Preparation method of low-temperature water-resistant and sulfur-resistant copper-based small-pore molecular sieve catalyst
By performing surface engineering treatment on copper-based microporous molecular sieve catalysts, an all-silica layer was constructed to enhance hydrophobic properties and micropore confinement effect, thus solving the problem of easy poisoning and deactivation of copper-based microporous molecular sieve catalysts in low-temperature, high-humidity, and sulfur-containing environments, achieving excellent water and sulfur resistance and long-term stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QINGYUAN INNOVATION LABORATORY
- Filing Date
- 2026-03-05
- Publication Date
- 2026-05-29
AI Technical Summary
Existing copper-based small-pore molecular sieve catalysts are easily poisoned and deactivated in low-temperature, high-humidity, and sulfur-containing environments, and existing methods rely on sacrificial agents, resulting in insufficient long-term stability.
By performing surface engineering on copper-based microporous molecular sieve catalysts and combining selective atomic etching and directional silicon replenishment techniques, an all-silicon layer is constructed to improve hydrophobic properties and micropore confinement effect, thereby avoiding water and sulfur poisoning.
It significantly improves the catalyst's water and sulfur resistance and long-term stability, with NOx conversion rate exceeding 93.5%, making it suitable for complex flue gas conditions and expanding the applicability of copper-based small-pore molecular sieve catalysts.
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Figure CN121755263B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of materials catalysis and nitrogen oxide pollution control technology, specifically relating to a method for preparing a low-temperature water- and sulfur-resistant copper-based small-pore molecular sieve catalyst. Background Technology
[0002] Nitrogen oxides (NO) x NO is one of the major air pollutants, posing a serious threat to the ecological environment and human health. Selective catalytic reduction of ammonia (NH3-SCR) is currently the most efficient and widely used method for NO removal globally. x Purification technology. In recent years, with increasingly stringent environmental policies, non-electric industries such as steel, cement, and glass have also been required to achieve NOx emission reduction targets. x Ultra-low emissions. However, flue gas from non-power industries is generally characterized by low temperature (usually below 150 °C) and high moisture content, which can easily lead to poisoning and deactivation of denitrification catalysts. This poses a severe challenge to the low-temperature activity and durability of NH3-SCR catalysts.
[0003] Currently, common low-temperature denitrification catalysts mainly include metal oxide catalysts (such as manganese-based and cerium-based catalysts) and copper-based small-pore molecular sieve catalysts (Cu-SAPO-34, Cu-SSZ-13, Cu-SSZ-39). While metal oxide catalysts possess good low-temperature activity, their nitrogen selectivity is poor, and their resistance to water and sulfur poisoning is weak, limiting their industrial applications. In contrast, copper-based small-pore molecular sieve catalysts exhibit superior low-temperature activity and nitrogen selectivity, showing greater application potential. However, they still face the problem of activity decline due to water and sulfur poisoning in actual flue gas environments.
[0004] To improve the water and sulfur resistance of copper-based microporous molecular sieve catalysts, existing technologies often employ a sacrificial system (e.g., Chinese patent applications CN114272949A and CN112169831A). However, these methods rely on the consumption of the sacrificial agent; once the sacrificial agent is depleted, the catalyst still faces the risk of poisoning and deactivation, making it difficult to meet the requirements for long-term stable operation. Therefore, developing a method that does not rely on sacrificial agents and can significantly improve the water and sulfur resistance of copper-based microporous molecular sieve catalysts has become crucial for promoting the industrial application of this material. This invention addresses this technical challenge by proposing a novel preparation method that aims to significantly improve the long-term stability and anti-poisoning ability of the molecular sieve in low-temperature, high-humidity, and sulfur-containing environments by strengthening the micropore confinement effect and the hydrophobic properties of its outer surface. This provides important technical support for promoting the practical application of copper-based microporous molecular sieve catalysts in ultra-low emissions of flue gas in non-power industries. Summary of the Invention
[0005] The purpose of this invention is to overcome the technical defects of existing copper-based small-pore molecular sieves that are easily poisoned and deactivated in low-temperature H2O and SO2-containing waste gas, and to provide a method for preparing a low-temperature water- and sulfur-resistant copper-based small-pore molecular sieve catalyst suitable for low-temperature, high-humidity, and sulfur-containing flue gas conditions. This method systematically improves the water and sulfur resistance of such catalysts by post-treating existing copper-based small-pore molecular sieve catalysts and constructing a full silicon layer on their surface.
