A crystallized pillared two-dimensional MFI molecular sieve and its preparation method and application

Abstract

The present invention discloses a crystallized pillared two-dimensional MFI molecular sieve and its preparation method and application, specifically relating to the field of molecular sieve modification technology. The preparation method of the crystallized pillared two-dimensional MFI molecular sieve provided by the present invention first introduces a silicon source between adjacent layers of unpillared two-dimensional MFI molecular sieve sheets for vapor phase pillaring, and then introduces a structure-directing agent for secondary crystallization, forming crystallized pillars between adjacent layers of the two-dimensional MFI molecular sieve. This not only improves the structural stability of the two-dimensional lamellae MFI molecular sieve, but also enhances the catalytic performance of the MFI molecular sieve in the alkylation reaction of phenol and tert-butanol, prolongs the catalyst life, and has excellent regeneration performance.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve modification, and in particular to a crystallized pillared two-dimensional MFI molecular sieve and a preparation method and application thereof. Background Art

[0002] 4-tert-Butylphenol (p-tert-butylphenol) is one of the most important alkylphenols in industry, produced by the Friedel-Crafts alkylation reaction of phenol with tert-butyl alcohol. This reaction typically uses liquid acids such as HF and H2SO4 as catalysts. This leads to a series of problems, including large waste acid emissions, severe equipment corrosion, and high energy consumption for subsequent separations. The use of a solid acid catalytic process based on MFI molecular sieves not only overcomes these environmental safety issues but also allows for catalyst regeneration, meeting the country's critical need for green, low-carbon, and clean production.

[0003] MFI molecular sieve has a ten-membered ring cross-pore structure It has the advantages of adjustable acidity and high thermal stability, making it suitable for catalyzing the alkylation reaction of phenol with tert-butanol. However, due to its single microporous structure, traditional microporous MFI molecular sieves are diffusion-limited in the alkylation reaction of phenol with tert-butanol, resulting in low catalytic activity and easy deactivation due to carbon deposition. Therefore, constructing a two-dimensional MFI molecular sieve with a two-dimensional ultra-thin layer structure can not only effectively shorten the diffusion path of guest molecules but also expose more accessible active sites, thereby reducing the mass transfer resistance of the MFI molecular sieve catalyst, improving catalytic activity, and extending its service life. However, during the calcination process of traditional two-dimensional MFI molecular sieves to remove the organic template, the ordered structure of the two-dimensional nanosheets stacked multilayers collapses and becomes irregularly stacked, resulting in the loss of mesopores between adjacent nanosheet layers of the two-dimensional MFI molecular sieve, and the inability to provide fast diffusion channels for the alkylation reaction of phenol with tert-butanol. Constructing pillars between adjacent layers of the two-dimensional MFI molecular sieve can solve this problem. Methods for introducing pillars into MFI molecular sieve sheets can be categorized into conventional pillaring and vapor-phase pillaring. The former employs a solid-liquid mixing method, which uses excessive amounts of solvent and has cumbersome synthesis and separation steps. Vapor-phase pillaring directly utilizes vapor under solid-liquid separation conditions to effectively introduce solute molecules between adjacent layers of the two-dimensional MFI molecular sieve. This process requires 10 times less silicon source than conventional pillaring, eliminates the need for product recovery and separation, and produces no liquid waste.

[0004] Prior art discloses a method for introducing pillars into a two-dimensional molecular sieve via a vapor-phase strategy. By exposing the molecular sieve to a vapor of ethyl orthosilicate and water, silica pillars are introduced into the molecular sieve sheets, resulting in a two-dimensional nanosheet-pillared molecular sieve. However, the pillars produced by this prior art are composed of amorphous silica, which is highly sensitive to water molecules generated during the alkylation reaction of phenol and tert-butanol, thus reducing the structural stability of the molecular sieve. Summary of the Invention

[0005] In order to solve the problem that the amorphous silica pillars in the pillared two-dimensional MFI molecular sieves prepared by the prior art are unstable when exposed to water, the present invention provides a method for preparing a crystallized pillared two-dimensional MFI molecular sieve. After the silica pillars are constructed between the molecular sieve layers by the vapor phase pillaring method, a structure directing agent is introduced to form crystallized silica pillars between the layers in the molecular sieve structure, thereby inhibiting the structural collapse of the molecular sieve that is prone to occur when exposed to water.

[0006] Another object of the present invention is to provide a crystallized pillared two-dimensional MFI molecular sieve.

[0007] Another object of the present invention is to provide an application of the above-mentioned crystallized pillared two-dimensional MFI molecular sieve in catalyzing the alkylation reaction of phenol and tert-butanol.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a crystallized pillared two-dimensional MFI molecular sieve comprises the following steps:

[0010] S1. The unpillared two-dimensional sheet MFI molecular sieve is placed in a silicon source vapor for vapor phase pillaring, and after the pillaring reaction is completed, a vapor phase pillared two-dimensional MFI molecular sieve is obtained;

[0011] S2. The vapor-phase pillared two-dimensional MFI molecular sieve obtained in step S1 is sequentially placed in structure-directing agent vapor and water vapor for crystallization. After the crystallization is completed, a crystallized pillared two-dimensional MFI molecular sieve can be obtained.

[0012] Conventional silicon sources and structure-directing agents in the art can be used in the present invention. Specifically, the silicon source in step S1 of the present invention can be ethyl orthosilicate; and the structure-directing agent in step S2 can be tetrapropylammonium hydroxide.

[0013] Step S1 is a conventional method for preparing a silica vapor-phase pillared two-dimensional MFI molecular sieve. In steps S1 and S2, the unpillared two-dimensional lamellae MFI molecular sieve is sequentially exposed to silicon source vapor, structure-directing agent vapor, and water vapor. This introduces silicon atoms into adjacent lamellae within the two-dimensional MFI molecular sieve. The structure-directing agent is then introduced between adjacent lamellae to achieve orderly alignment of the silicon atoms. Finally, the vapor-phase pillared molecular sieve is subjected to hydrolysis and crystallization in water vapor, converting the orderly aligned silicon atoms into crystallized MFI molecular sieve pillars, resulting in excellent stability.

