NH3-SCR (selective catalytic reduction) catalyst with high water resistance and sulfur resistance as well as preparation method and application of NH3-SCR catalyst

Abstract

The invention discloses a high-water-resistance sulfur-resistant NH3-SCR catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalysts. According to the preparation method, an ERI type molecular sieve membrane layer is successfully synthesized on a honeycomb cordierite support body by utilizing a one-pot hydrothermal method, and a bimetallic active component is introduced at the same time, so that a single-layer crystalline membrane CuFe-ERI catalyst is obtained; and under the induction of the crystal, a composite crystalline film CHA (at) CuFe-ERI (at) Cor catalyst with a sandwich type structure is hydrothermally synthesized. When the catalyst simulates that flue gas contains 100 ppm of SO2 and / or 5% of H2O, the NOx conversion rate of the whole temperature section is kept stable; especially in a test system containing H2O, the NOx conversion rate of the catalyst at a high temperature section (gt; 500 DEG C) is increased to 100%, which is far better than that of a single-layer film CuFe-ERI catalyst. The prepared catalyst shows a wide temperature conversion window when applied to NH3-SCR, and compared with a traditional denitration catalyst, the method is low in cost, high in yield and high in water resistance and sulfur resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a high water- and sulfur-resistant NH3-SCR catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] At present, with the continuous improvement of global environmental awareness, the ammonia selective catalytic reduction of nitrogen oxides (NH3-SCR) technology, as a key emission reduction means, is showing a strong growth trend in the market demand. To meet the increasingly strict environmental emission standards such as Euro 6, Tier 3, and National VI, many domestic and foreign enterprises have increased their R & D investment, accelerated the development of catalysts and the promotion of NH3-SCR technology, and promoted the diversification of this market. Among them, the research and development of new catalysts not only significantly improves the conversion efficiency of nitrogen oxides, but also effectively reduces the operating cost, finding a better balance point between the economy and environmental protection of the SCR system.

[0003] In recent years, the research on existing novel-structured NH3-SCR catalysts has mainly focused on their structural design. Most of them can construct redox active centers by introducing promoter metals (Fe, Cu, Ce) to regulate the electronic structure, which has been proven to effectively improve the denitrification performance of SCR catalysts (Nano Research, 2022, 15(4): 3001−3009; Inorg. Chem. Front., 2023, 10, 727-755; Journal of Industrial and Engineering Chemistry Volume 107, 25 March 2022, Pages 197-206). Professor Shi Jianwen of Xi'an Jiaotong University et al. (Applied Catalysis B: Environment and Energy, Volume 354, 5 October 2024, 124131) further constructed a TEOS&Mn-BTC catalyst with a hollow sea urchin-like microsphere structure with dual-ligand coordination, regulating the crystal morphology while regulating the electronic structure of the catalyst, thus breaking through the seesaw effect between the denitrification activity and nitrogen selectivity of the catalyst. In addition, in practical applications, due to the presence of SO2 and H2O, the active sites will be damaged, reducing the adsorption capacity of the catalyst for NOx. In order to design catalysts with outstanding selectivity, activity and anti-poisoning ability, core-shell structure materials have been widely used in the NH3-SCR reaction (Chemosphere 333 (2023) 138942; Inorg. Chem. Front., 2023, 10, 727–755). This structural catalyst has many advantages such as a large specific surface area, strong synergistic effect between core-shell materials, confinement effect, and protection of the core by the shell shielding effect. The common structures are two types: core@shell and yolk@shell, and other special structures such as sandwich structures have not been reported. Therefore, it is necessary to further study the influence mechanism of SO2 and H2O on sandwich-structured catalysts to optimize the preparation method, inhibit the adsorption of SO2 and H2O, and construct a new sandwich-structured catalyst with high activity and high water and sulfur resistance, which can fill the gap of such NH3-SCR catalysts. Summary of the Invention

[0004] An object of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a highly water- and sulfur-resistant NH3-SCR catalyst, its preparation method and application.

[0005] The technical solution of the present invention is as follows: The first aspect of the present invention provides a highly water- and sulfur-resistant NH3-SCR catalyst, whose structure includes cordierite with a supporting effect, an ERI molecular sieve membrane layer located on the cordierite, and a CHA molecular sieve membrane layer located on the ERI molecular sieve membrane layer. The ERI molecular sieve membrane layer contains Cu and Fe.

