A zinc oxide-based microwave heating material, its preparation method and application

Abstract

The present invention relates to the technical field of microwave heating, and particularly relates to a zinc oxide or zinc oxide-based microwave heating material, a preparation method thereof, and an application thereof in microwave treatment of carbon-containing materials. The present invention synthesizes the microwave heating material zinc oxide by a simple method, and uses a zinc oxide matrix by screening a suitable preparation method, and constructs a zinc oxide-based composite material with a micro-nano structural morphology of needles, petals and rods by using a modifier, so as to effectively improve the microwave heating efficiency of a variety of inorganic metals or non-metallic materials with poor microwave transparency or heating effect, and realize its application in the microwave treatment process of carbon-containing materials. In addition, the method of the present invention can also realize various morphologies of the microwave heating material by adjusting the ratio and synthesis method between the components. The method of the present invention has a simple process, cheap and easily available raw materials, and is more conducive to industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave heating, and particularly relates to a zinc oxide-based microwave heating material, a preparation method thereof, and an application thereof in microwave treatment of carbon-containing materials. Background Art

[0002] Microwave heating technology has been widely applied in the fields of food processing, pharmaceutical treatment, materials engineering, etc. Compared with traditional heating (such as oil bath or heating jacket, whose heat is transferred from the surface of the material to the center of the material through conduction, convection and radiation, and the heating speed is relatively slow and the efficiency is low, often depending on the thermal conductivity and convection of the material), microwave heating is that electromagnetic waves directly penetrate the material to realize the interaction between molecules and the electromagnetic field and convert electromagnetic energy into heat energy, without being limited by the thermal conductivity of the conventional heating method, so as to realize volume heating, with higher energy utilization efficiency and shorter heating time, so it is more and more widely used.

[0003] Microwaves contain mutually perpendicular electric and magnetic field components. According to the interaction between the material and the microwave electric field, materials can be generally divided into three categories: 1) insulators (low dielectric loss materials), microwaves basically completely pass through the material without any loss, that is, microwave transparent bodies; 2) conductors, microwaves are reflected and cannot penetrate the material; 3) absorbers (high dielectric loss materials), the material absorbs and converts microwave energy. When a dielectric material is in a microwave field, many response mechanisms will occur, such as: electronic polarization, atomic polarization, ionic conduction, dipole (orientation) polarization and interfacial polarization or Maxwell-Wagner polarization mechanism. At a microwave frequency of 2.45 GHz, for a material exposed to an alternating electromagnetic field, its dipoles reorient approximately 2.5 billion times per second, and this movement will cause friction and collision between molecules to achieve heat conversion. (R.M. Kelly; N.A. Rowson (1995). Microwave reduction of oxidised ilmenite concentrates., 8(11), 0–1438.).

[0004] For microwave absorbing materials, the microscopic morphology and size of microwave absorbers have a great influence on the microwave attenuation ability. The microwave absorption performances of different microscopic morphologies of the same material often vary greatly. Zinc oxide has a variety of 1D, 2D, and 3D structures, which is beneficial to achieve impedance matching and generate interfacial polarization, and finally leads to the dissipation of microwave energy in the form of heat, thereby realizing the microwave dissipation characteristics and can be used as a good wave-absorbing material.

[0005] However, when commercially available zinc oxide is used in the microwave pyrolysis process of carbon-containing materials, there is a problem of poor microwave heating efficiency. Therefore, it needs to be used in combination with an absorbent carbon material to meet the requirements of microwave heating. However, this also brings problems such as difficult catalyst separation, a significant temperature difference between the catalyst and the absorbent material, resulting in the catalyst being unable to fully function, and low reuse rate.

[0006] Based on the different structural characteristics of zinc oxide, the researchers of this application have also tried to redesign the structure of zinc oxide by selecting activated carbon powder as a template and performing microwave heating treatment, so as to obtain zinc oxide with rod-shaped and flake-shaped micro-nano structures, as Figure 3 shown. The zinc oxide material with this structure can be used as an absorbent material in the microwave pyrolysis process of carbon-containing materials, and can be heated to 300-1200°C in 15-180 seconds under the radiation of 2.45 GHz microwave frequency. However, since the template needs to be removed by calcination in the later stage of its preparation, the whole production process is cumbersome, and the cost and energy consumption are relatively high, which is not conducive to industrial production. Moreover, the structure of the obtained zinc oxide material has two micro-nano structures, rod-shaped and flake-shaped, and the overall is uneven, and the heating effect is not very ideal. Summary of the Invention

[0007] In view of the above problems, the present invention proposes a new preparation method of zinc oxide microwave heating material. The obtained zinc oxide material has high microwave absorption and heat conversion efficiency, and can meet the requirements of the microwave pyrolysis process of carbon-containing materials without being compounded with carbon materials.

