Mo element modified nano hierarchical pore ZSM-12 molecular sieve and application thereof in preparation of mesitylene by transalkylation of aromatic hydrocarbon

Abstract

The invention provides a Mo element modified nano hierarchical pore ZSM-12 molecular sieve and application thereof in preparation of mesitylene through arene transalkylation, and the Mo element modified ZSM-12 molecular sieve is prepared by the following steps: uniformly mixing a silicon source, an aluminum source, water and a template agent, adding a growth inhibitor, and carrying out a hydrothermal crystallization reaction; and separating and drying, and impregnating and modifying with metal Mo to obtain the catalyst. In the invention, the protection type catalyst is used for carrying out transalkylation reaction on C7-C10 aromatic hydrocarbon to prepare mesitylene, and the catalyst in the reaction has good catalytic activity and selectivity. And the Mo modified catalyst can effectively inhibit the generation of carbon deposition in the reaction process in the presence of hydrogen, so that the service life of the catalyst is prolonged, and the catalyst has a good industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the field of molecular sieve synthesis, and particularly relates to a Mo element-modified nano-multilevel pore ZSM-12 molecular sieve and application thereof in preparing mesitylene by aromatic hydrocarbon transalkylation. Background Art

[0002] Mesitylene is widely used as a raw material for fine chemicals, pesticide intermediates, and antioxidants. Its specific applications include the synthesis of the high-grade dye Reactive Brilliant Blue, the production of wheat herbicides, the antioxidant Lonox-330, the production of mesitylene formic acid, 3,5-dimethylbenzoic acid, and the synthesis of various resins. Currently, the price of mesitylene is approximately 20,000 yuan / ton, that of para-trimethylbenzene is approximately 8,000 yuan / ton, and that of C9 mixed aromatics is approximately 5,000 yuan / ton. Mesitylene has a wide range of applications, high added value, and growing demand annually. However, my country's mesitylene production capacity in 2020 was approximately 4,500 tons / year, with an annual output of approximately 2,800 tons, leaving a significant market gap. Utilizing the reformed C9 aromatics resource and converting it into high-purity mesitylene would yield substantial economic benefits.

[0003] Reforming C9 heavy aromatics to produce mesitylene via transalkylation is a Friedel-Crafts alkylation reaction. Commonly used catalysts include Lewis acids such as aluminum chloride, Lewis acid-supported catalysts, Lewis acids supported on polymer supports, molecular sieve catalysts, and heteropolyacid catalysts. Among these, there is considerable research on supporting Lewis acids on solid acid supports. For example, a literature report (JHClark, AJButterworth, et al. Environmentally friendly chemistry using supported reagent catalysts: chemically-modified mesoporous solid catalysts [J]. Journal of Chemical Technology and Biotechnology, 1997) reported that aluminum chloride was supported on supports such as molecular sieves, clay, and montmorillonite. The results showed that the supported catalysts performed better than the unsupported catalysts.

[0004] Patent CN 118420430A uses the isomerization of unsymmetrical trimethylbenzene to prepare mesitylene. In the presence of hydrogen, the catalyst is an HMOR molecular sieve with a silicon-aluminum ratio of 10 to 30. The Cu / HMOR molecular sieve is obtained by undergoing steps including organic base treatment, inorganic base treatment, molding, ammonium exchange, metal Cu loading (Cu loading of 2 to 10 wt%), and activation. The mesitylene yield and selectivity in the reaction can reach 33.11% and 75.94%.

[0005] CN 115872828 B discloses a method for separating and purifying mesitylene from reformed C9 aromatics using a eutectic solvent comprising choline chloride and urea in a molar ratio of 1:1 to 6. After a series of distillation steps, the final mesitylene yield is 90.38%, with a purity of 99.16% (mass percentage).

[0006] The literature (DA McCaulay, AP Lien, et al. Isomerization of pseudocumene on the catalyst HF-BF3[J]. Journal of the American Chemical Society, 1952. 74(6): 6246) reported a process for producing mesitylene by liquid-phase isomerization of pseudocumene using HF-BF3 as a catalyst. Experimental results showed that when the reaction temperature was 121°C and the molar ratio of HF to pseudocumene was greater than 7, the yield of mesitylene increased with the increase of the molar ratio of HF to pseudocumene, and the yield could reach 34% to 100%.

