Composite molecular sieves, their preparation methods and applications

Abstract

This invention relates to the field of catalytic material synthesis, and discloses a composite molecular sieve, its preparation method, and its applications. The composite molecular sieve comprises an ATV structure and an SFO structure. This composite molecular sieve exhibits high crystallinity, a large specific surface area, micropore area, and micropore volume, and shows potential application prospects in acid catalysis and gas adsorption.

Description

Technical Field

[0001] This invention relates to the field of catalytic material synthesis, specifically to a composite molecular sieve, a method for preparing the composite molecular sieve, the composite molecular sieve prepared by the method, and the application of the composite molecular sieve as a catalyst in acid catalytic reactions and in gas adsorption treatment. Background Technology

[0002] Composite molecular sieves are a type of molecular sieve with a special structure. They are co-crystallizations formed by two or more molecular sieves, or composite crystals possessing the structural characteristics of two or more molecular sieves. Due to the special structure of composite molecular sieves, they possess a more rationally distributed pore structure and acidity, overcoming the limitations of individual molecular sieves. This allows them to better meet the needs of applications such as catalysis and has broad application prospects.

[0003] SFO-structured molecular sieves are important phosphorus-aluminum based molecular sieves that have attracted widespread attention and research. The framework structure of SFO-structured molecular sieves belongs to the monoclinic crystal system, with space group C1² / m¹ and cell parameters of... With α = 90.00°, β = 90.016°, and γ = 90.00°, this sieve possesses a two-dimensional pore structure with intersecting twelve-membered and eight-membered rings. The twelve-membered ring pore size along the

[001] direction is 0.69 × 0.71 nm, and the eight-membered ring pore size along the

[010] direction is 0.39 × 0.31 nm, classifying it as a macroporous molecular sieve. Due to its unique pore structure and acidic characteristics, it shows potential catalytic application prospects in processes such as straight-chain alkane isomerization, xylene isomerization, and hydrotreating / cracking.

[0004] ATV-structured molecular sieves are also an important type of phosphorus-aluminum based molecular sieve, attracting widespread attention and research. The framework structure of ATV-structured molecular sieves belongs to the orthorhombic crystal system, with space group Cmme and cell parameters of [missing information]. With α = 90.00°, β = 90.016°, and γ = 90.00°, it possesses a one-dimensional eight-membered ring pore structure. The pore size of the eight-membered ring along the

[100] direction is 0.30 × 0.49 nm, classifying it as a small-pore molecular sieve. Due to its unique pore structure, it has potential applications in the adsorption and separation of small molecule gases and the isomerization of straight-chain alkanes.

[0005] While methods for synthesizing SFO and ATV structured molecular sieves using various template agents have been introduced, no methods for preparing composite molecular sieves containing both SFO and ATV structures have been reported. Summary of the Invention

[0006] The purpose of this invention is to provide a composite molecular sieve containing both SFO and ATV structures, its preparation method, and its application. In this invention, 4-dimethylaminopyridine is used as a template agent, and a composite molecular sieve containing both SFO and ATV structures is prepared and synthesized using raw materials in a certain ratio. This composite molecular sieve has high crystallinity, which solves the problem that existing technologies cannot synthesize composite molecular sieves containing both SFO and ATV structures.

[0007] To achieve the above objectives, the first aspect of the present invention provides a composite molecular sieve, the composite molecular sieve comprising an ATV structure and an SFO structure.

[0008] Preferably, by weight, the composite molecular sieve contains 10-90% ATV structured molecular sieve and 10-90% SFO structured molecular sieve.

[0009] The second aspect of the present invention provides a method for preparing a composite molecular sieve, the method comprising using a hydrothermal synthesis method to mix a combination of a phosphorus source and an aluminum source and / or a phosphorus-aluminum source with a silicon source, a template agent R and water and synthesize the composite molecular sieve.

