A denitration catalyst, a preparation method and application thereof

Abstract

The application provides a denitration catalyst and a preparation method and application thereof. The catalyst comprises an acidic porous material and a Beta molecular sieve, and is doped with a metal element A selected from any one or a combination of at least two of iron, cerium, manganese, tungsten or molybdenum. The catalyst utilizes the unique pore structure of the Beta molecular sieve to confine the reactant molecules, promotes the rapid SCR reaction by promoting the oxidation of NO to generate NO2, and then utilizes the non-oxidation and reduction site of the Beta molecular sieve to achieve high-temperature sulfur poisoning resistance, and through doping the metal element A to the Beta molecular sieve, the low-temperature activity of the catalyst is improved, and through physical mixing with the acidic porous material, low-temperature sulfur poisoning resistance is achieved.

Description

Technical Field

[0001] This invention belongs to the field of flue gas purification technology, and relates to a denitrification catalyst, its preparation method and application. Background Technology

[0002] Nitrogen oxides emitted from flue gas are serious air pollutants that can cause a series of environmental problems, including acid rain, photochemical smog, and the greenhouse effect, posing a serious threat to human health. Selective catalytic reduction (SCR) is currently the mainstream flue gas denitrification technology. This technology typically uses ammonia as a reducing agent to selectively reduce nitrogen oxides to nitrogen and water. However, SO2 in the flue gas can poison and deactivate the catalyst, specifically through physical poisoning caused by ammonium sulfate / ammonium bisulfate deposition and chemical poisoning caused by sulfation of active sites, thus affecting the catalyst's working life.

[0003] CN114272949A discloses a low-temperature resistant M1-type molybdenum molecular sieve denitrification catalyst and its preparation method. This method involves atomically dispersing VO6 octahedra on a MoO6 molecular sieve framework to obtain a low-temperature resistant catalyst. The catalyst exhibits a NO conversion rate exceeding 80% under sulfur stability testing at 210℃. However, the effective operating temperature range of this catalyst is relatively narrow (200–400℃), and it contains the toxic substance V.

[0004] CN115739171A discloses a method for preparing a low-temperature sulfur-resistant denitrification composite molecular sieve catalyst. This method uses CaO as an active site protectant and NiO as a decomposing agent for ammonium sulfate or ammonium bisulfate, achieving low-temperature sulfur resistance. However, this catalyst is suitable for low temperatures and has a narrow operating temperature window (<280℃).

[0005] Therefore, developing a sulfur-resistant denitrification catalyst with a wide operating temperature window is of great significance and industrial value. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a sulfur-resistant denitrification catalyst with a wide operating temperature window, its preparation method and application.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] One objective of this invention is to provide a catalyst comprising an acidic porous material and a Beta molecular sieve, wherein the catalyst is further doped with a metal element A, which is selected from any one or a combination of at least two of iron, cerium, manganese, tungsten, or molybdenum. Typical but non-limiting examples of such combinations include combinations of iron and cerium, cerium and manganese, manganese and tungsten, or tungsten and molybdenum.

[0009] The catalyst of this invention utilizes the unique pore structure of Beta molecular sieves to confine reactant molecules, thereby promoting the rapid SCR reaction by facilitating the oxidation of NO to NO2. Secondly, it utilizes the absence of redox sites in Beta molecular sieves to achieve resistance to sulfur poisoning at medium and high temperatures. Subsequently, it enhances the low-temperature activity of the catalyst by doping the Beta molecular sieve with metal element A, and achieves low-temperature resistance to sulfur poisoning by physically mixing it with acidic porous materials.

[0010] As a preferred technical solution of the present invention, the compound containing the metal element A includes any one or a combination of at least two of iron oxide, cerium oxide, manganese oxide, tungsten oxide or molybdenum oxide, wherein typical but non-limiting examples of the combination include: a combination of iron oxide and cerium oxide, a combination of cerium oxide and manganese oxide, a combination of manganese oxide and tungsten oxide or a combination of tungsten oxide and molybdenum oxide, etc.

