Cu / ssz-39 catalyst and use thereof

Abstract

The application relates to a Cu / SSZ-39 catalyst and application thereof, which comprises an SSZ-39 molecular sieve carrier and Cu loaded thereon, the molar ratio of SiO2 / Al2O3 in the catalyst is [5, 50], the molar ratio of Cu / Al is [0.1, 0.5], and the content of aluminum pairs is not less than 88%. The content of aluminum pairs in the prepared SSZ-39 molecular sieve is more than 88%, so that the Cu / SSZ-39 catalyst after loading of copper can withstand the severe hydrothermal treatment condition of 1000 DEG C-10h, that is, the catalyst shows excellent hydrothermal stability, which is much higher than the catalytic performance in the prior art.

Description

Technical Field

[0001] This application relates to a Cu / SSZ-39 catalyst and its application. Background Technology

[0002] In the entire diesel vehicle China VI after-treatment system, the NH3-SCR catalyst is responsible for removing NO. x The conversion of nitrogen to nitrogen (reaction formula: 4NH3 + 4NO + O2 → 4N2 + 6H2O, known as the standard SCR reaction; 2NH3 + NO + NO2 → 2N2 + 3H2O, known as the fast SCR reaction) plays a crucial role in ensuring that exhaust gases meet regulatory emission standards. Molecular sieves used in NH3-SCR research include ZSM-5, Beta, and SAPO-34, but all have not been widely adopted due to poor hydrothermal stability. SSZ-13 silica-alumina molecular sieve, which belongs to the CHA topology of SAPO-34, has seen some application, but copper-supported SSZ-13 catalysts still face the problem of unsatisfactory hydrothermal stability.

[0003] Literature reports (Chem. Commun., 2012, 48, 8264-8266) that the hydrothermal stability of Cu / SSZ-39 catalysts is superior to that of Cu / SSZ-13 catalysts, thus attracting widespread attention from scholars. However, the conventional preparation process of SSZ-39 molecular sieves usually uses USY as a raw material, which has a complex preparation process, high cost, and pollution problems. To broaden the raw material sources for the synthesis of SSZ-39 molecular sieves, ZSM-5 and Beta have been used as the sole silicon and aluminum sources. Although the raw material cost has been reduced, it is still relatively high. To further reduce the raw material cost, some researchers have reported the synthesis of SSZ-39 molecular sieves using common silicon and aluminum sources, but the crystallization temperature and time in this patent are long, resulting in low synthesis efficiency. Patent CN109336131B uses a homogeneous emulsification method to reduce the synthesis conditions to 130-150℃ for 3-24 hours of crystallization, but there is still room for optimization. Furthermore, stricter emission standards place higher demands on the hydrothermal stability of the Cu / SSZ-39 catalyst, necessitating measures to further improve its hydrothermal stability. Patent CN113019438B employs yttrium doping to enhance the hydrothermal stability of the Cu / SSZ-39 catalyst, with a hydrothermal treatment condition of 800℃-16h. However, this hydrothermal treatment condition is not stringent enough, and the high price of yttrium further increases the catalyst's preparation cost. Summary of the Invention

[0004] To address the aforementioned issues, this application proposes a Cu / SSZ-39 catalyst, comprising an SSZ-39 molecular sieve support and Cu supported thereon, wherein the molar ratio of SiO2 / Al2O3 in the catalyst is [5, 50], the molar ratio of Cu / Al is [0.1, 0.5], and the aluminum content is not less than 88%.

[0005] Preferably, the catalyst is synthesized according to the following steps:

[0006] The mordenite, template agent, alkali, and silicon source are mixed and stirred to obtain a mixture;

[0007] The mixture is crystallized to obtain a crystallized product;

[0008] The crystallized material is dried and calcined to obtain a carrier;

[0009] The support and copper source are ion exchanged to obtain a mixed solution, which is then spray-dried and calcined to obtain a catalyst.

[0010] Preferably, the mordenite is hydrogen-form mordenite, and the alkali is tetrabutylammonium hydroxide. This patent uses tetrabutylammonium hydroxide to replace the inorganic alkali in conventional methods, eliminating the subsequent ammonium exchange process, thereby significantly reducing the discharge of nitrogen-containing wastewater and making the preparation process more environmentally friendly.

[0011] Preferably, the SiO2 / Al2O3 molar ratio of the selected hydrogen-form mordenite is between 5 and 20; the template agent is N,N-dimethyl-3,5-dimethylpiperidinium hydroxide. This application uses hydrogen-form mordenite as the aluminum source and partially as the silicon source. Since hydrogen-form mordenite and SSZ-39 molecular sieve have the same primary structural unit 4MR, this structural unit can play a role in inducing synthesis, thus enabling the target product to be obtained at a lower crystallization temperature and in a shorter time.

