A system and method for treating VOCs based on a multi-pass rotating wheel and molten salt catalytic combustion

Abstract

The present application relates to the technical field of waste gas treatment, and particularly relates to a VOCs treatment system and method based on a multi-channel rotating wheel and molten salt catalytic combustion. The system comprises: a plurality of zeolite rotating wheels with different silicon-aluminum ratios, which are used to adsorb VOCs in VOCs waste gas to obtain purified gas; a molten salt catalytic combustion device connected with the zeolite rotating wheel, which is used to receive the desorbed VOCs from the zeolite rotating wheel and perform catalytic combustion treatment on the desorbed VOCs by using molten salt heat to obtain high-temperature purified gas; wherein the high-temperature purified gas comprises carbon dioxide and water vapor; a mixed flow device connected with the zeolite rotating wheel and the molten salt catalytic combustion device respectively, which is used to mix the external purified gas and the high-temperature purified gas to obtain target purified gas, and introduce the target purified gas into the zeolite rotating wheel to desorb VOCs. The scheme can efficiently remove VOCs waste gas with different concentrations and different component types.

Description

Technical Field

[0001] This invention relates to the field of waste gas treatment technology, and in particular to a VOCs treatment system and method based on a multi-channel rotor and molten salt catalytic combustion. Background Technology

[0002] As the world's largest producer of coatings, China has maintained its position as the world's leading producer and consumer of coatings for 14 consecutive years. By 2022, China's coating output reached 34.88 million tons, with industrial coating accounting for over 35% and showing a continuous upward trend. With the increasing demand for coatings, the resulting VOC emissions are also rapidly increasing, mainly from the storage, transportation, and use of coatings, hardeners, and thinners. Industrial coating emissions of VOCs are characterized by large emissions, large concentration fluctuations, and complex compositions. The differences in composition are related to the coating industry; for example, VOCs generated by furniture manufacturing are mainly esters, aromatic hydrocarbons, and aldehydes and ketones; automotive painting mainly uses ketones, aromatic hydrocarbons, olefins, and esters; and ship painting is primarily aromatic hydrocarbons. Therefore, how to efficiently remove VOCs of different concentrations and compositions has become a key challenge. Summary of the Invention

[0003] This invention provides a VOCs treatment system and method based on a multi-channel rotor and molten salt catalytic combustion, which can efficiently remove VOCs waste gas of different concentrations and different component types.

[0004] In a first aspect, embodiments of the present invention provide a VOCs treatment system based on a multi-path rotor and molten salt catalytic combustion, comprising:

[0005] Multiple zeolite rotors with different silicon-to-aluminum ratios are used to adsorb VOCs in VOCs waste gas to obtain purified gas.

[0006] A molten salt catalytic combustion device, connected to the zeolite rotor, is used to receive VOCs desorbed by the zeolite rotor and to catalytically combust the desorbed VOCs using molten salt heat to obtain high-temperature purified gas; wherein, the high-temperature purified gas includes carbon dioxide and water vapor.

[0007] The mixing device is connected to the zeolite rotor and the molten salt catalytic combustion device, respectively, and is used to mix the external purified gas and the high-temperature purified gas to obtain the target purified gas, and then pass the target purified gas into the zeolite rotor to desorb VOCs.

[0008] Secondly, embodiments of the present invention provide a VOCs treatment method based on a multi-path rotor and molten salt catalytic combustion, applied to the system described in the above embodiments, comprising:

[0009] Multiple zeolite rotors with different silicon-to-aluminum ratios are used to adsorb VOCs in VOCs waste gas to obtain purified gas;

[0010] The molten salt catalytic combustion device receives the VOCs desorbed by the zeolite rotor and uses the heat of molten salt to catalytically combust the desorbed VOCs to obtain high-temperature purified gas.

[0011] The mixing device is used to mix the external purified gas and the high-temperature purified gas to obtain the target purified gas, and the target purified gas is then introduced into the zeolite rotor to desorb VOCs.

