A copper-based molecular sieve catalyst, a method for preparing the same, and use thereof in the selective reduction of NO x ​

Abstract

The application provides a copper-based molecular sieve catalyst and a preparation method and application thereof in selective reduction of NO x , and belongs to the technical field of molecular sieves. The application can control and optimize Cu ion active sites on the surface of the catalyst by adjusting the ratio of a precursor directing agent Na + / TMAda + and the Cu loading amount in the preparation process of the SSZ-13 molecular sieve, so that a NH3-SCR copper-based molecular sieve catalyst capable of selectively reducing NO x is prepared. The catalyst can effectively inhibit the generation of N2O in diesel engine exhaust while maintaining high NO x conversion rate.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, specifically to a copper-based molecular sieve catalyst and its preparation method, and its application in the selective reduction of NO. x Applications in [the context of the text]. Background Technology

[0002] In all NO x Nitrous oxide (N2O) has received increasing attention in recent years as a novel and significant pollutant. N2O is a much stronger greenhouse gas than CO2, with an effect nearly 300 times greater under the same conditions. Furthermore, due to its highly stable structure, it has a remarkably long lifespan, persisting in the atmosphere for over 150 years and capable of diffusing into the stratosphere to deplete the ozone layer. It is considered the most important stratospheric ozone-depleting substance of the 21st century.

[0003] For diesel engines commonly used in heavy-duty trucks and cargo ships, the SCR reactor based on the NH3-SCR reaction process is an essential NO removal device for every engine. x Post-treatment equipment. As the problem of vanadium-based catalysts (V₂O₅) being easily poisoned and deactivated at high temperatures becomes increasingly apparent, copper-based molecular sieve catalysts (Cu / SSZ-13), which exhibit stronger low-temperature activity, greater hydrothermal stability, a wider effective catalytic temperature range, and are more economical and practical, are gradually becoming the main NO control equipment for vehicles and ships. x Post-treatment catalysts for emissions.

[0004] Studies have shown that Cu-based catalysts already exhibit excellent SCR activity at 300℃, achieving conversion rates exceeding 90%, and maintaining high conversion rates between 300 and 500℃. However, due to the unique structure of the Cu active center, during NO production... x During post-processing, copper-based molecular sieves generate the most N2O, exceeding that of existing vanadium-based and iron-based molecular sieve catalysts. Therefore, one of the main challenges of current SCR catalytic systems is reducing N2O generation. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a copper-based molecular sieve catalyst and its preparation method, as well as its application in the selective reduction of NO. x Applications in [the field]. The copper-based molecular sieve catalyst provided by this invention can maintain high NO [performance / quality]. x It effectively suppresses N2O generation while improving conversion rate.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a copper-based molecular sieve catalyst, comprising the following steps:

[0008] TMAdaOH, aluminum source, NaOH and water are mixed to obtain a premixed solution;

[0009] A silicon source is added to the premixed solution to form a gel solution;

[0010] The gel solution was subjected to hydrothermal treatment and first calcination in sequence to obtain Na-type SSZ-13 molecular sieve;

[0011] The Na-type SSZ-13 molecular sieve was mixed with an ammonium salt solution to undergo a first ion exchange, yielding NH4. + Type SSZ-13 molecular sieve;

[0012] The NH4 + SSZ-13 molecular sieve was mixed with a soluble copper salt solution and subjected to a second ion exchange and a second calcination to obtain a copper-based molecular sieve catalyst.

[0013] The Na content in the premixed solution is measured in molar amounts. + :TMAda + =0~1:1;

[0014] In molar quantities, the Si / Al ratio of the gel in the gel solution is 5–20:1, (Na + +TMAda + ) / Si=0.5.

[0015] Preferably, the aluminum source is Al(OH)3 and the silicon source is silica sol.

[0016] Preferably, the temperature for forming the gel solution is 10–40°C and the time is 0.5–3 h.

[0017] Preferably, the hydrothermal treatment is performed at a temperature of 160–200°C for a duration of 48–96 hours.

[0018] The first calcination temperature is 450–550℃, and the time is 8–10 hours.

[0019] Preferably, the concentration of the ammonium salt solution is 1 mol / L;

[0020] The temperature of the first ion exchange is 70-80℃, and the time is 12-16h.

[0021] Preferably, the concentration of the soluble copper salt is 0.5–1.5 mol / L.

[0022] Preferably, the temperature of the second ion exchange is 70–80°C, and the time is 6–8 hours;

[0023] The second calcination temperature is 450–550℃, and the time is 4–6 hours.

[0024] Preferably, after the second calcination, the obtained copper-based molecular sieve catalyst is subjected to hydrothermal aging treatment.

