Regeneration and performance enhancement method for sulfur poisoning problem of Cu / SSZ-13 catalyst in NH3-SCR

Abstract

The invention relates to a regeneration and performance enhancement method of a Cu / SSZ-13 catalyst in sulfur poisoning inactivated ammonia selective catalytic reduction (NH3-SCR). The method comprises the following steps: roasting a sulfur-poisoned Cu / SSZ-13 catalyst in inert atmosphere argon at high temperature for a period of time, and annealing and cooling to room temperature in the same atmosphere to obtain the regenerated Cu / SSZ-13 catalyst. According to the method, the process is simple, and meanwhile, the low-temperature denitration efficiency of the inactivated SCR denitration catalyst can be greatly improved. The low-temperature denitration performance of the regenerated catalyst even obviously exceeds that of a fresh catalyst, and particularly, the conversion rate of NOx at 170 DEG C is increased by 30%. The regenerated catalyst is suitable for various application scenes such as diesel tail gas denitration, and has a wide industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of regeneration technology for deactivated SCR catalysts, specifically to a method for regenerating and enhancing the performance of sulfur-poisoned deactivated SCR denitration catalysts. Background Technology

[0002] With the intensification of global industrialization and urbanization, nitrogen oxides (NOx) have increased significantly. x Emissions are becoming increasingly serious, posing a key challenge in air pollution control. x Not only are they precursors to secondary pollutants such as acid rain, photochemical smog, and fine particulate matter (PM2.5), but they can also react with volatile organic compounds (VOCs) to produce ozone, posing a threat to global warming and human health. Diesel engines, as a source of NO... x As a significant source of NO emissions, the exhaust gas treatment technology for diesel engines has attracted considerable attention. Ammonia selective catalytic reduction (NH3-SCR) technology is currently the most effective method for controlling NO emissions from diesel engines. x The mainstream method for emission reduction has advantages such as high reduction efficiency and a wide reaction temperature window. In recent years, small-pore zeolite catalysts (such as SSZ-13 and SAPO-34) have become a research hotspot due to their three-dimensional pore structure, high specific surface area, and good thermal stability. In particular, the copper-exchange SSZ-13 (Cu / SSZ-13) catalyst has shown excellent denitrification performance in the range of 150–450℃ and has been widely used in the exhaust purification systems of diesel vehicles that meet the China VI and Euro VI standards.

[0003] However, under actual operating conditions, sulfur sources such as SO2 and SO3 in engine emissions can cause sulfur poisoning in the Cu / SSZ-13 catalyst, especially at low temperatures. These sulfur sources will first react with the most reactive [ZCu] ring in the 8-membered ring (8-MR). 2+ (OH)] + The species react and form metastable substances such as CuHSO3, which are then easily oxidized into more stable and difficult-to-decompose CuSO4 species that deposit on the surface. These species then block the pore structure of SSZ-13Cu zeolite, ultimately inhibiting the adsorption of reactants on the active sites, thus leading to catalyst deactivation.

[0004] To address the aforementioned issue of sulfur poisoning in Cu / SSZ-13, the conventional method is high-temperature air calcination (oxidizing atmosphere) to regenerate the catalyst's active sites. However, during regeneration in an oxidizing atmosphere (typically above 550°C), sulfur poisoning occurs due to the reaction of [ZCu]... 2+ (OH)] +The metastable CuHSO3 formed will oxidize to the more stable CuSO4 or CuHSO4 at high temperatures. Meanwhile, in oxidizing atmospheres below 900℃, conventional desulfurization conditions are insufficient to completely redisperse CuSO4 or CuHSO4 species into active Cu sites, resulting in incomplete recovery of NH3-SCR activity. Therefore, to improve desulfurization efficiency, the temperature is often raised to 900℃ to promote the complete decomposition of surface-accumulated sulfate species. However, excessively high decomposition temperatures can severely damage or even completely destroy the structure of the SSZ-13 molecular sieve, thus also leading to a decrease in NH3-SCR activity. Therefore, developing a mild and effective Cu / SSZ-13 regeneration strategy to achieve deep recovery of sulfur-poisoned catalysts has become a critical technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a highly efficient method for the regeneration of Cu / SSZ-13 catalysts after sulfur poisoning. By changing the treatment atmosphere and selecting an inert argon atmosphere as the desulfurization and regeneration condition for high-temperature calcination of the catalyst, the decomposition of accumulated sulfate species and the redispersion of Cu active sites are promoted, while protecting the pore structure of the SSZ-13 molecular sieve, ultimately significantly improving the low-temperature SCR performance of the catalyst.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A regeneration method for addressing sulfur poisoning in Cu / SSZ-13 catalysts in NH3-SCR, comprising the following steps:

[0007] Step 1: Place the sulfur-poisoned and deactivated catalyst sample in a tube furnace and introduce inert argon gas.

