An in-situ construction method of a catalyst for microwave catalytic recovery of chlorofluoro hybrid waste plastics and a precursor thereof

Abstract

The application provides an in-situ construction method of a catalyst and a precursor thereof for microwave catalytic recovery of chlorofluorinated mixed waste plastics, and realizes high-value utilization of chlorofluorinated mixed waste plastics by constructing a catalyst with high catalytic activity and high stability in-situ. Compared with the prior art, the catalyst can realize one-step catalytic recovery of chlorofluorinated mixed waste plastics, and the hydrogen production efficiency, nanocarbon material production efficiency, element utilization rate and catalyst stability are greatly improved. The method uses one or more of cheap and readily available iron-containing, nickel-containing, cobalt-containing, manganese-containing, zinc-containing, copper-containing, tungsten-containing and magnesium-containing substances as raw materials, and obtains the catalyst precursor by a simple, solvent-free, fast and energy-saving microwave synthesis method in a few minutes, and then obtains the catalyst with high catalytic activity and high stability by in-situ reconstruction in the reaction process.

Description

Technical Field

[0001] This invention belongs to the field of high-value utilization technology of waste plastics, specifically relating to an in-situ construction method of a catalyst and its precursor for microwave catalytic recovery of chlorofluorocarbon mixed waste plastics, and the application of the catalyst. Background Technology

[0002] Municipal solid waste primarily originates from households, public places, small institutions, and businesses. It typically includes biodegradable and non-biodegradable organic and inorganic materials such as kitchen waste, polymers, rubber, metals, and electronic waste, with recalcitrant polymers (i.e., plastics) being the most prevalent. The recalcitrant nature of polymers causes long-term harm to the natural environment. Furthermore, these discarded polymers often exist in mixed forms, making them difficult to separate and recycle using conventional methods. This characteristic makes polymer waste difficult to manage and utilize, resulting in approximately 70% of the generated polymer waste ultimately ending up in landfills and the natural environment, causing serious environmental damage.

[0003] Hydrogen, as an important and clean energy source, plays a crucial role in future energy development. However, current global hydrogen production still relies heavily on fossil fuels. While this meets current demand, the production process generates significant carbon dioxide emissions, which is unacceptable for future development. Simultaneously, the rapid development of energy storage batteries is driving increasing demand for carbon nanomaterials, particularly carbon nanotubes. However, current production of carbon nanomaterials primarily relies on fossil fuels such as cracked methane and ethane. Therefore, developing green, low-carbon, and economical alternative methods for producing hydrogen and carbon nanomaterials is of great significance.

[0004] Due to its large volume and high hydrogen and carbon content, plastic waste is a high-quality raw material suitable for hydrogen production and the preparation of carbon nanomaterials. However, to achieve high-value utilization of plastic waste, reduce its environmental pollution, and realize sustainable circular development goals, it is necessary to research and develop a simple, green, universal, low-carbon, economical, and easy-to-apply technology. Current technologies mainly target chlorine-free, fluorine-free, and clean single-component plastics, but recycling technologies for chlorine-containing, fluorine-containing, or contaminated mixed plastic waste are yet to be developed. Therefore, there is an urgent need to formulate a strategy to transform chlorine- and fluorine-containing mixed plastic waste into valuable products, realize waste recycling and value-added utilization, and promote the development of a circular economy. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the first objective of this invention is to provide a simple, efficient, low-consumption, robust, and high-performance in-situ construction method for a catalyst and catalyst precursor for microwave catalytic recovery of chlorofluorocarbon mixed waste plastics. The method uses one or more inexpensive and readily available materials containing iron, nickel, cobalt, manganese, zinc, copper, tungsten, or magnesium as raw materials. The catalyst precursor can be prepared within minutes using a simple, solvent-free, rapid, and energy-saving microwave synthesis method. The catalyst precursor can then be reconstructed in situ during subsequent reaction processes to obtain a catalyst with high catalytic activity and high stability.

[0006] The second objective of this invention is to provide a microwave catalytic recovery method for chlorofluoropolymer mixed waste plastics. This method utilizes the catalyst prepared above, combined with microwave-assisted heating, to selectively break the chemical bonds in the chlorofluoropolymer mixed waste plastics, obtaining high-purity hydrogen in a short time. Simultaneously, the carbon elements in the chlorofluoropolymer mixed waste plastics are further deposited and grown into high-value nano-carbon materials (such as carbon nanotubes, graphene, etc.) under the catalytic action of the active sites. The chlorine and fluorine released during the reaction can be absorbed by aqueous solutions to prepare hydrochloric acid and hydrofluoric acid chemicals, inhibiting toxic and harmful chlorine and fluorine pollution while increasing the value of chlorine and fluorine utilization. The hydrogen-containing gas obtained by the microwave catalytic recovery method can be sold directly as a low-priced byproduct without separation, or it can be purified into high-purity hydrogen through pressure swing adsorption for use in hydrogen fuel cell power generation to power microwave instruments, achieving self-powered operation and mobile operation, and reducing the storage and transportation costs of hydrogen. The obtained high-purity hydrogen can also be used in transportation, ammonia synthesis, metal production, or the chemical industry. The high-value nano-carbon materials obtained by the microwave catalytic recovery method can be used as conductive or negative electrode materials for energy storage batteries, producing energy storage devices, and can also be used in electromagnetic shielding, nanomaterials, medicine, catalysis, sensors, separation and purification, and other fields. The hydrochloric acid and hydrofluoric acid obtained by the microwave catalytic recovery method can be used in basic chemical industries. The microwave catalytic recovery method can achieve comprehensive and efficient utilization of chlorofluorocarbon mixed waste plastics.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An in-situ construction method for a catalyst precursor for microwave catalytic recovery of chlorofluorocarbon mixed waste plastics, the method comprising the following steps:

[0009] (1) Mix the metal source and microwave heating medium, and irradiate them with microwaves in a normal pressure and low oxygen environment to obtain a solid component;

[0010] (2) After the solid components have cooled to room temperature, they are sieved using a 50-500 mesh sieve to obtain the microwave heating medium and the catalyst precursor.

