Preparation method of sulfur-tolerant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification

Abstract

This invention discloses a method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification. Using a mixed system of H₂O₂, ethers, and quaternary ammonium salts as a composite template agent, SSZ-13 molecular sieves are prepared via hydrothermal synthesis. Through structural regulation, Al atoms are preferentially distributed in the para-position of the eight-membered ring. Then, through a segmented ion exchange process, Cu species and sulfonic acid groups are sequentially introduced to obtain the Cu-SSZ-13 molecular sieve denitration catalyst. This invention specifically modifies the redox sites of the catalyst, constructing sulfonic acid-double copper active sites in situ at the eight-membered rings on the surface of the Cu-SSZ-13 molecular sieve. This allows the Cu-SSZ-13 molecular sieve denitration catalyst to maintain excellent low-temperature activity and hydrothermal stability while achieving long-term stable operation in low-temperature sulfur-containing atmospheres, demonstrating promising industrial application prospects.

Description

Technical Field

[0001] This invention belongs to the field of atmospheric pollutant control and environmental protection technology, specifically relating to a method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitrification catalyst based on surface Cu modification. Background Technology

[0002] Nitrogen oxides (NO) x NO is one of the major air pollutants, causing a series of environmental problems such as photochemical smog, acid rain, and haze, and harming human health. Selective catalytic reduction of ammonia (NH3-SCR) is currently the most widely used and most efficient method for detecting NO. x Purification Technology. Among numerous NH3-SCR catalysts, copper-exchanged SSZ-13 (Cu-SSZ-13) molecular sieve catalysts have become one of the most promising catalysts for industrial applications due to their wide temperature window (170~500 °C), excellent N2 selectivity, and superior hydrothermal stability. However, in practical applications, the flue gas produced by fuel combustion usually contains a certain concentration of SO2. For Cu-based molecular sieve catalysts, the presence of SO2 is one of the main reasons for the decrease in activity and deactivation at low temperatures. In particular, sulfur poisoning of Cu-SSZ-13 catalysts is mainly manifested as preferential deactivation of surface Cu active sites. Since the kinetic diameter of SO2 molecules (approximately 0.41 nm) is larger than the effective pore size of the eight-membered ring pores of SSZ-13 molecular sieve (approximately 0.38 nm), its diffusion into the pores at low temperatures is significantly restricted. Therefore, the poisoning process mainly concentrates on Cu active sites exposed on the outer surface of the molecular sieve and near the pore openings. The poisoning mechanism mainly involves: SO2 being adsorbed and oxidized to SO3 on the catalyst surface, which then reacts with H2O and NH3 in the flue gas to form viscous substances such as ammonium bisulfate (ABS) or ammonium sulfate, covering the catalyst surface and blocking the pores; more importantly, SO3 can directly interact strongly with Cu active sites to form CuSO4 species with high thermal stability. These sulfate species not only have very low activity themselves, but also occupy Cu active sites, blocking NH3 and NO. x The adsorption and reaction pathways lead to irreversible deactivation of the catalyst.

