A process, system and application for electrolytic recovery of PTA from PET degradation liquid

Abstract

The present invention belongs to the technical field of PET degradation and recycling, and particularly relates to a process, system and application for electrolytically recovering PTA from PET degradation liquid. The process flow includes constructing an electrolysis system, introducing the PET degradation clear liquid from the material clear liquid tank into the electrolysis system, and draining the PTA generated by electrolysis together with the PET degradation clear liquid to the material concentrated liquid tank. The PTA solid is separated from the aqueous solution containing terephthalate through a membrane filtration device. The PTA solid re-enters the material concentrated liquid tank for enrichment, and then is filtered, washed and dried to obtain PTA. The filtrate enters the material clear liquid tank for cyclic electrolysis; the inorganic alkali liquid generated by electrolysis enters the alkali liquid storage tank to collect the generated inorganic alkali. This process and system enable the PTA generated by electrolysis to continuously flow out of the anode chamber along with the PET degradation clear liquid, reducing the deposition of PTA on the surface of the anode plate, solving the problem that the PTA generated during electrolysis is likely to deposit on the surface of the anode plate and then cause the interruption of the electrolysis reaction, and significantly improving the electrolysis efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of PET degradation and recycling, and particularly relates to a process, system and application for electrolytically recovering PTA from PET degradation solution. Background Art

[0002] Polyethylene terephthalate (PET) has excellent transparency, strength and chemical resistance, and is widely used in plastic bottles, food packaging, textiles and other fields. However, the large-scale use of PET materials also brings great pressure to the ecological environment. Therefore, realizing the green and effective recycling of PET is of great significance for achieving green environmental protection and sustainable development.

[0003] In order to realize the reuse of resources, waste PET products are mostly degraded to recycle the raw material monomer terephthalic acid (TPA). When degrading PET, PET depolymerizes in an alkaline solution to form terephthalate salts. Through steps such as decolorization, acid adjustment and filtration of the aqueous solution of terephthalate salts, highly pure refined terephthalic acid (PTA) can be obtained. The operation steps are cumbersome and the production efficiency is low.

[0004] To simplify the subsequent treatment steps, there have been studies on electrochemically catalyzing the precipitation of terephthalic acid from PET degradation solution. This method does not require the steps of water-soluble decolorization and acid adjustment, reduces the generation of wastewater, and has broad application prospects. However, in the actual electrolysis process, the electrochemically precipitated PTA is likely to deposit on the electrode surface as the electrolysis reaction proceeds, thus affecting the progress of the electrolysis reaction, even causing the electrolysis reaction to interrupt, unable to ensure the continuous progress of the electrolysis reaction, and reducing the electrolysis efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide a process, system and application for electrolytically recovering PTA from PET degradation solution. This process and system can reduce the deposition of PTA on the anode plate surface by continuously flowing the electrolytically generated PTA out of the anode chamber with the PET degradation clear solution, thereby solving the problem that the PTA generated during electrolysis is likely to deposit on the anode plate surface and then causing the interruption of the electrolysis reaction, and significantly improving the electrolysis efficiency.

[0006] In view of this, the first aspect of the present invention provides a process for electrolytically recovering PTA from PET degradation liquid, comprising: constructing an electrolysis system, wherein the electrolysis system is formed by connecting a plurality of electrolysis components in parallel, each electrolysis component is divided into an anode chamber and a cathode chamber by a cation exchange membrane, the anode chamber is equipped with an anode plate and a plate frame arranged on both sides of the anode plate to form an anode plate slot, and the cathode chamber is equipped with a cathode plate and a plate frame arranged on both sides of the cathode plate to form a cathode plate slot; introducing the PET degradation clear liquid into the anode plate slot, and simultaneously introducing a sodium salt or a potassium salt into the cathode plate slot The PET degradation solution is prepared by mixing terephthalate with hydrogen ions in the anode chamber to generate terephthalic acid, and the terephthalate is discharged from the anode plate tank along with the PET degradation solution to obtain a PET degradation slurry. The sodium ions or potassium ions in the PET degradation solution enter the cathode chamber through a cation exchange membrane to generate an inorganic base, and the inorganic base is discharged from the cathode plate tank along with the sodium salt or potassium salt solution. The PET degradation slurry is filtered through a filter membrane, and the obtained clarified filtrate is combined with the PET degradation solution and circulated into an electrolytic cell for electrolysis. The obtained concentrated slurry is subjected to solid-liquid separation, and the solid phase is collected and dried to obtain PTA.