[0011] According to an embodiment of the present invention, in step (1), the metal source is selected from at least one of nickel, iron, cobalt, manganese, zinc, copper, tungsten, and magnesium. When one metal source is selected, a catalyst precursor containing one metal element can be prepared, thereby obtaining a catalyst containing one metal element. When two or more metal sources are selected, a catalyst precursor containing two or more metal elements can be prepared, thereby obtaining a catalyst containing two or more metal elements.

[0012] According to an embodiment of the present invention, in step (1), the iron source is selected from one or more of ferric nitrate, ferric acetate, ferric citrate, ferrocene, ferric acetylacetone, ferric chloride, ferric oxalate, and ferric carbonate; the nickel source is selected from one or more of nickel nitrate, nickel acetate, nickel acetylacetone, nickel chloride, nickel oxalate, nickel citrate, and nickel carbonate; the cobalt source is selected from one or more of cobalt acetate, cobalt nitrate, cobalt carbonyl, cobalt chloride, cobalt acetylacetone, cobalt oxalate, cobalt citrate, and cobalt carbonate; the manganese source is selected from one or more of manganese acetate, manganese acetylacetone, manganese carbonate, manganese chloride, manganese nitrate, manganese oxalate, and manganese citrate; the zinc source is selected from one or more of zinc acetate, zinc acetylacetone, zinc carbonate, zinc chloride, zinc nitrate, zinc citrate, and zinc oxalate; the copper source is selected from one or more of copper acetate, copper acetylacetone, copper carbonate, copper chloride, copper nitrate, copper citrate, and copper oxalate; the tungsten source is selected from tungsten chloride; and the magnesium source is selected from one or more of magnesium acetate, magnesium acetylacetone, magnesium carbonate, magnesium chloride, magnesium nitrate, magnesium citrate, and magnesium oxalate.

[0013] According to an embodiment of the present invention, in step (1), the microwave heating medium source is selected from one or more of graphite, activated carbon, carbon nanotubes, silicon carbide, carbon black, zinc oxide, indium oxide and indium tin oxide.

[0014] According to an embodiment of the present invention, in step (1), the particle size of the microwave heating medium source is ≥1 mm, for example, 1 mm-10 mm, for example, 2 mm-8 mm, such as 3 mm, 4 mm, 5 mm, 6 mm or 7 mm. When a microwave heating medium source with a particle size ≥1 mm is selected, a 50-500 mesh sieve can be used to separate the catalyst precursor and the microwave heating medium in the solid component after cooling to room temperature.

[0015] According to an embodiment of the present invention, in step (1), the mass ratio of the metal source to the microwave heating medium is 1:(0.01-100), for example, 1:0.01, 1:0.02, 1:0.05, 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:2, 1:5, 1:10, 1:20, 1:30, 1:50, 1:75, 1:80 or 1:100. When the mass ratio of the microwave heating medium is higher, it is beneficial for the absorption of microwaves by the raw material mixture, which can rapidly increase the temperature of the raw material mixture, and is beneficial for promoting the rapid decomposition of the metal source to form the catalyst precursor, thereby realizing the rapid preparation of the catalyst precursor. When the mass ratio of the metal source is higher, it is possible to prepare a large amount of catalyst precursor in a single step, and it is also beneficial for the sieving and separation of the microwave heating medium and the catalyst precursor after the solid components are cooled.

[0016] According to an embodiment of the present invention, in step (1), the microwave heating medium plays the role of microwave absorption, increasing the temperature of the raw material mixture, and promoting the decomposition of the metal source to form a catalyst precursor.

[0017] According to an embodiment of the present invention, in step (1), the low-oxygen environment is, for example, an environment in which a nitrogen atmosphere exists.

[0018] According to an embodiment of the present invention, in step (1), the microwave irradiation time is 1-60 min, for example 5-50 min, such as 8 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min or 55 min.

[0019] According to an embodiment of the present invention, in step (1), the power of the microwave irradiation is ≥50W, for example, 100-2000W, such as 100W, 200W, 300W, 400W, 500W, 600W, 800W, 1000W, 1200W, 1500W, 1600W, 1800W, or 2000W. The power of the microwave irradiation can be adjusted according to the mass of the metal source. For example, when the mass of the metal source is large, increasing the power of the microwave irradiation is beneficial to achieving efficient preparation of the catalyst precursor.

[0020] According to an embodiment of the present invention, in step (1), the frequency of the microwave irradiation is 2450MHz or 915MHz.

[0021] According to an embodiment of the present invention, in step (2), the microwave heating medium obtained by separation can be reused multiple times.

[0022] According to an embodiment of the present invention, the method further includes the following steps:

[0023] (3) The catalyst precursor obtained in step (2) is mixed with a metal source and microwave irradiated in a normal pressure and low oxygen environment to prepare the catalyst precursor.

