A foam nickel-supported MMO array structure microwave catalyst, a preparation method thereof and application thereof in chemical recycling of waste plastics

Abstract

The application provides a foam nickel-supported MMO array structure microwave catalyst, a preparation method thereof and application of the foam nickel-supported MMO array structure microwave catalyst in chemical recycling of waste plastics, and belongs to the technical field of catalysts and plastic chemical recycling.The MMO array structure in the form of a sheet in the foam nickel-supported MMO array structure microwave catalyst is in-situ grown on foam nickel, a CoNiFe ternary hydrotalcite precursor is prepared by a hydrothermal method and is calcined to obtain the foam nickel-supported MMO array structure microwave catalyst.The application constructs a ternary MMO microwave catalyst based on a CoNiFe-LDHs precursor template, and applies the catalyst to rapid catalytic conversion of polyolefin plastics into hydrogen and carbon nanotubes, realizes efficient, high-selective and high-stable conversion of waste polyolefin plastics, and has the advantages of simple operation, low price, high catalytic efficiency, green environmental protection and the like, and is easy to mass produce.

Description

Technical Field

[0001] This invention belongs to the field of catalyst and plastic chemical recycling technology, and particularly relates to a foamed nickel supported MMO array structure microwave catalyst, its preparation method and its application in waste plastic chemical recycling. Background Technology

[0002] Plastic is ubiquitous in people's daily lives. Its practical advantages, such as being lightweight, portable, low-cost, and durable, have made it an indispensable part of our daily routines. However, statistics show that the world has produced a cumulative total of 10.5 billion tons of plastic, with an annual growth rate of 360 million tons. Furthermore, due to its long natural degradation time and low recycling efficiency (<15%), a large amount of waste plastic has accumulated, leading to serious resource waste and white pollution.

[0003] To address the current state of white pollution, researchers have proposed several methods for recycling and reusing waste plastics, such as mechanical recycling and chemical decomposition recycling. Mechanical recycling uses physical methods to reprocess plastics into new, reusable products. Its simple process and low cost make it a common method for recycling polyolefin plastics. However, this method is only suitable for processing and recycling single types of plastics, while waste plastics generated in real life are often a mixture of multiple types, thus limiting its application. Chemical decomposition recycling uses chemical reagents to break down the long chains of plastics, transforming them into smaller monomer molecules. Also known as chemical recycling, it uses chemical processes such as pyrolysis, hydrocracking, solvent decomposition, and photo-reforming to convert plastics into valuable chemical substances. During this process, the repeating hydrocarbon backbone in the plastic is also broken down. Because the resulting oligomers with shorter chains are economically valuable, this strategy has received widespread attention.

[0004] Polyolefins constitute a large proportion of waste plastics, and the pyrolysis products are mainly hydrocarbons. Pyrolysis without a catalyst requires a temperature of at least 500℃. Simple pyrolysis suffers from high energy consumption, long reaction time, and low selectivity and conversion rate. Microwave catalysis, due to its rapid heating and high energy, can significantly shorten reaction time and reduce energy consumption. Factors affecting product conversion rate include microwave power, the ability to absorb microwaves and convert energy, reaction temperature, and the ratio of catalyst to raw materials. Microwave catalytic reactions exhibit significant differences in heating rate, product yield, and selectivity depending on the type of catalyst. The ratio of polyolefin plastic to catalyst also affects product yield and selectivity. A comprehensive analysis of these parameters is needed to obtain the optimal catalytic effect. Among the many parameter conditions, the development of microwave catalysts is still relatively rare. On the one hand, microwave catalysts need to effectively absorb microwaves for rapid heating and acceleration; on the other hand, they need to fully retain catalytic sites to activate the decomposition of plastics into small molecule hydrocarbon free radicals. Under the action of the catalyst, these small molecule hydrocarbon free radicals transfer electrons, breaking C-C and CH bonds to generate low-carbon gases such as H2 and solid carbon materials—industrial products with added value. Despite extensive previous work, there is still considerable room for improvement in the product selectivity and conversion rate of microwave catalytic reactions, as well as in the quality of the catalysts themselves. Furthermore, previously reported microwave catalysts are all powder structures, and their sites tend to lose activity after prolonged contact with plastics, while solid product separation also presents challenges. Therefore, the rational development of a catalyst with high catalytic performance and long-term recyclability is of significant research value. Summary of the Invention