[0006] The catalyst in the present invention is CHA@Cu x Fe y -ERI@Cor sandwich-structured catalyst (where x = 0.05 - 1.5, y = 0.1 - 0.2), a sandwich-structured monolithic catalyst composed of a lower-layer cordierite with a supporting effect, a middle-layer ERI membrane layer with a catalytic effect, and an upper-layer CHA membrane layer with a separation effect. The ERI molecular sieve membrane layer contains Cu and Fe; the catalyst prepared by the present invention shows a wide temperature conversion window when applied to NH3-SCR, and compared with traditional denitration catalysts, this method has low cost, high yield, and strong water- and sulfur-resistance.

[0007] Preferably, the Cu and Fe are uniformly dispersed in the crystal framework of the ERI molecular sieve membrane layer in the form of oxide clusters or ions.

[0008] The second aspect of the present invention provides a preparation method of the catalyst, including the following steps: S1. Prepare an impregnating solution containing ERI molecular sieve seeds, immerse honeycomb cordierite in the impregnating solution, and dry to obtain seeded cordierite; S2. Mix potassium hydroxide, sodium hydroxide, aluminum isopropoxide, silica sol HS-40 with water to form a mixed sol A; mix copper sulfate, ferric chloride, tetraethylenepentamine solution with water to form a mixed solution B; add the mixed solution B to the mixed sol A for aging treatment to obtain a mixed sol C; crystallize the mixed sol C with the seeded cordierite in S1 to obtain Cu x Fe y -ERI@Cor molecular sieve membrane (where x = 0.05 - 1.5, y = 0.1 - 0.2), abbreviated as CuFe-ERI@Cor molecular sieve membrane; S3. Mix N,N,N-trimethyladamantylammonium hydroxide, NaOH, aluminum isopropoxide, silica sol HS-40 with water to form a mixed solution D; crystallize the CuFe-ERI@Cor molecular sieve membrane in S2 with the mixed solution D, and after the reaction is completed, wash, dry, and calcine to obtain the NH3-SCR catalyst.

[0009] The present invention constructs a CHA@CuFe-ERI composite film layer on a honeycomb cordierite support by a secondary hydrothermal synthesis method, that is, a sandwich-structured monolithic catalyst composed of a lower cordierite layer with a supporting function, an intermediate ERI film layer with a catalytic function, and an upper CHA film layer with a separation function. Among them, the intermediate ERI film layer is innovatively hydrothermally synthesized in a dilute solution of an organic template-free. In this process, metal active components are introduced by a one-step method using Cu-TEPA and / or Fe-TEPA as precursors. This catalyst exhibits a wide temperature conversion window in the NH3-SCR reaction, especially still showing excellent NO x conversion rate.

[0010] Preferably, in S1, the preparation method of the ERI-type molecular sieve seeds includes the following steps: Dissolve aluminum sec-butoxide in tetraethylammonium hydroxide to prepare an aluminum source solution; Dropwise add silica sol HS-40 to the aluminum source solution, mix evenly, heat and stir for aging to obtain a solution; Add potassium hydroxide and hexamethylammonium bromide solution to the solution, mix evenly to obtain a mixed solution; Heat the mixed solution for reaction. After the reaction is completed, centrifuge, dry and grind the product, and calcine to obtain the final product.

[0011] Preferably, in the preparation method of the ERI-type molecular sieve seeds, The molar ratio of the components in the synthetic sol in the form of oxides is SiO2:Al2O3:K2O:TEAOH:C 12 H 30 Br2N2:H2O = 1:0.03:0.045:0.8:0.13:25; The aging temperature is 90-100 °C and the time is 16-24 hours; The heating reaction temperature is 140-160 °C and the time is 48-120 hours; The calcination temperature is 500-600 °C and the time is 8-12 hours.

[0012] Specifically, the process of the ERI-type molecular sieve seeds is as follows: Dissolve aluminum sec-butoxide in tetraethylammonium hydroxide (TEAOH) to prepare an aluminum source solution. Subsequently, dropwise add silica sol HS-40 to the aluminum source solution, transfer it to a PP bottle and stir evenly. Place the PP bottle in an oil bath at 90 °C and stir for aging for 20 hours. After aging, add potassium hydroxide and hexamethylammonium bromide (C 12 H 30A solution of Br2N2 was added and mixed thoroughly. Finally, the mixed solution was poured into a reaction kettle and reacted at 150 °C for 120 hours. After the reaction, the product was centrifuged, dried, and ground successively, and then calcined at 550 °C for 10 hours to remove the template agent, obtaining the final product.

[0013] Preferably, in S1, the concentration of the seed-containing impregnation solution is 4-6 wt%, and the number of impregnation times is 1-3 times.

[0014] Preferably, in S2, the molar ratio of the oxides of each component in the synthetic sol is SiO2:Al2O3:K2O:Na2O:H2O:Cu-TEPA:Fe-TEPA = 1:(0.03-0.07):0.11:0.34:120:(0.01-0.15):(0.01-0.2).

