AEI molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the technical field of molecular sieves, and particularly discloses an AEI molecular sieve and a preparation method and application thereof.The preparation method comprises the steps that a molecular sieve with the low silica-alumina ratio serves as all the aluminum source and part of the silicon source and is mixed with a supplementary silicon source, an alkali source, an alkyl-substituted piperidinium compound template agent, a strong acid and weak base salt pH regulator, a potassium source, an AEI seed crystal and pure water according to the specific molar ratio; performing aging, hydrothermal crystallization, drying and roasting to obtain a K / Na-SSZ-39 molecular sieve; by introducing the potassium source and regulating and controlling the dosage of the potassium source, the silica-alumina ratio of the molecular sieve can be effectively regulated, and the potassium source and the organic template agent are synergistically guided, so that the crystallization time is greatly shortened to 8-24 hours under the condition of no additional aluminum source, and the K / Na-SSZ-39 molecular sieve with pure phase, high crystallinity and regular morphology is obtained; the Cu-SSZ-39 catalyst prepared from the molecular sieve shows excellent low-temperature activity and wide-temperature window stability in a denitration reaction, and the denitration rate is close to 100% within the temperature range of 250-600 DEG C.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, and in particular to an AEI molecular sieve, its preparation method, and its application. Background Technology

[0002] Despite continued global economic development and rising energy consumption, air pollution remains a serious problem, with nitrogen oxides (NOx) being a major contributor. x The impact of nitrogen oxides on the environment is particularly prominent. As a major air pollutant, nitrogen oxides mainly originate from industrial waste gas and motor vehicle exhaust. Among them, nitrogen oxides in diesel vehicle exhaust are a key and difficult point in my country's air pollution control.

[0003] To continuously reduce vehicle exhaust pollution, the NOx emissions from automobiles... x Among denitrification technologies, ammonia selective catalytic reduction (NH3-SCR) is currently the most efficient and widely used denitrification solution due to its high efficiency and economy. Copper-based microporous CHA molecular sieves (such as Cu-SSZ-13) exhibit excellent NO reduction performance as SCR catalysts. x With its excellent denitrification performance, Cu-SSZ-13 molecular sieves are widely used in mobile source exhaust gas denitrification, but carbon buildup is quite serious during application. To avoid severe carbon buildup, people have turned their attention to AEI molecular sieves (such as SSZ-39).

[0004] AEI-type molecular sieves (such as SSZ-39) are structurally highly similar to CHA-type molecular sieves. Both belong to a three-dimensional small-pore eight-membered ring system, share the double six-membered ring (d6r) secondary structural unit, and have the same pore size (approximately 0.38 × 0.38 nm), thus both are suitable for preparing high-performance Cu-based SCR catalysts. The key difference lies in the framework arrangement; in CHA molecular sieves, the double six-membered rings are arranged parallel in the same direction, which may lead to framework expansion; while in AEI molecular sieves, adjacent double six-membered rings are arranged at a certain angle, forming a more compact structure. Therefore, both belong to the trigonal crystal system... Compared to CHA molecular sieves with space group C, AEI molecular sieves, belonging to the orthorhombic crystal system and space group Cmcm, have smaller effective pore sizes in their eight-membered ring channels. This not only results in superior resistance to carbon deposition but also enhances their catalytic activity, particularly in the purification of NO. x When used in exhaust gas, it exhibits better hydrothermal stability, which can well meet exhaust gas emission standards and has broad application prospects.