[0005] To address the aforementioned technical challenges, this invention proposes a microwave catalyst with high performance, stable structure, and low cost for the efficient and selective chemical recycling of plastics. The catalyst is based on a nickel-supported MMO array structure, its preparation method, and its application in the chemical recycling of waste plastics. The invention constructs a ternary MMO microwave catalyst using a CoNiFe-LDHs precursor template and applies it to the rapid catalytic conversion of polyolefin plastics into hydrogen and carbon nanotubes, achieving efficient, selective, and stable conversion of waste polyolefin plastics.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One of the technical solutions of the present invention:

[0008] A microwave catalyst with a nickel foam-supported MMO array structure, wherein the sheet-like MMO array structure is grown in situ on nickel foam, and MMO represents mixed metal oxide.

[0009] The catalyst exhibits an array structure and has excellent microwave absorption properties, thereby promoting the breaking of C-C and CH bonds in plastic molecules, enabling the reaction to proceed rapidly. This allows waste plastics to be quickly and efficiently converted into high-value-added industrial raw materials (H2, solid carbon materials, etc.), ultimately achieving efficient chemical recycling of waste plastics.

[0010] The second technical solution of the present invention:

[0011] A method for preparing the aforementioned nickel foam-supported MMO array structure microwave catalyst involves preparing a CoNiFe ternary hydrotalcite precursor via hydrothermal method and then calcining it to obtain the nickel foam-supported MMO array structure microwave catalyst, also known as the CoNiFe-MMO ternary array structure microwave catalyst.

[0012] Furthermore, the hydrothermal preparation of the CoNiFe ternary hydrotalcite precursor includes the following steps:

[0013] Cobalt nitrate, nickel nitrate, ferric nitrate, ammonium fluoride, and urea were dissolved in water, and then nickel foam was immersed in the resulting mixture for a hydrothermal reaction to obtain the CoNiFe ternary hydrotalcite precursor (CoNiFe-LDHs precursor).

[0014] Further, the hydrothermal reaction is carried out at a temperature of 80-120°C for a time of 12-36 hours. More preferably, the hydrothermal reaction is carried out at a temperature of 120°C for a time of 24 hours.

[0015] Under the above hydrothermal reaction conditions, LDHs can be fully crystallized, resulting in a more stable structure.

[0016] Furthermore, the molar ratio of cobalt nitrate, nickel nitrate, and ferric nitrate is 1.5:1.5:1.

[0017] By limiting the molar ratio of each raw material, a more stable LDH structure can be obtained.

[0018] Furthermore, the concentration of urea in the mixture is 300-500 mmol / L. -1 More preferably, the concentration of urea in the mixture is 400 mmol / L. -1 .

[0019] The slow decomposition of urea is utilized to achieve the pH required for the synthesis of LDHs materials.

[0020] Furthermore, the calcination temperature is 300-600℃, the calcination time is 0.5-2h, and the heating rate is 2-10℃ / min. -1 Preferably, the calcination time is 1 hour, and the heating rate is 5°C / min. -1 .

[0021] By controlling the calcination temperature, time, and heating rate, LDHs can be fully calcined to produce MMOs without damaging their structure and catalytic active sites by high temperatures. If the above range is exceeded, the corresponding technical effect will not be produced.

[0022] More specifically, the preparation method of the microwave catalyst with nickel foam-supported MMO array structure of the present invention includes the following steps:

[0023] Cobalt nitrate, nickel nitrate, ferric nitrate, ammonium fluoride, and urea were dissolved in 30 mL of deionized water to obtain a mixture. The molar ratio of cobalt nitrate, nickel nitrate, and ferric nitrate in the mixture was 1.5:1.5:1, and the concentration of urea in the mixture was 400 mmol / L. -1 The mixture was transferred to a hydrothermal reactor, and nickel foam was placed vertically in the reactor and submerged in the mixture. CoNiFe-LDHs precursor was prepared by hydrothermal synthesis. The hydrothermal synthesis temperature was controlled at 120℃ and held at a constant temperature for 24 hours. The prepared CoNiFe-LDHs precursor was washed with deionized water and dried at 60℃ for 12 hours.

