Preparation of hexamethylene diamine from 2-cyanocyclopentanone and adiponitrile

Process for the manufacture of hexamethylene diamine comprising the steps of contacting 2-cyanocyclopentanone alone or in mixture with adiponitrile with a mixture comprising ammonia and hydrogen in the presence of a catalyst prepared by reducing iron oxide with hydrogen. The process is conveniently conducted at a temperature in the range 100.degree. to 275.degree. C and at a pressure in the range of 300 to 600 kg/cm.sup.2. The mole ratio of ammonia to 2-cyanocyclopentanone is maintained at least 4:1 and the pressure of hydrogen is sufficient to essentially prevent conversion of the activated catalyst to iron oxide.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a process for the manufacture of 
hexamethylene diamine, and in particular, to a process for the manufacture 
of hexamethylene diamine from 2-cyanocyclopentanone, especially 
2-cyanocyclopentanone mixed with adiponitrile. 
2. Description of the Prior Art 
Adiponitrile can be obtained by reacting adipic acid with ammonia in the 
presence of a dehydrating catalyst, for example, by the techniques 
disclosed in U.S. Pat. No. 2,200,734 to Arnold and Lazier issued on May 
14, 1940 and in U.S. Pat. No. 2,273,633 to M. L. A. Fluchaire, issued on 
Feb. 17, 1942. The catalytic hydrogenation of dicyanobutene to 
adiponitrile is described in U.S. Pat. No. 2,532,311 to B. W. Howk and M. 
W. Farlow, issued on Dec. 5, 1950. Adiponitrile produced by these 
processes contains impurities, some of which boil at temperatures close to 
the boiling point of adiponitrile, e.g. 2-cyanocyclopentylideneimine. 
Impurities in the adiponitrile may lead to impurities in subsequent 
derivatives, in particular in hexamethylene diamine, that are difficult to 
remove. Failure to remove these latter impurities may result in inferior 
and variable properties, especially in polymers manufactured using such 
impure hexamethylene diamine. 
Adiponitrile can be purified by the process disclosed in U.S. Pat. No. 
3,879,436, issued on Apr. 22, 1975 to B. J. Kershaw and M. G. Pounder. 
2-Cyanocyclopentylideneimine in adiponitrile, may also be hydrolyzed to 
2-cyanocyclopentanone using a solid acidic catalyst in the presence of 
water and at a temperature of at least 140.degree. C. The solid acidic 
catalysts may be silica-alumina catalysts, crystalline aluminosilicates, 
boron phosphate of titania-alumina as disclosed in U.S. Pat. No. 3,775,258 
issued on Nov. 27, 1973 to B. J. Kershaw. The 2-cyanocyclopentanone is 
more easily separated from adiponitrile by techniques known in the art. 
SUMMARY OF THE INVENTION 
A process for the manufacture of hexamethylene diamine comprising 
contacting 2-cyanocyclopentanone with a mixture comprising ammonia and 
hydrogen in the presence of a catalyst selected from the group consisting 
essentially of promoted and unpromoted iron oxide, which catalyst has been 
activated by the reduction of said oxide, said process being conducted at 
a temperature in the range 100.degree. to 275.degree. C. and at a pressure 
in the range of 300 to 600 kg/cm.sup.2, wherein the mole ratio of ammonia 
to 2-cyanocyclopentanone is maintained at least 4:1 and the pressure of 
hydrogen is sufficient to prevent substantial conversion of the activated 
catalyst to iron oxide. More particularly, the reactants consist 
essentially of a mixture of adiponitrile and 2-cyanocyclopentanone 
containing 0.05 to 0.60% by weight of 2-cyanocyclopentanone and the 
process is conducted at a temperature in the range 100.degree. to 
200.degree. C. and at a pressure in the range of 300 to 600 kg/cm.sup.2. 
DETAILED DESCRIPTION OF THE INVENTION 
The 2-cyanocyclopentanone can be obtained from a variety of sources, e.g. 
it can be purified 2-cyanocyclopentanone obtained commercially or as a 
component of a process stream in an impure state, e.g. the 
2-cyanocyclopentanone can be a minor component in a stream of 
adiponitrile. However, it is important that any impurities present in the 
2-cyanocyclopenanone do not significantly deactivate the catalyst. 
