A method for preparing a low-temperature water-resistant molecular sieve catalyst for the purification of multiple air pollutants.

Abstract

This invention discloses a method for preparing a low-temperature water-resistant molecular sieve catalyst for the purification of multiple air pollutants. A silicon source, aluminum source, alkali source, water, template agent, metal salt, and phosphoric acid are aged and crystallized to obtain product A. This product A is then reacted in an acidic solution to obtain product B, followed by reaction in a metal solution to obtain product C. Ammonium and copper exchange processes are then performed to obtain the low-temperature water-resistant molecular sieve catalyst. This invention utilizes a synthesis strategy combining d-band center regulation with in-situ introduction and directional doping of molecular sieve confinement effects. Highly dispersed and electronically optimized metal cluster active sites are constructed within the molecular sieve cage. This design enables the catalyst to heterolytically dissociate water at low temperatures, generating highly active hydroxyl groups and protons, significantly enhancing the long-term water resistance of the catalyst in denitrification reactions, greatly improving the migration and reaction efficiency of oxygen species, and thus driving the efficient oxidation of CO at low temperatures.

Description

Technical Field

[0001] This invention belongs to the field of catalytic material preparation and air pollution control technology, and specifically relates to a method for preparing a low-temperature water-resistant molecular sieve catalyst for the purification of multiple air pollutants. Background Technology

[0002] Nitrogen oxides (NO) x NO and carbon monoxide (CO) are major air pollutants that pose serious threats to human health and the ecological environment. Currently, ammonia selective catalytic reduction (NH3-SCR) and catalytic oxidation technologies are used to remove NO. x The core of mainstream CO denitrification and oxidation technologies relies on high-performance catalysts. However, in actual industrial and mobile source emissions, whether from mobile sources like diesel engines or stationary sources like kilns in industries such as cement, steel, and glass, a certain amount of water vapor is commonly present in the exhaust gases. The presence of water vapor leads to a significant decrease in catalyst performance and lifespan at low temperatures. This is mainly because water molecules and reactant molecules compete for adsorption at the active sites on the catalyst surface, thus inhibiting the adsorption and reaction of pollutant molecules. This phenomenon is particularly pronounced at low temperatures. Therefore, the poisoning effect of water vapor on catalysts has become a key bottleneck restricting the practical application of existing denitrification and CO oxidation catalysts.

[0003] To improve the water resistance of catalysts, traditional strategies mainly focus on constructing hydrophobic surface structures or introducing reaction systems that preferentially adsorb water. The core idea is to physically block or prevent water molecules from contacting the catalytic active sites. However, different catalysts have different structures, and such strategies often require redesign and construction for specific systems, increasing R&D costs and time, and are limited by the stability and adaptability of the catalyst's own structure, resulting in poor universality. Starting from the properties of water molecules themselves, research shows that water molecules can undergo heterolytic dissociation at active sites with specific electronic structures, generating hydroxyl groups and protons. These dissociation products may participate in or even promote certain catalytic reaction processes, thereby changing the role of water in the reaction system. This means that if active sites that can induce the heterolytic dissociation of water molecules can be actively constructed on the catalyst, it is possible to transform water from a "poison" that inhibits the reaction into a "promoter" that participates in or promotes the reaction, improving the overall water resistance and reaction efficiency of the catalytic system while consuming water molecules. The core of this strategy lies in constructing water heterolytic dissociation centers, which imposes fewer restrictions on the overall catalyst structure, thus possessing broader potential applicability.