[0015] Preferably, in S2, the aging treatment time is 0.5-1.5 h, the crystallization reaction temperature is 170-180 °C, and the crystallization reaction time is 6-24 h.

[0016] Preferably, in S3, the molar ratio of the oxides of each component in the synthetic sol is SiO2:Al2O3:Na2O:H2O:TMAdaOH = 1:0.05:0.05:80:0.2; the crystallization reaction temperature is 150-160 °C, and the time is 1-4 h.

[0017] Specifically, a preparation method of a high water- and sulfur-resistant NH3-SCR catalyst includes the following steps: S1: Prepare an impregnation solution containing ERI molecular sieve seeds. Immerse the honeycomb cordierite in the impregnation solution to load the seeds, and then dry it at 80 °C for standby to obtain the seeded cordierite.

[0018] S2: First, dissolve potassium hydroxide (KOH), sodium hydroxide (NaOH), and aluminum isopropoxide in deionized water in sequence. After stirring until the solution is clear, slowly add silica sol HS-40 to form a mixed sol A. At the same time, dissolve copper sulfate (CuSO4) and ferric chloride (FeCl3) in deionized water in sequence. After stirring until completely dissolved, slowly add tetraethylenepentamine (TEPA) solution, and continue to stir at room temperature for 2 hours to form a mixed solution B. Dropwise add solution B into sol A, and then perform ultrasonic aging treatment for 1 hour.

[0019] Put the above-aged mixed sol and the seeded cordierite support in S1 into a reaction kettle and carry out crystallization at 175 °C. After the reaction, rinse the obtained sample with deionized water until neutral, and then dry it to obtain the product Cux Fe y -ERI@Cor molecular sieve membrane (where x = 0.05 - 1.5, y = 0.1 - 0.2), abbreviated as CuFe-ERI@Cor molecular sieve membrane; S3: Add N,N,N-trimethylammonium hydroxide (TMAdaOH) and NaOH to deionized water in sequence. After stirring until completely dissolved, add aluminum isopropoxide and continue stirring until the solution becomes clear. Subsequently, add silica sol HS-40 and continue stirring and aging to obtain a mixed solution. Put the sample prepared in S2 and the mixed solution into a reaction kettle and crystallize at 155 °C. After the reaction is completed, rinse the obtained sample with deionized water until neutral, dry it, and then calcine it in a muffle furnace to obtain the final product CHA@Cu x Fe y -ERI@Cor sandwich-structured catalyst (where x = 0.05 - 1.5, y = 0.1 - 0.2).

[0020] The third aspect of the present invention provides the application of the described catalyst in the NH3-SCR reaction. This catalyst can be applied in the NH3-SCR reaction.

[0021] The present invention has at least one of the following beneficial effects: (1) The present invention adopts a hydrothermal synthesis step-by-step strategy to construct a monolithic catalyst with a sandwich structure. This method can effectively integrate the support, the active catalytic membrane layer, and the separation membrane layer without relying on external equipment (such as a 3D printer), and has the advantages of simple operation and low cost.

[0022] (2) Under the condition of no organic template agent, the present invention simultaneously and successfully introduces copper ions and iron ions into the ERI-type molecular sieve membrane by a simple one-step hydrothermal method in a dilute solution synthesis sol, breaking through the technical bottleneck that it is difficult to form a film for the ERI-type molecular sieve.

[0023] (3) The catalyst prepared by the present invention has abundant catalytic active sites, exhibits extremely high catalytic activity and stability, and is a new type of catalyst with great development prospects. In the selective catalytic reduction of NO by NH3 x (NH3-SCR) reaction, according to the experimental data of this embodiment, this catalyst achieves 100% NO x conversion rate in a wide temperature range of 200 - 500 °C, and the N2 selectivity is close to 100%. In addition, even in a complex environment containing water and SO2, this catalyst still shows excellent catalytic performance and exhibits excellent water and sulfur resistance.

[0024] (4) The composite crystalline film layer (ERI film layer and CHA film layer) prepared by the present invention constructs a separation-catalysis integrated membrane reactor. Compared with the traditional impregnation coating or single-layer crystalline membrane monolithic catalyst, this composite film layer not only significantly broadens the temperature conversion activity window, but also expands its functions, such as realizing characteristics like dust removal, water resistance, and sulfur resistance, and has broad application prospects. Description of the Drawings

[0025] Figure 1 Shown are the X-ray diffraction (XRD) patterns of the seed crystals, the obtained catalysts in Example 1, and the obtained catalyst in Comparative Example 1. (a) XRD pattern of the molecular sieve seed crystals (the inserted small figure is its SEM image), (b) XRD patterns of the obtained catalysts in Example 1 and Comparative Example 1.

