Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
1999-09-21
2001-02-27
Shah, Mukund J. (Department: 1611)
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
C564S253000
Reexamination Certificate
active
06194570
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to a concurrently filed and commonly owned application entitled “Process for the Preparation of Lactams from the Corresponding Cycloalkanone Oximes”, attorney docket ATOCM-156 by OLLIVIER, based on French application 98/11733 filed on Sep. 21, 1998, respectively.
FIELD OF THE INVENTION
DESCRIPTION
The present invention relates to the preparation of lauryllactam which constitutes the basic monomer of polyamide 12. More precisely, it relates to a process for the preparation of lauryllactam from cyclododecane in which the photonitrosation and Beckmann rearrangement steps are carried out in the presence of methanesulphonic acid.
BACKGROUND OF THE INVENTION
Lauryllactam is widely used for the preparation of polyamide 12. Its production on an industrial scale is well known [see for example “Precédé de Pétrochimie” (Petrochemical Process), Volume 2, pp. 316-322, published by Technip, 1986]. It is possible, for example, to manufacture lauryllactam from cyclododecane (HULS and Ato Chimie process), from cyclododecanone (UBE process) or alternatively from cyclododecatriene monoozonide (Snia Viscosa process).
In the process developed by Ato Chimie, the lauryllactam is obtained in two stages:
in the first stage, cyclododecanone oxime hydrochloride is formed by photonitrosation of cyclododecane solubilized in a chlorinated solvent according to the following reaction:
and, in the second stage, the reaction product is subjected to a Beckmann rearrangement in the presence of sulphuric acid:
The cyclododecanone oxime hydrochloride formed during the photonitrosation is solid and very stable, and it becomes deposited on the walls of the irradiation lamps in contact with the reaction medium. Under the effect of light, the deposit is gradually converted to a tarry substance which, in the relatively long term, causes the termination of the photochemical reaction.
To overcome this difficulty, it is known to add sulphuric acid to the reaction mixture (see for example FR-B-1,335,822 and FR-B-1,553,268). In this manner, the sulphuric acid extracts the cyclododecanone oxime hydrochloride as it is formed. Having avoided any risk of deposition, it becomes possible to carry out the reaction continuously.
However, the use of sulphuric acid has disadvantages, both at the level of the first and second stage of the process.
In the photonitrosation stage, sulphuric acid:
colours the reaction medium, thus causing a loss in the number of photons essential for the reaction,
disperses with difficulty in the reaction medium because of its high viscosity and its ionized character,
reacts with nitrosyl chloride to form nitrosyl acid sulphate, which sulphate contributes towards degrading the oxime hydrochloride,
hydrolyses the oxime hydrochloride to cyclododecanone and hydroxylamine, and
reacts with the nitrosing agent, which has the effect of retarding the onset of the reaction and, consequently, of reducing production.
In the Beckmann rearrangement stage, the reaction is carried out at a high temperature, greater than 135° C. Consequently, the disadvantages linked to the use of sulphuric acid are as follows:
in the presence of organic compounds, sulphuric acid decomposes, releasing undesirable sulphur dioxide whose content increases during recycling of the organic phase containing the unreacted cyclododecane,
a portion of the oxime is hydrolysed to the corresponding ketone,
a portion of the lactam is hydrolysed to the corresponding amino acid which, under the process conditions, cannot be recovered and profitably exploited, and
sulphuric acid is capable of decomposing the chlorinated reaction solvent carried by the acidic phase to phosgene which is toxic for humans.
Furthermore, all the sulphuric acid-containing effluents generated by the industrial process can only be recycled at the cost of a long, difficult and costly treatment because it is in particular necessary to use steps for concentrating the acid and for removing organic compounds.
SUMMARY OF THE INVENTION
It has now been found that the abovementioned disadvantages can be overcome by advantageously replacing sulphuric acid with methanesulphonic acid, without affecting the overall yield of the process as a result.
The subject of the invention is therefore a new process for the preparation of lauryllactam which consists in:
a-photochemically reacting cyclododecane solubilized in an organic solvent, a nitrosing agent and hydrogen chloride in the presence of an acid in order to form cyclododecanone oxime, and
b-subjecting the said oxime to a Beckmann rearrangement in the presence of an acid, the said process being characterized in that the acid used is methanesulphonic acid.
The process according to the invention will be understood more clearly in the light of the following description.
Photonitrosation Stage
To carry out the reaction, the process is generally carried out in a reactor into which a mixture comprising cyclododecane in solution in an organic solvent and methanesulphonic acid, hydrogen chloride and a nitrosing agent is introduced, and the mixture is irradiated with light.
The cyclododecane may be obtained according to methods known to persons skilled in the art, for example by cyclotrimerization of butadiene and hydrogenation of the cyclotriene formed.
The cyclododecane is solubilized in an appropriate organic solvent, for example a chlorinated hydrocarbon such as chloroform or chlorobenzene. The content of cyclododecane in the solvent is generally between 0.1 and 40% by weight, and preferably 20 and 30% by weight.
The methanesulphonic acid is generally used in the form of an aqueous solution whose content may vary between 70 and 90% by weight, preferably 95 and 99% by weight.
The methanesulphonic acid used represents in general 6 to 12% of the volume of the reaction medium, and preferably 8 to 9%.
The nitrosing agent is chosen from nitrosyl chloride, a mixture of nitric oxide and chlorine, and compounds capable of forming nitrosyl chloride in the reaction medium, for example alkyl nitrites which react with hydrogen chloride. Nitrosyl chloride is preferably used.
The addition of the nitrosing agent is regulated such that its concentration in the reaction medium is between 0.1 and 25 g/l, and preferably 1 and 2 g/l.
The hydrogen chloride is introduced in the form of an anhydrous gas, in excess relative to the nitrosing agent. Preferably, it is used at saturation of the solution of cyclododecane in the solvent.
The irradiation is carried out by means of one or more mercury or sodium vapour lamps emitting radiation of wavelength between 500 and 700 nm, and preferably 565 and 620 nm.
The reaction is carried out at a temperature of between −20 and +40° C., and preferably +10 and +20° C.
The procedure is generally carried out with vigorous stirring. In the present invention, the expression “vigorous stirring” is understood to mean stirring such that the reaction volume is renewed at least 100 times per hour. It is possible, for that, to use any stirring means, for example one or more turbines or recirculating pumps.
The photonitrosation is generally carried out in a reactor which can function batchwise or continuously. Continuous operation is preferred.
After irradiation, the reaction mixture is separated after settling out and the cyclododecanone oxime is recovered in the acidic phase. The content of cyclododecanone oxime in the acidic phase may vary to a large degree. However, for reasons linked to industrial conditions, an oxime content of between 10 and 40% by weight, and better still 25 and 35%, is preferred.
Beckmann Rearrangement Stage
This stage is generally carried out in a reactor operating at high temperature and with vigorous stirring.
The cyclododecanone oxime obtained at the end of the preceding photonitrosation stage is generally introduced as it is into the reactor. For obvious safety reasons linked to the very high exothermicity of the reaction, it is preferable to introduce the oxime solution into a reactor which contains a suitabl
Drutel Damien
Ollivier Jean
Atofina
Kifle Bruck
Millen White Zelano & Branigan P.C.
Shah Mukund J.
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