[0005] Currently, the preparation methods for SSZ-39 molecular sieves have many shortcomings, such as: (1) Xiao et al. from Zhejiang University first proposed using conventional silicon source silica sol and conventional aluminum source sodium aluminate to replace the use of FAU type molecular sieve, and realized the synthesis of SSZ-39 molecular sieve. However, due to the limitations of the chemical conditions of the gel, the range of pure phase SSZ-39 molecular sieve synthesis by this method is narrow, and the product is always accompanied by heterogeneous molecular sieves with structures such as MOR and ANA. It requires strict condition control and is difficult to scale up production. (2) Manuel Moliner and Avelino Corma et al. (Chemical Communications, 2015, 51(55):11030-11033) synthesized AEI molecular sieve by using a complete crystallization method and according to the molar ratio of 1.0SiO2:0.047Al2O3:0.4DMDMPOH:0.2NaOH:15H2O, that is, both aluminum and silicon sources are NH4Y molecular sieves, and static crystallization was carried out at 135℃. However, the crystallization time was as long as 7 days, and the amount of template agent was too high, resulting in excessive cost. (3) Chinese patent CN 112871203A discloses a method for preparing SSZ-39 using potassium salt (mainly KOH) as an inorganic structure directing agent. With the addition of NaOH to adjust the pH value, the amount of organic template agent (DMDMPOH / SiO2=0.05-0.2) can be greatly reduced and the crystallization time can be reduced. However, this method requires the addition of aluminum isopropoxide to supplement the aluminum source based on Y molecular sieve as aluminum source. Later, researchers introduced seed crystals to further shorten the crystallization time. However, during the synthesis process, heterocrystalline phases such as analcime-C, gyrinite-Na, and faujasite often appear. In order to synthesize SSZ-39 molecular sieve with pure phase and high crystallinity, a crystallization time of 7-14 days is still required, which seriously limits the industrial application of SSZ-39 molecular sieve.

[0006] Therefore, there is an urgent need for a method to synthesize AEI molecular sieves that can rapidly and cost-effectively synthesize high-purity and high-crystallinity AEI molecular sieves. Summary of the Invention

[0007] To address the technical problems existing in the background art, this invention proposes a method for preparing AEI molecular sieves, comprising the following steps: S1. Mix the supplementary silicon source, molecular sieve, alkali source, pH adjuster, alkyl-substituted piperidinium compound, water, potassium source and AEI molecular sieve seed crystals, and age to obtain the initial sol. S2. The initial sol is subjected to a hydrothermal reaction, and the solid product is calcined to obtain pure phase AEI molecular sieve.

[0008] In this invention, a method of zeolite intercrystalline transformation is proposed, which involves adding supplementary silicon sources, template agents, inorganic bases, pH adjusters, seed crystals, and potassium sources to directly synthesize AEI-type SSZ-39 molecular sieves with adjustable silicon-to-aluminum ratios by topological reconstruction of low-silicon-to-aluminum ratio FAU-type NaY zeolite molecular sieves, thereby greatly shortening the crystallization time. Due to hydration K + The ionic radius is 0.331 nm, which is smaller than that of hydrated Na+. + The ionic radius is 0.358 nm, therefore, K + Than Na + It is easier for it to enter the small pore structure of SSZ-39 molecular sieve; this invention utilizes this characteristic to introduce a potassium source to improve the alkaline environment provided by NaOH and pH adjuster, while keeping the SiO2 / Al2O3 ratio in the raw materials unchanged. 3+ To regulate, by regulating K + The molar ratio of SiO2, thereby driving the different proportions of Al 3+ By incorporating the molecular sieve framework, the structural stability of SSZ-39 molecular sieve is improved, and pure-phase, highly crystalline AEI-type SSZ-39 molecular sieve is synthesized. Furthermore, the silicon-aluminum ratio of SSZ-39 molecular sieve can be controlled within a certain range.

[0009] The supplementary silicon source is any one or more of silica sol, water glass, silica, coarse-porous silica spheres, tetraethyl orthosilicate, or fumed silica. Preferably, the supplementary silicon source is silica sol and water glass.

[0010] The molecular sieve is any one or more of the following: low silica-alumina ratio Y molecular sieve, Beta molecular sieve, or MFI molecular sieve. Preferably, the molecular sieve is a Y molecular sieve with a low silica-to-alumina ratio; More preferably, the Y molecular sieve is any one or more of NH4Y molecular sieve, NaY molecular sieve, HY molecular sieve or USY molecular sieve; More preferably, the Y molecular sieve is an NH4Y or NaY molecular sieve with a silicon-aluminum oxide molar ratio of <10.