[0003] To improve the sulfur resistance of Cu-SSZ-13 catalysts, researchers have conducted extensive research, mainly including: (1) introducing other metal elements (such as Fe, Ce, La, etc.) for doping or modification, utilizing their preferential adsorption and storage of SO2 to protect Cu active sites. For example, Chinese patent application CN116510774A reported a CeO2 / Cu-SSZ-13 catalyst impregnated with cerium oxide (1 wt%), which was tested at 250 °C, with 500 ppm NO, 500 ppm NH3, 5 vol% O2, 10 vol% H2O, 50 ppm SO2, and N2 as the equilibrium gas and a space velocity of 200,000 h⁻¹. -1 Under the reaction conditions, its NO x The conversion rate is as high as 98%. (2) The catalyst is coated or encapsulated to physically block the contact of SO2. Chinese patent application CN112717990A reports a method of uniformly encapsulating Cu-SSZ-13 with Fe metal elements through a specific self-assembly process to form Cu-SSZ-13@Fe with a core-shell structure. x O y Catalyst. This catalyst was tested at 300 °C, 500 ppm NO, 500 ppm NH3, 5 vol% O2, 5 vol% H2O, 100 ppm SO2, and a space velocity of 400,000 h⁻¹. -1 Under continuous operation for 24 hours, NO x The conversion rate remained around 92%. However, existing anti-sulfur strategies still have significant shortcomings and cannot meet the needs of practical applications. Specifically, introducing sacrificial agents to protect Cu active sites can only temporarily maintain the high activity of the catalyst; once the sacrificial agent is depleted, the catalyst will rapidly deactivate. Constructing mechanical barriers to physically isolate SO2 from contact with active sites inevitably increases the mass transfer resistance within the reaction system, affecting the intrinsic reaction rate of the catalyst. Therefore, to achieve efficient anti-sulfur denitrification of NH3-SCR catalysts, it is urgent to develop Cu-SSZ-13 molecular sieve catalysts with excellent anti-sulfur capabilities to meet the current stringent environmental protection and practical application requirements. Summary of the Invention

[0004] The purpose of this invention is to overcome the technical defect of existing Cu-SSZ-13 catalysts being easily deactivated in SO2-containing flue gas, and to provide a method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitrification catalyst based on surface Cu modification. This method significantly improves the sulfur resistance and catalytic stability of the catalyst under low-temperature conditions by specifically modifying the redox sites.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification includes the following steps:

[0007] (1) Add silicon source, aluminum source, alkali source, H2O2, ether, quaternary ammonium salt and deionized water to the polytetrafluoroethylene liner in sequence, age at 30~80 °C for 1~8 h, then transfer to high pressure reactor, crystallize in constant temperature drying oven, and after crystallization, filter, wash and dry to obtain solid product.

[0008] (2) The above solid product was added to an ammonium salt solution for ammonium exchange, filtered, washed, dried and calcined to obtain H-SSZ-13 molecular sieve with Al evenly distributed in the para position of the eight-membered ring.

[0009] (3) Add H-SSZ-13 molecular sieve to copper salt solution, stir at 40~60 °C for 1~3 h to exchange copper, then heat to 65~85 °C, add sulfonate, stir reaction for 4~7 h to obtain slurry;

[0010] (4) The above slurry is washed and dried to obtain Cu-SSZ-13 molecular sieve denitration catalyst with sulfonic acid double copper active sites on its surface.

[0011] In step (1), the molar ratio of silicon source, aluminum source, alkali source, H2O2, ether, quaternary ammonium salt and deionized water is 1:0.01~3.3:0.005~2.8:0.1~1.560.01~2.78:0.01~3.33:10~300.

[0012] In step (1), the silicon source is at least one of ethyl silicate, fumed silica, silica sol, water glass, kaolin, and diatomaceous earth; the aluminum source is at least one of aluminum sulfate, aluminum oxide, aluminum hydroxide, aluminum isopropoxide, kaolin, and rettore; and the alkali source is at least one of sodium hydroxide, potassium hydroxide, and cesium hydroxide.

[0013] In step (1), the ether is at least one of di-n-propyl ether, ethylene glycol dimethyl ether, tetrahydrofuran, and crown ether.

[0014] In step (1), the quaternary ammonium salt is at least one of N,N,N-trimethyl-1-adamantane ammonium, tetra-n-propylammonium, hexamethylenebis(trimethylammonium), and C6-6-6 type bisquaternary ammonium salt.

[0015] In step (1), the crystallization time is 4~10 days and the temperature is 140~180 °C.

[0016] In step (2), the ammonium exchange temperature is 60~80 °C and the time is 1~6 h; the calcination temperature is 500~750 °C and the time is 4~7 h.

[0017] In step (2), the ammonium salt solution is at least one of ammonium chloride solution, ammonium sulfate solution, and ammonium nitrate solution.

