MXPA01001568A - Improved method for simultaneous preparation of 6-aminocapronitrile and hexamethylene diamine - Google Patents

Abstract

The invention relates to a method for simultaneous preparation of 6-aminocapronitrile and hexamethylene diamine from adipodinitrile, comprising the following steps:a) hydrogenating adipodinitrile in the presence of a catalyst containing an element of the eight subgroup as catalytically active component to obtain a mixture containing 6-aminocapronitrile, hexamethylene diamine, adipodinitrile and high boilers;b) separating by distillation hexamethylene diamine from the mixture containing 6-aminocapronitrile, hexamethylene diamine, adipodinitrile and high boilers and c1) separating by distillation 6-aminocapronitrile and subsequently d1) separating by distillation adipodinitrile or c2) simultaneously separating by distillation 6-aminocapronitrile and adipodinitrile into separate fractions. The method is characterized in that the temperature of the bottom in steps d1) or c2) is below 185°C.

Description

Improved procedure for the simultaneous obtaining of 6-amino-capronitrile and hexamethylenediamine Description The present invention relates to a process for the simultaneous obtaining of 6-aminocaproni ryl and hexamethylenediamine, starting from adiponitrile, comprising the following steps a) hydrogenation of adiponitrile in the presence of a catalyst, which contains as element a catalytically active component of the eighth secondary group, obtaining a mixture containing 6-aminocapronitrile, hexamethylenediamine, adiponitrile and high-boiling components, b) distillative separation of hexamethylenediamine from the mixture containing 6-aminocapronitrile, hexamethylenediamine, adiponitrile and high-boiling components, and, alternatively, cl) Distillative separation of 6-aminocapronitrile followed by di) the distillative separation of adiponitrile, or c2) Simultaneous distillative separation of 6-aminocapronitrile and adiponitrile in separate fractions. process which is characterized in that the background temperatures in steps d) or c2) are below 185 ° C.

It is known to hydrogenate adipodinitrile (DNA) in the presence of elements of the eighth secondary group, especially in the presence of catalysts predominantly containing iron, cobalt, nickel, ruthenium or rhodium, solvents, such as ammonia, amines or alcohols, and eventually additives, such as, for example, inorganic bases, giving mixtures of 6-aminocapryitrile, hexamethylenediamine and unreacted adiponitrile. Here, catalysts dissolved homogeneously in the liquid phase and fixed-bed catalysts used as a fixed or suspended bed are used. 15 The iron catalysts that are often used as high-pressure fixed-bed catalysts in the liquid phase are found "F * trans described, eg in DE 4,235,466, WO 96/20166, WO96 / 20,043 and DE 19,636,767. Co catalysts are known, for example, from DE 954,416, WO 96/20166 and DE 19,636,768. Nickel catalysts are used in DE 848,654, eg as support catalysts (nickel on A1203), but above all, for example, according to US 2,762,835, WO 96/18603 and WO 97 / 10,052 in the form of nickel Raney endowed or not endowed. Leak catalysts For example, in accordance with US Pat. No. 3,322,815, homogeneously dissolved ruthenium catalysts are known from WO 96/23802 and WO 96/23804. Rhodium catalysts, such as, for example, rhodium on magnesium oxide, are mentioned, for example, in US 4,601,859.

The partial hydrogenation of adiponitrile in mixtures from 6-aminocapronitrile, hexamethylenediamine and unreacted adiponitrile is carried out to obtain 6-aminocapronitrile and hexamethylenediamine in a desired ratio, regulated by appropriate selection of the reaction conditions. The 6-amino-capronitrile can be cyclized, eg according to US 5,646,277, in the liquid phase, in the presence of oxidic catalysts, giving caprolactam. Caprolactam is an important starting product for the production of nylon 6, hexamethylenediamine is one of the starting materials for obtaining nylon 6.6.

From DE-A 19,548,289 a method for the simultaneous obtaining of 6-aminocapronitrile and hexamethylenediamine is known.

Or by hydrogenation of adiponitrile in the presence of a catalyst reaching a partial concession, the separation of hexamethylenediamine and 6-aminocapronitrile from the mixture and the reaction of 6-aminocapronitrile in caprolactam, as well as the recycling of a part substantially consisting of adipodinitrile to the procedure. The disadvantage of this method is that the adiponitrile 20 recovered in the further processing of the reaction discharge contains undesired by-products, especially amines, such as p. ex. l-amino-2-cyanocyclopentene (ACCPE), 2- (5-cyanopentyl-amino) -tetrahydroazepine (CPATHA) and bishexamethylenetriamine (BHMTA), which can result in yield losses in valuable product.

