Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2000-04-17
2001-03-06
O'Sullivan, Peter (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C204S157830
Reexamination Certificate
active
06197999
ABSTRACT:
The present invention relates to the field of polymers of the polyamide-12 type obtained by polymerization of lauryllactam. It more particularly relates to a process for the preparation of cyclododecanone oxime (reaction intermediate of lauryllactam) which consists in photonitrosating cyclododecane in chloroform in a virtually anhydrous medium.
The production of cycloaliphatic oximes by the photochemical route has been known for many years. Conventionally, a cycloalkane is reacted photochemically with a nitrosating agent, in particular nitrosyl chloride, in the presence of an excess of hydrogen chloride, at temperatures varying from −30° C. to +40° C. The oxime thus formed, in the hydrochloride form, is extracted from the reaction mixture, for example using a strong inorganic acid. This oxime is subsequently subjected to a rearrangement stage by the Beckmann reaction to form the corresponding lactam.
The production of lauryllactam in an industrial process under continuous operation is dependent on several limiting factors.
In the photonitrosation stage, the significant parameters directly related to the photochemical reaction are:
the nature of the medium in which the cyclododecane is necessarily dissolved since the latter is solid at the normal reaction temperature (see, for example, DE-A-1,240,074 and GB-A-1,095,916),
the nature of the solvent to be introduced into the reaction medium to increase the solubility of the oxime and thus to prevent its deposition on the wall of the irradiation lamps (see, for example, FR-A-1,335,823, FR-A-1,552,268 and GB-A-1,136,747), and
the influence of the abovementioned solvents on the homogeneity and transparency of the reaction medium, which factors have a direct effect on the effectiveness of the light photons.
In the abovementioned state of the art, no reference is found to the influence of the water content in the reaction medium.
The Applicant Company has now found that the limitation of the water content in the industrial photonitrosation stage makes it possible to significantly increase the yield of cyclododecanone oxime and, consequently, to increase the profitability of the stages which are situated downstream, in particular the Beckmann rearrangement and the recycling of the acid used in the latter stage.
A subject-matter of the present invention is therefore a process for the preparation of cyclododecanone oxime which consists in photochemically reacting cyclododecane, dissolved in chloroform, a nitrosating agent and hydrogen chloride in a virtually anhydrous medium, that is to say under conditions such that the water content in the reaction medium does not exceed 1000 ppm.
The process according to the invention is carried out conventionally and under reaction conditions known for the photochemical nitrosation of cycloaliphatic compounds.
More specifically, in order to carry out the process according to the invention, cyclododecane is diluted in chloroform, the solution is saturated with gaseous hydrogen chloride, the nitrosating agent is added thereto and, finally, irradiation is carried out with light.
The moisture level in each reactant is chosen so that the overall water content in the reaction medium is between 50 and 1000 ppm and preferably 250 and 600 ppm.
The reaction is generally carried out in a reactor and the various reactants are introduced continuously.
The concentration of cyclododecane in the chloroform is generally between 0.1 and 35% by weight and preferably 20 and 30% by weight.
The nitrosating agent is generally chosen from nitrosyl chloride, a mixture of nitric oxide and of chlorine, or 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 nitrosating agent is adjusted so 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 generally introduced in the form of an anhydrous gas, in excess with respect to the nitrosating agent. It is preferably employed at saturation of the cyclododecane solution.
Irradiation is carried out by means of one or more mercury or sodium vapour lamps emitting radiation with a wavelength of between 500 and 700 nm and preferably 565 and 620 nm.
The reaction is generally carried out at a temperature of between −20 and +40° C. and preferably +10 and +20° C.
The reaction is generally carried out with vigorous stirring, for example by means of one or more recirculation pumps.
The concentration of cyclododecanone oxime in the reaction medium should not generally exceed 15% by weight during the photonitrosation.
The irradiated reaction mixture is continuously withdrawn and it is extracted with a strong acid, preferably sulphuric acid having a concentration of greater than 80% by weight, at a temperature of between 10 and 50° C., preferably of the order of 20 to 25° C.
The cyclododecanone oxime thus formed is subsequently subjected to a Beckmann rearrangement stage in the presence of sulphuric acid in order to form lauryllactam.
REFERENCES:
patent: 3853729 (1974-12-01), Lucas
patent: 5719316 (1998-02-01), Ollivier
patent: 1240074 (1967-05-01), None
patent: 0 798 290 (1997-10-01), None
patent: 1095916 (1967-12-01), None
patent: 1136747 (1968-12-01), None
Drutel Damien
Ollivier Jean
Atofina
Millen White Zelano & Branigan P.C.
O'Sullivan Peter
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