[0024] The dried CoNiFe-LDHs precursor was heated to 350-600℃ and calcined for 1 hour, with the heating rate controlled at 5℃ / min. -1 A microwave catalyst with a nickel foam-supported MMO array structure was obtained.

[0025] The third technical solution of the present invention:

[0026] The application of the described nickel-foamed MMO array structure microwave catalyst in microwave catalytic conversion of polyolefin plastics.

[0027] Furthermore, the microwave power during the microwave catalytic conversion process is 300-600W, and the temperature during the microwave catalytic conversion process is ≤600℃.

[0028] Furthermore, the microwave catalytic conversion process is carried out in an Ar atmosphere with an Ar gas flow rate of 5 L / min.

[0029] Furthermore, the polyolefin plastic includes polyethylene (PE), polypropylene (PP), and polystyrene (PS), etc.

[0030] Furthermore, the process of microwave catalytic conversion of polyolefin plastics using a nickel-supported MMO array structure microwave catalyst is as follows:

[0031] The nickel-supported MMO array structure microwave catalyst was uniformly mixed with polyolefin plastic and placed in a microwave reactor. Before microwave catalytic conversion, inert gas (Ar) was introduced at a flow rate of 5 L / min for 30 min to eliminate residual air. During the reaction, Ar was continuously introduced at the same flow rate until the reaction was completed. A microwave reactor with a frequency of 2.45 GHz was used as the energy source for the microwave catalytic experiment. The power of the microwave reactor was controlled at 800 W, and the maximum reaction temperature was 600 °C. Microwave irradiation was performed, and the gaseous and solid products generated by the reaction were collected.

[0032] The catalyst synthesized in this invention exhibits excellent microwave catalytic activity because:

[0033] This invention utilizes CoNiFe-LDHs precursors as templates to construct a CoNiFe-MMO ternary array microwave catalyst with excellent microwave catalytic conversion performance of polyolefin plastics through calcination. This microwave catalyst retains the original skeletal structure characteristics of the CoNiFe-LDHs precursors, exhibiting a sheet-like array structure with abundant pores, which facilitates substrate diffusion. Furthermore, the MMO array structure is grown in situ on nickel foam, fully exposing the active sites, thus enhancing microwave absorption and accelerating the heating rate. In addition, by immobilizing the catalyst on the nickel foam surface, the carbon nanotubes of the product can be separated, avoiding deactivation caused by plastic coating of the catalytic sites.

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] The CoNiFe-MMO ternary array structure microwave catalyst constructed in this invention exhibits significantly enhanced microwave energy absorption and conversion capabilities compared to single Co3O4, Fe3O4, and NiO microwave catalysts, with a markedly faster heating rate. Furthermore, the microwave catalyst prepared in this invention enables rapid catalytic conversion of polyolefin plastics. Compared to traditional chemical recycling technologies, it offers advantages such as ease of operation, low cost, high catalytic efficiency, and environmental friendliness, making it suitable for mass production and demonstrating broad commercial application value. Attached Figure Description

[0036] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0037] Figure 1 This is an X-ray powder diffraction pattern of the CoNiFe-LDHs precursor after drying treatment in Example 1 of the present invention;

[0038] Figure 2The X-ray powder diffraction pattern of the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 of this invention;

[0039] Figure 3 This is a scanning electron microscope image of the CoNiFe-LDHs precursor after drying treatment in Example 1 of the present invention;

[0040] Figure 4 This is a scanning electron microscope image of the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 of this invention;

[0041] Figure 5 This is a scanning electron microscope (SEM) energy dispersive spectroscopy (EDS) image of the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 of this invention after removing nickel foam.

