Promoter metal-modified active metal-supported ssz-39 molecular sieves, preparation and use

Abstract

The present application relates to the active metal supported SSZ-39 molecular sieve modified by the auxiliary metal, preparation and application, belong to the industrial catalysis technical field. The active metal salt and auxiliary metal salt are added to the complexing agent aqueous solution, and the metal complex is formed. The silicate gel mixture is mixed with the metal complex, and then the seed SSZ-39 is added to obtain the initial gel. Then, hydrothermal crystallization, washing and drying, ammonium exchange, high-temperature calcination to remove the template agent are carried out to obtain the active metal supported SSZ-39 molecular sieve modified by the auxiliary metal. Compared with the SSZ-39 molecular sieve, the NH3-SCR activity, N2 selectivity and high-temperature hydrothermal stability of the active metal supported SSZ-39 molecular sieve modified by the auxiliary metal synthesized by the method are improved, and the active metal supported SSZ-39 molecular sieve modified by the auxiliary metal can be applied to selective catalytic reduction of nitrogen oxides in mobile source and fixed source tail gas.

Description

Technical Field

[0001] This invention belongs to the field of industrial catalysis technology, and more specifically, relates to the active metal supported SSZ-39 molecular sieve modified with auxiliary metal, its preparation and application, especially to the active metal supported SSZ-39 molecular sieve modified with auxiliary metal, its preparation and application as a denitrification catalyst. Background Technology

[0002] With the continued progress of economic globalization, air pollution caused by industrial development has become a significant environmental problem. Nitrogen oxides (NOx) from both stationary and mobile sources are a major contributor to this problem. x NO is considered a major air pollutant. With increasingly stringent laws and regulations worldwide, controlling NO has become crucial. x NO emissions have become one of the most pressing problems to be solved in the field of catalytic purification both domestically and internationally. Currently, the most effective NO... x Elimination technology is the selective catalytic reduction (NH3-SCR) of NH3, and the core of SCR technology is the catalyst. Currently, the small-porous molecular sieves used for NH3-SCR catalysis are mainly SSZ-13 molecular sieves with a CHA configuration and SSZ-39 molecular sieves with an AEI configuration. Copper-based molecular sieves are widely used due to their excellent fresh activity and hydrothermal stability, while iron-based molecular sieves have also attracted attention due to their better catalytic activity and N2 selectivity at high temperatures. Although Cu-SSZ-39 and Fe-SSZ-39 molecular sieves have many advantages in NH3-SCR catalytic reactions, they still have problems such as poor denitrification effect for low-temperature flue gas and poor high-temperature hydrothermal stability. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for preparing a highly efficient denitrification catalyst using an active metal-supported SSZ-39 molecular sieve modified with an auxiliary metal. This method involves introducing an auxiliary metal onto a Cu-SSZ-39 or Fe-SSZ-39 molecular sieve to obtain an auxiliary metal-modified molecular sieve. This process does not require metal ion exchange, is simple and reliable, easily reproducible, and exhibits good consistency. The resulting active metal-supported SSZ-39 maintains excellent NH3-SCR catalytic activity and hydrothermal stability over a wide temperature window, while also demonstrating excellent N2 selectivity. It can be applied to both mobile and stationary source denitrification.

[0004] According to a first aspect of the present invention, a method for preparing SSZ-39 molecular sieves modified with auxiliary metals using an in-situ hydrothermal method is provided, comprising the following steps:

[0005] (1) An active metal salt and an auxiliary metal salt are added to a complexing agent aqueous solution to form a metal complex; the active metal salt is a copper salt or an iron salt; the auxiliary metal salt is an alkali metal salt, an alkaline earth metal salt, a transition metal salt or a rare earth metal salt.

[0006] (2) Add inorganic base and template agent to water, mix thoroughly, and then add silicon source and aluminum source to obtain aluminosilicate gel mixture;

[0007] (3) Mix the aluminosilicate gel mixture obtained in step (2) with the metal complex obtained in step (1), and then add seed crystal SSZ-39 to obtain the initial gel;

[0008] (4) The initial gel obtained in step (3) is subjected to hydrothermal reaction, and then the obtained solid powder is subjected to ammonium exchange, and then calcined to remove the template agent, thereby obtaining the active metal-supported SSZ-39 molecular sieve modified by the auxiliary agent.