[0025] The hydrothermal aging treatment is performed at a temperature of 750–850°C for 8–12 hours.

[0026] The present invention provides a copper-based molecular sieve catalyst prepared by the above preparation method, comprising SSZ-13 molecular sieve and Cu supported on the surface and internal pores of the SSZ-13 molecular sieve.

[0027] Preferably, the Cu loading in the copper-based molecular sieve catalyst is 0.5–1.5 wt%.

[0028] This invention provides the above-mentioned copper-based molecular sieve catalyst for the selective reduction of NO. x Applications in [the context of the text].

[0029] This invention provides a method for preparing a copper-based molecular sieve catalyst (abbreviated as Cu / SSZ-13), comprising the following steps: mixing TMAdaOH, an aluminum source, NaOH, and water to obtain a premix; adding a silicon source to the premix to form a gel solution; subjecting the gel solution to hydrothermal treatment and a first calcination sequentially to obtain a Na-type SSZ-13 molecular sieve; and mixing the Na-type SSZ-13 molecular sieve with an ammonium salt solution to a first ion exchange to obtain NH4. + Type SSZ-13 molecular sieve; NH4 + SSZ-13 molecular sieves were mixed with a soluble copper salt solution and subjected to a second ion exchange and a second calcination to obtain a copper-based molecular sieve catalyst. SSZ-13 molecular sieves contain paired Al sites, mainly distributed in different framework structures. Keeping the silica-alumina ratio of SSZ-13 molecular sieves constant, the precursor Na was increased... + Ion concentration increases the density of paired Al atoms in the molecular sieve framework, with most of the increased paired Al atoms distributed within the framework structure. This increase in paired Al atoms in the framework structure promotes the stability of Cu during ion exchange. 2+ Active center formation. This invention modulates the precursor directing agent Na during the preparation of SSZ-13 molecular sieves. + / TMAda + The ratio can control the number of paired aluminum sites that bind to Cu ions in the silica-alumina framework of the molecular sieve; by adjusting the concentration of the copper ion solution, the Cu loading on the molecular sieve can be controlled, thereby regulating and optimizing the binding strength and reactivity of the Cu ion active sites on the catalyst surface, thus preparing a catalyst capable of highly selectively reducing NO. x The NH3-SCR copper-based molecular sieve catalyst can maintain high NO content. xWhile improving conversion efficiency, it effectively suppresses N2O formation in diesel engine exhaust and exhibits good water and sulfur resistance. Example results show that the Cu / SSZ-13 catalyst provided by this invention, at 250℃, effectively reduces NO... x The conversion rate was 100%, and the N2O generation was 33.7 ppm; at 450℃, NO x The conversion rate was 89.3%, and the N2O generation was 21.9 ppm. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the catalyst performance testing system;

[0031] Figure 2 This is a flowchart illustrating the preparation process of the Cu / SSZ-13 catalyst in Example 1.

[0032] Figure 3 To test the NO of different catalysts in Example 1 x Conversion rate;

[0033] Figure 4 To test the N2O production of different catalysts in Example 1;

[0034] Figure 5 XPS Cu 2p spectra of different catalysts in Test Example 1;

[0035] Figure 6 To test the NO of different catalysts in Example 2 x Conversion rate;

[0036] Figure 7 To test the N2O production of different catalysts in Example 2;

[0037] Figure 8 To test the NO of the catalyst in Example 1 of Example 3 x Conversion rate;

[0038] Figure 9 To test the N2O production of the catalyst in Example 1 of Example 3;

[0039] Figure 10 The effects of H2O and SO2 on the performance of Cu / SSZ-13 (2.5 / 2.5) catalyst at 250℃ were investigated. Detailed Implementation

[0040] This invention provides a method for preparing a copper-based molecular sieve catalyst, comprising the following steps:

[0041] TMAdaOH, aluminum source, NaOH and water are mixed to obtain a premixed solution;

[0042] A silicon source is added to the premixed solution to form a gel solution;

[0043] The gel solution was subjected to hydrothermal treatment and first calcination in sequence to obtain Na-type SSZ-13 molecular sieve;

[0044] The Na-type SSZ-13 molecular sieve was mixed with an ammonium salt solution to undergo a first ion exchange, yielding NH4. + Type SSZ-13 molecular sieve;

[0045] The NH4 + SSZ-13 molecular sieve was mixed with a soluble copper salt solution and subjected to a second ion exchange and a second calcination to obtain a copper-based molecular sieve catalyst.

[0046] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0047] This invention involves mixing TMAdaOH (N,N-trimethyl-1-adamantane ammonium hydroxide), an aluminum source, NaOH, and water to obtain a premixed solution. In this invention, the aluminum source is preferably Al(OH)3, and the water is preferably deionized water. In this invention, the NaOH is preferably added in the form of an aqueous solution, and the concentration of the NaOH aqueous solution is preferably 20 wt%.

