Method for recovering F21 and F22 from F22 rectification residual liquid

Abstract

The invention discloses a method for recovering F21 and F22 from F22 rectification raffinate. The method comprises the steps: 1, cooling raffinate in an F22 rectification raffinate collecting tank by a refrigerant, and draining to remove a large amount of water; 2, transferring the F21 and the F22 into a gas phase by utilizing the fact that the boiling points of the F21 and the F22 are far lower than the boiling point of water, condensing the F21 and the F22 through a tower top condenser to obtain crude products of the F21 and the F22, and enabling the water to become heavy components to be remained in a tower kettle; 3, carrying out countercurrent contact on the F21 crude product and the F22 crude product for multiple times in an F22 separation tower, condensing the F22 with a low boiling point by a tower top condenser to obtain an F22 finished product, enabling F21 and a trace amount of water to form a heavy component, and discharging the heavy component from the tower bottom of an F22 separation tower; 4, drying the F21 crude product and the F22 crude product by a dryer to obtain an F21 crude product and an F22 crude product of which the water content is lower than 50 ppm; and 5, drying the heavy component F21 by the dryer to obtain an F21 finished product of which the water content is lower than 50 ppm.

Description

technical field [0001] The invention relates to a method for recovering F21 and F22 from F22 rectification raffinate. Background technique [0002] The production of F22 (difluorochloromethane) is based on chloroform and hydrogen fluoride as raw materials, under the catalysis of antimony pentachloride, and under heating conditions, it is produced in a certain proportion. The reaction is mainly carried out in two steps. The first step is the reaction of chloroform and hydrogen fluoride to generate the intermediate product F21 (chlorofluoromethane), and the second step is the continuous reaction of the intermediate product F21 and hydrogen fluoride to generate F22. In the early stage of the reaction, due to the high catalyst activity, the intermediate product F21 can continue to be fluorinated to form F22. As the reaction progresses, the catalyst activity gradually decreases, and a small amount of F21 will enter the subsequent refining process with F22 due to the failure to co...

AI Technical Summary

Problems solved by technology

In the long run, if it is not discharged in time, it will affect the operation of the F22 rectification tower, resulting in a decrease in the quality of the F22 product and increasing energy consumption

In order to ensure product quality and reduce energy consumption, most manufacturers choose to carry out simple dehydration and then return the remaining raffinate to the reaction system to continue the reaction. When F22 enters the reaction system, it will continue to be fluorinated to form F23 (trifluoromethane), resulting in excessive by-products and increased material consumption.