Multifunctional spinel catalyst, preparation method thereof and application of multifunctional spinel catalyst in plastic microwave catalytic cracking

Abstract

The invention belongs to the technical field of catalyst preparation, and discloses a multifunctional spinel catalyst, a preparation method thereof and application of the multifunctional spinel catalyst in plastic microwave catalytic cracking. The preparation method of the multifunctional spinel catalyst comprises the following steps: ultrasonically mixing ferric salt, aluminum salt, citric acid, water and a carbon source, and stirring to obtain gel; and sequentially drying and calcining the gel to obtain the multifunctional spinel catalyst. According to the obtained multifunctional spinel catalyst, through the synergistic effect of Fe-Ni, Fe-Co and the like, the activity of the catalyst is improved, the hydrogen yield is remarkably increased to 54.79 mmol / g, the anti-sintering capacity of the catalyst is improved through carbon source loading, and the catalytic life is prolonged; the absorptivity of the obtained multifunctional spinel catalyst at the frequency of 2.45 GHz reaches 90% or above, and uniform microwave heating of plastic is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, in particular to a multifunctional spinel catalyst, a preparation method thereof and application in microwave catalytic cracking of plastics. Background Art

[0002] With the intensification of the plastic pollution problem, the resource utilization of waste plastics has become an important research direction. Traditional methods of plastic disposal mainly include landfill and incineration, but these methods have problems such as occupying a large amount of land resources, producing harmful gases and low energy utilization. Therefore, it is crucial to develop efficient and environmentally friendly plastic resource utilization technologies. Plastic microwave pyrolysis technology is an important means to achieve high-value utilization of waste plastics. It can convert plastics into high-value-added products such as hydrogen and carbon nanotubes. Compared with traditional catalytic pyrolysis methods, microwave catalytic pyrolysis technology has attracted widespread attention due to its high energy utilization, high reaction selectivity, and fast heating rate. It can produce high-value carbon products and has obvious advantages.

[0003] However, the existing pyrolysis methods have the following problems: (1) Low hydrogen yield: The hydrogen selectivity of conventional pyrolysis technology is low, and the hydrogen yield is usually less than 40 mmol / g, which restricts its industrial application. Due to the stability of the plastic molecular structure, the activation energy of the C-H bond breakage is high, resulting in limited release of hydrogen during the pyrolysis process. (2) Unstable quality of carbon nanotubes: The carbon nanotubes generated by traditional catalysts have a low degree of graphitization and lack good conductivity and structural integrity, which limits their application as functional materials. The formation of carbon nanotubes depends on the distribution of active sites of the catalyst. Traditional catalysts often have problems such as metal cluster sintering and reduced catalytic activity. (3) Insufficient microwave absorption performance of the catalyst: Conventional catalysts have weak absorption capacity in the microwave field, resulting in local overheating and uneven heating, affecting the efficiency of the pyrolysis reaction. Since plastic itself is a non-polar material, its microwave absorption performance is poor, resulting in a slow heating rate and difficulty in forming an efficient catalytic reaction environment. (4) Catalysts are easily sintered and deactivated: Under high-temperature reaction conditions, catalyst particles are prone to sintering, resulting in reduced activity and short catalytic life. Especially under microwave heating conditions, the local temperature rises sharply, and the catalyst particles are prone to aggregation, which significantly reduces their catalytic activity.

[0004] Therefore, it is of great significance to study and obtain a multifunctional spinel catalyst and its preparation method that can improve the microwave absorption performance and catalytic activity of the catalyst, so that it can achieve efficient plastic microwave pyrolysis hydrogen production and the synthesis of high-quality carbon nanotubes. Summary of the Invention

[0005] The purpose of the present invention is to provide a multifunctional spinel catalyst, a preparation method thereof and application in microwave catalytic cracking of plastics, so as to solve the problems existing in the prior art such as low hydrogen yield, unstable quality of carbon nanotubes, insufficient microwave absorption performance of the catalyst and easy sintering and deactivation of the catalyst.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a multifunctional spinel catalyst, comprising the following steps:

[0008] 1) ultrasonically mixing iron salt, aluminum salt, citric acid, water and carbon source and stirring to obtain a gel;

[0009] 2) The gel is dried and calcined in sequence to obtain a multifunctional spinel catalyst.

