Method for recycling paradichlorobenzene in polyphenylene sulphide production mother liquor

Abstract

The invention discloses a method for recycling paradichlorobenzene in polyphenylene sulphide production mother liquor. The method comprises the following steps: (1) firstly filtering the polyphenylene sulphide production mother liquor and removing impurities; (2) distilling the filtered polyphenylene sulphide production mother liquor at the temperature of 150-200 DEG C, so that an NMP solvent and paradichlorobenzene waste water are obtained; (3) then settling the paradichlorobenzene waste water for 6-18 hours at the temperature of 0-30 DEG C; (4) centrifuging and separating settled paradichlorobenzene to obtain crude paradichlorobenzene crystals; (5) melting the crude paradichlorobenzene crystals at the temperature of 50-80 DEG C, so that liquid-state crude paradichlorobenzene is obtained; (6) filtering liquid-state crude paradichlorobenzene, and removing insoluble substances in liquid-state crude paradichlorobenzene; and (7) settling liquid-state paradichlorobenzene with the insoluble substances removed for 1-2 hours at the temperature of 0-20 DEG C, so that refined paradichlorobenzene crystals are obtained. The method disclosed by the invention has the advantage that paradichlorobenzene in the polyphenylene sulphide production mother liquor can be recycled.

Description

technical field [0001] The invention relates to a method for recovering p-dichlorobenzene in the mother liquor of polyphenylene sulfide production. Background technique [0002] The sodium sulfide method is mostly used in the production of polyphenylene sulfide at home and abroad. The raw materials used in the sodium sulfide method are p-dichlorobenzene and sodium sulfide, and the solvent used is N-methylpyrrolidone (NMP for short). The raw materials and solvent form polyphenylene sulfide. In the ether reaction mother liquor, the molar amount of p-dichlorobenzene in the raw material ratio generally needs to be 1-10% more than that of sodium sulfide. In the process of producing polyphenylene sulfide by the sodium sulfide method, after the polyphenylene sulfide in the polyphenylene sulfide reaction mother liquor completes the polycondensation reaction with sodium sulfide and p-dichlorobenzene, the polyphenylene sulfide in the polyphenylene sulfide reaction mother liquor is als...

AI Technical Summary

Problems solved by technology

At present, after the production of polyphenylene sulfide by the sodium sulfide method, it is impossible to recycle the p-dichlorobenzene remaining in the mother liquor of polyphenylene sulfide production, which not only causes waste of resources, but also greatly increases the cost of use of the enterprise, and due to p-dichlorobenzene With benzene ring structure, the biodegradability of polyphenylene sulfide production mother liquor is poor, and it is easy to pollute the environment