A core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier, its preparation method and application

Abstract

The present invention discloses a core-shell type SCR catalyst with SSZ-39 molecular sieve as a carrier, its preparation method and application. The catalyst uses SmMn-SSZ-39 as the core and SO4 2‑ -CeO2 film as the shell layer, and is prepared by an in-situ growth method from SmMn-SSZ-39, Ce source, quaternary ammonium salt ionic surfactant, hexamethylenetetramine, sulfuric acid, absolute ethanol and deionized water. The catalyst prepared by the present invention is beneficial to the catalytic activity of NH3-SCR, and inhibits the formation of ammonium nitrate and ammonium sulfate, blocks the active sites of metals Sm and Mn and avoids the formation of samarium sulfate and manganese sulfate. Moreover, the interaction between the core SmMn-SSZ-39 and the shell layer SO4 2‑ -CeO2 effectively improves the SO2 tolerance of the catalyst, and this research provides a strategy for the design and practical application of NH3-SCR molecular sieve catalysts.

Description

Technical Field

[0001] The present invention relates to a core-shell type SCR catalyst with SSZ-39 molecular sieve as a carrier, its preparation method and application, belonging to the technical field of catalysts. Background Art

[0002] At present, manganese-based molecular sieves are the most attractive and promising denitration catalysts. Typical microporous molecular sieves such as SAPO-34 and SSZ-13 have been used as commercial denitration catalysts. SSZ-39 molecular sieve is a microporous aluminosilicate material with an AEI structure, having a three-dimensional interconnected channel system with an asymmetric avocado-shaped cage (12.6 Å×11.2 Å) and eight-membered ring 8MR pores (3.8 Å×3.8 Å). Compared with Mn / SSZ-13 and Mn / SAPO-34, Mn / SSZ-39 still exhibits higher structural stability under hydrothermal aging conditions at 850 °C, thus maintaining excellent NH3-SCR catalytic activity (T = 200~500 °C). However, at low temperatures (T < 200 °C), the high-temperature SCR catalytic activity of the Mn / SSZ-39 catalyst is poor; meanwhile, the active component Mn of the Mn / SSZ-39 catalyst is liable to react with SO2 in diesel vehicle exhaust to form manganese sulfate salts, clogging the pores of the molecular sieve, and SO2 will form ammonium sulfate salts or ammonium sulfite salts on the surface of the catalyst, resulting in the poisoning and irreversible deactivation of the catalyst.

[0003] The molecular sieve catalyst with a core-shell structure can protect the active components in the core, inhibit the aggregation of metal species at high temperatures, and utilize the synergistic effect of multiple components to improve the SCR activity of the catalyst. In addition, its outer shell layer can prevent SO2 in the tail gas from reacting with the active components in the core to form sulfates or sulfites, improving the sulfur resistance of the catalyst.

[0004] In recent years, there have been many patent reports on the synthesis of core-shell structured SCR catalysts. Chinese Patent CN114956111A discloses a Cr-SSZ-13@Cu-SSZ-13 core-shell type molecular sieve, which is applied to the NH3-SCR reaction. The prepared Cr-SSZ-13@Cu-SSZ-13 core-shell type molecular sieve exhibits excellent N2 selectivity, a wide activity window, and high hydrothermal stability. However, there are few research reports on the SSZ-39 core-shell structured molecular sieve. Chinese Patent CN112299436A discloses a Cu-SSZ-39@SSZ-39 core-shell type molecular sieve. In a relatively wide and high temperature range, the conversion rate of nitrogen oxides reaches 90%, but the low-temperature activity and sulfur resistance need to be further studied. Chinese Patent CN112958148A discloses a Cu-SSZ-39@Cu-SSZ-13 composite molecular sieve with a core-shell structure, which combines the low-temperature activity advantage of Cu-SSZ-13 and the high-temperature activity advantage of Cu-SSZ-39, improves the catalytic activity of NH3-SCR, and exhibits excellent hydrothermal stability. However, SO2 in the tail gas reacts with metal active sites to form sulfates or sulfites, resulting in the poisoning and inactivation of the catalyst. Therefore, it is of great significance to develop a molecular sieve catalyst for the NH3-SCR reaction that simultaneously has excellent low-temperature activity, high-temperature activity, and sulfur resistance. Summary of the Invention

[0005] The purpose of the present invention is to provide a core-shell type SCR catalyst with a structure of (SmMn-SSZ-39)@SO4 2- -CeO2 supported on SSZ-39 molecular sieve, which can regulate the reaction site, reduce metal agglomeration, and simultaneously have low-temperature activity, high-temperature activity, and sulfur resistance in the NH3-SCR reaction;

[0006] The second purpose of the present invention is to provide a preparation method of the above catalyst;

[0007] The third purpose of the present invention is to provide the application of the above catalyst.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0009] A preparation method of a core-shell type SCR catalyst supported on SSZ-39 molecular sieve, comprising the following steps:

[0010] Step 1, preparation of SmMn-SSZ-39 inner core:

[0011] Mix the silicon source, zeolite seeds, alkali source, organic structure-directing agent, and deionized water uniformly and stir at room temperature for 1.0 - 5.0 h to obtain gel A; mix the manganese source, samarium source, and deionized water and stir at room temperature for 0.5 - 3.0 h to obtain solution B; mix solution B and gel A uniformly under stirring according to a mass ratio of 1:(1.20 - 1.87), transfer to a high-pressure reactor, and carry out hydrothermal reaction under γ-ray irradiation at a dose rate of 0.5 - 4.5 kGy / h for 8 - 24 h at 80 - 200 °C. After the reaction is completed and cooled to room temperature, filter; wash the filter cake with deionized water until the washing liquid is neutral and dry for 8 - 12 h, then calcine in an air stream of 5 - 50 mL / min at 400 - 850 °C for 3 - 8 h, and cool to room temperature to obtain the SmMn-SSZ-39 core;

[0012] Step 2, preparation of a core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier:

[0013] Add the SmMn-SSZ-39 core to a mixed solution of absolute ethanol and deionized water for dispersion and stir at room temperature for 0.5 - 2 h; then add the quaternary ammonium salt ionic surfactant to the mixed solution and stir at room temperature for 2 - 6 h to obtain solution C; mix the Ce source, hexamethylenetetramine, and sulfuric acid uniformly in a flask and continue to react at 60 - 80 °C for 2 - 8 h to obtain solution D; add solution D dropwise to solution C, with the mass ratio of solution D to solution C being 1:(9.23 - 17.21), continue to stir for 1 - 3 h, carry out in-situ growth at 80 - 120 °C for 8 - 12 h, dry at 60 - 80 °C for 6 - 8 h, and then calcine in an air stream of 5 - 50 mL / min at 400 - 850 °C for 3 - 8 h to obtain a core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier.

[0014] In gel A, the mass ratio of zeolite seeds, silicon source, alkali source, organic structure-directing agent, and deionized water is 1:(8.27 - 12.5):(5.26 - 8.33):(7.125 - 9.5):(22.86 - 35.42);

[0015] In solution B, the mass ratio of manganese source, samarium source, and deionized water is (1.27 - 2.13):1:(23.81 - 44.78).

[0016] The silicon source is selected from any one of amorphous silica, nano-silica, silica sol, or sodium silicate;

[0017] The zeolite seeds are selected from any one of Y zeolite, Beta zeolite, ZSM-5 zeolite, or MOR zeolite;

[0018] The alkali source is selected from any one of potassium hydroxide or sodium hydroxide;

[0019] The organic structure-directing agent is selected from any one of N,N-diethyl-2,6-dimethylpiperidinium hydroxide, N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, and N-methyl-N-ethyl-2,6-dimethylpiperidinium hydroxide;

[0020] The manganese source is selected from any one of manganese nitrate or manganese acetate;

[0021] The samarium source is selected from any one of samarium nitrate or samarium acetate monohydrate.

[0022] The γ-ray is sourced from 60 a Co ionization radiation source. The dose rate is 0.5 - 4.5 kGy / h. The irradiation exposure dose of the γ-ray is expressed in kg (1 kGy = 1 kJ / kg), the dose rate is expressed in kGy / h, and the dose is the product of the dose rate and the irradiation time.

[0023] In solution C, the mass ratio of the SmMn-SSZ-39 core, quaternary ammonium salt ionic surfactant, absolute ethanol, and deionized water is 1:(1.25 - 6.67):100:100;

[0024] In solution D, the mass ratio of the Ce source, hexamethylenetetramine, and sulfuric acid is 1:(3.75 - 10):(0.3675 - 0.588).

[0025] The Ce source is selected from any one of cerium nitrate hexahydrate or cerium acetate;

[0026] The quaternary ammonium salt ionic surfactant is selected from any one of polyvinylpyrrolidone or polydimethyldiallylammonium chloride;

[0027] The concentration of sulfuric acid is 0.1 - 0.3 M.

[0028] A core-shell type SCR catalyst with SSZ-39 zeolite as the carrier, where the catalyst uses SmMn-SSZ-39 as the core and SO4 2- -CeO2 film as the shell layer.

[0029] Application of a core-shell type SCR catalyst with SSZ-39 zeolite as the carrier in the ammonia selective catalytic reduction reaction NH3-SCR.

[0030] The present invention has the following beneficial effects:

[0031] The present invention uses sulfated metal oxides as the catalyst shell layer, and the outer shell can play a physical barrier role to prevent the aggregation of metal species, inhibit the combination of SO2 in the tail gas with active sites to form sulfates or sulfites, and solve the problems that the framework of the molecular sieve catalyst is prone to collapse during the reaction process, thus destroying the pore structure of the molecular sieve, and the formation of sulfates or sulfites at the active sites leads to catalyst poisoning and deactivation; the inner core serves as the main active site for NH3-SCR, and the interaction between the metal component and the carrier can effectively improve the low-temperature and high-temperature activities, solving the problem of poor high-temperature activity of the Mn-based molecular sieve catalyst.