[0010] Preferably, in step 1), the iron salt is Fe(NO3)3·9H2O, FeCl3 or Fe2(SO4)3, the aluminum salt is Al(NO3)3·9H2O, AlCl3 or Al2(SO4)3, and the carbon source is activated carbon, graphene or mesoporous carbon;

[0011] The ratio of iron salt, aluminum salt, citric acid and water is 0.8-1.2 mol:1.6-2.4 mol:1.6-2.4 mol:5-15 mL;

[0012] The molar ratio of the iron ions in the iron salt to the carbon atoms in the carbon source is 0.8-1.2:4-8.

[0013] Preferably, in step 1), the ultrasonic mixing time is 20 to 40 minutes, and the ultrasonic mixing power is 250 to 350W;

[0014] The stirring temperature is 70-90°C, and the stirring time is 5-7h.

[0015] Preferably, in step 2), the drying time is 10 to 15 hours and the drying temperature is 90 to 120°C.

[0016] Preferably, in step 2), the calcination is carried out in a nitrogen atmosphere, the calcination time is 2 to 4 hours, and the calcination temperature is 650 to 750°C.

[0017] Preferably, the step 1) further comprises a transition metal salt, and the transition metal salt comprises a nickel salt, a cobalt salt, a vanadium salt, a manganese salt or a molybdenum salt;

[0018] The molar ratio of the transition metal ions in the transition metal salt to the iron ions in the iron salt is 0.8-1.2:0.8-1.2.

[0019] The present invention also provides a multifunctional spinel catalyst prepared by the preparation method of the multifunctional spinel catalyst.

[0020] The present invention also provides the use of the multifunctional spinel catalyst in microwave catalytic cracking of plastics, comprising the following steps: mixing the multifunctional spinel catalyst with plastics and then sequentially performing nitrogen purification and microwave catalytic pyrolysis.

[0021] Preferably, the mass ratio of the multifunctional spinel catalyst to the plastic is 0.8-1.2:1.5-2.5;

[0022] During the nitrogen purification, the flow rate of nitrogen is 180 to 220 mL / min, and the nitrogen purification time is 8 to 15 minutes.

[0023] Preferably, in the microwave catalytic pyrolysis, the microwave frequency is 2400-2500 MHz, the microwave power is 800-1100 W, and the microwave catalytic pyrolysis time is 10-20 min.

[0024] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0025] The multifunctional spinel catalyst obtained by the present invention improves the catalytic activity through the synergistic effects of Fe-Ni, Fe-Co, etc., significantly increasing the hydrogen yield to 54.79 mmol / g, which is approximately 25% higher than the traditional catalytic system FeAlO catalyst (hydrogen yield of 43.03 mmol / g). The use of a carbon source as a supporting material improves the catalyst's resistance to sintering and extends the catalytic life. The multifunctional spinel catalyst obtained by the present invention has an absorption rate of over 90% at a frequency of 2.45 GHz, ensuring uniform microwave heating of plastics. The carbon nanotubes produced by the catalyst of the present invention exhibit excellent electrochemical stability in lithium-ion battery negative electrode applications, achieving a reversible capacity of 120 mAh / g at a high rate of 2 A / g.

