Application of liquid metal as catalyst for microwave pyrolysis of plastics and pyrolysis device

Abstract

The application provides application of liquid metal as a catalyst for microwave pyrolysis of plastics and a pyrolysis device; the microwave pyrolysis device comprises a protective gas generating device, a microwave generating device, a degradation reaction device and a product collecting device; the protective gas generating device is used for providing a protective gas, the microwave generating device is defined with an inner cavity for microwave action, the degradation reaction device is arranged in the inner cavity and is defined with a containing chamber for containing the liquid metal catalyst; the violent movement of internal electrons, free atoms and atomic groups in the liquid metal is used for heating, and at the same time, the inert protective atmosphere is induced to ionize to generate high-energy particles; based on the self-heating effect of the liquid metal and the high-energy particle arc discharge heat effect, the efficient catalytic cracking of the plastic polymer material is realized; the physical characteristics of the liquid metal catalyst enable the liquid metal catalyst to fully contact with the plastics, effectively increase the catalytic area, enhance the microwave energy utilization efficiency, effectively improve the reaction conversion efficiency, and the overall operation is simple, and the reaction conversion rate is high.

Description

Technical Field

[0001] This invention relates to the field of microwave pyrolysis technology for plastics, and more particularly to the application of liquid metal as a catalyst for microwave pyrolysis of plastics, as well as the pyrolysis apparatus and method. Background Technology

[0002] Most plastics are made from structurally stable high-molecular polymers, such as polyethylene, polystyrene, polypropylene, and polyvinyl chloride, which are very difficult to biodegrade and recycle. Currently, the main methods for disposing of plastic products are landfilling and incineration, which not only seriously pollute the environment but also lead to a huge waste of resources.

[0003] To address this issue, researchers invented microwave pyrolysis for recycling and processing waste plastics. This method utilizes microwaves; the absorbing medium rapidly converts microwave energy into heat, which then catalytically breaks down the plastic into high-value-added products such as solid carbon, pyrolysis oil, and pyrolysis gas. To enable practical application of microwave pyrolysis, researchers investigated the influencing factors, including microwave power, catalyst type, and pyrolysis temperature.

[0004] Regarding catalyst types, existing technologies mostly utilize inorganic non-metallic materials, such as carbon-based materials (graphite, carbon black, silicon carbide powder, silicon carbide fiber, carbon fiber), and microwave-absorbing materials like ferrites. The preparation process for these catalysts is relatively complex, and a common drawback is the difficulty in separating them from the products after plastic pyrolysis, resulting in low catalyst recovery rates. This not only increases reaction costs but also makes it difficult to further utilize some products, leading to resource waste. Furthermore, most existing catalysts are solid particles, resulting in point contact with the plastic and a limited contact area, which significantly restricts the conversion efficiency of the plastic. Summary of the Invention

[0005] This invention provides an application of liquid metal as a microwave pyrolysis catalyst for plastics and a pyrolysis device, which solves the defects of existing technologies such as complex catalyst preparation process, high cost, difficulty in separating from pyrolysis products, and low catalyst recovery rate, and fills the gap in the use of liquid metal as a microwave pyrolysis catalyst for plastics.

[0006] This invention provides the application of liquid metal as a catalyst for microwave pyrolysis of plastics.

[0007] This invention also provides the application of liquid metal-inorganic material composites as catalysts for microwave pyrolysis of plastics.

[0008] According to the present invention, the liquid metal is one or more of a metal, alloy, or metal derivative with a melting point below 300 °C.

[0009] According to the present invention, the liquid metal is used as a catalyst for microwave pyrolysis of plastics, wherein the liquid metal includes sodium, potassium, sodium-potassium alloy, gallium, bismuth, indium, tin, gallium-based alloy, and bismuth-based alloy.

[0010] According to the present invention, the application of liquid metal as a microwave pyrolysis catalyst for plastics includes inorganic materials such as ferrite powder, carbonyl iron powder, ultrafine metal powder, silicon carbide powder, silicon carbide fiber, carbon fiber, and metal fiber.

[0011] According to the application of liquid metal as a microwave pyrolysis plastic catalyst provided by the present invention, the mass percentage of liquid metal and inorganic material in the liquid metal-inorganic material composite is 1wt%-30wt%.