[0014] In a specific embodiment of the present invention, the silicon source vapor in step S1 is obtained by vaporizing a silicon source solution at 100-200°C; the structure-directing agent vapor in step S2 is obtained by vaporizing a structure-directing agent solution at 100-200°C, and the water vapor is obtained by vaporizing water at 60-100°C. The vaporization temperatures of the structure-directing agent solution and water in step S2 are the crystallization temperatures of the vapor-phase pillared two-dimensional MFI molecular sieve when crystallized in the structure-directing agent vapor and water vapor, respectively. This is because, in a specific embodiment of the present invention, the specific operation of crystallizing the molecular sieve is: the vapor phase pillared two-dimensional MFI molecular sieve is loaded into a small PTFE bottle, and the small PTFE bottle is placed in turn in another larger PTFE bottle respectively filled with a structure directing agent solution and water, the small PTFE bottle is opened and placed in the large PTFE bottle, and then placed in a hydrothermal reactor, and finally placed in an oven, and the oven temperature is adjusted to the crystallization temperature. At this time, the structure directing agent solution and water will be vaporized to form structure directing agent steam and water vapor respectively, and the structure directing agent molecules and water molecules will enter the two-dimensional MFI molecular sieve layers in turn to carry out the crystallization process.

[0015] Preferably, the molar ratio of the structure directing agent in step S2 to the silicon source in step S1 is 1:(1.5-2).

[0016] In a specific embodiment of the present invention, the silicon source vapor in step S1 and the structure directing agent vapor in step S2 are obtained by vaporizing the silicon source aqueous solution and the structure directing agent aqueous solution, respectively. Therefore, the molar ratio of the above-mentioned structure directing agent to the silicon source refers to the molar ratio of the silicon source in the silicon source aqueous solution and the structure directing agent in the structure directing agent.

[0017] Controlling the molar ratio of the structure directing agent to the silicon source to 1: (1.5-2) can fully crystallize the amorphous silica columns introduced between the two-dimensional MFI molecular sieve sheets, and the resulting molecular sieve has more microporous structures and higher The acidic site concentration can show higher catalytic activity in the alkylation reaction of phenol and tert-butanol. When the amount of structure directing agent added is too little, the amorphous silica pillars are difficult to be fully crystallized; when the amount of structure directing agent added is too much, the silicon atoms introduced between the two-dimensional MFI molecular sieve layers need to surround the structure directing agent to build crystallized pillars. Excessive structure directing agents will aggregate with each other, which makes it impossible for the silicon atoms around the structure directing agent to be tightly arranged. Therefore, the original amorphous silica pillars are difficult to crystallize, and the number of micropores and the number of micropores in the obtained molecular sieve are small. The concentration of acidic sites is also difficult to increase.

[0018] Preferably, the crystallization temperature in step S2 is 60-200°C.

[0019] Preferably, the total crystallization time in step S2 is 36 to 60 hours.

[0020] When the crystallization temperature and the total crystallization time in step S2 are controlled within the above ranges, the crystallization process inside the two-dimensional MFI molecular sieve layer can be fully carried out, and the reaction energy consumption is appropriate.

[0021] Preferably, after the crystallization is completed in step S2, the crystallized pillared two-dimensional MFI molecular sieve needs to be calcined, and after the calcination is completed, it is placed in an aqueous solution containing ammonium radicals for ion exchange.

[0022] In a specific embodiment of the present invention, the specific calcination conditions can be calcining in an N2 atmosphere at 400-500°C for 6-8h, and then calcining in an air atmosphere at 550-600°C for 10-12h; the aqueous solution containing ammonium ions can be an NH4Cl aqueous solution.

[0023] After crystallization, the obtained molecular sieve is calcined to remove the remaining structure-directing agent. After calcination, the molecular sieve is placed in an aqueous solution containing ammonium ions for ion exchange, which can utilize ammonium ions to change the properties of the molecular sieve surface and further improve the catalytic performance of the obtained crystallized pillared two-dimensional MFI molecular sieve.

[0024] Preferably, the mass ratio of the unpillared two-dimensional sheet MFI molecular sieve to the silicon source in step S1 is 1:(0.05-3.75).

[0025] Controlling the mass ratio of the two-dimensional MFI zeolite to the silicon source to 1:(0.05-3.75) ensures that the appropriate number of silicon atoms is introduced into the zeolite lamellae, thereby ensuring that the amorphous silica pillars formed by the silicon atoms and the subsequent crystallized silica pillars have an appropriate density. Too little silicon source results in fewer crystallized silica pillars within the zeolite, which has a minimal effect on improving the zeolite's stability during catalysis. Too much silicon source results in numerous and coarse pillars within the zeolite, making it difficult for reactants to diffuse within the zeolite during catalytic reactions, resulting in low reaction efficiency.

[0026] Preferably, the unpillared two-dimensional sheet MFI molecular sieve in step S1 is prepared by the following preparation method:

[0027] A bifunctional surfactant, a silicon source, and water are mixed to obtain liquid A, which is then mixed with an aluminum source and a strong protonic acid to obtain liquid B. Liquid B is aged to obtain gel C, which is then crystallized to obtain an unpillared two-dimensional lamellar MFI molecular sieve.

[0028] The above-mentioned bifunctional surfactant is a Bola-type surfactant, and the hydrophilic group of the surfactant is an amino group.

[0029] In a specific embodiment of the present invention, the molar ratio of the above-mentioned silicon source, aluminum source, bifunctional surfactant, strong protonic acid and water is 1:(0.01-0.04):(0.02-0.08):(0.16-0.2):(50-80); wherein the specific silicon source can be water glass, the aluminum source can be arbitrarily selected from one or more of aluminum chloride hexahydrate, aluminum sulfate 18hydrate and aluminum carbonate, the strong protonic acid can be sulfuric acid, the aging condition can be placed at 50-75°C for 4-8 hours, and the crystallization condition can be reacted at 100-150°C for 24 hours.