[0011] In this invention, a low-silicon-to-aluminum ratio NaY molecular sieve is used as the source of all aluminum and part of silicon. Since the NaY molecular sieve provides secondary structural units in the synthesis gel system, the crystallization time is shortened, and pure-phase SSZ-39 molecular sieve can be synthesized quickly, thus reducing the cost of the production process.

[0012] The alkali source is sodium hydroxide.

[0013] The pH adjuster is a salt of a strong acid and a weak base; Preferably, the pH adjuster is any one or more of ammonium sulfate, ammonium chloride, ammonium nitrate, or ammonium dihydrogen phosphate.

[0014] In this invention, the strong acid-weak base salt acts as a pH adjuster, which can combine with NaOH to provide an alkaline environment, significantly improving the yield of SSZ-39 molecular sieve. This method utilizes the hydrolysis of the strong acid-weak base salt to fine-tune the pH value of the synthesis environment. Compared with directly adjusting the alkali-silicon ratio (NaOH / SiO2), the yield can be increased from 40% to over 50%, an increase of more than 25%, and the product yield improvement effect is more significant. Unlike existing technologies, which often use citric acid or lactic acid as pH adjusters, these pH adjusters have limited effect on alkalinity regulation during the reaction process, and impurities will still appear in the final product. The strong acid-weak base salt of the present invention, in addition to improving the yield, also regulates the dissolution and polymerization rate of silicon / aluminum species, controls the formation and growth kinetics of crystal nuclei, and obtains crystals with regular cubic morphology. In addition, it can also make the final product have better hydrothermal stability and catalytic performance.

[0015] The alkyl-substituted piperidinium compound is any one or more of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, N,N-dimethyl-2,6-dimethylpiperidinium hydroxide, N,N-diethyl-3,5-dimethylpiperidinium hydroxide, N,N-diethyl-2,6-dimethylpiperidinium hydroxide, N,N-diethyl-3,5-diethylpiperidinium hydroxide, N,N-diethyl-2,6-diethylpiperidinium hydroxide, or N,N-dimethyl-2,6-diethylpiperidinium hydroxide. Preferably, the alkyl-substituted piperidinium compound is N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (DMDMPOH).

[0016] The potassium source is any one or more of potassium hydroxide, potassium carbonate, potassium phosphate, potassium hydrogen phosphate, dipotassium hydrogen phosphate, potassium oxalate, potassium carbonate, potassium chloride, potassium chlorate, potassium nitrate, potassium sulfate, potassium bicarbonate, potassium acetate, potassium aluminate, or potassium sulfide. Preferably, the potassium source is potassium chloride.

[0017] In this invention, introducing a potassium source as a silicon-to-aluminum ratio regulator into the synthetic gel system has three advantages; 1. In the reaction system of this invention, the potassium source interacts with the aluminate ions dissolved in a highly active aluminum source (such as sodium aluminate or NaY zeolite), promoting ordered crystallization. The silica-alumina ratio of the SSZ-39 molecular sieve can be rapidly adjusted by changing the amount of potassium source added. +By adjusting the SiO2 / Al2O3 molar ratio within the range of 0.005-0.304, the synthesis of AEI-type SSZ-39 molecular sieves with a SiO2 / Al2O3 molar ratio within the range of 1-100 can be achieved. 2. Under the molar ratio of this invention, the potassium source and the alkyl-substituted piperidinium compound have a synergistic effect on structure guidance. The alkyl-substituted piperidinium compound provides the main space filling and cage-like structure guidance, guiding aluminosilicate species to assemble around themselves into an AEI structure. Meanwhile, the potassium ion, as an alkali metal cation, regulates the charge density and basicity of the gel, influencing the nucleation pathway and accelerating crystallization. The two complement each other, with potassium... + Preferentially occupying specific cage or ring sites, while alkyl-substituted piperidinium compounds stabilize larger cage structures, precisely guiding the formation of AEI topology. This not only reduces the amount of expensive organic template agents used, but also eliminates heterocrystalline phases such as FAU, ANA, and GME that are prone to occur during synthesis, thus preparing pure-phase, highly crystalline SSZ-39 molecular sieves. 3. No additional aluminum source is added in the reaction system of this invention, which creatively reduces the amount of potassium source used. The dissolution rate of aluminate ions and the nucleation rate of SSZ-39 are matched, which significantly shortens the time for synthesizing pure phase SSZ-39 molecular sieves from the conventional synthesis time of 7-14 days to 8-24 hours.