[0009] Preferably, the alkali metal salt is a sodium or potassium salt; the alkaline earth metal salt is a magnesium or calcium salt; the transition metal salt is a zinc, manganese, or titanium salt; and the rare earth metal salt is a lanthanum, praseodymium, neodymium, or samarium salt.

[0010] Preferably, in step (2), the molar ratio of silicon atoms in the silicon source to aluminum atoms in the aluminum source is 5 to 30.

[0011] Preferably, in step (4), the ammonium salt used for ammonium exchange is ammonium sulfate or ammonium persulfate.

[0012] Preferably, in step (4), the calcination temperature is 600-800℃ and the time is 6-12h.

[0013] According to another aspect of the present invention, an active metal-supported SSZ-39 molecular sieve modified with auxiliary metals is provided, prepared by any one of the methods.

[0014] Preferably, the doping amount of the auxiliary metal in the active metal-supported SSZ-39 molecular sieve modified with auxiliary metal is 0.02 wt.% to 2 wt.%.

[0015] Preferably, the loading of active metal in the metal-modified active metal-supported SSZ-39 molecular sieve is 0.2 wt.% to 3 wt.%.

[0016] According to another aspect of the present invention, the application of the aforementioned auxiliary metal-modified active metal supported SSZ-39 molecular sieve as a denitrification catalyst is provided.

[0017] According to another aspect of the present invention, a selective catalytic reduction apparatus is provided, comprising the aforementioned auxiliary metal-modified active metal supported SSZ-39 molecular sieve.

[0018] According to another aspect of the present invention, a mobile source and / or stationary source exhaust gas treatment system is provided, including the aforementioned selective catalytic reduction device.

[0019] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0020] (1) The present invention introduces auxiliary metals into metal-supported SSZ-39 molecular sieves to improve the catalytic performance and hydrothermal stability of the catalyst.

[0021] (2) This invention synthesizes an active metal-supported SSZ-39 molecular sieve denitration catalyst modified with auxiliary metals via an in-situ hydrothermal method. The preparation method is simple, reproducible, and consistent, and the content of auxiliary metals and the active components of the catalyst are easily controlled. Compared with Cu-SSZ-39 catalysts, the Cu / M-SSZ-39 (M = Na, Mg, Zn, Mn, Pr, or Sm) molecular sieve catalyst provided by this invention has a higher T... 90 The temperatures corresponding to a 90% reactant conversion rate are 230℃, 215℃, 200℃, 195℃, 190℃, and 183℃, respectively. These are the T values ​​for the Cu-SSZ-39 molecular sieve catalyst. 90 The temperature was 206℃. Compared with Cu-SSZ-39, the low-temperature NH3-SCR activity of Cu / M-SSZ-39 (M = Zn, Mn, Pr or Sm) molecular sieve catalyst was improved. The temperature T of aged Cu / M-SSZ-39 (M = Na, Mg, Zn, Mn, Pr or Sm) molecular sieve catalyst was... 90 The temperatures were 241℃, 238℃, 226℃, 218℃, 210℃, or 205℃, respectively. The T values ​​for the aged Cu-SSZ-39 catalyst were... 90 The temperature is 264℃. Compared with Cu-SSZ-39, the Cu / M-SSZ-39 (M = Na, Mg, Zn, Mn, Pr or Sm) catalyst exhibits improved N2 selectivity and high-temperature hydrothermal stability. Compared with the Fe-SSZ-39 catalyst, the Fe / M-SSZ-39 (M = Na, Mg, Zn, Mn, Pr or Sm) molecular sieve catalyst provided by this invention has a higher T... 50 The temperatures were 296℃, 290℃, 280℃, 269℃, 264℃, 261℃, and 255℃, respectively. 90 The T values ​​of the Fe-SSZ-39 molecular sieve catalyst were 362℃, 342℃, 331℃, 320℃, 316℃, and 307℃, respectively. 50 The temperature is 301℃, T 90The temperature was 367℃. Compared with Fe-SSZ-39, the NH3-SCR activity of the Fe / M-SSZ-39 (M = Na, Mg, Zn, Mn, Pr or Sm) catalyst was improved. The To of the aged Fe / M-SSZ-39 (M = Na, Mg, Zn, Mn, Pr or Sm) molecular sieve catalyst was... 90 The temperatures were 431℃, 419℃, 402℃, 395℃, 387℃, and 361℃, respectively. The T values ​​for the aged Fe-SSZ-39 catalyst were... 50 At 335℃, its NO x The maximum conversion rate does not exceed 90%. Compared with Fe-SSZ-39, the N2 selectivity and high-temperature hydrothermal stability of the Fe / M-SSZ-39 (M = Na, Mg, Zn, Mn, Pr or Sm) catalyst are improved.

