A Cu-KFI molecular sieve catalyst for NH3-SCR reaction

Abstract

The application discloses a Cu-KFI molecular sieve catalyst used in NH3-SCR reaction, and relates to the field of environmental catalysis. The high-silicon KFI zeolite molecular sieve is prepared by directly hydrothermal synthesis by using a phosphoaluminate as a partial aluminum source. The synthesis method is simple, and the operation is convenient. In addition, the synthesis process is safer without using explosive potassium nitrate. The Si / Al ratio of the high-silicon KFI zeolite molecular sieve prepared under the optimal conditions is effectively increased to 6.6. The high-silicon Cu-KFI molecular sieve catalyst is prepared through ion exchange, and the catalyst exhibits excellent denitration reaction performance and hydrothermal stability when applied to NH3-SCR reaction.

Description

Technical Field

[0001] This invention relates to the field of environmental catalysis, and aims to provide a molecular sieve catalyst for the selective catalytic reduction reaction of ammonia (NH3-SCR) and its application. Background Technology

[0002] Nitrogen oxides (NO) x NO is one of the main air pollutants from coal-fired power plants, industrial boilers, and vehicle exhaust. It can trigger acid rain, photochemical smog, and fine particulate matter (PM2.5), posing serious threats to the environment and human health. Selective catalytic reduction (SCR) technology is currently the most mature and efficient method for NO removal. x Nitrogen removal methods, among which the NH3-SCR reaction using ammonia (NH3) as a reducing agent is widely used due to its high denitrification efficiency, good selectivity, and low byproduct formation. The core of this technology lies in the catalyst. Traditional V2O5–WO3 / TiO2 catalysts exhibit excellent activity at medium temperatures (300–400°C), but are prone to deactivation at low temperatures (<200°C) or under high sulfur and high water vapor conditions, and also suffer from vanadium toxicity. In recent years, non-vanadium-based catalysts (such as Mn, Fe, and Cu-based molecular sieves) have attracted widespread attention due to their wide temperature window, high activity, and environmental friendliness. However, improving the hydrothermal stability and poisoning resistance of catalysts under complex flue gas conditions remains a key challenge for the further development of NH3-SCR technology.

[0003] Compared to vanadium-based catalysts, molecular sieve catalysts have advantages such as good stability and high activity, making them the preferred catalysts for the NH3-SCR reaction. Currently, the mainstream commercial catalyst is Cu-SSZ-13 (CHA structure), but its traditional hydrothermal synthesis of SSZ-13 requires the use of organic structure directing agents (OSDA) such as TMAdaOH (N,N,N-trimethyl-1-adamantyl ammonium hydroxide), which is expensive and difficult to recover. Next are Cu-SAPO-34 (CHA structure, silica-alumina phosphate) and Cu-SSZ-39 (AEI structure) molecular sieve catalysts, which are often used for stationary source denitrification, but have poor hydrothermal stability. ZSM-5 (MFI structure) can be loaded with Fe or Cu, but it is prone to loss at high temperatures. Fe-BEA has excellent high-temperature activity (>350°C), but its low-temperature performance is poor, and its denitrification temperature window is narrow, far from meeting commercial standards.

[0004] KFI-type zeolites were first synthesized artificially by Barrer in 1948 and were the first zeolites not found in nature. Their three-dimensional microporous structure consists of d6r, pau, and lta cages with a pore size of approximately 3.9 × 3.9 × 3.9 Å, which makes them promising for applications in NH3-SCR catalysis. Early aluminum-rich KFI (Si / Al ≈ 3) required K... + 、Sr 2+ or Cs + Hydrothermal synthesis in the presence of isocations is possible, but the resulting material has a low Si / Al ratio, is prone to dealuminization under hydrothermal conditions, causing framework collapse and poor hydrothermal stability, which severely restricts its application in NO. x Industrial applications in the removal of silica. To increase the silicon-to-aluminum ratio, researchers have introduced organic templates such as 18-crown-6, raising the Si / Al ratio to approximately 4. Kim et al. also obtained KFI with a Si / Al ratio of 4 using high-silica FAU molecular sieves via a transcrystalline method (both share d6r structural units) (ACS Catal., 2017, 7, 6070-6081). Kamimura et al., on the other hand, used Sr... 2+ Similar results can be achieved using an auxiliary seed-directing method (Adsorption) , 2019, 25, 1099-1113). However, the above methods rely on high-cost high-silicon FAU or Sr. 2+ Furthermore, the product was still of the aluminum-rich type (denoted as KFI-4.0). Although Xiao et al. hydrothermally synthesized KFI with a Si / Al ratio >5 (ZJM-7) under organic template-free conditions (Applied Catalysis B: Environmental, 2021, 281, 119480), they used easily explosive potassium nitrate and had a long synthesis cycle, and the Si / Al ratio did not exceed 6, which still presents limitations. Currently, the preparation of high-silica KFI molecular sieves with a Si / Al ratio >6 remains a major challenge, while high-silica KFI molecular sieves are of great significance for improving their hydrothermal stability and promoting their practical application in NH3-SCR reactions. Summary of the Invention

