MXPA99007270A - Method for obtaining hexamethylene diamine from mixtures containing hexamethylene diamine - Google Patents

Abstract

The invention relates to a method for obtaining hexamethylene diamine (I) from a mixture (II) containing (I) hexamethylene diamine, (III) hexamethylenimine, (IV) a compound selected from the group consisting of 2-aminomethyl cyclopentylamine and 1,2-diaminocyclohexane, (V) an imine, and (VI) adipodinitrile and 6-aminocaproic acid nitrile. According to said method, (a) a mixture (II) is subjected to distillation, yielding (a1) a low-boiling fraction which essentially contains (III), (a2) a medium-boiling fraction (VII) containing (I), (IV) and (V), and (a3) a high-boiling fraction containing (V) and (VI);(b) a mixture (VII) is subjected to distillation, yielding (b1) an overhead which essentially contains (IV) and (b2) a mixture (VIII) containing (I) and (V) as bottom residue;and (c) a mixture (VIII) is subjected to distillation, yielding (c1) (I) as overhead and (c2) a bottom residue which contains the essential part of (V).

Description

Procedure for the generation of hexamethylenediamine from mixtures containing hexamethylenediamine Description The present invention relates to a process for the generation of hexamethylenediamine (I) from a mixture (II) containing (I) hexamethylenediamine, (III) hexamethyleneimine, (IV) a compound selected from the group comprising 2-amino-nomylcyclopentylamine and 1,2-diaminocyclohexane, (V) an imine (VI) adiponitrile and 6-aminocaproic acid nitrile, in whose procedure (a) a mixture (II) is subjected to a distillation, obtaining (a) a low boiling fraction containing substantially (III), (a2) a medium boiling fraction (VII) containing (I) , (IV), (V) and (a3) a high-boiling fraction that contains (V) • and (vi), (b) a (vile) mixture is subjected to a distillation, obtaining (bl) a product of heads containing, substantially (IV) and (b2) a mixture (VIII) which contains (I) and (V) as the background product (c) a mixture (VIII) is subjected to a distillation, obtaining (I) as heads and (c2) a bottom product containing the substantial part of (V). It is known, for example from: K. eissermel, H.-J. Arpe, Indu-strielle Organische Chemie, 4a. edition, page 270, VCH-Verlags-gesellschaft, hydrogenate adipodinitrile completely in the presence of iron, cobalt or nickel catalysts in the intermediate product of hexamethylenediamine fibers. Due to the quantitative conversion of adipodinitrile to hexamethylenediamine, the hydrogenation discharge contains practically no adiponitrile and no 6-aminocapronitrile. The purification of the hexamethylenediamine fiber quality can be carried out in a manner known per se, for example according to GB-A-731 819 by distillation or according to US Pat. No. 4,282,381 by crystallization.

In addition, it is known to partially hydrogenate adipodinitrile, giving mixtures of both intermediate products for fibers, 6-aminocapronitrile and hexamethylenediamine, as well as unreacted adiponitrile, for example, according to US-A-4, 601, 8591, US-2,762,835 , US-A-2,208, 598, DE-A 848 654, DE-A-44 46 893, DE-A-954 416, DE-A-42 35 466, WO 92/21650, DE-A-19 500 222 or the German patent application application 19 548 289.1, in the presence of nickel, cobalt, iron, ruthenium or rhodium catalysts.

The 6-aminocapronitrile can be cyclized in caprolactam or directly polymerized in nylon 6.

In the case of partial hydrogenation, by-products are obtained which are difficult to separate from hexamethylenediamine, such as, for example, hexamethyleneimine, 1,2-diaminocyclohexane and 2-aminomethylcyclopentylamine. In particular, tetrahydroazepine and the two cyclic diamines reduce, for example due to coloration, the quality of nylon 6.6 obtained from hexamethylenediamine thus impurified. It is therefore necessary to separate the mentioned impurities to residual contents of a few ppm of the hexamethylenediamine. The known processes for the purification of hexamethylene diamine prepared by complete hydrogenation of adiponitrile can not be transferred to the reaction mixture obtained by partial hydrogenation of adiponitrile, due to the higher contents in these by-products, the different quantitative relationships of the products. secondary, as well as the presence of nitrile of 6-aminocaprónico acid and adipodinitrilo.