[0008] In the first aspect, the preparation of the zinc oxide microwave heating material provided by the present invention uses a zinc salt as a raw material, which is dissolved by adding deionized water and then adding an alkali, and obtained through precipitation crystallization.

[0009] Research results show that the zinc oxide material obtained by the present invention has a single and uniform rod-shaped micro-nano structure, and has both absorbent and catalytic dual-functional characteristics. Therefore, it can be used alone without being paired with other absorbent materials; at the same time, it can also effectively reduce the microwave pyrolysis power of carbon-containing materials and facilitate the composition analysis of residual carbon (such as carbon nanotubes), etc. It solves the problems of low efficiency, difficult catalyst separation, a significant temperature difference between the catalyst and the absorbent material, resulting in the catalyst being unable to fully function, and low reuse rate existing in the use of existing zinc oxide microwave heating materials. At the same time, the zinc oxide microwave heating material obtained by the present invention also has the advantages of stable structure, long service life, and rapid heating.

[0010] Compared with the zinc oxide material obtained by the microwave synthesis method, the method of the present invention not only obtains a zinc oxide material with a more uniform and regular structure, further improving the microwave absorption and heat conversion efficiency, but also the preparation method does not require a template, is simpler to operate, and can construct the target structure by adjusting process conditions, so it is more universal and flexible.

[0011] Preferably, in the above preparation method, the zinc salt is one of zinc chloride, zinc sulfate, zinc acetate or zinc nitrate; the base is one of sodium hydroxide, ammonia water or urea; the mass ratio of the base to the zinc salt is (0.01 - 50):1; the reaction time is 0.1 - 50 hours, the reaction temperature is 40 - 200 °C; the stirring speed is 0 - 3000 revolutions per minute.

[0012] In the specific preparation process, according to actual needs, the above modifiers, types of bases, as well as raw material ratios and reaction conditions can be optimized to adjust the rod-like structure to meet the requirements of microwave pyrolysis.

[0013] Furthermore, based on the above preparation method, the present invention also provides a preparation method of the zinc oxide-based composite material, that is, the modification of the zinc oxide material. The modifier is one or more of tetraethyl orthosilicate, tetrabutyl titanate, iron salt, cobalt salt or nickel salt.

[0014] The present invention has found through research that through the action of the above modifiers, the microwave morphology of the zinc oxide material can be regulated and a multi-level interface can be introduced, so that the heating material has excellent microwave heating effects.

[0015] The research results show that compared with the existing commercial zinc oxide microwave absorbing materials, the zinc oxide-based materials obtained by the modification method of the present invention have micro-nano structures such as needle-like, petal-like and rod-like. Through this multiple interface, it has both the dual functions of microwave absorption and catalysis, thus being more conducive to achieving impedance matching and improving its microwave absorption and heat conversion efficiency. At the same time, the zinc oxide-based microwave heating material obtained by the present invention also has the advantages of stable structure, long service life and rapid heating.

[0016] Compared with the zinc oxide materials prepared by the microwave heating method, the preparation process of the method of the present invention does not necessarily rely on templates, is simpler to operate, and the raw materials are cheap and easily available; and the target structure can be constructed by adjusting the process conditions, so it has more universality and flexibility.

[0017] The modification method of the present invention includes two methods:

[0018] Method 1: Using the zinc oxide synthesized by the precipitation method as the raw material, and realizing the modification of metal oxides on its surface by using the modifier.

[0019] Method 2: Using the zinc salt as the raw material, and synthesizing through the co-precipitation method or hydrothermal synthesis method by using the prepared precursor solution containing zinc salt, modifier and base.

[0020] In Method 1 or Method 2, the morphology and structure of the zinc oxide-based modified material can be regulated by changing the raw material ratio and reaction conditions.

[0021] The present invention constructs a zinc oxide-based microwave heating material with the above-mentioned micro-nano structural morphology by screening a suitable preparation method, thereby effectively improving the microwave heating efficiency of various inorganic metals or non-metals that are microwave transparent or have poor heating effects, and realizing their use in the microwave treatment process of carbon-containing materials; at the same time, various morphologies of the microwave heating material can be achieved by adjusting the ratio and synthesis method between the components. In addition, the method of the present invention has the advantages of simple process and cheap and easily available raw materials.