[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- and sulfur-resistant copper-based small-porous molecular sieve catalyst includes the following steps:
[0008] (1) A silicon source, alkali source, aluminum source, template agent, deionized water, phosphoric acid and mineralizing agent are aged at 25~80 °C for 2~24h to obtain a mixture; the mixture is transferred to a high-pressure reactor and crystallized at 100~200 °C for 1~10 days to obtain a crystallized product; the crystallized product is filtered, washed and dried, and then calcined at 450~750 °C for 2~12h to obtain a Na-type small-pore molecular sieve;
[0009] The molar composition of the silicon source, alkali source, aluminum source, template agent, deionized water, phosphoric acid, and mineralizer is as follows: SiO2:alkali source:Al2O3:template agent:H2O:phosphoric acid:mineralizer = 1 : 0.005~5 : 0.001~6 : 0.01~7 : 10~180 : 0~3.6 : 0~4.1;
[0010] (2) Add the above Na-type small-pore molecular sieve into an ammonium salt solution, stir at 60~90 °C for 1~16 h to carry out ammonium exchange, and wash and dry after exchange to obtain ammonium-type small-pore molecular sieve.
[0011] (3) Add the ammonium-type microporous molecular sieve to an acidic solution, first etch it at 60~85 °C for 0.5~5 h, then add a supplementary silicon source and continue the reaction for 1~10 h. Wash and dry the obtained solid product, and then calcine it at 450~650 °C for 1~8 h to obtain an ammonium-type microporous molecular sieve with a surface full of silicon.
[0012] (4) The above-mentioned ammonium-type microporous molecular sieve with a completely silica surface is added to a copper salt solution and copper exchange is carried out at 30~80 °C for 1~8 h. After the exchange, the sieve is washed and dried, and then calcined at 400~600 °C for 1~15 h to obtain a low-temperature water-resistant and sulfur-resistant copper-based microporous molecular sieve catalyst.
[0013] In step (1), when the prepared copper-based small-pore molecular sieve catalyst is Cu-SAPO-34 molecular sieve, phosphoric acid must be used (as a phosphorus source to participate in the construction of the molecular sieve framework structure), and no mineralizing agent needs to be added; when the prepared copper-based small-pore molecular sieve catalyst is Cu-SSZ-39 molecular sieve (to promote crystal nucleation and growth and guide the synthesis of a specific framework), a mineralizing agent must be used, and phosphoric acid is not required. The mineralizing agent is at least one of hydrofluoric acid, ammonium fluoride, sodium fluoride, and potassium fluoride.
[0014] In step (1), the silicon source is at least one of silica sol, fumed silica, tetraethyl orthosilicate, silica gel, and sodium metasilicate; the aluminum source is at least one of alumina, sodium aluminate, aluminum hydroxide, aluminum isopropoxide, and aluminum sulfate; the alkali source is at least one of sodium hydroxide, potassium hydroxide, and cesium hydroxide; and the template agent is at least one of N,N,N-trimethyl-1-adamantane ammonium, N,N-dimethyl-3,5-dimethylpiperidinium salt, tetraethylammonium hydroxide, triethylamine, diethylamine, and morpholine.
[0015] In step (2), the concentration of the ammonium salt solution is 0.01~3 mol / L, and the ratio of Na-type small-pore molecular sieve to ammonium salt solution is 1g:50~150mL.
