A high-temperature sulfur-resistant Cu-ssz-13 molecular sieve catalyst, a preparation method and application thereof

Abstract

The application relates to the field of catalysts, and discloses a Cu-SSZ-13 molecular sieve catalyst with high-temperature sulfur resistance and a preparation method and application thereof. The preparation method comprises the following steps: dissolving ammonium acetate in deionized water, putting into H-type SSZ-13 molecular sieve for ion exchange, drying the obtained product after suction filtration, and obtaining NH4-type SSZ-13 molecular sieve; putting the NH4-type SSZ-13 molecular sieve into a copper acetate monohydrate solution for ion exchange, using acetic acid to control the pH during the ion exchange process; and suction filtering, drying and calcining the obtained product to obtain the Cu-SSZ-13 molecular sieve catalyst with high-temperature sulfur resistance. The application takes the H-type SSZ-13 molecular sieve as raw material, carries out twice ion exchange under the condition of controlling the acidity and alkalinity, controls the copper species into divalent copper ions in the obtained catalyst, and has obvious advantages in the high-temperature window in terms of the sulfur resistance.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst, its preparation method, and its application. Background Technology

[0002] With rapid societal development, the country is paying increasing attention to air pollution. Nitrogen oxides (NOx) are a significant contributor to smog formation. Aside from natural sources like lightning and nitrogen-fixing microorganisms, human activities such as thermal power generation, vehicle exhaust, and waste incineration produce large amounts of NOx, severely harming the ecological environment and human health. In my country, diesel vehicles have consistently been a major source of vehicle exhaust pollution, and the most crucial and effective means of reducing emissions per vehicle is exhaust purification. Currently, upgrading emission standards primarily involves upgrading exhaust catalytic converters, which necessitates efforts in the domestic research, development, and production of key denitrification technologies, equipment, and catalysts.

[0003] Cu-SSZ-13 catalysts, as one of the representative catalysts for NOx reduction in diesel aftertreatment systems via selective catalytic reaction (SCR), have been commercialized. Small-pore molecular sieves, represented by Cu-SSZ-13, possess shape-selective pore sizes that ensure the catalyst's hydrothermal stability and resistance to poisoning. On the one hand, the narrow pores limit the diffusion of hydrolyzed aluminum species and Cu... 2+ The accumulation of these molecules ensures the hydrothermal stability of the framework and active sites; on the other hand, some long-chain HCs and macromolecules are prevented from contacting the active sites. Therefore, copper-based microporous molecular sieves exhibit excellent denitrification efficiency in the NH3-SCR reaction. However, the Cu-SSZ-13 catalyst is highly sensitive to sulfur poisoning. During diesel combustion, the sulfur and some lubricating oil contained in the diesel are mainly converted into SO2. When SO2 passes through the diesel oxidation catalyst (DOC), a considerable portion is converted into SO3 due to the strong oxidizing function of DOC. Therefore, the downstream SCR catalyst is continuously exposed to SOx (SO2 and SO3) throughout its entire life cycle.

[0004] The high sulfur content in diesel fuel in my country poses a significant challenge to the development of diesel vehicle exhaust purification catalyst technology. Currently, Cu-SSZ-13 molecular sieve catalysts, while the most promising SCR catalysts, still have shortcomings in sulfur resistance. Even China V standard diesel fuel contains nearly 1 ppm of SO2 in its exhaust. SO2 readily reacts with copper to form stable copper sulfate compounds, reducing the number of active sites and decreasing the catalyst's redox properties, while also inhibiting NO oxidation, thus reducing the catalyst's NH3-SCR activity. Compared to the high-temperature range, SO2 has a greater impact on the low-temperature range of Cu-SSZ-13 molecular sieves, but it still reduces catalyst activity to some extent, with a significant impact within the normal operating temperature range of the catalytic converter. Sulfur-poisoned catalysts require prolonged high-temperature regeneration to restore activity, but prolonged high temperatures can lead to catalyst deactivation and increased fuel consumption. Therefore, while copper-based molecular sieve catalysts exhibit good low-temperature SCR activity, exploring their high-temperature sulfur resistance is a crucial research direction, significant for diesel vehicle exhaust denitrification and environmental protection. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst, its preparation method, and its application. The technical solution is as follows:

[0006] A method for preparing a high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst, comprising the following steps:

[0007] (1) Dissolve ammonium acetate in deionized water, place it in H-type SSZ-13 molecular sieve for ion exchange, filter the product and dry it to obtain NH4-type SSZ-13 molecular sieve;

[0008] (2) The NH4 type SSZ-13 molecular sieve was placed in a copper acetate monohydrate solution for ion exchange, and the pH was controlled by acetic acid during the ion exchange process;

[0009] (3) The product obtained in step (2) is filtered, dried and calcined to obtain Cu-SSZ-13 molecular sieve catalyst with high temperature sulfur resistance.

