CN117509667A - A method for seed-assisted synthesis of nanometer high-silicon AFX zeolite molecular sieves - Google Patents
A method for seed-assisted synthesis of nanometer high-silicon AFX zeolite molecular sieves Download PDFInfo
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Abstract
The invention provides a method for synthesizing a nano high-silicon AFX zeolite molecular sieve by crystal assistance, and relates to the technical field of molecular sieves. Mixing a silicon source, an aluminum source, water, inorganic alkali, seed crystals and a template agent to obtain initial gel; carrying out hydrothermal crystallization on the initial gel to obtain the nano high-silicon AFX zeolite molecular sieve; the seed crystal is one or more of SAPO-34, SAPO-44, SAPO-47, SAPO-5, SAPO-18, SAPO-56 and SSZ-16 molecular sieve seed crystal. The invention adopts the traditional hydrothermal synthesis method and uses a homogeneous or heterogeneous seed crystal auxiliary structure to conduct synthesis, thus obtaining the nano high-silicon AFX zeolite molecular sieve with the silicon-aluminum ratio of 7.3 and the grain diameter of 60-300 nm, and the invention has wide industrial application prospect in the fields of catalysis on diesel vehicles and non-road mobile machinery in the future, the preparation of low-carbon olefin by non-petroleum resource conversion, and the like.
Description
Technical Field
The invention relates to the technical field of molecular sieves, in particular to a method for synthesizing a nano high-silicon AFX zeolite molecular sieve by using seed crystals in an auxiliary way.
Background
The zeolite is a crystalline microporous material formed of interconnected TO4 tetrahedra (t=si, al) with uniform pores and voids, and a specific size and shape over a range of molecular sizesBy controlling the pore size, opening and cavity size, it can be divided into organic and inorganic species with a geometrical difference of less than +.> These remarkable shape-selective properties, as well as high thermal and chemical stability, make them useful as ion exchangers, adsorbents or catalysts.
The crystal structure of AFX zeolite molecular sieve belongs to hexagonal space group P6 3 Group/mmc and ABC-6, its stacking sequence is AABBCCBB, its skeleton density is 15.1t atom +.Further formation was achieved by construction of d6r, gme and aft cage. The AFX structure has a straight 8-ring channel +.>The three-dimensional pore system is a small pore molecular sieve with large pores, which is used as an efficient catalyst for preparing olefin (MTO) from methanol and uses ammonia as a reducing agent of NO x Plays an important role in the Selective Catalytic Reduction (SCR) of methane, the selective oxidation of methane to methanol, and the like.
However, the current literature on AFX zeolite molecular sieves is low, probably due to the fact that this material is synthesized only under limited conditions, resulting in a synthesis that yields a product with a molar ratio of silica to alumina of less than 5 and a relatively large crystal size (2-3 μm).
Chinese patent CN202210875382.7 discloses a process for synthesizing high-silicon AFX zeolite by using small molecular organic structure directing agent, which utilizes a series of simple and cheap small molecular organic template agents to synthesize high-silicon AFX zeolite molecular sieve, and the obtained product has a silicon-aluminum ratio of 7.1, which is very suitable for NH 3 SCR reaction, solving the problem that the silicon-aluminum ratio of the existing AFX zeolite molecular sieve is not higher than 5 (Si/Al)<5.0 A) technical problem. However, this method only gives AFX-type zeolite with a crystal size of the order of micrometers.
