In (at) CuO-SnO2-MnO-MgO (at) CePO4 core-shell structure catalyst and preparation method thereof

Abstract

The invention provides an In (at) CuO-SnO2-MnO-MgO (at) CePO4 core-shell structure catalyst and a preparation method thereof. According to the catalyst, In is used as a core layer, a CuO-SnO2-MnO-MgO layer is used as a middle layer, and a CePO4 layer is used as a shell layer. The In (at) CuO-SnO2-MnO-MgO (at) CePO4 core-shell structure catalyst provided by the invention has a core-shell structure, the core layer can provide abundant active sites, and the middle layer optimizes the oxidation-reduction performance and the surface acid-base property of the catalyst through the synergistic effect of multiple components, so that the catalytic activity and stability are further improved, and the catalyst has a good application prospect. The catalytic activity, the stability and the poisoning resistance of the catalyst are improved through the shell layer, all the layers are firmly combined, the catalytic activity, the stability and the poisoning resistance of the catalyst are high, the application range is wide, and the purification capacity on VOCs can be improved in the using process; the preparation method provided by the invention is green and environment-friendly in process, simple and easy to operate.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental governance, relates to a core-shell structure catalyst, and particularly relates to an In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst and a preparation method thereof. Background Art

[0002] VOC waste gas mainly consists of some hydrocarbons, lipids, and aldehyde substances, which belong to volatile organic compounds and float in the air. Such substances are considered key precursors of pollutants such as secondary aerosols, photochemical smog, ozone, and PM2.5. Moreover, due to high emissions, they have characteristics such as pungent odor, high toxicity, environmental pollution persistence, and easy photochemical reactivity leading to secondary pollution. They have become important pollution problems and have a serious impact on human health and the natural environment. With the continuous enhancement of environmental protection concepts, the treatment of VOC waste gas has become very crucial. To reasonably reduce the pollution of VOC waste gas and mitigate its damage to the environment, it is necessary to select the best waste gas treatment plan and cooperate with effective waste gas treatment means to achieve the purification of VOC waste gas. Catalytic combustion technology is considered the VOC gas control technology with the most promising development and application prospects.

[0003] Currently, the catalytic combustion catalysts that are more commonly used are noble metals Pt and Pd, which have high activity and relatively mature technologies. However, such catalysts have the following defects: when treating organic gases containing sulfur, they are prone to deactivation; the cost of noble metals is relatively high, resulting in a significant increase in the cost of factories. Therefore, it is necessary to develop a non-noble metal and sulfur-resistant VOC waste gas catalyst. Summary of the Invention

[0004] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide an In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst and a preparation method thereof, so as to solve the technical problems of easy deactivation and high cost of noble metal catalysts when treating sulfur-containing organic gases in the prior art.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions to achieve:

[0006] A preparation method of an In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst, wherein In of the catalyst is the core, the CuO-SnO2-MnO-MgO layer is the intermediate layer, and the CePO4 layer is the outer shell layer, and the method includes the following steps:

[0007] Step 1: Mix an indium trichloride aqueous solution with a reducing agent and stir magnetically to obtain solution A; place solution A in a reaction kettle for hydrothermal reaction to obtain reactant B; wash reactant B with deionized water and ethanol; place the washed reactant B in a tubular furnace and keep it at 400 - 450 °C for 0.5 - 2.0 h to obtain rod-shaped In2O3 powder;

[0008] Step 2: Add the prepared In2O3 powder into an aqueous surfactant solution and ultrasonically oscillate to obtain mixed solution C;

[0009] Step 3: Sequentially add the formulated amounts of copper salt, tin salt, manganese salt, and magnesium salt into mixed solution C to obtain reactant D. During the addition process, add a basic precipitating agent to control the pH value of the system to 8.5 - 9.5;

[0010] Among them, the molar ratio of the indium ion salt, copper ion salt, manganese ion salt, tin ion salt, and magnesium ion salt is (7.78×10 -5 ~1.762×10 -4 ): 1.00: (1.89 - 9.47): (0.89 - 4.46): (0.50 - 2.51);

[0011] Step 4: Add an NH2OH·HCl solution to reactant D and age it at room temperature for 1 h to obtain mixed solution E; centrifuge, wash, dry, and calcine mixed solution E to obtain

[0012] In@CuO - SnO2 - MnO - MgO powder;

