Distillation: processes – separatory – Convective distillation with normally gaseous medium – e.g. – air
Patent
1999-08-09
2000-10-31
Manoharan, Virginia
Distillation: processes, separatory
Convective distillation with normally gaseous medium, e.g., air
203 59, 203 60, 203 79, 203 80, 203 99, 203DIG19, 564492, 564498, B01D 310, B01D 334, C07C20984, C07C20986
Patent
active
061396931
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a process for recovering hexamethylenediamine (I) from a mixture (II) comprising 2-aminomethylcyclopentylamine and 1,2-diaminocyclohexane,
It is known, for example from: K. Weissermel, H.-J. Arpe, Industrielle Organische Chemie, 4th Edition, page 270, VCH-Verlagsgesellschaft, to fully hydrogenate adiponitrile in the presence of iron, cobalt or nickel catalysts to form the fiber intermediate hexamethylenediamine. As a consequence of the quantitative conversion of the adiponitrile into hexamethylenediamine, the hydrogenation effluent contains virtually no adiponitrile and no 6-aminocapronitrile.
The hexamethylenediamine can be purified to fiber grade quality in a conventional manner, for example by distillation as described in GB-A-731 819 or by crystallization as described in U.S. Pat. No. 4,282,381.
It is further known to hydrogenate adiponitrile partially to mixtures of the two fiber intermediates 6-aminocapronitrile and hexamethylenediamine and also unconverted adiponitrile, for example according to U.S. Pat. No. 4,601,8591, U.S. Pat. No. 2,762,835, U.S. Pat. No. 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 German Application 19 548 289.1, in the presence of nickel, cobalt, iron, ruthenium or rhodium catalysts.
6-Aminocapronitrile can be cyclized to form caprolactam or be polymerized directly to form nylon-6.
The partial hydrogenation gives rise to byproducts which are difficult to separate from hexamethylenediamine such as hexamethyleneimine, 1,2-diaminocyclohexane and 2-aminomethylcyclopentylamine. Tetrahydroazepine and the two cyclic diamines in particular reduce the quality of nylon-6,6 produced from such impure hexamethylenediamine, for example the color quality. For this reason, the impurities mentioned have to be removed from the hexamethylenediamine down to a residual level of a few ppm.
The processes known for the purification of hexamethylenediamine from the full hydrogenation of adiponitrile cannot be used for the reaction mixture obtained from the partial hydrogenation of adiponitrile because of the higher levels of these byproducts, the different mixing ratios of the byproducts and also the presence of 6-aminocapronitrile and adiponitrile.
It is an object of the present invention to provide a process for recovering hexamethylenediamine from an adiponitrile partial hydrogenation mixture comprising hexamethylenediamine, 6-aminocapronitrile and adiponitrile in a technically simple and economical manner.
We have found that this object is achieved by the process described at the beginning.
Mixtures (II) can be obtained in a conventional manner by partial hydrogenation of adiponitrile, for example according to a process as described in EP-A-161 419, EP-A-77 911, U.S. Pat. No. 4,389,348, U.S. Pat. No. 4,601,859, WO 93/1207, DE-A 42 35 466, U.S. Pat. No. 2,762,835, U.S. Pat. No. 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 and German Application 19 548 289.1 by, in general, conducting the hydrogenation in the presence of nickel, cobalt, iron, rhodium or ruthenium catalysts. The catalysts may be employed in the form of supported or unsupported catalysts. Examples of suitable catalyst supports are aluminum oxide, silicon dioxide, titanium dioxide, magnesium oxide, active carbons and spinels. Examples of unsupported catalysts are Raney nickel and Raney cobalt.
If the hydrogenation was carried out using liquid diluents, such as ammonia, these can be removed in a conventional manner, for example as described in DE-A-19 500 222.
The mixtures (II) generally comprise based on (II), based on (II), 2-aminomethylcyclopentylamine and 1,2-diaminocyclohexane or mixtures thereof, especially in amounts from 5 ppm to 5% by weight based on (II), which case the imines can be present as individual compounds or as adducts, especially with amines such as hexamethylenediamine or 6-aminocapronitrile, and such adducts shall for the purposes of the present invention li
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Bassler Peter
Fischer Rolf
Luyken Hermann
Rehfinger Alwin
Voit Guido
BASF Aktiengesellschaft Ludwigshafen
Manoharan Virginia
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