A zsm-11 molecular sieve, a preparation method and application thereof

Abstract

The application relates to a ZSM-11 molecular sieve and a preparation method and application thereof, the preparation method of the ZSM-11 molecular sieve comprising the following steps: in a microwave-assisted heating environment, an aluminum source is dissolved in an acid solution to realize uniform gelation of nanoparticles of the aluminum source and form aluminum cations; meanwhile, a silicon source and an intermediate product mixed solution A generate a nanoscale diffusion path under the action of an alcohol-water cosolvent, the interaction between ions in an initial mixed mother liquor is enhanced under a milder crystallization condition, and then a small-crystal, multi-stage-pore ZSM-11 molecular sieve catalyst is obtained through drying and calcination. The molecular sieve significantly improves the single-pass conversion rate and yield of a tert-butylamine reaction prepared by directly aminizing isobutylene, has good thermal stability, and is beneficial to industrial application.

Description

Technical Field

[0001] This invention belongs to the fields of coal chemical industry or petrochemical industry, specifically relating to a ZSM-11 molecular sieve, a method for preparing the molecular sieve, and the application of the molecular sieve as a catalyst in the direct catalytic amination of isobutylene to prepare tert-butylamine. Background Technology

[0002] ZSM-11 molecular sieve is a zeolite material with a MEL (Mobil Eleven) topology, consisting of intersecting two-dimensional straight channels (0.51 nm × 0.55 nm) of elliptical ten-membered rings, belonging to a typical microporous material. This unique channel structure endows ZSM-11 with excellent shape-selective catalytic performance, acid catalytic performance, high thermal stability, and resistance to carbon deposition, making it widely applicable in the petrochemical field, such as catalytic cracking, aromatic alkylation, methanol-to-olefins, and isomerization reactions. The framework aluminum of ZSM-11 molecular sieve is mainly distributed in the straight channels, and the silicon-to-aluminum ratio has a significant impact on its acid catalytic properties. A high silicon-to-aluminum ratio results in higher thermal stability in ZSM-11. The smaller amount of aluminum atoms (Al) replaces silicon atoms (Si) in the framework to form Brönsted acid sites, providing protons (H+) and promoting reactions such as electrophilic addition and proton transfer, such as the direct amination of isobutylene to tert-butylamine. Furthermore, the low acid density of molecular sieves with a high silicon-to-aluminum ratio avoids excessive adsorption and reaction of reactants on the catalyst surface, thereby improving the selectivity of the target product. Therefore, optimizing the preparation method of ZSM-11 molecular sieves with a high silicon-to-aluminum ratio to improve the utilization rate of silicon and aluminum atoms, the uniformity of aluminum distribution in the framework, and the mass transfer efficiency of the pore structure under mild conditions can reduce costs and increase efficiency, further improving the catalytic performance and product yield of the molecular sieve. Summary of the Invention

[0003] Existing studies mostly use microwave-assisted methods to replace traditional crystallization heating to shorten crystallization time, without considering the atom utilization rate or specifically improving the active centers of ZSM-11 molecular sieves. There are also few reports on the selection and optimization of the initial mother liquor solvent for ZSM-11 molecular sieves. The Brönsted acid centers in ZSM-11 molecular sieves mainly originate from the aluminum-oxygen tetrahedral structure. Reducing the detachment of the aluminum source framework under high-temperature conditions improves aluminum ion utilization and the uniformity of aluminum distribution in the active framework, providing a foundation for the catalytic activity of the molecular sieve. The selection and optimization of the initial mother liquor solvent directly affects the dispersion, interaction, and crystal formation process of various atoms during crystallization. Furthermore, constructing a mesoporous structure significantly improves the specific surface area and mass transfer performance of the molecular sieve, exhibiting higher catalytic efficiency.

[0004] To address the problems of low aluminum source utilization, resulting in few active centers, and low single-pass conversion rate of ZSM-11 molecular sieves due to their predominantly microporous structure, leading to low reactant molecule adsorption and poor diffusion of intermediate products, this invention provides a method for synthesizing ZSM-11 molecular sieves with nanocrystals and ordered hierarchical pores. This method explores the utilization rate of raw material atoms and their interactions, resulting in molecular sieves with good stability, high crystallinity, uniform grain size, and abundant mesopores.

[0005] This invention provides microwave-assisted aluminum source gelation of nanocrystals, an ordered hierarchical porous ZSM-11 molecular sieve, and a method for preparing the same. The specific method for preparing the catalyst is as follows: (1) Dissolve the aluminum source in water and add acid solution dropwise, then irradiate with microwave and stir to form a white translucent aluminum gel, and cool to room temperature for later use; (2) Mix a portion of aluminum gel, template agent T, alkali source and deionized water in a certain molar ratio and age it at a certain temperature to obtain mixed solution A; (3) After adding a certain amount of alcohol to deionized water, silicon source and additive P are added respectively, and the mixture is stirred until completely dissolved to obtain mixed solution B; (4) Add mixed solution A to mixed solution B, then add the remaining aluminum gel and alkali source to obtain alkaline gel C; (5) The alkaline gel C was placed in a dynamic segmented crystallization device for dynamic segmented crystallization. The resulting solid product was centrifuged and washed multiple times, then dried and calcined to obtain ZSM-11 molecular sieve with small crystals and ordered hierarchical pores.

[0006] This invention mainly solves the above-mentioned technical problems by using microwave-assisted heating to uniformly gel an aluminum source, thereby improving the formation rate of skeletal aluminum during crystallization; introducing mesoporous additives into an alcohol-water co-solvent to obtain an initial mixed mother liquor, adjusting the solvent polarity and dielectric constant to optimize the crystallization rate, promoting the interaction between silicon and aluminum ions during crystallization, improving the guiding efficiency of the template agent, and improving the pore size distribution of the molecular sieve.

[0007] In the method of this application, the amounts of silicon source, aluminum source, alkali source, template agent T, additive P, and water added satisfy the following molar ratio: SiO2:Al2O3:Na2O:T:P:H2O=1.0:(0.001-0.1):(0.01-1):(0.001-1):(0.0005-0.1):(1-50); The aluminum source is one or more of aluminum nitrate, aluminum chloride, aluminum sulfate, sodium aluminate, boehmite, aluminum acetate, and aluminum isopropoxide, with aluminum nitrate, boehmite, and aluminum isopropoxide being preferred as the aluminum source. The amount of aluminum sol added to the prepared mixed solution A is 50%-80% of the total amount of aluminum sol.