[0022] The iron salt is ferric chloride, ferric nitrate, or ferric sulfate; the cobalt salt is cobalt chloride, cobalt nitrate, or cobalt acetate; the nickel salt is nickel sulfate or nickel nitrate.

[0023] The modification method includes: mixing zinc oxide or zinc salt with deionized water, alkali, and a modifier to obtain a modified solution; reacting the modified solution by co-precipitation method or hydrothermal synthesis method; wherein, the mass ratio of the modifier, deionized water to zinc oxide or zinc salt is (0.01-10):(1-100):1;

[0024] The reaction time is 0.1-50 hours, the reaction temperature is 40-200 °C; the stirring speed is 0-3000 revolutions per minute.

[0025] Furthermore, the method of the present invention can also adjust the micro-nano structure by adding a template agent. The template agent is sodium dodecyl sulfate, cetyltrimethylammonium bromide, or tetraethylammonium hydroxide; the mass ratio of the template agent to zinc oxide / zinc salt is (0.01-20):1.

[0026] In addition, the method of the present invention can also adjust the micro-nano structure by calcination.

[0027] In the second aspect, the present invention also provides the microwave heating material obtained by the above method. The microwave heating material is a zinc oxide material or a zinc oxide-based composite material.

[0028] The zinc oxide material has a single rod-shaped micro-nano structure.

[0029] The zinc oxide-based composite material has a micro-nano structure including needle-shaped, petal-shaped, and rod-shaped; it is a composite of a metal oxide doped with zinc oxide as the matrix; the metal oxide is SiO2, TiO2, Fe x O y 、Co x O y or one or more of NiO, where x takes a value of 1-3 and y takes a value of 1-4.

[0030] In a third aspect, the present invention provides a microwave treatment process for carbon-containing materials, comprising: under the conditions of normal pressure and an oxygen-free atmosphere, using the above-mentioned microwave heating material to achieve high-efficiency decomposition of the carbon-containing materials; and the composition of the pyrolysis products can be regulated by adjusting the composition of the microwave heating material.

[0031] The carbon-containing materials are plastics, biomass, and fibers; the blending mass ratio of the microwave heating material to the carbon-containing materials is 0.01 - 100:1.

[0032] The microwave power used in the microwave treatment process is 60 - 600 W, and the treatment temperature is 250 - 800 °C; with reference to the amount of the carbon-containing material to be treated, the reaction time under microwave conditions is 5 - 300 minutes / kg; the process conditions of the microwave treatment are: the microwave frequency is 2.45 GHz, the microwave source is a magnetron, and the microwave heating mode is multimode.

[0033] The obtained gas products are mainly gases such as H2 and C1 - C5 light hydrocarbons; the obtained liquid products are mainly gasoline and diesel components mainly composed of isoparaffins and benzene series; and the composition of the pyrolysis products is regulated by adjusting the composition of the zinc oxide-based microwave heating material.

[0034] The oxygen-free atmosphere is achieved by pre-purging with an inert gas for more than 30 minutes; the inert gas can be nitrogen, argon, etc.

[0035] In a fourth aspect, the present invention also provides a recovery method for the above-mentioned microwave heating material, comprising: recovering the generated carbon material by an acid dissolution method; or, introducing an inert gas containing 5 - 10% by volume of oxygen during the long-cycle operation gap, and reactivating the microwave heating material by calcination at a temperature above 300 °C, and the treatment time is 1 - 5 hours.

[0036] The beneficial effects of the present invention are as follows:

[0037] 1. The present invention provides a zinc oxide and zinc oxide-based composite microwave heating material and a preparation method thereof. The obtained zinc oxide and zinc oxide-based microwave heating materials have the dual-functional characteristics of integrating catalysis and wave absorption, and have the advantages of effectively reducing the microwave power in the pyrolysis of carbon-containing materials and facilitating the composition analysis of residual carbon (such as carbon nanotubes), etc., solving the problems of low efficiency, difficult separation of the catalyst, significant temperature difference between the catalyst and the wave-absorbing material resulting in the catalyst being unable to fully play its role, and low recycling rate, etc. when the relevant catalyst and carbon-containing materials are mixed for microwave pyrolysis. At the same time, the obtained zinc oxide and zinc oxide-based composite microwave heating materials have the advantages of stable structure, long service life, and rapid heating.

[0038] 2. In the application of the zinc oxide-based microwave heating material of the present invention in the microwave treatment of carbon-containing materials, the microwave input power and reaction temperature can be significantly reduced, and the main gas products generated are gases such as H2 and C1-C5 light hydrocarbons; the liquid products are mainly gasoline and diesel components mainly composed of isoparaffins and benzene series.