[0010] Wherein, the template agent R is 4-dimethylaminopyridine;

[0011] Wherein, the phosphorus in the combination of phosphorus source and aluminum source and / or the phosphorus-aluminum source is calculated as P2O5, the aluminum as Al2O3, the silicon source as SiO2, and the molar ratio of P2O5, Al2O3, SiO2, template agent R and water is 0.8-1.2:1:0.1-0.5:1-5:10-80;

[0012] The hydrothermal crystallization temperature is 200-220℃, and the time is 6-9 days.

[0013] A third aspect of the present invention provides a composite molecular sieve prepared by the method described above.

[0014] The fourth aspect of the present invention provides the application of the composite molecular sieve described above as a catalyst in acid-catalyzed reactions.

[0015] The fifth aspect of the present invention provides the application of the composite molecular sieve described above as a catalyst in gas adsorption treatment.

[0016] This invention provides a composite molecular sieve containing both ATV and SFO structures. This composite molecular sieve has high crystallinity and large specific surface area, micropore area and micropore volume. It has potential catalytic application prospects in acid catalytic reactions such as the conversion of oxygen-containing compounds to olefins and the isomerization reaction of straight-chain alkanes. It is also suitable for gas adsorption treatment, such as the adsorption and separation of small molecule gases. Attached Figure Description

[0017] Figure 1 The XRD pattern of the composite molecular sieve sample synthesized in Example 1 is shown below.

[0018] Figure 2 SEM image of the composite molecular sieve sample synthesized in Example 1;

[0019] Figure 3 The XRD pattern of the composite molecular sieve sample synthesized in Example 2;

[0020] Figure 4 This is a SEM image of the composite molecular sieve sample synthesized in Example 2. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The first aspect of the present invention provides a composite molecular sieve, the composite molecular sieve comprising an ATV structure and an SFO structure.

[0023] Preferably, by weight, the ATV structure molecular sieve content in the composite molecular sieve is 10-90% by weight, for example, it can be 10, 20, 30, 40, 50, 60, 70, 80, 90% by weight or any range between any two values, and the SFO structure molecular sieve content is 10-90% by weight, for example, it can be 10, 20, 30, 40, 50, 60, 70, 80, 90% by weight or any range between any two values.

[0024] Preferably, the BET specific surface area of ​​the composite molecular sieve is not less than 560 m². 2 / g, for example, can be 560, 565, 570, 575, 580, 585, 590m 2 / g or higher and any range between any two values.

[0025] Preferably, the total pore volume of the composite molecular sieve is not less than 0.26 cm³. 3 / g, for example, can be 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32cm 3 / g or higher and any range between any two values.

[0026] Preferably, the micropore area of ​​the composite molecular sieve is not less than 550 m². 2 / g, for example, can be 550, 555, 560, 565, 570, 575, 580, 585, 590m 2 / g or higher and any range between any two values.

[0027] Preferably, the micropore volume of the composite molecular sieve is not less than 0.25 cm³. 3 / g, for example, can be 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32cm 3 / g or higher and any range between any two values.

[0028] The second aspect of the present invention provides a method for preparing a composite molecular sieve, the method comprising using a hydrothermal synthesis method to mix a combination of a phosphorus source and an aluminum source and / or a phosphorus-aluminum source with a silicon source, a template agent R and water and synthesize the composite molecular sieve.

[0029] Wherein, the template agent R is 4-dimethylaminopyridine;

[0030] Wherein, the phosphorus in the combination of phosphorus source and aluminum source and / or the phosphorus-aluminum source is calculated as P2O5, the aluminum as Al2O3, and the silicon source as SiO2, the molar ratio of P2O5, Al2O3, SiO2, template agent R and water is 0.8-1.2 (e.g., it can be 0.8, 0.9, 1, 1.1, 1.2 and any range between any two values): 1: 0.1-0.5 (e.g., it can be 0.1, 0.2, 0.3, 0.4, 0.5 and any range between any two values): 1-5 (e.g., it can be 1, 2, 3, 4, 5 and any range between any two values): 10-80 (e.g., it can be 10, 20, 40, 60, 80 and any range between any two values);

[0031] The hydrothermal crystallization temperature is 200-220℃, for example, it can be 200, 205, 210, 215, 220℃ or any range between any two values, and the time is 6-9 days, for example, it can be 6, 7, 8, 9 days or any range between any two values.

