A hierarchical porous Beta & MOR eutectic molecular sieve, its synthesis method and application.

Abstract

This application discloses a hierarchical porous Beta & MOR eutectic molecular sieve, its synthesis method, and its application. The method includes the following steps: mixing an alkali source, a structure-directing agent, and a silicon source; hydrolyzing the mixture; adding an aluminum source, a mesoporous pore-forming agent, and water; crystallizing the mixture in a sealed container; washing; drying; and calcining to obtain the hierarchical porous Beta & MOR eutectic molecular sieve. The degree of hydrolysis of the silicon source and the pore-forming agent jointly determine the pore size and volume of the mesopores; while the aluminum content, crystallization temperature, and amount of structure-directing agent jointly determine the ratio of Beta to MOR in the eutectic molecular sieve. By controlling the composition of the hydrothermal synthesis materials and the crystallization conditions, this application can achieve a Beta content in the Beta & MOR eutectic molecular sieve that can be varied between 5% and 95%.

Description

Technical Field

[0001] This application relates to a hierarchical porous Beta & MOR eutectic molecular sieve, its synthesis method and application, and belongs to the field of molecular sieve synthesis. Background Technology

[0002] Beta molecular sieves possess a three-dimensional twelve-membered ring cross-channel structure, wherein the diameter of the straight channels is [missing information]. The diameter of the sinusoidal channel is The pore structure of MOR molecular sieve consists of a twelve-membered ring main channel in the

[001] direction. and the eight-eight ring channel And

[010] oriented twisted bag-like channels. Since Beta and MOR zeolites contain the same secondary structural units and can both be synthesized using tetraethylammonium ion-directed synthesis, MOR zeolites often appear as an impurity phase during the synthesis of Beta zeolites. This characteristic also provides a framework for synthesizing Beta & MOR eutectic zeolites. Both Beta and MOR have important applications in the chemical industry; the development of eutectic zeolites provides more opportunities for modifying pore structure and acid properties, and also offers more possibilities for broadening the application scenarios of Beta and MOR zeolites.

[0003] Currently, researchers often focus their efforts on the synthesis of pure-phase Beta and pure-phase MOR, with the suppression of MOR impurity phase formation in the Beta synthesis system being a key research focus. This has led to relatively little research on Beta & MOR eutectic molecular sieves, especially on the regulation of the Beta to MOR ratio in eutectic molecular sieves. CN103058212B discloses a method for synthesizing Beta-MOR composite molecular sieves. This method uses mordenite zeolite treated with alkali as a structure directing agent, then adds Beta molecular sieves, and obtains the Beta-MOR composite molecular sieve through hydrothermal crystallization. CN1397493A discloses a class of twelve-membered ring structure two-phase symbiotic molecular sieves, including three types: β-zeolite-mordenite, β-zeolite-ZSM-12, and mordenite-ZSM-12. The key feature is the hydrothermal synthesis using tetraethylammonium salt as a template agent or tetraethylammonium salt-fluoride as a composite template agent. CN101177276B discloses a method for preparing a Beta@MOR core-shell composite zeolite, characterized by first synthesizing a Beta zeolite core, then directly adding aluminum, the organic template agent tetraethylammonium bromide, and a base to a mixture containing Beta zeolite, using Beta zeolite as the silicon source for the synthesis of mordenite zeolite, to obtain a binary composite zeolite material. CN114471691B reports a method for preparing a Beta / mordenite composite crystalline phase zeolite catalyst, characterized by using Beta as a seed crystal to obtain a composite crystalline phase molecular sieve. CN1648046A discloses a method for preparing a mixed crystalline material of mordenite and β-zeolite, characterized by adding mordenite as a seed crystal to a synthetic mixture of β-zeolite, followed by hydrothermal crystallization. CN102039164A relates to a method for preparing a binder-free mordenite / β-zeolite symbiotic molecular sieve catalyst. It is characterized by crystallizing β-zeolite after molding to obtain a binder-free mordenite / β-zeolite symbiotic molecular sieve catalyst. *Chemical Reaction Engineering and Technology*, 2011, 27:385-392, reported the synthesis of a core-shell molecular sieve coated with Beta on the surface of MOR. The prepared core-shell molecular sieve exhibited superior catalytic performance compared to a single molecular sieve in the thallium pyrolysis reaction. *JMater Sci.*, 2008, 43:5626-5633, studied the synthesis of Beta / MOR eutectic molecular sieves using tetraethylammonium fluoride as a template agent. The authors provided detailed characterization and analysis of the crystallization mechanism and the formation conditions of MOR, proposing that the eutectic molecular sieve possesses characteristics distinct from the physically mixed phase of Beta and MOR. *Chinese Journal of Catalysis*, 2006, 27:228-232, investigated the acidity of Beta / MOR symbiotic molecular sieves and their performance in methanol-to-dimethyl ether conversion. Summary of the Invention

