A manganese oxide catalyst for high-efficiency ozone catalytic decomposition at room temperature, and a preparation method and application thereof

Abstract

The application discloses a manganese oxide catalyst for high-efficiency ozone catalytic decomposition at normal temperature and a preparation method and application thereof, and belongs to the technical field of catalyst preparation and environmental protection. 2+ The preparation process of the catalyst is to convert high-valence manganese into low-valence manganese through oxidation and reduction, and then the low-valence manganese is mixed with Mn The hydroxyl group is grown on the low-valence manganese through low-temperature activation, and the high-efficiency manganese oxide catalyst for ozone catalytic decomposition at normal temperature is obtained after washing, filtering and drying after cooling. Compared with the existing preparation method, the preparation method of the catalyst is simple, the high-efficiency manganese oxide catalyst for ozone catalytic decomposition at normal temperature with the hydroxyl group as an active center is prepared, and the problem of poor water resistance of the manganese oxide catalyst is fundamentally solved. The catalyst can be applied to an environment with high humidity and high flux, and the removal rate of ozone can reach 98% at most within 12 hours under the condition of normal temperature and 70% relative humidity.

Description

Technical Field

[0001] This invention relates to the field of ozone catalyst technology, and more specifically, to a highly efficient manganese oxide catalyst for the catalytic decomposition of ozone at room temperature, its preparation method, and its application. Background Technology

[0002] Currently, the main ozone removal methods include thermal decomposition, catalytic decomposition, activated carbon adsorption, and chemical absorption. Compared with other removal methods, catalytic decomposition has advantages such as low energy consumption, good safety, rapid reaction, high treatment efficiency, and less secondary pollution, and is therefore widely used in research. The core of catalytic decomposition lies in the catalyst. Among various catalyst systems, including metal oxide catalysts, manganese oxide catalysts exhibit excellent activity, with oxygen vacancies being the main active sites, and have been extensively studied.

[0003] Chinese patent document CN102600861A discloses a manganese-based composite oxide catalyst, which comprises manganese oxide and at least one transition metal oxide. This invention uses non-toxic and harmless raw materials to prepare a manganese-based composite oxide catalyst with high catalytic activity, good moisture resistance, and high ozone decomposition capacity through homogeneous precipitation or hydrothermal synthesis.

[0004] Chinese patent document CN109603817A discloses a manganese oxide catalyst for catalyzing ozone decomposition. This invention utilizes Mn 2+ and Mn 7+ The mixtures were stirred at a certain molar ratio until precipitation was complete, and then washed and dried to obtain the manganese oxide catalyst. This invention achieves the purpose of manganese valence state control through micro-redox regulation, so that the average valence state of the manganese oxide catalyst is 3.3-3.8, and the ozone removal efficiency is maintained at about 100% within 800 min.

[0005] Chinese patent document CN110433795A discloses an activated carbon supported MnOx catalyst. The invention uses divalent manganese salt, ammonium bicarbonate, activated carbon and sodium dodecyl sulfate as raw materials to prepare a catalyst precursor by co-precipitation method, and then uses high temperature heat treatment to prepare an activated carbon supported MnOx catalyst with uniform MnOx loaded on activated carbon and controllable particle size.

[0006] However, manganese oxide catalysts with oxygen vacancies as active sites currently face two major challenges. The first is due to the presence of oxygen-containing intermediates ( Or O 2- The accumulation of ozone on oxygen vacancies makes desorption difficult, leading to catalyst deactivation. Secondly, water molecules and ozone exhibit strong competitive adsorption on oxygen vacancies, also causing catalyst deactivation.

[0007] Therefore, the present invention aims to provide a novel manganese oxide catalyst for catalytic ozone decomposition, which is prepared by controlling specific redox reaction conditions to obtain a manganese oxide catalyst with high water resistance and high catalytic activity. Summary of the Invention

[0008] The technical problem to be solved by this invention is to fundamentally address the defects and shortcomings of existing manganese oxide catalysts for room-temperature catalytic decomposition of ozone, namely, poor water resistance and low catalytic activity. This invention provides a highly efficient manganese oxide catalyst for room-temperature catalytic decomposition of ozone, its preparation method, and its application. By using hydroxyl groups generated on the surface of low-valence manganese as active centers, the water resistance and catalytic activity of the catalyst are improved, achieving excellent catalytic effects.

