Hierarchical porous SAPO-34 molecular sieve single crystal and accurate regulation and control method for each stage of pore channel thereof

Abstract

The invention relates to a hierarchical porous SAPO-34 molecular sieve single crystal and an accurate regulation and control method for each stage of pore channel thereof. The preparation method comprises the following steps: firstly, preparing carbon templates with different diameters by taking 3-aminophenol, an ethanol aqueous solution, ammonia water, a formaldehyde aqueous solution and the like as raw materials; uniformly mixing an aluminum source, a phosphorus source, a silicon source, the structure-directing agent and water, and fully stirring to obtain molecular sieve precursor gel; and finally, selecting a carbon template with a target size, uniformly mixing the carbon template with the molecular sieve precursor gel, and carrying out aging, hydrothermal crystallization and high-temperature roasting treatment on the obtained mixture to obtain the SAPO-34 molecular sieve single crystal with completely through pore channels, a micropore-mesopore-macropore structure and an inverse opal morphology. The method solves the problem that the existing synthesis method cannot accurately regulate and control the pore diameters of mesopores and macropores of the molecular sieve, has the advantages of simple process, easiness in implementation and the like, and has important significance and guiding effect on scientific research and actual production.

Description

Technical Field

[0001] The present invention relates to the field of new material technology, in particular to the field of porous material technology, and specifically to a hierarchical pore SAPO-34 molecular sieve single crystal and a method for accurately controlling pores at each level thereof. Background Art

[0002] Silicoaluminophosphate (SAPO) molecular sieve is a crystalline silicoaluminophosphate with a regular pore structure. SAPO molecular sieves with specific structures have pore structures of different sizes and shapes and mild acidity. They have good shape selectivity for specific reaction products and are commonly used solid acid catalysts in industrial catalysis. Among them, SAPO-34 molecular sieve with CHA structure is the most ideal catalyst for methanol to olefins (MTO) reaction due to its pore size of 0.38×0.38nm and suitable acidity. The market demand for SAPO-34 molecular sieves at home and abroad is relatively large.

[0003] However, conventional micron SAPO-34 molecular sieves are prone to carbon deposition in the pores when used as MTO reaction catalysts because they only have microporous structures. These carbon deposits cover the acidic sites of the molecular sieves, causing the molecular sieve catalyst to become inactive and must be frequently regenerated before continued use, which seriously restricts the application of SAPO-34 molecular sieves in MTO reactions.

[0004] The introduction of a hierarchical pore structure inside a single-crystal SAPO-34 molecular sieve can effectively improve its diffusion performance in the catalytic process while retaining crystallinity and a larger crystal size. It has been previously reported in the literature (Matter, 2020, 3, 1226-1245) that molecular sieves with regular pores and fully connected pores exhibit excellent performance in cracking reactions and MTO reactions. This scheme uses hierarchical pore carbon with an inverse opal structure as a hard template to synthesize hierarchical pore molecular sieves with opal morphology, including ZSM-5 (CN106283187A), TS-1 (CN106276958A), etc. However, in actual use, there is no consensus on the most suitable size of the pores at each level of the molecular sieve. The main reason is that it is difficult for existing methods to simultaneously accurately control the micropore and macropore pore sizes of the hierarchical pore molecular sieve. Summary of the invention

[0005] The present invention mainly solves the problem that the existing synthesis method of hierarchical pore SAPO-34 molecular sieve cannot accurately control the pore size of each level. By introducing a carbon sphere with highly uniform morphology, adjustable size and opal morphology as a hard template, an inverse opal morphology SAPO-34 molecular sieve single crystal with a micropore-mesopore-macroporous structure is prepared, thereby achieving precise control of the pore size of the molecular sieve mesopores and macropores.

[0006] One of the purposes of the present invention is to provide a method for accurately controlling the pores of each level of a hierarchical pore SAPO-34 molecular sieve single crystal, comprising: first preparing a precursor gel, and then mixing it evenly with a carbon template of a target diameter to prepare a hierarchical pore SAPO-34 molecular sieve single crystal with a target pore size and completely connected pores.

[0007] Furthermore, the preparation method of the precursor gel is as follows: the solvent, the aluminum source, the phosphorus source, the silicon source, and the organic structure directing agent are uniformly mixed to obtain the precursor gel.