[0007] The invention provides a process for electrolytically recovering PTA from PET degradation liquid. The process adopts an electrolysis system to electrolyze the PET degradation clear liquid. Specifically, the PET degradation clear liquid is introduced into an anode plate slot, terephthalate in the PET degradation clear liquid reacts with hydrogen ions on the surface of the anode plate to generate PTA through an electrolysis reaction, and the generated sodium ions or potassium ions enter the cathode plate slot through a cation exchange membrane and react with hydroxide ions on the cathode surface to form sodium hydroxide or potassium hydroxide; the PTA on the surface of the anode plate is discharged and collected along with the PET degradation clear liquid to obtain a PET degradation slurry containing PTA, the obtained PTA is filtered and recombined with the PET degradation slurry, the filtrate is recombined with the PET degradation clear liquid to be electrolyzed and then enters the electrolysis system, the PTA in the PET degradation slurry to be collected is enriched to a certain concentration, filtered, washed with water and dried to obtain PTA solid; the inorganic alkali solution generated in the cathode plate slot is discharged and recycled for reuse. The process provided by the present invention can realize the continuous electrolysis of PET degradation clear liquid, solves the problem that PTA produced by electrolysis is easily deposited on the surface of the anode plate and causes the electrolysis reaction to be interrupted, and is of great significance for realizing efficient and continuous electrolysis of PET degradation clear liquid.

[0008] In combination with the first aspect, the anode plate slot or cathode plate slot is a hollow plate slot, and two or more flow channels are arranged along the fluid flow direction, each flow channel is respectively provided with a pair of fluid inlet and outlet, wherein the flow channels are separated by arc-shaped corrugated isolation strips.

[0009] In combination with the first aspect, the plate frame is rectangular, the arc-shaped corrugated separator strip is arranged along the long side of the plate frame, and the curvature diameter of the arc-shaped corrugated separator strip is not less than the narrow-side dimension of the plate groove.

[0010] In combination with the first aspect, the average flow velocity of the PET degradation clear liquid in each flow channel is not less than 0.05 m / s; the ratio of the long side to the narrow side of the plate groove is 2 - 5:1, and the depth of the plate groove is 2 - 20 mm.

[0011] In combination with the first aspect, the PET degradation clear liquid is a degradation reaction liquid of PET, and its components include terephthalate, ethylene glycol, and inorganic base.

[0012] In combination with the first aspect, the pore diameter of the filter membrane is not greater than 0.5 μm.

[0013] In combination with the first aspect, before the electrolysis reaction starts, a sodium salt or potassium salt solution is introduced into the cathode plate groove.

[0014] The second aspect of the present invention provides a system for electrolytically recovering PTA from a PET degradation liquid, including: an electrolytic cell, the electrolytic cell includes end plates, and at least one group of an anode chamber and a cathode chamber separated by a cation exchange membrane, an anode plate and a plate frame are provided in the anode chamber, a cathode plate and a plate frame are provided in the cathode chamber, and the plate frames are respectively arranged on both sides of the anode plate and both sides of the cathode plate; a material clear liquid tank, which is connected to the anode chamber of the electrolytic cell through a pipeline equipped with a clear liquid pump, wherein terephthalate in the PET degradation clear liquid generates terephthalic acid in the anode chamber of the electrolytic cell; an alkali liquid storage tank, which is connected between the liquid outlet end and the liquid inlet end of the cathode chamber of the electrolytic cell for enriching the inorganic base formed in the cathode chamber; a material thick liquid tank, the material thick liquid tank is connected to the discharge port of the anode chamber for collecting the PET degradation slurry containing terephthalic acid derived from the anode chamber; and a filter membrane device for filtering the PET degradation slurry containing terephthalic acid in the material thick liquid tank, and the thick slurry of the filter membrane device flows back to the material thick liquid tank, and the clear liquid flows back to the material clear liquid tank.