[0048] In this invention, the mixing is preferably carried out by stirring at room temperature. The mixing time is preferably 20 minutes.

[0049] In this invention, the Na content in the premixed solution is measured in molar amounts. + :TMAda + =0~1:1, preferred, Na + :TMAda + =0.5~1:1; (Na + +TMAda + ) / Si=0.5.

[0050] A silicon source is added to the premixed solution to form a gel solution. In this invention, the silicon source is preferably silica sol. As a specific embodiment of this invention, the silicon source is Ludox AS-40 (purchased from Sigma-Aldrich). Preferably, the silicon source is added dropwise to the premixed solution.

[0051] In this invention, the gel formation process is preferably carried out under stirring conditions. In this invention, the gel formation temperature is preferably 10–40°C, more preferably room temperature, and the time is preferably 0.5–3 hours, more preferably 2 hours.

[0052] In this invention, the Si / Al ratio of the gel in the gel solution is preferably 5 to 20:1, more preferably 15:1, based on molar amounts.+ +TMAda + ) / Si=0.5. As a specific embodiment of the present invention, the composition of the gel is expressed in molar amounts as ANaOH:(0.5-A)TMAdaOH:0.033Al2O3:1SiO2:44H2O, wherein the value of A is 0.25, 0.1 and 0.

[0053] After obtaining the gel solution, the present invention subjectes the gel solution to hydrothermal treatment and a first calcination sequentially to obtain Na-type SSZ-13 molecular sieve. In the present invention, the hydrothermal reaction is preferably carried out in a rotating hydrothermal reactor. In the present invention, the hydrothermal treatment temperature is preferably 160–200°C, more preferably 180°C, and the time is preferably 48–96 h, more preferably 72–96 h. In the present invention, the Na-type SSZ-13 molecular sieve framework structure is formed during the hydrothermal treatment process.

[0054] After the hydrothermal treatment, the present invention preferably performs solid-liquid separation on the resulting hydrothermal reaction system, and washes and dries the resulting solid. In the present invention, the solid-liquid separation is preferably vacuum filtration, the washing is preferably water washing, and the washing is preferably performed 2 to 3 times. In the present invention, the drying is preferably oven drying, the drying temperature is preferably 100°C, and the drying time is preferably 12 hours.

[0055] In this invention, the first calcination is preferably carried out in a muffle furnace, and the atmosphere for the first calcination is preferably air; the temperature for the first calcination is preferably 450–550°C, more preferably 550°C, and the time is preferably 8–10 hours, more preferably 10 hours; in this invention, the heating rate to the first calcination temperature is preferably 1°C / min. In this invention, the first calcination process makes the Na-type SSZ-13 molecular sieve framework structure more stable.

[0056] After obtaining the Na-type SSZ-13 molecular sieve, the present invention mixes the Na-type SSZ-13 molecular sieve with an ammonium salt solution to perform a first ion exchange to obtain NH4. + SSZ-13 molecular sieve. In this invention, the ammonium salt is preferably NH4Cl. In this invention, the concentration of the ammonium salt solution is preferably 1 mol / L.

[0057] In this invention, the preferred temperature for the first ion exchange is 70–80°C, and the preferred time is 12–16 hours. This invention converts Na-type SSZ-13 molecular sieves into NH4 through the first ion exchange. + type.

[0058] In this invention, after the first ion exchange, the resulting first ion exchange system is preferably subjected to solid-liquid separation, and the resulting solid is washed and dried to obtain NH4. + The solid is SSZ-13 molecular sieve. In this invention, the solid-liquid separation is preferably performed by vacuum filtration. This invention does not have special requirements for the washing and drying processes; washing and drying methods well-known in the art can be used.

[0059] The NH4 was obtained + After using the SSZ-13 molecular sieve, the present invention will use the NH4 + SSZ-13 molecular sieve is mixed with a soluble copper salt solution, and then subjected to a second ion exchange and a second calcination to obtain a copper-based molecular sieve catalyst. In this invention, the soluble copper salt is preferably copper nitrate. The concentration of the soluble copper salt is preferably 0.5–1.5 mol / L, more preferably 1 mol / L.

[0060] In this invention, the second ion exchange is preferably carried out under stirring conditions. In this invention, the temperature of the second ion exchange is preferably 70–80°C, and the time is preferably 6–8 hours. This invention, through the second exchange, transforms Cu… 2+ Loaded on the surface and internal pores of the molecular sieve.