[0004] Furthermore, multiple pollutants often coexist in actual industrial waste gas, making it crucial to develop technologies capable of simultaneously and efficiently removing NO. xIntegrated catalysts for multiple pollutants, including CO, can significantly simplify waste gas treatment systems and reduce investment and operating costs, which is of great significance for enhancing enterprises' environmental competitiveness. Among many catalytic materials, molecular sieves exhibit unique advantages due to their regular and tunable microporous channel structure and locatable active centers. Their pore confinement effect can be used to precisely construct active sites with different functions, providing an ideal carrier for achieving synergistic multi-reaction processes. Therefore, based on the pore structure characteristics of molecular sieves, designing and preparing a bifunctional catalyst that can simultaneously possess high-efficiency denitrification and CO oxidation activities at low temperatures, and significantly enhance water resistance through built-in water heterolytic dissociation centers, has significant research value and application prospects. This is expected to overcome the bottleneck of existing multifunctional catalysts in terms of low-temperature water resistance, providing a new solution for developing efficient, stable, and economical multi-pollutant synergistic control technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a low-temperature water-resistant molecular sieve catalyst for the purification of multiple air pollutants, thereby solving the problem of poor low-temperature water resistance in existing multi-pollutant purification catalysts. Addressing the key bottleneck of significant efficiency reduction in existing technologies under low-temperature and high-humidity environments, the catalyst cleverly transforms water, a traditional harmful factor, into a promoter that enhances catalytic performance, achieving highly efficient synergistic removal of multiple pollutants such as nitrogen oxides and carbon monoxide under low-temperature conditions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants includes the following steps:

[0008] (1) The silicon source, aluminum source, alkali source, water, template agent, metal salt and phosphoric acid are stirred and aged at 30~85 °C for 1~24 h, and then transferred to a reaction vessel with a polytetrafluoroethylene liner. The product is crystallized at 140~200 °C for 1~10 d. The crystallized product is filtered, washed and dried, and calcined at 450~750 °C for 3~16 h to obtain product A.

[0009] (2) Place the above product A in an acidic solution of 0.0001~1 mol / L, stir at 25~70 °C for 1~36 h, then filter, wash thoroughly until the pH of the washing solution is 7, and then dry to obtain product B;

[0010] (3) Place product B in a 0.003~0.1 mol / L metal solution, stir and reflux at 80~120 °C for 12~72 h, then filter, wash and dry, and calcine at 500~650 °C for 2~8 h to obtain product C;

[0011] (4) Place product C in a 0.5-2 mol / L ammonium salt solution and exchange it at 60-90 °C for 2-18 h. Then filter, wash and dry to obtain product D.

[0012] (5) Place product D in a 0.01~1 mol / L copper salt solution and exchange it at 40~80 °C for 2~12 h. Then filter, wash, dry, and calcine at 450~650 °C for 2~10 h to obtain a low-temperature water-resistant molecular sieve catalyst with multiple pollutant removal functions.

[0013] In step (1), the molar ratio of the silicon source, aluminum source, alkali source, water, template agent, metal salt, and phosphoric acid is: 1SiO2 / 0.001~3Al2O3 / 0.001~2 alkali source / 10~1200H2O / 0.001~3.35 template agent / 0.0005~1.25 metal salt / 0~1 phosphoric acid. Phosphoric acid is required during the synthesis of SAPO-34.

[0014] In step (1), the silicon source is at least one of silica sol, silica gel, silica fume, fumed silica, water glass, and tetraethyl orthosilicate.

[0015] In step (1), the aluminum source is at least one of nano-alumina, aluminum hydroxide, boehmite, aluminum isopropoxide, sodium aluminate, and aluminum nitrate.

[0016] In step (1), the alkali source is at least one of sodium hydroxide, potassium hydroxide, cesium hydroxide, and ammonia water.

[0017] In step (1), the template agent is at least one of N,N-dimethyl-3,5-dimethylpiperidinium salt, tetrapropylammonium hydroxide, triethylamine, tetraethylenepentamine, and N,N,N-trimethyl-1-adamantylammonium hydroxide.

[0018] In step (1), the metal salt is at least one of nickel nitrate, ferric nitrate, cobalt nitrate, manganese nitrate, cerium nitrate, lanthanum nitrate, tungsten chloride, nickel chloride, ferrous chloride, tin chloride, zinc nitrate, manganese sulfate, sodium molybdate, and potassium molybdate.