[0004] Based on the easy coexistence of Beta and MOR, this invention proposes a method for preparing eutectic molecular sieve materials with adjustable Beta and MOR ratios. Simultaneously, based on the role of silicon-based templates and organic mesoporous directing agents, mesopores are introduced into the eutectic molecular sieve, resulting in the synthesis of hierarchical porous Beta & MOR eutectic molecular sieves with adjustable crystal phase ratios, pore structures, acid content, and acid strength.

[0005] The purpose of this invention is to develop a method for synthesizing hierarchical porous Beta & MOR eutectic molecular sieves. Mesopores are created in the eutectic molecular sieve using unhydrolyzed silicon source and mesoporous pore-forming agent; TEAOH and organic alcohol are used as template agent and pore-filling agent, respectively; based on the characteristics of rapid MOR crystal growth rate and more stable MOR structure at high temperatures, the ratio of Beta to MOR in the eutectic molecular sieve can be adjusted by varying the crystallization temperature, aluminum source, and template agent dosage, thus achieving a Beta content range of 5% to 95% in the Beta & MOR eutectic molecular sieve.

[0006] According to one aspect of this application, a method for synthesizing hierarchical porous Beta & MOR eutectic molecular sieves is provided, comprising the following steps:

[0007] The alkaline source, structure directing agent and silicon source are mixed and hydrolyzed. An aluminum source, mesoporous pore-forming agent and water are added. The mixture is then crystallized, washed, dried and calcined in a sealed container to obtain the multi-level porous Beta&MOR eutectic molecular sieve.

[0008] The alkali source is selected from at least one of sodium hydroxide and potassium hydroxide;

[0009] The structure-directing agent is selected from a mixture of TEAOH and organic alcohols;

[0010] The organic alcohol is selected from at least one of ethanol, propanol, or n-butanol;

[0011] The silicon source is selected from at least one of solid silica gel, tetraethyl orthosilicate, silica sol, or fumed silica.

[0012] The aluminum source is selected from at least one of sodium aluminate, aluminum nitrate, aluminum chloride, or aluminum sulfate;

[0013] The mesoporous pore-forming agent is selected from at least one of hexadecyltrimethylammonium bromide, polyethylene glycol, or N,N-dimethylhexadecylammonium.

[0014] The molar ratio of the alkali source to the silicon source is 0.01 to 0.25;

[0015] The molar ratio of the structure directing agent to the silicon source is 0.05 to 1;

[0016] The molar ratio of the silicon source to the aluminum source is 10 to 200;

[0017] The mass ratio of the mesoporous pore-forming agent to the silicon source is 0 to 0.3.

[0018] The molar ratio of water to silicon source is 5 to 30;

[0019] The molar amount or mass of the silicon source is expressed as the molar amount or mass of SiO2 contained therein;

[0020] The molar amount of aluminum source is expressed as the molar amount of Al2O3 in it.

