Manganese-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalyst preparation, and discloses a manganese-based catalyst as well as a preparation method and application thereof. The manganese-based catalyst contains mesoporous epsilon-MnO2, and the specific surface area of the catalyst is 140-200 m < 2 >. G <-1 >; the method comprises a MnCO3 decomposition method and a permanganate titration method, and the MnCO3 decomposition method is used for preparing spherical mesoporous epsilon-MnO2 by controlling the molar ratio of carbonate to manganese salt, the calcination time of MnCO3, the heating rate and other conditions; according to the method, by controlling the interface reaction speed of permanganate and manganese salt, the mesoporous epsilon-MnO2 with the sea urchin-shaped structure is prepared. The manganese-based catalyst prepared by the invention has a relatively large specific surface area and a good empty island structure, and is beneficial to improving the catalytic performance of the catalyst and increasing the temperature required by a catalytic reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a manganese-based catalyst and a preparation method and application thereof. Background Art

[0002] Manganese is a common non-precious metal that is widely used in the catalytic oxidation of volatile organic compounds due to its high activity, durability, low toxicity and unique chemical and physical properties. Its oxide manganese dioxide (MnO2) is a metal oxide with rich chemical states. It is considered to be a promising catalyst for catalytic oxidation reactions due to its advantages such as non-stoichiometric composition, rich chemical states, low cost and environmental friendliness. However, the specific surface area of ​​MnO2 catalysts in the prior art is relatively low, usually between 80-120 m 2 ·g -1 , and it is easy for particles to aggregate during the reaction, which leads to further sintering, further reducing the activity of the catalyst and limiting its application in catalytic reactions. In addition, when the MnO2 catalyst in the prior art performs catalytic oxidation reactions, a higher reaction temperature is usually required, thereby increasing the cost of VOCs treatment. Therefore, it is necessary and challenging to design a MnO2 catalyst with a large specific surface area, improve the reaction activity of MnO2, reduce the temperature required for the catalytic reaction, and reduce energy consumption. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems of small specific surface area of ​​MnO2, low catalytic activity and high temperature required for catalytic oxidation in the prior art, and to provide a manganese-based catalyst and its preparation method and application. The manganese-based catalyst contains mesoporous ε-MnO2, which is spherical or sea urchin-shaped, has a relatively rough surface and a good pore structure, and the specific surface area of ​​the catalyst is 140-200 m 2 ·g -1 , which is much higher than the specific surface area of ​​the ε-MnO2 catalyst in the prior art, thereby improving the catalytic performance of the catalyst and reducing the temperature required for the catalyst to be used in catalytic oxidation; the first method for preparing the aforementioned manganese-based catalyst provided by the present invention is a MnCO3 decomposition method, which controls the molar ratio of carbonate to manganese salt and the calcination conditions of MnCO3 to avoid sintering and agglomeration of ε-MnO2, thereby obtaining a mesoporous ε-MnO2 material with a spherical structure, the specific surface area of ​​the ε-MnO2 material (140-170 m 2 ·g -1) is much higher than the ε-MnO2 material in the prior art, has good catalytic activity, and can reduce the catalytic reaction temperature required for the ε-MnO2 material to be used in catalytic oxidation; the second method for preparing the aforementioned manganese-based catalyst provided by the present invention is a permanganate titration method, which is a preferred method. The method controls the interface reaction rate of permanganate and manganese salt to obtain a mesoporous ε-MnO2 material with a sea urchin-like structure. The ε-MnO2 material has a larger specific surface area (170-200 m 2 ·g -1 ), can further improve the catalytic activity of the catalyst.

[0004] In order to achieve the above object, the present invention provides a manganese-based catalyst in the first aspect, wherein the manganese-based catalyst contains mesoporous ε-MnO2, and the specific surface area of ​​the catalyst is 140-200 m 2 ·g -1 .

[0005] Preferably, the catalyst is a spherical structure.

