DE69317334T2 - Process for the preparation of secondary amines and catalyst to be used in this process - Google Patents

Description

The present invention relates to processes for producing secondary amines and to catalyst compositions suitable for use in the production of secondary amines.

Aminomethylation processes in which ammonia or a primary amine is reacted with carbon monoxide, hydrogen and an olefinic compound in the presence of a transition metal catalyst such as a ruthenium and/or rhodium catalyst to form a secondary amine are well known in the art, for example as described in US Patents 4,503,217, 4,526,936 and 4,832,702 and in European Patent Application Publication No. 0 457 386 (Applicant's Reference: T 412 EPC).

The overall aminomethylation process can be formally divided into three reactions. The first is a hydroformylation leading to the formation of aldehyde or metallacyl compounds, followed by a condensation leading to the intermediate formation of a Schiff base or enamine, and the subsequent hydrogenation of the C=N or C=C-N bond to form the desired amine final product (J. Org. Chem., 1982, 47, No. 3, pp. 445-447).

The transition metal catalysts generally used in the above-mentioned aminomethylation processes are homogeneous catalysts which, being soluble in the reaction medium, are difficult to recover for subsequent use. However, catalyst recovery is particularly important in the case of rhodium catalysts, in view of the high cost of rhodium metal.

Heterogeneous catalysts, which on the other hand are easily recoverable from the reaction medium, are known from US patents 3,636,159, 3,652,676, 4,178,314 and 4,189,448. The catalysts described in these patents are said to be useful in hydroformylation reactions, i.e. in the catalysis of the conversion of olefins to aldehydes, and optionally in hydrogenation reactions, for example in the catalysis of the conversion of aldehydes to alcohols.

More specifically, US Patent 3,636,159 describes heterogeneous hydroformylation catalysts containing a solid polymer of a pyridine having associated therewith a metal selected from the group consisting of cobalt, rhodium, ruthenium, platinum and palladium. The only catalysts described in the examples are cobalt-containing catalysts.

US Patent 3,652,676 describes heterogeneous hydroformylation catalysts comprising a solid polymer formed by polymerizing a pyridine and a styrene in the presence of a polyvinyl aromatic compound and having associated therewith a metal selected from the group consisting of cobalt, rhodium, ruthenium, platinum and palladium. The catalysts described in the examples are all cobalt-containing catalysts.

In column 2, lines 1 to 7 of US Patent 3,636,159 and in column 2, lines 4 to 10 of US Patent 3,652,676 it is stated: "The materials which can be used in this way are cobalt, rhodium, ruthenium, platinum and/or palladium which are in a form such that they form a metal carbonyl under the reaction conditions. In general, cobalt is the preferred metal and can advantageously be in the form of cobalt hydrocarbonyl or dicobalt octacarbonyl".

In neither of these two US patents is there a disclosure of any catalysts containing metal compounds other than carbonyls or naphthenates per se.

US Patent 4,178,314 describes heterogeneous hydroformylation and hydrogenation catalysts having the general structure -MCl₃, where M is rhodium or iridium and is a heterocyclic nitrogen-containing polymer. From the examples, in particular Examples 7 to 9 of US Patent 4,178,314 it can be seen that the catalysts described do not facilitate simultaneous hydroformylation and hydrogenation of an olefinic feedstock, so that alcohols can only be obtained from the olefinic feedstock via a two-stage process comprising a first hydroformylation stage and a second hydrogenation stage.

US-A-4 189 448 describes a heterogeneous hydroformylation and hydrogenation catalyst with the general structure

wherein n is from 1 to about 3, m is from 1 to about 2, M is rhodium or iridium, X is chlorine, bromine, iodine or hydrogen and P is a heterocyclic nitrogen-containing polymer. These catalysts are intended to enable a simple, two-step synthesis of alcohols from olefins with a single reaction catalyst.

French patent application publication number 2 476 655 discloses a one-step process for the formation of polymeric polyamines in the presence of a catalytic amount of a rhodium compound in an inert solvent such as the N-heterocyclic compound N-methylpyrrolidine.

Surprisingly, it has now been found that secondary amines can be obtained with high conversion and high selectivity in a one-step process using a special heterogeneous rhodium catalyst.

