Composite ERI molecular sieve as well as synthesis method and application thereof
By synthesizing a composite ERI molecular sieve, the problems of high synthesis cost and insufficient low-temperature activity of existing Cu-SSZ-13 and SAPO-17 molecular sieves in diesel vehicle exhaust gas have been solved. A molecular sieve material with excellent catalytic performance has been prepared, which is suitable for NH3-SCR reaction and achieves efficient removal of NOx from diesel vehicle exhaust gas.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2024-10-30
- Publication Date
- 2026-05-12
AI Technical Summary
Existing Cu-SSZ-13 molecular sieves have high synthesis costs and high energy consumption in the removal of NOx from diesel vehicle exhaust, and insufficient low-temperature activity and stability. Rapidly synthesized ERI molecular sieves have poor hydrothermal stability, while SAPO-17 molecular sieves are weakly acidic and have limited NH3-SCR catalytic effects.
A composite ERI molecular sieve containing two phases, SAPO-17 and ERI molecular sieve, was synthesized. By adjusting the silica-alumina ratio and phosphorus-alumina ratio, and using N,N,N',N'-tetramethyl-1,6-hexanediamine as a template agent, combined with hydrothermal or solid-phase crystallization methods, a composite ERI molecular sieve with a uniform crystal morphology was prepared and used for NH3-SCR catalysis via copper ion exchange.
A molecular sieve catalytic material with good hydrothermal stability at both high and low temperatures has been developed, which broadens the temperature window and improves the activity and stability of the NH3-SCR catalyst, making it suitable for the efficient removal of NOx from diesel vehicle exhaust.
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Figure CN122010141A_ABST
Abstract
Description
Technical Field
[0001] This application relates to a composite ERI molecular sieve, its synthesis method and application, and belongs to the field of molecular sieves. Background Technology
[0002] Nitrogen oxides emitted from diesel vehicle exhaust are a major urban air pollutant, contributing to environmental problems such as acid rain and photochemical smog, threatening human health. The selective catalytic reduction (SCR) technology proposed by Engelhard involves injecting NH3 with urea and then selectively reducing NO using a catalyst. X (NH3-SCR) has high reaction efficiency and good stability, and is the mainstream development direction of denitrification technology.
[0003] Due to its wide temperature window and high hydrothermal stability, Cu-SSZ-13 has been commercially used for NO removal from diesel exhaust. X However, the synthesis of this molecular sieve requires the use of expensive and toxic N,N,N-trimethyladamantane ammonium hydroxide (TMAdaOH) as an organic template, resulting in high synthesis costs, high energy consumption, and environmental pollution. At the same time, its low-temperature activity and stability still need to be further improved to meet increasingly stringent exhaust emission standards.
[0004] Developing more small-pore cage-type molecular sieves is an important way to improve the low-temperature activity of NH3-SCR catalysts. Among these, ERI-type (Erionite) molecular sieves, composed of ERI and CAN-D6R cages (producing isolated copper ions), have attracted researchers' attention due to their abundant acid sites and isolated copper ions. A rapidly synthesized ERI-type molecular sieve has been reported in the literature (Zhu J, Liu Z, Xu L, et al. Journal of Catalysis, 2020, 391:346-356.), which shortens the crystallization time; however, the rapidly synthesized ERI exhibits poor high-temperature hydrothermal stability. The silicon content and distribution of SAPO-17 molecular sieve are difficult to improve and optimize, and its weak acidity also limits its NH3-SCR catalytic effect. Summary of the Invention
[0005] In view of this, the present invention provides a composite ERI molecular sieve, its synthesis method and application, the main purpose of which is to synthesize a molecular sieve catalytic material with good high and low temperature hydrothermal stability and a wide temperature window in NH3-SCR.
[0006] According to the first aspect of this application, a composite ERI molecular sieve is provided.
[0007] A composite ERI molecular sieve, wherein the XRD diffraction pattern of the composite ERI molecular sieve includes X-ray diffraction peaks at positions listed in the table below.
