A pre-sulfatated CO-SCR catalyst, its preparation method and application

Abstract

This invention provides a pre-sulfatated CO-SCR catalyst, its preparation method, and its application, relating to the field of environmental materials technology. The process includes: mixing and drying an active component precursor solution with an HZSM-5 molecular sieve; calcining under a nitrogen atmosphere to form an iridium and copper oxide co-doped molecular sieve catalyst; and further sulfatating with gaseous sulfur dioxide and oxygen. This invention co-dops Ir-CuO onto an HZSM-5 support. The pre-sulfatation treatment not only anchors sulfate species to the support surface via pore mass transfer but also activates the synergistic effect of both through electron migration during Ir-Cu sulfatation, generating abundant reactive oxygen vacancies. The unique oxygen shielding effect of the sulfate species and the derived reactive oxygen vacancies jointly enhance the catalyst's CO-SCR catalytic activity under aerobic conditions, effectively mitigating oxygen consumption of the reducing agent and maintaining high and stable CO-SCR operating efficiency.

Description

Technical Field

[0001] This invention belongs to the field of environmental materials technology, specifically relating to a pre-sulfatated CO-SCR catalyst, its preparation method, and its application in the treatment of waste gas in the field of denitrification. Background Technology

[0002] Nitrogen oxides (NO) x NO is one of the major air pollutants, causing significant damage to human health and the environment. Although NH3-SCR has long been commercialized, it still has the following drawbacks: it requires a large external introduction of the reducing agent NH3, which carries the risk of leakage; furthermore, the synthesis, transportation, and storage of NH3 incur additional costs. CO is ubiquitous in various waste gases, and its high toxicity necessitates its removal from exhaust gases. The excellent reducing properties of its intrinsic component CO are utilized to reduce NO in waste gases. x This method can simultaneously remove two pollutants, achieving the goal of "treating waste with waste," and possesses strong practicality and high economic efficiency. Currently, O2, as a common component in the CO-SCR system, typically greatly promotes the oxidation of the reducing agent CO and inhibits the selective reduction of NO.

[0003] Noble metal-based catalysts, especially Ir-based catalysts, have become the optimal choice for CO reduction of NO under aerobic conditions due to their unique reaction mechanisms and stability. In recent years, many Ir-based catalysts have been reported and used in CO-SCR denitrification research, such as Ir / SiO2, Ir / Al2O3, Ir / WO3, Ir / WO3-SiO2, IrW-WO3 / KIT-7, Ir / HNTs-800, and Ir / ZSM-5. However, the NO conversion performance, selectivity, and stability of these catalysts are still not ideal, requiring effective enhancement methods to further improve their intrinsic activity and selectivity under aerobic conditions.

[0004] SO2, as an unavoidable atmospheric factor in SCR reaction systems, often has a strong poisoning effect on catalysts. Although pre-sulfation treatment has been applied in the NH3-SCR field and effectively promoted SCR activity, it has no significant enhancing effect on CO-SCR. Typically, the sulfate species formed by sulfation treatment are unstable, meaning this promoting effect is only significant in the presence of SO2; once the SO2 supply is blocked, this promoting effect is weakened or even lost. Furthermore, conventional Ir-based catalysts convert NO through the dissociation of Ir, and this single pathway limits the high catalytic activity, selectivity, and stability of pure Ir catalysts under aerobic conditions.

[0005] CuO not only readily reacts with SO2 to form stable metal sulfates, but as a co-component of the catalyst, it also readily generates a large number of active oxygen vacancies in the redox reaction system, accelerating electron interaction with the main active component and providing ample reaction space for catalytic conversion. Therefore, catalysts prepared using Ir and CuO as co-doping components hold promise for combining the dual synergistic pathways of sulfate species and oxygen vacancies, providing a new strategy for the development of highly active, selective, and stable CO-SCR catalysts. Summary of the Invention

[0006] The present invention aims to provide a pre-sulfatated CO-SCR catalyst and its preparation method. Ir and CuO are used as the active catalyst components (before sulfatation), and porous silica-alumina molecular sieves are used as the support. Sulfatation under an SO2+O2 atmosphere stabilizes Cu as a metal sulfate on the catalyst surface. During sulfatation, SO2 readily strips the metal oxygen around the Ir-Cu interface through metal sulfatation, forming oxygen vacancies. These oxygen vacancies act as new NO dissociation sites, feeding back into the active phase Ir and jointly participating in the CO-SCR reaction. This synergistic effect of Ir as the main active phase, Cu-derived sulfate, and oxygen vacancies as auxiliary phases inhibits CO oxidation under aerobic conditions (forming a shielding layer on the catalyst surface) and promotes the selective conversion of NO.

[0007] One of the objectives of this invention is to provide a method for preparing a pre-sulfatated CO-SCR catalyst.