[0008] In some embodiments, the acid solution is one or more of hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, phosphoric acid, citric acid and DL-malic acid, preferably sulfuric acid, nitric acid or hydrochloric acid; The silicon source is one of silica sol, solid silica gel, fumed silica, tetraethyl orthosilicate, sodium silicate, fumigated silica gel, and water glass, with tetraethyl orthosilicate and silica sol being preferred as silicon sources. The additive is one or more of Pluronic P123, Pluronic F127, Pluronic F68, hexadecyltrimethylammonium bromide, hexadecyltrimethoxysilane, hexadecylmethylterephthalic acid, polyacrylamide, or polydiallyldimethylammonium chloride, with preferred additives being Pluronic P123, Pluronic F127, Pluronic F68, and hexadecyltrimethylammonium bromide; The template agent is one of tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetrabutylammonium hydroxide, tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylphosphine hydroxide, hexamethylenediamine, 1,6-hexamethylenediamine, 1,8-octanediamine, 1,10-decanediamine, tetrabutylammonium chloride, and tetrabutylammonium fluoride, preferably tetrapropylammonium hydroxide and tetrabutylammonium hydroxide; The alkaline source is one of ammonia, sodium hydroxide, and potassium hydroxide, with sodium hydroxide being the preferred alkaline source. The alcohol is one or more of methanol, ethanol, and isopropanol; The molar ratio of hydrogen ions to aluminum ions in the aluminum gel is: [H + ] / [Al 3+ The molar ratio of hydrogen ions to aluminum ions in the aluminum gel is preferably 0.1-1.5, with a range of 0.1-3.0.

[0009] In some embodiments, the volume ratio of alcohol to deionized water in the mixed solution B is 1:1-10; The volume ratio of the alkaline gel C to the alcohol solution is <10% (V acid solution / V alcohol solution). The selected microwave radiation frequency range is 2.0 GHz to 20.0 GHz, with a preferred radiation frequency of 2.45 GHz and a corresponding wavelength of 12.2 cm; the radiation temperature is 50℃ to 90℃, with a preferred microwave radiation temperature of 70℃; the stirring rate is 200 r / min to 500 r / min, with a preferred stirring rate of 300 r / min; and the microwave radiation reaction time is 0.5 h to 3 h, with a preferred microwave radiation reaction time of 1 h.

[0010] In some embodiments, the selected hydrothermal crystallization temperature is 100°C-180°C, and the hydrothermal crystallization time is 24h-96h, preferably 140°C, and the hydrothermal crystallization time is 48h, 72h and 96h. The selected drying temperature is 50 ℃-100 ℃, preferably 80 ℃ and 100 ℃; the drying time is 10 h-50 h, preferably 10 h; the drying atmosphere is air, argon or vacuum drying, preferably vacuum drying; the drying method is step-by-step heating in stages or one-time drying, preferably step-by-step heating drying.

[0011] In some embodiments, the selected calcination temperature is 400℃-1000℃ and the calcination time is 2 h-10 h, preferably 500℃ and 4 h.

[0012] The present invention also provides a ZSM-11 molecular sieve with small crystallites and ordered hierarchical pores, which is prepared by the above method. It has a crystallinity of 90%-120%, a crystallite size of 60 nm-200 nm, a BET specific surface area of ​​400 m² / g-600 m² / g, and a mesopore volume of 0.22 cm³ / g-0.30 cm³ / g. In the method of preparing tert-butylamine by direct catalytic amination of isobutylene using a fixed-bed reactor, the selectivity of tert-butylamine is not less than 99%. Under low-temperature conditions, the aluminum source is uniformly gelled by microwave radiation heating to form aluminum cations, thereby improving the utilization rate of aluminum atoms and ensuring consistency between the theoretical and actual silicon-aluminum ratio. The introduction of a small amount of alcohol and mesoporous additives into the initial mother liquor is beneficial to the interaction between raw material atoms during crystallization. At the same time, it allows the subsequent crystallization reaction to occur more easily and quickly under milder conditions. After drying and calcination, a highly crystalline, small-grained, hierarchical porous ZSM-11 molecular sieve is obtained, which promotes the adsorption of reactants and the desorption and diffusion of intermediates, avoids carbon deposition problems, and improves the thermal stability when used as a catalyst.

[0013] The catalyst described in this invention can be applied to the direct catalytic amination of isobutylene to tert-butylamine in a fixed-bed reactor. The reaction conditions are: reaction pressure 10-100 bar, reaction temperature 100-450 °C, a nitrogen-to-olefin molar ratio of 1-5, and an isobutylene feed space velocity of 0.2 h⁻¹. -1 -5 h -1 Under these conditions, the single-pass conversion rate of isobutylene is 15%-35%, and the selectivity of tert-butylamine is ≥98%.

[0014] In addition, the technical solution of the present invention also brings many other advantages, which will be described in detail in the specific embodiments.

[0015] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit the invention. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0017] Figure 1 This is a distribution diagram of Al element in the ZSM-11 molecular sieve material prepared by the method described in Example 1 of this invention.

[0018] Figure 2 This is a distribution diagram of Al element in the ZSM-11 molecular sieve material prepared by the method described in Comparative Example 1 of the present invention.

[0019] Figure 3 The powder X-ray diffraction pattern of the ZSM-11 molecular sieve material prepared by the method described in Example 3 of this invention.

[0020] Figure 4 The powder X-ray diffraction pattern of the ZSM-11 molecular sieve material prepared by the method described in Comparative Example 4 of this invention.

[0021] Figure 5 This is a scanning electron microscope image of the ZSM-11 molecular sieve material prepared by the method described in Example 4 of the present invention. Detailed Implementation

[0022] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that the invention will be thorough and complete, and the concept of the exemplary embodiments will be fully conveyed to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0023] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of the invention. However, those skilled in the art will recognize that the technical solutions of the invention can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring aspects of the invention. It should be noted that the term "mixed solution" in this application refers to the entire reactant / reaction system, encompassing all substances within the reactant / reaction system, including solvents, solutes, and solid substances present therein.

[0024] This application provides the following implementation method: Implementation Method 1. A method for preparing ZSM-11 molecular sieves, characterized by comprising the following steps: (1) Preparation steps of aluminum gel: Dissolve aluminum source in deionized water and add acid solution dropwise, then heat and stir with microwave radiation to form white translucent aluminum gel, cool to room temperature for later use; (2) Preparation of mixed solution A: Mix part of aluminum gel, template agent T, alkali source and deionized water and age to obtain intermediate product mixed solution A; (3) Preparation of mixed solution B: After adding alcohol to deionized water, add silicon source and additive P respectively, and stir until completely dissolved to obtain mixed solution B; (4) Preparation of alkaline gel C: Add mixed solution A to mixed solution B, then add the remaining aluminum gel and alkali source to obtain alkaline gel C; (5) Segmented crystallization and post-processing steps: The alkaline gel C is dynamically segmented crystallized. The resulting solid product is centrifuged and washed multiple times, then dried and calcined to obtain ZSM-11 molecular sieve with small crystals and ordered hierarchical pores.

[0025] Implementation Method 2. The method according to Implementation Method 1, wherein the aluminum source is one or more of aluminum nitrate, aluminum chloride, aluminum sulfate, sodium aluminate, boehmite, aluminum acetate, and aluminum isopropoxide; The acid solution is one or more of hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, phosphoric acid, citric acid and DL-malic acid; The molar ratio of hydrogen ions to aluminum ions in the aluminum gel is: [H + ] / [Al 3+ =0.1-3.0; In the preparation of aluminum gel, the frequency range of microwave radiation is 2.0 GHz to 20.0 GHz, the radiation temperature is 50 ℃ to 90 ℃, the stirring rate is 200 rpm to 500 rpm, and the microwave radiation reaction time is 0.5 h to 3 h.

