| 摘要 |
Fluorination catalysts comprising chromium oxyfluorides are treated with elementary gaseous chlorine at a temperature above 100 DEG C. but below the temperature at which chlorination or decomposition of the compound to be fluorinated can take place, preferably at a temperature of from 200 DEG to 500 DEG C. Such treatment stabilizes the catalysts and prolongs their life. The treatment with chlorine may take place in the presence of hydrogen fluoride. The catalysts may be treated with chlorine either (a) during the catalytic fluorination process, when the amount of chlorine used is preferably from 0.1 to 50 mol. per cent based on the amount of substance to be fluorinated, or (b) in the absence of the substance to be fluorinated after temporary interruption of the fluorination process. Examples describe a chlorination treatment according to either method (a) or (b) in the catalytic fluorination by hydrogen fluoride of methylene chloride, carbon tetrachloride, trichloracetyl chloride and chloral, the fluorination catalyst used being one or a mixture of those prepared by methods described in Specification 1,025,759. |