The process is carried out at a temperature in the range of 100.degree. to 
275.degree. C., preferably in the range 100.degree. to 200.degree. C. when 
the 2-cyanocyclopentanone is admixed with adiponitrile. Lower temperatures 
are operable but not preferred because lower conversion rates can result. 
Temperatures above 275.degree. C. may result in losses of hexamethylene 
diamine especially as hexamethyleneimine. 
The preferred pressure range is 300 to 600 kg/cm.sup.2. Lower pressures 
favor the formation of incompletely hydrogenated compounds and secondary 
amines. Sufficient hydrogen pressure should be maintained to ensure that 
the activated iron catalysts are not converted to iron oxide, e.g. by 
water which is a by-product of the process of the present invention. 
Higher pressures are operable at an economic penalty. 
The mole ratio of ammonia to 2-cyanocyclopentanone may be as high as about 
270:1. Higher ratios can be used but may not be economically desirable. 
Undesirable by-products such as secondary amines can be formed at mole 
ratios below the preferred ratio of at least 4:1. 
Although it is preferred that the reaction pressure be attained through the 
use of hydrogen and ammonia, an inert gas, e.g. nitrogen, helium or argon, 
can be present as a minor component. 
The preferred catalysts in the present process are activated iron oxide 
catalysts which can be unpromoted or promoted by acidic and/or basic metal 
oxide promoters. The preparation of such catalysts is described in 
Canadian Pat. No. 907,059 issued on Aug. 8, 1972 to J. R. B. Boocock, F. 
T. Flood and B. J. Kershaw. The use of such catalysts for the 
hydrogenation of adiponitrile is described in U.S. Pat. No. 3,696,153 
issued on Oct. 3, 1972 to B. J. Kershaw, M. G. Pounder and K. R. Wilkins. 
The activation of such catalysts may be accomplished by heating the 
catalyst to 400.degree. C. in the presence of hydrogen or carbon monoxide. 
The present process can be batch or continuous. 
In one embodiment of the process of the present invention the 
2-cyanocyclopentanone is obtained in mixture with adiponitrile and is 
present at a concentration of 0.05 to 0.60% by weight based upon the 
weight of the mixture and preferably 0.10 to 0.50% by weight on the same 
basis. 
In a particularly preferred embodiment the process of the present invention 
is used in the manufacture of hexamethylene diamine from adiponitrile and 
especially from adiponitrile manufactured by the reaction of adipic acid 
and ammonia. Adiponitrile obtained by reacting adipic acid and ammonia 
usually contains 2-cyanocyclopentylideneimine. Prior to converting the 
adiponitrile to hexamethylene diamine, the 2-cyanocyclopentylideneimine is 
converted to 2-cyanocyclopentanone using, for example, the process 
described in Canadian Pat. No. 912,036. In the absence of steps to 
concentrate the 2-cyanocyclopentanone in the adiponitrile or to purify the 
adiponitrile by separating 2-cyanocyclopentanone from the adiponitrile, 
the amount of 2-cyanocyclopentanone in the adiponitrile will usually be in 
the range of 0.05 to 0.60% by weight and can be contacted with the 
activated catalyst under the conditions described hereinbefore, thereby 
economically converting both the adiponitrile and the 
2-cyanocyclopentanone into hexamethylene diamine.

The following examples are presented to illustrate, but not to restrict, 
the present invention. Parts and percentages are by weight unless 
otherwise indicated. 
EXAMPLE 1 
The conversion of 2-cyanocyclopentanone to hexamethylene diamine was 
carried out in two experiments in a 100 ml, high pressure stainless steel 
autoclave. The amount and type of catalyst shown in Table I along with 1.5 
grams of 2-cyanocyclopentanone were placed in the autoclave which had been 
purged with nitrogen. Approximately 32 ml of anhydrous ammonia were added 
followed by hydrogen until a pressure of about 110 kg/cm.sup.2 was 
obtained. The temperature of the contents of the autoclave was raised to 
the indicated temperature and maintained at that temperature for 90 
minutes following which the autoclave was allowed to cool to room 
temperature before being vented through a series of traps containing 
methanol and a trap cooled by ice. The trap and autoclave contents were 
analyzed by gas-liquid chromatography. The results are reported in Table 
I. 
