Method for treating process liquid generated in production process of polyphenylene sulfide

Abstract

The invention discloses a method for treating a process liquid generated in the process of producing polyphenylene sulfide, which has high separation efficiency, small energy consumption and low cost, and can be continuously performed. The method comprises the following steps: firstly, a dewatering liquid directly enters into a rectification tower for decompression rectification, and a solvent is collected; secondly, a washing solution enters into a triple-effect evaporator for decompression evaporation, and condensed liquids obtained by various effect evaporators are collected into a buffer tank, wherein a liquid subjected to two-effect evaporation and condensation is led off for centrifugal separation, and a separated liquid enters into a third effect evaporator; a liquid subjected to three-effect evaporation and condensation is also led off for centrifugal separation, and a separated liquid returns back to the third effect evaporator; and filtrate directly enters into the third effect evaporator for evaporation; and thirdly, the condensed liquid accumulated in the buffer tank is sent into the rectification tower for decompression rectification, a component with low boiling point - water is collected on the top of the tower, and a component with high boiling point - a solvent is collected at the bottom of the tower; and the process for treating the process liquid is completed.

Description

technical field [0001] The invention relates to a method for treating process liquid produced in the production process of polyphenylene sulfide using N-methyl-2-pyrrolidone (abbreviated as NMP). Background technique [0002] Polyphenylene sulfide (PPS for short) is a new type of high-performance thermoplastic resin with excellent thermal stability, chemical stability, corrosion resistance and electrical properties. It has a wide range of applications in industry, food, etc., and has a broad market prospect. At present, the method of industrial production of PPS resin is: using sodium sulfide and p-dichlorobenzene as raw materials, in the presence of solvent NMP, using alkali metal compounds as catalysts, polycondensation at a certain temperature and pressure to obtain a mixture containing the crude product of PPS resin . Hydrous sodium sulfide is generally used in production, so it needs to be dehydrated to produce a dehydration liquid; the mixture after the polycondensat...

AI Technical Summary

Problems solved by technology

This method directly carries out the recovery of catalyst in the mixed solution. At this time, the water content of the mixed solution is relatively large, which leads to a low recovery rate of the catalyst and high power consumption in the recovery and separation process; the mixed solution after separating the catalyst directly enters the rectifying tower, because In the presence of a large amount of sodium chloride, there is still the possibility of sodium chloride crystals being carried out by steam to block the tray during the rectification process; the use of batch rectification makes the production capacity of the equipment smaller, the process parameters are not easy to stabilize, and the rectification efficiency is low

[0006] In summary, the common problems in the prior art are: 1. High energy consumption, low solvent recovery efficiency, and high recovery cost; 2. Trays are easily blocked during rectification operation, and the operation is unstable; 3. Catalyst recovery rate is low , the purity is not high; 4, using intermittent operation, the process parameters fluctuate greatly, and the production capacity is small