The nano molecular sieve has excellent specific surface area and abundant available active site quantity, which effectively leads to the improvement of the catalytic reaction efficiency. Therefore, developing an AFX zeolite molecular sieve with high silicon-aluminum ratio and nano crystal size, which is synthesized by a simple and economical method, has important significance for further developing the function of the AFX zeolite molecular sieve in the industrial catalysis field.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for synthesizing nano high silicon AFX zeolite molecular sieve with the assistance of seed crystals. The method can prepare the AFX zeolite with high silicon and nanometer.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for synthesizing a nano high-silicon AFX zeolite molecular sieve by crystal assistance, which comprises the following steps:
mixing a silicon source, an aluminum source, water, inorganic alkali, seed crystals and a template agent to obtain initial gel;
carrying out hydrothermal crystallization on the initial gel to obtain the nano high-silicon AFX zeolite molecular sieve;
the seed crystal is one or more of SAPO-34, SAPO-44, SAPO-47, SAPO-5, SAPO-18, SAPO-56 and SSZ-16 molecular sieve seed crystal;
the silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 Calculated as M, the inorganic base 2 O meter, siO in the initial gel 2 、Al 2 O 3 、M 2 O, templating agent and H 2 The mol ratio of O is (20-60) 1 (5-40) 3-20 (600-1500), the mass of seed crystal in the initial gel is SiO 2 1 to 10% of the mass of the M 2 M in O is a metal element of inorganic base.
Preferably, the silicon source is one or more of sodium silicate, white carbon black, water glass, silica sol and tetraethyl orthosilicate, and the aluminum source is one or more of sodium metaaluminate, aluminum isopropoxide, pseudo-boehmite, aluminum chloride, aluminum sulfate and aluminum hydroxide.
Preferably, the silicon source and the aluminum source are simultaneously used by the Y molecular sieve.
Preferably, the inorganic base is one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.
Preferably, the template agent is-N, N ' -diethyl-N, N, N ', N ' -tetramethyl-1, 6-hexanediamine or hexamethyldiammonium hydroxide.
Preferably, the template agent is added in the form of an aqueous template agent solution, and the mass fraction of the aqueous template agent solution is 15-40%.
Preferably, the mixing method is as follows:
dissolving the inorganic alkali in water to obtain an alkali solution;
and cooling the alkali solution to room temperature, adding a template agent, an aluminum source, a silicon source and a seed crystal into the alkali solution, and uniformly stirring.
Preferably, the temperature of the hydrothermal crystallization is 120-200 ℃ and the time is 1-7 d.
Preferably, after the hydrothermal crystallization, the method further comprises the steps of sequentially filtering, washing a solid phase and drying the obtained crystallization reaction liquid, wherein the drying temperature is 75 ℃, and the time is 24 hours.
Preferably, the grain diameter of the nano high-silicon AFX zeolite molecular sieve is 60-300 nm, and the silicon-aluminum molar ratio is 5.7-7.3.
The invention provides a crystal auxiliary synthesized nano high-silicon AFX zeolite molecular sieveComprising the steps of: mixing a silicon source, an aluminum source, water, inorganic alkali, seed crystals and a template agent to obtain initial gel; carrying out hydrothermal crystallization on the initial gel to obtain the nano high-silicon AFX zeolite molecular sieve; the seed crystal is one or more of SAPO-34, SAPO-44, SAPO-47, SAPO-5, SAPO-18, SAPO-56 and SSZ-16 molecular sieve seed crystal; the silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 Calculated as M, the inorganic base 2 O meter, siO in the initial gel 2 、Al 2 O 3 、M 2 O, templating agent and H 2 The mol ratio of O is (20-60) 1 (5-40) 3-20 (600-1500), the mass of seed crystal in the initial gel is SiO 2 1 to 10% of the mass of the M 2 M in O is a metal element of inorganic base. The invention adopts the traditional hydrothermal synthesis method and uses a homogeneous or heterogeneous seed crystal auxiliary structure to conduct synthesis, thus obtaining the nano high-silicon AFX zeolite molecular sieve with the silicon-aluminum ratio of 5.7-7.3 and the grain diameter of 60-300 nm, and the invention has wide industrial application prospect in the fields of catalysis on future diesel vehicles and non-road mobile machinery, the preparation of low-carbon olefin by non-petroleum resource conversion, and the like.