[0008] No. 2θ 1 7.69±0.1 2 9.73±0.1 3 11.81±0.1 4 13.32±0.1 5 15.70±0.1 6 16.66±0.1 7 19.05±0.1 8 19.53±0.1 9 20.71±0.1 10 21.48±0.1 11 23.81±0.1 12 24.68±0.1
[0009] Optionally, the composite ERI molecular sieve contains two phases: SAPO-17 molecular sieve and ERI molecular sieve.
[0010] The weight of ERI molecular sieve is 10 to 300 wt% of the total weight of SAPO-17 molecular sieve.
[0011] Optionally, the weight of the ERI molecular sieve is 20 to 100 wt% of the total weight of the SAPO-17 molecular sieve.
[0012] Optionally, the weight of the ERI molecular sieve is a value of the total weight of the SAPO-17 molecular sieve independently selected from any value or a range between 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 80wt%, 100wt%, 120wt%, 150wt%, 170wt%, 200wt%, 220wt%, 250wt%, 270wt%, and 300wt%.
[0013] Optionally, the anhydrous chemical composition of the composite ERI molecular sieve is expressed as follows:
[0014] nK(SixAlyPz)O 72
[0015] K represents the K in ERI molecular sieves. + Cations, n is the number of moles of (SixAlyPz)O 72 The number of moles of potassium ions, n = 0.3 to 2;
[0016] x, y, and z represent the mole fractions of Si, Al, and P, respectively, with ranges of x = 7–31, y = 5–18, and z = 3–11, and x + y + z = 36.
[0017] Optionally, the composite ERI molecular sieve has a silica-alumina ratio of 0.75 to 3 and a phosphorus-alumina ratio of 0.38 to 1.0.
[0018] In this application, the composite ERI molecular sieve contains both silicon-aluminum and SAPO regions, and its composition is flexible and adjustable. The silicon-aluminum ratio is adjustable between 0.75 and 3, and the phosphorus / aluminum ratio is adjustable between 0.38 and 1.0.
[0019] Optionally, the composite ERI molecular sieve has a uniform crystal morphology, consisting of 10×200nm rod-shaped primary particles assembled into a bundle shape, with a secondary particle size of 300-500nm.
[0020] According to a second aspect of this application, a method for synthesizing the aforementioned composite ERI molecular sieve is provided.
[0021] The synthesis method of the composite ERI molecular sieve described above includes the following steps:
[0022] S1. Obtain silica-alumina type ERI molecular sieve;
[0023] S2. Obtain SAPO molecular sieve, calcine to remove template agent, dissolve in water, ball mill, dry to obtain precursor Q;
[0024] S3. Prepare an aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine, add an aluminum source, a phosphorus source, ammonium chloride, precursor Q and a silica-alumina type ERI molecular sieve to it, mix evenly to obtain a gel, crystallize it, and obtain a composite ERI molecular sieve.
[0025] Optionally, in step S2, the SAPO molecular sieve is selected from at least one of SAPO-34 molecular sieve, SAPO-56 molecular sieve, and DNL-6 molecular sieve.
[0026] Optionally, in step S3, the mass ratio of the silica-alumina type ERI molecular sieve to the precursor Q is 0.1 to 3:1.
[0027] Optionally, in step S3, the molar ratio of the phosphorus source to the aluminum source is 0.5 to 1.5:1;
[0028] The number of moles of phosphorus source is calculated as P2O5, and the number of moles of aluminum source is calculated as Al2O3.
[0029] The mass ratio of the precursor Q to the total amount of the aluminum source and phosphorus source is 0.5 to 20:1;
[0030] The mass ratio of the aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine to the precursor Q is 1 to 50:1.
[0031] The aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine has a mass percentage content of 2% to 50%.
[0032] Optionally, the mass ratio of the silica-alumina type ERI molecular sieve to the precursor Q is independently selected from any value among 0.1, 0.2, 0.3, 0.4, 0.5, 0.8, 1.0, 1.2, 1.5, 1.7, 2.0, 2.2, 2.5, 2.7 and 3.0 or a range between any two.
