AU2018101954A4 - Method for comprehensive recycling of by-product slurry during polyphenylene sulfide production - Google Patents
Method for comprehensive recycling of by-product slurry during polyphenylene sulfide production Download PDFInfo
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Abstract
The present invention discloses a method for comprehensive recycling of by-product slurry during polyphenylene sulfide (PPS) production. The method includes the following steps: adding Na2 CO 3 into slurry, distilling and drying to recover a solvent NMP, dissolving and leaching the obtained dried waste salt with an acid solution, regulating a pH value of leaching liquor, filtering to remove insoluble components, performing adsorption purification and evaporation concentration on a liquid phase to separate out NaCl, adding a Na2 CO 3 precipitate into a solution in which the NaCl is separated to obtain Li2 CO 3 , regulating a pH value of lithium-precipitated mother liquor, and mixing the mother liquor and the solution subjected to adsorption purification, thereby realizing a closed cycle of the process. The method may be applied to comprehensive recycling of by-product slurry during the PPS production, the recovered NaCl may be directly used for caustic soda preparation by virtue of ionic membrane electrolysis, and the Li 2CO 3 may directly serve as an industrial product or be further converted into LiCl to serve as a PPS production auxiliary for recycling. Destruct lithium-NMP Na2CO3 solution PPS by-product slurry Distilling/drying --------- - NMP Dissolving&leaching HCI solution - - - Dry waste salt Regulate pH NaOH solution -- cLaching liquor containing dissolved organic matters + insoluble oligomers and impurities I Filtering ------------ Insoluble oligomers and impurities Leaching liquor contains dissolved organic matters Adsorption and Dissolved organic matters purification --- Solution containing LiCl and NaCl Evaporation ---- y NaC1 Precipitate concentration Na2CO 3 solution lithium 3 Concentrated solution Filtering --- ~-- --- 2CO3 Regulate pH Precipitate lithium HCl solution mother liquor 2-Thetar
Description
METHOD FOR COMPREHENSIVE RECYCLING OF
BY-PRODUCT SLURRY DURING POLYPHENYLENE
SULFIDE PRODUCTION
TECHNICAL FIELD [0001] The present invention relates to the field of production of polyphenylene sulfide (PPS), and particularly relates to a method for high-efficiency comprehensive recycling of by-product slurry during industrial PPS production.
BACKGROUND OF THE PRESENT INVENTION [0002] Polyphenylene sulfide (PPS) is a special thermoplastic engineering plastic, has excellent properties such as excellent electrical insulating property, flame retardant property, chemical corrosion resistance and the like and is widely applied to the fields of aerospace, electronics & electrical appliances, chemical engineering and the like. In a process of synthesizing the PPS by taking Na2S and p-dichlorobenzene as raw materials, taking N-methyl pyrrolidone (NMP) as a solvent and taking LiCl as an auxiliary, lots of by-product NaCl may be produced, and the NaCl, LiCl and NMP finally form by-product slurry containing salts, water, NMP and the like. Since the LiCl and NMP are expensive, if the by-product slurry is not comprehensively recycled, rapid increase of production cost and severe environmental pollution may be caused.
[0003] At present, there are related research reports for a recycling method of the NMP and LiCl in PPS by-product slurry. In a patent CN102276838, the NMP is recycled by evaporating to dryness at a reduced pressure, and phosphoric acid or sodium aluminate is added into water leaching liquor to precipitate and recover lithium. In a patent CN 103965476, decompression dehydration is performed in an inert gas environment; NaCl is precipitated and separated; further reduced pressure distillation is performed to recover the NMP; and residual liquor is cooled to precipitate and recover the LiCl. In a patent CN102675683, reduced pressure distillation is performed to separate most of the water and NMP in the by-product slurry; the obtained viscous substance containing NaCl, LiCl, NMP and water is forced to evaporate to dryness by a spiral evaporator so as to obtain a powdered mixture containing LiCl, NaCl and the like; the NaCl is leached and separated with
2018101954 05 Dec 2018 methanol; and the LiCl is obtained by evaporating and drying. It should be noted that, the above methods have defects that the recovered product is low in purity, yield of the NMP and LiCl is low, and the like. In addition, after a polymerization reaction of the PPS is completed, although most of the NMP may be recovered by the conventional method, the residual 25%-30% of NMP may be combined with the LiCl to form a complex similar to a solid solution. In a process for performing conventional evaporation on the mixture to recover the NMP, since problems that an evaporation kettle is blocked or elimination is difficult and the like are easily caused by the viscous complex formed, industrial production is difficult to be realized. [0004] In order to solve the problem that the NMP and the LiCl form the complex, a patent CN1345892 discloses a method as follows: lithium is precipitated and recovered in a manner of adding carbonate into the by-product slurry, and hydrochloric acid is added into a filter cake to obtain a halide salt catalyst. However, the method is extremely low in product yield and purity. In addition to the above method, patents CN104277220 and CN102730721 disclose a method for recovering NaCl in a polyphenylene sulfide solvent; and a patent CN104877167 discloses a method for recycling an auxiliary LiCl in a polyphenylene sulfide production process. It should be noted that, a current method for recycling the PPS by-product slurry is only for recovering one or two components, the recovery process is complicated, and the obtained product is relatively low in purity and yield.