[0005] This invention aims to provide a method for preparing a high-silica Cu-KFI molecular sieve catalyst for use in the NH3-SCR reaction.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a method for the direct hydrothermal synthesis of high-silicon KFI molecular sieves. The KFI molecular sieve uses phosphoaluminate as a partial aluminum source, and the phosphoaluminate molecular sieve accounts for 10%-30% of the mixed aluminum source molar ratio. It is obtained through direct hydrothermal synthesis. The synthesis method of this invention is simple, convenient to operate, and does not require the use of explosive potassium nitrate, making the synthesis process safer. The Si / Al ratio in the Cu-KFI molecular sieve catalyst is 5.2-6.6. Under optimal conditions, the Si / Al ratio of the KFI zeolite molecular sieve is effectively increased to 6.6. Then, a high-silicon Cu-KFI molecular sieve catalyst is obtained through ion exchange. Preferably, the conventional aluminum source is selected from one or more of sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum nitrate, aluminum sec-butoxide, aluminum chloride, boehmite, or aluminum isopropoxide.

[0007] Preferably, the phosphoaluminate is selected from one or more of the phosphoaluminate molecular sieves having AFI, SFO, AEI, AEL, SFO, AEI, AFO, AFT, AST, AVE, EZT, OSI, PON, POR, PSI, SAF, and VFI type topologies, or phosphoaluminate with an amorphous structure.

[0008] The hydrothermal synthesis method includes the following steps: Organic template agent, silicon source, aluminum source, alkali source, low-silicon KFI seed crystals and water are mixed and hydrothermally crystallized to obtain high-silicon KFI zeolite molecular sieve; Preferably, the molar ratio of the conventional aluminum source, phosphoaluminate, alkali source, water, and silicon source is in the range of (0.7-0.9):(0.1-0.3):1.4:(650-750):22.0; The amount of conventional aluminum source added is calculated as aluminum oxide; the amount of phosphaaluminate added is calculated as phosphorus pentoxide; the mass fractions of Al2O3 and P2O5 contained in the SFO type phosphaaluminate are 41.96% and 58.04%, respectively; the mass fractions of Al2O3 and P2O5 contained in the AFI type phosphaaluminate AFI are 41.48% and 58.2%, respectively; the molar ratio of Al2O3 to P2O5 is 1:1; the amount of alkali source added is calculated as potassium monoxide; the amount of silicon source added is calculated as silicon dioxide.

[0009] Preferably, the molar ratio of water to silicon source is in the range of (650-750): 22.0; the hydrothermal crystallization temperature in the hydrothermal synthesis method is 130-150 ℃, and the time is 4-14 days; More preferably, the molar ratio of the conventional aluminum source, phosphoaluminate, alkali source, water, and silicon source is 0.7 : 0.3 : 1.4 : 700 : 22.0; Preferably, the aluminum source is one or more of sodium aluminate, aluminum hydroxide, and boehmite, and the phosphoaluminate is selected from one or more of aluminum phosphate molecular sieves having AFI, SFO, AEI, and AEL type topologies; unless otherwise specified, the raw materials used in this invention are all commercially available. Preferably, the silicon source is selected from LUDOX AS-40 silica sol; the aging treatment conditions are stirring at room temperature for 16 hours; and the hydrothermal crystallization conditions are reacting at 140 °C for 4-14 days under static conditions.