[0006] Preferably, the specific surface area of ​​the catalyst is 160-200 m 2 ·g -1 .

[0007] Preferably, the catalyst has a pore size of 2-8 nm and a pore volume of 0.1-0.6 cm 3 ·g -1 .

[0008] The second aspect of the present invention provides a method for preparing the above-mentioned manganese-based catalyst, which is a MnCO3 decomposition method, and the method comprises the following steps: adding a carbonate solution dropwise to a manganese salt solution, and calcining the obtained solid product after solid-liquid separation; Wherein, the molar ratio of carbonate to manganese salt is 1-2:1; The calcination conditions include: temperature of 200-500°C, time of 1-4 h, heating rate of 0.5-5°C·min -1 .

[0009] Preferably, the carbonate is selected from one or more of sodium carbonate, potassium carbonate or ammonium carbonate.

[0010] Preferably, the manganese salt is selected from one or more of manganese sulfate, manganese nitrate or manganese chloride.

[0011] Preferably, the concentration of the carbonate solution is 0.5-5 mol / L.

[0012] Preferably, the concentration of the manganese salt solution is 0.5-5 mol / L.

[0013] Preferably, the conditions for the dropwise addition include: a temperature of 10-50° C. and a speed of 60-120 drops / min.

[0014] Preferably, the calcination conditions include: temperature of 200-400°C, time of 2-4 h, heating rate of 1-3°C·min -1 .

[0015] The third aspect of the present invention provides a method for preparing the manganese-based catalyst described above, which is a permanganate titration method, and the method comprises the following steps: mixing a manganese salt, a polar organic solvent and water, adding permanganate to the resulting mixed solution and performing solid-liquid separation.

[0016] Preferably, the manganese salt is selected from one or more of manganese sulfate, manganese nitrate or manganese chloride.

[0017] Preferably, the permanganate is selected from potassium permanganate or sodium permanganate.

[0018] Preferably, the polar organic solvent is dichloromethane.

[0019] Preferably, the molar ratio of the manganese salt, the permanganate and the polar organic solvent is 1-10:1-6:1.

[0020] Preferably, the method further comprises: mixing the manganese salt, the polar organic solvent and water, and allowing the obtained mixed solution to stand for stratification.

[0021] Preferably, in the method described above, the permanganate is added dropwise into the mixed solution in the form of an aqueous solution.

[0022] Preferably, the permanganate is added to the mixed solution in a bottom-up manner.

[0023] Preferably, the concentration of the permanganate solution is 0.05-1 mol / L.

[0024] Preferably, the concentration of the manganese salt solution is 0.1-5 mol / L.

[0025] Preferably, the conditions for the dropwise addition include: a temperature of 10-30° C. and a speed of 15-40 drops / min.

[0026] Preferably, the method further comprises: adding permanganate in the form of an aqueous solution dropwise from bottom to top into the upper layer solution of the mixed solution.

[0027] The fourth aspect of the present invention provides a manganese-based catalyst prepared by the method described above.

[0028] A fifth aspect of the present invention provides a use of the manganese-based catalyst described above or a manganese-based catalyst prepared by the method described above in catalytic oxidation of VOCs.

[0029] Compared with the prior art, the present invention has at least the following advantages: (1) In the present invention, the manganese-based catalyst contains mesoporous ε-MnO2, which is spherical and has a relatively rough surface and a good pore structure. The specific surface area of ​​the catalyst is 140-200 m 2 ·g -1 , which is much higher than the specific surface area of ​​the ε-MnO2 catalyst in the prior art. The large specific surface area ε-MnO2 material can increase the number of active sites of Mn on the catalyst surface, improve the adsorption capacity of the catalyst for oxygen and hydrocarbon compounds, and improve the catalytic activity of the catalyst. At the same time, it can reduce the reaction temperature when the catalyst participates in the catalytic reaction and reduce the reaction energy consumption.

