A nano-silicon AFX zeolite molecular sieve and its preparation method and application

Abstract

The present invention provides a nano high silicon AFX zeolite molecular sieve and its preparation method and application, and relates to the technical field of zeolite molecular sieve. The nano high silicon AFX zeolite molecular sieve of the present invention is obtained by hydrothermal crystallization after raw material mixing; the raw materials include a tetravalent silicon source, an aluminum source, water, an inorganic base and a template; the tetravalent silicon source is measured in SiO2, the aluminum source is measured in Al2O3, the inorganic base is measured in M2O, and the molar ratio of SiO2, Al2O3, M2O, template, and H2O in the raw material is (20-60): 1: (5-20): (1-5): (600-1500), and the M is a metal element of the inorganic base; the template is 1,5-dipiperidinylhexane. The present invention uses 1,5-dipiperidinylhexane as a small molecule organic template to synthesize a nano high silicon AFX zeolite molecular sieve, and the obtained molecular sieve has a silicon-aluminum ratio of up to 9, which is very suitable for NH3-SCR reaction. The preparation method of the nanometer high-silicon AFX zeolite molecular sieve of the present invention is simple, the raw material price is low, the production cost is greatly reduced, and it is suitable for industrial promotion.

Description

Technical Field

[0001] The invention relates to the technical field of zeolite molecular sieves, and in particular to a nano high-silicon AFX zeolite molecular sieve and a preparation method and application thereof. Background Art

[0002] Zeolite is a porous crystalline or quasicrystalline aluminosilicate composed of repeating SiO 4 and AlO 4 Zeolites are made up of tetrahedral units that are interconnected to form a framework with regular intracrystalline cavities and molecular-sized channels. Currently, researchers have synthesized a variety of types of synthetic zeolites, each with a unique framework based on the specific arrangement of its tetrahedral units. By convention, the International Zeolite Association (IZA) assigns a unique three-letter code to each framework type.

[0003] AFX is a type of synthetic zeolite whose framework contains an AFT cage structure and a GME cage structure. These two cage structures are combined to form a unique AFX crystal structure. The traditional method for synthesizing AFX zeolite is to use Na-GME zeolite to directly provide the GME part in the crystal and use a structure directing agent (SDA) to form the AFT part in the crystal. SDA is usually a complex organic molecule, and its role is to place hydrated aluminum silicate as a mold around the zeolite crystal so that the zeolite crystal can be formed therein. After the crystal is formed, the SDA can be removed from the internal structure of the crystal, leaving an aluminosilicate cage with molecular-level pores. The AFX molecular sieve was originally discovered as an aluminum phosphate structure, and Wilson et al. named it SAPO-56 molecular sieve. Subsequently, Zones et al. successfully synthesized the silicon-aluminum structured AFX using the double-headed quaternary ammonium salt 1,4-bis(1-azoniabicyclo[2.2.2]octane)butyl dibromide as an organic template and named it SSZ-16 zeolite molecular sieve. Exchange Cu 2+ The SSZ-16 zeolite molecular sieve was used in the NOx selective catalytic reduction reaction (NH 3 -SCR) shows excellent NOx conversion rate. However, since the silicon-aluminum ratio of SSZ-16 zeolite molecular sieve product is not higher than 5 (Si / Al<5.0), its hydrothermal stability is poor, and it usually loses its activity completely after 16 hours of hydrothermal aging at 800°C. Corma et al. used a large rigid double-headed quaternary ammonium salt as an organic template to synthesize nano-sized high-silicon SSZ-16 (Si / Al=5.2~5.3) through the high-silicon USY crystal transformation method, but the organic template used in this method has a complex structure and is expensive, making it difficult to synthesize. Summary of the invention

[0004] In view of this, the present invention provides a nano-silicon AFX zeolite molecular sieve and its preparation method and application. The present invention uses 1,5-dipiperidinylhexane as a small molecule organic template to synthesize the nano-silicon AFX zeolite molecular sieve. The obtained molecular sieve has a silicon-aluminum ratio of up to 9, which is very suitable for NH 3 -SCR reaction. The preparation method of the nanometer high-silicon AFX zeolite molecular sieve of the present invention is simple, the raw material price is low, the production cost of the AFX zeolite molecular sieve is greatly reduced, and it is suitable for industrial promotion.