[0024] According to an embodiment of the present invention, in step (3), the mass ratio of the catalyst precursor and the metal source obtained in step (2) is 1:(0.01-100), for example, 1:0.01, 1:0.02, 1:0.05, 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:2, 1:5, 1:10, 1:20, 1:30, 1:50, 1:75, 1:80 or 1:100.

[0025] According to an embodiment of the present invention, in step (3), the metal source is defined as described above.

[0026] According to an embodiment of the present invention, the metal source added in step (3) may be the same as or different from the metal source added in step (1), preferably different. When the metal source added in step (3) is different from the metal source added in step (1), a catalyst precursor comprising two or more metal elements can be obtained.

[0027] According to an embodiment of the present invention, in step (3), the low-oxygen environment is, for example, an environment in which a nitrogen atmosphere exists.

[0028] According to an embodiment of the present invention, in step (3), the microwave irradiation time is 1-60 min, for example 5-50 min, such as 8 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min or 55 min.

[0029] According to an embodiment of the present invention, in step (3), the power of the microwave irradiation is ≥50W, for example, 100-2000W, such as 100W, 200W, 300W, 400W, 500W, 600W, 800W, 1000W, 1200W, 1500W, 1600W, 1800W, or 2000W. The power of the microwave irradiation can be adjusted according to the mass of the metal source. For example, when the mass of the metal source is large, increasing the power of the microwave irradiation is beneficial to achieving efficient preparation of the catalyst precursor.

[0030] According to an embodiment of the present invention, in step (3), the frequency of the microwave irradiation is 2450MHz or 915MHz.

[0031] The present invention also provides a catalyst precursor prepared by the above method.

[0032] According to an embodiment of the present invention, the catalyst precursor is a carbon-dispersed metal catalyst precursor.

[0033] According to an embodiment of the present invention, the carbon-dispersed metal catalyst precursor comprises a metal carbide, a metal, and carbon; wherein the metal is an elemental metal and / or a metal alloy. Preferably, the carbon-dispersed metal catalyst precursor is composed of a metal carbide, a metal, and carbon, and the metal carbide and the metal are dispersed on a carbon support.

[0034] For example, the carbon-dispersed metal catalyst precursor includes metal carbides, elemental metals, and carbon; preferably, the carbon-dispersed metal catalyst precursor is composed of metal carbides, elemental metals, and carbon, and the metal carbides and elemental metals are dispersed on a carbon support.

[0035] For example, the carbon-dispersed metal catalyst precursor includes metal carbides, metal alloys and carbon; preferably, the carbon-dispersed metal catalyst precursor is composed of metal carbides, metal alloys and carbon, and the metal carbides and metal alloys are dispersed on a carbon support.

[0036] For example, the carbon-dispersed metal catalyst precursor includes metal carbides, elemental metals, metal alloys, and carbon; preferably, the carbon-dispersed metal catalyst precursor is composed of metal carbides, elemental metals, metal alloys, and carbon, and the metal carbides, elemental metals, and metal alloys are dispersed on a carbon support.

[0037] According to embodiments of the present invention, the carbon is, for example, carbon nanotubes or graphene.

[0038] According to an embodiment of the present invention, the carbon-dispersed metal catalyst precursor undergoes an in-situ reconstruction reaction during microwave catalytic recovery of chlorofluoropolymer mixed waste plastics, thereby obtaining a catalyst with high catalytic activity and high stability.

[0039] This invention also provides an in-situ method for constructing a catalyst for microwave catalytic recovery of chlorofluoropolymer waste plastics, the method comprising the following steps:

[0040] (a) The catalyst precursor prepared above is mixed with chlorofluoropolymer waste plastic and microwave irradiated in an atmospheric pressure, low oxygen environment to prepare the catalyst.

[0041] According to an embodiment of the present invention, in step (a), the chlorofluoropolymer waste plastic is selected from at least one of polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene and polyvinylidene fluoride; or is selected from at least one of polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene and polyvinylidene fluoride and a combination of at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate and polyurethane.

[0042] According to an embodiment of the present invention, in step (a), the mass ratio of the catalyst precursor to the chlorofluoropolymer mixed waste plastic is 1:(0.05-50), for example, 1:0.05, 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:2, 1:5, 1:10, 1:20, 1:30 or 1:50.

[0043] According to an embodiment of the present invention, in step (a), the low-oxygen environment is, for example, an environment in which a nitrogen atmosphere is present.

[0044] According to an embodiment of the present invention, in step (a), the microwave irradiation time is 1-60 min, for example 5-50 min, such as 8 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min or 55 min.

[0045] According to an embodiment of the present invention, in step (a), the power of the microwave irradiation is ≥50W, for example, 100-2000W, such as 100W, 200W, 300W, 400W, 500W, 600W, 800W, 1000W, 1200W, 1500W, 1600W, 1800W, or 2000W. The power of the microwave irradiation can be adjusted according to the mass of the chlorofluorocarbon mixed waste plastics. For example, when the mass of the chlorofluorocarbon mixed waste plastics is large, increasing the power of the microwave irradiation is beneficial to achieving the catalytic recovery of the chlorofluorocarbon mixed waste plastics.

[0046] According to an embodiment of the present invention, in step (3), the frequency of the microwave irradiation is 2450MHz or 915MHz.

[0047] The present invention also provides a catalyst prepared by the above method.

[0048] According to an embodiment of the present invention, the catalyst is a carbon-dispersed metal alloy catalyst or a carbon-dispersed metal elemental catalyst.