[0039] 3. The preparation method of the microwave heating material has the advantages of simple operation, cheap and easily available raw materials, and can optimize the micro-nano structure by screening the synthesis method and adjusting the raw material ratio and reaction conditions; compared with the existing microwave heating method, the method of the present invention is more universal and flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 XRD patterns of zinc oxide, zinc oxide-silica, zinc oxide-titanium dioxide, zinc oxide-iron oxide, zinc oxide-cobalt oxide, and zinc oxide-nickel oxide prepared in Examples 1-6.

[0041] Figure 2 SEM images of zinc oxide, zinc oxide-silica, zinc oxide-titanium dioxide, zinc oxide-iron oxide, zinc oxide-cobalt oxide, and zinc oxide-nickel oxide prepared in Examples 1-6.

[0042] Figure 3 SEM image of the zinc oxide material obtained in Comparative Example 1.

[0043] Figure 4 Process flow chart for microwave pyrolysis of carbon-containing materials using the zinc oxide-based composite materials described in Examples 2-6. DETAILED DESCRIPTION OF THE INVENTION

[0044] The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0045] Example 1 Zinc Oxide - Co-Precipitation Method

[0046] This example provides a method for preparing a zinc oxide microwave heating material, including the following steps:

[0047] 1) Dissolve 300 grams of zinc sulfate heptahydrate in 3000 milliliters of deionized water, and stir at a speed of 2500 revolutions per minute for 20 minutes at room temperature to form a homogeneous solution S1;

[0048] 2) Add 20 milliliters of ammonia water to solution S1, and stir at a speed of 2500 revolutions per minute for 1 hour at room temperature to obtain solution S2.

[0049] 3) Place solution S2 in a reaction at 90 °C for 2 hours, wait for it to cool naturally to room temperature, then perform centrifugal separation, and dry the obtained powder in an oven at 80 °C for 2 hours to obtain it.

[0050] Comparative Example 1

[0051] This comparative example provides a zinc oxide microwave heating material, which is prepared by a microwave heating method using activated carbon as a template. The steps are as follows:

[0052] 1) Dissolve 12 g of zinc acetate dihydrate in 250 mL of deionized water and stir at a speed of 2500 revolutions per minute for 1 h at room temperature to form solution S1;

[0053] 2) Add 10 mL of ammonia water to solution S1 and stir at a speed of 2500 revolutions per minute for 1 h at room temperature to form solution S2;

[0054] 3) Take 0.2 g of activated carbon powder and add it to solution S2, and stir at a speed of 2500 revolutions per minute for 1 h at room temperature to form dispersion S3;

[0055] 4) Transfer dispersion S3 into a microwave oven and heat it at a power of 550 W for 70 min. After it naturally cools to room temperature, filter it and wash the powder with deionized water until it is neutral. Place the obtained sample in an oven at 80 °C for 4 h and then calcine it in a muffle furnace at 550 °C for 3 h to obtain the product.

[0056] See Figure 3 As shown, the SEM image of the microwave heating body zinc oxide obtained after calcination (different positions are selected for shooting to show different micro-nano structures). It can be seen that there are three different structures in the microwave heating body zinc oxide with activated carbon removed at high temperature. This is because the nucleation and growth rates of zinc oxide are different under different reaction conditions.

[0057] Effect test:

[0058] 1. Comparison of microstructures:

[0059] Figure 1 This is the XRD pattern of the zinc oxide material obtained in Example 1.

[0060] Figure 2 This is the SEM image of the zinc oxide material obtained in Example 1.

[0061] Figure 3 This is the SEM image of the zinc oxide material obtained in Comparative Example 1.

[0062] By comparison, it can be known that the micro-nano structure of the zinc oxide material obtained in Comparative Example 1 includes rod-shaped and sheet-shaped; while the structure of the zinc oxide material obtained in Example 1 is only rod-shaped, with a more single and uniform structure, and its preparation method does not require a template, making the operation simpler and more convenient.

[0063] 2. Comparison of microwave heating speed and power

[0064] The zinc oxide of the microwave heating element prepared in Comparative Example 1 was placed under a microwave power of 700 W for 80 seconds, and the temperature reached 600 °C.

[0065] However, the zinc oxide obtained in Example 1 can reach 600 °C in 30 seconds under a microwave power of 500 W.

[0066] 3. Microwave pyrolysis effect:

[0067] After the polystyrene foam collected on the market was subjected to low-temperature heat treatment to remove gas, it was crushed into particles with a particle size of 1 mm using a crusher, and then it was mechanically mixed with the above-prepared zinc oxide in the same mass ratio; the total mass of the reaction materials was 40 g.