[0016] In step (2), the ammonium salt solution is at least one of ammonium chloride solution, ammonium sulfate solution, and ammonium nitrate solution.
[0017] In step (3), the acidic solution is at least one of oxalic acid solution, citric acid solution, tartaric acid solution, ammonium fluoride solution or disodium ethylenediaminetetraacetate solution.
[0018] In step (3), the concentration of the acidic solution is 0.0001~0.5 mol / L, and the ratio of ammonium-type small-pore molecular sieve to acidic solution is 1g:10~100 mL.
[0019] In step (3), the supplementary silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane, and phenyltrimethoxysilane.
[0020] In step (3), the mass ratio of the supplementary silicon source to the ammonium-type microporous molecular sieve is 1:0.1~6.
[0021] In step (4), the concentration of the copper salt solution is 0.001~1 mol / L, and the ratio of the amount of the ammonium-type microporous molecular sieve with a surface of all-silica to the amount of copper salt solution is 1g:25~100 mL.
[0022] In step (4), the copper salt solution is at least one of copper chloride solution, copper sulfate solution, copper nitrate solution, and copper acetate solution.
[0023] This invention employs the above technical solution, which involves surface engineering of the precursor of conventional copper-based small-pore molecular sieve catalysts, namely ammonium-type small-pore molecular sieves. Combining selective atomic etching and directional silicon addition techniques, aluminum species are selectively removed from the surface, and silicon species are directionally introduced, thereby constructing a stable pure silicon structure on the surface of the ammonium-type small-pore molecular sieve. Subsequently, copper atoms are introduced to form a copper-based small-pore molecular sieve catalyst with a pure silicon surface structure. This pure silicon surface layer can achieve a dual function: firstly, by removing acid sites on its surface, it can effectively improve the hydrophobicity of the catalyst and inhibit the reaction of H2O and SO2 on its surface; secondly, combined with the characteristic that the pore size of the small-pore molecular sieve is smaller than the dynamic diameter of SO2 molecules, the microporous sieving effect can be used to physically block SO2 molecules from entering the pores and contacting the active Cu sites, thus fundamentally avoiding sulfur poisoning.
[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0025] 1. The present invention relates to a method for preparing copper-based microporous molecular sieves through surface removal and silicon replenishment, integrating selective atomic etching, directional silicon replenishment, and ion exchange technologies. For surface removal and silicon replenishment of microporous molecular sieves, this invention precisely removes surface aluminum atoms through selective atomic etching, and then directionally anchors and replenishes silicon species. This method eliminates the need for pre-protection of aluminum sites within the molecular sieve pores, achieving atomic-level precision removal of surface aluminum and directional repair of silicon. Through a surface modification strategy combining selective etching and directional silicon replenishment, this invention enables precise control of the thickness of the full silicon layer on the catalyst surface. This characteristic allows for the controlled preparation of copper-based microporous molecular sieve catalysts with different full silicon layer thicknesses based on the differences in SO2 and H2O concentrations in actual flue gas, thereby significantly expanding its applicability under complex flue gas conditions.
[0026] 2. This invention intrinsically and persistently enhances the catalyst's resistance to poisoning by synergistically utilizing the micropore confinement effect of the copper-based microporous molecular sieve and the hydrophobic effect of the all-silica layer on its outer surface. This design eliminates the need for externally introduced sacrificial or protective systems, fundamentally enhancing the catalyst's long-term operational stability under harsh environments.
[0027] 3. The low-temperature water- and sulfur-resistant copper-based small-pore molecular sieve catalyst prepared by the method of this invention was tested under simulated harsh conditions (temperature 140~150 °C, 300~500 ppm SO2, 25~50 vol% H2O). Its nitrogen oxide removal performance was excellent and stable. xThe conversion rate can be maintained above 93.5% for a long period, demonstrating excellent low-temperature water and sulfur resistance and long-term operational stability. The method of this invention has broad applicability and can be applied to the preparation of various copper-based small-pore molecular sieve denitration catalysts, including low-temperature water and sulfur resistant Cu-SAPO-34, Cu-SSZ-13, and Cu-SSZ-39, which can generally improve the water and sulfur resistance of existing copper-based small-pore molecular sieve catalysts. This method is simple, low-cost, and has good potential for industrial application. Attached Figure Description
[0028] Figure 1 This is a comparison chart showing the long-term water and sulfur resistance denitrification stability test results of the catalysts in Examples 1 and 2 of the present invention and Comparative Example 1.