[0010] Furthermore, the concentration of the ammonium acetate solution in step (1) is 0.50 mol / L.

[0011] Furthermore, in step (1) H-type SSZ-13 molecular sieve, the molar ratio of silicon oxide to aluminum oxide is 6.5-7.5.

[0012] Furthermore, the H-type SSZ-13 molecular sieve in step (1) is a pretreated molecular sieve. The pretreatment method is to place the H-type SSZ-13 molecular sieve in a muffle furnace and calcine it at 550°C for 4 hours to remove the template agent.

[0013] Furthermore, in step (1), the liquid-to-solid ratio is maintained at 25; ion exchange is performed at 80 °C for 4 hours.

[0014] Furthermore, the product obtained in step (1) is filtered and then dried in an oven at 100°C for 8 hours.

[0015] Furthermore, in step (2), the concentration of the copper acetate hydrate solution is 0.15-0.40 mol / L; the pH is adjusted to 4.0-4.5 with acetic acid of 99.5% mass concentration; the liquid-solid ratio is 10; and ion exchange is performed at 80℃ for 4 hours.

[0016] Further, in step (3), the product is filtered and dried in an oven at 100°C for 8 hours; the dried solid product is heated to 550°C at a heating rate of 5°C / min and calcined for 4 hours to obtain Cu-SSZ-13 molecular sieve catalyst.

[0017] A high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst is prepared by the method described above for preparing a high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst.

[0018] Application of a high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst in the selective catalytic reduction of nitrogen oxides in diesel vehicle exhaust and in the sulfur resistance test of 1% SO2.

[0019] The present invention has the following main technical advantages:

[0020] This invention uses H-type SSZ-13 molecular sieve as raw material and sequentially exchanges it with ammonium acetate and copper acetate under controlled pH conditions, thereby improving the dispersibility of divalent copper ions and Cu(2) ions. + The resulting Cu-SSZ-13 molecular sieve catalyst, containing Cu(2) / Al, controls the copper species to divalent copper ions, exhibiting atomic-level dispersion and Cu(2) / Al content. + The ratio of α to Al is approximately 0.11-0.17. Experimental results show that this catalyst exhibits excellent NH3-SCR performance at 200-500℃, and its sulfur resistance is exceptionally good at 600℃, indicating a significant advantage in sulfur resistance within the high-temperature window and promising application prospects. Attached Figure Description

[0021] Figure 1 The graphs show the NH3-SCR performance of the Cu-SSZ-13 molecular sieve catalysts prepared in Examples 1-4.

[0022] Figure 2The graph shows the NH3-SCR performance of the Cu-SSZ-13 molecular sieve catalysts prepared in Examples 1-4 in the presence of 100 ppm SO2.

[0023] Figure 3 The graph shows the NH3-SCR performance and sulfur resistance of the Cu-SSZ-13 molecular sieve catalyst prepared in Comparative Example 1.

[0024] Figure 4 Figure 1 shows the NH3-SCR performance and sulfur resistance of the Cu-SSZ-13 molecular sieve catalyst prepared in Comparative Example 2.

[0025] Figure 5 The figure shows the NH3-SCR performance and sulfur resistance of the Cu-SSZ-13 molecular sieve catalyst prepared in Comparative Example 3. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments and accompanying drawings. The embodiments are merely exemplary and do not limit the scope of protection of the present invention. Example 1

[0027] 1. Prepare a 0.5 mol / L ammonium acetate solution, add pretreated H-type SSZ-13 molecular sieve, maintain the liquid-solid ratio at 25, stir in an oil bath for 4 hours at 80℃, vacuum filter, and wash three times with deionized water to obtain a filter cake. Place the filter cake in an oven and dry at 100℃ for 8 hours to obtain NH4-SSZ-13.

[0028] 2. Dissolve 0.476 g of copper acetate monohydrate in 50 ml of deionized water, adjust the pH to 4.5 with 99.5% acetic acid, add 5 g of NH4-SSZ-13, and stir in an oil bath at 80℃ for 4 h, ensuring the pH is maintained between 4 and 4.5 during the exchange process. After the process, filter and wash three times with deionized water. Dry the filter cake in a 100℃ oven for 8 h. The dried solid product is then heated to 550℃ at a rate of 5℃ / min and calcined for 4 h to obtain catalyst Cu-SSZ-13-1. The concentration of n[Cu(Cu] is determined. 2+ ) / Al] is 0.11. Example 2

[0029] 1. Prepare a 0.5 mol / L ammonium acetate solution, add the pretreated H-type SSZ-13 molecular sieve, maintain the liquid-solid ratio at 25, stir in an oil bath at 80℃ for 4 hours, vacuum filter, and wash three times with deionized water to obtain the filter cake, then place it in an oven and dry at 100℃ for 8 hours.