[0008] The second objective of this invention is to provide a pre-sulfatated CO-SCR catalyst prepared by the above method.

[0009] A third objective of this invention is to provide an application of the pre-sulfatated CO-SCR catalyst in the CO-SCR denitrification reaction.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0011] In a first aspect, the present invention provides a method for preparing a pre-sulfatated CO-SCR catalyst, comprising the following steps:

[0012] (1) An impregnation solution is prepared by dissolving the active component precursor in water; the active component precursor includes iridium salt and copper salt;

[0013] (2) The impregnation solution obtained in step (1) is mixed with commercial porous silica-alumina HZSM-5 molecular sieve support, ultrasonicated, and dried to obtain catalyst precursor;

[0014] (3) The catalyst precursor obtained in step (2) was calcined in an inert gas atmosphere and cooled to room temperature to obtain the catalyst Ir-Cu / HZSM-5 containing the active phase (actually Ir-CuO / HZSM-5).

[0015] (4) The catalyst obtained in step (3) is placed in a sulfur-containing and oxygen-containing atmosphere for sulfation treatment to obtain a pre-sulfated CO-SCR catalyst.

[0016] In some embodiments, the iridium salt in step (1) is selected from at least one of iridium chloride trihydrate and chloroiridium acid; the copper salt is selected from at least one of copper nitrate trihydrate and copper acetate.

[0017] In some implementations, the ultrasound time in step (2) is 20 to 40 minutes. For example, the ultrasound time can be 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, etc., or any value within the range of 20 to 40 minutes.

[0018] In some embodiments, the drying temperature in step (2) is 70~90°C. For example, the drying temperature can be 70°C, 75°C, 80°C, 85°C, 90°C, etc., or any value within the range of 70~90°C.

[0019] In some implementations, the drying time in step (2) is 12 to 24 hours. For example, the drying time can be 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc., or any value within the range of 12 to 24 hours.

[0020] In some embodiments, the mass fraction of Ir in the catalyst Ir-Cu / HZSM-5 is 0.5~1.5wt%, preferably 1wt%, and the mass fraction of CuO in the HZSM-5 molecular sieve is 0.5~2wt%, preferably 1wt%. The required mass of iridium and copper salts is calculated based on the theoretical loading of Ir and CuO, combined with the relative molar masses of iridium and copper salts.

[0021] In some embodiments, the inert gas in step (3) is nitrogen.

[0022] In some embodiments, the calcination temperature in step (3) is 600~800℃. For example, the calcination temperature can be 600℃, 650℃, 700℃, 750℃, 800℃, etc., or any value within the range of 600~800℃.

[0023] In some embodiments, the calcination time in step (3) is 3 to 6 hours. For example, the calcination time can be 3 hours, 4 hours, 5 hours, 6 hours, etc., or any value within the range of 3 to 6 hours.

[0024] In some embodiments, the sulfur-containing and oxygen-containing atmosphere in step (4) is specifically 50 ppm SO2 and 5 vol% O2 (N2 as carrier gas), with a total gas flow rate of 100 mL / min.

[0025] In some embodiments, the sulfation treatment temperature in step (4) is 275~300℃. For example, the sulfation treatment temperature can be 275℃, 280℃, 285℃, 290℃, 295℃, 300℃, etc., or any value within the range of 275~300℃.

[0026] In some embodiments, the sulfation treatment time in step (4) is 2 to 4 hours. For example, the sulfation treatment time can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc., or any value within the range of 2 to 4 hours.

[0027] Secondly, the present invention provides a pre-sulfatated CO-SCR catalyst, which is prepared by the above-described preparation method.

[0028] Thirdly, the present invention provides an application of the above-mentioned pre-sulfatated CO-SCR catalyst in CO-SCR denitrification reaction.

[0029] The application includes the following steps: placing the catalyst in simulated waste gas containing NO and CO to carry out a denitrification reaction.

[0030] The catalyst was added at a dosage of 50 mg.

[0031] The simulated exhaust gas includes both an aerobic atmosphere and an anaerobic atmosphere, with an aerobic atmosphere being preferred.

[0032] The simulated exhaust gas composition is specifically 500ppm NO, 5000ppm CO, 5vol% O2 (when in use), with N2 as the carrier gas and a total gas flow rate of 100mL / min.

[0033] Beneficial effects:

[0034] (1) The catalyst preparation method is simple. The original catalyst is prepared by ordinary impregnation method, and the highly selective Ir-based CO-SCR catalyst with CO adsorption behavior is constructed by combining in-situ atmosphere pretreatment.

[0035] (2) This method uses low-dose active metal loading to enhance catalytic performance by using Ir active sites in conjunction with sulfated metal salt dual sites.

[0036] (3) Starting from the CO-NO reduction reaction pathway, the sulfation treatment greatly inhibits the oxidation of the reducing agent CO and promotes the selective reduction of NO.