[0010] The preparation method of the hydrothermal synthesis method is as follows: Step 1: Mix aluminum source, alkali source, water and organic template agent, and pre-treat by heating and stirring to obtain a solution; Step 2: A silicon source is subsequently added to the solution obtained in Step 1; Step 3: After aging the gel obtained in step 2, add low-silicon KFI seed crystals; Step 4: Perform hydrothermal crystallization treatment on the gel obtained in step 3 to obtain KFI type molecular sieve with high Si / Al ratio; Step 5: Filter, wash, dry and air-roast the product obtained in step 4 to obtain the final product.

[0011] The pretreatment involves stirring at 50-80 °C for 2-8 hours. Preferably, the pretreatment involves stirring at 70 °C for 5 hours; The aging process involves stirring at room temperature for 12-24 hours. Preferably, the aging treatment is a stirring treatment at room temperature for 16 hours; Preferably, the high-silicon KFI zeolite molecular sieve is subjected to ion exchange, including ammonium exchange and copper exchange, and then air-calcined to obtain a high-silicon Cu-KFI molecular sieve catalyst. And / or the conditions for the ion exchange, the ammonium exchange conditions are: 80 °C, 2 hours, ammonium chloride solution concentration is 1 mol / L, solid-liquid ratio is 1:100; the copper exchange conditions are: 80 °C, 1 hour, copper acetate solution concentration is 0.02 mol / L, solid-liquid ratio is 1:60; after the ammonium and copper exchanges are completed, air calcination is carried out at 550 °C for 6 hours.

[0012] Preferably, the high-silicon Cu-KFI molecular sieve catalyst is subjected to hydrothermal treatment under the following conditions: 750, 800, and 850 °C for 12 hours in 10% water and 10% air conditions, followed by cooling to room temperature.

[0013] Preferably, the NH3-SCR reaction is carried out by placing the catalyst in a tubular fixed-bed reactor and reacting under the following conditions: 500 ppm NO, 500 ppm NH3, 5% O2 and 5% H2O, with N2 as the balance gas, and a reaction space velocity (GHSV) of 80,000 h⁻¹. -1 The reaction temperature is 100-700 ℃. Beneficial effects

[0014] This invention prepares a high-silica Cu-KFI molecular sieve catalyst. The synthesis method is simple and convenient, and it eliminates the need for explosive potassium nitrate, making the synthesis process safer. It exhibits a high Si / Al ratio of 6.6 and demonstrates excellent denitrification performance in NH3-SCR reactions, retaining over 90% of NO reduction over a wide temperature range of 200-700 °C. x The conversion rate was high; after hydrothermal treatment at 750, 800, and 850 °C for 12 hours, its structure was still well preserved, and it maintained excellent denitrification reaction performance. It still achieved a NO conversion rate of over 90% in the temperature ranges of 200-600, 250-550, and 300-450 °C, respectively. x The high conversion rate means that the high-silica Cu-KFI molecular sieve catalyst prepared in this invention has excellent hydrothermal stability and superior denitrification reaction performance. Attached Figure Description

[0015] Figure 1 The image is a scanning electron microscope image of Example 3.

[0016] Figure 2 The XRD patterns are those of Examples 1-10.

[0017] Figure 3 The XRD spectra are for Examples 3, 11-14.

[0018] Figure 4 The XRD patterns are shown before and after hydrothermal treatment in Application Examples 1-4.

[0019] Figure 5 For example, NO before and after hydrothermal treatment at different temperatures in Examples 1-4 x Conversion rate.

[0020] Figure 6 The elemental composition of the product was determined by X-ray fluorescence spectrometry in Example 3.