[0026] The catalyst and preparation method of the present invention provide a new technical path for the resource utilization of waste plastics, and have broad application prospects in the fields of new energy, energy storage devices, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0028] Figure 1The dielectric properties test results of the catalysts obtained in Examples 1 to 4 and Comparative Example 1 are shown;

[0029] Figure 2 Graph showing the magnetic permeability test results of the catalysts obtained in Examples 1 to 4 and Comparative Example 1;

[0030] Figure 3 Graph showing impedance test results of batteries prepared using carbon nanotubes obtained in Application Examples 1 to 4 and Comparative Example 2;

[0031] Figure 4 CV curve of the battery to be tested prepared using the carbon nanotubes obtained in Comparative Example 2;

[0032] Figure 5 CV curve of the battery to be tested made from the carbon nanotubes obtained in Application Example 1;

[0033] Figure 6 CV curve of the battery to be tested made from the carbon nanotubes obtained in Application Example 2;

[0034] Figure 7 CV curve of the battery to be tested made from the carbon nanotubes obtained in Application Example 3;

[0035] Figure 8 The CV curve of the battery to be tested is made from the carbon nanotubes obtained in Application Example 4. DETAILED DESCRIPTION

[0036] The present invention provides a method for preparing a multifunctional spinel catalyst, comprising the following steps:

[0037] 1) ultrasonically mixing iron salt, aluminum salt, citric acid, water and carbon source and stirring to obtain a gel;

[0038] 2) The gel is dried and calcined in sequence to obtain a multifunctional spinel catalyst.

[0039] In the present invention, in step 1), the iron salt is preferably Fe(NO3)3·9H2O, FeCl3 or Fe2(SO4)3, the aluminum salt is preferably Al(NO3)3·9H2O, AlCl3 or Al2(SO4)3, and the carbon source is preferably activated carbon, graphene or mesoporous carbon;

[0040] The usage ratio of iron salt, aluminum salt, citric acid and water is preferably 0.8-1.2 mol:1.6-2.4 mol:1.6-2.4 mol:5-15 mL, more preferably 0.9-1.1 mol:1.7-2.2 mol:1.8-2.3 mol:7-13 mL, and more preferably 1 mol:1.8-2 mol:2-2.2 mol:8-10 mL;

[0041] The molar ratio of the iron ions in the iron salt to the carbon atoms in the carbon source is preferably 0.8-1.2:4-8, more preferably 0.9-1.1:4.5-7, and more preferably 1:5-6.

[0042] In the present invention, in the step 1), the ultrasonic mixing time is preferably 20 to 40 minutes, more preferably 25 to 35 minutes, more preferably 30 to 32 minutes, and the ultrasonic mixing power is preferably 250 to 350 W, more preferably 280 to 340 W, more preferably 300 to 320 W;

[0043] The stirring is preferably water bath heating stirring, the stirring temperature is preferably 70-90°C, more preferably 75-85°C, more preferably 78-80°C, the stirring time is preferably 5-7h, more preferably 5.5-6.5h, more preferably 6h, and the stirring rate is preferably 800-1200rpm, more preferably 900-1100rpm, more preferably 1000-1050rpm.

[0044] In the present invention, the step 1) is preferably to first mix the iron salt, aluminum salt, citric acid and water and then add the carbon source.

[0045] In the present invention, in step 2), the drying time is preferably 10 to 15 hours, more preferably 11 to 14 hours, more preferably 12 to 13 hours, and the drying temperature is preferably 90 to 120°C, more preferably 95 to 110°C, more preferably 100 to 105°C.

[0046] In the present invention, in the step 2), the calcination is preferably carried out in a nitrogen atmosphere, the calcination time is preferably 2 to 4 hours, more preferably 2.5 to 3.5 hours, more preferably 3 hours, and the calcination temperature is preferably 650 to 750°C, more preferably 680 to 740°C, more preferably 700 to 720°C.

[0047] In the present invention, in the step 2), grinding is performed after drying, and the particle size after grinding is preferably ≤0.01 mm, more preferably ≤0.008 mm, and even more preferably ≤0.007 mm.

