A bottle double-ship catalyst for ozone catalytic oxidation and a preparation method thereof

Abstract

The application discloses an ozone catalytic oxidation bottle double-ship catalyst and a preparation method thereof. The preparation method comprises the following steps: mixing a manganese salt solution and a dealuminized zeolite and performing ultrasonic treatment to obtain a first precursor; then, pyrolyzing in an inert atmosphere to obtain a second precursor; mixing the second precursor and a metal salt solution to perform an ion exchange reaction to obtain a third precursor; and finally, high-temperature calcining to obtain the catalyst. The catalyst can overcome the defect of low CO2 selectivity of the ozone catalyst of the zeolite catalyst loaded with metal by the impregnation method in the prior art, and has a good application prospect in the field of treating organic pollutants.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of ozone catalytic oxidation, and particularly relates to a bottle-in-bottle double-ship catalyst for ozone catalytic oxidation and a preparation method thereof. BACKGROUND

[0002] Volatile organic compounds (VOCs) have serious harm to human health and the environment, and have been proven to be important precursors of ozone, secondary organic aerosols and photochemical smog. Ozone catalytic oxidation technology has been widely concerned due to its effectiveness in oxidizing low concentration level VOCs under mild conditions. Compared with catalytic combustion, the addition of ozone greatly reduces the reaction temperature and the required activation energy. The effect of zeolite as a carrier for ozone catalytic oxidation catalyst in degrading VOCs at room temperature is obvious.

[0003] Zeolite is a carrier with unique framework structure and pore system, and its crystal structure is formed by connecting silicon (aluminum) oxygen tetrahedra into a three-dimensional structure, and there are various cavities and channels of different sizes in the structure. Zeolite is an advantageous carrier in ozone catalytic oxidation catalysts, however, for example, the structure of Y zeolite is composed of 13 Å supercages in the shape of a sphere, which are interconnected in a tetrahedral manner through small pores with a diameter of 7.4 Å, and the size of the guest molecules is also limited by the available space in these cavities. A reasonable method is to expand the internal pore volume of the zeolite so as to serve as a carrier for large-volume metal catalysts. After expanding the pore volume, mesopores completely surrounded by micropores have the additional advantage of easy formation of carrier-metal bonds, which reduces the mobility of metal particles and improves the selectivity of the catalyst.

[0004] Although the zeolite-based catalysts currently in use have good catalytic efficiency and relatively high removal rate of volatile organic pollutants, there is still a common problem that a high proportion of CO exists in the COx products of catalytic ozonation, which is a product that should be avoided in catalytic oxidation, and the method to deal with it is to improve the selectivity of CO2 so as to reduce the concentration of CO in the product.

[0005] Existing researches show that MnOx catalyst has a high removal efficiency for VOCs, and is one of the most promising non-noble metal catalysts. Compared with noble metals, manganese-based oxides have the advantages of large reserves, rich types and low price, although they do not have the best selectivity. Adding a second metal to Mn-based materials is an effective theoretical method for adjusting the reactivity and selectivity by adjusting the binding strength and configuration of intermediates on the catalytic surface.

[0006] In ozone catalytic oxidation, ozone is decomposed at oxygen vacancies to produce reactive oxygen species, which have stronger oxidation ability for intermediate product CO, and can further oxidize CO to CO2, thereby improving the selectivity of CO2. However, random distribution of Mn and the second metal M caused by traditional impregnation method for loading double metals makes it difficult to produce interaction, resulting in lack of oxygen vacancies for producing reactive oxygen species. SUMMARY

[0007] In order to solve the above problems of the prior art, the present application provides a bottle-in-bottle double-ship catalyst for ozone catalytic oxidation and a preparation method thereof, which can overcome the low CO2 selectivity of the ozone catalyst of the zeolite catalyst loaded with metal by impregnation method in the prior art, and has a good application prospect in the field of organic pollutant treatment.

[0008] To achieve the above object, the present application adopts the following technical solution:

[0009] The preparation method of the bottle-in-bottle double-ship catalyst for ozone catalytic oxidation comprises the following steps:

[0010] (1) mixing a manganese salt solution with a dealuminated zeolite and ultrasonic treatment to obtain a first precursor;

[0011] (2) pyrolyzing the first precursor in an inert atmosphere to obtain a second precursor (Mn-zeolite);

[0012] (3) mixing the second precursor and a metal salt solution to perform an ion exchange reaction to obtain a third precursor;

[0013] (4) high-temperature calcination of the third precursor to obtain the catalyst.

[0014] Preferably, the molar ratio of the manganese salt in step (1) to the metal salt in step (3) is 1:3~3:1.

