Process and system for electrolytically recovering PTA from PET degradation liquid and application

Abstract

The invention belongs to the technical field of PET (Polyethylene Terephthalate) degradation and recovery, and particularly relates to a process and a system for electrolytically recovering PTA (Pure Terephthalic Acid) from PET degradation liquid and application. The technological process comprises the following steps: constructing an electrolysis system, introducing PET degradation clear liquid into the electrolysis system from a material clear liquid tank, draining PTA generated by electrolysis and the PET degradation clear liquid into a material concentrated liquid tank, filtering by a filter membrane device to separate PTA solid from an aqueous solution containing terephthalic acid salt, re-entering the PTA solid into the material concentrated liquid tank for enrichment, and then filtering, washing and drying to obtain PTA, the filtrate enters a material clear liquid tank for circulating electrolysis; inorganic alkali liquor generated by electrolysis enters an alkali liquor storage tank, and generated inorganic alkali is collected. According to the process and the system, PTA generated by electrolysis continuously flows out of the anode chamber along with the PET degradation clear liquid, deposition of the PTA on the surface of the anode plate is reduced, the problem that the PTA generated in the electrolysis process is easily deposited on the surface of the anode plate to cause interruption of the electrolysis reaction is solved, and the electrolysis efficiency is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of PET degradation and recovery, and particularly relates to a process, system and application of electrolytically recovering PTA from PET degradation liquid. 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, achieving green and effective recycling of PET is of great significance to achieving green environmental protection and sustainable development.

[0003] In order to achieve resource reuse, waste PET products are often degraded to recover the raw material monomer terephthalic acid (TPA). When PET is degraded, PET depolymerizes in an alkaline solution to generate terephthalate. The aqueous solution of terephthalate is decolorized, acidified and filtered to obtain purified terephthalic acid (PTA) with high purity. The operation steps are cumbersome and the production efficiency is low.

[0004] In order to simplify the subsequent processing steps, there have been studies on the use of electrochemical catalysis to precipitate terephthalic acid from PET degradation liquid. This method does not require the use of water-soluble decolorization and acid adjustment steps, reduces the generation of wastewater, and has broad application prospects. However, in the actual electrolysis process, the PTA precipitated by electrolysis is easily deposited on the electrode surface as the electrolysis reaction proceeds, thereby affecting the electrolysis reaction and even causing the electrolysis reaction to be interrupted, making it impossible to ensure the continuous progress of the electrolysis reaction, thereby reducing the electrolysis efficiency. Summary of the invention

[0005] The object of the present invention is to provide a process, system and application for electrolytically recovering PTA from PET degradation liquid. The process and system reduce the deposition of PTA on the surface of the anode plate by allowing the PTA generated by electrolysis to continuously flow out of the anode chamber along with the PET degradation clear liquid, thereby solving the problem that the PTA generated during the electrolysis process is easily deposited on the surface of the anode plate and thus causes the electrolysis reaction to be interrupted, and significantly improves 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 pole plate frame is rectangular, the arc-shaped corrugated isolation strips are arranged along the long sides of the pole plate frame, and the curvature diameter of the arc-shaped corrugated isolation strips is not less than the narrow side size of the pole plate slot.

[0010] In combination with the first aspect, 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.

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

[0012] In combination with the first aspect, the pore size of the filter membrane is no greater than 0.5 μm.

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

[0014] The second aspect of the present invention provides a system for electrolytically recovering PTA from PET degradation liquid, comprising: an electrolytic cell, the electrolytic cell comprising an end plate, and at least one group of anode chamber and cathode chamber separated by a cation exchange membrane, the anode chamber is equipped with an anode plate and a plate frame, the cathode chamber is equipped with a cathode plate and a plate frame, the plate frames are respectively arranged on both sides of the anode plate and the cathode plate; 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 the terephthalate in the PET degradation clear liquid is Terephthalic acid is generated in the anode chamber of the electrolytic cell; an alkali solution storage tank is connected between the liquid outlet and liquid inlet of the cathode chamber of the electrolytic cell and is used to enrich the inorganic alkali formed in the cathode chamber; a material concentrate tank is connected to the discharge port of the anode chamber and is used to collect the PET degradation slurry containing terephthalic acid discharged from the anode chamber; and a filter membrane device is used to filter the PET degradation slurry containing terephthalic acid in the material concentrate tank, and the concentrated slurry of the filter membrane device flows back to the material concentrate tank, and the clear liquid flows back to the material clear liquid tank.

