METHOD FOR SEPARATING 2-AMINOMETHYLCYLCLOPENTYLAMINE FROM A MIXTURE CONTAINING HEXAMETHYLENE DIAMINE AND 2-AMINOMETHYLCYCLOPENTYLAMINE

PROCEDE POUR SEPARER DE LA 2-AMINOMETHYLCYCLOPENTYLAMINE CONTENUE DANS UN MELANGE COMPRENANT DE LA DIAMINE D'HEXAMETHYLENE ET DE LA 2-AMINOMETHYLCYCLOPENTYLAMINE

English Abstract

The invention relates to a method for separating 2-aminomethylcyclopentylamine
from a mixture containing hexamethylene diamine and 2-aminomethylcyclopentyl-
amine, characterized in that separation occurs by distillation in the presence
of water.

French Abstract

L'invention concerne un procédé permettant de séparer de la diamine de 2-aminométhylène et de la 2-aminométhylcyclopentylamine qui se caractérise en ce que la séparation s'effectue par distillation en présence d'eau.

Claims

claims
1. A process for separating 2-aminomethylcyclopentylamine from a
mixture comprising hexamethylenediamine and 2-aminomethyl-
cyclopentylamine, which comprises performing the separation
by distilling in the presence of water at a water content
[lacuna] 0.1 to 10% by weight, based on the distillation
mixture, at pressures from 1 to 1100 mbar and bottom
temperatures from 40 to 250°C.
2. A process as claimed in claim 1, wherein the distillation
apparatus used is a distillation column.
3. A process as claimed in claim 1 or 2, wherein the
distillation apparatus used is a packed column.
4. A process as claimed in any of claims 1 to 3, wherein the
distillation apparatus used is a distillation column having a
pressure drop of not more than 1 mbar per theoretical plate.
5. A process as claimed in any of claims 1 to 4, wherein the
pre-separation weight proportion of 2-aminomethylcyclo-
pentylamine, based on hexamethylenediamine, is within the
range from 1 to 10,000 ppm.
6. A process for preparing hexamethylenediamine having a weight
proportion of 2-aminomethylcyclopentylamine, based on
hexamethylenediamine, within the range from 0 to 100 ppm from
a mixture comprising hexamethylenediamine and
2-aminomethylcyclopentylamine by separating off
aminomethylcyclopentylamine, which comprises the process
steps as claimed in any of claims 1 to 5.

Description

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"1~9~.'IHOD FOR SEPARATING 2-AI~LVC~!~IYhCYC'LOPE~YhAI~~TE FROM A I~~IURE
CbNTAINING HF~CAMETHYLF1~1E DID AND 2-AMINOMCI~iYhCYC'LOPEI~TfYLAMll~IE"
Description
The present invention relates to a process for separating
2-aminoinethylcyclopentylamine (AMCPA) from a mixture comprising
hexamethylenediamine and AMCPA.
The complete hydrogenation of adiponitrile to hexamethylene-
diamine and also the partial hydrogenation with coproduction of
hexamethylenediamine and 6-aminocapronitrile in the presence of a
catalyst based on a metal such as nickel, cobalt, iron, rhodium
or ruthenium are generally known, for example from:
K. Weissermel, H.-J. Arpe, Industrielle Organische Chemie,
3rd edition, VCH Verlagsgesellschaft mbH, Weinheim, 1988,
page 266, US-A 4 601 859, US-A 2 762 835, US-A 2 208 598,
DE-A 848 654, DE-A 954 416, DE-A 42 35 466, US-A 3 696 153,
DE-A 19500222, WO 92/21650 and German Application 19548289.1.
Byproducts include hexamethyleneimine (HMI), 1,2-diaminocyclo-
hexane (DACH) and AMCPA.
US-A 3 696 153 discloses that the hexamethylenediamine obtained
by this hydrogenation comprises AMCPA as a byproduct which is
very difficult to separate from the mixture.
It is an object of the present invention to provide a process for
separating AMCPA from a mixture comprising essentially
hexamethylenediamine and AMCPA in a technically simple and
economical manner.
We have found that this object is achieved by a process for
separating AMCPA from a mixture comprising hexamethylenediamine
and AMCPA, which comprises performing the separation by
distilling in the presence of water.
The partial or complete hydrogenation of adiponitrile can be
carried out according to any of the known processes, for example
according to one of the aforementioned processes described in

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US 4 601 859, US 2 762 835, US 2 208 598, DE-A 848 654,
DE-A 954 416, DE-A 4 235 466, US-A 3 696 153, DE-A 9 500 222 or
WO 92/21650 by, in general, performing the hydrogenation in the
presence of nickel-, cobalt-, iron- or ruthenium-containing
catalysts. The catalysts used can be supported or unsupported
catalysts. Possible supports include, for example, aluminum

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oxide, silicon dioxide, titanium dioxide, magnesium oxide,
activated carbons and spinels. Examples of unsupported catalysts
are Raney nickel and Raney cobalt.
The hydrogenation gives rise to a mixture comprising hexa-
methylenediamine and AMCPA with or without 6-aminocapronitrile
and adiponitrile.
The separation from a mixture comprising hexamethylenediamine and
AMCPA can be effected in a conventional manner, preferably by
distillation, for example as described in DE-A 195 002 22 or
German Application 19 548 289.1, simultaneously or in succession,
for example in a distillation column or in a sidestream takeoff
column having a dividing wall (Petlyuk column), so that the
condensation temperature of the downstream purification column in
the AMCPA removal is generally higher and condensation is
facilitated. The low boiling DACH, if present, can with advantage
be separated off together with AMCPA, but the removal of DACH can
also be effected overhead in a separate column.
It is advantageous to precede the purification of the
hexamethylenediamine by the process of this invention by complete
or partial removal of low boilers, such as HMI, if present.
In the mixture comprising hexamethylenediamine and AMCPA, the
pre-separation weight proportion of AMCPA, based on
hexamethylenediamine, is generally within the range from 10 to
10,000 ppm, especially within the range from 100 to 1000 ppm,
although the process of the invention is not restricted to these
limits.
The separation of AMCPA from the mixture is advantageously
carried out by distillation at pressures from 1 to 1100 mbar,
preferably from 1 to 500 mbar, which results in bottom
temperatures within the range from 40 to 250°C.
The distillation can be carried out in customary apparatus as
described for example in: Kirk-Othmer, Encyclopedia of Chemical
Technology, 3rd Ed., Vol. 7, John Wiley & Sons, New York, 1979,
pages 870-881, such as sieve plate columns, bubble cap columns or
packed columns.
It is particularly advantageous to use distillation columns
having a low pressure drop, preferably not more than 1 mbar,
especially 0.5 mbar, per theoretical plate.

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Columns which are especially suitable are packed columns,
preferably with arranged packing such as metal sheet packing,
especially woven wire packing.
According to the invention, water is added to the distillation
mixture, preference being given to water contents from 0.01 to
10~ by weight, especially from 0.1 to 5$ by weight, based on the
distillation mixture.
The water can be added to the mixture prior to the distillation
or during the distillation, for example in the column, preferably
in the region below the feed point, especially in the bottom
region.
The process of the invention affords AMCPA and water as overhead
product, in general, if present in the mixture comprising
hexamethylenediamine and AMCPA, in the mixture with DACH and low
boiling components.
The distillation can be carried out in a plurality of columns,
such as 2 or 3 columns, but is advantageously carried out in a
single column.
Hexamethylenediamine can be processed with dicarboxylic acids
such as adipic acid into industrially important polymers.
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