[0026] Figure 2 Shown are the X-ray diffraction (XRD) patterns of the obtained catalysts in Examples 1, 4, and 5.

[0027] Figure 3 Shown are the X-ray diffraction (XRD) patterns of the obtained catalysts in Examples 1, 6, and Comparative Example 3.

[0028] Figure 4 Shown are the X-ray diffraction (XRD) patterns of the obtained catalysts in Examples 1, 7, and 8.

[0029] Figure 5 Shown are the X-ray diffraction (XRD) patterns of the obtained catalysts in Examples 1, 9, and 10.

[0030] Figure 6 Shown are the scanning electron microscope (SEM) images of the obtained catalysts in Example 1 and Comparative Examples 2, 3, 4, and 5; (a) and (b) are Comparative Example 2, (c) and (d) are Comparative Example 5, (e) and (f) are Comparative Example 3, (g) and (h) are Comparative Example 4, (i) and (j) are Example 1.

[0031] Figure 7 Shown are the denitrification performance diagrams of the obtained catalysts in Examples 1 to 10 and Comparative Examples 2, 3, 4, and 5.

[0032] Figure 8 Shown are the water and sulfur resistance performance diagrams of the obtained catalysts in Example 1 and Comparative Example 5 in NH3-SCR. Detailed Embodiments

[0033] In order to make the technical problems, technical solutions, and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Example 1 A preparation method of a high water and sulfur resistant NH3-SCR catalyst specifically includes the following steps: Step 1: Add 0.5 g of ERI molecular sieve into 9.5 g of deionized water, stir evenly and then ultrasonically disperse for 5 minutes to prepare a uniform seed impregnation solution. Subsequently, vertically and slowly immerse the honeycomb cordierite (height 10 cm, diameter 10 mm, Pingxiang Haichuan Chemical Co., Ltd.) into this impregnation solution to uniformly load the seeds, air dry and then repeat the impregnation once. Finally, dry it at 80 °C for standby to obtain the seeded cordierite.

[0035] The process of the ERI molecular sieve in Step 1 is as follows: Dissolve aluminum sec-butoxide in tetraethylammonium hydroxide (TEAOH) to prepare an aluminum source solution. Subsequently, add silica sol HS-40 (with a mass fraction of SiO2 of 40%, Sigma-Aldrich) dropwise to the aluminum source solution, transfer it to a PP bottle and stir evenly. Place the PP bottle in an oil bath at 90 °C and stir and age for 20 hours. After aging, add potassium hydroxide and hexamethylammonium bromide (C 12 H 30 Br2N2) solution in sequence, and mix well. Finally, pour the mixed solution into a reaction kettle and react at 150 °C for 120 hours. After the reaction, perform centrifugation, drying and grinding operations on the product in sequence, and calcine at 550 °C for 10 hours to remove the template agent to obtain the final product; the molar ratio of the oxides of each component in the synthesized sol is n (SiO2): n (Al2O3): n (K2O): n (TEAOH): n (C 12 H 30 Br2N2): n (H2O)=1:0.03:0.045:0.8:0.13:25.

[0036] Step 2: First, dissolve potassium hydroxide (KOH), sodium hydroxide (NaOH) and aluminum isopropoxide in deionized water in sequence. After stirring until the solution is clear, slowly add silica sol HS-40 (with a mass fraction of SiO2 of 40%, Sigma-Aldrich) to form a mixed sol A. At the same time, dissolve copper sulfate (CuSO4) and ferric chloride (FeCl3) in deionized water in sequence. After stirring until completely dissolved, slowly add tetraethylenepentamine (TEPA) solution and continue to stir at room temperature for 2 hours to form a mixed solution B. Dropwise add solution B into sol A, and the ratio of the components in the form of oxides (molar ratio) is n(SiO2): n (Al2O3): n (K2O): n (Na2O): n (H2O): n (Cu-TEPA): n (Fe-TEPA) = 1: 0.05: 0.11: 0.34: 120: 0.1: 0.1. Subsequently, ultrasonic aging treatment is carried out for 1 hour.

