Catalyst for Degrading Ozone, Preparation Method Thereof, and Method for Degrading Ozone

Abstract

The present invention relates to the technical field of ozone degradation, and specifically relates to a catalyst for degrading ozone, a preparation method thereof, and a method for degrading ozone. The catalyst comprises a composite support and an active component supported on the composite support. The composite support comprises cordierite and a microwave absorption component. Among them, the microwave absorption component is selected from at least one of silicon carbide, titanium dioxide, barium titanate, and tungsten disulfide. The active component comprises manganese oxide and a second metal oxide. The second metal oxide is selected from at least one of oxides of cobalt, cerium, zirconium, chromium, and molybdenum. By using the composite material of cordierite and the microwave absorption component as the catalyst support, the present invention can increase the microwave absorption capacity of the catalyst bed layer, enable the catalyst to absorb microwaves and convert them into heat, and has a fast response speed, so that the catalyst can be heated quickly and evenly, thereby improving the treatment efficiency of ozone.

Description

Technical Field

[0001] The present invention relates to the technical field of ozone degradation, and specifically relates to a catalyst for degrading ozone, a preparation method thereof, and a method for degrading ozone. Background Art

[0002] In recent years, the problem of excessive ozone concentration has gradually replaced the problem of excessive PM2.5 and become the biggest obstacle to improving the air quality of cities. Ozone treatment has become one of the main goals of the next step of air pollution control. The sources of ozone mainly include two parts. One part is generated by the photochemical reaction of nitrogen oxides and volatile organic compounds (VOCs) emitted by industries. This part of ozone is unorganized and is greatly affected by temperature and weather. The best current control method is to control the precursors of ozone generation and strengthen the treatment of VOCs and nitrogen oxides. The other part of ozone is generated during industrial production or gas treatment processes, and this part of ozone is discharged in an organized manner and needs to be centrally treated.

[0003] The ozone discharged in an organized manner has the following characteristics: the ozone concentration generated during industrial production processes is relatively low; some production devices operate intermittently, resulting in intermittent ozone emissions.

[0004] Currently, the treatment method for ozone discharged in an organized manner is: passing ozone into a catalyst bed containing a catalyst for degradation, and heating the catalyst bed to make the catalyst reach the catalytic reaction temperature; this method has the following disadvantages: 1. The heating rate of the catalyst is slow and the heating is uneven; 2. The catalytic device needs to operate continuously for a long period and cannot operate intermittently, resulting in high production energy consumption and low energy utilization rate. Therefore, the traditional catalytic degradation technology cannot meet the requirements, so it is urgent to develop a new type of efficient ozone degradation technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the fact that traditional catalysts cannot meet the requirements for efficient ozone degradation, and to provide a catalyst for degrading ozone, a preparation method thereof, and a method for degrading ozone.

[0006] To achieve the above purpose, in the first aspect of the present invention, a catalyst for degrading ozone is provided. The catalyst includes a composite support and an active component supported on the composite support. The composite support includes cordierite and a microwave absorption component; wherein, the microwave absorption component is selected from at least one of silicon carbide, titanium dioxide, barium titanate, and tungsten disulfide;

[0007] The active component includes manganese oxide and a second metal oxide; the second metal oxide is selected from at least one of oxides of cobalt, cerium, zirconium, chromium, and molybdenum.

[0008] The second aspect of the present invention provides a method for preparing the catalyst described in the first aspect above, the method comprising:

[0009] (1) Compressing and molding a mixture obtained by mixing magnesium oxide, aluminum oxide, silicon dioxide and a microwave absorption component to obtain a pressed sample; then subjecting the pressed sample to a first calcination to obtain a composite support;

[0010] Reacting potassium permanganate with a manganese salt to obtain precursor 1;

[0011] (2) Mixing a second metal oxide with the precursor 1 in an aluminum sol to obtain a mixed solution;

[0012] (3) Acidifying the composite support, and then impregnating the acidified support obtained by the acidification treatment in the mixed solution to obtain precursor 2;

[0013] (4) Subjecting the precursor 2 to a second calcination to obtain a catalyst;

[0014] Wherein, the microwave absorption component is selected from at least one of silicon carbide, titanium dioxide, barium titanate, and tungsten disulfide;

[0015] The second metal oxide is selected from at least one of oxides of cobalt, cerium, zirconium, chromium and molybdenum.