[0022] (3) The introduction of transition metals into Cu-SSZ-39 and Fe-SSZ-39 in this invention helps to promote an increase in the number of active ions, inhibits the migration and aggregation of metal ions, and enhances hydrothermal stability; at the same time, the introduction generates new... The presence of Lewis acid sites increases the adsorption and activation of NH3, as well as the adsorption of NO. Introducing rare earth metals into Cu-SSZ-39 and Fe-SSZ-39 helps inhibit the aggregation of metal ions and promotes the formation of more isolated metal ions. Furthermore, rare earth metals can fill vacancies in the molecular sieve framework, acting as Lewis acid sites to adsorb NH3 and increase the acidity of the molecular sieve; all of these contribute to improving the SCR activity of the catalyst. Moreover, rare earth metal ions tend to fill defect sites in the molecular sieve, reducing the attack of water molecules on the molecular sieve framework and ultimately improving hydrothermal stability. Introducing small amounts of alkali / alkaline earth metals into Cu-SSZ-39 and Fe-SSZ-39 allows the alkali / alkaline earth metal ions to regulate the distribution of active sites and replace those easily attacked by water. The presence of acidic sites enhances high-temperature hydrothermal stability. These combined factors ultimately improve the catalytic performance of Cu / M-SSZ-39 and Fe / M-SSZ-39 catalysts modified with additive metals.

[0023] (4) Preferably, the ammonium salt used for ammonium exchange is ammonium sulfate or ammonium persulfate, which are non-corrosive to the metal equipment used in the post-treatment of molecular sieves. In addition, ammonium sulfate or ammonium persulfate has weak ion exchange capacity. By controlling the concentration of ammonium sulfate or ammonium persulfate solution, the degree of ion exchange of the molecular sieve can be effectively controlled, thereby regulating the catalytic performance of the metal-supported SSZ-39 molecular sieve modified by the auxiliary metal. Attached Figure Description

[0024] Figure 1The X-ray diffraction (XRD) patterns of Cu / M-SSZ-39 (Na, Mg, Zn, Mn, Pr or Sm) and Cu-SSZ-39 molecular sieves prepared in Examples 1-6 and Comparative Example 1 are shown.

[0025] Figure 2 The X-ray diffraction (XRD) patterns of Fe / M-SSZ-39 (Na, Mg, Zn, Mn, Pr or Sm) and Fe-SSZ-39 molecular sieves prepared in Examples 7-12 and Comparative Example 2 are shown.

[0026] Figure 3 The Cu / M-SSZ-39 molecular sieves (Na, Mg, Zn, Mn, Pr or Sm) prepared in Examples 1-6 and Comparative Example 1, and the NO content of the Cu-SSZ-39 molecular sieves. X Conversion rate and N2 selectivity plot.

[0027] Figure 4 NO content of Cu / M-SSZ-39 molecular sieves (Na, Mg, Zn, Mn, Pr, or Sm) and Cu-SSZ-39 molecular sieves prepared in Examples 1-6 and Comparative Example 1 after hydrothermal aging at 750°C for 12 hours X Conversion rate and N2 selectivity plot.

[0028] Figure 5 The Fe / M-SSZ-39 molecular sieves (Na, Mg, Zn, Mn, Pr or Sm) prepared in Examples 7-12 and Comparative Example 2, and the NO content of the Fe-SSZ-39 molecular sieves. X Conversion rate and N2 selectivity plot.

[0029] Figure 6 NO content of Fe / M-SSZ-39 molecular sieves (Na, Mg, Zn, Mn, Pr, or Sm) prepared in Examples 7-12 and Comparative Example 2 and Fe-SSZ-39 molecular sieves after hydrothermal aging at 750°C for 12 h X Conversion rate and N2 selectivity plot. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] In a first aspect, this invention provides a method for preparing a metal-supported SSZ-39 molecular sieve high-efficiency denitration catalyst with auxiliary metal modification using an in-situ hydrothermal crystallization method, mainly comprising the following steps:

[0032] (1) Preparation of metal complex A: Copper sulfate or ferrous sulfate and an auxiliary metal salt (M = Na, Mg, K, Ca, Ti, Mn, Zn, La, Pr, Nd, or Sm) are added to an aqueous solution of tetrasodium ethylenediaminetetraacetate for a complexation reaction of 0.5–3 h to form a metal complex. The auxiliary metal salt is a nitrate, sulfate, or chloride of the corresponding metal.