[0049] According to an embodiment of the present invention, the carbon-dispersed metal alloy catalyst comprises a metal alloy and carbon; preferably, the carbon-dispersed metal alloy catalyst is composed of a metal alloy and carbon, and the metal alloy is dispersed on a carbon support; or, the carbon-dispersed metal alloy catalyst comprises a metal alloy, a metal element, and carbon; preferably, the carbon-dispersed metal alloy catalyst is composed of a metal alloy, a metal element, and carbon, and the metal alloy and the metal element are dispersed on a carbon support.

[0050] According to an embodiment of the present invention, the carbon-dispersed metal catalyst comprises a metal element and carbon; preferably, the carbon-dispersed metal catalyst is composed of a metal element and carbon, and the metal element is dispersed on a carbon support.

[0051] According to embodiments of the present invention, the carbon-dispersed metal alloy catalyst or carbon-dispersed metal elemental catalyst exhibits high catalytic activity and high stability when used in microwave catalytic recovery of chlorofluorocarbon mixed waste plastics.

[0052] This invention also provides a microwave catalytic recycling method for chlorofluoropolymer mixed waste plastics, the method comprising the following steps:

[0053] (i) The catalyst precursor prepared above is mixed with chlorofluorocarbon mixed waste plastics, and microwave irradiated in a normal pressure, low-oxygen environment to prepare hydrogen and nano-carbon materials, thereby realizing the microwave catalytic recovery of chlorofluorocarbon mixed waste plastics; and / or,

[0054] (ii) The catalyst prepared above is mixed with chlorofluoropolymer waste plastics and microwave irradiated in an atmospheric pressure and low oxygen environment to prepare hydrogen and nano-carbon materials, thereby realizing microwave catalytic recycling of chlorofluoropolymer waste plastics.

[0055] According to an embodiment of the present invention, in step (i), the mass ratio of the catalyst precursor to the chlorofluoropolymer mixed waste plastic is 1:(0.05-50), for example, 1:0.05, 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:2, 1:5, 1:10, 1:20, 1:30 or 1:50.

[0056] According to an embodiment of the present invention, in step (ii), the mass ratio of the catalyst to the chlorofluoropolymer waste plastic is 1:(0.05-50), for example, 1:0.05, 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:2, 1:5, 1:10, 1:20, 1:30 or 1:50.

[0057] According to an embodiment of the present invention, in steps (i) and (ii), the definition of the chlorofluoropolymer waste plastic is as described above.

[0058] According to an embodiment of the present invention, in steps (i) and (ii), the low-oxygen environment is, for example, an environment in which a nitrogen atmosphere is present.

[0059] According to an embodiment of the present invention, in steps (i) and (ii), the microwave irradiation time is the same or different, and is independent of each other from 1 to 60 min, for example from 5 to 50 min, such as 8 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min or 55 min.

[0060] According to an embodiment of the present invention, in steps (i) and (ii), the power of the microwave irradiation is the same or different, and is independently ≥50W, for example, 100-2000W, such as 100W, 200W, 300W, 400W, 500W, 600W, 800W, 1000W, 1200W, 1500W, 1600W, 1800W or 2000W.

[0061] According to an embodiment of the present invention, in steps (i) and (ii), the microwave irradiation frequencies are the same or different, and are independently 2450MHz or 915MHz.

[0062] According to an embodiment of the present invention, in steps (i) and (ii), the nano-carbon material is at least one of graphene, carbon nanotubes, etc.

[0063] The beneficial effects of this invention are:

[0064] This invention provides an in-situ construction method for a catalyst and its precursor for microwave catalytic recovery of chlorofluorocarbon (CFC) mixed waste plastics, as well as the application of the catalyst. This invention achieves high-value utilization of CFC mixed waste plastics through in-situ construction of a catalyst with high catalytic activity and high stability. Compared with existing technologies, the catalyst of this invention not only enables one-step catalytic recovery of CFC mixed waste plastics, but also significantly improves hydrogen production efficiency, nano-carbon material production efficiency, element utilization rate, and catalyst stability. The method of this invention uses one or more inexpensive and readily available substances containing iron, nickel, cobalt, manganese, zinc, copper, tungsten, or magnesium as raw materials. A simple, solvent-free, rapid, and energy-saving microwave synthesis method is used to prepare the catalyst precursor within minutes. Subsequently, the catalyst with high catalytic activity and high stability is obtained through in-situ reconstruction during the reaction process. The catalyst of this invention exhibits high catalytic activity. Under microwave-assisted heating, it can almost 100% catalytically upgrade chlorofluorocarbon mixed waste plastics into high-value-added hydrogen and nano-carbon materials. Simultaneously, the highly toxic chlorine and fluorine elements released during the catalytic process can be absorbed by water to obtain hydrochloric acid, hydrofluoric acid, and other products. The catalyst of this invention also possesses excellent catalytic stability; each ton of catalyst can continuously process more than 50 tons of chlorofluorocarbon mixed waste plastics, yielding more than 40 tons of nano-carbon materials and more than 890m³ of hydrogen. 3 The method yields hydrogen gas with a purity of 80-99.9%; simultaneously, the metal element content in the obtained nano-carbon materials is less than 5 wt%, meeting industrial requirements without acid treatment, resulting in significant economic and social benefits. Compared to traditional thermocatalytic methods based on heat conduction and convection, the method described in this invention significantly reduces energy consumption, increases product value, enhances raw material adaptability, and reduces chlorine / fluorine pollution. It represents a green, economical, high-yield, and promising strategy for recycling mixed chlorofluorocarbon waste plastics. Attached Figure Description

[0065] Figure 1 This is a process flow diagram of microwave catalytic recovery of chlorofluoropolymer waste plastics according to a preferred embodiment of the present invention.

