Patent GB-631831-A (GB)
Title: A process for the production of cyclo-paraffins
IPC: C07C13/18
Filed: 1947-05-06
Abstract: An extractive distillation is described in which cycloparaffins of non-hydroaromatic structure free from any substantial proportion of aromatic hydrocarbons are separated from hydrocarbon mixtures comprising cycloparaffins of hydro- and nonhydro-aromatic structure in admixture with close boiling aromatic hydrocarbons. "Hydroaromatic cycloparaffins" are those having a hexamethylene ring, e.g. cyclohexane and alkyl-substituted cyclohexanes and "non-hydroaromatic cycloparaffins" are those having pentamethylene rings, e.g. methylcyclopentane and other cyclopentanes.  The process may be used in the production of pure cyclohexane from hydrocarbon mixtures comprising methylcyclopentane, cyclohexane, benzene and open-chain hexanes; extractive distillations to remove (a) hexanes; (b) hexanes and methylcyclopentane, and (c) methylcyclopentane being described. For further details see Group IV (b).  Specification 606,797 is referred to.ALSO:Cycloparaffins of hydroaromatic structure free from any substantial proportion of aromatic hydrocarbons are obtained from hydrocarbon mixtures comprising cycloparaffins of hydroaromatic and non-hydroaromatic structure in admixture with close boiling aromatic hydrocarbons by extractively distilling cycloparaffins of non-hydroaromatic structure free from any substantial proportion of aromatic hydrocarbons from said mixture and contacting them with an isomerisation catalyst to obtain cycloparaffins of hydroaromatic structure which are isolated. "Hydroaromatic cycloparaffins" are those having a hexamethylene ring, e.g. cyclohexane and alkyl cyclohexanes and "non-hydroaromatic cycloparaffins" are those having pentamethylene rings, e.g. methylcyclopentane and other cyclopentanes.  The process may be used for the production of pure cyclohexane from hydrocarbon mixtures comprising methylcyclopentane, cyclohexane, benzene and open-chain hexanes such as may be obtained by, e.g. fractionation from naphthenic natural and straight run gasolines or naphthenic mixtures boiling in the gasoline range obtained from the products of thermal or catalytic treatment of hydrocarbons or carbonaceous materials such as coal, tar and oil. Solvents specified for extractive distillation are phenol, benzoic acid, isobutyric acid, aniline, N-methyl- and N - cyclohexyl - aniline, cyclohexyl -, diphenyl-, naphthyl - and hexamethylene - di - amine, benzaldehyde, furfuraldehyde, benzoic anhydride, ethylbenzoate, benzophenone, acetophenone, cyclohexanone, benzoin, benzonitrile, nitrobenzene, nitropropane, pentachlorethane, diphenyl, ether, acetal, acetamide, ethylphosphate, dimethylsulpholane or the alkyl-substituted sulpholanes.  Isomerisation catalysts specified are the Friedel Crafts metal halide type particularly aluminium halides, e.g. the bromide and chloride, the organo-aluminium halide complexes, preferably a preformed aluminium chloride-hydrocarbon complex, molten salt type catalysts containing aluminium chloride in admixture with one or more halide salts and hydrogen halides, e.g. the chloride, may be present as promoters in proportions of e.g. 0.1 to 5 per cent, preferably below 1 per cent.  Temperatures instanced for this stage are 20 DEG  to 150 DEG  C., preferably 50 DEG  to 95 DEG  C. and with an aluminium chloride-hydrocarbon catalyst, preferably 65 DEG  to 85 DEG  C.  The hydrocarbon mixture to be treated, e.g. methylcyclopentane, cyclohexane and benzene mixed with close boiling open chain paraffins, may first be fractionated to remove cyclo-paraffins of hydroaromatic structure, e.g. cyclohexane, substantially free of aromatic hydrocarbons, e.g. benzene, with or without an initial extraction distillation to remove paraffins or paraffins and some methylcyclopentane in which latter case the methylcyclopentane is fractionated from the paraffins and either passed into the cycloparaffin fractionating zone together with the extract from the extractive distillation stage or into the isomerisation zone together with the said extract which has been subjected to cycloparaffin fractionation.  In an example, a straight run naphthenic gasoline is fractionated to obtain a hexane fraction of boiling range 65 DEG  to 85 DEG  C., which is again fractionated to give a C6 cycloparaffin concentrate of boiling range 65 DEG  to 78 DEG  C. containing 41-14 per cent methylcyclopentane, 11.10 per cent cyclohexane, 4-5 per cent benzene, 2-28 per cent dimethylpentanes and small quantities of higher and lower boiling paraffins, this fraction is extractively distilled with phenol as solvent to give paraffins overhead the stripped extract, being fractionated together with the hydrocarbon effluent from the reaction zone to give overhead a mixture of 7.5 per cent normal hexane, 84.07 per cent methylcyclopentane, 0.9 per cent cyclohexane and 6.07 per cent benzene and a bottoms product of benzene-free cyclohexane, the overhead being extractively distilled with phenol to give a mixture of 8 per cent normal hexane, 89.4 per cent methylcyclopentane and 1 per cent cyclohexane overhead and an extract which after stripping yields 99.8 per cent pure benzene, the overhead is isomerised by contact with an aluminium chloride-hydrocarbon complex at 80 DEG  C. in the presence of 0.4 per cent hydrogen chloride to give an effluent containing 40.7 per cent methylcyclopentane and 48.7 per cent cyclohexane which as indicated above is passed back to the cycloparaffin fractionator, the benzene-free cyclohexane thus obtained being purified by fractionation.  Specification 606,797, [Group III], is referred to.