[0005] The nanometer high silicon AFX zeolite molecular sieve provided by the present invention is obtained by hydrothermal crystallization after mixing raw materials, wherein the raw materials include a tetravalent silicon source, an aluminum source, water, an inorganic base and a template agent, wherein the tetravalent silicon source in the raw materials is calculated as SiO2, and the aluminum source is calculated as Al 2 O 3 The inorganic base is in M 2 O meter, SiO 2 、Al 2 O 3 、M 2 O, template, H 2 The molar ratio of O is (20-60):1:(5-20):(1-5):(600-1500), wherein M is a metal element of an inorganic base; and the template is 1,5-dipiperidinylhexane.

[0006] Preferably, the tetravalent silicon source is at least one of silicate, silica sol, tetraethyl orthosilicate, precipitated silica, white carbon black and clay. More preferably, the tetravalent silicon source is silica sol.

[0007] Preferably, the aluminum source is at least one of Y molecular sieve, sodium aluminate, alumina powder, and pseudo-boehmite.

[0008] Preferably, the inorganic base is at least one of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide. More preferably, the inorganic base is sodium hydroxide.

[0009] The present invention also provides a method for preparing nano high-silicon AFX zeolite molecular sieve, which specifically comprises the following steps:

[0010] S1, template, inorganic base and water are mixed and stirred evenly, an aluminum source is added and stirred evenly, and then a silicon source is added and stirred evenly to obtain a reaction gel;

[0011] S2, hydrothermally crystallizing the reaction gel of S1, filtering, drying and calcining after hydrothermal crystallization to obtain nano high-silicon AFX zeolite molecular sieve.

[0012] Preferably, the hydrothermal crystallization reaction temperature is 100°C to 200°C, and the reaction time is 24 to 96 hours. More preferably, the hydrothermal crystallization reaction temperature is 140°C to 160°C, and the reaction time is 72 to 96 hours. Further preferably, the hydrothermal crystallization reaction temperature is 150°C, and the hydrothermal crystallization reaction time is 72 hours.

[0013] Preferably, the hydrothermal crystallization reaction adopts a dynamic hydrothermal crystallization reaction, and the crystallization process is carried out in an autoclave.

[0014] Preferably, the drying temperature is 80° C. to 150° C., the drying time is 10 to 20 hours, the roasting temperature is 450° C. to 600° C., and the roasting time is 2 to 6 hours.

[0015] The present invention also provides a nano high silicon AFX zeolite molecular sieve in NH 3 -SCR reaction, the nano high silicon AFX zeolite molecular sieve is the nano high silicon AFX zeolite molecular sieve described in the above scheme.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are:

[0017] The nanometer high-silicon AFX zeolite molecular sieve provided by the present invention has a silicon-aluminum ratio of up to 9, can maintain a high catalytic activity under high temperature and high humidity conditions, and overcomes the problem of easy deactivation of traditional catalysts.

[0018] The nano high-silicon AFX zeolite molecular sieve prepared by the present invention has a small particle size (nanoscale), a larger specific surface area, and a uniform pore distribution, which helps to improve the mass transfer efficiency in the SCR reaction and further enhance the catalytic activity.

[0019] The invention has a simple synthesis route, low production cost and controllable conditions, which greatly reduces the production cost, is suitable for large-scale production and meets the needs of industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings.

[0021] Figure 1 The PXRD spectrum of the nano-high silicon AFX zeolite molecular sieve prepared in Example 1;

[0022] Figure 2 The PXRD spectrum of the nano-high silicon AFX zeolite molecular sieve prepared in Example 2;

[0023] Figure 3 The PXRD spectrum of the nano-high-silicon AFX zeolite molecular sieve prepared in Example 3;

[0024] Figure 4The PXRD spectrum of the nano-high silicon AFX zeolite molecular sieve prepared in Example 4;

[0025] Figure 5 This is the SEM image of the nano-high-silicon AFX zeolite molecular sieve prepared in Example 1. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The small molecule organic template used in the present invention synthesizes nanometer high silicon AFX zeolite molecular sieve, the preparation method is simple, the raw material price is low, the production cost is greatly reduced, and it is suitable for industrial promotion. The silicon-aluminum ratio of the AFX molecular sieve of the present invention is as high as 9, which is very suitable for NH 3 -SCR reaction.

[0028] The nanometer high silicon AFX zeolite molecular sieve provided by the present invention is obtained by hydrothermal crystallization after mixing raw materials, wherein the raw materials include a tetravalent silicon source, an aluminum source, water, an inorganic base and a template agent, wherein the tetravalent silicon source in the raw materials is in the form of SiO 2 The aluminum source is Al 2 O 3 The inorganic base is in M 2 O meter, SiO 2 、Al 2 O 3 、M 2 O, template, H 2 The molar ratio of O is (20-60):1:(5-20):(1-5):(600-1500), and M is a metal element of the inorganic base.