[0032] The present invention mainly solves the problems of poor low-temperature activity, poor high-temperature activity and poor sulfur resistance of the molecular sieve catalyst; Sm is mainly beneficial to high-temperature activity, but has poor sulfur resistance, and the core-shell structure can overcome the problem of poor sulfur resistance of SmMn-SSZ-39. Mn is beneficial to low-temperature activity, and the core-shell structure mainly solves the problem of poor sulfur resistance. The inner core SmMn-SSZ-39 has the problem of poor sulfur resistance, while Mn-SSZ-39 has the problem of poor high-temperature activity.

[0033] The preparation methods of the inner core and the shell layer of the present invention are the γ-ray assisted method and the in-situ growth method respectively.

[0034] The technical problems that cannot be solved by the prior art are: the problems of poor sulfur resistance and poor high-temperature activity of the Mn-based molecular sieve catalyst; the core-shell structure inhibits the aggregation of metal species and improves the SCR activity of the catalyst; the introduction of Sm can improve the high-temperature activity of the Mn-based molecular sieve catalyst. The introduction of the Sm element in the present invention can effectively improve the stability of the catalytic activity in the high-temperature section, and the introduction of the Mn element can effectively improve the stability of the catalytic activity in the low-temperature section. Therefore, the combination of the Sm and Mn metal species ensures the excellent characteristics of the low-temperature activity and high-temperature activity of the catalyst.

[0035] The technical effects achieved by the core-shell structure of the present application are: the core-shell structure blocks the contact between the active components and SO2 and H2O, improves the sulfur resistance and SCR catalytic activity of the catalyst, and avoids the poisoning and deactivation of the catalyst.

[0036] (1) The present invention uses the "γ-ray assisted method" to achieve the uniform dispersion of metal Mn and Sm species in the SSZ-39 molecular sieve. Compared with the in-situ synthesis method, the γ-ray assisted method used in the present invention shortens the synthesis time of the catalyst (the catalytic synthesis time of the γ-ray assisted method used in the present invention is 8-24 h, while the catalytic synthesis time of the in-situ synthesis method is 3 d-6 d), avoids the phenomena of sintering and aggregation of the metal Mn and Sm active sites in the SCR catalytic reaction, has high stability, and thus has high reaction activity and selectivity.

[0037] (2) The active site in the molecular sieve catalyst involved in the present invention is the SmMn component in the core. Compared with the traditional Mn-based molecular sieve catalyst, the addition of the second metal Sm 2+ improves the high-temperature activity of the catalyst. Sm 2+ can also provide another adsorption and activation site for the reactants, enabling the catalyst to achieve dual-site catalysis, alleviating the problem of competitive adsorption of the reactants, solving the problems of poor anti-toxicity and poor thermal stability of the Mn-based catalyst, and greatly enhancing the activity and stability of the catalyst by utilizing the synergistic effect between metal elements.

[0038] (3) The SO4 2- -CeO2 thin film shell of the core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier in the present invention can effectively protect the core SmMn-SSZ-39 catalyst. On the one hand, the shell avoids the contact between SO2 in the tail gas and the active components, inhibits the generation of sulfates or sulfites, and improves the catalytic activity and sulfur resistance of the catalysis; on the other hand, the presence of SO2 in the catalytic reaction will generate ammonium sulfate, and ammonium sulfate may cause the blockage of the molecular sieve pores, while the shell can combine with SO2 to avoid the blockage of the pores, thereby improving the catalytic activity, structural stability and sulfur resistance of the catalyst.

[0039] (4) A core-shell interface can be formed between the shell and the core of the core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier in the present invention. The core-shell interface effect provides a stable redox cycle site for the catalytic reaction. At the same time, the shell has good sulfur resistance, further enhancing the catalytic activity and anti-poisoning ability of the catalyst.

[0040] (5) The preparation method of the core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier in the present invention is coherent and easy to operate. The prepared SO4 2- -CeO2 thin film shell uniformly wraps on the surface of the SSZ-39 molecular sieve, and the core-shell product has good structural consistency, which is suitable for commercial promotion.

[0041] The present invention discloses a core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier and its preparation method. The catalyst uses SmMn-SSZ-39 as the core and SO4 2- -CeO2 thin film as the shell, and is prepared by the in-situ growth method from SmMn-SSZ-39, Ce source, quaternary ammonium salt ionic surfactant, hexamethylenetetramine, sulfuric acid, absolute ethanol and deionized water; the core SmMn-SSZ-39 is prepared by the γ-ray assisted method from silicon source, zeolite seeds, alkali source, manganese source, samarium source and deionized water under the action of an organic structure directing agent. The SmMn component in the core of the catalyst prepared in the present invention can effectively improve the high-temperature activity of the catalyst, and the SO4 2--CeO2 shell is beneficial to the NH3-SCR catalytic activity, inhibits the formation of ammonium nitrate and ammonium sulfate, blocks the active sites of metals Sm and Mn, and avoids the formation of samarium sulfate and manganese sulfate. Moreover, the interaction between the core SmMn-SSZ-39 and the shell SO4 2- -CeO2 effectively improves the SO2 tolerance of the catalyst. This study provides strategies for the design and practical application of NH3-SCR molecular sieve catalysts. Brief Description of the Drawings

[0042] Figure 1 It is the X-ray diffraction pattern of the catalyst in Example 1 of the present invention;