[0030] The two-dimensional lamella MFI molecular sieve prepared by the above method is subjected to crystallization pillaring modification, and the resulting molecular sieve has better catalytic performance because the molecular sieve prepared in this way has a more complete and regular lamella structure. Bola-type surfactants are compounds composed of two hydrophilic polar groups connected and bonded to one or two hydrophobic chains. They have a "hydrophilic at both ends and hydrophobic in the middle" structure and can form a micellar structure that matches the MFI molecular sieve structure, that is, they can be used as templates in the process of synthesizing MFI molecular sieves. The Bola-type surfactants used in the present invention contain amino groups, N + It can be used as a structure-directing agent to induce the synthesis of MFI molecular sieves. Therefore, in the present invention, the Bola type surfactant is called a bifunctional surfactant. In a specific embodiment of the present invention, the amine-containing Bola type surfactant can be C ph-10-6-6 、C 22-6-6 and BCph-12-6-6 Any one or more of Br4, where C ph-10-6-6 The molecular structure is [C6H5-O-(CH2) 10 -N + (CH3)2-C6H 12 -N + (CH3)2-C6H 13 ]·2[Br - ]; C 22-6-6 The molecular structure is [C 22 H 45 -N + (CH3)2-C6H 12 -N + (CH3)2-C6H 13 ]·2[Br - ]; BC ph-12-6-6 The molecular structure of Br4 is: [C6H 13 -N + (CH3)2-C6H 12 -N + (CH3)2-(CH2) 12 -O-(p-C6H4)2-O-(CH2) 12 -N + (CH3)2-C6H 12 -N + (CH3)2-C6H 13 ]·4[Br - ].

[0031] After the Bola-type surfactant is mixed with the silicon source and the aluminum source, the Bola-type surfactant can form micelles and act as a template to guide the silicon source and the aluminum source to form the MFI molecular sieve structure (the silicon atoms and the aluminum atoms will be arranged in order on the outer surface of the micelles). + The group can serve as a structural directing agent for inducing the generation of MFI molecular sieves, and the hydrophobic long chain in the middle of the Bola-type surfactant can prevent the growth of the MFI molecular sieve in the b-axis direction through hydrophobic interaction, ensuring that the MFI molecular sieve can form a two-dimensional structure. In addition, the hydrophobic long chain in the middle of the Bola-type surfactant ensures that the micelle structure formed is mesoporous, thereby ensuring that the obtained two-dimensional MFI molecular sieve has a mesoporous structure, which can enable the reactants to pass quickly without clogging when catalyzing the alkylation reaction of phenol and tert-butanol. The purpose of also adding a strong proton acid in the above steps is to regulate the pH of the reaction system so that the aluminum source and the silicon source can form the framework of the MFI molecular sieve around the stable micelles formed by the surfactant under suitable conditions. After building the MFI molecular sieve framework (obtaining liquid B), aging and crystallization are carried out to prepare conventional two-dimensional sheet-like MFI molecular sieves.

[0032] When the molar ratio of silicon source, aluminum source, bifunctional surfactant, protonic acid and water in step S1 is 100:(1-4):(2-8):(16-20):(5000-8000), the MFI molecular sieve can be formed after the process of steps S1-S3. When the amount of silicon source or aluminum source added is too much or too little, the required MFI molecular sieve structure cannot be synthesized, or the synthesized molecular sieve does not have a two-dimensional morphology; the bifunctional surfactant acts as a template agent and a structure-directing agent at the same time. Therefore, when the amount of bifunctional surfactant is too little, the required MFI molecular sieve cannot be synthesized. When the amount of bifunctional surfactant is too much, the template in the system is too much, which will cause the structure of the MFI molecular sieve to be loose and the molecular sieve to be easily decomposed. The purpose of adding protonic acid in the present invention is to regulate the pH of the system. If the amount of protonic acid is too little, the acidity of the reaction system will be insufficient, and the sol required for synthesizing the molecular sieve cannot be formed. When the amount of protonic acid is too much, the acidity of the system is too strong, and the sol cannot be formed.

[0033] More preferably, the bifunctional surfactant is BC ph-12-6-6 Br4.

[0034] Adopt BC ph-12-6-6 Br4 is used as a surfactant in the process of constructing unpillared two-dimensional sheet MFI molecular sieves, and the resulting molecular sieve has a more stable structure. This is because BC ph-12-6-6 The phenyl ring of Br4 can stabilize the micelle structure through strong π-π stacking interactions, forming a stable cylindrical assembly unit that matches the MFI topology. In other words, it can be used as a stable template, so that the synthesized molecular sieve has a more regular structure, and can therefore exist stably at high temperatures above 500°C.

[0035] The present invention also protects a crystallized pillared two-dimensional MFI molecular sieve prepared by the above-mentioned preparation method of the crystallized pillared two-dimensional MFI molecular sieve.

[0036] The present invention also protects the use of the above-mentioned crystallized pillared two-dimensional MFI molecular sieve in catalyzing the alkylation reaction of phenol and tert-butanol.

[0037] Preferably, the mass space velocity of phenol and tert-butanol when the crystallized pillared two-dimensional MFI molecular sieve catalyzes the alkylation reaction of phenol and tert-butanol is 2 to 10 h -1 .

[0038] Space velocity refers to the amount of raw material passing through a unit catalyst per unit time, which reflects the processing capacity of the catalyst. In the specific embodiment of the present invention, the mass space velocity when the reaction solution is passed into the reactor is the raw material mass flow rate (unit: kgh -1In industry, when catalyzing the alkylation reaction between phenol and tert-butyl alcohol, the mass space velocity of the reaction liquid entering the reactor is generally 0.5 to 2 h -1 The crystallized pillared two-dimensional MFI molecular sieve catalyst provided by the present invention has the advantage of high catalytic activity and can rapidly carry out the alkylation reaction between phenol and tert-butyl alcohol. Therefore, the mass space velocity of the reaction solution when it is introduced into the reactor can be 2 to 10 h -1 catalytic reaction under harsh conditions.

[0039] Preferably, when the crystallized pillared two-dimensional MFI molecular sieve catalyzes the alkylation reaction of phenol and tert-butanol, the molar ratio of phenol to tert-butanol is 1:(1-4).

