Manufacture of ethylene diamine from ethylene dihalide

The present invention relates to the manufacture of ethylene amines from ethylene dihalides. More particularly the invention relates to the manufacture of ethylene diamine from ethylene dichloride or ethylene dibromide utilizing solvent extraction techniques for product isolation. The term ethylene diamine (EDA) when used in a general sense in this application means a series of ethylene amines which also includes diethylene triamine, triethylene tetramine, tetraethylene, pentamine and other polyethylene amines, such as piperazine and aminoethyl piperazine.

Ethylene amines in general and in particular ethylene diamine, is recognized as an inportant reagent in the chemical industry. Polyamines, find use in paper and textile industry and also as chelating and water treating agents. The most encountered method for their manufacture is the ammonolysis of ethylene dichloride using an excess of aqueous ammonia. After neutralization of the resultant amine hydrochloride salts with sodium hydroxide and concentration of the reaction products, ethylene diamine is recovered by distillation leaving a residue containing higher polyamines along with sodium chloride. The sodium chloride is separated by centrifugation or filtration and washed. The disadvantages of this method are connected with the corrosion problems involved during distillation in the presence of salts, co-production of about 3¾ of vinyl chloride (now suspected to be carcinogenic), as well as ecological problems due to disposal of the aqueous streams and waste salts contaminated with amines resulting from the process. A very recent review on ethylene diamine (The Leonard Process Co., Englewood Cliffs, 1978) points out correctly the long felt need for a more convenient process in this field: There is apparent concern with the conventional process for manufacturing ethylene diamine since major environmental problems exist with the process. This has led to continued research into other ways of producing the ethylene amines and polyamines and also research into ways of improving the ethylene dichloride route to EDA.

Ethylene dibromide has also been suggested as a raw material instead of ethylene dichloride, its potential advantages being the feasibility of operating at lower temperatures and pressure, and possibility of utilizing weaker ammonia solutions. It was also claimed that the primary amines produced with ethylene dibromide are of a higher purity than these obtained with ethylene dichloride. But nevertheless up to now no actual plant utilizing ethylene dibromide as starting material is known. The reason seems to be connected with the economic handicap of the more expensive bromine derivative and the absolute requirement to achieve a complete recovery of the more expensive bromine values from the system. This points up the inefficiency in the recovery of the chemical values by the technologies known up to .now. Kirk^Othmer in his Encyclopedia (Vol 2 page 350) stipulates that almost quantitative recovery and reutilization of the bromine value would be essential as relatively low percentage losses of bromine would render the costs prohibitive.

Two other processes are also known to produce ethylene diamine, starting with raw materials other than ethylene dichloride. Hie more important of the two is the route of ammonolysis of monoethafltf.amine, which obviates the waste disposal problem, overcomes the difficulties caused by vinyl chloride formation and eliminates the need for sodium hydroxide. However this route has the inherent drawback of the more expensive starting raw material (the price of monoethan01amine being more than twice that of ethylene dichloride) along with the more drastic reaction conditions required such as higher temperature and pressures and the exclusive amounts of the cyclic condensation products produced. The second process is based on the use of ethylene oxide or glycol as raw material, which suffers essentially from the same drawback as with that using ethanolamine. ... fince the present invention is based on using ethylene dihalide as starting material, further discussion on this route is warranted. Though the reaction between the ethylene dihalide and ammonia seems to be simple, there are several alternatives for the course of this reaction, including various by-products, due to the bifunctional character of both the dichloride and diamine. These by-products include secondary and tertiary amines, along with higher polyamines such as triethylene tetramine, and cyclic piperazine which result from the polycondensation reactions. There are many references describing various embodiments for carrying out the reaction, claiming special apparatus and/or one or more parameters (such as temperature, pressure, concentration), in order to obtain a purer product or a higher yield of the desired product.