The by-products can not be separated by distillation of the adiponitrile by the described process due to the formation of azeotropes or quasi-azeotropes. This results, especially when the adiponitrile is recycled, to an accumulation in the total process.

In recycle, the 2-aminomethylcyclopentylamine derivative (AMCPA), which contaminates the valuable product, hexamethylenediamine, can be formed from the ACCPE in the hydrogenation step. From US-A 3,696,153 it is known that AMCPA is very difficult to separate from hexamethylenediamine.

In this recycling, the 2-aminomethylcyclopentyl-mine derivative (AMCPA) can be formed from ACCPE in the hydrogenation stage, which contaminates the hexamethylenediamine-valued product. From US-A 3,696,153 it is known that AMCPA is very difficult to separate from hexamethylenediamine.

From DE 19,636,766 it is known to add adiponitrile to recycle 0.01 to 10% by weight of an acid, with respect to adiponitrile, or an acid ion exchanger, separate the adiponitrile from this mixture and recycle it in the hydrogenation reactor . Here the basic by-products containing nitrogen are neutralized by the addition of the acids. The disadvantage of this method is that salts are formed, which must be removed from the process and eliminated. For which an additional procedural stage is needed.

The object of the present invention is therefore to provide a process for separating, in a technically simple and economical manner, adiponitrile from a mixture containing adiponitrile, hexamethylenediamine, 6-amincaprony-trile and components with a boiling point above that of the adipodinitrile ("high-boiling components), obtained by partial hydrogenation of adiponitrile, avoiding the disadvantages mentioned, as well as the recovery of adiponitrile as pure as possible, which contains, in particular, very little ACCPE.

This object is achieved by the procedure defined above.

The adiponitrile used in the process of the invention can generally be prepared by processes known per se, preferably by reaction of hydrocyanic acid in the presence of catalysts, especially nickel- (0) -compound compounds and cocatalyst containing phosphorus, by pentenenitrile as intermediate stage.

In a preferred embodiment the content of l-amino-2-cyano-cyclopentene, with respect to adiponitrile, in the adiponitrile used in step a) should be below 5000 ppm by weight, advantageously, between 10 and 5000 ppm by weight, preferably, between 10 and 3000 ppm by weight, most preferably between 10 and 1500 ppm by weight, especially between 10 and 100 ppm by weight.

In this way, the yield of 6-aminocapro-nitrile and hexamethylenediamine can be increased and the purification of hexamethylene diamine can be facilitated.

The partial hydrogenation of adiponitrile can be carried out according to one of the known processes, for example, according to one of the aforementioned processes, described in US 4,601,859.1, US 2,762,835, US 2,208,598, DE-A 848,654, DE- A 95.44.161, WO 96/18603, WO 97 / 10,052, DE-A 42.35.466 or WO 92/21650, carrying out the hydrogenation, in general, in the presence of an element of the eighth secondary group or its mixtures, for example , catalysts containing nickel, cobalt, iron, ruthenium or rhodium. The catalysts can be used as homogeneously dissolved or suspended catalysts or as support catalysts or solidly arranged catalysts. Suitable support catalysts are, for example, aluminum oxide, silicon dioxide, titanium dioxide, magnesium oxide, active carbons and spinels. Suitable red catalysts are, for example, Raney nickel and Raney cobalt, which may additionally be provided with other elements. coughs Generally, the catalyst loading in the region of 0.05 to 10 kg, preferably 0.1 to 5 kg of adiponitrile / 1 cat is selected. x h. The hydrogenation is generally carried out at temperatures of 20 to 220 ° C, preferably 50 to 150 ° C, and at partial hydrogen pressures of 0.1 to 40 MPa, preferably 0.5 to 30 MPa. Preferably, hydrogenation is carried out in the presence of a solvent, such as, for example, ammonia, amines or alcohols, espe¬ *) cially ammonia. The amount of ammonia is usually selected in such a way that it ranges from 0.1 to 10 kg, prefe¬ Finally, 0.5 to 3 kg of ammonia / kg of adiponitrile.