[0061] In this invention, the second calcination is preferably carried out in a muffle furnace, and the atmosphere for the second calcination is preferably air. In this invention, the temperature of the second calcination is preferably 450–550°C, more preferably 500°C; the time is preferably 4–6 hours; and the heating rate to the second calcination temperature is preferably 1°C / min. Through the second calcination, Cu… 2+ It will combine with the molecular sieve framework to form Cu-SSZ-13 molecular sieve.

[0062] After the second calcination, the present invention preferably further includes hydrothermal aging treatment of the obtained copper-based molecular sieve catalyst. In the present invention, the temperature of the hydrothermal aging treatment is preferably 750–850°C, more preferably 800°C, and the time is preferably 8–12 hours, more preferably 10–12 hours. The present invention further improves the catalytic performance of the copper-based molecular sieve catalyst through the hydrothermal aging treatment.

[0063] After the second calcination, the copper-based molecular sieve catalyst is preferably subjected to tableting, grinding, sieving, and granulation. The present invention does not have special requirements for the above operations; tableting, grinding, sieving, and granulation processes well-known in the art can be used.

[0064] This invention provides a copper-based molecular sieve catalyst prepared by the above-described method, comprising an SSZ-13 molecular sieve and Cu supported on the surface and internal pores of the SSZ-13 molecular sieve, wherein the Cu is preferably Cu 2+ and Cu + It exists in the form of [missing information]. In this invention, the Cu loading in the copper-based molecular sieve catalyst is preferably 0.5–1.5 wt%, more preferably 1 wt%. In this invention, the particle size of the copper-based molecular sieve catalyst is preferably 0.02–0.1 μm, and the specific surface area is preferably 100–500 m². 2 / g, total pore volume 0.1~0.3cm 3 / g, average pore size

[0065] This invention provides the above-mentioned copper-based molecular sieve catalyst for the selective reduction of NO. x Applications in [the field]. In this invention, the selective reduction of NO [is described]. x Preferred is the selective reduction of NO in diesel engine exhaust. x .

[0066] In this invention, the method of application preferably includes the following steps:

[0067] The reaction gas is passed into the copper-based molecular sieve catalyst to carry out the reduction reaction.

[0068] In this invention, the composition of the reaction gas, by volume concentration, preferably includes 0.01-0.1% NO, 0.01-0.1% NH3, 1-10% O2, and the equilibrium gas N2.

[0069] In this invention, the reaction space velocity of the reactant gas is preferably 10,000 to 60,000 mL·g. -1 ·h -1 In this invention, the temperature of the reduction reaction is preferably 200–400°C.

[0070] The following examples illustrate the copper-based molecular sieve catalyst and its preparation method provided by the present invention, as well as its application in the selective reduction of NO. x The applications described in detail are not intended to limit the scope of protection of this invention.

[0071] In the following embodiments and test examples, the catalyst performance testing system mainly consists of three parts: a gas path control module, a catalytic reaction module, and a gas concentration detection module. Figure 1 As shown.

[0072] In the gas path control module, standard gas cylinders provide the gases required for the reaction, such as O2, N2, N2O, NO, and NH3. A precisely calibrated mass flow meter controls the flow rate of each branch gas path. During experiments on the catalyst's water resistance, a constant-temperature water bath is used to heat distilled water to generate water vapor, and the water vapor content is determined based on the heating temperature and gas flow rate. Furthermore, to prevent water vapor condensation in the pipeline, a heating belt is wrapped around the inlet pipe for heating.

[0073] The catalytic reaction module mainly consists of two parts: a programmed temperature-controlled tubular furnace and a quartz tube reactor. Before the pretreatment experiment begins, the catalyst is filled into the quartz tube reactor, and both ends of the catalyst are plugged with quartz wool to prevent the catalyst from being blown into the subsequent gas pool and affecting the measurement results. Before the gas reaction officially begins, the catalyst needs to be pretreated. Pretreatment is carried out in a pure nitrogen stream, so the N2 gas control valve is opened to purge the air from the tube, and the furnace temperature is raised to 500℃ and maintained at this temperature for 60 minutes. After the pretreatment is completed and the furnace temperature drops to room temperature, the performance testing experiment begins. The performance testing temperature range is between 50℃ and 600℃, with a heating rate of 5℃ / min. Each sampling point is maintained for 10 minutes to ensure the reaction reaches a steady state.

[0074] The gas concentration detection module mainly consists of two parts: a Fourier transform infrared spectrometer and computer analysis software. All gas components measured by the testing equipment have been accurately calibrated using corresponding standard gas cylinders. During the experiment, the concentration of the reacting gases can be viewed in real time using dedicated computer software connected to the testing equipment.