[0037] Put the above-aged mixed sol and the seeded cordierite support in Step 1 into a reaction kettle and carry out crystallization at 175 °C for 12 hours. After the reaction is completed, rinse the obtained sample with deionized water until neutral, and dry it to obtain the product CuFe-ERI@Cor molecular sieve membrane; Step 3: Add N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH) and NaOH to deionized water in sequence. After stirring until completely dissolved, add aluminum isopropoxide and continue stirring until the solution is clear. Subsequently, dropwise add silica sol HS-40 and then continue stirring and aging to obtain a mixed solution. The ratio of each component in the form of oxide (molar ratio) is n (SiO2): n (Al2O3): n (Na2O): n (H2O): n (TMAdaOH) = 1: 0.05: 0.05: 80: 0.2.

[0038] Put the above mixed solution and the membrane sample in Step 2 into a reaction kettle and carry out crystallization at 155 °C for 2 hours. After the reaction is completed, rinse the obtained sample with deionized water until neutral, dry it and then calcine it in a muffle furnace at 550 °C for 10 hours to obtain the final product CHA@Cu 0.1 Fe 0.1 -ERI@Cor sandwich-structured catalyst.

[0039] Example 2 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the steps of which are the same as those in Example 1, except that the crystallization time in Step 3 of Example 1 is changed to 1 hour, and finally the catalyst is obtained.

[0040] Example 3 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the steps of which are the same as those in Example 1, except that the crystallization time in Step 3 of Example 1 is changed to 4 hours, and finally the catalyst is obtained.

[0041] Example 4 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the steps of which are the same as those in Example 1, except that the n (Cu-TEPA) / n (SiO2) ratio is changed to 0.15:1, and finally the catalyst is obtained.

[0042] Example 5 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the steps of which are the same as those in Example 1, except that the n (Cu-TEPA) / n (SiO2) ratio is changed to 0.05:1, and finally the catalyst is obtained.

[0043] Example 6 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the steps of which are the same as those in Example 1, except that the n (Fe-TEPA) / n (SiO2) ratio is changed to 0.2:1, and finally the catalyst is obtained.

[0044] Example 7 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the steps of which are the same as those in Example 1, except that the n (Al2O3) / n (SiO2) ratio is changed to 0.07:1, and finally the catalyst is obtained.

[0045] Example 8 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the steps of which are the same as those in Example 1, except that the n (Al2O3) / n (SiO2) ratio is changed to 0.03:1, and finally the catalyst is obtained.

[0046] Example 9 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the steps of which are the same as those in Example 1, except that the crystallization reaction time in step 2 of Example 1 is changed to 6 hours, and finally the catalyst is obtained.

[0047] Example 10 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the steps of which are the same as those in Example 1, except that the crystallization reaction time in step 2 of Example 1 is changed to 24 hours, and finally the catalyst is obtained.

[0048] Comparative Example 1 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the preparation steps of which are the same as those in Example 1, and the only difference is that the seeding coating in Step 1 is not carried out, that is, the honeycomb cordierite is not impregnated in the seeding impregnation solution and is directly used in Step 2.

[0049] The results are as Figure 1 shown in b. From the corresponding XRD patterns, the diffraction peaks that appear are only those of the cordierite support, and no obvious molecular sieve diffraction peaks are observed, indicating that the product is amorphous, which shows that a crystalline film layer cannot be formed without adding ERI seeds.

[0050] In contrast, in Example 1, after loading the ERI seeds, the corresponding XRD pattern shows clear diffraction peaks, which are exactly the same as the standard peaks of the cordierite support, ERI crystal and CHA crystal, indicating that a crystalline film layer was successfully hydrothermally synthesized under the induction of the ERI seeds.

[0051] In addition, from Figure 1 the XRD and SEM images of the ERI seeds in a, it can be seen that the ERI seeds are oval in shape, with a size of about 250 nm × 450 nm.

[0052] Comparative Example 2 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the preparation steps of which are the same as those in Example 1, except that Step 2 in Example 1 is not carried out, and finally a monolayer CHA@Cor catalyst is obtained.

[0053] Comparative Example 3 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the preparation steps of which are the same as those in Example 1, except that the n (Fe-TEPA) / n (SiO2) ratio in Step 2 of Example 1 is changed to 0, and finally a catalyst containing only copper active components is obtained.

[0054] Comparative Example 4 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the preparation steps of which are the same as those in Example 1, except that the n (Cu-TEPA) / n (SiO2) ratio in Step 2 of Example 1 is changed to 0, and finally a catalyst containing only iron active components is obtained.

[0055] Comparative Example 5 A preparation method of a highly water- and sulfur-resistant NH3-SCR catalyst, the preparation steps of which are the same as those in Example 1, except that Step 3 in Example 1 is not carried out, and finally a monolayer CuFe-ERI@Cor catalyst is obtained.