[0066] Figure 2 These are transmission electron microscope (TEM) images of the nano-carbon materials obtained in Examples 1, 5, and 7 of this invention. Detailed Implementation

[0067] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0068] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0069] Example 1

[0070] The specific steps for microwave catalytic recovery of mixed low-density polyethylene and polyvinyl chloride plastics are as follows:

[0071] 1) The collected low-density polyethylene and polyvinyl chloride plastics were crushed and mixed at a mass ratio of 9:1, and then mixed with FeC-FeNi / Ni@CNTs catalyst precursor at a mass ratio of 3:1 to obtain a mixture.

[0072] 2) Place 44g of the mixture in the lower layer of the reaction vessel, and place 3g of the catalyst precursor separately in the upper layer of the reaction vessel. Then purge the oxygen in the reaction vessel with nitrogen for 10 min at a flow rate of 100 ml / min. After purging, set the microwave irradiation power to 800 W and the frequency to 2450 MHz, and react for 20 min under a nitrogen atmosphere. The catalyst described in this embodiment was used continuously for 10 rounds. After the reaction, the obtained gas components and nano-carbon materials were analyzed. The composition of the gas products, the cumulative hydrogen, and the yield of nano-carbon materials are shown in Table 1.

[0073] Table 1

[0074]

[0075] The synthesis steps of the FeC-FeNi / Ni@CNTs catalyst precursor used in this embodiment are as follows:

[0076] (1) Mix nickel acetylacetone and silicon carbide at a mass ratio of 1:2, and then irradiate them under a nitrogen atmosphere and a microwave power of 700W (frequency of 2450MHz) for 20min.

[0077] (2) After cooling to room temperature, Ni@CNTs catalyst precursor and silicon carbide are obtained by sieving with a 100-mesh sieve. The silicon carbide can be reused.

[0078] (3) The obtained Ni@CNTs catalyst precursor and ferric chloride were mixed evenly at a mass ratio of 60:1, and then irradiated under a nitrogen atmosphere and a microwave power of 600W (frequency of 2450MHz) for 10min to obtain the FeC-FeNi / Ni@CNTs catalyst precursor.

[0079] Comparative Example 1

[0080] The other operations are the same as in Example 1, except that the preparation method of the catalyst precursor used is different.

[0081] The catalyst precursor used in Comparative Example 1 was a FeC-FeNi / Ni@CNTs catalyst precursor, and the synthesis steps of the FeC-FeNi / Ni@CNTs catalyst precursor are as follows:

[0082] (1) Heat nickel acetylacetone in a tube furnace at 400°C for 20 min under a nitrogen atmosphere;

[0083] (2) After cooling to room temperature, the collected product and ferric chloride are mixed evenly at a mass ratio of 60:1. Then, the mixture is heated in a tube furnace at 400°C under a nitrogen atmosphere for 10 minutes and cooled to room temperature to obtain the FeC-FeNi / Ni@CNTs catalyst precursor.

[0084] The catalyst described in this comparative example was used continuously for 10 rounds. After the reaction was completed, the obtained gas components and nano-carbon materials were analyzed. The composition of gas products, cumulative hydrogen and nano-carbon material yield are shown in Table 1.

[0085] Example 2

[0086] The specific steps for microwave catalytic recovery of mixed plastics consisting of low-density polyethylene, polyvinyl chloride, and polytetrafluoroethylene are as follows:

[0087] 1) The collected low-density polyethylene, polyvinyl chloride and polytetrafluoroethylene plastics were crushed and mixed in a mass ratio of 8:1:1, and then mixed with FeC-FeCo / Co@CNTs catalyst precursor in a mass ratio of 1:1 to obtain a mixture.

[0088] 2) Place 30g of the mixture in the lower layer of the reaction vessel, and place 5g of the catalyst precursor separately in the upper layer of the reaction vessel. Then purge the oxygen in the reaction vessel with nitrogen for 10 min at a flow rate of 100 ml / min. After purging, set the microwave irradiation power to 600 W and the frequency to 2450 MHz, and react for 10 min under a nitrogen atmosphere. The catalyst described in this embodiment was used continuously for 30 rounds. After the reaction, the obtained gas components and nano-carbon materials were analyzed. The composition of the gas products, the cumulative hydrogen, and the yield of nano-carbon materials are shown in Table 2.

[0089] Table 2

[0090]

[0091] The synthesis steps of the FeC-FeCo / Co@CNTs catalyst precursor used in this example are as follows:

[0092] (1) Mix ferric chloride, cobalt citrate and activated carbon in a mass ratio of 1:5:1 and then irradiate them in a nitrogen atmosphere with a microwave power of 400W (frequency of 2450MHz) for 30 minutes.

[0093] (2) After cooling to room temperature, the FeC-FeCo / Co@CNTs catalyst precursor and activated carbon are obtained by sieving with a 100-mesh sieve. The activated carbon can be reused.

[0094] Example 3

[0095] The specific steps for microwave catalytic recovery of mixed plastics including low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polytetrafluoroethylene are as follows:

[0096] 1) The collected low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyvinyl chloride and polytetrafluoroethylene plastics were crushed and mixed in a mass ratio of 15:7:2:5:7:5, and then mixed with W / Ni@CNTs catalyst precursor in a mass ratio of 5:1 to obtain a mixture.