[0015] The system for electrolytic recovery of PTA from PET degradation liquid provided by the present invention realizes efficient and continuous electrolysis of PET degradation clear liquid through the combined use of an electrolytic cell, a material clear liquid tank, an alkali liquid storage tank, a material concentrated liquid tank and a membrane filtration device, and solves the problem that PTA solids are easily deposited on the surface of the anode plate during electrolysis, resulting in the interruption of the electrolysis reaction. Specifically, the PET degradation clear liquid enters the electrolytic cell from the material clear liquid tank at a certain flow rate and undergoes an electrolysis reaction in the electrolytic cell. The hydrogen ions generated by the anode plate combine with the terephthalate ions in the PET degradation clear liquid to form terephthalic acid (PTA) and precipitate out (PTA has extremely low solubility in water, so it precipitates out). PTA forms a PET degradation slurry with the PET degradation clear liquid and flows from the electrolytic cell into the material concentrated liquid tank for collection. The PET degradation slurry in the material concentrated liquid tank is filtered through the membrane filtration device. The PTA intercepted by the membrane returns to the material concentrated liquid tank. After the PTA is enriched to a certain concentration, it is filtered, washed with water and dried to obtain PTA solids; the clear liquid re-enters the material clear liquid tank; the hydroxide ions generated at the cathode of the electrolytic cell form sodium hydroxide or potassium hydroxide solution with the sodium ions or potassium ions migrating to the cathode chamber through the cation exchange membrane and flow from the cathode chamber into the alkali liquid storage tank, realizing the recovery of inorganic alkali.

[0016] Combined with the second aspect, the cathode plate or the anode plate is placed in a hollow plate electrode tank formed with a plate electrode frame. At least 2 flow channels are arranged in the hollow plate electrode tank along the fluid flow direction, and each flow channel is respectively provided with a pair of fluid inlets and outlets. Among them, the flow channels are separated by arc-shaped corrugated isolation strips.

[0017] Combined with the second aspect, the plate electrode frame is rectangular, the arc-shaped corrugated isolation strip is arranged along the long side of the plate electrode frame, and the curvature diameter of the arc-shaped corrugated isolation strip is not less than the narrow side dimension of the plate electrode tank; the distance between the upstream edge of the plate and the upper edge of the plate electrode tank is greater than 1 / 8 of the length of the plate electrode tank, and the distance between the downstream edge of the plate and the lower edge of the plate electrode tank is not less than 1 / 4 of the length of the plate electrode tank.

[0018] Combined with the second aspect, the cathode plate or the anode plate is at least one of titanium plated with ruthenium, titanium plated with iridium or titanium plated with platinum; the voltage between the cathode plate and the anode plate is 1.5 - 5V.

[0019] The third aspect of the present invention provides a refined PTA, which is prepared by the process of electrolytic recovery of PTA from PET degradation liquid as described above or by using the system for electrolytic recovery of PTA from PET degradation liquid as described above.

[0020] The fourth aspect of the present invention provides an application of the above-mentioned refined PTA in the preparation of PET products, and the PET products include films, fibers and / or bottle chips made of PET material.

[0021] Exemplarily, the PET-based films prepared from refined PTA can be applied in multiple fields and industries, such as: food packaging films, heat-sealing films, and stretch films in the packaging industry, etc., and can also be used for electronic protection films, light diffusion films, and anti-reflection films in the electronic and optical fields, etc., and can also be used for industrial and functional films such as anti-static films, high-temperature resistant films, and electrical insulation films, etc., and can also be biaxially stretched films or uniaxially stretched films.

[0022] Exemplarily, the PET-based fibers prepared from refined PTA can also be applied in multiple fields and industries, such as: can be polyester filament or polyester staple fiber produced in the textile industry, can also be high-strength fibers, low-elastic fibers, or high-modulus fibers commonly used in the industrial field, or some functional fibers such as moisture-absorbing and sweat-releasing fibers, anti-static fibers, anti-ultraviolet fibers, or flame-retardant fibers, or pre-oriented yarns, fully drawn yarns, or drawn textured yarns obtained according to different production processes.