Thus according to U.S. Patent 1,832.534, the reaction is performed continuously by utilizing a horizontal pressure reactor equipped with a stirrer. According to a recent published study (Z.Trocsany and Z.Varga, cf. C.A. 89, 59620, 1978) a homogeneous phase of the reactants is obtained when working with an ammonia concentration of above 57% at 120°C. It is mentioned that under these conditions the sum of ethylene diamine and diethylene triamine obtained as products is of the order of 15-20% of the total amines whereas the amount of tetraethylene pentamine is about 10-15% of the total amines. It is generally known in this manufacture that a tedious separation operation is imposed, normally carried out by a combination of distillation and centrifugation of the precipitated amine salts. Incrustations of alkaline chlorides (resulted from the prior neutralization of the amine salts by alkaline hydroxide) during distillation, interfere with the smooth separation and also cause high corrosion of the equipment. For this reason, several methods have been suggested to obviate the difficulties encountered in the known separation. According to a review by P.Beltrame (La Chimica

E. L'Industria, 43, 9, 985-988, 1961), an ion exchange resin is suggested for the isolation of ethylene diamine from the aqueous solutions of ethylene diamine hydrochloride. According to this review, it is possible to fix the chloride ion on an anionic resin (e.g. Amberlite IRA 410) ; and obtain the free bases in solution. The second alternative to fix the bases on a cationic resin and then to displace them quantitatively by the means of an alkaline solution, is mentioned by the author to be less economic. The inherent disadvantages in the use of resins on an industrial scale are:

- The partial attrition of the resin particles which takes place on continuous use, which renders the process economically unattractive in view of the relatively high cost of the resin.

Very slow rates of mass transfer.

The need to use dilute solutions which require large volumes and 15 consequently large investment costs for equipment.

The requirement of bases for regeneration of the resins and excessive washing in regeneration.

The use of solvent extraction has also been suggested for the separation of ethylene diamine. Thus in accordance with U.S. Patent 20 3,055.809, the ethylene diamine is extracted from a non-salt containing aqueous solution using polyhydric alcohols, glycols ethers and alkanol amines. Volatile primary amines have also been suggested as extractants (cf. Chemical Abstracts 53, 1155) of ethylene diamine from aqueous sodium hydroxide solution. The light phase obtained, consisted of a mixture of ethylene diamine and polyethylene polyamine which was further separated by fractional distillation. This does not overcome the contamination of the aqueous phase with amines which requires distillation of a corrosive salt solution.

It is an object of the present invention to provide a new process for the manufacture of ethylene diamine starting with ethylene dichloride or ethylene dibromide. It is another object of the present invention to provide a new process for the manufacture of ethylene diamine which obviates the corrosion problems during distillation in the presence of salts. Thus the invention consists in a process for the manufacture of ethylene diamine from ethylene dichloride or ethylene dibromide by ammonolysis being characterized by the separation of the halide ion from the ammonolysis reaction product by solvent extraction, using ion active solvent prior to subjecting the ethylene diamine product to distillation and further characterized by the practice of effecting the neutralization in the appropriate stage by a member selected fron! the group consisting of NaOil^and CaCOil)^. I°n active solvents are defined as functional organic compounds capable of interacting by providing counter ion either for amine or halide ion.

According to one embodiment, the ion active solvent is an organic solvent comprising acidic organic constituent having a pK of not less than 7,5 into which the ethylene diamine is transferred, and finally the solvent extract is back-washed by water to recover the ethylene diamine product. It has been surprisingly found that extraction efficiencies of about 30% per stage are obtained, while the metal halides (sodium chloride, magnesium chloride and calcium chloride or the corresponding bromides) remain quantitatively in the aqueous phase. This is a surprising feature in view of the known property of amine salts of acidic organic compounds to extract inorganic salts from brines. The phase separation between the solvent extract and the aqueous raffinate is rapid with no solid precipitation.

Acidic organic constituents which are useful for the present invention should have the following requirements:

A selective extraction and high capacity of ethylene diamine towards the alkali halide.