[0030] (2) The first method for preparing the aforementioned manganese-based catalyst provided by the present invention is a MnCO3 decomposition method. This method avoids the sintering and agglomeration of ε-MnO2 by controlling the molar ratio of carbonate to manganese salt and the calcination time and heating rate of MnCO3, thereby obtaining a mesoporous ε-MnO2 material with a uniform spherical structure. The specific surface area of ​​the ε-MnO2 material is (140-170 m 2 ·g -1 ) is much higher than the ε-MnO2 material in the prior art, thereby being able to improve the catalytic activity of the ε-MnO2 material.

[0031] (3) The first method for preparing the aforementioned manganese-based catalyst provided by the present invention is a permanganate titration method, which is a preferred method. In the method, permanganate is passed through an oil phase formed by a polar organic solvent, and reacts at the oil-water interface of the polar organic solvent and the manganese salt solution. At the same time, the method controls the speed at which permanganate is dripped into the oil-water system to obtain a mesoporous ε-MnO2 material having a sea urchin-like structure. The ε-MnO2 material has a relatively larger specific surface area (170-200 m 2 ·g -1 ); In a preferred embodiment, the method adds the permanganate solution dropwise into the upper solution of the mixed solution from bottom to top, which can further increase the specific surface area and catalytic activity of the ε-MnO2 material.

[0032] (4) In the present invention, the manganese-based catalyst has good catalytic activity in the catalytic oxidation of VOCs compared to the ε-MnO2 material in the prior art, and can significantly reduce the temperature required for the catalytic reaction, effectively reducing the energy consumption required for catalytic oxidation. At the same time, the method of the present invention has a simple preparation process and low cost, which is conducive to industrial implementation. In a preferred embodiment, the manganese-based catalyst is used for the catalytic oxidation of toluene, and the toluene conversion rate can reach more than 90% at about 240°C, and the required temperature is much lower than that of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the XRD spectrum of the manganese-based catalyst prepared in Example 1; Figure 2 is the XRD spectrum of the manganese-based catalyst prepared in Example 2; Figure 3 is a SEM spectrum of the manganese-based catalyst prepared in Example 1; Figure 4 is a SEM spectrum of the manganese-based catalyst prepared in Example 2; Figure 5 is the adsorption isotherm and pore size distribution diagram of the manganese-based catalyst prepared in Example 1; Figure 6 is the adsorption isotherm and pore size distribution diagram of the manganese-based catalyst prepared in Example 2; Figure 7 is the reaction activity data of toluene oxidation catalyzed by the manganese-based catalyst prepared in Example 1; Figure 8 This is the reaction activity data of toluene oxidation catalyzed by the manganese-based catalyst prepared in Example 2. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0035] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0036] The first aspect of the present invention provides a manganese-based catalyst, the manganese-based catalyst contains mesoporous ε-MnO2, and the specific surface area of ​​the catalyst is 140-200 m 2·g -1 .

[0037] In a specific embodiment, the catalyst has a spherical structure. In a preferred embodiment, the catalyst has a spherical or sea urchin-like structure.

[0038] In a preferred embodiment, the specific surface area of ​​the catalyst is 160-200 m 2 ·g -1 .

[0039] In a specific embodiment, the catalyst has a pore size of 2-8 nm and a pore volume of 0.1-0.6 cm 3 ·g -1 In a preferred embodiment, the catalyst has a pore size of 2-5 nm and a pore volume of 0.2-0.5 cm 3 ·g -1 .

[0040] In the present invention, the manganese-based catalyst contains mesoporous ε-MnO2, which is spherical or sea urchin-shaped, has a relatively rough surface and a good pore structure, and the specific surface area of ​​the catalyst is 140-200 m 2 ·g -1 , which is much higher than the specific surface area of ​​the ε-MnO2 catalyst in the prior art. The large specific surface area ε-MnO2 material can increase the number of active sites of Mn on the catalyst surface, improve the adsorption capacity of the catalyst for oxygen and hydrocarbon compounds, and improve the catalytic activity of the catalyst. At the same time, it can reduce the reaction temperature when the catalyst participates in the catalytic reaction and reduce the reaction energy consumption.