[0018] In step (2), the concentration of the ammonium salt solution is 0.1~1 mol / L, and the ratio of solid product to ammonium salt solution is 1g:80-120mL.

[0019] In step (3), the copper salt solution is at least one of copper acetate solution, copper nitrate solution, copper sulfate solution, and copper chloride solution, the concentration of the copper salt solution is 0.1~1.5 mol / L, and the ratio of H-SSZ-13 molecular sieve to copper salt solution is 1g:30-150mL.

[0020] In step (3), the sulfonate is at least one of sodium sulfonate, potassium sulfonate, and calcium sulfonate.

[0021] In step (4), the washing liquid used is a mixture of deionized water and ethanol, and the drying is carried out at 60-80 °C for 12-24 h under nitrogen.

[0022] This method employs the above-mentioned technical scheme, using a mixed system of H2O2, ethers, and quaternary ammonium salts as a composite template agent. SSZ-13 molecular sieves are prepared via hydrothermal synthesis. Through structural regulation, Al atoms are preferentially distributed in the para-position of the eight-membered ring, laying the structural foundation for the precise construction of subsequent active sites. Subsequently, through a segmented ion exchange process, Cu species and sulfonic acid groups are sequentially introduced to construct sulfonic acid-based double copper active sites in situ at the eight-membered ring on the surface of the Cu-SSZ-13 molecular sieve. These active sites possess unique spatial and chemical characteristics: on the one hand, the steric hindrance effect generated by the sulfonic acid groups effectively shields the direct coordination of SO2 molecules with the Cu active center, thereby inhibiting the formation and deposition of sulfates or sulfites and significantly enhancing the catalyst's resistance to sulfur poisoning; on the other hand, sulfonic acid itself has a strong adsorption effect on basic molecules such as NH3, which can promote the activation and transformation of reactants at low temperatures, thereby improving the low-temperature denitrification performance of the catalyst.

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

[0024] 1. A segmented ion exchange method was used to construct sulfonic acid-modified double copper active centers on the eight-membered rings on the surface of Cu-SSZ-13 molecular sieves. This design utilizes the steric hindrance effect of sulfonic acid groups to protect key Cu sites on the surface at the molecular scale, selectively preventing the contact and coordination of SO2 molecules, thereby effectively inhibiting the formation and deposition of sulfate / sulfite. This achieves precise local protection of easily poisoned active sites on the surface and significantly improves the structural stability of Cu-SSZ-13 in sulfur-containing environments.

[0025] 2. To achieve precise protection of surface Cu sites, the key lies in ensuring that the Cu sites are positioned on the eight-membered rings on the surface of the Cu-SSZ-13 molecular sieve. To this end, this invention introduces a composite template agent during the hydrothermal synthesis of SSZ-13. Through its guiding effect during crystallization, it promotes the preferential entry of Al atoms into the eight-membered ring positions, forming an eight-membered ring-based aluminum structure within the SSZ-13 molecular sieve. This lays an ideal structural foundation for the subsequent stable anchoring of Cu ions. This pre-designed framework environment allows the internal Cu ions to be firmly integrated into the bulk structure of the molecular sieve. The surface modification process mainly acts externally, thereby maximally maintaining the intrinsic chemical environment and catalytic performance of the internal Cu active sites while introducing a sulfonic acid protective layer, ensuring the integrity of the catalyst's core active structure.

[0026] 3. The sulfonic acid-based double copper active site constructed in this invention is a multifunctional structure: on the one hand, its sulfonic acid group readily adsorbs basic NH3 molecules, significantly enhancing the catalyst's ammonia adsorption and activation capacity under low-temperature conditions, directly driving the improvement of low-temperature catalytic performance; on the other hand, this site utilizes the same sulfonic acid group to achieve physical shielding against SO2, cleverly combining the functional group (sulfonic acid group) that promotes low-temperature activity with the anti-sulfur protection mechanism. This unique design breaks through the traditional constraint that it is difficult to simultaneously achieve anti-sulfur properties and low-temperature activity, enabling the prepared catalyst to maintain excellent low-temperature activity and hydrothermal stability while achieving long-term stable operation in low-temperature sulfur-containing atmospheres, showing good prospects for industrial application. Attached Figure Description

[0027] Figure 1 The XRD spectra of the catalysts obtained in Examples 1-5 of this invention are compared.