[0033] (2) Preparation of aluminosilicate gel mixture B: NaOH, 1,1,3,5-tetramethylpiperidine hydroxide and silica sol were added to distilled water in sequence and stirred for 0.5 to 3 hours; then Y-type molecular sieve with low silica-to-alumina ratio was slowly added and stirred for 0.5 to 3 hours to obtain aluminosilicate gel mixture.

[0034] (3) Mix metal complex A and aluminosilicate gel mixture B, add seed crystals, and stir for 0.5 to 3 hours to obtain the initial gel of the reactants.

[0035] (4) Transfer the initial gel of the reactants formed in step (3) to a stainless steel reactor with a polytetrafluoroethylene liner and crystallize it at a temperature of 130℃~170℃ for 2~7 days.

[0036] After the reaction is complete, a solid powder is obtained by filtration, washing, and drying. The solid powder is then subjected to ammonium exchange and high-temperature calcination to remove the template agent, ultimately yielding a molecular sieve catalyst modified with auxiliary metal.

[0037] The molar ratios of the materials are as follows: SiO2:Al2O3:Na2O:R:H2O:Cu / Fe:M:CA=0.1~2.5:0.017~0.15:0.25:0.15:0.50:0.0006~0.003:x:0.0012~0.006; where R is the template agent, M is the auxiliary metal, and CA is the complexing agent.

[0038] In some embodiments, the ammonium salt used for ammonium exchange in step (4) is 0.05-1M ammonium sulfate or 0.05-1M ammonium persulfate.

[0039] In some embodiments, the calcination temperature in step (4) is 600–800°C and the calcination time is 6–12 h.

[0040] In a second aspect, the present invention provides two highly efficient denitrification catalysts, Cu / M-SSZ-39 and Fe / M-SSZ-39, comprising an active component and an auxiliary metal; wherein the active component is a Cu species and an Fe species, and the auxiliary metal is at least one selected from sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), titanium (Ti), manganese (Mn), zinc (Zn), lanthanum (La), praseodymium (Pr), neodymium (Nd), and samarium (Sm).

[0041] In some embodiments, the loading of the active component Cu in the support is 0.2 wt.% to 3 wt.%, and the loading of the active component Fe in the support is 0.2 wt.% to 3 wt.%, more preferably 1.4 wt.%.

[0042] In some embodiments, the metal-supported SSZ-39 molecular sieve described above is further doped with an auxiliary metal, wherein the auxiliary metal is at least one selected from sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), titanium (Ti), manganese (Mn), zinc (Zn), lanthanum (La), praseodymium (Pr), neodymium (Nd), and samarium (Sm). Preferably, the auxiliary metal is Na, Mg, Zn, Mn, Pr, or Sm.

[0043] In some embodiments, the doping amount of the additive metal (Zn, Mn, Pr, or Sm) in the molecular sieve support is 0.02 wt.% to 2 wt.%, more preferably 0.7 wt.%. The doping amount of the additive metal (Na or Mg) in the molecular sieve support is 0.02 wt.% to 2 wt.%, more preferably 0.2 wt.%.

[0044] In some embodiments, the silica-to-alumina ratio of the metal-loaded SSZ-39 molecular sieve modified with additive metal is 5 to 30, more preferably 8.

[0045] In a third aspect, the present invention provides a selective catalytic reduction apparatus comprising a metal-supported SSZ-39 molecular sieve catalyst modified with the aforementioned auxiliary agent.

[0046] In a fourth aspect, the present invention provides a mobile source and a stationary source exhaust gas treatment system comprising the above-described selective catalytic reduction device.

[0047] The following are specific embodiments.

