System and method for thermoelectric coupling synergistic catalysis of PET waste plastic conversion and coupling hydrogen production

Abstract

The invention provides a system and a method for thermoelectric coupling synergistic catalysis of PET waste plastic conversion and coupling hydrogen production. The system comprises a PET pretreatment unit, a PET depolymerization unit, a terephthalic acid separation unit, a thermoelectric coupling catalysis unit, a product separation device and an automatic control unit. According to the system and the method for conversion and coupling hydrogen production of the PET waste plastics through thermoelectric coupling concerted catalysis, the problems of high energy consumption, low selectivity, equipment complexity and the like in a traditional PET treatment technology are remarkably solved by innovatively combining thermoelectric coupling concerted catalysis. By synergistically coupling thermocatalysis and electrocatalysis technologies, respective thermodynamic and dynamic bottlenecks in a traditional single catalysis technology are solved. The traditional thermocatalytic method generally needs high-temperature and high-pressure conditions, resulting in high energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of waste plastic conversion coupled with hydrogen production, and specifically to a system and method for thermoelectric coupling synergistic catalysis of PET waste plastic conversion coupled with hydrogen production. Background Art

[0002] Polyethylene terephthalate (PET), as a widely used plastic material, has an annual output as high as 70 million tons, but its recovery rate is less than 10%, resulting in a large amount of waste causing serious environmental impacts. Although PET itself does not directly harm the environment, its degradation period in nature is as long as 16 to 48 years, greatly affecting the ecological balance.

[0003] At present, the vast majority of PET is disposed of by landfilling or incineration, which exacerbates plastic pollution. Landfilling is simple but occupies a large amount of land resources, and PET is difficult to degrade in the natural environment, and long-term accumulation will pollute the soil and water bodies. Incineration can reduce the volume of waste, but it will produce a large amount of harmful gases (such as dioxins, hydrogen chloride, etc.), causing secondary pollution to the atmospheric environment, and the carbon dioxide released during the incineration process exacerbates the greenhouse effect.

[0004] Traditional thermal catalytic degradation technology can convert PET into high-value-added chemicals such as terephthalic acid and ethylene glycol. However, this method has problems such as high energy consumption, high carbon emissions, low selectivity, and complex equipment, which limit its large-scale application and sustainable development. In addition, high-temperature and high-pressure conditions are often required during the thermal catalytic process, increasing the operation difficulty and equipment cost.

[0005] In recent years, electrocatalytic technology, as an emerging PET treatment method, has gradually attracted attention. Electrocatalytic technology depolymerizes PET into ethylene glycol and terephthalic acid in an alkaline environment, and obtains high-value-added chemicals such as pyruvic acid under electrocatalytic oxidation conditions, and can also produce hydrogen. This process is carried out under mild conditions, can effectively utilize renewable energy, and reduce carbon emissions. However, electrocatalytic technology also has some limitations, such as high energy consumption, slow reaction rate, and usually requires the use of catalysts containing precious metals such as platinum and iridium, increasing the cost.

[0006] In addition, most of the existing PET recycling technologies focus on single treatment methods and lack the synergistic utilization of multiple technologies. For example, thermal catalysis and electrocatalysis each have their own advantages, but they often cannot meet the requirements of high efficiency, low energy consumption, and high selectivity when used alone. Therefore, developing a new PET treatment technology that can combine the advantages of thermal catalysis and electrocatalysis has important practical significance and application prospects. Summary of the Invention

[0007] In view of the deficiencies of the prior art, the present invention provides a system and method for the thermoelectric coupling and synergistic catalysis of the conversion of waste PET plastics to couple hydrogen production, which solves the problems of high energy consumption, low selectivity, complex equipment and dependence on noble metal catalysts.