[0023] Exemplarily, the PET-based bottle chips prepared from refined PTA can also be applied in multiple fields and industries, such as: can be used to produce food packaging bottles, beverage packaging bottles, pharmaceutical packaging bottles, cosmetic packaging bottles, or industrial chemical bottles, can also be used to produce PET bottles with different structures such as single-layer PET bottles, multi-layer PET bottles, or composite PET bottles, and can also be used to produce PET bottles with specific functions such as anti-ultraviolet PET bottles, high-temperature resistant PET bottles, low-temperature resistant PET bottles, or high-barrier PET bottles. Description of the Drawings

[0024] Figure 1 Schematic diagram of the system process for electrolytic recovery of PTA from PET degradation liquid provided by the present invention;

[0025] Figure 2 Schematic diagram of the electrolytic cell structure in the system for electrolytic recovery of PTA from PET degradation liquid provided by the present invention;

[0026] Figure 3 Schematic cross-sectional view of the plate frame flow channel structure in the system for electrolytic recovery of PTA from PET degradation liquid provided by the present invention.

[0027] In the figure:

[0028] 010, material clear liquid tank;

[0029] 020, electrolytic cell; 021, cathode chamber; 022, anode chamber; 023, cation exchange membrane; 024, cathode plate; 025, anode plate; 026, plate frame; 027, sealing gasket; 028, end plate;

[0030] 030, material concentrated liquid tank;

[0031] 040, filter membrane device;

[0032] 050, lye storage tank;

[0033] 200, plate frame; 301, upstream edge of the plate; 302, downstream edge of the plate; 400, arc-shaped corrugated isolation strip; 401, first flow channel; 402, second flow channel; 501, flow channel inlet; 502, flow channel outlet. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] Please also read Figure 1 and Figure 2 The process for electrolytically recovering PTA from PET degradation liquid provided by the present invention is now described. The process comprises: constructing an electrolysis system, the electrolysis system is formed by a plurality of electrolysis components connected in parallel, each electrolysis component is divided into an anode chamber 022 and a cathode chamber 021 by a cation exchange membrane 023, the anode chamber is equipped with an anode plate 025 and a plate frame 026 arranged on both sides of the anode plate 025 to form an anode plate slot, the cathode chamber is equipped with a cathode plate 024 and a plate frame 026 arranged on both sides of the cathode plate 024 to form a cathode plate slot; introducing PET degradation clear liquid into the anode plate slot, and at the same time introducing a sodium salt or potassium salt solution into the cathode plate slot, electrolysis After the reaction occurs, the terephthalate in the PET degradation clear liquid reacts with hydrogen ions in the anode chamber 022 to generate terephthalic acid, and is discharged from the anode plate tank along with the PET degradation clear liquid and collected to obtain a PET degradation slurry. The sodium ions or potassium ions in the PET degradation clear liquid enter the cathode chamber 021 through the cation exchange membrane 023 to generate an inorganic base, and are discharged from the cathode plate tank along with the sodium salt or potassium salt solution. The PET degradation slurry is filtered through a filter membrane, and the obtained clarified filtrate is combined with the PET degradation clear liquid and circulated into the electrolytic cell for electrolysis. The obtained concentrated slurry is subjected to solid-liquid separation, and the solid phase is collected and dried to obtain PTA.

[0036] The present invention provides a process for electrolytically recovering PTA from PET degradation liquid. The electrolysis system is used to electrolyze the PET degradation clear liquid. Specifically, the PET degradation clear liquid is introduced into an anode plate slot, and terephthalate in the PET degradation clear liquid reacts with hydrogen ions on the surface of an anode plate 025 to generate PTA through an electrolysis reaction. Meanwhile, the generated sodium ions or potassium ions enter the cathode plate slot through a cation exchange membrane 023, and react with hydroxide ions on the surface of a cathode 024 to form sodium hydroxide or potassium hydroxide; the PTA on the surface of the anode plate 025 is discharged and collected along with the PET degradation clear liquid to obtain a PET degradation slurry containing PTA, and the obtained PTA is filtered and recombined with the PET degradation slurry, and the filtrate is recombined with the PET degradation clear liquid to be electrolyzed and then enters the electrolysis system. After the PTA in the PET degradation slurry to be collected is enriched to a certain concentration, it is filtered, washed with water and dried to obtain a PTA solid; the inorganic alkali solution generated in the cathode plate slot is discharged and recycled for reuse. The process provided by the present invention can realize the continuous electrolysis of PET degradation clear liquid, solves the problem that PTA produced by electrolysis is easily deposited on the surface of the anode plate and causes the electrolysis reaction to be interrupted, and is of great significance for realizing efficient and continuous electrolysis of PET degradation clear liquid.