[0068] The reaction materials were placed in a microwave reactor, the nitrogen flow rate was set to (50 ml / min), and nitrogen was passed for 30 minutes before the microwave reactor worked to remove the residual oxygen in the reaction system;

[0069] The reaction was carried out for 1 hour under the conditions of a microwave power of 160 W, a microwave frequency of 2.45 GHz, and a cold trap temperature of -30 °C. After the reaction, the component analysis of the generated gas and liquid distribution was carried out.

[0070] Table 1

[0071]

[0072]

[0073] Example 2 (Zinc Oxide Modification)

[0074] This example provides a preparation method of a zinc oxide-silica microwave heating material, including the following steps:

[0075] 1) Dissolve 50 g of zinc oxide prepared in Example 1 in 250 ml of deionized water, and stir at a speed of 1500 revolutions per minute at room temperature for 1 hour to form a homogeneous solution S1;

[0076] 2) Dissolve 3 g of sodium hydroxide in 15 ml of deionized water and then add it to the S1 solution, and drop 10 ml of the modifier tetraethyl orthosilicate into the S1 solution, and stir at a speed of 1500 revolutions per minute at room temperature for 1 hour to obtain solution S2.

[0077] 3) Add 6 g of the template agent cetyltrimethylammonium bromide to the S2 solution, and stir at a speed of 1500 revolutions per minute at room temperature for 1 hour to obtain solution S3.

[0078] 4) Place the solution S3 under the conditions of 70 °C and a rotation speed of 1500 revolutions per minute for 4 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an oven at 80 °C for 3 hours and then calcine it in a muffle furnace at 400 °C for 3 hours to obtain the product.

[0079] This embodiment also provides a microwave pyrolysis process, and the steps are as follows:

[0080] 1) Wash the polyethylene collected on the market and then use a pulverizer to crush it into particles with a particle size of 1 mm. Then, mechanically mix it with the above-prepared zinc oxide-silica in a mass ratio of 2:1.

[0081] 2) The total mass of the reaction materials is 100 g. Place the reaction materials in a microwave reactor, set the nitrogen gas flow rate to (50 ml / min), and purge with nitrogen for 30 minutes before the microwave reactor operates to remove the residual oxygen in the reaction system.

[0082] 3) React for 20 minutes under the conditions of a microwave power of 300 W, a microwave frequency of 2.45 GHz, and a cold trap temperature of -30 °C. After the reaction ends, analyze the components of the generated gas and liquid distribution.

[0083] Table 2

[0084]

[0085]

[0086] Example 3 (zinc oxide modification)

[0087] This embodiment provides a preparation method of a zinc oxide-cobalt oxide microwave heating material, including the following steps:

[0088] 1) Dissolve 100 g of zinc oxide prepared in Example 1 and 80 g of the modifier cobalt chloride hexahydrate in 600 ml of deionized water, and stir at a speed of 2000 revolutions per minute at room temperature for 15 minutes to form a homogeneous solution S1.

[0089] 2) Add 30 g of urea to the S1 solution and stir at a speed of 2000 revolutions per minute at room temperature for 30 minutes to obtain solution S2.

[0090] 3) Place the solution S2 in a hydrothermal reaction kettle and react at 110 °C for 20 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an oven at 80 °C for 3 hours and then calcine it in a muffle furnace at 350 °C for 2 hours to obtain the product.

[0091] This embodiment also provides a microwave pyrolysis process, and the steps are as follows:

[0092] 1) Wash the collected Eucommia ulmoides leaves, and then use a pulverizer to crush the mixture of the two to particles with a particle size of 1 mm. Then, mechanically mix it with the above-prepared zinc oxide-cobalt oxide in a mass ratio of 10:1;

[0093] 2) The total mass of the reaction materials is 60 g. Place the reaction materials in a microwave reactor, set the nitrogen gas flow rate to (50 ml / min), and purge with nitrogen for 30 minutes before the microwave reactor operates to remove the residual oxygen in the reaction system;

[0094] 3) React for 15 minutes under the conditions of a microwave power of 500 W, a microwave frequency of 2.45 GHz, and a cold trap temperature of -30 °C. After the reaction is completed, perform a component analysis on the gas distribution generated.