[0005] In view of this, in order to realize green production of the PPS and reduce the production cost, a high-efficiency method for recovering a solvent of the PPS by-product slurry, removing and purifying organic impurities and comprehensively recycling sodium chloride and lithium carbonate is developed, which has important significances for promoting green sustainable development of PPS industry.
SUMMARY OF PRESENT INVENTION [0006] With respect to defects in an existing technical method for recycling by-product slurry during PPS production, a purpose of the present invention is to provide a method for comprehensive recycling of oligomers such as NMP, NaCl, LiCl and PPS in PPS by-product slurry, thereby reducing production cost of the PPS and realizing green production of the PPS.
[0007] Technical solutions and technical processes provided in the present invention are as follows:
2018101954 05 Dec 2018 [0008] A method for comprehensive recycling of by-product slurry during polyphenylene sulfide (PPS) production includes the following steps:
[0009] 1) adding Na2CO3 into PPS by-product slurry to destruct a complex formed by N-methyl pyrrolidone (NMP) and lithium, converting the lithium into L12CO3, distilling and drying the slurry to separate and recover the NMP and water, and obtaining a dry waste salt containing oligomers such as NaCI, L12CO3, Na2CC>3 and PPS;
[0010] 2) adding an acid solution into the dry waste salt in the step 1) for reacting, dissolving and leaching, respectively converting L12CO3 and Na2CO3 into LiCl and NaCI, and dissolving to enter a liquid phase;
[0011] 3) regulating a pH value of leaching liquor in the step 2), filtering to remove insoluble components, adsorbing and purifying the liquid phase to remove dissolved organic components to obtain a solution containing LiCl and NaCI only;
[0012] 4) evaporating and concentrating the solution containing LiCl and NaCI only in the step 3) to separate out the NaCI, and adding a Na2CC>3 solution into a concentrated solution after separating the NaCI to precipitate L12CO3; and [0013] 5) regulating a pH value of mother liquor in which the L12CO3 is precipitated and separated in the step 4), and mixing the mother liquor with the adsorbed and purified solution, thereby realizing closed cycle of the process.
[0014] Moreover, in the method for comprehensive recycling of by-product slurry during PPS production, when the lithium-containing waste salt is dissolved and leached with an acidic aqueous solution in the step 2), the used acid is hydrochloric acid, quantities of the added hydrochloric acid and water are more than a theoretical quantity by 1-10%, and dissolving and leaching time is more than or equal to half an hour.
[0015] Moreover, in the method for comprehensive recycling of by-product slurry during PPS production, when the pH value of the leaching liquor is regulated in the step 3), used alkali is NaOH having a mass fraction more than or equal to 5%, and a final regulated pH value is equal to 5.0-9.0.
[0016] Moreover, in the method for comprehensive recycling of by-product slurry during PPS production, an adsorbent used for adsorption and purification in the step
3) is activated carbon.
[0017] Moreover, in the method for comprehensive recycling of by-product slurry during PPS production, when the solution containing LiCl and NaCI only is
2018101954 05 Dec 2018 evaporated and concentrated in the step 4), a lithium ion concentration in the concentrated solution is more than or equal to 5 g/L, and the crystallized NaCl is washed with water having a liquid-solid ratio more than or equal to 0.5, so as to remove entrained lithium ions.
[0018] Moreover, in the method for comprehensive recycling of by-product slurry during PPS production, when the concentrated solution is precipitated to recover L12CO3 in the step 4), a used precipitator is Na2CC>3 having a mass fraction more than or equal to 10%, and precipitation reaction time is more than or equal to 5 min. Moreover, full stirring is performed in the process, and the precipitated L12CO3 is washed with water having a liquid-solid ratio more than or equal to 1, thereby removing entrained chloride ions.
