Patent GB-789441-A (GB)
Title: Improved process for the fluorination of organic compounds
IPC: C07C17/10
Filed: 1943-06-17
Abstract: A process for the fluorination of an aliphatic hydrocarbon or the product of partially fluorinating the aliphatic hydrocarbon comprises feeding in the vapour state the compound to be fluorinated to a reaction zone in which finely divided cobalt trifluoride is maintained at fluorinating temperature in a fluidized condition whereby fluorination of the compound and concurrent conversion of the cobalt trifluoride to the difluoride occur, separating the cobalt difluoride from the hydrocarbon fluorination products and any unchanged hydrocarbon, reacting the separated cobalt difluoride in fluidized condition with gaseous free fluorine to regenerate the trifluoride and reacting the regenerated cobalt trifluoride in fluidized condition with further quantities of the aliphatic hydrocarbon or the product of partially fluorinating the aliphatic hydrocarbon, in the vapour state.  In one embodiment (Fig. 1), a vaporized hydrocarbon, e.g. n-heptane and an inert gaseous diluent such as HF, N2 or CF4 are fed through lines 1, 2 and a heater 4 to a reactor 5 <PICT:0789441/IV (b)/1> wherein cobalt trifluoride is maintained in fluidized condition at a fluorinating temperature below 400 DEG  C., preferably at 100-300 DEG  C., part of the fluidized cobalt trifluoride being recycled through line 6 and heater 4.  The gaseous fluorination products leave the reactor via a solids-separator 8 and pass through a cooler 11 to a separator 12 to separate liquid condensate from CF4 vapour which is recycled via line 20 to the reactor. The liquid condensate is fed to a distillation column 15 to remove HF which is recycled to the reactor via lines 16, 18 and 20.  The liquid bottoms from column 15 are allowed to settle in a tank 22 wherein a bottom layer of completely fluorinated hydrocarbon is separated from a layer of incompletely fluorinated material which is recycled to the reactor via line 23.  If desired, the condensate from the first separator 12 may be recycled for further reaction via lines 13 and 16.  When most of the cobalt trifluoride has been converted to difluoride, the hydrocarbon feed through line 1 is stopped and free fluorine is fed to the reactor via line 3, the inert gas fed through line 2 maintaining the cobalt fluoride in fluidized state, and unused fluorine may be recycled through lines 19 and 20.  A regeneration temperature between about 200 and 400 may be used.  In another embodiment (Fig. 2, not shown) two reactors similar to reactor 5 and containing fluidized cobalt trifluoride are used.  The hydrocarbon is fed to the first reactor maintained, for example, at about 100-200 DEG  C., where partial fluorination occurs and the gaseous fluorination products are passed into the second reactor, maintained at a higher temperature, say 200-300 DEG  C., where the fluorination is completed.  The gaseous products from the second reactor are condensed to recover the resulting fluorocarbons and the gaseous residue (CF4 and HF) is removed for recycling to the first reactor.  Regeneration of the cobalt fluoride is effected by withdrawing suspended solids from the two reactors and feeding them to a separate regenerator supplied with fluorine wherein the cobalt fluoride is regenerated while in the fluidized state and the resulting cobalt trifluoride is then fed back to the two reactors.  If desired, more than two reactors may be used in this embodiment.  The Specification as open to inspection under Sect. 91 of the Acts 1946 comprises the halogenation of hydrocarbons with metal trihalides, which have the property of decomposing into metal dihalides at temperatures below the decomposition temperature of the hydrocarbons, in a fluidized state.  The hydrocarbons may be gaseous, liquid or solid and aliphatic or aromatic and reference is made to their chlorination, bromination or fluorination.  Suitable metal halides are those of cobalt, silver or manganese.  Any of the metal halides may be used in the methods described above with reference to Figs. 1 and 2, and in modifications of these methods the hydrocarbon feed may be introduced into the reactor or reactors in conjunction with free halogen so as to dispense with the separate regeneration of the metal trihalides.  This subject-matter does not appear in the Specification as accepted.ALSO:Cobalt di-fluoride particles, obtained in the fluorination of certain organic compounds with cobalt trifluoride (see Group IV (b)), is reconverted to the trifluoride for re-use by reacting the cobalt difluoride in a fluidized state with free gaseous fluorine, suitably at a temperature between about 200 DEG  and about 400 DEG  C.  The regeneration may be effected by passing the fluorine into a reactor wherein the cobalt fluoride having a particle size less than about 50 mesh is maintained in fluidized state by means of a stream of inert gas.  The required temperature is established by circulating part of the fluidized cobalt fluoride through a heating coil and back to the reactor. Unused fluorine leaving the reactor through a solids separator may be recycled to the reactor.  The Specification as open to inspection under Sect. 91 of the Acts, 1946, relates to the regeneration of a dihalide of any metal having a trihalide which decomposes to the dihalide at temperatures below the decomposition temperatures of halogenatable hydrocarbons, e.g. silver, manganese or cobalt, by the above method with the appropriate free halogen, the metal dihalides being obtained by halogenation, including chlorination or bromination as well as fluorination of the organic compounds with the metal trihalides.  This subject-matter does not appear in the Specification as accepted.