[0007] Currently, acidic molecular sieves used in catalysts for the production of mesitylene include HZSM-5, mordenite, and β-zeolite. These catalysts primarily consist of a molecular sieve, a support, and a metal component, with their activity primarily derived from the acid and metal centers of the molecular sieve. Their drawbacks primarily include low selectivity, insufficient conversion, and demanding reaction conditions. Furthermore, side reactions such as dealkylation and disproportionation can lead to the formation of xylenes and tetramethylbenzenes, reducing the yield of the target product. Furthermore, carbon deposition shortens the catalyst life, requiring frequent catalyst replacement and impacting economic efficiency.

[0008] ZSM-12 zeolite molecular sieve has one-dimensional, linear, non-intersecting pores composed of twelve-membered rings, with a pore size of 0.57 x 0.61 nm. It belongs to the high-silica class of zeolites. This pore size, intermediate between that of medium-pore and large-pore zeolites, enables effective shape-selective catalytic conversion of most organic molecules. It exhibits high acid resistance, good thermal and hydrothermal stability, low coking, and excellent regeneration performance, demonstrating excellent catalytic performance in a wide range of reactions, including hydrocarbon cracking, isomerization, dehydration, and reforming. Creating a nanoscale multi-level pore ZSM-12 molecular sieve that combines the advantages of both nanoscale and multi-level pore sieves and modifying the catalyst with metallic Mo could further improve the mass transfer efficiency and active site utilization of the ZSM-12 molecular sieve. However, no method for preparing nanoscale multi-level pore Mo / ZSM-12 molecular sieves has been publicly disclosed.

[0009] The present invention provides a nano-multi-level porous Mo / ZSM-12 molecular sieve and a preparation method thereof. The nano-multi-level porous ZSM-12 molecular sieve is synthesized by adding a crystal growth inhibitor to a precursor gel for preparing the molecular sieve. Finally, metallic Mo is loaded onto the ZSM-12 molecular sieve using an isovolumetric impregnation method. The preparation method described herein is simple to operate, has low raw material costs, and a high molecular sieve yield. The synthesized molecular sieve has a large specific surface area, a small particle size, and both micropores and mesopores. This overcomes the technical problem of existing technologies that prevent the provision and preparation of nano-multi-level porous Mo / ZSM-12 molecular sieves.

[0010] This patent provides a nano-multi-level porous Mo / ZSM-12 molecular sieve and its preparation method and application, which can be used in the reaction of aromatic hydrocarbon transalkylation to produce mesitylene. Summary of the Invention

[0011] One of the technical problems to be solved by the present invention is to provide a nano-multilevel pore ZSM-12 molecular sieve, which overcomes the problem that the nano-multilevel pore ZSM-12 molecular sieve cannot be precisely controlled in the prior art.

[0012] The present invention is achieved through the following technical solutions:

[0013] The first aspect of the present invention provides a nano-multi-level pore ZSM-12 molecular sieve, which solves the technical problem that the traditional ZSM-12 molecular sieve has a large particle size and a single pore structure, which limits the mass transfer efficiency. The specific solution is as follows:

[0014] A nano-multi-level pore ZSM-12 molecular sieve, wherein the particle size of the nano-multi-level pore ZSM-12 molecular sieve is 30 to 1000 nm, preferably 100 to 700 nm; the specific surface area of the nano-multi-level pore ZSM-12 molecular sieve is 200 to 1000 m 2 / g, preferably 500-800m 2 / g, total pore volume of 0.01~0.95cm 3 / g, preferably 0.70~0.90cm 3 / g, the mesopore diameter of the nano-multilevel pore ZSM-12 molecular sieve catalyst is 30 to 55 nm, preferably 40 to 50 nm, the nano-multilevel pore ZSM-12 molecular sieve contains micropore and mesopore structures, and the mesopore volume / micropore volume ratio is 1 to 8:1, preferably 2 to 6; the Si / Al atomic ratio in the nano-multilevel pore ZSM-12 molecular sieve is 1 to 8000:1.