[0048] In the present invention, the step 1) preferably further comprises a transition metal salt, and the transition metal salt includes a nickel salt, a cobalt salt, a vanadium salt, a manganese salt or a molybdenum salt;

[0049] The molar ratio of the transition metal ions in the transition metal salt to the iron ions in the iron salt is preferably 0.8-1.2:0.8-1.2, more preferably 0.9-1.1:0.9-1.1, and even more preferably 1:1.

[0050] In the present invention, the transition metal salt is added in step 1) by first mixing the transition metal salt with the iron salt, the aluminum salt, citric acid and water and then adding the carbon source.

[0051] In the present invention, the doping of the transition metal salt can optimize the catalytic performance, improve the hydrogen selectivity and the quality of carbon nanotubes. The synergistic effect of different metal elements can enhance the stability of the catalyst and regulate the growth morphology of carbon nanotubes. The carbon source is used as a microwave absorbing material to accelerate the rise of the reaction temperature and improve the pyrolysis efficiency.

[0052] In the present invention, the obtained catalyst has excellent catalytic activity and structural stability, can effectively promote the breaking of the C—H bond, and improve the hydrogen yield.

[0053] The present invention also provides a multifunctional spinel catalyst prepared by the preparation method of the multifunctional spinel catalyst.

[0054] The present invention also provides the use of the multifunctional spinel catalyst in microwave catalytic cracking of plastics, comprising the following steps: mixing the multifunctional spinel catalyst with plastics and then sequentially performing nitrogen purification and microwave catalytic pyrolysis.

[0055] In the present invention, the multifunctional spinel catalyst is preferably mixed with plastic and placed in layers, specifically, the lower layer is 50% by mass of the catalyst mixed with all plastics, and the upper layer is 50% by mass of the catalyst placed alone.

[0056] In the present invention, the mass ratio of the multifunctional spinel catalyst to the plastic is preferably 0.8-1.2:1.5-2.5, more preferably 0.9-1.1:1.7-2.3, and more preferably 1:1.8-2;

[0057] In the nitrogen purification, the flow rate of nitrogen is preferably 180 to 220 mL / min, more preferably 190 to 210 mL / min, more preferably 200 to 205 mL / min, and the nitrogen purification time is preferably 8 to 15 min, more preferably 10 to 13 min, more preferably 11 to 12 min.

[0058] In the present invention, in the microwave catalytic pyrolysis, the microwave frequency is preferably 2400-2500 MHz, more preferably 2420-2480 MHz, more preferably 2440-2450 MHz, the microwave power is preferably 800-1100 W, more preferably 850-1050 W, more preferably 900-1000 W, and the microwave catalytic pyrolysis time is preferably 10-20 min, more preferably 12-18 min, more preferably 15-16 min.

[0059] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0060] In the embodiment of the present invention, the model of the tube furnace used is OTF-1200X.

[0061] Example 1

[0062] 1 mol Fe(NO3)3·9H2O, 2 mol Al(NO3)3·9H2O, and 2 mol citric acid (C6H8O7·H2O) were mixed with 10 mL of water, and activated carbon (the molar ratio of Fe ions to carbon atoms in the activated carbon was 1:6) was added. After ultrasonic mixing at a power of 300 W for 30 min, the mixture was stirred in a water bath at 80°C and 1000 rpm for 6 h to form a gel;

[0063] The obtained gel was placed in a blast dryer and dried at 100°C for 12 hours. The dried product was then placed in a mortar and ground into a precursor powder with a particle size of 0.008 mm. The precursor powder was then placed in a tube furnace and calcined at 700°C for 3 hours in a nitrogen atmosphere, and then slowly cooled to room temperature to obtain a Fe@C catalyst.

[0064] The specific surface area of ​​Fe@C catalyst is 145.09m 2 / g; the reflection loss is -2.55 dB. The larger the absolute value of the reflection loss, the better the microwave absorption performance. It can be seen that the Fe@C catalyst obtained in Example 1 has excellent microwave absorption performance.

