A piezoelectric effect manganese-based catalyst for efficient catalytic decomposition of ozone and its preparation and application

Abstract

The present invention belongs to the field of catalytic decomposition of ozone and environmental protection, and discloses a novel piezoelectric effect manganese-based catalyst for efficient catalytic decomposition of ozone, as well as its preparation and application. The present invention mixes molybdate with thiourea, obtains an odd-numbered layer of molybdenum disulfide through a hydrothermal reaction, and then mixes the odd-numbered layer of molybdenum disulfide with potassium permanganate, and obtains manganese dioxide @ an odd-numbered layer of molybdenum disulfide through a hydrothermal reaction. The manganese dioxide @ an odd-numbered layer of molybdenum disulfide is then spot-coated on fan blades, thereby realizing the application of the catalyst in ozone decomposition. The manganese-based catalyst of the present invention is simple to manufacture, low in cost, has high catalytic activity, and strong stability; when it is spot-coated on fan blades, ozone is more easily contacted with the flaky material, thereby being rapidly decomposed.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic decomposition of ozone and environmental protection, and particularly relates to a piezoelectric effect manganese-based catalyst for efficient catalytic decomposition of ozone, and its preparation and application. Background Art

[0002] Ground-level ozone (O3) is a major atmospheric pollutant and a primary component of greenhouse gases and photochemical smog. It is primarily generated by photochemical reactions of precursors such as volatile organic compounds and nitrogen oxides under high temperatures and strong sunlight. The rapid increase in ozone precursor emissions has led to increasingly severe ozone pollution, posing a serious threat to human health and the ecological environment. The development of efficient ozone decomposition technologies has become an urgent need.

[0003] Heterogeneous catalytic decomposition technology is one of the effective methods for decomposing ozone. It converts ozone into oxygen through electron transfer between the catalyst and ozone, and has the advantages of rapid reaction, low energy consumption, and no secondary pollution. Among them, manganese-based catalysts (such as MnO2) have a variety of variable valence states and good ozone affinity, and are widely used in ozone catalytic decomposition. Although many studies have been conducted on ozone catalytic decomposition technology, the performance of ozone catalytic decomposition is still not ideal. In the reaction process of decomposing ozone, manganese-based catalysts transfer electrons to ozone molecules to decompose ozone. If the electrons of the manganese-based catalyst are not effectively compensated, the valence state of manganese will change, thereby reducing the catalytic activity, which restricts the application of manganese-based catalytic systems in ozone decomposition. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a piezoelectric effect manganese-based catalyst that can efficiently catalyze the decomposition of ozone.

[0005] Another object of the present invention is to provide a piezoelectric effect manganese-based catalyst for efficiently catalyzing and decomposing ozone prepared by the above method.

[0006] Another object of the present invention is to provide the use of the aforementioned piezoelectric manganese-based catalyst for catalytic ozone decomposition. The piezoelectric material deforms within the fan blades, generating piezoelectric charge. These electrons are transferred to the manganese-based catalyst, compensating for electron loss during the ozone decomposition reaction, thereby significantly enhancing the catalytic ozone decomposition activity and long-term stability.

[0007] The purpose of the present invention is achieved through the following solutions:

[0008] The preparation of a piezoelectric effect manganese-based catalyst for efficient catalytic decomposition of ozone comprises the following steps:

[0009] (1) mixing molybdate and thiourea and dissolving them in water, adding acid to adjust the pH value of the mixed solution, stirring, performing a hydrothermal reaction, washing, centrifuging to obtain a precipitate, and drying to obtain an odd number of layers of molybdenum disulfide;

[0010] (2) dispersing the odd-numbered molybdenum disulfide obtained in step (1) and potassium permanganate in water, adding acid to adjust the pH value of the mixed solution, stirring, performing a hydrothermal reaction, washing, centrifuging to obtain a precipitate, and drying to obtain manganese dioxide @ odd-numbered molybdenum disulfide.

[0011] The molybdate described in step (1) is at least one of sodium molybdate or ammonium molybdate, preferably sodium molybdate dihydrate.