[0013] Step 5: Add a CeCl3 solution to a Na3PO4 solution and add dilute hydrochloric acid to adjust the pH value of the system to 0.85 - 1.15 to obtain solution F; add In@CuO - SnO2 - MnO - MgO powder to solution F, stir magnetically for 1 - 2 h, ultrasonically disperse for 1 - 2 h to obtain a suspension; transfer the suspension into a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal product; filter, wash, dry, and grind the hydrothermal product to obtain an In@CuO - SnO2 - MnO - MgO@CePO4 core - shell structure catalyst;

[0014] The mass ratio of In@CuO - SnO2 - MnO - MgO, CeCl3, and Na3PO4 is 1: (4.20 - 5.24): (2.79 - 3.49), and in the mixed solution F, the molar ratio of Ce 3+ to HnPO4 (3-n)- is 1:1.

[0015] The present invention also has the following technical features:

[0016] Specifically, in step 1, the reducing agent is selected from one or both of sodium borohydride and urea; the mass ratio of indium trichloride to the reducing agent is 1:(3-4).

[0017] Furthermore, in step 1, the magnetic stirring time is 8-15 min, the temperature of the hydrothermal reaction is 90-100 °C, and the time of the hydrothermal reaction is 10-12 h.

[0018] Furthermore, in step 2, the mass ratio of In2O3 to the surfactant is 1:(20-30); the ultrasonic oscillation time is 8-15 min;

[0019] The surfactant is selected from any one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium lauryl polyether sulfate, sodium succinate sulfonate, cetyltrimethylammonium bromide, and dodecyltrimethylammonium chloride.

[0020] Furthermore, in step 3, the basic precipitating agent is selected from one or more of NaOH, KOH, and ammonia water; the copper salt is selected from any one of copper nitrate, copper chloride, and copper acetate; the tin salt is selected from any one of tin tetrachloride and tin acetate; the manganese salt is selected from any one of manganese nitrate and manganese acetate; the magnesium salt is selected from any one of magnesium nitrate and magnesium acetate.

[0021] Furthermore, in step 3, the basic precipitating agent is added to the system in a dropwise manner, and the concentration of the basic precipitating agent is 2.0-4.0 mol / L.

[0022] Furthermore, in step 4, the concentration of NH2OH·HCl is 0.2-0.3 mol / L.

[0023] Furthermore, in step 4, the drying temperature is 80-100 °C, the drying time is 8-10 h, the calcination temperature is 400-450 °C, and the calcination time is 4-6 h.

[0024] Furthermore, it is specifically prepared by the following steps:

[0025] Step 1: Mix the indium trichloride aqueous solution with sodium borohydride, and magnetically stir for 8-15 min to obtain solution A; place solution A in a reaction kettle and keep it at 90-100 °C for 10-12 h to obtain reactant B; wash reactant B with deionized water and ethanol; place the washed reactant B in a tubular furnace and keep it at 400-450 °C for 0.5-2.0 h to obtain In2O3 powder;

[0026] Step 2: Add the prepared In2O3 powder into an aqueous solution of sodium dodecyl sulfate and ultrasonically vibrate for 8 - 15 min to obtain a mixed solution C; the mass ratio of the In2O3 powder to sodium dodecyl sulfate is 1:25;

[0027] Step 3: Sequentially add the formula amounts of copper nitrate, tin tetrachloride, manganese nitrate, and magnesium nitrate into the mixed solution C to obtain a reactant D. During the addition process, add a NaOH solution to control the pH value of the system to 9;

[0028] Among them, the molar ratio of indium ions, copper ions, manganese ions, tin ions, and magnesium ions is 1.27×10 -4 :1:1.89:0.89:0.50;

[0029] Step 4: Add a NH2OH·HCl solution with a concentration of 0.2 mol / L into the reactant D, age at room temperature for 1 h to obtain a mixed solution E; perform centrifugation on the mixed solution E, wash with deionized water and absolute ethanol, dry in a blast drying oven at 80 - 100 °C for 8 - 10 h, and then calcine in a muffle furnace at 400 - 450 °C for 4 - 6 h to obtain In@CuO - SnO2 - MnO - MgO powder;

[0030] Step 5: Add the formula amount of CeCl3 solution into the Na3PO4 solution, and add dilute hydrochloric acid to adjust the system until the mixed solution becomes clear and the pH value is 1 to obtain a solution F; add the In@CuO - SnO2 - MnO - MgO powder into the solution F, magnetically stir for 1 - 2 h, ultrasonically disperse for 1 - 2 h to obtain a suspension; transfer the suspension into a hydrothermal reactor for hydrothermal reaction for 8 - 10 h to obtain a hydrothermal product; perform filtration, washing, drying in a drying oven at 60 - 80 °C for 20 - 30 h, and grinding on the hydrothermal product to obtain the In@CuO - SnO2 - MnO - MgO@CePO4 core - shell structure catalyst;

[0031] The mass ratio of In@CuO - SnO2 - MnO - MgO, CeCl3, and Na3PO4 is 1:4.72:3.14, and in the mixed solution F, the molar ratio of Ce 3+ to HnPO4 (3-n)- is 1:1.