[0009] The technical solution adopted in this invention is as follows:

[0010] A method for preparing a highly efficient manganese oxide catalyst for the catalytic decomposition of ozone at room temperature includes the following steps: adding potassium permanganate solid and thiourea solid to lactic acid liquid, mixing, and then adding Mn... 2+ The target catalyst is obtained by stirring the salt solution until it is homogeneous, heating to activate it, cooling, filtering, washing, and drying.

[0011] Furthermore, the divalent Mn salt is at least one of manganese acetate, manganese chloride, and manganese sulfate.

[0012] Furthermore, the molar ratio of potassium permanganate to thiourea is 1:0.1–0.5. The addition of thiourea generates MnS, and the presence of MnS can improve the stability of the hydroxyl active sites on low-valent manganese on the MnOx surface.

[0013] Furthermore, the molar ratio of potassium permanganate to lactic acid is 1:0.1 to 2, preferably 1:0.25 to 0.6.

[0014] Furthermore, the molar ratio of potassium permanganate to divalent Mn salt is 1:0.05 to 1, preferably 1:0.05 to 0.3.

[0015] Furthermore, the activation temperature is 100–160°C, and the time is 1–4 hours. At the relatively low activation temperature of 100–160°C, a structure rich in hydroxyl groups can be formed on the surface of low-valence manganese. This prevents the surface hydroxyl groups from being destroyed by high temperature, thus obtaining a manganese oxide catalyst suitable for room-temperature catalytic decomposition of ozone in high-humidity, high-flux environments.

[0016] This invention also provides the application of the aforementioned manganese oxide catalyst in the catalytic decomposition of ozone at room temperature.

[0017] The preparation method of the catalyst of the present invention controls the valence state of manganese in the manganese oxide catalyst by changing the order of adding permanganate and liquid organic acid. After further activation by atmospheric pressure low temperature hydrothermal method, a manganese oxide catalyst with hydroxyl groups generated on the surface of low-valence manganese as active centers and rich in hydroxyl groups on the surface can be obtained.

[0018] Preferably, the specific operation of adding potassium permanganate and lactic acid to the divalent Mn salt solution is as follows: potassium permanganate is slowly added to lactic acid, mixed evenly, and then added dropwise to the divalent Mn salt solution.

[0019] If lactic acid is added dropwise to potassium permanganate, the manganese oxide produced will have a higher valence state; if potassium permanganate is added to lactic acid, the manganese oxide produced will have a lower valence state; and if it is added to a divalent Mn salt solution, the manganese oxide produced will have an even lower valence state.

[0020] The present invention provides a method for preparing a highly efficient manganese oxide catalyst for room-temperature catalytic decomposition of ozone. The method prepares a manganese oxide catalyst for room-temperature catalytic decomposition of ozone with hydroxyl groups generated on the surface of low-valence manganese as active centers. The surface of the manganese oxide catalyst for room-temperature catalytic decomposition of ozone has abundant hydroxyl active centers, and it is suitable for catalytic decomposition of ozone in high humidity and high flux environments.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The method of the present invention is simple, uses few types of raw materials that are cheap and readily available, and has mild reaction conditions, making it suitable for large-scale industrial production.

[0023] (2) The high-efficiency room-temperature catalytic decomposition of ozone provided by the present invention is a catalytic decomposition of ozone by a hydroxyl group generated on the surface of low-valence manganese as the active center. This changes the previous catalytic decomposition of ozone by a ...

[0024] (3) Existing catalysts are generally activated by high-temperature calcination (≥300℃), while the present invention uses low-temperature activation, which has low energy consumption and meets the requirements of energy conservation and emission reduction. Moreover, the method of the present invention forms a specific surface rich in hydroxyl structure at a lower temperature of 100~160℃, which prevents the surface hydroxyl from being destroyed by high temperature and obtains a manganese oxide catalyst suitable for room temperature catalytic decomposition of ozone in high humidity and high flux environments.