[0008] Furthermore, the solvent is specifically water, the aluminum source is selected from at least one of pseudo-boehmite, aluminum isopropoxide, and aluminum hydroxide, the phosphorus source is selected from at least one of phosphoric acid and ammonium dihydrogen phosphate, the silicon source is selected from at least one of silica sol, fumed silica, and tetraethyl silicate, and the organic structure directing agent is selected from at least one of morpholine, triethylamine, tetraethylammonium hydroxide, and diethylamine.

[0009] Furthermore, the mass ratio of the phosphorus source (in terms of P2O5), aluminum source (in terms of Al2O3), silicon source (in terms of SiO2), organic structure directing agent and solvent in the precursor gel is 0.5-1.5:0.5-1.5:0.01-1:1-10:30-100, preferably 1:1-1.2:0.4-0.9:3-4:70.

[0010] Furthermore, the preparation process of hierarchical pore SAPO-34 molecular sieve single crystal is as follows: the precursor gel is evenly mixed with the carbon template of the target diameter, and the resulting mixture is subjected to aging, hydrothermal crystallization, and high-temperature calcination to obtain the hierarchical pore SAPO-34 molecular sieve single crystal.

[0011] Furthermore, the mass ratio of the precursor gel to the carbon template is 1 to 100:1, preferably 1 to 6:1.

[0012] Furthermore, the diameter of the carbon template is 50-800 nm, and the apertures of the pores of each level of the hierarchical pore SAPO-34 molecular sieve single crystal prepared by using the carbon template are equal to the diameter of the selected carbon template.

[0013] Furthermore, the carbon template is a spherical particle and has an opal structure, and the hierarchical pore SAPO-34 molecular sieve single crystal has an inverse opal structure.

[0014] Furthermore, the aging temperature of the precursor gel and carbon template mixture is 40 to 150° C., preferably 40 to 80° C.; the aging time is 5 to 60 hours, preferably 10 to 24 hours.

[0015] Furthermore, the hydrothermal crystallization temperature is 150 to 250° C., preferably 180 to 220° C.; the hydrothermal crystallization time is 1 to 200 hours, preferably 12 to 72 hours.

[0016] Furthermore, the material after hydrothermal crystallization needs to be fully washed and dried at a drying temperature of 60 to 150° C., preferably 80 to 110° C.; the dried product is placed in an air atmosphere and calcined at a high temperature of 400 to 750° C., preferably 500 to 650° C.

[0017] The second object of the present invention is to provide a hierarchical pore SAPO-34 molecular sieve single crystal prepared according to the above method.

[0018] Compared with existing similar products or technologies, the improved effects of the present invention are mainly reflected in the following aspects:

[0019] (1) The present invention synthesized a carbon sphere material with highly uniform morphology, adjustable size and opal morphology, and used it as a hard template for preparing hierarchical pore SAPO-34 molecular sieves. By controlling the size of the carbon sphere template, precise regulation of the pore size of the molecular sieve mesopores and macropores was successfully achieved.

[0020] (2) The hierarchical pore SAPO-34 molecular sieve prepared in the present invention has an inverse opal morphology and a micropore-mesopore-macroporous structure, wherein the macropores come from the occupancy of carbon spheres during the crystallization process, and the mesopores come from the "windows" connecting the macropores, ultimately achieving precise control of the pore sizes of the mesopores and macropores at the same time.

[0021] (3) The above-mentioned pore size regulation process and regulation ideas proposed in the present invention have not been reported before, which has important scientific research significance in studying the influence of the pore size of molecular sieves on catalytic performance, and also has a certain guiding role in actual production.

[0022] (4) The process of the present invention is relatively simple and easy to implement, and the structure and performance of the molecular sieve product can be flexibly and quickly controlled. This method is expected to be further applied to the preparation process of other molecular sieves or inorganic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the SEM image of the carbon template with a diameter of about 500 nm prepared in Example 1.

[0024] Figure 2 This is the XRD spectrum of the hierarchical pore SAPO-34 molecular sieve single crystal prepared in Example 4.