[0008] To achieve the above objectives, the present invention is realized through the following technical solutions: A system and method for the thermoelectric coupling and synergistic catalysis of the conversion of waste PET plastics to couple hydrogen production, including:

[0009] A PET pretreatment unit, a PET depolymerization unit, a terephthalic acid separation unit, a thermoelectric coupling catalytic unit, a product separation device and an automatic control unit;

[0010] The PET pretreatment unit uses grinding equipment to grind the waste PET plastics treated with liquid nitrogen and filters them through a 200-mesh sieve to obtain PET powder;

[0011] The PET depolymerization unit depolymerizes PET into small molecule substances ethylene glycol and terephthalic acid by using potassium hydroxide solution;

[0012] The terephthalic acid separation unit separates terephthalic acid from the products of the PET depolymerization unit by suction filtration to obtain an ethylene glycol solution;

[0013] The thermoelectric coupling catalytic unit conducts thermocatalysis by means of water bath heating while conducting electrocatalysis to achieve the synergistic catalytic effect of thermochemistry and electrochemistry. The thermoelectric coupling catalytic unit can convert ethylene glycol into pyruvic acid and simultaneously generate clean fuel hydrogen at the cathode. The heat required for the thermoelectric coupling catalysis comes from industrial waste heat, and the electricity required comes from renewable energy electricity;

[0014] The product separation device is used to separate and purify pyruvic acid and collect the hydrogen generated at the cathode;

[0015] The automatic control unit includes a data acquisition, analysis and feedback control module. The data acquisition module is used to collect parameters such as temperature, voltage, pH value, reaction time and product concentration. The analysis and feedback control module is used to process data in real time and dynamically adjust the relevant parameters of thermocatalysis and electrocatalysis according to the catalytic reaction rate to optimize the reaction process.

[0016] Preferably, the PET pretreatment unit includes a liquid nitrogen treatment device, a grinder and a sieve, which are used to shear, ball mill and filter waste PET plastics to obtain powdery PET, facilitating subsequent depolymerization reactions.

[0017] Preferably, the PET depolymerization unit adopts an alkaline alcoholysis system, such as an ethylene glycol solution of sodium hydroxide, potassium hydroxide, etc. The added ethylene glycol serves as an alcoholysis agent to provide nucleophilic hydroxyl groups, effectively breaking the ester bonds in the PET chain and releasing terephthalic acid and more ethylene glycol molecules, enabling efficient depolymerization of waste PET plastics. The PET depolymerization unit uses a hydrothermal reaction kettle, and a mechanical stirring paddle is provided inside the reaction kettle to fully mix the PET powder with the alkaline ethylene glycol solution, depolymerizing PET into ethylene glycol and terephthalic acid.

[0018] Preferably, the terephthalic acid separation unit separates terephthalic acid from the depolymerization product by suction filtration, using a PTFE polytetrafluoroethylene filter paper with a pore size less than 0.45 microns to ensure efficient separation of terephthalic acid.

[0019] Preferably, the thermoelectric coupling catalytic unit includes an electrolytic cell and a thermoelectric bifunctional catalyst. The heat of the thermoelectric coupling catalytic unit comes from industrial waste heat, and the electricity comes from renewable energy electricity.

[0020] Preferably, the electrolytic cell has an inner and outer layer structure divided into an inner reaction vessel and an outer reaction vessel. The inner reaction vessel space is filled with electrolyte, and a thermoelectric bifunctional electrocatalyst is provided as an electrode. The outer reaction vessel space circulates heat-conducting water. Under the synergistic action of electrocatalysis and thermocatalysis, ethylene glycol is converted into pyruvic acid, and hydrogen is generated at the cathode. The thermoelectric bifunctional catalyst is prepared from non-precious metal materials, with excellent thermocatalytic and electrocatalytic properties, significantly improving the reaction efficiency and product selectivity.

[0021] Preferably, the product separation device includes a gas collection device, a vacuum distiller, and an extraction device, used to separate and recover target products such as pyruvic acid and hydrogen, ensuring high-purity extraction of the products.

[0022] Preferably, the automatic control unit includes a data acquisition module, an analysis module, and a feedback control module, used to collect temperature, voltage, pH value, reaction time, and product concentration in real time, and dynamically adjust the relevant parameters of thermocatalysis and electrocatalysis according to the catalytic reaction rate, ensuring the efficiency and accuracy of the reaction process.