[0019] In step (2), the acidic solution is at least one of hydrochloric acid solution, nitric acid solution, sulfuric acid solution, oxalic acid solution, and citric acid solution; the ratio of product A to acidic solution is 1g:30~120mL.

[0020] In step (3), the metal solution is at least one of the following: hexaamminecobalt nitrate solution, iron acetylacetone solution, cobalt acetylacetone solution, nickel acetylacetone solution, and manganese acetylacetone solution. The ratio of product B to the metal solution is 1g:25~200mL.

[0021] In step (4), the ammonium salt solution is at least one of ammonium sulfate solution, ammonium nitrate solution, and ammonium chloride solution; the ratio of product C to ammonium salt solution is 1g:50~300mL.

[0022] In step (5), the copper salt solution is at least one of copper nitrate solution, copper chloride solution, copper sulfate solution, and copper acetate solution; the ratio of product D to copper salt solution is 1g:10~100mL.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. This invention proposes a synthesis strategy combining in-situ introduction and directional doping based on d-band center regulation and the confinement effect of molecular sieves. During the hydrothermal synthesis of molecular sieves, metal oxide clusters (such as CeO2, MnO2, etc.) are introduced in-situ into the sieve cage. Subsequently, acid exchange yields a hydrogen-type molecular sieve structure, providing an effective channel for subsequent metal atom doping. Simultaneously, hydroxyl sites for anchoring metal atoms are constructed on the surface of the metal oxide within the cage. Further, an ion exchange strategy is employed to directionally introduce metal atoms onto the metal oxide clusters within the molecular sieve cage, thereby precisely constructing highly dispersed and electronically tunable active sites for metal clusters within the confinement space of the molecular sieve. Specifically, this structural design enables the catalyst to heterolytically dissociate water at low temperatures, generating highly active hydroxyl groups and protons. The dynamically generated hydroxyl groups effectively replenish the Brønsted acid sites in the molecular sieve framework, significantly enhancing the long-term water resistance of the catalyst in denitration reactions and overcoming the deactivation problem caused by competitive adsorption of water molecules. Meanwhile, the protons generated can efficiently activate the lattice oxygen on the surface of metal clusters, greatly improving the migration and reaction efficiency of oxygen species, thereby driving the efficient oxidation reaction of CO at low temperatures.

[0025] 2. The preparation method of this invention breaks through the dependence of catalyst design on specific molecular sieve topologies, exhibiting high versatility and tunability. It can be widely applied to various mainstream molecular sieve framework systems such as CHA, MFI, and BEA. Through the d-band center control strategy, different supports can be systematically endowed with excellent low-temperature water resistance and synergistic purification functions for multiple pollutants. This provides a novel and customizable technical path and material platform for the targeted design and development of a new generation of efficient and stable integrated purification catalysts for complex and variable atmospheric pollution conditions. Attached Figure Description

[0026] Figure 1 The graph shows the CO oxidation performance evaluation of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4.

[0027] Figure 2 The graph shows the water resistance evaluation of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 for the CO oxidation reaction.

[0028] Figure 3 The graphs show the water resistance performance of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 for the denitrification reaction. Detailed Implementation

[0029] Example 1

[0030] A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants includes the following steps:

[0031] (1) 46 g of deionized water, 0.52 g of sodium hydroxide, 5.32 g of fumed silica, 0.73 g of aluminum isopropoxide, and 9.75 g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide were added to a beaker and stirred for 3 h. Then 1.67 g of tetraethylenepentamine and 0.25 g of cerium nitrate were added and aged at 60 °C for 6 h. The mixture was then transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 170 °C for 7 d. After filtration, washing and drying, the crystallized solid product was calcined at 650 °C for 6 h to obtain CeO2@SSZ-13, an in-situ confined product in which CeO2 nanoclusters are distributed in SSZ-13 cages.

[0032] (2) Weigh 3g CeO2@SSZ-13 and add it to 300 mL of 0.0005 mol / L nitric acid solution. Stir at 35℃ for 2 h, then filter, wash thoroughly (pH=7) and dry to obtain the in-situ confined product H-CeO2@SSZ-13.