[0075] The catalytic performance of the catalyst is mainly characterized by NO conversion rate, N2O decomposition / reduction efficiency, and N2O selectivity at different temperatures, and the calculation formulas are shown in Equations 1 to 3:

[0076] NO conversion = ([NO]) in -[NO] out ) / [NO] in ×100% Formula 1;

[0077] N2O conversion = ([N2O]) in -[N2O] out ) / [N2O] in ×100% Equation 2;

[0078] N2O selectivity = ([N2O]) out [NO] in Formula 3: ) × 100%.

[0079] In equations 1 through 3, [NO] in and [NO]out These represent the NO volume concentration at the reactor inlet and outlet, respectively, and [N₂O] concentration. in and [N2O] out This represents the volume concentration of N2O at the reactor outlet.

[0080] The following examples and test cases used inductively coupled plasma atomic emission spectrometry (ICP) to determine the Cu loading in copper-based molecular sieve catalysts.

[0081] Example 1

[0082] according to Figure 2 The preparation process flow chart for copper-based molecular sieve catalysts is as follows:

[0083] First, 52.83 g of TMAdaOH was mixed with 20 g of deionized water, then 5.15 g of Al(OH)3 was slowly added. Next, 10.0 g of a 20 wt% NaOH aqueous solution was added dropwise while stirring at room temperature for 20 min. Then, 150.00 g of the silicon source Ludox AS-40 was slowly added dropwise, and the mixture was further homogenized and stirred for 2 hours to obtain a gel composed of ANaOH: (0.5-A)TMAdaOH:0.033Al2O3:1SiO2:44H2O, where the A value was 0.25.

[0084] After obtaining the gel solution, it was placed in a reaction vessel and subjected to hydrothermal treatment at 180°C and a rotation speed of 40 rpm for 96 hours. The resulting sample was then filtered, washed three times, and the precipitate was collected to obtain the synthesized Na-type SSZ-13 molecular sieve precursor. This precursor was then dried in an oven at 100°C for 12 hours, and finally calcined in a muffle furnace at 550°C for 10 hours at a heating rate of 1°C / min to obtain the Na-type SSZ-13 molecular sieve. + / TMAda + The ratio is named Na-SSZ-13 (2.5 / 2.5).

[0085] After the Na-type SSZ-13 molecular sieve is prepared, it is placed in a 1 mol / L NH4Cl solution and subjected to ion exchange at 80℃ for 12 h to obtain NH4Cl. + Type SSZ-13 molecular sieve will yield NH4 + The SSZ-13 molecular sieve is filtered, washed, and dried.

[0086] Take 100 mL of a 1 mol / L Cu(NO3)2·6H2O solution, and add NH4 +SSZ-13 molecular sieve powder was placed in a solution and stirred at 80°C for 6 hours in a magnetically stirred water bath. The resulting mixture was filtered and washed three times, then dried in an oven at 100°C for 12 hours. Finally, the dried sample was placed in a muffle furnace and calcined at 550°C for 4 hours at a heating rate of 1°C / min to obtain a copper-based molecular sieve catalyst with a Cu loading of 1 wt%, denoted as Cu / SSZ-13(2.5 / 2.5).

[0087] Test Example 1: Different Na + / TMAda + Effect of ratio on SCR performance and N2O formation of Cu / SSZ-13 catalyst

[0088] Following the method described in Example 1, a Cu loading of 1 wt% and Na were prepared. + / TMAda + Cu / SSZ-13 catalysts prepared in proportions of 0 / 5, 1 / 4, and 2.5 / 2.5, both fresh and after hydrothermal aging (800℃, 12h hydrothermal aging treatment), were designated as Cu / SSZ-13(0 / 5)Fresh, Cu / SSZ-13(1 / 4)Fresh, Cu / SSZ-13(2.5 / 2.5)Fresh (i.e., Example 1), Cu / SSZ-13(0 / 5)Aged, Cu / SSZ-13(1 / 4)Aged, and Cu / SSZ-13(2.5 / 2.5)Aged, respectively. The difference between Cu / SSZ-13(0 / 5) and Example 1 is that the amount of NaOH aqueous solution added is 0.

[0089] The difference between Cu / SSZ-13(1 / 4) and Example 1 is that the amount of NaOH aqueous solution added is 4.0g.

[0090] The effect of the above catalysts on NO was determined. x The catalytic activity of NH3- in the standard SCR reaction and the production of N2O during the SCR process. Reaction space velocity: 60000 mL·g -1 ·h -1 The inlet gas conditions for the reaction are 1000ppm NO, 1000ppm NH3, 10% O2, and equilibrium gas N2.