[0012] As can be seen from the above scheme, the VOCs treatment system and method based on multi-channel rotors and molten salt catalytic combustion provided by this invention can effectively improve the adsorption efficiency of zeolite rotors by setting multiple zeolite rotors with different silicon-to-aluminum ratios, breaking the limitations and selectivity of adsorption, thereby efficiently removing VOCs waste gas of different concentrations and component types. Furthermore, by utilizing the heat of molten salt to catalytically combust the desorbed VOCs, a stable and continuous supply of heat to the combustion chamber can be ensured. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the structure of a VOCs treatment system based on a multi-path rotor and molten salt catalytic combustion, provided in an embodiment of the present invention.

[0015] Figure label:

[0016] 1-Zeolite rotor;

[0017] 2- Molten salt catalytic combustion device;

[0018] 21-Heat exchanger;

[0019] 211-Helical pipe section;

[0020] 22-Catalytic combustion section;

[0021] 221 - Catalyst layer;

[0022] 23-High-temperature molten salt tank;

[0023] 24- Low-temperature molten salt tank;

[0024] 25 - Molten salt heater;

[0025] 3-Mixing device. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1 One embodiment of the present invention provides a VOCs treatment system based on multi-channel rotors and molten salt catalytic combustion. The system includes multiple zeolite rotors 1 with different silicon-to-aluminum ratios, a molten salt catalytic combustion device 2, and a mixing device 3, wherein:

[0028] Zeolite rotor 1 is used to adsorb VOCs in VOCs waste gas to obtain purified gas;

[0029] The molten salt catalytic combustion device 2 is connected to the zeolite rotor 1 and is used to receive the VOCs desorbed by the zeolite rotor 1 and use the heat of molten salt to catalytically combust the desorbed VOCs to obtain high-temperature purified gas; wherein, the high-temperature purified gas includes carbon dioxide and water vapor.

[0030] The mixing device 3 is connected to the zeolite rotor 1 and the molten salt catalytic combustion device 2 respectively. It is used to mix the external purified gas and the high-temperature purified gas to obtain the target purified gas, and then pass the target purified gas into the zeolite rotor 1 to desorb VOCs.

[0031] In this embodiment, by setting multiple zeolite rotors 1 with different silicon-to-aluminum ratios, the adsorption efficiency of the zeolite rotors can be effectively improved, overcoming the limitations and selectivity of adsorption, thereby efficiently removing VOCs waste gas of different concentrations and composition types. Furthermore, by utilizing molten salt heat to catalytically combust the desorbed VOCs, a stable and continuous supply of heat to the combustion chamber can be ensured.

[0032] Industrial coating involves numerous raw materials and technological processes, resulting in large emissions of VOCs with fluctuating concentrations and complex compositions. These complex mixtures compete for adsorption on the zeolite rotor, severely impacting adsorption efficiency. Furthermore, zeolite rotors cannot simultaneously meet the needs of multiple application scenarios.

[0033] To solve this technical problem, in one embodiment of the present invention, the number of zeolite rotors 1 is three, and the silicon-to-aluminum ratios of the three zeolite rotors 1 are 1500-3000, 500-1500 and 50-500, respectively.

[0034] In one embodiment of the present invention, a zeolite rotor 1 with a silicon-to-aluminum ratio in the range of 1500 to 3000 is used to adsorb esters, a zeolite rotor 1 with a silicon-to-aluminum ratio in the range of 500 to 1500 is used to adsorb olefins, and a zeolite rotor 1 with a silicon-to-aluminum ratio in the range of 50 to 500 is used to adsorb aromatic hydrocarbons and ketones.

[0035] It should be noted that increasing the silicon-to-aluminum ratio improves the hydrophobicity of the zeolite molecular sieve; therefore, the appropriate silicon-to-aluminum ratio range can be selected based on the humidity of the exhaust gas. Furthermore, by adjusting the pipe valves, the three zeolite rotors 1 can be used in parallel or in series; no specific limitations are specified here.

[0036] In one embodiment of the present invention, multiple zeolite rotors 1 with different silicon-to-aluminum ratios are interconnected by pipes. The pipes are connected in parallel and in series, and electronic valves (not shown in the figure) are installed on the pipes.

[0037] Based on the VOCs waste gas and humidity generated by different industries, the on / off state of multiple zeolite rotors 1 with different silicon-aluminum ratios is controlled by adjusting electronic valves.