[0033] (3) Weigh 3 g of H-CeO2@SSZ-13 and add it to 420 mL of 0.006 mol / L hexaamminecobalt nitrate solution. Reflux at 100 °C for 24 h, then filter, wash and dry, and calcine at 600 °C for 3 h to obtain the in-situ confined sample product Co-CeO2@SSZ-13.

[0034] (4) Weigh 3 g of Co-CeO2@SSZ-13 and add it to 350 mL of 0.5 mol / L ammonium nitrate solution. Stir at 80 °C for 6 h, then filter, wash and dry to obtain the in-situ confined product Co-CeO2@NH4-SSZ-13.

[0035] (5) Weigh 3 g of Co-CeO2@NH4-SSZ-13 and add it to 150 mL of copper acetate solution with a concentration of 0.35 mol / L. Stir at 60 °C for 3 h, then filter, wash and dry, and calcine at 500 °C for 6 h to obtain the in-situ confined product Co-CeO2@Cu-SSZ-13.

[0036] Example 2

[0037] A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants includes the following steps:

[0038] (1) 32 g deionized water, 0.67 g sodium hydroxide, 5.59 g silica sol, 1.61 g alumina, 0.65 g phosphoric acid and 8.25 g triethylamine were added to a beaker and stirred for 5 h. Then 1.28 g tetraethylenepentamine and 0.18 g manganese nitrate were added and aged at 70 ℃ for 5 h. The mixture was then transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 180 ℃ for 4 d. After filtration, washing and drying, the crystallized solid product was calcined at 600 ℃ for 5 h to obtain the in-situ confined product MnO2@SAPO-34 in which MnO2 nanoclusters are distributed in SAPO-34 cages.

[0039] (2) Weigh 3g of MnO2@SAPO-34 and add it to 270 mL of hydrochloric acid solution with a concentration of 0.0003 mol / L. Stir at 30 °C for 6 h, then filter, wash thoroughly (pH=7) and dry to obtain the in-situ confined product H-MnO2@SAPO-34.

[0040] (3) Weigh 3 g of H-MnO2@SAPO-34 and add it to 350 mL of 0.006 mol / L iron acetylacetone solution. Reflux at 110 °C for 25 h, then filter, wash and dry, and calcine at 500 °C for 5 h to obtain the in-situ confined product Fe-MnO2@SAPO-34.

[0041] (4) Weigh 3 g Fe-MnO2@SAPO-34 and add it to 300 mL of ammonium sulfate solution with a concentration of 0.67 mol / L. Stir at 70 °C for 5 h, then filter, wash and dry to obtain the in-situ confined product Fe-MnO2@NH4-SAPO-34.

[0042] (5) Weigh 3 g Fe-MnO2@NH4-SAPO-34 and add it to 180 mL of copper sulfate solution with a concentration of 0.28 mol / L. Stir at 70 °C for 2 h, then filter, wash and dry, and calcine at 600 °C for 6 h to obtain the in-situ confined product Fe-MnO2@Cu-SAPO-34.

[0043] Example 3

[0044] A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants includes the following steps:

[0045] (1) 50 g of deionized water, 0.76 g of potassium hydroxide, 15.88 g of water glass, 1.47 g of boehmite and 13.35 g of tetrapropylammonium hydroxide were added to a beaker and stirred for 6 h. Then 2.11 g of tetraethylenepentamine and 0.37 g of sodium molybdate were added and aged at 80 °C for 4 h. The mixture was then transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 180 °C for 2 d. After filtration, washing and drying, the crystallized solid product was calcined at 600 °C for 8 h to obtain the in-situ confined product MoO3@ZSM-5 in which MoO3 nanoclusters are distributed in the ZSM-5 cage.

[0046] (2) Weigh 3g of MoO3@ZSM-5 and add it to 360 mL of 0.0002 mol / L sulfuric acid solution. Stir at 40℃ for 1.5 h, then filter, wash thoroughly (pH=7) and dry to obtain the in-situ confined product H-MoO3@ZSM-5.