[0015] The second aspect of the present invention provides a method for preparing the above-mentioned nano-multi-level porous Mo / ZSM-12 molecular sieve, which addresses the current lack of technical means for synthesizing nano-multi-level porous Mo / ZSM-12 molecular sieves. The technical solution adopted by the present invention is as follows:

[0016] A method for preparing a nano-scale hierarchical ZSM-12 molecular sieve is disclosed. The molecular sieve is synthesized using a hydrothermal method. The preparation process includes uniformly mixing water, an aluminum source, a template, a silicon source, and lysine in appropriate proportions. The resulting mixture is stirred for 0.1 to 50 hours, placed in a reactor, and crystallized at 120 to 180°C for 0.1 to 1200 hours. The mixture is then filtered and washed with boiled water, dried at 50 to 120°C for 0.1 to 50 hours, and the dried sample is calcined at 400 to 800°C to obtain the nano-scale hierarchical ZSM-12 molecular sieve. Finally, the ZSM-12 molecular sieve is impregnated in an ammonium heptamolybdate solution at 20 to 99°C for 1 to 8 hours using an equal volume impregnation method. The loaded sample is dried at 105°C for 12 hours, and finally calcined at 400 to 800°C for 2 hours to obtain ZSM-12 molecular sieves loaded with different Mo contents.

[0017] The aluminum source used in the raw material contains at least one of sodium metaaluminate, pseudo-boehmite, aluminum isopropoxide, aluminum hydroxide, aluminum chloride, alumina, kaolin, montmorillonite, and aluminum-containing spinel; preferably, the aluminum source is sodium metaaluminate;

[0018] The silicon source used in the raw materials contains at least one of silica sol, methyl orthosilicate, propyl orthosilicate, tetraethyl orthosilicate, white carbon black, kaolin, montmorillonite, sodium silicate, fly ash and water glass; preferably, the silicon source is silica sol;

[0019] The template used in the raw materials contains at least one of tetraethylammonium hydroxide, hexamethyleneimine, methyltriethylammonium bromide, benzyltrimethylammonium bromide, etc.; preferably, the template is tetraethylammonium hydroxide;

[0020] The crystal growth inhibitor used in the raw material is lysine;

[0021] The molybdenum source used in the raw material contains at least one of molybdic acid, ammonium heptamolybdate, sodium molybdate, and tetrathiomolybdate; preferably, the template is ammonium heptamolybdate;

[0022] Preferably, the raw materials of water, aluminum source, silicon source, and growth inhibitor used in synthesizing molecular sieves are prepared according to the molar ratio of water: aluminum source: silicon source: template: growth inhibitor = (10-500): (0.1-3.0): (1-5.0): (0.1-4.0): (0.1-1.0).

[0023] The molecular sieve crystallization temperature is 120-180° C., and the crystallization time is 0.1-1200 h;

[0024] The molecular sieve drying temperature is 50-120°C and the drying time is 0.1-48h;

[0025] The molecular sieve is calcined at a temperature of 400 to 800° C. for a time of 1 to 20 hours.

[0026] A third aspect of the present invention provides the use of the aforementioned nanoscale multi-level pore Mo / ZSM-12 molecular sieve as a catalyst for aromatic transalkylation to produce mesitylene. This addresses the issues of conventional molecular sieves with small pore sizes, resulting in low conversion rates, low selectivity, and poor stability in aromatic transalkylation and alkylation reactions.

[0027] A method for producing mesitylene molecular sieve using nano-multilevel pore Mo / ZSM-12 molecular sieve as a catalyst, the method specifically comprising: using the nano-multilevel pore Mo / ZSM-12 molecular sieve as a catalyst, and raw materials including toluene, ethylbenzene, xylene, C9 heavy aromatics, C 10 One of the heavy aromatic hydrocarbons, at a reaction temperature of 150-600°C, a reaction pressure of 0.1-4.5 MPa, and a space velocity of 0.1-10 h -1 Under the conditions of , the reactants are brought into contact with the catalyst bed to react and generate products containing mesitylene.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The particle size of the nano-multi-level pore Mo / ZSM-12 molecular sieve of the present invention is 30 to 1000 nm; the specific surface area of the nano-multi-level pore Mo / ZSM-12 molecular sieve is 200 to 1000 m 2 / g, total pore volume of 0.01~0.95cm 3 / gm 2 / g, the mesopore diameter is 30-55nm, and the mesopore volume / micropore volume is 1-8:1; the nano-multi-level pore Mo / ZSM-12 molecular sieve synthesized by the present invention has a smaller particle size and has a microporous and mesoporous structure, which reduces the diffusion resistance of macromolecular reactants and products in the pores, is beneficial to reducing carbon deposition, and prevents the occurrence of some side reactions.