[0038] In this embodiment, the average pore sizes of the zeolite rotors with low, medium, and high silica-to-alumina ratios (i.e., silica-to-alumina ratios ranging from 50 to 500, 500 to 1500, and 1500 to 3000, respectively) are approximately 2.4–5.3 nm, 2.4 nm, and 3–3.3 nm, respectively. These pore sizes are generally larger than the diameters of all common components in VOCs waste gas, allowing for adsorption. However, the type of VOCs waste gas components, their molecular dynamic diameter, molecular weight, and polarity all affect their adsorption efficiency on the zeolite rotor. Therefore, competitive adsorption occurs when treating waste gases with complex compositions. Esters, due to their larger molecular weight, larger molecular dynamic diameter, and stronger polarity, are preferentially adsorbed, significantly affecting the adsorption of other components. Therefore, the usage of the three rotors needs to be adjusted according to different industries.

[0039] For example, VOCs waste gas from the shoe manufacturing industry is mainly composed of ketones, with small amounts of esters and aromatic hydrocarbons. The configuration is as follows: 30%–40% of the waste gas is introduced into a zeolite rotor with a silica-to-alumina ratio (S / A ratio) of 1500–3000. After adsorbing esters, the waste gas is then introduced into a zeolite rotor with a S / A ratio of 50–500. The remaining 60%–70% of the waste gas is directly introduced into a zeolite rotor with a S / A ratio of 50–500. At this point, the concentration of esters becomes very low, insufficient to affect the adsorption of other components. After eliminating the influence of esters, aromatic hydrocarbons, due to their low polarity, still have a disadvantage in adsorption. The low S / A ratio mainly adsorbs ketones. Therefore, the waste gas exiting the low S / A ratio rotor then enters the zeolite rotor with a S / A ratio of 500–1500, where the adsorption capacity of aromatic hydrocarbons increases.

[0040] For example, in the furniture manufacturing industry, the main components are esters, followed by ketones and aromatic hydrocarbons. The connection method is as follows: 70%–80% of the waste gas is introduced into a zeolite rotor with a silicon-to-alumina ratio of 1500–3000; the waste gas after adsorbing esters is then introduced into a zeolite rotor with a silicon-to-alumina ratio of 50–500; the remaining 20%–30% of the waste gas is directly introduced into a zeolite rotor with a silicon-to-alumina ratio of 50–500; and all the waste gas exits from this rotor and then enters a zeolite rotor with a silicon-to-alumina ratio of 500–1500.

[0041] For example, the exhaust gas from the shipbuilding industry is mainly composed of aromatic hydrocarbons (around 77%), with small amounts of ketones and alcohols. The approach is as follows: ketones, due to their high polarity, are more easily adsorbed than aromatic hydrocarbons. Since their content is low, a portion is adsorbed first to achieve overall dilution before treating the aromatic hydrocarbons. 50%-60% of the exhaust gas is passed through a zeolite rotor with a silicon-to-alumina ratio of 50-500, followed by a zeolite rotor with a silicon-to-alumina ratio of 500-1500. The remaining 40%-50% of the exhaust gas is directly passed through a zeolite rotor with a silicon-to-alumina ratio of 500-1500.

[0042] For example, the exhaust gas from the automotive painting industry mainly consists of ketones, aromatic hydrocarbons, and esters. The connection method is as follows: 50%–60% of the exhaust gas is introduced into a zeolite rotor with a silicon-to-alumina ratio (Si / A ratio) of 1500–3000. After adsorbing the esters, the exhaust gas is then introduced into a zeolite rotor with a Si / A ratio of 50–500. The remaining 40%–50% of the exhaust gas is directly introduced into a zeolite rotor with a Si / A ratio of 50–500. All the exhaust gas is discharged from this rotor and then enters a zeolite rotor with a Si / A ratio of 500–1500.