[0037] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Attached Figure Description

[0038] Figure 1 The NO conversion activity diagrams for the catalysts 1%Ir-0.5%Cu / HZSM-5, 1%Ir-1%Cu / HZSM-5, 1%Ir-2%Cu / HZSM-5 and 1%Ir-5%Cu / HZSM-5 prepared in this invention are shown.

[0039] Figure 2 The diagram shows the CO conversion activity of the catalysts 1%Ir-0.5%Cu / HZSM-5, 1%Ir-1%Cu / HZSM-5, 1%Ir-2%Cu / HZSM-5 and 1%Ir-5%Cu / HZSM-5 prepared in this invention.

[0040] Figure 3 The N2 selectivity diagrams are for the catalysts 1%Ir-0.5%Cu / HZSM-5, 1%Ir-1%Cu / HZSM-5, 1%Ir-2%Cu / HZSM-5 and 1%Ir-5%Cu / HZSM-5 prepared in this invention.

[0041] Figure 4 The NO conversion activity of the catalyst prepared in this invention, 1%Ir-1%Cu / HZSM-5, without pre-sulfatation, is shown in the diagram.

[0042] Figure 5 This is a graph showing the NO conversion activity of the catalyst 1%Ir / HZSM-5 prepared in this invention;

[0043] Figure 6 This is a graph showing the NO conversion activity of the catalyst 1%Cu / HZSM-5 prepared in this invention;

[0044] Figure 7 The NO conversion activity diagram of the catalyst 1%Ir-1%Fe / HZSM-5 prepared in this invention is shown.

[0045] Figure 8 This is a graph showing the NO conversion activity of the catalyst prepared in this invention after treatment with sulfuric acid solution of 1%Ir-1%Cu / HZSM-5.

[0046] Figure 9The effect of O2 concentration on the activity of the catalyst 1%Ir-1%Cu / HZSM-5 prepared in this invention is shown in the diagram.

[0047] Figure 10 The effect of CO / NO concentration ratio on the activity of the catalyst prepared in this invention (1%Ir-1%Cu / HZSM-5);

[0048] Figure 11 X-ray diffraction patterns of the catalysts 1%Ir / HZSM-5, 1%Ir-1%Cu / HZSM-5 and unsulfated 1%Ir-1%Cu / HZSM-5 prepared in this invention;

[0049] Figure 12 Transmission electron microscope image of the catalyst 1%Ir-1%Cu / HZSM-5 prepared in this invention;

[0050] Figure 13 The in-situ Raman spectrum of the catalyst 1%Ir-1%Cu / HZSM-5 prepared in this invention after injection of SO2+O2 and reaction gas CO+NO+O2 is shown.

[0051] Figure 14 The electron paramagnetic resonance spectra of the catalysts 1%Ir-1%Cu / HZSM-5, 1%Ir-1%Cu / HZSM-5 (unpre-sulfated), 1%Ir / HZSM-5, 1%Cu / HZSM-5, and 1%Ir-1%Fe / HZSM-5 prepared in this invention are shown. Detailed Implementation

[0052] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0053] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0054] This invention does not have specific requirements for the purity of raw materials. To ensure experimental consistency, raw materials of analytical grade or conventional purity in the field of CO-SCR denitrification catalysts are preferred.

[0055] The present invention calculates the NO conversion rate, CO conversion rate and N2 selectivity using the following formula.

[0056]

[0057]

[0058]

[0059] Example 1

[0060] A method for preparing a pre-sulfatated CO-SCR catalyst, comprising the following specific steps:

[0061] 0.016 g IrCl3·3H2O and 0.015 g Cu(NO3)2·3H2O were mixed and dissolved in deionized water to prepare a 2 mL mixed impregnation solution. 1 g of HZSM-5 molecular sieve (Auscatalytic Materials Co., Ltd., Si / Al=20) was added to the molecular sieve, and the mixture was sonicated at 60 kHz for 30 minutes to further homogenize, ensuring that the theoretical loadings of Ir and CuO were 1% and 0.5% of the support mass, respectively. The uniformly impregnated catalyst sample was placed in an oven and dried at 80 °C for 12 hours at a heating rate of 10 °C / min. The dried sample was then removed and calcined at 600 °C for 3 hours under a N2 atmosphere at a heating rate of 5 °C / min for 50 mL / min to obtain an unsulfated 1% Ir-0.5% Cu / HZSM-5 catalyst. The catalyst was further subjected to 50 ppm... Pretreatment at 275°C for 2 hours with SO2 and 5 vol% O2 and N2 in equilibrium, under a total flow rate of 100 mL / min, yielded a pre-sulfated 1% Ir-0.5% Cu / HZSM-5 catalyst.