[0016] The third aspect of the present invention provides a catalyst prepared by the method described in the second aspect above.

[0017] The fourth aspect of the present invention provides a method for degrading ozone, the method comprising: reacting ozone with a catalyst in the presence of microwaves, wherein the catalyst comprises the catalyst described in the first aspect or the third aspect above.

[0018] By the above technical solutions, the present invention has the following technical effects:

[0019] 1. By using a composite material of cordierite and a microwave absorption component as a catalyst support, the present invention can increase the microwave absorption capacity of the catalyst bed layer, enable the catalyst to absorb microwaves and convert them into heat, and has a fast response speed, so that the catalyst can be heated quickly and evenly, thereby improving the treatment efficiency of ozone;

[0020] 2. The catalyst provided by the present invention can exhibit high ozone degradation ability in a microwave field;

[0021] 3. The catalyst provided by the present invention can intermittently treat ozone, and the catalytic reaction device does not need to operate for a long period, which can reduce production energy consumption;

[0022] 4. The preparation method of the catalyst is simple and suitable for industrial production. Detailed implementation manners

[0023] The endpoint values and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0024] As mentioned above, the first aspect of the present invention provides a catalyst for degrading ozone. The catalyst includes a composite carrier and an active component supported on the composite carrier. The composite carrier includes cordierite and a microwave absorption component. Among them, the microwave absorption component is selected from at least one of silicon carbide, titanium dioxide, barium titanate, and tungsten disulfide.

[0025] The active component includes manganese oxide and a second metal oxide.

[0026] The second metal oxide is selected from at least one of oxides of cobalt, cerium, zirconium, chromium, and molybdenum.

[0027] The present invention uses a composite material of cordierite and a microwave absorption component as a catalyst carrier, and loads a specific active component on the catalyst carrier, so that the catalyst has high catalytic activity in a microwave field and can achieve rapid and efficient degradation of ozone without a heat source.

[0028] In some preferred implementation manners of the present invention, in order to improve the microwave absorption ability and microwave conversion ability of the catalyst, under preferred conditions, the weight ratio of the cordierite to the microwave absorption component is 2-10:1, preferably 3-9:1.

[0029] According to the present invention, in order to improve the catalytic activity of the catalyst in a microwave field, under preferred conditions, based on the total amount of the catalyst, the weight content of the active component is 2wt%-5wt%, for example, it can be 2wt%, 3wt%, 4wt%, 5wt% or any value within the range composed of any two of the above numerical values.

[0030] According to the present invention, in order to further optimize the catalytic performance of the catalyst in a microwave field, under preferred conditions, the molar ratio of the manganese oxide to the second metal oxide is 3-8:1; for example, it can be 3:1, 4:1, 5:1, 8:1 or any value within the range composed of any two of the above ratios; further preferably, the second metal oxide is preferably one of oxides of cobalt (Co), cerium (Ce), zirconium (Zr), chromium (Cr), molybdenum (Mo), and silver (Ag); most preferably, it is cerium oxide or zirconium oxide.

[0031] The second aspect of the present invention provides a method for preparing the catalyst described in the first aspect above, and the method includes:

[0032] (1) Compressing and molding a mixture obtained by mixing magnesium oxide, aluminum oxide, silicon dioxide and a microwave absorbing component to obtain a pressed sample; then subjecting the pressed sample to a first calcination to obtain a composite support;

[0033] Reacting potassium permanganate with a manganese salt to obtain a precursor 1;

[0034] (2) Mixing a second metal oxide with the precursor 1 in an aluminum sol to obtain a mixed solution;

[0035] (3) Acidifying the composite support, and then impregnating the acidified support obtained by the acidification treatment in the mixed solution to obtain a precursor 2;

[0036] (4) Subjecting the precursor 2 to a second calcination to obtain a catalyst;

[0037] Wherein, the microwave absorbing component is selected from at least one of silicon carbide, titanium dioxide, barium titanate, and tungsten disulfide;

[0038] The second metal oxide is selected from at least one of oxides of cobalt, cerium, zirconium, chromium, and molybdenum.

[0039] In the present invention, by calcining magnesium oxide, aluminum oxide, silicon dioxide and a microwave absorbing component, the obtained composite support can convert microwaves into heat in a microwave field, enabling the catalyst to be heated quickly and uniformly.