[0021] The hydrolysis temperature is 40–90°C;

[0022] The hydrolysis time is 1–10 hours;

[0023] The crystallization temperature is 80–200°C;

[0024] The crystallization time is 24–120 hours;

[0025] The drying temperature is 80–120°C;

[0026] The drying time is 5 to 20 hours;

[0027] The calcination temperature is 400–600°C;

[0028] The roasting time is 2 to 15 hours.

[0029] The washing process is carried out using at least one of the following: water, ethanol, or cyclohexane.

[0030] According to another aspect of this application, a hierarchical porous Beta & MOR eutectic molecular sieve prepared by the above-described preparation method is provided, wherein the content of Beta molecular sieve in the hierarchical porous Beta & MOR eutectic molecular sieve is 5-95 wt%.

[0031] The hierarchical porous Beta&MOR eutectic molecular sieve synthesized based on the above method is a sodium / potassium type molecular sieve, which can be converted into a hydrogen type eutectic molecular sieve through ion exchange.

[0032] The beneficial effects that this application can produce include:

[0033] The synthesis method of multi-level porous Beta & MOR eutectic molecular sieve provided by the present invention can adjust the Beta content in the Beta & MOR eutectic molecular sieve between 5% and 95% by controlling the composition of the hydrothermal synthesis materials and the crystallization conditions. Attached Figure Description

[0034] Figure 1 The X-ray diffraction pattern of the sample is shown in the example. Detailed Implementation

[0035] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0036] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0037] Example 1

[0038] The material ratios in Example 1 are as follows: the molar ratio of alkali source (MOH) to silicon source is MOH / SiO2 = 0.096; the molar ratio of structure directing agent (S) to silicon source is S / SiO2 = 0.76; the molar ratio of silicon source to aluminum source is SiO2 / Al2O3 = 21.7; the mass ratio of mesoporous pore-forming agent (M) to silicon source is M / SiO2 = 0.27; and the molar ratio of water to silicon source is H2O / SiO2 = 15.6.

[0039] The specific operation is as follows: First, 0.480g sodium hydroxide, 29.270g tetraethylammonium hydroxide solution (40wt%), 1.100g n-butanol, 2.253g silica gel and 18.228g tetraethyl orthosilicate were mixed and hydrolyzed at 40℃ for 7h; then 2.157g aluminum nitrate nonahydrate, 17.500g water and 2.000g hexadecyltrimethylammonium bromide were added to the hydrolyzed mixture and stirred evenly. The mixture was then crystallized in a reactor at 140℃ for 72h. After washing by ethanol filtration, it was dried at 100℃ for 12h. Finally, the temperature was increased to 500℃ at 1℃ / min and held for 3.5h to obtain hierarchical porous Beta&MOR eutectic molecular sieve (Z1).

[0040] like Figure 1 As shown, the X-ray diffraction pattern of Z1 shows characteristic diffraction peaks containing Beta and MOR molecular sieves; by calculation, the mass percentage of Beta molecular sieve is 90%.

[0041] Example 2

[0042] The material ratios in Example 2 are as follows: the molar ratio of alkali source (MOH) to silicon source is MOH / SiO2 = 0.096; the molar ratio of structure directing agent (S) to silicon source is S / SiO2 = 0.61; the molar ratio of silicon source to aluminum source is SiO2 / Al2O3 = 16.7; the mass ratio of mesoporous pore-forming agent (M) to silicon source is M / SiO2 = 0.13; and the molar ratio of water to silicon source is H2O / SiO2 = 13.7.

[0043] The specific operation is as follows: First, 0.480g sodium hydroxide, 22.270g tetraethylammonium hydroxide solution (40wt%), 1.200g n-butanol, 5.257g silica gel and 7.812g tetraethyl orthosilicate were mixed and hydrolyzed at 40℃ for 7h; then 2.800g aluminum nitrate nonahydrate, 17.500g water and 1.000g hexadecyltrimethylammonium bromide were added to the hydrolyzed mixture and stirred evenly. The mixture was then crystallized in a reactor at 160℃ for 72h. After washing by ethanol filtration, it was dried at 100℃ for 12h. Finally, the temperature was increased to 500℃ at 1℃ / min and held for 3.5h to obtain hierarchical porous Beta&MOR eutectic molecular sieve (Z2).