[0026] Implementation Method 3. According to the method described in Implementation Method 1, the step of preparing mixed solution A is characterized in that, in the step of preparing mixed solution A, the aluminum sol, alkali source, template agent T and deionized water are mixed in a molar ratio of Al2O3:Na2O:T:H2O = 1.0:(1-50):(0.01-100):(10-5000) and aged at 30℃-70℃ for 0.5 hours to 6 hours; The amount of aluminum sol added to the prepared mixed solution A is 50%-80% of the total amount of aluminum sol.

[0027] The template agent T includes at least one of the following: tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetrabutylammonium hydroxide, tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylphosphine hydroxide, hexamethylenediamine, 1,6-hexamethylenediamine, 1,8-octanediamine, 1,10-decanediamine, tetrabutylammonium chloride, and tetrabutylammonium fluoride. The alkaline source includes at least one selected from the following: ammonia, sodium hydroxide, and potassium hydroxide.

[0028] Implementation Method 4. The method according to Implementation Method 1, characterized in that, The alcohol includes one or more selected from methanol, ethanol, and isopropanol; The volume ratio of alcohol to deionized water in the mixed solution B is 1:1-10; The silicon source includes one or more of the following: silica sol, solid silica gel, fumed silica, tetraethyl orthosilicate, sodium silicate, fumigated silica gel, and water glass. The additive P includes one or more selected from Pluronic P123 (Mav=5800, EO20PO70EO20), Pluronic F127 (Mav=12600, EO106PO70EO106), Pluronic F68 (Mav=8400, EO77PO29EO77), hexadecyltrimethylammonium bromide, hexadecyltrimethoxysilane, hexadecylmethylterephthalic acid, polyacrylamide, or polydiallyldimethylammonium chloride.

[0029] Implementation Method 5. According to the method described in Implementation Method 1, the amounts of silicon source, aluminum source, alkali source, template agent, additive, and deionized water added satisfy the following molar ratio: SiO2:Al2O3:Na2O:T:P:H2O = 1.0:(0.001-0.1):(0.01-1):(0.001-1):(0.0005-0.1):(1-50); The volume ratio of acid solution to alcohol solution in the alkaline gel C is less than or equal to 10%.

[0030] Implementation Method 6. The method according to Implementation Method 1 is characterized in that, in the segmented crystallization and post-treatment steps, "dynamic segmented crystallization of alkaline gel C" includes: first pre-crystallizing at 80℃-120℃ for 6h-24h, and then raising the temperature to 130℃-180℃ for crystallization for 24h-72h. The drying temperature is 50℃-100℃; the drying time is 10h-50h; the drying atmosphere is air, argon or vacuum drying; the drying method is step-by-step heating in stages or one-time drying. The calcination temperature is 400℃-1000℃, and the calcination time is 2h-10h; Embodiment 7. A ZSM-11 molecular sieve, characterized in that it has a crystallinity of 90%-120%, a crystal size of 60nm-200nm, a BET specific surface area of ​​400 m² / g-600 m² / g, a mesopore volume of 0.22 cm³ / g-0.30 cm³ / g, and a tert-butylamine selectivity of not less than 99% in a method for the direct catalytic amination of isobutylene to prepare tert-butylamine using a fixed-bed reactor, wherein the ZSM-11 molecular sieve is prepared by any one of Embodiments 1-6.

[0031] Implementation Method 8. A method for preparing tert-butylamine by direct catalytic amination of isobutylene using a fixed-bed reactor, characterized in that it comprises: Contact step: Isobutylene is contacted with liquid ammonia in the presence of ZSM-11 molecular sieve as a catalyst, according to Embodiment 7, to obtain tert-butylamine.

[0032] Implementation Method 9. The method according to Implementation Method 8, characterized in that it further includes: Catalyst pretreatment steps: Under a nitrogen atmosphere at room temperature, the catalyst was pretreated at 500℃ for 2 h by heating at a rate of 3℃ / min, and then cooled to 250℃.

[0033] Implementation Method 10. The method according to Implementation Method 8, characterized in that the reaction conditions of the contact step are: reaction pressure of 10 bar-100 bar, reaction temperature of 100°C-450°C, ammonia-to-olefin molar ratio of 1-5, and isobutylene feed space velocity of 0.2 h⁻¹. -1 -5h -1 .

[0034] The technical solution of the present invention will be described in detail and clearly below with reference to the embodiments of the present invention. Obviously, the content of the present invention is not limited to the embodiments described below.

[0035] Unless otherwise specified, all raw materials used in the embodiments of this invention are purchased commercially, and the specific specifications of the raw materials used are as follows: Silica sol (30wt% SiO2); Tetraethyl orthosilicate (28wt% SiO2); Nitric acid (HNO3, 67 wt.%); Sodium hydroxide (NaOH, 95 wt%) Aluminum isopropoxide (C9H) 21 AlO3, 98.5 wt%); aluminum nitrate Al(NO3)3·9H2O, 99 wt%; boehmite (99 wt%) Tetrabutylammonium hydroxide (TBAOH, 40wt%); Tetrapropylammonium hydroxide (TPAOH, 40wt%); Additive P may be one or more of the following combinations: Pluronic® P-123 (PEG-PPG-PEG, Mn~5800, Shanghai Aladdin Reagent Co., Ltd.), Pluronic F127 (Mav=12600, EO106PO70EO106, Shanghai Aladdin Reagent Co., Ltd.), Pluronic F68 (Mav=8400, EO77PO29EO77, Shanghai Aladdin Reagent Co., Ltd.), cetyltrimethylammonium bromide (CTBA, Sinopharm Group), cetyltrimethoxysilane (Aladdin), cetylmethylterephthalic acid (Aladdin), polyacrylamide (Aladdin), or polydiallyldimethylammonium chloride (Aladdin).