[0048] Examples 1-4

[0049] A method for preparing Cu / M-SSZ-39 (M = Mn, Zn, Sm or Pr) molecular sieve includes the following steps:

[0050] 1.1 g of tetrasodium ethylenediaminetetraacetate was dissolved in 4 g of distilled water and stirred until homogeneous. Then, 0.44 g of copper sulfate and 0.25 g of zinc nitrate (or 0.26 g of manganese nitrate, 0.17 g of samarium nitrate, or 0.17 g of praseodymium nitrate) were added, and stirring continued for 1 h to obtain metal complex A. 2.5 g of sodium hydroxide, 5 g of distilled water, and 25 g of 1,1,3,5-tetramethylpiperidine hydroxide were mixed and stirred for 1 h to obtain mixture B. A and B were mixed and stirred for 1 h, then 20 g of silica sol was added and stirred for 1.5 h. Next, 8 g of Y-type molecular sieve was added and stirred for 1 h. Then, seed crystal SSZ-39 was added, and stirring continued for 1.5 h to obtain the initial reaction gel. The initial gel was transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 170 °C for 6 days. After crystallization, the solid powder was obtained by filtration, washing, and drying. The obtained solid powder was subjected to ammonium exchange with 1M ammonium sulfate. After the exchange was completed, the powder was filtered, washed, and dried. The dried powder was then calcined at 600℃ for 8 hours to finally obtain a Cu / M-SSZ-39 molecular sieve catalyst with a Cu loading of 1.4 wt.%, an auxiliary metal doping amount of 0.7 wt.%, and a Si / Al molar ratio of 8.

[0051] Examples 5-6

[0052] A method for preparing Cu / M-SSZ-39 (M = Mg or Na) molecular sieve includes the following steps:

[0053] 1.1 g of tetrasodium ethylenediaminetetraacetate was dissolved in 4 g of distilled water and stirred until homogeneous. Then, 0.44 g of copper sulfate and 0.15 g of magnesium nitrate (0.14 g of sodium nitrate) were added, and stirring was continued for 1 h to obtain metal complex A. 2.5 g of sodium hydroxide, 5 g of distilled water, and 25 g of 1,1,3,5-tetramethylpiperidine hydroxide were mixed and stirred for 1 h to obtain mixture B. A and B were mixed and stirred for 1 h, then 20 g of silica sol was added and stirred for 1.5 h. Next, 8 g of Y-type molecular sieve was added and stirred for 1 h. Then, seed crystal SSZ-39 was added, and stirring was continued for 1.5 h to obtain the initial reaction gel. The initial gel was transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 170 °C for 6 days. After crystallization, the solid powder was obtained by filtration, washing, and drying. The obtained solid powder was subjected to ammonium exchange with 1M ammonium sulfate. After the exchange was completed, the powder was filtered, washed, and dried. The dried powder was then calcined at 600℃ for 8 hours to finally obtain a Cu / M-SSZ-39 molecular sieve catalyst with a Cu loading of 1.4 wt.%, an auxiliary metal doping amount of 0.2 wt.%, and a Si / Al molar ratio of 8.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Examples 1-6 is that no auxiliary metal salt was added when preparing the metal complex. All other conditions were exactly the same as in Example 1, and a Cu-SSZ-39 molecular sieve catalyst with no metal auxiliary agent, a Cu loading of 1.4 wt.%, and a Si / Al molar ratio of 8 was finally obtained.

[0056] Examples 7-10

[0057] A method for preparing Fe / M-SSZ-39 (M = Mn, Zn, Sm or Pr) molecular sieve includes the following steps:

[0058] 1.1 g of tetrasodium ethylenediaminetetraacetate was dissolved in 4 g of distilled water and stirred until homogeneous. Then, 0.56 g of ferrous sulfate and 0.25 g of zinc nitrate (or 0.26 g of manganese nitrate, 0.17 g of samarium nitrate, or 0.17 g of praseodymium nitrate) were added, and stirring was continued for 1 h to obtain metal complex A. 2.5 g of sodium hydroxide, 5 g of distilled water, and 25 g of 1,1,3,5-tetramethylpiperidine hydroxide were mixed and stirred for 1 h to obtain mixture B. A and B were mixed and stirred for 1 h, then 20 g of silica sol was added and stirred for 1.5 h. Next, 8 g of Y-type molecular sieve was added and stirred for 1 h. Then, seed crystal SSZ-39 was added, and stirring was continued for 1.5 h to obtain the initial reaction gel. The initial gel was transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 170 °C for 6 days. After crystallization, the solid powder was obtained by filtration, washing, and drying. The obtained solid powder was subjected to ammonium exchange with 1M ammonium sulfate. After the exchange was completed, the powder was filtered, washed, and dried. The dried powder was then calcined at 600℃ for 8 hours to obtain a Fe / M-SSZ-39 molecular sieve catalyst with a Fe loading of 1.4 wt.%, an auxiliary metal doping amount of 0.7 wt.%, and a Si / Al molar ratio of 8.