[0042] Figure 6 The following are the elemental analysis results of the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 of this invention after removing nickel foam;

[0043] Figure 7 The graphs show the performance of microwave catalysts prepared at different calcination temperatures in Examples 1-4 and Comparative Example 1 in the microwave catalytic conversion of PE to hydrogen.

[0044] Figure 8 The graph shows the selectivity of gaseous products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1.

[0045] Figure 9 The graph shows the selectivity of gaseous products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 2.

[0046] Figure 10 This is a selectivity diagram of gaseous products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 3.

[0047] Figure 11 This is a selectivity diagram of the gas products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 4.

[0048] Figure 12 Scanning electron microscope image of the reaction solid products collected from the microwave catalytic conversion of PE using the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1.

[0049] Figure 13The scanning electron microscope energy spectrum of the reaction solid products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 is shown.

[0050] Figure 14 The elemental analysis results are for the reaction solid products collected from the microwave catalytic conversion of PE using the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1.

[0051] Figure 15 Raman spectra of the reaction solid products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1.

[0052] Figure 16 Selectivity of PE gas products after four cycles of microwave catalytic conversion using the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1.

[0053] Figure 17 The selectivity diagram of the microwave catalytic conversion of PP gas products by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 5 is shown.

[0054] Figure 18 The selectivity diagram of the microwave catalytic conversion of PS gas products by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 6 is shown.

[0055] Figure 19 The selectivity diagram of the microwave catalytic conversion of waste plastic gas products by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 7 is shown.

[0056] Figure 20 The graph shows a comparison of the microwave catalytic performance of the microwave catalysts prepared in Example 1 and Comparative Examples 2-4 in converting PE to hydrogen. Detailed Implementation

[0057] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0058] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0059] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0060] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0061] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0062] This invention proposes a nickel foam-supported MMO array structure microwave catalyst, wherein the sheet-like MMO array structure is grown in situ on nickel foam, and MMO represents mixed metal oxide.

[0063] The catalyst exhibits an array structure and has excellent microwave absorption properties, thereby promoting the breaking of C-C and CH bonds in plastic molecules, enabling the reaction to proceed rapidly. This allows waste plastics to be quickly and efficiently converted into high-value-added industrial raw materials (H2, solid carbon materials, etc.), ultimately achieving efficient chemical recycling of waste plastics.

[0064] This invention also proposes a method for preparing the aforementioned nickel-foamed MMO array structure microwave catalyst. A CoNiFe ternary hydrotalcite precursor is prepared by hydrothermal method and then calcined to obtain the nickel-foamed MMO array structure microwave catalyst, also known as the CoNiFe-MMO ternary array structure microwave catalyst.

[0065] In some preferred embodiments of the present invention, the preparation of the CoNiFe ternary hydrotalcite precursor by hydrothermal method includes the following steps:

[0066] Cobalt nitrate, nickel nitrate, ferric nitrate, ammonium fluoride, and urea were dissolved in water, and nickel foam was immersed in the resulting mixture for hydrothermal reaction to obtain the CoNiFe ternary hydrotalcite precursor (CoNiFe-LDHs precursor).

[0067] In this embodiment of the invention, the hydrothermal reaction is carried out at a temperature of 80-120°C for a duration of 12-36 hours.

[0068] In a preferred embodiment of the present invention, the hydrothermal reaction is carried out at a temperature of 120°C for 24 hours.

[0069] In some preferred embodiments of the present invention, the molar ratio of cobalt nitrate, nickel nitrate and ferric nitrate is 1.5:1.5:1.

[0070] In this embodiment of the invention, the concentration of urea in the mixture is 300-500 mmol / L. -1 .

[0071] In a preferred embodiment of the present invention, the concentration of urea in the mixture is 400 mmol / L. -1 .

[0072] In this embodiment of the invention, the calcination temperature is 300-600℃, the calcination time is 0.5-2h, and the heating rate is 2-10℃ / min. -1 .

[0073] In a preferred embodiment of the present invention, the calcination time is 1 hour and the heating rate is 5°C / min. -1 .

