MXPA97004863A - Simultaneous preparation of caprolactama yhexametilendiam - Google Patents

Abstract

The present invention relates to a compound for the simultaneous preparation of caprolactam and hexamethylenediamine starting with adiponitrile, wherein: a) the adiponitrile is partially hydrogenated to give a mixture containing mainly 6-aminocapronitrile, hexamethylenediamine, ammonia, adiponitrile and hexamethyleneimine, b) the mixture obtained in (a) is subjected to a distillation to give ammonia as an upper product and a lower product I, carrying out the distillation at a lower temperature of 60 to 220 cc and a pressure of 10 to 30 bar in the presence of a compound A which is inert under the distillation conditions and boils from 60 to 220 ° C at 18 bar, and not completely separating the ammonia, c) the lower product I containing mainly 6-aminocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine, the compound inerete A and ammonia, the ammonia content being lower than that of the mixture used in stage (b), is subjected to a second distillation to give a mixture containing the inert compound A and ammonia as upper product and lower product II, carrying out the distillation at a lower temperature of 100 to 200 ° C and from 2 to 15 bar, as long as the pressures in the first and second columns coincide with each other, so that the upper temperature is obtained above 20 ° C at a lower temperature of not more than 220 ° C, d) the lower product II containing mainly 6-aminocapronitrile, hexamethylenediamine, adiponitrile, Hexamethyleneimine and the inert compound A are subjected, in a third column to a distillation to give an inert compound A as an upper product and a lower product III, the distillation is carried out at a lower temperature of 100 to 220§cy from 0.1 to 2 bar, provided that the inert compound A obtained as the upper product is fed to the second column, and if desired, the distillation is carried out in the presence of a compound B which is inert under the distillation conditions and boils from 50 to 220 ° C at 0.3 bar, e) the lower product III containing mainly 6-aminocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine and if desired an inert compound B is subjected, in a fourth column, to a distillation to give a superior KP1 product, which mainly contains hexamethyleneimine and if desired an inert port B and hexamethylene diamine, which is obtained at a lower temperature of 100 to 220 ° C and 10 to 500 mbar, and a lower IV product , f) the upper KP1 product is subjected, in a fifth column, to a distillation to give an upper KP2 product, which contains mainly hexamethyleneimine and, if desired, the inert compound B which is obtained at a temperature lower than 100 to 220§C and from 50 to 2000 mbar and an inferior product V containing mainly hexamethylenediamine in a purity of at least 95%, the upper KP2 product is fed to the third column or, if desired, only something of this upper product is fed to the third column and the remainder is discharged, and g) the lower IV product containing mainly 6-aminocapronitrile and adiponitrile are subjected, in a sixth column, to a distillation to give 6-aminocapronitrile in a purity of at least 95% as the top product and adiponitrile as the bottom product, carrying out the distillation at a lower temperature of 100 to 220§c and from 1 to 500 mbar, and the 6-amylopronitrile asynchronous then cyclized to give caprolacta

Description

SIMULTANEOUS PREPARATION OF CAPROLACTAMA AND HEXAMETILENDLAMI A The present invention relates to a process for the simultaneous preparation of caprolactam and 1: examethylenediamine starting from adiponitrile.

The present invention also relates to an improved process for the simultaneous preparation of 6-aminocapronitrile and hexamethylenediamine from a mixture containing these substances.

The partial hydrogenation of adiponitrile to 6-a-incapronitrile in the presence of ammonia and various catalysts has been described in a sufficient amount, for example, U.S. Patent No. 4,601,859 describes the use of rhodium-based catalysts on magnesium oxide, US Pat. No. 2,762,835 discloses the use of the Raney nickel catalyst, US Patent 2,208,598 discloses the use of nickel on alumina, DE-A 840 654 discloses er-based sand bed catalysts. copper spinels / cobait / zinc and iron spinel / cobalt, DE-A 954 416 describes the use of cobalt on silica gel and DE-A 4 235 466 describes the use of iron sponges.

In the process described in WO 92/21650, the yield of aminocapronitrile is 60% at a conversion of 70% and the yield of hexamethylenediamine is 9% in the presence of Raney nickel. At an 80% conversion speed the yield is 62%.

It is also known that 6-aminocapronitrile can be reacted with water, in gas phase or liquid phase, in the presence or absence of catalysts with release of ammonia to produce caprolactam. For example, U.S. Patent No. 2,301,964 describes a process in which solutions of 10 to 25% concentration of 6-α-incapronitrile are converted, in liquid phase, at 200-290 ° C into caprolactam with yields up to 76%.

In addition, cyclization of solutions at 25-35% concentration of 6-aminocapronitrile at 220 ° C in liquid phase in water, with the addition of organic solvents in the presence of zinc compounds, copper compounds, lead compounds and compounds of Mercury is described in FR-A 2, 029 540. In this reaction caprolactam yields up to 83% are obtained.

The cyclization of 6-aminocapronitrile can also be carried out in the gas phase (US 2 357 484): starting with 80% aqueous solutions, caprolactam yields of 92% to 305 ° are obtained by using alumina as a catalyst.

EP-A 150 295 describes the conversion of 6-aminocapronitrile, in gas phase, in the presence of copper / vanadium, hydrogen, water and ammonia catalysts at 290 ° C with caprolactam yield of 77%.

Furthermore, DE-A 43 19 134 describes the conversion of 6-aminocapronitrile in water, in liquid phase, without addition of a catalyst to give caprolactam.

In the aforementioned documents, a process to obtain caprolactam through 6-aminocapronitrile beginning with adiponitrile in a general process by combining the two steps is not evident.

An object of the present invention is to provide a process for the simultaneous preparation of caprolactam and hexamethylenediamine starting from adiponitrile. In addition, a process is proposed which produces pure 6-aminocapronitrile and hexamellilene in a continuous process from the reaction mixture obtained from the partial hydrogenation of adiponitrile, cyclizing 6-aminocapronitrile in an additional step to give caprolactam. It is also proposed, as much as possible, to reuse the byproducts obtained in this process, preferably recycling them at an early stage of the process.