[0097] 2) Place 60g of the mixture in the lower layer of the reaction vessel, and place 5g of the catalyst precursor separately in the upper layer of the reaction vessel. Then purge the oxygen in the reaction vessel with nitrogen for 10 min at a flow rate of 100 ml / min. After purging, set the microwave irradiation power to 1000 W and the frequency to 2450 MHz, and react for 5 min under a nitrogen atmosphere. The catalyst described in this embodiment was used continuously for 7 rounds. After the reaction, the obtained gas components and nano-carbon materials were analyzed. The composition of the gas products, the cumulative hydrogen, and the yield of nano-carbon materials are shown in Table 3.

[0098] Table 3

[0099]

[0100] The synthesis steps of the W / Ni@CNTs catalyst precursor used in this embodiment are as follows:

[0101] (1) Nickel acetate, tungsten chloride and graphite were mixed evenly in a mass ratio of 4:30:15, and then irradiated in a nitrogen atmosphere with a microwave power of 600W (frequency of 2450MHz) for 10min.

[0102] (2) After cooling to room temperature, W / Ni@CNTs catalyst precursor and graphite are obtained by sieving with a 300-mesh sieve. Graphite can be reused.

[0103] Example 4

[0104] The specific steps for microwave catalytic recovery of mixed plastics including low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polytetrafluoroethylene are as follows:

[0105] 1) The collected low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyvinyl chloride and polytetrafluoroethylene plastics were crushed and mixed in a mass ratio of 40:30:40:20:5:1. Then, they were mixed with FeC / Zn / Co@CNTs catalyst precursor in a mass ratio of 4:1 to obtain a mixture.

[0106] 2) Place 70g of the mixture in the lower layer of the reaction vessel, and place 10g of the catalyst precursor separately in the upper layer of the reaction vessel. Then purge the oxygen in the reaction vessel with nitrogen for 10 min at a flow rate of 100 ml / min. After purging, set the microwave irradiation power to 1500 W and the frequency to 2450 MHz, and react for 5 min under a nitrogen atmosphere. The catalyst described in this embodiment was used continuously for 15 rounds. After the reaction, the obtained gas components and nano-carbon materials were analyzed. The composition of the gas products, the cumulative hydrogen, and the yield of nano-carbon materials are shown in Table 4.

[0107] Table 4

[0108]

[0109] The synthesis steps of the FeC / Zn / Co@CNTs catalyst precursor used in this embodiment are as follows:

[0110] (1) Mix iron acetylacetone and silicon carbide at a mass ratio of 1:1, and then irradiate them under a nitrogen atmosphere and microwave power of 800W (frequency of 2450MHz) for 5 minutes.

[0111] (2) After cooling to room temperature, FeC catalyst precursor and silicon carbide are obtained by sieving with a 200-mesh sieve. Silicon carbide can be reused.

[0112] (3) The obtained FeC catalyst precursor was mixed with zinc chloride and cobalt chloride at a mass ratio of 20:3:5. Then, it was irradiated in a nitrogen atmosphere and microwave power of 800W (frequency of 2450MHz) for 30min to obtain the FeC / Zn / Co@CNTs catalyst precursor.

[0113] Example 5

[0114] The specific steps for microwave catalytic recovery of mixed plastics consisting of low-density polyethylene, polyvinyl chloride, and polytetrafluoroethylene are as follows:

[0115] 1) The collected low-density polyethylene, polyvinyl chloride and polytetrafluoroethylene plastics were crushed and mixed in a mass ratio of 1:9:1, and then mixed with FeC / Cu / Mg@CNTs catalyst precursor in a mass ratio of 1:1 to obtain a mixture.

[0116] 2) Place 50g of the mixture in the lower layer of the reaction vessel, and place 10g of the catalyst precursor separately in the upper layer of the reaction vessel. Then purge the oxygen in the reaction vessel with nitrogen for 10 min at a flow rate of 100 ml / min. After purging, set the microwave irradiation power to 600 W and the frequency to 2450 MHz, and react for 5 min under a nitrogen atmosphere. The catalyst described in this embodiment was used continuously for 35 rounds. After the reaction, the obtained gas components and nano-carbon materials were analyzed. The composition of the gas products, the cumulative hydrogen, and the yield of nano-carbon materials are shown in Table 5.

[0117] Table 5

[0118]

[0119] The synthesis steps of the FeC / Cu / Mg@CNTs catalyst precursor used in this example are as follows:

[0120] (1) Mix iron acetylacetone and zinc oxide at a mass ratio of 3:1, and then irradiate them under a nitrogen atmosphere and a microwave power of 500W (frequency of 2450MHz) for 25 minutes.

[0121] (2) After cooling to room temperature, FeC catalyst precursor and zinc oxide are obtained by sieving with a 200-mesh sieve. Zinc oxide can be reused.

[0122] (3) The obtained FeC catalyst precursor, copper chloride and magnesium nitrate were mixed evenly in a mass ratio of 5:2::2, and then irradiated under a nitrogen atmosphere and a microwave power of 500W (frequency of 2450MHz) for 30min to obtain the FeC / Cu / Mg@CNTs catalyst precursor.

[0123] Example 6

[0124] The specific steps for microwave catalytic recovery of mixed plastics including low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polytetrafluoroethylene are as follows:

[0125] 1) The collected low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyvinyl chloride and polytetrafluoroethylene plastics were crushed and mixed in a mass ratio of 10:10:3:10:5:5, and then mixed with Co / W@CNTs catalyst precursor in a mass ratio of 2:1 to obtain a mixture.