[0074] This invention also proposes the application of the above-mentioned nickel foam-supported MMO array structure microwave catalyst in microwave catalytic conversion of polyolefin plastics.

[0075] In this embodiment of the invention, the microwave power during the microwave catalytic conversion process is 600-1000W, and the temperature during the microwave catalytic conversion process is ≤600℃.

[0076] In a preferred embodiment of the present invention, the power of the microwave during the microwave catalytic conversion process is 800W, and the temperature of the microwave catalytic conversion process is ≤600℃.

[0077] In some preferred embodiments of the present invention, the microwave catalytic conversion process is carried out in an Ar atmosphere with an Ar gas flow rate of 5 L / min.

[0078] In some preferred embodiments of the present invention, the polyolefin plastic includes polyethylene (PE), polypropylene (PP), and polystyrene (PS), etc.

[0079] All raw materials used in the embodiments of this invention were obtained through commercial purchase.

[0080] The technical solution of the present invention will be further illustrated by the following embodiments.

[0081] Example 1

[0082] 0.218 g of cobalt nitrate hexahydrate (0.00075 mol), 0.218 g of nickel nitrate hexahydrate (0.00075 mol), 0.202 g (0.0005 mol) of ferric nitrate nonahydrate, 0.185 g of ammonium fluoride, and 0.72 g of urea were dissolved in 30 mL of deionized water to obtain a mixture. The molar ratio of cobalt nitrate, nickel nitrate, and ferric nitrate in the mixture was 1.5:1.5:1, and the concentration of urea in the mixture was 400 mmol / L. -1 The mixture was transferred to a hydrothermal reactor, and a 2cm×3cm nickel foam was placed vertically in the reactor and submerged in the mixture. CoNiFe-LDHs precursor was prepared by hydrothermal synthesis. The hydrothermal synthesis temperature was controlled at 120℃ and held at that temperature for 24h. The prepared CoNiFe-LDHs precursor was washed with deionized water and dried at 60℃ for 12h.

[0083] The dried CoNiFe-LDHs precursor was heated to 500℃ and calcined for 1 hour, with the heating rate controlled at 5℃ / min. -1 A microwave catalyst with a CoNiFe-MMO ternary array structure was obtained and designated as CoNiFe-500.

[0084] 1.5g of the CoNiFe-MMO ternary array structure microwave catalyst prepared above was mixed evenly with 1.5g of commercial polyolefin plastic (PE) and placed in a microwave reactor. Before microwave catalytic conversion, inert gas (Ar) was introduced at a flow rate of 5L / min for 30min to eliminate residual air. During the reaction, Ar was continuously introduced at the same flow rate until the reaction was completed. A microwave reactor with a frequency of 2.45GHz was used as the energy source for the microwave catalytic experiment. The power of the microwave reactor was controlled at 800W and the maximum reaction temperature was 600℃. Microwave irradiation was performed, and the gases produced by the reaction were collected. The composition of the products was analyzed by gas chromatography. The solid products of the reaction were collected and characterized by Raman spectroscopy and BET method.

[0085] Figure 1 This is an X-ray powder diffraction pattern of the CoNiFe-LDHs precursor after drying treatment in Example 1 of the present invention. Figure 2 This is the X-ray powder diffraction pattern of the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 of this invention. (Comparison) Figure 1 and Figure 2 It can be seen that the CoNiFe-LDHs precursor and the CoNiFe-MMO ternary array structure microwave catalyst were successfully prepared.

[0086] Figure 3 This is a scanning electron microscope image of the CoNiFe-LDHs precursor after drying treatment in Example 1 of the present invention. Figure 4This is a scanning electron microscope image of the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 of this invention. (Comparison) Figure 3 and Figure 4 It can be seen that both LDHs and MMO array structures were successfully grown on nickel foam.