[0044] Example 2 is based on Example 1, but with a reduced amount of template agent and increased crystallization temperature and aluminum content, promoting the formation of a more thermodynamically stable MOR phase. Figure 1 As shown, the X-ray diffraction pattern of Z2 reveals characteristic diffraction peaks containing Beta and MOR molecular sieves; calculations show that the mass percentage of Beta molecular sieve is 71%.

[0045] Example 3

[0046] The material ratios in Example 3 are as follows: the molar ratio of alkali source (MOH) to silicon source is MOH / SiO2 = 0.096; the molar ratio of structure directing agent (S) to silicon source is S / SiO2 = 0.58; the molar ratio of silicon source to aluminum source is SiO2 / Al2O3 = 15.6; the mass ratio of mesoporous pore-forming agent (M) to silicon source is M / SiO2 = 0.13; and the molar ratio of water to silicon source is H2O / SiO2 = 13.1.

[0047] The specific operation is as follows: First, 0.480g sodium hydroxide, 20.000g tetraethylammonium hydroxide solution (40wt%), 1.300g n-butanol, 5.257g silica gel and 7.812g tetraethyl orthosilicate were mixed and hydrolyzed at 40℃ for 7h; then 3.000g aluminum nitrate nonahydrate, 17.500g water and 1.000g hexadecyltrimethylammonium bromide were added to the hydrolyzed mixture and stirred evenly. The mixture was then crystallized in a reactor at 180℃ for 72h, washed by ethanol filtration, dried at 100℃ for 12h, and finally heated to 500℃ at 1℃ / min and held for 3.5h to obtain hierarchical porous Beta&MOR eutectic molecular sieve (Z3).

[0048] Example 3 is based on Example 2, further reducing the amount of template agent, increasing the crystallization temperature to 180℃, and increasing the aluminum nitrate nonahydrate content to 3.000g. Figure 1 As shown, the X-ray diffraction pattern of Z3 reveals characteristic diffraction peaks containing Beta and MOR molecular sieves; calculations show that the mass percentage of Beta molecular sieve is reduced to 57%.

[0049] Example 4

[0050] The material ratios in Example 4 are as follows: the molar ratio of alkali source (MOH) to silicon source is MOH / SiO2 = 0.096; the molar ratio of structure directing agent (S) to silicon source is S / SiO2 = 0.54; the molar ratio of silicon source to aluminum source is SiO2 / Al2O3 = 13.4; the mass ratio of mesoporous pore-forming agent (M) to silicon source is M / SiO2 = 0.13; and the molar ratio of water to silicon source is H2O / SiO2 = 12.6.

[0051] The specific operation is as follows: First, 0.480g sodium hydroxide, 18.000g tetraethylammonium hydroxide solution (40wt%), 1.400g n-butanol, 5.257g silica gel and 7.812g tetraethyl orthosilicate are mixed and hydrolyzed at 40℃ for 7h; then 3.500g aluminum nitrate nonahydrate, 17.500g water and 1.000g hexadecyltrimethylammonium bromide are added to the hydrolyzed mixture and stirred evenly. The mixture is then crystallized in a reactor at 180℃ for 80h, washed by ethanol filtration, dried at 100℃ for 12h, and finally heated to 500℃ at 1℃ / min and held for 3.5h to obtain hierarchical porous Beta&MOR eutectic molecular sieve (Z4).

[0052] Example 4 is based on Example 3, further reducing the amount of template agent and increasing the content of aluminum nitrate nonahydrate to 3.500g. Figure 1 As shown, the X-ray diffraction pattern of Z4 reveals characteristic diffraction peaks containing both Beta and MOR molecular sieves; calculations show that the mass percentage of Beta molecular sieve is reduced to 39%.

