GB612390A - Improvements relating to the production of cyclohexane - Google Patents

Abstract

Cyclohexane is obtained from an olefine-free hydrocarbon mixture of cyclohexane, benzene, 2.2-dimethylpentane and 2.4-dimethylpentane having a boiling range about 76-81 DEG C., and which contains sufficient isoparaffins to form an azeotropic mixture with the benzene, by fractional distillation in a column having at least 20 theoretical plates. A fraction is produced substantially free from benzene and of boiling range 80-81 DEG C. which is then chilled in one or more stages within the range 0 DEG C. to -31 DEG C. to separate solid cyclohexane from a liquid phase rich in isoparaffins. Where the initial mixture has an isoparaffin/benzene ratio less than 53 : 47 by weight, further isoparaffins, preferably from the liquid phase of the chilling process, are added to provide at least that ratio. An example shows the fractionation of an Iranian naphtha in a batch column equivalent to 100 theoretical plates, to give a fraction distilling between 80 DEG and 81 DEG C. which is then fractionally crystallized, first at -26 DEG C. and then at -9 DEG C., the residue from both these stages being crystallized at -26 DEG C. Specification 608,606 is referred to.ALSO:Cyclohexane is obtained from an olefine-free hydrocarbon mixture of cyclohexane, benzene, 2,2-dimethylpentane and 2,4-dimethylpentane, having a boiling range about 76-81 DEG C., and which contains sufficient isoparaffins to form an azeotropic mixture with the benzene, by fractional distillation in a column having at least 20 theoretical plates. A fraction is produced substantially free from benzene and of boiling range 80-81 DEG C. which is then chilled in one or more stages within the range 0 DEG C. to - 31 DEG C. to separate solid cyclohexane from a liquid phase rich in isoparaffins. Where the initial mixture has an isoparaffin/benzene ratio less than 53 : 47 by weight, further isoparaffins, preferably from the liquid phase of the chilling process, are added to provide at least that ratio. An example shows the fractionation of an Iranian naphtha in a bath column equivalent to 100 theoretical plates, to give a fraction distilling between 80 DEG and 81 DEG C. which is then fractionally crystallized, first at -26 DEG C. and then at -9 DEG C., the residue from both these stages being crystallized at -26 DEG C. Specification 608,606, [Group III], is referred to.