[0021] Figure 7 The topological structures of the two aluminum phosphate molecular sieves used in Examples 1-10 and the product KFI zeolite molecular sieve are shown. Detailed Implementation

[0022] This invention provides a method for preparing high-silica KFI zeolite molecular sieves, comprising the following steps: To better illustrate the present invention and understand its technical solutions, typical but non-limiting examples of the present invention are as follows: Example 1

[0023] Step 1: Sodium aluminate, SSZ-51 phosphoaluminate molecular sieve (with SFO topology), potassium hydroxide, water and 18-crown-6 were mixed and reacted according to the following molar ratio: 0.9 Al2O3: 0.1 P2O5: 2.2 K2O: 700 H2O: 12.3 18-crown-6: 22.0 SiO2: 8.0 wt.% Seed. The mixture was heated at 70 °C and stirred for 5 hours to pretreat the solution. Step 2: Add LUDOX AS-40 to the mixture obtained in Step 1 and stir. Step 3: The gel obtained in Step 3 is aged at room temperature for 16 hours, and then low-silicon KFI seed crystals are added and stirred. Step 4: The gel obtained in Step 3 is placed in a high-pressure reactor with a liner for hydrothermal synthesis and crystallization at 140 °C for 5 days. Step 5: Filter, wash, dry and air-calcine the product obtained in Step 4 to obtain the final product; Its crystal structure was tested by powder X-ray diffraction, and the silicon-to-aluminum ratio of the product was tested by X-ray fluorescence spectroscopy.

[0024] Example 2

[0025] Except for adjusting the gel composition to 0.8 Al2O3: 0.2 P2O5: 2.2 K2O: 700 H2O: 12.3 18-crown-6: 22.0 SiO2: 8.0 wt.% Seed and adjusting the crystallization conditions to crystallization at 140 °C for 8 days, the rest is the same as in Example 1; Example 3

[0026] Except for adjusting the gel composition to 0.7 Al2O3: 0.3 P2O5: 2.2 K2O: 700 H2O: 12.3 18-crown-6: 22.0 SiO2: 8.0 wt.% Seed and adjusting the crystallization conditions to crystallization at 140 °C for 5 days, the rest is the same as in Example 1; Example 4

[0027] Except for changing the aluminum source sodium aluminate to aluminum hydroxide, the rest is the same as in Example 1; Example 5

[0028] Except for changing the aluminum source sodium aluminate to aluminum hydroxide, the rest is the same as in Example 2; Example 6

[0029] Except for changing the aluminum source sodium aluminate to aluminum hydroxide, the rest is the same as in Example 3; Example 7

[0030] Except for changing the SSZ-51 phosphoaluminate molecular sieve (with SFO topology) to AlPO-5 phosphoaluminate molecular sieve (with AFI topology), the rest is the same as in Example 1; Example 8

[0031] Except for changing the SSZ-51 phosphoaluminate molecular sieve (with SFO topology) to AlPO-5 phosphoaluminate molecular sieve (with AFI topology), the rest is the same as in Example 2; Example 9

[0032] Except for changing the SSZ-51 phosphoaluminate molecular sieve (with SFO topology) to AlPO-5 phosphoaluminate molecular sieve (with AFI topology), the rest is the same as in Example 3; Example 10

[0033] Except for adjusting the SSZ-51 phosphoaluminate molecular sieve (with SFO topology) to amorphous phosphoaluminate, the rest is the same as in Example 3; Table 1. Analysis of the product structure results and Si / Al ratio of Examples 1-10 sample Product phase Si / Al ratio Example 1 KFI 5.20 Example 2 KFI 5.91 Example 3 KFI 6.60 Example 4 KFI 5.26 Example 5 KFI 5.54 Example 6 KFI 6.21 Example 7 KFI 5.22 Example 8 KFI 5.92 Example 9 KFI 6.39 Example 10 KFI 6.22 Table 1 shows the structural analysis results and Si / Al ratio results of KFI zeolite molecular sieves obtained by using mixed aluminum sources composed of different conventional aluminum sources and phosphaaluminates. The results show that KFI-type zeolite molecular sieves with different Si / Al ratios can be obtained by replacing the conventional aluminum source with a portion of phosphaaluminate while keeping the Si / Al ratio constant. As the amount of phosphaaluminate replacing the conventional aluminum source increases, the Si / Al ratio of the obtained KFI-type zeolite molecular sieves also increases. Adding AlPO-5 and SSZ-51 phosphate molecular sieves with AFI and SFO type topologies can synthesize pure-phase KFI-type zeolite molecular sieves, and the Si / Al ratio of the products is above 5.2. In addition, using amorphous phosphaaluminate to replace crystalline phosphaaluminate SSZ-51 molecular sieves can also obtain pure-phase KFI-type zeolite molecular sieves. Figure 1 Scanning electron microscope (SEM) images of the high-silica KFI zeolite molecular sieve of Example 3 are provided. Figure 2 The XRD patterns of Examples 1-10 are given. Figure 6 Example 3 provides the elemental composition of the product determined by X-ray fluorescence spectrometry. Figure 7 The topological structures of the two aluminum phosphate molecular sieves used in Examples 1-10 and the product KFI zeolite molecular sieve are given.