[0025] Figure 3 This is a SEM image of the hierarchical pore SAPO-34 molecular sieve single crystal prepared in Example 4.

[0026] Figure 4This is the SEM image of the carbon template with a diameter of about 200 nm prepared in Example 6.

[0027] Figure 5 This is the SEM image of the carbon template with a diameter of about 600 nm prepared in Example 7.

[0028] Figure 6 This is a SEM image of the hierarchical pore SAPO-34 molecular sieve single crystal prepared in Example 7. DETAILED DESCRIPTION

[0029] In order to enable ordinary technicians in the field to fully understand the technical solutions and beneficial effects of the present invention, the following is a further detailed description in conjunction with specific embodiments and drawings.

[0030] The preparation method of the carbon template used in the present invention is as follows: 3-aminophenol, solvent, ammonia and formaldehyde are mixed evenly and reacted fully, then solid-liquid separation is performed and the solid product is placed in a tube furnace, and heated to 500-600° C. for high-temperature carbonization under a protective atmosphere, and finally a spherical carbon template with an opal structure is obtained, and the particle diameter thereof is about 50nm-800nm. The solvent required for the reaction is selected from at least one of water and ethanol, and the raw materials ammonia and formaldehyde are introduced in the form of respective aqueous solutions.

[0031] Example 1

[0032] (1) 3.63 g of 3-aminophenol was mixed with 240 mL of water and 96 mL of ethanol, and then 2.25 g of 25 wt% ammonia water was added and stirred, followed by 2.67 g of 37 wt% formaldehyde solution and continued stirring for 4 hours. After the reaction, the mixture was centrifuged, washed, and dried to obtain phenolic resin beads with highly uniform size. The phenolic resin beads were transferred to a tubular furnace, heated to 550° C. in a nitrogen atmosphere, and carbonized for 6 hours to obtain a carbon template with an opal structure.

[0033] The scanning electron microscopy (SEM) of the carbon template is shown in Figure 1 As shown in the figure, it can be seen that the carbon template particles are all spherical and have a very close diameter of about 500nm.

[0034] (2) Add an appropriate amount of water into a beaker, and then add aluminum isopropoxide, phosphoric acid, silica sol, and triethylamine (TEA) in sequence and stir for 5 hours to mix them evenly to obtain a molecular sieve precursor gel. The mass ratio of P2O5, Al2O3, SiO2, TEA, and H2O in the gel is 1:1:0.6:4:70.

[0035] The molecular sieve precursor gel and the carbon template were mixed evenly at a mass ratio of 6:1, and the resulting mixture was heated to 60°C for aging overnight to obtain a mixture dry gel. The mixture dry gel was transferred to a vial, and the vial was fixed in a polytetrafluoroethylene-lined hydrothermal autoclave. A small amount of water was added to the outside of the vial for water vapor-assisted crystallization, wherein the hydrothermal crystallization temperature was 200°C and the hydrothermal crystallization time was 24 hours.

[0036] After the hydrothermal crystallization, the product was washed with water by centrifugation until neutral, and then dried in an oven at 100°C overnight. The dried product was transferred to a muffle furnace, heated to 550°C in an air atmosphere and calcined for 7 hours to remove the template agent, and finally a hierarchical pore SAPO-34 molecular sieve single crystal with through-holes was obtained.

[0037] Example 2

[0038] (1) According to the method in Example 1, a carbon template with a particle diameter of about 500 nm and an opal structure was prepared.

[0039] (2) Add an appropriate amount of water into a beaker, and then add pseudo-boehmite, phosphoric acid, silica sol, and triethylamine (TEA) in sequence and stir for 5 hours to mix them evenly to obtain a molecular sieve precursor gel. The mass ratio of P2O5, Al2O3, SiO2, TEA, and H2O in the gel is 1:1:0.4:4:70.

[0040] The molecular sieve precursor gel and the carbon template were mixed evenly at a mass ratio of 5:1, and the resulting mixture was heated to 60°C for aging overnight to obtain a mixture dry gel. The mixture dry gel was transferred to a vial, and the vial was fixed in a polytetrafluoroethylene-lined hydrothermal autoclave. A small amount of water was added to the outside of the vial for water vapor-assisted crystallization, wherein the hydrothermal crystallization temperature was 200°C and the hydrothermal crystallization time was 24 hours.