[0126] 2) Place 10g of the mixture in the lower layer of the reaction vessel, and place 3g of the catalyst precursor separately in the upper layer of the reaction vessel. Then purge the oxygen in the reaction vessel with nitrogen for 10 min at a flow rate of 100 ml / min. After purging, set the microwave irradiation power to 800 W and the frequency to 2450 MHz, and react for 8 min under a nitrogen atmosphere. The catalyst described in this embodiment was used continuously for 20 rounds. After the reaction, the obtained gas components and nano-carbon materials were analyzed. The composition of the gas products, the cumulative hydrogen, and the yield of nano-carbon materials are shown in Table 6.

[0127] Table 6

[0128]

[0129] The synthesis steps of the Co / W@CNTs catalyst precursor used in this embodiment are as follows:

[0130] (1) Cobalt acetate and indium oxide were mixed evenly at a mass ratio of 5:1, and then irradiated under a nitrogen atmosphere and a microwave power of 400W (frequency of 2450MHz) for 30min.

[0131] (2) After cooling to room temperature, the Co@CNTs catalyst precursor and indium oxide are obtained by sieving with a 100-mesh sieve. The indium oxide can be reused.

[0132] (3) The obtained Co@CNTs catalyst precursor and tungsten chloride were mixed evenly at a mass ratio of 30:7, and then irradiated under a nitrogen atmosphere and a microwave power of 400W (frequency of 2450MHz) for 5 minutes to obtain the Co / W@CNTs catalyst precursor.

[0133] Example 7

[0134] The specific steps for microwave catalytic recovery of mixed plastics including low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyvinylidene chloride, polyvinylidene fluoride, and polyethylene terephthalate are as follows:

[0135] 1) The collected low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyvinylidene chloride, polyvinylidene fluoride and polyethylene terephthalate plastics were crushed and mixed in a mass ratio of 6:3:10:6:3:1:5, and then mixed with Ni / Co / W@CNTs catalyst precursor in a mass ratio of 2:1 to obtain a mixture.

[0136] 2) Place 50g of the mixture in the lower layer of the reaction vessel, and place 10g of the catalyst separately in the upper layer of the reaction vessel. Then purge the oxygen in the reaction vessel with nitrogen for 10 min at a flow rate of 100 ml / min. After purging, set the microwave irradiation power to 1000 W and the frequency to 2450 MHz, and react for 10 min under a nitrogen atmosphere. The catalyst described in this embodiment was used continuously for 20 rounds. After the reaction, the obtained gas components and nano-carbon materials were analyzed. The composition of the gas products, the cumulative hydrogen, and the yield of nano-carbon materials are shown in Table 7.

[0137] Table 7

[0138]

[0139] The synthesis steps of the Ni / Co / W@CNTs catalyst precursor used in this embodiment are as follows:

[0140] (1) Nickel citrate, cobalt chloride, tungsten chloride and activated carbon were mixed evenly in a mass ratio of 2:33:10:5, and then irradiated under a nitrogen atmosphere and a microwave power of 600W (frequency of 2450MHz) for 15 minutes.

[0141] (2) After cooling to room temperature, Ni / Co / W@CNTs catalyst precursor and activated carbon are obtained by sieving with a 100-mesh sieve. The activated carbon can be reused.

[0142] Example 8

[0143] Microwave catalytic recycling of contaminated mixed plastics, polyvinylidene chloride (PVDC), and polyvinylidene fluoride (PVDF) mixtures from landfills follows these steps:

[0144] 1) The collected contaminated mixed plastics, polyvinylidene chloride and polyvinylidene fluoride plastics from the landfill were crushed and mixed in a mass ratio of 8:1:1. The contaminated mixed plastics from the landfill mainly consist of polyethylene, polypropylene, polystyrene, polyethylene terephthalate and impurities, with contents of 40wt%, 35wt%, 4wt%, 11wt% and 10wt%, respectively. Then, it was mixed with FeC / Cu / Mg@CNTs catalyst precursor in a mass ratio of 5:1 to obtain the mixture.

[0145] 2) Place 60g of the mixture in the lower layer of the reaction vessel, and place 5g of the catalyst precursor separately in the upper layer of the reaction vessel. Then purge the oxygen in the reaction vessel with nitrogen for 10 min at a flow rate of 100 ml / min. After purging, set the microwave irradiation power to 1800 W and the frequency to 2450 MHz, and react for 6 min under a nitrogen atmosphere. The catalyst described in this embodiment was used continuously for 15 rounds. After the reaction, the obtained gas components and nano-carbon materials were analyzed. The composition of the gas products, the cumulative hydrogen, and the yield of nano-carbon materials are shown in Table 8.

[0146] Table 8

[0147]

[0148] The synthesis steps of the FeC / Cu / Mg@CNTs catalyst precursor used in this example are as follows:

[0149] (1) Mix iron acetylacetone and zinc oxide at a mass ratio of 3:1, and then irradiate them under a nitrogen atmosphere and a microwave power of 500W (frequency of 2450MHz) for 25 minutes.

[0150] (2) After cooling to room temperature, FeC catalyst precursor and zinc oxide are obtained by sieving with a 300-mesh sieve. Zinc oxide can be reused.

[0151] (3) The obtained FeC catalyst precursor, copper chloride and magnesium nitrate were mixed evenly in a mass ratio of 5:2:2, and then irradiated under a nitrogen atmosphere and a microwave power of 500W (frequency of 2450MHz) for 30min to obtain the FeC / Cu / Mg@CNTs catalyst precursor.