[0041] The second aspect of the present invention provides a method for preparing the above-mentioned manganese-based catalyst, which is a MnCO3 decomposition method, and the method comprises the following steps: adding a carbonate solution dropwise to a manganese salt solution, and calcining the obtained solid product after solid-liquid separation; Wherein, the molar ratio of carbonate to manganese salt is 1-2:1; The calcination conditions include: temperature of 200-500°C, time of 1-4 h, heating rate of 0.5-5°C·min -1 .

[0042] In a preferred embodiment, the method comprises the following steps: adding a carbonate solution dropwise into a manganese salt solution, stirring and separating the solid from the liquid, and washing, drying and calcining the obtained solid product.

[0043] In a preferred embodiment, the stirring time can be selected conventionally in the field until the carbonate and the manganese salt react completely. In a further preferred embodiment, the stirring time can be 1-5 hours.

[0044] In a preferred embodiment, the solid-liquid separation may be a conventional method in the art, as long as the purpose of the present invention can be achieved. In a further preferred embodiment, the solid-liquid separation may be filtration.

[0045] In a preferred embodiment, the washing may be a conventional method in the art, as long as the purpose of the present invention can be achieved. In a further preferred embodiment, the washing specifically comprises: washing the solid product obtained by solid-liquid separation with deionized water and anhydrous ethanol in sequence.

[0046] In a preferred embodiment, the drying can be selected conventionally in the field, as long as the purpose of the present invention can be achieved. In a further preferred embodiment, the drying conditions include: a temperature of 50-90°C and a time of 8-16 hours.

[0047] In a specific embodiment, the carbonate may be any conventional water-soluble carbonate in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, the carbonate may be one or more of sodium carbonate, potassium carbonate or ammonium carbonate.

[0048] In a specific embodiment, the manganese salt can be a conventional water-soluble manganese salt in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, the manganese salt can be one or more of manganese sulfate, manganese nitrate or manganese chloride.

[0049] In a further preferred embodiment, the manganese salt may be manganese sulfate or manganese sulfate monohydrate.

[0050] In a specific embodiment, the concentration of the carbonate solution may be 0.5-5 mol / L. In a preferred embodiment, the concentration of the carbonate solution may be 0.8-3 mol / L.

[0051] In a specific embodiment, the concentration of the manganese salt solution may be 0.5-5 mol / L. In a preferred embodiment, the concentration of the carbonate solution may be 0.8-3 mol / L.

[0052] In a specific embodiment, the dripping conditions include: a temperature of 10-50°C and a speed of 60-120 drops / min. In a preferred embodiment, the dripping temperature is 10-35°C.

[0053] In a preferred embodiment, the calcination conditions include: a temperature of 200-400°C, a time of 2-4 h, and a heating rate of 1-3°C·min -1 Through the above preferred manner, the method can further increase the specific surface area of ​​the prepared manganese-based catalyst, thereby increasing the catalytic activity of the manganese-based catalyst and reducing the temperature required for the catalytic reaction.

[0054] In the present invention, the MnCO3 decomposition method controls the molar ratio of carbonate to manganese salt, slowly drips the carbonate solution into the manganese salt solution, and reduces the calcination time of MnCO3 and the heating rate during calcination to avoid the sintering and agglomeration of ε-MnO2, thereby obtaining a mesoporous ε-MnO2 material with a uniform spherical structure. The specific surface area of ​​the ε-MnO2 material (140-170 m 2 ·g -1 ) is much higher than the ε-MnO2 material in the prior art manganese-based catalyst, thereby being able to improve the catalytic activity of the ε-MnO2 material.