[0030] 2. Dissolve 0.635 g of copper acetate monohydrate in 50 ml of deionized water, adjust the pH to 4.4 with 99.5% acetic acid, add 5 g of NH4-SSZ-13, and stir in an oil bath at 80℃ for 4 h, ensuring the pH is maintained between 4 and 4.5 during the exchange process. After the process, filter and wash three times with deionized water. Dry the filter cake in a 100℃ oven for 8 h. The dried solid product is then heated to 550℃ at a rate of 5℃ / min and calcined for 4 h to obtain catalyst Cu-SSZ-13-2. The concentration of n[Cu(Cu] is determined. 2+ ) / Al] is 0.13. Example 3

[0031] 1. Prepare a 0.5 mol / L ammonium acetate solution, add the pretreated H-type SSZ-13 molecular sieve, maintain the liquid-solid ratio at 25, stir in an oil bath at 80℃ for 4 hours, vacuum filter, and wash three times with deionized water to obtain the filter cake, then place it in an oven and dry at 100℃ for 8 hours.

[0032] 2. Dissolve 0.952 g of copper acetate monohydrate in 50 ml of deionized water, adjust the pH to 4.0 with 99.5% acetic acid, add 5 g of NH4-SSZ-13, and stir in an oil bath at 80℃ for 4 h, ensuring the pH is maintained between 4 and 4.5 during the exchange process. After the process, filter and wash three times with deionized water. Dry the filter cake in a 100℃ oven for 8 h. The dried solid product is then heated to 550℃ at a rate of 5℃ / min and calcined for 4 h to obtain the catalyst Cu-SSZ-13-3. The n[Cu(Cu] 2+ ) / Al] is 0.15. Example 4

[0033] 1. Prepare a 0.5 mol / L ammonium acetate solution, add the pretreated H-type SSZ-13 molecular sieve, maintain the liquid-solid ratio at 25, stir in an oil bath at 80℃ for 4 hours, vacuum filter, and wash three times with deionized water to obtain the filter cake, then place it in an oven and dry at 100℃ for 8 hours.

[0034] 2. Dissolve 1.270 g of copper acetate monohydrate in 50 ml of deionized water, adjust the pH to 4.2 with 99.5% acetic acid, add 5 g of NH4-SSZ-13, and stir in an oil bath at 80℃ for 4 h, ensuring the pH is maintained between 4 and 4.5 during the exchange process. After the process, filter and wash three times with deionized water. Dry the filter cake in a 100℃ oven for 8 h. The dried solid product is then heated to 550℃ at a rate of 5℃ / min and calcined for 4 h to obtain the catalyst Cu-SSZ-13-4. The n[Cu(Cu] 2+ ) / Al] is 0.17.

[0035] Comparative Example 1

[0036] 1. Prepare a 0.5 mol / L ammonium acetate solution, add the pretreated H-type SSZ-13 molecular sieve, maintain the liquid-solid ratio at 25, stir in an oil bath at 80℃ for 4 hours, vacuum filter, and wash three times with deionized water to obtain the filter cake, then place it in an oven and dry at 100℃ for 8 hours.

[0037] 2. Dissolve 1.270 g of copper acetate monohydrate in 50 ml of deionized water, adjust the pH to 4.2 with dilute sulfuric acid, add 5 g of NH4-SSZ-13, and stir in an oil bath at 80 °C for 4 h, ensuring the pH is maintained between 4 and 4.5 during the exchange process. After completion, filter and wash three times with deionized water. Place the filter cake in a 100 °C oven and dry for 8 h. The dried solid product is then heated to 550 °C at a rate of 5 °C / min and calcined for 4 h to obtain control catalyst 1.

[0038] Comparative Example 2

[0039] 1. Prepare a 0.5 mol / L ammonium acetate solution, add pretreated H-type SSZ-13 molecular sieve, maintain a liquid-to-solid ratio of 25, and stir in an oil bath at 80℃ for 4 hours. Vacuum filter and wash three times with deionized water to obtain a filter cake. Place the cake in an oven and dry at 100℃ for 8 hours. Measure n[Cu(Cu] 2+ ) / Al] is 0.20.

[0040] 2. Dissolve 1.270 g of copper acetate monohydrate in 50 ml of deionized water, adjust the pH to 5 with ammonia, add 5 g of NH4-SSZ-13, and stir in an oil bath at 80 °C for 4 h, ensuring the pH is maintained at 5 during the exchange process. After the process, filter and wash three times with deionized water. Place the filter cake in a 100 °C oven and dry for 8 h. The dried solid product is then heated to 550 °C at a rate of 5 °C / min and calcined for 4 h to obtain control catalyst 2. The obtained product has a higher proportion of copper oxide species.