[0019] Moreover, in the method for comprehensive recycling of by-product slurry during PPS production, when the pH value of the solution in which the L12CO3 is precipitated and separated in the step 5), a used acid is HC1 having a mass fraction more than or equal to 5%, a final regulated pH value is equal to 5.0-9.0, and the solution with regulated pH returns to the system and is mixed with the adsorbed and purified solution to be continuously evaporated and concentrated.
[0020] The present invention has advantages and positive effects as follows:
[0021] 1. The method in the present invention only relates to conventional operations such as precipitation, dissolution, filtration, adsorption and the like, so industrial production is easily realized.
[0022] 2. The NaCl product obtained in the present invention is high in product purity and can directly serve as a raw material for preparing caustic soda by virtue of ionic membrane electrolysis, thereby realizing effective coincidence with chlorine-alkali industry.
[0023] 3. The L12CO3 recovered in the present invention may directly serve as a commodity or be further converted into LiCl, thereby recycling a LiCl auxiliary during the PPS production and reducing the production cost of the PPS.
[0024] 4. The closed cycle is realized by the process in the present invention, so the NaCl and LiCl in the PPS by-product slurry may be totally recovered.
DESCRIPTION OF THE DRAWINGS [0025] FIG. 1 is a flow chart of a process for comprehensive recycling of PPS by-product slurry in embodiments;
2018101954 05 Dec 2018 [0026] FIG. 2 is an XRD spectrum of a dry waste salt containing NaCl, L12CO3 and the like after drying by-product slurry;
[0027] FIG. 3 is an XRD spectrum of a NaCl product obtained after evaporative crystallization and washing; and [0028] FIG. 4 is an XRD spectrum of a L12CO3 product obtained after precipitating and washing.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0029] The present invention is further described below in combination with the drawings and specific embodiments.
[0030] PPS by-product slurry is recycled through a process solution shown in FIG. 1. The slurry is subjected to reduced pressure distillation and drying to obtain a lithium-containing dry waste salt shown in FIG. 2. According to XRD (FIG. 3) and quantitative analysis of composition of the dry waste salt, contents of NaCl, L12CO3 and organic matters are respectively 84.6%, 7% and 6.8%, and other components account for 1.6%.
[0031] The dry waste salt is reacted and leached with a HCI solution at a liquid-solid ratio of 2.9, leaching time is 2 h, and a final pH value of the solution is controlled to be 3.2; then, the pH of leaching liquor is regulated with 5% of a NaOH solution, and a final pH value is controlled to be 6.8; and the solution with regulated pH is filtered to recover insoluble PPS oligomers, and the filtered solution is adsorbed and purified with activated carbon having 20-40 meshes, thereby removing dissolved organic components in the solution.
[0032] The adsorbed and purified solution is evaporated and concentrated to obtain NaCl, wherein water evaporation capacity is 71%, and single yield of the NaCl is 75.95%; and the crystallized NaCl is repeatedly washed and dried with water having a liquid-solid ratio of 1.0, and finally a NaCl product (FIG. 4) having purity of 99.94% is obtained.
[0033] The solution in which the NaCl is separated is added into a saturated Na2CO3 solution (Na2CO3 is excessive by 2%), full stirring is performed in the process, charging and stirring time is 20 min, single yield of precipitated Li2CO3 is 82.16%, and a mean particle size is 64.3 pm; and Li2CO3 is separated and repeatedly washed and dried with water having a liquid-solid ratio of 1.5, and finally a Li2CO3 product (FIG. 6) having purity of 99.81% is obtained.
2018101954 05 Dec 2018 [0034] The pH of the solution in which the L12CO3 is separated is regulated to 6.5 with 5% of NaOH solution, and the solution returns to the process and is mixed with the adsorbed and purified solution to be continuously evaporated and concentrated, thereby realizing mother liquor recycling and closed cycle of the process.
[0035] Technical solutions of embodiments or drawings in the present invention are shown and described above, and advantages of the present invention and effects of efficiently recovering the NMP, NaCl and LiCl from the PPS by-product slurry are achieved. It should be understood that, detailed description of the technical solutions in the present invention is illustrative and nonrestrictive in preferred embodiments. On the basis of reading the specification of the present invention, those skilled in the art may make improvements or transformations according to the above description. If regulation of the pH of the leaching liquor before filtration is modified as regulation of leaching liquor after filtration in the embodiments, all the improvements or transformations shall belong to the protection scope of attached claims in the present invention.