[0028] Figure 2 These are SEM images of the H-SSZ-13 molecular sieve obtained in Example 1 of this invention before and after segmented ion exchange treatment.

[0029] Figure 3 The reaction temperature window is shown for the catalysts obtained in Example 1 and Comparative Examples 1-2 of this invention.

[0030] Figure 4The graph shows the NH3-SCR performance evaluation of the catalysts obtained in Example 1 and Comparative Examples 1-2 of this invention under an atmosphere containing SO2. Detailed Implementation

[0031] Example 1

[0032] A method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification includes the following steps:

[0033] 9 g of water glass, 0.56 g of alumina, 0.86 g of sodium hydroxide, 1.25 g of H₂O₂, 1.61 g of di-n-propyl ether, 10.89 g of tetra-n-propylammonium, and 35 g of deionized water were weighed and added sequentially to a polytetrafluoroethylene liner. The mixture was aged at 60 °C for 3 h, then transferred to a high-pressure reactor and crystallized at 170 °C for 8 days. After crystallization, the mixture was filtered, washed, and dried to obtain a solid product.

[0034] 3 g of the above solid product was added to 300 ml of 0.5 mol / L ammonium chloride solution, and the mixture was exchanged at 60 °C for 3 h. After filtration, washing, drying, and calcination at 600 °C for 6 h, H-SSZ-13 molecular sieve with Al uniformly distributed in the para position of the eight-membered ring was obtained.

[0035] 3 g of H-SSZ-13 molecular sieve was added to 275 mL of 0.2 mol / L copper nitrate solution and exchanged at 50 °C for 1 h. Subsequently, the solution was heated to 75 °C, and 25 g of sodium sulfonate was added, continuing the exchange process for 6 h. After the exchange was complete, the solution was thoroughly washed in an ethanol / deionized water (3 / 7) solution. Finally, the solution was dried at 60 °C for 12 h under nitrogen to obtain a Cu-SSZ-13 molecular sieve denitration catalyst with sulfonic acid-based double copper active sites on its surface.

[0036] Example 2

[0037] A method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification includes the following steps:

[0038] 6 g of fumed silica, 0.66 g of aluminum hydroxide, 0.56 g of potassium hydroxide, 1.55 g of H₂O₂, 1.27 g of ethylene glycol dimethyl ether, 8.13 g of N,N,N-trimethyl-1-adamantane ammonium, and 30 g of deionized water were weighed and added sequentially to a polytetrafluoroethylene liner. The mixture was aged at 65 °C for 4 h, then transferred to a high-pressure reactor and crystallized at 165 °C for 7 days. After crystallization, the mixture was filtered, washed, and dried to obtain a solid product.

[0039] 3 g of the above solid product was added to 300 ml of 0.3 mol / L ammonium nitrate solution, and exchanged at 70 °C for 2 h. After filtration, washing, drying, and calcination at 650 °C for 5 h, H-SSZ-13 molecular sieve with Al uniformly distributed in the para position of the eight-membered ring was obtained.

[0040] 3 g of H-SSZ-13 molecular sieve was added to 280 mL of 0.3 mol / L copper acetate solution and exchanged at 60 °C for 1.5 h. Subsequently, the solution was heated to 70 °C, and 20 g of potassium sulfonate was added, continuing the exchange process for 5 h. After the exchange was complete, the solution was thoroughly washed in an ethanol / deionized water (3 / 7) solution. Finally, the solution was dried at 65 °C under nitrogen for 16 h to obtain a Cu-SSZ-13 molecular sieve denitration catalyst with sulfonic acid-based double copper active sites on its surface.