[0012] The molar ratio of the molybdate to thiourea in step (1) is 1-2:4-8, preferably 1:5.

[0013] The amount of water used in step (1) satisfies the requirement that the concentration of thiourea is 0.4 to 1.0 mol / L, preferably 0.67 mol / L.

[0014] The stirring time in step (1) is 0.5 to 2 hours, preferably 1 hour.

[0015] The hydrothermal reaction temperature in step (1) is 100-200° C., preferably 200° C.; the hydrothermal reaction time is 12-48 h, preferably 24 h.

[0016] The number of layers of the odd-numbered molybdenum disulfide layers in step (1) is 1, 3, or 5.

[0017] The molar ratio of the odd-numbered layers of molybdenum disulfide to potassium permanganate in step (2) is 1-3:0.5-2, preferably 2:1.

[0018] The amount of water used in step (2) satisfies the requirement that the concentration of potassium permanganate is 0.02 to 0.10 mol / L, preferably 0.05 mol / L.

[0019] The stirring time in step (2) is 0.5 to 2 hours, preferably 0.5 hours.

[0020] The hydrothermal reaction temperature in step (2) is 100-200° C., preferably 140° C.; the hydrothermal reaction time is 1-5 hours, preferably 1 hour.

[0021] The acid in step (1) and step (2) is at least one of hydrochloric acid or nitric acid, preferably hydrochloric acid; the mass fraction of the acid is 36-38%, preferably 37%; the pH value of the mixed solution after acid adjustment is 0.5-1, preferably 0.9.

[0022] After the hydrothermal reaction in step (1) and step (2) is completed, the obtained mixed solution is cooled to room temperature before washing, and the solid-liquid separation is performed.

[0023] The washing in step (1) and step (2) is to wash the obtained solid with water and anhydrous ethanol until the pH of the supernatant is neutral.

[0024] The centrifugal speed in step (1) and step (2) is 4000-15000 rpm, preferably 8000 rpm; the centrifugal time is 5-10 min, preferably 6 min.

[0025] The drying temperature in step (1) and step (2) is 50-80°C, preferably 60°C; the drying time is 8-24h, preferably 12h.

[0026] A piezoelectric effect manganese-based catalyst for catalytically decomposing ozone with high efficiency prepared by the method.

[0027] The application of the piezoelectric effect manganese-based catalyst in catalytic decomposition of ozone includes the following steps:

[0028] S1: dispersing the piezoelectric effect manganese-based catalyst into anhydrous ethanol to form a catalyst dispersion;

[0029] S2: Apply the catalyst solution to the air inlet surface of the reaction fan and place it in an oven for drying;

[0030] S3: Start the fan to make the ozone flow from the fan air inlet to the fan air outlet to perform a catalytic reaction, thereby decomposing the ozone.

[0031] The concentration of the catalyst dispersion in step S1 is 10-50 g / L, preferably 25 g / L.

[0032] The oven temperature in step S2 is 40-80° C., preferably 60° C.; the drying time is 5-20 min, preferably 10 min.

[0033] The ozone concentration in step S3 is 30-100 ppm, preferably 50 ppm; the ozone flow rate is 500-2000 mL / min, preferably 1000 mL / min.

[0034] The mechanism of the present invention is:

[0035] The piezoelectric effect can be achieved by applying mechanical forces (such as ultrasound or wind) to polarize the piezoelectric material, inducing an asymmetric distribution of surface charge and generating a large number of electrons and holes. This invention combines a manganese-based catalyst with a piezoelectric material. Electrons generated by the piezoelectric material under mechanical stress are transferred to the manganese-based catalyst, compensating for electron loss during the ozone decomposition reaction, thereby significantly improving the catalytic decomposition activity and long-term stability of the ozone.