A complete miscibility with the organic confounds used as diluents.

Easy phase separation of the organic solvent extract, containing the ethylene diamine, from the raffinate aqueous phase containing the alkali halide.

Easy backwashing of the ethylene diamine from the solvent extract by water, without emulsion formation.

Fortunately enough the literature abounds in many acidic organic constituents possessing the above requirements and having a pK^ of not less than 7.5. Most of these organic compounds are also commercially available being produced in large quantities.

The acidic organic constituents found in particular to be preferred are substituted phenols such as: alkyl phenols (e.g. 4-isopropy'l-phenol,

4-nonylphenol, bisphenol-A, 2,6-ditert butylphenol), halogenated phenols (e.g. o-chlorophenol, 2,4,6-tribromophenol), nitrophenol and other substituted phenols provided that they possess a pK_a of not less than

7.5. As will be shown in the experimental part, when the same reaction product was contacted with a strongly acidic cation exchange resin (e.g. polystyrene sulfonic acid known under the Trade Mark Amberlite IR 120) or naphtenic acid it was found that no selectivity whatsoever was found, the metal ion (introduced as hydroxide in the neutralization step) along with ethylene diamine being adsorbed on the resin.

Although theoretically the acidic organic constituents themselves could extract the ethylene amines from the neutralized reaction product, it is preferred to utilize these compounds in conjunction with an organic solvent as diluent, for better phase separation and ease of handling.

Organic diluents which are suitable for use in the present invention are generally slightly water immiscible aromatic and aliphatic hydrocarbons, or substituted hydrocarbons, alcohols, ethers, and esters. Examples of these organic diluents are: benzene, toluene, xylene, octanol, butyl acetate, cumene_יchiorobenzene, a_nisole etc. In general any proportion of the acidic organic constituent to the organic diluent

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can be used, but low proportions on a volume basis of the acidic constituent to the organic diluent, result in the necessity to use unduly large volumes of solutions for removal of the ethylene diamine. In most instances, the amounts of acidic organic constituents which are well suited for use in the organic diluent are between 10¾ and 80% by volume and preferably between about 30% and 70% by volume. There are cases when two or more organic diluents are preferred to be used in conjunction with the acidic organic constituent.

The term ammonolysis in the context of this invention is used in the broad, general sense as discussed in Kirk-Othmer's Encyclopedia of Chemical Technology Vol. II, Pg. 332 and in P.H. Groggins' Unit Processes in Organic Synthesis Sth Ed.,Pg. 388, that is, the aminating agent can be either ammonia, ethylene diamine or mixtures thereof. The nature and composition of the aminating agent will affect the distribution of ethylene amines in the product as will be understood by those versed in the art.

According to a most preferred embodiment of the process described above, the starting material is ethylene dibromide and the neutralization is carried out by calcium hydroxide, followed by extracting the ethylene diamine with the acidic organic constituent in an organic diluent.

The following advantages are thereby obtained :

- Vinyl bromide which might be obtained in very small amounts is both less toxic and less volatile than vinyl chloride; it also polymerizes much less readily than vinyl chloride, thereby minimizing the danger of plugging reactor's pipes with polymer.

- Calcium hydroxide is much less expensive compared with sodium hydroxide.

aCalcium bromide which is obtained as by-product, in a concentrated form is substantially free of any organic constituents, and can be easily marketed without further treatment. As known, calcium bromide is now considered an important reagent for use in drilling fluids and can also be envisaged as an easy mode of bromine or bromide transport since it can easily be transformed into free bromine or any desired bromide.

The process can easily be integrated into any existent plant of ethylene diamine using the conventional method, by adding to the plant liquid-liquid extraction batteries (mixer-settlers or columns).

No solid waste product would be associated according tb this embodiment. As known in the conventional method, using ethylene

D dichloride and neutralizing with sodium hydroxide, the salt co-produced must be chemically or biologically treated (in slurry form) prior to being wasted. In this regard it should be pointed out that the cost of sodium hydroxide comprises as much as 25-30¾ of raw materials costs, when starting with ethylene dichloride.