[0032] The present invention also protects an In@CuO - SnO2 - MnO - MgO@CePO4 core - shell structure catalyst, which is prepared by the above - mentioned preparation method.

[0033] Compared with the prior art, the present invention has the following technical effects:

[0034] (1) The In@CuO-SnO2-MnO-MgO@CePO4 catalyst prepared by the method of the present invention has a core-shell structure, with strong bonding between each layer. The catalyst has high catalytic activity, stability, and anti-poisoning ability, a wide range of applications, and can improve the purification ability of VOCs during use.

[0035] (2) The core-shell structure catalyst provided by the present invention has an In core layer, a CuO-SnO2-MnO-MgO intermediate layer, and a CePO4 outer layer. The core layer can provide abundant active sites. Through the synergistic effect of multiple components in the intermediate layer, the redox performance and surface acidity and basicity of the catalyst are optimized, further improving the catalytic activity and stability. The outer layer improves the catalytic activity, stability, and anti-poisoning ability of the catalyst, enabling more efficient and stable decomposition and purification of VOCs.

[0036] (3) The preparation method provided by the present invention is green, environmentally friendly, simple, and easy to operate. Brief Description of the Drawings

[0037] Figure 1 It is the SEM structure diagram of the In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst prepared in Example 1.

[0038] Figure 2 It is the structure schematic diagram of the In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst.

[0039] The following further elaborates on the specific content of the present invention in conjunction with examples. Detailed Embodiments

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by any ordinary person skilled in the art belong to the scope of protection of the present invention.

[0041] It should be noted that all raw materials in the present invention, such as indium trichloride, sodium borohydride, urea, copper salts, etc., are all raw materials known in the art without special instructions.

[0042] The technical concept of this application is as follows: By adopting a multi-layer core-shell structure design, the catalytic activity, stability, and anti-poisoning ability are improved through the synergistic effect of different components. Specifically, it includes: using In as the core layer, which provides abundant active sites, facilitating the adsorption and activation of VOCs molecules and enhancing the rate and efficiency of the catalytic oxidation reaction; using CuO-SnO2-MnO-MgO as the intermediate layer, and optimizing the catalytic performance through the interaction of multiple components. Among them, CuO: As the main active component, it participates in the catalytic oxidation reaction of VOCs; SnO2, MnO, MgO: These oxides form a composite structure with CuO, and through electronic interaction and synergistic effect, optimize the redox performance and surface acidity and basicity of the catalyst, further enhancing the catalytic activity and stability. The multi-component composite not only improves the catalytic performance of single components but also enhances the overall performance of the catalyst, such as anti-poisoning ability and stability, through the interaction between different components. CePO4 is used as the outer shell layer and has three major characteristics: stability (CePO4 has good thermal stability and chemical stability, which can protect the internal active components from the influence of the external environment and extend the service life of the catalyst); selectivity (by regulating the thickness and pore structure of CePO4, selective catalytic oxidation of specific VOCs molecules can be achieved); anti-poisoning ability (the CePO4 outer shell layer can also effectively block the invasion of toxic substances to the internal active components and improve the anti-poisoning ability of the catalyst).

[0043] Following the above technical solution, the present invention discloses a preparation method of an In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst. The catalyst uses In as the core layer, CuO-SnO2-MnO-MgO layer as the intermediate layer, and CePO4 layer as the outer shell layer, and is prepared through the following steps:

[0044] Step 1: Mix an indium trichloride aqueous solution with a reducing agent and stir magnetically to obtain solution A; place solution A in a reaction kettle for hydrothermal reaction to obtain reactant B; wash reactant B with deionized water and ethanol; place the washed reactant B in a tube furnace and keep it at 400 - 450 °C for 0.5 - 2.0 h to obtain rod-shaped In2O3 powder;

[0045] Preferably, the reducing agent is selected from one or two of sodium borohydride and urea; the mass ratio of indium trichloride to the reducing agent is 1:(3 - 4).