[0043] Figure 2 It is the comparison chart of NOx removal efficiency of SCR catalysts in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3;

[0044] Figure 3 It is the sulfur resistance performance chart of the catalysts in Example 1 and Comparative Example 1;

[0045] Figure 4 It is the microstructure diagram of the uniform dispersion of Mn and Sm on the SSZ-39 molecular sieve in the present invention;

[0046] Figure 5 It is the microstructure diagram of the comparative example (CuMn-SSZ-39);

[0047] Figure 6 It is the microstructure diagram of the comparative example (microstructure of CuSmMn-SSZ-39);

[0048] Figure 7 In the present invention, SO4 2- -CeO2 thin film shell uniformly wraps the surface of the SSZ-39 molecular sieve. Detailed Description of the Invention

[0049] The present invention will be further described in detail below with reference to the drawings and specific embodiments. The following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0050] Example 1

[0051] A preparation method of a core-shell type SCR catalyst using SSZ-39 molecular sieve as a carrier, comprising the following steps:

[0052] (1) Preparation of SmMn-SSZ-39 core: 2.4 g Y zeolite, 30 g white carbon black, 20 g NaOH, 22.5 g N,N-diethyl-2,6-dimethylpiperidinium hydroxide and 85 g deionized water were mixed and stirred for 2 h to obtain gel A; 80 g (80 mL) 0.1 M Mn(NO3)2, 20 g (20 mL) 0.1 M Sm(NO3)2 and 30 g deionized water were mixed and stirred for 0.5 h at room temperature to obtain solution B; after the above gel A and solution B were stirred, they were transferred to a high-pressure reactor and irradiated with gamma rays at a dose rate of 3.5 kGy / h. The gamma rays came from 60 Co ionizing radiation source, hydrothermal crystallization at 180°C for 8h; after the reaction is completed and cooled to room temperature, it is filtered and separated, the filter cake is washed with deionized water until neutral, dried at 80°C for 10h, and then calcined at 650°C for 6h in an air flow of 20mL / min, and cooled to room temperature to obtain the SmMn-SSZ-39 core.

[0053] (2) Preparation of core-shell SCR catalyst with SSZ-39 molecular sieve as carrier: 50 g of anhydrous ethanol and 50 g of deionized water were weighed, 0.5 g of SmMn-SSZ-39 was weighed, and the mixture was stirred at room temperature for 1 h. 1 g of polyvinyl pyrrolidone was weighed and added to the above solution. After stirring for 3 h, solution C was obtained. A mixed solution of 0.4 g of Ce(NO3)2·6H2O, 4 g of hexamethylenetetramine and 5 g (about 5 mL) of 0.3MH2SO4 was mixed evenly and reacted at 80 °C for 2 h to obtain solution D. Solution D was added dropwise to solution C, and the mixture was stirred for 1 h. The mixture was grown in situ at 120 °C for 8 h, dried at 60 °C for 8 h, and then calcined at 650 °C for 6 h in an air flow of 20 mL / min. The mixture was cooled to room temperature to obtain a core-shell SCR catalyst with SSZ-39 molecular sieve as carrier.

[0054] See also Figure 1 The figure shows the crystal phase structure of SSZ-39 molecular sieve and CeO2, indicating that the material has a composite molecular sieve with an AEI eutectic framework structure, and the core-shell structure does not destroy the AEI framework structure of the molecular sieve.

[0055] See also Figure 2 It can be observed in the figure that compared with Comparative Examples 1, 2 and 3, (SmMn-SSZ-39)@SO4 in Example 1 2- -CeO2 catalyst exhibits high low-temperature catalytic activity and high high-temperature catalytic activity. At a temperature of 500°C, (SmMn-SSZ-39)@SO4 in Example 1 2-The NO conversion rate of the -CeO2 catalyst is as high as 96%, while the NO conversion rate of the catalyst in Mn-SSZ-39 in Comparative Example 2 is only 72%, indicating that Sm 2+ The addition and core-shell structure significantly improve the low-temperature and high-temperature activities of the catalyst for SCR; the catalytic activities of Comparative Example 3 and Example 1 are not much different, but the crystallization time required for the preparation of the inner core SmMn-SSZ-39 prepared by the γ-ray assisted method is greatly shortened.

[0056] See Figure 3 In the figure, it can be observed that after 25 minutes of introducing SO2, the NO conversion rate of Comparative Example 1 decreased sharply, and its denitrification performance dropped to about 20%; while the NO conversion rate of Example 1 started to decrease after 50 minutes, and its denitrification performance could also be maintained at about 70%, indicating that the outer shell SO4 2- -CeO2 can improve the sulfur resistance of the catalyst and prevent the catalyst from poisoning and deactivating.

[0057] See Figure 4 For Example 1, it is the microscopic structure diagram of the uniform dispersion of Mn and Sm on the SSZ-39 molecular sieve. Figure 5 And Figure 6 are the microscopic structure diagrams of two comparative examples (Comparative Example 4 and Comparative Example 5) respectively. Figure 5 (Comparative Example 4, CuMn-SSZ-39 inner core) and Figure 6 (Comparative Example 5, CuSmMn-SSZ-39 inner core).

