MXPA00008163A - Method for separating an azepine derivative from a mixture containing an amine and an azepine derivative - Google Patents

Abstract

The invention relates to a method for separating by distillation all or part of an azepine derivative (III) selected from the group consisting of amino hexylidenimine, tetrahydroazepine, hexylhexahydroazepine and amino hexylhexahydroazepine, from a mixture (II) containing an azepine derivative (III) and an amine (I). The invention is characterized in that the distillation is carried out at an overhead temperature of between 160 and 250°C.

Description

SEPARATION OF A AZEPINE DERIVATIVE FROM A MIXTURE CONTAINING AN AMINE AND A AZEPINE DERIVATIVE The present invention relates to a process for the distillative separation of part or all of an azepine derivative (III) selected from the group consisting of tetrahydroazepine, 2-aminoazepan, N- (2-azepane) -1,6-diaminohexane and N- (2-azepane) -6-aminocapronitrile from a mixture (II) containing a derivative of azepine (III) and an amine (I) selected from the group consisting of 6-aminocapronitrile and hexamethylenediamine, which consists of distillation with a temperature in the upper part from 160 to 250 ° C. Mixtures containing an amine and an azepine derivative are commonly obtained in the hydrogenation of nitriles to amines. A common practice is the complete hydrogenation of adiponitrile (DNA) in hexamethylenediamine (HMD), and also the partial hydrogenation with co-production of HMD and 6-aminocapronitrile (ACN), in the presence of a catalyst based on a metal such as nickel, cobalt, iron, rhodium or ruthenium, for example, from: K. Weisser, HJArpe, Industrielle Organische Chemie, 3rd edition, VCH Verlagsgesellschaft mbH, Weinheim, 1988, page 266, US-A 4 601 859, US-A 2 762 835, US-A 2 208 598, DE-A 848 654, DE-A 954 416, DE-A 42 35 466, US-A 3 696 153, DE-A 1900222, WO 92/21650 and German Application 19548289.1 . The byproducts that are formed include azepine derivatives such as N- (2-azepane) -1, 6-diaminohexane and N- (2-azepane) -6-aminocapronitrile, especially 2-aminoazepan and tetrahydroazepine. These azepine derivatives, which, due to their color and deleterious effects on the properties of the product, constitute undesirable impurities in the amines, which are commonly used to manufacture fibers, are difficult to separate from the amines. example, GB-A-893 709 describes the installation of a delayed time vessel in the reflux line of a distillation column used to purify hexa ethyldiamine. GB-A-1 238 351 describes the separation of HMD from mixtures containing HMD and azepine derivatives, by the addition of mixtures of alkali metal hydroxide. GB-A-1 041 442 describes the passage of carbon dioxide to a distillation column used to separate HMD from mixtures containing HMD and azepine derivatives, during distillation. The disadvantages with these mentioned processes are the use of large reservoirs, which is done for the reduced control of the distillation columns, and the formation of solids, which leads to blockages. It is an object of the present invention to provide a process for separating an azepine derivative from mixtures containing an amine and an azepine derivative in a technically simple and inexpensive manner. We have found that this object is achieved through the process defined at the beginning. Convenient amines I include aromatic amines such as benzylamine, aliphatic amines such as cyclic amines, for example, isophoronediamine, preferably acyclic amines, for example, 1,4-diaminobutyl, especially HMD or ACN, and also mixtures thereof. These amines can be prepared in a conventional manner. For example, HMD can be obtained by partial or complete catalytic hydrogenation with a gas containing molecular hydrogen, from DNA to HMD or mixtures containing HMD and ACN. The catalysts used for this hydrogenation can conveniently be those based on a metal selected from the group consisting of ruthenium, rhodium, nickel, cobalt; preferably iron, in which case the catalysts may include other elements as promoters. In the case of iron-based catalysts, suitable promoters especially include one or more, such as two, three, four or five, elements selected from the group consisting of: aluminum, silicon, zirconium, titanium and vanadium. Such catalysts and the process conditions for the mentioned reaction are described, for example, in WO-A-96/20166, German Application 19 636 768.9 and German Application 19 646 436. The products obtained by the aforementioned processes can be post-hydrogenated with gases containing molecular hydrogen, conveniently in the presence of catalysts based on noble metals such as platinum, palladium or mixtures thereof. The contemplated azepine III derivatives include especially 2-aminoazepan of the formula: N- (2-azepane) -1,6-diaminohexane of the formula: N- (2-azepane) -6-aminocapronitrile: (CH 2) 5-CN and THA of the formula: and mixtures thereof. The azepine (III) derivatives may be present in the mixture (II) as individual compounds or as addition products, for example with an amine (I), in which case these addition products, for the purposes of the present invention , in the same way they should be called azepine derivatives (III). The azepine derivatives and processes for their preparation are commonly known. For example, 2-aminoazepan, N- (2-azepane) -1,6-diaminohexane and N- (2-azepane) -6-aminocapronitrile and tetrahydroazepine can generally be obtained in mixtures (II) in amounts from 1 to 10,000. ppm, based on the mixture, on the partial catalytic hydrogenation of DNA with a gas containing molecular hydrogen to form HMD or mixtures containing HMD and ACN according to the described process for preparing the amines (I). According to the present invention, the distillation is carried out with a temperature in the upper part in the range from 160 to 250 ° C, preferably in the range from 175 to 230 ° C, especially in the range from 185 to 220. ° C. If HMD is used as amine (I) and one or more compounds selected from the group consisting of: AH, HHA, AHHA and THA as azepine derivative (III), then the pressure of the distillation, measured at the top of the apparatus of distillation, it should be within the range from 0.3 to 3 bar, preferably within the range from 0.5 to 2 bar, especially within the range from 0.7 to 1.5 bar. A distillation at pressures around the ambient pressure has the advantage that there is no leakage of air that carries atmospheric oxygen to the distillation apparatus. Oxygen can lead to the formation of a derivative of azepine (III) from an amine (I), for example for the formation of THA from HMD. If ACN is used as amine (I) and one or more compounds are selected from the group consisting of: 2-aminoazepan, N- (2-azepane) -1, 6-diaminohexane and N- (2-azepane) -6- aminocapronitrile and tetrahydroazepine as azepine (III) derivatives, then the distillation pressure, measured in the upper part of the distillation apparatus, should be within the range from 0.1 to 1.3 bar, preferably within the range from 0.18 to 0.85 bar, especially within the range from 0.25 to 0.65 bar.