[0062] Example 2

[0063] A method for preparing a pre-sulfatated CO-SCR catalyst, comprising the following specific steps:

[0064] 0.016 g IrCl3·3H2O and 0.03 g Cu(NO3)2·3H2O were mixed and dissolved in deionized water to prepare a 2 mL mixed impregnation solution. 1 g of HZSM-5 molecular sieve was added to the impregnation solution, and the mixture was sonicated at 60 kHz for 30 minutes to further homogenize, ensuring that the theoretical loadings of Ir and CuO were both 1% of the support mass. The uniformly impregnated catalyst sample was placed in an oven and dried at 80 °C for 12 hours at a heating rate of 10 °C / min. The dried sample was then removed and calcined at 600 °C for 3 hours under a N2 atmosphere at a heating rate of 5 °C / min for 50 mL / min to obtain an unsulfated 1% Ir-1% Cu / HZSM-5 catalyst. The catalyst was further subjected to 50 ppm SO2 and 5 vol%... Pretreatment at 275℃ for 2 hours under O2 and N2 equilibrium and a total flow rate of 100 mL / min yielded a pre-sulfated 1%Ir-1%Cu / HZSM-5 catalyst.

[0065] Example 3

[0066] A method for preparing a pre-sulfatated CO-SCR catalyst, comprising the following specific steps:

[0067] 0.016 g IrCl3·3H2O and 0.06 g Cu(NO3)2·3H2O were mixed and dissolved in deionized water to prepare a 2 mL mixed impregnation solution. 1 g of HZSM-5 molecular sieve was added to the impregnation solution, and the mixture was sonicated at 60 kHz for 30 minutes to further homogenize, ensuring that the theoretical loadings of Ir and CuO were 1% and 2% of the support mass, respectively. The uniformly impregnated catalyst sample was placed in an oven and dried at 80 °C for 12 hours at a heating rate of 10 °C / min. The dried sample was then removed and calcined at 600 °C for 3 hours under a N2 atmosphere at a heating rate of 5 °C / min for 50 mL / min to obtain an unsulfated 1% Ir-2% Cu / HZSM-5 catalyst. The catalyst was further subjected to 50 ppm SO2 and 5 vol%... Pretreatment at 275℃ for 2 hours under O2 and N2 equilibrium and a total flow rate of 100 mL / min yielded a pre-sulfated 1%Ir-2%Cu / HZSM-5 catalyst.

[0068] Example 4

[0069] A method for preparing a pre-sulfatated CO-SCR catalyst, comprising the following specific steps:

[0070] 0.016 g IrCl3·3H2O and 0.15 g Cu(NO3)2·3H2O were mixed and dissolved in deionized water to prepare a 2 mL mixed impregnation solution. 1 g of HZSM-5 molecular sieve was added to the impregnation solution, and the mixture was sonicated at 60 kHz for 30 minutes to further homogenize, ensuring that the theoretical loadings of Ir and CuO were 1% and 5% of the support mass, respectively. The uniformly impregnated catalyst sample was placed in an oven and dried at 80 °C for 12 hours at a heating rate of 10 °C / min. The dried sample was then removed and calcined at 600 °C for 3 hours under a N2 atmosphere at a heating rate of 5 °C / min for 50 mL / min to obtain an unsulfated 1% Ir-5% Cu / HZSM-5 catalyst. The catalyst was further subjected to 50 ppm SO2 and 5 vol%... Pretreatment at 275℃ for 2 hours under O2 and N2 equilibrium and a total flow rate of 100 mL / min yielded a pre-sulfated 1%Ir-5%Cu / HZSM-5 catalyst.

[0071] Comparative Example 1

[0072] 0.016 g of IrCl3·3H2O and 0.03 g of Cu(NO3)2·3H2O were mixed and dissolved in deionized water to prepare a 2 mL mixed impregnation solution. 1 g of HZSM-5 molecular sieve was taken, and the obtained impregnation solution was added to the molecular sieve. The mixture was sonicated at 60 kHz for 30 minutes to further mix it so that the theoretical loading of Ir and CuO was 1% of the support mass. The uniformly impregnated catalyst sample was placed in an oven and dried at 80 °C for 12 hours at a heating rate of 10 °C / min. The dried sample was then removed and calcined at 600 °C for 3 hours under a N2 atmosphere at a heating rate of 5 °C / min to obtain a 1%Ir-1%Cu / HZSM-5 catalyst without pre-sulfatation.