[0036] Example 1

[0037] Dissolve 4.6 g of boehmite in 20 ml of deionized water, then add 2 ml of 1 mol / L hydrochloric acid solution dropwise. Stir for 1 h under microwave radiation at 70 °C (12.2 cm wavelength) and a stirring rate of 300 r / min. –1 Continue stirring until a white, translucent aluminum gel is formed, then cool to room temperature for later use. Dissolve 60% of the aluminum sol in 80 ml of deionized water, then add 6 g of sodium hydroxide powder and 32 g of tetrabutylammonium hydroxide. Stir continuously at 45°C for 30 min, then stop stirring and continue aging at 45°C for 2 h to obtain intermediate product A, with a molar ratio of Al2O3:Na2O:T:H2O = 1.0:24:16.65:2085. Add 150 ml of anhydrous ethanol solution to 300 g of deionized water, stir well, then add 200 g of silica sol and 8 g of sodium hydroxide powder. Hexadecyltrimethylammonium bromide was stirred thoroughly at 50°C until completely dissolved to obtain mixed solution B. Stirring continued at 50°C, and intermediate product A was added to mixed solution B, followed by 40% aluminum gel and 10g sodium hydroxide powder to obtain alkaline gel C with a molar ratio of 1SiO2:0.006Al2O3:0.2Na2O:0.005T:0.0006P:30H2O. Dynamic crystallization was carried out in a crystallization vessel, first at 120°C for 12 hours, then at 160°C for 20 hours. The resulting product was then subjected to solid-liquid separation, washed with deionized water until the pH was neutral, and dried in an oven at 120°C for 16 hours. The resulting solid product was ground and calcined in a muffle furnace at 500°C for 4 hours to obtain ZSM-11 molecular sieve, designated as No. 1.

[0038] The ZSM-11 molecular sieve No. 1 has a relative crystallinity of 98%, a grain size of 100 nm, a BET specific surface area of ​​482.1 m² / g, and a mesopore volume of 0.30 cm³ / g.

[0039] The direct catalytic amination reaction of isobutylene with molecular sieve No. 1 was carried out in a high-pressure fixed-bed reactor with a quartz tube liner. The detailed operating procedures are as follows: (1) System airtightness check. Before the reaction starts, nitrogen gas is introduced to increase the pressure to 1 MPa, which is greater than the reaction pressure. Then, the inlet and outlet valves of nitrogen gas are closed, and the total pressure of the system is observed. If the pressure drop is less than 0.2 MPa after 10 hours, it proves that the airtightness of the reaction device is good.

[0040] (2) Catalyst loading. Take 5 g of catalyst (pressed into tablets and sieved to 20-60 mesh) and place it in a quartz tube (inner diameter D=6.0 mm, length L=400 mm). Fill the upper and lower ends of the catalyst with quartz wool to keep it in a constant temperature zone. Then place the quartz tube in a stainless steel reaction tube and finally install it on a fixed bed reactor for the next step.

[0041] (3) Start the catalytic reaction. Under a nitrogen atmosphere at room temperature, the catalyst was pretreated to 500 °C for 2 h by heating at a rate of 3 °C / min, and then cooled to 250 °C. Liquid ammonia was pumped in first at a pressure of 20 bar, and then isobutylene was introduced, keeping the ammonia-to-olefin molar ratio at 2.

[0042] (4) Product analysis. After being cooled under reduced pressure, the reaction products were introduced into the product tank for gas-liquid separation. Unreacted olefins and ammonia were discharged. The liquid phase material was weighed and analyzed by an online Agilent 7890A gas chromatograph equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD) with a PONA capillary column. The isobutylene conversion, tert-butylamine selectivity and yield were calculated.

[0043] (5) End the catalytic reaction. Turn off all heating programs of the device, slowly adjust the system pressure to atmospheric pressure, switch to nitrogen for purging, and after the system temperature drops to room temperature, turn off the gas valves and the power supply of the reaction device. Remove the catalyst after the reaction and keep it for subsequent sample analysis.

[0044] Catalytic performance of ZSM-11 molecular sieve No. 1: isobutylene conversion rate of 16.3% and tert-butylamine selectivity of 99.8%.

[0045] Comparative Example 1 4.6 g of boehmite was dissolved in 20 ml of deionized water, and then 2 ml of 1 mol / L hydrochloric acid solution was added dropwise. The mixture was then stirred in a 70°C water bath for 1 h until aluminum gel was formed. The solution was then cooled to room temperature. 60% of the aluminum sol was dissolved in 80 ml of deionized water, followed by the addition of 6 g of sodium hydroxide powder and 32 g of tetrabutylammonium hydroxide. The mixture was stirred continuously at 45°C for 30 min, then stopped and aged at 45°C for 2 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.0:24:16.65:2085. 200 g of silica sol was added to 300 g of deionized water and stirred thoroughly at 50°C until completely dissolved to obtain mixed solution B. The mixture was stirred continuously at 50°C, and intermediate product A was added to mixed solution B, along with 40% of the aluminum gel and 10 g of... g of sodium hydroxide powder was used to obtain alkaline gel C with a molar ratio of 1SiO2:0.006Al2O3:0.2Na2O:0.005T:30H2O. Dynamic crystallization was carried out in a crystallization kettle, first at 120℃ for 12 h, and then at 160℃ for 20 h. After that, the obtained product was subjected to solid-liquid separation, washed with deionized water until the pH value was neutral, and then dried in an oven at 120℃ for 16 h. The obtained solid product was ground and then calcined in a muffle furnace at 500℃ for 4 h to obtain ZSM-11 molecular sieve, which is designated as No. 2.

[0046] The direct catalytic amination reaction of isobutylene using molecular sieve No. 2 was carried out in a high-pressure fixed-bed reactor with a quartz tube liner. The detailed operating procedures were the same as those for molecular sieve No. 1. The ZSM-11 molecular sieve No. 2 has a relative crystallinity of 85%, a crystal size of 300 nm, a BET specific surface area of ​​387.6 m² / g, a mesopore volume of 0.19 cm³ / g, and catalytic performance: isobutylene conversion rate of 12.1% and tert-butylamine selectivity of 97.3%.

[0047] Comparative Example 2 Dissolve 4.6 g of boehmite in 20 ml of deionized water, then add 2 ml of 1 mol / L hydrochloric acid solution. Stir for 1 h in a 70°C water bath until aluminum gel forms, then cool to room temperature. Dissolve 60% of the aluminum sol in 80 ml of deionized water, then add 6 g of sodium hydroxide powder and 32 g of tetrabutylammonium hydroxide. Stir continuously at 45°C for 30 min, then stop stirring and continue aging at 45°C for 2 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.0:24:16.65:2085. Add 150 ml of anhydrous ethanol solution to 300 g of deionized water and stir until homogeneous. Then add 200 g of silica sol and 8 g of hexadecyltrimethylammonium bromide, and stir thoroughly at 50°C until completely dissolved to obtain mixed solution B. Continue stirring at 50°C, add intermediate product A to mixed solution B, then add 40% of the aluminum gel and 10 g of sodium hydroxide powder. g of sodium hydroxide powder was used to obtain alkaline gel C with a molar ratio of 1SiO2:0.006Al2O3:0.2Na2O:0.05T:0.0006P:30H2O. Dynamic crystallization was carried out in a crystallization kettle, first at 120℃ for 12 h, and then at 160℃ for 20 h. The obtained product was then subjected to solid-liquid separation, washed with deionized water until the pH value was neutral, and dried in an oven at 120℃ for 16 h. The obtained solid product was ground and then calcined in a muffle furnace at 500℃ for 4 h to obtain ZSM-11 molecular sieve, which is designated as No. 3.