[0065] Example 2

[0066] 1 mol Fe(NO3)3·9H2O, 2 mol Al(NO3)3·9H2O, 1 mol Ni(NO3)3·6H2O, and 2 mol C6H8O7·H2O were mixed with 10 mL of water, and activated carbon (the molar ratio of Fe ions to carbon atoms in the activated carbon was 1:6) was added. After ultrasonic mixing at a power of 300 W for 30 min, the mixture was stirred in a water bath at 80°C and 1000 rpm for 6 h to form a gel;

[0067] The obtained gel was placed in a blast dryer and dried at 100°C for 12 hours, and then the dried product was placed in a mortar and ground into a precursor powder with a particle size of 0.008 mm. The precursor powder was then placed in a tube furnace and calcined at 700°C for 3 hours in a nitrogen atmosphere, and then slowly cooled to room temperature to obtain a FeNi@C catalyst.

[0068] After testing, the reflection loss of the FeNi@C catalyst is -1.25 dB. The larger the absolute value of the reflection loss, the better the microwave absorption performance. It can be seen that the FeNi@C catalyst obtained in Example 2 has excellent microwave absorption performance.

[0069] Example 3

[0070] 7mol Fe(NO3)3·9H2O, 14mol Al(NO3)3·9H2O, 1mol

[0071] (NH4)6Mo7O 24 4H2O, 14 mol citric acid (C6H8O7·H2O) and 70 mL water were mixed, and activated carbon (the molar ratio of Fe ions to carbon atoms in the activated carbon was 1:6) was added. After ultrasonic mixing at a power of 300 W for 30 min, the mixture was stirred in a water bath at 80°C and 1000 rpm for 6 h to form a gel.

[0072] The obtained gel was placed in a blast dryer and dried at 100°C for 12 hours. The dried product was then placed in a mortar and ground into a precursor powder with a particle size of 0.008 mm. The precursor powder was then placed in a tube furnace and calcined at 700°C for 3 hours in a nitrogen atmosphere, and then slowly cooled to room temperature to obtain a FeMo@C catalyst.

[0073] After testing, the reflection loss of the FeMo@C catalyst is -1.75 dB. The larger the absolute value of the reflection loss, the better the microwave absorption performance. It can be seen that the FeMo@C catalyst obtained in Example 3 has excellent microwave absorption performance.

[0074] Example 4

[0075] 1 mol Fe(NO3)3·9H2O, 2 mol Al(NO3)3·9H2O, 1 mol Co(NO3)2·6H2O, and 2 mol C6H8O7·H2O were mixed with 10 mL of water, and activated carbon (the molar ratio of Fe ions to carbon atoms in the activated carbon was 1:6) was added. After ultrasonic mixing at a power of 300 W for 30 min, the mixture was stirred in a water bath at 80°C and 1000 rpm for 6 h to form a gel;

[0076] The obtained gel was placed in a blast dryer and dried at 100°C for 12 hours. The dried product was then placed in a mortar and ground into a precursor powder with a particle size of 0.008 mm. The precursor powder was then placed in a tube furnace and calcined at 700°C for 3 hours in a nitrogen atmosphere, and then slowly cooled to room temperature to obtain a FeCo@C catalyst.

[0077] After testing, the reflection loss of the FeCo@C catalyst is -2.0 dB. The larger the absolute value of the reflection loss, the better the microwave absorption performance. It can be seen that the FeCo@C catalyst obtained in Example 4 has excellent microwave absorption performance.

[0078] Comparative Example 1

[0079] 1 mol Fe(NO3)3·9H2O, 2 mol Al(NO3)3·9H2O, and 2 mol citric acid (C6H8O7·H2O) were mixed with 10 mL of water, ultrasonically mixed at a power of 300 W for 30 min, and then stirred in a water bath at 80°C and 1000 rpm for 6 h to form a gel;

[0080] The obtained gel was placed in a blast dryer and dried at 100°C for 12 hours, and then the dried product was placed in a mortar and ground into a precursor powder with a particle size of 0.008 mm. The precursor powder was then placed in a tube furnace and calcined at 700°C for 3 hours in a nitrogen atmosphere, and then slowly cooled to room temperature to obtain an Fe catalyst.