[0029] In some specific embodiments of the present invention, the tetravalent silicon source is at least one of silicate, silica sol, tetraethyl orthosilicate, precipitated silica, white carbon black and clay. In some preferred embodiments of the present invention, the tetravalent silicon source is silica sol. In some more preferred embodiments of the present invention, the tetravalent silicon source is AS-40 silica sol.

[0030] In some specific embodiments of the present invention, the aluminum source is at least one of Y molecular sieve, sodium metaaluminate, alumina powder, and pseudo-boehmite. In some preferred embodiments of the present invention, the aluminum source is Y molecular sieve.

[0031] In some specific embodiments of the present invention, the inorganic base is at least one of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide. In some preferred embodiments of the present invention, the inorganic base is sodium hydroxide.

[0032] In some specific embodiments of the present invention, the template agent is an aqueous solution of 1,5-dipiperidinylhexane, and the mass fraction of the template agent aqueous solution is 15% to 40%.

[0033] The present invention also provides a method for preparing nano high-silicon AFX zeolite molecular sieve, which specifically comprises the following steps:

[0034] S1, template, inorganic base and water are mixed and stirred evenly, an aluminum source is added and stirred for 1 to 3 hours, and then a silicon source is added and stirred for 1 to 3 hours to obtain a reaction gel;

[0035] S2, hydrothermally crystallizing the reaction gel of S1, filtering, drying and calcining after hydrothermal crystallization to obtain nano high-silicon AFX zeolite molecular sieve.

[0036] In some specific embodiments of the present invention, the hydrothermal crystallization reaction temperature is 100°C to 200°C, and the reaction time is 24 to 96 hours. In some preferred embodiments of the present invention, the hydrothermal crystallization reaction temperature is 140°C to 160°C, and the reaction time is 72 to 96 hours. In some more preferred embodiments of the present invention, the hydrothermal crystallization reaction temperature is 150°C, and the hydrothermal crystallization reaction time is 72 hours. The hydrothermal crystallization reaction of the present invention adopts a dynamic hydrothermal crystallization reaction, and the crystallization process is carried out in an autoclave so that the reaction mixture reacts under autogenous pressure to form a small-pore zeolite molecular sieve.

[0037] In some specific embodiments of the present invention, the drying temperature is 80°C to 150°C, the drying time is 10 to 20 hours, the roasting temperature is 450°C to 600°C, and the roasting time is 2 to 6 hours. In some preferred embodiments of the present invention, the drying temperature is 100 to 150°C, the roasting temperature is 550°C, and the roasting time is 4 hours.

[0038] The nano high silicon AFX zeolite molecular sieve prepared by the present invention is used for NH 3 -SCR reaction.

[0039] In order to further illustrate the present invention, the following examples are provided for detailed description. The raw materials used in the following examples of the present invention are all commercially available.

[0040] Example 1 A method for preparing a nano-high silicon AFX zeolite molecular sieve, the steps are as follows:

[0041] S1. 10.6 g of 1,5-dipiperidine hexane solution with a mass fraction of 19.87% and 0.35 g of NaOH were mixed evenly in 60 g of deionized water, and then 5.8 g of Y molecular sieve was added and stirred for 1 h, and then 13 g of AS-40 was added and stirred for 2 h to obtain a reaction gel;

[0042] S2, transferring the reaction gel into a crystallization kettle and dynamically crystallizing at 150° C. for 72 h to obtain a reaction slurry;

[0043] S3, the reaction slurry was filtered, washed with water until neutral, dried at 100°C for 12h, and then calcined at 550°C for 4h to obtain nano high silicon AFX zeolite molecular sieve. The PXRD of the sample was as follows: Figure 1 The silicon-aluminum ratio of the obtained sample is 9.26.

[0044] Example 2 A method for preparing a nano-high silicon AFX zeolite molecular sieve, the steps are as follows:

[0045] S1. 15.35 g of a 19.87% 1,5-dipiperidine hexane solution and 0.26 g of NaOH were mixed evenly in 60 g of deionized water, and then 3.95 g of Y molecular sieve was added and stirred for 1 h, and then 13.6 g of AS-40 was added and stirred for 2 h to obtain a reaction gel;

[0046] S2, transferring the reaction gel into a crystallization kettle and dynamically crystallizing at 150° C. for 72 h to obtain a reaction slurry;

[0047] S3, the reaction slurry was filtered, washed with water until neutral, dried at 100°C for 12h, and then calcined at 550°C for 4h to obtain nano high silicon AFX zeolite molecular sieve. The PXRD of the sample was as follows: Figure 2 The silicon-aluminum ratio of the obtained sample is 9.08.