[0040] Preferably, the reaction temperature of the crystallized pillared two-dimensional MFI molecular sieve when catalyzing the alkylation reaction of phenol and tert-butanol is 100-180°C.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The crystallized pillared two-dimensional MFI molecular sieve prepared by the preparation method provided by the present invention has crystallized silica pillars that can remain stable in the presence of water, thereby effectively preventing the molecular sieve from collapsing when catalyzing the alkylation reaction of phenol and tert-butanol. The molecular sieve prepared by the present invention catalyzes the alkylation reaction of phenol and tert-butanol. The molecular sieve is heated to a mass space velocity of 5h when the reactants phenol and tert-butanol are introduced into the system. -1 Under the condition of low temperature and high pressure, the single-pass service life is as long as 29 hours, while the conversion rate of phenol is 80-85% and the selectivity of tert-butylphenol is 70-80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 1 is the XRD pattern of the crystallized pillared two-dimensional MFI molecular sieve obtained in Examples 1 to 3 of the present invention.

[0044] Figure 2 When pyridine and 2,6-di-tert-butylpyridine are used as probe molecules, the MFI molecular sieves obtained in Examples 1 to 3 of the present invention are at 1600 to 1400 cm -1 Infrared spectra of , where (a) is the infrared spectrum obtained using pyridine as the probe molecule, and (b) is the infrared spectrum obtained using 2,6-di-tert-butylpyridine as the probe molecule.

[0045] Figure 3 These are the nitrogen adsorption-desorption isotherms of the crystallized pillared two-dimensional MFI molecular sieves obtained in Examples 1 to 3 of the present invention and the pore size distribution diagrams calculated therefrom, wherein (a) is the nitrogen adsorption-desorption isotherm diagram, and (b) is the pore size distribution diagram.

[0046] Figure 4 The XRD patterns of the MFI molecular sieves obtained in Example 1 and Comparative Examples 1 to 4 of the present invention are shown.

[0047] Figure 5 When pyridine and 2,6-di-tert-butylpyridine are used as probe molecules, the MFI molecular sieves obtained in Example 1 of the present invention and Comparative Examples 1 to 4 are at 1600 to 1400 cm -1 Infrared spectra of , where (a) is the infrared spectrum obtained using pyridine as the probe molecule, and (b) is the infrared spectrum obtained using 2,6-di-tert-butylpyridine as the probe molecule.

[0048] Figure 6 The nitrogen adsorption-desorption isotherms of the two-dimensional MFI molecular sieves obtained in Example 1 of the present invention and Comparative Examples 1 to 4 and the pore size distribution diagrams calculated therefrom are shown, wherein (a) is the nitrogen adsorption-desorption isotherm diagram and (b) is the pore size distribution diagram.

[0049] Figure 7 The MFI molecular sieves obtained in Example 1 and Comparative Examples 1 to 4 of the present invention are 800 to 400 cm -1 and 4000~1500cm -1 Infrared spectra of the MFI molecular sieves obtained in Example 1 and Comparative Examples 1 to 4 at 800 to 400 cm -1 Infrared spectra of (b) the MFI molecular sieves obtained in Example 1 and Comparative Examples 1 to 4 at 4000 to 1500 cm -1 Infrared spectrum of .

[0050] Figure 8 This is a TEM image of the crystallized pillared two-dimensional MFI molecular sieve obtained in Example 1 of the present invention.

[0051] Figure 9 The catalytic performance comparison of the MFI molecular sieves obtained in Example 1 of the present invention and Comparative Examples 1 to 4 in catalyzing the alkylation reaction of phenol and tert-butanol is shown in FIG. 1 , wherein (a) is a graph showing the conversion rate of phenol and (b) is a graph showing the selectivity of p-tert-butylphenol.

[0052] Figure 10 1 is a performance comparison diagram of the MFI molecular sieves obtained in Example 1 of the present invention and Comparative Example 3 when catalyzing the alkylation reaction of phenol and tert-butanol after regeneration, wherein (a) is a graph showing the conversion rate of phenol, and (b) is a graph showing the selectivity of p-tert-butylphenol. DETAILED DESCRIPTION

[0053] The present invention will be further described below in conjunction with specific embodiments, but the examples do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the examples of the present invention are conventionally purchased raw materials and reagents.

[0054] Example 1

[0055] A method for preparing a crystallized pillared two-dimensional MFI molecular sieve comprises the following steps:

[0056] S1. The unpillared two-dimensional lamellar MFI molecular sieve was placed in a 150 ° C ethyl orthosilicate vapor for vapor phase pillaring and reacted for 24h. After the pillaring reaction was completed, a vapor phase pillared two-dimensional MFI molecular sieve was obtained;

[0057] S2. The vapor-phase pillared two-dimensional MFI molecular sieve obtained in step S1 is sequentially placed in tetraethylammonium hydroxide (structure-directing agent) vapor at 150° C. and water vapor at 80° C. for 24 hours each for crystallization, i.e., crystallization is performed at 150° C. and 80° C. for 24 hours each, for a total crystallization time of 48 hours; after calcination to remove the template, ion exchange is performed using an NH4Cl aqueous solution to obtain a crystallized pillared two-dimensional MFI molecular sieve;

[0058] The mass ratio of the unpillared two-dimensional sheet MFI molecular sieve to the silicon source in step S1 is 1:0.5;

[0059] The molar ratio of the structure directing agent in step S2 to the silicon source in step S1 is 1:1.67;

[0060] The unpillared two-dimensional sheet MFI molecular sieve used in step S1 is prepared by the following preparation method:

[0061] A bifunctional surfactant, water glass and water are mixed to obtain liquid A, which is then mixed with aluminum chloride hexahydrate and sulfuric acid to obtain liquid B. Liquid B is aged to obtain gel C, which is then crystallized to obtain an unpillared two-dimensional lamellar MFI molecular sieve.

[0062] The above-mentioned bifunctional surfactant is a Bola-type surfactant, specifically BC ph-12-6-6 Br4; meanwhile, the molar ratio of silicon source (water glass), aluminum source (aluminum chloride hexahydrate), bifunctional surfactant, strong protonic acid (sulfuric acid) and water is 1:0.02:0.06:0.186:60.