[0025] (4) The manganese oxide catalyst for the efficient room temperature catalytic decomposition of ozone provided by the present invention is applied to the catalytic ozone decomposition reaction. The reaction space velocity is 600 L / g / h, the ozone inlet concentration is 40 ppm, and the catalyst can achieve a maximum ozone removal rate of 98% within 12 hours under the conditions of room temperature and relative humidity of 70%. Attached Figure Description

[0026] Figure 1 XPS plot of O1s for the manganese oxide catalyst in Example 1.

[0027] Figure 2 XPS plot of O1s for the manganese oxide catalyst in Example 2.

[0028] Figure 3 XPS plot of O1s for the manganese oxide catalyst in Example 3.

[0029] Figure 4 XPS plot of Mn 2p for the manganese oxide catalyst in Example 1.

[0030] Figure 5 XPS plot of Mn 2p for the manganese oxide catalyst in Comparative Example 1. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] Example 1

[0033] 1 g of potassium permanganate solid (6.33 mmol) and 0.048 g of thiourea solid (0.633 mmol) were added to 0.16 g of lactic acid (1.78 mmol) and mixed. Then, the mixture was added to 10 ml of aqueous solution containing 0.109 g of manganese acetate (0.63 mmol) and stirred for 1 min. After stirring evenly, the mixture was activated at 100 °C for 1 h. After filtration and washing three times with deionized water, the mixture was dried at 100 °C for 1 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0034] Example 2

[0035] 1 g of potassium permanganate solid (6.33 mmol) and 0.096 g of thiourea solid (1.26 mmol) were added to 0.057 g of lactic acid (0.633 mmol) and mixed. Then, the mixture was added to 20 ml of aqueous solution containing 0.067 g of manganese chloride (0.53 mmol) and stirred for 2 min. After stirring evenly, the mixture was activated at 120 °C for 2 h. After filtration and washing once with deionized water, the mixture was dried at 80 °C for 5 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0036] Example 3

[0037] 1 g of potassium permanganate solid (6.33 mmol) and 0.144 g of thiourea solid (1.89 mmol) were added to 1.14 g of lactic acid (12.66 mmol) and mixed. Then, the mixture was added to 50 ml of aqueous solution containing 0.956 g of manganese sulfate (6.33 mmol) and stirred for 3 min. After stirring evenly, the mixture was activated at 140 °C for 3 h. After filtering and washing twice with deionized water, the mixture was dried at 110 °C for 10 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0038] Example 4

[0039] 1 g of potassium permanganate solid (6.33 mmol) and 0.192 g of thiourea solid (2.52 mmol) were added to 0.57 g of lactic acid (9.5 mmol) and mixed. Then, the mixture was added to 30 ml of aqueous solution containing 0.055 g of manganese acetate (0.32 mmol) and stirred for 1 min. After stirring evenly, the mixture was activated at 160 °C for 4 h. After filtration and washing 4 times with deionized water, the mixture was dried at 120 °C for 15 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0040] Example 5

[0041] 1 g of potassium permanganate solid (6.33 mmol) and 0.24 g of thiourea solid (3.15 mmol) were added to 0.91 g of lactic acid (10.1 mmol) and mixed. Then, the mixture was added to 40 ml of aqueous solution containing 0.064 g of manganese chloride (0.51 mmol) and stirred for 2 min. After stirring evenly, the mixture was activated at 160 °C for 2.5 h. After filtration and washing 5 times with deionized water, the mixture was dried at 90 °C for 20 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0042] Example 6

[0043] 1 g of potassium permanganate solid (6.33 mmol) and 0.18 g of thiourea solid (2.36 mmol) were added to 0.31 g of lactic acid (3.44 mmol) and mixed. Then, the mixture was added to 20 ml of aqueous solution containing 0.11 g of manganese sulfate (0.73 mmol) and stirred for 3 min. After stirring evenly, the mixture was activated at 140 °C for 3 h. After filtration and washing once with deionized water, the mixture was dried at 100 °C for 15 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0044] Comparative Example 1