[0034] Example 11

[0035] Except for adjusting the gel composition to 0.7 Al2O3: 0.3 P2O5: 2.2 K2O: 650 H2O: 12.3 18-crown-6: 22.0 SiO2: 8.0 wt.% Seed, and adjusting the crystallization time to 10 days, the rest is the same as in Example 3; Example 12

[0036] Except for adjusting the gel composition to 0.7 Al2O3: 0.3 P2O5: 2.2 K2O: 670 H2O: 12.3 18-crown-6: 22.0 SiO2: 8.0 wt.% Seed, and adjusting the crystallization time to 11 days, the rest is the same as in Example 3; Example 13

[0037] Except for adjusting the gel composition to 0.7 Al2O3: 0.3 P2O5: 2.2 K2O: 720 H2O: 12.3 18-crown-6: 22.0 SiO2: 8.0 wt.% Seed, and adjusting the crystallization time to 13 days, the rest is the same as in Example 3; Example 14

[0038] Except for adjusting the gel composition to 0.7 Al2O3: 0.3 P2O5: 2.2 K2O: 750 H2O: 12.3 18-crown-6: 22.0 SiO2: 8.0 wt.% Seed, and adjusting the crystallization time to 14 days, the rest is the same as in Example 3; Table 2. Analysis of the product structure results and Si / Al ratio of Examples 11-14 sample Product phase Si / Al ratio Example 11 KFI 6.19 Example 12 KFI 6.34 Example 3 KFI 6.60 Example 13 KFI 6.44 Example 14 KFI 6.36 As shown in Table 2, Table 2 presents the structural analysis results and Si / Al ratio results of the KFI zeolite molecular sieve products obtained by using different water-to-silicon ratios (H2O:SiO2) while keeping the molar ratio of other components constant. The results showed that KFI-type zeolite molecular sieves with different Si / Al ratios could be obtained by adjusting different water-to-silica ratios (H2O:SiO2) while keeping the molar ratios of other components constant. Within the water-to-silica ratio (H2O:SiO2) range of 650-700, the molar ratios of other components were consistent with those in Example 3, and the Si / Al ratios of the products were all above 6. Moreover, when the water-to-silica ratio (H2O:SiO2) was within the range of 650-700, the crystallization time was less than 12 days in Example 3, and the Si / Al ratio of the final product was in the range of 6-6.6. When the water-to-silica ratio (H2O:SiO2) was within the range of 700-750, the crystallization time was greater than 12 days in Example 3, and the Si / Al ratio of the final product was in the range of 6-6.6. This indicates that the water-to-silica ratio profoundly affects the nucleation-growth path, crystallization quality, and structural characteristics of molecular sieves by regulating the physicochemical environment of the reaction system (concentration, viscosity, mass transfer, template agent behavior, etc.). Choosing the right water-to-silica ratio is one of the keys to achieving the controllable synthesis of high-purity, highly crystalline molecular sieves with the desired pore structure. Figure 3 XRD spectra of Examples 3, 11-14 are given.