[0023] A method for thermoelectric coupling synergistic catalysis of waste PET plastics to convert and couple hydrogen production includes the following steps:

[0024] a. Mechanically pretreat the collected waste PET plastics, including liquid nitrogen freezing, grinding, and sieving, to obtain powdered PET;

[0025] b. Introduce the pretreated PET powder into the PET depolymerization unit, add an alkaline alcoholysis solution of potassium hydroxide and ethylene glycol, and depolymerize PET into ethylene glycol and terephthalic acid;

[0026] c. Separate terephthalic acid by the suction filtration method, and introduce the remaining liquid phase into the thermoelectric coupling catalytic unit;

[0027] d. In the thermoelectric coupling catalytic unit, ethylene glycol is electrolyzed to generate high-value chemicals such as pyruvic acid under the appropriate voltage and temperature conditions maintained by the automatic control unit, and hydrogen is generated at the cathode;

[0028] e. After the reaction is completed, separate and collect chemicals such as pyruvic acid and hydrogen through the product separation device.

[0029] The present invention provides a system and method for the conversion of waste PET plastics with thermoelectric coupling synergistic catalysis and coupled hydrogen production. It has the following beneficial effects:

[0030] The system and method for the conversion of waste PET plastics with thermoelectric coupling synergistic catalysis and coupled hydrogen production significantly overcome the problems of high energy consumption, low selectivity, and equipment complexity existing in traditional PET treatment technologies by innovatively combining thermoelectric coupling synergistic catalysis. By synergistically coupling thermal catalysis and electrocatalysis technologies, the thermodynamic and kinetic bottlenecks of traditional single catalysis technologies are solved. Traditional thermal catalysis methods usually require high-temperature and high-pressure conditions, resulting in large energy consumption; while single electrocatalysis, although mild in operation, has a slow reaction rate and requires a high voltage. In contrast, in the thermoelectric coupling catalytic unit of the present invention, through the synergistic effect of thermal catalysis and electrocatalysis, the reaction proceeds at a lower temperature and pressure, while improving the reaction efficiency and product selectivity. Secondly, the use of non-precious metal thermoelectric bifunctional catalysts not only effectively improves the reaction efficiency, but also optimizes the product selectivity. At the same time, driven by industrial waste heat and renewable energy electricity, low-carbon and energy-saving reaction conditions are realized. In addition, during the thermoelectric coupling catalytic process, while ethylene glycol is efficiently converted into high-value chemicals such as pyruvic acid, hydrogen is simultaneously generated at the cathode, achieving the dual goals of high-value conversion of waste PET and clean energy production. Finally, through the real-time monitoring and dynamic adjustment of the reaction conditions by the automatic control unit, the stability and efficiency of the reaction process are ensured, further improving the operability and accuracy of the system. Therefore, the present invention not only significantly improves the conversion efficiency of PET waste, but also realizes green and sustainable resource utilization, with broad application prospects and significant environmental protection significance. Description of the Drawings

[0031] Figure 1 It is the front view of the container structure of the thermoelectric coupling catalytic unit.

[0032] Figure 2 It is the side view of the container structure of the thermoelectric coupling catalytic unit.

[0033] Figure 3 It is the schematic flow diagram of the present invention.

[0034] In the figure: 1. reference electrode; 2. working electrode; 3. electrolyte sampling port; 4. bottle cap; 5. bottle body; 6. anion exchange membrane; 7. counter electrode; 8. outlet of heat-conducting water flow; 9. inlet of heat-conducting water injection. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] As Figures 1-3 shown, the embodiments of the present invention provide a system and method for coupling hydrogen production through thermoelectric coupling synergistic catalysis for the conversion of waste PET plastics, including a PET pretreatment unit, a PET depolymerization unit, a terephthalic acid separation unit, a thermoelectric coupling catalysis unit, a product separation device, and an automatic control unit. The PET pretreatment unit includes a liquid nitrogen treatment device, a grinder, and a sieve, which are used to shear, ball-mill, and sieve the waste PET plastics to obtain powdered PET, facilitating subsequent depolymerization reactions.