[0029] Figure 2 This is a comparison chart showing the long-term water and sulfur resistance denitrification stability test results of the catalysts in Examples 3 and 4 of the present invention and Comparative Example 2.
[0030] Figure 3 This is a comparison chart showing the long-term water and sulfur resistance denitrification stability test results of the catalysts in Examples 5 and 6 of the present invention and Comparative Example 3. Detailed Implementation
[0031] Example 1
[0032] A method for preparing a low-temperature, water- and sulfur-resistant copper-based small-porous molecular sieve catalyst includes the following steps:
[0033] (1) 4.8 g silica gel, 0.51 g Al2O3, 0.64 g sodium hydroxide, and 13.5 g of 25% N,N,N-trimethyl-1-adamantane ammonium solution were sequentially added to 52 g of deionized water and aged at 35 °C for 5 h. Then, the mixture was transferred to a steel sleeve in a reactor and crystallized at 160 °C for 4 days. The crystallized product was then filtered, washed, dried, and calcined at 600 °C for 6 h to obtain Na-SSZ-13 molecular sieve.
[0034] (2) Add 4 g of Na-SSZ-13 molecular sieve to 400 mL of 1 mol / L ammonium sulfate solution, exchange at 80 °C for 6 h, and then wash and dry to obtain NH4-SSZ-13 molecular sieve.
[0035] (3) 3 g of NH4-SSZ-13 molecular sieve was added to 100 mL of deionized water, followed by 1.6 g of oxalic acid, and stirred at 60 °C for 2 h. Then 0.87 g of tetraethyl orthosilicate was added, and the reaction was continued for 3 h. After the reaction was completed, the sample was washed, filtered, dried, and finally calcined at 600 °C for 3.5 h to obtain the surface-hollow NH4-SSZ-13 molecular sieve.
[0036] (4) 2 g of surface-all-silica type NH4-SSZ-13 molecular sieve was added to 200 mL of 0.27 mol / L copper acetate solution, and exchanged at 60 °C for 2 h. After washing and drying, it was calcined at 500 °C for 6 h to obtain low-temperature water-resistant and sulfur-resistant Cu-SSZ-13 molecular sieve.
[0037] Example 2
[0038] A method for preparing a low-temperature, water- and sulfur-resistant copper-based small-porous molecular sieve catalyst includes the following steps:
[0039] (1) 18.6 g silica sol, 0.21 g Al2O3, 0.75 g sodium hydroxide, and 16.5 g of 25% N,N,N-trimethyl-1-adamantane ammonium solution were sequentially added to 40 g deionized water and aged at 60 °C for 3 h. Then, the mixture was transferred to a steel sleeve of a reactor and crystallized at 160 °C for 6 days. The crystallized product was washed, dried, and calcined at 650 °C for 8 h to obtain Na-SSZ-13 molecular sieve.
[0040] (2) Add 3 g of Na-SSZ-13 molecular sieve to 360 mL of 0.5 mol / L ammonium chloride solution, exchange at 70 °C for 8 h, and then wash and dry to obtain NH4-SSZ-13 molecular sieve.
[0041] (3) 2.5 g of NH4-SSZ-13 molecular sieve was added to 120 mL of deionized water, followed by 1.8 g of oxalic acid, and stirred at 80 °C for 3 h. Then 0.72 g of tetraethyl orthosilicate was added, and the reaction continued for 2 h. After the reaction was completed, the sieve was washed, filtered, dried, and finally calcined at 600 °C for 2.5 h to obtain the surface-hollow NH4-SSZ-13 molecular sieve.