[0039] Application Example 1

[0040] Based on Example 3, step 6 is performed, whereby the product obtained in step 5 undergoes ion exchange, including two ammonium exchanges and one copper exchange. After the ammonium and copper exchanges, the product is calcined in air (550 °C, 6 hours). The ammonium exchange conditions are: a solid-liquid ratio of 1:100, an ammonium chloride solution concentration of 1 mol / L, and exchange at 80 °C for 2 hours in a water bath. The copper exchange conditions are: a solid-liquid ratio of 1:60, a copper acetate solution concentration of 0.02 mol / L, and exchange at 80 °C for 1 hour in a water bath. Finally, a fresh Cu-KFI molecular sieve catalyst is obtained. The catalyst is then sieved to a size of 40-60 mesh for later use. Application Example 2

[0041] Except for further hydrothermal treatment (the hydrothermal treatment conditions were 750 °C for 12 hours under 10% water and 10% air conditions), the rest was the same as in Application Example 1. Application Example 3

[0042] Except for further hydrothermal treatment (the hydrothermal treatment conditions were 800 °C for 12 hours under 10% water and 10% air conditions), the rest was the same as in Application Example 1. Application Example 4

[0043] Except for further hydrothermal treatment (the hydrothermal treatment conditions were 850 °C for 12 hours under 10% water and 10% air conditions), the rest was the same as in Application Example 1.

[0044] The catalysts prepared in Examples 1-4 were used for the NH3-SCR reaction. They were placed in a tubular fixed-bed reactor under the following conditions: 500 ppm NO, 500 ppm NH3, 5% O2 and 5% H2O, with N2 as the equilibrium gas, and a reaction space velocity (GHSV) of 80000 h⁻¹. -1 The reaction temperature ranges from 100 to 700 ℃. The reaction results are shown in the table below: Table 3 NO levels at different temperatures before and after hydrothermal treatment in Application Examples 1-4 x Conversion rate results <![CDATA[200°CNO x Conversion rate (%) <![CDATA[300°CNO x Conversion rate (%) <![CDATA[400°CNO x Conversion rate (%) <![CDATA[500°CNO x Conversion rate (%) <![CDATA[600°CNO x Conversion rate (%) <![CDATA[700°CNO x Conversion rate (%) Example 1 98.65 99.88 99.31 97.57 99.51 91.51 Example 2 91.28 99.72 96.54 98.87 90.51 53.10 Example 3 35.81 99.73 95.99 97.01 60.25 18.32 Example 4 14.39 95.31 93.21 80.11 22.1 The table above shows the NH3-SCR performance test results of Cu-KFI molecular sieve catalysts before and after hydrothermal treatment with different Si / Al ratios. The results show that the fresh high-silica Cu-KFI molecular sieve catalyst (Application Example 1) exhibits excellent denitrification performance, achieving over 90% NO removal within the 200-700 °C range. x The conversion rate was further improved after hydrothermal treatment at 750, 800, and 850 °C for 12 hours (Application Examples 2-4). The structure was still well preserved, and over 90% of the NO content was maintained within the temperature ranges of 200-600, 250-550, and 300-450 °C, respectively. x The conversion rate indicates that the high-silica Cu-KFI molecular sieve catalyst prepared in this invention has excellent denitrification reaction performance and hydrothermal stability. Figure 4 The XRD patterns before and after hydrothermal treatment in Examples 1-4 are shown. Figure 5 For example, NO at different temperatures before and after hydrothermal treatment in Examples 1-4 x Conversion rate.

Claims

1. A Cu-KFI molecular sieve catalyst for use in the NH3-SCR reaction, characterized in that, The Si / Al ratio in the Cu-KFI molecular sieve catalyst is 5.2-6.

6. The Cu-KFI molecular sieve catalyst is synthesized by hydrothermal synthesis, wherein the aluminum source in the hydrothermal synthesis is a mixed aluminum source, which is composed of phosphaaluminate molecular sieve and conventional aluminum source, and the phosphaaluminate molecular sieve accounts for 10%-30% of the molar proportion of the mixed aluminum source. The conventional aluminum source is selected from one or more of sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum nitrate, aluminum sec-butoxide, aluminum chloride, boehmite, or aluminum isopropoxide.

2. The Cu-KFI molecular sieve catalyst according to claim 1, characterized in that, The phosphoaluminate is selected from one or more of the phosphoaluminate molecular sieves having AFI, SFO, AEI, AEL, SFO, AEI, AFO, AFT, AST, AVE, EZT, OSI, PON, POR, PSI, SAF, and VFI type topologies, or phosphoaluminate with an amorphous structure.