The molar ratio between 6-aminocapronitrile and hexamethylenediamine and thus the ratio between caprolactam and hexamethylenediamine can be regulated by selective conversion. nothing of adiponitrile. Preferably, adiponitrile conversions are worked from 10 to 90%, preferably from 30 to 80%, in order to obtain high selectivities of 6-aminocapronitrile.

As a general rule, the sum of 6-aminocapronitrile and hexamethylenediamine is increased according to the catalyst and the reaction conditions to 95 to 99%, the most important by-product being hexamethylene-mine.

As catalysts, preferably compounds containing nickel, ruthenium, rhodium, iron and cobalt are used, especially those of the Raney type, especially Raney nickel and Raney cobalt. The catalysts can also be used as support catalysts, using as support, for example, aluminum oxide, silicon dioxide, zinc oxide, active carbon or titanium dioxide (S. Appl. Cat. Het, 1987, p. 106 to 122; Catalysis, Vol. 4 (1981) pp. 1 to 30). Above all, Raney nickel is preferred.

The nickel, ruthenium, rhodium, iron and cobalt catalysts may be advantageously modified with metals of the groups VIB (Cr, Mo, W) and VIII (Fe, Ru, Os, Co (only in case of nickel), Rh , Go, Pd, Pt) of the periodic system. According to the observations made to date, for example, according to DE-A 22.60.978; Bull. Soc. Chem. 13 (1946) p. 208), the use of, in particular, modified Raney nickel catalysts, for example with chromium and / or iron, provides higher selectivities of 6-aminocapronitrile.

The amount of the catalyst is generally selected in such a way that the amount of cobalt, ruthenium, rhodium, iron or nickel varies from 1 to 50% by weight, preferably from 5 to 20% by weight, based on the amount of dinitrile used.

The catalysts can be used as fixed bed catalysts in the depletion or runoff method, or as suspended catalysts.

In another preferred embodiment, the adipodinitrile is partially hydrogenated in 6-aminocapronitrile at high temperature and high pressure, in the presence of a solvent and a catalyst, using a catalyst containing i) a compound based on a metal selected from the group comprising nickel, cobalt, iron, ruthenium and rhodium, ii) from 0.01 to 25% by weight, preferably from 0.1 to 5% by weight, with respect to a), of a promoter based on a metal selected from the group comprising palladium, platinum, iridium, osmium, copper , silver, gold, chromium, molybdenum, tungsten, manganese, rhenium, zinc, cadmium, lead, alumunium, tin, phosphorus, arsenic, antimony, bismuth and rare earths, as well as iii) from 0 to 5% by weight, preferably from 0.1 to 3% by weight, with respect to i), of a compound based on an alkali metal or alkaline earth metal, being possible, preferably, when component i) is selected as a compound based only on ruthenium or rhodium or ruthenium and rhodium or nickel and rhodium, if desired, it is preferable to use promoter ii), and that component i), preferably, does not consist of iron when component ii) is aluminum.

Preferred catalysts are those, in which component i) contains, at least, a compound based on a metal, selected from the group nickel, cobalt and iron, in an amount of 10 to 95% by weight, as well as ruthenium and / or rhodium in an amount of 0.1 to 5% by weight, each time with respect to the sum of components i) to iii), component ii) contains, as a minimum, a promoter based on a metal selected from the group comprising silver, copper, manganese, rhenium, lead and phosphorus, in an amount of 0.1 to 5% by weight, with respect to i), and component iii) contains, at least, one compound based on an alkali metal and alkaline earth, selected from the group comprising lithium, sodium, potassium, cesium, magnesium and calcium, in an amount of 0.1 to 5% by weight.

Especially preferred catalysts are those, which contain i) an iron-based compound, such as, for example, iron oxide and ii) from 0 to 5% by weight, with respect to i) of a promoter based on an element or 2, 3, 4, 5 or 6 elements selected from the group comprising aluminum, silicon, zirconium, vanadium, manganese and titanium, as well as iii) from 0 to 5% by weight, preferably from 0.1 to 3% by weight, in particular from 0.1 to 0.5% by weight, with respect to i), of a compound based on an alkali metal or alkaline earth metal, selected of the group that covers lithium, sodium, potassium, rubidium, cesium, magnesium and calcium.

The catalysts used can preferably be mastic catalysts or support catalysts. Suitable support materials are porous oxides, for example, aluminum oxide, silicon oxide, aluminum silicates, lanthanide oxide, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide and zeolites, and as active carbon or mixtures thereof.