[0033] Optionally, the molar ratio of the phosphorus source and the aluminum source is independently selected from any value among 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 and 1.5 or a range between any two.
[0034] Optionally, the mass ratio of the precursor Q to the total amount of the aluminum source and phosphorus source is independently selected from any value of 0.5, 1.0, 2.0, 5.0, 7.5, 10.0, 12.5, 15.0, 17.5 and 20 or a range between any two.
[0035] Optionally, the mass of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution and the precursor Q are independently selected from any value of 1,2,5,10,15,20,25,30,35,40,45 and 50 or a range between any two.
[0036] Optionally, the mass percentage of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution is independently selected from any value or a range between 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%.
[0037] Optionally, the phosphorus source is selected from at least one of phosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, and monoammonium hydrogen phosphate;
[0038] The aluminum source is selected from at least one of alumina, boehmite, and aluminum hydroxide.
[0039] In this application, the phosphorus and aluminum sources can be selected from common phosphorus and aluminum sources in the prior art. Phosphoric acid and NH4Cl are typically added during synthesis. If diamine hydrogen phosphate or monoammonium hydrogen phosphate is used directly as the phosphorus source, ammonium chloride is not required.
[0040] Optionally, the crystallization conditions are: a crystallization temperature of 150–220°C and a crystallization time of 2–72 h.
[0041] Optionally, after crystallization, the process may also include drying and calcination.
[0042] Optionally, the crystallization temperature is independently selected from any value or a range between 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, and 220°C.
[0043] Optionally, the crystallization time is independently selected from any value or a range between 2h, 5h, 10h, 20h, 30h, 40h, 50h, 60h, 70h, and 72h.
[0044] In this application, the crystallization process may be one or more of hydrothermal crystallization, solid-like phase crystallization, steam-assisted crystallization, and atmospheric pressure rotational crystallization.
[0045] In this application, in step S1, the silica-alumina type ERI molecular sieve can be commercially available or synthesized using existing techniques, such as the synthesis method described in the reference (Zhu, Jie, et al. Journal of Catalysis 391(2020):346-356.).
[0046] In this application, in step S2, the high-silica SAPO molecular sieve can be commercially available or synthesized using existing techniques.
[0047] As a specific implementation method, the synthesis method of the composite ERI molecular sieve includes the following steps:
[0048] (1) According to the methods in the prior art, a silica-alumina type ERI molecular sieve is hydrothermally synthesized for later use;
[0049] (2) The synthesized SAPO molecular sieve was calcined at 600℃ for 2 hours to remove the template agent and then dispersed in an aqueous medium. After ball milling for about 5 hours, the precursor Q was obtained.
[0050] (3) The N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution, aluminum source, phosphorus source, ERI seed crystals described in step (1) and precursor Q described in step (2) are mixed and sealed under hydrothermal reaction conditions. After complete crystallization, the product is separated, washed and dried to obtain composite ERI molecular sieve.
[0051] According to a third aspect of this application, an application of the aforementioned composite ERI molecular sieve is provided.
[0052] The aforementioned composite ERI molecular sieve, after copper ion exchange, is used in the selective reduction denitrification reaction of ammonia. This composite ERI molecular sieve is loaded with Cu. 2+ After ionization, it can be used as a denitrification catalyst (NH3-SCR), showing excellent activity and catalyst stability.
[0053] Optionally, the copper ion exchange is performed by placing the composite ERI molecular sieve in a copper salt solution for ion exchange.
[0054] Specifically, the composite ERI molecular sieve was added to 100g of 0.02mol / L copper acetate solution and ion exchanged at 80℃ for 5h.
[0055] Optionally, after ion exchange, the catalyst is obtained by calcination at 550–650 °C for 2–6 h.
[0056] Optionally, the catalyst is loaded into the reactor and activated by passing reactant gas through it at 550–650°C for 30 min, then cooled to 110–150°C, and tested point by point; wait 20 min at each temperature point until the reaction stabilizes, and record the data; the test temperature range is 150–650°C.