[0018] The initial sol components consist of a total silicon source, a total aluminum source, an alkali source, a pH adjuster, an alkyl-substituted piperidinium compound, a potassium source, AEI molecular sieve seed crystals, and water in a molar ratio of 1: (0.01-1): (0.1-0.5): (0.015-0.045): (0.05-0.2): (0.005-0.304): (0.001-0.01): (15-30). The total silicon source includes a supplementary silicon source and a molecular sieve. The total silicon source is calculated as SiO2, the total aluminum source as Al2O3, the alkali source as NaOH, and the potassium source as K. + count.

[0019] The present invention also proposes an AEI molecular sieve, which is obtained by the above preparation method.

[0020] This invention also proposes an application of AEI molecular sieve in exhaust gas removal, wherein K / Na-SSZ-39 molecular sieve is subjected to ammonium exchange, copper exchange, calcination and aging to obtain Cu-SSZ-39 molecular sieve catalyst, which is then applied to exhaust gas removal. Preferably, copper salt is used during copper exchange. The copper salt is any one or more of copper nitrate, copper acetate, copper sulfate, or copper oxalate, and the amount of copper salt used is adjusted according to the load requirements.

[0021] The AEI-type SSZ-39 molecular sieve described in this invention is mainly used as a Cu-SSZ-39 molecular sieve catalyst and its role in the removal of NO from diesel engine exhaust. x Removal, using NH3 as a reducing agent, to remove NO x Selective catalytic reduction to N2 and water enables diesel vehicle exhaust to meet emission standards; the Cu-SSZ-39 molecular sieve prepared in this invention exhibits good low-temperature activity and high NO content. x It exhibits high conversion rate and good hydrothermal stability.

[0022] Beneficial effects of this invention: (1) In this invention, compared with the prior art, under the condition of no additional aluminum source, by introducing potassium source as silicon-aluminum ratio regulator, the final molecular sieve has high crystallinity, no impurities, uniform particle size, regular crystal shape and morphology and does not agglomerate. (2) By controlling the amount of potassium source and other raw materials used, the yield of pure phase SSZ-39 molecular sieve can be significantly improved without additional aluminum source, thereby increasing the revenue per batch in actual industrial production. (3) Through K + The SiO2 / Al2O3 molar ratio can be adjusted within the range of 0.005-0.304 to accurately obtain AEI-type SSZ-39 molecular sieves with low SiO2 / Al2O3 molar ratio (SiO2 / Al2O3 molar ratio = 1-100) and adjustable SiO2 / Al2O3 molar ratio. (4) The amount of organic template agent, silicon source and aluminum source used is greatly reduced, and the synthesis time is shortened to 8-24h, which greatly reduces the economic cost and time cost of production. Attached Figure Description

[0023] Figure 1 SEM images of the K / Na-SSZ-39 molecular sieve in Examples 1-4; Figure 2 The XRD patterns of SSZ-39 molecular sieves in Examples 1-4 and Comparative Example 1 are shown. Figure 3 The low-temperature NH3-SCR test results (150-250℃) of Cu-SSZ-39 molecular sieve catalysts prepared by SSZ-39 molecular sieves in Examples 1-4 and Comparative Example 1 are shown. Figure 4 The full-temperature range NH3-SCR test results (150-650℃) of Cu-SSZ-39 molecular sieve catalysts prepared by SSZ-39 molecular sieves in Examples 1-4 and Comparative Example 1 are shown. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0026] The technical solution of the present invention will now be described more clearly and completely with reference to specific embodiments and comparative examples.