[0043] Furthermore, the adsorption efficiency is also related to the humidity of the VOCs waste gas. When the humidity of the waste gas is too high, it can be first passed through a zeolite rotor with a silicon-to-alumina ratio (Si / A ratio) of 50–500. When the Si / A ratio is low, the molecular sieve has strong polarity and a certain water absorption capacity. Moreover, zeolites with low Si / A ratios are much cheaper than those with high Si / A ratios, so they act as a sacrificial layer, absorbing most of the moisture in the gas before being passed through the other two types of zeolite rotors, depending on their composition. Increasing the Si / A ratio increases the non-polar surface area of ​​the material; therefore, molecular sieves with medium to high Si / A ratios have better hydrophobicity and can cope with the influence of moisture in low-humidity waste gas.

[0044] In one embodiment of the present invention, the zeolite rotor 1 is obtained by the following method:

[0045] Sodium hydroxide and tetrapropylammonium hydroxide were dissolved uniformly in water, and then aluminum isopropoxide and tetraethyl orthosilicate were added in sequence and stirred until completely dissolved to obtain a mixed solution.

[0046] Add phenyltriethoxysilane to the mixed solution, stir at 50-80°C for 30-120 min, and age at 30-90°C for 8-72 h;

[0047] The aged mixed solution was transferred to a high-pressure reactor and crystallized at 100–190°C for 40–120 h. The solid product was obtained by centrifugation and washed until neutral.

[0048] After the washed solid product is dried and ground, it is calcined at 550-650℃ for 3-10 hours to obtain zeolite molecular sieve, and the zeolite molecular sieve is processed into zeolite rotor 1.

[0049] In one embodiment of the present invention, the molten salt catalytic combustion device 2 includes a heat exchanger 21, a catalytic combustion section 22, a high-temperature molten salt tank 23, a low-temperature molten salt tank 24, and a molten salt heater 25. A spiral tube section 211 is provided inside the heat exchanger 21.

[0050] The inlet of the spiral section 211 is connected to the zeolite rotor 1, and the outlet is connected to the gas inlet of the catalytic combustion section 22;

[0051] The gas outlet of the catalytic combustion section 22 is connected to the cavity inlet of the heat exchanger 21, and the cavity outlet of the heat exchanger 21 is connected to the mixing device 3.

[0052] The heat exchanger 21 is used to preheat the desorbed VOCs with the high-temperature purified gas output from the gas outlet of the catalytic combustion section 22, and output the preheated gas to the gas inlet of the catalytic combustion section 22, while the high-temperature purified gas after heat release is output to the mixing device 3.

[0053] The catalytic combustion section 22 is connected to the high-temperature molten salt tank 23 and the low-temperature molten salt tank 24 respectively, and is used to transfer the molten salt heat of the high-temperature molten salt tank 23 to the catalytic combustion section 22. After the catalytic combustion section 22 absorbs heat, it outputs low-temperature molten salt to the low-temperature molten salt tank 24.

[0054] Molten salt heater 25 is connected to high-temperature molten salt tank 23 and low-temperature molten salt tank 24 respectively, and is used to heat low-temperature molten salt to high-temperature molten salt; wherein, molten salt heater 25 is selected from solar energy or off-peak electricity.

[0055] In this embodiment, by setting up a heat exchanger 21, heat recovery and utilization can be realized to reduce equipment energy consumption; furthermore, by setting up a spiral tube section 211, the preheating effect of desorbed VOCs can be guaranteed.

[0056] In addition, for the heat storage and heating section of the molten salt catalytic combustion device 2, the molten salt in the low-temperature molten salt tank 24 enters the molten salt heater 25 through the molten salt pump. After being heated and melted by solar energy or off-peak electricity in the molten salt heater 25, it enters the high-temperature molten salt tank 23 and is then pumped into the catalytic combustion section 22 to provide energy for the combustion and decomposition of VOCs. After releasing energy, the molten salt flows back to the low-temperature molten salt tank 24 for the next cycle.

[0057] In one embodiment of the present invention, the catalytic combustion section 22 is a catalyst made of transition metal.

[0058] In this embodiment, the use of a catalyst made of transition metals can effectively reduce material costs compared to catalysts made of precious metals.

[0059] In one embodiment of the present invention, the catalyst is obtained in the following manner:

[0060] Precursors were obtained by heat-treating nitrates of two target transition metals, including cobalt, manganese, cerium, and copper.