[0032] The hydrothermal synthesis method can be either the aluminum phosphate liquid-phase conversion method or a traditional hydrothermal synthesis method. The aluminum phosphate liquid-phase conversion method means that the phosphorus and aluminum sources are provided at least in the form of aluminum phosphate, while the traditional hydrothermal synthesis method means that the phosphorus and aluminum sources need to be added separately.

[0033] Preferably, the synthesis method includes:

[0034] (1) Mix a combination of phosphorus source and aluminum source and / or phosphorus-aluminum source, silicon source, template agent R and water and perform hydrothermal crystallization;

[0035] (2) The hydrothermal crystallization product is subjected to solid-liquid separation, and the obtained solid phase is dried and optionally calcined to obtain the composite molecular sieve.

[0036] Preferably, the phosphorus source is selected from at least one of orthophosphoric acid, phosphorous acid, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and organophosphorus compounds, wherein the organophosphorus compound is preferably trimethylphosphorus and / or triethylphosphorus.

[0037] Preferably, the aluminum source is selected from at least one of aluminum salts, boehmite, aluminum isopropoxide, aluminum hydroxide gel, and activated alumina, and the aluminum salt is preferably aluminum chloride and / or aluminum sulfate.

[0038] Preferably, the aluminum phosphate source is aluminum phosphate; preferably, the aluminum phosphate is crystalline aluminum phosphate. Crystalline aluminum phosphate can be prepared according to CN111422843A, which is incorporated herein by reference.

[0039] Preferably, the silicon source is selected from at least one of silica sol, activated silica, solid silica gel, silicon-containing organic compounds of Formula I, and precipitated silica.

[0040]

[0041] In Formula I, R1, R2, R3 and R4 are each independently a C1-C4 alkyl group.

[0042] Preferably, the silicon-containing organic compound is tetraethyl orthosilicate.

[0043] Unless otherwise specified, all reagents or raw materials used in this invention can be obtained commercially.

[0044] Preferably, the conditions for hydrothermal crystallization include a temperature of 200-215°C and a time of 6-8 days. Hydrothermal crystallization can be carried out in conventional containers, such as closed polytetrafluoroethylene containers, under autogenous pressure during the reaction.

[0045] In this invention, there are no particular limitations on the method of solid-liquid separation of the hydrothermal crystallization product; for example, the solid-liquid separation method can be filtration. The product after solid-liquid separation can be washed, and the conditions are not particularly limited and can be carried out according to conventional techniques in the art, which will not be elaborated further here.

[0046] According to one specific embodiment of the present invention, the hydrothermal crystallization product is first cooled to room temperature and then filtered.

[0047] In this invention, the drying conditions are not particularly limited, but drying at 60-120°C for 10-24 hours is preferred.

[0048] Preferably, the roasting conditions include: a temperature of 500-700℃ and a time of 3-6 hours.

[0049] A third aspect of the present invention provides a composite molecular sieve prepared by the method described above.

[0050] For a description of the composite molecular sieve, please refer to the first aspect, which will not be repeated here.

[0051] The fourth aspect of the present invention provides the application of the composite molecular sieve described above as a catalyst in acid-catalyzed reactions.

[0052] Preferably, the acid-catalyzed reaction is a reaction of oxygen-containing compounds to olefins or a straight-chain alkane isomerization reaction.

[0053] The conditions for the acid-catalyzed reaction can be adjusted according to specific circumstances.

[0054] The fifth aspect of the present invention provides the application of the composite molecular sieve described above as a catalyst in gas adsorption treatment.

[0055] The present invention will be described in detail below through embodiments.