[0046] Preferably, the magnetic stirring time is 8 - 15 min, the temperature of the hydrothermal reaction is 90 - 100 °C, and the time of the hydrothermal reaction is 10 - 12 h.

[0047] Step 2: Add the prepared In2O3 powder into an aqueous solution of a surfactant and ultrasonically vibrate to obtain a mixed solution C;

[0048] Preferably, the mass ratio of In2O3 to the surfactant is 1:(20 - 30); the ultrasonic oscillation time is 8 - 15 min;

[0049] Preferably, the surfactant is selected from any one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium lauryl polyether sulfate, sodium succinate sulfonate, cetyltrimethylammonium bromide, and dodecyltrimethylammonium chloride, and sodium dodecyl sulfate is preferred.

[0050] Step 3: Sequentially add the formulated amounts of copper salt, tin salt, manganese salt, and magnesium salt to the mixed solution C to obtain reactant D. During the addition process, add a basic precipitating agent to control the pH value of the system to 8.5 - 9.5;

[0051] Among them, the molar ratio of indium ions, copper ions, manganese ions, tin ions, and magnesium ions is (7.78×10 -5 ~1.762×10 -4 ):1.00:(1.89 - 9.47):(0.89 - 4.46):(0.50 - 2.51).

[0052] Preferably, the basic precipitating agent is selected from one or more of NaOH, KOH, and ammonia water; the copper salt is selected from any one of copper nitrate, copper chloride, and copper acetate, and copper nitrate is preferred; the tin salt is selected from any one of tin tetrachloride and tin acetate; the manganese salt is selected from any one of manganese nitrate and manganese acetate; the magnesium salt is selected from any one of magnesium nitrate and magnesium acetate, and magnesium nitrate is preferred.

[0053] Preferably, the basic precipitating agent is added to the system in a dropwise manner, and the concentration of the basic precipitating agent is 2.0 - 4.0 mol / L.

[0054] Step 4: Add NH2OH·HCl solution to reactant D, age at room temperature for 1 h to obtain mixed solution E; perform centrifugation, washing, drying, and calcination on mixed solution E to obtain

[0055] In@CuO - SnO2 - MnO - MgO powder;

[0056] Preferably, the concentration of NH2OH·HCl is 0.2 - 0.3 mol / L.

[0057] Preferably, the drying temperature is 80 - 100 °C, the drying time is 8 - 10 h, the calcination temperature is 400 - 450 °C, and the calcination time is 4 - 6 h.

[0058] Step 5: Add the CeCl3 solution to the Na3PO4 solution, and add dilute hydrochloric acid to adjust the pH value of the system to 0.85 - 1.15 to obtain solution F; add the In@CuO-SnO2-MnO-MgO powder to solution F, magnetically stir for 1 - 2 h, and ultrasonically disperse for 1 - 2 h to obtain a suspension; transfer the suspension to a hydrothermal reactor for hydrothermal reaction to obtain a hydrothermal product; filter, wash, dry, and grind the hydrothermal product to obtain the In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst;

[0059] The mass ratio of In@CuO-SnO2-MnO-MgO, CeCl3, and Na3PO4 is 1:(4.20 - 5.24):(2.79 - 3.49), and in the mixed solution F, the molar ratio of Ce 3+ to HnPO4 (3-n)- is 1:1; deionized water and absolute ethanol can be used for washing.

[0060] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solutions of this application fall within the protection scope of the present invention.

[0061] Example 1

[0062] This example provides a preparation method of an In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst. The catalyst has In as the core layer, CuO-SnO2-MnO-MgO layer as the intermediate layer, and CePO4 layer as the outer shell layer, and is specifically prepared through the following steps:

[0063] Step 1: Mix the indium trichloride aqueous solution with sodium borohydride, and magnetically stir for 8 - 15 min to obtain solution A; place solution A in a reaction kettle and keep it at 90 - 100 °C for 10 - 12 h to obtain reactant B; wash reactant B with deionized water and ethanol; place the washed reactant B in a tubular furnace and keep it at 400 - 450 °C for 0.5 - 2.0 h to obtain In2O3 powder;

[0064] Step 2: Add the prepared In2O3 powder to the sodium dodecyl sulfate aqueous solution and ultrasonically vibrate for 8 - 15 min to obtain a mixed solution C; the mass ratio of the In2O3 powder to sodium dodecyl sulfate is 1:25;