[0015] Preferably, the dealuminated zeolite in step (1) is prepared by the following method: placing dry zeolite in an acid solution to perform a dealuminating reaction. More preferably, the zeolite is one of beta zeolite, Y zeolite or ZSM-5, and the silica-alumina ratio in the zeolite is above 5.

[0016] Preferably, the acid solution is a nitric acid solution with a concentration of 0.5~2 mol / L.

[0017] Preferably, the volume ratio of the zeolite to the acid solution is 1:(8~12).

[0018] Preferably, the temperature of the dealuminating reaction is 60~100℃.

[0019] Preferably, the time of the dealuminating reaction is 4~6h.

[0020] Preferably, the dealuminating reaction further comprises the steps of water washing and drying after the reaction is completed.

[0021] Preferably, the manganese salt in step (1) is manganese acetate, manganese nitrate, manganese chloride or manganese sulfate.

[0022] Preferably, the solvent of the manganese salt solution in step (1) is ethanol, methanol or butanol.

[0023] Preferably, the concentration of the manganese salt solution in step (1) is 50-200 μmol / mL. -1 .

[0024] Preferably, the time of the ultrasonic treatment in step (1) is 180-270 min.

[0025] Preferably, the temperature of the pyrolysis in step (2) is 450-550℃.

[0026] Preferably, the time of the pyrolysis in step (2) is 70-110 min.

[0027] Preferably, the metal salt solution in step (3) is a salt solution of Cu, Co, Ce or Fe.

[0028] Preferably, the concentration of the metal salt solution in step (3) is 0.1-1 mol / L.

[0029] Preferably, the volume ratio of the second precursor to the metal salt solution in step (3) is 1:(50-80).

[0030] Preferably, the temperature of the ion exchange reaction in step (3) is 70℃.

[0031] Preferably, the time of the ion exchange reaction in step (3) is 3-6 h.

[0032] Preferably, the ion exchange reaction in step (3) further comprises a step of washing with deionized water after the reaction.

[0033] Preferably, the metal salt solution in step (3) is an acetate, sulfate, nitrate or chloride.

[0034] Preferably, the temperature of the calcination in step (4) is 500-550℃.

[0035] Preferably, the time of the calcination in step (4) is 180 min.

[0036] The second object of the present application is to provide a bottle-type double-boat catalyst for ozone catalytic oxidation prepared by the above method.

[0037] The present application has the following advantages:

[0038] The zeolite-encapsulated bottle-in-bottle catalyst restricts the two metals in the zeolite channels to enhance the interaction to generate Mn-OV-M asymmetric oxygen vacancies, promotes the conversion of ozone to active oxygen species, and catalyzes the oxidation of VOCs to improve the selectivity of CO2.

[0039] The zeolite-encapsulated Mn-M bottle-in-bottle catalyst of the present application selects a zeolite with a high specific surface area and a moderate pore size as a carrier, first uses a dealumination method to expand the internal cavity of the zeolite to form a microporous mesoporous zeolite material, and then introduces a Mn metal precursor into the channel to form a Mn-zeolite bottle-in-bottle catalyst using the bottle-in-boat method. The excess unreacted Mn is used as a template, and the second metal M is replaced into the position of the template Mn by using the post-ion exchange method to form a bottle-in-bottle catalyst. The lattice oxygen of the dealuminated zeolite carrier forms a metal carrier bond with Mn, which anchors the positions of Mn and the second metal, and the change in the coordination environment enhances the interface effect between the Mn-M metal nanoparticles. The two metals are restricted in the zeolite channels to enhance the interaction to generate Mn-OV-M asymmetric oxygen vacancies, promote the conversion of ozone to active oxygen species, improve the activity of oxygen vacancies, thereby improve the utilization efficiency of active oxygen species generated in the catalytic oxidation process of O3, which further promotes the selectivity of CO2 in the product of ozone catalytic oxidation of VOCs, and deep mineralization of VOCs into non-toxic products such as carbon dioxide. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a graph of the conversion efficiency of the catalyst prepared in Example 1 for toluene.

[0041] Figure 2 is a graph of the conversion efficiency of the catalyst prepared in Example 2 for toluene.

[0042] Figure 3 is a graph of the conversion efficiency of the catalyst prepared in Example 3 for toluene.

[0043] Figure 4 is a comparison graph of the selectivity of carbon dioxide of the catalyst prepared in Examples 1-3.