According to the present invention, therefore, there is provided a process for preparing a secondary amine which comprises reacting a primary amine with carbon monoxide, hydrogen and an olefinic compound in the presence of a catalyst composition comprising a source of cationic rhodium, a source of an anion other than a halide and, as a support, a polymer of an N-heterocyclic compound.

The primary amine used in the process of the present invention may be a monoamine, for example an alkylamine, a cycloalkylamine or an arylamine, or a polyamine containing at least one primary amine group.

In the present specification, unless otherwise stated, an alkyl group or an alkyl residue in an alkoxy group may be straight or branched and preferably contain up to 20, more preferably up to 10 and especially up to 6 carbon atoms. A cycloalkyl group may have 3 to 8, preferably 3 to 6 carbon atoms. An aryl group may be any aromatic hydrocarbon group, in particular a phenyl or naphthyl group. An alkaryl group can be any aryl group which is substituted by at least one alkyl group, for example a methylphenyl group.

The alkyl, cycloalkyl or aryl group in an alkylamine, a cycloalkylamine or an arylamine can be substituted by one or more, for example up to 6, preferably up to 4 substituent groups.

Examples of substituents include alkoxy, alkyl, cycloalkyl, aryl and alkaryl groups.

Examples of monoamines are methylamine, ethylamine, propylamine, n-butylamine, 5-butylamine, t-butylamine, cyclopentylamine, cyclohexylamine and aniline.

The polyamine may consist of carbon, hydrogen and nitrogen atoms or it may additionally contain oxygen and/or sulfur atoms. For example, the polyamine may be a compound with the general formula

wherein each x ranges from 1 to 3, each y ranges from 1 to 3, each A is independently -O- or -S, m is 0, 1 or 2 and n is in the range 1 to 10, and when m is 1, n is 1 and A is -O- or -S-, or n is 2 and A is -5-, and when m is 2, n is 1; and each of R¹ and R² is independently hydrogen or an alkyl group.

In the above formula 1, it is preferred that each of the radicals R¹ and R² independently represents a hydrogen atom or a C₁-C₆ alkyl group, in particular a methyl group. Particularly preferred polyamines of the formula I are those in which each of the radicals R¹ and R² independently represents a hydrogen atom or a methyl group, y has the value 2 or 3, m is 0 and n is in the range from 1 to 6, for example 3-dimethylamino-1-propylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and hexaethyleneheptamine.

The compounds of the above formula I can be prepared according to the methods of H.R. Ing and R.H.F. Manske, J. Chem. Soc., 1926, p. 2348 ff.; D.S. Tarbell, N. Shakespeare, C.J. Claus and J.R. Bunnett, J. Am. Chem. Soc., 1946, 68, p. 1217 ff.; R.C. O'Gee and H.M. Woodburn, J. Am. Chem. Soc., 1951, 73, p. 1370 ff.; A.F. Mckay, D.L. Garmaise and A. Halsaz, Can. J. Chem., 1956, 341 p. 1567 ff.; Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 7 (Wiley Interscience, New York, 3rd ed., 1979), pp. 580-601, US Patent No. 2,318,729, S. Gabriel, Reports, 1891, 24, pp. 1110-1121; F.P.J. Dwyer and F. Lions, J. Am. Chem. Soc., 1950, 72, pp. 1545-1550: F.P.J. Dwyer, N.S. Gill, E.C. Gyarfas and F. Lions, J. Am. Chem. Soc., 1953, 75, pp. 1526-1528; US Patent No. 3,362,996; or manufactured using analogous processes.

The olefinic compound used in the process of the present invention contains at least two carbon atoms and may contain 1, 2 or more olefinic bonds. The olefinic compound preferably contains 2 to 7200, more preferably 2 to 1000, even more preferably 2 to 500 and especially 2 to 100 carbon atoms.

Examples of olefinic compounds include alkenes, cycloalkenes, alkadienes and cycloalkadienes optionally substituted by one or more, for example up to 6, preferably up to 4 substituents selected from alkoxy, alkyl, cycloalkyl, aryl and alkaryl groups; and oligomers and polymers thereof (hereinafter referred to as "polyolefins")

An alkene or alkadiene can contain terminal or internal olefinic bonds. Terminal olefinic bonds are preferred.