[0027] Example 1

[0028] This embodiment proposes an AEI molecular sieve, the preparation method of which includes the following steps: (1) Place 2.223g of NaOH and 21.476g of distilled water in a polytetrafluoroethylene bottle, stir at 60rpm to dissolve and mix evenly, then add 0.045g of KCl (silicon-aluminum ratio adjuster) and 10.795g of DMDMPOH (25% aqueous solution) (organic template agent) in sequence, stir to dissolve and mix evenly, then add 20g of silica sol (30% aqueous solution) and 1.276g of NaY molecular sieve (SAR=5) in sequence, stir until fully emulsified; then add 0.461g of (NH4)2SO4, stir to dissolve and mix evenly; finally add 0.145g of AEI molecular sieve seed crystals, age at 30℃ for 3h, and fully age to obtain precursor dispersion sol-gel; The molar ratio of SiO2:Al2O3:NaOH:(NH4)2SO4:DMPDMPOH:KCl:AEI seed crystals:H2O in the precursor dispersion sol-gel composition is 1:0.026:0.47:0.03:0.145:0.005:0.001:20.72; (2) The precursor dispersion sol-gel was transferred to a reaction vessel and placed in a homogeneous reactor. Crystallization was carried out at 150°C and 60 rpm for 8 hours. After crystallization, the vessel was opened, and the product was removed, filtered, washed, and dried. The dried product was then calcined at 600°C for 6 hours. Finally, XRD analysis revealed a pure-phase AEI-type molecular sieve, specifically a K / Na-SSZ-39 molecular sieve with a silica-alumina ratio of approximately 25.

[0029] Example 2

[0030] This embodiment proposes an AEI molecular sieve, the preparation method of which includes the following steps: (1) Place 2.223g of NaOH and 21.476g of distilled water in a polytetrafluoroethylene bottle, stir at 50rpm to dissolve and mix evenly, then add 0.907g of KCl, a silicon-aluminum ratio adjuster, and 10.795g of DMDMPOH (25% aqueous solution), an organic template agent, and stir to dissolve and mix evenly. Then add 20g of silica sol (30% aqueous solution) and 1.276g of NaY molecular sieve (SAR=5), and stir until fully emulsified. Then add 0.461g of (NH4)2SO4, stir to dissolve and mix evenly. Finally, add 0.145g of AEI molecular sieve seed crystals, and age at 30℃ for 4h to fully age. The precursor dispersion sol-gel is obtained. The molar ratio of SiO2:Al2O3:NaOH:(NH4)2SO4:DMPDMPOH:KCl:AEI seed crystals:H2O in the precursor dispersion sol-gel composition is 1:0.026:0.47:0.03:0.145:0.103:0.001:20.72. (2) The precursor dispersion sol-gel was transferred to a reaction vessel and placed in a homogeneous reactor. Crystallization was carried out at 150°C and 50 rpm for 24 hours. After crystallization, the vessel was opened, and the product was removed, filtered, washed, and dried. The dried product was then calcined at 600°C for 6 hours. Finally, XRD analysis revealed a pure-phase AEI-type molecular sieve, specifically a K / Na-SSZ-39 molecular sieve with a silica-alumina ratio of approximately 19.

[0031] Example 3

[0032] This embodiment proposes an AEI molecular sieve, the preparation method of which includes the following steps: (1) Place 2.223g of NaOH and 21.476g of distilled water in a polytetrafluoroethylene bottle, stir at 70rpm to dissolve and mix evenly, then add 1.814g of KCl, a silicon-aluminum ratio adjuster, and 10.795g of DMDMPOH (25% aqueous solution), an organic template agent, and stir to dissolve and mix evenly. Then add 20g of silica sol (30% aqueous solution) and 1.276g of NaY molecular sieve (SAR=5), and stir until fully emulsified. Then add 0.461g of (NH4)2SO4, stir to dissolve and mix evenly. Finally, add 0.145g of AEI molecular sieve seed crystals, and age at 30℃ for 2h to fully age. The precursor dispersion sol-gel is obtained. The molar ratio of SiO2:Al2O3:NaOH:(NH4)2SO4:DMPDMPOH:KCl:AEI seed crystals:H2O in the precursor dispersion sol-gel composition is 1:0.026:0.47:0.03:0.145:0.206:0.001:20.72. (2) The precursor dispersion sol-gel was transferred to a reaction vessel and placed in a homogeneous reactor. Crystallization was carried out at 150°C and 70 rpm for 24 hours. After crystallization, the vessel was opened, and the product was removed, filtered, washed, and dried. The dried product was then calcined at 600°C for 6 hours. Finally, XRD analysis revealed a pure-phase AEI-type molecular sieve, specifically a K / Na-SSZ-39 molecular sieve with a silica-alumina ratio of approximately 15.