[0036] The wind force generated when the fan rotates causes the piezoelectric material on the fan blades to deform and generate piezoelectric charges. The charges are transferred to the active sites of the manganese-based catalyst, improving the efficiency of electron transfer between the active sites and ozone molecules during the ozone decomposition reaction, thereby greatly improving the ozone catalytic decomposition performance and truly realizing a green, environmentally friendly and sustainable catalytic reaction process.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] 1. The manganese-based catalyst of the present invention is simple to manufacture, low in cost, high in catalytic activity and strong in stability.

[0039] 2. The present invention overcomes the problems of catalyst deactivation in the ozone catalysis process of traditional catalysts, utilizes the piezoelectric effect to enhance the ozone catalytic reaction and efficiently decompose ozone gas.

[0040] 3. The manganese-based catalyst prepared by the present invention has better catalytic performance, and ozone is more likely to contact the flaky material and then be quickly decomposed. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the ozone catalytic decomposition reaction process of the present invention.

[0042] Figure 2 This is a transmission electron microscope image of the piezoelectric effect manganese-based catalyst MnO2@MoS2 prepared in Example 1 of the present invention.

[0043] Figure 3 This is the X-ray diffraction pattern of the piezoelectric effect manganese-based catalyst MnO2@MoS2 prepared in Example 1 of the present invention.

[0044] Figure 4 1 is a diagram showing the ozone decomposition effects in different reaction systems in Test Example 1 of the present invention.

[0045] Figure 5 This is a diagram showing the long-term ozone decomposition effect of MnO2@MoS2 in Test Example 2 of the present invention.

[0046] Figure 6 This is a diagram showing the ozone decomposition effects of different manganese-based catalysts in Test Example 3 of the present invention. DETAILED DESCRIPTION

[0047] The present invention will be described in further detail below with reference to the Examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. Where specific conditions are not specified in the Examples, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0048] Unless otherwise specified, all reagents used in the examples can be purchased from the market.

[0049] like Figure 1 Figure 1 shows a schematic diagram of the process for catalytic ozone decomposition using a piezoelectric effect manganese-based catalyst. The diagram includes: 1: gas cylinder, 2: mass flow meter, 3: ozone generator (purchased from Guangzhou Chuanghuan Ozone Electrical Equipment Co., Ltd., model: CH-ZTW3G), 4: air valve, 5: humidifier bottle, 6: fan assembly, 7: fan cross-section, 8: catalyst, 9: ozone detector (purchased from Guangzhou Zed Instrument Equipment Co., Ltd., model: Model-106L).

[0050] Example 1: MnO2@MoS2 catalyst

[0051] (1) Preparation of MoS2:

[0052] 8mmol sodium molybdate (Na2MoO4·2H2O) and 40mmol thiourea were dissolved in 60mL deionized water. The solution was then adjusted to pH 0.9 with 37% concentrated hydrochloric acid and stirred for 1 hour. The solution was then transferred to a 100mL stainless steel autoclave and subjected to a hydrothermal reaction in an oven at 200°C for 24 hours. After the reaction, the mixture was cooled to room temperature and precipitated by centrifugation. The resulting solid was washed several times with deionized water and anhydrous ethanol until the supernatant was neutral, centrifuged at 8000rpm for 6 minutes, and dried in a 60°C oven for 12 hours to yield an odd-numbered layer of molybdenum disulfide.

[0053] (2) Preparation of MnO2@MoS2 manganese-based catalyst:

[0054] 0.56g of MoS2 and 0.28g of potassium permanganate were dispersed in 35mL of deionized water under ultrasound. The pH of the solution was then adjusted to 0.9 with 37% concentrated hydrochloric acid and stirred for 30 minutes. The solution was then transferred to a 100mL stainless steel autoclave and subjected to a hydrothermal reaction in an oven at 140°C for 1 hour. After the reaction, the mixture was cooled to room temperature and centrifuged. The resulting solid was washed several times with deionized water and anhydrous ethanol until the supernatant was neutral, centrifuged at 8000rpm for 6 minutes, and dried in a 60°C oven for 12 hours to obtain MnO2@MoS2.