[0012] The present invention also provides a pyrolysis apparatus for performing a pyrolysis method on plastics. The apparatus includes a protective gas generator, a microwave generator, a degradation reaction apparatus, and a product collection apparatus. The protective gas generator provides a protective gas. The microwave generator defines an inner cavity for microwave action. The degradation reaction apparatus is installed in the inner cavity and defines a accommodating chamber for holding a mixture of liquid metal and plastic, or a mixture of liquid metal-inorganic material composite and plastic. The product collection apparatus collects the products after plastic degradation. The protective gas generator and the degradation reaction apparatus are connected via a first connecting pipe, and the product collection apparatus is connected to the degradation reaction apparatus via a second connecting pipe.

[0013] According to the present invention, a pyrolysis plastic apparatus is provided, wherein the product collection device includes a liquid phase product collector and a gas phase product collector, and a heat-resistant insulation layer is provided between the microwave generator and the degradation reaction device.

[0014] According to the present invention, a pyrolysis apparatus for plastics is provided, wherein the microwave generator produces a microwave frequency of 915 MHz or 2.45 GHz, a microwave power of 80~1000 W, and a microwave catalytic pyrolysis time of 5 min~10 h.

[0015] According to the present invention, a pyrolysis apparatus for plastics is provided, and the pyrolysis method for plastics includes the following steps:

[0016] (1) Crush the plastic;

[0017] (2) The crushed plastic is placed in a accommodating chamber and mixed with liquid metal or liquid metal-inorganic material composite, and the accommodating chamber is placed in an inert protective atmosphere;

[0018] (3) Under microwave irradiation, the liquid metal or the liquid metal-inorganic material composite rapidly reaches a high temperature, thereby causing the plastic to decompose; wherein the mass ratio between the plastic and the liquid metal or the liquid metal-inorganic material composite is 0.1 to 10:1.

[0019] According to the pyrolysis apparatus for plastics provided by the present invention, the pyrolysis method for plastics further includes the following steps:

[0020] (4) The pyrolysis products from step (3) are collected using a product collection device;

[0021] (5) Separate the liquid metal or the liquid metal-inorganic material composite by taking advantage of the difference in physical properties between the products of plastic pyrolysis and the liquid metal.

[0022] (6) Store or purify the separated liquid metal or liquid metal-inorganic material composite for later use.

[0023] This invention provides an application of liquid metal as a catalyst for microwave pyrolysis of plastics and a pyrolysis device. By using liquid metal as a catalyst in microwave pyrolysis of plastics, the need for adding microwave absorbing medium to existing catalysts is eliminated. The liquid metal discharge phenomenon has a significant thermal effect, and it can rapidly heat up to the required temperature without the addition of microwave absorbing medium. Local high temperatures will appear in the discharge area, and the discharge process can also change the composition of products during plastic degradation.

[0024] Furthermore, the fluid characteristics of liquid metal catalysts allow for full contact with plastics, effectively increasing the catalytic surface area. The amorphous liquid interface effectively enhances microwave energy utilization efficiency and suppresses the reflection of electromagnetic waves by the metal. Its high electrical and thermal conductivity facilitates efficient microwave energy introduction and rapid conduction, thereby effectively improving reaction conversion efficiency. Based on the inherent differences in boiling point and density properties between liquid metals and plastic degradation products, the complete recovery of high-value-added products generated from the degradation of plastics using liquid metal catalysts can also be achieved. The overall operation is simple, with a high reaction conversion rate, achieving nearly 100% plastic conversion in a short time. It also allows for selective degradation and recycling of different plastics and biomass, making it suitable for practical industrial applications. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the microwave pyrolysis plastic apparatus provided by the present invention.

[0027] Figure label:

[0028] 1: Protective gas generator; 2: First connecting pipe; 3: Microwave generator; 4: Degradation reaction device; 5: Mixed material; 6: Heat-resistant insulation layer; 7: Second connecting pipe; 8: Product collection device; Liquid phase product collector 8-1; Gas phase product collector 8-2; 9: Third connecting pipe. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," etc., should be interpreted broadly. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances. Furthermore, the terms "first," "second," "third," etc., in this invention are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] In existing technologies, due to the conventional understanding of metals—that they possess high electrical conductivity—and the fact that the attenuation coefficient of microwaves within a material is inversely proportional to its conductivity (meaning that microwaves attenuate at higher concentrations in metals, resulting in a lower skin depth), metals are generally considered to be non-absorbent. Consequently, metals have long been used as microwave shielding materials. This has prevented the emergence of solutions on the market that utilize liquid metals as catalysts for microwave pyrolysis of plastics.