[0033] Example 4

[0034] This embodiment proposes an AEI molecular sieve, the preparation method of which includes the following steps: (1) Place 2.223g of NaOH and 21.476g of distilled water in a polytetrafluoroethylene bottle, stir at 60rpm to dissolve and mix evenly, then add 2.675g of KCl, a silicon-aluminum ratio adjuster, and 10.795g of DMDMPOH (25% aqueous solution), an organic template agent, and stir to dissolve and mix evenly. Then add 20g of silica sol (30% aqueous solution) and 1.276g of NaY molecular sieve (SAR=5), and stir until fully emulsified. Then add 0.461g of (NH4)2SO4, stir to dissolve and mix evenly. Finally, add 0.145g of AEI molecular sieve seed crystals, and age at 30℃ for 3h to fully age. The precursor dispersion sol-gel is obtained. The molar ratio of SiO2:Al2O3:NaOH:(NH4)2SO4:DMPDMPOH:KCl:AEI seed crystals:H2O in the precursor dispersion sol-gel composition is 1:0.026:0.47:0.03:0.145:0.304:0.001:20.72. (2) The precursor dispersion sol-gel was transferred to a reaction vessel and placed in a homogeneous reactor. Crystallization was carried out at 150°C and 60 rpm for 24 hours. After crystallization, the vessel was opened, and the product was removed, filtered, washed, and dried. The dried product was then calcined at 600°C for 6 hours. Finally, XRD analysis revealed a pure-phase AEI-type molecular sieve, specifically a K / Na-SSZ-39 molecular sieve with a silica-alumina ratio of approximately 11.

[0035] Comparative Example 1 This comparative example presents an AEI molecular sieve, the preparation method of which is the same as that in Example 2, except that the silicon-aluminum ratio adjuster KCl is not added in step (1); thus, the composition of the precursor dispersion sol-gel becomes the molar ratio of SiO2:Al2O3:NaOH:(NH4)2SO4:DMPDMPOH:AEI seed crystals:H2O = 1:0.026:0.47:0.03:0.145:0.001:20.72; Finally, XRD identification revealed that the AEI-type molecular sieve was a heterogeneous phase, specifically a coexistence of AEI with heterogeneous phases such as GME, ANA, and FAU.

[0036] Comparative Example 2 This comparative example presents an AEI molecular sieve, the preparation method of which is the same as that of Example 1, except that "0.045g of silicon-aluminum ratio adjuster KCl" in step (1) is replaced with "3.08g of silicon-aluminum ratio adjuster KCl". As a result, the composition of the precursor dispersion sol-gel becomes SiO2:Al2O3:NaOH:(NH4)2SO4:DMPDMPOH:KCl:AEI seed crystals:H2O molar ratio = 1:0.026:0.47:0.03:0.145:0.35:0.001:20.72; Finally, XRD identification revealed that the AEI-type molecular sieve was a heterogeneous phase, specifically a coexistence of AEI with heterogeneous phases such as GME, ANA, and FAU.

[0037] Comparative Example 3 This comparative example presents an AEI molecular sieve, the preparation method of which is the same as that of Example 1, except that in step (1) an additional "0.5g aluminum sulfate (Al2O3 content is 15.2%)" is added. As a result, the composition of the precursor dispersion sol-gel becomes SiO2:Al2O3:NaOH:(NH4)2SO4:DMPDMPOH:KCl:AEI seed crystals:H2O molar ratio = 1:0.033:0.47:0.03:0.145:0.005:0.001:20.72; Finally, XRD identification revealed that the AEI-type molecular sieve was a heterogeneous phase, specifically a coexistence of AEI with heterogeneous phases such as GME, ANA, and FAU.