[0042] (4) 2 g of all-silica type NH4-SSZ-13 was added to 180 mL of 0.17 mol / L copper nitrate solution and exchanged at 70 °C for 1.5 h. After washing and drying, it was calcined at 550 °C for 4 h to obtain low-temperature water-resistant and sulfur-resistant Cu-SSZ-13 molecular sieve.
[0043] Example 3
[0044] A method for preparing a low-temperature, water- and sulfur-resistant copper-based small-porous molecular sieve catalyst includes the following steps:
[0045] (1) 3.7 g of fumed silica, 7.3 g of aluminum isopropoxide, 0.28 g of sodium hydroxide, 7.5 g of triethylamine and 1.27 g of phosphoric acid were added sequentially to 35 g of deionized water and aged at 50 °C for 4 h. Then, the mixture was transferred to a steel sleeve of a reactor and crystallized at 180 °C for 2 days. The crystallized product was washed, dried and calcined at 650 °C for 7 h to obtain Na-SAPO-34 molecular sieve.
[0046] (2) 3.5 g of Na-SAPO-34 molecular sieve was added to 450 mL of 1 mol / L ammonium chloride solution, and the exchange was carried out at 75 °C for 9 h. After washing and drying, NH4-SAPO-34 molecular sieve was obtained.
[0047] (3) Add 3 g of NH4-SAPO-34 molecular sieve to 125 mL of deionized water, then add 3.2 g of citric acid and stir at 80 °C for 3 h. Then add 1.06 g of methyltriethoxysilane and continue the reaction for 1 h. After the reaction is complete, wash, filter, dry, and finally calcine at 650 °C for 5 h to obtain NH4-SAPO-34 molecular sieve with all-silica surface.
[0048] (4) 3 g of surface-all-silica NH4-SAPO-34 molecular sieve was added to 300 mL of 0.59 mol / L copper nitrate solution, exchanged at 65 °C for 3 h, washed, dried and calcined at 550 °C for 3 h to obtain low-temperature water-resistant and sulfur-resistant Cu-SAPO-34 molecular sieve.
[0049] Example 4
[0050] A method for preparing a low-temperature, water- and sulfur-resistant copper-based small-porous molecular sieve catalyst includes the following steps:
[0051] (1) 4.7 g of fumed silica, 5.2 g of aluminum hydroxide, 0.32 g of sodium hydroxide, 8.2 g of tetraethylammonium hydroxide, and 1.41 g of phosphoric acid were added sequentially to 37 g of deionized water and aged at 70 °C for 3 h. Then, the mixture was transferred to a steel sleeve in a reactor and crystallized at 170 °C for 4 days. The crystallized product was washed, dried, and calcined at 600 °C for 6 h to obtain Na-SAPO-34 molecular sieve.
[0052] (2) 3 g Na-SAPO-34 was placed in 350 mL of 1 mol / L ammonium sulfate solution and exchanged at 80 °C for 6 h. After washing and drying, NH4-SAPO-34 molecular sieve was obtained.
[0053] (3) 2.5 g of NH4-SAPO-34 molecular sieve was placed into 100 mL of deionized water, followed by 2.7 g of citric acid, and stirred at 80 °C for 2 h. Then 0.91 g of methyltriethoxysilane was added, and the reaction was continued for 1.5 h. After the reaction was completed, the sieve was washed, filtered, dried, and finally calcined at 650 °C for 6 h to obtain NH4-SAPO-34 molecular sieve with a completely silica surface.
[0054] (4) 2 g of surface-hollow NH4-SAPO-34 molecular sieve was added to 250 mL of 0.51 mol / L copper nitrate solution and exchanged at 60 °C for 2 h. After washing and drying, it was calcined at 500 °C for 4 h to obtain low-temperature water-resistant and sulfur-resistant Cu-SAPO-34 molecular sieve.