Claims (7)
1) adding Na2CO3 into PPS by-product slurry to destruct a complex formed by N-methyl pyrrolidone (NMP) and lithium, converting the lithium into Li2CO3, distilling and drying the slurry to separate and recover the NMP and water, and obtaining a dry waste salt containing oligomers such as NaCl, Li2CO3, NaoCO, and PPS;
1. A method for comprehensive recycling of by-product slurry during polyphenylene sulfide (PPS) production, comprising the following steps:
2. The method for comprehensive recycling of by-product slurry during polyphenylene sulfide (PPS) production according to claim 1, wherein when the lithium-containing waste salt is dissolved and leached with an acidic aqueous solution in the step 2), the used acid is hydrochloric acid, quantities of the added hydrochloric acid and water are more than a theoretical quantity by 1-10%, and dissolving and leaching time is more than or equal to half an hour.
2) adding an acid solution into the dry waste salt in the step 1) for reacting, dissolving and leaching, respectively converting Li2CO3 and Na2CC>3 into LiCl and NaCl, and dissolving to enter a liquid phase;
3. The method for comprehensive recycling of by-product slurry during polyphenylene sulfide (PPS) production according to claim 1, wherein when the pH value of the leaching liquor is regulated in the step 3), used alkali is NaOH having a mass fraction more than or equal to 5%, and a final regulated pH value is equal to 5.0-9.0.
2018101954 05 Dec 2018
3) regulating a pH value of leaching liquor in the step 2), filtering to remove insoluble components, adsorbing and purifying the liquid phase to remove dissolved organic components to obtain a solution containing LiCl and NaCl only;
4. The method for comprehensive recycling of by-product slurry during polyphenylene sulfide (PPS) production according to claim 1, wherein an adsorbent used for adsorption and purification in the step 3) is activated carbon.
4) evaporating and concentrating the solution containing LiCl and NaCl only in the step 3) to separate out the NaCl, and adding a NaoCO, solution into a concentrated solution after separating the NaCl to precipitate Li2CO3; and
5. The method for comprehensive recycling of by-product slurry during polyphenylene sulfide (PPS) production according to claim 1, wherein when the solution containing LiCl and NaCl only is evaporated and concentrated in the step 4), a lithium ion concentration in the concentrated solution is more than or equal to 5 g/L, and the crystallized NaCl is washed with water having a liquid-solid ratio more than or equal to 0.5, so as to remove entrained lithium ions.
5) regulating a pH value of mother liquor in which the Li2CO3 is precipitated and separated in the step 4), and mixing the mother liquor with the adsorbed and purified solution, thereby realizing closed cycle of the process.
6. The method for comprehensive recycling of by-product slurry during polyphenylene sulfide (PPS) production according to claim 1, wherein when the concentrated solution is precipitated to recover L12CO3 in the step 4), a used precipitator is Na2CO3 having a mass fraction more than or equal to 10%, and precipitation reaction time is more than or equal to 5 min; moreover, full stirring is performed in the process, and the precipitated LfiCCfi is washed with water having a liquid-solid ratio more than or equal to 1, thereby removing entrained chloride ions.
7. The method for comprehensive recycling of by-product slurry during polyphenylene sulfide (PPS) production according to claim 1, wherein when the pH value of the solution in which the Li2CO3 is precipitated and separated in the step 5), a used acid is HC1 having a mass fraction more than or equal to 5%, a final regulated pH value is equal to 5.0-9.0, and the solution with regulated pH returns to the system and is mixed with the adsorbed and purified solution to be continuously evaporated and concentrated.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2018101954A AU2018101954A4 (en) | 2016-10-21 | 2018-12-05 | Method for comprehensive recycling of by-product slurry during polyphenylene sulfide production |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610919243.4 | 2016-10-21 | ||
| PCT/CN2017/106950 WO2018072739A1 (en) | 2016-10-21 | 2017-10-20 | Method for comprehensive recycling of by-product slurry during polyphenylene sulfide production |
| AU2018101954A AU2018101954A4 (en) | 2016-10-21 | 2018-12-05 | Method for comprehensive recycling of by-product slurry during polyphenylene sulfide production |
Related Parent Applications (1)
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| PCT/CN2017/106950 Division WO2018072739A1 (en) | 2016-10-21 | 2017-10-20 | Method for comprehensive recycling of by-product slurry during polyphenylene sulfide production |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113680128A (en) * | 2021-07-27 | 2021-11-23 | 山东明化新材料有限公司 | Continuous washing and purifying system and purifying method for polyarylene sulfide resin |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113680128A (en) * | 2021-07-27 | 2021-11-23 | 山东明化新材料有限公司 | Continuous washing and purifying system and purifying method for polyarylene sulfide resin |
| CN113680128B (en) * | 2021-07-27 | 2023-06-06 | 山东明化新材料有限公司 | Continuous washing and purifying system and purifying method for polyarylene sulfide resin |
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