[0037] The PET pretreatment unit uses grinding equipment to grind the waste PET plastics treated with liquid nitrogen and sieves them through a 200-mesh sieve to obtain PET powder. The PET depolymerization unit adopts an alkaline alcoholysis system, such as an ethylene glycol solution of sodium hydroxide, potassium hydroxide, etc. The added ethylene glycol serves as an alcoholysis agent to provide nucleophilic hydroxyl groups, effectively breaking the ester bonds in the PET chain and releasing terephthalic acid and more ethylene glycol molecules, enabling the efficient depolymerization of waste PET plastics. The PET depolymerization unit uses a hydrothermal reaction kettle, and a mechanical stirring paddle is provided inside the reaction kettle to fully mix the PET powder with the alkaline ethylene glycol solution, depolymerizing PET into ethylene glycol and terephthalic acid.

[0038] The PET depolymerization unit depolymerizes PET into small molecule substances ethylene glycol and terephthalic acid using a potassium hydroxide solution.

[0039] The terephthalic acid separation unit separates terephthalic acid from the products of the PET depolymerization unit by suction filtration to obtain an ethylene glycol solution. The terephthalic acid separation unit separates terephthalic acid from the depolymerization products by suction filtration, and selects a PTFE polytetrafluoroethylene filter paper with a pore diameter less than 0.45 microns to ensure the efficient separation of terephthalic acid.

[0040] The thermoelectric coupled catalytic unit performs thermal catalysis by water bath heating while performing electrocatalysis to achieve synergistic catalytic effects of thermochemistry and electrochemistry. The thermoelectric coupled catalytic unit can convert ethylene glycol into pyruvic acid and simultaneously produce clean fuel hydrogen at the cathode. The heat required for thermoelectric coupled catalysis comes from industrial waste heat, and the required electricity comes from renewable energy. The thermoelectric coupled catalytic unit includes an electrolytic cell and a thermoelectric bifunctional catalyst. The heat of the thermoelectric coupled catalytic unit comes from industrial waste heat, and the electricity comes from renewable energy. The electrolytic cell has an inner and outer two-layer structure divided into an inner reaction vessel and an outer reaction vessel. The space of the inner reaction vessel is filled with electrolyte, and a thermoelectric bifunctional electrocatalyst is provided as an electrode. The space of the outer reaction vessel circulates heated water. Under the synergistic effect of electrocatalysis and thermocatalysis, ethylene glycol is converted into pyruvic acid and hydrogen is produced at the cathode. The thermoelectric bifunctional catalyst is made of non-precious metal materials and has excellent properties of both thermal catalysis and electrocatalysis, which significantly improves the reaction efficiency and product selectivity.

[0041] The product separation device is used to separate and purify pyruvic acid and collect the hydrogen generated by the cathode. The product separation device includes a gas collection device, a vacuum distiller and an extraction device, which are used to separate and recover pyruvic acid and other target products and hydrogen to ensure high-purity extraction of the product;

[0042] The automatic control unit includes a data acquisition, analysis and feedback control module. The data acquisition module is used to collect temperature, voltage, pH value, reaction time and product concentration parameters. The analysis and feedback control module is used to process data in real time and dynamically adjust the relevant parameters of thermal catalysis and electrocatalysis according to the catalytic reaction rate to optimize the reaction process. The automatic control unit includes a data acquisition module, an analysis module and a feedback control module. It is used to collect temperature, voltage, pH value, reaction time and product concentration in real time, and dynamically adjust the relevant parameters of thermal catalysis and electrocatalysis according to the catalytic reaction rate to ensure the efficiency and accuracy of the reaction process.