[0063] Example 2

[0064] A method for preparing a crystallized pillared two-dimensional MFI molecular sieve, which differs from Example 1 in that:

[0065] The molar ratio of the structure directing agent in step S2 to the silicon source in step S1 is 1:1.11.

[0066] Example 3

[0067] A method for preparing a crystallized pillared two-dimensional MFI molecular sieve, which differs from Example 1 in that:

[0068] The molar ratio of the structure directing agent in step S2 to the silicon source in step S1 is 1:0.83.

[0069] Comparative Example 1

[0070] A method for preparing a vapor phase pillared two-dimensional MFI molecular sieve, which differs from Example 1 in that:

[0071] Only step S1 is performed.

[0072] Comparative Example 2

[0073] A method for preparing an unpillared two-dimensional sheet MFI molecular sieve, which differs from Example 1 in that:

[0074] Steps S1 to S2 are not performed.

[0075] Comparative Example 3

[0076] A method for preparing a conventional pillared two-dimensional MFI molecular sieve, which differs from Example 1 in that:

[0077] S1. The unpillared two-dimensional sheet MFI molecular sieve was added to a conventional pillared ethyl orthosilicate solution at room temperature, and the reaction was carried out for 12 hours to obtain a conventional pillared two-dimensional MFI molecular sieve precursor;

[0078] S2. The conventional pillared two-dimensional MFI molecular sieve precursor obtained in step S1 is placed in water at 90°C for 12 hours for crystallization, and the conventional pillared two-dimensional MFI molecular sieve is obtained after calcination at 550°C to remove the template.

[0079] Comparative Example 4

[0080] A commercial MFI molecular sieve, specifically ZSM-5 molecular sieve NKF-5D-25HWGRYH, was purchased from Tianjin Nanhua Catalyst Co., Ltd.

[0081] The preparation method of the commercial ZSM-5 molecular sieve provided in Comparative Example 4 is a conventional preparation method in the art, and differs from Comparative Example 2 in at least the following:

[0082] S1. Mixing a structure-directing agent TPAOH, ethyl orthosilicate, and water to obtain Solution A, then mixing Solution A with aluminum chloride hexahydrate and sodium oxide to obtain Solution B, and aging Solution B to obtain Gel C;

[0083] S2. The gel C obtained in step S1 is crystallized to obtain a commercial MFI molecular sieve;

[0084] The molar ratio of the silicon source, aluminum source, structure directing agent, sodium oxide and water in step S1 is 30:1:1:3.25:958.

[0085] Performance Testing

[0086] XRD test: The MFI molecular sieves with different morphologies prepared in the examples and comparative examples were characterized using a D8 Advance X-ray diffractometer from Bruker, Germany.

[0087] The distribution of acidic sites in the molecular sieve pore framework was tested: pyridine and 2,6-di-tert-butylpyridine were used as probe molecules, and data were collected on a German Bruker Vertex 70 Fourier transform infrared spectrometer for two-dimensional MFI molecular sieves with different morphologies prepared in the examples and comparative examples, and Beer's law was used to calculate the distribution of acidic sites in the molecular sieve pore framework. Acid and Lewis acid concentrations.

[0088] Specific surface area and pore size test: The data of the two-dimensional MFI molecular sieves with different morphologies prepared in the examples and comparative examples were collected using the ASAP 2460 multi-station fully automatic specific surface area and pore size analyzer produced by McMurray, USA.

[0089] TEM test: A FEI Talos 200S transmission electron microscope was used to characterize the crystallized pillared two-dimensional MFI molecular sieve prepared in Example 1, and a transmission electron microscope image was obtained.

[0090] Catalytic performance test: The catalysts obtained in the examples and comparative examples were pelletized to obtain catalyst samples, which were sieved through a 20-30 mesh sieve. About 1.0 g of the sample was placed in an oven and activated at 550°C for 3 hours in an air atmosphere. Phenol and tert-butyl alcohol were prepared into a reaction solution in a molar ratio of 1:2, and a certain amount of n-dodecane was added as an internal standard. The reaction solution flow rate was adjusted to a mass space velocity of 5 h. -1 , the pressure is normal pressure, and after a certain reaction time, a certain reaction liquid is taken as a sample, the content of tert-butylphenol therein is determined, and the selectivity of the catalyst for the target reaction and the conversion rate of the reactant phenol are calculated.

[0091] The performance test data are shown in Tables 1 to 4 and Figures 1 to 10 As shown:

[0092] Table 1 Acidic site concentrations of molecular sieves of Examples and Comparative Examples

[0093]

[0094] It can be seen from Table 1 that the crystallized pillared two-dimensional MFI molecular sieves prepared in Examples 1 to 3 of the present invention all have a Lewis acid site concentration lower than that of the unpillared two-dimensional MFI molecular sieve obtained in Comparative Example 2. The concentration of acidic sites is higher, which can confirm that the method provided by the present invention can indeed introduce pillars between the two-dimensional MFI molecular sieve layers, because the Lewis acidic sites on the surface of the molecular sieve will react with the silanol groups on the surface of the molecular sieve during the pillaring process to form Si-O-Si or Al-O-Si bonds, making the defect sites on the surface of the molecular sieve complete, and the Lewis acidic sites are then converted into

[0095] The unpillared MFI molecular sieve provided in Comparative Example 2 of the present invention is a two-dimensional structure, while the commercial molecular sieve provided in Comparative Example 4 has an ideal three-dimensional structure, maintaining the integrity of the crystal (i.e., fewer defect sites). Acidic site concentration is higher.