[0058] The surface of SSZ-39 is rough, while see Figure 7 For this catalyst, the surface is smooth, indicating that the SO4 2- -CeO2 thin film shell grows on its surface.

[0059] A core-shell type SCR catalyst using SSZ-39 molecular sieve as a carrier, the catalyst has SmMn-SSZ-39 as the inner core and SO4 2- -CeO2 thin film as the shell layer.

[0060] Application of a core-shell type SCR catalyst using SSZ-39 molecular sieve as a carrier in the ammonia selective catalytic reduction reaction NH3-SCR.

[0061] Example 2

[0062] A preparation method of a core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier, comprising the following steps: (1) Preparation of the SmMn-SSZ-39 core: Mix 3 g of Beta zeolite, 24.8 g of silica sol, 20 g of NaOH, 28.5 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide and 85 g of deionized water, and stir well for 2 h to obtain gel A; Mix 80 g of 0.1 M Mn(NO3)2, 20 g of 0.1 M Sm(NO3)2 and 30 g of deionized water, and stir well at room temperature for 3.0 h to obtain solution B; After thoroughly stirring the above gel A and solution B, transfer them to a high-pressure reactor, and irradiate with γ-rays at a dose rate of 3.5 kGy / h, and hydrothermally crystallize at 180 °C for 24 h; After the reaction is completed and cooled to room temperature, filter and separate, wash the filter cake with deionized water until neutral, dry at 80 °C for 10 h, then calcine in an air stream of 20 mL / min at 650 °C for 6 h, and cool to room temperature to obtain the SmMn-SSZ-39 core.

[0063] (2) Preparation of the core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier: Weigh 80 g of absolute ethanol and 80 g of deionized water, weigh 0.8 g of SmMn-SSZ-39, stir well at room temperature for 1 h, weigh 1 g of polyvinylpyrrolidone and put it into the above solution, stir for 3 h to obtain solution C. After mixing a mixed solution of 0.4 g of Ce(NO3)2·6H2O, 4 g of hexamethylenetetramine and 5 g of 0.3 M H2SO4 evenly, react at 80 °C for 2 h to obtain solution D; Slowly add solution D dropwise to solution C, continue to stir for 1 h, grow in situ at 120 °C for 8 h, dry at 80 °C for 6 h, cool to room temperature, wash with deionized water until the washing liquid is neutral and dry, then calcine in an air stream of 20 mL / min at 650 °C for 6 h, and cool to room temperature to obtain the core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier.

[0064] A core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier, the catalyst uses SmMn-SSZ-39 as the core and SO4 2- -CeO2 film as the shell layer.

[0065] Application of a core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier in the ammonia selective catalytic reduction reaction NH3-SCR.

[0066] Example 3

[0067] A preparation method of a core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier, comprising the following steps: (1) Preparation of the SmMn-SSZ-39 core: Mix 3.8 g of ZSM-5 zeolite, 35.8 g of sodium silicate, 20 g of KOH, 28.5 g of N-methyl-N-ethyl-2,6-dimethylpiperidinium hydroxide, and 90 g of deionized water, and stir well for 2 h to obtain gel A; Mix 60 g of 0.1 M Mn(NO3)2, 25 g of 0.1 M Sm(NO3)2, and 20 g of deionized water, and stir well at room temperature for 1 h to obtain solution B; After thoroughly stirring the above gel A and solution B, transfer them to a high-pressure reaction kettle, irradiate with γ-rays at a dose rate of 3.5 kGy / h, and hydrothermally crystallize at 180 °C for 1 d; After the reaction is completed and cooled to room temperature, filter and separate, wash the filter cake with deionized water until neutral, dry at 80 °C for 10 h, then calcine in an air stream of 20 mL / min at 650 °C for 6 h, and cool to room temperature to obtain the SmMn-SSZ-39 core.

[0068] (2) Preparation of the core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier: Weigh 100 g of absolute ethanol and 100 g of deionized water, weigh 1 g of SmMn-SSZ-39, stir well at room temperature for 1 h, weigh 3 g of polyvinylpyrrolidone and put it into the above solution, stir for 3 h to obtain solution C. After mixing a mixed solution of 0.8 g of Ce(NO3)2·6H2O, 3 g of hexamethylenetetramine, and 12 g of 0.3 M H2SO4 evenly, react at 80 °C for 2 h to obtain solution D; Dropwise add solution D to solution C, continue to stir for 1 h, grow in situ at 120 °C for 8 h, cool to room temperature, wash with deionized water until the washing liquid is neutral and dry, then calcine in an air stream of 20 mL / min at 650 °C for 6 h, and cool to room temperature to obtain the core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier.

[0069] A core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier, where the catalyst has a SmMn-SSZ-39 core and a SO4 2- -CeO2 thin film as the shell layer.

[0070] Application of a core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier in the ammonia selective catalytic reduction reaction NH3-SCR.