One of the advantages of the method is the very high efficiency of extraction obtained. It was found that as high as 80¾ (at a molar ratio of 4:1 acidic organic constituent to amine) were obtained. Diluents may be selected from the groups mentioned above, which also will enhance the 10 effectiveness of the overall separation process.

The entire process is very simple to carry out using conventional equipment. The extraction of the ethylene diamine by the acidic organic constituent is performed generally at ambient temperature, lower temperatures enhancing further the transfer of amine into the organic phase. The release of the amine from the organic phase can be easily performed by backwashing with plain water and preferably by hot water, at a temperature of between 40-95°C whereby efficiencies of about 60 to 80¾ can be obtained per stage. Persons skilled in the art will certainly be aware of the fact that a compromise should be attained to optimise the efficiency of extraction of the amine from the reaction mixture and the backwash efficiency of the amine from the solvent. This efficiency is also influenced by the ratio of the components.

According to another embodiment of the present invention, the hydrogen halide (hydrogen bromide or hydrogen chloride) is separated from 25 the ethylene amines present in the reaction product prior to the neutralization. The invention will therefore consist in a process for the manufacture of ethylene diamine from ethylene dichloride or ethylene dibromide by ammonolysis being characterized by the fact that the reaction mixture comprising the ethylene diamine hydrohalide salt is 30 contacted with an organic solvent comprising an organic amine having a basicity expressed by pk^ of below 4, whereby hydrogen halide is extracted, leaving in the aqueous solution ethylene diamine, the organic solvent being regenerated by removal of the halide constituent from the solvent extract. It was surprisingly found that about 90¾ of the hydrohalide acid is extracted by the organic solvent in a single stage while the ethylene diamine remained completely in the aqueous phase. The ethylene diamine product is subsequently separated from the aqueous solution which contains no alkali salts,by distillation as known in the art.

The main requirement of such organic amines is that they possess a stronger basicity than the ethylene amine produced in the reaction.

The most preferred organic solvents will comprise an organic amine which has a pk^ of about 3. Examples of such organic amines are primary, secondary or tertiary amines such as: long chain primary amines ' Primene (Trade Mark), dilaurylamine, trilaurylamine, long chain liquid secondary amine (LA-1 Amberlite), dicyclohexylamine etc.

Although the organic amine can extract by itself the hydrogen halide from the reaction product, it is preferred to utilize the organic amine in conjunction with an organic solvent as diluent, for better phase separation, lower viscosity and ease of handling. Any organic solvent which will dissolve the organic amine, can be used such as various slightly water immiscible aliphatic, aromatic hydrocarbons, or substituted hydrocarbon> , alcohols, ethers, esters, etc. Typical examples of such organic solvents are:decane, benzene, xylene, cumene, iso-amyl alcohol phenylethyl ether, nitrobenzene, chlorobenzene, etc.

The hydrohalide extraction from the reaction product is carried out at any convenient temperature such as ambient temperature, using known equipment for this purpose.

The removal of the halide coiqponent from the solvent extract and regeneration of the organic solvent can be easily performed by a simple neutralization, the particular cation utilized depending on the desired salt to be produced. Thus in case that calcium bromide would be required to be co-produced, calcium hydroxide will be utilized as a neutralizing agent of the hydrobromide salt, resulting in a quantitative conversion into calcium bromide, while the organic solvent containing the free amine is recycled in the process.

While the invention has been described in connection with specific embodiments thereof it will be understood that it is capable of further modifications, and this patent is intended to cover any variations, uses or adaptations of the invention following in general the principle of the invention and including such departures from the present disclosure as come within the known or customary practice in the art to which the present invention pertains and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention.

The invention will be hereinafter illustrated by the following examples without being limited thereto. In the Examples the parts given are expressed as parts by weight unless otherwise stated.