[0044] Figure 5 is the characterization result of H2-TPR of the catalyst in Example 5. DETAILED DESCRIPTION

[0045] The following detailed description of exemplary embodiments of the application references the drawings, in which the exemplary embodiments of the application are described in sufficient detail to enable those skilled in the art to practice the application, although variations of those exemplary embodiments can be made and will be apparent to those of ordinary skill in the art. The following detailed description of the application is not intended to limit the scope of the application as claimed, but is merely intended to describe exemplary embodiments of the application in sufficient detail to enable one of ordinary skill in the art to practice the application, and to describe the principles and features of the application to those of ordinary skill in the art. The scope of the application is defined solely by the appended claims. Example 1

[0046] After the beta zeolite was ground and broken, it was sieved into a 20-40 mesh particle powder and dried. A 1 mol / L nitric acid solution was prepared, and the above zeolite and the prepared nitric acid solution were placed in a three-necked flask at a solid-liquid ratio of 1:10, stirred and reacted in a 80°C reflux device for 6h. After the reaction was completed, the sample was washed with water 5 times and dried overnight. 0.11 g of manganese acetate tetrahydrate was added to 5 mL of ethanol to prepare a 150 μmol mL -1 Mn(CH3COO)2ethanol solution. 1.7 mL of the prepared Mn(CH3COO)2ethanol solution was added to 250 mg of the expanded beta zeolite, and ultrasonic treatment was performed for 250 min.

[0047] After vacuum drying overnight, the above material was pyrolyzed at 500°C for 90 min under an argon atmosphere, and then removed to obtain Mn-zeolite.

[0048] A 0.1 mol / L aqueous copper nitrate solution was prepared, and the Mn-zeolite and the copper nitrate solution were mixed at a solid-liquid ratio of 1:60 and heated and stirred to replace the unreacted Mn ions with Cu ions. After washing with deionized water 10 times, drying was performed at 110°C overnight.

[0049] The obtained powder was calcined at 550°C for 180 min in an air atmosphere, and then removed to obtain the product.

[0050] Catalyst performance evaluation: As shown in Table 1, the reaction temperature was 30°C, the catalyst mass was 0.1 g, the gas flow rate was 0.5 L / min, the toluene inlet concentration was 200 ppm, and the ozone inlet concentration was 3000 ppm. The toluene conversion rate reached 100%, the CO2 conversion rate reached 72%, no ozone was detected at the outlet, and the catalyst performance did not change significantly after 30 hours of operation. Figure 1 , 4 Example 2

[0051] ​The Y zeolite was ground and sieved to a particle powder of 2-40 mesh and dried. A 2 mol / L nitric acid solution was prepared, and the above zeolite and the prepared nitric acid solution were placed in a three-necked flask at a solid-liquid ratio of 1:8, stirred in a 60°C reflux device for 6 h, and after the reaction was completed, the sample was washed with water 5 times and dried overnight. Manganese nitrate was added to 5 mL of methanol to prepare a 200 μmol / mL -1 Mn(NO3)2methanol solution. 1 mL of the prepared Mn(NO3)2methanol solution was added to 250 mg of the expanded zeolite, and ultrasonic treatment was performed for 270 min.

[0052] After vacuum drying overnight, the above material was pyrolyzed at 550°C under an argon atmosphere for 110 min, and then removed to obtain Mn-zeolite.

[0053] A 0.1 mol / L cobalt nitrate aqueous solution was prepared, and the Mn-zeolite and the cobalt nitrate solution were mixed at a solid-liquid ratio of 1:80 and heated and stirred to replace the unreacted Mn ions with Co ions. After washing with deionized water 10 times, drying was performed at 110°C overnight.

[0054] The obtained powder was calcined at 500°C in an air atmosphere for 180 min, and then removed to obtain the product.

[0055] The catalyst performance was evaluated as in Example 1, and the results are shown in Figure 2 , 4 . Example 3

[0056] The ZSM-5 zeolite was ground and sieved to a particle powder of 20-40 mesh and dried. A 0.5 mol / L nitric acid solution was prepared, and the above zeolite and the prepared nitric acid solution were placed in a three-necked flask at a solid-liquid ratio of 1:12, stirred in a 100°C reflux device for 4 h, and after the reaction was completed, the sample was washed with water 5 times and dried overnight. Manganese chloride was added to 5 mL of butanol to prepare a 50 μmol / mL -1 MnCl2butanol solution; 1.7 mL of the prepared MnCl2butanol solution was added to 250 mg of the expanded zeolite, and ultrasonic treatment was performed for 180 min.

[0057] After vacuum drying overnight, the above material was pyrolyzed at 450°C under an argon atmosphere for 70 min, and then removed to obtain Mn-zeolite.