[0073] Comparative Example 2

[0074] 0.016 g of IrCl3·3H2O was dissolved in deionized water to prepare a 2 mL impregnation solution. 1 g of HZSM-5 molecular sieve was taken, and the obtained impregnation solution was added to the molecular sieve. The mixture was sonicated at 60 kHz for 30 minutes and further mixed to ensure that the theoretical loading of Ir was 1% of the support mass. The uniformly impregnated catalyst sample was placed in an oven and dried at 80 °C for 12 hours at a heating rate of 10 °C / min. The dried sample was then removed and calcined at 600 °C for 3 hours at a heating rate of 5 °C / min under a N2 atmosphere of 50 mL / min to obtain an unsulfated 1% Ir / HZSM-5 catalyst. The catalyst was further pretreated at 275 °C for 2 hours under a gas flow of 50 ppm SO2 and 5 vol% O2, N2 equilibrium, and a total flow rate of 100 mL / min to obtain a presulfated 1% Ir / HZSM-5 catalyst.

[0075] Comparative Example 3

[0076] 0.03 g Cu(NO3)2·3H2O was dissolved in deionized water to prepare a 2 mL impregnation solution. 1 g HZSM-5 molecular sieve was taken, and the obtained impregnation solution was added to the molecular sieve. The mixture was sonicated at 60 kHz for 30 minutes to further mix, so that the theoretical loading of CuO was 1% of the support mass. The uniformly impregnated catalyst sample was placed in an oven and dried at 80 °C for 12 hours at a heating rate of 10 °C / min. The dried sample was taken out and calcined at 600 °C for 3 hours at a heating rate of 5 °C / min under a N2 atmosphere of 50 mL / min to obtain an unsulfated 1% Cu / HZSM-5 catalyst. The catalyst was further pretreated at 275 °C for 2 hours under a gas flow of 50 ppm SO2 and 5 vol% O2, N2 equilibrium, and a total flow rate of 100 mL / min to obtain a presulfated 1% Cu / HZSM-5 catalyst.

[0077] Comparative Example 4

[0078] 0.016 g IrCl3·3H2O and 0.051 g Fe(NO3)3·9H2O were mixed and dissolved in deionized water to prepare a 2 mL mixed impregnation solution. 1 g of HZSM-5 molecular sieve was added to the impregnation solution, and the mixture was sonicated at 60 kHz for 30 minutes to further homogenize, ensuring that the theoretical loadings of Ir and Fe2O3 were both 1% of the support mass. The uniformly impregnated catalyst sample was placed in an oven and dried at 80 °C for 12 hours at a heating rate of 10 °C / min. The dried sample was then removed and calcined at 600 °C for 3 hours under a N2 atmosphere at a heating rate of 5 °C / min for 50 mL / min to obtain an unsulfated 1% Ir-1% Fe / HZSM-5 catalyst. The catalyst was further subjected to 50 ppm SO2 and 5 vol%... Pretreatment at 275℃ for 2 hours under O2 and N2 equilibrium and a total flow rate of 100 mL / min yielded a pre-sulfated 1%Ir-1%Fe / HZSM-5 catalyst.

[0079] Comparative Example 5

[0080] 0.016 g of IrCl3·3H2O and 0.03 g of Cu(NO3)2·3H2O were mixed and dissolved in deionized water to prepare a 2 mL mixed impregnation solution. 1 g of HZSM-5 molecular sieve was added to the impregnation solution, and the mixture was sonicated at 60 kHz for 30 minutes to further homogenize, ensuring that the theoretical loadings of Ir and CuO were both 1% of the support mass. The uniformly impregnated catalyst sample was placed in an oven and dried at 80 °C for 12 hours at a heating rate of 10 °C / min. The dried sample was then calcined at 600 °C for 3 hours under a N2 atmosphere at a heating rate of 5 °C / min for 50 mL / min to obtain a non-pre-sulfatated 1%Ir-1%Cu / HZSM-5 catalyst. This catalyst was further treated by soaking in a 5% (w / w) sulfuric acid solution for 2 hours, followed by drying at 80 °C for 12 hours to obtain a sulfuric acid-treated 1%Ir-1%Cu / HZSM-5 catalyst.

[0081] Test case

[0082] The catalyst samples prepared in Examples 1-4 were subjected to CO-SCR activity tests to investigate the effect of different Ir / Cu ratios on catalyst activity. The catalyst samples prepared in Comparative Examples 1-5 were subjected to NO conversion tests to confirm the existence of a synergistic enhancement mechanism between the Ir-Cu / HZSM-5 catalysts.

[0083] The specific experimental method is as follows: The sieved catalyst (40-60 mesh, 50 mg) was placed in a custom-made quartz reaction tube (inner diameter = 7 mm, outer diameter = 8 mm). The quartz tube was then inserted into a programmable heated fixed reactor bed device, ensuring the catalyst was located in the center of the heating zone. Before the reaction, the catalyst was pretreated with pure nitrogen gas at 300℃ for 30 min to shield against interference from other weakly adsorbed gases. The concentrations of NO, NO2, N2O, and CO at the catalyst bed inlet and outlet were measured using a Fourier transform infrared spectroscopy (Thermo Scientific Nicolet iS50, USA).