[0056] In the following embodiments, X-ray powder diffraction phase analysis (XRD) was performed using a Panaco Empyrean diffractometer from the Netherlands, which is equipped with a PIXcel. 3D Detector. Test conditions: Cu target, Kα radiation, Ni filter, tube voltage 40kV, tube current 40mA, scanning range 5°-50°. The weight percentage of molecular sieves with different phase structures in the composite molecular sieve is determined based on the highest intensity characteristic peak before 10° in the XRD spectrum of each molecular sieve. That is, the weight percentage of each phase is calculated based on the peak height of the highest intensity characteristic peak before 10° of each molecular sieve. The specific calculation method is as follows: the highest intensity characteristic peak before 10° of the ATV structure molecular sieve is 9.5°; the highest intensity characteristic peak before 10° of the SFO structure molecular sieve is 7.7°; the peak heights of the highest intensity characteristic peak before 10° of the ATV structure molecular sieve and the SFO structure molecular sieve are denoted as S1 and S2, respectively; the weight percentage of ATV structure molecular sieve in the composite molecular sieve = S1 / (S1+S2)×100%; the weight percentage of SFO structure molecular sieve = S2 / (S1+S2)×100%.

[0057] In the following examples, scanning electron microscopy (SEM) morphology analysis was performed using a Hitachi S4800 SEM. Test conditions: After drying and grinding, the samples were adhered to conductive adhesive. The accelerating voltage of the analytical electron microscope was 5.0 kV, and the magnification ranged from 20 to 800,000 times.

[0058] In the following examples, the BET analysis was performed using a Micromeritics ASAP 2010 adsorption analyzer. Test conditions: The weighed sample was evacuated to a vacuum of 1.33 × 10⁻⁶ at 350°C. -2 Sample pretreatment was performed at constant temperature and pressure for 15 hours. At liquid nitrogen temperature -196℃, the adsorption and desorption of nitrogen were measured under different specific pressures p / p0, yielding nitrogen adsorption-desorption isotherms. The BET specific surface area was calculated using the BET formula, and the micropore specific surface area and micropore volume were calculated using the t-plot method. The total pore volume was calculated based on the adsorption amount at p / p0 = 0.98.

[0059] In the following examples, crystalline aluminum phosphate was prepared according to the method described in Example 2 of CN111422843A, with a solid content of 100% and P2O5 / Al2O3 = 0.99.

[0060] Example 1

[0061] Add deionized water to a polytetrafluoroethylene liner, then add crystalline aluminum phosphate (100% solid content, P2O5 / Al2O3 = 0.99), followed by solid silica gel (90% SiO2 mass fraction), and then 4-dimethylaminopyridine (C7H) 10 N2 (mass fraction 99%), stirred and mixed evenly. The molar ratios of the components added are: P2O5 / Al2O3 = 0.99, SiO2 / Al2O3 = 0.3, R / Al2O3 = 3.0, H2O / Al2O3 = 20.

[0062] The polytetrafluoroethylene liner containing the above reaction mixture was capped, placed in a stainless steel autoclave and sealed, and then placed in a rotating convection oven at a speed of 20 r / min for crystallization under autogenous pressure: crystallization at 210℃ for 6 days. After crystallization, the product was removed from the room temperature, filtered, washed, and dried at 110℃ for 12 hours to obtain a solid sample.

[0063] The XRD pattern of the solid sample is shown in the figure. Figure 1 Referring to the XRD pattern of SFO structure molecular sieve in patent CN114455605B and the XRD pattern of ATV structure molecular sieve in Microporous and Mesoporous Materials 344(2022):112245, it was confirmed that the prepared solid sample was a composite molecular sieve of ATV and SFO structures. Quantitative XRD diffraction showed that the weight percentage of ATV structure molecular sieve in the composite molecular sieve was 37.9% and the weight percentage of SFO structure molecular sieve was 62.1%.

[0064] SEM photos are available. Figure 2The solid samples exhibit two different crystal morphologies: small granular and large blocky.