[0055] Example 5
[0056] A method for preparing a low-temperature, water- and sulfur-resistant copper-based small-porous molecular sieve catalyst includes the following steps:
[0057] (1) 6.32 g sodium metasilicate, 1.07 g aluminum sulfate, 0.61 g potassium hydroxide, 9.5 g N,N-dimethyl-3,5-dimethylpiperidinium salt, and 0.75 g hydrofluoric acid were sequentially added to 32 g deionized water and aged at 60 °C for 6 h. Then, the mixture was transferred to a steel sleeve in a reactor and crystallized at 165 °C for 8 days. The crystallized product was washed, dried, and calcined at 650 °C for 5 h to obtain Na-SSZ-39 molecular sieve.
[0058] (2) 2 g of Na-SSZ-39 molecular sieve was added to 200 mL of 1 mol / L ammonium chloride solution, and the exchange was carried out at 85 °C for 9 h. After washing and drying, NH4-SSZ-39 molecular sieve was obtained.
[0059] (3) 1.5 g of NH4-SSZ-39 was added to 80 mL of deionized water, followed by 3.5 g of disodium ethylenediaminetetraacetate solution, and stirred at 85 °C for 5 h. Then 0.63 g of dimethyldiethoxysilane was added, and the reaction was continued for 3 h. After the reaction was completed, the sample was washed, filtered, dried, and finally calcined at 600 °C for 5 h to obtain NH4-SSZ-39 molecular sieve with a completely silica surface.
[0060] (4) 1 g of surface-hollow NH4-SSZ-39 molecular sieve was added to 100 mL of 0.32 mol / L copper acetate solution and exchanged at 70 °C for 3 h. After washing and drying, it was calcined at 550 °C for 5 h to obtain low-temperature water-resistant and sulfur-resistant Cu-SSZ-39 molecular sieve.
[0061] Example 6
[0062] A method for preparing a low-temperature, water- and sulfur-resistant copper-based small-porous molecular sieve catalyst includes the following steps:
[0063] (1) 17.3 g silica sol, 0.97 g sodium aluminate, 0.53 g cesium hydroxide, 10.7 g N,N-dimethyl-3,5-dimethylpiperidinium salt, and 0.68 g hydrofluoric acid were sequentially added to 28 g deionized water and aged at 70 °C for 4 h. Then, the mixture was transferred to a steel sleeve in a reactor and crystallized at 170 °C for 7 days. The crystallized product was washed, dried, and calcined at 700 °C for 3 h to obtain Na-SSZ-39 molecular sieve.
[0064] (2) 2.5 g of Na-SSZ-39 molecular sieve was added to 250 mL of 1 mol / L ammonium chloride solution, and the exchange was carried out at 85 °C for 9 h. After washing and drying, NH4-SSZ-39 molecular sieve was obtained.
[0065] (3) 2 g of NH4-SSZ-39 molecular sieve was added to 120 mL of deionized water, followed by 3.2 g of disodium ethylenediaminetetraacetate solution, and stirred at 85 °C for 4 h. Then 0.59 g of dimethyldiethoxysilane was added, and the reaction was continued for 3.5 h. After the reaction was completed, the sample was washed, filtered, dried, and finally calcined at 600 °C for 6 h to obtain NH4-SSZ-39 molecular sieve with a completely silica surface.
[0066] (4) 1.5 g of surface-hollow NH4-SSZ-39 molecular sieve was added to 150 mL of 0.3 mol / L copper sulfate solution and exchanged at 65 °C for 2 h. After washing and drying, it was calcined at 600 °C for 6 h to obtain low-temperature water-resistant and sulfur-resistant Cu-SSZ-39 molecular sieve.
[0067] Comparative Example 1
[0068] Except for not performing the etching and silicon replenishment in step (3), the other steps are the same as in Example 1, and a conventional Cu-SSZ-13 molecular sieve is prepared.