[0012] Preferably, the molar ratio of the mixture is SiO2:Al2O3:template:tetrabutylammonium hydroxide:H2O = (10-65):1:(0.2-5):(4-25):(200-1500).

[0013] Preferably, the crystallization temperature for the crystallization treatment is 100-120℃, and the crystallization time is 1-2h.

[0014] Preferably, the calcination temperature after crystallization is 300-550℃, and the calcination time is 4-8h.

[0015] Preferably, the selected copper source is copper acetate monohydrate.

[0016] Preferably, the liquid-to-solid ratio of the selected ion exchange is between 2 and 5, the copper ion concentration is 0.1-1.0 mol / L, the exchange temperature is 25-80℃, and the exchange time is 1-4 h;

[0017] The spray drying temperature of the ion exchange mixture is 100-120℃, the calcination temperature is 300-550℃, and the calcination time is 2-4h.

[0018] This application also discloses the application of the Cu / SSZ-39 catalyst in the NH3-SCR catalytic reaction. This application describes a catalyst that can induce the formation of more aluminum pairs, thereby giving the prepared Cu / SSZ-39 catalyst superior hydrothermal stability.

[0019] This application can bring the following beneficial effects:

[0020] 1. This application uses hydrogen-form mordenite as the aluminum source and part of the silicon source. Since hydrogen-form mordenite and SSZ-39 molecular sieve have the same primary structural unit 4MR, this structural unit can play a role in inducing synthesis, thus the target product can be obtained at a lower crystallization temperature and in a shorter time.

[0021] 2. This patent uses tetrabutylammonium hydroxide to replace the inorganic base in conventional methods, eliminating the subsequent ammonium exchange process, thereby significantly reducing the discharge of nitrogen-containing wastewater and making the preparation process more environmentally friendly.

[0022] 3. The aluminum content of the SSZ-39 molecular sieve prepared by this invention reaches more than 88%, which enables the copper-loaded Cu / SSZ-39 catalyst to withstand the harsh hydrothermal treatment conditions of 1000℃-10h. That is, the catalyst exhibits excellent hydrothermal stability, which is far superior to the catalytic performance of existing inventions. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0024] Figure 1 The image shows the XRD pattern of the SSZ-39 molecular sieve sample prepared in Example 1.

[0025] Figure 2 SEM image of the SSZ-39 molecular sieve sample prepared in Example 1.

[0026] Figure 3 The image shows the XRD pattern of the SSZ-39 molecular sieve sample prepared in Example 2.

[0027] Figure 4SEM image of the SSZ-39 molecular sieve sample prepared in Example 2.

[0028] Figure 5 The image shows a SEM image of the SSZ-39 molecular sieve sample prepared in Example 3.

[0029] Figure 6 The XRD pattern of the SSZ-39 molecular sieve sample prepared for Comparative Example 1.

[0030] Figure 7 SEM image of the SSZ-39 molecular sieve sample prepared for Comparative Example 1.

[0031] Figure 8 SEM image of the sample prepared for Comparative Example 2. Detailed Implementation

[0032] To clearly illustrate the technical features of this solution, the following detailed description, in conjunction with the accompanying drawings, will be provided.

[0033] The phase structure of the samples was determined using a Bruker D2 X-ray diffractometer (XRD). The morphology of the samples was analyzed using a FEIQUANTA 400 scanning electron microscope (SEM), with all samples subjected to gold sputtering before analysis. The elemental composition of the samples was determined using a Rigaku ZSX Primus II X-ray fluorescence spectrometer (XRF). Nitrogen physical adsorption was determined using a Micromeritics ASAP 2020 physical adsorption analyzer. The aluminum content was determined using the method described in the literature (Chem. Mater. 2016, 28, 7, 2236-2247).

