A composite catalyst for synergistically removing nitrogen oxides and chlorine-containing organic compounds, a preparation method and application thereof

Abstract

The application discloses a preparation method of a composite catalyst for synergistically removing chlorine-containing organic matters and NOx, and the steps are as follows: raw materials, i.e., piezoelectric materials and nitrate of transition metal, are added into a ball mill jar according to a mass ratio of 1:(0.25-4) to obtain ball-milled material A; the ball-milled material A is dried in a vacuum oven to obtain material B; the material B is calcined in an air atmosphere to obtain the composite catalyst; the nitrate of transition metal is a mixed nitrate of manganese nitrate and one of cerium nitrate, cobalt nitrate and nickel nitrate. The heterojunction is constructed by ball milling to reduce the high dielectric constant and electron transfer resistance of the composite catalyst, improve the transfer rate of holes and electrons, increase the charge amount participating in the surface redox reaction, and thus improve the synergistic catalytic degradation performance of pollutants in waste incineration flue gas.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalyst preparation, and in particular relates to a composite catalyst for synergistic denitration and dechlorinated organic matter, and a preparation method and application thereof. BACKGROUND

[0002] Incineration has become the main way of waste disposal, and the emission standard of waste incineration flue gas is becoming increasingly stringent, and the control of incineration pollutants needs to be strengthened. In the existing pollutant treatment process, a single module is often used to treat a single pollutant, resulting in a large number of modules in series, large space requirements, and high investment costs. Therefore, the research on the synergistic removal of nitrogen oxides and chlorinated organic matter in low-temperature incineration flue gas is an inevitable trend in this field, and the development of a synergistic catalyst with good low-temperature activity has become an urgent need for current incineration flue gas purification. However, the existing problems such as poor synergistic performance and low selectivity greatly restrict the rapid development of synergistic catalytic technology. In view of this problem, methods such as metal oxide doping and separation of active sites are currently used to make certain improvements, but there is still a lot of room for development.

[0003] In recent years, it has been found that the built-in electric field generated by the piezoelectric effect is beneficial to promoting charge separation and transfer. BaTiO3 is a typical ABO3 type perovskite with excellent piezoelectric properties and thermal stability. Under the action of external mechanical force, the surface of BaTiO3 will induce charges due to the piezoelectric effect, and if the potential of these charges exceeds a certain value, they will participate in the corresponding reaction. Metal oxides have high dielectric constant and electron transfer resistance, and the transfer rate of holes and electrons is slow and multiple, which reduces the amount of charges participating in the surface oxidation-reduction reaction, thereby significantly inhibiting the synergistic catalytic performance. Therefore, inducing the formation of a heterojunction between the piezoelectric material and the metal oxide through ball milling is an attractive strategy.

[0004] Although there have been many studies on improving catalyst performance by constructing a heterojunction, these improvements in catalytic performance are mainly achieved through the synergistic effect of light and pressure field, however, this method cannot effectively solve the problem of poor catalytic performance without light or pressure field. The present patent proposes a method for preparing a high-performance composite catalyst through the piezoelectric effect of piezoelectric materials during ball milling, which realizes the synergistic denitration and dechlorinated organic matter in the temperature field. SUMMARY

[0005] In order to solve at least one of the above problems, the present application provides a composite catalyst for synergistic denitration and dechlorinated organic matter, and a preparation method and application thereof. The composite catalyst is a metal oxide-based piezoelectric catalyst material, which can be used for the synergistic degradation of multiple pollutants in waste incineration flue gas in a wide temperature range of 90-400℃.

[0006] In order to achieve the above object, the present application adopts the following technical means:

[0007] The first aspect of the present application provides a preparation method of a composite catalyst for synergistic denitration and dechlorinated organic matter removal, comprising the following steps:

[0008] S1, raw materials: piezoelectric material and nitrate of transition metal are added into a ball mill jar in a mass ratio of 1:(0.25-4) for ball milling to obtain a ball milled material A;

[0009] S2, the ball milled material A is placed in a vacuum oven for drying to obtain a material B;

[0010] S3, the material B is calcined in an air atmosphere to obtain the composite catalyst;

[0011] The nitrate of transition metal is a mixed nitrate of manganese nitrate and one or more of cerium nitrate, cobalt nitrate and nickel nitrate.

[0012] In some embodiments of the present application, preferably, the mass ratio of the piezoelectric material to the nitrate of transition metal is 1:4.