[0048] Example 3 A method for preparing a nano-high silicon AFX zeolite molecular sieve, the steps are as follows:

[0049] S1. 13.5 g of 1,5-dipiperidine hexane solution with a mass fraction of 19.87% and 0.74 g of NaOH were mixed evenly in 66 g of deionized water, and then 3.68 g of Y molecular sieve was added and stirred for 1 h, and then 12.8 g of AS-40 was added and stirred for 2 h to obtain a reaction gel;

[0050] S2, transferring the reaction gel into a crystallization kettle and dynamically crystallizing at 150° C. for 72 h to obtain a reaction slurry;

[0051] S3, the reaction slurry was filtered, washed with water until neutral, dried at 100°C for 12h, and then calcined at 550°C for 4h to obtain nano high silicon AFX zeolite molecular sieve. The PXRD of the sample was as follows: Figure 3The silicon-aluminum ratio of the obtained sample is 9.23.

[0052] Example 4 A method for preparing a nano-high silicon AFX zeolite molecular sieve, the steps are as follows:

[0053] S1. 16.3 g of 1,5-dipiperidine hexane solution with a mass fraction of 19.87% and 0.74 g of NaOH were mixed evenly in 66 g of deionized water, and then 3.68 g of Y molecular sieve was added and stirred for 1 h, and then 12.8 g of AS-40 was added and stirred for 2 h to obtain a reaction gel;

[0054] S2, transferring the reaction gel into a crystallization kettle and dynamically crystallizing at 150° C. for 72 h to obtain a reaction slurry;

[0055] S3, the reaction slurry was filtered, washed with water until neutral, dried at 100°C for 12h, and then calcined at 550°C for 4h to obtain nano high silicon AFX zeolite molecular sieve. The PXRD of the sample was as follows: Figure 3 The silicon-aluminum ratio of the obtained sample is 9.23.

[0056] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A nano high-silicon AFX zeolite molecular sieve, characterized in that: The nano high-silicon AFX zeolite molecular sieve is obtained by hydrothermal crystallization after mixing raw materials; The raw materials include a tetravalent silicon source, an aluminum source, water, an inorganic base and a template agent; The tetravalent silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the inorganic base is calculated as M2O. The molar ratio of SiO2, Al2O3, M2O, template, and H2O in the raw material is (20-60):1:(5-20):(1-5):(600-1500), and M is a metal element of the inorganic base; The template agent is 1,5-dipiperidinylhexane.

2. The nano-silicon AFX zeolite molecular sieve according to claim 1, characterized in that: The tetravalent silicon source is at least one of silicate, silica sol, tetraethyl orthosilicate, precipitated silica, white carbon black and clay.

3. The nano-silicon AFX zeolite molecular sieve according to claim 1, characterized in that: The tetravalent silicon source is silica sol.

4. The nano-silicon AFX zeolite molecular sieve according to claim 1, characterized in that: The aluminum source is at least one of Y molecular sieve, sodium aluminate, alumina powder, and pseudo-boehmite.

5. The nano-silicon AFX zeolite molecular sieve according to claim 1, characterized in that: The inorganic base is at least one of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.

6. The method for preparing nano high-silicon AFX zeolite molecular sieve according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, template, inorganic base and water are mixed and stirred evenly, an aluminum source is added and stirred evenly, and then a silicon source is added and stirred evenly to obtain a reaction gel; S2, hydrothermally crystallizing the reaction gel of S1, filtering, drying and calcining after hydrothermal crystallization to obtain nano high-silicon AFX zeolite molecular sieve.

7. The preparation method according to claim 6, characterized in that: The hydrothermal crystallization reaction temperature is 100° C. to 200° C., and the reaction time is 24 to 96 hours.

8. The preparation method according to claim 6, characterized in that: The hydrothermal crystallization reaction adopts a dynamic hydrothermal crystallization reaction, and the crystallization process is carried out in an autoclave.

9. The preparation method according to claim 6, characterized in that: The drying temperature is 80° C. to 150° C., the drying time is 10 to 20 hours, the roasting temperature is 450° C. to 600° C., and the roasting time is 2 to 6 hours.

10. Application of nano high silicon AFX zeolite molecular sieve in NH3-SCR reaction, characterized in that: The nano-high-silicon AFX zeolite molecular sieve is the nano-high-silicon AFX zeolite molecular sieve described in claims 1 to 5 or the nano-high-silicon AFX zeolite molecular sieve prepared by the method described in any one of claims 6 to 9.

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