[0071] Example 4

[0072] A preparation method of a core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier, comprising the following steps: (1) Preparation of the SmMn-SSZ-39 core: Mix 4 g of MOR zeolite, 38.5 g of sodium silicate, 25 g of NaOH, 28.5 g of N-methyl-N-ethyl-2,6-dimethylpiperidinium hydroxide, and 100 g of deionized water, and stir well for 1 h to obtain gel A; Mix 60 g of 0.1M Mn(NO3)2, 25 g of 0.1M Sm(NO3)2, and 20 g of deionized water, and stir well at room temperature for 2 h to obtain solution B; After fully stirring the above gel A and solution B, transfer them to a high-pressure reactor, irradiate with γ-rays at a dose rate of 0.5 kGy / h, and hydrothermally crystallize at 80 °C for 10 h; After the reaction is completed and cooled to room temperature, filter and separate, wash the filter cake with deionized water until neutral, dry at 80 °C for 8 h, then calcine in an air stream of 5 mL / min at 400 °C for 8 h, and cool to room temperature to obtain the SmMn-SSZ-39 core.

[0073] (2) Preparation of the core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier: Weigh 80 g of absolute ethanol and 80 g of deionized water, weigh 0.8 g of SmMn-SSZ-39, stir well at room temperature for 0.5 h, weigh 3 g of polyvinylpyrrolidone and put it into the above solution, stir at room temperature for 2 h to obtain solution C; After mixing a mixed solution of 0.6 g of Ce(NO3)2·6H2O, 3 g of polydimethyldiallylammonium chloride, and 10 g of 0.3M H2SO4 evenly, react at 60 °C for 8 h to obtain solution D; Dropwise add solution D to solution C, continue to stir for 3 h, grow in situ at 80 °C for 12 h, cool to room temperature, wash with deionized water until the washing liquid is neutral and dry, then calcine in an air stream of 5 mL / min at 400 °C for 8 h, and cool to room temperature to obtain the core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier.

[0074] A core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier, the catalyst has SmMn-SSZ-39 as the core, and SO4 2- -CeO2 film as the shell layer.

[0075] Application of a core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier in the ammonia selective catalytic reduction reaction NH3-SCR.

[0076] Example 5

[0077] A preparation method of a core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier, comprising the following steps: (1) Preparation of the SmMn-SSZ-39 core: Mix 3.5 g of Y zeolite, 30 g of amorphous silica, 20 g of NaOH, 30 g of N-methyl-N-ethyl-2,6-dimethylpiperidinium hydroxide, and 80 g of deionized water, and stir well at room temperature for 5 h to obtain gel A; Mix 60 g of 0.1 M Mn(NO3)2, 25 g of 0.1 M Sm(NO3)2, and 20 g of deionized water, and stir well at room temperature to obtain solution B; After fully stirring the above gel A and solution B, transfer them to a high-pressure reaction kettle, and irradiate with γ-rays at a dose rate of 4.5 kGy / h, and hydrothermally crystallize at 200 °C for 9 h; After the reaction is completed and cooled to room temperature, filter and separate, wash the filter cake with deionized water until neutral, dry at 90 °C for 12 h, and then calcine in an air stream of 50 mL / min at 850 °C for 3 h, and cool to room temperature to obtain the SmMn-SSZ-39 core.

[0078] (2) Preparation of the core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier: Weigh 60 g of absolute ethanol and 60 g of deionized water, weigh 0.6 g of SmMn-SSZ-39, stir well at room temperature for 2 h, weigh 4 g of polyvinylpyrrolidone and put it into the above solution, and stir at room temperature for 6 h to obtain solution C; After mixing the mixed solution of 0.5 g of Ce(NO3)2·6H2O, 3 g of polydimethyldiallylammonium chloride, and 10 g of 0.3 M H2SO4 evenly, react at 80 °C for 4 h to obtain solution D; Dropwise add solution D to solution C, continue to stir for 1 h, react at 120 °C for 8 h, cool to room temperature, wash with deionized water until the washing liquid is neutral and dry, and then calcine in an air stream of 50 mL / min at 850 °C for 3 h, and cool to room temperature to obtain the core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier.

[0079] A core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier, the catalyst uses SmMn-SSZ-39 as the core, and SO4 2- -CeO2 film as the shell layer.

[0080] Application of a core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier in the ammonia selective catalytic reduction reaction NH3-SCR.

[0081] Example 6

[0082] The difference between this example and Example 1 is only that: the Ce source is cerium acetate, the manganese source is manganese acetate, the samarium source is samarium acetate monohydrate, the silicon source is nano-silica, and the sulfuric acid concentration is 0.1 M.

[0083] Comparative Example 1 (only the SmMn-SSZ-39 core was prepared in this comparative example)

[0084] Preparation of the SmMn-SSZ-39 core: Mix 2.4 g of Y zeolite, 30 g of silica white, 20 g of NaOH, 22.5 g of N,N-diethyl-2,6-dimethylpiperidinium hydroxide, and 85 g of deionized water, and stir well for 2 h to obtain Gel A; Mix 80 g of 0.1 M Mn(NO3)2, 20 g of 0.1 M Sm(NO3)2, and 30 g of deionized water, and stir well to obtain Solution B; After fully stirring the above Gel A and Solution B, transfer them to a high-pressure reaction kettle, irradiate with γ-rays at a dose rate of 3.5 kGy / h, and hydrothermally crystallize at 180 °C for 1 d; After the reaction is completed, filter and separate, wash the filter cake with deionized water until neutral, dry at 80 °C for 10 h, then calcine in an air flow of 20 mL / min at 650 °C for 6 h, and cool to room temperature to obtain the SmMn-SSZ-39 core.