[0069] Comparative Example 2
[0070] Except for not performing the etching and silicon replenishment in step (3), the other steps are the same as in Example 3, and a conventional Cu-SAPO-34 molecular sieve is prepared.
[0071] Comparative Example 3
[0072] Except for not performing the etching and silicon replenishment in step (3), the other steps are the same as in Example 5, and conventional Cu-SSZ-39 molecular sieve is prepared.
[0073] Catalyst water resistance, sulfur resistance and denitrification performance test
[0074] The performance of NH3-SCR was evaluated in a fixed-bed quartz tube reactor. The catalyst loading was 0.4 g (20-40 mesh). The reaction gas composition was: 500 ppm NO, 500 ppm NH3, 5 vol% O2, 25-50 vol% H2O, 500 ppm SO2, 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 was stabilized at 145 °C. The concentrations of NO and NO2 at the reactor inlet and outlet were continuously monitored using an online Fourier transform infrared gas analyzer. x The formula for calculating conversion rate is:
[0075] NO x conversion (%)=
[0076] Among them, 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.
[0077] Test results are as follows Figure 1 As shown. Examples 1 and 2 are Cu-SSZ-13 catalysts with different silicon-to-aluminum molar ratios after surface full-silica treatment, while Comparative Example 1 is a conventional Cu-SSZ-13 catalyst. In the same simulated flue gas environment, the Cu-SSZ-13 catalysts with different silicon-to-aluminum ratios and surface full-silica treatment all exhibited excellent low-temperature water and sulfur resistance, while the conventional Cu-SSZ-13 catalyst had a denitrification performance of less than 10% after 350 h of evaluation. Figure 2 This study evaluates the water and sulfur resistance of Cu-SAPO-34 catalysts with different silicon-to-aluminum molar ratios after surface full-silicon treatment, as well as conventional Cu-SAPO-34 catalysts. Under the same simulated flue gas environment, Cu-SAPO-34 catalysts with different silicon-to-aluminum ratios and surface full-silicon treatment all exhibited excellent low-temperature water and sulfur resistance, while the conventional Cu-SAPO-34 catalyst showed a denitrification performance of less than 10% after 350 hours of evaluation. Figure 3This study evaluates the water and sulfur resistance of Cu-SSZ-39 catalysts with different silicon-to-aluminum molar ratios after surface-to-silica treatment, as well as conventional Cu-SSZ-39 catalysts. Under the same simulated flue gas environment, the Cu-SSZ-39 catalysts with different silicon-to-aluminum ratios and surface-to-silica treatment all exhibited excellent low-temperature water and sulfur resistance, while the conventional Cu-SSZ-39 catalyst showed a denitrification performance of less than 10% after 350 h of evaluation. Therefore, the method of this invention can be used to prepare copper-based small-pore molecular sieve catalysts with excellent water and sulfur resistance.
Claims
1. A method for preparing a low-temperature, water- and sulfur-resistant copper-based small-porous molecular sieve catalyst, characterized in that, Includes the following steps: (1) After mixing silicon source, alkali source, aluminum source, template agent, deionized water, phosphoric acid and mineralizing agent, Na-type small-pore molecular sieve is obtained by aging, crystallization and calcination. The molar composition of the silicon source, alkali source, aluminum source, template agent, deionized water, phosphoric acid, and mineralizer is as follows: SiO2:alkali source:Al2O3:template agent:H2O:phosphoric acid:mineralizer = 1 : 0.005~5 : 0.001~6 : 0.01~7 : 10~180 : 0~3.6 : 0~4.1; (2) Add the above Na-type small-pore molecular sieve into an ammonium salt solution, stir at 60~90 °C for 1~16 h to carry out ammonium exchange, and wash and dry after exchange to obtain ammonium-type small-pore molecular sieve. (3) Add the ammonium-type microporous molecular sieve to an acidic solution, first etch it at 60~85 °C for 0.5~5 h, then add a supplementary silicon source and continue the reaction for 1~10 h. Wash and dry the obtained solid product, and then calcine it at 450~650 °C for 1~8 h to obtain an ammonium-type microporous molecular sieve with a surface full of silicon. The acidic solution is at least one of oxalic acid solution, citric acid solution, tartaric acid solution, ammonium fluoride solution, or disodium ethylenediaminetetraacetate solution; the concentration of the acidic solution is 0.0001~0.5 mol / L, and the ratio of ammonium-type small-pore molecular sieve to acidic solution is 1g:10~100mL; (4) The above-mentioned ammonium-type microporous molecular sieve with a completely silica surface is added to a copper salt solution and copper exchange is carried out at 30~80 °C for 1~8 h. After the exchange, the sieve is washed and dried, and then calcined at 400~600 °C for 1~15 h to obtain a low-temperature water-resistant and sulfur-resistant copper-based microporous molecular sieve catalyst.