[0087] Figure 5 The image shows the scanning electron microscope (SEM) energy dispersive spectroscopy (EDS) spectrum of the CoNiFe-MMO ternary array microwave catalyst prepared in Example 1 of this invention after ultrasonic oscillation to remove nickel foam (to avoid interference from the nickel content of the nickel foam on the elemental analysis of the catalyst). Figure 6 These are the results of elemental analysis. (From...) Figure 5 and Figure 6 It can be seen that the array structure is a CoNiFe ternary MMORPG.

[0088] Example 2

[0089] Same as Example 1, except that the dried CoNiFe-LDHs precursor was heated to 350°C and calcined for 1 hour, and is denoted as CoNiFe-350.

[0090] Example 3

[0091] Same as Example 1, except that the dried CoNiFe-LDHs precursor was heated to 400°C and calcined for 1 hour, and is denoted as CoNiFe-400.

[0092] Example 4

[0093] Same as Example 1, except that the dried CoNiFe-LDHs precursor was heated to 600°C and calcined for 1 hour, and is denoted as CoNiFe-600.

[0094] Example 5

[0095] Same as Example 1, except that the commercial polyolefin plastic is PP.

[0096] Example 6

[0097] Same as Example 1, except that the commercial polyolefin plastic is PS.

[0098] Example 7

[0099] Same as Example 1, except that commercial polyolefin plastic (PE) is replaced with waste plastic (collected from a daily necessities supermarket).

[0100] Comparative Example 1

[0101] Same as Example 1, except that the dried CoNiFe-LDHs precursor was heated to 700°C and calcined for 1 hour, and is denoted as CoNiFe-700.

[0102] The microwave catalysts prepared at different calcination temperatures in Examples 1-4 and Comparative Example 1 show the performance of microwave catalysis in converting PE to hydrogen. Figure 7 .Depend on Figure 7 It can be seen that the catalyst in Example 1 has the best ability to convert PE into hydrogen via microwave catalysis, with a hydrogen content of up to 95% in the collected gas. Examples 2-4 also basically reached about 80%, while the catalyst in Comparative Example 1 has the worst ability to convert PE into hydrogen, with a hydrogen content of less than 20%.

[0103] The selectivity of the gaseous products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 is shown in the figure. Figure 8 The selectivity of the gaseous products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 2 is shown in the figure. Figure 9 The selectivity of the gas products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 3 is shown in the figure. Figure 10 The selectivity of the gas products collected from the microwave catalytic conversion of PE by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 4 is shown in the figure. Figure 11 .Depend on Figures 8-11 It can be seen that the catalyst prepared by the method of the present invention can achieve rapid conversion of PE plastic, with H2 as the main gaseous product, and the calcination temperature of the catalyst with the highest performance is 500℃.

[0104] Scanning electron microscope image of the reaction solid products collected from the microwave catalytic conversion of PE using the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 is shown below. Figure 12 .

[0105] The scanning electron microscope (SEM) energy dispersive spectroscopy (EDS) spectrum of the reaction solid products collected from the microwave catalytic conversion of PE using the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 is shown below. Figure 13 , Figure 14 These are the results of elemental analysis.

[0106] The Raman spectrum of the reaction solid products collected from the microwave catalytic conversion of PE using the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 is shown below. Figure 15 .

[0107] Depend on Figures 12-15 It can be seen that the solid product of the catalyst in converting PE plastic is mainly carbon nanotubes.

[0108] The selectivity of the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 1 for the microwave catalytic conversion of PE gas in four cycles is shown in the figure. Figure 16.

[0109] The selectivity of the microwave catalytic conversion of PP gas products by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 5 is shown in the figure. Figure 17 .

[0110] The selectivity of the microwave catalytic conversion of PS gas products by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 6 is shown in the figure. Figure 18 .

[0111] The selectivity diagram of the microwave catalytic conversion of waste plastic gas products by the CoNiFe-MMO ternary array structure microwave catalyst prepared in Example 7 is shown in the figure. Figure 19 .

[0112] Depend on Figure 16-19 It can be seen that the catalyst prepared by the method of the present invention maintains good selectivity in the multiple cycles of plastic conversion and can convert a variety of different plastics, including those used in daily life.