[0032] Within metallic material systems, there exists a large class of metals with highly unique physicochemical properties: liquid metals. These metals are typically composed of metals, alloys, and their derivatives with melting points below 300 °C. Among them, liquid metal systems, represented by gallium-based and bismuth-based alloys, exhibit excellent fluidity at room temperature or higher, as well as low melting / high boiling points, high thermal / electrical conductivity, and good biocompatibility. Compared to solid metals, liquid metals have lower electrical conductivity and a greater skin depth. Utilizing these properties as catalysts for microwave pyrolysis of plastics could solve the problems of low conversion efficiency, complex preparation processes, high costs, and low catalyst recovery rates found in existing catalysts.

[0033] like Figure 1 As shown, based on the physical properties of the liquid metal described above, the microwave pyrolysis plastic apparatus provided by the present invention includes a protective gas generating device 1, a microwave generating device 3, a degradation reaction device 4, and a product collecting device 8. The protective gas generating device 1 is used to provide a protective gas. The microwave generating device 3 defines an inner cavity for microwave action. The degradation reaction device 4 is installed in the inner cavity and defines a receiving chamber. The receiving chamber is used to hold a mixture 5 of liquid metal and plastic, or a mixture 5 of liquid metal-inorganic material composite and plastic. The product collecting device 8 is used to collect the products after plastic degradation. The protective gas generating device 1 and the degradation reaction device 4 are connected by a first connecting pipe 2, and the product collecting device 8 is connected to the degradation reaction device 4 by a second connecting pipe 7. A heat-resistant insulation layer 6 is also provided between the microwave generating device 3 and the degradation reaction device 4, and the heat-resistant insulation layer 6 is filled with heat-resistant insulation material.

[0034] In this embodiment, under the action of the protective gas generating device 1, the degradation reaction device 4 is made into an inert protective atmosphere with no or low oxygen. Under the oxygen-free or low oxygen atmosphere, the liquid metal is heated by the violent movement of internal electrons, free atoms and atomic groups through microwave irradiation. Due to the significant thermal effect of the liquid metal discharge phenomenon, the temperature can be rapidly raised to above 600 ℃ without the addition of an external microwave absorbing medium. The discharge area will have local high temperature, and the discharge process can also change the composition of the products in the plastic degradation process. At the same time, it induces the ionization of the inert protective atmosphere to generate high-energy particles. Based on the self-heating effect of the liquid metal and the thermal effect of the high-energy particle arc discharge, the efficient catalytic cracking of plastic polymer materials is realized. After the products are condensed and separated, high-value-added gases are obtained, such as ethylene, propylene, butene and wax oil, which can be used as raw materials for chemical production.

[0035] To better collect the products, the product collection device 8 is divided into a liquid phase product collector 8-1 and a gas phase product collector 8-2. The liquid phase product collector 8-1 is connected to the degradation reaction device 4 through a second connecting pipe 7, and the gas phase product collector 8-2 is connected to the liquid phase product collector 8-1 through a third connecting pipe 9.

[0036] In the above embodiments, the liquid metal includes sodium, potassium, sodium-potassium alloy, gallium, bismuth, indium, tin, gallium-indium alloy, gallium-tin alloy, gallium-indium-tin alloy, bismuth-indium alloy, bismuth-tin alloy, and bismuth-indium-tin alloy, preferably one or more of gallium, bismuth, indium, tin, gallium-indium alloy, gallium-tin alloy, gallium-indium-tin alloy, and bismuth-indium alloy.

[0037] Furthermore, the inorganic material is in powder or fibrous form, including ferrite powder, carbonyl iron powder, various ultrafine metal powders, silicon carbide powder, silicon carbide fiber, carbon fiber, and metal fiber, preferably iron, nickel, or silicon carbide.

[0038] Furthermore, the degraded plastics include one or a mixture of general-purpose plastic products and engineering plastic products, specifically one or more of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and polypropylene.

[0039] Furthermore, the inert protective atmosphere is an atmosphere with an oxygen content of less than 5000 ppm, and the inert gas is one of nitrogen, helium, neon, argon, krypton, and xenon, preferably nitrogen, argon, or helium.