[0095] Table 3

[0096]

[0097]

[0098] Example 4 (Zinc Oxide Modification)

[0099] This example provides a method for preparing a zinc oxide-nickel oxide microwave heating material, which includes the following steps:

[0100] 1) Dissolve 100 g of zinc oxide and 100 g of modified cobalt chloride hexahydrate prepared in Example 1 in 500 ml of deionized water, and stir at a speed of 2000 revolutions per minute at room temperature for 30 minutes to form a homogeneous solution S1;

[0101] 2) Add 20 g of urea to the S1 solution and stir at a speed of 2000 revolutions per minute at room temperature for 30 minutes to obtain solution S2.

[0102] 3) Place the solution S2 in a hydrothermal reaction kettle and react at 90 °C for 24 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an oven at 80 °C for 1 hour and then calcine it in a muffle furnace at 500 °C for 3 hours to obtain the product.

[0103] This example also provides a microwave pyrolysis process, and the steps are as follows:

[0104] 1) Wash the collected masks and then use a pulverizer to crush them to particles with a particle size of 1 mm. Then, mechanically mix them with the above-prepared zinc oxide-nickel oxide in a mass ratio of 7:1;

[0105] 2) The total mass of the reaction materials is 120 g. Place the reaction materials in a microwave reactor, set the nitrogen gas flow rate to (50 ml / min), and purge with nitrogen for 30 minutes before the microwave reactor operates to remove the residual oxygen in the reaction system;

[0106] 3) React for 10 minutes under the conditions of a microwave power of 600 W, a microwave frequency of 2.45 GHz, and a cold trap temperature of -30 °C. After the reaction, perform a component analysis on the gas distribution generated.

[0107] Table 4

[0108]

[0109] Example 5 (Zinc salt modification)

[0110] This example provides a preparation method for a zinc oxide - titanium dioxide microwave heating material, which includes the following steps:

[0111] 1) Dissolve 30 grams of zinc sulfate heptahydrate in 300 milliliters of deionized water, and stir at a speed of 2500 revolutions per minute for 20 minutes at room temperature to form a homogeneous solution S1;

[0112] 2) Add 2 milliliters of ammonia water to solution S1, and drop 5 milliliters of the modifier tetrabutyl titanate into solution S1, and stir at a speed of 2500 revolutions per minute for 1 hour at room temperature to obtain solution S2.

[0113] 3) Add 0.2 grams of the template agent sodium dodecyl sulfonate to solution S2, and stir at a speed of 2500 revolutions per minute for 30 minutes at room temperature to obtain solution S3.

[0114] 4) React solution S3 at 90 °C and a rotation speed of 2500 revolutions per minute for 2 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an oven at 80 °C for 3 hours and then calcine it in a muffle furnace at 400 °C for 3 hours to obtain the product.

[0115] This example also provides a microwave pyrolysis process, and the steps are as follows:

[0116] 1) Wash the polypropylene collected on the market and use a crusher to crush it into particles with a particle size of 1 millimeter, and then mechanically mix it with the above - prepared zinc oxide - titanium dioxide according to a mass ratio of 3:1;

[0117] 2) The total mass of the reaction materials is 150 grams. Place the reaction materials in a microwave reactor, set the nitrogen gas flow rate to (50 ml / min), and first pass nitrogen gas for 30 minutes before the microwave reactor operates to remove the residual oxygen in the reaction system;

[0118] 3) React for 20 minutes under the conditions of a microwave power of 300 W, a microwave frequency of 2.45 GHz, and a cold trap temperature of -30 °C. After the reaction, perform a component analysis on the gas and liquid distributions generated.

[0119] Table 5

[0120]

[0121] Example 6 (Zinc Salt Modification)

[0122] This example provides a preparation method of a zinc oxide - iron oxide microwave heating material, which includes the following steps:

[0123] 1) Dissolve 100 grams of zinc acetate dihydrate and 20 grams of ferric nitrate nonahydrate in 600 milliliters of deionized water, and stir at a speed of 2500 revolutions per minute for 10 minutes at room temperature to form a homogeneous solution S1;

[0124] 2) Add 10 milliliters of ammonia water to solution S1, and stir at a speed of 2500 revolutions per minute for 10 minutes at room temperature to obtain solution S2.

[0125] 3) Place solution S2 in a hydrothermal reaction kettle and react at 120 °C for 12 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an oven at 80 °C for 3 hours and then calcine it in a muffle furnace at 350 °C for 2 hours to obtain the product.

