Patent GB-877331-A (GB)
Title: Fluoroperhalocarbon compounds and electrolytic methods of preparing such compounds
IPC: C25B3/28
Filed: 1958-02-10
Abstract: 877,331. Production of fluoroperhalocarbons by fused salt electrolysis. MINNESOTA MINING & MANUFACTURING CO. Feb. 10, 1958, No. 4241/58. Class 41. Fluoroperhalocarbons, i.e. hydrocarbons fully substituted with the halogens fluorine, chlorine and/or bromine of which fluorine is always present, are produced by electrolysis at a temperature above 400 C. of one or more molten metal fluorides free of oxygen-containing compounds using a cathode having a boiling-point above that of the melt and a carbon anode in contact with added chlorine and/or bromine, .or a hydrocarbon, or a hydrocarbon substituted by chlorine and/or bromine with or without fluorine atoms. Examples are given in which mixtures of fluoroperhalocarbons are produced on adding chlorine and/or bromine, acetylene, carbon tetrachloride, tetrachloroethylene, or trichloroethylene. Helium is passed through the cell to maintain an inert atmosphere. Reference is also made to the electrolytic fluorination of acyclic and alicyclic hydrocarbons having from 1 to 10 carbon atoms such as ethylene, propylene, butadiene, cyclohexane, benzene, xylenes, naphthalene and halogenated alkanes, alkenes (mono-, di-, and tri-enes) and aryl and alkaryl hydrocarbons. The metal fluorides used may be simple fluorides of metals of Groups In, IIA, IVA, VA, VIA, VIB and aluminium, double metal fluorides of sodium or potassium with beryllium aluminium, titanium, zirconium, germanium, niobium, tantalum or fluosilicates of potassium, caesium or barium or sodium fluoborate. Non-metallic components such as boron, carbon, silicon, phosphorus, sulphur, selenium and tellurium may also be included in the melt. For cathodes carbon may be used or a metal having a melting-point above 1650 C., e.g. the metals of Groups IVA, VA, VIA, rhenium, ruthenium, rhodium, osmium, iridium, platinum and ytterbium. By electrolysis of appropriate melts, cathodic deposits of refractory metals such as titanium, vanadium, niobium, tantalum, molybdenum, and tungsten may be produced simultaneously with the fluoroperhalocarbon. Typically the electrolysis is carried out in an externally-heated cell (Fig. 1, not shown), having a tantalum cathode and a dividing barrier formed by solidified salt around a pocket containing a cooling coil, a hollow carbon anode extending into the melt on one side of the barrier and a gaseous take-up vent is provided above the melt in the anode compartment for the fluorohalocarbon. Alternatively, as shown, the cell comprises a waterjacketed copper funnel 61 through the neck of which passes a carbon or tungsten cathode 69 and is covered by a heat-resistant glass cover 63 through which projects into the melt 79 a carbon anode 71, the height of the melt being controlled by adding solid electrolyte from the container 83. Inert gas such as helium is fed to the cell by conduit 66 and is removed together with the gaseous products of electrolysis via conduit 67. If added hydrocarbon, halogenated hydrocarbon or halogen is required, it is introduced with the helium through a hollow anode 71. The electrolyte is melted by striking an arc and electrolysis is effected on drawing the electrodes apart in the melt. The current employed may be D.C., pulsating D.C., A.C. superimposed on D.C. or A.C. when both electrodes are of carbon. The cell atmosphere pressure may range from a few millimetres of mercury to 10 atmospheres.