[0040] Furthermore, the microwave power is 80~1000 W, the microwave frequency is 915 MHz or 2.45 GHz, and the microwave-assisted catalytic pyrolysis time is 5 min~10 h.

[0041] The microwave pyrolysis method for plastics provided by the present invention is described below. The microwave pyrolysis method for plastics described below can be referred to in correspondence with the microwave pyrolysis apparatus for plastics described above.

[0042] (1) The plastic is crushed, specifically, the plastic is crushed so that the particle size of the crushed plastic is 1~10 mm;

[0043] (2) The crushed plastic and liquid metal or liquid metal-inorganic material composite are placed in a accommodating chamber and mixed, and the accommodating chamber is in an inert protective atmosphere; specifically, the ratio of the mixed material 5 is 0.1 to 10:1 by mass of liquid metal or liquid metal-inorganic material composite to plastic, preferably 0.2 to 3:1 by mass. The mixing is carried out by mechanical stirring or ball milling, and the mixing time is 1 to 60 min.

[0044] (3) Under microwave irradiation, the liquid metal or the liquid metal-inorganic material composite rapidly reaches a high temperature, thereby causing the plastic to decompose; specifically, depending on the type and amount of the mixed products, the microwave power is adjusted to 80~1000W, the microwave frequency is 915 MHz or 2.45 GHz, and the microwave irradiation time is 5 min~10 h.

[0045] (4) The degradation products in step (3) are collected by the product collection device 8. Specifically, the gaseous and liquid products after degradation in the degradation reaction device 4 are both introduced into the liquid product collector 8-1 through the second connecting pipe 7. Then, the gaseous products are introduced into the gaseous product collector 8-2 through the third connecting pipe 9 to complete the collection of gaseous and liquid products.

[0046] (5) Separate the products of plastic pyrolysis from the liquid metal or the liquid metal-inorganic material composite by taking advantage of the difference in physical properties. Specifically, during catalyst separation, take advantage of the high density and high boiling point of the liquid metal to achieve autonomous stratification of the liquid metal with the solid and liquid phase degradation products, as well as active separation from the gas phase degradation products.

[0047] (6) Store or purify the separated liquid metal or liquid metal-inorganic material composite for later use. Specifically, when the purity of the separated catalyst is sufficient, it can be used directly for the next catalytic reaction. For catalysts with more impurities, acid washing, alkali washing, or calcination are used to further improve the purity before the next catalytic reaction.

[0048] In the above-mentioned microwave pyrolysis method for plastics, the purification method for the catalyst is as follows: the pickling solution is a strong acid solution, preferably a mixture of one or more of hydrochloric acid, sulfuric acid, and nitric acid with a concentration of 0.01~10 mol / L; the alkaline pickling solution is a strong alkaline solution, preferably a mixture of one or more of sodium hydroxide and potassium hydroxide with a concentration of 0.01~10 mol / L; the calcination temperature in air atmosphere is 300~1000 ℃, and the calcination time is 10 min~10 h.

[0049] In the above-mentioned microwave pyrolysis plastics process, the separated gas phase components are mainly ethylene, propylene and butene, which can be used as raw materials for the production of chemicals; the separated liquid phase components are mainly wax oil, which can be used to produce gasoline, diesel and lubricating oil.

[0050] The present invention will be further described below through specific embodiments. The embodiments described below can be referred to in correspondence with the microwave pyrolysis plastic apparatus and microwave pyrolysis plastic process described above.

[0051] Example 1

[0052] An application of liquid metal as a catalyst for microwave pyrolysis of plastics, along with the pyrolysis apparatus and method, is described in [reference needed]. Figure 1 This includes the following steps:

[0053] (1) After mechanically crushing the recovered polypropylene plastic container, mix it evenly with liquid metal catalyst and plastic at a mass ratio of 1:3, wherein the catalyst is liquid metal gallium; (2) Add the evenly mixed liquid metal and plastic mixture 5 to the degradation reaction device 4; (3) Place the degradation reaction device 4 loaded with materials into the microwave generator 3; (4) Connect the protective gas generator 1 and the degradation reaction device 4 with the first connecting pipe 2; connect the liquid phase product collector 8-1 and the degradation reaction device 4 with the second connecting pipe 7; connect the liquid phase product collector 8-1 and the gas phase product collector 8-2 with the third connecting pipe 9; exhaust the degradation reaction device 4 for 15 minutes with argon gas (70 mL / min) generated by the protective gas generator 1 to remove oxygen in the reaction device; (5) Set the microwave power of the microwave generator 3 to 300 W for microwave-assisted pyrolysis; (6) The gaseous products generated in the reaction are condensed and separated into wax oil and gas in sequence through the liquid phase product collector 8-1 and the gas phase product collector 8-2.