[0065] Step 3: Sequentially add the formulated amounts of copper nitrate, tin tetrachloride, manganese nitrate, and magnesium nitrate to the mixed solution C to obtain reactant D. During the addition process, add a NaOH solution to the system to control the pH value of the system to 9;

[0066] Among them, the molar ratio of the indium ions, copper ions, manganese ions, tin ions and magnesium ions is 1.27×10 -4 :1:1.89:0.89:0.50;

[0067] The specific addition process includes: according to the volume ratio of the NaOH solution to the reactant D being 1:40, slowly dropwise add a 2.0 mol·L -1 NaOH solution to the reactant D and stir for 2 - 5 min to obtain a first mixed solution. Then, according to the volume ratio of the copper nitrate trihydrate Cu(NO3)2 aqueous solution to the first mixed solution being 1:5.5, add a 0.1 mol / L copper nitrate Cu(NO3)2 aqueous solution to the solution E, and ultrasonically oscillate for 8 - 15 min to obtain a second mixed solution. Follow the operation steps of the copper nitrate trihydrate (Cu(NO3)2·3H2O) aqueous solution, and then successively add stannic chloride (SnCl4) aqueous solution, manganese nitrate hexahydrate (Mn(NO3)2·6H2O) aqueous solution, and magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) aqueous solution.

[0068] Step 4: Add a 0.2 mol / L NH2OH·HCl solution to the reactant D, age at room temperature for 1 h to obtain a mixed solution E; perform centrifugation on the mixed solution E, wash with deionized water and absolute ethanol, dry in a blast drying oven at 80 - 100 °C for 8 - 10 h, and then calcine in a muffle furnace at 400 - 450 °C for 4 - 6 h to obtain In@CuO-SnO2-MnO-MgO powder;

[0069] Step 5: Add the CeCl3 solution with the equal formula amount to the Na3PO4 solution, and add dilute hydrochloric acid to adjust the system until the mixed solution becomes clear and the pH value is 1 to obtain a solution F; add the In@CuO-SnO2-MnO-MgO powder to the solution F, magnetically stir for 1 - 2 h, ultrasonically disperse for 1 - 2 h to obtain a suspension; transfer the suspension to a hydrothermal autoclave for hydrothermal reaction for 8 - 10 h to obtain a hydrothermal product; filter, wash, dry in a drying oven at 60 - 80 °C for 20 - 30 h and grind the hydrothermal product to obtain the In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst;

[0070] The mass ratio of the In@CuO-SnO2-MnO-MgO, CeCl3, and Na3PO4 is 1:4.72:3.14, and in the mixed solution F, the molar ratio of Ce 3+ to HnPO4 (3-n)- is 1:1.

[0071] The SEM structure photograph of the In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst prepared in this example is asFigure 1 As shown in Figure 1 Figure 1 , it can be seen that the In@CuO-SnO2-MnO-MgO@CePO4 core-shell catalyst presents a granular state, but there are differences in the particle sizes, indicating that the nucleation effect in the preparation process of the present invention is good, but the nucleation size has randomness; the particle surface is rough, reflecting that the catalyst surface has a complex microscopic interface, which is beneficial to increasing the specific surface area and providing more active sites for the catalytic reaction.

[0072] The core-shell structure catalyst prepared in this example can be used for the catalytic oxidation of volatile organic compounds (VOCs), and the target pollutants that can be removed include benzene, toluene, xylene (BTEX), formaldehyde, acetaldehyde, acetone, TVOCs, etc.

[0073] The reaction conditions for catalytic oxidation are: temperature: 100 - 400 °C, space velocity (GHSV): 5000 - 50000 h -1 , VOCs concentration: 500 - 5000 ppm, O2 content: excessive (usually 5% - 20% volume ratio) to ensure sufficient oxidation reaction, pressure: atmospheric pressure or slightly positive pressure (1 - 5 bar), humidity: water resistance allows 5% - 18% water vapor to exist.

[0074] The core-shell structure catalyst prepared in this example was used to test the purification efficiency of VOCs at different temperatures to explore its influence on the purification efficiency of VOCs, and the results are shown in Table 1.

[0075] Example 2

[0076] The preparation method of the In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst disclosed in this example is the same as the steps of the preparation method disclosed in Example 1, except that the raw material component ratio of the CuO-SnO2-MnO-MgO layer is different. In this example, the molar ratio of indium ions, copper ions, manganese ions, tin ions and magnesium ions is: 1.27×10 -4 : 1: 4.74: 2.23: 1.26;

[0077] The core-shell structure catalyst prepared in this example was used to test the purification efficiency of VOCs at different temperatures to explore its influence on the purification efficiency of VOCs, and the results are shown in Table 1.