[0055] The third aspect of the present invention provides a method for preparing the manganese-based catalyst described above, which is a permanganate titration method, and the method comprises the following steps: mixing a manganese salt, a polar organic solvent and water, adding permanganate to the resulting mixed solution and performing solid-liquid separation.

[0056] In a specific embodiment, the manganese salt can be a conventional water-soluble manganese salt in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, the manganese salt can be one or more of manganese sulfate, manganese nitrate or manganese chloride.

[0057] In a further preferred embodiment, the manganese salt may be manganese sulfate or manganese sulfate monohydrate.

[0058] In a specific embodiment, the permanganate may be any conventional water-soluble permanganate in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, the permanganate may be potassium permanganate or sodium permanganate.

[0059] In a specific embodiment, the polar organic solvent is dichloromethane. In the present invention, by reacting permanganate with a manganese salt solution in CH2Cl2, it is advantageous to obtain a sea urchin-like mesoporous ε-MnO2 material having a large specific surface area, a rough surface structure and a good pore structure.

[0060] In a specific embodiment, the molar ratio of the manganese salt, permanganate and polar organic solvent is 1-10:1-6:1. In a preferred embodiment, the molar ratio of the manganese salt, permanganate and polar organic solvent is 1-5:1-3:1.

[0061] In a further preferred embodiment, the molar ratio of the manganese salt, the permanganate and the polar organic solvent is 2.3-2.8:1.5-2:1.

[0062] In a preferred embodiment, the method further comprises: mixing the manganese salt, the polar organic solvent and water, and allowing the obtained mixed solution to stand for stratification.

[0063] In a preferred embodiment, in the method described above, the permanganate is added dropwise into the mixed solution in the form of an aqueous solution.

[0064] In a preferred embodiment, the permanganate is added to the mixed solution in a bottom-up manner.

[0065] In a further preferred embodiment, the method further comprises: adding permanganate in the form of an aqueous solution dropwise from bottom to top into the upper layer solution of the mixed solution.

[0066] In a preferred embodiment, the method comprises the following steps: (1) dissolving a manganese salt and a permanganate in water respectively, and then mixing the obtained manganese salt solution with a polar organic solvent and standing to separate the layers, wherein the upper layer is dichloromethane and the lower layer is the manganese salt solution; (2) adding the permanganate solution dropwise from bottom to top into the dichloromethane layer in the mixed solution obtained in step (1), allowing the mixture to stand for aging, and then subjecting the obtained mixed system to solid-liquid separation, and washing and drying the obtained solid product.

[0067] In the present invention, the manganese salt is first mixed with water to form a stable solution, and then a polar organic solvent CH2Cl2 is added. After an oil-water separation interface is formed, a permanganate solution is added from bottom to top, and the permanganate solution is reacted with the manganese salt solution in CH2Cl2, which is beneficial to obtaining a sea urchin-like mesoporous ε-MnO2 material with a large specific surface area, a rough surface structure and a good pore structure.

[0068] In a specific embodiment, the concentration of the permanganate solution is 0.05-1 mol / L. In a preferred embodiment, the concentration of the permanganate solution is 0.1-0.5 mol / L.

[0069] In a further preferred embodiment, the concentration of the permanganate solution is 0.2-0.3 mol / L.

[0070] In a specific embodiment, the concentration of the manganese salt solution is 0.1-5 mol / L. In a preferred embodiment, the concentration of the manganese salt solution is 0.8-3 mol / L.

[0071] In a further preferred embodiment, the concentration of the manganese salt solution is 0.9-1.1 mol / L.

[0072] In a specific embodiment, the conditions for the dripping include: a temperature of 10-30° C. and a speed of 15-40 drops / min. In a preferred embodiment, the conditions for the dripping include: a temperature of 10-20° C. and a speed of 30-40 drops / min.

[0073] In a preferred embodiment, in step (1), the standing time can be selected conventionally in the field, as long as the non-polar solvent and the manganese salt solution can be separated into layers. In a further preferred embodiment, the standing time can be 2-10 min.