[0030] (2) The present invention provides a method for preparing nano-multi-level pore Mo / ZSM-12 molecular sieves, which overcomes the problem that the existing technology cannot prepare and provide nano-multi-level pore Mo / ZSM-12 molecular sieves.

[0031] (3) The nano-multi-level porous Mo / ZSM-12 molecular sieve prepared by the present invention exhibits excellent performance in catalyzing the alkylation and transalkylation reactions of aromatic hydrocarbons. The catalytic effect of the molecular sieve is improved by loading metal ions on the modified zeolite. The matching of the active site structure and pore size of the molecular sieve catalyst for this catalytic reaction is addressed, thereby improving the selectivity of mesitylene. This technical solution successfully solves the problem of rapid catalyst deactivation caused by excessive carbon deposition in traditional aromatic hydrocarbon transalkylation processes, thereby extending the catalyst life. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the XRD pattern of the nano-multi-level porous Mo / ZSM-12 molecular sieve prepared in Example 1;

[0033] Figure 2 This is a SEM image of the nano-multi-level porous Mo / ZSM-12 molecular sieve prepared in Example 1. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] [Example 1]

[0036] The preparation methods and operating conditions used in the following examples are conventional methods unless otherwise specified; the reagents, gases, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0037] The specific method of hydrothermal synthesis of nano-multi-level porous Mo / ZSM-12 molecular sieve in this embodiment is carried out according to the following steps:

[0038] Under magnetic stirring, 0.46g of sodium metaaluminate, 43.2g of deionized water, 64.5g of tetraethylammonium hydroxide, and 6.5g of lysine were added sequentially to a polytetrafluoroethylene (PTFE) liner and stirred until a clear solution was obtained. Finally, 67.5g of silica sol was slowly added dropwise using a dropping funnel at a rate of 1 drop / s. The gel was stirred and aged at room temperature for 0.5h. The resulting gel had a molar composition of 4.0TEAOH:9.4H2O:0.086NaAlO2:1SiO2:0.1L-lysine. The PTFE liner containing the solution was sealed in a stainless steel reactor and crystallized in a 160°C oven for 6 days. After crystallization, the product was rinsed with cold water, filtered, stirred, dried, and calcined at 550°C for 6h to obtain a nano-hierarchical ZSM-12 molecular sieve. Finally, metallic Mo was loaded onto ZSM-12 molecular sieve by the equal volume impregnation method. After drying at 105°C for 12 hours, the catalysts loaded with different Mo contents were calcined at 550°C for 2 hours, and named as x% Mo / ZSM-12 molecular sieve (x is 0.1-10).

[0039] The nano-multi-level pore Mo / ZSM-12 molecular sieve prepared in this embodiment has a particle size of 30 to 1000 nm and a specific surface area of 200 to 1000 m 2 / g, total pore volume of 0.01~0.95cm 3 / g, the mesopore diameter is 30-55 nm, and the mesopore volume / micropore volume is 1-8:1; the XRD pattern and SEM pattern of the nano-multi-level pore Mo / ZSM-12 molecular sieve prepared in this embodiment are as follows: Figure 1 and Figure 2 shown.

[0040] [Example 2-30]

[0041] Water, aluminum source, silicon source, organic template and crystal growth inhibitor are used as raw materials according to the preparation conditions in Table 1 and the same steps as in Example 1 to obtain nano-hierarchical Mo / ZSM-12 molecular sieve.

[0042] Table 1 Reaction conditions and properties of molecular sieves obtained in Examples 2-30

[0043]

[0044]

[0045] [Examples 31-60]

[0046] Nano-hierarchical Mo / ZSM-12 molecular sieves were used for aromatic hydrocarbon transalkylation to produce mesitylene.

[0047] Containing at least toluene, ethylbenzene, xylene, C9 heavy aromatics, C 10 Using one of the heavy aromatics as a raw material, the nano-multilevel porous Mo / ZSM-12 molecular sieve obtained in Example 1-30 was used to evaluate the catalyst performance according to the reaction conditions in the table below, and a product rich in mesitylene was obtained.

[0048] Table 2 Summary of reactions for preparing mesitylene in Examples 31-60

[0049]

[0050]

[0051] The above description merely represents the preferred embodiments of the present invention, and while the description is relatively specific and detailed, it should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make various modifications, improvements, and substitutions without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing Mo-modified nano-scale multi-level pore ZSM-12 molecular sieve, characterized in that: include: The nano-multilevel pore ZSM-12 zeolite molecular sieve is loaded with metal Mo and then calcined to obtain the product.