[0126] This example also provides a microwave pyrolysis process, and the steps are as follows:

[0127] 1) Wash the polyethylene and polypropylene collected from the market, and use a crusher to crush the mixture of the two to particles with a particle size of 1 millimeter. Then, mechanically mix it with the above - prepared zinc oxide - iron oxide according to a mass ratio of 1:1;

[0128] 2) The total mass of the reaction materials is 100 grams. Place the reaction materials in a microwave reactor, set the nitrogen gas flow rate to (50 ml / min), and purge with nitrogen for 30 minutes before the microwave reactor operates to remove the residual oxygen in the reaction system;

[0129] 3) React for 10 minutes under the conditions of a microwave power of 600 W, a microwave frequency of 2.45 GHz, and a cold trap temperature of - 30 °C. After the reaction, analyze the components of the generated gas and liquid distribution.

[0130] Table 6

[0131]

[0132] Comparative Example 2

[0133] CN111100662A discloses a continuous operation method for microwave high - temperature pyrolysis of waste plastics. In the microwave pyrolysis process disclosed in its Example 15, the microwave power is 1000 W and 1500 W, which is much higher than the microwave power in the microwave pyrolysis process of the present invention.

[0134] Effect description:

[0135] Figure 1 XRD patterns of zinc oxide, zinc oxide-silica, zinc oxide-titanium dioxide, zinc oxide-iron oxide, zinc oxide-cobalt oxide, and zinc oxide-nickel oxide prepared in Examples 1-6 are shown.

[0136] Figure 2 SEM images of zinc oxide, zinc oxide-silica, zinc oxide-titanium dioxide, zinc oxide-iron oxide, zinc oxide-cobalt oxide, and zinc oxide-nickel oxide prepared in Examples 1-6 are shown.

[0137] Figure 4 The process flow diagram of the zinc oxide-based microwave pyrolysis of carbon-containing materials according to the present invention is shown.

[0138] Based on the test results in Table 1-6 above, the zinc oxide materials and zinc oxide-based composite materials obtained by the present invention have the following advantages:

[0139] (1) Compared with the microwave heating method of Comparative Example 1, the hydrothermal synthesis or co-precipitation method of the microwave heating material of the present invention is simple in operation, easy to obtain raw materials, and the structure can be adjusted, so it is more universal and flexible.

[0140] (2) The zinc oxide material obtained by the present invention has a single and uniform rod-shaped micro-nano structure, and the zinc oxide-based composite material has a multi-interface micro-nano structure including needle-shaped, petal-shaped, and rod-shaped, so it has higher microwave absorption and heat conversion efficiency compared with the existing commercial zinc oxide microwave heating materials.

[0141] (3) The zinc oxide materials and zinc oxide-based composite materials obtained by the present invention have the advantages of stable structure, long service life, simple preparation process, and cheap and easily available raw materials.

[0142] (4) The zinc oxide materials and zinc oxide-based composite materials obtained by the present invention have a high gas yield, especially H2 yield, in the microwave pyrolysis of carbon-containing materials.

[0143] (5) On the premise of the same pyrolysis rate, the zinc oxide materials and zinc oxide-based composite materials obtained by the present invention can significantly reduce the microwave input power and reaction temperature of the microwave treatment process of carbon-containing materials.

[0144] (6) After the zinc oxide-based microwave heating material obtained by the present invention works continuously for a long time, the carbon material generated can be recovered by acid dissolution; or, an inert gas containing 5-10% volume fraction of oxygen is introduced during the long-cycle operation gap and calcined at a temperature above 300°C to reactivate the microwave heating material, and the treatment time is 1-5 hours.

[0145] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made thereto based on the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of the present invention claimed.