A particularly preferred olefinic compound is a C2-C10 alkene, or an oligomer or polymer thereof.

Examples of unsubstituted alkenes are ethene, propene, butene, isobutene, isomeric pentenes or hexenes, 1-octene, diisobutylene and of the substituted alkenes styrene and methylstyrene. Examples of cycloalkenes are cyclohexene and norbornene. Examples of alkadienes are 1,5-hexadiene, 1,7-octadiene and 1,9-undecadiene. Examples of cycloalkadienes are norbornadiene and dicyclopentadiene.

The polyolefin may be partially hydrogenated, but it is important that there is some residual olefinic unsaturation in the polyolefin.

The polyolefin has a number average molecular weight (Mn) preferably in the range of 200 to 100,000, more preferably 200 to 5,000 and especially 500 to 2,500.

Examples of polyolefins are atactic polypropylene, which can be easily prepared by a process analogous to that of Comparative Example 1 of EP-A-268 214, or more generally by the process described in EP-A-69 951; partially hydrogenated polyisoprene, which can be easily prepared by a process analogous to Example 1(a) of GB-A-1 575 507, with partial hydrogenation of the resulting polymer according to Example 1(c); polyisobutylene; polyalphaolefins, i.e. see partially hydrogenated oligomers, especially trimers, tetramers and pentamers of alpha-olefin monomers, generally containing 6 to 12, more often 8 to 12 carbon atoms, which products can be prepared by a process as described in Hydrocarbon Processing, Feb. 1982, p. 75 ff.; as well as hydrocarbons prepared by a plasma process as described in EP-A-346 999.

Polyisobutylenes such as those sold by the British Petroleum Company under the trademarks "Ultravis", "Hyvis" and "Napvis" are particularly preferred for use in the present invention, for example "Ultravis 10", "Ultravis 30", "Hyvis 10", "Hyvis 30", "Hyvis 150" and "Napvis 10" polyisobutylenes having a number average molecular weight (Mn) of 970*, 1300*, 1026*, 1320, 2500 and 971* respectively, the Mn values marked with an asterisk being determined by gel permeation chromatography and the unmarked values being determined by quantitative reaction with ozone.

The process according to the invention is conveniently carried out at a temperature in the range from 60 to 200°C, preferably from 100 to 200°C and in particular from 125 to 170°C.

The present process is conveniently carried out at a total pressure, determined at ambient temperature (20°C), of from 200 to 25,000 kPa, preferably from 2,000 to 20,000 kPa and in particular from 2,000 to 10,000 kPa, in particular at 6,000 kPa. It is understood, however, that if the process is carried out in batches at a constant temperature, the pressure will decrease during the course of the reaction.

A source of cationic rhodium can be any material containing rhodium and capable of providing rhodium cations. Examples of suitable sources include compounds of rhodium such as oxides; salts such as nitrates, sulfates, sulfonates (e.g. trifluoromethanesulfonates or p-toluenesulfonates), borates (e.g. tetrafluoroborates such as Rh(CO)₂(BF₄)), phosphates, phosphonates (e.g. benzenephosphonates), carboxylates (e.g. acetates, propionates or butyrates) and acetylacetonates (e.g. Rh(CO)₂(acac), where acac denotes an acetylacetonate anion); and hydrides (e.g. HRh(CO)(pH₃P)₃).

The source of an anion other than a halide may be a salt or an acid. It may also be a metal complex, for example a rhodium complex. The anion is preferably a nitrate, sulfate, sulfonate, borate, phosphate, phosphonate, carboxylate or acetylacetonate anion. Preferably the anion source is a complex or salt of rhodium or an acid.

The N-heterocyclic compound is preferably selected from piperidine, morpholine, piperazine, pyridine, bipyridine, pyrrole, benzopyrrole, oinoline, indole, imidazole, carbazole, phenanthroline, each of these compounds being substituted by alkenyl, preferably by vinyl, or 4-methyl-4'-vinyl-2,2'-bipyridine.

More preferably, the N-heterocyclic compound is selected from 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine and 4-methyl-4'-vinyl-2,2'-bipyridine.

The polymer of the N-heterocyclic compound may be a homopolymer or a copolymer. Copolymers are preferred.