[0058] A 1 mol / L cerium nitrate aqueous solution was prepared, and the Mn-zeolite and the cerium nitrate solution were mixed at a solid-liquid ratio of 1:50 and heated and stirred to replace the unreacted Mn ions with Ce ions. After washing with deionized water 10 times, drying was performed at 110°C overnight.

[0059] The obtained powder was taken out after calcination at 500°C for 180 min in an air atmosphere to obtain a catalyst.

[0060] The catalyst performance was evaluated as in Example 1, and the results are shown in Table 1. Figure 3 、 4 Table 1 Example 4

[0061] After the beta zeolite was ground and crushed, it was sieved into a 20-40 mesh granular powder and dried. A 1 mol / L nitric acid solution was prepared, and the above zeolite and the prepared nitric acid solution were placed in a three-necked flask at a solid-liquid ratio of 1:10, and stirred in a 80°C reflux device for 6 h. After the reaction was completed, the sample was washed with water 5 times and dried overnight. 0.11 g of manganese acetate tetrahydrate was added to 5 mL of ethanol to prepare a 150 μmol / mL Mn(CH3COO)2ethanol solution. 1.7 mL of the prepared Mn(CH3COO)2ethanol solution was added to 250 mg of the expanded beta zeolite, and ultrasonic treatment was performed for 250 min. -1

[0062] After vacuum drying overnight, the above material was pyrolyzed at 500°C for 90 min in an argon atmosphere, and then taken out to obtain a Mn-zeolite.

[0063] A 0.1 mol / L aqueous ferric nitrate solution was prepared, and the Mn-zeolite and the ferric nitrate solution were mixed at a solid-liquid ratio of 1:60 and heated and stirred to replace the unreacted Mn ions with Fe ions. After washing with deionized water 10 times, drying was performed at 110°C overnight.

[0064] The obtained powder was taken out after calcination at 550°C for 180 min in an air atmosphere to obtain a Fe-Mn / beta.

[0065] As a control, the above method was used, except that the aqueous ferric nitrate solution was not used for replacement, and a Mn / beta catalyst was obtained directly by secondary calcination.

[0066] The prepared catalysts Fe-Mn / beta and Mn / beta were characterized by H2-TPR, and the results are shown in Table 2. Figure 5 ​The signal value around 472 °C can be detected in Fe-Mn / beta, which may correspond to the reduction of some FeOx species. Since the first reduction peak of the catalyst usually determines its reducibility, it can be seen that the first reduction peak in Fe-Mn / beta moves to low temperature compared with Mn / beta and Fe-Mn / beta, indicating that the increase of Fe improves the reducibility of metal oxides. In addition, unlike Mn / beta, a reduction peak around 359 °C is observed in Fe-Mn / beta. The results show that the addition of the second metal increases the electron transfer between Fe-Mn complex oxides, changes the reducibility of the catalyst, and further confirms the interaction between the second metal and Mn.

Claims

1. A method for preparing a double-boat catalyst for ozone catalytic oxidation in a bottle, characterized by, The method comprises the following steps: (1) mixing a manganese salt solution with a dealuminated zeolite and ultrasonic treatment to obtain a first precursor; The dealuminated zeolite is prepared by the following method: placing dry zeolite in an acid solution for dealuminization reaction; the zeolite is one of beta zeolite, Y zeolite or ZSM-5, and the silica-alumina ratio in the zeolite is above 5; (2) pyrolyzing the first precursor in an inert atmosphere to obtain a second precursor; (3) mixing the second precursor with a metal salt solution for ion exchange reaction to obtain a third precursor; The molar ratio of the manganese salt in step (1) to the metal salt in step (3) is 1:3-3:1; the metal salt solution is a salt solution of Cu, Co, Ce or Fe; (4) high-temperature calcination of the third precursor to obtain the catalyst.

2. The production method according to claim 1, characterized by, The manganese salt in step (1) is manganese acetate, manganese nitrate, manganese chloride or manganese sulfate.

3. The preparation method according to claim 1, characterized in that The ultrasonic treatment time in step (1) is 180-270 min.

4. The production method according to claim 1, characterized by, The pyrolysis temperature in step (2) is 450-550℃, and the pyrolysis time is 70-110 min.

5. The method of claim 1, wherein, The metal salt solution in step (3) is an acetate, a sulfate, a nitrate or a chloride.

6. The method of claim 1, wherein, The calcination temperature in step (4) is 500-550℃, and the calcination time is 180 min.

7. A bottle-shaped double-boat catalyst for ozone catalytic oxidation prepared by the preparation method of any one of claims 1-6.

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