[0096] Table 2 Pore data of the embodiment and comparative example molecular sieves

[0097]

[0098] As can be seen from Table 2 above, the crystallized pillared two-dimensional MFI molecular sieves prepared in Examples 1 to 3 of the present invention have a higher specific surface area than the unpillared two-dimensional MFI molecular sieve obtained in Comparative Example 2. This also confirms that the method provided by the present invention can introduce pillars between the two-dimensional MFI molecular sieve layers, because the two adjacent two-dimensional MFI molecular sieve layers form a new pore structure after the introduction of pillars, which can increase the specific surface area; at the same time, compared with the vapor phase pillared two-dimensional MFI molecular sieve obtained in Comparative Example 1, the crystallized pillared two-dimensional MFI molecular sieves provided in Examples 1 to 3 of the present invention have higher micropore specific surface area and micropore volume. This is because the preparation method provided by the present invention can introduce crystallized pillars between the two-dimensional MFI molecular sieve layers, and the pillars will form a microporous structure during crystallization, so the micropore channels are increased, and the micropore specific surface area and micropore volume are both improved.

[0099] Comparing the data of Examples 1 to 3 in Tables 1 to 2, it can be seen that when the molar ratio of tetraethylammonium hydroxide in the tetraethylammonium hydroxide solution in step S3 to ethyl orthosilicate in the ethyl orthosilicate solution in step S2 is within the preferred range of 1: (1.5 to 2) of the present invention (Example 1), the obtained molecular sieve has more microporous structures and higher Acid site concentration. When the molar ratio of the structure-directing agent tetraethylammonium hydroxide to ethyl orthosilicate is lower (Examples 2-3), the number of micropores and the number of micropores in the obtained molecular sieve are The concentration of acid sites will decrease; when this molar ratio is higher, the number of micropores and the It is difficult to increase the concentration of acidic sites.

[0100] Table 3 Conversion rate of phenol by molecular sieves in Examples and Comparative Examples

[0101]

[0102] Table 4 Selectivity of p-tert-butylphenol of the molecular sieves of the examples and the comparative examples

[0103]

[0104] Note: The data results of Examples 2 and 3 in Tables 3 and 4 above are similar to those of Example 1 but slightly lower.

[0105] As can be seen from Tables 3 and 4 above, the alkylation reaction of phenol and tert-butyl alcohol catalyzed by the crystallized pillared two-dimensional MFI molecular sieve provided in the embodiment of the present invention has the highest reactant (phenol) conversion rate and the highest product (p-tert-butylphenol) selectivity throughout the process compared with the catalysis of various two-dimensional MFI molecular sieves provided in the comparative examples. This is because the crystallized pillars introduced between the two-dimensional MFI molecular sieve layers of the present invention can increase the number of micropores and improve The concentration of acid sites, when using molecular sieves to catalyze reactions between organic compounds Acidic site is the active site where the catalytic reaction is carried out, so the alkylation reaction between phenol and tert-butyl alcohol is catalyzed by the molecular sieve provided by the present invention, which can not only facilitate the effective contact of reactants with the active site (increase in the number of active sites), but also strengthen the internal diffusion of the reactant molecules (increase in micropore channels), so that the alkylation reaction activity can be improved. When the catalytic reaction has been carried out for 29h, the molecular sieve provided by Example 1 of the present invention still has excellent catalytic activity, which shows that the crystallized pillared two-dimensional MFI molecular sieve provided by the present invention has excellent stability, because water molecules will be produced in the alkylation reaction of phenol and tert-butyl alcohol, but the generation of water molecules can not cause the hydrolysis of the crystallized silica pillars in the molecular sieve. It should be noted that when a series of two-dimensional MFI molecular sieves provided by the present invention are used to catalyze the alkylation reaction of phenol and tert-butyl alcohol, the mass space velocity when the reactants are passed into the system is 5h -1 In industry, when catalyzing the alkylation reaction between phenol and tert-butyl alcohol, the mass space velocity of the reaction liquid entering the reactor is generally 0.5 to 2 h -1 The crystallized pillared two-dimensional MFI molecular sieve catalyst provided by the present invention has the advantage of high catalytic activity and can rapidly carry out the alkylation reaction between phenol and tert-butyl alcohol. Therefore, the mass space velocity of the reaction solution when it is introduced into the reactor is 5h -1 catalytic reaction under harsh conditions.

[0106] The crystallized pillared two-dimensional MFI molecular sieves provided in Examples 2 and 3 of the present invention have lower catalytic activity than the molecular sieves prepared by controlling the molar ratio of tetraethylammonium hydroxide in the tetraethylammonium hydroxide solution in step S3 to ethyl orthosilicate in the ethyl orthosilicate solution in step S2 in Example 1 within the preferred range of 1: (1.5 to 2) of the present invention. This is because when the above molar ratio is not within the preferred range, the obtained molecular sieve has a lower number of micropores and Acid site concentration.

[0107] Figure 1 The XRD patterns of the crystallized pillared two-dimensional MFI molecular sieves obtained in Examples 1 to 3 of the present invention are shown in FIG. Figure 1 It can be seen that the core-pillared two-dimensional MFI molecular sieves provided in Examples 1 to 3 of the present invention all exhibit diffraction peaks at 2θ of 7.9°, 8.8°, 23.2°, and 23.8°, which are characteristic peaks in the XRD spectrum of the MFI molecular sieve. This confirms that a typical MFI molecular sieve is prepared in the present invention and that the MFI molecular sieve structure is preserved during the pillaring process. Furthermore, the X-ray diffraction peaks of the molecular sieves obtained in Examples 1 to 3 of the present invention are all sharp, indicating that the structure of the two-dimensional MFI molecular sieve remains orderly after the introduction of the crystallized pillars.

[0108] Figure 2 When pyridine and 2,6-di-tert-butylpyridine are used as probe molecules, the MFI molecular sieves obtained in Examples 1 to 3 of the present invention are at 1600 to 1400 cm -1 Infrared spectra of , where (a) is the infrared spectrum obtained with pyridine as the probe molecule, and (b) is the infrared spectrum obtained with 2,6-di-tert-butylpyridine as the probe molecule. Figure 2 (a) (b) It can be seen that when pyridine is used as the probe molecule, the absorption peak intensity of the infrared spectrum of Example 1 is higher, while when 2,6-di-tert-butylpyridine with a larger molecular volume is used as the probe molecule, the infrared absorption peak intensity of Examples 2-3 is higher, which indicates that the pores in the molecular sieve obtained in Example 1 are The acid site concentration is higher, while the surface of the molecular sieve in Examples 2 to 3 The acid site concentration is higher because when pyridine with a smaller molecular volume is used as a probe molecule, pyridine will be adsorbed in the micropores of the molecular sieve. On the acid site.