[0059] Examples 11-12

[0060] A method for preparing Fe / M-SSZ-39 (M = Mg or Na) molecular sieve includes the following steps:

[0061] 1.1 g of tetrasodium ethylenediaminetetraacetate was dissolved in 4 g of distilled water and stirred until homogeneous. Then, 0.56 g of ferrous sulfate and 0.15 g of magnesium nitrate (0.14 g of sodium nitrate) were added, and stirring was continued for 1 h to obtain metal complex A. 2.5 g of sodium hydroxide, 5 g of distilled water, and 25 g of 1,1,3,5-tetramethylpiperidine hydroxide were mixed and stirred for 1 h to obtain mixture B. A and B were mixed and stirred for 1 h, then 20 g of silica sol was added and stirred for 1.5 h. Next, 8 g of Y-type molecular sieve was added and stirred for 1 h. Then, seed crystal SSZ-39 was added, and stirring was continued for 1.5 h to obtain the initial reaction gel. The initial gel was transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 170 °C for 6 days. After crystallization, the solid powder was obtained by filtration, washing, and drying. The obtained solid powder was subjected to ammonium exchange with 1M ammonium sulfate. After the exchange was completed, the powder was filtered, washed, and dried. The dried powder was then calcined at 600℃ for 8 hours to obtain a Fe / M-SSZ-39 molecular sieve catalyst with a Fe loading of 1.4 wt.%, an auxiliary metal doping amount of 0.2 wt.%, and a Si / Al molar ratio of 8.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Examples 7-12 is that no auxiliary metal salt was added when preparing the metal complex. All other conditions were exactly the same as in Example 7, and the final product was a Fe-SSZ-39 molecular sieve catalyst with no metal auxiliary agent, an Fe loading of 1.4 wt.%, and a Si / Al molar ratio of 8.

[0064] XRD tests were performed on the Cu / M-SSZ-39 and Fe / M-SSZ-39 molecular sieve catalysts prepared in Examples 1-12, and the results are as follows: Figure 1 and Figure 2 As shown, Cu / M-SSZ-39 and Fe-SSZ-39 modified with additive metals (Na, Mg, Mn, Zn, Pr or Sm) still maintain the typical AEI structure, and no diffraction peaks of additive metal species were observed, indicating that the additive metals are uniformly distributed on the catalyst, or that the additive metal species particles are too small to be detected by XRD.

[0065] Example 13

[0066] The Cu / M-SSZ-39, Fe / M-SS3-39 and Cu-SSZ-39, Fe-SSZ-39 molecular sieve catalysts prepared in Examples 1-12 and Comparative Examples 1 and 2 were subjected to hydrothermal aging as follows: 1.5g of catalyst (60-80 mesh) was placed in a quartz tube and aged in air containing 10% water vapor at 750°C for 12 hours.

[0067] The denitrification performance of Cu / M-SSZ-39, Fe / M-SS3-39, and Cu-SSZ-39, Fe-SSZ-39 molecular sieve catalysts prepared in Examples 1-12 and Comparative Examples 1 and 2, as well as the corresponding aged catalysts prepared in Examples 1-12 and Comparative Examples 1 and 2, was tested. The test conditions were: catalyst dosage 0.25 g (60-80 mesh), simulated flue gas composition of 500 ppm NO, 500 ppm NH3, 5% H2O, 10% O2, and 8% CO2, and a reaction space velocity of 200,000 h⁻¹. -1 .

