation under reduced or normal pressure, filtration, membrane filtration, sedimentation, washing with water, preferably acids, salt solutions or alcohol.

Non-protolyzed catalyst (metal alkyl amide or metal hydride) can then be recycled 5.

In the hydroamination, by-products, for example trimethylamine or diethylmethylamine, can be formed by transalkylation reactions in addition to the desired products. This by-product formation can be suppressed by a suitable reaction procedure, a suitable choice of the catalyst or its amount and further measures known to the person skilled in the art. The reaction is preferably carried out in such a way that 0.5% by weight, preferably <0.3% by weight, in particular <0.1% by weight, of by-products are formed by transalkylation.

In one embodiment of the present invention, the amine mixtures obtained after the removal of the catalyst are separated and part of the triethylamine is isomerized with the addition of ammonia. After any further separation, the diethylamine formed is then recycled as a starting material. In this way, the inventive method can be designed flexibly and the product range

_20th Market requirements.

The transalkylation, which is carried out under conditions known to the person skilled in the art, thus provides an eductamine for the hydroamination.

25 The isomerization / hydrogenation stage can optionally be designed as a reactive distillation.

The described reaction of the transalkylation of the amines is carried out at temperatures from 80 to 400 ° C. 30

In particular, the reaction of the hydroamination product under transalkylating conditions, e.g. B. as described in Houben Weyl Volume XI / 1, nitrogen compounds II, 1957, Georg Thieme Verlag Stuttgart, pp. 248 to 261.

35 Accordingly, the ammum alkylation ("amine exchange") will be carried out in the presence of dehydration catalysts and hydrogenation / dehydrogenation catalysts. Suitable dehydration catalysts as transalkylation catalysts are e.g. B. disclosed in the application DE 101 55 524.5 of the applicant dated November 12, 2001. The transalkylation catalysts disclosed in this application are an integral part of the present invention and are incorporated by reference.

In the case of a reaction in the gas phase, the pressure is generally from 1 to 70 bar.

In the case of a reaction in the liquid phase, the pressure is generally 70 to 250 bar.

The temperature is generally 80 to 400 ° C., in particular between 100 and 350 ° C., preferably between 120 and 250 ° C., very particularly preferably between 150 and 230 ° C.

Depending on the temperature selected, an equilibrium of the alkylamines plus, if appropriate, ammonia is established, which depends on the ratio of nitrogen to steric stress and the length of the alkyl groups. The more sterically demanding the alkyl groups, the lower the proportion of the corresponding tertiary alkylamine.

The loading of the catalyst with the starting material can be between 0.05 and 2 kg of starting material per liter of catalyst and per hour (kg / l * h), preferably between 0.1 and 1 kg / l * h, particularly preferably between 0.2 and 0.6 kg / l * h.

The molar ratio of the amines obtained to one another can vary widely depending on the desired product mix. After depressurization, the discharge can be distilled off and diethylamine returned or triethylamine removed as product. Any monoethylamine that may be formed is removed from the reaction cycle. Ammonia can be recycled to the transalkylation.

example 1

Synthesis of ethyldimethylamine and triethylamine

Sodium diethylamide (50 mmol) and the diethylamide / dimethylamide mixture (5 mol / 2 mol) were introduced into the reactor in a 250 ml autoclave under a weak stream of argon. The reactor was brought to working temperature (70 ° C.) with stirring and then 40 bar of ethene were injected. During the trial, the pressure of rectification was reduced Ethene was kept at 40 bar and samples were taken. After the end of the experiment, the autoclave was cooled, decompressed and the remaining catalyst was deactivated with ethanol.

GC analysis: 50 ° C (5 min) -15 ° C / min -280 ° C (25 min). The running sample was drawn over a riser pipe, the receiver was cooled with CO ₂ and the sample was then treated with 50 percent KOH. Further data are summarized in Table 1.

Time GC - analysis FL% inside jacket pressure ethene ethene min N-ethyl - triethyl - in ° C in ° C in bar g inlet g absorption dimethylamine amine