[0045] 1 g of potassium permanganate solid (6.33 mmol) and 0.048 g of thiourea solid (0.633 mmol) were added to 0.16 g of lactic acid (1.78 mmol) and mixed. 10 ml of deionized water was added, and the mixture was stirred for 1 min. After stirring until homogeneous, the mixture was activated at 100 °C for 1 h. After filtration and washing three times with deionized water, the mixture was dried at 100 °C for 1 h to obtain a catalyst for the catalytic decomposition of ozone manganese oxides at room temperature.

[0046] Comparative Example 2

[0047] 1 g of potassium permanganate solid (6.33 mmol) was added to 0.16 g of lactic acid (1.78 mmol) and mixed. Then, it was added to 10 ml of aqueous solution containing 0.109 g of manganese acetate (0.63 mmol) and stirred for 1 min. After stirring evenly, it was activated at 100 °C for 1 h. After filtration and washing three times with deionized water, it was dried at 100 °C for 1 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0048] Comparative Example 3

[0049] 1 g of potassium permanganate solid (6.33 mmol) and 0.049 g of sodium sulfide solid (0.633 mmol) were added to 0.16 g of lactic acid (1.78 mmol) and mixed. Then, the mixture was added to 10 ml of aqueous solution containing 0.109 g of manganese acetate (0.63 mmol) and stirred for 1 min. After stirring evenly, the mixture was activated at 100 °C for 1 h. After filtration and washing three times with deionized water, the mixture was dried at 100 °C for 1 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0050] Comparative Example 4

[0051] 1 g of potassium permanganate solid (6.33 mmol) and 0.069 g of potassium sulfide solid (0.633 mmol) were added to 0.16 g of lactic acid (1.78 mmol) and mixed. Then, the mixture was added to 10 ml of aqueous solution containing 0.109 g of manganese acetate (0.63 mmol) and stirred for 1 min. After stirring evenly, the mixture was activated at 100 °C for 1 h. After filtration and washing three times with deionized water, the mixture was dried at 100 °C for 1 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0052] Comparative Example 5

[0053] 1 g of potassium permanganate solid (6.33 mmol) and 0.048 g of thiourea solid (0.633 mmol) were added to 0.16 g of oxalic acid (1.78 mmol) and mixed. Then, the mixture was added to 10 ml of aqueous solution containing 0.109 g of manganese acetate (0.63 mmol) and stirred for 1 min. After stirring evenly, the mixture was activated at 100 °C for 1 h. After filtration and washing three times with deionized water, the mixture was dried at 100 °C for 1 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0054] Comparative Example 6

[0055] 1 g of potassium permanganate solid (6.33 mmol) and 0.048 g of thiourea solid (0.633 mmol) were added to 0.27 g of tartaric acid (1.78 mmol) and mixed. Then, the mixture was added to 10 ml of aqueous solution containing 0.109 g of manganese acetate (0.63 mmol) and stirred for 1 min. After stirring evenly, the mixture was activated at 100 °C for 1 h. After filtration and washing three times with deionized water, the mixture was dried at 100 °C for 1 h to obtain a catalyst for the catalytic decomposition of manganese oxides at room temperature.

[0056] Comparative Example 7

[0057] 0.16 g of lactic acid (1.78 mmol) was added to 1 g of potassium permanganate solid (6.33 mmol) and 0.048 g of thiourea solid (0.633 mmol) and mixed. Then, the mixture was added to 10 ml of aqueous solution containing 0.109 g of manganese acetate (0.63 mmol) and stirred for 1 min. After stirring evenly, the mixture was activated at 100 °C for 1 h. After filtration and washing three times with deionized water, the mixture was dried at 100 °C for 1 h to obtain a catalyst for the catalytic decomposition of ozone manganese oxides at room temperature.