[0078] Example 3

[0079] The preparation method of the In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst disclosed in this example is the same as the preparation method disclosed in Example 1, except that the raw material composition ratio of the CuO-SnO2-MnO-MgO layer is different. In this example, the molar ratio of indium ions, copper ions, manganese ions, tin ions and magnesium ions is: 1.27×10 -4 :1:9.47:4.46:2.51;

[0080] The core-shell structure catalyst prepared by this example was tested for the purification efficiency of VOCs at different temperatures to explore its influence on the purification efficiency of VOCs. The results are shown in Table 1.

[0081] Comparative Example 1

[0082] This example presents a preparation method of a CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst. This catalyst uses the CuO-SnO2-MnO-MgO layer as the core layer and the CePO4 layer as the outer shell layer, and is specifically prepared through the following steps:

[0083] Step 1: Sequentially add the formulated amounts of copper nitrate, tin tetrachloride, manganese nitrate and magnesium nitrate to a beaker to obtain reactant D. During the addition process, add NaOH solution to the system to control the pH value of the system to 9;

[0084] Among them, the molar ratio of the copper ions, manganese ions, tin ions and magnesium ions is 1:1.89:0.89:0.50;

[0085] The specific addition process includes: slowly adding a 2.0 mol·L -1 NaOH solution to reactant D according to the volume ratio of the NaOH solution to reactant D of 1:40, and stirring for 2 to 5 minutes to obtain a first mixed solution. Then, according to the volume ratio of the aqueous solution of copper nitrate Cu(NO3)2 to the first mixed solution of 1:5.5, add a 0.1 mol / L aqueous solution of copper nitrate Cu(NO3)2 to solution E, and ultrasonically oscillate for 8 to 15 minutes to obtain a second mixed solution. Follow the operation steps of the aqueous solution of copper nitrate (Cu(NO3)2·3H2O), and then sequentially add the aqueous solution of tin tetrachloride (SnCl4), the aqueous solution of manganese nitrate hexahydrate (Mn(NO3)2·6H2O), and the aqueous solution of magnesium nitrate hexahydrate (Mg(NO3)2·6H2O).

[0086] Step 2: Add NH2OH·HCl solution with a concentration of 0.2 mol / L to reactant D, age it at room temperature for 1 h to obtain a mixed solution E; perform centrifugation on the mixed solution E, wash it with deionized water and absolute ethanol, dry it in a blast drying oven at 80 - 100 °C for 8 - 10 h, and then calcine it in a muffle furnace at 400 - 450 °C for 4 - 6 h to obtain CuO-SnO2-MnO-MgO powder;

[0087] Step 3: Add an equal-formula amount of CeCl3 solution to Na3PO4 solution, and add dilute hydrochloric acid to adjust the pH value of the system to 1 to obtain solution F; add CuO-SnO2-MnO-MgO powder to solution F, stir magnetically for 1 - 2 h, disperse ultrasonically for 1 - 2 h to obtain a suspension; transfer the suspension into a hydrothermal autoclave for hydrothermal reaction for 8 - 10 h to obtain a hydrothermal product; filter, wash, dry the hydrothermal product in a drying oven at 60 - 80 °C for 20 - 30 h and perform grinding treatment to obtain the powdered CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst;

[0088] In the said solution F, the molar ratio of Ce 3+ to HnPO4 (3-n)- is 1:1.

[0089] The core-shell structure catalyst prepared by this comparative example was tested for the purification efficiency of VOCs at different temperatures to explore its influence on the purification efficiency of VOCs, and the results are shown in Table 1.

[0090] Comparative Example 2

[0091] This example gives a preparation method of an In@CePO4 core-shell structure catalyst. This catalyst uses In as the core layer and CePO4 layer as the shell layer, and is specifically prepared through the following steps:

[0092] Step 1: Mix an indium trichloride aqueous solution with sodium borohydride, stir magnetically for 8 - 15 min to obtain solution A; place solution A in a reaction kettle and keep it warm at 90 - 100 °C for 10 - 12 h to obtain reactant B; wash reactant B with deionized water and ethanol; place the washed reactant B in a tubular furnace and keep it warm at 400 - 450 °C for 0.5 - 2.0 h to obtain In2O3 powder;

[0093] Step 2: Add CeCl3 solution with equal formula amount into Na3PO4 solution, and add dilute hydrochloric acid to adjust the pH value of the system to 1 to obtain solution F; add In2O3 powder into solution F, stir magnetically for 1 - 2 h, and disperse ultrasonically for 1 - 2 h to obtain a suspension; transfer the suspension into a hydrothermal reactor for hydrothermal reaction for 8 - 10 h to obtain a hydrothermal product; filter, wash the hydrothermal product, dry it in an oven at 60 - 80 °C for 20 - 30 h, and grind it to obtain the powdered In@CePO4 core-shell structure catalyst;

[0094] In the solution F, the molar ratio of Ce 3+ to HnPO4 (3-n)- is 1:1.