[0109] Figure 3 The nitrogen adsorption-desorption isotherm diagram of the crystallized pillared two-dimensional MFI molecular sieve obtained in Examples 1 to 3 of the present invention and the pore size distribution diagram calculated therefrom, wherein (a) is the nitrogen adsorption-desorption isotherm diagram and (b) is the pore size distribution diagram. Figure 3 It can be seen that the molecular sieve provided by Example 1 of the present invention has a higher number of micropores and specific surface area.

[0110] Figure 4 The XRD patterns of the MFI molecular sieves obtained in Example 1 and Comparative Examples 1 to 4 of the present invention are shown in FIG. Figure 4 It can be seen that the MFI molecular sieves obtained in Example 1 of the present invention and Comparative Examples 1 to 4 all have diffraction peaks at the characteristic peaks corresponding to the MFI molecular sieves. At the same time, it can be seen from the small-angle XRD pattern that the commercial molecular sieve provided in Comparative Example 4 has no diffraction peaks, while the molecular sieves provided in other embodiments or comparative examples all have diffraction peaks in the small-angle XRD spectrum, which shows that the molecular sieves in other embodiments or comparative examples all have ordered lamellar structures. In addition, in the XRD spectrum, from the unpillared two-dimensional MFI molecular sieve (Comparative Example 2) to the conventional pillared two-dimensional MFI molecular sieve (Comparative Example 3) and the vapor phase pillared two-dimensional MFI molecular sieve (Comparative Example 1), and then to the crystallized pillared two-dimensional MFI molecular sieve (Example 1), the sharpness of the diffraction peaks is gradually enhanced, indicating that the molecular sieve provided by the present invention has a higher degree of structural order.

[0111] Figure 5 When pyridine and 2,6-di-tert-butylpyridine are used as probe molecules, the MFI molecular sieves obtained in Example 1 of the present invention and Comparative Examples 1 to 4 are at 1600 to 1400 cm -1 Infrared spectra of , where (a) is the infrared spectrum obtained with pyridine as the probe molecule, and (b) is the infrared spectrum obtained with 2,6-di-tert-butylpyridine as the probe molecule. Figure 5 As can be seen from (a), the MFI molecular sieves provided by the examples of the present invention and the comparative examples all exhibit The characteristic absorption peaks of acid sites and Lewis acid sites are at ~1545cm -1 The characteristic absorption peak is attributed to the pyridine molecule in Adsorption of acid sites at ∼1455 cm -1 The characteristic absorption peak is attributed to the adsorption of pyridine molecules on the Lewis acid sites. Compared with the unpillared two-dimensional MFI molecular sieve provided in Comparative Example 2, the two-dimensional MFI molecular sieves introduced with different pillars provided in Comparative Examples 1 to 3 and Example 1 have lower Lewis acid site concentrations and higher The acid site concentration is high, which proves that the method provided by the present invention can indeed introduce pillars between the two-dimensional MFI molecular sieve layers, because the Lewis acid sites on the molecular sieve surface will react with the silanol groups on the molecular sieve surface during the pillaring process to form Si-O-Si or Al-O-Si bonds, making the defect sites on the molecular sieve surface complete, and the Lewis acid sites are then converted into The commercial molecular sieve provided in Comparative Example 4 has an ideal three-dimensional structure and maintains the integrity of the crystal (ie, fewer defect sites). The concentration of acidic sites is also higher. Figure 5 (b) Medium ~ 1616cm -1 For the outer surface The characteristic peaks of acid sites. Figure 5 As can be seen from (b), the unpillared two-dimensional MFI molecular sieve provided in Comparative Example 2 of the present invention can expose more internal acid centers, so the outer surface The acid is higher than that of other molecular sieves. In Example 1 and Comparative Examples 1 and 3, the two-dimensional MFI molecular sieves after the pillars are introduced are partially blocked by the pillars, so the outer surface The number of acid sites is reduced. The commercial MFI molecular sieve provided in Comparative Example 4 is a three-dimensional microporous structure, so The acid centers are mainly located inside the framework of the molecular sieve rather than on the outer surface.

[0112] Figure 6 The nitrogen adsorption-desorption isotherms of the two-dimensional MFI molecular sieves obtained in Example 1 and Comparative Examples 1 to 4 of the present invention and the pore size distribution diagrams calculated therefrom are shown in FIG. (a) is the nitrogen adsorption-desorption isotherm diagram and (b) is the pore size distribution diagram. Figure 6 As can be seen from (a), all the two-dimensional MFI molecular sieves provided by the present invention exhibit obvious hysteresis loops when P / P0>0.5, which is mainly attributed to the mesopores generated by the stacking of the two-dimensional MFI lamellar structure. The commercial MFI molecular sieve provided by Comparative Example 4 does not show any hysteresis loops based on its typical three-dimensional microporous structure. At the same time, the crystallized pillared two-dimensional MFI molecular sieve provided by Example 1 of the present invention has the highest total pore volume among all the molecular sieves of the present invention, which means that the molecular sieve provided by Example 1 has the highest specific surface area. Figure 6 It can be seen from (b) that all the two-dimensional MFI molecular sieves provided by the present invention have a mesoporous structure (at ~4 nm), and the two-dimensional MFI molecular sieves provided in Example 1 and Comparative Examples 1 and 3 that introduce pillars by various means all show a narrow mesopore size distribution at ~4 nm, indicating that the pillared molecular sieves have uniform mesopore size, among which the vapor phase pillared two-dimensional MFI molecular sieve provided in Example 1 has the most mesopore channel distribution.