[0048] The direct catalytic amination reaction of isobutylene using molecular sieve No. 3 was carried out in a high-pressure fixed-bed reactor with a quartz tube liner. The detailed operating procedures were the same as those for molecular sieve No. 1. The ZSM-11 molecular sieve No. 3 has a relative crystallinity of 77%, a grain size of 450 nm, a BET specific surface area of ​​398.3 m² / g, a mesopore volume of 0.19 cm³ / g, and catalytic performance: isobutylene conversion rate of 10.4% and tert-butylamine selectivity of 97.6%.

[0049] Table 1. ICP-OES detection results of ZSM-11 molecular sieve samples

[0050] *Si / Al = (Si content / 28.09) / (Al content / 26.98) Approximate calculation: *Aluminum doping rate = (*Si / Al) / (Feed Si / Al) Compared with Comparative Examples 1 and 2, Example 1, prepared using the preparation steps of this invention, yielded a higher aluminum incorporation rate in the ZSM-11 molecular sieve. This indicates that using microwaves to prepare aluminum sol and adding alcohols is beneficial for improving the distribution and utilization of the aluminum source.

[0051] Example 2

[0052] 2.1 g of aluminum sulfate was dissolved in 30 ml of deionized water, and then 3 ml of 1.2 mol / L nitric acid solution was added dropwise. The mixture was then stirred for 1 h under microwave radiation heating at 70 °C (12.2 cm wavelength, 300 r / min) until a white, translucent aluminum gel was formed. The gel was then cooled to room temperature. 50% of the aluminum sol was dissolved in 50 ml of deionized water, followed by the addition of 2.5 g of sodium hydroxide powder and 33.4 g of tetrapropylammonium hydroxide. The mixture was stirred continuously at 50 °C for 30 min, then stopped and aged at 50 °C for 2.5 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.0:11.71:20.34:1866.48. 100 ml of anhydrous ethanol solution was added to 20 g of deionized water and stirred until homogeneous. Then, 175 g of silica sol and 6.96 g of... F-127 was thoroughly stirred at 50℃ until completely dissolved to obtain mixed solution B. Stirring continued at 50℃, and intermediate product A was added to mixed solution B, followed by 50% aluminum gel and 4 g sodium hydroxide powder to obtain alkaline gel C with a molar ratio of 1SiO2:0.0058Al2O3:0.08Na2O:0.05T:0.0006P:14H2O. Dynamic crystallization was carried out in a crystallization vessel, first at 120℃ for 16 h, then at 160℃ for 22 h. The resulting product was then subjected to solid-liquid separation, washed with deionized water until the pH was neutral, and then vacuum dried in an oven at 80℃ and 100℃ for 48 h each. The resulting solid product was ground and calcined in a muffle furnace at 550℃ for 4 h to obtain ZSM-11 molecular sieve, designated as No. 4.

[0053] The direct catalytic amination reaction of isobutylene using molecular sieve No. 4 was carried out in a high-pressure fixed-bed reactor with a quartz tube liner. The detailed operating procedures were the same as those for molecular sieve No. 1. The ZSM-11 molecular sieve No. 4 has a relative crystallinity of 94%, a crystal size of 100 nm, a BET specific surface area of ​​444.2 m² / g, a mesopore volume of 0.28 cm³ / g, and catalytic performance: isobutylene conversion rate of 17.8% and tert-butylamine selectivity of 99.6%.

[0054] Comparative Example 3 Dissolve 2.1 g of aluminum sulfate in 30 ml of deionized water, then add 3 ml of 1.2 mol / L nitric acid solution. Stir for 1 h at 70 °C (12.2 cm wavelength, 300 r / min) under microwave radiation heating until a white, translucent aluminum gel forms. Cool to room temperature. Dissolve 50% of the aluminum sol in 50 ml of deionized water, then add 2.5 g of sodium hydroxide powder and 33.4 g of tetrapropylammonium hydroxide. Stir continuously at 50 °C for 30 min, then stop stirring and continue aging at 50 °C for 2.5 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.0:11.71:20.34:1866.48. Add 175 ml of nitric acid solution to 22.5 g of deionized water. g of silica sol was stirred thoroughly at 50℃ until completely dissolved to obtain mixed solution B. Stirring continued at 50℃, and intermediate product A was added to mixed solution B, followed by 50% aluminum gel and 4 g of sodium hydroxide powder to obtain alkaline gel C with a molar ratio of 1SiO2:0.0058Al2O3:0.08Na2O:0.05T:14H2O. Dynamic crystallization was carried out in a crystallization vessel, first at 120℃ for 16 h, then at 160℃ for 22 h. The resulting product was then subjected to solid-liquid separation, washed with deionized water until the pH was neutral, and then vacuum dried in an oven at 80℃ and 100℃ for 48 h each. The resulting solid product was ground and calcined in a muffle furnace at 550℃ for 4 h to obtain ZSM-11 molecular sieve, designated as No. 5.

[0055] The direct catalytic amination reaction of isobutylene using molecular sieve No. 5 was carried out in a high-pressure fixed-bed reactor with a quartz tube liner. The detailed operating procedures were the same as those for molecular sieve No. 1. The ZSM-11 molecular sieve No. 5 has a relative crystallinity of 88%, a grain size of 380 nm, a BET specific surface area of ​​376.01 m² / g, a mesopore volume of 0.18 cm³ / g, and catalytic performance: isobutylene conversion rate of 12.2% and tert-butylamine selectivity of 98.2%.

[0056] Table 2 Texture properties data of ZSM-11 molecular sieve samples

[0057] Compared with Comparative Example 3, Example 2, prepared using the preparation steps of this invention, has a higher BET specific surface area, higher total pore volume, higher micropore volume and mesopore volume, and a larger average pore size. This indicates that adding alcohols and additives is beneficial to improving the BET specific surface area, pore volume and average pore size.

[0058] Example 3

[0059] 7.57 g of aluminum nitrate was dissolved in 30 mL of deionized water, and then 4 mL of 1.5 mol / L nitric acid solution was added dropwise. The mixture was then stirred for 2 h under microwave radiation at 60 °C (12.2 cm wavelength, 400 r / min) until a white, translucent aluminum gel was formed. The gel was then cooled to room temperature. 70% of the aluminum sol was dissolved in 90 mL of deionized water, followed by the addition of 6.83 g of sodium hydroxide powder and 58.35 g of 1,8-octanediamine. The mixture was stirred continuously at 50 °C for 30 min, then stopped and aged at 50 °C for 2.5 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.0:11.60:12.88:1162.40. 80.0 mL of anhydrous ethanol was added to 100 g of deionized water, followed by the addition of 300 g of silica sol and 5.6 g of Pluronic acid. F68 was thoroughly stirred at 50℃ until completely dissolved to obtain mixed solution B. Stirring continued at 50℃, and intermediate product A was added to mixed solution B, followed by 30% aluminum gel and 10 g sodium hydroxide powder to obtain alkaline gel C with a molar ratio of 1SiO2:0.0066Al2O3:0.13Na2O:0.06T:0.0006P:16H2O. Dynamic crystallization was carried out in a crystallization vessel, first at 120℃ for 16 h, then at 160℃ for 22 h. The resulting product was then subjected to solid-liquid separation, washed with deionized water until the pH was neutral, and then vacuum dried in an oven at 80℃ and 100℃ for 48 h each. The resulting solid product was ground and calcined in a muffle furnace at 550℃ for 4 h to obtain ZSM-11 molecular sieve, designated as No. 6.