[0152] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for in-situ construction of a catalyst precursor for microwave catalytic recovery of chlorofluorocarbon mixed waste plastics, the method comprising the following steps: (1) Mix the metal source and microwave heating medium, and irradiate them with microwaves in a normal pressure and low oxygen environment to obtain a solid component; (2) After the solid components have cooled to room temperature, they are sieved using a 50-500 mesh sieve to obtain the microwave heating medium and the catalyst precursor.

2. The method according to claim 1, wherein, In step (1), the metal source is selected from at least one of nickel, iron, cobalt, manganese, zinc, copper, tungsten, and magnesium sources; and / or, In step (1), the microwave heating medium source is selected from one or more of graphite, activated carbon, carbon nanotubes, silicon carbide, carbon black, zinc oxide, indium oxide, and indium tin oxide; and / or, In step (1), the particle size of the microwave heating medium source is ≥1 mm, for example, 1 mm-10 mm; and / or, In step (1), the mass ratio of the metal source to the microwave heating medium is 1:(0.01-100). In step (1), the microwave irradiation time is 1-60 min; and / or, In step (1), the power of the microwave irradiation is ≥50W, for example, 100-2000W; and / or, In step (1), the frequency of the microwave irradiation is 2450MHz or 915MHz.

3. The method according to claim 1 or 2, wherein, The method further includes the following steps: (3) The catalyst precursor obtained in step (2) is mixed with a metal source and microwave irradiated in a normal pressure and low oxygen environment to prepare the catalyst precursor.

4. The method according to claim 3, wherein, In step (3), the mass ratio of the catalyst precursor to the metal source obtained in step (2) is 1:(0.01-100); and / or, In step (3), the microwave irradiation time is 1-60 min; and / or, In step (3), the power of the microwave irradiation is ≥50W; and / or, In step (3), the frequency of the microwave irradiation is 2450MHz or 915MHz.

5. The catalyst precursor prepared by the method according to any one of claims 1-4. Preferably, the catalyst precursor is a carbon-dispersed metal catalyst precursor. Preferably, the carbon-dispersed metal catalyst precursor comprises a metal carbide, a metal, and carbon; the metal is an elemental metal and / or a metal alloy. Preferably, the carbon-dispersed metal catalyst precursor is composed of a metal carbide, a metal, and carbon, and the metal carbide and the metal are dispersed on a carbon support.

6. An in-situ construction method for a catalyst used in microwave catalytic recovery of chlorofluorocarbon mixed waste plastics, the method comprising the following steps: (a) The catalyst precursor prepared by any one of the methods of claims 1-4 is mixed with chlorofluoropolymer waste plastic and subjected to microwave irradiation in a normal pressure and low oxygen environment to prepare the catalyst.

7. The method according to claim 6, wherein, In step (a), the chlorofluoropolymer waste plastic is selected from at least one of polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, and polyvinylidene fluoride; or a combination of at least one of polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, and polyvinylidene fluoride, and at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyurethane; and / or, In step (a), the mass ratio of the catalyst precursor to the chlorofluorocarbon mixed waste plastic is 1:(0.05-50); and / or, In step (a), the microwave irradiation time is 1-60 min; and / or, In step (a), the power of the microwave irradiation is ≥50W, for example, 100-2000W; and / or, In step (3), the frequency of the microwave irradiation is 2450MHz or 915MHz.

8. The catalyst prepared by the method of claim 6 or 7. Preferably, the catalyst is a carbon-dispersed metal alloy catalyst or a carbon-dispersed elemental metal catalyst. Preferably, the carbon-dispersed metal alloy catalyst comprises a metal alloy and carbon; preferably, the carbon-dispersed metal alloy catalyst is composed of a metal alloy and carbon, and the metal alloy is dispersed on a carbon support; or, the carbon-dispersed metal alloy catalyst comprises a metal alloy, a metal element, and carbon; preferably, the carbon-dispersed metal alloy catalyst is composed of a metal alloy, a metal element, and carbon, and the metal alloy and the metal element are dispersed on a carbon support. Preferably, the carbon-dispersed metal catalyst comprises a metal element and carbon; preferably, the carbon-dispersed metal catalyst is composed of a metal element and carbon, and the metal element is dispersed on a carbon support.

9. A microwave catalytic recycling method for chlorofluorocarbon mixed waste plastics, the method comprising the following steps: (i) The catalyst precursor prepared by the method according to any one of claims 1-4 is mixed with chlorofluorocarbon mixed waste plastics, and microwave irradiated in a normal pressure, low oxygen environment to prepare hydrogen and nano-carbon materials, thereby realizing the microwave catalytic recovery of chlorofluorocarbon mixed waste plastics; and / or, (ii) The catalyst prepared by the method of claim 6 or 7 is mixed with chlorofluoropolymer waste plastics and microwave irradiated in an atmospheric pressure and low oxygen environment to prepare hydrogen and nano-carbon materials, thereby realizing microwave catalytic recycling of chlorofluoropolymer waste plastics.

10. The method according to claim 9, wherein, In step (i), the mass ratio of the catalyst precursor to the chlorofluorocarbon mixed waste plastic is 1:(0.05-50); and / or, In step (ii), the mass ratio of the catalyst to the chlorofluorocarbon mixed waste plastic is 1:(0.05-50); and / or, In steps (i) and (ii), the microwave irradiation time may be the same or different, and is independently between 1 and 60 min; and / or, In steps (i) and (ii), the power of the microwave irradiation may be the same or different, and is independently ≥50W, for example, 100-2000W; and / or, In steps (i) and (ii), the microwave irradiation frequencies are the same or different, and are 2450MHz or 915MHz independently of each other.

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