3. The Cu-KFI molecular sieve catalyst according to claim 1, characterized in that, The hydrothermal synthesis method includes the following steps: Organic template agent, silicon source, aluminum source, alkali source, low-silicon KFI seed crystals and water are mixed and hydrothermally crystallized to obtain high-silicon KFI zeolite molecular sieve; The molar ratio of the conventional aluminum source, phosphoaluminate, alkali source, water, and silicon source ranges from (0.7-0.9):(0.1-0.3):1.4:(650-750):22.0; The amount of conventional aluminum source added is calculated as aluminum oxide; the amount of phosphaaluminate added is calculated as phosphorus pentoxide; the mass fractions of Al2O3 and P2O5 contained in the SFO type phosphaaluminate are 41.96% and 58.04%, respectively; the mass fractions of Al2O3 and P2O5 contained in the AFI type phosphaaluminate are 41.48% and 58.2%, respectively; the molar ratio of Al2O3 to P2O5 is 1:1; the amount of alkali source added is calculated as potassium monoxide; the amount of silicon source added is calculated as silicon dioxide.

4. The Cu-KFI molecular sieve catalyst according to claim 3, characterized in that, The molar ratio of water to silicon source is (650-750): 22.0; the hydrothermal crystallization temperature in the hydrothermal synthesis method is 130-150 ℃, and the time is 4-14 days.

5. The Cu-KFI molecular sieve catalyst according to any one of claims 1-4, characterized in that, The conventional aluminum source is one or more of sodium aluminate, aluminum hydroxide, and boehmite, and the phosphoaluminate is selected from one or more of aluminum phosphate molecular sieves with AFI, SFO, AEI, and AEL type topologies.

6. The Cu-KFI molecular sieve catalyst according to claim 3, characterized in that: The preparation method of the hydrothermal synthesis method is as follows: Step 1: Mix aluminum source, alkali source, water and organic template agent, and pre-treat by heating and stirring to obtain a solution; Step 2: A silicon source is subsequently added to the solution obtained in Step 1; Step 3: After aging the gel obtained in step 2, add low-silicon KFI seed crystals; Step 4: Perform hydrothermal crystallization treatment on the gel obtained in step 3 to obtain KFI type molecular sieve with high Si / Al. Step 5: Filter, wash, dry and air-roast the product obtained in step 4 to obtain the final product.

7. The Cu-KFI molecular sieve catalyst according to claim 6, characterized in that: In step 2, the silicon source is selected from LUDOX AS-40 silica sol; in step 3, the aging treatment condition is stirring at room temperature for 16 hours; in step 4, the hydrothermal crystallization condition is reacting at 140 ℃ for 4-14 days under static conditions.

8. The Cu-KFI molecular sieve catalyst according to claim 6, characterized in that, The high-silicon KFI zeolite molecular sieve obtained in step 5 was subjected to ion exchange, including ammonium exchange and copper exchange. After the exchange, it was calcined in air to obtain a high-silicon Cu-KFI molecular sieve catalyst. And / or the conditions for the ion exchange, the ammonium exchange conditions are: 80 °C, 2 hours, ammonium chloride solution concentration is 1 mol / L, solid-liquid ratio is 1:100; the copper exchange conditions are: 80 °C, 1 hour, copper acetate solution concentration is 0.02 mol / L, solid-liquid ratio is 1:60; after the ammonium and copper exchanges are completed, air calcination is carried out at 550 °C for 6 hours.

9. The Cu-KFI molecular sieve catalyst according to claim 8, characterized in that, The high-silicon Cu-KFI molecular sieve catalyst was subjected to hydrothermal treatment under the following conditions: 750, 800, and 850 °C for 12 hours in 10% water and 10% air, followed by cooling to room temperature.

10. The Cu-KFI molecular sieve catalyst according to any one of claims 1-9, characterized in that: The NH3-SCR reaction is specifically carried out by placing the catalyst in a tubular fixed-bed reactor. The reaction conditions are: 500 ppm NO, 500 ppm NH3, 5% O2 and 5% H2O, with N2 as the balance gas, and a reaction space velocity (GHSV) of 80,000 h⁻¹. -1 The reaction temperature is 100-700 ℃.

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