[0058] Results Detection: The ozone removal rate of the manganese oxide catalysts in the examples and comparative examples was detected using an ozone analyzer (2B Technology Model 106-M, USA). The detection temperature was 25℃, the relative humidity was 70%, the gas flow rate was 600 L / (g·h), and the initial ozone concentration was 40 ppm. The ozone removal efficiency test results are shown in Table 1 below.

[0059] Table 1. Results of ozone removal efficiency test of the catalyst

[0060]

[0061]

[0062] Sample Analysis

[0063] XPS plots of O1s of the manganese oxide catalysts for room-temperature catalytic decomposition of ozone prepared in Examples 1, 2, and 3 are shown below. Figure 1 , 2 As shown in Figures 1 and 3, the surface hydroxyl oxygen (O) in Examples 1, 2, and 3 is... surf The contents were 32.1%, 23.3%, and 16.3%, respectively.

[0064] XPS plots of Mn2p for the manganese oxide catalysts for room-temperature catalytic decomposition of ozone prepared in Example 1 and Comparative Example 1 are shown below. Figure 4 , 5 As shown, the average oxidation state (AOS) of Example 1 was calculated to be 2.2 using Mn3s, and the average oxidation state (AOS) of Comparative Example 1 was 3.0.

[0065] The manganese oxide catalysts for room-temperature catalytic decomposition of ozone obtained in Examples 1-6 were placed in a fixed-bed reactor for activity evaluation. The simulated total gas flow rate was 1 L / min, containing 40 ppm O3, RH = 70%, the catalyst dosage was 0.1 g, the reaction space velocity was 600 L / g / h, and the test temperature was 25 °C. After 3 hours of testing, the ozone decomposition rate was above 50% in all cases. Among them, the sample with the highest ozone decomposition rate was the sample in Example 1, which reached 100%. Furthermore, the sample in Example 1 was tested repeatedly five times, each time for 12 hours, and the ozone decomposition rate was about 98% in each case, indicating that the catalyst has good reusability.

[0066] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for preparing a highly efficient manganese oxide catalyst for the catalytic decomposition of ozone at room temperature, characterized in that... Includes the following steps: Potassium permanganate solid and thiourea solid were added to lactic acid liquid, mixed, and then Mn was added. 2+ After stirring evenly in a salt solution, the mixture is heated to activate it at a temperature of 100-160 °C for 1-4 h. After cooling, the mixture is filtered, washed, and dried with deionized water to obtain the manganese oxide catalyst for the catalytic decomposition of ozone at room temperature.

2. The preparation method of a highly efficient manganese oxide catalyst for room-temperature catalytic decomposition of ozone as described in claim 1, characterized in that... The divalent Mn salt is at least one of manganese acetate, manganese chloride, and manganese sulfate.

3. The method for preparing a highly efficient manganese oxide catalyst for room-temperature catalytic decomposition of ozone as described in claim 1, characterized in that... The molar ratio of potassium permanganate to thiourea is 1:0.1~0.

5.

4. The preparation method of a highly efficient manganese oxide catalyst for room-temperature catalytic decomposition of ozone as described in claim 1, characterized in that... The molar ratio of potassium permanganate to lactic acid is 1:0.1~2.

5. The preparation method of a highly efficient manganese oxide catalyst for room-temperature catalytic decomposition of ozone as described in claim 4, characterized in that... The molar ratio of potassium permanganate to lactic acid is 1:0.25-0.

6.

6. The method for preparing a highly efficient manganese oxide catalyst for room-temperature catalytic decomposition of ozone as described in claim 1, characterized in that... The molar ratio of potassium permanganate to divalent Mn salt is 1:0.05~1.

7. The preparation method of a highly efficient manganese oxide catalyst for room-temperature catalytic decomposition of ozone as described in claim 6, characterized in that... The molar ratio of potassium permanganate to divalent Mn salt is 1:0.05~0.

3.

8. A highly efficient manganese oxide catalyst for the room-temperature catalytic decomposition of ozone, prepared by any one of claims 1-7.

9. The application of the manganese oxide catalyst as described in claim 8 for the catalytic decomposition of ozone at room temperature.

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