Drawings
FIG. 1 is an XRD spectrum of a high silicon AFX zeolite molecular sieve product synthesized in example 1;
FIG. 2 is a Scanning Electron Microscope (SEM) image of a high silicon AFX zeolite molecular sieve product synthesized in example 1;
FIG. 3 is an XRD spectrum of AFX molecular sieve products obtained by different seed crystal-assisted synthesis in examples 1-5 and example 11;
FIG. 4 is an XRD spectrum of AFX molecular sieve products synthesized from different organic templates in example 5 and example 10;
FIG. 5 is a scanning electron microscope image of a high silicon AFX zeolite molecular sieve product synthesized in example 11;
FIG. 6 is a scanning electron microscope image of the high silicon AFX zeolite molecular sieve product synthesized in example 12;
FIG. 7 is a scanning electron microscope image of an AFX zeolite molecular sieve product synthesized in comparative example 1;
FIG. 8 is a scanning electron microscope image of an AFX zeolite molecular sieve product synthesized in comparative example 2.
Detailed Description
The invention provides a method for synthesizing a nano high-silicon AFX zeolite molecular sieve by crystal assistance, which comprises the following steps:
mixing a silicon source, an aluminum source, water, inorganic alkali, seed crystals and a template agent to obtain initial gel;
carrying out hydrothermal crystallization on the initial gel to obtain the nano high-silicon AFX zeolite molecular sieve;
the seed crystal is one or more of SAPO-34, SAPO-44, SAPO-47, SAPO-5, SAPO-18, SAPO-56 and SSZ-16 molecular sieve seed crystal;
the silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 Calculated as M, the inorganic base 2 O meter, siO in the initial gel 2 、Al 2 O 3 、M 2 O, templating agent and H 2 The mol ratio of O is (20-60) 1 (5-40) 3-20 (600-1500), the mass of seed crystal in the initial gel is SiO 2 1 to 10% of the mass of the M 2 M in O is a metal element of inorganic base.
According to the invention, a silicon source, an aluminum source, water, inorganic alkali, seed crystals and a template agent are mixed to obtain initial gel.
In the invention, the silicon source is preferably one or more of sodium silicate, white carbon black, water glass, silica sol and tetraethyl orthosilicate, more preferably white carbon black, and the aluminum source is preferably one or more of sodium metaaluminate, aluminum isopropoxide, pseudo-boehmite, aluminum chloride, aluminum sulfate and aluminum hydroxide, more preferably pseudo-boehmite; alternatively, a Y molecular sieve is preferably used as both the silicon source and the aluminum source, and the silicon to aluminum ratio of the Y molecular sieve is preferably 30. In the present invention, when the Y molecular sieve is used as the silicon source and the aluminum source at the same time, the method for synthesizing the AFX zeolite molecular sieve is a crystal transition synthesis method.
In the present invention, the water is preferably deionized water.
In the present invention, the inorganic base is preferably one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide, more preferably sodium hydroxide.
In the invention, the seed crystal is one or more of SAPO-34, SAPO-44, SAPO-47, SAPO-5, SAPO-18, SAPO-56 and SSZ-16 molecular sieve seed crystal, wherein SAPO-34, SAPO-44, SAPO-47, SAPO-5, SAPO-18 and SAPO-56 are heterogeneous seed crystals, and SSZ-16 is a homogeneous seed crystal. In the present invention, the seed crystal is preferably SAPO-56. The source of the seed crystal is not particularly limited in the present invention, and the seed crystal may be prepared by commercially available products or by methods well known to those skilled in the art.
In the present invention, the template is preferably-N, N '-diethyl-N, N' -tetramethyl-1, 6-hexanediamine or hexamethyldiammonium hydroxide; the template is preferably added in the form of an aqueous template solution, and the mass fraction of the aqueous template solution is preferably 15-40%, more preferably 25%. The source of the template agent is not particularly limited, and the template agent can be prepared by adopting commercial products or adopting a method well known to a person skilled in the art. In the present invention, the hydroxy-N, N '-diethyl-N, N' -tetramethyl-1, 6-hexanediamine is provided by kente catalytic materials, inc, and has the following structural formula:
in the present invention, the mixing method is preferably:
dissolving the inorganic alkali in water to obtain an alkali solution;
and cooling the alkali solution to room temperature, adding a template agent, an aluminum source, a silicon source and a seed crystal into the alkali solution, and uniformly stirring.