[0055] The MnO2@MoS2 obtained in Example 1 has a shape as follows Figure 2 The transmission electron microscope image is shown in Figure 2, and the X-ray diffraction pattern is shown in Figure 2. Figure 3 shown. Figure 2The figure shows MnO2@MoS2. The fine particles are manganese dioxide clusters, which indicates the uniform loading of manganese dioxide on molybdenum disulfide and the synthesis of MnO2@MoS2. Figure 3 The diffraction peaks shown in the figure are mainly due to molybdenum disulfide, which corresponds well to the typical spectrum of molybdenum disulfide (JCPDS No.75-1539). Since manganese dioxide particles are small and form clusters, it is difficult for the corresponding diffraction peaks to appear.

[0056] Comparative Example 1: MnO2@ZnO catalyst

[0057] 0.29g of ZnO (commercial ZnO, purchased from McLean) and 0.28g of potassium permanganate were dispersed in 35mL of deionized water under ultrasonication. The pH of the solution was then adjusted to 0.9 with 37% concentrated hydrochloric acid and stirred for 30 minutes. The solution was then transferred to a 100mL stainless steel autoclave and subjected to a hydrothermal reaction in an oven at 140°C for 1 hour. After the reaction, the mixture was cooled to room temperature and centrifuged. The resulting solid was washed several times with deionized water and anhydrous ethanol until the supernatant was neutral, centrifuged at 8000rpm for 6 minutes, and dried in an oven at 60°C for 12 hours to obtain MnO2@ZnO.

[0058] Comparative Example 2: MnO2@BaTiO3 catalyst

[0059] 0.82g of BaTiO3 (commercial BaTiO3, purchased from McLean) and 0.28g of potassium permanganate were dispersed in 35mL of deionized water under ultrasonication. The pH of the solution was then adjusted to 0.9 with 37% concentrated hydrochloric acid and stirred for 30 minutes. The solution was then transferred to a 100mL stainless steel autoclave and subjected to a hydrothermal reaction in an oven at 140°C for 1 hour. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The resulting solid was washed several times with deionized water and anhydrous ethanol until the supernatant was neutral, centrifuged at 8000rpm for 6 minutes, and dried in an oven at 60°C for 12 hours to obtain MnO2@BaTiO3.

[0060] Test Example 1

[0061] In this example, ozone was used as the target decomposition product. Different catalyst systems were selected to investigate the decomposition of ozone under continuous flow reaction conditions with a fan rotating and wind-driven reaction. The results showed that the different catalyst systems (system 1: fan rotating; system 2: MnO2-loaded fan rotating; system 3: MoS2-loaded fan rotating; system 4: MnO2@MoS2-loaded fan rotating) could be used.

[0062] The specific experimental steps are as follows:

[0063] S1: Ultrasonic dispersion of 100 mg of the MnO2@MoS2 manganese-based catalyst prepared in Example 1 in 4 mL of anhydrous ethanol was performed to obtain a MnO2@MoS2 catalyst dispersion. The MnO2@MoS2 catalyst dispersion was then dripped onto the air inlet surfaces of five reaction fans and dried in a 60°C oven for 10 minutes to secure the MnO2@MoS2 manganese-based catalyst to the fan blades (System 4).

[0064] The way in which the loads of System 2 and System 3 are fixed on the fan blades is the same as that of System 4 except for the following features: System 2 replaces the MnO2@MoS2 prepared in Example 1 with MnO2 (commercial MnO2, purchased from McLean); System 3 replaces the MnO2@MoS2 prepared in Example 1 with MoS2 prepared in step (1) of Example 1.

[0065] S2: For system 1, connect the fan directly to the outlet of the ozone generator, generate ozone with a concentration of 50 ppm through the ozone generator, and set the gas flow rate V 流 =1000mL / min, fan running, online detection of ozone concentration in exhaust gas, and calculation of ozone removal rate.

[0066] For system 2, a fan coated with 100 mg of MnO2 catalyst was connected to the outlet of the ozone generator. The ozone generator was used to generate ozone with a concentration of 50 ppm. The gas flow rate V was set to 流 =1000mL / min, fan running, online detection of ozone concentration in exhaust gas, and calculation of ozone removal rate.