[0047] (3) Weigh 3 g of H-MoO3@ZSM-5 and add it to 455 mL of nickel acetylacetone solution with a concentration of 0.007 mol / L. Reflux at 115 °C for 36 h, then filter, wash and dry, and calcine at 550 °C for 6 h to obtain the in-situ confined product Ni-MoO3@ZSM-5.

[0048] (4) Weigh 3 g of Ni-MoO3@ZSM-5 and add it to 385 mL of ammonium chloride solution with a concentration of 0.65 mol / L. Stir at 85 °C for 9 h, then filter, wash and dry to obtain the in-situ confined product Ni-MoO3@NH4-ZSM-5.

[0049] (5) Weigh 3 g Ni-MoO3@NH4-ZSM-5 and add it to 185 mL of copper chloride solution with a concentration of 0.29 mol / L. Stir at 75 °C for 3.5 h, then filter, wash and dry, and calcine at 500 °C for 3 h to obtain the in-situ confined product Ni-MoO3@Cu-ZSM-5.

[0050] Example 4

[0051] A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants includes the following steps:

[0052] (1) 55 g of deionized water, 0.83 g of cesium hydroxide, 7.06 g of silica gel, 1.57 g of aluminum nitrate, and 16.22 g of N,N-dimethyl-3,5-dimethylpiperidinium salt were added to a beaker and stirred for 8 h. Then, 3.21 g of tetraethylenepentamine and 0.17 g of lanthanum nitrate were added and aged at 75 °C for 6.5 h. The mixture was then transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 185 °C for 9 d. After filtration, washing and drying, the crystallized solid product was calcined at 700 °C for 5 h to obtain the in-situ confined product La2O3@SSZ-39 in which La2O3 nanoclusters are distributed in SSZ-39 cages.

[0053] (2) Weigh 3g of La2O3@SSZ-39 and add it to 315 mL of oxalic acid solution with a concentration of 0.0015 mol / L. Stir at 45℃ for 5 h, then filter, wash thoroughly (pH=7) and dry to obtain the in-situ confined product H-La2O3@SSZ-39.

[0054] (3) Weigh 3 g of H-La2O3@SSZ-39 and add it to 480 mL of 0.0081 mol / L manganese acetylacetone solution. Reflux at 110 °C for 30 h, then filter, wash and dry, and calcine at 600 °C for 5 h to obtain the in-situ confined product Mn-La2O3@SSZ-39.

[0055] (4) Weigh 3 g of Mn-La2O3@SSZ-39 and add it to 500 mL of ammonium nitrate solution with a concentration of 0.8 mol / L. Stir at 85 °C for 9 h, then filter, wash and dry to obtain the in-situ confined product Mn-La2O3@NH4-SSZ-39.

[0056] (5) Weigh 3 g of Mn-La2O3@NH4-SSZ-39 and add it to 175 mL of copper nitrate solution with a concentration of 0.46 mol / L. Stir at 65 °C for 2.5 h, then filter, wash and dry, and calcine at 600 °C for 5 h to obtain the in-situ confined product Mn-La2O3@Cu-SSZ-39.

[0057] Comparative Example 1

[0058] A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants includes the following steps:

[0059] (1) Except for not adding 1.67 g tetraethylenepentamine and 0.25 g cerium nitrate, the other steps are the same as step (1) in Example 1, and SSZ-13 is obtained.

[0060] (2) Weigh 3g of SSZ-13 and follow the same steps as step (4) in Example 1 to obtain NH4-SSZ-13.

[0061] (3) Weigh 3 g of NH4-SSZ-13 and follow the same steps as step (5) in Example 1 to obtain Cu-SSZ-13.

[0062] Comparative Example 2

[0063] A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants includes the following steps:

[0064] (1) Except for not adding 1.28 g tetraethylenepentamine and 0.18 g manganese nitrate, the other steps are the same as step (1) in Example 2 to obtain SAPO-34.

