阅读说明：本技术 用于合成聚苯硫醚的催化剂氯化锂的回收方法 (Method for recovering lithium chloride used as catalyst for synthesizing polyphenylene sulfide ) 是由 张德明 杨伟明 周鸿文 叶维雪 于 2021-01-20 设计创作，主要内容包括：一种用于合成聚苯硫醚的催化剂氯化锂的回收方法,通过对合成聚苯硫醚的混合溶液分离得到的残留溶液,进行脱水,提出氯化钠和未反应的碱金属硫化物,将得到的溶液回用于合成完成大部分的氯化锂回收,剩下的固体焚烧后与NMP混合进一步回收含有氯化锂的NMP溶液,一样地重新投入合成所用,通过以上步骤可以实现86%左右的氯化锂的回收,采用的设备简单,过程易于操作,不仅提高了氯化锂的回收率,且降低了回收的成本,实现了资源的高度回收利用。(A recovery method of catalyst lithium chloride for synthesizing polyphenylene sulfide comprises the steps of dehydrating residual solution obtained by separating mixed solution for synthesizing polyphenylene sulfide, extracting sodium chloride and unreacted alkali metal sulfide, recycling the obtained solution for synthesizing most lithium chloride, mixing the rest solid after incineration with NMP, further recovering NMP solution containing lithium chloride, and putting the solution into synthesis again in the same way, wherein about 86% of lithium chloride can be recovered through the steps.)

1. A method for recovering lithium chloride used as a catalyst for synthesizing polyphenylene sulfide is characterized by comprising the following steps:

step one, solid-liquid separation: carrying out solid-liquid separation on a mixed solution obtained by p-dichlorobenzene and alkali metal sulfide and/or alkali metal hydrogen sulfide in a polar solvent, removing solid sodium chloride and leaving a residual solution;

step two, dehydration: dehydrating the residual solution in the step one, adding fresh NMP (N-methyl pyrrolidone) with the total weight of 1/3 of the residual solution into the residual solution before dehydration, wherein the dehydration degree is lower than 0.5 percent, and sodium chloride, unreacted alkali metal sulfide and a small amount of lithium chloride can be separated out in the dehydration process;

step three, solid-liquid separation: after dehydration, carrying out solid-liquid separation to obtain a separated solid A and a separated filtrate B; the filtrate B contains most of lithium chloride, and the solid A contains a small amount of lithium chloride;

step four, directly transferring the filtrate B containing most lithium chloride back to be used for synthesizing the polyphenylene sulfide; transferring the solid A to an incinerator for incineration; wherein the incineration conditions are as follows: burning for 2-8 hours at the temperature of 450-850 ℃, cooling to 20-100 ℃, adding fresh NMP, stirring for 10-50 fractions, performing solid-liquid separation for the second time, continuously adding the liquid obtained after the solid-liquid separation into the polyphenylene sulfide, and discarding the solid.

2. The method for recovering lithium chloride as a catalyst for synthesizing polyphenylene sulfide as claimed in claim 1, wherein the solid-liquid separation process in the first step can be performed by centrifugation or filtration.

3. The method for recovering lithium chloride as a catalyst for synthesizing polyphenylene sulfide according to claim 1, wherein the polar solution in the first step is N-methyl-2-pyrrolidone, NMP for short, and the mixed solution in the first step is a mixed solution obtained by reacting p-dichlorobenzene with an alkali metal sulfide and/or an alkali metal hydrogen sulfide in NMP under lithium chloride conditions, and the mixed solution mainly contains PAS (polymer particles), oligomers, lithium chloride, sodium chloride, a polar solvent, water, and unreacted monomers.

4. The method for recovering lithium chloride as a catalyst for synthesizing polyphenylene sulfide according to claim 1, wherein dehydration is performed by distillation under reduced pressure when dehydration is performed in the second step.

5. The method for recovering lithium chloride as a catalyst for synthesizing polyphenylene sulfide according to claim 1, wherein the residual solution is a solution obtained by filtering out solid components of NMP, which is an organic solvent used repeatedly in the polyphenylene sulfide synthesis process for 10 times, and the residual solution contains NMP, lithium chloride, a small amount of sodium chloride, water, and unreacted monomers.

[ technical field ] A method for producing a semiconductor device

The invention relates to a method for recovering lithium chloride, in particular to a method for recovering lithium chloride serving as a catalyst used in a process of synthesizing polyphenylene sulfide.

[ background of the invention ]

Polyphenylene sulfides produced by reacting dihaloaromatic compounds with alkali metal sulfides and/or alkali metal hydrogen sulfides in the presence of polar solvents such as N-methyl-2-pyrrolidone NMP are low in molecular weight and are oligomers. In this case, potassium chloride, a catalyst, is used as a polymerization aid in chemical reactions to increase the molecular weight of polyphenylene sulfide. Polymerizing the polyphenylene sulfide to obtain the high polymer.

Lithium chloride is used as a polymerization aid, and because it is expensive, it is necessary to recycle the lithium chloride after the reaction in order to reduce the cost, thereby reducing the cost of the whole production process. Therefore, many proposals have been made to solve the problem of how to recover the catalyst lithium chloride in the preparation process of polyphenylene sulfide. Aluminum chloride is recovered from the reaction mixture during the preparation of polyphenylene sulfide.

For example, there are known methods for recovering lithium chloride including removing a solvent from a reaction mixture, washing the reaction mixture with an acidic aqueous solution, blowing carbon dioxide into the reaction mixture or adding a carbonate to the washing solution to precipitate lithium carbonate, and recovering lithium carbonate; and recovering lithium chloride from the reaction mixture during calcination.