[0095] The core-shell structure catalyst prepared in this comparative example was tested for the purification efficiency of VOCs at different temperatures to explore its effect on the purification efficiency of VOCs. The results are shown in Table 1.

[0096] Comparative Example 3

[0097] Prepare a catalyst for catalytic oxidation of VOCs according to the method disclosed in CN 119236950 A.

[0098] The catalyst prepared in this comparative example was tested for the purification efficiency of VOCs at different temperatures to explore its effect on the purification efficiency of VOCs. The results are shown in Table 1.

[0099] Table 1 Purification efficiency of VOCs

[0100]

[0101] Note: The VOCs used in the experiment were toluene. C6H5CH3 + O2 →→ CO2 + H2O; the reaction conditions were: space velocity (GHSV) 20000 h -1 , VOCs concentration 1000 ppm, O2 content 8%, H2O vapor content 6%, pressure 1.2 bar, and two temperature points of 100 and 300 were taken.

[0102] It can be seen from Examples 1 - 3 and Comparative Examples 1 - 3 that:

[0103] The catalysts prepared in Comparative Examples 1 - 3 have significantly lower VOC purification performance than the In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst prepared by the method of the present invention. By adjusting the raw material ratio, the synergistic effect regulation, active site regulation, structural stability optimization, and anti-poisoning mechanism strengthening among various components can be realized, achieving high activity, long life, and wide adaptability of the catalyst in VOC catalytic oxidation, and the effect gets better as the temperature increases.

[0104] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0105] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A preparation method of an In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst, characterized in that The catalyst has an In core layer, a CuO-SnO2-MnO-MgO layer as the intermediate layer, and a CePO4 layer as the outer shell layer, and is prepared by the following steps: Step 1: Mix an aqueous solution of indium trichloride with a reducing agent and stir magnetically to obtain solution A; place solution A in a reaction kettle for hydrothermal reaction to obtain reactant B; wash reactant B with deionized water and ethanol; place the washed reactant B in a tubular furnace and keep it at 400-450 °C for 0.5-2.0 h to obtain rod-shaped In2O3 powder; Step 2: Add the prepared In2O3 powder to an aqueous solution of a surfactant and ultrasonically vibrate to obtain a mixed solution C; Step 3: Sequentially add the formulated amounts of copper salt, tin salt, manganese salt, and magnesium salt to the mixed solution C to obtain reactant D. During the addition process, add a basic precipitating agent to control the pH value of the system to 8.5-9.5; Among them, the molar ratio of the indium ion salt, copper ion salt, manganese ion salt, tin ion salt and magnesium ion salt is (7.78×10 -5 ~1.762×10 -4 ): 1.00: (1.89~9.47): (0.89~4.46): (0.50~2.51); Step 4: Add an NH2OH·HCl solution to reactant D and age at room temperature for 1 h to obtain a mixed solution E; centrifuge, wash, dry, and calcine the mixed solution E to obtain In@CuO-SnO2-MnO-MgO powder; Step 5: Add a CeCl3 solution to a Na3PO4 solution and add dilute hydrochloric acid to adjust the pH value of the system to 0.85-1.15 to obtain solution F; add In@CuO-SnO2-MnO-MgO powder to solution F, stir magnetically for 1-2 h, and ultrasonically disperse for 1-2 h to obtain a suspension; transfer the suspension to a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal product; filter, wash, dry, and grind the hydrothermal product to obtain an In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst; The mass ratio of the described In@CuO-SnO2-MnO-MgO, CeCl3, and Na3PO4 is 1:(4.20 to 5.24):(2.79 to 3.49), and in the mixed solution F, the molar ratio of Ce 3+ to HnPO4 (3-n)- is 1:

1.

2. The preparation method according to claim 1, wherein, In Step 1, the reducing agent is selected from one or two of sodium borohydride and urea; the mass ratio of indium trichloride to the reducing agent is 1:(3-4).