[0065] (2) Weigh 3g of SAPO-34 and follow the same steps as step (4) in Example 2 to obtain NH4-SAPO-34.

[0066] (3) Weigh 3 g of NH4-SAPO-34 and follow the same steps as step (5) in Example 2 to obtain Cu-SAPO-34.

[0067] Comparative Example 3

[0068] A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants includes the following steps:

[0069] (1) Except for not adding 2.11 g tetraethylenepentamine and 0.37 g sodium molybdate, the other steps are the same as step (1) in Example 3 to obtain ZSM-5.

[0070] (2) Weigh 3g of ZSM-5 and follow the same steps as step (4) in Example 3 to obtain NH4-ZSM-5.

[0071] (3) Weigh 3 g of NH4-ZSM-5 and follow the same steps as step (5) in Example 3 to obtain Cu-ZSM-5.

[0072] Comparative Example 4

[0073] A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants includes the following steps:

[0074] (1) Except for not adding 3.21 g tetraethylenepentamine and 0.17 g lanthanum nitrate, the other steps are the same as step (1) in Example 4, and SSZ-39 is obtained.

[0075] (2) Weigh 3g of SSZ-39 and follow the same steps as step (4) in Example 4 to obtain NH4-SSZ-39.

[0076] (3) Weigh 3 g of NH4-SSZ-39 and follow the same steps as step (5) in Example 4 to obtain Cu-SSZ-39.

[0077] Catalyst performance evaluation

[0078] The catalysts synthesized in Examples 1-4 and Comparative Examples 1-4 were tested for CO removal efficiency and water resistance. The amount of all catalysts used was 0.35 g, and the simulated exhaust gas composition was CO (3000 ppm) and NO. x The equilibrium gases are NH3 (300 ppm), O2 (5 vol%), H2O (10 vol%), and N2, with a space velocity of 120,000 h⁻¹. -1 .

[0079] CO and NO x Conversion rate calculation formula:

[0080] CO conversion (%)=

[0081] NO x conversion (%)=

[0082] Among them, [CO] inlet This represents the CO concentration in the imported flue gas composition; [CO] outle t Represents the CO concentration in the flue gas composition; NO x Represents NO and NO2; [NO x ] inlet This represents the sum of NO and NO2 concentrations in the imported flue gas; [NO x ] outlet This represents the total concentration of NO and NO2 in the flue gas exiting the outlet.

[0083] Figure 1 The graph shows a comparison of the CO oxidation efficiency of the catalysts in Examples 1-4 and Comparative Examples 1-4. It is evident that the temperature at which the CO oxidation efficiency of the catalysts in Examples 1-4 reaches 100% is significantly lower than that of the catalysts in Comparative Examples 1-4. These results confirm that the protons generated by the heterolytic dissociation of water can activate the lattice oxygen at the heterolytic dissociation sites, thereby improving its oxidation efficiency and significantly enhancing the CO oxidation performance of the catalysts.

[0084] Figure 2 and Figure 3 These are the water-resistant CO and NO catalysts of Examples 1-4 and Comparative Examples 1-4 at 135 °C.x The removal efficiency charts show that, in comparison, catalysts in Examples 1-4 all had CO removal efficiencies below 10% during the 150-hour water resistance evaluation, while NO removal efficiency was also low. x The removal efficiency was all below 40%. However, the catalysts in Examples 1-4 all showed CO removal efficiencies above 90% during the 150-hour water resistance evaluation, and NO removal efficiency was also below 40%. x The removal efficiency is higher than 93%. These results indicate that the strategy proposed in this invention can give the catalyst excellent water resistance.