[0054] After the reaction was completed, the collected gas was analyzed for its components, and the gas and wax oil yields were calculated. The results are shown in Table 1.

[0055]

[0056] Table 1

[0057] Example 2

[0058] An application of liquid metal as a catalyst for microwave pyrolysis of plastics, along with the pyrolysis apparatus and method, is described in [reference needed]. Figure 1 This includes the following steps:

[0059] (1) After mechanically crushing the recycled polyethylene plastic bags, mix them evenly with liquid metal catalyst and plastic in a mass ratio of 1:1, wherein the catalyst is liquid metal gallium indium; (2) Add the evenly mixed liquid metal and plastic mixture 5 to the degradation reaction device 4; (3) Place the degradation reaction device 4 loaded with materials into the microwave generator 3; (4) Connect the protective gas generator 1 and the degradation reaction device 4 with the first connecting pipe 2; connect the liquid phase product collector 8-1 and the degradation reaction device 4 with the second connecting pipe 7; connect the liquid phase product collector 8-1 and the gas phase product collector 8-2 with the third connecting pipe 9; exhaust the degradation reaction device 4 for 15 min with argon gas (70 mL / min) generated by the protective gas generator 1 to remove oxygen in the reaction device; (5) Set the microwave power of the microwave generator 3 to 300 W for microwave-assisted pyrolysis; (6) The gaseous products generated in the reaction are condensed and separated into wax oil and gas in sequence through the liquid phase product collector 8-1 and the gas phase product collector 8-2.

[0060] After the reaction was completed, the collected gas was analyzed for its components, and the gas and wax oil yields were calculated. The results are shown in Table 2.

[0061]

[0062] Table 2

[0063] Example 3

[0064] An application of liquid metal as a catalyst for microwave pyrolysis of plastics, along with the pyrolysis apparatus and method, is described in [reference needed]. Figure 1 This includes the following steps:

[0065] (1) After mechanically crushing the recycled polyethylene plastic straws, mix them evenly with liquid metal catalyst and plastic at a mass ratio of 1:5. The catalyst is a composite of liquid metal gallium-tin alloy and ferrite powder, and the ferrite powder doping amount is 5 wt%. (2) Add the evenly mixed liquid metal and plastic mixture 5 to the degradation reaction device 4. (3) Place the degradation reaction device 4 loaded with materials into the microwave generator 3. (4) Connect the protective gas generator 1 and the degradation reaction device 4 using the first connecting pipe 2. Connect the liquid phase product collector 8-1 and the degradation reaction device 4 using the second connecting pipe 7. Connect the liquid phase product collector 8-1 and the gas phase product collector 8-2 using the third connecting pipe 9. Exhaust the degradation reaction device 4 for 15 min with argon gas (70 mL / min) generated by the protective gas generator 1 to remove oxygen in the reaction device. (5) Set the microwave power of the microwave generator 3 to 260 W is subjected to microwave-assisted pyrolysis; (6) the gaseous products generated in the reaction are condensed and separated into wax oil and gas by liquid product collector 8-1 and gas product collector 8-2 in sequence.

[0066] After the reaction was completed, the collected gas was analyzed for its components, and the gas and wax oil yields were calculated. The results are shown in Table 3.

[0067]

[0068] Table 3

[0069] Example 4

[0070] An application of liquid metal as a catalyst for microwave pyrolysis of plastics, along with the pyrolysis apparatus and method, is described in [reference needed]. Figure 1 This includes the following steps:

[0071] (1) After mechanically crushing the recovered polypropylene plastic container, mix it evenly with the catalyst and plastic at a mass ratio of 1:10, wherein the catalyst is liquid metal bismuth-indium alloy; (2) Add the evenly mixed liquid metal and plastic mixture 5 to the degradation reaction device 4; (3) Place the degradation reaction device 4 loaded with materials into the microwave generator 3; (4) Connect the protective gas generator 1 and the degradation reaction device 4 with the first connecting pipe 2; connect the liquid phase product collector 8-1 and the degradation reaction device 4 with the second connecting pipe 7; connect the liquid phase product collector 8-1 and the gas phase product collector 8-2 with the third connecting pipe 9; exhaust the degradation reaction device 4 for 15 min with argon gas (70 mL / min) generated by the protective gas generator 1 to remove oxygen in the reaction device; (5) Set the microwave power of the microwave generator 3 to 600W for microwave-assisted pyrolysis; (6) The gaseous products generated in the reaction are condensed and separated into wax oil and gas in sequence through the liquid phase product collector 8-1 and the gas phase product collector 8-2.