We have found that this goal is achieved through a process for the simultaneous preparation of caprolactam and hexamethylenediamine starting from adiponitrile, where (a) the adipone is partially hydrogenated to give a mixture containing mainly 6-aminocapronitrile, hexamethylenediamine, ammonia, adiponitrile and hexamethyleneimine, (b) the mixture obtained in (a) is subjected to a distillation to give ammonia as the upper product and a lower product I, the distillation is carried out at a lower temperature from 60 to 220 ° C and a pressure from 10 to 30 bar in the presence of a compound A which is inert under the distillation conditions and boils from 60 to 220 ° C at 18 bar, and the ammonia is not completely separated,(c) the lower product 1 containing mainly 6-aminocapronitrile, hexamentylenediamine, adiponitrile, hexamethyleneimine, the inert compound A and ammonia, the ammonia content being lower than that of the mixture used in step (a), subjected to a second distillation to give a mixture containing the inert compound A and ammonia as the upper product and a lower product II, the distillation is carried out at a lower temperature from 100 to 220 ° C and from 2 to 15 bar, as long as the pressures in the first and second column coincide with each other so that a higher temperature is obtained above 20 ° C at a lower temperature of no more than 220 ° C in each case, (d) the lower product i i containing mainly 6-aminocapronitrile, hexamentylenediamine, adiponitrile, hexamethyleneimine and the inert compound A are subjected, in a third column, to distillation to give the inert compound A as the superior product and a lower product III, the distillation is carried out at a lower temperature of 100 to 220 ° C and 0.1 to 2 bar, with the proviso that the inert compound A obtained as the superior product is fed to the second column, and, if you wish, the distillation is carried out in the presence of a compound B which is inert under the distillation conditions and boils from 50 to 220QC at 0.3 bar, (e) the lower product III containing mainly 6-aminocapronitrile, hexamentylenediamine, adiponitrile, hexamethyleneimine, and, if desired, an inert compound B is subjected, in a fourth column, to a distillation to give an upper product Pl, which contains mainly hexamethylene imine, and, if desired, inert compound B and hexamethylenediamine, which is obtained at a temperature lower than 100 to 220 ° C and from 10 to 500 mbar, and a lower product IV, (f) the upper product KP1 is subjected, in a fourth column, to a distillation to give an upper product KP2, which contains mainly hexamethyleneimine, and, if desired, an inert compound B and is obtained at a temperature below 100 at 220 ° C and from 50 to 2000 mbar, and an inferior product V containing mainly hexamethylenediamine in a purity of at least 95%, the upper product KP2 being fed to the third column or, if desired, only some of this Top product is fed to the third column and the rest is discharged, and (g) the lower IV product containing mainly 6-aminocapronitrile and adiponitrile, is subjected, in a sixth column, to a distillation to give 6-aminocapronitrile in a purity of at least 95% as a superior product and adiponitrile as the product lower, the distillation is carried out at a lower temperature of 100 to 220 ° C and of -1 to 500 mbar, and the 6-aminocapronitrile thus obtained is then cyclized to give caprolactam.

We have also found a process for the simultaneous separation of 6-aminocapronitrile and hexamentylenediamine from a mixture containing these substances.

The partial hydrogenation of adiponitrile can be carried out by one of the known processes, for example, one of the aforementioned processes as described in US Pat. No. 4,601,859, US Pat. No. 2,762,835, US Pat. No. 2,208,598, DE-A 848 654, DE-A 954 416, DE-A 4 235 466 or WO 92/21650, in general, by hydrogenation in the presence of catalysts containing nickel, cobalt, iron or rhodium. The catalysts can be used as supported catalysts or as unsupported catalysts. Examples of suitable catalyst carriers are alumina, silica, titanium dioxide, magnesium oxide, active carbon and spinels. Examples of suitable unsupported catalysts are Raney nickel and Raney cobalt.

The catalyst space velocity, in general, is chosen in the range of 0.05 to 10, preferably from 0.1 to 5, kg of adiponitrile per L of catalyst per hour.

The hydrogenation is carried out, as a general rule, from 20 to 220 ° C, preferably from 50 to 150 ° C and at partial hydrogen pressures from 0.1 to 20, preferably from 0.5 to 10 MPa.

Preferably, the hydrogenation is carried out in the presence of a solvent, in particular ammonia. The amount of ammonia is generally chosen from 0.1 to 10, preferably from 0.5 to 3 kg of ammonia per kg of adiponitrile.

The molar ratio of 6-aminocapronitrile with hexamentylenediamine and, therefore, the molar ratio of caprolactam and hexamethylenediamine can be controlled by the particular conversion of adipone? ilo that is chosen. Preference is given to the adiponitrile conversions of 10 to 80%, preferably 30 to 60%, to obtain high selectivities of 6-aminocapronitrile.

As a general rule, the total amount of 6-aminocapronitrile and hexamethylenediamine is from 95 to 99% depending on the catalyst and the reaction conditions, with hexamethyleneimine being the most important byproduct in terms of quantity.

In a preferred embodiment, the reaction is carried out in the presence of ammonia and lithium hydroxide, or of a lithium compound which forms lithium hydroxide under the conditions of the reaction, from 40 to 120 ° C, preferably from 50 to 100 ° C, particularly preferably 60 to 90 ° C; the pressure is chosen, in general, from 2 to 12, preferably from 3 to 10, particularly preferably from 4 to 8 MPa. The residence times depend mainly on the desired performance and selectivity and the conversion required, in general, the residence time is chosen so that the maximum performance is obtained, for example, in the range of 50 to 275, preferably 70. 200 minutes.

The pressure and temperature ranges are preferably chosen so that the reaction can be carried out in a liquid phase.

Generally, the ammonia is used in an amount such that the ratio of ammonia to dinitrile is from 9: 1 to 0.1: 1, preferably from 2.3: 1 to 0.25: 1, particularly preferably from 1.5: 1 to 0.4: 1.

The amount of lithium hydroxide is chosen as a general rule of 0.1 to 20%, preferably 1 to 10% by weight based on the amount of catalyst used.

Examples of lithium compounds that form lithium hydroxide under the reaction conditions are lithium metal, alkyl- and aryllithium compounds, such as n-butyllithium and phenyllithium. The amount of these compounds is chosen, in general, so that the above-mentioned amount of lithium hydroxide is obtained.

The compounds containing nickel, ruthenium, rhodium and cobalt, preferably those of the Raney type, in particular Raney nickel and Raney cobalt, are preferably used as catalysts. The catalysts can also be used in the form of supported catalysts, the carriers that can be used are, for example, alumina, silica, zinc oxide, active carbon or titanium dioxide (see Appl.Het Cat. 1907, 106-122; Catalysis 4 (1981), 1-30). The Raney nickel catalyst (for example from BASF AG, Degussa and Grace) is particularly preferred.

The nickel, ruthenium, rhodium and cobalt catalysts can be modified with metals of group VIB (Cr, Mo, or W) and group VIII (Fe, Ru, Os, Co) (only in the case of nickel), Rh, Go, Pd, or Pt) of the Periodic Table. The observations to date have shown that the use of, in particular, modified nickel Raney catalysts, for example, the corcydicides. chromium and / or iron, give rise to higher selectivities of inonitrile (for the preparation, see DE-A 2 260 978; Bull. Soc. Chem. 13 (1946), 208).

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

The catalysts can be used in the form of fixed bed catalysts by the liquid phase or percolator bed process or, preferably, as suspension catalysts.