[0040] In some preferred embodiments of the present invention, in order to optimize the microwave absorption ability of the composite support in a microwave field and improve the heating rate and catalytic effect of the catalyst, under preferred conditions, in step (1), the weight ratio of magnesium oxide, aluminum oxide, silicon dioxide and the microwave absorbing component is 13.5 - 13.9: 34.5 - 35: 51 - 52: 10 - 35, for example, it can be 13.7: 34.9: 51.4: 10 - 35.

[0041] According to the present invention, in step (1), the mixing includes: ball milling a slurry obtained by mixing magnesium oxide, aluminum oxide, silicon dioxide and a microwave absorbing component in a solvent; wherein, the solvent is acetone and / or ethanol, preferably composed of acetone and ethanol in a volume ratio of 1: 0.8 - 1.2; preferably, based on the total amount of the slurry, the content of the solvent is 30 - 50 wt%.

[0042] Under preferred conditions, step (1) further includes: drying the mixture obtained by ball milling at 80 - 100°C for 12 - 48 h.

[0043] Under preferred conditions, in step (1), the pressing and forming includes: adding a solvent to the product obtained by the above drying, then stirring at a rotation speed of 500 - 2000 rpm for 6 - 24 h, and then standing for 12 - 48 h before pressing and forming, wherein the conditions for the pressing and forming include: the pressure is 100 - 200 MPa; under preferred conditions, the solvent is acetone and / or ethanol, preferably composed of acetone and ethanol in a volume ratio of 1:0.8 - 1.2; preferably, based on the total amount of the product obtained by the drying, the dosage of the solvent is 3 - 8 wt%.

[0044] Under preferred conditions, step (1) further includes: drying the pressed sample at 80 - 100°C for 4 - 8 h.

[0045] In the present invention, under preferred conditions, in step (1), the conditions for the first roasting include: heating the pressed sample from room temperature to 750 - 850°C at a heating rate of 6 - 10°C / min; then heating the pressed sample from 750 - 850°C to 1150 - 1250°C at a heating rate of 3 - 5°C / min; then holding at 1150 - 1250°C for 2 - 4 h, and then cooling the pressed sample from 1150 - 1250°C to 750 - 850°C at a cooling rate of 2 - 4°C / min; then naturally cooling to room temperature. Under the above preferred conditions, the pore size uniformity and specific surface area of the composite support can be improved.

[0046] According to the present invention, in order to remove impurities on the surface of the composite support, under preferred conditions, step (1) further includes: cleaning and drying the composite support obtained by the first roasting; the cleaning method can be known to those skilled in the art, for example, it can be ultrasonic cleaning, and the frequency of the ultrasonic cleaning is 30 - 60 kHz; the drying method can be known to those skilled in the art, for example, it can be: the temperature is 80 - 120°C, and the time is 1 - 3 h.

[0047] According to the present invention, acidifying the composite support can increase the specific surface area and surface roughness of the support, which is more conducive to the loading of the active component; in step (1), the acidification includes: soaking the precursor 1 in an acidic solution for 2.5 - 3.5 h; preferably, the acidic solution is selected from one of oxalic acid, hydrochloric acid, and nitric acid; further preferably, the weight concentration of the oxalic acid is 40 - 60 wt%, for example, it can be 40 wt%, 50 wt%, 60 wt%, or any value within the range composed of any two of the above values; the concentration of the hydrochloric acid is 0.5 - 2 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, or any value within the range composed of any two of the above values; the concentration of the nitric acid is 0.5 - 2 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, or any value within the range composed of any two of the above values.

[0048] In some preferred embodiments of the present invention, in step (2), the weight ratio of the second metal oxide to the precursor 1 is 1:3 - 8; preferably 1:4 - 6.5.

[0049] In some preferred embodiments of the present invention, in step (3), the impregnation time is 10 - 30 min.

[0050] In the present invention, the second calcination can cause the active component to adhere to the support. Under preferred conditions, in step (4), the conditions of the second calcination include: the temperature is 250 - 350 °C, and the time is 2.5 - 4 h;

[0051] Preferably, in order to improve the adhesion strength between the active component and the support, the conditions of the second calcination further include: heating the precursor 2 from room temperature to 250 - 300 °C at a heating rate of 1 - 3 °C / min.