[0008] Step 2: Set the heating rate of the tube furnace, heat the sample to a certain temperature and maintain it for a period of time.

[0009] Step 3: Stop heating and allow the catalyst to cool naturally to room temperature in an inert atmosphere.

[0010] Step 4: Turn off the inert gas supply to obtain the regenerated catalyst.

[0011] The present invention also provides an application of the deactivated and regenerated Cu / SSZ-13 catalyst, wherein the catalyst is used in NH3-SCR.

[0012] Furthermore, the reaction atmosphere consisted of 500 ppm NO, 500 ppm NH3, 5% O2, 5% H2O, and argon as the equilibrium gas, with a reaction space velocity of 180,000 mL·g. -1 ·h -1 .

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The high-temperature regeneration strategy at 800℃ under an inert argon atmosphere proposed in this invention successfully avoids the conversion of CuHSO3 to stable inert species such as CuSO4 under a traditional oxygen atmosphere, significantly improving regeneration efficiency. This method not only restores the original performance of the catalyst but also promotes Cu… 2+ Species preferentially distribute within the 8-MR channels of SSZ-13, forming more [ZCu 2+ (OH)] + The active sites enhance the low-temperature NH3-SCR activity. Under typical denitrification reaction conditions, the regenerated catalyst represents a rare activity-enhancing regeneration pathway in currently known catalyst systems.

[0015] (2) The regeneration method is simple, does not damage the molecular sieve skeleton, and has good cycle stability and industrial promotion value. Attached Figure Description

[0016] Figure 1 Low-temperature NH3-SCR performance of catalysts

[0017] Figure 2 XRD patterns of catalysts

[0018] Figure 3 H2-TPR spectrum of the catalyst Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0020] Example 1

[0021] A certain amount of H-SSZ-13 (Si / Al = 9) was placed in 10 mL of aqueous solution, followed by the addition of a certain amount of Cu(NO3)2·5H2O, controlling the Cu to Al molar ratio to be 0.45:1. After stirring in a water bath at 80 °C for 1 hour, the solvent water was removed by vacuum rotary evaporation of the resulting dispersion. The resulting solid was dried at 110 °C for 12 hours and calcined in air at 550 °C for 4 hours to obtain an unpoisoned fresh catalyst, denoted as Cu / SSZ-13-air.

[0022] Example 2

[0023] A certain amount of Cu / SSZ-13 catalyst from Example 1 was mixed with (NH4)2SO4 at a S / Cu molar ratio of 1:1. 2 mL of deionized water was added for wet impregnation. The mixture was stirred at room temperature for 30 min, dried at 120 °C for 6 h, and calcined at 500 °C for 2 h in air atmosphere to obtain a sulfur-poisoned catalyst, denoted as Cu / SSZ-13-S.

[0024] Example 3

[0025] A certain amount of the sulfur-poisoned Cu / SSZ-13 catalyst from Example 2 was taken and placed in a tube furnace, and calcined at 800°C for 2 hours under an inert argon atmosphere (120 mL / min). After cooling to room temperature under an inert argon atmosphere, the argon gas was turned off to obtain the regenerated catalyst treated with inert argon atmosphere at high temperature, denoted as Cu / SSZ-13-S-Ar.

[0026] Comparative Example 1

[0027] The solid calcination atmosphere was changed to argon, and the rest of the preparation method was the same as in Example 1, resulting in an unpoisoned fresh catalyst, denoted as Cu / SSZ-13-Ar.

[0028] Comparative Example 2

[0029] The atmosphere of the high-temperature calcination treatment of the sulfur-poisoned catalyst was changed to oxygen, and the remaining steps were the same as in Example 3, to obtain a regenerated catalyst treated at high temperature in an oxidizing atmosphere, denoted as Cu / SSZ-13-S-air.

[0030] Performance Evaluation

[0031] The catalytic performance evaluation conditions for NH3-SCR were as follows: 0.1 g of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2 were placed in a quartz tube fixed-bed reactor, respectively. The reaction gases were 500 ppm NO, 500 ppm NH3, 5% O2, and 5% H2O, with Ar as the equilibrium gas. The total flow rate of the reaction gases was 300 mL / min, and the mass hourly space velocity (WHSV) was 180,000 mL·g. -1 ·h -1 The denitrification performance was tested under the specified conditions, and the reaction tail gas was detected using a NOx analyzer.