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

[0016] In combination with the second aspect, the cathode plate or anode plate is placed in a hollow plate groove formed with the plate frame, and at least two flow channels are arranged in the hollow plate groove 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.

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

[0018] In combination 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; and 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 obtained according to the above-mentioned process for electrolytically recovering PTA from PET degradation liquid or using the above-mentioned system for electrolytically recovering PTA from PET degradation liquid.

[0020] A fourth aspect of the present invention provides a use of the above-mentioned refined PTA in the preparation of PET products, wherein the PET products include films, fibers and / or bottle flakes made of PET material.

[0021] Illustratively, films made of PET prepared from refined PTA can be used in multiple fields and industries, such as food packaging films, heat-sealing films and stretch films in the packaging industry, electronic protective films, light diffusion films and anti-reflective films in the electronics and optics fields, industrial and functional films such as antistatic films, high temperature resistant films and electrical insulation films, and can also be biaxially stretched films or uniaxially stretched films.

[0022] Illustratively, fibers made of PET prepared from refined PTA can also be used in multiple fields and industries, for example: they can be polyester filaments or polyester staple fibers produced by the textile industry, they can also be high-strength fibers, low-elasticity fibers or high-modulus fibers commonly used in the industrial field, or they can be some functional fibers such as moisture wicking fibers, antistatic fibers, anti-ultraviolet fibers or flame retardant fibers, or they can be pre-oriented yarns, fully stretched yarns or stretched deformed yarns obtained according to different production processes.

[0023] Illustratively, PET bottle flakes prepared from refined PTA can also be used in multiple fields and industries, for example: they can be used to produce food packaging bottles, beverage packaging bottles, medicine packaging bottles, cosmetic packaging bottles or industrial chemical bottles, and 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 UV-resistant PET bottles, high-temperature resistant PET bottles, low-temperature resistant PET bottles or high-barrier PET bottles. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the system flow for electrolytically recovering PTA from PET degradation liquid provided by the present invention; Figure 2 A schematic diagram of the structure of an electrolytic cell in a system for electrolytically recovering PTA from PET degradation liquid provided by the present invention; Figure 3 The present invention provides a schematic cross-sectional view of the plate frame flow channel structure in the system for electrolytically recovering PTA from PET degradation liquid provided by the present invention.

[0025] In the figure: 010. Material clearing tank; 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; 030, material concentrate tank; 040. Filter membrane device; 050, lye storage tank; 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

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 .

[0030] 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.

[0031] 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.

[0032] As a specific embodiment of the process for electrolytically recovering PTA from PET degradation liquid of the present invention, please refer to Figure 3The plate frame 026 is rectangular, the arc-shaped corrugated spacer strip 400 is arranged along the long side of the plate frame 200, and the curvature diameter of the arc-shaped corrugated spacer strip 400 is not less than the narrow side size of the plate slot. Too small a curvature diameter will affect the turbulence effect of the generated PTA solid, causing local static points and making PTA easy to deposit.

[0033] As a specific implementation method of the process for electrolytically recovering PTA from PET degradation liquid of the present invention, 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.

[0034] As a specific implementation of the process of 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 length of the plate slot 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.

[0035] As a specific embodiment of the process for electrolytically recovering PTA from PET degradation liquid of the present invention, the PET degradation clear liquid is a degradation reaction liquid of PET, and its components include terephthalate, ethylene glycol and inorganic alkali. The PET degradation clear liquid is a material liquid after the PET product is degraded, and mainly includes sodium terephthalate or potassium terephthalate, sodium hydroxide or potassium hydroxide and ethylene glycol.

[0036] As a specific embodiment of the process of electrolytically recovering PTA from PET degradation liquid of the present invention, the pore size 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 nano filter membrane or a micron filter membrane, and the PTA solid is separated from the PET degradation clear liquid by filtration of the filter membrane to achieve the enrichment and recovery of PTA.

[0037] As a specific embodiment of the process for electrolytically recovering PTA from PET degradation liquid of the present invention, before the electrolysis reaction starts, a sodium salt or potassium salt solution is introduced into the cathode plate slot. 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 slot to generate sodium hydroxide or potassium hydroxide with the hydroxide generated at the cathode when the electrolysis reaction starts.

[0038] Please also read Figure 1 and Figure 2The system for electrolytically recovering PTA from PET degradation liquid provided by the present invention is now described. The system comprises: an electrolytic cell 020, the electrolytic cell 020 comprises an end plate 028, and at least one set of anode chamber 022 and 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, and the plate frame 026 is provided on both sides of the anode plate 025 and the cathode plate 024 respectively; a material clear liquid tank 010 is connected to the anode chamber 022 of the electrolytic cell 020 through a pipeline equipped with a clear liquid pump, wherein the terephthalate in the PET degradation clear liquid is discharged in the electrolytic cell 020. The terephthalic acid is generated in the anode chamber 022; the alkali solution storage tank 050 is connected between the liquid outlet and the liquid inlet of the cathode chamber 021 of the electrolytic cell 020, and is used to enrich the inorganic alkali formed in the cathode chamber 021; the material concentrated solution tank 030, the material concentrated solution 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 discharged from the anode chamber 022; and the filter membrane device 040 is used to filter the PET degradation slurry containing terephthalic acid in the material concentrated solution tank 030, and the concentrated slurry of the filter membrane device 040 is refluxed to the material concentrated solution tank 030, and the clear liquid is refluxed to the material clear liquid tank 010.

[0039] The system for electrolytically recovering PTA from PET degradation liquid provided by the present invention realizes efficient and continuous electrolysis of PET degradation liquid through the coordinated use of electrolytic cell 020, material liquid tank 010, alkali solution storage tank 050, material concentrated liquid tank 030 and filter membrane device 040, and solves the problem that PTA solid is easily deposited on the surface of the anode plate during the electrolysis process, resulting in interruption of the electrolysis reaction. Specifically, the PET degradation liquid enters the electrolytic cell 020 from the material liquid tank 010 at a certain flow rate, and an electrolysis reaction occurs 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 liquid to generate terephthalic acid (PTA) and precipitate (PTA has extremely low solubility in water, so it precipitates). PTA and the PET degradation liquid form PET degradation slurry, which flows from the electrolytic cell 020 into the material concentrated liquid tank 030 for collection. The PET degradation slurry in the material concentrated liquid tank 030 is collected. The PET degradation slurry is filtered through the filter membrane device 040, and the PTA retained by the filter membrane is returned 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 solid; the clear liquid re-enters the material clear liquid tank 010; the hydroxide ions generated by the cathode 024 of the electrolytic cell 020 and the sodium ions or potassium ions that migrate to the cathode chamber 021 through the cation exchange membrane 023 form sodium hydroxide or potassium hydroxide solution, and flow from the cathode chamber 021 into the alkali solution storage tank 050 to realize the recovery of inorganic alkali.

[0040] As a specific embodiment of the system for electrolytically recovering PTA from PET degradation liquid of the present invention, please refer to Figure 3 The cathode plate 024 or the anode plate 025 is placed in a hollow plate groove formed with the plate frame 200, and at least two flow channels (a first flow channel 401 and a second flow channel 402) are arranged in the hollow plate groove along the fluid flow direction, and 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.

[0041] As a specific embodiment of the system for electrolytically recovering PTA from PET degradation liquid of the present invention, the electrode frame 200 is rectangular, the arc-shaped corrugated isolation strips 400 are arranged along the long side of the electrode frame 200, and the curvature diameter of the arc-shaped corrugated isolation strips 400 is not less than the narrow side size of the electrode plate groove; the distance between the upstream edge 301 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 302 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.