[0037] As a specific embodiment of the process for electrolytically recovering PTA from PET degradation liquid of the present invention, a sealing gasket 027 is provided between the cation exchange membrane 023 and the plate frame 026, between the plate frame 026 and the cathode plate 024 or the anode plate 025, and between the plate frame 026 and the end plate 028 in the electrolytic cell 020 provided by the present invention. Each component is fixed by a through screw and nuts at both ends. For the specific structure, please refer to Figure 2 .

[0038] As a specific embodiment of the process for electrolytically recovering PTA from PET degradation liquid of the present invention, please refer to Figure 3 The anode plate slot or the cathode plate slot is a hollow plate slot, and at least two flow channels (a first flow channel 401 and a second flow channel 402) are arranged along the fluid flow direction, each flow channel is respectively provided with a pair of fluid inlet 501 and fluid outlet 502, wherein the flow channels are separated by arc-shaped corrugated isolation strips 400.

[0039] The arc-shaped corrugated isolation strips 400 are used to separate the flow channels. When the liquid flows in the electrode plate groove, it collides with the flow channel with a certain curvature separated by the arc-shaped corrugated isolation strips 400, thereby increasing its own flow velocity. The fluid with increased flow velocity has a greater impact force on the PTA generated on the surface of the anode plate 025, thereby preventing it from being stably deposited on the surface of the anode plate 025.

[0040] As a specific embodiment of the process for electrolytically recovering PTA from PET degradation liquid of the present invention, please refer to Figure 3, the plate frame 026 is rectangular, and the arc-shaped corrugated isolation strip 400 is arranged along the long side of the plate frame 200, and the curvature diameter of the arc-shaped corrugated isolation strip 400 is not less than the narrow side dimension of the plate groove. If the curvature diameter is too small, it will affect the turbulence effect of the generated PTA solid, causing local static points and making PTA prone to deposition.

[0041] As a specific implementation manner of the process for electrolytically recovering PTA from PET degradation liquid in the present invention, the average flow velocity of the PET degradation clear liquid in each flow channel is not less than 0.05 m / s; the ratio of the long side to the narrow side of the plate groove is 2 - 5:1, and the depth of the plate groove is 2 - 20 mm.

[0042] As a specific implementation manner of the process for electrolytically recovering PTA from PET degradation liquid in the present invention, the length of the long side of the plate frame 200 is 30 cm, the length of the narrow side is 10 cm, the length of the plate groove space is 26 cm, the width is 6 cm, the depth is 5 mm, and the curvature diameter of the arc-shaped corrugated isolation strip 400 is 6 cm.

[0043] As a specific implementation manner of the process for electrolytically recovering PTA from PET degradation liquid in the present invention, the PET degradation clear liquid is the degradation reaction liquid of PET, and the components include terephthalate, ethylene glycol and inorganic base. This PET degradation clear liquid is the material liquid after PET products are degraded, mainly including sodium terephthalate or potassium terephthalate, sodium hydroxide or potassium hydroxide, and ethylene glycol.

[0044] As a specific implementation manner of the process for electrolytically recovering PTA from PET degradation liquid in the present invention, the pore diameter of the filter membrane used for filtering the PET degradation slurry is not greater than 0.5 μm. For example, the filter membrane can be a hollow fiber filter membrane, a nanofiltration membrane or a microfiltration membrane. By filtering with the filter membrane, the PTA solid is separated from the PET degradation clear liquid to achieve the enrichment and recovery of PTA.