[0011] Preferably, the acidic porous material includes any one or a combination of at least two of MOR molecular sieve, Y molecular sieve, SBA-15 molecular sieve, MCM-56 molecular sieve, or montmorillonite. Typical but non-limiting examples of such combinations include: a combination of MOR molecular sieve and Y molecular sieve, a combination of Y molecular sieve and SBA-15 molecular sieve, a combination of SBA-15 molecular sieve and MCM-56 molecular sieve, or a combination of MCM-56 molecular sieve and montmorillonite, etc.

[0012] As a preferred technical solution of the present invention, the mass ratio of the compound containing the metal element A to the Beta molecular sieve is 1:(1 to 10), wherein the mass ratio can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, etc., but is not limited to the listed values, and other unlisted value ranges are also applicable.

[0013] Preferably, the mass ratio of the acidic porous material to the Beta molecular sieve is (1-5):(5-1), wherein the mass ratio can be 1:5, 2:5, 3:5, 4:5, 5:5, 5:4, 5:3, 5:2 or 5:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] A second objective of this invention is to provide a method for preparing the catalyst as described in one objective, the method comprising:

[0015] (1) Dissolve the Beta molecular sieve in a solution containing metal element A and carry out a hydrothermal reaction to obtain an intermediate product;

[0016] (2) After calcining the intermediate product described in step (1), it is mixed with an acidic porous material to obtain the catalyst.

[0017] Metal element A is first chemically mixed with Beta molecular sieve, and then physically mixed with acidic porous material. The initial chemical mixing allows metal A to bind with the Beta molecular sieve, acting as a low-temperature active site. The subsequent physical mixing ensures the independence of the acidic porous material (an independent low-temperature sulfur-resistant component). This utilizes the porous nature of the acidic porous material to adsorb ammonium sulfate and ammonium bisulfate generated at low temperatures, preventing physical poisoning of the catalyst due to the presence of sulfur dioxide. Directly mixing these three components—metal element A, Beta molecular sieve, and acidic porous material—in a one-step hydrothermal process would negatively impact the performance of the acidic porous material, affecting the catalyst's low-temperature sulfur-resistant effect.

[0018] As a preferred technical solution of the present invention, the preparation method of the solution containing metal element A in step (1) includes: dissolving the precursor salt containing metal element A in a solvent to obtain the solution containing metal element A.

[0019] Preferably, the precursor salt containing metal element A includes any one or a combination of at least two of ferric nitrate, cerium nitrate, manganese nitrate, manganese sulfate, ammonium metatungstate, ammonium paratungstate, or ammonium molybdate. Typical but non-limiting examples of such combinations include: combinations of ferric nitrate and cerium nitrate, combinations of cerium nitrate and manganese nitrate, combinations of manganese nitrate and manganese sulfate, combinations of manganese sulfate and ammonium metatungstate, combinations of ammonium metatungstate and ammonium paratungstate, or combinations of ammonium paratungstate and ammonium molybdate, etc.

[0020] Preferably, the mass ratio of the precursor salt containing metal element A to the Beta molecular sieve is 1:(1 to 10), wherein the mass ratio can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, etc., but is not limited to the listed values, and other unlisted value ranges are also applicable.

[0021] Preferably, the solvent includes water.

[0022] As a preferred technical solution of the present invention, the temperature of the hydrothermal reaction in step (1) is 80 to 140°C, wherein the temperature can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 125°C, 130°C, 135°C or 140°C, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0023] If the hydrothermal reaction temperature is too high, it will damage the pore structure of the Beta molecular sieve; if the hydrothermal reaction temperature is too low, it will be detrimental to the bonding of metal element A with the Beta molecular sieve.

[0024] Preferably, the hydrothermal reaction time in step (1) is 20 to 40 hours, wherein the time can be 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours or 40 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] In this invention, a hydrothermal reaction time that is too short is not conducive to the bonding of metal element A with Beta molecular sieve; a hydrothermal reaction time that is too long will destroy the pore structure of Beta molecular sieve.