[0091] NO from different catalysts x Conversion rate, etc. Figure 3 As shown, the amount of N2O generated is as follows Figure 4 As shown. By Figure 3 , Figure 4 It can be seen that at 60000 mL·g -1 ·h -1At the given reaction space velocity, all fresh Cu / SSZ-13 molecular sieve catalysts exhibited high NO levels at temperatures ranging from 200℃ to 400℃. x Regarding conversion efficiency, the Cu / SSZ-13 (0 / 5) and Cu / SSZ-13 (1 / 4) catalysts showed better NO catalytic activity than Cu / SSZ-13 (2.5 / 2.5) at temperatures below 200℃. However, when the temperature continued to rise above 400℃, due to the non-selective oxidation of NH3, the NO conversion efficiency of all molecular sieves decreased. x The conversion rates decreased to varying degrees. Among them, the Cu / SSZ-13 (2.5 / 2.5) catalyst showed the smallest decrease in conversion efficiency and maintained a high conversion efficiency of over 80%. In contrast, the activity of the Cu / SSZ-13 (0 / 5) and Cu / SSZ-13 (1 / 4) catalysts decreased significantly, especially Cu / SSZ-13 (0 / 5), whose activity decreased by nearly 50%.

[0092] After hydrothermal treatment at 800℃, the three catalysts showed more obvious differences in high-temperature activity: the aged Cu / SSZ-13 (2.5 / 2.5) catalyst showed better catalytic performance than the aged Cu / SSZ-13 (0 / 5) and Cu / SSZ-13 (1 / 4) catalysts in almost the entire temperature range.

[0093] The XPSCu 2p spectra of Cu / SSZ-13(0 / 5)Fresh, Cu / SSZ-13(1 / 4)Fresh, and Cu / SSZ-13(2.5 / 2.5)Fresh are as follows Figure 5 As shown. By Figure 5 As shown, the Cu2p orbital can be divided into two main peaks (Cu 2p1 / 2 and Cu 2p3 / 2) and one satellite peak (Sat.). The Cu 2p2 / 3 orbital contains two types of Cu active center peaks, located in the binding energy range of 934.8–936.2 eV and at 933.5 eV, respectively. Meanwhile, the Cu 2p2 / 3 orbital contains Cu... 2+ The binding energy of the peak is around 935.5 eV, while the peak binding energies of isolated Cu, CuO, and Cu₂O are all around 933.5 eV. When the Cu loading is less than 3%, it exists on the molecular sieve surface not in the form of CuO, but only in the form of Cu(OH). + and Cu 2+ Therefore, the characteristic peak on the Cu 2p2 / 3 orbital corresponds to Cu. 2+ And the intensity peak of isolated Cu. Based on the Cu 2p2 / 3 orbital spectra of the three, it is determined that Cu is present in all three types of molecular sieves. 2+ Active center, and Cu / SSZ-13 (2.5 / 2.5) Cu 2+The orbital peak area is significantly larger than that of the other two catalysts.

[0094] Further research on Cu in the three catalysts 2+ Furthermore, the content distribution of isolated Cu was analyzed, and semi-quantitative calculations were performed on the two Cu forms deconvolved at Cu 2p² / ³. The peak areas of the two forms were calculated using Gaussian functions and compared to obtain the Cu content of different catalysts. 2+ and Cu + The proportions of Cu are shown in Table 1. It can be seen that among the three different catalysts, Cu... 2+ The ratio of Na + / TMAda + The increase is proportional to the increase in the ratio, reaching a maximum of 29.6% at a ratio of 1:1, which is higher than using only TMAda. + Cu / SSZ-13(0 / 5) synthesized as an inorganic directing agent 2+ The proportion nearly doubled, indicating that adjusting the Na content in the precursor inorganic directing agent... + / TMAda + The ratio of [specific component] can effectively affect the Al content after molecular sieve synthesis. paired Number of sites, and Cu after ion exchange 2+ The number of active sites is reduced, thereby effectively reducing the amount of N2O generated during the SCR process of the Cu / SSZ-13 catalyst.

[0095] Table 1 Cu content in different Cu / SSZ-13 catalysts 2+ and the content distribution of isolated Cu

[0096] Cu / SSZ-13(0 / 5)Fresh Cu / SSZ-13(1 / 4)Fresh Cu / SSZ-13(2.5 / 2.5)Fresh <![CDATA[Cu 2+ Ions 14.6％ 19.5％ 29.6％ <![CDATA[Cu + Ions 85.4％ 80.5％ 70.4％

[0097] The specific surface area, total pore volume and average pore size of different Cu / SSZ-13 catalysts are shown in Table 2.