[0084] The simulated test flue gas contained no water or sulfur. The test conditions were as follows: reaction temperature 275℃, 2-hour interval between each test point, gas flow rate 100 mL / min, NO concentration 500 ppm, CO concentration 5000 ppm, O2 concentration 5 vol%, N2 as the balance gas, and space velocity 30000 h⁻¹. -1 .

[0085] The catalysts prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to CO-SCR denitrification activity tests, and the corresponding NO and CO conversion rates and N2 selectivity are shown in Table 1. All NO conversion, CO conversion, and N2 selectivity values ​​are the activity recorded at the final time of 65 h.

[0086] Table 1. NO conversion, CO conversion, and N2 selectivity of the examples and comparative examples under different Ir / Cu ratios.

[0087]

[0088] - indicates that it has not been tested.

[0089] See Figure 1 , Figure 1 The figure shows the NO conversion rate of the catalyst samples prepared in Examples 1-4 of this invention. As shown in the figure, the catalyst prepared by the in-situ sulfation method provided by this invention has good NO conversion activity. In particular, for the 1%Ir-1%Cu / HZSM-5 catalyst with an Ir / Cu ratio of 1:1, the NO conversion rate is 81.9%, which is higher than that of other catalyst samples with Ir / Cu ratios.

[0090] See Figure 2 , Figure 2The figure shows the CO conversion rates of the catalyst samples prepared in Examples 1-4 of this invention. As shown, the catalysts prepared by the in-situ sulfation method provided by this invention exhibit good CO conversion activity. However, for the 1%Ir-5%Cu / HZSM-5 catalyst with an Ir:Cu ratio of 1:5, the CO conversion rate is only 13.2%, which is lower than that of other catalyst samples with different Ir / Cu ratios. A suitable Ir / Cu ratio is beneficial for sulfate species to exert a promoting effect on CO-SCR, while sulfates generated by excessive CuO loading will reduce the CO-SCR activity of the catalyst.

[0091] See Figure 3 , Figure 3 The figures show the N2 selectivity of the catalyst samples prepared in Examples 1-4 of this invention. As shown, the catalysts prepared by the in-situ sulfation method provided by this invention exhibit good N2 selectivity, especially for the 1%Ir-1%Cu / HZSM-5 catalyst with an Ir:Cu ratio of 1:1, where the N2 selectivity is 91.1%. This is higher than that of other catalyst samples with different Ir / Cu ratios.

[0092] See Figure 4 , Figure 4 The figure shows the NO conversion rate of the catalyst sample prepared in Comparative Example 1 without pre-sulfation treatment. As shown in the figure, the NO conversion rate of the untreated 1%Ir-1%Cu / HZSM-5 is about 34.5%. In contrast, the catalyst prepared by the in-situ sulfation method provided by this invention can significantly improve the NO conversion activity of the Ir-Cu catalyst.

[0093] See Figure 5 , Figure 5 The figure shows the NO conversion rate of the catalyst sample prepared for Comparative Example 2, which underwent pre-sulfatation treatment. As shown in the figure, the NO conversion rate of 1% Ir / HZSM-5 after pre-sulfatation treatment is approximately 26.7%. In contrast, this invention, by using CuO as an auxiliary active component of Ir / HZSM-5, effectively stabilizes the promoting effect brought about by pre-sulfatation treatment. At the same time, by utilizing its own electronic properties, it introduces a large number of active oxygen vacancies, providing more reaction space for the CO-SCR reaction of the catalyst, and fully leveraging the synergistic regulatory mechanism of Ir and CuO under pre-sulfatation conditions.

[0094] See Figure 6 , Figure 6 The figure shows the NO conversion rate of the catalyst sample prepared in Comparative Example 3 after pre-sulfation treatment. As shown in the figure, the NO conversion rate of 1% Cu / HZSM-5 after pre-sulfation treatment is only about 2.4%, which is almost no NO catalytic conversion ability. In contrast, the pre-sulfated Ir-CuO co-doped HZSM-5 catalyst provided by this invention can not only effectively improve the selective catalytic performance of NO through the bidirectional synergistic effect of Ir-CuO, but also maintain good stability under long-term operation.

[0095] See Figure 7 , Figure 7 The figure shows the NO conversion rate of the catalyst sample prepared in Comparative Example 4 after pre-sulfation treatment. As shown in the figure, the NO conversion rate of 1%Ir-1%Fe / HZSM-5 after pre-sulfation treatment is only about 31.4%, indicating weak NO catalytic conversion ability. This suggests that compared with CuO, Fe2O3 lacks electronic interaction with Ir and is difficult to produce a strong synergistic effect, resulting in low promotion ability for its CO-SCR activity.