[0026] As a preferred technical solution of the present invention, after the hydrothermal reaction in step (1), the hydrothermal reaction product is filtered, washed and dried to obtain the intermediate product.

[0027] Preferably, the drying temperature is 60 to 100°C, wherein the temperature can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] Preferably, the drying time is 5 to 10 hours, wherein the time can be 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] As a preferred technical solution of the present invention, the mass ratio of the acidic porous material in step (2) to the Beta molecular sieve in step (1) is (1-5):(5-1), wherein the mass ratio can be 1:5, 2:5, 3:5, 4:5, 5:5, 5:4, 5:3, 5:2 or 5:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the calcination temperature in step (2) is 400 to 600°C, wherein the temperature can be 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C or 600°C, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] If the calcination temperature is too high, the pore structure of the Beta molecular sieve will be destroyed; if the calcination temperature is too low, the oxide containing metal element A generated by calcination will not be complete.

[0032] Preferably, the calcination time in step (2) is 3 to 5 hours, wherein the time can be 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours or 5 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] If the calcination time is too long, the pore structure of the Beta molecular sieve will be destroyed; if the calcination time is too short, the oxide containing metal element A generated by calcination will not be complete.

[0034] As a preferred technical solution of the present invention, the preparation method includes:

[0035] (1) Dissolve Beta molecular sieve in a solution containing metal element A and carry out a hydrothermal reaction at a temperature of 80-140℃ for 20-40h. After centrifugation, washing and drying at 60-100℃ for 5-10h, the intermediate product is obtained.

[0036] (2) After calcining the intermediate product described in step (1) at a temperature of 400-600℃ for 3-5 hours, it is mixed with an acidic porous material to obtain the catalyst.

[0037] A third objective of this invention is to provide an application of the catalyst as described in one objective, wherein the catalyst is used in any one of the reactions of selective catalytic reduction of nitrogen oxides by NH3, stationary source gas denitrification devices, or mobile source gas denitrification devices.

[0038] In the stationary source gas denitrification device of this invention, the stationary source refers to industrial kiln or steel sintering flue gas, wherein the industrial kiln can be an industrial kiln in a thermal power plant, boiler plant, coking plant, or glass plant. The mobile source refers to any one of a diesel engine, gas turbine, or aircraft engine.

[0039] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) In the denitrification catalyst against sulfur poisoning provided by the present invention, metal element A is used as a low-temperature active component, physically mixed acidic porous material is used as a low-temperature anti-sulfur component, and Beta molecular sieve is used as a medium- and high-temperature active component and anti-sulfur component, so that the catalyst has high activity and high sulfur resistance in the range of 150 to 800°C, and can carry out SNCR reaction after 800°C, realizing the connection between SCR and SNCR reaction.

[0042] (2) The preparation method of the sulfur poisoning-resistant denitrification catalyst provided by the present invention is simple to operate, low in cost, and can be applied industrially.

[0043] (3) The sulfur poisoning-resistant denitrification catalyst provided by the present invention is used for the selective catalytic reduction of nitrogen oxides by NH3, which enhances the collision between reactant molecules and does not produce the byproduct N2O, thus exhibiting excellent catalytic effect. Detailed Implementation

[0044] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0045] Example 1

[0046] This embodiment provides a method for preparing a denitrification catalyst resistant to sulfur poisoning, the method comprising the following steps:

[0047] (1) Dissolve 1g of Beta molecular sieve in 80mL of precursor solution, wherein the precursor solution is a solution of manganese nitrate, and the mass of MnO2 in the manganese nitrate accounts for 10% of the mass of Beta molecular sieve. Transfer the above solution to a 100mL stainless steel reactor lined with polytetrafluoroethylene and react hydrothermally at 90℃ for 24h. After centrifugation, filtration, washing and drying at 80℃ for 10h, an intermediate product is obtained.

[0048] (2) After calcining the intermediate product described in step (1) at 550°C for 4 hours, take 0.5g of the calcined sample and mix it with 1.0g of montmorillonite by thorough grinding to obtain the sulfur-resistant denitrification catalyst.

