Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
2000-08-23
2001-07-24
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
Reexamination Certificate
active
06265602
ABSTRACT:
The present invention relates to a process for hydrogenation of aliphatic alpha, omega-dinitriles in the presence of a heterogeneous fixed bed catalyst, which comprises using a reaction mixture comprising from 2 &mgr;mol to 30 mmol Na, K, Rb, Cs, Mg, Ca, Sr, Ba or Mn or mixtures thereof in the form of a basic salt, based on 10 mol of aliphatic alpha, omega-dinitrile used.
Processes for preparing aliphatic alpha, omega-aminonitriles or alpha, omega-diamines by hydrogenation of aliphatic alpha, omega-dinitriles in the presence of a heterogeneous fixed bed catalyst are common knowledge.
A disadvantage with these processes is the formation of major amounts of undesirable by-products. For instance, the hydrogenation of adiponitrile (ADN) to form a mixture of 6-aminocapronitrile (ACN) and hexamethylenediamine (HMD) byproduces especially tetrahydrazepine (THA) of the formula (I)
which is difficult to separate from the product or product mixture, in amounts of more than 1000 ppm (based on HMD).
DE-A 44 46 894 discloses hydrogenating ADN to a mixture of ACN and HMD over an Ni, Ru, Rh or Co catalyst, in the suspension mode especially, by adding lithium hydroxide to the reaction mixture to increase the ACN yield.
WO-A 93/16034 discloses hydrogenating ADN to a mixture of ACN and HMD over a Raney Ni catalyst in the suspension mode by adding lithium hydroxide, sodium hydroxide or potassium hydroxide to the reaction mixture to increase the ACN yield.
Unfortunately, the suspension process over Raney catalysts raises the THA level to more than 1% by weight (based on HMD).
It is an object of the present invention to provide a process for the hydrogenation of aliphatic alpha, omega-dinitriles in the presence of a heterogeneous fixed bed catalyst without the aforementioned disadvantages and with the capability of enabling the production of aliphatic alpha, omega-aminonitriles and/or alpha, omega-diamines to take place in a technically simple and economical manner.
We have found that this object is achieved by the process defined at the beginning.
The starting materials used in the process of the present invention are aliphatic alpha,omega-dinitriles of the general formula II
NC—(CH
2
)
n
—CN II
where n is an integer from 1 to 10, especially 2, 3, 4, 5 or 6. Particularly preferred compounds I are succinonitrile, glutaronitrile, adiponitrile, pimelonitrile and suberonitrile, most preferably adiponitrile.
The process of the present invention partially hydrogenates the above-described dinitriles II, preferably in the presence of a solvent, using a heterogeneous fixed bed catalyst to form alpha,omega-aminonitriles of the general formula III
NC—(CH
2
)
n
—CH
2
—NH
2
III
and/or alpha, omega-diamines of the general formula IV H
2
N—CH
2
—(CH
2
)n—CH
2
—NH
2
IV, where n is as defined above. Particularly preferred aminonitriles III are those where n is 2, 3, 4, 5 or 6, especially 4, i.e., 4-aminobutanenitrile, 5-aminopentanenitrile, 6-aminohexanenitrile (“6-aminocapronitrile”), 7-aminoheptanenitrile and 8-aminooctanenitrile, most preferably 6-aminocapronitrile.
Particularly preferred diamines IV are those where n is 2, 3, 4, 5 or 6, especially 4, i.e. 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane (HMD), 1,7-diaminoheptane and 1,8-diaminooctane, most preferably HMD.
Similarly, the coproduction of ACN and HMD is most preferable.
The partial hydrogenation can preferably be carried out batchwise or continuously in a fixed bed reactor in trickle or upflow mode, in which case it is customary to select a temperature within the range from 20 to 150° C., preferably within the range from 30 to 120° C., and a pressure which is generally within the range from 2 to 40 MPa, preferably within the range from 3 to 30 MPa. The partial hydrogenation can advantageously be carried out in the presence of a solvent, preferably ammonia, amines, diamines and triamines having from 1 to 6 carbon atoms such as trimethylamine, triethylamine, tripropylamine and tributylamine or alcohol, preferably methanol and ethanol, particularly preferably ammonia. In a preferred embodiment, ammonia is chosen within the range from 0.5 to 10, preferably from 0.5 to 6, g per g of adiponitrile. The catalyst space velocity chosen is preferably within the range from 0.1 to 2.0, preferably within the range from 0.3 to 1.0, kg of adiponitrile/L*h. Here, too, the residence time can be varied to control the conversion and hence the selectivity in a specific manner.
In the case of aolipoolinitrile [sic] as dinitrile, the molar ratio of 6-aminocapronitrile to hexamethylenediamine, and hence the molar ratio of caprolactam to hexamethylenediamine, can be controlled by means of the particular choice of adiponitrile conversion. Preference is given to using adiponitrile conversions within the range from 10 to 90%, preferably within the range from 30 to 80%, to obtain high 6-aminocapronitrile selectivity.
In general, the sum of 6-aminocapronitrile and hexamethylenediamine is within the range from 98 to 99%, depending on catalyst and reaction conditions.
According to the invention, the hydrogenation is carried out in such a way that the reaction mixture comprises from 2 &mgr;mol to 30 mmol, preferably from 10 &mgr;mol to 3 mmol, especially from 10 &mgr;mol to 300 &mgr;mol, of Na, K, Rb, Cs, Mg, Ca, Sr, Ba or Mn or mixtures thereof, preferably Na, K or Ca or mixtures thereof, especially Ca, in the form of a basic organic, preferably inorganic, salt (V), such as carbonate, preferably oxide, especially hydroxide, or mixtures thereof, based on 10 mol of aliphatic alpha, omega-dinitrile used.
Particular preference is given to such a salt (V) which is fully soluble in the reaction mixture.
A salt (V) can be added to the reaction mixture prior to the hydrogenation dissolved, preferably, in at least one of the constituents of the reaction mixture or in solid form. It is also possible to add a salt (V) to the reaction mixture during the hydrogenation, in which case the advantageous effect is less compared with an addition prior to the hydrogenation.
The hydrogenation can be carried out in princple according to one of the known processes by, in general, conducting the hydrogenation in the presence of nickel, cobalt, iron or rhodium catalysts. These catalysts can be used as supported catalysts or as unsupported catalysts. Examples of possible catalyst supports are aluminum oxide, silicon dioxide, titanium dioxide, magnesium oxide, activated carbons and spinels.
In a preferred embodiment, the dinitrile is hydrogenated at elevated temperature and elevated pressure in the presence of a solvent and of a heterogeneous fixed bed catalyst by using a catalyst containing
(a) a compound based on a metal selected from the group consisting of nickel, cobalt, iron, ruthenium and rhodium, and
(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 also
(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 on 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), the promoter (b) can be dispensed with, if desired, and also with the further proviso that component (a) is not based on iron when component (b) is aluminum.
Preferred catalysts are those in which component (a) contains at least one compound based on a metal selected from the group consisting of nickel, cobalt and iron in an amount within the range from 10 to 95% by weight and also ruthenium and/or rhodium in an amount within the range from 0.1 to 5% by weight, each percentage being based on the sum total of components (a) to (c),
component (b) contains at least one promoter based on a metal selected from the group consi
Ansmann Andreas
Bassler Peter
Fischer Rolf Hartmuth
Luyken Hermann
Merger Martin
BASF - Aktiengesellschaft
Keil & Weinkauf
McKane Joseph K.
Murray Joseph
LandOfFree
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