[0096] See Figure 8 , Figure 8 The figure shows the NO conversion rate of the catalyst sample prepared by Comparative Example 5 after treatment with sulfuric acid solution. As shown in the figure, the NO conversion rate of 1%Ir-1%Cu / HZSM-5 after sulfuric acid treatment is only about 2.2%, which is almost no NO catalytic conversion ability. This indicates that sulfuric acid treatment is difficult to exert the synergistic effect between Ir-CuO. On the contrary, sulfuric acid treatment may cause loss of active phase or collapse of Al atoms in the catalyst support structure, which will greatly limit the CO-SCR reaction process.

[0097] The catalyst sample prepared in Example 2 was subjected to an O2 concentration effect test. The simulated test flue gas contained no water and no sulfur. The test conditions were as follows: reaction temperature 275℃, 2-hour interval between each test point, gas flow rate 100 mL / min, NO concentration 500 ppm, CO concentration 5000 ppm, O2 concentrations of 0%, 2.5%, 5%, 7.5%, and 10%, N2 as the balance gas, and space velocity 30000 h⁻¹. -1 See also Figure 9 , Figure 9 The graph shows the effect of O2 concentration on the activity of the 1%Ir-1%Cu / HZSM-5 catalyst sample prepared in Example 2 of this invention. As shown in the figure, this catalyst exhibits excellent O2 resistance, maintaining a NO conversion rate of 76.8% even under 10% O2 concentration conditions.

[0098] The effect of CO / NO concentration ratio on the catalyst sample prepared in Example 2 was tested. The simulated test flue gas contained no water and no sulfur. The test conditions were as follows: reaction temperature 275℃, 2-hour interval between each test point, gas flow rate 100 mL / min, NO concentration 500 ppm, CO concentrations of 500 ppm, 2500 ppm, 5000 ppm, 7500 ppm, and 10000 ppm, O2 concentration 5%, N2 as the balance gas, and space velocity 30000 h⁻¹. -1 See also Figure 10 , Figure 10The graph shows the effect of CO / NO concentration ratio on the activity of the 1%Ir-1%Cu / HZSM-5 catalyst sample prepared in Example 2 of this invention. As shown in the figure, the catalyst still exhibits good activity at low CO concentrations. It maintains a NO conversion rate of 73.2% even at a CO concentration of 500 ppm.

[0099] The results show that the in-situ sulfation-treated Ir-Cu co-doped molecular sieve catalyst prepared in this invention exhibits excellent NO conversion activity, as well as excellent CO conversion and N2 selectivity. The sulfation-treated 1%Ir-1%Cu / HZSM-5 catalyst still maintains an 81.9% NO conversion, a 100.00% CO conversion, and an N2 selectivity of 91.1% after 65 hours of stable reaction. Under high O2 concentration conditions, the catalyst can still maintain a NO conversion of 76.8%. x Conversion rate. Under low CO concentration conditions, the catalyst still maintained a NO conversion rate of 73.2%. The results indicate that the catalyst possesses excellent oxygen resistance and good stability.

[0100] The catalysts prepared in Example 2 and Comparative Example 2 of this invention were characterized.

[0101] X-ray diffraction analysis was performed on the catalysts 1%Ir-1%Cu / HZSM-5 and 1%Ir / HZSM-5 prepared in Example 2 and Comparative Example 2, respectively. See [link to example]. Figure 11 , Figure 11 The X-ray diffraction patterns are those of the 1%Ir-1%Cu / HZSM-5 and 1%Ir / HZSM-5 catalyst samples prepared in Example 2 and Comparative Example 2 of this invention. Figure 11 As shown, compared to 1%Ir / HZSM-5, the surface of 1%Ir-1%Cu / HZSM-5 clearly exhibits diffraction peaks corresponding to the metal sulfate CuSO4 species. This indicates that the S species are anchored on the catalyst surface in the form of metal sulfate, thereby enhancing the catalyst's inhibitory effect on CO oxidation and thus improving the catalyst's selective catalytic reduction performance to a certain extent. Simultaneously, Cu doping also slows down the crystallinity of Ir species, promoting the dispersion of active species and providing more reaction sites for the catalytic reaction.

[0102] The microstructure of the 1%Ir-1%Cu / HZSM-5 prepared in Example 2 was studied. See [link to relevant documentation]. Figure 12 , Figure 12 This is a transmission electron microscope image of the 1%Ir-1%Cu / HZSM-5 catalyst sample prepared in Example 2 of this invention. Figure 12 As shown, Ir and Cu active components are uniformly loaded on HZSM-5 molecular sieve, and the metal active component particles are uniformly distributed on its surface to achieve a more uniform gas-phase sulfation level and improve the selective catalytic activity of the catalyst.