[0049] Example 2

[0050] This embodiment provides a method for preparing a denitrification catalyst resistant to sulfur poisoning, the method comprising the following steps:

[0051] (1) 1g of Beta molecular sieve was dissolved in 80mL of precursor solution, which was a mixed solution of manganese nitrate and ammonium molybdate. The sum of the mass of MnO2 in the manganese nitrate and the mass of MoO3 in the ammonium molybdate accounted for 10% of the mass of Beta molecular sieve. The above solution was transferred to a 100mL stainless steel reactor lined with polytetrafluoroethylene and hydrothermally reacted at 100℃ for 20h. After centrifugation, filtration, washing and drying at 90℃ for 6h, an intermediate product was obtained.

[0052] (2) After calcining the intermediate product described in step (1) at 500°C for 4.5 hours, take 1.0 g of the calcined sample and mix it with 1.0 g of Y molecular sieve by grinding and physical mixing to obtain the sulfur poisoning-resistant denitrification catalyst.

[0053] Example 3

[0054] This embodiment provides a method for preparing a denitrification catalyst resistant to sulfur poisoning, the method comprising the following steps:

[0055] (1) Dissolve 1g of Beta molecular sieve in 80mL of precursor solution, wherein the precursor solution is a mixed solution of cerium nitrate and ammonium metatungstate, wherein the sum of the mass of CeO2 in the cerium nitrate and the mass of WO3 in the ammonium metatungstate accounts for 10% of the mass of Beta molecular sieve. Transfer the above solution to a 100mL stainless steel reactor lined with polytetrafluoroethylene and hydrothermally react at 110℃ for 30h. After centrifugation, filtration, washing and drying at 100℃ for 5h, an intermediate product is obtained.

[0056] (2) After calcining the intermediate product described in step (1) at 600°C for 5 hours, take 1.0 g of the calcined sample and mix it with 0.5 g of SBA-15 molecular sieve by grinding and physical mixing to obtain the sulfur poisoning-resistant denitrification catalyst.

[0057] Example 4

[0058] This embodiment provides a method for preparing a denitrification catalyst resistant to sulfur poisoning, the method comprising the following steps:

[0059] (1) Dissolve 1g of Beta molecular sieve in 80mL of precursor solution, wherein the precursor solution is a mixed solution of manganese nitrate, ferric nitrate and ammonium metatungstate, wherein the sum of the masses of the corresponding MnO2 in the manganese nitrate, the corresponding Fe2O3 in the ferric nitrate and the corresponding WO3 in the ammonium metatungstate accounts for 10% of the mass of Beta molecular sieve. Transfer the above solution to a 100mL stainless steel reactor lined with polytetrafluoroethylene and react hydrothermally at 140℃ for 24h. After centrifugation, filtration, washing and drying at 90℃ for 10h, an intermediate product is obtained.

[0060] (2) After calcining the intermediate product described in step (1) at 550°C for 4.5 hours, take 1.0 g of the calcined sample and mix it with 0.2 g of MOR molecular sieve by thorough grinding to obtain the sulfur poisoning-resistant denitrification catalyst.

[0061] Example 5

[0062] This embodiment provides a method for preparing a denitrification catalyst resistant to sulfur poisoning, the method comprising the following steps:

[0063] (1) Dissolve 1g of Beta molecular sieve in 80mL of precursor solution, wherein the precursor solution is a mixed solution of manganese nitrate, cerium nitrate and ammonium molybdate, wherein the sum of the masses of MnO2 in manganese nitrate, CeO2 in cerium nitrate and MoO3 in ammonium molybdate accounts for 10% of the mass of Beta molecular sieve. Transfer the above solution to a 100mL stainless steel reactor lined with polytetrafluoroethylene and hydrothermally react at 120℃ for 24h. After centrifugation, filtration, washing and drying at 100℃ for 10h, an intermediate product is obtained.

[0064] (2) After calcining the intermediate product described in step (1) at 450°C for 5 hours, take 1.5g of the calcined sample and mix it with 1.0g of MCM-56 molecular sieve by grinding and physical mixing to obtain the sulfur poisoning-resistant denitrification catalyst.