[0034] Example 1

[0035] 122.02 g of deionized water, 236.30 g of TBAOH (25% concentration), 18.17 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (25% concentration), and 80.24 g of silica sol (30% SiO2 concentration) were added to a beaker and stirred for 1 h. Then, 23.27 g of mordenite (SiO2 / Al2O3 = 5.2) was added to the beaker, and stirring was continued for 1 h. The mixture was poured into a dynamic crystallization reactor and crystallized at 120 °C for 1 h. After the temperature of the reactor was reduced to room temperature, the crystallized product was filtered, washed, and placed in a 120 °C oven for 4 h. Then, it was calcined in a muffle furnace at 550 °C for 4 h to obtain the hydrogen-form SSZ-39 molecular sieve. Using copper acetate monohydrate as the copper source, with a liquid-to-solid ratio of 5 and a copper ion concentration of 0.28 mol / L, the reaction was carried out at 25 °C for 4 h. Subsequently, spray drying was performed, with the discharge temperature controlled at 110 °C. Finally, calcination was carried out at 550 °C for 2 h to obtain the Cu / SSZ-39 catalyst. Figure 1 , Figure 2 The images show the XRD and SEM images of the SSZ-39 molecular sieve sample prepared in Example 1. According to the XRF analysis, the SiO2 / Al2O3 ratio of the product obtained in Example 1 is 10.5, and the Cu / Al ratio is 0.33. 2+ The UV-Vis spectra after the exchange showed that the aluminum content in Example 1 reached 95.2%.

[0036] Example 2

[0037] 141.56 g of deionized water, 236.51 g of TBAOH (25% concentration), 24.25 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (25% concentration), and 45.34 g of silica sol (30% SiO2 concentration) were added to a beaker and stirred for 1 h. Then, 32.34 g of mordenite (SiO2 / Al2O3 = 13.4) was added to the beaker, and stirring continued for 1 h. The mixture was then poured into a dynamic crystallization reactor and crystallized at 110 °C for 1 h. After the reactor temperature dropped to room temperature, the crystallized product was filtered, washed, and placed in a 120 °C oven for 4 h. Then, it was calcined in a muffle furnace at 540 °C for 5 h to obtain the hydrogen-form SSZ-39 molecular sieve. Using copper acetate monohydrate as the copper source, with a liquid-to-solid ratio of 4 and a copper ion concentration of 0.25 mol / L, the reaction was carried out at 40 °C for 4 h. Subsequently, spray drying was performed, with the discharge temperature controlled at 110 °C. Finally, calcination was carried out at 520 °C for 4 h to obtain the Cu / SSZ-39 catalyst. Figure 3 , Figure 4The images show the XRD and SEM images of the SSZ-39 molecular sieve sample prepared in Example 2. According to the XRF analysis, the SiO2 / Al2O3 ratio of the product obtained in Example 2 is 16.6, and the Cu / Al ratio is 0.30. 2+ The UV-Vis spectra after the exchange showed that the aluminum content in Example 2 reached 92.8%.

[0038] Example 3

[0039] 168.91 g of deionized water, 227.19 g of TBAOH (25% concentration), 25.95 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (25% concentration), and 18.01 g of silica sol (30% SiO2 concentration) were added to a beaker and stirred for 1 h. Then, 39.94 g of mordenite (SiO2 / Al2O3 = 20.2) was added to the beaker, and stirring continued for 1 h. The mixture was poured into a dynamic crystallization reactor and crystallized at 100 °C for 2 h. After the temperature of the reactor was reduced to room temperature, the crystallized product was filtered, washed, and placed in an oven at 120 °C for 4 h. Then, it was calcined in a muffle furnace at 520 °C for 6 h to obtain the hydrogen-form SSZ-39 molecular sieve. Using copper acetate monohydrate as the copper source, with a liquid-to-solid ratio of 3.5 and a copper ion concentration of 0.22 mol / L, the reaction was carried out at 60 °C for 2 h. Subsequently, spray drying was performed, with the discharge temperature controlled at 120 °C. Finally, calcination was carried out at 540 °C for 3 h to obtain the Cu / SSZ-39 catalyst. Figure 5 This is a SEM image of the SSZ-39 molecular sieve sample prepared in Example 3. According to XRF analysis, the SiO2 / Al2O3 ratio of the product obtained in Example 3 is 18.8, and the Cu / Al ratio is 0.26. (Co) 2+ The UV-Vis spectra after the exchange showed that the aluminum content in Example 3 reached 88.6%.