In another preferred embodiment, the adiponitrile is partially hydrogenated to 6-aminocapronitrile at elevated temperatures and superatmospheric pressure in the presence of a solvent and a catalyst, by the use of a catalyst which (a) contains a compound based on a metal that is selects from the group consisting of nickel, cobalt, iron, ruthenium and rhodium, and (b) contains from 0.1 to 25, preferably from 0.1 to 5% by weight, based "on (a), from a promoter based on a metal that is selected from the group consisting of palladium, platinum and lithium, osmium, copper, silver, gold, chromium, molybdenum, tungsten, manganese, rhenium, zinc, cadmium, lead, aluminum, tin, phosphorus, arsenic, antimony, bismuth , and rare earth metals, and (c) from 0 to 5, preferably from 0.1 to 3% by weight, based on (a), of a compound based on an alkali metal or an alkaline earth metal, with the proviso that, if the compound based only on ruthenium and rhodium or on rhodium and ruthenium or nickel or rhodium is chosen as component (a), the promoter (b) may, if desired, be omitted. Preferred catalysts are those in which component (a) contains at least one compound based on a metal which is selected from the group consisting of nickel, cobalt and iron in an amount from 10 to 95% by weight, and ruthenium and / or rhodium in an amount of 0.1 to 5% by weight with base, in each case, in the sum of components (a) to (c), component (b) contains at least one promoter based on a metal that it is selected from the group consisting of silver, copper, manganese, rhenium, lead and phosphorus, in an amount from 0.1 to 5% by weight based on (a), and component (c) contains at least one compound based on the alkali metals and alkaline earth metals that are selected from the group consisting of lithium, sodium, potassium, cesium, magnesium and calcium, in an amount from 0.1 to 5% by weight, based on (a). Particularly preferred catalysts are: catalyst A, which contain 90% by weight of cobalt oxide (CoO), 5% by weight of manganese oxide (Mn203), 3% by weight of phosphorus pentoxide and 2% by weight of sodium oxide (Na20), • catalyst B, which has 20% by weight of cobalt oxide (CoO), 5% by weight of manganese oxide (Mn? Oj), 3% by weight of silver oxide (Ag20) ), 70% by weight of silica (Si02), 3.5% by weight of alumina (Al203), 0.4% by weight of iron oxide (Fe203), 0.4% by weight of magnesium oxide (MgO) and 0.4% by weight of calcium oxide (CaO), and catalyst C, which has 20% by weight of nickel oxide (NiO), 67.42% by weight of silica (SiO2), 3.7% by weight of alumina (A1203), 0.8% by weight weight of iron oxide (Fe203), 0.76% by weight of magnesium oxide (MgO), 1.92% by weight of calcium oxide (CaO), 3.4% by weight of sodium oxide (NaO) and 2.0 by weight of potassium oxide (KzO). The preferred catalysts can be supported or unsupported catalysts. Examples of suitable carriers are porous oxides, such as alumina, silica, aluminosilicates, lanthanum oxide, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide and zeolites, as well as active carbon or mixtures thereof. As a general rule, the preparation is carried out by precipitating the precursors of the components (a) together with the precursors of the promoters (components (b)) and, if desired, with the precursors of the trace components (c) in the presence or absence of the carrier materials (depending on the type of catalyst desired), if desired, processing the catalyst precursor thus obtained to give the extrudates or tablets, drying the product and then calcination. Supported catalysts are also generally obtained by impregnating the carrier with a solution of components (a), (b) and, if desired, (c), wherein the individual components can be added simultaneously or in succession, spraying the components (a), (b), and if desired, (c), on the carrier by a method known per se. Suitable precursors of the components (a) are, as a rule, readily soluble salts in water of the aforementioned metals, such as nitrates, chlorides, acetates, formations and sulfates, preferably nitrates. Suitable precursors of the components (b) are, as a general rule, easily soluble salts in water or in a complicit manner? dt. »J? >; Lau1;) ari .-) mtjncionodoa, such as nitrates, chlorides, acetates, formats and sulfates and in particular hexachloroplatinate, preferably nitrates and hexachloroplatinate. Suitable precursors of the components (c) are, as a rule, readily soluble salts in water of the alkali metals and alkaline earth metals mentioned above, such as hydroxides, carbonates, nitrates, chlorides, acetates, formates and sulfates, preferably hydroxides and carbonates. The precipitation is generally carried out from the aqueous solutions, either by adding precipitating reagents or changing the pH or temperature.

The initial catalyst material thus obtained is usually dried at 80 to 150 ° C, preferably at 80 to 120 ° C.

The calcination is generally carried out at 150 to 500 ° C, preferably at 200 to 450 ° C in a gas stream containing air or nitrogen. After calcination, the obtained catalyst material is generally exposed to a reducing atmosphere (activation), for example, to an atmosphere of hydrogen or a mixture of gases containing hydrogen and an inert gas, such as nitrogen, for 2 to 24 hours. hours and from 80 to 250 ° C, preferably from 80 to 180 ° C, in the case of catalysts based on ruthenium or rhodium as component (a) or from 200 to 500 ° C, preferably from 250 to 400 ° C in the case of catalysts based on a material that is selected from the group consisting of nickel, cobalt or iron as component (a). The catalyst space velocity, at present, is preferably 100 to 300, particularly preferably 200, 1 to 1 of catalyst. Activation of the catalyst is advantageously carried out directly in the synthesis reactor, since this avoids an otherwise necessary intermediate step, that is, neutralization of the surface, generally from 20 to 80 ° C, preferably from 25 to 35 ° C, by means of an oxygen / nitrogen mixture, such as air. The activation of the neutralized catalysts is then preferably carried out in the synthesis reactor at 180 to 500 ° C, preferably at 200 to 350 ° C in a hydrogen-containing atmosphere.

The catalysts can be used as fixed-bed catalysts by the liquid-phase or percolator-bed process or as suspension catalysts.

If the reaction is carried out in a suspension, temperatures of from 40 to 150 ° C, caprolactam of from 50 to 100 ° C, particularly preferably from 60 to 90 ° C, are generally chosen; the pressure is generally chosen from 2 to 20, preferably from 3 to 10, particularly preferably from 4 to 9 MPa. The residence times depend mainly on the desired yield and selectivity and on the conversion required; the residence time is usually chosen so that the maximum yield is obtained, for example, in the range of 50 to 275, preferably from 70 to 200 minutes.

In the suspension process, the solvents which are preferably used are ammonia, amines, diamines and triamines of 1 to 6 carbon atoms, such as trimethylamine, triethylamine, tripropylamine and tributylamine, or alcohols, in particular methanol and ethanol, in particular Ammonia is preferred. It is convenient to choose a dinitrile concentration from 10 to 90, preferably from 30 to 80, particularly preferably from 40 to 70% by weight based on the sum of dinitrile and the solvent.

The amount of catalyst is generally chosen from 1 to 50, preferably from 5 to 20% by weight based on the amount of dinitrile that is used.

The hydrogenation in suspension can be carried out batchwise or, preferably, continuously, as a rule, in the liquid phase.

The partial hydrogenation can also be carried out batchwise or continuously in a fixed bed reactor by the percolating bed or liquid phase process at a temperature of 20 to 150 ° C, preferably 30 to 90 ° C. and a pressure, as a general rule, from 2 to 30, preferably from 3 to 20 MPa is usually chosen. The partial hydrogenation is preferably carried out in the presence of a solvent, preferably ammonia, amines, diamines and triamines of 1 to 6 carbon atoms, such as trimethylamine, triethylamine, tripropylamine and tributylamine, or alcohols, preferably methanol and ethanol, particularly preferably ammonia. In a preferred embodiment, an ammonia content of 1 to 10, preferably 2 to 6 g per g of adiponitrile is chosen. Preferably, a catalyst space velocity is chosen from 0.1 to 2.0, preferably from 0.3 to 1.0 kg of adiponitrile per 1 per hour. Also in this case, the conversion and therefore the selectivity can be controlled by changing the stay time.