[0043] like Figure 3 As shown, the method for thermoelectric coupling synergistic catalytic conversion of PET waste plastics coupled to produce hydrogen in an embodiment of the present invention is as follows:

[0044] PET pretreatment: collect a certain amount of PET waste plastic, freeze it with liquid nitrogen after sufficient shearing, then grind it with a grinder, and filter it through a 200-mesh sieve to obtain uniform powdered PET.

[0045] PET depolymerization: The pretreated PET powder was added to a hydrothermal reactor, followed by the addition of 2 mol / L potassium hydroxide and ethylene glycol to form an alcoholysis solution. The reaction was carried out at 160°C for 1 hour to depolymerize PET into ethylene glycol and terephthalic acid. A mechanical stirring paddle was used for continuous stirring during the process to ensure that the PET powder and the alcoholysis solution were fully mixed.

[0046] Separation of terephthalic acid: After the reaction is completed, the terephthalic acid is separated by suction filtration using a PTFE (polytetrafluoroethylene) filter paper, which is hydrophilic and has a pore size smaller than 0.45 microns. The remaining liquid phase containing ethylene glycol is collected.

[0047] Thermoelectric coupling catalysis: Unscrew the bottle caps 4 of the cathode chamber and the anode chamber of the bottle body 5. The liquid phase containing ethylene glycol, after being collected, is directly poured into the inner reaction vessel space of the thermoelectric coupling catalysis unit through the bottle cap 4 without being cooled to room temperature. Tighten the bottle cap 4 to ensure the tightness of the cathode chamber and the anode chamber. Use industrial waste heat to heat the heat-conducting water. The heat-conducting water heated to the set temperature of 80 °C is introduced into the outer reaction vessel space through the heat-conducting water injection port 9, and the heat-conducting water flows out from the heat-conducting water outlet 8 to form a heat-conducting water circulation, providing the heat required for thermoelectric coupling catalysis. Apply appropriate voltages to the working electrode 2, the reference electrode 1, and the counter electrode 7 respectively to provide the electrical conditions required for thermoelectric coupling catalysis. The electricity introduced comes from renewable energy electricity. An anion exchange membrane 6 is provided between the cathode chamber and the anode chamber, which can selectively transport anions such as hydroxide ions while blocking the passage of cations, thus ensuring the efficiency of the electrochemical process and the purity of the product. Under the action of a non-noble metal bifunctional electrocatalyst, ethylene glycol in the electrolyte is catalytically oxidized to pyruvic acid at the anode under the synergistic catalysis of thermochemical and electrochemical conditions and exists in the form of ions near the anode. At the same time, a reduction reaction occurs in the cathode chamber, reducing water molecules to hydrogen gas.

[0048] Separation and collection of products: Hydrogen gas is collected from the electrolyte sampling port 3 in the cathode chamber through a gas separation and collection device. In the anode chamber, the oxidation product pyruvic acid at the anode is separated and collected using a vacuum distiller and an extraction device.

[0049] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A system for the conversion of waste PET plastics and coupled hydrogen production through thermoelectric coupling and synergistic catalysis, characterized in that, Comprising: PET pretreatment unit, PET depolymerization unit, terephthalic acid separation unit, thermoelectric coupling catalytic unit, product separation device and automatic control unit; The PET pretreatment unit uses grinding equipment to grind the PET waste plastics treated with liquid nitrogen and filters them through a 200-mesh sieve to obtain PET powder; The PET depolymerization unit depolymerizes PET into small molecule substances ethylene glycol and terephthalic acid by using potassium hydroxide solution; The terephthalic acid separation unit separates terephthalic acid from the product of the PET depolymerization unit by suction filtration to obtain ethylene glycol solution; The thermoelectric coupling catalytic unit conducts thermal catalysis by means of water bath heating while conducting electrocatalysis to achieve the synergistic catalytic effect of thermochemistry and electrochemistry. The thermoelectric coupling catalytic unit can convert ethylene glycol into pyruvic acid and simultaneously generate clean fuel hydrogen at the cathode. The heat required for the thermoelectric coupling catalysis comes from industrial waste heat, and the electricity required comes from renewable energy electricity; The product separation device is used to separate and purify pyruvic acid and collect the hydrogen generated at the cathode; The automatic control unit includes data acquisition, analysis and feedback control modules. The data acquisition module is used to acquire parameters such as temperature, voltage, pH value, reaction time and product concentration. The analysis and feedback control module is used to process data in real time and dynamically adjust the relevant parameters of thermal catalysis and electrocatalysis according to the catalytic reaction rate to optimize the reaction process.