[0074] In a preferred embodiment, in step (2), the standing aging time can be selected conventionally in the field, as long as the purpose of the present invention can be achieved. In a further preferred embodiment, the standing aging time can be 20-36 hours.

[0075] In a preferred embodiment, the solid-liquid separation may be a conventional method in the art, as long as the purpose of the present invention can be achieved. In a further preferred embodiment, the solid-liquid separation may be filtration.

[0076] In a preferred embodiment, the washing may be a conventional method in the art, as long as the purpose of the present invention can be achieved. In a further preferred embodiment, the washing is specifically: washing the solid product obtained by solid-liquid separation with deionized water three times.

[0077] In a preferred embodiment, the drying can be selected conventionally in the field, as long as the purpose of the present invention can be achieved. In a further preferred embodiment, the drying conditions include: a temperature of 50-90° C. and a time of 8-16 h.

[0078] In the present invention, the permanganate titration method is the preferred method, in which the permanganate is dripped into the oil phase formed by the polar organic solvent, and the reaction is slowly carried out at the oil-water interface of the polar organic solvent and the manganese salt solution. At the same time, the method can prepare a mesoporous ε-MnO2 material with a sea urchin-like structure by controlling the permanganate to drip into the oil-water system of the non-polar solvent and the manganese salt solution at a slower speed. The ε-MnO2 material has a relatively larger specific surface area (170-200 m 2 ·g -1 ), in a preferred embodiment, the method adds the permanganate solution dropwise into the upper solution of the mixed solution from bottom to top, which can further increase the specific surface area and catalytic activity of the ε-MnO2 material.

[0079] The fourth aspect of the present invention provides a manganese-based catalyst prepared by the method described above.

[0080] A fifth aspect of the present invention provides a use of the manganese-based catalyst described above or a manganese-based catalyst prepared by the method described above in catalytic oxidation of VOCs.

[0081] In the present invention, compared with the ε-MnO2 material in the prior art, the manganese-based catalyst has good catalytic activity in the catalytic oxidation of VOCs, and can significantly reduce the temperature required for the catalytic reaction, effectively reducing the energy consumption required for catalytic oxidation; in a preferred embodiment, the manganese-based catalyst is used for catalytic oxidation of toluene, and the toluene conversion rate can reach more than 90% at about 240°C, and the required temperature is much lower than the prior art.

[0082] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0083] In the following examples and comparative examples, unless otherwise specified, the reagents used are all commercially available products.

[0084] Example 1 (1) At room temperature, weigh 8.45 g of manganese sulfate monohydrate and 5.3 g of sodium carbonate and mix them with 50 mL of deionized water respectively until they are completely dissolved to obtain a manganese sulfate solution and a sodium carbonate solution; (2) At 25 °C, sodium carbonate solution was added dropwise to manganese sulfate solution to form a white precipitate at a rate of 80 drops / min; the suspension was stirred at room temperature for 3 h, filtered, and the solid product was washed four times with deionized water and once with anhydrous ethanol; the washed solid product was placed in an oven and dried at 70 °C for 12 h, and then the dried solid product was calcined at 300 °C for 3 h (heating rate 1 °C / min) to obtain spherical large specific surface area mesoporous ε-MnO2.

[0085] According to the attached picture Figure 1 In the XRD spectrum of the catalyst prepared in this embodiment, the position of the diffraction peak is consistent with the ε-MnO2 diffraction spectrum (JCPDS PDF#30-0820), which shows that the component of the manganese-based catalyst prepared in this embodiment is ε-MnO2; according to the attached drawing Figure 3 It can be seen that the catalyst prepared in this embodiment has a uniform spherical structure without sintering or agglomeration; according to the accompanying drawings Figure 5 From the adsorption isotherm and pore size distribution diagram of the catalyst prepared in this example, it can be seen that the ε-MnO2 prepared in this example has a mesoporous structure.