[0032] The results are as follows Figure 1 As shown in Figure a, compared to fresh catalysts, sulfur-poisoned catalysts exhibit a significant decreasing trend in NOx conversion. And from... Figure 1 As shown in b, regardless of whether the catalyst is calcined and regenerated in an air atmosphere or an inert argon atmosphere, the high-temperature treatment significantly suppresses the deactivation effect caused by sulfur poisoning. However, for catalysts regenerated in an air atmosphere, from... Figure 1 As can be seen from c, the low-temperature NH3-SCR activity recovery is incomplete, and NO at 170℃... x The conversion rate was 15% lower than that of the fresh sample. However, for catalysts regenerated under an inert argon atmosphere, the conversion rate was... Figure 1 The results from the CD analysis show that its low-temperature catalytic activity even surpasses that of fresh catalysts, exhibiting NO catalytic activity in the range of 170–310 °C. xThe conversion rate consistently exceeded 80%, and compared to freshly calcined catalysts at 170℃, its effect on NO... x The conversion rate can be increased by up to approximately 30%.

[0033] Figure 2 The X-ray diffraction (XRD) patterns of the catalysts prepared in Examples 1-3 and Comparative Example 2 are shown. All three samples exhibit typical CHA-type molecular sieve diffraction characteristic peaks, indicating that poisoning and regeneration treatments did not damage the molecular sieve crystal framework structure. Compared to the fresh sample, the XRD pattern of Cu / SSZ-13-S shows a decrease in peak intensity at some diffraction angles, possibly related to local framework defects caused by sulfur poisoning and Cu-S species deposition. The diffraction peak intensities of the regenerated sample Cu / SSZ-13-S-Ar are basically consistent with those of the fresh sample, indicating that high-temperature treatment under an inert atmosphere not only did not cause structural damage but also restored crystal order to a certain extent, exhibiting good structural stability.

[0034] Figure 3 The results of H2 temperature-programmed reduction (H2-TPR) tests on the catalysts prepared in Examples 1-3 and Comparative Example 2 are presented. The fresh Cu / SSZ-13-air catalyst exhibits typical [ZCu] behavior in the range of 250–350 °C. 2+ (OH)] + Species reduction peak, and no obvious high-temperature CuO x The reduction peak indicates that Cu 2+ It is anchored in the molecular sieve framework in a highly dispersed state. In Cu / SSZ-13-S, this peak shifts to the right and broadens, indicating that the Cu species are affected by sulfur species, leading to a decrease in its redox properties. However, in the regenerated sample Cu / SSZ-13-S-Ar, [ZCu 2+ (OH)] + The reduction peak shifted forward and its intensity increased significantly, while no obvious CuO or CuO was observed. x The high-temperature reduction-like signal indicates that high-temperature treatment in an inert atmosphere can promote the migration of Cu species in a dispersed state back to the framework sites, which is the key to the significant improvement of the catalyst's low-temperature activity.

Claims

1. A method for sulfur poisoning deactivation, regeneration, and performance enhancement of an NH3-SCR denitration catalyst, characterized in that, Includes the following steps: Step 1: Place the sulfur-poisoned and deactivated catalyst sample in a tube furnace and introduce inert argon gas. Step 2: Set the heating rate of the tube furnace, heat the sample to a certain temperature and maintain it for a period of time. Step 3: Stop heating and allow the catalyst to cool naturally to room temperature in an inert atmosphere. Step 4: Turn off the inert gas supply to obtain the regenerated catalyst.

2. The modified regeneration method according to claim 1, characterized in that, The deactivated SCR denitration catalyst to be treated is a Cu / SSZ-13 series SCR denitration catalyst.

3. The modified regeneration method according to claim 1, characterized in that, In step 1, the flow rate of the inert argon gas introduced into the sample is 100–200 mL / min.

4. The modified regeneration method according to claim 1, characterized in that, In step 2, the high-temperature roasting treatment of the sample is carried out at a temperature of 700-900℃ for 1-4 hours.

5. The application of the Cu / SSZ-13 series catalyst according to claims 1-4, characterized in that, The reaction conditions were as follows: the reaction atmosphere consisted of 500 ppm NO, 500 ppm NH3, 5% O2, 5% H2O, and argon as the equilibrium gas; the reaction space velocity was 180,000 mL·g. -1 ·h -1 .

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