[0052] In the present invention, the morphology of the composite support can be adjusted during the pressing and forming process according to actual needs; for example, when used for industrial treatment of ozone, a honeycomb - shaped composite support is required. During pressing and forming, the mixture obtained by mixing the raw materials can be put into a specific mold and pressed into a honeycomb - shaped pressed sample; after the honeycomb - shaped pressed sample is subjected to the first calcination, a honeycomb - shaped composite support is obtained.

[0053] In the present invention, the preparation method of the aluminum sol may be known to those skilled in the art. In a preferred embodiment of the present invention, the preparation method of the aluminum sol includes: ultrasonically dissolving aluminum isopropoxide in absolute ethanol to obtain an ethanol solution of aluminum isopropoxide; then, at 60-100 °C, dropping a mixed solution of dilute nitric acid and ethanol into the ethanol solution of aluminum isopropoxide, and then stirring for 1-3 h to fully hydrolyze aluminum isopropoxide to obtain an aluminum sol.

[0054] According to a particularly preferred embodiment of the present invention, the method for preparing the catalyst includes:

[0055] 1. Preparation of the composite support:

[0056] Ball-milling a slurry obtained by mixing magnesium oxide, aluminum oxide, silicon dioxide and a microwave absorption component in a weight ratio of 13.7:34.9:51.4:10-35 in a solvent, wherein the solvent is composed of acetone and ethanol in a volume ratio of 1:0.8-1.2; based on the total amount of the slurry, the content of the solvent is 30-50 wt%;

[0057] Drying the ball-milled product at 80-100 °C for 12-48 h, adding a solvent to the dried product, then stirring at a rotation speed of 500-2000 rpm for 6-24 h, and then standing for 12-48 h and then pressing and molding to obtain a honeycomb-shaped pressed sample, and the conditions for the pressing and molding include: the pressure is 100-200 MPa; the solvent is composed of acetone and ethanol in a volume ratio of 1:0.8-1.2; based on the total amount of the product obtained by drying, the amount of the solvent used is 3-8 wt%;

[0058] Placing the pressed sample in a high-temperature sintering furnace for the first roasting after drying, and the conditions for the first roasting include: heating the pressed sample from room temperature to 750-850 °C at a heating rate of 6-10 °C / min; then heating the pressed sample from 750-850 °C to 1150-1250 °C at a heating rate of 3-5 °C / min; then keeping the temperature at 1150-1250 °C for 2-4 h, and then cooling the pressed sample from 1150-1250 °C to 750-850 °C at a cooling rate of 2-4 °C / min; then naturally cooling to room temperature to obtain a honeycomb-shaped composite support;

[0059] 2. Preparation of precursor 1:

[0060] Under the condition that the stirring speed is 500 - 800 rpm, the potassium permanganate solution is dropped into the solution containing manganese salt at a rate of 3 - 8 mL / min. After the dropping is completed, it is stirred for 10 - 15 h under the condition that the stirring speed is 1000 - 1200 rpm, and then filtered. The obtained filter residue is washed and dried to obtain precursor 1;

[0061] 3. Preparation of the catalyst:

[0062] The honeycomb composite carrier is ultrasonically cleaned and then immersed in an acidic solution for 2.5 - 3.5 h to obtain an acidified carrier;

[0063] The second metal oxide and the precursor 1 are dispersed in aluminum sol at a weight ratio of 1:4 - 6.5, and then stirred at a rotation speed of 800 - 1200 rpm for 2 - 4 h to obtain a mixed solution; the second metal oxide is selected from zirconium oxide or cerium oxide;

[0064] The acidified carrier is impregnated in the mixed solution for 10 - 30 min. After impregnation, the impregnation solution on the surface is purged with compressed air. After purging, it is dried at 100 - 150 °C for 15 - 60 min to obtain precursor 2;

[0065] In an air atmosphere, the precursor 2 is heated from room temperature to 250 - 300 °C at a heating rate of 1 - 3 °C / min and subjected to a second calcination at 250 - 350 °C for 2.5 - 4 h to obtain the catalyst.

[0066] The third aspect of the present invention provides a catalyst prepared by the method according to the second aspect described above.