2. The Mo element modified nano-multilevel pore ZSM-12 molecular sieve according to claim 1, characterized in that: The loading amount of the metal Mo is 0.1-10wt%, and the molybdenum source contains at least one of molybdic acid, ammonium heptamolybdate, sodium molybdate, and tetrathiomolybdate; The molybdenum impregnation treatment temperature is 20-120° C., and the impregnation treatment time is 1-24 hours.

3. The Mo element modified nano-multilevel pore ZSM-12 molecular sieve according to claim 1, characterized in that: The metal Mo is loaded on the outer surface of the ZSM-12 zeolite molecular sieve.

4. The method for preparing a Mo-loaded nano-multilevel pore ZSM-12 molecular sieve according to any one of claims 1 to 3, characterized in that: The steps include: (1) The Na-HZSM-12 molecular sieve is subjected to ammonium ion exchange treatment, washed, filtered, dried and calcined to obtain an ammonium-exchanged catalyst. (2) Preparation of Mo-loaded nanoporous ZSM-12 molecular sieve An appropriate amount of ZSM-12 molecular sieve prepared in (1) was used to load metallic Mo onto the ZSM-12 molecular sieve using an equal volume impregnation method. After drying at 105°C for 12 hours, the catalyst was finally calcined at 550°C for 2 hours to obtain catalysts loaded with different Mo contents, designated as x% Mo / ZSM-12 molecular sieve (x is 0.1-10). The loading temperature was 20-99°C and the loading time was 1-8 hours. (3) The particle size of the nano-multi-level pore Mo / ZSM-12 molecular sieve is 30 to 1000 nm; The nano-multi-level pore Mo / ZSM-12 molecular sieve contains micropores and mesopores, and has a specific surface area of 200 to 1000 m 2 / g, total pore volume of 0.01~0.95cm 3 / g, the mesopore diameter is 30-55 nm, and the mesopore volume / micropore volume ratio is 1-8:1; The Si / Al ratio of the nano-multilevel pore Mo / ZSM-12 molecular sieve is 1-8000:

1.

5. The method for preparing nano-multilevel pore Mo / ZSM-12 molecular sieve according to claim 4, characterized in that: The ammonium exchange solution is selected from ammonium nitrate solution or ammonium chloride solution, and the concentration is 1 to 5 mol / L; The ammonium exchange reaction temperature is 30-80° C., and the reaction time is 1-8 hours.

6. The method for preparing nano-multilevel pore Mo / ZSM-12 molecular sieve according to claim 4, characterized in that: The aluminum source contains at least one of pseudo-boehmite, aluminum isopropoxide, sodium metaaluminate, aluminum hydroxide, aluminum chloride, aluminum oxide, aluminum sulfate and aluminum nitrate; The template contains at least one of tetraethylammonium hydroxide, hexamethyleneimine, methyltriethylammonium bromide, and benzyltrimethylammonium bromide; The silicon source contains at least one of silica sol, methyl orthosilicate, propyl orthosilicate, tetraethyl orthosilicate, white carbon black, kaolin, montmorillonite, sodium silicate, fly ash and water glass; The aging temperature is 10-50° C., and the aging time is 1-24 hours; The crystallization temperature is 100-160° C., and the crystallization time is 1-120 hours; The drying temperature is 20 to 300° C. and the drying time is 1 to 48 hours; The calcination temperature is 350-800° C., and the calcination time is 1-20 hours.

7. The use of the nano-multi-level porous Mo / ZSM-12 molecular sieve according to claim 4, characterized in that: The application of the nano-multilevel porous Mo / ZSM-12 molecular sieve in a catalyst is used for aromatic hydrocarbon transalkylation reaction including the preparation of mesitylene.

8. The use of the nano-multi-level pore Mo / ZSM-12 molecular sieve according to claim 4, characterized in that: The preparation method of mesitylene is specifically as follows: using the nano multi-level porous Mo / ZSM-12 molecular sieve as a catalyst, a mixture containing at least toluene, ethylbenzene, xylene, C9 heavy aromatics, C 10 One of the heavy aromatic hydrocarbons is used as the raw material, the reaction temperature is 150℃~600℃, the reaction pressure is 0.1~4.5MPa, and the space velocity is 0.1~10h -1 Under the conditions of , the reactants are brought into contact with the catalyst bed to react and generate products containing mesitylene.

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