The partial hydrogenation can be carried out in a conventional reactor suitable for this purpose (Rl in the drawing).

The distillation in the first column (step (b); Kl in the drawing) is carried out, according to the invention, in such a way that the mixture of step (a) containing mainly 6-aminocapronitrile, hexamethylenediamine, ammonia , adiponitrile and hexamethyleneimine, preferably a mixture containing mainly (the established numbers must add 100% by weight) from 1 to 70, preferably from 5 to 40% by weight of 6-aminocapronitrile, from 1 to 70, preferably from 5 to 40% by weight of adiponitrile, from 0.1 to 30, preferably from 0.5 to 20% by weight of hexamethylenediamine, from 0.1 to 10, preferably from 0.5 to 5% by weight of hexamethyleneimine, and from 5 to 95, preferably from 20 to 85% by weight of ammonia, are subjected to distillation, as a rule, in a conventional distillation column, at a temperature lower than 60 to 220 ° C, preferably 100 to 200. ° C and from 10 to 30, preferably from 12 to 25 bar in the presence of a compound A which is inert under the distillation conditions and boils from 60 to 220 ° C at 18 bar, to give ammonia as the superior product and a inferior product I, not completely separating the ammonia.

According to the invention, suitable compounds A are inert substances under the conditions of distillation and have a boiling point of 60 to 220 ° C, preferably 60 to 150 ° C at 18 bar. Examples are alkanes, cycloalkanes, aromatics, naphthenes, alcohols, ethers, nitriles and amines having the aforementioned properties, in particular C5-C alkanes? and C2-C4 alkanes, particularly n-pentane, cyclohexane, triethylamine, ethanol, acetonitrile, n-hexane, di-n-propyl ether, isopropanol, n-butylamine or benzene, particularly preferably ethanol.

In general, compound A is added in an amount of 0.1 to 50, preferably 1 to 10% by weight based on the lower product I.

In step (c) the lower product I containing mainly 6-aminocapronitrile, hexamentylenediamine, adiponitrile, hexamethyleneimine, inert compound A and ammonia, the content of ammonia being lower than that of the mixture obtained from step (a) and it is used in step (b), it is subjected to a second distillation to give a mixture consisting of the inert compound A and ammonia as the upper product and a lower product II, carrying out the distillation at a lower temperature from 100 to 220 ° C, preferably 140 to 200 ° C, and 2 to 15, preferably 4 to 12 bar, with the proviso that the pressures in the first column and in the second column (K2 in the drawing) are corresponding to each other so that a higher temperature above 20 ° C is obtained at a lower temperature of no more than 220 ° C in each case.

In step (d), the lower product II containing mainly 6-aminocapronitrile, hexamentylenediamine, adiponitrile, hexamethyleneimine and the inert compound A are subjected in a third column (K3 in the drawing), to a distillation to give the inert compound A as the upper product and a lower product III, the distillation being carried out at a lower temperature from 100 to 220 ° C, preferably from 140 to 200 ° C, and from 0.1 to 2, preferably from 0.2 to 1 bar, always and when the inert compound A obtained as the upper product is fed to the second column, and, if desired, the distillation is carried out in the presence of an inert compound B under the conditions of distillation and boiling at 50 to 220 ° C, preferably from 60 to 150 ° C at a given pressure of 0.3 bar.

Examples of compound B are alkanes, cycloalkanes, aromatics, naphthenes alcohols, ethers, nitriles and amines having the aforementioned properties, in particular di-n-butyl ether, valeronitrile, n-octane, cyclooctane, n-hexylamine and hexamethyleneimine, particularly preferably hexamethyleneimine.

In a preferred embodiment, hexamethyleneimine is chosen as the compound B, or, particularly preferably no compound B is added.

The compound B is preferably added in an amount from 0.1 to 50, preferably from 0.5 to 10% by weight based on the lower product II.

In step (e), the lower product III, which contains mainly 6-aminocapronitrile, hexamentylenediamine, adiponitrile, hexamethyleneimine, and, if desired, inert compound B, is subjected in a fourth column (K4 in the drawing) to a distillation to give a superior product KP1, which contains mainly hexamethyleneimine, if desired the inert compound B and hexamethylenediamine, which is obtained at a temperature lower than 100 to 220 ° C, preferably 140 to 200 ° C and 10 to 500, preferably from 40 to 200 mbar, and an inferior product IV.

In step (f), the upper product KP1 is subjected, in a fifth column (K5 in the drawing), to a distillation to give an upper product KP2 containing mainly hexamethyleneimine, and, if desired, inert compound B obtains at a lower temperature from 100 to 220 ° C, preferably from 140 to 200 ° C and from 50 to 2000, preferably from 300 to 1000 mbar, and a lower product V containing mainly hexamentylenediamine in a purity of at least 95%, preferably 99 to 99.9%, the upper product KP2 is fed to the third column or, preferably, if desired, only some of the upper product is fed to the third column and the remainder is discharged.

Upon discharging some of the superior KP2 product consisting mainly of hexamethyleneimine, and, if desired, compound B, preferably hexamethyleneimine only if compound B is not added or if hexamethyleneimine is used as compound B (see step (d)) , the concentration of hexamethyleneimine and, if desired, compound B is usually avoided.

In step (g), the lower compound IV, which contains mainly 6-aminocapronitrile and adiponitrile, is subjected, in a sixth column (K6 in the drawing), to a distillation to give 6-aminocapronitrile with a purity of at least 95%. %, preferably from 99 to 99.9% as the superior product and adiponitrile as the lower product, the distillation is carried out at a temperature below 100 to 220 ° C preferably and from 1 to 500, preferably from 5 to 100. mbar According to the invention, the obtained 6-aminocapronitrile is converted to caprolactam. This cyclization can be carried out by a liquid phase or gas phase process known, for example, by a process of US 2 301 964, US 237 584, EP-A 150 295 or DE-A 43 19 134, generally by reacting 6-aminocapronitrile with water in liquid phase to give caprolactam and ammonia.

In the reaction in the absence of a catalyst a temperature of 200 to 375CC and reaction times of 10 to 90, preferably 10 to 30 minutes, is chosen. The solvent that is used is, as a general rule, water, the content of 6-aminocapronitrile is generally chosen to be below 30, preferably 10 to 25% by weight based on water.

In the reaction in the liquid phase in the presence of a catalyst, a temperature of from 50 to 330 ° C, an amount of water of from 1.3 to 50, preferably from 1.3 to 30 mol per mol of 6-aminocapronitrile and a time are generally chosen. reaction time from 10 minutes to several hours. When an organic solvent, in particular alcohol, is used, the amount of water is usually chosen from 1.3 to 5 moles per mole of 6-aminocapronitrile.

The reaction mixture obtained in the cyclization is usually handled initially by distillation, to remove ammonia, water, and if desired, the organic solvent. The catalyst, if used, is present in the lower product and, as a general rule, is separated from the catalyst by one of the conventional methods and recycled to the cyclization reactor (R2 in the drawing). The impure caprolactam is usually converted to pure lactam using the purification operations known per se, such as distillation, and the pure lactam is then available for polycaprolactam polymerization.