[0057] The composition of the reaction feed gas includes:
[0058] NO: 500ppm, NH3: 500ppm, O2: 14%, H2O: 4.5%, N2 as the balance gas, gas flow rate 1000mL / min, corresponding to a space velocity of 180000h. -1 .
[0059] The beneficial effects that this application can produce include:
[0060] 1) The composite ERI molecular sieve provided in this application not only has the ERI topology and uniform submicron bundle-like crystal morphology, but also has silicon-aluminum and SAPO regions, combining the characteristics and advantages of SAPO-17 and silicon-aluminum ERI molecular sieves.
[0061] 2) The composite ERI molecular sieve provided in this application, in DeNO... x It exhibits excellent catalytic performance in catalytic selective reduction denitrification. Attached Figure Description
[0062] Figure 1 The X-ray diffraction pattern is shown for the composite ERI sample prepared in Example 1 of this invention.
[0063] Figure 2 The image shown is a scanning electron microscope image of the composite ERI sample prepared in Example 1 of this invention, at a scale of 500 nm.
[0064] Figure 3 The X-ray diffraction pattern is shown for the composite ERI sample prepared in Example 2 of this invention.
[0065] Figure 4 The image shown is a scanning electron microscope image of the composite ERI sample prepared in Example 2 of this invention, at a scale of 500 nm.
[0066] Figure 5 This is a scanning electron microscope image of the silicon-aluminum type ERI sample prepared in Comparative Example 1 of this invention, with a scale of 1 μm.
[0067] Figure 6 This is a scanning electron microscope image of the SAPO-17 sample prepared in Comparative Example 2 of this invention, with a scale of 2 μm.
[0068] Figure 7 The composite ERI sample prepared in Example 1 of this invention was used for the selective catalytic reduction of NO by NH3-.x (NH3-SCR) performance test result curve.
[0069] Figure 8 The ERI sample prepared for Comparative Example 1 of this invention underwent selective catalytic reduction of NO by NH3-. x (NH3-SCR) performance test result curve.
[0070] Figure 9 The SAPO-17 sample prepared for Comparative Example 2 of this invention underwent selective catalytic reduction of NO by NH3-. x (NH3-SCR) performance test result curve. Detailed Implementation
[0071] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0072] Unless otherwise specified, the raw materials used in the embodiments of this application are all purchased commercially and used directly without special treatment.
[0073] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.
[0074] The analysis method in the embodiments of this application is as follows:
[0075] X-ray powder diffraction (XRD) phase analysis was performed using an X'Pert PRO X-ray diffractometer from PANalytical, Netherlands, with a Cu target, Kα radiation source (λ = 0.15418 nm), voltage 40 kV, and current 40 mA.
[0076] The scanning electron microscope (SEM) used for testing was a Hitachi SU8020 field emission scanning electron microscope with an accelerating voltage of 2kV.
[0077] In the examples, the bulk elemental composition was determined using a Philips Magix 2424 X-ray fluorescence analyzer (XRF).
[0078] The specific experimental procedures and test conditions for the NH3-SCR catalytic reaction in this application are as follows:
[0079] First, 5g of the composite ERI molecular sieve prepared in Example 1 was added to 100g of 0.02mol / L copper acetate solution, and ion exchange was performed at 80℃ for 5h. The sample was then centrifuged and washed with deionized water until neutral. After drying in a 120℃ oven, it was calcined at 600℃ for 5h. The calcined sample was further pressed into tablets and sieved. 0.3g of 60-80 mesh sample was weighed and mixed with 1.9g of quartz sand (60-80 mesh), and loaded into a fixed-bed reactor. Nitrogen gas was purged at 600℃ for 40min, and then the temperature was lowered to 150℃ to begin the reaction. Tests were performed point by point; each temperature point was allowed to stabilize for 20min before data was recorded. The test temperature range was 150–650℃.
[0080] The reactant gases were: NO: 500 ppm, NH3: 500 ppm, O2: 14%, H2O: 4.5%, with N2 as the equilibrium gas. The gas flow rate was 1000 mL / min, corresponding to a space velocity of 180,000 h⁻¹. -1 .