The apparatus suitable for distillation is any distillation apparatus customary as described, for example, in Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd edition, vol. 7, John Wiley & Sons, New York, 1979, pages 870-881, such as the columns of sieve plates, bubble cap columns or packed columns with arranged or filled packing. The distillation can be carried out in a plurality of columns, such as two or three, but conveniently it is carried out in a single column. The process of the invention usually produces the predominant portion of the azepine derivative (III) as a lower or residual product. This residual product can conveniently be mixed with a compound containing at least one carbon-nitrogen (IV) multiple bond, such as DNA, and this mixture can be subjected in a conventional manner, for example in accordance with the aforementioned processes for preparing HMD or mixtures containing HMD and ACN, for the catalytic hydrogenation in order to obtain an amine (I), such as HMD or mixtures containing HMD and ACN. The HMD and ACN are intermediaries for polyamides of industrial importance, such as nylon 6 or nylon Examples The percentages are by weight, unless otherwise mentioned. THA is tetrahydroazepine. The product mixtures were analyzed by gas chromatography. THA concentrations below 20 ppm were determined by polarography.

Example of the inventive 1 269 g / h of a mixture containing 0.088% THA and HMD as the remainder were fed continuously to a distillation column with a low pressure loss fabric [sic] packing corresponding to approximately 33 theoretical plates. The pressure in the upper part of the column was adjusted to 400 mbar, and a constant distillation of 256 g / h was withdrawn and 256 g / h of applied reflux (reflux rate = 1). The effluent in the upper part collected under steady-state conditions for a period of 17 hours included 0.024% THA, as well as HMD. The residual effluent (13 g / h) included 1.7% THA. Examples of Inventive 2-4 and Comparative Examples 1 and 2 were performed in the same manner as the Example of Inventive 1, but with the parameters shown in Table 1. Table 1

Claims (1)

1. CLAIMS A process for the distillative separation of part or all of an azepine derivative (III) selected from the group consisting of: tetrahydroazepine, 2-aminoazepan, N- (2-azepane) -1,6-diaminohexane and N- (2- azepane) -6-aminocapronitrile from a mixture (II) containing a derivative of azepine (III) and an amine (I) selected from the group consisting of: 6-aminocapronitrile and hexamethylenediamine, which consists in carrying out the distillation with a temperature in the upper part from 160 to 250 ° C, the distillation pressure, measured in the upper part of the distillation apparatus, being within the range from 0.3 to 3 bar if hexamethylenediamine is used as amine (I); and within the range of 0.1 to 1.3 bar if 6-aminocapronitrile is used as amine (I). The process as recited in claim 1, wherein the azepine derivative (III) is obtained primarily as the residual product of the distillation, and this residual product is mixed with adiponitrile, and this mixture is subjected to hydrogenation to obtain an amine ( I).