In the present invention, the silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 Meter (when the silicon source and the aluminum source are simultaneously used by a Y molecular sieve, the Y molecular sieve is formed by SiO 2 And Al 2 O 3 Calculated as M) of the inorganic base 2 O meter, siO in the initial gel 2 、Al 2 O 3 、M 2 O, templating agent and H 2 Molar ratio of O1 (20-60): 1 (5-40): 3-20): 600-1500, preferably (30-40): 1 (5-10): 1000-1500, the mass of seed crystal in the initial gel is SiO 2 1 to 10% by mass, preferably 5 to 10% by mass, of said M 2 M in O is a metal element of inorganic base.
After the initial gel is obtained, the initial gel is subjected to hydrothermal crystallization, and the nano high-silicon AFX zeolite molecular sieve is obtained.
In the present invention, the temperature of the hydrothermal crystallization is preferably 120 to 200 ℃, more preferably 150 to 160 ℃, and the time is preferably 1 to 7 days, more preferably 4 to 5 days. The initial gel is preferably placed in a stainless steel reaction kettle with a polytetrafluoroethylene lining for carrying out the hydrothermal crystallization.
In the invention, after the hydrothermal crystallization, the method also preferably comprises the steps of sequentially filtering, solid-phase washing and drying the obtained crystallization reaction liquid to obtain the nano high-silicon AFX zeolite molecular sieve; the solid phase washing is preferably deionized water washing, the drying temperature is preferably 75 ℃, and the drying time is preferably 24 hours.
In the invention, the grain diameter of the nano high-silicon AFX zeolite molecular sieve is 60-300 nm, preferably 120-200 nm, and the silicon-aluminum molar ratio is 5.7-7.3. In the embodiment of the invention, the silicon-aluminum molar ratio of the nano high-silicon AFX zeolite molecular sieve is 5.7, 6.4, 7.1 or 7.3.
At present, the conventional synthesis is generally easy to obtain the AFX zeolite molecular sieve with the crystal grain diameter of 5-10 microns, while the AFX zeolite molecular sieve with the grain diameter of 60-300 nm is obtained through synthesis, and the nano molecular sieve has excellent specific surface area and abundant available active site quantity, which effectively leads to the improvement of the catalytic reaction efficiency. Meanwhile, the conventional synthesis generally and easily obtains the AFX zeolite molecular sieve with the Si/Al ratio not more than 5, and the AFX zeolite molecular sieve has lower hydrothermal stability, and the high-silicon AFX zeolite molecular sieve with the silicon-aluminum ratio of up to 7.3 can be synthesized in the invention, so that the method has wide industrial application prospect in the fields of catalysis on future diesel vehicles and non-road mobile machinery, the field of preparing low-carbon olefin through non-petroleum resource conversion and the like.
The existing improvement technology is complex, high silicon property is obtained by specially designing a template agent or other methods, or nano property is obtained by post-treatment or introducing a crystal growth inhibitor, and the like. The invention adopts specific seed crystal to reduce the crystal size and change the element composition of zeolite, which results in the dual functions of high silicon-aluminum ratio and nanometer size.
For further explanation of the present invention, the method of synthesizing nano high silicon AFX zeolite molecular sieves with the assistance of seed crystals provided by the present invention is described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
In various embodiments, OSDA1 is a 25% aqueous solution of N, N '-diethyl-N, N' -tetramethyl-1, 6-hexanediamine hydroxide and OSDA2 is a 25% aqueous solution of hexamethyldiammonium hydroxide.
Example 1
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.18g of sodium hydroxide was added to 3.6mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 2.7g of OSDA1,0.04g of pseudo-boehmite, 0.05g of SAPO-56 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 0.5g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio (atomic ratio) of the product is determined to be 7.3.
