Catalysts suitable for preparing aliphatic alpha-, omega-aminoni

Catalyst – solid sorbent – or support therefor: product or process – Regenerating or rehabilitating catalyst or sorbent – Treating with a liquid or treating in a liquid phase,...

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Details

502260, 558459, B01J 2034, C07C25504

Patent

active

061108561

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to catalysts suitable for the preparation of aliphatic alpha, omega-aminonitriles by partial hydrogenation of aliphatic dinitriles.
It further relates to processes for preparing aliphatic alpha, omega-aminonitriles by partial hydrogenation of aliphatic dinitriles in the presence of such catalysts and to the use of the catalysts for preparing aliphatic alpha, omega-aminonitriles by partial hydrogenation of aliphatic dinitriles.
WO 92/21650 describes the partial hydrogenation of adiponitrile to 6-aminocapronitrile in the presence of a Raney nickel catalyst and ammonia as solvent with a yield of 60% at a conversion of 70%. Hexamethylendiamine is formed as a by-product in a 9% yield. The disadvantage of this process is the short on-stream time of the catalyst.
U.S. Pat. No. 2,257,814 and U.S. Pat. No. 2,208,598 likewise describe processes for preparing 6-aminocapronitrile starting from adiponitrile using Raney cobalt and iron, nickel and cobalt catalysts on various supports. The disadvantages of these processes are the selectivities of 50-60%, which are too low for industrial utilization.
According to the process of WO 93/16034, the yield of aminocapronitrile can be increased by hydrogenating adiponitrile in the presence of Raney nickel, a base such as sodium hydroxide, potassium hydroxide, lithium hydroxide or ammonium hydroxide and a transition metal complex including for example iron, cobalt, chromium or tungsten as transition metal, and a solvent. Reacting within the range from 45 to 60% is said to afford quantitative yields of aminocapronitrile. The disadvantage of this process is the need to recover the usually toxic transition metal complex from the resulting reaction mixture.
EP-A 161,419 describes the partial hydrogenation of adiponitrile using a rhodium catalyst on a magnesium oxide support. A selectivity of 94% is achieved at a conversion of 70%. The disadvantage is the complicated preparation of the Rh/MgO catalysts (see J. Cat. 112 (1988), 145-156).
DE-A 4,235,466 describes the fixed bed hydrogenation of adiponitrile to 6-aminocapronitrile over unsupported iron sponge catalysts prepared from iron ore by a special method and subsequently doped with cobalt, titanium, manganese, chromium, molybdenum, ruthenium or iridium. Owing to their small surface area (0.8 m.sup.2 /g), these catalysts generally exhibit useful activity only at high pressures and high temperatures. A further disadvantage of this process is the rapid loss of activity: the conversion decreased by 5% over 24 h in Example 7 despite reducing the adiponitrile and hydrogen flow rates, which usually leads to an increase in the conversion.
DE-A 848,654 describes the continuous fixed bed hydrogenation of adiponitrile over palladium on silica gel and over metals of the eighth group of the Periodic Table, these metals preferably being used in the form of spinelums. The essential disadvantage of these catalysts is their satisfactory on-stream time.
It is an object of the present invention to provide suitable catalysts for preparing aliphatic alpha, omega-aminonitriles by partial hydrogenation of aliphatic dinitriles with a high selectivity in respect of the alpha, omega-aminonitriles and in respect of the sum total of alpha, omega-aminonitriles and alpha, omega-diamines.
We have found that this object is achieved by catalysts suitable for preparing aliphatic alpha, omega-aminonitriles by partial hydrogenation of aliphatic dinitriles, comprising of metallic cobalt based on (a) being from 20 to 100% by weight, further iron compound or a mixture thereof, the proportion of iron oxide based on (b) being from 20 to 100% by weight,
The invention further provides processes for preparing aliphatic alpha, omega-aminonitriles by partial hydrogenation of aliphatic dinitriles in the presence of such catalysts and for the use of the catalysts for preparing aliphatic alpha, omega-aminonitriles by partial hydrogenation of aliphatic dinitriles.
Preference is given to those catalysts whose precursor, prior to activation with hydroge

REFERENCES:
patent: 2208598 (1940-07-01), Rigby et al.
patent: 2257814 (1941-10-01), Rigby et al.
patent: 5151543 (1992-09-01), Ziemecki
patent: 5527946 (1996-06-01), Flick et al.
patent: 5557004 (1996-09-01), Flick et al.
Jrl. Of Cat. 112, 145-156 (1988).

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