[0081] High-temperature hydrothermal aging conditions: O2: 14%, H2O: 4.5%, N2 as balance gas, aging temperature 750℃, aging time 16h;
[0082] Low-temperature hydrothermal treatment conditions: The sample was soaked in water at 80℃ for 24 hours, then centrifuged, dried in an oven at 120℃, and then loaded into a fixed-bed reactor. The above experimental process was repeated.
[0083] The reaction tail gas was analyzed online using a Bruker Tensor 27 instrument.
[0084] Example 1
[0085] (1) Add 10.2g tetrapropylammonium hydroxide, 6g silica sol (27.3%), and 0.82g aluminum sec-butoxide to a 50ml reactor. Stir at room temperature for 1 hour until the sol is completely homogeneous. Seal the reactor and crystallize in an oven at 95℃ for 20h. After cooling, add 0.14g KOH and 1.68g hexamethylammonium bromide to the resulting solution. Stir until homogeneous, seal the reactor, and crystallize in an oven at 150℃ for 72h to obtain ERI molecular sieves for later use.
[0086] (2) The preparation method of the precursor Q is as follows: 5g of SAPO-34 molecular sieve that has been calcined to remove the organic template agent is evenly dispersed in 20g of water, placed in a ball mill, balanced with agate balls, and then ball milled at high speed at 500Hz for 5h. The slurry is then collected, dried in an oven, and the solid is collected as precursor Q for later use.
[0087] (3) Prepare 20g of 10wt% N,N,N,N-tetramethyl-1,6-hexanediamine (R) aqueous solution, and add 2g of precursor Q, 0.178g of phosphoric acid, 0.108g of alumina, 0.12g of ammonium chloride and 0.2g of the prepared ERI seed crystals to it in sequence. After stirring evenly at room temperature, transfer the gel to a stainless steel reactor. After placing the reactor in an oven, heat it to 200℃ and react for a certain time, then cool it down to complete the crystallization. Centrifuge the solid product, wash it, dry it in air at 120℃, and calcine it at 550℃ for 6h to obtain a molecular sieve sample (sample name: SAPO-17-ERI 10%). The XRD pattern and SEM image of the product in Example 1 are attached. Figure 1 and 2 .
[0088] like Figure 1 As shown, the XRD diffraction pattern of SAPO-17-ERI 10% molecular sieve includes X-ray diffraction peaks at the positions listed in Table 1 below.
[0089] Table 1
[0090] No. 2θ 1 7.69 2 9.73 3 11.81 4 13.32 5 15.70 6 16.66 7 19.05 8 19.53 9 20.71 10 21.48 11 23.81 12 24.68
[0091] like Figure 2 As shown in the SEM image of SAPO-17-ERI 10% molecular sieve, the molecular sieve crystals have a uniform morphology and are assembled from 10×200nm rod-shaped primary particles into a bundle-like shape. The secondary particle size of the crystals is between 300-500nm.
[0092] Example 2
[0093] (1) Add 10.2g tetrapropylammonium hydroxide, 6g silica sol (27.3%), and 0.82g aluminum sec-butoxide to a 50ml reactor. Stir at room temperature for 1 hour until the sol is completely homogeneous. Seal the reactor and crystallize in an oven at 95℃ for 20h. After cooling, add 0.14g KOH and 1.68g hexamethylammonium bromide to the solution. Stir until homogeneous, seal the reactor, and crystallize in an oven at 150℃ for 72h to obtain ERI molecular sieves for later use.
[0094] (2) The preparation method of the precursor Q is as follows: 5g of SAPO-56 molecular sieve that has been calcined to remove the organic template agent is evenly dispersed in 20g of water, placed in a ball mill, balanced with agate balls, and then ball milled at high speed at 500Hz for 5h. The slurry is then collected, placed in an oven to dry, and the solid is collected as precursor Q for later use.