[0085] Comparative Example 2 (no samarium source was added in this comparative example, and only the Mn-SSZ-39 core was prepared)

[0086] Preparation of the Mn-SSZ-39 catalyst: Mix 2.4 g of Y zeolite, 30 g of silica white, 20 g of NaOH, 22.5 g of N,N-diethyl-2,6-dimethylpiperidinium hydroxide, and 85 g of deionized water, and stir well for 2 h to obtain Gel A; Mix 80 g of 0.1 M Mn(NO3)2 and 30 g of deionized water, and stir well to obtain Solution B; After fully stirring the above Gel A and Solution B, transfer them to a high-pressure reaction kettle, irradiate with γ-rays at a dose rate of 3.5 kGy / h, and hydrothermally crystallize at 180 °C for 1 d; After the reaction is completed, filter and separate, wash the filter cake with deionized water until neutral, dry at 80 °C for 10 h, then calcine in an air flow of 20 mL / min at 650 °C for 6 h, and cool to room temperature to obtain the Mn-SSZ-39 catalyst.

[0087] Comparative Example 3 (γ-ray irradiation and in-situ growth method were not used in this comparative example)

[0088] Preparation of SmMn-SSZ-39 core: Mix 2.4 g of Y zeolite, 30 g of silica white, 20 g of NaOH, 22.5 g of N,N-diethyl-2,6-dimethylpiperidinium hydroxide, and 85 g of deionized water. After stirring well for 2 h, gel A is obtained; Mix 80 g of 0.1 M Mn(NO3)2, 20 g of 0.1 M Sm(NO3)2, and 30 g of deionized water. After stirring well, solution B is obtained; After stirring gel A and solution B well, transfer them to a high-pressure reactor and hydrothermally crystallize at 180 °C for 4 d; After the reaction, filter and separate, wash the filter cake with deionized water until neutral, dry at 80 °C for 10 h, then calcine in an air flow of 20 mL / min at 650 °C for 6 h, and cool to room temperature to obtain the SmMn-SSZ-39 core.

[0089] Preparation of core-shell SCR catalyst with SSZ-39 molecular sieve as carrier: Weigh 50 g of absolute ethanol and 50 g of deionized water, weigh 0.5 g of SmMn-SSZ-39, stir well at room temperature for 1 h, weigh 1 g of polyvinylpyrrolidone and put it into the above solution. After stirring for 3 h, add a mixed solution of 0.4 g of Ce(NO3)2, 4 g of hexamethylenetetramine, and 5 g of 0.3 M H2SO4 to the above solution. After reacting at 80 °C for 8 h, a pale yellow gel appears. Transfer the pale yellow gel to an oven at 120 °C and dry for 12 h; After grinding the dried sample, then calcine in an air flow of 20 mL / min at 650 °C for 6 h, and cool to room temperature to obtain the core-shell SCR catalyst with SSZ-39 molecular sieve as carrier.

[0090] Comparative Example 4

[0091] The difference between this comparative example and Example 1 is only that: Cu(NO3)2 is used to replace Sm(NO3)2, and finally the CuMn-SSZ-39 core is obtained. The core synthesis time of this comparative example is 2 d.

[0092] Comparative Example 5

[0093] The difference between this comparative example and Example 1 is only that: "Mix 80 g of 0.1 M Mn(NO3)2, 20 g of 0.1 M Sm(NO3)2, and 30 g of deionized water" in Example 1 is modified to "Mix 40 g of 0.1 M Mn(NO3)2, 40 g of 0.1 M Cu(NO3)2, 20 g of 0.1 M Sm(NO3)2, and 30 g of deionized water", and finally the CuSmMn-SSZ-39 core is obtained. The core synthesis time of this comparative example is 3 d.

[0094] See Figure 5 and Figure 6, it can be seen that the metal species cannot be evenly dispersed on the kernels obtained in Comparative Example 4 and Comparative Example 5, indicating that only the SmMn-SSZ-39 of the present invention can play a role in evenly dispersing and shortening the synthesis time of the catalyst.

[0095] NH3-SCR performance test of the catalyst: Weigh 500 mg of the catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 respectively, and conduct NH3-SCR performance tests in simulated diesel exhaust gas. The simulated exhaust gas composition is: 500 ppm NO, 500 ppm NH3, 3% O2, and carrier gas N2 as the balance gas. The gas hourly space velocity (GHSV) is 60,000 h -1 .

[0096] SO2 tolerance test of the catalyst: Compare the sulfur resistance performance of the catalysts prepared in Example 1 and Comparative Example 1. The reaction conditions are as follows: temperature is 240 °C, 500 ppm NO, 500 ppm NH3, 3% O2, 100 ppm SO2, and carrier gas N2 as the balance gas. The gas hourly space velocity (GHSV) is 60,000 h -1 .