[0113] Figure 7 The MFI molecular sieves obtained in Example 1 and Comparative Examples 1 to 4 of the present invention are 800 to 400 cm -1 and 4000~1500cm -1 Infrared spectra of the MFI molecular sieves obtained in Example 1 and Comparative Examples 1 to 4 at 800 to 400 cm -1 Infrared spectra of (b) the MFI molecular sieves obtained in Example 1 and Comparative Examples 1 to 4 at 4000 to 1500 cm -1Infrared spectrum of the tested molecular sieve at 800-400 cm -1 and 4000~1500cm -1 The purpose of the infrared spectrum is to explore the changes in the groups in the molecular sieve. Figure 7 All samples can be observed at 450cm -1 and 554cm -1 There are obvious absorption peaks at two positions, which are the Si-O-Si stretching vibration absorption peaks, proving the successful synthesis of multi-level pore MFI molecular sieve. Figure 7 (b) shows that after the introduction of crystallization pillars, the molecular sieve obtained in Example 1 has a peak at 450 cm -1 and 554cm -1 The infrared absorption peaks at the two locations are wider and the characteristic peak intensities are higher, indicating that the number of Si-OH groups has increased. This is because the pillars after crystallization support are crystalline molecular sieve structures rather than simple amorphous silica structures, and the T sites in the pillars (where the pillars meet the molecular sieve sheets) are converted into Si-OH.

[0114] Figure 8 This is a TEM image of the crystallized pillared two-dimensional MFI molecular sieve obtained in Example 1 of the present invention. Figure 8 It can be seen that the crystallized pillared two-dimensional MFI molecular sieve after high-temperature calcination to remove the template agent is successfully pillared during the crystallization pillaring process, showing staggered stripes and white gaps, confirming that the crystallization pillaring is successful and maintains the ordered multilayer assembly structure of the two-dimensional MFI molecular sieve.

[0115] Figure 9 The catalytic performance comparison of the MFI molecular sieves obtained in Example 1 of the present invention and Comparative Examples 1 to 4 in catalyzing the alkylation reaction of phenol and tert-butanol is shown in FIG. 1 , wherein (a) is a graph showing the conversion rate of phenol and (b) is a graph showing the selectivity of p-tert-butylphenol.

[0116] Figure 10 1 is a performance comparison diagram of the MFI molecular sieves obtained in Example 1 of the present invention and Comparative Example 3 when catalyzing the alkylation reaction of phenol and tert-butanol after regeneration, wherein (a) is a graph showing the conversion rate of phenol, and (b) is a graph showing the selectivity of p-tert-butylphenol.

[0117] from Figures 9-10 It can be seen that the alkylation reaction of phenol and tert-butyl alcohol catalyzed by the crystallized pillared two-dimensional MFI molecular sieve provided in the embodiment of the present invention has the highest reactant (phenol) conversion rate and the highest product (p-tert-butylphenol) selectivity throughout the process compared with the catalysis of various two-dimensional MFI molecular sieves provided in the comparative examples. This is because the crystallized pillars introduced between the two-dimensional MFI molecular sieve layers of the present invention can increase the number of micropores and improve The concentration of acid sites, when using molecular sieves to catalyze reactions between organic compounds Acidic sites are active sites where catalytic reactions occur. Therefore, using the molecular sieve provided by the present invention to catalyze the alkylation reaction between phenol and tert-butanol not only facilitates effective contact between the reactants and the active sites (increases the number of active sites), but also strengthens the internal diffusion of the reactant molecules (increases the number of micropores), thereby improving the activity of the alkylation reaction. When the catalytic reaction has been carried out for 29 hours, the molecular sieve provided by Example 1 of the present invention still has excellent catalytic activity, which indicates that the crystallized pillared two-dimensional MFI molecular sieve provided by the present invention has excellent stability. Because water molecules are generated in the alkylation reaction of phenol and tert-butanol, the generation of water molecules does not lead to hydrolysis of the crystallized silica pillars in the molecular sieve.

[0118] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a crystallized pillared two-dimensional MFI molecular sieve, characterized in that: The steps include: S1. The unpillared two-dimensional sheet MFI molecular sieve is placed in a silicon source vapor for vapor phase pillaring, and after the pillaring reaction is completed, a vapor phase pillared two-dimensional MFI molecular sieve is obtained; S2. The vapor-phase pillared two-dimensional MFI molecular sieve obtained in step S1 is sequentially placed in structure-directing agent vapor and water vapor for crystallization. After the crystallization is completed, a crystallized pillared two-dimensional MFI molecular sieve can be obtained.

2. The method for preparing a crystallized pillared two-dimensional MFI molecular sieve according to claim 1, wherein: The molar ratio of the structure directing agent in step S2 to the silicon source in step S1 is 1:(1.5-2).

3. The method for preparing the crystallized pillared two-dimensional MFI molecular sieve according to claim 1, wherein: The crystallization temperature in step S2 is 60-200°C.

4. The method for preparing the crystallized pillared two-dimensional MFI molecular sieve according to claim 1, wherein: The total crystallization time in step S2 is 36 to 60 hours.

5. The method for preparing the crystallized pillared two-dimensional MFI molecular sieve according to claim 1, wherein: After the crystallization is completed in step S2, the crystallized pillared two-dimensional MFI molecular sieve needs to be calcined, and after the calcination is completed, it is placed in an aqueous solution containing ammonium radicals for ion exchange.

6. The method for preparing the crystallized pillared two-dimensional MFI molecular sieve according to claim 1, wherein: The mass ratio of the unpillared two-dimensional sheet MFI molecular sieve to the silicon source in step S1 is 1:(0.05-3.75).

7. A crystallized pillared two-dimensional MFI molecular sieve prepared by the preparation method of the crystallized pillared two-dimensional MFI molecular sieve according to any one of claims 1 to 6.

8. Use of the crystallized pillared two-dimensional MFI molecular sieve according to claim 7 in catalyzing the alkylation reaction of phenol and tert-butanol.

9. The use according to claim 8, characterized in that The crystallized pillared two-dimensional MFI molecular sieve catalyzes the alkylation reaction of phenol and tert-butanol, and the mass space velocity of phenol and tert-butanol is 2 to 10 h -1 .

10. The use according to claim 9, characterized in that When the crystallized pillared two-dimensional MFI molecular sieve catalyzes the alkylation reaction of phenol and tert-butanol, the molar ratio of phenol to tert-butanol is 1:(1-4).

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