[0038] Application examples (1) The molecular sieves prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to multiple ammonium exchange reactions with 1 mol / L NH4NO3 solution at 80°C. After the reaction was completed, the sieves were repeatedly filtered, washed with distilled water, and dried overnight at 120°C. The dried NH4NO3 solution was then used to prepare the NH4NO3 solution. + -SSZ-39 molecular sieve in air atmosphere Calcination yields H-SSZ-39 molecular sieve; (2) The obtained H-SSZ-39 molecular sieve and The aqueous solution was stirred until homogeneous, and an ion exchange reaction was carried out at 80℃ for 3 hours. After the reaction was completed, the mixture was filtered and washed, and the ion exchange was repeated 2-3 times. The mixture was then dried at 120℃ for 10 hours (generally 8-12 hours), and calcined at 600℃ in air for 7 hours (generally 6-8 hours) to obtain Cu-SSZ-39 molecular sieve. The copper loading (based on Cu) 2+ The copper loading is 3wt% (for Cu-SSZ-39 molecular sieves used in general testing, the copper loading is 2.8-4wt%). (3) The obtained Cu-SSZ-39 molecular sieve powder was pressed, pulverized, and sieved to collect particles with a size of 60-80 mesh as Cu-SSZ-39 molecular sieve catalyst; the catalyst particles were loaded into a moving bed reactor and N2 1.0 L / min, O2 0.1 L / min and 10 vol.% water vapor were introduced at a volume hourly space velocity of 500,000 h⁻¹. -1 The aged Cu-SSZ-39 molecular sieve catalyst can be obtained by hydrothermal aging at 850℃ for 16 hours. (4) The aged Cu-SSZ-39 molecular sieve catalyst particles were packed into a fixed-bed reactor, and 500 ppm NO, 500 ppm NH3, 10% O2, 8% CO2, and 5.0% H2O were introduced. N2 was balanced, and the volume hourly space velocity was 240,000 h⁻¹. -1 Selective catalytic reduction reaction of NH3-SCR was tested at 150-650℃, and the content of nitrogen oxides and other components in the products was detected and quantitatively analyzed online using a flue gas analyzer.

[0039] Test case Figure 1 The images shown are SEM images of the K / Na-SSZ-39 molecular sieves from Examples 1-4. Figure 1 It can be seen that the molecular sieve is a relatively uniform cube with regular crystal shape and morphology and no aggregation; XRD analysis was performed on the molecular sieves obtained in Examples 1-4 and Comparative Example 1, where, Figure 2 The XRD patterns of SSZ-39 molecular sieves in Examples 1-4 and Comparative Example 1 are shown. Analysis revealed that the crystallinity and purity of K / Na-SSZ-39 molecular sieves in Examples 1-4 were significantly higher than those in Comparative Example 1. Figure 3 The figures show the low-temperature NH3-SCR test results (150-250℃) of the Cu-SSZ-39 molecular sieve catalysts prepared using SSZ-39 molecular sieves in Examples 1-4 and Comparative Example 1. Figure 3 It can be seen that the Cu-SSZ-39 molecular sieve catalyst prepared in this invention exhibits a denitrification rate that increases to nearly 100% with increasing temperature within a relatively low temperature range. Figure 4 The figures show the full-temperature range NH3-SCR test results (150-650℃) of the Cu-SSZ-39 molecular sieve catalysts prepared using SSZ-39 molecular sieves in Examples 1-4 and Comparative Example 1. Figure 4 It can be seen that the Cu-SSZ-39 molecular sieve catalyst prepared in this invention has a wide denitrification temperature window, and the denitrification rate is stably maintained at close to 100% in the temperature range of 250-600℃. Table 1 shows the XRF detection results of SSZ-39 molecular sieves in Examples 1-4 and Comparative Example 1.

