Patent GB-359997-A (GB)
Title: Improvements in or relating to the manufacture of organic compounds containing fluorine
IPC: C07C17/20
Filed: 1930-06-24
Abstract: Fluorine derivatives of aliphatic hydrocarbons for use as refrigerants, fire extinguishing substances, an sthetics, or the like, are obtained by replacing one or more halogen atoms of an aliphatic halide with fluorine, for example, by means of antimony trifluoride in presence of a catalyst such as antimony pentachloride, the reaction products being withdrawn from the reaction zone and insufficiently fluorinated compounds returned thereto during the process.  The products preferably contain another halogen or other halogens in addition to fluorine.  It is desirable to carry out the reaction under non-aqueous conditions. The process may be carried out in a reaction chamber 20 provided with a fractionating column 23 and dephlegmator 24 maintained at a suitable temperature, for example, by circulating cooling water through a jacket 28, so that insufficiently fluorinated compounds are returned to the reaction.  The initial halogen compound may be forced into the reaction chamber from a container 21 by pressure of gas from a vessel 36.  Other materials may be added through an opening 22, and the residue after the reaction may be removed through another opening 22a.  The gaseous product is purified by means of washers 25, 26, and a drier 27, supplied respectively with dilute caustic soda solution from vessels 29, 30 and with sulphuric acid from a vessel 31.  The desired pressure is maintained in the apparatus by controlling the rate at which the products condensed in <PICT:0359997/IV/1> a suitably cooled condenser 32 are discharged through a valve 32a into a container 33. A safety release diaphragm 34 and a pressure gauge 35 are provided. Another form of apparatus is also described for use when operating at atmospheric or low pressures, wherein the dephlegmator jacket is supplied with a liquid refrigerant which is circulated through a compressor provided with an automatic control to ensure maintenance of the proper temperature in the jacket, and an auxiliary condenser. The fluorinated product is finally condensed with the aid of a compressor.  In all cases when carrying out the process the temperature and pressure in the dephlegmator should be adjusted to correspond to a point on or near (preferably slightly below) the vapour pressure temperature curve for the fluorine derivative which it is desired to obtain; a list of suitable dephlegmator temperatures, and pressures for various compounds is given. Products which may be obtained starting with chloroform, carbon tetrachloride, or other suitable chloromethanes are CH2ClF, CHCl2F, CCl3F, CHClF2, CCl2F2, CClF3, and CF4.  Suitable chlorine derivatives of ethane, ethylene, propane, butane, &c., may also be used as starting materials.  Thus hexachlorethane may be converted by means of antimony trifluoride and a catalyst such as antimony pentachloride to hexafluorethane, CHCl2 - CHCl2 may be similarly converted to CHCl2 - CHClF or into a mixture of CHClF - CHClF and CHCl2 - CHF2, or starting with CHCl = CHCl, CHF = CHCl and CHF = CHF may be obtained. As examples of compounds containing other halogens, CBr2F2 may be obtained from CBr4, CHI2F from CHI3, or two acetylene derivatives C2BrF and C2IF may be prepared from C2Br2 and C2I2 respectively.  An example is given. Specification 357,263, [Group XIII], is referred to.