Claims

1. A method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants, characterized in that, Includes the following steps: (1) The silicon source, aluminum source, alkali source, water, template agent, metal salt and phosphoric acid are stirred and aged at 30~85 °C for 1~24 h, and then transferred to a reaction vessel with a polytetrafluoroethylene liner. The product is crystallized at 140~200 °C for 1~10 d. The crystallized product is filtered, washed, dried and calcined to obtain product A. (2) Place the above product A in an acidic solution and stir at 25~70 °C for 1~36 h, then filter, wash and dry to obtain product B; (3) Place product B in a metal solution and stir and reflux at 80~120 °C for 12~72 h. Then filter, wash, dry and calcine to obtain product C. (4) Place product C in an ammonium salt solution and exchange it at 60~90 °C for 2~18 h. Then filter, wash and dry to obtain product D. (5) Place product D in a copper salt solution and exchange it at 40~80 °C for 2~12 h. Then filter, wash, dry and calcine to obtain a low-temperature water-resistant molecular sieve catalyst with multiple pollutant removal functions.

2. The method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants according to claim 1, characterized in that, In step (1), the molar ratio of silicon source, aluminum source, alkali source, water, template agent, metal salt and phosphoric acid is: 1SiO2 / 0.001~3Al2O3 / 0.001~2 alkali source / 10~1200H2O / 0.001~3.35 template agent / 0.0005~1.25 metal salt / 0~1 phosphoric acid.

3. The method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants according to claim 1, characterized in that, In step (1), the silicon source is at least one of silica sol, silica gel, silica fume, fumed silica, water glass, and tetraethyl orthosilicate; the aluminum source is at least one of nano alumina, aluminum hydroxide, boehmite, aluminum isopropoxide, sodium aluminate, and aluminum nitrate; the alkali source is at least one of sodium hydroxide, potassium hydroxide, cesium hydroxide, and ammonia; and the template agent is at least one of N,N-dimethyl-3,5-dimethylpiperidinium salt, tetrapropylammonium hydroxide, triethylamine, tetraethylenepentamine, and N,N,N-trimethyl-1-adamantylammonium hydroxide.

4. The method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants according to claim 1, characterized in that, In step (1), the metal salt is at least one of nickel nitrate, ferric nitrate, cobalt nitrate, manganese nitrate, cerium nitrate, lanthanum nitrate, tungsten chloride, nickel chloride, ferrous chloride, tin chloride, zinc nitrate, manganese sulfate, sodium molybdate, and potassium molybdate.

5. The method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants according to claim 1, characterized in that, In step (2), the acidic solution is at least one of hydrochloric acid solution, nitric acid solution, sulfuric acid solution, oxalic acid solution, and citric acid solution; the concentration of the acidic solution is 0.0001~1 mol / L, and the ratio of product A to acidic solution is 1g:30~120mL.

6. The method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants according to claim 1, characterized in that, In step (3), the metal solution is at least one of the following: hexaamminecobalt nitrate solution, iron acetylacetone solution, cobalt acetylacetone solution, nickel acetylacetone solution, and manganese acetylacetone solution; the concentration of the metal solution is 0.003~0.1 mol / L, and the ratio of product B to metal solution is 1g:25~200mL.

7. The method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants according to claim 1, characterized in that, In step (4), the ammonium salt solution is at least one of ammonium sulfate solution, ammonium nitrate solution, and ammonium chloride solution; the concentration of the ammonium salt solution is 0.5~2 mol / L, and the ratio of product C to ammonium salt solution is 1g:50~300mL.

8. The method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants according to claim 1, characterized in that, In step (5), the copper salt solution is at least one of copper nitrate solution, copper chloride solution, copper sulfate solution, and copper acetate solution; the concentration of the copper salt solution is 0.01~1 mol / L, and the ratio of product D to copper salt solution is 1g:10~100mL.

9. The method for preparing a low-temperature water-resistant molecular sieve catalyst for purifying multiple air pollutants according to claim 1, characterized in that, The roasting in step (1) is carried out at 450~750 °C for 3~16 h; the roasting in step (3) is carried out at 500~650 °C for 2~8 h; the roasting in step (5) is carried out at 450~650 °C for 2~10 h.

10. The low-temperature water-resistant molecular sieve catalyst with multi-pollutant removal function obtained by the preparation method according to any one of claims 1 to 9.

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