In a preferred embodiment, the 6-aminocapronitrile is reacted with water in the liquid phase using heterogeneous catalyst.

The reaction is carried out in the liquid phase in general from 140 to 320 ° C, preferably from 160 to 280 ° C; the pressure is in general from 1 to 250, preferably from 5 to 150 bar, it being necessary to ensure that the reaction mixture is predominantly liquid under the conditions that are used. The times of stay are in general from 1 to 120, preferably from 1 to 90, in particular from 1 to 60 minutes. In some cases, the stay times of 1 to 10 minutes have proven to be completely sufficient.

In general, at least 0.01, preferably from 0.1 to 20, in particular from 1 to 5 moles of water are used per mole of 6-aminocapronitrile.

It is advantageous to use 6-aminocapronitrile in the form of a solution of 1-50, in particular of 5-50, particularly preferably 5-30% by weight of concentration in water (in which case the solvent is at the same time a reactant ) or in a water / solvent mixture. Examples of the solvents are alkaloids, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and tert-butanol, polyols such as diethylene glycol and tetraethylene glycol, hydrocarbons such as petroleum ethers, benzene, toluene and xylene, lactams such as pyrrolidone and caprolactam and alkyl substituted lactams such as N-methylpyrrolidone, N-caprolactam and N-ethylene caprolactam and carboxylates preferably of carboxylic acids of 1 to 8 carbon atoms. Ammonia may also be present in the reaction. Of course you can also use mixtures of organic solvents. Water and alkane mixtures in a water / alkanol weight ratio of 1-75 / 25-99, preferably 1-50 / 50-99, have proven to be particularly advantageous in some cases.

In principle, it is also possible to use 6-aminocapronitrile as a reagent and at the same time as a solvent.

Examples of heterogeneous catalysts that may be used are acidic, basic or amphoteric oxides of the elements of the second, third or fourth main groups of the Periodic Table, such as calcium oxide, magnesium oxide, boron oxide, alumina, tin or silica in the form of pyrogenic silica, silica gel, kieselguhr, quartz or mixtures thereof and metal oxide of the second to sixth subgroup of the Periodic Table, as amorphous titanium oxide, or as anatase or rutile, zirconium oxide, zinc oxide, manganese oxide or mixtures of these. The oxides of the lanthanides and actinides such as cerium oxide, thorium oxide, praseodymium oxide, samarium oxide, mixed rare earth oxides or mixtures thereof with the aforementioned oxides can also be used. Examples of other catalysts can be: vanadium oxide, niobium oxide, iron oxide, chromium oxide, molybdenum oxide, tungsten oxide or mixtures thereof, mixtures of the aforementioned oxides with other oxide are also possible. Some sulphides, selenides, and tellurides can also be used, such as zinc teluriide, tin selenide, molybdenum sulfide, tungsten sulfide, and nickel, zinc, and chromium sulfides.

The aforementioned compounds can be doped with compounds of the first and seventh major groups of the Periodic Table or can contain these compounds.

Zeolites, phosphates and heteropolyacids and acidic and alkaline exchangers, for example Naphionß, are other suitable catalysts.

If required, these catalysts can contain up to 50% by weight of copper, tin, zinc, manganese, iron, cobalt, nickel, ruthenium, palladium, platinum, silver or rhodium.

Depending on the composition of the catalyst, it can be used as a catalyst without support or supported catalyst. For example, titanium dioxide can be used as a titanium dioxide extrudate or as titanium dioxide applied in a thin layer on a carrier. All the methods described in the literature can be used to apply titanium dioxide to a carrier such as silica, alumina or zirconium dioxide. In this way it is possible to apply a thin layer of titanium dioxide by hydrolysis of titanium organils, such as titanium isopropylate or titanium butylate, or by hydrolysis of TiCl 4 or other inorganic compounds containing titanium. Sols containing titanium dioxides can also be used.

Other suitable compounds are zirconyl chloride, aluminum nitrate or cerium nitrate.

Suitable carriers are powders, extrudates or granules of the aforementioned oxides or other stable oxides, such as silica. The carriers that are used can be made macroporous to improve mass transport.

In another preferred embodiment, the 6-aminocapronitrile is cyclized in liquid phase with water at elevated temperatures in the absence of catalyst by heating an aqueous solution of 6-aminocapronitrile in liquid phase without the addition of catalyst in a reactor to give a mixture I consisting mainly of in water, caprolactam and a fraction with high boiling point (high boiler). In this preferred embodiment, the water is preferably used in excess, particularly preferably from 10 to 150, in particular from 20 to 100 moles of the water used per mole of 6-aminocapronitrile and an aqueous solution of 6-aminocapronitrile is obtained . In another preferred embodiment, generally from 5 to 25 moles of water are used per mole of 6-aminocapronitrile and the solution can in general also be diluted to 5-25% by weight of 6-aminocapronitrile by adding an organic solvent.

Examples of suitable solvents are: I-AC aldernes such as methanol, ethanol, n-propanol, isopropanol and butanols, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol, ethers such as methyl ether butyl ether and diethylene glycol diethyl ether, C6-C alkanes, such as n-hexane , n-heptane, n-octane, n-nonane and n-decane and cyclohexanes, benzene, toluene, xylene, lactams such as pyrrolidone and caprolactam, and N-alkyl (of C1-C4) lactams, N-methylpyrrolidone, N-methyl caprolactam and N-ethylcaprolactam.

In another embodiment, from 0 to 5, preferably from 0.1 to 2% by weight of ammonia, hydrogen or nitrogen can be added to the reaction mixture.

The preferred reaction is carried out at 200 to 370 ° C, preferably at 220 to 350 ° C, particularly preferably at 240 to 320 ° C.

Generally, the reaction is carried out under superatmospheric pressure, the pressure, as a general rule, is chosen in the range of 0.1 to 50, preferably from 5 to 25 MPa, so that the reaction mixture is preferably found as a phase liquid The duration of the reaction depends mainly on the parameters chosen for the process and is generally 20 to 180 and preferably 20 to 90 minutes in the continuous process. As a general rule, the conversion decreases in the case of shorter reaction times and observations to date have shown that annoying oligomers are formed in the case of longer reaction times.

The preferred cyclization is carried out continuously, preferably in a tube reactor, a stirred kettle or a combination thereof.

Cyclization can also be carried out batchwise. The reaction then, in general, takes 30 to 180 minutes.

As a general rule, the discharged mixture consists mainly of 50 to 98, preferably 80 to 95% by weight of water and 2 to 50, preferably 5 to 20% by weight of a mixture containing mainly 50 to 90% by weight. , preferably from 65 to 85% by weight of caprolactam and from 10 to 50, preferably from 15 to 35% by weight of a fraction with a high boiling point.

In a preferred embodiment, any abradid catalyst material and high boiling nonvolatile substance present after partial hydrogenation and after the ammonia and inert compound A (bottom product of column 3) have been separated, are removed by means of an evaporation step in which the undesirable substances are obtained as a lower product.

In another preferred embodiment, the adiponitrile is distilled off from the bottom product of column 6, which contains adiponitrile and substances with a high boiling point and is fed to stage (a). It is also possible to discharge bleeding vapor from the lower part of column 6.