[0013] In some embodiments of the present application, the piezoelectric material is one of barium titanate, lithium niobate and sodium potassium niobate.

[0014] In some embodiments of the present application, in the mixed nitrate, the mass fraction of manganese nitrate is 35-45%.

[0015] In some embodiments of the present application, in the step S1, the mass ratio of the raw materials to the ball milling beads in the ball mill jar is (0.5-2.5):(10-15), and the raw materials occupy 1 / 3 of the volume of the ball mill jar.

[0016] In some embodiments of the present application, in the step S1, the ball milling conditions of the ball mill jar are: ball milling speed 300-600 r / min, and ball milling time 2-6 hours.

[0017] In some embodiments of the present application, in the step S2, the drying conditions are: drying temperature 90-110℃, and drying time 10-24 hours.

[0018] In some embodiments of the present application, in the step S3, the calcination conditions are: calcination temperature 300-500℃, and calcination time 2-5 hours.

[0019] The second aspect of the present application provides a composite catalyst prepared by the method according to the first aspect.

[0020] The third aspect of the present application provides the use of the composite catalyst of the second aspect in synergistically catalyzing the degradation of gaseous pollutants, including nitrogen oxides and chlorine-containing organic compounds. It can be applied in the degradation of atmospheric pollutants, and also in the synergistic catalysis of multiple pollutants in waste incineration flue gas.

[0021] In some embodiments of the present application, the temperature range of the synergistically catalyzed degradation of the composite catalyst is 90-400℃.

[0022] In some embodiments of the present application, the application process is as follows: the composite catalyst is placed in a temperature programmed fixed bed, and the synergistic catalytic degradation of nitrogen oxides and chlorine-containing organic compounds is carried out at a temperature range of 90-400℃.

[0023] Advantages of the present application

[0024] Compared with the prior art, the present application has the following advantages: the present application provides a metal oxide-based piezocatalyst, which is prepared by sintering a mixture material prepared by a ball milling method. The ball milling method is simple and can be mass-produced. The present application reduces the high dielectric constant and electron transfer resistance of the metal oxide catalyst by constructing a heterojunction through ball milling, improves the transfer rate of holes and electrons, and increases the amount of charges participating in the surface redox reaction, thereby improving the synergistic catalytic degradation performance of pollutants in waste incineration flue gas. The preparation method of the present application has the characteristics of simple process, safety, environmental protection, and low price, and the catalyst exhibits high synergistic catalytic performance. It can simultaneously catalyze and degrade nitrogen oxides and chlorine-containing organic compounds at a temperature range of 90-400℃. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A scanning electron microscope photograph of the catalyst prepared in Example 1 of the present application is shown;

[0026] Figure 2 A transmission electron microscope photograph of the catalyst prepared in Example 2 of the present application is shown;

[0027] Figure 3 A scanning electron microscope photograph of the catalyst prepared in Comparative Example 1 of the present application is shown;

[0028] Figure 4 A scanning electron microscope photograph of the catalyst prepared in Comparative Example 2 of the present application is shown;

[0029] Figure 5 A scanning electron microscope photograph of the catalyst prepared in Comparative Example 3 of the present application is shown;

[0030] Figure 6FIG. 1 shows a graph of 1,2-dichlorobenzene degradation efficiency of the synergistic catalysis of the chlorine-containing organic matter and NOx by the composite catalyst prepared in Examples 1-7 of the present application;

[0031] Figure 7 FIG. 2 shows a graph of NOx degradation efficiency of the synergistic catalysis of the chlorine-containing organic matter and NOx by the composite catalyst prepared in Examples 1-7 of the present application;

[0032] Figure 8 FIG. 3 shows a graph of 1,2-dichlorobenzene degradation efficiency of the synergistic catalysis of the chlorine-containing organic matter and NOx by the catalyst prepared in Comparative Examples 1-6 of the present application;

[0033] Figure 9 FIG. 4 shows a graph of NOx degradation efficiency of the synergistic catalysis of the chlorine-containing organic matter and NOx by the catalyst prepared in Comparative Examples 1-6 of the present application.

[0034] Figure 10 FIG. 5 shows the electronic band structure of Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4. DETAILED DESCRIPTION

[0035] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present application, and are not intended to limit the scope of what the inventors regard as their application nor are they intended to represent that the experiments below are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (for example, amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Centigrade, and pressure is at or near atmospheric.

