Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
2002-11-01
2004-06-15
Kifle, Bruck (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
C540S536000
Reexamination Certificate
active
06750336
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for continuously producing lactams from oximes under high-temperature and high-pressure conditions, and more particularly to a novel method for continuously producing lactams by which lactams are continuously produced by conducting a rearrangement reaction of oximes dissolved in an organic solvent under high-temperature and high-pressure water mixture conditions. The present invention makes it possible to produce lactams by a method requiring no neutralization of a large quantity of spent sulfuric acid, as required in the conventional methods for producing lactams which use concentrated sulfuric acid as a catalyst.
2. Description of the Related Art
In industrial production of lactams, for example, &egr;-caprolactam employed as a starting material for Nylon 6, the lactams have been produced by a Beckman rearrangement reaction method from oximes of carbonyl compounds such as cyclohexanone oxime. The rearrangement reaction uses an acid catalyst, and because the acid boils during the reaction, the presence of water, though in a very small quantity, causes hydrolysis of oximes, thereby decreasing the yield of lactams. In order to prevent this decrease, a method is typically employed in which fuming sulfuring acid is used as an acid catalyst and the acid boils during the reaction. With such a method, the reaction is conducted under severe conditions and is known to create problems in terms of corrosion of equipment materials, danger of the production process, and treatment of ammonium sulfate which is a byproduct. Sulfuric acid used during lactam recovery had to be neutralized with ammonia, producing ammonium sulfate as a byproduct at no less than 2 kg per 1 kg of lactam. Because ammonium sulfate is of a low industrial value, it is difficult to use and has to be treated.
In recent years, the development of simple and effective chemical processes in which the reaction is completed within a short time and which use no hazardous substances, such as fuming sulfuric acid, has been pursued in the field of chemical industry against the background of growing concerns about the degradation of global environment. In the production of lactams, a demand has been created for the development of effective new production processes which use no fuming sulfuric acid that creates problems in terms of corrosion of equipment materials, operational safety, and environmental pollution and in which no byproducts are produced.
The following two methods have been suggested to resolve those problems, both methods employing reaction under high-temperature and high-pressure water and using absolutely no high-concentration strong acid catalysts such as fuming sulfuric acid and the like: (A) batch synthesis method (O. Sato, Y. Ikushima and T. Yokoyama, Journal of Organic Chemistry 1998, 63, 9100-9102) and (B) flow synthesis method (Y. Ikushima, K. Hatakeda, O. Sato, T. Yokoyama and M. Arai, Journal of American Chemical Society 2000, 122, 1908-1918).
With the batch synthesis method (A), cyclohexanone oxime is sealed in a stainless steel tube with an inner capacity of 10 mL, the tube is placed in a salt bath, the temperature is raised to 200 to 400° C. within a time of about 30 seconds, and the product is obtained by conducting the reaction for 3 minutes. This method apparently was not designed for large-scale industrial production, but attracted attention as a synthesis method using no acid catalyst such as fuming sulfuric acid and the like. Because with this method the reaction is completed in a single cycle, the operations are intermittent and a time of about 20 to 30 seconds is required to raise the temperature to a set temperature. Therefore, the drawback is that a large quantity of cyclohexanone which is a hydrolyzate is formed when the temperature is raised, and the yield of the target &egr;-caprolactam is decreased. Furthermore, because cyclohexanone is a starting material for cyclohexanone oxime, a reverse reaction is initiated in this method and the method can be considered as a deathblow to the industrial process.
(B) With the flow synthesis method, the operation is continuous which is apparently advantageous for mass production, but because an aqueous solution of cyclohexanone oxime at room temperature is heated and used as a high-temperature and high-pressure carrier, a certain time is apparently required to raise the temperature to a set reaction temperature. The results obtained in the experiment in which the substrate was caused to react for 113 seconds under the conditions of 350° C. and 22.1 MPa, showed that only cyclohexanone was obtained as a product and absolutely no &egr;-caprolactam was obtained. Furthermore, the results indicated that even under a temperature condition of 374.5° C., both &egr;-caprolactam and cyclohexanone were formed. Therefore, the drawback of this method is that time is required to raise the temperature, similarly to the batch synthesis method (A) and, for example, while water serving as a solvent is in a hydrothermal state at 100 to 300° C., hydrolysis of cyclohexanone oxime proceeds resulting in the formation of cyclohexanone and decrease in the yield of target &egr;-caprolactam. Another drawback of this method is that cyclohexanone oxime has poor solubility in water. Therefore, the method was suitable only for reactions with low-concentration substrates, was ineffective, and required improvement.
With the above-described prior art technology in view and against the aforesaid background, the inventors have conducted a comprehensive study of methods for producing lactams from oximes at a high temperature and under a high pressure. In the course of the study, the inventors have discovered that increasing the temperature of high-concentration oximes to a set reaction temperature within a short time is important for continuous and effective manufacture of lactams from oximes under high-temperature and high-pressure conditions. The research was further advanced based on this finding and eventually brought the present invention to completion.
SUMMARY OF THE INVENTION
Thus, the production method in accordance with the present invention that has been developed by the inventors via a variety of experiments is, for example, a method for producing caprolactam selectively, effectively, and within a short time, while suppressing hydrolysis of an oxime, by directly and continuously introducing an organic solvent having the oxime dissolved therein into a reaction field under high-temperature and high-pressure water conditions and attaining a set reaction temperature within a short time.
It is an object of the present invention to provide a method for selectively producing large quantities of lactams without the formation of cyclohexanone, by introducing an oxime dissolved into an organic solvent in high-temperature and high-pressure water and conducting a reaction of the high-concentration substrate with the reduced temperature increase time.
The present invention that resolves the above-described problems comprises the following technological means.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described hereinbelow in greater detail.
To facilitate the explanation of the present invention, it will be described in detail with reference to a process in which an acetonitrile solution containing an oxime dissolved therein is introduced into high-temperature and high-pressure water, the reaction temperature is attained within a short time of no more than 3 seconds, and a lactam is produced under a reaction pressure condition of 40 MPa.
The production method in accordance with the present invention that has been developed by the inventors via a variety of experiments is, for example, a method for synthesizing &egr;-caprolactam by the rearrangement reaction of cyclohexanone oxime, without a hydrolysis reaction, by continuously introducing an acetonitrile solution having cyclohexanone oxime dissolved therein into a reaction field under flowing high-temperature and high-pr
Hatakeda Kiyotaka
Ikushima Yutaka
Sato Osamu
Torii Kazuo
Kifle Bruck
National Institute of Advanced Industrial Science and Technology
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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