Generally, the catalysts are obtained in such a way that precursors of component (i) are precipitated, if desired, together with precursors of the promoter components. (ii) and, if desired, with precursors of the components (iii), the individual components can be added simultaneously or successively, or by spraying the components (i), (ii), if desired, (iii), on the support according to methods known per se.

As precursors of components i), generally well-soluble salts are suitable in water of the aforementioned metals, such as mitrates, chloride, acetates, formates and sulfates, preferably nitrates.

Suitable precursors of component ii) are generally salts which are well soluble in water or complex salts of the aforementioned metals, such as nitrates, chlorides, acetates, formates and sultates, as well as hexachloroplatinate, preferably nitrates and hexachloroplatinate.

Suitable precursors of components iii) are generally water-soluble salts of the aforementioned alkali and alkaline earth metals, such as hydroxides, carbonates, nitrates, chlorides, acetates, formates and sulphates, preferably hydroxides and carbonates.

The precipitation is generally carried out from the aqueous solutions, adding, if necessary, precipitation reagents, varying the pH value or varying the temperature.

Normally, the intermediate catalyst mass thus obtained is dried at temperatures of, generally, 80 to 150 ° C, preferably 80 to 120 ° C. Calcination is usually carried out at temperatures of 150 to 500 ° C, preferably 200 to 450 ° C in a gas stream from air or nitrogen.

After calcination, the mass of the catalyst obtained is generally subjected to a reducing atmosphere ("activation"), for example by subjecting it for 2 to 24 hours at a temperature of 80 to 250 ° C, preferably 80 to 180 ° C. to catalysts based on ruthenium or rhodium as components i), or from 200 to 500 ° C, preferably from 250 to 400 ° C to catalysts based on one of the metals selected from the group nickel, cobalt and iron as component i), to an atmosphere of hydrogen or a mixture of gas containing hydrogen and an inert gas, such as, for example, nitrogen. The catalyst charge here preferably is 200 1 per liter of catalyst.

Advantageously, activation of the catalyst is carried out directly in the synthesis reactor, since in this way, the intermediate step normally required, namely the passivation of the surface at temperatures of, generally, 20 to 80 ° C, is generally suppressed. , preferably from 25 to 35 ° C by nitrogen-oxygen mixtures, such as, for example, air. The activation of passivated catalysts is then preferably carried out in the synthesis reactor at a temperature of 180 to 500 ° C, preferably of 200 to 350 ° C, under an atmosphere containing hydrogen.

The catalysts can be used in a Rl reactor as fixed bed catalysts in the depletion or draining method. or as suspension catalysts (see Figure 1). c) When the reaction is carried out in a suspension, then temperatures are generally chosen in the region of 40 to 150 ° C, preferably 50 to 100 ° C, most preferably 60 to 15 90 ° C; the pressure is generally chosen in the region of 2 to 30 MPa, preferably 3 to 30 MPa, most preferably 4 to 9 MPa. The residence times depend substantially on the performance, the desired selectivity and the desired conversion; Normally, residence time is chosen in such a way that a maximum yield is reached, for example, in the region of 50 to 275 minutes, preferably 70 to 200 minutes.

In the suspension method, they can be added, advantageously, Liquid diluents, advantageously primary, secondary or tertiary amines, such as monoamines, diamines and triamines with 1 to 6 carbon atoms, for example, trimethylamine, triethylamine, tripropylamine and tributylamine, or alcohols, especially methanol and ethanol, preferably ammonia or its 30 mixtures. Suitably, a concentration in adiponitrile is chosen in the region of 10 to 90% by weight, preferably from 30 to 80% by weight, most preferably from 40 to 70% by weight, with respect to the sum of adiponitrile and diluent.

The amount of catalyst is generally chosen to vary in the region from 1 to 50% by weight, preferably from 5 to 20% by weight, based on the amount of adiponitrile used.

It is also possible to perform partial hydrogenation in the form discontinuous or continuous in a fixed bed catalyst, applying the method by exhaustion or runoff, selecting, :) generally, a temperature in the region of 20 to 150 ° C, preferably 30 to 90 ° C, and, generally, a pressure in the region of 2 to 40 MPa, preferably 3 to 30 MPa. Advantageously, liquid diluents, advantageously primary, secondary or tertiary amines, such as monoamines, diamines and triamines with 1 to 6 carbon atoms, for example, trimethylamine, triethylamine, tripropylamine and tributylamine, or alcohols, can be added. especially, methanol and ethanol, preferably ammonia, or mixtures thereof.