[0072] After the reaction was completed, the collected gas was analyzed for its components, and the gas and wax oil yields were calculated. The results are shown in Table 4.

[0073]

[0074] Table 4

[0075] Example 5

[0076] An application of liquid metal as a catalyst for microwave pyrolysis of plastics, along with the pyrolysis apparatus and method, is described in [reference needed]. Figure 1 This includes the following steps:

[0077] (1) After mechanically crushing the recovered polyethylene and polypropylene plastic containers, they are mixed evenly with a catalyst to plastic mass ratio of 1:2. The catalyst is a composite of liquid metal gallium indium tin alloy and silicon carbide powder, and the doping amount of silicon carbide powder is 8 wt%. (2) The evenly mixed liquid metal and plastic mixture 5 is added to the degradation reaction device 4. (3) The degradation reaction device 4 loaded with the material is placed in the microwave generator 3. (4) The protective gas generator 1 is connected to the degradation reaction device 4 by the first connecting pipe 2; the liquid phase product collector 8-1 is connected to the degradation reaction device 4 by the second connecting pipe 7; the liquid phase product collector 8-1 is connected to the gas phase product collector 8-2 by the third connecting pipe 9; and the degradation reaction device 4 is vented by argon gas (70 mL / min) generated by the protective gas generator 1. min to remove oxygen in the reaction device; (5) set the microwave power of microwave generator 3 to 500W for microwave-assisted pyrolysis; (6) the gaseous products generated in the reaction are condensed and separated into wax oil and gas by liquid product collector 8-1 and gas product collector 8-2 in sequence.

[0078] After the reaction was completed, the collected gas was analyzed for its components, and the gas and wax oil yields were calculated. The results are shown in Table 5.

[0079]

[0080] Table 5

[0081] Example 6

[0082] An application of liquid metal as a catalyst for microwave pyrolysis of plastics, along with the pyrolysis apparatus and method, is described in [reference needed]. Figure 1 This includes the following steps:

[0083] (1) The recovered polypropylene plastic bags and rice straw were mechanically crushed at a mass ratio of 10:1 to obtain a mixed carbon-containing material. The catalyst and the above-mentioned carbon-containing material were mixed evenly at a ratio of 2:1. The catalyst was a composite of liquid metal bismuth and nickel powder, and the amount of nickel powder was 5 wt%. (2) The evenly mixed liquid metal and plastic mixture 5 was added to the degradation reaction device 4. (3) The degradation reaction device 4 loaded with the material was placed in the microwave generator 3. (4) The protective gas generator 1 and the degradation reaction device 4 were connected by the first connecting pipe 2. The liquid phase product collector 8-1 was connected to the degradation reaction device 4 by the second connecting pipe 7. The liquid phase product collector 8-1 was connected to the gas phase product collector 8-2 by the third connecting pipe 9. The degradation reaction device 4 was vented by argon gas (70 mL / min) generated by the protective gas generator 1. min to remove oxygen in the reaction device; (5) set the microwave power of microwave generator 3 to 750W for microwave-assisted pyrolysis; (6) the gaseous products generated in the reaction are condensed and separated into wax oil and gas by liquid product collector 8-1 and gas product collector 8-2 in sequence.

[0084] After the reaction was completed, the collected gas was analyzed for its components, and the gas and wax oil yields were calculated. The results are shown in Table 6.