[0067] Under preferred conditions, the catalyst includes a composite carrier and active components supported on the composite carrier. The composite carrier includes cordierite and a microwave absorption component; wherein, the microwave absorption component is selected from at least one of silicon carbide, titanium dioxide, barium titanate, and tungsten disulfide; the active components include manganese oxide and optionally a second metal oxide; the second metal oxide is selected from one of the oxides of cerium, zirconium, chromium, and molybdenum.

[0068] Further preferably, the weight ratio of the cordierite to the microwave absorption component is 2 - 10:1, preferably 3 - 9:1.

[0069] According to the present invention, in order to improve the catalytic activity of the catalyst in a microwave field, under preferred conditions, based on the total amount of the catalyst, the weight content of the active components is 2 wt% - 5 wt%; the molar ratio of the manganese oxide to the second metal oxide is 3 - 8:1, preferably 4 - 6.5:1.

[0070] In the fourth aspect of the present invention, a method for degrading ozone is provided. The method includes: reacting ozone with a catalyst in the presence of microwaves, wherein the catalyst comprises the catalyst described in the foregoing first aspect or the foregoing fourth aspect; preferably, the frequency of the microwaves is 900 - 2500 MHz, for example, it can be 915 MHz or 2450 MHz.

[0071] The present invention will be described in detail below through examples.

[0072] In the following examples, the room temperature is 25 ± 5 °C.

[0073] The dielectric constant parameter and loss tangent parameter are measured by the oscilloscope Agilent E8363C; the heating rate of the catalyst = (T1 - T2) / t; where T1 is the initial temperature of the catalyst in the microwave field; T2 is the temperature of the catalyst after being treated by microwaves in the microwave field; t is the time required for the catalyst to be heated from T1 to T2 in the microwave field; in the following examples, T1 is 25 °C and T2 is 150 °C.

[0074] In the following examples, the preparation method of the aluminum sol is as follows:

[0075] A. Add 100 g of aluminum isopropoxide to a single-necked flask containing 800 mL of absolute ethanol, then ultrasonicate at 40 kHz for 1 h to fully dissolve the aluminum isopropoxide, and then heat to 75 °C to obtain an ethanol solution of aluminum isopropoxide;

[0076] B. Mix 1.2 mol / L of dilute nitric acid and ethanol to obtain a mixed solution, where the dilute nitric acid is calculated as nitric acid, and the molar ratio of dilute nitric acid to ethanol is 1.1:1; at 80 °C, add the mixed solution dropwise to the ethanol solution of aluminum isopropoxide at a dropping rate of 10 drops per minute. After the dropping is completed, continue to react for 2 h to fully hydrolyze the aluminum isopropoxide to obtain the aluminum sol.

[0077] Preparation of Precursor 1:

[0078] 1) Add 40 g of potassium permanganate to 500 mL of deionized water, stir at 500 rpm for 30 min at room temperature to obtain an aqueous solution of potassium permanganate (Solution A);

[0079] 2) Add 90 g of manganese acetate to 500 mL of deionized water, stir at 500 rpm for 30 min at room temperature to obtain an aqueous solution of manganese acetate (Solution B);

[0080] 3) Drop Solution A into Solution B at a dropping rate of 5 mL / min and a stirring speed of 600 rpm. After the dropping is completed, increase the stirring speed to 1000 rpm and stir for 12 h;

[0081] 4) Filter, wash, and dry the product precipitate obtained in step 3, and then vacuum dry it at 80 °C for 24 h to obtain precursor 1.

[0082] Preparation Example 1

[0083] The raw materials are composed of magnesium oxide powder, aluminum oxide powder, silicon dioxide powder, and silicon carbide in a weight ratio of 10:26:39:25;

[0084] Mix the raw materials and conduct vacuum drying, then add a solvent (the volume ratio of acetone to absolute ethanol is 1:1) to obtain a slurry, and ball-mill the slurry. Based on the total amount of the slurry, the weight content of the solvent is 40 wt%;

[0085] Dry the ball-milled product at 90 °C for 24 h to obtain a dried product; then add a solvent (the volume ratio of acetone to absolute ethanol is 1:1) accounting for 5 wt% of the weight of the dried product, and stir at 1000 rpm for 12 h. After stirring, let it stand for 24 h, and then use a press to press the sample at a pressure of 150 MPa to obtain a pressed sample; dry the pressed sample at 90 °C for 6 h;

[0086] Place the dried pressed sample in a high-temperature sintering furnace for the first roasting. The conditions for the first roasting are: at a heating rate of 8 °C / min, heat the pressed sample from room temperature to 800 °C; then at a heating rate of 5 °C / min, heat the pressed sample from 800 °C to 1200 °C; then hold at 1200 °C for 3 h, and then cool the pressed sample from 1200 °C to 800 °C at a cooling rate of 3 °C / min; then naturally cool to room temperature to obtain composite support A1.