[0041] Example 3

[0042] A method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification includes the following steps:

[0043] 12 g of silica sol, 0.93 g of aluminum isopropoxide, 0.59 g of potassium hydroxide, 1.67 g of H2O2, 1.83 g of tetrahydrofuran, 6.47 g of hexamethylenebis(trimethylammonium) and 40 g of deionized water were weighed and added sequentially to a polytetrafluoroethylene liner. The mixture was aged at 80 °C for 5 h, and then transferred to a high-pressure reactor for crystallization at 175 °C for 6 days. After crystallization, the product was obtained by filtration, washing and drying.

[0044] 3 g of the above solid product was added to 300 ml of 0.8 mol / L ammonium nitrate solution, and exchanged at 80 °C for 2 h. After filtration, washing, drying, and calcination at 700 °C for 7 h, H-SSZ-13 molecular sieve with Al uniformly distributed in the para position of the eight-membered ring was obtained.

[0045] 3 g of H-SSZ-13 molecular sieve was added to 255 mL of 0.3 mol / L copper sulfate solution and exchanged at 60 °C for 1.5 h. Subsequently, the solution was heated to 80 °C and 45 g of sodium sulfonate was added, and the exchange continued for 5 h. After the exchange was completed, the solution was thoroughly washed in an ethanol / deionized water (3 / 7) solution. Finally, the solution was dried at 80 °C for 24 h under nitrogen to obtain a Cu-SSZ-13 molecular sieve denitration catalyst with sulfonic acid-based double copper active sites on its surface.

[0046] Example 4

[0047] A method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification includes the following steps:

[0048] 13.6 g of ethyl silicate, 0.79 g of aluminum sulfate, 0.45 g of sodium hydroxide, 1.82 g of H₂O₂, 1.53 g of crown ether, 7.78 g of C6-6-6 type bisquaternary ammonium salt, and 32 g of deionized water were weighed and added sequentially to a polytetrafluoroethylene liner. The mixture was aged at 70 °C for 5 h, then transferred to a high-pressure reactor and crystallized at 175 °C for 6 days. After crystallization, the product was filtered, washed, and dried to obtain a solid product.

[0049] 3 g of the above solid product was exchanged in 300 ml of 0.6 mol / L ammonium chloride solution at 65 °C for 4.5 h. After filtration, washing, drying, and calcination at 650 °C for 7 h, H-SSZ-13 molecular sieve with Al uniformly distributed in the para position of the eight-membered ring was obtained.

[0050] 3 g of H-SSZ-13 molecular sieve was added to 290 mL of 0.5 mol / L copper chloride solution and exchanged at 60 °C for 2 h. Subsequently, the solution was heated to 80 °C, and 10 g of calcium sulfonate was added, continuing the exchange process for 4 h. After the exchange was complete, the solution was thoroughly washed in an ethanol / deionized water (3 / 7) solution. Finally, the solution was dried at 75 °C under nitrogen for 20 h to obtain a Cu-SSZ-13 molecular sieve denitration catalyst with sulfonic acid-based double copper active sites on its surface.

[0051] Example 5

[0052] A method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification includes the following steps:

[0053] 5.6 g of kaolin, 0.23 g of alumina, 0.5 g of cesium hydroxide, 1.43 g of H₂O₂, 0.71 g of ethylene glycol dimethyl ether, 0.89 g of di-n-propyl ether, 11.83 g of N,N,N-trimethyl-1-adamantane ammonium, and 41 g of deionized water were weighed and added sequentially to a polytetrafluoroethylene liner. The mixture was aged at 70 °C for 4 h, then transferred to a high-pressure reactor and crystallized at 165 °C for 6 days. After crystallization, the solid product was obtained by filtration, washing, and drying. 3 g of this solid product was exchanged in 300 ml of 0.8 mol / L ammonium nitrate solution at 70 °C for 5 h. After filtration, washing, and drying, the product was calcined at 700 °C for 5 h to obtain H-SSZ-13 molecular sieve with Al uniformly distributed in the eight-membered ring at the para-position.