[0086] Example 2 (1) At room temperature, weigh 5.07 g of manganese sulfate monohydrate and add it to 30 mL of pure water until it is completely dissolved to obtain a manganese sulfate solution; then mix the manganese sulfate solution with 80 mL of dichloromethane, and let the resulting mixture stand for 5 min to obtain a dichloromethane-manganese sulfate layered solution; (2) Weigh 3.16 g of potassium permanganate and add it to 80 mL of pure water until it is completely dissolved to obtain a potassium permanganate solution; uniformly add the potassium permanganate solution dropwise into the dichloromethane-manganese sulfate layered solution at a rate of 30 drops / min. After the addition is completed, the obtained mixed system is allowed to stand for aging for 24 h and then filtered. The obtained solid product is washed once with anhydrous ethanol and then washed three times with deionized water; the washed solid product is then placed in an oven and dried at 80 °C for 12 h to obtain sea urchin-shaped large specific surface area mesoporous ε-MnO2.

[0087] According to the attached picture Figure 2 In the XRD spectrum of the catalyst prepared in this embodiment, the position of the diffraction peak is consistent with the ε-MnO2 diffraction spectrum (JCPDS PDF#30-0820), which shows that the component of the manganese-based catalyst prepared in this embodiment is ε-MnO2; according to the attached drawing Figure 4 It can be seen that the catalyst prepared in this embodiment has a uniform sea urchin-like structure without sintering or agglomeration; according to the accompanying drawings Figure 6 From the adsorption isotherm and pore size distribution diagram of the catalyst prepared in this example, it can be seen that the ε-MnO2 prepared in this example has a mesoporous structure.

[0088] Test Example 1 XRD characterization of the manganese-based catalysts prepared in Examples 1 and 2; SEM characterization of the manganese-based catalysts prepared in Examples 1 and 2; N2 adsorption characterization of the manganese-based catalysts prepared in Examples 1 and 2.

[0089] The results are shown in Table 1.

[0090] Table 1

[0091] It can be seen from the results in Table 1 that by adopting the technical solution of the present invention, the manganese-based catalysts prepared in Examples 1 and 2 have a specific surface area of ​​140-200 m 2 ·g -1 , which is much higher than the specific surface area of ​​the ε-MnO2 catalyst in the prior art and has a good empty island structure, which is beneficial to further improve the catalytic activity of the catalyst.

[0092] Test Example 2 Characterization of the reaction activity of the manganese-based catalyst prepared in Examples 1 and 2 for catalytic toluene oxidation: The activity evaluation test of the catalyst was carried out on a fixed bed reactor independently developed and designed by Suzhou Furande Co., Ltd. Toluene gas is vaporized by a precision vaporization module to achieve real-time quantitative output. First, the toluene inlet amount is accurately calculated according to the toluene concentration, and liquid toluene is injected by a precision injection pump, and then the toluene is vaporized by a vaporizer.

[0093] Weigh 0.1 g of the catalyst sample and fix the catalyst with quartz wool in the center of the quartz tube (id = 8.00 mm) of the tube furnace. The vaporized toluene gas is evenly mixed with air. The mixed gas is synthetic air (20 vol.% O2, N2 balance) containing 1000 ppm toluene. The total flow rate of the mixed gas is 50 mL / min, and the gas space velocity (GHSV) is 30000 mL / g·h. A gas chromatograph (GC-7900, Techcomp, Shanghai) equipped with a flame ionization detector (FID) is used to detect the gas before and after the reaction multiple times at the same temperature point. The conversion rate of the catalyst to toluene is calculated by the following formula (1):

[0094] Where X toluene (%) is the conversion rate of toluene, C toluene, in (ppm) and C toluene, out (ppm) are the concentrations of toluene at the fixed bed inlet and outlet, respectively. The toluene concentration was measured multiple times at the same temperature point, and the average value was taken to obtain the conversion rate of toluene.

[0095] The results are as follows Figure 7 and Figure 8 shown.