[0087] Preparation Example 2

[0088] According to the method of Preparation Example 1, except that the raw materials are composed of magnesium oxide powder, aluminum oxide powder, silicon dioxide powder, and silicon carbide in a weight ratio of 13:31:46:10, composite support A2 is obtained.

[0089] Preparation Example 3

[0090] According to the method of Example 1, except that the raw materials are composed of magnesium oxide powder, aluminum oxide powder, silicon dioxide powder, and titanium dioxide in a weight ratio of 11:28:41:20, composite support A3 is obtained.

[0091] Preparation Example 4

[0092] According to the method of Example 1, except that the raw materials are composed of magnesium oxide powder, aluminum oxide powder, silicon dioxide powder, and tungsten disulfide in a weight ratio of 12:30:43:30, composite support A4 is obtained.

[0093] Table 1

[0094] <![CDATA[MgO: Al2O3: SiO2: Microwave component]]> Microwave component Preparation Example 1 10：26：39：25 SiC Preparation Example 2 13：31：46：10 SiC Preparation Example 3 11：28：41：20 <![CDATA[TiO2]]> Preparation Example 4 12：30：43：30 <![CDATA[WS2]]>

[0095] Preparation Example 5

[0096] According to the method of Example 1, except that the conditions of the first calcination are as follows: at a heating rate of 20 °C / min, the pressed sample is heated from room temperature to 800 °C; then at a heating rate of 10 °C / min, the pressed sample is heated from 800 °C to 1200 °C; then it is held at 1200 °C for 3 h, and then the pressed sample is cooled from 1200 °C to 800 °C at a cooling rate of 20 °C / min; then it is naturally cooled to room temperature to obtain the composite support A5.

[0097] Preparation Example 6

[0098] According to the method of Example 1, except that the conditions of the first calcination are as follows: at a heating rate of 15 °C / min, it is heated from room temperature to 1200 °C; then it is held at 1200 °C for 3 h, and then it is naturally cooled to room temperature to obtain the composite support A6.

[0099] Preparation Example 7

[0100] According to the method of Example 1, except that the conditions of the first calcination are as follows: at a heating rate of 8 °C / min, the pressed sample is heated from room temperature to 500 °C; then at a heating rate of 5 °C / min, the pressed sample is heated from 500 °C to 800 °C; then it is held at 800 °C for 1 h, and then the pressed sample is cooled from 800 °C to 400 °C at a cooling rate of 3 °C / min; then it is naturally cooled to room temperature to obtain the composite support A7.

[0101] Preparation Example 8

[0102] According to the method of Example 1, except that the conditions of the first calcination are as follows: at a heating rate of 8 °C / min, the pressed sample is heated from room temperature to 1000 °C; then at a heating rate of 5 °C / min, the pressed sample is heated from 1000 °C to 1300 °C; then it is held at 1300 °C for 3 h, and then the pressed sample is cooled from 1300 °C to 500 °C at a cooling rate of 3 °C / min; then it is naturally cooled to room temperature to obtain the composite support A8.

[0103] Example 1

[0104] The composite support A1 was ultrasonically cleaned with deionized water (ultrasonic frequency 40 kHz) to remove surface impurities, and then dried at 100 °C for 120 min; the dried composite support A1 was acidified in 50 wt% oxalic acid for 180 min to obtain an acidified support, and then the acidified support was washed with deionized water until neutral, vacuum dried at 100 °C for 180 min, and cooled to room temperature for standby;

[0105] 0.8 parts by weight of cerium oxide and 5 parts by weight of precursor 1 were dispersed in 20 parts by weight of aluminum sol, and vigorously stirred at 10,000 rpm for 180 min to obtain a mixed solution;

[0106] The acidified support was impregnated in the mixed solution for 15 min. After impregnation, the impregnation solution on the surface was purged with compressed air. After purging, it was dried at 120 °C for 30 min to obtain precursor 2;

[0107] Precursor 2 was placed in a muffle furnace for the second calcination. The conditions for the second calcination were: air atmosphere, heating rate of 2 °C / min to 300 °C, and then calcined at 300 °C for 3 h to obtain catalyst B1.