%%

Rt = 4.588 Rt = 8.675

room temperature

0 0 2.6 67.5 - 85.7 79.0 0 - 20 0 - 30.6 in 1 min

10 72.0 - 77.0 70.0 2 - 20 54.8 in 1 min

15 18.28 6.5 ₄ 77.3 69.6 10 57.0 2.2

30 22.89 1 ₄ , 35 69.5 79.1 42.0 140.5 83.5

60 22.27 25.89 71.4 76.0 42.0 161.5 21.0

90 71.4 75.8 42.0 177.2 15.7

120 20.89 38.59 69.2 77.0 40.0 182.9 5.7

180 19.61 48.8 ₄ 70.9 75.3 41.5 205.2 22.3

240 70.6 76.2 43.0 224.9 19.7

270 18.78 60.09 70.6 75.9 43.0 228.0 3.1

360 17.98 66.68 69.1 76.3 43.0 2 ₄ 5.5 17.5

Table 1: Addition of DMA (2 molVDEA (5 mol) to ethene 70 ° C, 40 bar, cat: 50 mmol NaNEt ₂

The evaluation of the experiment shows that the addition of ethylene to dimethylamine proceeds faster than the corresponding addition to diethylamine. Dimethylethylamine is formed within a short time (30 min). The formation of triethylamine is also after

360 min not yet completed.

Example 2.

Comparison of the activity of diethylamide and dimethylamide in the synthesis of triethylamine

Na-dimethylamide and Na-diethylamide (in each case 60 mmol) and diethylamine (450 g, 6.08 mol) were introduced into the reactor in a 11-autoclave under a weak stream of argon. With stirring, the reactor was brought to working temperature (70 ° C) u. then 40bar ethene pressed. During the experiment, the reaction pressure with ethene was kept at 40 bar u. Samples taken. After the end of the experiment, the autoclave was cooled, let down, and the remaining catalyst was deactivated with ethanol. GC analysis: capillary column 30 m long, 1.5 μm, 0.32 mm Rtx-5-amine temp. Program: 50 ° C (5 min) -15 ° C / min -280 ° C (25min). The running sample was drawn over a riser pipe, the receiver was cooled with CO ₂ and the sample was then treated with 50 percent KOH.

The evaluation of the experiment shows that the conversion of the reaction when using sodium dimethylamide is higher than the corresponding catalyzed with sodium diethylamide. Since Na-dimethylamide is much more stable than Na-diethylamide, the decomposition to the hydride is also slowed down. At the same time, more can be implemented with the much more active amide.

Triethylamine synthesis: 40 bar, 70 ° C, catalyzed with 60 mmol sodium diethylamide

Table 2: Triethylamine synthesis at 40 bar, 70 ° C, catalyzed with 60 mmol

Natriumdimethylamid

Claims

DPatentansprüche

1. A process for producing ethyldimethylamine and trie ylamine, comprising the following steps:

(i) reacting a mixture of Diemyla in and dimemylamine with ethylene in the presence of a catalyst from the group of alkali metal dimethylamides, alkali metal diethylamides and alkali metal hydrides

(ii) separating the catalyst

(iv) optionally recycling the catalyst and the starting amines into the

Reaction.

2. The method according to claim 1, characterized in that diethylamine is used in excess, preferably the ratio diethylamine / triethylamine (8 to 15): 1, in particular 10: 1.

3. The method according to claim 1 or 2, characterized in that ethylene is used in excess.

4. The method according to any one of claims 1 to 3, characterized in that the alkali metal is selected from Li, Na or K, preferably Na.

5. The method according to any one of claims 1 to 4, characterized in that the catalyst is selected from Na-diethylamide and Na-dimethylamide and mixtures thereof.

6. The method according to any one of claims 1 to 5, characterized in that the metal amide is prepared before use in the reaction of dimethylamine or diethylamine or a mixture thereof in a manner known per se.

7. The method according to any one of claims 1 to 6, characterized in that the streams fed to the reactor 0 to 1 wt .-%, preferably <0.1 wt .-% ammonia, O

0 to 5% by weight, preferably <1% by weight (monoemylamine + monomemylamine), 20 to 80% by weight, preferably 40 to 70% by weight, (piethylamine + dimethylamine), 0 to 50% by weight %, preferably <40% by weight of triethylamine, 5 to 50% by weight, preferably 10 to 30% by weight of ethylene, 0.01 to 20% by weight, preferably 0.1 to 2% by weight of the catalyst and contain 0 to 20% of a solvent for the catalyst.

8. The method according to any one of claims 1 to 7, characterized in that the production of the amide and the hydroamination are carried out in a single process step.

9. The method according to any one of claims 1 to 8, characterized in that a cocatalyst from the group of cyclic or open-chain imine or tautomeric enamine compounds is used.

10. The method according to any one of claims 1 to 9, characterized in that part of the amine mixtures obtained after separating the catalyst is separated, part of the triethylamine isomerized with the addition of ammonia, and the diethylamine obtained is separated off as a starting material and recycled into the reactor ,