[0054] 3 g of H-SSZ-13 molecular sieve was added to 280 mL of 0.3 mol / L copper acetate solution and exchanged at 65 °C for 1.5 h. Subsequently, the solution was heated to 75 °C, and 20 g of potassium sulfonate was added, continuing the exchange process for 7 h. After the exchange was complete, the solution was thoroughly washed in an ethanol / deionized water (3 / 7) solution. Finally, the solution was dried at 70 °C for 18 h under nitrogen to obtain a Cu-SSZ-13 molecular sieve denitration catalyst with sulfonic acid-based double copper active sites on its surface.

[0055] Comparative Example 1

[0056] Except for the omission of 1.25g H2O2 and 1.61g di-n-propyl ether, the other processes are the same as those in Example 1.

[0057] Comparative Example 2

[0058] Except for the omission of 25 g of sodium sulfonate, the process is identical to that in Example 1.

[0059] Catalyst XRD determination

[0060] The catalysts prepared in Examples 1-5 were tested using a Rigaku D / max Ultima X-ray diffractometer. The results are as follows: Figure 1 As shown, all catalysts exhibited typical CHA structural diffraction peaks (PDF #34-0137), with sharp peak shapes and no impurity phases, indicating that Cu-SSZ-13 molecular sieve denitration catalysts with sulfonic acid-based double copper active sites on the surface could be successfully prepared.

[0061] Catalyst SEM Measurement

[0062] The morphology of the H-SSZ-13 molecular sieve before and after fractional ion exchange treatment in Example 1 was observed using a Regulus 8100 high-resolution field emission scanning electron microscope. The results are as follows: Figure 2 As shown, both the pre- and post-treatment catalyst particles exhibited regular cubic or near-cubic morphologies, with sizes generally ranging from 1 to 5 μm. The post-treatment process did not cause significant particle agglomeration or morphological changes.

[0063] Catalyst sulfur resistance test

[0064] The catalysts prepared in Example 1 and Comparative Examples 1 and 2 were placed in a fixed-bed reactor for sulfur denitrification performance evaluation. The catalysts were tableted and sieved, and 0.2 g of 20-40 mesh particles were loaded into a quartz tube reactor. The simulated gas composition for the NH3-SCR reaction was 300 ppm NO, 300 ppm NH3, 5 vol% O2, 300 ppm SO2 (added if necessary), with N2 as the balance gas. The total gas flow rate was 500 mL / min, corresponding to a space velocity of approximately 150,000 h⁻¹. -1 The reaction temperature range is 135 °C. The chemical composition of the flue gas exiting the fixed bed was determined using an Antaris™ IGS infrared gas analyzer manufactured by Thermo Fisher Scientific.

[0065] NO x Conversion rate calculation formula:

[0066] NO x conversion (%)=

[0067] Activity testing: First, the NO content of each catalyst was tested under a reaction atmosphere free of SO2. x Conversion rate. Results are as follows: Figure 2 As shown, the catalyst in Example 1 already exhibited nearly 100% NO at 135 °C. x The conversion rate was high, while the catalysts in comparative examples 1 and 2 showed a NO conversion rate close to 100%. x The conversion temperature was 175 °C, indicating that the strategy of the present invention can improve the low-temperature performance of the catalyst.

[0068] Sulfur stability test: At 135 °C, 300 ppm SO2 was simultaneously introduced into the reaction atmosphere, and a long-term (e.g., 600 h) durability test was conducted. The results are as follows: Figure 3 As shown, the catalyst of Example 1 exhibits excellent sulfur resistance and catalytic activity stability in a sulfur-containing atmosphere, maintaining a denitrification efficiency above 90.0% even after 25 hours of reaction. In contrast, the denitrification performance of catalysts in Comparative Examples 1 and 2 rapidly diminishes after 25 hours, almost completely losing their denitrification capabilities. This result demonstrates that the Cu-SSZ-13 molecular sieve denitrification catalyst with sulfonic acid-based double copper active sites on its surface, prepared using the strategy of this invention, possesses excellent low-temperature sulfur resistance.