[0067] For system 3, a fan coated with 100 mg of MoS2 catalyst was connected to the outlet of the ozone generator. The ozone generator was used to generate ozone with a concentration of 50 ppm. The gas flow rate V was set to 流 =1000mL / min, fan running, online detection of ozone concentration in exhaust gas, and calculation of ozone removal rate.

[0068] For system 4, the reaction fan coated with 100 mg MnO2@MoS2 manganese-based catalyst was connected to the outlet of the ozone generator. The ozone generator was used to generate ozone with a concentration of 50 ppm. The gas flow rate V was set to 流 =1000mL / min, the fan is running, the ozone concentration in the exhaust gas is detected online, and the ozone removal rate is calculated.

[0069] The calculation method of ozone removal rate is:

[0070] Ozone removal rate (%) = [(initial ozone concentration - ozone concentration in tail gas) / initial ozone concentration] × 100%.

[0071] The fan rotates, driven by wind. The ozone removal effects of different catalyst systems are as follows: Figure 4 As shown in the figure, in reaction system 1, only the fan rotates, and ozone is basically not decomposed. In reaction system 2, when the fan blades are loaded with MnO2 catalyst, the initial ozone removal rate is 40%. As the reaction time increases, the catalyst activity gradually decreases, and after 2 hours, the removal rate is only 20%. In reaction system 3, when the fan blades are loaded with MoS2 catalyst, the ozone removal rate is about 10%. In reaction system 4, the fan blades are loaded with MnO2@MoS2 manganese-based catalyst, and the ozone removal rate remains 100% within 2 hours of reaction. This shows that in the reaction fan, due to the piezoelectric effect of MoS2, after the fan rotates, the piezoelectric charge generated by MoS2 under wind drive is transferred to the active site of MnO2, compensating for the electron loss during the ozone decomposition reaction, thereby significantly improving the ozone catalytic decomposition activity.

[0072] Test Example 2

[0073] In the actual atmospheric environment, ozone exists continuously and flows continuously. In this embodiment, a long-term continuous flow experiment will be used to simulate the actual ozone pollution situation, so as to study the long-term ozone catalytic decomposition effect of the present invention and provide an effective demonstration for ozone control in the actual atmospheric environment.

[0074] The experimental steps are as follows:

[0075] S1: Ultrasonic dispersion of 100 mg of the MnO2@MoS2 manganese-based catalyst prepared in Example 1 in 4 mL of anhydrous ethanol was performed to obtain a MnO2@MoS2 manganese-based catalyst dispersion. The catalyst solution was then dripped onto the air inlet surfaces of five reaction fans and dried in a 60°C oven for 10 minutes, thereby securing the MnO2@MoS2 manganese-based catalyst to the fan blades.

[0076] S2: Fix the reaction fan loaded with MnO2@MoS2 in the reactor, pass the gas flow containing 50ppm ozone through the reactor, and set the gas flow rate V 流 =1000mL / min, the fan is running, the ozone concentration in the reactor is monitored online by the detector, and the ozone removal rate is calculated.

[0077] The results are as follows Figure 5 As shown, after 8 hours of reaction under a continuous ozone flow, the fan loaded with 100 mg of MnO2@MoS2 maintained an ozone removal rate of 100% under the condition of blade rotation. This verifies that the present invention can achieve efficient, long-lasting, and stable catalytic decomposition of ozone driven by wind.

[0078] Test Example 3

[0079] In this example, the catalytic decomposition effects of three different manganese-based catalysts, MnO2@MoS2, MnO2@ZnO, and MnO2@BaTiO3, on ozone were compared.