The object of the present invention is therefore to provide a process which allows the generation of hexamethylenediamine in a technically simple and inexpensive manner from a mixture obtained by partial hydrogenation of adiponitrile and containing hexamethylenediamine, 6-aminocaproic acid nitrile and adiponitrile.

Therefore, the procedure described above was found. The mixtures (II) can be obtained in a known manner by partial hydrogenation of adiponitrile, using, for example, the process according to EP-A-161 419, EP-A-77 911, US-A-4,389,348, US-A-4,601,859, WO 93/1207, DE-A 42 35 466, US-A-2, 762, 835, US-A-2,208,598, DE- A 848 654, DE-A-44 46 893, D? -A-954 416, DE-A-42 35 466, WO 92/21650, DE-A 19 500 222 and German patent application application 19 548 289.1 , performing, generally, the hydrogenation in the presence of nickel, cobalt, iron, rhodium or ruthenium catalysts. Either the catalysts can be used as support catalysts or mastic catalysts. Suitable support catalysts are, for example, aluminum oxide, silicon dioxide, titanium dioxide, magnesium oxide, active carbons and spinels. Suitable dimethyl catalysts are, for example, Raney niguel and Raney cobalt.

When liquid diluents are used in the hydrogenation, they must be removed in a known manner, for example, according to DE-A-19 500 222.

The mixtures (II) contain, generally: hexamethylenediamine (I), especially in amounts of 5 to 20 90% by weight, with respect to (II), • hexamethyleneimine (III), especially in amounts of 0.1 to 10% by weight, with respect to (II), A compound (IV) selected from the group comprising 2-aminomethylcyclopentylamine and 1,2-diaminecyclohexane or mixtures thereof, especially in amounts of 5 ppm to 5% by weight, with respect to (II), Or an imine (V) or mixtures of such imines, such as, for example, tetrahydro-azepine, the imines being able to be present as individual compounds or as adducts, especially with amines, such as hexamethylenediamine or 6-aminocaproic acid nitrile, and being referred to for the purposes of the present invention such adducts 5 as imines (V, especially in amounts of 5 to 10,000 ppm, with respect to (II) adiponitrile and nitrile of 6-aminocaproic acid (VI), the nitrile content of 6-aminocaproic acid at 5 0 to 90% by weight, with respect to (II), and the adiponitrile content at 5 to 90% by weight, with respect to (II).

According to the invention, the mixture (I) is subjected to a distillation (a). In this distillation, substantially, hexamethyleneimine (III) is obtained as a low-boiling fraction. This low-boiling (al) fraction may contain other compounds, such as residues of the liquid diluent used, for example, ammonia, or residues of the water obtained as a by-product in the hydrogenation.

A mixture (VII) containing, substantially, hexamethylenediamine (I), a compound (IV) and a compound (IVb) is obtained as the medium boiling fraction (a2), the content of hexamethylenediamine in the mixture (VII) preferably give 80 to 100% by weight, with respect to (VII), the content in the compound (IV) in the mixture (VII) preferably from 5 ppm to 0.5% by weight, with respect to (VII) and the content in the compound (IVb) in the mixture (VII), preferably from 1 to 10,000 ppm, with respect to (VII).

As a high-boiling fraction (a3), substantially, adiponitrile and mixture (vi) are obtained containing 6-aminocaproic acid nitrile, from which adiponitrile and 6-aminocaproic acid nitrile can be generated, preferably, by distillation . The adiponitrile can be recycled, advantageously, in the partial hydrogenation described.

For distillation, the usual distillation coloums can be used for this purpose, as are dectite, for example in: Kirk-Othmer, Encyclopedia of Chemical Technology, 3.Ed., Vol. 7, John Wiley & Sons, New York, 1979, pages 870-881,, such as, for example, perforated tray columns, tray columns with hood, packing columns or filling columns. Distillation apparatuses having a bottom pressure drop to the head of from 1 to 500 mbar, preferably from 5 to 50 mbar, are preferred, it being advantageous for the bottom pressure to be between 1 and 500 mbar and the pressure at the top of the head. 1 to 500 mbar. In this way, bottom temperatures of 100 to 300, especially 150 to 250 ° C, are obtained.

The distillation can be carried out in several columns, for example 2 or 3 or more columns, preferably in a single column.

If the distillation is carried out in a column, it is advantageously obtained (a) as heads, (a2) as lateral outlet and (a3) as the bottom product.

When the separation is carried out in two columns, it is advantageous to obtain a mixture from (a) and (a2) in the first column as heads and separate this mixture in the second column, so that in the second column there is obtained (al) as heads.