Claims

1. A microwave treatment process for carbon-containing materials, characterized in that, Including: Under the conditions of normal pressure and an oxygen-free atmosphere, a microwave heating material is used to achieve efficient decomposition of carbon-containing materials; When the microwave heating material is a zinc oxide microwave heating material, the preparation method of the microwave heating material includes the following steps a1) to a3): a1) Dissolve 300 grams of zinc sulfate heptahydrate in 3000 milliliters of deionized water, and stir at a speed of 2500 revolutions per minute for 20 minutes at room temperature to form a homogeneous solution S1; a2) Add 20 milliliters of ammonia water to the S1 solution in step a1), and stir at a speed of 2500 revolutions per minute for 1 hour at room temperature to obtain a solution S2; a3) Place the solution S2 in step a2) at 90 °C and react for 2 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an 80 °C oven for 2 hours to obtain it; When the microwave heating material is a zinc oxide-silica microwave heating material, the preparation method of the microwave heating material includes the following steps b1) to b4): b1) Dissolve 50 grams of the zinc oxide microwave heating material prepared in steps a1) to a3) in 250 milliliters of deionized water, and stir at a speed of 1500 revolutions per minute for 1 hour at room temperature to form a homogeneous solution S1; b2) Dissolve 3 grams of sodium hydroxide in 15 milliliters of deionized water and then add it to the S1 solution in step b1), and drop 10 milliliters of the modifier tetraethyl orthosilicate into the S1 solution in step b1), and stir at a speed of 1500 revolutions per minute for 1 hour at room temperature to obtain a solution S2; b3) Add 6 grams of the template agent cetyltrimethylammonium bromide to the S2 solution in step b2), and stir at a speed of 1500 revolutions per minute for 1 hour at room temperature to obtain a solution S3; b4) Place the solution S3 in step b3) at 70 °C and a rotation speed of 1500 revolutions per minute and react for 4 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an 80 °C oven for 3 hours and then calcine it in a muffle furnace at 400 °C for 3 hours to obtain it; When the microwave heating material is a zinc oxide-cobalt oxide microwave heating material, the preparation method of the microwave heating material includes the following steps c1) to c3): c1) Dissolve 100 grams of the zinc oxide microwave heating material prepared in steps a1) to a3) and 80 grams of the modifier cobalt chloride hexahydrate in 600 milliliters of deionized water, and stir at a speed of 2000 revolutions per minute for 15 minutes at room temperature to form a homogeneous solution S1; c2) Add 30 grams of urea to the S1 solution in step c1), and stir at a speed of 2000 revolutions per minute for 30 minutes at room temperature to obtain a solution S2; c3) Place the solution S2 in step c2) in a hydrothermal reaction kettle at 110 °C and react for 20 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an 80 °C oven for 3 hours and then calcine it in a muffle furnace at 350 °C for 2 hours to obtain it; When the microwave heating material is a zinc oxide-titanium dioxide microwave heating material, the preparation method of the microwave heating material includes the following steps d1) to d4): d1) Dissolve 30 g of zinc sulfate heptahydrate in 300 mL of deionized water and stir at a speed of 2500 revolutions per minute for 20 minutes at room temperature to form a homogeneous solution S1; d2) Add 2 mL of ammonia water to the S1 solution in step d1), and drop 5 mL of the modifier tetrabutyl titanate into the S1 solution in step d1), stir at a speed of 2500 revolutions per minute at room temperature for 1 hour to obtain solution S2; d3) Add 0.2 g of the template sodium dodecylsulfonate to the S2 solution in step d2), and stir at a speed of 2500 revolutions per minute at room temperature for 30 minutes to obtain solution S3; d4) Place the solution S3 in step d3) under the conditions of 90 °C and a rotation speed of 2500 revolutions per minute for reaction for 2 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an oven at 80 °C for 3 hours and then calcine it in a muffle furnace at 400 °C for 3 hours to obtain the product; When the microwave heating material is a zinc oxide - iron oxide microwave heating material, the preparation method of the microwave heating material includes the following steps e1) - e3): e1) Dissolve 100 g of zinc acetate dihydrate and 20 g of iron(III) nitrate nonahydrate in 600 mL of deionized water and stir at a speed of 2500 revolutions per minute for 10 minutes at room temperature to form a homogeneous solution S1; e2) Add 10 mL of ammonia water to the S1 solution in step e1), and stir at a speed of 2500 revolutions per minute at room temperature for 10 minutes to obtain solution S2; e3) Place the solution S2 in step e2) in a hydrothermal reaction kettle and react at 120 °C for 12 hours. After it naturally cools to room temperature, perform centrifugal separation. Dry the obtained powder in an oven at 80 °C for 3 hours and then calcine it in a muffle furnace at 350 °C for 2 hours to obtain the product.

2. The microwave treatment process according to claim 1, wherein, Regulate the composition of the pyrolysis product by adjusting the composition of the microwave heating material; The blending mass ratio of the microwave heating material to the carbon - containing material is 0.01 - 100:1; The carbon - containing material is plastic, biomass or fiber; The microwave power used in the microwave treatment process is 60 - 600 W, and the treatment temperature is 250 - 800 °C; Taking the amount of the carbon - containing material to be treated as a reference, the reaction time under microwave conditions is 5 - 300 minutes / kg; The process conditions of the microwave treatment are: the microwave frequency is 2.45 GHz, the microwave source is a magnetron, and the microwave heating mode is multimode.

3. The microwave treatment process of the carbon-containing material according to claim 1, wherein It also includes the recovery method of the microwave heating material. The recovery method includes: recovering the generated carbon material by an acid - dissolution method; or, introducing an inert gas containing 5 - 10% by volume of oxygen during the long - cycle operation gap, and re - activating the microwave heating material by calcination above 300 °C, and the treatment time is 1 - 5 hours.

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