[0056] Example 11 In this example, the relevant characterization data analysis of the catalysts prepared in Examples 1 - 10 was carried out, and the specific results are as follows: Figure 2 The X-ray diffraction patterns of the catalysts obtained in Examples 1, 4, and 5 of the present invention are shown. As can be seen Figure 2 from it, the XRD diffraction peaks of all samples are consistent with the standard characteristic diffraction peaks of cordierite support and ERI-type molecular sieve, and there are no other miscellaneous crystal phases; and at 2 θ is 12.9 o and 30.8 o weak diffraction peaks are observed, which match the standard characteristic diffraction peaks of CHA-type molecular sieve. This indicates that we have successfully synthesized ERI and CHA-type molecular sieve film layers on the cordierite support.

[0057] It is worth noting that there are no diffraction peaks of Cu and Fe species in the XRD pattern. This shows that by introducing Cu and Fe species into the catalyst crystal interior through the one-step synthesis method of Cu-TEPA and Fe-TEPA, their crystal structures have not been changed. And the Cu and Fe species may be uniformly dispersed in the crystal framework in the form of oxide clusters or ions. In addition, as the content of copper ions in the synthesis sol increases, the intensity of the corresponding overall diffraction peak gradually decreases, indicating that copper ions may inhibit the crystal growth rate.

[0058] Figure 3 The X-ray diffraction (XRD) patterns of the catalysts obtained in Examples 1, 6, and Comparative Example 3 are shown. As can be seen from the figure, the XRD diffraction peaks of all samples are consistent with the standard characteristic diffraction peaks of cordierite support and ERI-type molecular sieve, and there are no other miscellaneous crystal phases; and at 2 θ is 12.9 o and 30.8 o weak diffraction peaks are observed, which match the standard characteristic diffraction peaks of CHA-type molecular sieve. This indicates that we have successfully synthesized ERI and CHA-type molecular sieve film layers on the cordierite support. At the same time, there are also no diffraction peaks of Cu and Fe species in the XRD pattern. This also shows that the Cu and Fe species may be uniformly dispersed in the crystal framework in the form of oxide clusters or ions, without changing their crystal structures. And as the content of iron ions in the synthesis sol increases, the change in the intensity of the corresponding overall diffraction peak is not significant, indicating that iron ions have little effect on crystal growth.

[0059] Figure 4 The X-ray diffraction (XRD) patterns of the catalysts obtained in Examples 1, 7, and 8 are shown. As can be seen from the figure, the XRD diffraction peaks of all samples are consistent with the standard characteristic diffraction peaks of cordierite support and ERI-type molecular sieve, and there are no other miscellaneous crystal phases; and at 2 θ is 12.9 o and 30.8o Weak diffraction peaks were observed at this position, which matched the standard characteristic diffraction peaks of CHA-type zeolites. This indicates that we successfully synthesized ERI and CHA-type zeolite membrane layers on the cordierite support. At the same time, no diffraction peaks of Cu and Fe species appeared in the XRD pattern. This also shows that Cu and Fe species may be uniformly dispersed in the crystal framework in the form of oxide clusters or ions without changing their crystal structure. With the increase in the content of aluminum ions in the synthesis sol, the intensity of the corresponding ERI diffraction peak increased, indicating that aluminum ions promoted the growth of ERI-type crystals.

[0060] Figure 5 Shown are the X-ray diffraction (XRD) patterns of the catalysts obtained in Examples 1, 9, and 10. From Figure 5 it can be seen that the XRD diffraction peaks of all samples are basically similar to those before, consistent with the standard characteristic diffraction peaks of the cordierite support and ERI-type zeolites. Weak CHA diffraction peaks were observed at 2 θ at 12.9 o and 30.8 o without other impurity crystal phases, indicating that we successfully synthesized ERI and CHA-type zeolite membrane layers on the cordierite support. At the same time, no diffraction peaks of Cu and Fe species appeared in the XRD pattern. This also shows that Cu and Fe species may be uniformly dispersed in the crystal framework in the form of oxide clusters or ions without changing their crystal structure. With the increase in the crystallization time, the intensity of the corresponding cordierite diffraction peak decreased, and the intensity of the crystal diffraction peak increased slightly, indicating that the extension of the crystallization time led to an increase in the number of crystals and an increase in the membrane layer thickness. It is worth mentioning that when the crystallization time was extended from 6 hours to 24 hours, the diffraction peak observed at 2 θ at 9.7 o (attributed to

[101] orientation) gradually increased, indicating that the membrane layer crystals grew along the a﹠c preferred direction.