Advantageously, the distillation mixture will have in at least one, preferably 1 to 15, very preferably 1 to 7, especially 1, 2 or 3 levels of the distillation column an average residence time of at least 5 minutes, preferably, at least 15 minutes, especially 45 minutes, at least.

Preferably, the distillation mixture is discharged into at least one level, it is conducted through a residence vessel and then recycled to the distillation column. Recycling can be done in this case at the discharge level or at a level above or below it.

Advantageously, the reflux of the distillation column can be recycled, first, through a residence vessel and then into the distillation column.

The discharging of the column distillation fluid, the conduction through the residence vessel, the recycling to the distillation column and, optionally, the circulation of the liquid in the residence vessel can be carried out with the apparatuses known per se, such as eg pumps, recycling can be carried out at the discharge level of the distillation column, especially in the case of the column of dishes, or at a level above the level of discharge, especially in the case of a packing column. , or at a level below the download level.

The distillation of the mixture (II) can be carried out, advantageously, with the addition of an inert compound (IX) against the components of the mixture under the conditions of distillation, whose boiling point under the distillation conditions is higher the boiling point of the median fraction (a2).

Suitable compounds (IX) are compounds of the group of the aromatic, aliphatic, such as acyclic and cyclic aliphatics, and the aliphatic aromatic compounds. These compounds can contain substituents, such as, for example, an alkyl, aryl, cycloalguyl, aralguyl, ester, amide, nitrile or amino group, preferably a nitrile or amino group, or several identical or different substituents of these groups.

The compound (IX) can consist of a compound or mixtures of such compounds.

Advantageous are those compounds (IX), which can be converted in a simple manner, eg by hydrogenation with, for example, a gas containing molecular hydrogen, in the presence of a catalyst, to give hexamethylenediamine or 6-aminocapronic acid nitrile .

The products obtained in this reaction can be used, advantageously, again in the process of the invention.

After the distillation, a mixture containing a compound (IX) is obtained as the bottom product.

If the mixture additionally contains hexamethylenediamine (I), then the bottom temperature in the distillation can advantageously be reduced.

The compound (IX) can be recovered from the mixture in a known manner, for example, by physical methods, such as distillation or extraction, or chemical processes, such as chemical absorption or hydrogenation.

This compound (IX) obtained from the mixture can be re-cycled to steps (a) or (c) or both. The difference of the boiling points between the fraction of medium boiling point (a2) and the compound (IX) should rise under the distillation conditions at 1 to 200 ° C, preferably 5 to 100 ° C. It has proven to be especially advantageous to use adiponitrile or 6-aminocaproic acid nitrile or mixtures thereof. ' The compound (IX) can be added to the mixture (II) before or during the distillation.

The addition of the compound (IX) to the mixture (II) before the distillation can be carried out in a manner known per se in the usual distillation apparatuses.

The compound (IX) can be added to the mixture (II) during the distillation by introducing the compound (IX) into the distillation apparatus, preferably at the bottom.

The distillation of the mixture (II) can advantageously be carried out in the presence of carbon dioxide.

The carbon dioxide can be added to the reaction mixture before or, preferably during the distillation, in the form of a compound releasing carbon dioxide under the distillation conditions, such as, for example, ammonium carbonate or urea or mixtures of these compounds, these compounds can be added in pure form or in diluted form in a lichened diluent, such as one or more of the components of the mixture (II), or in the form of solid, liquid or, preferably gaseous, carbon dioxide, for example in form of a gas containing, or especially in the form of pure gaseous carbon dioxide, which only contains the usurious impurities.

The carbon dioxide content in the distillation mixture should amount to 0.1 to 1000 moles of carbon dioxide per mole of the imine fraction of the imines, such as tetrahydroaze-pine.

According to the invention, the mixture (VII) is subjected to a distillation (b).

In this distillation, a compound (IV) containing, substantially, 2-aminamethylcyclopentylamin, 1,2-diaminecyclohexane or mixtures thereof is obtained as heads (bl). The heads may also contain hexamethyleneimine or hexamethylenediamine or mixtures thereof.