[0060] The direct catalytic amination reaction of isobutylene using molecular sieve No. 6 was carried out in a high-pressure fixed-bed reactor with a quartz tube liner. The detailed operating procedures were the same as those for molecular sieve No. 1. The ZSM-11 molecular sieve No. 6 has a relative crystallinity of 95%, a crystal size of 100 nm, a BET specific surface area of ​​445.1 m² / g, a mesopore volume of 0.29 cm³ / g, and catalytic performance: isobutylene conversion rate of 18.1% and tert-butylamine selectivity of 99.9%.

[0061] Comparative Example 4 7.57 g of aluminum nitrate was dissolved in 30 ml of deionized water, and then 4 ml of 1.5 mol / L nitric acid solution was added dropwise. The mixture was then stirred for 2 h under microwave radiation heating at 60 °C (12.2 cm wavelength, 400 r / min) until a white, translucent aluminum gel was formed. The gel was then cooled to room temperature. 70% of the aluminum sol was dissolved in 90 ml of deionized water, followed by the addition of 6.83 g of sodium hydroxide powder and 58.35 g of 1,8-octanediamine. The mixture was stirred continuously at 50 °C for 30 min, then stirring was stopped, and the mixture was aged at 50 °C for 2.5 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.0:11.60:12.88:1162.40. 300 g of silica sol and 5.6 g of Pluronic acid were added to 100 g of deionized water. F68 was stirred thoroughly at 50℃ until completely dissolved to obtain mixed solution B. Stirring continued at 50℃, and intermediate product A was added to mixed solution B, followed by 30% aluminum gel and 10 g sodium hydroxide powder to obtain alkaline gel C with a molar ratio of 1SiO2:0.0066Al2O3:0.13Na2O:0.06T:0.0006P:16H2O. Dynamic crystallization was carried out in a crystallization vessel, first at 120℃ for 16 h, then at 160℃ for 22 h. The resulting product was then subjected to solid-liquid separation, washed with deionized water until the pH was neutral, and then vacuum dried in an oven at 80℃ and 100℃ for 48 h each. The resulting solid product was ground and calcined in a muffle furnace at 550℃ for 4 h to obtain ZSM-11 molecular sieve, designated as No. 7.

[0062] The direct catalytic amination reaction of isobutylene using molecular sieve No. 7 was carried out in a high-pressure fixed-bed reactor with a quartz tube liner. The detailed operating procedures were the same as those for molecular sieve No. 1. The ZSM-11 molecular sieve No. 7 has a relative crystallinity of 82%, a grain size of 450 nm, a BET specific surface area of ​​368.2 m² / g, a mesopore volume of 0.18 cm³ / g, and catalytic performance: isobutylene conversion rate of 14.2% and tert-butylamine selectivity of 96.7%.

[0063] Table 3 XRD results of ZSM-11 molecular sieve samples

[0064] Note: Crystallinity (%) = Sample characteristic peak intensity / Standard characteristic peak intensity * 100% Compared with Comparative Example 4, Example 3, prepared using the preparation steps of this invention, yielded ZSM-11 molecular sieve with relatively high crystallinity. This indicates that adding alcohols is beneficial for improving the distribution of aluminum source, resulting in more uniform crystal growth and achieving a relatively high crystallinity.

[0065] Example 4

[0066] 4.21 g of pseudoboehmite was dissolved in 30 mL of deionized water, followed by the addition of 4 mL of 1 mol / L hydrochloric acid solution. The mixture was then stirred for 2 h under microwave radiation at 70 °C (12.2 cm wavelength, 350 r / min) until a white, translucent aluminum gel was formed. The gel was then cooled to room temperature. 70% of the aluminum sol was dissolved in 98 mL of deionized water, followed by the addition of 2.8 g of sodium hydroxide powder and 25.9 g of tetrabutylammonium hydroxide. The mixture was stirred continuously at 50 °C for 30 min, then stopped and aged at 50 °C for 3 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.0:4.75:5.72:1070.76. 80 mL of anhydrous ethanol was added to 30 g of deionized water, followed by the addition of 160 g of silica sol and 9 g of Pluronic acid. F127 was thoroughly stirred at 50℃ until completely dissolved to obtain mixed solution B. Stirring continued at 50℃, and intermediate product A was added to mixed solution B, followed by 30% aluminum gel and 4.0 g sodium hydroxide powder to obtain alkaline gel C with a molar ratio of 1SiO2:0.0125Al2O3:0.1Na2O:0.05T:0.00075P:18.75H2O. Dynamic crystallization was performed in a crystallization vessel, first at 120℃ for 16 h, then at 160℃ for 22 h. The resulting product was then subjected to solid-liquid separation, washed with deionized water until the pH was neutral, and then vacuum dried in an oven at 80℃ and 100℃ for 48 h each. The resulting solid product was ground and calcined in a muffle furnace at 550℃ for 4.5 h to obtain ZSM-11 molecular sieve, designated as No. 8. Electron micrographs of this molecular sieve are shown below. Figure 5 As shown, its grain size is approximately 100 nm.

[0067] The ZSM-11 molecular sieve No. 8 has a relative crystallinity of 105%, a crystal size of 100 nm, a BET specific surface area of ​​514.4 m² / g, a mesopore volume of 0.29 cm³ / g, and catalytic performance: isobutylene conversion rate of 18.9% and tert-butylamine selectivity of 99.9%.

[0068] The direct catalytic amination reaction of isobutylene with molecular sieve No. 8 was carried out in a high-pressure fixed-bed reactor with a quartz tube liner. The detailed operating procedures were the same as those for molecular sieve No. 1.

[0069] Example 5

[0070] 9.66 g of aluminum isopropoxide was dissolved in 30 mL of deionized water, and then 6 mL of 1 mol / L hydrochloric acid solution was added dropwise. The mixture was then stirred for 2 h under microwave radiation heating at 70 °C (12.2 cm wavelength, 350 r / min) until a white, translucent aluminum gel was formed. The gel was then cooled to room temperature. 70% of the aluminum sol was dissolved in 130 g of deionized water, followed by the addition of 10.4 g of sodium hydroxide powder and 45.33 g of tetrabutylammonium hydroxide. The mixture was stirred continuously at 50 °C for 30 min, then stopped and aged at 50 °C for 3 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.0:7.56:4.29:608.20. 150.0 mL of anhydrous ethanol was added to 176 g of deionized water, followed by the addition of 250.0 g of tetraethyl orthosilicate and 52.2 g of Pluronic acid. P123 was stirred thoroughly at 50℃ until completely dissolved to obtain mixed solution B. Stirring continued at 50℃, and intermediate product A was added to mixed solution B, followed by 30% aluminum gel and 2.0 g sodium hydroxide powder to obtain alkaline gel C with a molar ratio of 1SiO2:0.004Al2O3:0.14Na2O:0.06T:0.00054P:16H2O. Dynamic crystallization was carried out in a crystallization vessel, first at 120℃ for 16 h, then at 160℃ for 22 h. The resulting product was then subjected to solid-liquid separation, washed with deionized water until the pH was neutral, and then vacuum dried in an oven at 80℃ and 100℃ for 48 h each. The resulting solid product was ground and calcined in a muffle furnace at 500℃ for 4.5 h to obtain ZSM-11 molecular sieve, designated as No. 9.