[0053] Example 5

[0054] The material ratios in Example 5 are as follows: the molar ratio of alkali source (MOH) to silicon source is MOH / SiO2 = 0.096; the molar ratio of structure directing agent (S) to silicon source is S / SiO2 = 0.49; the molar ratio of silicon source to aluminum source is SiO2 / Al2O3 = 11.7; the mass ratio of mesoporous pore-forming agent (M) to silicon source is M / SiO2 = 0.13; and the molar ratio of water to silicon source is H2O / SiO2 = 11.8.

[0055] The specific operation is as follows: First, 0.480g sodium hydroxide, 15.000g tetraethylammonium hydroxide solution (40wt%), 1.500g n-butanol, 5.257g silica gel and 7.812g tetraethyl orthosilicate are mixed and hydrolyzed at 40℃ for 7h; then 4.000g aluminum nitrate nonahydrate, 17.500g water and 1.000g hexadecyltrimethylammonium bromide are added to the hydrolyzed mixture and stirred evenly. The mixture is then crystallized in a reactor at 180℃ for 96h, washed by ethanol filtration, dried at 100℃ for 12h, and finally heated to 500℃ at 1℃ / min and held for 3.5h to obtain hierarchical porous Beta&MOR-5 eutectic molecular sieve (Z5).

[0056] Example 5 is based on Example 4, further reducing the amount of template agent and increasing the content of aluminum nitrate nonahydrate to 4.000g. Figure 1 As shown, the X-ray diffraction pattern of Z5 reveals characteristic diffraction peaks containing Beta and MOR molecular sieves; calculations show that the mass percentage of Beta molecular sieve is reduced to 20%.

[0057] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for synthesizing a hierarchical porous Beta & MOR eutectic molecular sieve, characterized in that, Includes the following steps: The alkaline source, structure directing agent and silicon source are mixed and hydrolyzed. An aluminum source, mesoporous pore-forming agent and water are added. The mixture is then crystallized, washed, dried and calcined in a sealed container to obtain the multi-level porous Beta&MOR eutectic molecular sieve.

2. The method according to claim 1, characterized in that, The alkali source is selected from at least one of sodium hydroxide and potassium hydroxide; The structure-directing agent is selected from a mixture of TEAOH and organic alcohols; The organic alcohol is selected from at least one of ethanol, propanol, or n-butanol; The silicon source is selected from at least one of solid silica gel, tetraethyl orthosilicate, silica sol, or fumed silica. The aluminum source is selected from at least one of sodium aluminate, aluminum nitrate, aluminum chloride, or aluminum sulfate; The mesoporous pore-forming agent is selected from at least one of hexadecyltrimethylammonium bromide, polyethylene glycol, or N,N-dimethylhexadecylammonium.

3. The method according to claim 1, characterized in that, The molar ratio of the alkali source to the silicon source is 0.01 to 0.25; The molar ratio of the structure directing agent to the silicon source is 0.05 to 1; The molar ratio of the silicon source to the aluminum source is 10 to 200; The mass ratio of the mesoporous pore-forming agent to the silicon source is 0 to 0.

3. The molar ratio of water to silicon source is 5 to 30; The molar amount or mass of the silicon source is expressed as the molar amount or mass of SiO2 contained therein; The molar amount of aluminum source is expressed as the molar amount of Al2O3 in it.

4. The method according to claim 1, characterized in that, The hydrolysis temperature is 40–90°C; The hydrolysis time is 1–10 hours; The crystallization temperature is 80–200°C; The crystallization time is 24–120 hours; The drying temperature is 80–120°C; The drying time is 5 to 20 hours; The roasting temperature is 400–600°C; The roasting time is 2 to 15 hours.

5. The method according to claim 1, characterized in that, The washing process is carried out using at least one of the following: water, ethanol, or cyclohexane.

6. A hierarchical porous Beta & MOR eutectic molecular sieve prepared by the preparation method according to any one of claims 1 to 5, characterized in that, The content of Beta molecular sieve in the multi-level porous Beta&MOR eutectic molecular sieve is 5-95 wt%.

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