[0061] Figure 6 Shown are the scanning electron microscope (SEM) images of the catalysts obtained in Example 1 and Comparative Examples 2, 3, 4, and 5. From the SEM surface images of the composite membranes (as shown in Figure 6 e, 6h, and 6i), it can be seen that massive crystals grew interactively on the surface, forming a continuous and relatively dense membrane layer. Its morphology was close to that of the single-layer membrane Figure 6 a, indicating that the top layer of the composite membrane was covered with a layer of CHA-type zeolite membrane with a thickness of about 2 μm (as shown in Figure 6 b, 6f, 6h, and 6j); from the SEM surface image of the single-layer membrane (as shown in Figure 6 c), it can be seen that fine rod-shaped crystals were stacked on the surface. Such a membrane layer was not continuous and dense enough, and obvious small pores could be observed. Its thickness was about 15 μm (as shown inFigure 6 as shown in d), which is consistent with the thickness of the middle layer of the composite membrane (such as Figure 6 as shown in f, 6h, and 6j).

[0062] Example 12 The catalysts prepared in Examples 1-10 and Comparative Examples 2-5 of the present invention were applied to the NH3-SCR reaction. The specific process was as follows: The catalyst was directly placed in a quartz tube (inner diameter 5 mm, length 500 mm) for testing. To ensure the accuracy of the test, the catalyst was placed in the middle of the quartz tube, above the thermocouple, and then the temperature of the heating furnace was controlled by a temperature control system. The test temperature range was 100-600 °C. The simulated flue gas for the experiment was [NO]=[NH3]=500 ppm, 5% O2 (volume fraction), with N2 as the balance gas. The total gas flow rate was set to 100 mL / min, and the space velocity GHSV was calculated as 60000 h -1 . Before the test, the simulated flue gas was fully mixed in a mixer, and after stabilization, it bypassed into a flue gas analyzer to record the total inlet value of NO x (the total of NO and NO2). Subsequently, the mixed gas was switched to the reaction path, and after stabilization, the temperature was increased. One data point was recorded every 50 °C. To ensure that the reaction reached a stable state, after staying at each target temperature for 20-30 min, the outlet values of NO x , NH3, and N2O were recorded. The results are shown in Figure 7 .

[0063] Figure 7 For the catalytic performance of all catalysts in the NH3-SCR reaction. When there was only a single-layer crystalline CHA membrane on the cordierite support in Comparative Example 2, the conversion rate of NO x was only below 10% throughout the temperature range, with almost no catalytic performance; while in Comparative Example 5, when only a single layer of CuFe-ERI membrane containing active components was coated, the conversion rate of NO x was close to 100% in the medium and high temperature regions (200-450 °C). In contrast, in Example 1, an additional layer of CHA membrane was added on the basis of Comparative Example 5 to form a composite membrane catalyst. The conversion rate of NO x of this catalyst was nearly 100% in the medium and high temperature regions (200-500 °C), and it still maintained high catalytic performance in the low temperature region (150-200 °C), with the conversion rate of NO x being greater than 80%, showing the best denitrification performance. In addition, for the catalysts with other optimized conditions, the conversion rate of NO x was greater than 90% in the medium and high temperature regions (200-400 °C).

[0064] Example 13 The catalysts prepared by Example 1 and Comparative Example 5 of the present invention were applied to the water and sulfur resistance test in the NH3-SCR reaction. The specific process is as follows: In order to test the water and sulfur resistance of the denitrification catalyst, 100 ppm SO2 and 5% H2O (water vapor) were introduced into the simulated flue gas, and the flue gas analyzer values ​​at different times were recorded. The H2O in the simulated flue gas can be taken out from the heated steam generator through N2. The actual heating temperature of the steam generator can be calculated through the comparison table of saturated steam pressure and water content at different temperatures and the Clapeyron equation; when the water resistance test is not performed, N2 does not pass through the pipeline of the steam generator, and the flow is controlled by the switch of the three-way valve. If 100 ppm SO2 and 5% H2O are introduced at the same time, NH4HSO4 and NH4HSO3 are easily generated to cover the catalyst and block the pipeline. They can be decomposed above 150 ℃. Therefore, in order to ensure the denitrification efficiency and prevent pipeline clogging, the upper, lower and spare pipeline temperatures need to be set to 120 ℃, 160 ℃, and 160 ℃ respectively to decompose nitrates and nitrites. The results are shown in Figure 8 .