[0045] As a specific implementation manner of the process for electrolytically recovering PTA from PET degradation liquid in the present invention, before the electrolysis reaction starts, a sodium salt or potassium salt solution is introduced into the cathode plate groove. To ensure the ion balance and charge balance in the electrolysis system, before the electrolysis reaction starts, a sodium sulfate solution or a potassium sulfate solution is introduced into the cathode plate groove to generate sodium hydroxide or potassium hydroxide with the hydroxide ions generated at the cathode when the electrolysis reaction starts.

[0046] Please refer to Figure 1 and Figure 2, the system for electrolytic recovery of PTA from PET degradation solution provided by the present invention will be described. The system includes: an electrolytic cell 020, the electrolytic cell 020 includes end plates 028, and at least one set of an anode chamber 022 and a cathode chamber 021 separated by a cation exchange membrane 023. An anode plate 025 and a plate frame 026 are provided in the anode chamber 022, and a cathode plate 024 and a plate frame 026 are provided in the cathode chamber. The plate frames 026 are respectively arranged on both sides of the anode plate 025 and both sides of the cathode plate 024; a material clear liquid tank 010, which is connected to the anode chamber 022 of the electrolytic cell 020 through a pipeline equipped with a clear liquid pump. Among them, the terephthalate in the PET degradation clear liquid generates terephthalic acid in the anode chamber 022 of the electrolytic cell 020; an alkali liquid storage tank 050, which is connected between the liquid outlet end and the liquid inlet end of the cathode chamber 021 of the electrolytic cell 020, and is used to enrich the inorganic alkali formed in the cathode chamber 021; a material concentrated liquid tank 030, the material concentrated liquid tank 030 is connected to the discharge port of the anode chamber 022, and is used to collect the PET degradation slurry containing terephthalic acid derived from the anode chamber 022; and a filter membrane device 040, which is used to filter the PET degradation slurry containing terephthalic acid in the material concentrated liquid tank 030. The concentrated slurry of the filter membrane device 040 returns to the material concentrated liquid tank 030, and the clear liquid returns to the material clear liquid tank 010.

[0047] The system for electrolytic recovery of PTA from PET degradation solution provided by the present invention realizes the efficient and continuous electrolysis of PET degradation clear liquid through the coordinated use of the electrolytic cell 020, the material clear liquid tank 010, the alkali liquid storage tank 050, the material concentrated liquid tank 030 and the filter membrane device 040, and solves the problem that PTA solids are easily deposited on the surface of the anode plate during electrolysis, resulting in the interruption of the electrolysis reaction. Specifically, the PET degradation clear liquid enters the electrolytic cell 020 from the material clear liquid tank 010 at a certain flow rate and undergoes an electrolysis reaction in the electrolytic cell 020. The hydrogen ions generated by the anode plate 025 in the anode chamber 022 combine with the terephthalate ions in the PET degradation clear liquid to form terephthalic acid (PTA) and precipitate (PTA has extremely low solubility in water, so it precipitates). PTA forms a PET degradation slurry with the PET degradation clear liquid and flows into the material concentrated liquid tank 030 from the electrolytic cell 020 for collection. The PET degradation slurry in the material concentrated liquid tank 030 is filtered through the filter membrane device 040. The PTA intercepted by the filter membrane returns to the material concentrated liquid tank 030. After PTA is enriched to a certain concentration, it is filtered, washed with water and dried to obtain PTA solids; the clear liquid re-enters the material clear liquid tank 010; the hydroxide ions generated by the cathode 024 of the electrolytic cell 020 form sodium hydroxide or potassium hydroxide solution with the sodium ions or potassium ions migrating to the cathode chamber 021 through the cation exchange membrane 023, and flow into the alkali liquid storage tank 050 from the cathode chamber 021 to realize the recovery of inorganic alkali.

[0048] As a specific embodiment of the system for electrolytic recovery of PTA from PET degradation solution of the present invention, please refer toFigure 3 , the cathode plate 024 or the anode plate 025 is placed in the hollow plate groove formed with the plate frame 200. At least two flow channels (the first flow channel 401 and the second flow channel 402) are arranged in the hollow plate groove along the fluid flow direction. Each flow channel is respectively provided with a pair of fluid inlets 501 and fluid outlets 502. Among them, the flow channels are separated by an arc-shaped corrugated isolation strip 400.