[0040] Comparative Example 1

[0041] 253.08 g of deionized water, 40.53 g of NaOH solution (25% concentration), 78.11 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (25% concentration), and 56.18 g of silica sol (30% SiO2 concentration) were added to a beaker and stirred for 1 h. Then, 52.09 g of USY (SiO2 / Al2O3 = 22.2) was added to the beaker, and stirring continued for 1 h. The mixture was poured into a dynamic crystallization reactor and crystallized at 150 °C for 24 h. After the crystallization was completed, the reactor temperature was allowed to drop to room temperature. The crystallized product was filtered, washed, and placed in a 120 °C oven for 4 h. Then, it was calcined in a muffle furnace at 520 °C for 6 h to obtain the hydrogen-form SSZ-39 molecular sieve. Using copper acetate monohydrate as the copper source, with a liquid-to-solid ratio of 3.5 and a copper ion concentration of 0.22 mol / L, the reaction was carried out at 60 °C for 2 h. Subsequently, spray drying was performed, with the discharge temperature controlled at 120 °C. Finally, calcination was carried out at 540 °C for 3 h to obtain the Cu / SSZ-39 catalyst. Figure 6 , Figure 7 The images show the XRD and SEM images of the SSZ-39 molecular sieve sample prepared in Comparative Example 1, respectively. According to the XRF analysis, the SiO2 / Al2O3 ratio of the product obtained in Comparative Example 1 is 17.5, and the Cu / Al ratio is 0.27. 2+ The UV-Vis spectra after the exchange showed that the aluminum content in Comparative Example 1 was 24.8%.

[0042] Comparative Example 2

[0043] In Example 1, tetrabutylammonium hydroxide was replaced with tetrapropylammonium hydroxide, while all other preparation conditions remained the same. Figure 8 This is a SEM image of the sample prepared in Comparative Example 2. From... Figure 8 As can be seen, the product is an amorphous substance, and the target molecular sieve product was not obtained, thus indicating that tetrabutylammonium hydroxide is the key raw material of this invention.

[0044] Tables 1 and 2 show the NH3-SCR performance test results of the aluminum-rich Cu / SSZ-39 catalyst prepared in Example 2 and the conventional Cu / SSZ-39 catalyst in Comparative Example 1 in their fresh state and after aging.

[0045] Table 1

[0046]

[0047] Table 2

[0048]

[0049] The crystallization results of Examples 1-3 show that the technical solution of the present invention can obtain pure-phase SSZ-39 molecular sieves at a lower crystallization temperature and in a shorter time. Furthermore, compared with Comparative Example 1, it can be seen that the SSZ-39 molecular sieve obtained by the present invention has a higher aluminum content.

[0050] Catalyst performance testing: The Cu-SSZ-39 molecular sieve powder prepared in Example 2 and Comparative Example 1 was tableted, crushed, and sieved. Samples of 20-40 mesh particles were used for NH3-SCR performance testing. The test conditions were as follows: [NO] = 500 ppm, [NH3] = 500 ppm, [O2] = 10%, [H2O] = 10%, N2 as the equilibrium gas, reaction temperature 125-600℃, and reaction space velocity 30000 h⁻¹. -1 The conditions for hydrothermal aging of the catalyst were: 10% H2O and N2 as the equilibrium gas, treatment temperature of 1000℃, treatment time of 10 h, and space velocity of 30000 h⁻¹. -1 .

[0051] As can be seen from the data in Table 1-2, the Cu / SSZ-39 catalyst rich in aluminum pairs obtained in Example 2, after undergoing a rigorous hydrothermal treatment at 1000℃ for 10h, showed very little change in NO conversion rate compared to the fresh catalyst, while the catalyst performance in Comparative Example 1 decreased significantly. This demonstrates that the Cu / SSZ-39 catalyst rich in aluminum pairs prepared in this invention has excellent hydrothermal stability.

[0052] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method of making a Cu / SSZ-39 catalyst, characterized by: Includes the following steps: Add 122.02g of deionized water, 236.30g of 25% TBAOH, 18.17g of 25% N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, and 80.24g of 30% SiO2 silica sol to a beaker and stir for 1 hour. Then, 23.27g of mordenite with SiO2 / Al2O3 = 5.2 was added to the beaker and stirred for another 1 hour. Pour the above mixture into a dynamic crystallization vessel and crystallize at 120°C for 1 hour. After the heat preservation is completed, and the temperature of the reactor is cooled to room temperature, the crystallized product is filtered, washed, and placed in a 120℃ oven for 4 hours. Then it is placed in a muffle furnace and calcined at 550℃ for 4 hours to obtain hydrogen-form SSZ-39 molecular sieve. Copper acetate monohydrate was used as the copper source, the liquid-to-solid ratio was 5, the copper ion concentration was 0.28 mol / L, and the reaction was carried out at 25℃ for 4 h. Then, spray drying is carried out, and the discharge temperature is controlled at 110℃; Finally, the catalyst was calcined at 550℃ for 2 hours to obtain Cu / SSZ-39 catalyst.

2. The application of the Cu / SSZ-39 catalyst obtained by the preparation method according to claim 1 in the NH3-SCR catalytic reaction.

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