GB805503A - Improved fluorination catalyst and process - Google Patents

Abstract

A catalyst for the fluorination of halogen-substituted hydrocarbons, contains basic aluminium fluoride, and is formed by impregnating porous alumina with an aqueous solution of a halide of Cr, Co, Ni or Pd and treating the wet alumina with anhydrous hydrofluoric acid until it is dry. In examples, a porous alumina, e.g. chi, gamma, alpha or kappa alumina made by controlled calcination of aluminium hydrate, or calcined aluminium tri-hydrate obtained from bauxite, is impregnated with 6N solution of hydrochloric acid containing NiCl2. After standing, the mixture is filtered and the wet impregnated alumina is treated with dry HF for several hours, until the alumina is dry. Mild heating is applied in the later stage of drying. The dry catalyst may be further treated with HF while heating at 150 DEG to 500 DEG C. The product contains unchanged alumina, aluminium fluoride and basic aluminium fluoride in addition to from 0.1 to 10 per cent of nickel which may be chemically combined with the aluminium fluoride. Nickel chloride may be replaced by nickel fluoride, cobalt chloride, chromium hydroxide dissolved in HF, or palladium chloride dissolved in HF. After use, the catalyst may be regenerated by treating at 400 DEG C. with oxygen or air pre-heated to 300 DEG C. The carbon-free catalyst is then treated with anhydrous HF at about 400 DEG C. The halo-alkane, which preferably contains 1 to 4 C atoms, and is free from iodine, is passed as vapour in admixture with HF over the catalyst at about 300 DEG C. The gaseous products are fractionated, washed with alkali, water, and dried, (see Group IV (b)). U.S.A. Specifications 2,005,707, 2,110,369, 2,458,551, 2,531,372 and 2,553,518 are referred to.ALSO:Halogen-substituted alkanes are fluorinated by passing vapours of them together with at least an equimolecular proportion of HF over a catalyst containing basic aluminium fluoride, and made by impregnating porous alumina with an aqueous solution of a halide of Cr, Co, Ni or Pd and treating with anhydrous HF until it is dry. The starting material preferably contains 1 to 4 C atoms and the halogen substituents may be F, Cl or Br, but not I. Compounds specified include halogenated methanes containing at least two halogen atoms which may be the same or different and halogenated ethanes, propanes and butanes containing at least two halogen atoms attached to the same carbon atom. For example, CBr4 vapour admixed with an equimolecular amount of HF is passed over the catalyst at a temperature of 150 DEG to 500 DEG C., and preferably about 300 DEG C. The gaseous reaction products are cooled and fractionated, and the main product consisting of CBrF3 is washed with alkali, water and dried. Other examples describe the conversion of CBr4 to CBr2F2 with lesser amounts of CBrF3, CHBr2F, CBr3F and CHBr3, of CH2Br2 to CH2F2 and some CH2BrF, of CH2Cl2 to CH2F2 and some CH2ClF, of Cl3CH3 to CH3CF3 and some CH3CClF2 and CH2=CClF, of CCl3CCl3 to CClF2CClF2 CClF2 CCl2F and some CF3CClF2 and CCl2FCCl2F, of CCL- to CClF3, CCl2F2, CCl3F and CF- (different proportions of these products being obtained with different catalysts and under different reaction conditions), of CBr2F2 to CBrF3 and some CHF3 and CHBrF2, and of CBr4 to CBrF3 and some CF4, CBr2F2, CHF3, CHBr2F and CBr3F (the proportions varying as above). U.S.A. Specifications 2,005,707, 2,110,369, 2,458,551, 2,531,372 and 2,553,518 are referred to.