[0049] As a specific embodiment of the system for electrolytically recovering PTA from PET degradation liquid of the present invention, the plate frame 200 is rectangular. The arc-shaped corrugated isolation strip 400 is arranged along the long side of the plate frame 200, and the curvature diameter of the arc-shaped corrugated isolation strip 400 is not less than the narrow side dimension of the plate groove; the distance between the upstream edge 301 of the plate and the upper edge of the plate groove is greater than 1 / 8 of the length of the plate groove, and the distance between the downstream edge 302 of the plate and the lower edge of the plate groove is not less than 1 / 4 of the length of the plate groove.

[0050] As a specific embodiment of the system for electrolytically recovering PTA from PET degradation liquid of the present invention, the long side length of the plate frame 200 is 30 cm, the narrow side length is 10 cm, the inner length of the groove is 26 cm, the width is 6 cm, and the depth is 5 mm. The distance between the upstream edge 301 of the plate and the upper edge of the plate groove is 3.5 cm, and the distance between the downstream edge 302 of the plate and the lower edge of the plate groove is 6.5 cm.

[0051] As a specific embodiment of the system for electrolytically recovering PTA from PET degradation liquid of the present invention, the cathode plate 024 or the anode plate 025 is at least one of titanium coated with ruthenium, titanium coated with iridium, or titanium coated with platinum; the voltage between the cathode plate 024 and the anode plate 025 is 1.5 - 5V.

[0052] The following is an illustration of the process and system for electrolytically recovering PTA from PET degradation liquid provided by the present invention through specific embodiments:

[0053] Using 25 kg of PET degradation clear liquid as the raw material, the PET degradation clear liquid is an aqueous solution of PET degradation products, and the contents of sodium terephthalate, ethylene glycol, and sodium hydroxide are 10.5%, 1.2%, and 0.32% respectively (the theoretical yield of PTA is 2.075 kg). Under normal temperature conditions, the PET degradation clear liquid is introduced into the anode chamber 022 of the electrolytic cell 020 at a flow rate of 1.8 L / min. The hydrogen ions generated by the anode plate 025 combine with the terephthalic acid ions in the PET degradation clear liquid to form terephthalic acid (PTA) and precipitate. The PET degradation clear liquid containing PTA solid flows into the material concentrated liquid tank 030, and is collected as PET degradation slurry. The PET degradation slurry is filtered through the hollow fiber filter membrane of the filter membrane device 040. The filtered filtrate, the aqueous solution of sodium terephthalate, enters the material clear liquid tank 010, and the PTA intercepted by the filter membrane re-enters the material concentrated liquid tank 030; The alkali liquid storage tank 050 contains 25 kg of sodium sulfate solution with a mass fraction of 0.1%, and enters the cathode chamber 021 of the electrolytic cell 020 at a flow rate of 1.8 L / min. During the electrolysis process, the plate voltage is set to 2 V and the current is 77.0 A, and the current is kept constant during the electrolysis process. After 9 h of electrolysis reaction, the plate voltage rises to 2.2 V, indicating that the deposition amount of the generated PTA on the surface of the anode plate 025 is very small and will not affect the electrolysis reaction. The PET degradation slurry in the material concentrated liquid tank 030 is filtered, washed with water, and dried to obtain 2.05 kg of PTA solid, and the recovery rate reaches 98.8%.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process for electrolytically recovering PTA from PET degradation liquid, characterized in that, include: Constructing an electrolysis system, wherein the electrolysis system is formed by connecting a plurality of electrolysis components in parallel, each electrolysis component is divided into an anode chamber and a cathode chamber by a cation exchange membrane, the anode chamber is equipped with an anode plate and a plate frame arranged on both sides of the anode plate to form an anode plate slot, and the cathode chamber is equipped with a cathode plate and a plate frame arranged on both sides of the cathode plate to form a cathode plate slot; The PET degradation clear liquid is introduced into the anode plate tank, and the sodium salt or potassium salt solution is introduced into the cathode plate tank. After the electrolysis reaction occurs, the terephthalate in the PET degradation clear liquid reacts with the hydrogen ions in the anode chamber to generate terephthalic acid, and is discharged from the anode plate tank along with the PET degradation clear liquid to obtain a PET degradation slurry. The sodium ions or potassium ions in the PET degradation clear liquid enter the cathode chamber through the cation exchange membrane to generate an inorganic base, and are discharged from the cathode plate tank along with the sodium salt or potassium salt solution. The PET degradation slurry is filtered through a filter membrane, the obtained clarified filtrate is combined with the PET degradation clear liquid, and circulated into an electrolytic cell for electrolysis, the obtained concentrated slurry is subjected to solid-liquid separation, the solid phase is collected and dried to obtain PTA; The anode plate slot or cathode plate slot is a hollow plate slot, and two or more flow channels are arranged along the fluid flow direction, and each flow channel is respectively provided with a pair of fluid inlet and outlet, wherein the flow channels are separated by arc-shaped corrugated isolation strips, the plate frame is rectangular, the arc-shaped corrugated isolation strips are arranged along the long side of the plate frame, and the curvature diameter of the arc-shaped corrugated isolation strips is not less than the narrow side size of the plate slot.