[0040] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for preparing an AEI molecular sieve, characterized in that, Includes the following steps: S1. Mix the supplementary silicon source, molecular sieve, alkali source, pH adjuster, alkyl-substituted piperidinium compound, water, potassium source and AEI molecular sieve seed crystals, and age to obtain the initial sol. S2. The initial sol was subjected to a hydrothermal reaction, and the solid product was calcined to obtain K / Na-SSZ-39 molecular sieve.

2. The method of claim 1, wherein the AEI molecular sieve is prepared by the method comprising the steps of: The supplementary silicon source is any one or more of silica sol, water glass, silica, coarse-porous silica spheres, tetraethyl orthosilicate, or fumed silica. Preferably, the supplementary silicon source is silica sol or water glass.

3. The method of making the AEI molecular sieve of claim 1 or 2, wherein, The molecular sieve is any one or more of the following: low silica-alumina ratio Y molecular sieve, Beta molecular sieve, or MFI molecular sieve. Preferably, the molecular sieve is a Y molecular sieve with a low silica-to-alumina ratio; More preferably, the Y molecular sieve is any one or more of NH4Y molecular sieve, NaY molecular sieve, HY molecular sieve or USY molecular sieve; More preferably, the Y molecular sieve is an NH4Y or NaY molecular sieve with a silicon-aluminum oxide molar ratio of <10.

4. The method for preparing AEI molecular sieve according to any one of claims 1-3, characterized in that, The alkali source is sodium hydroxide.

5. The method for preparing AEI molecular sieve according to any one of claims 1-4, characterized in that, The pH adjuster is a salt of a strong acid and a weak base. Preferably, the pH adjuster is any one or more of ammonium sulfate, ammonium chloride, ammonium nitrate, or ammonium dihydrogen phosphate.

6. The method for preparing AEI molecular sieve according to any one of claims 1-5, characterized in that, The alkyl-substituted piperidinium compound is any one or more of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, N,N-dimethyl-2,6-dimethylpiperidinium hydroxide, N,N-diethyl-3,5-dimethylpiperidinium hydroxide, N,N-diethyl-2,6-dimethylpiperidinium hydroxide, N,N-diethyl-3,5-diethylpiperidinium hydroxide, N,N-diethyl-2,6-diethylpiperidinium hydroxide, N,N-dimethyl-3,5-diethylpiperidinium hydroxide, and N,N-dimethyl-2,6-diethylpiperidinium hydroxide. Preferably, the alkyl-substituted piperidinium compound is N,N-dimethyl-3,5-dimethylpiperidinium hydroxide.

7. The method for preparing AEI molecular sieve according to any one of claims 1-6, characterized in that, The potassium source is any one or more of potassium hydroxide, potassium carbonate, potassium phosphate, potassium hydrogen phosphate, dipotassium hydrogen phosphate, potassium oxalate, potassium carbonate, potassium chloride, potassium chlorate, potassium nitrate, potassium sulfate, potassium bicarbonate, potassium acetate, potassium aluminate, or potassium sulfide. Preferably, the potassium source is potassium chloride.

8. The method for preparing AEI molecular sieve according to any one of claims 1-7, characterized in that, The initial sol components consist of a total silicon source, a total aluminum source, an alkali source, a pH adjuster, an alkyl-substituted piperidinium compound, a potassium source, AEI molecular sieve seed crystals, and water in a molar ratio of 1: (0.01-1): (0.1-0.5): (0.015-0.045): (0.05-0.2): (0.005-0.304): (0.001-0.01): (15-30). wherein the total silicon source comprises a make-up silicon source and a molecular sieve, the total silicon source is in terms of SiO2, the total aluminum source is in terms of Al2O3, the base source is in terms of NaOH, and the potassium source is in terms of K + .

9. An AEI molecular sieve, characterized in that, It is obtained by the preparation method described in any one of claims 1-8.

10. The application of the AEI molecular sieve of claim 9 in exhaust gas removal.

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