GB977812A - Separation of cycloalkanone oximes - Google Patents

Abstract

A cycloalkanone oxime hydrochloride is separated from a reaction mixture formed by the action of nitrosyl chloride, or of nitric oxide and chlorine, on a cycloalkane under the influence of light by removing the reaction mixture from the reaction zone in which the photochemical reaction takes place into an extraction zone in which a photochemical reaction is not taking place, adding to this latter zone phosphoric acid of 70 to 90% strength, sulphuric acid of 80% to 100% strength or oleum with a content of up to 10% of free sulphur trioxide, mixing the concentrated acid with the reaction mixture at a temperature below 70 DEG C., separating the two phases formed, recycling the organic phase in the reaction zone in which the photochemical reaction takes place, and removing the acid solution which contains the extracted cycloalkanone oxime as such or in the form of its salt with the extraction acid used. The photonitrosation reaction used to produce the reaction mixtures containing the cycloalkanone oxime hydrochlorides may be carried out in an inert solvent at -30 DEG to +40 DEG C. under a pressure of from 1 to 10 atmospheres using light having an effective wavelength of 300 to 500 millimicrons, and in the presence of added hydrogen chloride. Cycloalkanes which can be used in this process include those having 5 to 12 ring carbon atoms which may contain 1 or 2 alkyl side chains having 1 to 5 carbon atoms, e.g. cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, cyclododecane, methyl cyclopentane, methyl cyclohexane and ethyl cyclohexane; the cycloalkane may also contain an attached aromatic ring as in tetrahydronaphthalene or an attached cycloaliphatic ring as in decahydronaphthalene. The extraction may be carried out with both the extraction acid and the reaction mixture as stationary phases, stirring being used to promote diffusion of the oxime hydrochloride into the extraction acid, or one of the components may be arranged as a stationary phase and the other component passed over the surface of the stationary phase or through it. In the latter procedure when the acid is the stationary phase, part of the acid containing the oxime may be continually removed and replaced by fresh extraction acid. It is also possible to contact the two components with each other in concurrent or countercurrent manner by stirring and/or distribution over suitable baffle or packing means, plates or other flow interrupters. The solutions of cycloalkanone oxime or its salt in the extraction acid used may be subjected directly to the Beckmann rearrangement to form an o -amino fatty acid lactam by heating the solution at 100 to 150 DEG C. and then pouring the solution on to an amount of water equivalent to at least the weight of extraction acid. In examples, caprolactam, caprylolactam and laurolactam are prepared by this method. Specifications 788,436, 789,732, 873,257 and U.S.A. Specifications 2,719,116 and 2,818,310 are referred to.