In another embodiment, the lower product III can be fed to a fourth column by carrying out the distillation in such a way that a higher product containing hexamethyleneimine is obtained and, if desired, the compound B and a lower product IV. Some of the superior product is recycled to column III and the rest is discharged to avoid concentration.

The lower product IV is fed to a fifth column, carrying out the distillation under conditions so that a superior product containing hexamethylenediamine and a lower product V is obtained. This lower product V is fed to a sixth column to give 6-aminocapronitrile as the top product and adiponitrile as the bottom product.

The distillation in the fourth column of the last mentioned modality preferably is carried out at a lower temperature of 100 to 220 ° C, preferably of 140 to 200 ° C and of 50 to 2000, preferably of 300 to 1000 mbar.

The distillation in the fifth column of the last mentioned mode is preferably carried out at a lower temperature of 100 to 220 ° C, preferably of 140 to 200 ° C and of 10 to 500, preferably of 40 to 200 mbar .

The distillation in the sixth column of the last mentioned mode is preferably carried out at a temperature lower than 100 to 220 ° C, preferably 140 to 200 ° C and 1 to 500, preferably 5 to 100 mbar .

Further processing of the hexamethylenediamine, 6-aminocapronitrile and adiponitrile products obtained in this preferred embodiment is advantageously carried out in a manner similar to the novel process.

In another preferred embodiment, substances with high boiling point are removed from the lower product III by distillation before the lower product is fed to the fourth column. Any separation of the substances with high boiling point from the lower product of column 6 containing adiponitrile, can thus be omitted.

The hexamethylenediamine obtained according to the invention can be further purified by conventional methods and used for the preparation of polymers and copolymers such as polyamide 66.

According to the invention, part of the process for the preparation of caprolactam from adiponitrile can also be used for the simultaneous separation of 6-aminocapronitrile and hexamentylenediamine by distillation of a mixture containing mainly these compounds, by a process in which. (a) a mixture containing mainly 6-aminocapronitrile, hexamentylenediamine, ammonia adiponitrile and hexamethyleneimine, are subjected to a distillation to give ammonia as the upper product and a lower product I, carrying out the distillation at a lower temperature from 60 to 220 ° C, and from 10 to 30 bar in the presence of a compound A which is inert under the distillation conditions and boils from 60 to 220 ° C at 18 bar, and not completely separating the ammonia, (b) the lower product I which contains mainly 6-aminocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine, inert compound A and ammonia, the ammonia content being lower than that of the mixture used in step (b), is subjected to a second distillation to give a mixture that contains the inert compound A and ammonia as the upper product and an inferior product II, carrying out the distillation at a lower temperature of 100 to 220 ° C and from 2 to 15 bar, always and when the pressures in the first and second columns coincide with each other so that the upper temperature above 20 ° C is obtained at a lower temperature of not more than 220 ° C, (c) the lower product II which contains mainly aminocapronitrile, hexamentylenediamine, adiponitrile, hexamethyleneimine and the inert compound A are subjected, in a third column, to a distillation to give the inert compound A as the upper product and a lower product III, carrying out the distillation at a lower temperature of 100. at 220 ° C and from 0.1 to 2 bar, provided that the inert compound A obtained as the upper product is fed to the second column, and, if desired, the distillation is carried out in the presence of a compound B which is inert under the distillation conditions and boils off. 50 to 220 ° C at 0.3 bar, (d) the lower product III containing mainly 6- to inocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine, and, if desired, an inert compound B is subjected, in a fourth column, to a distillation to give an upper KP1 product, which contains mainly hexamethyleneimine, and, if desired, an inert compound B and hexamethylenediamine, which are obtained at a temperature lower than 100 to 220 ° C and from 10 to 500 mbar, and a product lower IV. (e) the upper KP1 product is subjected, in a fifth column, to a distillation to give an upper KP2 product, which contains mainly hexamethyleneimine and, if desired, the inert compound B and is obtained at a temperature lower than 100 to 220 ° C and from 50 to 2000 mbar, and an inferior product V containing mainly hexamethylenediamine in a purity of at least 95%, the upper KP2 product is fed to the third column or, if desired, only some of this product the upper one is fed to the third column and the rest is discharged, and (f) the lower IV product containing mainly 6-aminocapronitrile and adiponitrile are subjected, in a sixth column, to a distillation to give 6-aminocapronitrile in a purity of at least 95% as a superior product and adiponitrile as the lower product, carrying out the distillation at a lower temperature of 100 to 220 ° C and 1 to 500 mbar.

The novel process has the advantage that it is a continuous process for the preparation of caprolactam, simultaneously obtaining hexamethylenediamine starting from adiponitrile.

Examples Example 1 (a) Hydrogenation of adiponitrile to 6-aminocapronitrile A mixture of 4.6 kg of adiponitrile (DNA), 4.6 kg of ammonia, 0.45 kg of suspended Raney nickel catalyst (H 1-50, BASF) and 8 g of lithium hydroxide was hydrogenated at 80 ° C and at a total pressure of 70 bar for one hour in an autoclave with stirring (partial pressure of H2 = 40 bar). After removing the Raney nickel catalyst, the discharged hydrogenation mixture had the following concentration: 2.5 kg of DNA, 2 kg of 6-aminocapronitrile (ACN) 0.2 kg of hexamethylenediamine (HMD), 10 g of hexamethyleneimine (HMI) and 4.5 kg from. ammonia (b) Handling of the hydrogenation mixture discharged by distillation. The discharged hydrogenation mixture that was obtained from step (a) and freed from the catalyst was fed to the top of a first column with two theoretical plates. 4.5 kg of ammonia containing 200 ppm of ACN were separated at the top at 47 ° C and 19 bar and used for hydrogenation (step (a)). The lower product of the first column, a reaction mixture containing ethanol and small amounts of ammonia, was fed at a lower temperature of 180 ° C in a second column with 13 theoretical plates. 0.4 kg of a mixture of 25% by weight of ammonia and 75% by weight of ethanol were recycled from the top of this column at 50 ° C and 10 bar to the first column. The bottom product of the second column, which contained 30% by weight of ethanol, 30 ppm of ammonia and was at 180 ° C, was fed to a third column with 14 theoretical plates. 2 kg of ethanol were removed from the top of this column at 50 ° C / 300 mbar and recycled to the second column. 4.8 kg of product with a content of hexamethyleneimine (HMI) at 2% by weight were removed from the bottom of the third column, which was at 180 ° C and fed to a fourth column with 20 theoretical plates. 0.3 kg of the product containing 65% by weight of HMD, 35% by weight of HMI and 1000 ppm of ACN was removed from the top of this column at 90 ° C / 85 mbar.