[0103] In-situ Raman analysis was performed on the in-situ gas-phase sulfation process and catalytic reaction process of the 1%Ir-1%Cu / HZSM-5 prepared in Example 2. (See also...) Figure 13 , Figure 13 The image shows the in-situ Raman spectrum of the 1%Ir-1%Cu / HZSM-5 catalyst prepared in Example 2 of this invention after injection of SO2+O2 and the reaction gas CO+NO+O2. Figure 13 As shown, the catalyst, when not subjected to gas-phase sulfation, only reaches 210 cm⁻¹. -1 The peak value appears at 371 cm⁻¹, indicating that the Cu species exist in the form of CuO at this point. After SO₂ + O₂ injection, the peak value appears at 371 cm⁻¹. -1 A distinct peak appears at the point corresponding to the formation of bulk sulfate. After gas-phase sulfation treatment, the injected reaction gas CO + NO + O2 causes the sulfate species on the catalyst surface to undergo self-reforming, manifested as the release of weakly bound sulfur species and the formation of bulk sulfate. This further stabilizes the promoting effect brought by SO2, and at the same time, more active oxygen vacancies are generated at the Ir sites through electronic interaction, synergistically achieving the catalyst's high selectivity for catalytic reduction of NO.

[0104] Figure 14 The electron paramagnetic resonance (EPR) spectra of the catalysts 1%Ir-1%Cu / HZSM-5, unpre-sulfated 1%Ir-1%Cu / HZSM-5, 1%Ir / HZSM-5, 1%Cu / HZSM-5, and 1%Ir-1%Fe / HZSM-5 prepared in Examples 2 and Comparative Examples 1-4 of this invention are shown. Figure 14 As shown, compared to the 1%Ir / HZSM-5 and 1%Cu / HZSM-5 catalysts, the 1%Ir-1%Cu / HZSM-5 catalyst exhibits a higher signal intensity. Pre-sulfatation treatment allows the synergistic effect between Ir and CuO to act on the oxygen vacancies in the catalyst, generating abundant surface oxygen vacancies. Furthermore, the signal intensity of the un-pre-sulfatated 1%Ir-1%Cu / HZSM-5 is also lower than that of the pre-sulfatated 1%Ir-1%Cu / HZSM-5, indicating that the pre-sulfatation process activates the synergistic effect between Ir and CuO, enabling more active sites to be used for the selective catalytic reduction of CO-SCR. Additionally, the peak signal intensity of the 1%Ir-1%Fe / HZSM-5 is also weaker than that of the 1%Ir-1%Cu / HZSM-5, meaning that CuO, as an auxiliary phase, effectively promotes the stability of sulfate species and, through electron interaction and oxygen migration, feeds back oxygen vacancies to the Ir main phase, forming dual catalytic active sites of iridium and oxygen vacancies, achieving Ir-CuO synergistic enhancement of the selective catalytic reduction of NO from CO. In contrast, Fe2O3 does not exhibit this obvious synergistic behavior.

[0105] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. The application of a pre-sulfatated CO-SCR catalyst in CO-SCR denitration reaction, characterized in that, The preparation method of the pre-sulfatated CO-SCR catalyst includes the following steps: (1) An impregnation solution is prepared by dissolving the active component precursor in water; the active component precursor includes iridium salt and copper salt; (2) The impregnation solution obtained in step (1) is mixed with the silicon-aluminum HZSM-5 molecular sieve support, sonicated, and dried to obtain the catalyst precursor; (3) The catalyst precursor obtained in step (2) was calcined in an inert gas atmosphere and cooled to room temperature to obtain the catalyst Ir-Cu / HZSM-5 containing the active phase; (4) The catalyst obtained in step (3) is placed in a sulfur-containing and oxygen-containing atmosphere for sulfation treatment to obtain a pre-sulfated CO-SCR catalyst; In the catalyst Ir-Cu / HZSM-5, the active phases are calculated as Ir and CuO, with Ir accounting for 1 wt% of the mass fraction of the HZSM-5 molecular sieve and CuO accounting for 1 wt% of the mass fraction of the HZSM-5 molecular sieve. In step (4), the sulfation treatment temperature is 275~300℃ and the time is 2~4h.

2. The application according to claim 1, characterized in that, The iridium salt in step (1) is selected from at least one of iridium chloride trihydrate and chloroiridium acid; the copper salt is selected from at least one of copper nitrate trihydrate and copper acetate.

3. The application according to claim 1, characterized in that, In step (2), the ultrasound time is 20-40 min and the ultrasound frequency is 50-80 kHz.

4. The application according to claim 1, characterized in that, In step (2), the drying temperature is 70~90℃ and the drying time is 12~24h.

5. The application according to claim 1, characterized in that, The inert gas mentioned in step (3) is nitrogen; the calcination temperature is 600~800℃ and the calcination time is 3~6h.

6. The application according to claim 1, characterized in that, The sulfur-containing and oxygen-containing atmosphere mentioned in step (4) is specifically 50ppm SO2 and 5vol% O2, with N2 as the carrier gas and a total gas flow rate of 100mL / min.

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