As the bottom product (b2) of the distillation column, a mixture (VIII) is obtained which substantially contains hexamethylenediamine (I) and an imine (V), the content of hexamethylenediamine in the mixture (VIII) preferably increasing to 50 to 100% by weight, with respect to (VIII). Typical distillation columns are suitable for distillation, such as, for example, those described in: Kirk-Othmer, Encyclopedia of Chemical Technology, 3a.Ed., Vol. 7, John Wiley & Sons, New York, 1979, pages 870-881, such as columns of perforated plates, columns of plates with bell, packing columns or filling columns.

Distillation apparatuses having a bottom pressure drop of from 0 to 200 mbar, preferably from 0 to 50 mbar, are preferred, with the bottom pressure advantageously rising to 3 to 300 mbar, especially 1 to 200 mbar, and in the head at 1 to 300 mbar, especially 1 up to 200 mbar. This results in bottom temperatures of 100 to 300, especially 150 to 250 ° C.

The distillation can be carried out in several, eg 2, 3 or more columns, advantageously in a single column.

Particularly suitable are the distillation columns, which have a lower pressure loss, preferably of not more than 1 mbar, especially 0.3 bar-bar per theoretical separation step.

Packing columns are particularly suitable, preferably with ordered fillers, such as sheet metal gaskets, especially wire tissue gaskets.

Advantageously, water can be added to the distillation mixture, water contents of 0.001 to 10., especially 0.01 to 5% by weight of water, with respect to the distillation mixture being preferred.

The water can be added to the mixture before distillation or during distillation, for example in the column in the lower region. According to the invention, the mixture (VIII) is subjected to a distillation (c). In this distillation, heads (cl) hexamethylenediamine (I) are obtained, advantageously in the appropriate purity for obtaining fibers.

As the bottom product (c2) the essential parts of (V) are obtained, as well as other compounds which have a higher boiling point than hexamethylenediamine.

Typical distillation columns are suitable for distillation, such as, for example, those described in: Kirk-Othmer, Encyclopedia of Chemical Technology, 3.Ed., Vol. 7, John Wiley & Sons, New York, 1979, pages 870-881, such as columns of perforated plates, columns of plates with bell, packing columns or filling columns.

Distillation apparatuses having a pressure head pressure to the bottom of 1 to 1000 mbar, preferably 1 to 500 mbar are preferred, with the bottom pressure advantageously increasing to 10 to 900 mbar and in the head at 50 to 500 mbar. Of this moso results temperatures in the bottom of 100 until 300, especially 150 until 250 ° C.

The distillation can be carried out in several, for example in 2 or 3 columns, advantageously in a single column.

The distillation mixture will have at least one, preferably 1 to 15, very preferably 1 to 7, especially 1, 2 or 3 levels of the distillation column an average residence time of at least 5 minutes, preferably at least 15 minutes, especially 45 minutes, at least.

Preferably, the distillation mixture is discharged from the distillation column into at least one level, it is conducted through a residence vessel and recycled back to the distillation column. on a level above or below it.

Advantageously, the reflux of the distillation column can be passed, first, through a residence vessel and then recirculated to the distillation column.

The discharge of the column distillation fluid, the conduction through the residence vessel, recycling to the distillation column and, optionally, the circulation of the liquid in the residence vessel can be carried out with the known apparatuses, such as pumps, perform recycling at the discharge level of the distillation column, especially in the case of a column of dishes, or at a level above it, especially in the case of an e-payment column, or at a level below Download level.

The distillation of the mixture (VIII) can advantageously be carried out with the addition of a compound (X) inert to the components of the mixture under the distillation conditions, whose boiling point is higher than that of hexamethylenediamine ( I). Suitable compounds (X) are the compounds of the group of the aromatics of the aliphatics, for example acyclic and cyclic aliphatics and the aliphatic aromatic compounds. These compounds can carry substituents, such as an alkyl, aryl, cycloalkyl, aralkyl, ester, amide, nitrile or amino group, preferably a nitrile or amino group, or several identical or different substituents of these groups.

The compound (X) can be composed of a compound or mixtures of such compounds.

Advantageous are those compounds (X), which can be prepared in a simple manner, eg by hydrogenation, for example with a gas containing molecular hydrogen, in the presence of a catalyst, to give hexamethylenediamine or 6-aminocaproic acid nitrile.

The products obtained in this reaction can be used advantageously again for the process of the invention. After the distillation, a mixture containing a compound (X) is preferably obtained as the bottom product.

If the mixture additionally contains hexamethylenediamine (I), the bottom temperature in the distillation can advantageously be reduced.