- ΙλEXAMPLE 1

Ethylene dibromide (EDB), 35 parts by weight, was placed in a glass pressure bottle and aqueous NH^ (47%) 133 parts by weight was added at 0°C. The pressure bottle containing a magnetic bar was closed by a stainless steel valve and immersed in a thermostated bath heated to 95°C. The heterogeneous solution was stirred and heated for fifteen minutes, in which time a homogeneous phase was obtained.

After cooling and releasing the pressure, the solution was analyzed for its ionic Br content. It was found that a 98.4$ conversion was obtained.

The product distribution (from G.C. analysis of a neutralized sample) was the following : 61$ EDA, 38$ DETA, approximately

1$ polyamines. This solution was used for neutralization with various alkalies and for separation of products.

EXAMPLE 2

EDB, 30 parts by weight and 109 parts by weight of aqueous NH₃(25$) was mixed as described in Example 1 and heated for fifteen minutes at 95°C, in which time a homogeneous solution was obtained. From the ionic Br' concentration of the solution it was found that a quantitative yield was obtained. The product distribution (from G.C. analysis of a neutralized sample) was the following : 36$ EDA, 32$ DETA, 0.5$ piperazine, 1.6$ aminoethylpiperazine and 29.8$ polyamines.

EXAMPLE 3

Ethylene dichloride, 15.8 parts by weight and 109 parts by weight of aqueous NHg (25$) was mixed and heated as described in Example 2 at 95°C. After 75 minutes only 84$ of ionic Cl' initially present was found in solution. The product distribution was the following : 31% EDA, 26% DETA,

0.9% piperazine, 2% 2-aminoethyl piperazine and 39% polyamines.

EXAMPLE 4

The product from Example 1, 100 parts by weight was mixed with 7.4 parts by weight of lime, whereby the lime reacted and dissolved. The solution obtained, consisting of the ethylene amines and CaBr^, further called solution A-C-B, was separated by solvent extraction as described below. Similarly, Mg hydroxide was also found to be effective for the neutralization.

EXAMPLE 5

The product from Example 1, 100 parts by weight was mixed with 8 parts by weight of solid NaOH, whereby a clear, neutral solution was obtained, from which the amines are recoverable by solvent extraction similar to that described below.

EXAMPLE 6

Solution A-C-B 11 parts by weight was mixed with 22 parts by weight of a 1/1 solution of p-nonylphenol in benzene. After equilibration of the two phases at ambient temperature and separation, the organic phase was found to be completely free of CaBr2» but loaded to an extent of 57% of ethylene amines with respect to the molar concentration of the phenol.

The aqueous phase was contacted in the same manner with fresh portions of the solvent five more times, leaving an aqueous CaBrg brine essentially free of amines. The CaB^ originally present in solution A-C-B was found essentially quantitatively in this residual aqueous phase.

The first organic extract, was contacted with 40 parts by weight of hot HgO (80°C), whereby in a single stage 72% of the extracted amines were recovered in the water wash.

After three similar stages, a nearly quantitative recovery of the amines was obtained. This aqueous solution containing mainly EDA and DETA was distilled by conventional means to isolate the products.

EXAMPLE 7

Example 6 was repeated at a lower than ambient temperature, ca 5°C ,whereby the extraction efficiency per stage increased from 57% to 62%.

EXAMPLE 8

A similar experiment to that described in Example 6 was performed using a 1/1 xylene solution of o-chlorophenol.

The organic extract was free of CaB^. Eighty percent of the amines initially present were transferred into the organic phase by one contact. After three stages, an almost quantitative recovery of the amines in the organic phase was achieved.

The loaded extract was contacted with H^O»!:1 by volume at 80°C, whereby 62% of the amines were backwashed with the aqueous phase. After 5 stages the backwash was complete, the amines processed from the HgO by distillation and the solvent recycled in the process.