[0068] NO x The conversion rate and N2 selectivity test results are shown in the figure. Figure 3 , Figure 4 It is evident that after aging at 750℃ for 12 hours, the activity of Cu-SSZ-39 decreased significantly. This is mainly due to the presence of numerous unstable framework structures in Cu-SSZ-39, which are prone to dealuminization during aging, leading to catalyst structural collapse. Introducing auxiliary metals such as Zn, Mn, Pr, or Sm into Cu-SSZ-39 improved the low-temperature NH3-SCR activity, hydrothermal stability, and N2 selectivity of Cu / M-SSZ-39. Introducing small amounts of auxiliary metals such as Na and Mg into Cu-SSZ-39 improved the high-temperature hydrothermal stability of Cu / M-SSZ-39. Figure 5 , Figure 6 It is evident that the activity of Fe-SSZ-39 decreased significantly after aging at 750℃ for 12 hours. This is mainly due to the presence of numerous unstable framework structures in Fe-SSZ-39, which are prone to dealuminization during aging, leading to catalyst structural collapse. Introducing auxiliary metals such as Zn, Mn, Pr, Sm, Na, or Mg into Fe-SSZ-39 improved the low-temperature NH3-SCR activity, hydrothermal stability, and N2 selectivity of Fe / M-SSZ-39.

[0069] Introducing transition metals (Zn or Mn) into Cu-SSZ-39 and Fe-SSZ-39 helps to increase the number of active ions, inhibits the migration and aggregation of metal ions, and enhances hydrothermal stability; at the same time, the introduction generates new... The presence of Lewis acid sites increases the adsorption and activation of NH3, as well as the adsorption of NO. Introducing rare earth metals (Sm or Pr) into Cu-SSZ-39 and Fe-SSZ-39 helps inhibit the aggregation of metal ions and promotes the formation of more isolated metal ions. Furthermore, rare earth metals can fill vacancies in the molecular sieve framework, acting as Lewis acid sites to adsorb NH3 and increase the acidity of the molecular sieve; all of these contribute to improving the SCR activity of the catalyst. Moreover, rare earth metal ions tend to fill defect sites in the molecular sieve, reducing the attack of water molecules on the molecular sieve framework and ultimately improving hydrothermal stability. Introducing small amounts of alkali / alkaline earth metals (Na or Mg) into Cu-SSZ-39 and Fe-SSZ-39 allows the alkali / alkaline earth metal ions to regulate the distribution of active sites and replace those easily attacked by water. The presence of acidic sites enhances high-temperature hydrothermal stability. These combined factors ultimately improve the catalytic performance of Cu / M-SSZ-39 and Fe / M-SSZ-39 catalysts modified with additive metals.

[0070] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An application of SSZ-39 molecular sieve modified with an active metal and supported on an in-situ hydrothermal method as a denitrification catalyst, characterized in that, The preparation method of the active metal-supported SSZ-39 molecular sieve modified with the auxiliary metal includes the following steps: (1) An active metal salt and an auxiliary metal salt are added to a complexing agent aqueous solution to form a metal complex; the active metal salt is a copper salt or an iron salt; the auxiliary metal salt is an alkali metal salt, an alkaline earth metal salt, a transition metal salt or a rare earth metal salt. The alkali metal salt is a sodium or potassium salt; the alkaline earth metal salt is a magnesium or calcium salt; the transition metal salt is a zinc, manganese, or titanium salt; and the rare earth metal salt is a lanthanum, praseodymium, neodymium, or samarium salt. (2) Add the inorganic base and template agent to water, mix thoroughly, and then add the silicon source and aluminum source to obtain a silicate gel mixture; (3) Mix the aluminosilicate gel mixture obtained in step (2) with the metal complex obtained in step (1), and then add seed crystal SSZ-39 to obtain the initial gel; (4) The initial gel obtained in step (3) is subjected to hydrothermal reaction and crystallized at a temperature of 130 ℃~170 ℃ for 2~7 days. Then, the obtained solid powder is subjected to ammonium exchange and calcined to remove the template agent, thereby obtaining the active metal-loaded SSZ-39 molecular sieve modified by the auxiliary agent.

2. The application as described in claim 1, characterized in that, In step (2), the molar ratio of silicon atoms in the silicon source to aluminum atoms in the aluminum source is 5 to 30.

3. The application as described in claim 1, characterized in that, In step (4), the ammonium salt used for ammonium exchange is ammonium sulfate or ammonium persulfate.

4. The application as described in claim 1, characterized in that, In step (4), the calcination temperature is 600~800 ℃ and the time is 6~12 h.

5. The application as described in claim 1, characterized in that, The doping amount of the auxiliary metal in the active metal-supported SSZ-39 molecular sieve modified with the auxiliary metal is 0.02 wt.%~2 wt.%.

6. The application as described in claim 1, characterized in that, The active metal loading in the SSZ-39 molecular sieve modified with the auxiliary metal is 0.2 wt.%~3 wt.%.

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