Production of perfluoro-n-heptane

Claim 1

A process for the electrochemical fluorination of n-heptane to perfluoro-n-heptane which comprises in combination, the steps of: (a) passing n-heptane into a first electrochemical fluorination cell zone and therein fluorinating at least a portion of said n-heptane under conditions sufficient to produce a first effluent stream comprising unconverted n-heptane, partially fluorinated n-heptanes and perfluoro-n-heptane; (b) passing said first effluent stream to a cooling zone wherein said stream is cooled to a temperature sufficient to condense said n-heptane, said partially fluorinated-n-heptanes and said perfluoro-n-heptane; (c) passing the resulting condensed stream to a phase separation zone and separating therefrom a hydrocarbon-rich phase comprising n-heptane and partially fluorinated n-heptanes, and a fluorocarbon-rich phase comprising perfluoro-n-heptane, partially fluorinated n-heptanes and n-heptane; (d) passing said fluorocarbon-rich phase into a second electrochemical fluorination cell zone and therein fluorinating at least a portion of said n-heptane and said partially fluorinated n-heptanes under conditions sufficient to produce a second effluent stream comprising partially fluorinated n-heptanes, perfluoro-n-heptane and a small amount of n-heptane; (e) passing said second effluent stream to a first fractionation zone and recovering therefrom an overhead stream consisting essentially of a major amount of perfluoro-n-heptane together with a minor amount of hydrogen fluoride and a minor amount of an n-heptane/perfluoro-n-heptane azeotrope, and a bottoms stream comprising partially fluorinated n-heptanes; and (f) passing said first fractionation zone overhead stream to a second fractionation zone and recovering therefrom an overhead stream consisting essentially of said azeotrope and said hydrogen fluoride, and a bottoms product stream consisting essentially of perfluoro-n-heptane.