A method for improving the stability of a catalyst in recycling HFC-23 is provided. The recycling is realized by means of a fluorine-chlorine exchange reaction with HFC-23 and a halogenated hydrocarbon. The catalyst for the fluorine-chlorine exchange reaction comprises a main body catalyst and a metal oxide, wherein the metal oxide is selected from at least one metal oxide of K, Na, Fe, Co, Cu, Ni, Zn or Ti, and has an addition amount of 0.1-5 wt %. The method has advantages such as a good catalyst stability, a long life, and a low content of by-product CFC-12.

The invention relates to an improved process for preparing bromochloromethane by reacting dichloromethane and dibromomethane in the presence of catalysts.

The invention relates to an improved process for preparing bromochloromethane by reacting dichloromethane and dibromomethane in the presence of catalysts.

The present invention aims at that in a series of processes of producing 1,2,3,4-tetrachlorohexafluorobutane from 1,3-butadiene, by-products can be converted to a target substance by a relatively simple operation, raising the production efficiency as the whole process. There is provided a method for producing 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane including step (a) of reacting chlorofluorobutane represented by the formula (1): C.sub.4Cl.sub.nF.sub.10-n (1), wherein n is an integer satisfying 5n7, with chlorine monofluoride (ClF) to thereby produce 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane.

The present invention aims at that in a series of processes of producing 1,2,3,4-tetrachlorohexafluorobutane from 1,3-butadiene, by-products can be converted to a target substance by a relatively simple operation, raising the production efficiency as the whole process. There is provided a method for producing 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane including step (a) of reacting chlorofluorobutane represented by the formula (1): C.sub.4Cl.sub.nF.sub.10-n (1), wherein n is an integer satisfying 5n7, with chlorine monofluoride (ClF) to thereby produce 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane.