Continuous production system and process for efficiently recovering PTA from waste pet, and use thereof

Abstract

Provided are a continuous production system and process for efficiently recovering PTA from waste PET, and the use thereof. The continuous production system and process for efficiently recovering PTA from waste PET achieve the continuous production of PTA, by means of the mutual cooperation of an enzymolysis unit, a first solid-liquid separation unit, a filter cake dissolution and decolorization unit, an electrolysis unit, a second solid-liquid separation unit and a recrystallization unit, by using waste PET as the raw material. Moreover, by adjusting the structure of a flow channel in an electrolysis assembly of the electrolysis unit, the deposition of TA on the surface of an anode plate generated by means of electrolysis is avoided, thereby achieving the continuous operation of the whole degradation recovery process.

Description

Continuous production systems, processes, and applications for efficient PTA recovery from waste PET.

[0001] This patent application claims priority to Chinese Patent Application No. CN202510293682.8, filed on March 13, 2025. The disclosure of the earlier application is incorporated herein by reference in its entirety. Technical Field

[0002] This application belongs to the field of waste PET recycling technology, and specifically relates to a continuous production system, process and application for efficiently recovering PTA from waste PET. Background Technology

[0003] Polyethylene terephthalate (PET) is widely used in many fields, including plastic bottles, food packaging, and textiles, due to its excellent transparency, strength, and chemical resistance. However, the widespread use of PET materials has placed enormous pressure on the ecological environment. Therefore, achieving green recycling and effective utilization of PET is of vital importance to promoting green environmental protection and sustainable development.

[0004] To promote resource recycling, waste PET products are typically recycled to recover the raw material monomer terephthalic acid (TA) through degradation processes. Current recycling processes are mostly intermittent. For example, waste PET is first chemically degraded into terephthalate and ethylene glycol, and then the terephthalate undergoes decolorization, acidification, and filtration to obtain high-purity refined terephthalic acid (PTA). However, this series of operations is complex and inefficient. Some research has explored obtaining higher-purity TA through the electrolysis of terephthalate solutions, but this process is still intermittent, requiring the terephthalate solution as the raw material for electrolysis, making it impossible to directly use waste PET as the initial raw material for the entire process. Furthermore, in actual electrolysis, the electrolyzed TA easily deposits on the electrode surface, affecting the continuity of the electrolysis reaction and potentially causing it to be interrupted, thus compromising the continuity of the electrolysis process and resulting in low efficiency.

[0005] Therefore, there is an urgent need for a process that can directly and continuously recover high-purity PTA from waste PET, thereby achieving continuous recycling from "waste PET to PTA". Technical issues

[0006] The purpose of this application is to provide a continuous production system and process for efficiently recovering PTA directly from waste PET. The continuous production system includes an enzymatic hydrolysis unit, a solid-liquid separation unit, an electrolysis unit, a recrystallization unit, and an ethylene glycol recovery unit. Through specific connections and coordination between the units and a special design of the electrolysis component structure in the electrolysis unit, continuous production from waste PET to PTA is achieved, while ethylene glycol is recovered. Technical solutions

[0007] In view of this, the first aspect of this application provides a continuous production system for efficiently recovering PTA from waste PET, the continuous production system comprising:

[0008] Multiple enzymatic hydrolysis units are configured to sequentially perform enzymatic hydrolysis of PET to obtain a slurry containing TA alkaline salts;

[0009] A processing unit comprising a first solid-liquid separation unit, a filter cake dissolution and decolorization unit, an electrolysis unit, a second solid-liquid separation unit, and a recrystallization unit connected in sequence; the processing unit is used to perform solid-liquid separation, dissolution and decolorization, and electrolysis of the slurry containing TA alkaline salt to obtain crude TA slurry, and then to perform solid-liquid separation and recrystallization of the crude TA slurry to obtain PTA; and

[0010] The switching control unit is configured to: connect the processing unit to the first enzymatic hydrolysis unit to initiate the processing operation when the first enzymatic hydrolysis unit completes the PET hydrolysis reaction; during the processing operation of the processing unit on the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit performs the PET hydrolysis reaction; and in response to the processing unit completing the processing operation on the first enzymatic hydrolysis unit, switch the processing unit to be connected to the second enzymatic hydrolysis unit, so that the processing unit cyclically connects each enzymatic hydrolysis unit to achieve continuous processing.

[0011] The electrolysis unit consists of multiple electrolysis components connected in parallel. Each electrolysis component is divided into an anode chamber and a cathode chamber by a cation exchange membrane. An anode plate and electrode frames arranged on both sides of the anode plate are provided in the anode chamber to form an anode plate groove. A cathode plate and electrode frames arranged on both sides of the cathode plate are provided in the cathode chamber to form a cathode plate groove. A TA alkaline salt solution enters the electrolysis unit from the anode chamber. Crude TA slurry is recovered in the anode plate groove, and the alkaline solution is recovered in the cathode plate groove. The anode and cathode plate grooves are hollow plate grooves with two or more flow channels arranged along the fluid flow direction. Each flow channel has a pair of fluid inlets and outlets. Adjacent flow channels are separated by arc-shaped corrugated isolation strips perpendicular to the corresponding anode or cathode plate.

[0012] The continuous production system for efficiently recovering PTA from waste PET provided in this application includes multiple enzymatic hydrolysis units, each connected to a first solid-liquid separation unit. These units continuously supply the first solid-liquid separation unit with slurry containing TA alkaline salts obtained from enzymatic hydrolysis of PET, ensuring continuous production. After the enzymatic hydrolysis units are connected to the first solid-liquid separation unit, the TA alkaline salt-containing slurry enters the first solid-liquid separation unit for solid-liquid separation. The separated TA alkaline salt solids enter a filter cake dissolution and decolorization unit for dissolution, decolorization, impurity removal, and filtration. The resulting TA alkaline salt solution enters an electrolysis unit, where crude TA slurry is recovered in the anode plate tank, and an alkaline solution is recovered in the cathode plate tank. The obtained crude TA slurry is filtered by a second solid-liquid separation unit to collect solid crude TA, which is then refined into PTA through a recrystallization unit.

[0013] In conjunction with the first aspect, the first solid-liquid separation unit is used to separate the TA basic salt from the slurry containing TA basic salt; the filter cake dissolving and decolorizing unit is used to dissolve, decolorize and filter the TA basic salt to obtain a TA basic salt solution; the second solid-liquid separation unit is used to separate the crude TA from the crude TA slurry; and the recrystallization unit is used to refine the crude TA.

[0014] In conjunction with the first aspect, the continuous production system further includes a distillation unit connected to the solution side of the first solid-liquid separation unit, which is used to recover and reuse ethylene glycol in the solution.

[0015] The second aspect of this application provides a continuous production process for efficiently recovering PTA from waste PET, comprising:

[0016] The enzymatic hydrolysis step includes multiple enzymatic hydrolysis units. The enzymatic hydrolysis step uses PET degrading enzyme, the enzymatic hydrolysis temperature is 40℃~70℃, the pH of the enzymatic hydrolysis process is 8~10, and a slurry containing TA alkaline salt is obtained.

[0017] The first solid-liquid separation step separates the TA basic salt from the slurry containing TA basic salt;

[0018] In the filter cake dissolution and decolorization step, 5 to 10 times the weight of water is added to the TA alkaline salt to dissolve the TA alkaline salt, and a decolorizing agent is added and filtered to obtain a TA alkaline salt solution.

[0019] The electrolysis step includes multiple electrolysis units arranged in parallel. Each electrolysis unit is divided into an anode chamber and a cathode chamber by a cation exchange membrane. An anode plate and a plate frame are provided in the anode chamber, and a cathode plate and a plate frame are provided in the cathode chamber. The plate frames are respectively arranged on both sides of the anode plate and the cathode plate, forming an anode plate tank and a cathode plate tank. The TA alkaline salt solution enters the electrolysis unit from the anode side. The crude TA slurry is recovered in the anode plate tank, and the alkaline solution is recovered in the cathode plate tank. Oxygen and hydrogen are collected respectively. The plate frame is rectangular, and at least one arc-shaped corrugated isolation strip is provided along the long side of the plate frame. The curvature diameter of the arc-shaped corrugated isolation strip is not less than the narrow side dimension of the plate tank (anode plate tank or cathode plate tank, the same below).

[0020] The second solid-liquid separation step involves filtering the crude TA slurry to obtain crude TA; and

[0021] In the refining step, the crude TA product is recrystallized to obtain PTA;

[0022] Specifically, when the first enzymatic hydrolysis unit completes the enzymatic hydrolysis reaction and performs the first solid-liquid separation step, the second enzymatic hydrolysis unit performs the enzymatic hydrolysis step. After completing the processing operation of the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit performs the first solid-liquid separation step, thus completing continuous production.

[0023] The continuous production process for efficiently recovering PTA from waste PET provided in this application achieves continuous production of PTA from waste PET by sequentially performing an enzymatic hydrolysis step, a first solid-liquid separation step, a filter cake dissolution and decolorization step, an electrolysis step, a second solid-liquid separation step, and a refining step. Specifically, pretreated waste PET is enzymatically hydrolyzed using PET-degrading enzymes to obtain a slurry containing TA basic salts. Since the solubility of TA basic salts in the crude enzyme solution used for enzymatic hydrolysis is low, TA basic salts gradually precipitate as the degree of enzymatic hydrolysis increases. The slurry containing TA basic salts is then separated into solid TA basic salts through a first solid-liquid separation step. The TA basic salt filter cake is dissolved in a soluble amount of water, and a decolorizing agent is added for decolorization and impurity removal. After removing the decolorizing agent, the resulting TA basic salt solution is electrolyzed. Crude TA slurry is obtained at the anode of the electrolysis unit, and an alkaline solution is obtained at the cathode. The crude TA slurry generated at the anode of each electrolysis unit is separated into solids and collected in a second solid-liquid separation step to obtain crude TA. Further recrystallization of the crude TA yields PTA. Specifically, while the first enzymatic hydrolysis unit completes the enzymatic hydrolysis reaction and performs the first solid-liquid separation step, the second enzymatic hydrolysis unit performs the enzymatic hydrolysis step. After completing the processing operations of the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit performs the first solid-liquid separation step, completing continuous production.

[0024] In conjunction with the second aspect, the continuous production process further includes a distillation step, in which the solution obtained from the first solid-liquid separation step is distilled to recover ethylene glycol.

[0025] In conjunction with the second aspect, the enzymatic hydrolysis step is specifically as follows: prepare a 10 mmol / L to 1000 mmol / L sodium phosphate buffer, add 100 g to 1000 g of waste PET to each liter of buffer, add 0.1% to 1% of crude PET degrading enzyme solution by weight of the buffer, and perform enzymatic hydrolysis for 5 h to 25 h;

[0026] The refining step specifically involves: conveying the crude TA product to a pulping tank, adding a mixed solvent to make the mass concentration of the crude TA product 20wt% to 35wt%, wherein the mixed solvent is a mixture of water and at least one of dimethylformamide, diethylformamide, and dimethyl sulfoxide; heating to 265℃ to 280℃ and pressurizing to 6.0MPa to 8.0MPa to dissolve the crude TA product; passing the obtained crude TA product solution through an adsorption column for decolorization and removal of metal impurities, and then performing stepwise crystallization through a 1-6 stage cooling and depressurization flash crystallizer; washing and drying to obtain PTA.

[0027] For example, at least one of dimethylformamide, diethylformamide and dimethyl sulfoxide is formulated with demineralized water to form a mixed solvent, wherein the demineralized water accounts for 80% to 95% of the mass of the mixed solvent.

[0028] In conjunction with the second aspect, the ratio of the long side to the narrow side of the electrode groove is 2 to 5:1, and the depth of the electrode groove is 2 mm to 20 mm; the distance between the upstream edge of the electrode plate and the upper edge of the electrode groove is greater than 1 / 8 of the length of the electrode groove, and the distance between the downstream edge of the electrode plate and the lower edge of the electrode groove is not less than 1 / 4 of the length of the electrode groove.

[0029] A PTA is produced using the above-described continuous production system for efficiently recovering PTA from waste PET or according to the above-described continuous production process for efficiently recovering PTA from waste PET.

[0030] An application of the above-mentioned PTA in the preparation of PET products, said PET products including PET films, fibers and / or bottle flakes.

[0031] For example, PET films made from 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 oriented or uniaxially oriented films.

[0032] For example, PET fibers made from PTA can also be used in multiple fields and industries. For instance, they can be polyester filaments or polyester staple fibers produced in the textile industry, high-strength fibers, low-elasticity fibers or high-modulus fibers commonly used in the industrial field, or some functional fibers, such as moisture-wicking fibers, antistatic fibers, UV-resistant fibers or flame-retardant fibers, or pre-oriented yarns, fully drawn yarns or drawn textured yarns obtained according to different production processes.

[0033] For example, PET flakes made from PTA can also be used in a variety of fields and industries, such as: food packaging bottles, beverage packaging bottles, pharmaceutical packaging bottles, cosmetic packaging bottles or industrial chemical bottles; they 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 they 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. Beneficial effects

[0034] The continuous production system and process provided in this application can realize the continuous production of PTA by using waste PET as raw material. Moreover, by adjusting the flow channel structure in the electrolysis component, the electrolysis interruption caused by the easy deposition of TA on the surface of the anode plate is avoided, thus ensuring the continuous operation of the entire degradation and recycling process. This continuous production system and process is of great significance for realizing the efficient degradation and recycling of waste PET. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the continuous production process for efficiently recovering PTA from waste PET provided in this application;

[0036] Figure 2 is a schematic diagram of the electrolysis unit and the second solid-liquid separation unit of the continuous production process for efficiently recovering PTA from waste PET provided in this application;

[0037] Figure 3 is a schematic diagram of the electrolysis unit in the continuous production process for efficiently recovering PTA from waste PET provided in this application;

[0038] Figure 4 is a cross-sectional schematic diagram of the electrolysis unit, wherein Figure 4(a) is a cross-sectional schematic diagram of the anode chamber in the electrolysis unit, and Figure 4(b) is a cross-sectional schematic diagram of the cathode chamber in the electrolysis unit.

[0039] Figure 5 is a flowchart illustrating the refining steps of the continuous production process for efficiently recovering PTA from waste PET provided in this application.

[0040] In the picture:

[0041] 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;

[0042] 301. Upstream edge of the electrode plate; 302. Downstream edge of the electrode plate;

[0043] 400. Arc-shaped corrugated isolation strip; 401. First flow channel; 402. Second flow channel;

[0044] 601. Fluid inlet of anode chamber; 602. Fluid outlet of anode chamber; 701. Fluid pipe at the upstream edge of anode plate frame; 702. Fluid pipe at the downstream edge of anode plate frame; 801. Fluid inlet of cathode chamber; 802. Fluid outlet of cathode chamber; 901. Fluid pipe at the upstream edge of cathode plate frame; 902. Fluid pipe at the downstream edge of cathode plate frame. Embodiments of the present invention

[0045] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0046] In this application, unless otherwise expressly specified, the terms “first,” “second,” or “third” are used to distinguish different objects, not to describe a specific order.

[0047] Please refer to Figure 1. The continuous production system for efficiently recovering PTA from waste PET, as provided in this application, will now be described. This continuous production system includes: multiple enzymatic hydrolysis units configured to sequentially perform enzymatic hydrolysis of PET to obtain a slurry containing TA alkaline salts; a processing unit comprising a first solid-liquid separation unit, a filter cake dissolution and decolorization unit, an electrolysis unit, a second solid-liquid separation unit, and a recrystallization unit connected in sequence; the processing unit is used to perform solid-liquid separation, dissolution and decolorization, and electrolysis of the TA alkaline salt-containing slurry to obtain crude TA slurry, which is then subjected to solid-liquid separation and recrystallization to obtain PTA; and a switching control unit configured to: connect the processing unit to the first enzymatic hydrolysis unit to initiate the processing operation when the first enzymatic hydrolysis unit completes the enzymatic hydrolysis of PET; during the processing operation of the processing unit on the first enzymatic hydrolysis unit, the second enzymatic hydrolysis unit performs the enzymatic hydrolysis of PET; and in response to the processing unit completing the processing operation on the first enzymatic hydrolysis unit, switch the processing unit to be connected to the second enzymatic hydrolysis unit, so that the processing unit cyclically connects each enzymatic hydrolysis unit to achieve continuous processing.

[0048] The continuous production system for efficiently recovering PTA from waste PET provided in this application includes multiple enzymatic hydrolysis units, each connected to a first solid-liquid separation unit. These units continuously supply the first solid-liquid separation unit with slurry containing TA alkaline salts obtained from enzymatic hydrolysis of PET, ensuring continuous production. The subsequent processing operations are identical for each enzymatic hydrolysis unit. Taking the subsequent processing operations after one enzymatic hydrolysis unit (e.g., the first enzymatic hydrolysis unit) is connected to the processing unit as an example: After the first enzymatic hydrolysis unit is connected to the first solid-liquid separation unit, the TA alkaline salt-containing slurry enters the first solid-liquid separation unit for solid-liquid separation. The separated TA alkaline salt solids enter a filter cake dissolution and decolorization unit for dissolution, decolorization, impurity removal, and filtration. The filtered TA alkaline salt solution enters an electrolysis unit. In the anode plate tank of the electrolysis unit, crude TA slurry is recovered, and in the cathode plate tank, alkaline solution is recovered. The obtained crude TA slurry is filtered by a second solid-liquid separation unit to collect solid crude TA. The recrystallization unit then refines the crude TA to obtain PTA.

[0049] As a specific embodiment of the continuous production system for efficiently recovering PTA from waste PET in this application, the continuous production system also includes a control unit, which is connected to the liquid outlet of multiple enzymatic hydrolysis units respectively; when the enzymatic hydrolysate of one enzymatic hydrolysis unit is processed by the processing unit, the control unit controls the liquid outlet of another enzymatic hydrolysis unit to connect with the first solid-liquid separation unit.

[0050] By setting up a control unit to control the connection between the enzymatic hydrolysis unit and the first solid-liquid separation unit, it is ensured that the enzymatic hydrolysate produced by the enzymatic hydrolysis unit is sufficient to supply the processing of subsequent units, thus ensuring that the entire continuous production system can produce continuously.

[0051] As a specific embodiment of the continuous production system for efficiently recovering PTA from waste PET according to this application, the continuous production system further includes a distillation unit connected to the solution side of the first solid-liquid separation unit for recovering and reusing ethylene glycol in the solution.

[0052] Please refer to Figure 2. As a specific embodiment of the continuous production system for efficiently recovering PTA from waste PET according to this application, the electrolysis unit includes at least two sets of electrolysis components, which are composed of alternating anodes and cathodes. The TA alkaline salt solution (i.e., decolorizing solution) generated by the filter cake dissolution and decolorization unit enters the electrolysis unit from the anode side, and the alkaline solution generated by electrolysis flows out from the cathode side.

[0053] Please refer to Figure 3. As a specific embodiment of the continuous production system for efficiently recovering PTA from waste PET in this application, each electrolysis assembly is provided with a sealing gasket 027 between the cation exchange membrane 023 and the electrode frame 026, between the electrode frame 026 and the cathode plate 024 or the electrode frame 026 and the anode plate 025, and between the electrode frame 026 and the end plate 028. Each assembly is fixed by a through screw and nuts at both ends of the screw.

[0054] As a specific embodiment of the continuous production system for efficiently recovering PTA from waste PET in this application, electrode frames 026 are respectively arranged on both sides of the anode plate 025 and the cathode plate 024, correspondingly forming anode electrode slots and cathode electrode slots. That is, the electrode frames 026 arranged parallel on both sides of the anode plate 025 form the anode electrode slots, and the electrode frames 026 arranged parallel on both sides of the cathode plate 024 form the cathode electrode slots. Both the anode electrode slots and the cathode electrode slots are hollow electrode slots, with two or more flow channels arranged along the fluid flow direction. Each flow channel has a pair of fluid inlets and outlets. Adjacent flow channels are separated by arc-shaped corrugated isolation strips 400, which are perpendicular to the corresponding anode plate 025 or cathode plate 024. Please refer to Figure 4 for the specific structure.

[0055] As a specific embodiment of the continuous production system for efficiently recovering PTA from waste PET in this application, please refer to Figure 4(a). In the hollow anode plate groove formed by the anode plate 025 and the plate frame 026, at least two flow channels (first flow channel 401 and second flow channel 402) are arranged along the fluid flow direction. Adjacent flow channels are separated by an arc-shaped corrugated isolation strip 400, which is perpendicular to the anode plate 025. Each flow channel is provided with a pair of anode chamber fluid inlets 601 and anode chamber fluid outlets 602. A pair of anode plate frame upstream edge fluid pipes 701 and anode plate frame downstream edge fluid pipes 702 are respectively provided at the upstream edge and downstream edge of the plate frame corresponding to each flow channel. The anode plate 025 is installed between the upstream edge 301 and the downstream edge 302 of the plate. Please refer to Figure 4(b). In the hollow cathode plate groove formed by the cathode plate 024 and the plate frame 026, at least two flow channels (first flow channel 401 and second flow channel 402) are provided along the fluid flow direction. Adjacent flow channels are separated by an arc-shaped corrugated isolation strip 400, which is perpendicular to the cathode plate 024. Each flow channel is provided with a pair of cathode chamber fluid inlets 801 and cathode chamber fluid outlets 802. A pair of cathode plate frame upstream edge fluid pipes 901 and cathode plate frame downstream edge fluid pipes 902 are provided at the upstream edge and downstream edge of the plate frame corresponding to each flow channel, respectively. The cathode plate 024 is installed between the upstream edge 301 and the downstream edge 302 of the plate.

[0056] An arc-shaped corrugated isolation strip 400 is used to separate two adjacent flow channels. When the liquid flows in the anode plate groove, it collides with the flow channel with a certain curvature formed by the arc-shaped corrugated isolation strip 400, which increases its own flow velocity. The liquid with increased flow velocity exerts a greater impact force on the TA crude slurry generated on the surface of the anode plate 025, thus making it impossible for it to be stably deposited on the surface of the anode plate 025.

[0057] When electrolysis is performed using an electrolysis unit consisting of two electrolysis components connected in parallel, the TA alkaline salt solution (i.e., the decolorizing solution) first enters the anode chamber 022 through the anode chamber fluid inlet 601, or first flows through the upstream edge fluid pipe 901 of the cathode plate frame and then enters the anode chamber 022 through the anode chamber fluid inlet 601. In the anode chamber 022, the TA alkaline salt combines with hydrogen ions generated by anodic electrolysis to form crude TA. The crude TA slurry flows out from the anode chamber fluid outlet 602 and passes through the downstream edge fluid pipe 902 of the cathode plate frame, where it meets the hydrogen ions from the anode chamber 022 of the other electrolysis unit. After the crude TA slurry flowing out of 22 is mixed, it enters the main pipeline, where oxygen escapes and is collected. At the same time, the water required for electrolysis enters the cathode chamber 021 through the cathode chamber fluid inlet 801 and the downstream edge fluid pipe 702 of the anode plate frame. The hydroxide ions generated by the cathode electrolysis of water react with sodium or potassium ions that pass through the cation exchange membrane 023 into the cathode chamber 021 to form an alkaline solution. This solution then flows out of the cathode chamber fluid outlet 802 and mixes with the alkaline solution flowing out of the cathode chamber 021 of another electrolysis unit through the upstream edge fluid pipe 701 of the anode plate frame before entering the main pipeline.

[0058] The second aspect of this application provides a continuous production process for efficiently recovering PTA from waste PET, comprising:

[0059] The enzymatic hydrolysis step includes multiple enzymatic hydrolysis units. The enzymatic hydrolysis step uses PET degrading enzyme to hydrolyze waste PET. The enzymatic hydrolysis temperature is 40℃~70℃, and the pH of the enzymatic hydrolysis process is 8~10, to obtain a slurry containing TA alkaline salt.

[0060] The first solid-liquid separation step separates the TA basic salts from the slurry containing TA basic salts;

[0061] In the filter cake dissolution and decolorization step, 5 to 10 times the weight of water is added to the TA basic salt to dissolve the TA basic salt, and a decolorizing agent is added and filtered to obtain a TA basic salt solution.

[0062] The electrolysis step includes multiple electrolysis units arranged in parallel. Each electrolysis unit is divided into an anode chamber and a cathode chamber by a cation exchange membrane. The TA alkaline salt solution enters the electrolysis unit from the anode side. At the anode, crude TA slurry is obtained, and at the cathode, the alkaline solution is recovered, and oxygen and hydrogen are collected respectively.

[0063] The second solid-liquid separation step involves filtering the crude TA slurry to obtain crude TA; and

[0064] The refining step involves recrystallizing crude TA to obtain PTA.

[0065] The continuous production process for efficiently recovering PTA from waste PET provided in this application achieves continuous production of PTA from waste PET by sequentially performing an enzymatic hydrolysis step, a first solid-liquid separation step, a filter cake dissolution and decolorization step, an electrolysis step, a second solid-liquid separation step, and a refining step. Specifically, pretreated waste PET is enzymatically hydrolyzed with PET-degrading enzyme to obtain a slurry containing TA basic salt. Since the solubility of TA basic salt in the crude enzyme solution used for enzymatic hydrolysis is low, TA basic salt will gradually precipitate as the degree of enzymatic hydrolysis increases. The slurry containing TA basic salt is separated into solid TA basic salt through a first solid-liquid separation step. The TA basic salt filter cake is dissolved in a soluble amount of water and a decolorizing agent is added for decolorization and impurity removal. After removing the decolorizing agent, the obtained TA basic salt solution is electrolyzed. A crude TA slurry is obtained at the anode of the electrolysis unit, and an alkaline solution is obtained at the cathode. The crude TA slurry generated at the anode of each electrolysis unit is separated into solids and liquids through a second solid-liquid separation step, and the solids are collected to obtain crude TA. The crude TA is then recrystallized to obtain PTA.

[0066] As a specific embodiment of the continuous production process for efficiently recovering PTA from waste PET in this application, the continuous production process further includes a TA alkaline salt slurry control step. After the TA alkaline salt slurry in one of the enzymatic hydrolysis units is processed, the TA alkaline salt slurry in another enzymatic hydrolysis unit is controlled to undergo a first solid-liquid separation step.

[0067] As a specific embodiment of the continuous production process for efficiently recovering PTA from waste PET in this application, the continuous production process further includes a distillation step, in which the solution obtained from the first solid-liquid separation step is distilled to recover ethylene glycol.

[0068] As a specific implementation of the continuous production process for efficiently recovering PTA from waste PET in this application, the enzymatic hydrolysis step is as follows: prepare a sodium phosphate buffer solution of 10 mmol / L to 1000 mmol / L, add 100 g to 1000 g of waste PET to each kilogram of buffer solution, add 0.1% to 1% of crude PET degrading enzyme solution by weight of buffer solution, and react for 5 h to 25 h.

[0069] After the enzymatic hydrolysis step is completed, in order to precipitate more TA alkaline salts, the slurry can be appropriately cooled according to the actual temperature before proceeding to the first solid-liquid separation step.

[0070] As a specific embodiment of the continuous production process for efficiently recovering PTA from waste PET in this application, each electrolysis unit is divided into an anode chamber 022 and a cathode chamber 021 by a cation exchange membrane 023. An anode plate 025 and an electrode frame 026 are provided in the anode chamber 022, and a cathode plate 024 and an electrode frame 026 are provided in the cathode chamber 021. The electrode frames 026 are respectively arranged on both sides of the anode plate 025 and the cathode plate 024, forming the anode electrode tank and the cathode electrode tank, respectively. The crude PTA slurry is recovered in the anode electrode tank, and the alkaline solution is recovered in the cathode electrode tank. Since the electrode frames 026 in the anode chamber 022 and the cathode chamber 021 are identical, the anode electrode tank and the cathode electrode tank have the same dimensions. In the following description, "electrode tank" refers to both the anode electrode tank and / or the cathode electrode tank. The electrode frame is rectangular. The length of the electrode slot is the length of the electrode frame minus the dimensions of the upper and lower edges along the long side of the electrode frame. The width of the electrode slot is the width of the electrode frame minus the dimensions of the left and right edges along the narrow side of the electrode frame. The depth of the electrode slot is the horizontal width of the two parallel electrode frames that hold the electrode. At least one arc-shaped corrugated isolation strip 400 is provided along the long side of the electrode frame, and the curvature diameter of the arc-shaped corrugated isolation strip 400 is not less than the narrow side dimension of the electrode slot. The ratio of the length of the electrode slot to the width of the electrode slot is 2 to 5:1, and the depth of the electrode slot is 2 mm to 20 mm. The distance between the upstream edge 301 of the electrode and the upper edge of the electrode slot is greater than 1 / 8 of the length of the electrode slot, and the distance between the downstream edge 302 of the electrode and the lower edge of the electrode slot is not less than 1 / 4 of the length of the electrode slot.

[0071] Specifically, the long side of the electrode frame is 30cm long and the narrow side is 10cm long. The electrode groove is 26cm long, 6cm wide, and 5mm deep. The curvature diameter of the arc-shaped corrugated isolation strip 400 is 6cm. The distance between the upstream edge 301 of the electrode and the upper edge of the electrode groove is 3.5cm, and the distance between the downstream edge 302 of the electrode and the lower edge of the electrode groove is 6.5cm.

[0072] As a specific embodiment of the continuous production process for efficiently recovering PTA from waste PET in this application, 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 1.5V to 5V.

[0073] Please refer to Figure 5. As a specific embodiment of the continuous production process for efficiently recovering PTA from waste PET in this application, the refining steps of the process are as follows: crude TA is conveyed to a pulping tank, and a TA slurry with a concentration of 20wt% to 35wt% is prepared with at least one of dimethylformamide, diethylformamide, and dimethyl sulfoxide and demineralized water. The crude TA is dissolved by heating to 265℃ to 280℃ and pressurizing to 6.0MPa to 8.0MPa. The obtained crude TA solution is decolorized and demetallic impurity removed by an adsorption column, and then crystallized stepwise by a 1 to 6-stage cooling and depressurization flash crystallizer. The crystallized slurry is filtered by a filtration system, and the obtained solid is washed and dried to obtain PTA.

[0074] As a specific implementation of the continuous production process for efficiently recovering PTA from waste PET in this application, the specific parameters of the step-by-step crystallization process are as follows: the temperature of the first-stage crystallizer is controlled at 250℃~260℃, and the pressure is controlled at 4.0MPa~4.5MPa; the temperature of the second-stage crystallizer is controlled at 200℃~210℃, and the pressure is controlled at 3.0MPa~4.0MPa; the temperature of the third-stage crystallizer is controlled at 160℃~185℃, and the pressure is controlled at 0.7MPa~1.1MPa; and the temperature of the fourth-stage crystallizer is controlled at 130℃~155℃, and the pressure is controlled at 0.3MPa~0.65MPa.

[0075] As a specific implementation of the continuous production process for efficiently recovering PTA from waste PET in this application, the resulting solution is decolorized and demetallic impurities are removed by passing it through an adsorption column. Specifically, this can be achieved through a combination of one or more processes, such as fixed-bed continuous adsorption, precision filtration, and membrane separation, to remove colored substances and metallic impurities from the crude TA solution. The adsorption material can be at least one of coconut shell activated carbon, zeolite molecular sieves, diatomaceous earth, or chitosan, or other adsorption materials with decolorization and metallic impurity adsorption functions.

[0076] As a specific implementation of the continuous production process for efficiently recovering PTA from waste PET in this application, as shown in Figure 5, in the refining step, the flash vapor generated by the cooling and depressurizing flash crystallizer can be introduced into the upstream dissolved crude TA and pulping process to achieve energy recovery and utilization.

[0077] The following specific embodiments illustrate the continuous production process and system for efficiently recovering PTA from waste PET provided in this application:

[0078] Prepare a 1000 mmol / L sodium phosphate buffer solution with a pH of 9.0. Add 1000 g of pre-crushed waste PET to each kilogram of buffer solution, and add 1 wt% crude PET degrading enzyme solution for enzymatic hydrolysis. Control the reaction temperature at 40℃~70℃ and react for 5h~25h. During the reaction, add 5%~50% sodium hydroxide solution dropwise to maintain the pH of the system between 8 and 10.

[0079] After the enzymatic hydrolysis reaction was completed, the hydrolysate was naturally cooled to room temperature and then filtered. The filtrate was sent to the distillation unit to recover ethylene glycol, yielding 1531g of TA basic salt filter cake. 11kg of water was added to dissolve the TA basic salt, followed by the addition of 30g of decolorizing agent and stirring for 1 hour for decolorization and impurity removal. The decolorizing agent and other insoluble substances were removed by filtration, and the filtrate was sent to the electrolysis unit. During electrolysis, the electrode voltage was set to 2V, and the current was 77.0A, which was maintained constant throughout the electrolysis process. After 9 hours of electrolysis, the electrode voltage increased to 2.2V, indicating that the amount of crude TA slurry deposited on the 025 anode plate was very small and would not affect the electrolysis reaction. The crude TA slurry produced by electrolysis is filtered, and the resulting solid crude TA is recrystallized. Specifically, 1200g of crude TA is transported to a TA slurry tank through a spiral pipeline, and 2369g of mixed solvent is added to obtain a TA slurry (the mixed solvent is obtained by mixing demineralized water and dimethylformamide at a mass ratio of 85:15). The temperature is raised to 280℃ and the pressure is raised to 6.4MPa to dissolve the crude TA. After that, it is decolorized and demetallic impurity removed by an adsorption column filled with coconut shell activated carbon. The treated crude TA solution is then sent to a 1-4 stage cooling and depressurization flash evaporation process. The crystallizer performs step-by-step crystallization, with the following parameters set: The temperature of the first-stage crystallizer is controlled at 250℃~260℃, and the pressure at 4.0MPa~4.5MPa; the temperature of the second-stage crystallizer is controlled at 200℃~210℃, and the pressure at 3.0MPa~4.0MPa; the temperature of the third-stage crystallizer is controlled at 160℃~185℃, and the pressure at 0.7MPa~1.1MPa; the temperature of the fourth-stage crystallizer is controlled at 130℃~155℃, and the pressure at 0.3MPa~0.65MPa. The crystallized slurry is filtered and washed using a filtration system, and finally dried to obtain 811g of PTA with a purity of 99.91% and a yield of 93.8%. The yield (%) is calculated as 811 / (1000 / 192×166) = 93.8%.

[0080] However, when the above-mentioned mixed solvent used in the recrystallization dissolution in the purification step was replaced with a mixed solvent of water: ethanol: isopropanol in a mass ratio of 80:10:10, the yield of PTA decreased to 91.5% and the purity decreased to 98.4%, indicating that the above-mentioned recrystallization solvent used in this application can ensure that the obtained PTA has high purity and higher yield.

[0081] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

A continuous production system for efficiently recovering PTA from waste PET, characterized in that, comprises: a plurality of enzymatic units configured to sequentially perform enzymatic PET reaction to obtain a slurry containing TA alkaline salt; a processing unit comprising a first solid-liquid separation unit, a filter cake dissolution and decolorization unit, an electrolysis unit, a second solid-liquid separation unit and a recrystallization unit connected in sequence; the processing unit is used to separate the TA alkaline salt from the slurry containing TA alkaline salt, dissolve and decolorize the TA alkaline salt, electrolyze to obtain a TA crude product slurry, and then separate the TA crude product from the TA crude product slurry by solid-liquid separation and recrystallization to obtain PTA; and a switching control unit configured to: when the first enzymatic unit completes the enzymatic PET reaction, connect the processing unit with the first enzymatic unit to start the processing operation; during the processing operation of the processing unit on the first enzymatic unit, the second enzymatic unit performs the enzymatic PET reaction; in response to the processing unit completing the processing operation on the first enzymatic unit, switching the processing unit to be connected with the second enzymatic unit to make the processing unit cycle with each enzymatic unit to realize continuous processing; wherein the electrolysis unit is formed by connecting a plurality of electrolysis components in parallel, each electrolysis component is separated into an anode chamber and a cathode chamber by a cation exchange membrane, wherein an anode plate and an electrode plate frame arranged on both sides of the anode plate are arranged in the anode chamber to form an anode electrode plate groove, a cathode plate and an electrode plate frame arranged on both sides of the cathode plate are arranged in the cathode chamber to form a cathode electrode plate groove, TA alkaline salt solution enters the electrolysis unit from the anode chamber, TA crude product slurry is recovered in the anode electrode plate groove, and alkaline solution is recovered in the cathode electrode plate groove; the anode electrode plate groove and the cathode electrode plate groove are hollow electrode plate grooves, and 2 or more flow channels are arranged along the fluid flow direction, each flow channel is respectively provided with a pair of fluid inlets and outlets, wherein adjacent two flow channels are separated by arc-shaped corrugated isolation strips; the arc-shaped corrugated isolation strips are perpendicular to the corresponding anode plate or cathode plate. The continuous production system for efficiently recycling PTA from waste PET according to claim 1, wherein: the first solid-liquid separation unit is used to separate the TA alkaline salt from the slurry containing TA alkaline salt; the filter cake dissolution and decolorization unit is used to dissolve, decolorize and filter the TA alkaline salt to obtain a TA alkaline salt solution; the second solid-liquid separation unit is used to separate the TA crude product from the TA crude product slurry; the recrystallization unit is used to refine the TA crude product. The continuous production system for efficiently recovering PTA from waste PET according to claim 1, wherein Further comprising a rectification unit connected to the solution side of the first solid-liquid separation unit, used for recycling ethylene glycol in the solution. A continuous production process for efficiently recovering PTA from waste PET, characterized in that, comprises: an enzymatic step comprising a plurality of enzymatic units, the enzymatic step uses PET degrading enzyme, the enzymatic temperature is 40-70℃, the pH of the enzymatic process is 8-10, and a slurry containing TA alkaline salt is obtained; a first solid-liquid separation step for separating TA alkaline salt from the slurry containing TA alkaline salt; a filter cake dissolution and decolorization step, wherein 5-10 times the weight of water is added to the TA alkaline salt to dissolve the TA alkaline salt, a decolorizing agent is added, and the TA alkaline salt is filtered to obtain a TA alkaline salt solution; The electrolysis step comprises a plurality of electrolysis assemblies arranged in parallel, each electrolysis assembly being separated by a cation exchange membrane into an anode chamber and a cathode chamber, an anode plate and an anode plate frame being arranged in the anode chamber, and a cathode plate and a cathode plate frame being arranged in the cathode chamber, the anode plate frame and the cathode plate frame being arranged on both sides of the anode plate and the cathode plate respectively, and corresponding to form an anode plate groove and a cathode plate groove, the TA alkaline salt solution entering the electrolysis assembly from the anode side, TA crude product slurry being recovered in the anode plate groove, and alkaline solution being recovered in the cathode plate groove, and oxygen and hydrogen being collected respectively; the plate frame is rectangular, at least one arc-shaped corrugated isolation strip being arranged along the long side of the plate frame, and the curvature diameter of the arc-shaped corrugated isolation strip being not less than the narrow side size of the plate groove. The second solid-liquid separation step filters the TA crude product slurry to obtain TA crude product. The refining step recrystallizes the TA crude product to obtain PTA. When the first enzyme hydrolysis unit completes the enzyme hydrolysis reaction, the second enzyme hydrolysis unit performs the enzyme hydrolysis step, and after completing the processing operation of the first enzyme hydrolysis unit, the second enzyme hydrolysis unit performs the first solid-liquid separation step to complete the continuous production. The rectification step rectifies the solution obtained in the first solid-liquid separation step to recover ethylene glycol. The continuous production process for efficiently recovering PTA from waste PET according to claim 4, characterized in that, The enzyme hydrolysis step specifically comprises: preparing 10 mmol / L-1000 mmol / L sodium phosphate buffer, adding 100 g-1000 g waste PET to each liter of the buffer, adding 0.1%-1% PET degradation enzyme crude enzyme solution based on the mass of the buffer, and performing enzyme hydrolysis for 5 h-25 h. The continuous production process for efficiently recovering PTA from waste PET according to claim 4, characterized in that, The refining step specifically comprises: The TA crude product is transported to a beater tank, and a mixed solvent is added to make the mass concentration of the TA crude product 20 wt%-35 wt%, wherein the mixed solvent is a mixture of water and at least one of dimethylformamide, diethylformamide and dimethyl sulfoxide; The TA crude product is dissolved by heating to 265°C-280°C and pressurizing to 6.0 MPa-8.0 MPa; The obtained TA crude product solution is subjected to decolorization and metal impurity removal treatment by an adsorption column, and then subjected to step-by-step crystallization by 1-6 stage temperature and pressure reduction flash crystallizers, to obtain the PTA after washing and drying. The length and narrow size ratio of the plate groove is 2-5:1, and the depth of the plate groove is 2 mm-20 mm; the distance between the upstream edge 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 of the plate and the lower edge of the plate groove is not less than 1 / 4 of the length of the plate groove. The continuous production process for efficiently recovering PTA from waste PET according to claim 4, characterized in that, ​

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