[0036] Unless defined otherwise, all technical and scientific terms and any acronyms used herein have the same meanings as commonly understood by one of ordinary skill in the art in the field of the application, and any materials described herein will be understood to be incorporated by reference. Those of ordinary skill will recognize many methods and materials analogous to those described herein but known by those of ordinary skill in the art that could be used in the practice of the present application. The present application embraces all such analogs and equivalents.

[0037] The technical solutions of the present application are further described in detail below in conjunction with the specific embodiments.

[0038] Example 1

[0039] A preparation method of a TB-MnCe2:8 composite catalyst, comprising the following steps: manganese nitrate and cerium nitrate are weighed according to a mass ratio of 4:6, 4.8 g of manganese nitrate and 7.2 g of cerium nitrate; barium titanate and metal oxides are weighed according to a mass ratio of 2:8, 3 g of barium titanate is placed in a ball mill tank together, wherein the ball milling parameters are set as a ball powder mass ratio of 15:1, wherein the zirconia balls are 5mm:10mm=1:1, the rotating speed is 600 rpm, and the time is 6h, to obtain material A after preliminary ball milling, material A is placed in a vacuum oven at 100 DEG C and dried for 10 hours to obtain material B. Material B is calcined in a muffle furnace under an air atmosphere at 400 DEG C for 3 hours, to obtain the composite catalyst, which is recorded as TB-MnCe2:8.

[0040] Example 2

[0041] A preparation method of a TB-MnCe4:6 composite catalyst, comprising the following steps: manganese nitrate and cerium nitrate are weighed according to a mass ratio of 4:6, 3.6 g of manganese nitrate and 5.4 g of cerium nitrate; barium titanate and metal oxides are weighed according to a mass ratio of 4:6, 6 g of barium titanate is placed in a ball mill tank together, wherein the ball milling parameters are set as a ball powder mass ratio of 15:1, wherein the zirconia balls are 5mm:10mm=1:1, the rotating speed is 600 rpm, and the time is 6h, to obtain material A after preliminary ball milling, material A is placed in a vacuum oven at 100 DEG C and dried for 10 hours to obtain material B. Material B is calcined in a muffle furnace under an air atmosphere at 400 DEG C for 3 hours, to obtain the composite catalyst, which is recorded as TB-MnCe4:6.

[0042] Example 3

[0043] A preparation method of a TB-MnCe6:4 composite catalyst, comprising the following steps: manganese nitrate and cerium nitrate are weighed according to a mass ratio of 4:6, 2.4 g of manganese nitrate and 3.6 g of cerium nitrate; barium titanate and metal oxides are weighed according to a mass ratio of 6:4, 9 g of barium titanate is placed in a ball mill tank together, wherein the ball milling parameters are set as a ball powder mass ratio of 15:1, wherein the zirconia balls are 5mm:10mm=1:1, the rotating speed is 600 rpm, and the time is 6h, to obtain material A after preliminary ball milling, material A is placed in a vacuum oven at 100 DEG C and dried for 10 hours to obtain material B. Material B is calcined in a muffle furnace under an air atmosphere at 400 DEG C for 3 hours, to obtain the composite catalyst, which is recorded as TB-MnCe6:4.

[0044] Example 4

[0045] A preparation method of a TB-MnCe8:2 composite catalyst, comprising the following steps: manganese nitrate and cerium nitrate are weighed according to a mass ratio of 4:6, 0.6 g of manganese nitrate and 2.4 g of cerium nitrate; barium titanate and metal oxides are weighed according to a mass ratio of 8:2, 12 g of barium titanate is placed in a ball mill tank, ball powder mass ratio is 15:1, zirconia balls are 5 mm:10 mm=1:1, the rotating speed is 600 rpm, the time is 6 h, material A after preliminary ball milling is obtained, material A is placed in a vacuum oven at 100 DEG C and dried for 10 hours to obtain material B. Material B is calcined in a muffle furnace under air atmosphere at 400 DEG C for 3 hours to obtain the composite catalyst, which is recorded as TB-MnCe8:2.

[0046] Example 5

[0047] A preparation method of a TB-MnCo2:8 composite catalyst, comprising the following steps: manganese nitrate and cobalt nitrate are weighed according to a mass ratio of 4:6, 4.8 g of manganese nitrate and 7.2 g of cerium nitrate; barium titanate and metal oxides are weighed according to a mass ratio of 2:8, 3 g of barium titanate is placed in a ball mill tank, ball powder mass ratio is 15:1, zirconia balls are 5 mm:10 mm=1:1, the rotating speed is 600 rpm, the time is 6 h, material A after preliminary ball milling is obtained, material A is placed in a vacuum oven at 100 DEG C and dried for 10 hours to obtain material B. Material B is calcined in a muffle furnace under air atmosphere at 400 DEG C for 3 hours to obtain the composite catalyst, which is recorded as TB-MnCo2:8.