In a preferred embodiment, an ammonia content is chosen in the region of 1 to 10 g, preferably 2 to 6 g per g of adiponitrile. Preferably, a catalyst loading is chosen in the region of 0.1 to 2.0 kg, preferably 0.3 to 1.0 kg of adiponitrile / 1 x h. Here, too, the conversion can be specifically regulated and with it the selectivity, varying the residence time. 30 It has proven advantageous to add basic additives, especially hydroxides, carbonates or alcoholates of the alkali metals or calcalinotérreos or mixtures of such compounds, in the hydrogenation according to step a).

When a diluent is used in step a), it can be removed advantageously between step a) and step b) in a manner known per se, preferably by distillation, and, for example, be used again in stage a) . The hydrogenation discharge contains before step b) and 3 in addition to 6-aminocapronitrile, hexamethylenediamine and adiponitrile, generally also, inter alia, hexamethyleneimine, bis-hexamethylenetriamine and as high boiling point components, 2- (5-cyano-pentylamino) -tetrahydroazepine and 2- (6-amino-hexylamino) -tetrahydroazepine, namely, nitrogenous bases. «# The discharge of hydrogenation can be processed further¬ according to the invention in two stages by distillation (see FIGS. 1 and 2).

From the reaction discharge, hexamethylenediamine can be separated, together with the secondary product, hexamethylene. nimina, (stage b)). This can be done in two or more columns, preferably in a column (K 1).

From adiponitrile, in the presence of the nitrogenous bases contained in the bottom products, greater amounts of ACCPE can be formed than in the absence of such nitrogenous bases.

In a preferred embodiment the background temperature in step b) must be below 185 ° C, preferably below 180 ° C, it being advisable, due to the reduced vapor pressure of the compounds to be separated, to work at a background temperature of at least 100 ° C, preferably at least 130 ° C. The pressures at the bottom of the column should advantageously be from 0.1 to 100, in particular from 5 to 40 mbar. Preferably, the residence times of the bottom product in the distillation according to step b) must amount to 1 to 10 60, especially 5 to 15 minutes. The bottom product obtained from the distillation according to step b) can be further elaborated by two alternative methods, according to steps cl) and di), or step c2). According to step c2 (FIG. 1), the bottom product is introduced into a K 2 column, in which the 6-aminocapronitrile is separated as heads, the adiponitrile in a side discharge and the high-boiling components through the bottom . The background temperature in step c2) is, according to the invention, below 185 ° C, preferably below 180 ° C, being recommended, due to the low vapor pressure of the compounds to be separated, a temperature of fond of, as minimum, 100 ° C, preferably at least 130 ° C. The pressures at the bottom of the column should advantageously be from 0.1 to 100, in particular from 5 to 40 mbar. Preferably, the residence times of the bottom product in the distillation according to step c2) amount to 1 to 60, especially mind, to 5 to 15 minutes.

According to steps cl) / dl) (FIG. 2), the bottom product is introduced into a K 2a column, in which the 6-amino-capronitrile is detylated as heads (step cl)), the product is introduced. bottom in a column K 2b where the adiponitrile is distilled as heads (stage di)) and the components of high boiling point by the bottom.

In a preferred embodiment, the background temperature in step cl) should be below 185 ° C, preferably by 10 below 180 ° C, being recommended, due to the reduced J vapor pressure of the compounds to be separated, work at a bottom temperature of at least 100 ° C, preferably at least 130 ° C. The pressures at the bottom of the column should advantageously be from 0.1 to 100, in particular from 5 to 15, 40 mbar. Preferably, the residence times of the bottom product in the distillation according to step cl) must amount to 1 to 60, especially 5 to 15 minutes. and The background temperature in stage di) is, according to the invention , below 185 ° C, preferably below 180 ° C, it being recommended, due to the low vapor pressure of the compounds to be separated, to work at a background temperature of at least 100 ° C, preferably at least 130 ° C. The pressures at the bottom of the column should advantageously rise to 0.1 to 100, especially 5 to 40 mbar. Preferably, the residence times of the bottom product in the distillation according to step di) must amount to 1 to 60, especially 5 to 15 minutes.