[0081] The electromagnetic wave performance of the catalysts obtained in Examples 1 to 4 and the catalyst obtained in Comparative Example 1 was tested respectively, and the testing steps were as follows:

[0082] Electromagnetic wave performance measurement: The catalysts obtained in Examples 1 to 4 and Comparative Example 1 were placed in a vector network analyzer (model PNA-N5244A) and the complex magnetic permeability (ε r ) and dielectric constant (μ r ), wherein the combination of catalyst and paraffin is 1:1 (inner diameter 5 mm, outer diameter 7 mm, thickness 2 mm);

[0083] The material is processed into a cylindrical shape that matches the coaxial cavity, ensuring close contact with the inner and outer conductors. When no sample is placed, the resonant frequency and quality factor of the cavity are measured. The sample is placed in the coaxial cavity, the new resonant frequency and quality factor are recorded, and the complex dielectric constant is calculated by the deviation of the resonant frequency. The test results are as follows Figures 1-2 shown.

[0084] Application Example 1

[0085] 1 g of the Fe@C catalyst obtained in Example 1 and 2 g of polyethylene plastic particles were placed in a microwave reactor (the Fe@C catalyst and the polyethylene plastic particles were placed in layers: the lower layer was a mixture of 50% by mass of the Fe@C catalyst and all the polyethylene plastic particles, and the upper layer was a separate Fe@C catalyst at 50% by mass). Nitrogen was introduced into the microwave reactor at a rate of 200 mL / min to purge both the upper and lower layers for 10 min.

[0086] After the purification was completed, nitrogen was continuously introduced at a rate of 200 mL / min, and then a microwave reactor (microwave frequency of 2450 MHz, microwave power of 1000 W) was started to react for 15 min, and the product was collected.

[0087] Calculations show that the solid yield is 14.4 wt %, the liquid yield is 57.5 wt %, and the gas yield is 28.1 wt %. The gas phase products obtained are analyzed by gas chromatography, and the volume fraction of hydrogen in the obtained gas is determined to be 96.57%.

[0088] The obtained solid is subjected to the following operations to obtain carbon nanotubes:

[0089] The solid was acid-washed in aqua regia solution (32 wt% HCl, 68 wt% HNO3) at 80°C with continuous stirring at 1500 rpm to remove metallic impurities, isolating the carbon nanotubes (CNTs) produced by the plastic pyrolysis. The solid was then filtered and rinsed with ultrapure water until the filtrate reached a neutral pH. The resulting product was dried in a forced-air oven overnight and then ground to obtain CNTs with a particle size of 0.008 mm.

[0090] Application Example 2

[0091] The “Fe@C catalyst obtained in Example 1” in Application Example 1 was replaced with “FeNi@C catalyst obtained in Example 2”, and the other steps were the same as those in Application Example 1.

[0092] Calculation shows that the solid yield is 37.2 wt %, the liquid yield is 46.7 wt %, and the gas yield is 16.1 wt %. The gas phase product obtained by gas chromatography analysis shows that the volume fraction of hydrogen in the obtained gas is 96.82%.

[0093] Application Example 3

[0094] The “Fe@C catalyst obtained in Example 1” in Application Example 1 was replaced with “FeMo@C catalyst obtained in Example 3”, and the other steps were the same as those in Application Example 1.

[0095] Calculations show that the solid yield is 32.5 wt %, the liquid yield is 49.3 wt %, and the gas yield is 18.2 wt %. The gas phase product obtained is analyzed by gas chromatography, and the volume fraction of hydrogen in the obtained gas is determined to be 96.2%.

