Separation of narrow boiling hydrocarbon fractions

Claim 1

A PROCESS FOR THE TREATMENT OF A HYDROCARBON MIXTURE BOILING APPROXIMATELY IN THE RANGE 69-85* C. CONSISTING ESSENTIALLY OF CYCLOHEXANE, BENZENE, 2,2-DIMETHYLPENTANE, METHYLCYCLOPENTANE AND MINOR PROPORTIONS OF OTHER HYDROCARBONS, WHICH COMPRISES FRACTIONALLY DISTILLING THE SAID MIXTURE TO PRODUCE A METHYL-CYCLOPENTANECONTAINING FRACTION BOILING APPROXIMATELY IN THE RANGE 69-74* C. AND AN ISOPHEPTANE AND CYCLOHEXANE-CONTAINING FRACTION BOILING APPROXIMATELY IN THE RANGE 74-85* C., THE METHYL-CYCLOPENTANE-CONTAINING FRACTION BEING PASSED TO AN ISOMERISATION ZONE, IN WHICH METHYLCYCLOPENTANE IS CONVERTED INTO CYCLOHEXANE, THE FRACTION THEREUPON BEING PASSED TO A FRACTIONATION ZONE IN WHICH THE CRUDE CYCLOHEXANE IS RECOVERED AS BOTTOMS PRODUCT, THE OVERHEAD PRODUCT BEING FRACTIONATED IN ANOTHER ZONE TO SEPARATE THE UNCONVERTED METHYLCYCLOPENTANE AND BENZENE STILL PRESENT FROM THE HEXANES, THE CRUDE CYCLOHEXANE RECOVERED BEING ADMIXED WITH THE ISOHEPTANE AND CYCLOHEXANE-CONTAINING FRACTION, AND THEREAFTER ADJUSTING THE PROPORTION OF BENZENE IN THE MIXTURE SO OBTAINED TO PROVIDE SUFFICIENT BENZENE TO FORM A MINIMUM CONSTANT BOILING MIXTURE WITH ALL OF THE ISOHEPTANE PRESENT BUT INSUFFICIENT BENZENE TO BRING OVER IN AN OVERHEAD FRACTION ANY SUBSTANTIAL QUANTITY OF CYCLOHEXANE AND THEREAFTER SUBJECTING THE ADJUSTED MIXTURE TO FRICTIONAL DISTILLATION WITH PRECISION WHEREBY THE ISOHEPTANES AND BENZENE ARE REMOVED, IN AN OVERHEAD FRACTION, AS MINIMUM CONSTANT BOILING MIXTURES AND WHEREBY SUBSTANTIALLY PURE CYCLOHEXANE IS RECOVERED AS A BOTTOMS PRODUCT.