[0071] The ZSM-11 molecular sieve No. 9 has a relative crystallinity of 95%, a grain size of 150 nm, a BET specific surface area of ​​429.2 m² / g, a mesopore volume of 0.28 cm³ / g, and catalytic performance: isobutylene conversion rate of 16.1% and tert-butylamine selectivity of 99.8%.

[0072] The direct catalytic amination reaction of isobutylene using molecular sieve No. 9 was carried out in a high-pressure fixed-bed reactor with a quartz tube liner. The detailed operating procedures were the same as those for molecular sieve No. 1. Example 6

[0073] Dissolve 7.57 g of aluminum nitrate powder in 30 ml of deionized water, then add 4 ml of 1 mol / L concentrated hydrochloric acid dropwise. Stir the solution for 2 hours at 70°C under microwave radiation (wavelength 12.2 cm, stirring rate 350 r / min). –1The mixture was stirred until a white, translucent aluminum gel was formed and cooled to room temperature. 70% of the aluminum sol was dissolved in 80 g of deionized water, followed by the addition of 5.95 g of sodium hydroxide powder and 32.38 g of tetrabutylammonium hydroxide. The mixture was stirred continuously at 50°C for 30 min, then stopped and aged at 50°C for 3 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.0:10.10:7.15:958.87. 90.0 mL of anhydrous ethanol was added to 90 g of deionized water, followed by the addition of 200.0 g of silica sol and 29 g of Pluronic P123. The mixture was stirred thoroughly at 50°C until completely dissolved to obtain mixed solution B. The mixture was stirred continuously at 50°C, and intermediate product A was added to mixed solution B, followed by the addition of 30% of the aluminum gel and 5 g of sodium hydroxide powder. g of sodium hydroxide powder was used to obtain alkaline gel C with a molar ratio of 1SiO2:0.005Al2O3:0.13Na2O:0.05T:0.0005P:19H2O. Dynamic crystallization was carried out in a crystallization kettle, first at 120℃ for 14h, and then at 160℃ for 26h. The obtained product was then subjected to solid-liquid separation, washed with deionized water until the pH value was neutral, and then vacuum dried in an oven at 80℃ and 100℃ for 48h each. The obtained solid product was ground and then calcined in a muffle furnace at 500℃ for 5h to obtain ZSM-11 molecular sieve, which is designated as No. 10.

[0074] The ZSM-11 molecular sieve No. 10 has a relative crystallinity of 108%, a crystal size of 120 nm, a BET specific surface area of ​​532.3 m² / g, a mesopore volume of 0.30 cm³ / g, and catalytic performance: isobutylene conversion rate of 17.5% and tert-butylamine selectivity of 99.9%.

[0075] The direct catalytic amination reaction of isobutylene with molecular sieve No. 10 was carried out in a high-pressure fixed-bed reactor lined with quartz tubes. The detailed operating procedures were the same as those for molecular sieve No. 1. Table 4 shows the reaction of the ZSM-11 molecular sieves obtained in Examples 4-6 in a fixed-bed reactor after ammonium exchange, calcination, tableting, and sieving.

[0076] The ZSM-11 molecular sieve prepared using this invention has a conversion rate higher than 16.1% and a selectivity higher than 99.8% under the reaction conditions.

[0077] Comparative Example 6 7.57 g of aluminum nitrate powder was dissolved in 30 mL of deionized water, followed by the addition of 4 mL of 1 mol / L hydrochloric acid solution. The mixture was then stirred for 2 h at 70 °C (12.2 cm wavelength, 350 r / min) under microwave radiation heating until a white, translucent aluminum gel was formed. The gel was then cooled to room temperature. 100% of the aluminum sol was dissolved in 80 g of deionized water, followed by the addition of 5.95 g of sodium hydroxide powder and 32.38 g of tetrabutylammonium hydroxide. The mixture was stirred continuously at 50 °C for 30 min, then stopped and aged at 50 °C for 3 h to obtain intermediate product A, with a molar ratio of Al₂O₃:Na₂O:T:H₂O = 1.43:10.10:7.15:958.87. 90.0 mL of anhydrous ethanol was added to 90 g of deionized water, followed by the addition of 200.0 g of silica sol and 29 g of Pluronic acid. P123 was stirred thoroughly at 50℃ until completely dissolved to obtain mixed solution B. Stirring continued at 50℃, and intermediate product A was added to mixed solution B, followed by 5 g of sodium hydroxide to obtain alkaline gel C with a molar ratio of 1SiO2:0.005Al2O3:0.13Na2O:0.05T:0.0005P:19H2O. Dynamic crystallization was carried out in a crystallization vessel, first at 120℃ for 14 h, then at 160℃ for 26 h. The resulting product was then subjected to solid-liquid separation, washed with deionized water until the pH was neutral, and then vacuum dried in an oven at 80℃ and 100℃ for 48 h each. The resulting solid product was ground and calcined in a muffle furnace at 500℃ for 5 h to obtain ZSM-11 molecular sieve, designated as No. 11.

[0078] Comparative Example 7 Dissolve 7.57 g of aluminum nitrate powder in 30 ml of deionized water, then add 4 ml of 1 mol / L hydrochloric acid solution. Stir for 2 hours in a 70°C water bath, using a microwave at 12.2 cm wavelength and a stirring rate of 350 r / min, until a white, translucent aluminum gel is formed. Cool to room temperature before use. Dissolve 100% aluminum sol in 80 g of deionized water, then add 5.95 g of sodium hydroxide powder, 32.38 g of tetrabutylammonium hydroxide, 90 g of deionized water, and 90.0 mL of anhydrous ethanol. Then add 200.0 g of silica sol, 29 g of Pluronic P123, and 5 g of... g of sodium hydroxide powder was used to obtain alkaline gel C with a molar ratio of 1SiO2:0.005Al2O3:0.13Na2O:0.05T:0.0005P:19H2O. Dynamic crystallization was carried out in a crystallization kettle, first at 120℃ for 14 h, and then at 160℃ for 26 h. After that, the obtained product was subjected to solid-liquid separation, washed with deionized water until the pH value was neutral, and then vacuum dried in an oven at 80℃ and 100℃ for 48 h each. The obtained solid product was ground and then calcined in a muffle furnace at 500℃ for 5 h to obtain ZSM-11 molecular sieve, which is designated as No. 12.

