A method for comprehensive recovery and utilization of lithium containing mixed salts in a polyphenylene sulfide production process

Abstract

A method for comprehensive recovery and utilization of lithium containing mixed salts in a polyphenylene sulfide (PPS) production process is disclosed. Na<2>CO3 is added into PPS byproduct slurry, rectification is performed to separate and recover a solvent that is NMP, then obtained lithium containing mixed salts are subjected to dissolution and leaching through an acidic methanol solution, and a wet solid phase and a liquid phase are obtained after pH adjustment and filtration. The wet solid phase is dried, dissolved with water and purified to obtain a refined NaCl solution. The liquid phase is subjected to rectification, ethanol leaching, evaporation, water leaching, purification and evaporative crystallization to obtain a high-purity water-free LiCl product. The method can be used for comprehensive recovery and utilization of the lithium containing mixed salts in the PPS production process. The recovered refined NaCl solution can be directly used for ionic membrane electrolysis to prepare caustic soda, and the LiCl can be directly used as a PPS production auxiliary agent for cyclic use.

Description

technical field [0001] The invention belongs to the production field of polyphenylene sulfide (PPS), and relates to a method for comprehensive recovery and utilization of by-products in the industrial production of polyphenylene sulfide, especially a method for comprehensive recovery and utilization of lithium-containing mixed salts in the production process of polyphenylene sulfide . Background technique [0002] In the process of producing PPS with sodium sulfide and p-dichlorobenzene as raw materials, a large amount of NaCl will be produced by-product, and because the process needs to add N-methylpyrrolidone (NMP) as a solvent and LiCl as an auxiliary agent, after separating PPS The slurry contains NaCl, LiCl, NMP and other components. Since LiCl and NMP are expensive, if they are not recycled effectively, the production cost will increase dramatically. [0003] For the recovery of by-products, solvents, additives, etc. in the PPS production process, there are currently...

AI Technical Summary

Problems solved by technology

It is worth noting that there are certain defects in the current relevant recycling methods, such as the inability to realize the comprehensive recycling of the by-product slurry, or the low purity of some recovered products, etc.

In addition, after the PPS polymerization reaction is completed, although most of the NMP can be recovered by conventional methods, the remaining 25% to 30% of the NMP will combine with LiCl to form a complex similar to a solid solution. In the process of conventional evaporation recovery of NMP, because the viscous complexes formed are likely to cause problems such as blockage of the evaporation kettle or difficulty in removal, it is difficult to industrialize production

[0004] The current recycling method for PPS by-product slurry is only for one or two components, and the recovery process is cumbersome, and the product purity and yield are low

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