[0096] Application Example 4

[0097] The “Fe@C catalyst obtained in Example 1” in Application Example 1 was replaced with “FeCo@C catalyst obtained in Example 4”, and the other steps were the same as those in Application Example 1.

[0098] Calculations show that the solid yield is 40.8 wt %, the liquid yield is 48.7 wt %, and the gas yield is 10.5 wt %. The gas phase products obtained were analyzed by gas chromatography, and the volume fraction of hydrogen in the obtained gas was determined to be 96.2%.

[0099] Comparative Application Example 1

[0100] Commercial fast-charging graphite materials were purchased from BTR New Materials Co., Ltd.

[0101] Application Comparative Example 2

[0102] The “Fe@C catalyst obtained in Example 1” in Application Example 1 was replaced with the “Fe catalyst obtained in Comparative Example 1”, and the other steps were the same as those in Application Example 1.

[0103] The following performance tests were conducted on the carbon nanotubes obtained in Examples 1 to 4 and Comparative Example 2 and the fast-filling graphite material in Comparative Example 1:

[0104] The carbon nanotubes obtained in Application Examples 1 to 4 and Application Comparative Example 2 and the fast-charging graphite material in Application Comparative Example 1 were used as active materials to prepare batteries in the following steps (before the battery was assembled, the components were placed in a vacuum oven at 80°C with a temperature of 1×10 -2 Pa vacuum drying for 12 h to ensure purity).

[0105] The active material, SuperP conductive agent and sodium alginate binder were mixed in a mass ratio of 8:1:1, and the mixture was printed and coated on copper foil using a doctor blade coater (the doctor blade pressure was 0.3 MPa and the doctor blade thickness was 200 μm). -2 Pa) in an oven at 120° C. for 12 h to ensure complete removal of moisture, and then roll-pressed using a double-roller machine to obtain an anode;

[0106] A CR2032 button cell was assembled in an argon-filled glove box using polyethylene as the separator and lithium foil as the counter electrode with the obtained anode and electrolyte. The electrolyte was a mixed solution of 80 μL 1 M LiPF6 solution (the solvent was a mixed solution of ethylene carbonate and diethyl carbonate in a volume ratio of 1:1) and 8 μL fluoroethylene carbonate. The cell was allowed to stand for 12 h to allow the electrolyte to penetrate thoroughly, and then pre-cycled 5 times at 50 mA / g in constant current mode to stabilize the electrode before the cycle and rate performance evaluation to obtain the battery to be tested.

[0107] Perform the following performance tests on the battery to be tested:

[0108] The reversible cycle capacity of the battery to be tested was measured at a current of 2 A / g. The measurement results are shown in Table 1.

[0109] Table 1 Performance test results of carbon nanotubes obtained in Application Examples 1 to 3 and fast-filling graphite materials in Comparative Example 1

[0110]

[0111] As can be seen from Table 1, the quality of the carbon nanotubes produced by the catalyst obtained by the present invention is relatively stable and has excellent reversible cycle capacity. Although Application Example 1 is slightly inferior to Application Comparative Example 1 in terms of reversible cycle capacity, Application Example 1 still has great advantages in hydrogen production and carbon production.

[0112] Electrochemical impedance spectroscopy (EIS) tests were performed on the batteries prepared using the carbon nanotubes obtained in Examples 1 to 4 and Comparative Example 2 using a CHI600 potentiostat in the frequency range of 1 MHz to 100 kHz. The test results are shown in FIG. Figure 3 As shown by Figure 3 It can be seen that at high frequencies, a distinct concave semicircle corresponds to the combined resistance of charge transfer (Rct) and the solid electrolyte interface (SEI) film (Rf). In addition, there is a slanted line in the low-frequency region, representing the Warburg impedance (W1), which is related to ion diffusion within the electrode matrix. The FeNi@C electrode exhibits the lowest Rct, which means that the interfacial charge transfer between the measured electrodes is the fastest.