However, this method has problems in that the recovery equipment and operation process are complicated, and a large amount of auxiliary materials are required to obtain lithium carbonate, and most importantly, lithium chloride cannot be directly recovered, but lithium carbonate as an intermediate product of the recovered lithium chloride is obtained; the second problem of recovering lithium chloride by calcining the reaction mixture is that the calcining difficulty is high, and the calcining condition requires strict control of temperature and calcining condition to avoid volatilization of lithium chloride during calcining.

[ summary of the invention ]

The invention provides a simple way for recycling lithium chloride in the process of preparing polyphenylene sulfide back and forth aiming at the situations, and the simplest equipment is adopted to recycle the lithium chloride relatively quickly with low cost.

The invention relates to a method for recovering lithium chloride used as a catalyst for synthesizing polyphenylene sulfide, which is characterized in that

Step one, solid-liquid separation: carrying out solid-liquid separation on a mixed solution obtained by p-dichlorobenzene and alkali metal sulfide and/or alkali metal hydrogen sulfide in a polar solvent, removing solid sodium chloride and leaving a residual solution;

step two, dehydration: dehydrating the residual solution in the step one, and adding fresh NMP (N-methyl pyrrolidone) with the total weight of 1/3 of the residual solution into the residual solution before dehydration, wherein the dehydration degree is lower than 0.5%, and sodium chloride, unreacted alkali metal sulfide and a small amount of lithium chloride can be separated out in the dehydration process;

step three, solid-liquid separation: after dehydration, carrying out solid-liquid separation to obtain a separated solid A and a separated filtrate B; the filtrate B contains most of lithium chloride, and the solid A contains a small amount of lithium chloride;

step four, directly transferring the filtrate B containing most lithium chloride back to be used for synthesizing the polyphenylene sulfide; transferring the solid A to an incinerator for incineration; wherein the incineration conditions are as follows: burning for 2-8 hours at the temperature of 450-850 ℃, cooling to 20-100 ℃, adding fresh NMP, stirring for 10-50 fractions, performing solid-liquid separation for the second time to obtain liquid containing lithium chloride, continuously adding polyphenylene sulfide for synthesis, and discarding solids.

The solid-liquid separation process in the step one can be completed by centrifugation or filtration;

the polar solution in the first step is N-methyl-2-pyrrolidone, NMP for short, and the mixed solution in the first step is a mixed solution obtained by reacting p-dichlorobenzene with alkali metal sulfide and/or alkali metal hydrogen sulfide in NMP under the condition of lithium chloride, and the mixed solution mainly contains PAS (polymer particles), oligomers, lithium chloride, sodium chloride, a polar solvent, water and unreacted monomers.

When the dehydration is carried out in the second step, reduced pressure distillation is adopted for dehydration;

the residual solution is a solution which is continuously applied by 10 times of polyphenylene sulfide synthesis and in which solid components are filtered, and the residual solution contains NMP, lithium chloride, a small amount of sodium chloride, water and unreacted monomers.

The invention relates to a method for recovering lithium chloride used as a catalyst for synthesizing polyphenylene sulfide, which comprises the steps of separating again through dehydration separation and solid incineration extraction, recovering the obtained polar solvent containing lithium chloride and repeatedly putting the polar solvent into a synthesis reaction, and realizing the recovery of about 86% of lithium chloride through the steps.

[ detailed description ] embodiments

The present invention will be described in further detail with reference to specific embodiments. The specific embodiments are only provided for illustrating the scheme and are not used for limiting the core technical scheme of the invention.

Example 1:

1286.5g of sodium sulfide trihydrate, 180g of lithium chloride and 5 liters of NMP are charged into a reaction kettle and dehydrated. Dehydrating in a reduced pressure distillation mode, adding 1470g of p-dichlorobenzene into a reaction system after the dehydration is finished, and then heating to 260 ℃ for reacting for three hours to generate a reaction mixture.

Filtration was carried out to filter the polyphenylene sulfide particles and the solvent-insoluble sodium chloride from the reaction mixture to obtain 4300g of a residual solution containing 168g of lithium chloride as measured by ultraviolet spectrophotometry.

The residual solution contains lithium chloride, sodium chloride, a polar solvent, water, unreacted monomers, and the like.

4300g of the solution was taken and treated as follows:

the residual solution is dehydrated. Before dehydration, 1433g of fresh NMP is added into the residual solution, and then dehydration is carried out to remove the water to below 0.5 percent, and the sodium chloride and the unreacted alkali metal sulfide in the residual solution are separated out and removed. This process is carried out under reduced pressure, and the dehydration is carried out by distillation under reduced pressure to minimize decomposition of the polar solvent.

After the dehydration is finished, solid-liquid separation is carried out, and the separated solid A and the filtrate B are respectively treated.

4100g of the obtained filtrate B is directly transferred back to be used for the synthesis of polyphenylene sulfide. 142g of lithium chloride is detected in the filtrate B, and the recovery rate reaches 84.5 percent.

98g of the obtained solid A is transferred to an incinerator, the solid A is treated at the temperature of 450-850 ℃ for 2-8 hours, then the temperature is reduced to 20-100 ℃, 300g of NMP is added, the mixture is stirred for 10-50 minutes, solid-liquid separation is carried out, 3g of lithium chloride in liquid is measured, the liquid can be continuously recycled and put into the polyphenylene sulfide synthesis, and the solid is discarded.

By the above treatment, the lithium chloride recovered by the two parts reaches 145g, and the total recovery rate of the lithium chloride is 86.3%.

The invention relates to a method for recovering lithium chloride used as a catalyst for synthesizing polyphenylene sulfide, which comprises the steps of separating again through dehydration separation and solid incineration extraction, recovering the obtained polar solvent containing lithium chloride and repeatedly putting the polar solvent into a synthesis reaction, and realizing the recovery of about 86% of lithium chloride through the steps.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.