[0061] The precursor is calcined to obtain the catalyst; wherein the calcination temperature is 250-550℃ and the calcination time is 0.5-3h.

[0062] In one embodiment of the present invention, the step of "heat-treating the nitrates of two target transition metals to obtain precursors" may specifically include:

[0063] The nitrates of two target transition metals and terephthalic acid are dissolved in an organic solvent, thoroughly mixed, and then packaged into a second high-pressure reactor. The organic solvent is N,N-dimethylformamide and ethanol. The molar ratio of the nitrates of the two target transition metals is 1:4 to 4:1, and the molar ratio of the nitrates to terephthalic acid is 2:5.

[0064] The second high-pressure reactor was placed in a constant temperature oven; the reaction temperature was 90–120℃ and the reaction time was 12–26 h.

[0065] After the reaction was completed, the liner was removed after the temperature of the second high-pressure reactor dropped to room temperature. The solid products generated by the reaction were thoroughly washed with anhydrous ethanol and dried to obtain the precursor.

[0066] In some implementations, the second high-pressure reactor is made of stainless steel.

[0067] Furthermore, embodiments of the present invention also provide a VOCs treatment method based on a multi-path rotor and molten salt catalytic combustion, applicable to the system mentioned in any of the above embodiments, comprising:

[0068] Multiple zeolite rotors with different silicon-to-aluminum ratios were used to adsorb VOCs in VOCs waste gas to obtain purified gas.

[0069] The VOCs desorbed by the zeolite rotor 1 are received by the molten salt catalytic combustion device 2, and the desorbed VOCs are catalytically combusted using the heat of molten salt to obtain high-temperature purified gas.

[0070] The external purified gas and the high-temperature purified gas are mixed using the mixing device 3 to obtain the target purified gas, and the target purified gas is then introduced into the zeolite rotor 1 to desorb VOCs.

[0071] It is understood that the method embodiments and system embodiments provided by the present invention are based on the same inventive concept and have the same beneficial effects. The beneficial effects of the method embodiments will not be elaborated here.

[0072] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0073] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A VOCs treatment method based on a multi-channel rotor and molten salt catalytic combustion, characterized in that, A VOCs treatment system based on a multi-channel rotor and molten salt catalytic combustion is applied, the system comprising: Multiple zeolite rotors (1) with different silicon-to-aluminum ratios are used to adsorb VOCs in VOCs waste gas to obtain purified gas; A molten salt catalytic combustion device (2) is connected to the zeolite rotor (1) and is used to receive the VOCs desorbed by the zeolite rotor (1) and use the heat of molten salt to catalytically combust the desorbed VOCs to obtain high-temperature purified gas; wherein the high-temperature purified gas includes carbon dioxide and water vapor. The mixing device (3) is connected to the zeolite rotor (1) and the molten salt catalytic combustion device (2) respectively, and is used to mix the external purified gas and the high temperature purified gas to obtain the target purified gas, and to pass the target purified gas into the zeolite rotor (1) to desorb VOCs; The number of the zeolite rotors (1) is three, and the silicon-to-aluminum ratios of the three zeolite rotors (1) are 1500~3000, 500~1500 and 50~500, respectively. The method includes: VOCs in VOCs waste gas are adsorbed by using multiple zeolite rotors (1) with different silicon-to-aluminum ratios to obtain purified gas; The molten salt catalytic combustion device (2) receives the VOCs desorbed by the zeolite rotor (1) and uses the heat of molten salt to catalytically combust the desorbed VOCs to obtain high-temperature purified gas. The external purified gas and the high-temperature purified gas are mixed using the mixing device (3) to obtain the target purified gas, and the target purified gas is introduced into the zeolite rotor (1) to desorb VOCs. The zeolite rotor (1) with a silicon-to-aluminum ratio of 1500 to 3000 is used to adsorb esters, the zeolite rotor (1) with a silicon-to-aluminum ratio of 500 to 1500 is used to adsorb olefins, and the zeolite rotor (1) with a silicon-to-aluminum ratio of 50 to 500 is used to adsorb aromatic hydrocarbons and ketones. Multiple zeolite rotors (1) with different silicon-to-aluminum ratios are interconnected by pipes, which are connected in parallel and in series, and are equipped with electronic valves. Based on the VOCs waste gas and humidity generated by different industries, the on / off state of multiple zeolite rotors (1) with different silicon-to-aluminum ratios is controlled by adjusting the electronic valves; among them, the type, molecular dynamics diameter, molecular weight and polarity of VOCs waste gas components will affect their adsorption effect on the zeolite rotors (1), and the mixed components in the VOCs waste gas will compete for adsorption on the zeolite rotors (1).