[0095] (3) Prepare 20g of 10wt% N,N,N,N-tetramethyl-1,6-hexanediamine (R) aqueous solution, and add 2g of precursor Q, 0.178g of phosphoric acid, 0.108g of alumina, 0.12g of ammonium chloride and 0.4g of the prepared ERI seed crystals to it in sequence. After stirring evenly at room temperature, transfer the gel to a stainless steel reactor. After placing the reactor in an oven, heat it to 200℃ and react for a certain time, then cool it down to complete the crystallization. Centrifuge the solid product, wash it, dry it in air at 120℃, and calcine it at 550℃ for 6h to obtain a molecular sieve sample (sample name: SAPO-17-ERI20%). The XRD pattern and SEM image of the product in Example 2 are attached. Figure 3 and 4 .
[0096] like Figure 3 As shown, the XRD diffraction pattern of SAPO-17-ERI 20% molecular sieve includes X-ray diffraction peaks at the positions listed in Table 2 below.
[0097] Table 2
[0098]
[0099]
[0100] like Figure 4 As shown in the SEM image of SAPO-17-ERI 20% molecular sieve, the molecular sieve crystals have a uniform morphology and are assembled from 10×200nm rod-shaped primary particles into a bundle-like shape. The secondary particle size of the crystals is between 300-500nm.
[0101] Examples 3-7
[0102] The operation is the same as in Example 1, except that the ratio of ERI is changed, as shown in Table 3.
[0103] Table 3
[0104]
[0105] Application Example 1 (NH3-SCR Catalytic Reaction)
[0106] S17-ERI10% (Example 1) NH3- selective catalytic reduction of NO x (NH3-SCR) performance test.
[0107] Specific experimental procedures and reaction conditions are detailed in the detailed implementation method section. The copper loading in the sample was 3.0%. The reaction results are shown below. Figure 7The activity temperature window of the composite ERI molecular sieve is 175–550℃, which is basically the same as that of SAPO-17; however, compared to SAPO-17 (see... Figure 9 The composite ERI molecular sieve exhibits excellent low-temperature hydrothermal stability, achieving a conversion rate of over 90% at 250–550℃; simultaneously, compared to pure ERI samples (see...), it demonstrates superior performance. Figure 8 The composite ERI molecular sieve exhibits better high-temperature hydrothermal stability, with a conversion rate exceeding 90% within a temperature window of 250–500℃. This demonstrates that the composite ERI sample possesses excellent high and low-temperature hydrothermal stability and a wide temperature window.
[0108] Comparative Example 1
[0109] 10.2 g tetrapropylammonium hydroxide, 6 g silica sol (27.3%), and 0.82 g aluminum sec-butoxide were added to a 50 ml reactor. The mixture was stirred at room temperature for 1 hour until the sol was completely homogeneous. The reactor was then sealed and crystallized in an oven at 95 °C for 20 h. After cooling, 0.14 g KOH and 1.68 g hexamethylammonium bromide were added to the CDM solution. The mixture was stirred until homogeneous, and the reactor was sealed and crystallized in an oven at 150 °C for 72 h to obtain the ERI molecular sieve (named ERI-0.14-72h), which served as control sample 1. The corresponding SEM image of control sample 1 is shown below. Figure 5 The particles exhibit an ellipsoidal shape of approximately 500 nm. The copper loading in the copper-exchanged sample was 2.8%, and the catalytic reaction results are shown below. Figure 8 It can be seen that the SCR activity of the ERI-0.14-72h sample after hydrothermal aging was poor.
[0110] Comparative Example 2
[0111] (1) The preparation method of the precursor Q is as follows: 5g of high-silica SAPO molecular sieve that has been calcined to remove the organic template agent is evenly dispersed in 20g of water, placed in a ball mill, balanced with agate balls, and then ball-milled at high speed at 500Hz for 5h. The sauce is then collected, placed in an oven to dry and collect the solid, which is used as precursor Q for later use.