To further reduce the content of byproducts, such as nitrogenous bases, especially bis-hexamethylene triamine and ACCPE, in the recovered adiponitrile is In the process of the invention, it is advantageous to add, in the bottom of the column K 2b in batch form or, preferably, continuously, an organic or inorganic acid, or to purify the adiponitrile obtained after the K 2 or K columns. 2b in discontinuous form or, preferably, continuously with an organic or inorganic acid.

The adipodinitrile obtained after the two alternatives can be used, advantageously, in the partial hydrogenation giving 6-aminocapronitrile and hexamethylenediamine, for example, recycling it to step a) of the process of the invention, or in a complete hydrogenation process giving hexamethylenediamine .

Surprisingly, it has been found in the recycling of the adiponitrile recovered according to the process of the invention in partial hydrogenation, that the reduction according to the invention = - The amount of l-amino-2-cyanocyclopentene in the recycled adiponitrile is very advantageous for the hydrogenation, the distillative purification of the hexamethylenediamine and the permanence of the hydrogenation catalyst.

Example 1: a) Obtaining the iron hydrogenation catalyst For the partial hydrogenation of adiponitrile in 6-aminocapronitrile and hexamethylenediamine, an iron catalyst based on a magnetite, obtained according to DE 30,636,767, example 2 a), is used. The granulometric fraction of the particle size of 3 to 5 mm is used. b) Adipodinitrile partial hydrogenation A tubular reactor (length 180 cm, d = 30 mm) is filled with 720 ml (1630 g) of the mass of catalyst prepared according to a) and without pressure it is reduced in the hydrogen stream (500 Nl / h). In this process the temperature rises within 24 hours from 30 ° C to 340 ° C and then it is maintained for 72 hours at 340 ° C.

After lowering the temperature, 330 g / h of DNA (prepared from butadiene and hydrocyanic acid in the presence of Ni- (O) complexes as catalyst and compounds) are introduced into the reactor at 250 bar and 90 ° C feed temperature. of phosphorus as cocatalysts), 1200 g / h of ammonia and 140 Nl / h of hydrogen.

Hydrogenation is carried out for 1500 hours under the indicated conditions. During the whole course, the hydrogenation and given a 60% DNA conversion, a constant total selectivity (sum of the selectivities of 6-aminocapronitrile and hexamethylenediamine) of 99% is found. The selectivity of 6-aminocapronitrile decreases during the process from 50% to 48.5%. c) Further elaboration of the hydrogenation discharge For subsequent batch processing, hydrogenation discharges are collected during the test.

From these discharges, ammonia is first distilled in a column with 20 theoretical plates by the head. As a background product, a mixture is obtained, which according to gas chromatographic analysis consists of approx. 30 mol% 6-aminocapronitrile, 39 mol% adiponitrile and 30 mol% hexamethylenediamine. The most important secondary product in terms of quantity is hexamethyleneimine, in addition, 0.15 mol%, respectively, of 2- (5-cyano-pentylamino) -tetrahydroazepine and 2- (6-amino-hexylamino) - tetrahydroazepine.

From 1000 g of bottom product obtained sepa¬ in the same column per head 296 g of hexamethylenediamine at a background temperature of 180 ° C, containing apros. 0.5% by weight of hexamethyleneimine. 695 g of the obtained bottom product are distilled in a continuous-running column in such a way that about 305 g of 6-aminocapronitrile are removed from the head, 380 g of adiponitrile are expelled from the side and * ^% for the bottom 10 g of high-boiling components containing adiponitrile. It is distilled at a head pressure of 20 to 40 mbar.

The bottom temperature of the column is varied, changing the head pressure. The reflux ratio is 2: 1. Table 1 shows how the amount of 25 l-amino-2-cyano-cyclopentene in the adiponitrile of the lateral discharge varies as a function of the background temperature of the column.

Table 1 1) ppm of l-amino-2-cyanocyclopentene, with respect to the adiponitrile contained in the side discharge Comparative example 300 g of DNA (prepared from butadiene and hydrocyanic acid in the presence of Ni- (O) complexes as a catalyst and phosphorus compounds as cocatalysts) with a purity of 99.9% and a content of l-amino-2 cyano-pentene of 21 ppm by weight, with respect to DNA, are distilled at a background temperature of 200-205 ° C, a pressure of 70 mbar and a boiling temperature of 200 ° C. Only traces of high-boiling components remain as a background product.