[0065] Example 6

[0066] In this embodiment, the only difference is that the temperature of the hydrothermal reaction in step (1) is replaced with 70°C. All other conditions are the same as in Example 1.

[0067] Example 7

[0068] In this embodiment, the only difference is that the temperature of the hydrothermal reaction in step (1) is replaced with 150°C. All other conditions are the same as in Example 1.

[0069] Example 8

[0070] In this embodiment, the calcination temperature in step (2) is replaced with 380°C, and all other conditions are the same as in Example 1.

[0071] Example 9

[0072] In this embodiment, the calcination temperature in step (2) is replaced with 630°C, and all other conditions are the same as in Example 1.

[0073] Comparative Example 1

[0074] Except for step (1) where Beta molecular sieve was not added, all other conditions in this comparative example were the same as in Example 1.

[0075] Comparative Example 2

[0076] Except for step (2) where montmorillonite is not added, all other conditions in this comparative example are the same as in Example 1.

[0077] Comparative Example 3

[0078] Except for step (1) where manganese nitrate is not added, all other conditions in this comparative example are the same as in Example 1.

[0079] Comparative Example 4

[0080] Except for step (1) where manganese nitrate was not added and step (2) where montmorillonite was not added, i.e. the catalyst only contained Beta molecular sieve, all other conditions in this comparative example were the same as in Example 1.

[0081] Comparative Example 5

[0082] Except for step (1) where Beta molecular sieves were not added and step (2) where montmorillonite was not added, i.e. the catalyst only contained manganese nitrate, all other conditions in this comparative example were the same as in Example 1.

[0083] The catalysts prepared in Examples 1-9 and Comparative Examples 1-5 were subjected to catalytic reactions under the conditions of space velocity of 40000 mL / (g·h), NO 500 ppm, NH3 500 ppm, O2 5% (volume percentage), SO2 50 ppm, and N2 as carrier gas. The catalytic activity of the catalysts at 100–800 °C was measured, and the test results are shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] As can be seen from the table above, the data from Examples 1-5 show that the sulfur poisoning-resistant denitrification catalyst provided by this invention achieves a catalytic activity of over 90% at 150°C, and over 99% under preferred conditions; over 90% at 200°C, and over 98% under preferred conditions; over 89% at 300°C, and over 95% under preferred conditions; over 87% at 400°C, and over 96% under preferred conditions; over 85% at 500°C, and over 92% under preferred conditions; over 80% at 600°C, and over 84% under preferred conditions; over 71% at 700°C, and over 76% under preferred conditions; and over 67% at 800°C, and over 70% under preferred conditions.

[0088] A comprehensive comparison of the data from Examples 1-5 shows that the method of combining the low-temperature active component metal element A, the low-temperature sulfur-resistant component acidic porous material, and the Beta molecular sieve in this invention has significant implications for broadening the working temperature window of the catalyst and improving its low-temperature sulfur resistance.

[0089] As can be seen from the data of Examples 1 and Examples 6-7, when the temperature of the hydrothermal reaction is too low, the low-temperature activity of Example 6 is significantly lower than that of Example 1; when the temperature of the hydrothermal reaction is too high, the high-temperature activity of Example 7 is significantly lower than that of Example 1. The temperature of the hydrothermal reaction is preferably controlled between 80 and 140°C.

[0090] As can be seen from the data of Examples 1 and Examples 8-9, when the calcination temperature is too low, the low-temperature activity of Example 8 is significantly lower than that of Example 1; when the calcination temperature is too high, the high-temperature activity of Example 9 is significantly lower than that of Example 1. The calcination temperature is preferably controlled at 400-600℃.