[0080] The specific experimental steps are as follows:

[0081] S1: Disperse 100 mg of the MnO2@MoS2, MnO2@ZnO, and MnO2@BaTiO3 composite catalysts prepared in Example 1 and Comparative Examples 1 and 2 in 4 mL of anhydrous ethanol to obtain MnO2@MoS2, MnO2@ZnO, and MnO2@BaTiO3 catalyst dispersions. The catalyst dispersions were dripped onto the air inlet surface of the reaction fan and dried in a 60°C oven for 10 minutes to obtain fans loaded with the MnO2@MoS2, MnO2@ZnO, and MnO2@BaTiO3 composite catalysts, respectively.

[0082] S2: Fans loaded with MnO2@MoS2, MnO2@ZnO and MnO2@BaTiO3 catalysts were fixed in the reactor respectively, and a gas flow containing 50 ppm ozone was passed through the reactor, and the gas flow rate V was set. 流 =1000mL / min, the fan is running, the ozone concentration in the reactor is monitored online by the detector, and the ozone removal rate is calculated.

[0083] The effects of three different manganese-based catalysts on the catalytic decomposition of ozone are as follows Figure 6 As shown in the figure, under 2 hours of continuous flow experiment conditions, the catalytic removal efficiency of the MnO2@MoS2 composite catalyst reaction system for ozone was 100%, while that of MnO2@ZnO was approximately 60%, and that of MnO2@BaTiO3 was only about 50%. This result confirms that the piezoelectric charge generated by different piezoelectric materials under wind power can enhance the catalytic performance of MnO2 to some extent, with the manganese-based MnO2@MoS2 catalyst performing the best.

[0084] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. Application of a piezoelectric effect manganese-based catalyst for efficient catalytic decomposition of ozone, characterized in that The following steps are involved: S1: dispersing a piezoelectric effect manganese-based catalyst into anhydrous ethanol to form a catalyst dispersion; the concentration of the catalyst dispersion is 10 to 50 g / L; S2: Apply the catalyst solution to the air inlet surface of the reaction fan and place it in an oven for drying; S3: Start the fan to make the ozone flow from the fan inlet to the fan outlet to perform a catalytic reaction, thereby decomposing the ozone; The catalyst is prepared by the following method: (1) Molybdate and thiourea are mixed and dissolved in water, acid is added to adjust the pH value of the mixed solution, stirred, subjected to hydrothermal reaction, washed, centrifuged to obtain a precipitate, and dried to obtain an odd number of layers of molybdenum disulfide; (2) The odd-numbered molybdenum disulfide obtained in step (1) and potassium permanganate are dispersed in water, an acid is added to adjust the pH value of the mixed solution, the mixture is stirred, a hydrothermal reaction is carried out, the mixture is washed, and a precipitate is obtained by centrifugation. The precipitate is dried to obtain manganese dioxide@odd-numbered molybdenum disulfide.

2. The use according to claim 1, characterized in that: The molybdate described in step (1) is at least one of sodium molybdate or ammonium molybdate.

3. The use according to claim 1, characterized in that: The molar ratio of molybdate to thiourea in step (1) is 1-2:4-8; The amount of water used in step (1) is such that the concentration of thiourea is 0.4 to 1.0 mol / L.

4. The use according to claim 1, characterized in that: The hydrothermal reaction temperature in step (1) is 100-200°C; the hydrothermal reaction time is 12-48 hours; The number of odd-numbered layers of molybdenum disulfide in step (1) is 1, 3, or 5.

5. The use according to claim 1, characterized in that: The molar ratio of the odd-numbered layers of molybdenum disulfide to potassium permanganate in step (2) is 1-3:0.5-2; The amount of water used in step (2) is such that the concentration of potassium permanganate is 0.02 to 0.10 mol / L.

6. The use according to claim 1, characterized in that: The hydrothermal reaction temperature in step (2) is 100-200° C., and the hydrothermal reaction time is 1-5 h.

7. The use according to claim 1, characterized in that: The acid in step (1) and step (2) is at least one of hydrochloric acid or nitric acid; the mass fraction of the acid is 36-38%; and the pH value of the mixed solution after acid adjustment is 0.5-1.

8. The application according to claim 1, characterized in that: The ozone concentration in step S3 is 30-100 ppm; the ozone flow rate is 500-2000 mL / min.

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