The DNA obtained by distillation contains 138 ppm by weight of l-amino-2-cyano-cyclopentene according to gas chromatography analysis.

Claims (18)

Claims

1. Procedure for the simultaneous obtaining of 6-aminoca-pronitrilo and hexamethylenediamine, starting from adiponitrile, which comprises the following steps a) hydrogenation of adiponitrile in the presence of a catalyst, which contains as catalytic component¬ An element of the eighth secondary group was active, yielding a mixture containing 6-aminocapronic acid and trile, hexamethylenediamine, adiponitrile and high-boiling components. 15 b) distillative separation of hexamethylenediamine from the mixture containing 6-aminocapronitrile, hexamethylenediamine, adiponitrile and high-boiling components, and, alternatively, 20 cl) distillative separation of 6-aminocapronitrile followed by di) the distillative separation of adiponitrile, 25 or c2) Simultaneous distillative separation of 6-aminocapronitrile and adipoditiitrile in separate fractions, 30 The process is characterized in that the background temperatures in steps d) or c2) are below 185 ° C.

The method according to claim 1, wherein the background temperatures in steps di) or c2) are below 180 ° C.

The process according to claim 1 or 2, wherein the catalyst in step a) contains as a catalytically active element iron, cobalt, nickel, ruthenium or J rubidium or its mixtures.

4. Process according to claims 1 to 3, wherein the catalyst in step a) contains iron, cobalt or nickel or their mixtures as a catalytically active element.

5. Process according to claims 1 to 4, wherein the catalyst in step a) is based on Raney nickel or Raney cobalt or mixtures thereof.

6. Process according to claims 1 to 4, wherein in step a) a catalyst is used, which contains 25 i) a compound based on a metal selected from the group comprising nickel, cobalt, iron, ruthenium and rhodium, Ii) from 0.01 to 25% by weight, preferably from 0.1 to 5% by weight, based on a), of a promoter based on a metal selected from the group comprising 35 dio, platinum, iridium, osmium, copper, silver, gold, chromium, molybdenum, tungsten, manganese, rhenium, zinc, cadmium, lead, alumunium, tin, phosphorus, arsenic, antimony, bismuth and rare earths, as well as iii) from 0 to 5% by weight, preferably from 0.1 to 3% by weight, with respect to i), of a compound based on an alkali metal or alkaline earth metal.

The method according to claim 6, wherein as component i) a ruthenium or rhodium or ruthenium or rhodium or nickel and rhodium based compound is selected, the promoter ii) and component i) may be dispensed with if desired. it is not iron-based when the component ii) 15 is aluminum.

Process according to claims 1 to 4, wherein in step a) a catalyst is used, which contains 20 an iron-based compound, ii) from 0 to 5% by weight, with respect to i) of a promoter based on one element or 2, 3, 4, 5 or 6 elements selected from the group comprising aluminum, silicon, 25 zirconium, vanadium, manganese and titanium, as well as iii) from 0 to 5% by weight, with respect to i), of a compound based on an alkali metal or alkaline earth metal.

9. Process according to claims 1 to 8, wherein in step a) a diluent is additionally used.

10. Process according to claim 9, wherein primary, secondary or tertiary amines, ammonia or alcohols or their mixtures are used as the diluent.

11. Process according to claim 9 or 10, wherein the diluent is separated between steps a) and b).

12. Process according to claims 1 to 11, wherein in step a) basic substances are additionally added.

13. Process according to claim 12, wherein hydroxides, carbonate or alcoholates of the alkali or alkaline earth metals or their mixtures are used as basic substances.

14. Process according to claims 1 to 13, wherein after step di) or c2) the adiponitrile is recycled to step a).

15. Process according to claims 1 to 13, wherein after steps di) or c2) adiponitrile is hydrogenated in hexamethylenediamine.

16. Process according to claims 1 to 15, wherein the content of l-amino-2-cyano-cyclopentene in the adiponitrile used in step a) amounts to less than 5000 ppm by weight, with respect to adiponitrile.

17. Process according to claims 1 to 16, wherein in step d) an organic or inorganic acid is introduced into the bottom.

18. Process according to claims 1 to 17, wherein the adipodinitrile obtained according to steps di) or c2) is purified with an organic or inorganic acid. 10 fifteen twenty 25 30 35