[0042] 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, 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.

[0043] 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 plated with ruthenium, titanium plated with iridium or titanium plated with platinum; the voltage between the cathode plate 024 and the anode plate 025 is 1.5-5V.

[0044] The process and system for electrolytically recovering PTA from PET degradation liquid provided by the present invention are described below by means of specific embodiments: 25 kg of PET degradation supernatant is used as the raw material. The PET degradation supernatant is an aqueous solution of PET degradation products, wherein 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 generate terephthalic acid (PTA) and precipitate, and the PET degradation clear liquid containing PTA solid flows into the material concentrated liquid tank 030 and is collected as the PET degradation slurry. The PET degradation slurry is filtered through the hollow fiber filter membrane of the filter membrane device 040, and the filtrate sodium terephthalic acid salt solution enters the material clear liquid tank 010, and the PTA retained by the filter membrane re-enters the material concentrated liquid tank 030; the alkali liquid storage tank 050 is filled with 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 2V, the current is 77.0A, and the current is kept unchanged during the electrolysis process. After 9 hours of electrolysis, the plate voltage increased to 2.2 V, indicating that the amount of PTA generated on the surface of the anode plate 025 was very small and would not affect the electrolysis reaction. The PET degradation slurry in the material concentrate tank 030 was filtered, washed and dried to obtain 2.05 kg of PTA solid, with a recovery rate of 98.8%.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should 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.

2. The process for electrolytically recovering PTA from PET degradation solution as claimed in claim 1, characterized in that: 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.

3. The process for electrolytically recovering PTA from PET degradation solution as claimed in claim 2, characterized in that: 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; 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.

4. The process for electrolytically recovering PTA from PET degradation solution as claimed in claim 1, characterized in that: 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.

5. A system for electrolytically recovering PTA from PET degradation liquid, characterized in that: include: The electrolytic cell comprises an end plate, and at least one group of anode chamber and cathode chamber 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, and the plate frames are arranged on both sides of the anode plate and the cathode plate respectively; 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 connected between the liquid outlet and liquid inlet of the cathode chamber of the electrolytic cell and used for enriching the inorganic alkali formed in the cathode chamber; A material concentrate tank, the material concentrate tank is connected to the discharge port of the anode chamber and is used to collect the PET degradation slurry containing terephthalic acid discharged from the anode chamber; and The filter membrane device is used to filter the PET degradation slurry containing terephthalic acid in the material concentrated liquid tank. The concentrated liquid of the filter membrane device flows back to the material concentrated liquid tank, and the clear liquid flows back to the material clear liquid tank.

6. The system for electrolytically recovering PTA from PET degradation liquid as claimed in claim 5, characterized in that: The cathode plate or anode plate is placed in a hollow plate groove formed with the plate frame, and at least two flow channels are arranged in the hollow plate groove along the fluid flow direction, each flow channel is provided with a pair of fluid inlet and outlet, wherein the flow channels are separated by arc-shaped corrugated isolation strips.

7. The system for electrolytically recovering PTA from PET degradation liquid as claimed in claim 6, characterized in that: 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; the distance between the upstream edge of the plate and the upper edge of the plate slot is greater than 1 / 8 of the length of the plate slot, and the distance between the downstream edge of the plate and the lower edge of the plate slot is not less than 1 / 4 of the length of the plate slot.

8. The system for electrolytically recovering PTA from PET degradation liquid as claimed in claim 5, 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.

9. Refined PTA, characterized in that It is prepared by the process for electrolytically recovering PTA from PET degradation liquid as described in any one of claims 1 to 4 or by the system for electrolytically recovering PTA from PET degradation liquid as described in any one of claims 5 to 8.

10. Use of the refined PTA according to claim 9 in preparing PET products, characterized in that: The PET products include films, fibers and / or bottle flakes made of PET material.

Images