FIG. 1 shows XRD patterns of the high-silicon AFX zeolite molecular sieve product synthesized in example 1, which are consistent with standard patterns, and have high purity and crystallization degree.
FIG. 2 is a Scanning Electron Microscope (SEM) of a high silicon AFX zeolite molecular sieve product synthesized in example 1, the product having a crystal morphology and an average particle size of about 120 nm.
Example 2
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.25g sodium hydroxide was added to 3.4mL water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 4.2g of OSDA1,0.04g of pseudo-boehmite, 0.06g of SAPO-44 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 0.6g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is determined to be 7.1.
Example 3
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.40g of sodium hydroxide was added to 6.8mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 5.4g of OSDA1,0.04g of pseudo-boehmite, 0.09g of SAPO-5 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 0.90g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is measured to be 6.4.
Example 4
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.21g of sodium hydroxide was added to 3.0mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 2.9g of OSDA1,0.04g of pseudo-boehmite, 0.05g of SAPO-18 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 0.5g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is determined to be 7.3.
Example 5
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.21g of sodium hydroxide was added to 3.4mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 2.6g of OSDA1,0.04g of pseudo-boehmite, 0.06g of SAPO-34 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 0.6g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is determined to be 7.3.
Example 6
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.22g of sodium hydroxide was added to 3.8mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 3.2g of OSDA2,0.04g of pseudo-boehmite, 0.06g of SAPO-56 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 0.6g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is measured to be 7.3, and the average particle diameter is about 120 nm.
Example 7
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.33g of sodium hydroxide was added to 4.2mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 5.2g of OSDA2,0.04g of pseudo-boehmite, 0.12g of SAPO-44 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 1.0g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is measured to be 5.7.
Example 8
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.19g of sodium hydroxide was added to 2.9mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 5.1g of OSDA2,0.04g of pseudo-boehmite, 0.08g of SAPO-5 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 0.80g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is determined to be 7.3.
Example 9
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.22g of sodium hydroxide was added to 1.9mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 5.8g of OSDA2,0.04g of pseudo-boehmite, 0.06g of SAPO-18 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 0.6g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is determined to be 7.3.
Example 10
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.22g of sodium hydroxide was added to 3.5mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 4.2g of OSDA2,0.04g of pseudo-boehmite, 0.06g of SAPO-34 seed crystal was added and stirred for 1 hour.
(3) And (3) adding 0.6g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is determined to be 7.3.
Example 11
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of the seed crystal comprises the following steps:
(1) 0.15g of sodium hydroxide was added to 3.6mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 2.6g of OSDA1,0.04g of pseudo-boehmite, 0.06g of SSZ-16 seed crystal were added and stirred for 1 hour.
(3) And (3) adding 0.6g of white carbon black into the suspension obtained in the step (2), and uniformly stirring at room temperature for 16 hours.
(4) Transferring the mixture obtained in the step (3) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(5) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is determined to be 7.3.
The high silicon AFX zeolite molecular sieve products obtained in examples 2-5 and examples 7-10 were tested to have particle sizes in the range of 60-300 nm.
Example 12
The method for synthesizing the nano high-silicon AFX zeolite molecular sieve (Y crystal transformation synthesis and adding SAPO-56 crystal seeds) by the assistance of crystal seeds comprises the following steps:
(1) 0.20g of sodium hydroxide was added to 7.8mL of water and stirred until uniformly dissolved.
(2) After the above solution was cooled to room temperature, 2.6g of OSDA1,1g of Y molecular sieve (silica alumina ratio: 30), 0.06g of SAPO-56 seed crystal was added and stirred for 24 hours.
(3) Transferring the mixture obtained in the step (2) into a stainless steel reaction kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 160 ℃, and the crystallization time is 96 hours.
(4) And collecting the crystallized product by filtering, washing and drying at 75 ℃ for 24 hours to obtain the product, wherein the silicon-aluminum ratio of the product is determined to be 7.3.
FIG. 3 shows XRD patterns of AFX molecular sieve products obtained by different seed crystal-assisted synthesis in examples 1-5 and example 11, which are consistent with standard patterns and have high purity and crystallization degree.