[0112] (2) Prepare 20g of 10wt% N,N,N,N-tetramethyl-1,6-hexanediamine (R) aqueous solution. Add 2g of precursor Q, 0.178g of phosphoric acid, 0.108g of boehmite, and 0.12g of ammonium chloride sequentially to the solution. After stirring evenly at room temperature, transfer the gel to a stainless steel reactor. Place the reactor in an oven, heat to 200℃, react for a certain time, then cool to complete crystallization. Centrifuge the solid product, wash, and dry in air at 120℃ to obtain the molecular sieve powder sample SAPO-17, which serves as control sample 2. The SEM image of control sample 2 is shown below. Figure 6It exhibits hexagonal prism-shaped crystals with a wavelength of approximately 600 nm. The copper loading in the copper-exchanged sample is 3.0%, and the catalytic reaction results are shown in [Figure number missing]. Figure 9 The SAPO-17 sample has a wide catalytic temperature window, but its low-temperature SCR activity is poor.
[0113] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A composite ERI molecular sieve, characterized in that, The XRD diffraction pattern of the composite ERI molecular sieve includes X-ray diffraction peaks at positions listed in the table below. 。 2. The composite ERI molecular sieve according to claim 1, characterized in that, The composite ERI molecular sieve contains two phases: SAPO-17 molecular sieve and ERI molecular sieve. Among them, the weight of ERI molecular sieve is 10 to 300 wt% of the total weight of SAPO-17 molecular sieve; Preferably, the weight of the ERI molecular sieve is 20 to 100 wt% of the total weight of the SAPO-17 molecular sieve.
3. The composite ERI molecular sieve according to claim 1, characterized in that, The anhydrous chemical composition of the composite ERI molecular sieve is expressed as follows: nK·(SixAlyPz)O 72 K represents the K in ERI molecular sieves. + Cations, n is the number of moles of (SixAlyPz)O 72 The number of moles of potassium ions, n = 0.3 to 2; x, y, and z represent the mole fractions of Si, Al, and P, respectively, with ranges of x = 7–31, y = 5–18, and z = 3–11, and x + y + z = 36.
4. The composite ERI molecular sieve according to claim 1, characterized in that, The composite ERI molecular sieve has a silica-to-alumina ratio of 0.75–3 and a phosphorus-to-alumina ratio of 0.38–1.
0.
5. The composite ERI molecular sieve according to claim 1, characterized in that, The composite ERI molecular sieve has a uniform crystal morphology, consisting of rod-shaped primary particles of 10×200nm assembled into a bundle shape, with a secondary particle size of 300-500nm.
6. The method for synthesizing the composite ERI molecular sieve according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Obtain silica-alumina type ERI molecular sieve; S2. Obtain SAPO molecular sieve, calcine to remove template agent, dissolve in water, ball mill, dry to obtain precursor Q; S3. Prepare an aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine, add an aluminum source, a phosphorus source, ammonium chloride, precursor Q and a silica-alumina type ERI molecular sieve to it, mix evenly to obtain a gel, crystallize it, and obtain a composite ERI molecular sieve.
7. The synthesis method according to claim 6, characterized in that, In step S2, the high-silica SAPO molecular sieve is selected from at least one of SAPO-34 molecular sieve, SAPO-56 molecular sieve, and DNL-6 molecular sieve.
8. The synthesis method according to claim 6, characterized in that, In step S3, the mass ratio of the silica-alumina type ERI molecular sieve to the precursor Q is 0.1 to 3:1; The mass ratio of the precursor Q to the total amount of the aluminum source and phosphorus source is 0.5 to 20:1; The mass ratio of the aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine to the precursor Q is 1 to 50:
1. The mass percentage of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution is 2% to 50%. Preferably, the molar ratio of the phosphorus source to the aluminum source is 0.5 to 1.5:1; The number of moles of phosphorus source is calculated as P2O5, and the number of moles of aluminum source is calculated as Al2O3. Preferably, the phosphorus source is selected from at least one of phosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, and monoammonium hydrogen phosphate; The aluminum source is selected from at least one of alumina, boehmite, and aluminum hydroxide.
9. The synthesis method according to claim 6, characterized in that, The crystallization conditions are: a crystallization temperature of 150–220°C and a crystallization time of 2–72 h; Preferably, after crystallization, the process further includes drying and calcination steps.
10. The application of the composite ERI molecular sieve according to any one of claims 1 to 5 after copper ion exchange in the selective reduction denitrification reaction of ammonia.