EXAMPLES 9-18

Similar experiments were performed using additional solvents to those described above. These runs are described in Table I:

־־5/TABLE I

<td> EXAMPLE</td><td> SOLVENT/DILUENT (v/v)</td><td> EXTRACTION OF AMINES PER STAGE (¾)</td><td> BACKWASH EFFICIENCY PER STAGE (¾) -</td>

<td> 9</td><td> p-Isopropylphenol/ Cumene 1/1</td><td> 71</td><td> 45</td>

<td> 10</td><td> bis-Phenol A/Butylacetate 1/2</td><td> 26</td><td> -</td>

<td> 11</td><td> bis-Phenol A/0ctanol- Benzene(l-l) 1/4</td><td> 39</td><td> 95</td>

<td> 12</td><td> 2,4,6-Tribromophenol/ Nitrobenzene 1/1</td><td> 91</td><td> -</td>

<td> 13</td><td> 2,4,6-Tribromophenol/ iAmOH 1/2</td><td> 96</td><td> 16</td>

<td> 14</td><td> 2,4,6-Tribromophenol/ Chlorobenzene 1/1</td><td> 90</td><td> -</td>

<td> 15</td><td> 2,4,6-Tribromophenol/ Anisole 1/4</td><td> 89</td><td> -</td>

<td> 16</td><td> O-Nitrophenol/Benzene 1/1</td><td> Quantitative</td><td> -</td>

<td> 17</td><td> Amberlite - IR-120</td><td> ** 87</td><td> -</td>

<td> 18</td><td> Naphthenic acid/Decane</td><td> **</td><td></td>

<td></td><td> 1/1</td><td> 95</td><td> -</td>

* Equal volume of HgO at 80°C +4 ** Ca is coextracted

-/CEXAMPLE 19

A reaction product obtained as described in Example 1 was used. A hundred parts by weight of the product was contacted at ambient temperature with 180 parts by weight of dicyclohexylamine in xylene (1:1). The solid di cyclohexyl amine hydrobromide which formed was separated, leaving in the aqueous solution all the ethylene amines and approximately 15% of the HBr initially present. This could be removed by an additional portion of dicyclohexyl amine.

The solid was mixed with xylene and HgO and lime was added. The solid dissolved. An aqueous solution of CaBr₂ and an organic solution containing the recovered dicyclohexyl amine were obtained. Thus in a single extraction step 85% of the HBr bound to the ethylene amines was separated and recovered as an aqueous CaBr₂ solution. The ethylene amines product was subsequently distilled to obtain the pure products.

EXAMPLE 20

A similar experiment to that described in Example 19 was performed, replacing dicyclohexyl amine with Primene (a commercial long chain primary amine) in benzene (1:1). This reagent extracted in one stage 50% of the HBr initially bound to the ethylene amines. After neutralization with lime, aqueous CaBr₂ was obtained and the reagent recovered for further use.

EXAMPLES 21-23

Similar experiments to that described in Example 19 were performed using the following amines dissolved in benzene ¢1:1):

Tri lauryl amine Dilaurylamine ן_^ן Amberlite (Trade name of a long chain liquid, secondary amine). The results are tabulated below :

<td> Example</td><td> Amine</td><td> HBr extraction *</td>

<td></td><td> Extractant</td><td> Efficiency per stage</td>

<td></td><td></td><td> %</td>

<td> 21</td><td> TLA</td><td> 14</td>

<td> 22</td><td> DLA</td><td> 44</td>

<td> 23</td><td> LA-1</td><td> 20</td>

* At ambient temperature

The extracted HBr was separated by neutralization with lime, whereby CaBr^ solutions were obtained, while the reagent was recovered. Example 24

EDB, 35 parts by weight and 22 parts by weight of EDA were reacted at 55°C. From the ionic Br concentration of the product mixture, a conversion of 92% was achieved. The product contained polyamines to the extent of 89%.

Example 25

A reaction was performed as described in Example 2 with the exception that the reactant mixture also contained 4.8 parts by weight of EDA. The polyamine content of the product was thereby increased to 37%.