[0097] It should be understood that, in order to streamline the present disclosure and assist in understanding one or more of the various inventive aspects, in the above description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the disclosed method should not be construed as reflecting the intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected by the claims, the inventive aspects lie in less than all the features of the previously disclosed embodiments. Thus, the claims following the detailed description are hereby expressly incorporated into the detailed description, where each claim stands on its own as a separate embodiment of the present invention.

[0098] Although the present invention has been described in terms of a limited number of embodiments, those skilled in the art within the technical field will appreciate, from the above description, that other embodiments can be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification has been principally selected for readability and teaching purposes rather than for the purpose of explaining or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. For the scope of the present invention, the disclosure of the present invention is illustrative rather than restrictive, and the scope of the present invention is defined by the appended claims.

[0099] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier, characterized in that, It includes the following steps: Step 1, Preparation of SmMn-SSZ-39 core: Mix the silicon source, zeolite seeds, alkali source, organic structure-directing agent and deionized water evenly and stir for 1.0 - 5.0 h at room temperature to obtain gel A; mix the manganese source, samarium source and deionized water and stir for 0.5 - 3.0 h at room temperature to obtain solution B; mix solution B and gel A evenly under stirring according to the mass ratio of 1:(1.20 - 1.87), transfer to a high-pressure reactor, and carry out hydrothermal reaction under γ-ray irradiation with a dose rate of 0.5 - 4.5 kGy / h, hydrothermal at 80 - 200 °C for 8 - 24 h. After the reaction ends and cools to room temperature, filter; wash the filter cake with deionized water until the washing liquid is neutral and dry for 8 - 12 h, then calcine in an air flow of 5 - 50 mL / min at 400 - 850 °C for 3 - 8 h, cool to room temperature to obtain the SmMn-SSZ-39 core; Step 2, Preparation of core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier: Disperse the SmMn-SSZ-39 core in a mixed solution of absolute ethanol and deionized water and stir for 0.5 - 2 h at room temperature; then add the quaternary ammonium salt ionic surfactant to the mixed solution and stir for 2 - 6 h at room temperature to obtain solution C; mix the Ce source, hexamethylenetetramine and sulfuric acid evenly in a flask and continue to react at 60 - 80 °C for 2 - 8 h to obtain solution D; add solution D dropwise to solution C, and the mass ratio of solution D to solution C is 1:(9.23 - 17.21), continue to stir for 1 - 3 h, in-situ grow at 80 - 120 °C for 8 - 12 h, dry at 60 - 80 °C for 6 - 8 h, then calcine in an air flow of 5 - 50 mL / min at 400 - 850 °C for 3 - 8 h to obtain the core-shell SCR catalyst with SSZ-39 molecular sieve as the carrier.

2. The preparation method according to claim 1, characterized in that, In gel A, the mass ratio of zeolite seeds, silicon source, alkali source, organic structure-directing agent and deionized water is 1:(8.27 - 12.5):(5.26 - 8.33):(7.125 - 9.5):(22.86 - 35.42); In solution B, the mass ratio of manganese source, samarium source and deionized water is (1.27 - 2.13):1:(23.81 - 44.78).

3. The preparation method according to claim 1, characterized in that, The silicon source is selected from any one of amorphous silica, nano-silica, silica sol or sodium silicate; The zeolite seeds are selected from any one of Y zeolite, Beta zeolite, ZSM-5 zeolite or MOR zeolite; The alkali source is selected from any one of potassium hydroxide or sodium hydroxide; The organic structure-directing agent is selected from any one of N,N-diethyl-2,6-dimethylpiperidinium hydroxide, N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, N-methyl-N-ethyl-2,6-dimethylpiperidinium hydroxide; The manganese source is selected from any one of manganese nitrate or manganese acetate; The samarium source is selected from any one of samarium nitrate or samarium acetate monohydrate.

4. The preparation method according to claim 1, characterized in that, γ rays originate from 60 a Co ionization radiation source.

5. The preparation method according to claim 1, characterized in that, In solution C, the mass ratio of the SmMn-SSZ-39 core, the quaternary ammonium salt ionic surfactant, absolute ethanol, and deionized water is 1:(1.25 - 6.67):100:100; In solution D, the mass ratio of the Ce source, hexamethylenetetramine, and sulfuric acid is 1:(3.75 - 10):(0.3675 - 0.588).

6. The preparation method according to claim 1, characterized in that, The Ce source is selected from any one of cerium nitrate hexahydrate or cerium acetate; The quaternary ammonium salt ionic surfactant is selected from any one of polyvinylpyrrolidone or polydimethyldiallylammonium chloride; The concentration of sulfuric acid is 0.1 - 0.3 M.

7. A core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier obtained by the preparation method according to claim 1, characterized in that, The catalyst has a core of SmMn-SSZ-39 and a shell layer of SO4 2- -CeO2 film.

8. Application of the core-shell type SCR catalyst with SSZ-39 molecular sieve as the carrier according to claim 7 in the ammonia selective catalytic reduction reaction NH3-SCR.

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