[0065] The obtained composite molecular sieve was calcined at 550℃ for 3 hours and subjected to BET analysis. The results of its surface area and pore volume are shown in Table 1. The obtained composite molecular sieve has good micropore area and micropore volume, indicating that the composite molecular sieve has a complete crystal structure and high crystallinity.

[0066] Example 2

[0067] Add deionized water to a polytetrafluoroethylene liner, then add crystalline aluminum phosphate (100% solid content, P2O5 / Al2O3 = 0.99), followed by solid silica gel (90% SiO2 mass fraction), and then 4-dimethylaminopyridine (C7H) 10 N2 (mass fraction 99%), stirred and mixed evenly. The molar ratios of the components added are: P2O5 / Al2O3 = 0.99, SiO2 / Al2O3 = 0.2, R / Al2O3 = 2.5, H2O / Al2O3 = 25.

[0068] The polytetrafluoroethylene liner containing the above reaction mixture was capped, placed in a stainless steel autoclave and sealed, and then placed in a rotating convection oven at a speed of 20 r / min for crystallization under autogenous pressure: crystallization at 210℃ for 7 days. After crystallization, the product was removed from the room temperature, filtered, washed, and dried at 110℃ for 12 hours to obtain a solid sample.

[0069] The XRD pattern of the solid sample is shown in the figure. Figure 3 It is a composite molecular sieve with ATV and SFO structures. Quantitative analysis by XRD diffraction shows that the weight percentage of ATV structure molecular sieve in the composite molecular sieve is 38.0%, and the weight percentage of SFO structure molecular sieve is 62.0%.

[0070] SEM photos are available. Figure 4 The solid samples exhibit two different crystal morphologies: small granular and large blocky.

[0071] The obtained composite molecular sieve was calcined at 550℃ for 3 hours and subjected to BET analysis. The results of its surface area and pore volume are shown in Table 1. The obtained composite molecular sieve has good micropore area and micropore volume, indicating that the composite molecular sieve has a complete crystal structure and high crystallinity.

[0072] Example 3

[0073] Add deionized water to the polytetrafluoroethylene liner, then add crystalline aluminum phosphate (100% solid content, P2O5 / Al2O3 = 0.99), followed by silica sol (30% SiO2 mass fraction), and then add 4-dimethylaminopyridine (C7H). 10N2 (mass fraction 99%), stirred and mixed evenly. The molar ratios of the components added are: P2O5 / Al2O3 = 0.99, SiO2 / Al2O3 = 0.1, R / Al2O3 = 2.0, H2O / Al2O3 = 20.

[0074] The polytetrafluoroethylene liner containing the above reaction mixture was capped, placed in a stainless steel autoclave and sealed, and then placed in a rotating convection oven at a speed of 20 r / min for crystallization under autogenous pressure: crystallization at 210℃ for 7 days. After crystallization, the product was removed from the room temperature, filtered, washed, and dried at 110℃ for 12 hours to obtain a solid sample.

[0075] XRD analysis of the solid sample revealed it to be a composite molecular sieve of ATV and SFO structures. Quantitative XRD analysis showed that the ATV structure molecular sieve comprised 45.7% by weight, while the SFO structure molecular sieve comprised 54.3% by weight. SEM images showed that the solid sample exhibited two different crystal morphologies: small particles and large masses.

[0076] The obtained composite molecular sieve was calcined at 550℃ for 3 hours and subjected to BET analysis. The results of its surface area and pore volume are shown in Table 1. The obtained composite molecular sieve has good micropore area and micropore volume, indicating that the composite molecular sieve has a complete crystal structure and high crystallinity.

[0077] Table 1

[0078]

[0079] Example 4

[0080] The operation was carried out according to the method described in Example 1, except that R / Al2O3 = 4.5 and H2O / Al2O3 = 50.

[0081] XRD analysis of the solid sample revealed it to be a composite molecular sieve of ATV and SFO structures. Quantitative XRD analysis showed that the ATV structure molecular sieve comprised 49.2% by weight, while the SFO structure molecular sieve comprised 50.8% by weight. SEM images showed that the solid sample exhibited two different crystal morphologies: small particles and large masses.