[0048] Example 6

[0049] A preparation method of a Ni-MnCe2:8 composite catalyst, comprising the following steps: manganese nitrate and cerium nitrate are weighed according to a mass ratio of 4:6, 4.8 g of manganese nitrate and 7.2 g of cerium nitrate; lithium niobate and metal oxides are weighed according to a mass ratio of 2:8, 3 g of barium titanate is placed in a ball mill tank, ball powder mass ratio is 15:1, zirconia balls are 5 mm:10 mm=1:1, the rotating speed is 600 rpm, the time is 6 h, material A after preliminary ball milling is obtained, material A is placed in a vacuum oven at 100 DEG C and dried for 10 hours to obtain material B. Material B is calcined in a muffle furnace under air atmosphere at 400 DEG C for 3 hours to obtain the composite catalyst, which is recorded as Ni-MnCe2:8.

[0050] Example 7

[0051] A preparation method of a NiK-MnCe2:8 composite catalyst, comprising the following steps: manganese nitrate and cerium nitrate are weighed according to a mass ratio of 4:6, 4.8 g of manganese nitrate and 7.2 g of cerium nitrate; sodium potassium niobate and metal oxide are weighed according to a mass ratio of 2:8, 3 g of barium titanate is placed in a ball mill tank, wherein the ball milling parameters are set as a ball powder mass ratio of 15:1, wherein the zirconia ball is 5mm:10mm=1:1, the rotating speed is 600 rpm, and the time is 6h, to obtain material A after preliminary ball milling, material A is placed in a vacuum oven at 100 DEG C and dried for 10 hours to obtain material B. Material B is calcined in a muffle furnace at 400 DEG C in an air atmosphere for 3 hours, to obtain the composite catalyst, which is recorded as NiK-MnCe2:8.

[0052] Comparative example 1

[0053] A preparation method of a MnCe metal oxide catalyst, comprising the following steps: manganese nitrate and cerium nitrate are weighed according to a mass ratio of 4:6, 6 g of manganese nitrate and 9 g of cerium nitrate; the mixture is placed in a ball mill tank, wherein the ball milling parameters are set as a ball powder mass ratio of 15:1, wherein the zirconia ball is 5mm:10mm=1:1, the rotating speed is 600 rpm, and the time is 6h, to obtain material A after preliminary ball milling, material A is placed in a vacuum oven at 100 DEG C and dried for 10 hours to obtain material B. Material B is calcined in a muffle furnace at 400 DEG C in an air atmosphere for 3 hours, to obtain the metal oxide catalyst, which is recorded as MnCe.

[0054] Comparative example 2

[0055] A preparation method of a SiO2-MnCe metal oxide-based piezoelectric catalyst, comprising the following steps: manganese nitrate and cerium nitrate are weighed according to a mass ratio of 4:6, 4.8 g of manganese nitrate and 7.2 g of cerium nitrate; metal oxide and silicon dioxide are weighed according to a mass ratio of 8:2, 3 g of silicon dioxide is placed in a ball mill tank, wherein the ball milling parameters are set as a ball powder mass ratio of 15:1, wherein the zirconia ball is 5mm:10mm=1:1, the rotating speed is 600 rpm, and the time is 6h, to obtain material A after preliminary ball milling, material A is placed in a vacuum oven at 100 DEG C and dried for 10 hours to obtain material B. Material B is calcined in a muffle furnace at 400 DEG C in an air atmosphere for 3 hours, to obtain the metal oxide catalyst, which is recorded as SiO2-MnCe.

[0056] Comparative example 3

[0057] A preparation method of a TBH-MnCe2:8 composite piezoelectric catalyst, comprising the following steps: manganese nitrate and cerium nitrate are weighed according to a mass ratio of 4:6, 4.8 g of manganese nitrate and 7.2 g of cerium nitrate; sodium potassium niobate and metal oxide are weighed according to a mass ratio of 2:8, 3 g of barium titanate is weighed and dissolved together, and a material A after preliminary ball milling is prepared by a coprecipitation method; the material A is placed in a 100℃ vacuum oven and dried for 10 hours to obtain a material B. The material B is calcined in a muffle furnace under an air atmosphere at 400℃ for 3 hours, and a composite piezoelectric catalyst is obtained, which is recorded as TBH-MnCe2:8.