[0108] Example 2

[0109] The composite support A1 was ultrasonically cleaned with deionized water (ultrasonic frequency 40 kHz) to remove surface impurities, and then dried at 100 °C for 120 min; the dried composite support A1 was acidified in 1 mol / L nitric acid for 200 min to obtain an acidified support, and then the acidified support was washed with deionized water until neutral, vacuum dried at 100 °C for 180 min, and cooled to room temperature for standby;

[0110] 0.5 parts by weight of cerium oxide and 4 parts by weight of precursor 1 were dispersed in 18 parts by weight of aluminum sol, and vigorously stirred at 10,000 rpm for 180 min to obtain a mixed solution;

[0111] The acidified support was impregnated in the mixed solution for 15 min. After impregnation, the impregnation solution on the surface was purged with compressed air. After purging, it was dried at 120 °C for 30 min to obtain precursor 2;

[0112] Precursor 2 was placed in a muffle furnace for the second calcination. The conditions for the second calcination were: air atmosphere, heating rate of 2 °C / min to 300 °C, and then calcined at 300 °C for 3 h to obtain catalyst B2.

[0113] Example 3

[0114] According to the method of Example 1, the difference was that cobalt oxide was used instead of cerium oxide, and the amount of cobalt oxide used was 1 part by weight to obtain catalyst B3.

[0115] Example 4

[0116] According to the method of Example 1, except that zirconia is used instead of ceria, and the amount of zirconia is 0.5 parts by weight, catalyst B4 is obtained.

[0117] Example 5

[0118] According to the method of Example 1, except that the conditions for the second calcination are: air atmosphere, heating rate of 5 °C / min to 500 °C, and then calcination at 500 °C for 3 h, catalyst B6 is obtained.

[0119] Example 6

[0120] According to the method of Example 1, except that the conditions for the second calcination are: air atmosphere, heating rate of 2 °C / min to 800 °C, and then calcination at 800 °C for 3 h, catalyst B6 is obtained.

[0121] Examples 7 - 13

[0122] According to the method of Example 1, except that composite supports A2 - A8 are used instead of composite support A1 respectively, catalysts B7 - B13 are obtained.

[0123] Comparative Example 1

[0124] According to the method of Example 1, except that composite support A1 is not acidified, catalyst C1 is obtained.

[0125] Comparative Example 2

[0126] The commercially available cordierite support is ultrasonically cleaned with deionized water (ultrasonic frequency 40 kHz) to remove surface impurities, and then dried at 100 °C for 120 min to obtain a support; the dried support is acidified in 50 wt% oxalic acid for 180 min, and then the acidified support is washed with deionized water until neutral, vacuum dried at 100 °C for 180 min, and cooled to room temperature to obtain an acidified support;

[0127] 4 parts by weight of precursor 1 is dispersed in 20 parts of aluminum sol and stirred vigorously at 10000 rpm for 180 min to obtain a mixed solution;

[0128] The acidified support is impregnated in the mixed solution for 15 min. After impregnation, the surface impregnation solution is purged with compressed air. After purging, it is dried at 120 °C for 30 min to obtain precursor 2;

[0129] Precursor 2 is placed in a muffle furnace for the second calcination. The conditions for the second calcination are: air atmosphere, heating rate of 2 °C / min to 300 °C, and then calcination at 300 °C for 3 h to obtain catalyst C2.

[0130] Comparative Example 3

[0131] According to the method of Example 1, except that cerium oxide was not added, catalyst C3 was obtained.

[0132] Comparative Example 4

[0133] According to the method of Example 1, except that 1 part by weight of cerium oxide and 4 parts by weight of precursor 1 were dispersed in 18 parts by weight of water and vigorously stirred at 10000 rpm for 180 min to obtain a mixture, catalyst C4 was obtained.

[0134] Table 2

[0135]

[0136] In Table 2, M2Ox refers to the second metal oxide.