[0082] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite molecular sieve, characterized in that, The composite molecular sieve comprises an ATV structure and an SFO structure; The method for preparing the composite molecular sieve includes using a hydrothermal synthesis method to mix a combination of phosphorus source and aluminum source and / or phosphorus-aluminum source with silicon source, template agent R and water to obtain a composite molecular sieve. Wherein, the template agent R is 4-dimethylaminopyridine; the combination of phosphorus source and aluminum source and / or the phosphorus-aluminum source is crystalline aluminum phosphate; Wherein, the phosphorus in the combination of phosphorus source and aluminum source and / or the phosphorus-aluminum source is calculated as P2O5, the aluminum as Al2O3, the silicon source as SiO2, and the molar ratio of P2O5, Al2O3, SiO2, template agent R and water is 0.8-1.2:1:0.1-0.5:1-5:10-80; The hydrothermal crystallization temperature is 200-220℃, and the time is 6-9 days.

2. The composite molecular sieve according to claim 1, wherein, By weight, the composite molecular sieve contains 10-90% ATV structured molecular sieve and 10-90% SFO structured molecular sieve; and / or The BET specific surface area of ​​the composite molecular sieve is not less than 560 m². 2 / g; and / or The micropore area of ​​the composite molecular sieve is not less than 550 m². 2 / g; and / or The total pore volume of the composite molecular sieve is not less than 0.26 cm³. 3 / g; and / or The micropore volume of the composite molecular sieve is not less than 0.25 cm³. 3 / g.

3. A method for preparing the composite molecular sieve according to claim 1 or 2, characterized in that, This method includes using a hydrothermal synthesis method to mix a combination of phosphorus and aluminum sources and / or a phosphorus-aluminum source with a silicon source, a template agent R, and water to synthesize a composite molecular sieve. Wherein, the template agent R is 4-dimethylaminopyridine; the combination of phosphorus source and aluminum source and / or the phosphorus-aluminum source is crystalline aluminum phosphate; Wherein, the phosphorus in the combination of phosphorus source and aluminum source and / or the phosphorus-aluminum source is calculated as P2O5, the aluminum as Al2O3, the silicon source as SiO2, and the molar ratio of P2O5, Al2O3, SiO2, template agent R and water is 0.8-1.2:1:0.1-0.5:1-5:10-80; The hydrothermal crystallization temperature is 200-220℃, and the time is 6-9 days.

4. The method according to claim 3, wherein, The synthesis method includes: (1) A combination of phosphorus and aluminum sources and / or a phosphorus-aluminum source is mixed with a silicon source, template agent R and water and subjected to hydrothermal crystallization; (2) The hydrothermal crystallization product is subjected to solid-liquid separation, and the obtained solid phase is dried and optionally calcined to obtain the composite molecular sieve.

5. The method according to claim 3 or 4, wherein, The silicon source is selected from at least one of silica sol, activated silica, solid silica gel, silicon-containing organic compounds of Formula I, and precipitated silica. (Formula I) In Formula I, R1, R2, R3 and R4 are each independently a C1-C4 alkyl group.

6. The method according to claim 5, wherein, The silicon-containing organic compound is tetraethyl orthosilicate.

7. The method according to claim 4, wherein, The conditions for hydrothermal crystallization include: a temperature of 200-215℃ and a time of 6-8 days; and / or The roasting conditions include a temperature of 500-700℃ and a time of 3-6 hours.

8. The application of the composite molecular sieve as a catalyst in acid-catalyzed reactions according to claim 1 or 2.

9. The application according to claim 8, wherein, The acid-catalyzed reaction is a reaction in which oxygen-containing compounds are converted into olefins or a reaction in which straight-chain alkane isomerizes.

10. The application of the composite molecular sieve according to claim 1 or 2 in gas adsorption treatment.

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