Comonomers suitable for preparing the copolymers include N-heterocyclic compounds such as the compounds described above; C1-C20, preferably C1-C10 alkyl (meth)acrylates, in particular methyl acrylate; C2-C20, preferably C2-C10 alkenyl (di)(meth)acrylates, in particular ethene diacrylate; and divinylbenzene. Divinylbenzene is a particularly preferred comonomer.

The preferred copolymers are 2-vinylpyridine/methyl acrylate/ethene diacrylate, 2-vinylpyridine/divinylbenzene, 3-vinylpyridine/divinylbenzene, 4-vinylpyridine/divinylbenzene and 4-methyl-4'-vinyl-2,2'-bipyridine/divinylbenzene) copolymers.

The preparation of a polymer of an N-heterocyclic compound is known in the art. The polymer can be conveniently prepared by heating the N-heterocyclic monomers, optionally with one or more different comonomers, to a temperature in the range of 50 to 150°C in an organic solvent and in the presence of an initiator such as azoisobutyronitrile, for example according to the method of Hjortkjaer, Chen and Heinrich, Applied Catalysis, 1991, 67, pp. 269-279.

The number of moles of anion per gram atom of rhodium is preferably at least 0.5, more preferably 1 to 50, even more preferably 1 to 25 and especially 1 to 10.

The number of moles of polymer support per gram atom of rhodium is preferably in the range of 10⁻⁸ to 10⁻¹, more preferably from 10⁻⁷ to 10⁻³ and especially from 10⁻⁷ to 10⁻⁷.

The number of gram atoms of rhodium used per mole of olefinic compound is not critical. It is preferably in the range of 10⁻⁶ to 10⁻² gram atoms of rhodium per mole of olefinic compound.

The CO/H₂ ratio is preferably in the range of 1:10 to 10:1, more preferably from 1:5 to 5:1 and is especially 1:2.

The process according to the invention can be carried out in the presence of a solvent. Typical examples of solvents are ethers, such as diethylene glycol dimethyl ether (diglyme), 1,4-dioxane or tetrahydrofuran; amides such as dimethylformamide or dimethylacetamide; alcohols such as hexanol or tetraethylene glycol; Esters such as ethyl acetate; and hydrocarbons such as hexane, cyclohexane, toluene and the xylenes.

The present invention further provides a catalyst composition comprising a source of cationic rhodium, a source of an anion other than a halide or a hydride, and, as a support, a polymer of an N-heterocydic compound.

The invention will be further understood from the following illustrative examples.

example 1 Preparation of a heterogeneous catalyst Poly(4-vinylridine/divinylbenzene)-[Rh(CO)₂][BF₄]

The reaction was carried out in a glove box. To a suspension of 10.00 g of poly(4-vinylpyridine) cross-linked with 2% divinylbenzene (available from Aldrich Chemical Company Ltd., UK) in 600 mL of methanol was added 1.849 g (4.75 mmol) of [Rh(Co)2Cl]2 and the reaction mixture was stirred for 48 hours at room temperature (20°C). Then 1.044 g (9.50 mmol) of NaBF4 was added to the reaction mixture and stirring was continued for a further 36 hours. The desired final product poly(4-vinylpyridine/divinylbenzene){Rh(CO)2][BF4], a solid, was filtered off, washed with methanol and water and then dried under vacuum. The final product was obtained in 98% yield and contained 7.5% Rh as determined by ICP-MS (calculated 7.7%).

Example 2 Production of secondary amine

Into a 250 ml "Hastelloy C" (trade mark) metal autoclave equipped with a magnetic stir bar and a heating mantle were charged 77 mmol of "Hyvis 10" (trade mark) polyisobutylene (ex BP, number average molecular weight (Mn) 1025, determined by gel permeation chromatography), 105 mmol of 3-dimethylamino-1-propylamine, 75 ml of 1,4-dioxane and 0.3 g of the heterogeneous catalyst obtained in Example 1. The autoclave contents were stirred while the gas space was evacuated (12 kPa). After cleaning the gas feed line, the autoclave was pressurized with carbon monoxide gas to a pressure of 2500 kPa. A slight pressure drop of the carbon monoxide gas was observed due to the dissolution of some Carbon monoxide gas in the reaction mixture. The carbon monoxide pressure was therefore readjusted to the desired value of 2500 kPa. The autoclave was further pressurized with hydrogen gas (4000 kPa) following the same procedure as described for carbon monoxide to give a total pressure at ambient temperature (20ºC) of 6000 kPa. Once the pressure was stable, the autoclave contents were heated to 170ºC with stirring for 24 hours. After cooling, the autoclave was depressurized and the contents were poured into a separatory funnel. An upper product-containing phase was separated from a lower solvent-containing phase and the former was added to 50 ml of hexane. The resulting mixture was then washed three times with 50 ml portions of water. Evaporation of the hexane at 110ºC and 0.3 kPa using a rotary evaporator gave the reaction product which was subsequently analyzed for active content (i.e. polyisobutylene conversion) and basic nitrogen, secondary nitrogen and tertiary nitrogen content.