[0058] Comparative example 4

[0059] A preparation method of a piezoelectric catalyst, comprising the following steps: 15 g of barium titanate is placed in a ball milling tank, wherein the ball milling parameters are set as a ball-powder mass ratio of 15:1, wherein the zirconia balls are 5mm:10mm=1:1, the rotating speed is 600rpm, and the time is 6h, to obtain a material A after preliminary ball milling; the material A is placed in a 100℃ vacuum oven and dried for 10 hours to obtain a material B. The material B is calcined in a muffle furnace under an air atmosphere at 400℃ for 3 hours, and a piezoelectric catalyst is obtained, which is recorded as TB.

[0060] Comparative example 5

[0061] A preparation method of a piezoelectric catalyst, comprising the following steps: 15 g of lithium niobate is placed in a ball milling tank, wherein the ball milling parameters are set as a ball-powder mass ratio of 15:1, wherein the zirconia balls are 5mm:10mm=1:1, the rotating speed is 600rpm, and the time is 6h, to obtain a material A after preliminary ball milling; the material A is placed in a 100℃ vacuum oven and dried for 10 hours to obtain a material B. The material B is calcined in a muffle furnace under an air atmosphere at 400℃ for 3 hours, and a piezoelectric catalyst is obtained, which is recorded as Ni.

[0062] Comparative example 6

[0063] A preparation method of a piezoelectric catalyst, comprising the following steps: 15 g of lithium niobate is placed in a ball milling tank, wherein the ball milling parameters are set as a ball-powder mass ratio of 15:1, wherein the zirconia balls are 5mm:10mm=1:1, the rotating speed is 600rpm, and the time is 6h, to obtain a material A after preliminary ball milling; the material A is placed in a 100℃ vacuum oven and dried for 10 hours to obtain a material B. The material B is calcined in a muffle furnace under an air atmosphere at 400℃ for 3 hours, and a piezoelectric catalyst is obtained, which is recorded as Ni.

[0064] Performance test and result analysis

[0065] (1) The prepared TB-MnCe catalysts of Example 1, Example 2, Example 3, Example 4, and Comparative Example 1 and Comparative Example 2 were subjected to the performance test of catalytic degradation of NOx and 1,2-dichlorobenzene by using a temperature programmed fixed bed. After granulation, 0.6 g of the catalyst of 40-60 mesh and 0.4 g of quartz sand of the same particle size were mixed and loaded into a quartz tube, and the quartz tube was loaded on a temperature programmed fixed bed. 200 ppm of 1,2-dichlorobenzene, 400 ppm of NO, 400 ppm of NH3, and 10% of O2 / N2 were introduced at a flow rate of 300 mL / min.

[0066] (2) The composite catalysts prepared in Examples 1-7 above were prepared by the method of the present application under different conditions. The SEM image of the catalyst prepared in Example 1 is shown in Figure 1 , the SEM image of the catalyst prepared in Example 2 is shown in Figure 2 , the SEM image of the catalyst prepared in Comparative Example 1 is shown in Figure 3 , the SEM image of the catalyst prepared in Comparative Example 2 is shown in Figure 4 , and the SEM image of the catalyst prepared in Comparative Example 3 is shown in Figure 5 .

[0067] From the SEM image of Figures 1-2 , it can be seen that the composite catalyst synthesized by ball milling has an ordered and regular polygonal morphology, and the size is uniform and at the nanoscale.

[0068] (3) We conducted degradation experiments of 1,2-dichlorobenzene and NOx using the catalysts prepared in Examples 1-7, and the conversion rates of 1,2-dichlorobenzene and NOx at different temperatures are shown in Table 1, Table 2, and Figure 6 , Figure 7 .

[0069] Table 1 Conversion rate of 1,2-dichlorobenzene at different temperatures in Examples 1-7 (%)

[0070]

[0071] Table 2 Conversion rate of NOx at different temperatures in Examples 1-7 (%)

[0072]

[0073] From the SEM image of Figure 6It can be seen that the composite catalysts obtained by ball milling in Examples 1-4 have good low-temperature 1,2-dichlorobenzene conversion effect, and the effect of the ratio of manganese cerium metal oxide and barium titanate being 8:2 is better than that of other ratios. Example 5 uses ball milling to replace one of the metal salts, manganese nitrate, with cerium nitrate to prepare a composite catalyst, and Examples 6-7 use ball milling to replace the piezoelectric material barium titanate with lithium niobate and sodium potassium niobate, respectively, to have excellent degradation effect on 1,2-dichlorobenzene. Figure 7 It can be seen that the composite catalysts obtained by ball milling in Examples 1-4 have good NO degradation effect, higher conversion rate at low temperature and wider temperature range, and the overall trend is similar to that of 1,2-dichlorobenzene.