[0041] Comparative Example 3

[0042] 1. Prepare a 0.5 mol / L ammonium acetate solution, add the pretreated H-type SSZ-13 molecular sieve, maintain the liquid-solid ratio at 25, stir in an oil bath at 80℃ for 4 hours, vacuum filter, and wash three times with deionized water to obtain the filter cake, then place it in an oven and dry at 100℃ for 8 hours.

[0043] 2. Dissolve 1.270 g of copper acetate monohydrate in 50 ml of deionized water, adjust the pH to 4 with 99.5% acetic acid, add 5 g of NH4-SSZ-13, and stir in an oil bath at 80 °C until the solvent evaporates to dryness. After drying, place the product in a 100 °C oven and dry for 8 h. The dried solid product is then heated to 550 °C at a rate of 5 °C / min and calcined for 4 h to obtain control catalyst 3, which is loaded with a large amount of copper oxide.

[0044] Application examples

[0045] Using the Cu-SSZ-13 catalysts obtained in Examples 1-4 and Comparative Examples 1-3 as experimental samples, appropriate amounts of each sample were pressed into tablets, and sieved to 40-60 mesh for use as catalysts for activity testing. The catalyst loading in each reaction tube was 1 ml, with appropriate amounts of quartz sand placed above and below as a bed. The reaction temperature was monitored using thermocouples. The reaction gas composition was 500 ppm NO, 500 ppm NH3, 5% O2, with N2 as the balance gas (100 ppm SO2 was introduced on top of this for sulfur resistance testing), and the reaction space velocity was 60,000 h⁻¹. -1 The reaction gas was introduced at a flow rate of 450 mL / min, and the concentrations of NO and NO2 in the tail gas were detected using a NOx analyzer. During the test, the reaction temperature ranged from 100 to 620℃, and a temperature point was taken every 30℃ or 60℃, and the corresponding values ​​were recorded after holding the temperature for 30 minutes.

[0046] from Figure 1 , Figure 2 It can be seen that the Cu-SSZ-13 in Examples 1-4 have similar performance, exhibiting ideal NH3-SCR performance at 190-500℃ and excellent sulfur resistance at 600℃.

[0047] Figure 3 , Figure 4 , Figure 5 The figures show the NH3-SCR performance and sulfur resistance curves of the products from Comparative Examples 1, 2, and 3, respectively. It can be seen that when dilute sulfuric acid is used to adjust the acidity, ammonia is used to adjust the alkalinity, and the solvent is evaporated, the temperature window for NOx conversion of the obtained products becomes significantly narrower, and the sulfur resistance is much lower than that of the products corresponding to Examples 1-4.

Claims

1. A method for preparing a high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst, characterized in that, Includes the following steps: (1) H-type SSZ-13 molecular sieve was placed in 0.5 mol / L ammonium acetate solution for ion exchange with a liquid-solid ratio of 25. The resulting product was filtered and dried to obtain NH4-type SSZ-13 molecular sieve. The H-type SSZ-13 molecular sieve was a pretreated molecular sieve. The pretreatment method was to place the H-type SSZ-13 molecular sieve in a muffle furnace and calcine it at 550°C for 4 hours to remove the template agent. (2) The NH4 type SSZ-13 molecular sieve was placed in a 0.15-0.40 mol / L copper acetate monohydrate solution for ion exchange with a liquid-solid ratio of 10. During the ion exchange process, the pH was controlled to be maintained at 4.0-4.5 with acetic acid of 99.5% mass concentration. (3) The product obtained in step (2) is filtered, dried and calcined to obtain Cu-SSZ-13 molecular sieve catalyst with high temperature sulfur resistance; In steps (1) and (2), ion exchange is performed at 80 °C for 4 hours; the products obtained in steps (1) and (3) are filtered and dried in a vacuum oven at 100 °C for 8 hours.

2. The method for preparing a high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst according to claim 1, characterized in that, In step (1) of the H-type SSZ-13 molecular sieve, the molar ratio of silicon oxide to aluminum oxide is 6.5-7.

5.

3. The method for preparing a high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst according to claim 1, characterized in that, The solid product dried in step (3) is heated to 550°C at a heating rate of 5°C / min and calcined for 4 hours to obtain Cu-SSZ-13 molecular sieve catalyst.

4. A high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst, characterized in that, The Cu-SSZ-13 molecular sieve catalyst is prepared by the method described in any one of claims 1-3 for preparing a high-temperature sulfur-resistant Cu-SSZ-13 molecular sieve catalyst.

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