The superior product that was removed from the fourth column was fed to a fifth column with 15 theoretical plates. At 114 ° C / 500 mbar, 90 g of HMI containing 1000 ppm of HMD were removed as the top product and recycled to the third column. 190 g of HMD containing 100 ppm of HMI was taken from the bottom of the column at 177 ° C and removed from the process. The lower product removed from the fourth column was fed to a sixth column with 15 theoretical plates. 2 kg of the ACN containing 1000 ppm of HMD and 100 ppm of DNA were taken from the top of this column at 11 ° C / 15 bar and discharged. 2.5 kg of DNA containing 500 ppm of ACN were discharged from the bottom. (c) Cyclization of 6-amicapronitrile to caprolactam A solution of 2 kg of ACN (from (b)), 0.64 kg of water and 17.4 kg of ethanol was passed, at 230 ° C and 80 bar in a residence time of 15 minutes, through a reactor. tube heated with oil filled with 4 mm titanium dioxide extrudates and with a length / diameter ratio of 100. The discharged reaction mixture contained 1.8 kg of caprolactam 0.05 kg of ethyl 6-aminocaproate, 0.04 kg of inocapronitrile ( determined by gas chromatography) 0.11 kg of 6-aminocaproic acid and oligomers and caprolactam polymers (determined by CLAP) from this were obtained 1.7 kg of caprolactam by fractional distillation.

Example 2 (a) Hydrogenation of adiponitrile to 6-amicapronitrile A tube reactor with a length of 2 cm and an internal diameter of 2.5 cm was filled with 750 ml (1534 g) of catalyst consisting of 90% by weight of CoO, 5% by weight of Mn203, 3% by weight of P205, and 2% by weight of Mn20, and the catalyst was then activated for 48 hours in a stream of hydrogen (500 1 / h) by increasing the temperature from 30 to 280 ° C under pressure atomospheric After the temperature had dropped to 42 ° C (entry) and 80 ° C (exit), a mixture of 380 g / h of adiponitrile, 380 g / h of ammonia and 500 1 / h of hydrogen was fed to the reactor at 200 bar (total pressure). In addition, 4 times the feeding speed (approx. 3 kg / h) was circulated to eliminate the heat. Under these conditions 60% adiponitrile reacted. The reaction mixture consisted of 50% by weight of ammonia, 20% by weight of DNA, 18% by weight of ACN, 11.9% by weight of HMD, 0.05% by weight of HMI and 0.05% by weight of others (preferably substances with a high boiling point) (ACN selectivity: 60%, selectivity of ACN + HMD: >; 99 ?,). (b) Handling of the hydrogenation mixture discharged by distillation. 10 kg of the discharged hydrogenation mixture obtained from step (a) was fed to the top of a first column with two theoretical plates. 5.0 kg of ammonia containing 20 ppm of ACN were separated at the top at 47 ° C and 19 bar and used for hydrogenation (step (a)). The lower product of the first column, a reaction mixture containing ethanol and small amounts of ammonia, was fed, at a temperature lower than 180 ° C, into a second column with 10 theoretical plates. 1.2 kg of a mixture of 30% by weight of ammonia and 70% by weight of ethanol was recycled from the top of this column at 50 ° C and 10 bar towards the first column. The lower product of the second column, which contained 40% by weight of ethanol and 90 ppm of ammonia and was at 177 ° C, was fed to a third column with 10 theoretical plates. 3.2 kg of ethanol was removed from the top of this column at 47 ° C / 300 mbar and recycled to the second column. 5 kg of the product with an HMI content of 0.55% by weight were removed from the bottom of the third column, which was at 180 ° C and fed to a fourth column with 20 theoretical plates. 1.22 kg of the product containing 2.2% by weight of HMI, 97.8% by weight of HMD and 1000 ppm of ACN was removed from the top of this column at 90 ° C / 85 mbar. The superior product that had been removed from, the fourth column was fed to a fifth column with 15 theoretical plates. At 114 ° C / 500 mbar, 26 g of HMI containing 1000 ppm of HMD were removed as the top product. 22 g of it was recycled to the third column. 1.19 kg of HMD containing 100 ppm HMI was taken from the bottom of the column at 17 ° C and removed from the process. The lower product withdrawn from the fourth column was fed into a. Column column with 15 theoretical plates. 1.8 kg of the ACN containing 1000 ppm of HMD and 100 ppm of DNA were taken from the top of this column at 111 ° C / 15 mbar and discharged. 2.0 kg of DNA containing 500 ppm of ACN was discharged from the bottom. (c) Cyclization of 6-amicapronitrile to caprolactam A solution of 2 kg of ACN (from example 2 (b)), 0.64 kg of water and 17.4 kg of ethanol were passed, at 230 ° C and 80 bar at a time of stay 15 minutes, through an oil-filled tube reactor filled with 4 mm titanium dioxide extrudates and with a length / diameter ratio of 100. The discharged reaction mixture contained 1.8 kg of caprolactam 0.05 kg of 6- ethyl aminocaproate, 0.04 kg of 6-aminocapronitrile (determined by gas chromatography) 0.11 kg of 6-amicaproic acid and caprolactam oligomers and polymers (determined by CLAP) from this were obtained 1.7 kg of caprolactam by fractional distillation.

Claims (6)