Results

Active material (00) : 60.8 (58.6 sec. amine; 2.2 byproducts)

Basic N (% N) : 1,330

sec. N (% N) : 0.641

tert. N (% N) 0.689

Catalyst selectivity: on sec. amine (%) 58.6/60.8 x 100 = 96

Example 3

The procedure described in Example 2 was repeated with the difference that 1.0 g of the heterogeneous catalyst obtained in Example 1 was used and the reaction temperature was lowered to 150°C.

Results

Active material (%) : 50.6 (46.0 sec. amine; 4.6 by-products)

Basic N (% N) : 1.094

sec. N (% N) : 0.497

tert. N (% N) : 0.597

Catalyst selectivity: on sec. amine (%) 46.0/50.6 x 100 = 91

The catalyst was recovered and recycled twice, each time giving comparable results to the above results.

Example 4

The procedure described in Example 2 was repeated except that 50 mM 1-octene was used instead of "Hyvis 10" polyisobutylene, 50 ml of 1,4-dioxane and 0.5 g of the heterogeneous catalyst of Example 1 were used and the reaction temperature was maintained at 125°C for 19 hours. Analysis of the reaction product showed that it contained 98% secondary amine (i.e. C9H19-NH-(CH2)3-N(CH3)2). The catalyst selectivity for the secondary amine was calculated to be 99%.

Claims (10)

1. A process for preparing a secondary amine which comprises reacting a primary amine with carbon monoxide, hydrogen and an olefinic compound in the presence of a catalyst composition comprising a source of cationic rhodium, a source of an anion other than a halide and, as a support, a polymer of an N-heterocyclic compound. 2. A process according to claim 1, wherein the primary amine is a compound having the general formula: wherein each x ranges from 1 to 3, each y ranges from 1 to 3, each A is independently -O- or -S-, m is 0, 1 or 2 and n is -1 to 10, and when m is 1, n is 1 and A is -O- or -S-, or n is 2 and A is -S-, and when m is 2, n is 1; and each of R¹ and R² is independently a hydrogen atom or an alkyl group. 3. A process according to claim 1 or 2, wherein the olefinic compound is an alkene, cycloalkene, alkadiene or cycloalkadiene, optionally substituted by one or more substituents selected from alkoxy, alkyl, cycloalkyl, aryl and alkaryl groups; or an oligomer or polymer thereof. 4. A process according to any one of claims 1 to 3, wherein the olefinic compound contains 2 to 100 carbon atoms. 5. A process according to any preceding claim, which is carried out at a temperature in the range of 125 to 170ºC. 6. A process according to any preceding claim, which is carried out at a total pressure in the range of 2000 to 10,000 kPa. 7. A process according to any preceding claim, wherein the source of cationic rhodium is an oxide, salt or hydride. 8. A process according to any one of the preceding claims, wherein the anion is a nitrate, sulfate, sulfonate, borate, phosphate, phosphonate, carboxylate or acetylacetonate anion. 9. A process according to any one of the preceding claims, wherein the N-heterocyclic compound is selected from piperidine, morpholine, piperazine, pyridine, bipyridine, pyrrolidone, pyrrole, benzopyrrole, quinoline, indole, imidazole, carbazole, phenanthroine, each alkenyl-substituted, and 4-methyl-4'-vinyl-2,2'-bipyridine. 10. A catalyst composition comprising a source of cationic rhodium, a source of an anion other than a halide or a hydride and, as a support, a polymer of an N-heterocyclic compound.