[0079] Table 5. ICP-OES detection results of ZSM-11 molecular sieve samples obtained in Example 6, Comparative Example 6, and Comparative Example 7.

[0080] *Si / Al = (Si content / 28.09) / (Al content / 26.98) Approximate calculation: *Aluminum doping rate = (*Si / Al) / (Feed Si / Al) Compared to Comparative Example 6, Example 6 uses a step-by-step addition of aluminum gel, which facilitates aluminum source distribution and improves the aluminum incorporation rate. Compared to Comparative Example 7, Example 6 uses synthetic intermediate A, and the prepared ZSM-11 molecular sieve significantly improves the aluminum incorporation rate and exhibits excellent product performance.

[0081] In summary, the method and molecular sieve of this application achieve simultaneous leaps in five dimensions: aluminum utilization (atom economy), mesoporousness (mass transfer efficiency), crystallinity (structural stability), catalytic activity (conversion rate), and selectivity (product purity), providing an irreplaceable technical solution for the large-scale application of ZSM-11 molecular sieve in amination reactions in fine chemicals.

[0082] Exemplary embodiments of this disclosure have been specifically shown and described above. It should be understood that this disclosure is not limited to the detailed structures, arrangements, or implementations described herein; rather, this disclosure is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. A method for preparing ZSM-11 molecular sieves, characterized in that, The steps include the following: (1) Preparation steps of aluminum gel: Dissolve aluminum source in deionized water and add acid solution dropwise, then heat and stir with microwave radiation to form white translucent aluminum gel, cool to room temperature for later use; (2) Preparation of mixed solution A: Mix part of aluminum gel, template agent T, alkali source and deionized water and age to obtain intermediate product mixed solution A; (3) Preparation of mixed solution B: After adding alcohol to deionized water, add silicon source and additive P respectively, and stir until completely dissolved to obtain mixed solution B; (4) Preparation of alkaline gel C: Add mixed solution A to mixed solution B, then add the remaining aluminum gel and alkali source to obtain alkaline gel C; (5) Segmented crystallization and post-processing steps: The alkaline gel C is dynamically segmented crystallized. The resulting solid product is centrifuged and washed multiple times, then dried and calcined to obtain ZSM-11 molecular sieve with small crystals and ordered hierarchical pores.

2. The method according to claim 1, characterized in that, The aluminum source is one or more of aluminum nitrate, aluminum chloride, aluminum sulfate, sodium aluminate, boehmite, aluminum acetate, and aluminum isopropoxide. The acid solution is one or more of hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, phosphoric acid, citric acid and DL-malic acid; The molar ratio of hydrogen ions to aluminum ions in the aluminum gel is: [H + ] / [Al 3+ =0.1-3.0; In the preparation of aluminum gel, the frequency range of microwave radiation is 2.0 GHz to 20.0 GHz, the radiation temperature is 50 ℃ to 90 ℃, the stirring rate is 200 rpm to 500 rpm, and the microwave radiation reaction time is 0.5 h to 3 h.

3. The method according to claim 1, characterized in that, In the step of preparing mixed solution A, the aluminum sol, alkali source, template agent T and deionized water are mixed in a molar ratio of Al2O3:Na2O:T:H2O = 1.0:(1-50):(0.01-100):(10-5000) and aged at 30 ℃-70 ℃ for 0.5 h-6 h; The amount of aluminum sol added to the prepared mixed solution A is 50%-80% of the total amount of aluminum sol. The template agent T includes at least one of the following: tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetrabutylammonium hydroxide, tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylphosphine hydroxide, hexamethylenediamine, 1,6-hexamethylenediamine, 1,8-octanediamine, 1,10-decanediamine, tetrabutylammonium chloride, and tetrabutylammonium fluoride. The alkaline source includes at least one selected from the following: ammonia, sodium hydroxide, and potassium hydroxide.

4. The method according to claim 1, characterized in that, The alcohol includes one or more selected from methanol, ethanol, and isopropanol; The volume ratio of alcohol to deionized water in the mixed solution B is 1:1-10; The silicon source includes one or more selected from silica sol, solid silica gel, fumed silica, tetraethyl orthosilicate, sodium silicate, fumigated silica gel, and water glass; The additive P includes one or more of Pluronic P123 (Mav=5800, EO20PO70EO20), Pluronic F127 (Mav=12600, EO106PO70EO106), Pluronic F68 (Mav=8400, EO77PO29EO77), hexadecyltrimethylammonium bromide, hexadecyltrimethoxysilane, hexadecylmethylterephthalic acid, polyacrylamide, or polydiallyldimethylammonium chloride.

5. The method according to claim 1, characterized in that, The amounts of silicon source, aluminum source, alkali source, template agent, additive, and deionized water added satisfy the following molar ratio: SiO2:Al2O3:Na2O:T:P:H2O= 1.0:(0.001-0.1):(0.01-1):(0.001-1):(0.0005-0.1):(1-50)； The volume ratio of acid solution to alcohol solution in the alkaline gel C is less than or equal to 10%.

6. The method according to claim 1, characterized in that, In the segmented crystallization and post-treatment steps, "dynamic segmented crystallization of alkaline gel C" includes: first pre-crystallizing at 80 ℃-120 ℃ for 6 h-24 h, and then raising the temperature to 130 ℃-180 ℃ for crystallization for 24 h-72 h. The drying temperature is 50 ℃-100 ℃; the drying time is 10 h-50 h; the drying atmosphere is air, argon or vacuum drying; the drying method is step-by-step heating in stages or one-time drying. The calcination temperature is 400 ℃-1000 ℃, and the calcination time is 2 h-10 h.

7. A ZSM-11 molecular sieve, characterized in that, Its crystallinity is 90%-120%, the crystal size is 100 nm-200 nm, the BET specific surface area is 400 m² / g-600 m² / g, and the mesopore volume is 0.22 cm³ / g-0.30 cm³ / g. In the method of preparing tert-butylamine by direct catalytic amination of isobutylene using a fixed-bed reactor, the selectivity of tert-butylamine is not less than 99%. The ZSM-11 molecular sieve is prepared by the method of any one of claims 1-6.

8. A method for preparing tert-butylamine by direct catalytic amination of isobutylene using a fixed-bed reactor, characterized in that... include: Contact step: Isobutylene is contacted with liquid ammonia in the presence of ZSM-11 molecular sieve as a catalyst according to claim 7 to obtain tert-butylamine.

9. The method according to claim 8, characterized in that, Also includes: Catalyst pretreatment steps: Under a nitrogen atmosphere at room temperature, the catalyst was pretreated to 500 °C for 2 h by heating at a rate of 3 °C / min, and then cooled to 250 °C.

10. The method according to claim 8, characterized in that, The reaction conditions for the contact step are: reaction pressure of 10-100 bar, reaction temperature of 100-450 °C, amino-to-olefin molar ratio of 1-5, and isobutylene feed space velocity of 0.2 h⁻¹. -1 -5 h -1 .

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