[0113] Comparative Example 2

[0114] Same as Example 1, except that 0.218g cobalt nitrate hexahydrate (0.00075mol), 0.218g nickel nitrate hexahydrate (0.00075mol), and 0.202g (0.0005mol) ferric nitrate nonahydrate were replaced with 0.436g cobalt nitrate hexahydrate (0.0015mol) and 0.188g aluminum nitrate nonahydrate (0.0005mol) to obtain the Co3O4 microwave catalyst.

[0115] Comparative Example 3

[0116] Same as Example 1, except that 0.218g cobalt nitrate hexahydrate (0.00075mol), 0.218g nickel nitrate hexahydrate (0.00075mol), and 0.202g (0.0005mol) ferric nitrate nonahydrate were replaced with 0.385g magnesium nitrate hexahydrate (0.0015mol) and 0.202g ferric nitrate nonahydrate (0.0005mol) to obtain the Fe3O4 microwave catalyst.

[0117] Comparative Example 4

[0118] Same as Example 1, except that 0.218g cobalt nitrate hexahydrate (0.00075mol), 0.218g nickel nitrate hexahydrate (0.00075mol), and 0.202g (0.0005mol) ferric nitrate nonahydrate were replaced with 0.436g nickel nitrate hexahydrate (0.0015mol) and 0.188g aluminum nitrate nonahydrate (0.0005mol) to obtain the NiO microwave catalyst.

[0119] The performance comparison chart of microwave catalysis for the conversion of PE to hydrogen using microwave catalysts of Example 1 and Comparative Examples 2-4 (Co3O4, Fe3O4, NiO) is shown below. Figure 20 .

[0120] In summary, the CoNiFe-MMO ternary array microwave catalyst prepared by the method of this invention exhibits an array structure, which is beneficial for promoting the diffusion of reaction products and substrates during the catalytic process. The numerous exposed active sites enhance the electron transfer efficiency between the catalyst and plastics. Furthermore, this CoNiFe-MMO ternary array microwave catalyst possesses excellent microwave absorption capabilities, enabling rapid conversion of microwave energy into heat energy for rapid heating, thus promoting the activation and cleavage of C-C and CH bonds in polyolefin plastics. Compared to traditional plastic chemical recycling technologies, this invention utilizes a CoNiFe-MMO ternary array microwave catalyst for efficient plastic conversion via microwave catalysis, offering advantages such as being environmentally friendly, operating under mild conditions, and consuming low energy, thus possessing broad commercial application prospects.

[0121] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. The application of a foamed nickel-supported MMO array structure microwave catalyst in the microwave catalytic conversion of polyolefin plastics to produce hydrogen and carbon nanotubes, characterized in that, In the microwave catalyst with nickel foam-supported MMO array structure, the sheet-like MMO array structure is grown in situ on nickel foam. The preparation method of the nickel foam-supported MMO array structure microwave catalyst includes the following steps: Cobalt nitrate, nickel nitrate, ferric nitrate, ammonium fluoride, and urea are dissolved in water, and then nickel foam is immersed in the resulting mixture for a hydrothermal reaction to obtain a CoNiFe ternary hydrotalcite precursor; the hydrothermal reaction is carried out at a temperature of 80-120 ℃ for a time of 12-36 h. The CoNiFe ternary hydrotalcite precursor was calcined to obtain the foamed nickel supported MMO array structure microwave catalyst; the calcination temperature was 300-600℃, the calcination time was 0.5-2 h, and the heating rate was 2-10℃·min. -1 .

2. The application according to claim 1, characterized in that, The molar ratio of cobalt nitrate, nickel nitrate, and ferric nitrate is 1.5:1.5:

1.

3. The application according to claim 1, characterized in that, The concentration of urea in the mixture is 300-500 mmol / L. -1 .

4. The application according to claim 1, characterized in that, The microwave power during microwave catalytic conversion is 600-1000 W, and the temperature during microwave catalytic conversion is ≤600 ℃.

5. The application according to claim 1, characterized in that, The microwave catalytic conversion process was carried out in an Ar atmosphere at a flow rate of 5 L / min.

Images