[0096] pass Figure 7 and Figure 8 It can be seen from the results that by adopting the technical solution of the present invention, the manganese-based catalyst prepared in Examples 1 and 2 has good catalytic activity in the catalytic oxidation of VOCs, and can significantly reduce the temperature required for the catalytic reaction, effectively reducing the energy consumption required for catalytic oxidation. At the same time, the method of the present invention has a simple preparation process and low cost, which is conducive to industrial implementation. In a preferred embodiment, the manganese-based catalyst is used for catalytic oxidation of toluene, and the toluene conversion rate can reach more than 90% at about 240°C, and the required temperature is much lower than that of the prior art.

[0097] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A manganese-based catalyst, characterized in that The manganese-based catalyst contains mesoporous ε-MnO2, and the specific surface area of ​​the catalyst is 140-200 m 2 ·g -1 .

2. The catalyst according to claim 1, characterized in that The catalyst is a spherical structure; Preferably, the specific surface area of ​​the catalyst is 160-200 m 2 ·g -1 ; Preferably, the catalyst has a pore size of 2-8 nm and a pore volume of 0.1-0.6 cm 3 ·g -1 .

3. A method for preparing the manganese-based catalyst according to claim 1, characterized in that: The method comprises the following steps: adding a carbonate solution dropwise into a manganese salt solution, and calcining the obtained solid product after solid-liquid separation; Wherein, the molar ratio of carbonate to manganese salt is 1-2:1; The calcination conditions include: temperature of 200-500°C, time of 1-4 h, heating rate of 0.5-5°C·min -1 .

4. The method according to claim 3, characterized in that The carbonate is selected from one or more of sodium carbonate, potassium carbonate or ammonium carbonate; Preferably, the manganese salt is selected from one or more of manganese sulfate, manganese nitrate or manganese chloride; Preferably, the concentration of the carbonate solution is 0.5-5 mol / L; Preferably, the concentration of the manganese salt solution is 0.5-5 mol / L.

5. The method according to claim 3 or 4, characterized in that: The conditions for the dropwise addition include: a temperature of 10-50° C. and a speed of 60-120 drops / min; Preferably, the calcination conditions include: temperature of 200-400°C, time of 2-4 h, heating rate of 1-3°C·min -1 .

6. A method for preparing the manganese-based catalyst according to claim 1, characterized in that: The method comprises the following steps: mixing manganese salt, polar organic solvent and water, adding permanganate to the obtained mixed solution and performing solid-liquid separation.

7. The method according to claim 6, characterized in that The manganese salt is selected from one or more of manganese sulfate, manganese nitrate or manganese chloride; Preferably, the permanganate is selected from potassium permanganate or sodium permanganate; Preferably, the polar organic solvent is dichloromethane; Preferably, the molar ratio of manganese salt, permanganate and polar organic solvent is 1-10:1-6:

1.

8. The method according to claim 6 or 7, characterized in that: The method further comprises: mixing the manganese salt, the polar organic solvent and water, and allowing the obtained mixed solution to stand for stratification.

9. The method according to any one of claims 6 to 8, characterized in that: The permanganate is added dropwise into the mixed solution in the form of an aqueous solution; Preferably, the permanganate is added to the mixed solution in a bottom-up manner; Preferably, the concentration of the permanganate solution is 0.05-1 mol / L; Preferably, the concentration of the manganese salt solution is 0.1-5 mol / L; Preferably, the conditions for the dropwise addition include: a temperature of 10-30° C. and a speed of 15-40 drops / min.

10. The method according to any one of claims 6 to 9, characterized in that: The method further comprises: adding permanganate in the form of an aqueous solution dropwise into the upper layer of the mixed solution from bottom to top.

11. A manganese-based catalyst prepared by the method according to any one of claims 3 to 10.

12. Use of the manganese-based catalyst according to claim 1 or 2 or the manganese-based catalyst according to claim 11 in catalytic oxidation of VOCs.

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