Process for preparing 1,1,1-trifluoro-2-chloroethane and/or 1,1,1, 2- tetrafluoroethane

摘要

A process for preparing 1,1,1-trifluoro-2-chloroethane and/or 1,1,1,2- tetrafluoroethane, comprising the steps of reacting trichloroethylene and/or 1,1,1-trifluoro-2-chloroethane with hydrogen fluoride in the presence of a fluorinating catalyst in a gas pase, separating 1,1,1- trifluoro-2-chloroethane, hydrogen fluoride, and optionally trichloroethylene, from the reaction mixture obtained by the above reaction which contains 1,1,1-trifluoro-2-chloroethane, 1,1,1,2- tetrafluoroethane, hydrogen fluoride, and optionally trichloroethylene, and recycling them to the reaction step above, characterized in that at least a part of the reaction mixture is distilled in a distillation tower, 1,1,1,2-tetrafluoroethane-rich components are discharged from the top of the tower, and a mixture of 1,1,1-trifluoro-2-chloroethane and hydrogen fluoride, and optionally trichloroethylene, is discharged in the form of gas from the middle part of the tower at a temperature which is above the boiling point of the azeotropic mixture of 1,1,1-trifluoro-2-choroethane and hydrogen fluoride and at least 5 C. below the boiling point of anhydrous hydrogen fluoride under the internal pressure in the distillation tower and returned to the reaction step.PP The discharging at the middle part of the tower provides a recycling gas in high purity, while leaving higher-boiling substances such as water, tar, etc. on the bottom of the tower. The gas can be used for the reaction system as a recycling gas, which can eliminate a process of vaporizing high-boiling mixture which is conventionally discharged at the bottom of the tower by means of a vaporizer and the like and reduce the equipment cost significantly.