[0041] After the hydrothermal crystallization, the product was washed with water by centrifugation until neutral, and then dried in an oven at 100°C overnight. The dried product was transferred to a muffle furnace, heated to 550°C in an air atmosphere and calcined for 7 hours to finally obtain a hierarchical pore SAPO-34 molecular sieve single crystal with through-holes.

[0042] Example 3

[0043] (1) According to the method in Example 1, a carbon template with a particle diameter of about 500 nm and an opal structure was prepared.

[0044] (2) Add an appropriate amount of water into a beaker, and then add pseudo-boehmite, phosphoric acid, silica sol, and morpholine (MOR) in sequence and stir for 5 hours to mix them evenly to obtain a molecular sieve precursor gel. The mass ratio of P2O5, Al2O3, SiO2, MOR, and H2O in the gel is 1:1:0.6:3:70.

[0045] The molecular sieve precursor gel and the carbon template were mixed evenly at a mass ratio of 6:1, and the resulting mixture was heated to 60°C for aging overnight to obtain a mixture dry gel. The mixture dry gel was transferred to a vial, and the vial was fixed in a polytetrafluoroethylene-lined hydrothermal autoclave. A small amount of water was added to the outside of the vial for water vapor-assisted crystallization, wherein the hydrothermal crystallization temperature was 200°C and the hydrothermal crystallization time was 24 hours.

[0046] After the hydrothermal crystallization, the product was washed by centrifugation with water until neutral, and then dried in an oven at 100°C overnight. The dried product was transferred to a muffle furnace, heated to 550°C in an air atmosphere and calcined for 7 hours to finally obtain a hierarchical pore SAPO-34 molecular sieve single crystal with through-holes.

[0047] Example 4

[0048] (1) According to the method in Example 1, a carbon template with a particle diameter of about 500 nm and an opal structure was prepared.

[0049] (2) Add an appropriate amount of water into a beaker, and then add pseudo-boehmite, phosphoric acid, tetraethyl silicate, and morpholine (MOR) in sequence and stir for 5 hours to mix them evenly to obtain a molecular sieve precursor gel. The mass ratio of P2O5, Al2O3, SiO2, MOR, and H2O in the gel is 1:1:0.6:4:70.

[0050] The molecular sieve precursor gel and the carbon template were mixed evenly at a mass ratio of 6:1, and the resulting mixture was heated to 60°C for aging overnight to obtain a mixture dry gel. The mixture dry gel was transferred to a vial, and the vial was fixed in a polytetrafluoroethylene-lined hydrothermal autoclave. A small amount of water was added to the outside of the vial for water vapor-assisted crystallization, wherein the hydrothermal crystallization temperature was 200°C and the hydrothermal crystallization time was 24 hours.

[0051] After the hydrothermal crystallization, the product was washed by centrifugation with water until neutral, and then dried in an oven at 100°C overnight. The dried product was transferred to a muffle furnace, heated to 550°C in an air atmosphere and calcined for 7 hours to finally obtain a hierarchical pore SAPO-34 molecular sieve single crystal with through-holes.

[0052] The XRD pattern of the hierarchical pore SAPO-34 molecular sieve single crystal prepared in this embodiment is as follows: Figure 2 As shown in the figure, it can be seen that the molecular sieve sample has a typical CHA structure diffraction peak, which indicates that the molecular sieve sample used for testing is a pure phase.

[0053] The scanning electron microscope (SEM) photograph of the hierarchical pore SAPO-34 molecular sieve single crystal prepared in this example is as follows: Figure 3As shown in the figure, it can be seen that the molecular sieve sample particles show a cubic structure, and the overall single crystal morphology is an inverse opal structure, and the macropore size (about 500nm) corresponds well to the size of the carbon template.

[0054] Example 5

[0055] (1) According to the method in Example 1, a carbon template with a particle diameter of about 500 nm and an opal structure was prepared.

[0056] (2) Add an appropriate amount of water into a beaker, and then add pseudo-boehmite, phosphoric acid, silica sol, and morpholine (MOR) in sequence and stir for 5 hours to mix them evenly to obtain a molecular sieve precursor gel. The mass ratio of P2O5, Al2O3, SiO2, MOR, and H2O in the gel is 1:1.2:0.6:4:70.