[0085]

[0086] Table 6

[0087] Example 7

[0088] An application of liquid metal as a catalyst for microwave pyrolysis of plastics, along with the pyrolysis apparatus and method, is described in [reference needed]. Figure 1 This includes the following steps:

[0089] (1) The recovered polypropylene plastic bags and rice straw were mechanically crushed at a mass ratio of 10:1 to obtain a mixed carbon-containing material. The catalyst and the above-mentioned carbon-containing material were mixed evenly at a ratio of 1:2. The catalyst was a liquid metal gallium-tin alloy and a carbon fiber composite, and the carbon fiber doping amount was 1 wt%. (2) The evenly mixed liquid metal and plastic mixture 5 was added to the degradation reaction device 4. (3) The degradation reaction device 4 loaded with the material was placed in the microwave generator 3. (4) The protective gas generator 1 and the degradation reaction device 4 were connected by the first connecting pipe 2. The liquid phase product collector 8-1 was connected to the degradation reaction device 4 by the second connecting pipe 7. The liquid phase product collector 8-1 was connected to the gas phase product collector 8-2 by the third connecting pipe 9. The argon gas (70) generated by the protective gas generator 1 was used to generate the gas. (5) The microwave power of the microwave generator 3 is set to 450W for microwave-assisted pyrolysis; (6) The gaseous products generated in the reaction are condensed and separated into wax oil and gas in sequence through the liquid phase product collector 8-1 and the gas phase product collector 8-2.

[0090] After the reaction was completed, the collected gas was analyzed for its components, and the gas and wax oil yields were calculated. The results are shown in Table 7.

[0091]

[0092] Table 7

[0093] Through the description of the specific embodiments above, those skilled in the art can clearly understand that in each embodiment, liquid metal or liquid metal-inorganic material composite is used as a catalyst for microwave pyrolysis of plastics, thereby achieving the degradation of plastics; and the present invention also has advantages such as low reaction energy consumption and adjustable catalyst type, the reaction device used has a simple structure, is easy to disassemble and assemble, and is convenient to maintain; the device parts are easy to replace, easy to customize as needed, highly flexible, long working life, stable and reliable.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A microwave pyrolysis method for plastics, characterized in that, The microwave pyrolysis method for plastics includes the following steps: (1) Crush the plastic; (2) The crushed plastic is placed in a accommodating chamber and mixed with liquid metal or liquid metal-inorganic material composite, and the accommodating chamber is placed in an inert protective atmosphere; (3) Under microwave irradiation, the liquid metal or the liquid metal-inorganic material composite rapidly reaches a high temperature, thereby causing the plastic to decompose; (4) The pyrolysis products from step (3) are collected using a product collection device; (5) Separate the liquid metal or the liquid metal-inorganic material composite by taking advantage of the difference in physical properties between the products of plastic pyrolysis and the liquid metal. (6) Store or purify the separated liquid metal or the liquid metal-inorganic material composite for later use; The microwave pyrolysis method for plastics includes a microwave pyrolysis apparatus, the microwave pyrolysis apparatus comprising: A protective gas generator is used to provide protective gas. A microwave generating device having an internal cavity for microwave action; A degradation reaction device is installed in the inner cavity and defines the receiving chamber, the receiving chamber being used to hold a mixture of liquid metal and plastic; Or, for containing a mixture of the liquid metal-inorganic material composite and plastic; and The product collection device is used to collect the products after plastic degradation; The protective gas generator is connected to the degradation reaction device via a first connecting pipe, and the product collection device is connected to the degradation reaction device via a second connecting pipe.

2. The microwave pyrolysis method for plastics according to claim 1, characterized in that, The liquid metal is one or more of a metal, alloy, or metal derivative with a melting point below 300°C.

3. The microwave pyrolysis method for plastics according to claim 2, characterized in that, The liquid metal is one or more of sodium, potassium, sodium-potassium alloy, gallium, bismuth, indium, tin, gallium-based alloy, and bismuth-based alloy.

4. The microwave pyrolysis method for plastics according to claim 2, characterized in that, The inorganic material and the liquid metal have a mass percentage of 1wt%-8wt%.

5. The microwave pyrolysis method for plastics according to claim 4, characterized in that, The inorganic material is one or more of the following: ferrite powder, carbonyl iron powder, ultrafine metal powder, silicon carbide powder, silicon carbide fiber, carbon fiber, and metal fiber.

6. The microwave pyrolysis method for plastics according to claim 1, characterized in that, The product collection device includes a liquid-phase product collector and a gas-phase product collector, and a heat-resistant insulation layer is provided between the microwave generator and the degradation reaction device.

7. The microwave pyrolysis method for plastics according to claim 1, characterized in that, The microwave generator produces microwaves at a frequency of 915 MHz or 2.45 GHz, with a microwave power of 80~1000 W and a microwave catalytic pyrolysis time of 5 min~10 h.

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