Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
1999-03-10
2001-03-27
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
Reexamination Certificate
active
06207851
ABSTRACT:
DESCRIPTION
The present invention relates to a process for coproduction of 6-aminocapronitrile and hexamethylenediamine starting from adiponitrile by partial conversion and recovery of unconverted adiponitrile.
DE-A 19 500 222 and German Application 19 548 289.1 disclose a process for coproduction of 6-aminocapronitrile and hexamethylenediamine by hydrogenation of adiponitrile in the presence of a catalyst with partial conversion, the removal of hexamethylenediamine and 6-aminocapronitrile from the mixture and conversion of 6-aminocapronitrile into caprolactam and also recycling into the process of a portion consisting essentially of adiponitrile. The disadvantage of this process is that the recycled stream consisting essentially of adiponitrile comprises by-products of adiponitrile hydrogenation, especially amines such as 1-amino-2-cyanocyclopentene (ACCPE), 2-(5-cyanopentylamino)tetrahydroazepine (CPATRA) and bishexamethylenetriamine (BHMTA).
The by-products cannot be removed from adiponitrile by distillation in the processes described because of the formation of azeotropes or quasi-azeotropes, but build up in the process as a result of the recycling. ACCPE recycled into the hydrogenation forms 2-aminomethylcyclopentylamine (AMCPA), which contaminates the hexamethylenediamine product. It is known from U.S. Pat. No. 3,696,153 that AMCPA is very difficult to separate from hexamethylenediamine.
It is an object of the present invention to provide a process for coproduction of 6-aminocapronitrile and hexamethylenediamine from adiponitrile by partial conversion and recovery of unconverted adiponitrile without the disadvantages mentioned and whereby the unconverted adiponitrile is technically simple and economical to separate off and purify.
We have found that this object is achieved by a process for coproduction of 6-aminocapronitrile and hexamethylenediamine starting from adiponitrile, which comprises
(1) partially hydrogenating adiponitrile in the presence of a catalyst to obtain a mixture comprising 6-aminocapronitrile, hexamethylenediamine and adiponitrile,
(2) removing 6-aminocapronitrile and hexamethylenediamine from the mixture,
(3) adding to the portion comprising essentially adiponitrile from 0.01 to 10% by weight of an acid, based on adiponitrile, or an acidic ion exchanger and removing the adiponitrile from the mixture, and
(4) recycling the adiponitrile into step (1).
The partial hydrogenation of adiponitrile can be carried out by one of the known processes, for example by one of the abovementioned processes described in U.S. Pat. No. 4,601,859, U.S. Pat. No. 2,762,835, U.S. Pat. No. 2,208,598, DE-A 848 654, DE-A 954 416, DE-A 4 235 466 or WO 92/21650, by effecting the hydrogenation in general in the presence of nickel-, cobalt-, iron- or rhodium-containing catalysts. The catalysts may be used in the form of supported catalysts or unsupported catalysts. Examples of suitable catalyst carriers are alumina, silica, titanium dioxide, magnesium oxide, active carbons and spinels. Examples of suitable unsupported catalysts are Raney nickel and Raney cobalt.
The catalyst space velocity is usually chosen in the range from 0.05 to 10, preferably from 0.1 to 5, kg of adiponitrile per 1 of catalyst per hour.
Hydrogenation is carried out, as a rule, at from 20 to 200° C., preferably from 50 to 150° C., and at hydrogen partial pressures of from 0.1 to 40, preferably from 0.5 to 30, MPa.
The hydrogenation is preferably carried out in the presence of a solvent, in particular ammonia. The amount of ammonia is chosen in general in the range from 0.1 to 10, preferably from 0.5 to 3, kg of ammonia per kg of adiponitrile.
The molar ratio of 6-aminocapronitrile to hexamethylenediamine and hence the molar ratio of caprolactam to hexamethylenediamine can be controlled by the adiponitrile conversion chosen in each case. Adiponitrile conversions of from 10 to 90%, preferably from 30 to 80%, are preferably employed in order to obtain high 6-aminocapronitrile selectivities.