2. The method according to claim 1, characterized in that, The zeolite rotor (1) is obtained in the following manner: Sodium hydroxide and tetrapropylammonium hydroxide were dissolved uniformly in water, and then aluminum isopropoxide and tetraethyl orthosilicate were added in sequence and stirred until completely dissolved to obtain a mixed solution. Add phenyltriethoxysilane to the mixed solution, stir at 50-80°C for 30-120 min, and age at 30-90°C for 8-72 h; The aged mixed solution was transferred to a high-pressure reactor and crystallized at 100-190°C for 40-120 hours. The solid product was obtained by centrifugation and washed until neutral. After washing, the solid product is dried and ground, and then calcined at 550~650℃ for 3~10h to obtain zeolite molecular sieve, and the zeolite molecular sieve is processed into zeolite rotor (1).

3. The method according to any one of claims 1-2, characterized in that, The molten salt catalytic combustion device (2) includes a heat exchanger (21), a catalytic combustion section (22), a high-temperature molten salt tank (23), a low-temperature molten salt tank (24), and a molten salt heater (25). The heat exchanger (21) is provided with a spiral tube section (211). The inlet of the spiral tube section (211) is connected to the zeolite rotor (1), and the outlet is connected to the gas inlet of the catalytic combustion section (22); The gas outlet of the catalytic combustion section (22) is connected to the cavity inlet of the heat exchanger (21), and the cavity outlet of the heat exchanger (21) is connected to the mixing device (3). The heat exchanger (21) is used to preheat the desorbed VOCs with the high-temperature purified gas output from the gas outlet of the catalytic combustion section (22), and output the preheated gas to the gas inlet of the catalytic combustion section (22), while outputting the high-temperature purified gas after heat release to the mixing device (3). The catalytic combustion section (22) is connected to the high-temperature molten salt tank (23) and the low-temperature molten salt tank (24) respectively, and is used to transfer the molten salt heat of the high-temperature molten salt tank (23) to the catalytic combustion section (22), and output low-temperature molten salt to the low-temperature molten salt tank (24) after the catalytic combustion section (22) absorbs heat; The molten salt heater (25) is connected to the high-temperature molten salt tank (23) and the low-temperature molten salt tank (24) respectively, and is used to heat the low-temperature molten salt to the high-temperature molten salt; wherein, the molten salt heater (25) is selected from solar energy or off-peak electricity.

4. The method according to claim 3, characterized in that, The catalyst used in the catalytic combustion section (22) is a catalyst made of transition metal.

5. The method according to claim 4, characterized in that, The catalyst was obtained in the following manner: Precursors were obtained by heat-treating nitrates of two target transition metals, including cobalt, manganese, cerium, and copper. The precursor is calcined to obtain the catalyst; wherein the calcination temperature is 250~550℃ and the calcination time is 0.5~3 h.

6. The method according to claim 5, characterized in that, The heat treatment of nitrates of two target transition metals to obtain precursors includes: Two target transition metal nitrates and terephthalic acid are dissolved in an organic solvent, thoroughly mixed, and then packaged into a second high-pressure reactor; wherein the organic solvent is N,N-dimethylformamide and ethanol, the molar ratio of the two target transition metal nitrates is 1:4 to 4:1, and the molar ratio of the nitrates to the terephthalic acid is 2:5; The second high-pressure reactor is placed in a constant temperature oven; wherein the reaction temperature is 90~120℃ and the reaction time is 12~26h. After the reaction is complete, once the temperature of the second high-pressure reactor has dropped to room temperature, the liner is removed, and the solid products generated by the reaction are thoroughly washed with anhydrous ethanol and dried to obtain the precursor.

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