[0057] The molecular sieve precursor gel and the carbon template were mixed evenly at a mass ratio of 6:1, and the resulting mixture was heated to 60°C for aging overnight to obtain a mixture dry gel. The mixture dry gel was transferred to a vial, and the vial was fixed in a polytetrafluoroethylene-lined hydrothermal autoclave. A small amount of water was added to the outside of the vial for water vapor-assisted crystallization, wherein the hydrothermal crystallization temperature was 200°C and the hydrothermal crystallization time was 24 hours.

[0058] After the hydrothermal crystallization, the product was washed with water by centrifugation until neutral, and then dried in an oven at 100°C overnight. The dried product was transferred to a muffle furnace, heated to 550°C in an air atmosphere and calcined for 7 hours to finally obtain a hierarchical pore SAPO-34 molecular sieve single crystal with through-holes.

[0059] Example 6

[0060] (1) 1.82 g of 3-aminophenol was mixed with 240 mL of water and 96 mL of ethanol, and then 2.25 g of 25 wt% ammonia water was added and stirred, followed by 2.05 g of 37 wt% formaldehyde solution and continued stirring for 4 hours. After the reaction, the mixture was centrifuged, washed, and dried to obtain phenolic resin beads with highly uniform size. The phenolic resin beads were transferred to a tubular furnace, heated to 550° C. in a nitrogen atmosphere, and carbonized for 6 hours to obtain a carbon template with an opal structure.

[0061] The scanning electron microscopy (SEM) of the carbon template is shown in Figure 4 As shown in the figure, it can be seen that the carbon template particles are all spherical and have a very close diameter of about 200nm.

[0062] (2) Add an appropriate amount of water into a beaker, and then add pseudo-boehmite, phosphoric acid, tetraethyl silicate, and morpholine (MOR) in sequence and stir for 5 hours to mix them evenly to obtain a molecular sieve precursor gel. The mass ratio of P2O5, Al2O3, SiO2, MOR, and H2O in the gel is 1:1:0.6:4:70.

[0063] The molecular sieve precursor gel and the carbon template were mixed evenly at a mass ratio of 6:1, and the resulting mixture was heated to 60°C for aging overnight to obtain a mixture dry gel. The mixture dry gel was transferred to a vial, and the vial was fixed in a polytetrafluoroethylene-lined hydrothermal autoclave. A small amount of water was added to the outside of the vial for water vapor-assisted crystallization, wherein the hydrothermal crystallization temperature was 200°C and the hydrothermal crystallization time was 24 hours.

[0064] After the hydrothermal crystallization, the product was washed with water by centrifugation until neutral, and then dried in an oven at 100°C overnight. The dried product was transferred to a muffle furnace, heated to 550°C and calcined for 7 hours in an air atmosphere, and finally a hierarchical SAPO-34 molecular sieve single crystal with through-holes was obtained. The molecular sieve sample particles showed a cubic structure, and the overall single crystal morphology was an inverse opal structure, and the pore size (about 200nm) corresponded well to the size of the carbon template.

[0065] Example 7

[0066] (1) 5.5 g of 3-aminophenol was mixed with 240 mL of water and 96 mL of ethanol, and then 2.25 g of 25 wt% ammonia water was added and stirred, followed by 4.1 g of 37 wt% formaldehyde solution and continued stirring for 4 hours. After the reaction, the mixture was centrifuged, washed, and dried to obtain phenolic resin beads with highly uniform size. The phenolic resin beads were transferred to a tubular furnace, heated to 550° C. in a nitrogen atmosphere, and carbonized for 6 hours to obtain a carbon template with an opal structure.

[0067] The scanning electron microscope (SEM) image of the carbon template is shown in Figure 5 As shown in the figure, it can be seen that the carbon template particles are all spherical and have a very close diameter of about 600nm.

[0068] (2) Add an appropriate amount of water into a beaker, and then add pseudo-boehmite, phosphoric acid, tetraethyl silicate, and morpholine (MOR) in sequence and stir for 5 hours to mix them evenly to obtain a molecular sieve precursor gel. The mass ratio of P2O5, Al2O3, SiO2, MOR, and H2O in the gel is 1:1:0.4:4:70.