As a rule, the sum total of 6-aminocapronitrile and hexamethylenediamine is from 95 to 99%, depending on the catalyst and reaction conditions, hexamethyleneimine being the most important by-product in terms of quantity.
In a preferred embodiment, the reaction is carried out in the presence of ammonia and lithium hydroxide or a lithium compound which forms lithium hydroxide under the reaction conditions, at from 40 to 120° C., preferably from 50 to 100° C., particularly preferably from 60 to 90° C.; the pressure is chosen in general in the range from 2 to 12, preferably from 3 to 10, particularly preferably from 4 to 8, MPa. The residence times are essentially dependent on the desired yield, the selectivity and the desired conversion; usually, the residence time is chosen so that a maximum yield is achieved, for example in the range from 50 to 275, preferably from 70 to 200, minutes.
The pressure and temperature ranges are preferably chosen so that the reaction can be carried out in the liquid phase.
Ammonia is used in general in an amount such that the weight ratio of ammonia to dinitrile is from 9:1 to 0.1:1, preferably from 2.3:1 to 0.25:1, particularly preferably from 1.5:1 to 0.4:1.
The amount of lithium hydroxide is chosen as a rule in the range from 0.1 to 20, preferably from 1 to 10, % by weight, based on the amount of catalyst used.
Examples of lithium compounds which form lithium hydroxide under the reaction conditions are lithium metal and alkyllithium and aryllithium compounds such as n-butyllithium and phenyllithium. The amount of these compounds is chosen in general so that the abovementioned amount of lithium hydroxide is obtained.
Preferred catalysts are nickel-, ruthenium-, rhodium-, iron- and cobalt-containing compounds, preferably those of the Raney type, in particular Raney nickel and Raney cobalt. The catalysts may also be used in the form of supported catalysts, carriers which may be used being, for example, alumina, silica, zinc oxide, active carbon and titanium dioxide (cf. Appl. Het. Cat. (1987), 106-122; Catalysis 4 (1981), 1-30). Raney nickel (for example from BASF AG, Degussa and Grace) is particularly preferred.
The nickel, ruthenium, rhodium, iron and cobalt catalysts may be modified with metals of groups VIB (Cr, Mo, W) and VIII (Fe, Ru, Os, Co (only in the case of nickel), Rh, Ir, Pd, Pt) of the Periodic Table. Observations to date have shown that the use of, in particular, modified Raney nickel catalysts, for example modified with chromium and/or iron, leads to higher aminonitrile selectivities (for preparation, cf. DE-A 2 260 978 and Bull. Soc. Chem. 13 (1946), 208).
The amount of catalyst is chosen in general so that the amount of cobalt, ruthenium, rhodium, iron or nickel is from 1 to 50, preferably from 5 to 20, % by weight, based on the amount of dinitrile used.
The catalysts may be used as fixed-bed catalysts by the liquid phase or trickle-bed procedure or as suspended catalysts.
In a further preferred embodiment, adiponitrile is partially hydrogenated to 6-aminocapronitrile at elevated temperatures and high pressure in the presence of a solvent and of a catalyst which comprises
(a) a compound based on a metal selected from the group consisting of nickel, cobalt, iron, ruthenium and rhodium,
(b) from 0.01 to 25, preferably from 0.1 to 5, % by weight, based on (a), of a promoter based on a metal selected from the group consisting of palladium, platinum, iridium, osmium, copper, silver, gold, chromium, molybdenum, tungsten, manganese, rhenium, zinc, cadmium, lead, aluminum, tin, phosphorus, arsenic, antimony, bismuth and rare earth metals, and
(c) from 0 to 5, preferably from 0.1 to 3, % by weight, based on (a), of a compound based on an alkali metal or an alkaline earth metal,
with the proviso that, if a compound based on only ruthenium or rhodium or ruthenium and rhodium or nickel and rhodium is chosen as component (a), said promoter (b) can, if desired, be dispensed with, and with the further proviso that said component (a) shall not be based on iron when said component (b) is aluminum.
Bassler Peter
Fischer Rolf
Luyken Hermann
Rehfinger Alwin
Voit Guido
BASF - Aktiengesellschaft
Keil & Weinkauf
McKane Joseph K.
Murray Joseph
LandOfFree
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