Compounds (X) can be recovered from the mixture in a manner which is itself acidic, for example by physical processes, such as distillation or extraction, or by chemical methods, such as chemical absorption or hydrogenation.

The compound (X) obtained from this mixture can be recycled, advantageously, to stages (a) or (c) or both. The difference between the boiling points of the hexamethylenediamine (I) and the compound (X) under the distillation conditions should amount to 1 to 200 ° C, preferably 5: to 100 ° C. It has proven to be especially advantageous to use adiponitrile, 6-aminocaproic acid nitrile or mixtures thereof.

The compound (X) can be mixed into the mixture (VIII) before or during the distillation.

The addition of the compound (X) to the mixture (VIII) before the distillation can be carried out in a known manner in customary mixing apparatuses.

The addition of the compound (X) to the mixture (VIII) during the distillation can be carried out by feeding the compound (X) into the distillation apparatus, preferably at the bottom.

The distillation of the mixture (VIII) can be carried out, inter alia, in the presence of carbon dioxide.

The carbon dioxide can be added to the distillation mixture before or, preferably, during the distillation in the form of a compound which, under the conditions of distillation, releases carbon dioxide, such as, for example, ammonium carbonate or urea or mixtures of such compounds these compounds can be added in pure form or in a liquid diluent, such as, for example, one or more of the components of the mixture (VIII), or in the form of solid, liquid or preferably gaseous carbon dioxide, for example in the form of of a gas containing carbon dioxide or, especially, in the form of pure gaseous carbon dioxide, which contains only the usual impurities.

The content of carbon dioxide in the distillation mixture should amount to 0.01 to 1000 moles of carbon dioxide per mole of imine function of the imines, such as, for example, tetrahydroazepine.

Claims (11)

1. CLAIMS 1 . A process for recovering hexarnetlylenediamine (I) from a mixture (II) containing: (I) hexamethylenediamine (III) hexamethyleneimine, (IV) a compound selected from the group consisting of 2-amino-methyl-ethyl ester -t na and 1, 2-diaminocyclohexane, (V) a -mine, (VI) adiponitrile and 6-aminocapronitrils, which consists of distilling: (a) a mixture (II) in a column with a pressure drop from the lower part to the upper one from 1 to 500 mbar, a pressure in the lower part within the range from 1 to 500 mbar, a pressure cn the upper part within the range of 1 to 500 mbar and a temperature in the lower parturition from 100 at 300 ° C, to obtain: (a) a low boiling fraction consisting essentially of (III) as a superheated product, (a2) an average boiling fraction (VII) consisting of (I), ( IV) and (V) as a side stream intake / y (a3) a high boiling fraction consisting of (V) and (VI) as residual product, (b) a mixture (VIL) to obtain (bl) a superheated product consisting mainly of (IV), and (b2) a mixture (VIII) consisting of (I) and (V) as waste product, and (c) ) a mixture (HIV) to obtain (cl) (I) as a superheated product, and (c2) a residual product consisting of the main portion dc (V).
2. 2. The procoso somo eo mentioned in claim 1, wherein the average residence time of the distillation mixture in the distillation apparatus is at least 5 minutes in step (a).
3. 3, The process, as mentioned in claim 1 or 2, wherein the average residence time of the distillation mixture in the distillation apparatus is at least 5 minutes in step (c),
4. 4. The process as it is mentioned in any of claims 1 to 3, wherein carbon dioxide is added to the distillation in step (a).
5. 5, The process as mentioned in any of claims 1 to 4, wherein carbon dioxide is added to the distillation in step (c).
6. 6. The process as mentioned in any one of the remarks 1 to 5, wherein a compound (IX) which is inert to the components of the mixture under the distillation conditions and has a boiling point higher than the point of Boiling hexameti lendi mine (I) is added to the distillation mixture in step (a).
7. 7. The process as recited in any of claims 1 to 6, wherein a compound (X) has a boiling point above the boiling point of the mixture (VII) is added to the mixture or apparatus of the invention. distillation in step (c).
8. 8. The process as recited in claim 7, wherein the compound (X) consists of a compound (VI).
9. 9. The process as mentioned in claim 7 or 8, wherein the. compound (X) is adiponitrile, 6-aminocapronitrile or a mixture thereof.
10. The process as mentioned in any of claims 7 to 8, wherein the compound (X) consists of the residual product of step (a3).
11. 11. The process as mentioned in any of claims 1 to 10, wherein water is added to the deethylation mixture in step (b).