[0113] Cyclic voltammetry tests were performed on the batteries prepared using the carbon nanotubes obtained in Examples 1 to 4 and Comparative Example 2 in a potential range of 0.01 to 2 V at a scan rate of 0.1 to 0.5 mV / s. The test results are shown in FIG. Figures 4 to 8 As shown. Figures 4 to 8 As can be seen, within the voltage range of 0.01 to 3 V, the redox peak currents of FeMo@C and FeCo@C are significantly higher than those of the other materials, reflecting their higher electrochemical activity. Furthermore, the CV curves of these two materials exhibit good symmetry and a small peak potential difference, indicating good reversibility of the electrode reactions. The CV curves gradually stabilize with increasing cycle number, especially for FeMo@C, which maintains stable electrochemical performance during repeated charge and discharge.

[0114] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a multifunctional spinel catalyst, characterized in that: The steps include: 1) ultrasonically mixing iron salt, aluminum salt, citric acid, water and carbon source and stirring to obtain a gel; 2) The gel is dried and calcined in sequence to obtain a multifunctional spinel catalyst.

2. The method for preparing a multifunctional spinel catalyst according to claim 1, wherein In the step 1), the iron salt is Fe(NO3)3·9H2O, FeCl3 or Fe2(SO4)3, the aluminum salt is Al(NO3)3·9H2O, AlCl3 or Al2(SO4)3, and the carbon source is activated carbon, graphene or mesoporous carbon; The ratio of iron salt, aluminum salt, citric acid and water is 0.8-1.2 mol:1.6-2.4 mol:1.6-2.4 mol:5-15 mL; The molar ratio of the iron ions in the iron salt to the carbon atoms in the carbon source is 0.8-1.2:4-8.

3. The method for preparing a multifunctional spinel catalyst according to claim 2, wherein: In the step 1), the ultrasonic mixing time is 20 to 40 minutes, and the ultrasonic mixing power is 250 to 350W; The stirring temperature is 70-90°C, and the stirring time is 5-7h.

4. The method for preparing a multifunctional spinel catalyst according to claim 2, wherein: In the step 2), the drying time is 10 to 15 hours and the drying temperature is 90 to 120°C.

5. The method for preparing a multifunctional spinel catalyst according to claim 4, wherein: In the step 2), calcination is carried out in a nitrogen atmosphere, the calcination time is 2 to 4 hours, and the calcination temperature is 650 to 750°C.

6. The method for preparing a multifunctional spinel catalyst according to any one of claims 1 to 5, characterized in that: The step 1) further comprises a transition metal salt, which includes a nickel salt, a cobalt salt, a vanadium salt, a manganese salt or a molybdenum salt; The molar ratio of the transition metal ions in the transition metal salt to the iron ions in the iron salt is 0.8-1.2:0.8-1.

2.

7. A multifunctional spinel catalyst prepared by the method for preparing a multifunctional spinel catalyst according to any one of claims 1 to 6.

8. Use of the multifunctional spinel catalyst according to claim 7 in microwave catalytic cracking of plastics, characterized in that: The method comprises the following steps: mixing a multifunctional spinel catalyst with plastic and then sequentially performing nitrogen purification and microwave catalytic pyrolysis.

9. The use of the multifunctional spinel catalyst in microwave catalytic cracking of plastics according to claim 8, characterized in that: The mass ratio of the multifunctional spinel catalyst to the plastic is 0.8-1.2:1.5-2.5; During the nitrogen purification, the flow rate of nitrogen is 180 to 220 mL / min, and the nitrogen purification time is 8 to 15 minutes.

10. Use of the multifunctional spinel catalyst according to claim 9 in microwave catalytic cracking of plastics, characterized in that: In the microwave catalytic pyrolysis, the microwave frequency is 2400-2500 MHz, the microwave power is 800-1100 W, and the microwave catalytic pyrolysis time is 10-20 minutes.

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