FIG. 4 shows XRD spectra of AFX molecular sieve products synthesized by different organic templates in example 5 and example 10, which are consistent with standard spectra and have high purity and crystallization degree.
FIG. 5 is a scanning electron microscope image of a high silicon AFX zeolite molecular sieve product synthesized in example 11, with a crystal size of about 200nm.
FIG. 6 is a scanning electron microscope image of a high silicon AFX zeolite molecular sieve product synthesized in example 12, with a crystal size of about 160nm.
Comparative example 1
With reference to experimental example 1, only seed crystals were not added, and the rest was the same as that of example 1.
The AFX zeolite molecular sieve obtained had a silica to alumina ratio of 3.7 and a crystal size of about 10. Mu.m. The scanning electron microscope of the product is shown in fig. 7.
Comparative example 2
With reference to experimental example 6, only seed crystals were not added, and the rest was the same as that of example 6.
The AFX zeolite molecular sieve obtained had a silica to alumina ratio of 3.7 and a crystal size of about 6. Mu.m. The scanning electron microscope of the product is shown in fig. 8.
The embodiment shows that the AFX molecular sieve with high silicon-aluminum ratio and nanometer size is obtained through the simple and convenient breakthrough by the assistance of the seed crystal.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be comprehended within the scope of the present invention.
Claims (10)
1. The method for synthesizing the nano high-silicon AFX zeolite molecular sieve with the assistance of seed crystals is characterized by comprising the following steps of:
mixing a silicon source, an aluminum source, water, inorganic alkali, seed crystals and a template agent to obtain initial gel;
carrying out hydrothermal crystallization on the initial gel to obtain the nano high-silicon AFX zeolite molecular sieve;
the seed crystal is one or more of SAPO-34, SAPO-44, SAPO-47, SAPO-5, SAPO-18, SAPO-56 and SSZ-16 molecular sieve seed crystal;
the silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 Calculated as M, the inorganic base 2 O meter, siO in the initial gel 2 、Al 2 O 3 、M 2 O, templating agent and H 2 The mol ratio of O is (20-60) 1 (5-40) 3-20 (600-1500), the mass of seed crystal in the initial gel is SiO 2 1 to 10% of the mass of the M 2 M in O is a metal element of inorganic base.
2. The method according to claim 1, wherein the silicon source is one or more of sodium silicate, white carbon black, water glass, silica sol and tetraethyl orthosilicate, and the aluminum source is one or more of sodium metaaluminate, aluminum isopropoxide, pseudo-boehmite, aluminum chloride, aluminum sulfate and aluminum hydroxide.
3. The method of claim 1, wherein the silicon source and the aluminum source are simultaneously formed from a Y molecular sieve.
4. The method according to claim 1, wherein the inorganic base is one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.
5. The method of claim 1, wherein the templating agent is-N, N '-diethyl-N, N' -tetramethyl-1, 6-hexanediamine or hexamethyldiammonium hydroxide.
6. The method according to claim 5, wherein the template is added in the form of an aqueous template solution, and the mass fraction of the aqueous template solution is 15-40%.
7. The method according to any one of claims 1 to 6, wherein the mixing method is:
dissolving the inorganic alkali in water to obtain an alkali solution;
and cooling the alkali solution to room temperature, adding a template agent, an aluminum source, a silicon source and a seed crystal into the alkali solution, and uniformly stirring.
8. The method according to claim 1, wherein the hydrothermal crystallization is carried out at a temperature of 120 to 200 ℃ for a time of 1 to 7d.
9. The method according to claim 1, further comprising sequentially filtering, solid phase washing and drying the obtained crystallization reaction liquid after the hydrothermal crystallization, wherein the drying temperature is 75 ℃ and the time is 24 hours.
10. The method according to claim 1, wherein the nano high silicon AFX zeolite molecular sieve has a particle size of 60-300 nm and a silicon to aluminum molar ratio of 5.7-7.3.
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