TABLE I 
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Run A*** 
Run B 
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Catalyst No.* I II 
Catalyst weight (gm) 1.9 2.0 
Reaction temperature (.degree. C.) 
252-260 256-259 
Reaction pressure (kg/cm.sup.2) 
480-520 470-485 
Yield (%)** 
Hexamethylene diamine 
54 66 
Hexamethyleneimine 16 17 
Caprolactam 0 5 
Cyclopentylamine 30 6 
N-hexylamine 0 2 
2-(aminomethyl)cyclopentylamine 
-- -- 
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*Catalyst I was alumina promoted iron oxide activated by reduction with 
hydrogen at 400.degree. C. Catalyst II was ferric oxide activated at 
325.degree. C. for 18 hours in the presence of carbon monoxide. 
**Mole percent based on moles of 2-cyanocyclopentanone charged. 
***Analysis done on sample which accounted for only 67% of 
2-cyanocyclopentanone charged. 
EXAMPLE 2 
Adiponitrile containing 10% 2-cyanocyclopentanone was mixed with ammonia 
and hydrogen and fed at the rates shown in Table II and at a pressure of 
350 kg/cm.sup.2, to a continuous stainless steel tubular reactor 
containing 380 grams of catalyst. The reactor measured approximately 14 
inches in length by one inch in diameter. The catalyst was 8/14 mesh iron 
oxide containing the promoters Al.sub.2 O.sub.3 -- K.sub.2 O--CaO that had 
been activated by reduction at 400.degree. C. for 65 hours with 55-60 scfh 
of hydrogen at which time the catalyst was 91% reduced. The products of 
the reaction were analyzed by gas-liquid chromatography. The results are 
reported in Table II. 
TABLE II 
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Run A Run B 
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2-Cyanocyclopentanone (gm/hr) 
44 62 
(in adiponitrile) 
Ammonia (gm/hr) 1810 1870 
Hydrogen (1/hr) 2290 2210 
Reactor temperature (inlet) .degree. C. 
105 107 
(outlet) .degree. C. 
155 148 
Yield (%)* 
Hexamethylene diamine 
55 54 
Caprolactam 5 9 
2-(aminomethyl)cyclopentylamine 
8 4 
Unidentified low boiling point 
12 15 
fraction (approx. 138.degree. C.) 
Unidentified high boiling point 
20 18 
fraction (approx. 234.degree. C.) 
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*Moles percent based on the amount of 2-cyanocyclopentanone charged. 
EXAMPLE 3 
Adiponitrile, that has been manufactured from adipic acid ammonia and 
treated to convert 2-cyanocyclopentylideneimine to 2-cyanocyclopentanone, 
was continuously fed to a commercial scale reactor containing an iron 
catalyst. The iron catalyst was activated by reducing a naturally 
occurring iron oxide ore with hydrogen at about 400.degree. C. 
Four runs were conducted under the following conditions: 
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Reaction Temperature (.degree. C.) 
110-120 
Pressure (kg/cm.sup.2) 315-364 
Ammonia (kg/kg of adiponitrile) 
4.0-4.5 
Hydrogen (1/hr per kg of adiponitrile) 
2600-3200 
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The results are reported in Table III. 
TABLE III 
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Analysis of Adiponitrile 
Run A 
Run B 
Run C 
Run D 
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2-Cyanocyclopentylidene- 
1740 1950 940 1790 
imine (ppm) 
2-Cyanocyclopentanone (ppm) 
650 1200 3370 3820 
Analysis of Hexamethylene Diamine 
(No detectable ketone) 
Hexamethyleneimine (ppm) 
NA NA NA 0.2 
2-(aminomethyl)cyclopentyl- 
1540 1480 1180 1670 
amine (ppm) 
Under-conversion products 
&lt;100 &lt;100 &lt;100 &lt;100 
(ppm) 
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NA - not available 
No adverse effects on the conversion of adiponitrile to hexamethylene 
diamine or on the hexamethylene diamine obtained when adiponitrile 
containing 2-cyanocyclopentanone was fed to the reactor. The amount of 
2-(aminomethyl)cyclopentylamine in the hexamethylene diamine produced 
corresponded to the 2-cyanocyclopentylideneimine in the feed.