1. REINVINDICATIONS
2. A process for the simultaneous preparation of caprolactam and hexamethylenediamine starting with adiponitrile, wherein: (a) the adiponitrile is partially hydrogenated to give a mixture containing mainly 6-aminocapronitrile, hexamethylenediamine, ammonia, adiponitrile and hexamethyleneimine, (b) the mixture obtained in (a) it is subjected to a distillation to give ammonia as an upper product and a lower product I, carrying out the distillation at a lower temperature of 60 to 220 ° C and at a pressure of 10 to 30 bar in the presence of a compound A which is inert under the distillation conditions and boils from 60 to 220 ° C at 18 bar, and not completely separating the ammonia, (c) the lower product I containing mainly 6-amincapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine, the compound Inert A and ammonia, the ammonia content being lower than that of the mixture used in step (b), is subjected to a second distillation to give a mixture which it contains the inert compound A and ammonia as the upper product and an inferior product II, carrying out the distillation at a lower temperature of 100 to 220 ° C and from 2 to 15 bar, as long as the pressures in the first and second columns coincide each other, so as to obtain the upper temperature above 20 ° C at a lower temperature of not more than 220 ° C, (d) the lower product II containing mainly 6-aminocapronitrile, hexamentylenediamine, adiponitrile, hexamethyleneimine and the compound Inert A are subjected, in a third column, to a distillation to give an inert compound A as the upper product and a lower product III, the distillation is carried out at a lower temperature of 100 to 220 ° C and 0.1 to 2 bar, provided that the inert compound A obtained as the upper product is fed to the second column, and, if desired, the distillation is carried out in the presence of a compound B which is inert under the distillate conditions. and boils from 50 to 220 ° C at 0.3 bar, (e) the lower product III containing mainly 6-aminocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine, and, if desired an inert compound B is subjected, in a fourth column, to a distillation to give a superior KP1 product, containing mainly hexamethyleneimine, and, if desired, an inert compound B and hexamethylenediamine, which is obtained at a temperature lower than 100 to 220 ° C and from 10 to 500 mbar, and a lower IV product. (f) the upper KP1 product is subjected, in a fifth column, to a distillation to give an upper KP2 product, which contains mainly hexamethyleneimine and, if desired, inert compound B which is obtained at a temperature lower than 100 to 220 ° C and from 50 to 2000 mbar and a lower product V containing mainly hexamethylenediamine in a purity of at least 95%, the upper KP2 product is fed to the third column or, if desired, only some of this superior product the third column is fed and the remainder is discharged, and (g) the lower IV product containing mainly 6-aminocapronitrile and adiponitrile is subjected, in a sixth column, to a distillation to give 6-aminocapronitrile in a purity of less 95% as the superior product and adiponitrile as the inferior product, carrying out the distillation at a temperature lower than 100 to 220 ° C and from 1 to 500 mbar, and the 6-amicapronitrile thus obtained is then cyclized to give capr olactam 2. The process according to claim 1, wherein the adiponitrile is distilled off from the bottom product of column 6, which contains adiponitrile and a high-boiling fraction, and is fed in step (a) . A process for the simultaneous separation of 6-aminocapronitrile and hexamentylenediamine by distillation of a mixture containing mainly these compounds, wherein: (a) a mixture containing mainly 6-aminocapronitrile, hexamentylenediamine, ammonia adiponitrile and hexamethyleneimine, are subjected to a distillation to give ammonia as an upper product and a lower product I, carrying out the distillation at a lower temperature from 60 to 220 ° C, and from 10 to 30 bar in the presence of a compound A which is inert under the distillation conditions and boils from 60 to 220 ° C at 18 bar, and not completely separating the ammonia, (b) the lower product I containing mainly 6-aminocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine , the inert compound A and ammonia, the content of ammonia being lower than that of the mixture used in step (a), is subjected to a second distillation to give a mixture containing the inert compound A and ammonia as the superior product and a lower product II, carrying out the distillation at a lower temperature of 100 to 220 ° C and from 2 to 15 bar, as long as the pressures in the first and second columns coincide with each other, so that the upper temperature is obtained above 20 ° C at a lower temperature of not more than 220 ° C, (c) the lower product II containing mainly 6-aminocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine and the inert compound A are subjected , in a third column, to a distillation to give the inert compound A as an upper product and an inferior product III, carrying out the distillation at a lower temperature of 100 to 220 ° C and from 0.1 to 2 bar, as long as the The inert compound A obtained as the upper product is fed to the second column, and, if desired, the distillation is carried out in the presence of a compound B which is inert under the distillation conditions and boils from 50 to 220 ° C. at 0.3 bar, (d) the lower product III containing mainly 6-aminocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine and, if desired, an inert compound B is subjected, in a fourth column, to a distillation for r a superior KP1 product, containing mainly hexamethyleneimine, and, if desired, an inert compound B and hexamethylenediamine, which is obtained at a temperature lower than 100 to 220 ° C and from 10 to 500 mbar and a lower product IV . (e) the upper KP1 product is subjected, in a fifth column, to a distillation to give an upper KP2 product, which contains mainly hexamethyleneimine and, if desired, the inert compound B and is obtained at a temperature lower than 100 to 220 ° C and from 50 to 2000 mbar and a lower product V containing mainly hexamethylenediamine in a purity of at least 95%, the upper KP2 product is fed to the third column or, if desired, only some of this superior product is fed to the third column and the remainder is discharged, and (f) the lower IV product containing mainly 6-aminocapronitrile and adiponitrile are subjected, in a sixth column, to a distillation to give 6-aminocapronitrile in a purity of less 95% as a higher product and adiponitrile as the lower product, carrying out the distillation at a lower temperature of 100 to 220 ° C and of 1 to 500 mbar. The process, according to claim 1 or 2, wherein a mixture consisting mainly of from 1 to 70% by weight of 6-aminocapronitrile, from 1 to 70% by weight of adiponitrile. from 0.1 to 30% by weight of hexamethylenediamine. from 0.01 to 10% by weight of hexamethyleneimine, and from 5 to 95% by weight of ammonia, the numbers that are established must add 100% by weight, is used in stage (b).
3. The process according to claim 3, wherein a mixture consisting mainly of from 1 to 70 by weight of 6-aminocapronitrile, from 1 to 70% by weight of adiponitrile. from 0.1 to 30% by weight of hexamethylenediamine. from 0.1 to 10% by weight of hexamethyleneimine, and from 5 to 95% by weight of ammonia, the numbers that are set add up to 100% by weight, is used in stage (a)
4. The process, in accordance with the claim 1 to
5. 5, where ethanol is used as the inert compound A. The process, in accordance with claim 1 to 6, where hexamethyleneimine is used as compound B. SUMMARY OF THE INVENTION The present invention relates to the compounds caprolactam and hexamethylenediamine which are prepared simultaneously starting with adiponitrile by a process in which: (a) the adiponitrile is partially hydrogenated to give a mixture containing mainly 6-aminocapronitrile, hexamethylenediamine, ammonia, adiponitrile and hexamethyleneimine, (b) the mixture obtained in (a) is subjected to a distillation to give ammonia as a byproduct and a lower product I, carrying out the distillation at a lower temperature of 60 to 220 ° C and at a pressure of 10 to 30 bar in the presence of a compound A which is inert under the distillation conditions and boils from 60 to 220 ° C at 18 bar, and not completely separating the ammonia. c) the lower product I containing mainly 6- amincapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine, the inert compound A and ammonia, the ammonia content being lower than that of the mixture used in step (b), is subjected to a second distillation to give a mixture containing the inert compound A and ammonia as upper product and a lower product II, carrying out the distillation at a lower temperature of 100 to 220 ° C and of 2 to 15 bar, as long as the pressures in the first and second columns coincide with each other, so that the upper temperature is obtained above 20 ° C at a lower temperature of no more than 220 ° C, (d) the lower product II containing mainly 6-aminocapronitrile, hexamentylenediamine, Adiponitrile, hexamethyleneimine and the inert compound A are subjected, in a third column, to a distillation to give an inert compound A as the upper product and a lower product III, the distillation n is carried out at a lower temperature of 100 to 220 ° C and 0.1 to 2 bar, as long as the inert compound A obtained as the upper product is fed to the second column, and, if desired, the distillation is carry out in the presence of a compound B which is inert under distillation conditions and boils from 50 to 220 ° C at 0.3 bar, (e) the lower product III containing mainly 6-aminocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine, and, if desired, an inert compound B is subjected, in a fourth column, to a distillation to give a superior KP1 product, containing mainly hexamethyleneimine, and, if desired, an inert compound B and hexamethylenediamine, which is obtained at a temperature lower than 100 to 220 ° C and from 10 to 500 mbar, and a lower IV product. (f) the upper KP1 product is subjected, in a fifth column, to a distillation to give an upper KP2 product, which contains mainly hexamethyleneimine and, if desired, inert compound B which is obtained at a temperature lower than 100 to 220 ° C and from 50 to 2000 mbar and a lower product V containing mainly hexamethylenediamine in a purity of at least 95%, the upper KP2 product is fed to the third column or, if desired, only some of this superior product it is fed to the third column and the rest is discharged, and (g) the lower IV product containing mainly 6- to inocapronitrile and adiponitrile are subjected, in a sixth column, to a distillation to give 6-aminocapronitrile in a purity of at least 95% as the top product and adiponitrile as the bottom product, carrying out the distillation at a lower temperature of 100 to 220 ° C and 1 to 500 mbar, and the
6. 6-aminocapronitrile thus obtained is then cyclized to give caprolactam