Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Patent
1996-05-16
1998-04-14
Ford, John M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
540220, 540451, 540482, 546243, 548486, 548553, C07D20108, C07D22310
Patent
active
057393249
DESCRIPTION:
BRIEF SUMMARY
This is a 371 of PCT/EP94/03781, filed 15 Nov. 1994, which claims priority of German Application P 4339648.8, filed 20 Nov. 1993.
The present invention relates to a novel process for preparing cyclic lactams by reacting amino carbonitriles with water in the presence of catalysts.
U.S. Pat. No. 4,628,085 discloses the reaction of 6-aminocapronitrile with water in the gas phase on acidic silica gel at 300.degree. C. The reaction takes place quantitatively with an initial selectivity of 95% to produce caprolactam, but the productivity and selectivity are found to decline rapidly. A similar process is described in U.S. Pat. No. 4,625,023, in which a highly diluted gas stream composed of 6-aminocapronitrile, adiponitrile, ammonia, water and carrier gas is passed over a silica gel catalyst bed and a copper/chromium/barium/titanium oxide catalyst bed. Caprolactam is obtained with a selectivity of 91% and a conversion of 85%. In this case too there is rapid inactivation of the catalyst.
U.S. Pat. No. 2,301,964 relates to the uncatalyzed conversion of 6-aminocapronitrile to caprolactam in aqueous solution at 285.degree. C. The yields are below 80%.
FR-A 2 029 540 describes a process for cyclization of 6-aminocapronitrile to caprolactam using homogeneous metal catalysts from the zinc and copper group in aqueous solution, caprolactam being obtained in yields of up to 83%. However, there are problems in complete removal of the catalyst from the required caprolactam because the latter forms complexes with the metals used.
It is an object of the present invention to provide a process for preparing cyclic lactams by reacting amino carbonitriles with water which does not entail the disadvantages described above.
We have found that this object is achieved by carrying out the reaction in liquid phase in the presence of heterogeneous catalysts based on titanium dioxide, zirconium oxide, cerium oxide and aluminum oxide.
Preferred embodiments of the process according to the invention are evident from the dependent claims.
The starting materials employed in the process according to the invention are amino carbonitriles, preferably those of the general formula I ##STR1## where n and m are each 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9, and n+m total at least 3, preferably at least 4.
R.sup.1 and R.sup.2 can, in principle, be substituents of any type, it merely being necessary to ensure that the required cyclization is unaffected by the substituents. R.sup.1 and R.sup.2 are preferably, independently of one another, each C.sub.1 -C.sub.6 -alkyl, C.sub.5 -C.sub.7 -cycloalkyl or C.sub.6 -C.sub.12 -aryl.
Particularly preferred starting compounds are amino carbonitriles of the general formula 6-aminocapronitrile.
In the process according to the invention, the amino carbonitriles described above are reacted with water in liquid phase using heterogeneous catalysts to give cyclic lactams. Use of amino carbonitriles of the formula I results in the corresponding cyclic lactams of the formula II ##STR2## where n, m, R.sup.1 and R.sup.2 have the abovementioned meanings. Particularly preferred lactams are those where n is 0 and m is 4, 5 or 6, in particular 5 (in the latter case, caprolactam is obtained).
The reaction is carried out in liquid phase at, in general, from 140.degree. to 320.degree. C., preferably 160.degree. to 280.degree. C.; the pressure is generally in the range from 1 to 250 bar, preferably from 5 to 150 bar, it being necessary to ensure that the reaction mixture is predominantly liquid under the conditions employed. The holdup times are generally in the range from 1 to 120, preferably 1 to 90 and, in particular, 1 to 60 min. In some cases, holdup times of 1-10 min have proved to be entirely sufficient.
In general, at least 0.01 mol, preferably 0.1-20 mol and, in particular, 1-5 mol of water are employed per mol of amino carbonitrile.
The amino carbonitrile is advantageously employed in the form of a 1-50% by weight, in particular 5-50% by weight, particularly preferably 5-30% by weight, solution in water (in which case the solvent is
REFERENCES:
patent: 4625023 (1986-11-01), Mares et al.
patent: 4628085 (1986-12-01), Mares et al.
Fuchs Eberhard
Witzel Tom
BASF - Aktiengesellschaft
Ford John M.
Sripada Pavanaram K.
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