[0074] (4) We will use ball milling to prepare catalysts for 1,2-dichlorobenzene and NOx degradation experiments in Comparative Examples 1-6. The conversion rates of 1,2-dichlorobenzene and NOx at different temperatures are shown in Tables 3, 4 and Figure 8 , Figure 9 .

[0075] Table 3 Conversion rate of 1,2-dichlorobenzene at different temperatures in Comparative Examples 1-6 (%)

[0076]

[0077] Table 4 Conversion rate of NOx at different temperatures in Comparative Examples 1-6 (%)

[0078]

[0079] Comparative Examples 1-3 are pure manganese cerium metal oxide catalysts MnCe obtained by ball milling, catalysts SiO2-MnCe obtained by replacing piezoelectric materials with ordinary silica, and catalysts TBH-MnCe prepared by using manganese cerium metal oxide and impregnation method. Compared with Figure 6 , the degradation efficiency of 1,2-dichlorobenzene at low temperature of the catalysts in the comparative examples is poor. Comparative Examples 4-6 are pure piezoelectric material catalysts obtained by ball milling, and Figure 8 it can be seen that the overall effect is significantly lower than that of the catalyst without adding metal oxide. From Figure 9 it can be seen that the NO degradation effect of the catalysts in the comparative examples is significantly lower than that of the catalysts in the examples. The specific performance is that the NO low-temperature degradation efficiency is poor and the temperature range is narrow.

[0080] (5) The materials obtained in Examples 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 are tested by UV diffuse reflection and VB XPS to obtain the band gap and valence band top VB of the materials, respectively, and the conduction band bottom CB is calculated. The energy level diagram of the obtained materials is shown in Figure 10 .

[0081] From the comparison of the energy level diagrams, it can be seen that the TB-MnCe in Example 1 has the narrowest band gap, and the narrower band gap promotes more efficient charge separation and transfer. This is also consistent with the previous performance test structure.

[0082] All documents mentioned in the present application are incorporated herein by reference as if each individual document were specifically and individually incorporated by reference. In addition, it is to be understood that the present application can be carried out by specifically different embodiments and that many changes and modifications can be accomplished. It is, therefore, the intent that all such changes and modifications be included within the scope of the present application as defined by the following claims.

Claims

1. A method for preparing a composite catalyst for synergistic de-NOx and de-chlorinated organic compound removal, characterized by, The method comprises the following steps: S1, adding raw materials: piezoelectric material and nitrate of transition metal according to the mass ratio of 1:(0.25-4) into a ball mill tank for ball milling to obtain ball milled material A; S2, drying the ball milled material A in a vacuum oven to obtain material B; S3, calcining the material B in an air atmosphere to obtain the composite catalyst; The nitrate of transition metal is a mixed nitrate of manganese nitrate and cerium nitrate; the mass fraction of manganese nitrate in the mixed nitrate is 35-45%; and the piezoelectric material is barium titanate.

2. The method of claim 1, wherein: In the step S1, the mass ratio of raw materials to ball milling beads in the ball mill tank is (0.5-2.5):(10-15), and the raw materials account for 1 / 3 of the volume of the ball mill tank.

3. The method of claim 1, wherein: In the step S1, the ball milling conditions of the ball mill tank are as follows: ball milling speed 300-600 r / min, and ball milling time 2-6 hours.

4. The method of claim 1, wherein: In the step S2, the drying conditions are as follows: drying temperature 90-110 ℃, and drying time 10-24 hours.

5. The method of claim 1, wherein: In the step S3, the calcining conditions are as follows: calcining temperature 300-500 ℃, and calcining time 2-5 hours.

6. A composite catalyst prepared by the method according to any one of claims 1-5.

7. Use of the composite catalyst according to claim 6 for the synergistic catalytic degradation of flue gas pollutants, characterized by: The flue gas pollutants include nitrogen oxides and chlorine-containing organic matter.

8. Use according to claim 7, characterized in that: The temperature range of the composite catalyst for synergistically catalyzing degradation is 90-400 ℃.

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