Claims

1. A preparation method of a sulfur-tolerant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification, characterized in that, Includes the following steps: (1) Add silicon source, aluminum source, alkali source, H2O2, ether, quaternary ammonium salt and water to the polytetrafluoroethylene liner in sequence, age at 30~80 °C for 1~8 h, then transfer to high pressure reactor, crystallize in constant temperature drying oven, and after crystallization, filter, wash and dry to obtain solid product. (2) The above solid product was added to an ammonium salt solution for ammonium exchange, filtered, washed, dried and calcined to obtain H-SSZ-13 molecular sieve with Al evenly distributed in the para position of the eight-membered ring. (3) Add H-SSZ-13 molecular sieve to copper salt solution, stir at 40~60 °C for 1~3 h to exchange copper, then heat to 65~85 °C, add sulfonate, stir reaction for 4~7 h to obtain slurry; (4) The above slurry is washed and dried to obtain Cu-SSZ-13 molecular sieve denitration catalyst with sulfonic acid double copper active sites on its surface.

2. The method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification according to claim 1, characterized in that, In step (1), the molar ratio of silicon source, aluminum source, alkali source, H2O2, ether, quaternary ammonium salt and water is 1:0.01~3.3:0.005~2.8:0.1~1.560.01~2.78:0.01~3.33:10~300.

3. The method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification according to claim 1, characterized in that, In step (1), the silicon source is at least one of ethyl silicate, fumed silica, silica sol, water glass, kaolin, and diatomaceous earth; the aluminum source is at least one of aluminum sulfate, alumina, aluminum hydroxide, aluminum isopropoxide, kaolin, and rettore; the alkali source is at least one of sodium hydroxide, potassium hydroxide, and cesium hydroxide; the ether is at least one of di-n-propyl ether, ethylene glycol dimethyl ether, tetrahydrofuran, and crown ether; and the quaternary ammonium salt is at least one of N,N,N-trimethyl-1-adamantaneammonium, tetra-n-propylammonium, hexamethylenebis(trimethylammonium), and C6-6-6 type bisquaternary ammonium salt.

4. The method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification according to claim 1, characterized in that, In step (1), the crystallization time is 4~10 days and the temperature is 140~180 °C.

5. The method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification according to claim 1, characterized in that, In step (2), the ammonium exchange temperature is 60~80 °C and the time is 1~6 h; the calcination temperature is 500~750 °C and the time is 4~7 h.

6. The method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification according to claim 1, characterized in that, In step (2), the ammonium salt solution is at least one of ammonium chloride solution, ammonium sulfate solution, and ammonium nitrate solution; the concentration of the ammonium salt solution is 0.1~1 mol / L, and the ratio of solid product to ammonium salt solution is 1g:80-120mL.

7. The method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification according to claim 1, characterized in that, In step (3), the copper salt solution is at least one of copper acetate solution, copper nitrate solution, copper sulfate solution, and copper chloride solution; the concentration of the copper salt solution is 0.1~1.5 mol / L, and the ratio of H-SSZ-13 molecular sieve to copper salt solution is 1g:30-150mL.

8. The method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification according to claim 1, characterized in that, In step (3), the sulfonate is at least one of sodium sulfonate, potassium sulfonate, and calcium sulfonate.

9. The method for preparing a sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst based on surface Cu modification according to claim 1, characterized in that, In step (4), the washing liquid used is a mixture of deionized water and ethanol, and the drying is carried out at 60-80 °C for 12-24 h under nitrogen.

10. A surface-modified, sulfur-resistant Cu-SSZ-13 molecular sieve denitration catalyst prepared by the preparation method according to any one of claims 1 to 9.

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