[0137] Test Example

[0138] Catalysts B7 - B13 and catalysts C1 - C4 were respectively placed in a microwave reactor. The power of the microwave power supply was 1 kW, generating microwaves with a frequency of 2450 MHz, and the microwaves were fed into the microwave reactor. A simulator with a composition of 10000 ppm (mass) ozone was introduced into the reactor. The gas inlet temperature was at room temperature, the gas residence time was 0.1 s, the dosage of the catalyst was 1 L, and an ozone concentration analyzer was used to detect the ozone concentration at the gas outlet. The experimental results are shown in Table 3.

[0139] Among them, the conversion rate = (C in - C out ) / C in × 100%.

[0140] C in represents the concentration of ozone at the reactor inlet, with the unit of ppm;

[0141] C out represents the concentration of ozone at the reactor outlet, with the unit of ppm.

[0142] Table 3

[0143]

[0144] As can be seen from Table 3, the catalysts prepared in the embodiments of the present invention all have high catalytic performance in the microwave field, and ozone can be completely converted. Different contents and types of microwave-absorbing components in the catalysts cause these catalysts to exhibit different heating rates in the microwave field. In Comparative Example 2, since the carrier does not contain microwave-absorbing components, the temperature of the bed layer is low under microwave irradiation, and only local hot spots exist on the catalyst, so the conversion rate of ozone is very low. In Comparative Example 4, without using aluminum sol, the loading and specific surface area of the overall catalyst are low, resulting in a low conversion rate of ozone.

[0145] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst, characterized in that, The method includes: (1) Compressing and molding a mixture obtained by mixing magnesium oxide, aluminum oxide, silicon dioxide, and a microwave absorption component to obtain a pressed sample; then subjecting the pressed sample to a first calcination to obtain a composite support; the weight ratio of magnesium oxide, aluminum oxide, silicon dioxide, and the microwave absorption component is 13.5 - 13.9:34.5 - 35:51 - 52:10 - 35; Reacting potassium permanganate with a manganese salt to obtain precursor 1; (2) Mixing a second metal oxide with the precursor 1 in an aluminum sol to obtain a mixed solution; the weight ratio of the second metal oxide to the precursor 1 is 1:3 - 8; (3) Acidifying the composite support, and then impregnating the acidified support obtained by the acidification treatment in the mixed solution to obtain precursor 2; (4) Subjecting the precursor 2 to a second calcination to obtain a catalyst; Wherein, the microwave absorption component is selected from at least one of silicon carbide, titanium dioxide, barium titanate, and tungsten disulfide; The second metal oxide is selected from at least one of oxides of cobalt, cerium, zirconium, chromium, and molybdenum.

2. The method according to claim 1, wherein, In step (1), the conditions of the first calcination include: heating the pressed sample from room temperature to 750 - 850 °C at a heating rate of 6 - 10 °C / min; then heating the pressed sample from 750 - 850 °C to 1150 - 1250 °C at a heating rate of 3 - 5 °C / min; then holding at 1150 - 1250 °C for 2 - 4 h, and then cooling the pressed sample from 1150 - 1250 °C to 750 - 850 °C at a cooling rate of 2 - 4 °C / min; then naturally cooling to room temperature.

3. The method according to claim 1, wherein, In step (1), the acidification treatment includes: soaking the precursor 1 in an acidic solution for 2.5 - 3.5 h.

4. The method according to claim 3, wherein, The acidic solution is selected from at least one of oxalic acid, hydrochloric acid, and nitric acid.

5. The method according to claim 1, wherein, In step (2), the weight ratio of the second metal oxide to the precursor 1 is 1:4 - 6.

5.

6. The method according to any one of claims 1-5, wherein, In step (3), the impregnation time is 10 - 30 min.

7. The method according to any one of claims 1-5, wherein, In step (4), the conditions of the second calcination include: the temperature is 250 - 350 °C, and the time is 2.5 - 4 h.

8. The method according to claim 7, wherein, The conditions of the second calcination further include: heating the precursor 2 from room temperature to 250 - 300 °C at a heating rate of 1 - 3 °C / min.

9. A catalyst prepared by the method according to any one of claims 1-8.

10. A method for degrading ozone, characterized in that, The method includes: reacting ozone with the catalyst in the presence of microwaves, wherein the catalyst comprises the catalyst as claimed in claim 9.

11. The method for degrading ozone according to claim 10, wherein, The frequency of the microwaves is 900 - 2500 MHz.

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