[0065] Figure 8 The water and sulfur resistance of the composite crystalline film CHA@CuFe-ERI@Cor in Example 1 in the simulated flue gas system with 100 ppm SO2 and / or 5% H2O added. Whether the simulated flue gas contains only 100 ppm SO2, 5% H2O, or both 100 ppm SO2 and 5% H2O, the catalyst has a good NO resistance in the whole temperature range. x The conversion rate remains stable, even in the high temperature range (>500℃) x The conversion rate was significantly improved. Especially in the test system containing H2O, the NO conversion rate of the catalyst in the high temperature range (>500℃) was x The conversion rate reached 100%. In contrast, when 100 ppm SO2 was added to the simulated flue gas, the single-layer crystalline film CuFe-ERI@Cor only maintained a high NO x Conversion rate, while in the low temperature range (≤150℃) NO x The conversion rate decreased by 25%, and the high temperature section (≥500℃) NO x Conversion rates dropped by 50%.

[0066] It can be seen that the sandwich structure catalyst synthesized in the present invention shows significant advantages in water and sulfur resistance, and can maintain efficient denitrification performance under complex working conditions.

[0067] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A high water- and sulfur-resistant NH3-SCR catalyst, characterized in that, Its structure includes cordierite with a supporting effect, an ERI molecular sieve membrane layer located on the cordierite, and a CHA molecular sieve membrane layer located on the ERI molecular sieve membrane layer. The ERI molecular sieve membrane layer contains Cu and Fe.

2. The catalyst according to claim 1, wherein The Cu and Fe are uniformly dispersed in the crystal framework of the ERI molecular sieve membrane layer in the form of oxide clusters or ions.

3. A method for preparing a catalyst according to any one of claims 1 to 2, characterized in that, It includes the following steps: S1. Prepare an impregnating solution containing ERI molecular sieve seeds, immerse the honeycomb cordierite in the impregnating solution, and dry it to obtain seeded cordierite. S2. Mix potassium hydroxide, sodium hydroxide, aluminum isopropoxide, silica sol HS-40 and water to form a mixed sol A; mix copper sulfate, ferric chloride, tetraethylenepentamine solution and water to form a mixed solution B; add the mixed solution B to the mixed sol A for aging treatment to obtain a mixed sol C; crystallize the mixed sol C with the seeded cordierite in S1 to obtain a CuFe-ERI@Cor molecular sieve membrane. S3. Mix N,N,N-trimethyladamantylammonium hydroxide, NaOH, aluminum isopropoxide, silica sol HS-40 and water to form a mixed solution D; crystallize the CuFe-ERI@Cor molecular sieve membrane in S2 with the mixed solution D, and after the reaction is completed, wash, dry and calcine to obtain an NH3-SCR catalyst.

4. The preparation method according to claim 3, wherein, In S1, the preparation method of the ERI-type molecular sieve seeds includes the following steps: Dissolve aluminum sec-butoxide in tetraethylammonium hydroxide to prepare an aluminum source solution. Dropwise add silica sol HS-40 to the aluminum source solution, mix evenly, heat and stir for aging to obtain a solution. Add potassium hydroxide and hexamethylammonium bromide solution to the solution, mix evenly to obtain a mixed solution. Carry out a heating reaction on the mixed solution. After the reaction is completed, centrifuge, dry and grind the product, and calcine it to obtain the final product.

5. The preparation method according to claim 4, wherein In the preparation method of the ERI-type molecular sieve seeds, The molar ratio of the oxides of each component in the synthetic sol is SiO2:Al2O3:K2O:TEAOH:C 12 H 30 Br2N2:H2O = 1:0.03:0.045:0.8:0.13:25; The aging temperature is 90-100 °C, and the time is 16-24 hours. The heating reaction temperature is 140-160 °C, and the time is 48-120 hours. The calcination temperature is 500-600 °C, and the time is 8-12 hours.

6. The preparation method according to claim 3, wherein In S1, the concentration of the seeded impregnating solution is 4-6 wt%, and the impregnation times are 1-3 times.

7. The preparation method according to claim 3, characterized in that, In S2, the molar ratio of the components in the synthesis sol in the form of oxides is SiO2:Al2O3:K2O:Na2O:H2O:Cu-TEPA:Fe-TEPA = 1:(0.03-0.07):0.11:0.34:120:(0.01-0.15):(0.01-0.2).

8. The preparation method according to claim 3, characterized in that, In S2, the aging treatment time is 0.5-1.5 h, the crystallization reaction temperature is 170-180 °C, and the crystallization reaction time is 6-24 h.

9. The preparation method according to claim 3, characterized in that In S3, The molar ratio of the components in the synthesis sol in the form of oxides is SiO2:Al2O3:Na2O:H2O:TMAdaOH = 1:0.05:0.05:80:0.

2. The crystallization reaction temperature is 150-160 °C, and the time is 1-4 h.

10. Use of the catalyst according to any one of claims 1 to 2 in the NH3-SCR reaction.

Images