[0091] The data from Examples 1 and Comparative Examples 1-5 show that the high-temperature activity of Comparative Example 1 is significantly lower than that of Example 1, the low-temperature activity of Comparative Examples 2-4 is significantly lower than that of Example 1, and the low-temperature and high-temperature activities of Comparative Example 5 are both significantly lower than those of Example 1. This demonstrates that the Beta molecular sieve of the present invention is beneficial for improving medium- and high-temperature activity and medium- and high-temperature sulfur resistance, manganese nitrate is beneficial for improving low-temperature activity, and montmorillonite is beneficial for improving low-temperature sulfur resistance. The sulfur-poisoning-resistant denitrification catalyst and its preparation method provided by the present invention exhibit excellent catalytic effects.

[0092] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A denitrification catalyst, characterized in that, The denitration catalyst comprises an acidic porous material and a Beta molecular sieve, and the denitration catalyst is also doped with a metal element A, wherein the metal element A is selected from any one or a combination of at least two of iron, cerium, manganese, tungsten or molybdenum; The acidic porous material includes any one or a combination of at least two of the following: MOR molecular sieve, Y molecular sieve, SBA-15 molecular sieve, MCM-56 molecular sieve, or montmorillonite. The denitrification catalyst is prepared by the following method, which includes the following steps: (1) Dissolve the Beta molecular sieve in a solution containing metal element A and carry out a hydrothermal reaction to obtain an intermediate product; (2) After calcining the intermediate product described in step (1), it is mixed with an acidic porous material to obtain the catalyst; The hydrothermal reaction in step (1) is carried out at a temperature of 80~140℃ for 20~40h. The calcination temperature in step (2) is 400~600℃, and the calcination time is 3~5h.

2. The denitrification catalyst according to claim 1, characterized in that, The mass ratio of the acidic porous material to the Beta molecular sieve is (1~5):(5~1).

3. A method for preparing the denitrification catalyst as described in claim 1 or 2, characterized in that, The preparation method includes: (1) Dissolve the Beta molecular sieve in a solution containing metal element A and carry out a hydrothermal reaction to obtain an intermediate product; (2) After calcining the intermediate product described in step (1), it is mixed with an acidic porous material to obtain the catalyst; The hydrothermal reaction in step (1) is carried out at a temperature of 80~140℃ for 20~40h. The calcination temperature in step (2) is 400~600℃, and the calcination time is 3~5h.

4. The preparation method according to claim 3, characterized in that, The preparation method of the solution containing metal element A in step (1) includes: dissolving the precursor salt containing metal element A in a solvent to obtain the solution containing metal element A.

5. The preparation method according to claim 4, characterized in that, The precursor salt containing metal element A includes any one or a combination of at least two of the following: ferric nitrate, cerium nitrate, manganese nitrate, manganese sulfate, ammonium metatungstate, ammonium paratungstate, or ammonium molybdate.

6. The preparation method according to claim 4, characterized in that, The mass ratio of the precursor salt containing metal element A to the Beta molecular sieve is 1:(1~10).

7. The preparation method according to claim 4, characterized in that, The solvent includes water.

8. The preparation method according to claim 3, characterized in that, After the hydrothermal reaction in step (1), the hydrothermal reaction product is filtered, washed and dried to obtain the intermediate product.

9. The preparation method according to claim 8, characterized in that, The drying temperature is 60~100℃.

10. The preparation method according to claim 8, characterized in that, The drying time is 5-10 hours.

11. The preparation method according to claim 3, characterized in that, The mass ratio of the acidic porous material in step (2) to the Beta molecular sieve in step (1) is (1~5):(5~1).

12. The preparation method according to claim 3, characterized in that, The preparation method includes: (1) Dissolve Beta molecular sieve in a solution containing metal element A and carry out a hydrothermal reaction at a temperature of 80~140℃ for 20~40h. After centrifugation, washing and drying at 60~100℃ for 5~10h, the intermediate product is obtained. (2) After calcining the intermediate product in step (1) at a temperature of 400~600℃ for 3~5h, it is mixed with acidic porous material to obtain the catalyst.

13. The application of a denitrification catalyst as described in claim 1 or 2, characterized in that, The denitrification catalyst is used for the selective catalytic reduction of nitrogen oxides by NH3.

14. The application according to claim 13, characterized in that, The denitrification catalyst is used in stationary source gas denitrification devices or mobile source gas denitrification devices.

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