[0098] Table 2. Specific surface area, total pore volume, and average pore size of different Cu / SSZ-13 catalysts

[0099]

[0100] Test Example 2: Effect of different Cu loadings on SCR performance and N2O formation of Cu / SSZ-13 catalyst

[0101] Na is prepared according to the above method. + / TMAda + Cu / SSZ-13 catalysts with a ratio of 2.5 / 2.5 and Cu loadings of 0.5 wt%, 1 wt%, and 1.5 wt%, respectively, are denoted as Cu... 0.5 / SSZ-13(2.5 / 2.5), Cu / SSZ-13(2.5 / 2.5) (Example 1) and Cu1.5 / SSZ-13(2.5 / 2.5). Wherein, Cu 0.5 The difference between / SSZ-13 (2.5 / 2.5) and Example 1 is that the concentration of the Cu(NO3)2·6H2O solution is 0.5 mol / L, and the Cu... 1.5 The difference between / SSZ-13 (2.5 / 2.5) and Example 1 is that the concentration of Cu(NO3)2·6H2O solution is 1.5 mol / L.

[0102] Determination of the effect of catalyst on NO x The catalytic activity of NH3 in the standard SCR reaction and the production of N2O during the SCR process. Reaction space velocity: 60000 mL·g -1 ·h -1 The inlet gas conditions for the reaction are 1000ppm NO, 1000ppm NH3, 10% O2, and equilibrium gas N2.

[0103] NO from different catalysts x Conversion rate, etc. Figure 6 As shown, the amount of N2O generated is as follows Figure 7 As shown. By Figure 6 , Figure 7 It can be seen that when the Cu loading is less than 1 wt%, the low-temperature activity of the Cu / SSZ-13 (2.5 / 2.5) catalyst is poor, and the high-activity temperature range shifts to a later stage, reaching a conversion rate of over 90% only at around 350℃. However, with the increase of Cu loading, when the Cu loading exceeds 1 wt%, the overall low-temperature activity of the catalyst is significantly improved, reaching a conversion rate of over 90% at around 225℃ and maintaining a high conversion rate up to over 500℃. However, when the Cu loading exceeds 1 wt%, the high-temperature activity of the Cu / SSZ-13 (2.5 / 2.5) catalyst decreases to some extent after 400℃. At a temperature of 550℃, the NO conversion rate of the Cu / SSZ-13 (2.5 / 2.5) catalyst is 87%, while the Cu... 1.5 The / SSZ-13 (2.5 / 2.5) catalyst concentration dropped to 79%, at which point Cu... 0.5 The SSZ-13 (2.5 / 2.5) catalyst has the highest NO content. x Conversion rate. Further analysis of N₂O generation in the SCR process using Cu / SSZ-13 (2.5 / 2.5) catalysts with different Cu loadings revealed that N₂O generation at both high and low temperatures increased with increasing Cu loading. However, when the Cu loading was below 1 wt%, Cu… 0.5 The / SSZ-13 (2.5 / 2.5) catalyst produces almost no N2O at low temperatures (below 300℃).

[0104] NO at 250℃ and 450℃ with different Cu / SSZ-13 catalysts x The conversion rate and N2O generation are shown in Table 3.

[0105] Table 3 NO content of different Cu / SSZ-13 catalysts at 250℃ and 450℃ x Conversion rate and N2O generation

[0106]

[0107] Table 3 shows the NO content of Cu / SSZ-13 (2.5 / 2.5) at 250℃. x The highest conversion rate was achieved, reaching 100% (N2O formation of 33.7 ppm). When the temperature rose to 450℃, NO... x The conversion rate can be maintained at 89.3% (N2O generation 21.9 ppm); Cu 0.5 / SSZ-13(2.5 / 2.5) NO x The conversion rate was highest at 450℃, reaching 95.7% (N2O generation 17.7ppm), but only 49.4% (N2O generation 11.7ppm) at a lower temperature of 250℃.

[0108] Test Example 3: Effect of different reaction space velocities on SCR performance and N2O formation of Cu / SSZ-13 catalyst

[0109] Determination of the effect of catalyst in Example 1 on NO x The catalytic activity of the NH3-standard SCR reaction and the N2O production during the SCR process were determined. The reaction space velocities were 30000, 60000, and 90000 mL·g⁻¹. -1 ·h -1 The inlet gas conditions for the reaction are 1000ppm NO, 1000ppm NH3, 10% O2, and equilibrium gas N2.

[0110] Example 1: NO from the catalyst x Conversion rate, etc. Figure 8 As shown, the amount of N2O generated is as follows Figure 9 As shown. By Figure 8 , Figure 9 It can be seen that as the space velocity gradually increases, the NO content of the Cu / SSZ-13 (2.5 / 2.5) catalyst decreases across the entire temperature range. x The conversion efficiency gradually decreased, but it could still maintain a high conversion efficiency of over 90% between 225 and 400°C. However, as the temperature increased, the efficiency of the catalyst with the higher space velocity decreased faster in the experiment.