2. The method for preparing a low-temperature water- and sulfur-resistant copper-based small-porous molecular sieve catalyst according to claim 1, characterized in that, In step (1), the specific preparation process of the Na-type small-pore molecular sieve is as follows: the silicon source, alkali source, aluminum source, template agent, deionized water, phosphoric acid and mineralizing agent are aged at 25~80 °C for 2~24 h to obtain a mixture; the mixture is transferred to a high-pressure reactor and crystallized at 100~200 °C for 1~10 days to obtain a crystallized product; The crystallized product was filtered, washed, and dried, and then calcined at 450~750 °C for 2~12 h to obtain Na-type small-pore molecular sieve.
3. The method for preparing a low-temperature water- and sulfur-resistant copper-based small-pore molecular sieve catalyst according to claim 1, characterized in that, In step (1), the mineralizing agent is at least one of hydrofluoric acid, ammonium fluoride, sodium fluoride, and potassium fluoride.
4. The method for preparing a low-temperature water- and sulfur-resistant copper-based small-pore molecular sieve catalyst according to claim 1, characterized in that, In step (1), the silicon source is at least one of silica sol, fumed silica, tetraethyl orthosilicate, silica gel, and sodium metasilicate; the aluminum source is at least one of alumina, sodium aluminate, aluminum hydroxide, aluminum isopropoxide, and aluminum sulfate; the alkali source is at least one of sodium hydroxide, potassium hydroxide, and cesium hydroxide; and the template agent is at least one of N,N,N-trimethyl-1-adamantane ammonium, N,N-dimethyl-3,5-dimethylpiperidinium salt, tetraethylammonium hydroxide, triethylamine, diethylamine, and morpholine.
5. The method for preparing a low-temperature water- and sulfur-resistant copper-based small-pore molecular sieve catalyst 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 0.01~3 mol / L, and the ratio of Na-type small-pore molecular sieve to ammonium salt solution is 1g:50~150mL.
6. The method for preparing a low-temperature water- and sulfur-resistant copper-based small-porous molecular sieve catalyst according to claim 1, characterized in that, In step (3), the supplementary silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane, and phenyltrimethoxysilane.
7. The method for preparing a low-temperature water- and sulfur-resistant copper-based small-pore molecular sieve catalyst according to claim 1, characterized in that, In step (3), the mass ratio of the supplementary silicon source to the ammonium-type microporous molecular sieve is 1:0.1~6.
8. The method for preparing a low-temperature water- and sulfur-resistant copper-based small-porous molecular sieve catalyst according to claim 1, characterized in that, In step (4), the copper salt solution is at least one of copper chloride solution, copper sulfate solution, copper nitrate solution, and copper acetate solution; the concentration of the copper salt solution is 0.001~1 mol / L, and the ratio of the amount of the ammonium-type microporous molecular sieve with a completely silica surface to the amount of copper salt solution is 1g:25~100 mL.
9. The low-temperature water- and sulfur-resistant copper-based small-pore molecular sieve catalyst obtained by the preparation method according to any one of claims 1 to 8.