2. The process for electrolytically recovering PTA from PET degradation solution as claimed in claim 1, characterized in that: The average flow rate of the PET degradation clear liquid in each flow channel is not less than 0.05 m / s; The ratio of the long side to the narrow side of the electrode plate groove is 2-5:1, and the depth of the electrode plate groove is 2-20 mm.

3. The process for electrolytically recovering PTA from PET degradation liquid as claimed in claim 1, wherein, The PET degradation clear liquid is a PET degradation reaction liquid, and its components include terephthalate, ethylene glycol and inorganic alkali; the pore size of the filter membrane is not greater than 0.5 μm; before the electrolysis reaction starts, a sodium salt or potassium salt solution is introduced into the cathode plate slot.

4. A system for electrolytically recovering PTA from PET degradation liquid, characterized in that, include: An electrolytic cell, comprising an end plate, and at least one group of anode chambers and cathode chambers separated by a cation exchange membrane, wherein an anode plate and a plate frame are arranged in the anode chamber, and a cathode plate and a plate frame are arranged in the cathode chamber, wherein the plate frames are arranged on both sides of the anode plate and the cathode plate, respectively; the cathode plate or the anode plate is placed in a hollow plate slot formed with the plate frame, wherein at least two flow channels are arranged in the hollow plate slot along the direction of fluid flow, and each flow channel is provided with a pair of fluid inlet and outlet, wherein each flow channel is separated by an arc-shaped corrugated isolation strip, the plate frame is rectangular, the arc-shaped corrugated isolation strip is arranged along the long side of the plate frame, and the curvature diameter of the arc-shaped corrugated isolation strip is not less than the narrow side size of the plate slot; A material clear liquid tank is connected to the anode chamber of the electrolytic cell through a pipeline equipped with a clear liquid pump, wherein terephthalate in the PET degradation clear liquid generates terephthalic acid in the anode chamber of the electrolytic cell; An alkali solution storage tank is connected between the liquid outlet end and the liquid inlet end of the cathode chamber of the electrolytic cell for enriching the inorganic alkali formed in the cathode chamber; A material concentrated solution tank, the material concentrated solution tank is connected to the discharge port of the anode chamber for collecting the PET degradation slurry containing terephthalic acid derived from the anode chamber; and A filter membrane device is used for filtering the PET degradation slurry containing terephthalic acid in the material concentrated solution tank, and the concentrated slurry of the filter membrane device flows back to the material concentrated solution tank, and the clear liquid flows back to the material clear liquid tank.

5. The system for electrolytically recovering PTA from PET degradation liquid according to claim 4, characterized in that, The distance between the upstream edge of the electrode plate and the upper edge of the electrode plate groove is greater than 1 / 8 of the length of the electrode plate groove, and the distance between the downstream edge of the electrode plate and the lower edge of the electrode plate groove is not less than 1 / 4 of the length of the electrode plate groove.

6. The system for electrolytically recovering PTA from PET degradation liquid according to claim 4, characterized in that, The cathode plate or the anode plate is at least one of titanium plated with ruthenium, titanium plated with iridium or titanium plated with platinum; the voltage between the cathode plate and the anode plate is 1.5 - 5V.

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