[0069] The molecular sieve precursor gel and the carbon template were mixed evenly at a mass ratio of 6:1, and the resulting mixture was heated to 60°C for aging overnight to obtain a mixture dry gel. The mixture dry gel was transferred to a vial, and the vial was fixed in a polytetrafluoroethylene-lined hydrothermal autoclave. A small amount of water was added to the outside of the vial for water vapor-assisted crystallization, wherein the hydrothermal crystallization temperature was 200°C and the hydrothermal crystallization time was 48 hours.

[0070] After the hydrothermal crystallization, the product was washed by centrifugation with water until neutral, and then dried in an oven at 100°C overnight. The dried product was transferred to a muffle furnace, heated to 550°C in an air atmosphere and calcined for 7 hours to finally obtain a hierarchical pore SAPO-34 molecular sieve single crystal with through-holes.

[0071] The scanning electron microscope (SEM) photograph of the hierarchical pore SAPO-34 molecular sieve single crystal prepared in this example is as follows: Figure 6 As shown in the figure, it can be seen that the molecular sieve sample particles show a cubic structure, and the overall single crystal morphology is an inverse opal structure. The size of the macropore channel (600nm) corresponds well to the size of the carbon template.

[0072] The above results indicate that by controlling the size of the carbon template with an opal structure, the mesopore and macropore sizes of the hierarchical pore SAPO-34 molecular sieve single crystals can indeed be precisely controlled.

Claims

1. A method for precisely controlling the pores of each level of hierarchical SAPO-34 molecular sieve single crystal, characterized in that The method comprises: uniformly mixing a solvent, an aluminum source, a phosphorus source, a silicon source and an organic structure directing agent to obtain a precursor gel; uniformly mixing the precursor gel with a carbon template of a target diameter, and subjecting the obtained mixture to aging, hydrothermal crystallization and high-temperature calcination to obtain a hierarchical pore SAPO-34 molecular sieve single crystal with a target pore diameter and completely connected pores.

2. The method according to claim 1, characterized in that: The mass ratio of the precursor gel to the carbon template is 1 to 100:

1.

3. The method according to claim 1, characterized in that: The diameter of the carbon template is 50nm-800nm, and the aperture of each level of the hierarchical pore SAPO-34 molecular sieve single crystal prepared by using the carbon template is equal to the diameter of the carbon template.

4. The method according to claim 1, characterized in that: The carbon template is a spherical particle and has an opal structure, and the hierarchical pore SAPO-34 molecular sieve single crystal has an inverse opal structure.

5. The method according to claim 1, characterized in that: The solvent is specifically water, the aluminum source is selected from at least one of pseudo-boehmite, aluminum isopropoxide, and aluminum hydroxide, the phosphorus source is selected from at least one of phosphoric acid and ammonium dihydrogen phosphate, the silicon source is selected from at least one of silica sol, fumed silica, and tetraethyl silicate, and the organic structure directing agent is selected from at least one of morpholine, triethylamine, tetraethylammonium hydroxide, and diethylamine.

6. The method according to claim 1, characterized in that: The mass ratio of the phosphorus source (calculated as P2O5), the aluminum source (calculated as Al2O3), the silicon source (calculated as SiO2), the organic structure directing agent and the solvent in the precursor gel is 0.5-1.5:0.5-1.5:0.01-1:1-10:30-100.

7. The method according to claim 1, characterized in that: The aging temperature of the mixture is 40 to 150° C., and the aging time is 5 to 60 hours.

8. The method according to claim 1, characterized in that: The hydrothermal crystallization temperature of the mixture is 150-250° C., and the hydrothermal crystallization time is 1-200 h.

9. The method according to claim 1, characterized in that: The material after hydrothermal crystallization of the mixture needs to be fully washed and dried at a drying temperature of 60 to 150° C. The dried product is calcined at a high temperature of 400 to 750° C. in an air atmosphere.

10. A hierarchical pore SAPO-34 molecular sieve single crystal, characterized in that: The hierarchical pore SAPO-34 molecular sieve single crystal is prepared according to any one of the methods of claims 1-9.

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