3. The preparation method according to claim 1, characterized in that, In Step 1, the magnetic stirring time is 8-15 min, the temperature of the hydrothermal reaction is 90-100 °C, and the time of the hydrothermal reaction is 10-12 h.

4. The preparation method according to claim 1, characterized in that In Step 2, the mass ratio of In2O3 to the surfactant is 1:(20-30); the ultrasonic vibration time is 8-15 min; The surfactant is selected from any one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium lauryl polyether sulfate, sodium succinate sulfonate, cetyltrimethylammonium bromide, and dodecyltrimethylammonium chloride.

5. The preparation method according to claim 1, characterized in that, In Step 3, the basic precipitating agent is selected from one or more of NaOH, KOH, and ammonia water; the copper salt is selected from any one of copper nitrate, copper chloride, and copper acetate; the tin salt is selected from any one of tin tetrachloride and tin acetate; the manganese salt is selected from any one of manganese nitrate and manganese acetate; the magnesium salt is selected from any one of magnesium nitrate and magnesium acetate.

6. The preparation method according to claim 1, characterized in that, In Step 3, the basic precipitating agent is added to the system in a dropwise manner, and the concentration of the basic precipitating agent is 2.0-4.0 mol / L.

7. The preparation method according to claim 1, characterized in that, In Step 4, the concentration of NH2OH·HCl is 0.2-0.3 mol / L.

8. The preparation method according to claim 1, characterized in that, In step 4, the drying temperature is 80 - 100 °C, the drying time is 8 - 10 h, the calcination temperature is 400 - 450 °C, and the calcination time is 4 - 6 h.

9. The preparation method according to claim 1, characterized in that It is specifically prepared through the following steps: Step 1: Mix an aqueous solution of indium trichloride with sodium borohydride, and magnetically stir for 8 - 15 min to obtain solution A; place solution A in a reaction kettle and keep it warm at 90 - 100 °C for 10 - 12 h to obtain reactant B; wash reactant B with deionized water and ethanol; place the washed reactant B in a tube furnace and keep it warm at 400 - 450 °C for 0.5 - 2.0 h to obtain In2O3 powder; Step 2: Add the prepared In2O3 powder into an aqueous solution of sodium dodecyl sulfate and ultrasonically vibrate for 8 - 15 min to obtain mixed solution C; the mass ratio of the In2O3 powder to sodium dodecyl sulfate is 1:25; Step 3: Sequentially add the formulated amounts of copper nitrate, tin tetrachloride, manganese nitrate, and magnesium nitrate into mixed solution C to obtain reactant D. During the addition process, add NaOH solution to control the pH value of the system to 9; Among them, the molar ratio of the indium ions, copper ions, manganese ions, tin ions and magnesium ions is 1.27×10 -4 :1:1.89:0.89:0.50; Step 4: Add a 0.2 mol / L NH2OH·HCl solution to reactant D, age at room temperature for 1 h to obtain mixed solution E; perform centrifugation on mixed solution E, wash with deionized water and absolute ethanol, dry in a blast drying oven at 80 - 100 °C for 8 - 10 h, and then calcine in a muffle furnace at 400 - 450 °C for 4 - 6 h to obtain In@CuO - SnO2 - MnO - MgO powder; Step 5: Add the formulated amount of CeCl3 solution into the Na3PO4 solution, and add dilute hydrochloric acid to adjust the system until the mixed solution becomes clear and the pH value is 1 to obtain solution F; add In@CuO - SnO2 - MnO - MgO powder into solution F, magnetically stir for 1 - 2 h, ultrasonically disperse for 1 - 2 h to obtain a suspension; transfer the suspension into a hydrothermal kettle for hydrothermal reaction for 8 - 10 h to obtain a hydrothermal product; filter, wash, dry in a drying oven at 60 - 80 °C for 20 - 30 h, and grind the hydrothermal product to obtain the In@CuO - SnO2 - MnO - MgO@CePO4 core - shell structure catalyst; The mass ratio of the In@CuO-SnO2-MnO-MgO, CeCl3, and Na3PO4 is 1:4.72:3.14, and in the mixed solution F, the 3+ molar ratio of Ce (3-n)- to HnPO4 is 1:

1.

10. A kind of In@CuO-SnO2-MnO-MgO@CePO4 core-shell structure catalyst, characterized in that, This catalyst is prepared by the preparation method described in any one of claims 1 - 9.

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