2. A system for the conversion of waste PET plastics into hydrogen through thermoelectric coupling and synergistic catalysis, as claimed in claim 1, wherein: The PET pretreatment unit includes a liquid nitrogen treatment device, a grinder and a sieve, which are used to shear, ball mill and filter the waste PET plastics to obtain powdery PET, facilitating subsequent depolymerization reactions.

3. A system for the conversion of waste PET plastics by thermoelectric coupling and synergistic catalysis to produce hydrogen by coupling, characterized in that: The PET depolymerization unit adopts an alkaline alcoholysis system and a hydrothermal reaction kettle. A mechanical stirring paddle is arranged in the reaction kettle to fully mix the PET powder with the alkaline ethylene glycol solution.

4. A system for thermoelectric coupling collaborative catalysis of PET waste plastics conversion coupled with hydrogen production according to claim 1, characterized in that: The terephthalic acid separation unit separates terephthalic acid from the depolymerization product by suction filtration, and selects PTFE polytetrafluoroethylene filter paper with a pore diameter less than 0.45 microns to ensure the efficient separation of terephthalic acid.

5. The system for thermoelectric coupling synergistic catalysis of PET waste plastics conversion coupled with hydrogen production according to claim 1, wherein, The thermoelectric coupling catalytic unit includes an electrolytic cell and a thermoelectric bifunctional catalyst. The heat of the thermoelectric coupling catalytic unit comes from industrial waste heat, and the electricity comes from renewable energy electricity.

6. The thermoelectric coupling catalytic unit according to claim 5, wherein The electrolytic cell has an inner and outer two-layer structure, which is divided into an inner reaction vessel and an outer reaction vessel. The space of the inner reaction vessel is filled with electrolyte, and a thermoelectric bifunctional electrocatalyst is provided as an electrode. The space of the outer reaction vessel circulates and conducts hot water. The thermoelectric bifunctional catalyst is prepared from non-precious metal materials.

7. The system for the conversion of waste PET plastics and coupled hydrogen production by thermoelectric coupling and synergistic catalysis according to claim 1, wherein The product separation device includes a gas collection device, a vacuum distiller and an extraction device, which are used to separate and recover target products such as pyruvic acid and hydrogen.

8. The system for the conversion of waste PET plastics and coupled hydrogen production by thermoelectric coupling synergistic catalysis according to claim 1, wherein The automatic control unit includes a data acquisition module, an analysis module and a feedback control module, which are used to real-time collect temperature, voltage, pH value, reaction time and product concentration.

9. A method for the conversion of waste PET plastics and coupled hydrogen production by thermoelectric coupling and synergistic catalysis, characterized in that, Including the following steps: a. Mechanically pretreat the collected PET waste plastics, including liquid nitrogen freezing, grinding and sieving, to obtain powdery PET; b. Introduce the pretreated PET powder into the PET depolymerization unit, and add an alkaline alcoholysis solution of potassium hydroxide and ethylene glycol to depolymerize PET into ethylene glycol and terephthalic acid; c. Separate terephthalic acid by filtration, and introduce the remaining liquid phase into the thermoelectric coupling catalytic unit; d. In the thermoelectric coupling catalytic unit, ethylene glycol is electrolyzed to generate high-value chemicals such as pyruvic acid under the appropriate voltage and temperature conditions maintained by the automatic control unit, and hydrogen is produced at the cathode; e. After the reaction is completed, separate and collect chemicals such as pyruvic acid and hydrogen through the product separation device.

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