GB770640A - Manufacture of aliphatic fluorine compounds - Google Patents

Abstract

Aliphatic fluorine compounds in which halogen (other than fluorine) has been replaced by fluorine are obtained by reacting hydrogen fluoride vapour with the vapour of a halogenated aliphatic hydrocarbon containing one or more halogen atoms other than fluorine and which may additionally contain one or more fluorine atoms in the presence of a catalyst which consists of or comprises aluminium fluoride at a temperature within the range of 300 DEG to 700 DEG C. The halogenated aliphatic hydrocarbon is preferably saturated and the process may be carried out in a continuous or discontinuous manner. In a modification of the process a halogenated ethylene containing halogen other than fluorine but which may additionally contain fluorine is reacted in the vapour phase in the presence of an aluminium fluoride catalyst with hydrogen fluoride and, if desired, chlorine, at a temperature within the range of 300 DEG to 500 DEG C. to produce a fluorinated ethane. The catalyst may comprise aluminium fluoride alone or aluminium fluoride in admixture with magnesium fluoride or with a copper halide, particularly copper fluoride. The catalyst may be obtained by passing hydrogen fluoride over small pieces of metallic aluminium or over pieces of porous alumina at raised temperature or by treating aluminium or porous aluminium oxide and copper or magnesium metal, or porous aluminium oxide impregnated with a solution of a soluble salt of copper or magnesium, e.g. a halide, sulphate, nitrate, or acetate of the metal, with hydrogen fluoride at elevated temperature (see Group III). The reaction vessel may be a tube made of nickel or of steel coated with nickel. In examples: (1) hydrogen fluoride is passed at elevated temperature through a nickel tube filled with aluminium turnings and over the aluminium fluoride formed is passed at elevated temperature a mixture of the vapours of hydrogen fluoride and carbon tetrachloride to form a product consisting of a mixture of difluorodichloromethane, trifluorochloromethane, and monofluorotrichloromethane; (2) as in (1) except that the catalyst is formed by passing hydrogen fluoride over porous alumina at elevated temperature; (3) as in (2) except that the alumina is impregnated with magnesium chloride solution, a smaller amount of trifluoromonochloro methane being obtained in this case; (4) as in (1) except that the catalyst is made by treating a mixture of porous alumina and copper turnings with hydrogen fluoride at elevated temperature, an increased amount of trifluorochloromethane being obtained in this case; it is stated that when no copper turnings are added some tetrafluoromethane is formed; (5) as in (3) except that the alumina is impregnated with a cuprous chloride solution, a considerably increased yield of trifluoro chloromethane being obtained in this case and no tetrafluoromethane being formed; (6) as in (5) except that difluorodichloromethane is used instead of carbon tetrachloride, the product in this case being trifluoromethane; (7) a mixture of tetrachlorethylene, chlorine and hydrogen fluoride is passed at 400-450 DEG C. over the catalyst obtained as in (2) to form 1 : 1 : 2-trifluoro-1 : 2 : 2-trichloroethane and a small amount of 1,2-difluoro-tetrachlorethane. Reference is also made to the reaction of trichlorethylene with hydrogen fluoride in the presence of aluminium fluoride catalyst to form 1 : 1 : 1-trifluoro 2-chlorethane.ALSO:An aluminium fluoride catalyst used in the production of aliphatic fluorine compounds by reacting a halogenated aliphatic hydrocarbon containing one or more halogen atoms other than fluorine with hydrogen fluoride (see Group IV(b)) may comprise aluminium fluoride obtained by passing hydrogen fluoride over small pieces of metallic aluminium or porous alumina at elevated temperature or may comprise a mixture of aluminium fluoride with magnesium fluoride or with a copper halide, particularly copper fluoride. Suitable mixed catalysts may be obtained by treating aluminium or porous aluminium oxide and copper or magnesium metal, or porous aluminium oxide impregnated with a solution of a soluble salt of copper or magnesium, e.g. a halide, sulphate, nitrate, or acetate, with hydrogen fluoride at elevated temperature. An alloy of aluminium with magnesium or copper may be used for the treatment with hydrogen fluoride. In the examples the catalysts used are prepared by (1) passing hydrogen fluoride vapour at elevated temperature through a nickel tube filled with aluminium turnings; (2) passing hydrogen fluoride over porous alumina at 360-400 DEG C.; (3) impregnating alumina with magnesium chloride and treating with hydrogen fluoride as in (2); (4) treating a mixture of porous alumina and copper turnings with hydrogen fluoride at a temperature rising from 80 DEG to 500 DEG C; and (5) treating alumina impregnated with a solution of cuprous chloride with hydrogen fluoride at elevated temperature.