[0111] At different space velocities, the concentration of N2O generated by the catalyst showed the same trend: it first increased, then decreased, and finally increased again with increasing temperature, unlike NO. x Conversely, the N2O concentration decreased with increasing space velocity, especially at 30000 mL·g⁻¹. -1 ·h -1 Under low space velocity conditions, the concentration peak of N2O shifts to the left at low temperatures, appearing around 225℃. However, as the space velocity increases, the peak continuously shifts towards higher temperatures, reaching a peak at 90000 mL·g⁻¹. -1 ·h -1 At airspeed, the temperature reaches approximately 250°C.

[0112] Test Example 4: Water and Sulfur Resistance of Cu / SSZ-13 Catalyst

[0113] The H2O and SO2 poisoning performance of the Cu / SSZ-13 (2.5 / 2.5) catalyst in Example 1 was tested at 250°C. The reaction gas conditions were 1000 ppm NO, 1000 ppm NH3, 10% O2, and equilibrium gas N2. The reaction space velocity was 60000 ml·g. -1 ·h -1 During the water resistance and sulfur resistance tests, an additional 10 vol.% H2O and 50 ppm SO2 were introduced, respectively.

[0114] The effects of H2O and SO2 on the performance of Cu / SSZ-13 (2.5 / 2.5) catalyst at 250℃ are as follows: Figure 10 As shown. By Figure 10 It can be seen that under the standard SCR reaction gas conditions for the first 4 hours, the Cu / SSZ-13 (2.5 / 2.5) catalyst exhibits stable performance, and NO... x The conversion efficiency remained at around 100%, but after introducing 10 vol.% H2O gas at 4.5 h, the NOx conversion rate decreased significantly, dropping from 100% to around 84% within 0.5 h.

[0115] After closing the H2O gas line for 2 hours, opening the SO2 gas line and introducing SO2 at a concentration of 50 ppm resulted in NO being detected. x The conversion rate decreased to some extent, stabilizing at around 85% after 30 minutes. After shutting off the gas path, the SCR performance of the catalyst recovered somewhat, but did not return to the 100% level before SO2 was introduced, reaching only around 92%. Two hours later, the catalyst was subjected to desulfurization regeneration at 500℃ for 1 hour under a pure N2 atmosphere, and then placed back into a standard SCR gas atmosphere for further experiments. The results showed that it could essentially recover to 100% conversion rate.

[0116] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-based molecular sieve catalyst, characterized by, consisting of the following steps: mixing TMAdaOH, an aluminum source, NaOH and water to obtain a premixing solution; adding a silicon source into the premixing solution to form a gel solution; subjecting the gel solution to hydrothermal treatment and first calcination in sequence to obtain Na-type SSZ-13 molecular sieve; mixing the Na-type SSZ-13 molecular sieve with an ammonium salt solution to perform a first ion exchange to obtain NH4 + SSZ-13 molecular sieve; The NH4 + The copper-based molecular sieve catalyst is obtained by mixing the SSZ-13 molecular sieve of formula (I) with a soluble copper salt solution, sequentially performing a second ion exchange and a second calcination. The premix solution contains Na + :TMAda + =1:1; The Si / Al ratio of the gel in the gel solution is 5-20:1 by molar amount, (Na + +TMAda + ) / Si = 0.5; the concentration of the soluble copper salt is 1 mol / L; the temperature of the hydrothermal treatment is 180℃, and the time is 96h; the temperature of the first calcination is 550℃, and the time is 10h; the temperature of the first ion exchange is 80℃, and the time is 12h; the temperature of the second ion exchange is 80℃, and the time is 6h; the temperature of the second calcination is 550℃, and the time is 4h.

2. The production method according to claim 1, characterized by, the aluminum source is Al(OH)3, and the silicon source is silica sol; the temperature of the process of forming the gel solution is 10-40℃, and the time is 0.5-3h.

3. The preparation method according to claim 1, characterized in that, the concentration of the ammonium salt solution is 1 mol / L.

4. The method of claim 1, wherein, after the second calcination, further comprising subjecting the obtained copper-based molecular sieve catalyst to hydrothermal aging treatment; the temperature of the hydrothermal aging treatment is 750-850℃, and the time is 8-12h.

5. The copper-based molecular sieve catalyst prepared by the preparation method of any one of claims 1-4, comprising SSZ-13 molecular sieve and Cu supported on the surface and internal pores of the SSZ-13 molecular sieve.

6. The copper-based molecular sieve catalyst of claim 5, wherein, the Cu loading in the copper-based molecular sieve catalyst is 0.5-1.5wt%.

7. Use of a copper-based molecular sieve catalyst according to claim 5 or 6 for the selective reduction of NO x .

Images