Catalyzed fluorination of chlorocarbons

#1. Field of the Invention

#This invention relates to the catalyzed production of chlorofluorocarbons, for example, trichlorofluoromethane, from chlorocarbons and ammonium bifluoride.

#2. Prior Art

#The drawing described more fully below is a schematic representation of apparatus in which the reaction constituting the present invention may be carried out.

#In accordance with the present invention, it has been found that certain chlorocarbons, e.g., carbon tetrachloride, chloroform, can be fluorinated to useful chlorofluorocarbons, e.g., trichlorofluoromethane, dichlorofluoromethane, by ammonium bifluoride in the presence of selected catalysts at elevated temperature. It is merely necessary to contact the reactants briefly under the conditions noted for the reaction to occur.

#Catalysts useful in the reaction include the Group IIa fluorides, i.e., those of calcium, magnesium, strontium and barium, as well as ferric cluoride, anhydrous chromic fluoride and chromic phosphate. Mixtures of these catalysts can also be used, e.g., the Group IIa fluorides and ferric fluoride are operable in mixture with each other.

#The fluorides of the Group IIa metals, Fe(III) and Cr(III) may be prepared in place from the corresponding chlorides by vapor phase reaction with HF or with NH.sub.4 HF.sub.2. "Chromic fluoride" as used here means the product resulting from reaction of chromic chloride with NH.sub.4 HF.sub.2 following dehydration on heating to 300.degree. C. under vacuum as taught in U.S. Pat. No. 3,600,450. X-ray diffraction shows that most of the chlorine originally present is replaced by fluorine.