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

Abstract

The application discloses a ZSM-11 molecular sieve, a preparation method of the ZSM-11 molecular sieve and application of the ZSM-11 molecular sieve in preparation of toluene and xylene from benzene and methanol alkylation. The morphology of the molecular sieve is a conical body particle formed by ordered accumulation of nanorods, the particle size is 500nm-2mu.m, the radial size of the nanorod is 20-60nm, and the bottom surface of the conical body has a protrusion. The ZSM-11 molecular sieve is used as a catalyst in a benzene and methanol alkylation reaction process, and can significantly improve benzene conversion rate, toluene and xylene selectivity and yield.

Description

Technical Field

[0001] This invention belongs to the field of zeolite catalysis, specifically relating to a ZSM-11 molecular sieve and a catalyst prepared from the molecular sieve, as well as the application of the catalyst in the alkylation reaction of benzene and methanol. Background Technology

[0002] The closed channels and cage-like structures of microporous materials (zeolites) are used in a wide range of applications, from catalysis and adsorption to selective separation. A common goal in zeolite material design is to overcome the inherent mass transport limitations of micropores. In zeolite catalysts, narrow pore sizes and longer diffusion paths lead to more rapid deactivation due to the accumulation of carbonaceous deposits (coke). This is particularly true for zeolites with low-dimensional pore networks. Studies have shown that the preparation of nanocrystals can improve catalyst lifetime and / or alter product selectivity. For example, the emergence of two-dimensional (2D) or self-pillared molecular sieves, with a size of approximately one crystal unit cell (~2-4 nm), has shown superior catalytic performance compared to conventional molecular sieves; however, the preparation of these materials has only been demonstrated for a few framework types. In fact, only a relatively small number of zeolite crystals smaller than 100 nm have been reported, highlighting the challenges associated with synthesizing nanoscale microporous materials. This has spurred the development of alternative approaches, such as the preparation of hierarchical zeolites, where the introduction of mesopores has a similarly favorable effect on mass transport. Practical challenges in the synthesis of nanoscale zeolites include the conventional requirements for non-traditional organics and the drawback of low product yields. Therefore, there is a need for a simpler, more efficient method that can be scaled up to a wide range of framework types to produce nanozeolites.

[0003] ZSM-11 molecular sieves are another member of the Pentasil family, with a framework density and pore size similar to ZSM-5 molecular sieves. Unlike ZSM-5, which has intersecting straight and sinusoidal channels, ZSM-11 only has straight channels (5.3 × 5.4 Å). Therefore, some unique catalytic and adsorption properties have been observed in this material (such as higher selectivity for paraffin hydroisomerization and excellent catalytic performance in the dehydration of glycerol to acrolein). The topology of three-dimensional ZSM-11 molecular sieves consists only of straight channels along the a-axis and b-axis. Therefore, the accessibility of active sites in the channels of ZSM-11 molecular sieves is very poor. To fully utilize the low diffusion resistance of the straight channels in ZSM-11 molecular sieves and overcome the disadvantage of no openings along the c-axis hindering molecule entry into the channels, it is crucial to synthesize ZSM-11 molecular sieves with short diffusion paths.

[0004] Template-based synthesis is an effective method for preparing mesoporous molecular sieves. ZSM-11 molecular sieves are typically synthesized using a hydrothermal method, which requires specific template agents. CN 106673003B discloses a method for synthesizing halogen-containing ZSM-11 molecular sieves and the synthesized halogen-containing ZSM-11 molecular sieves. This method involves contacting a silicon source, aluminum source, alkali source, halogen source, organic template agent, and water under crystallization conditions to obtain the molecular sieve. The organic template agent is selected from at least one of 1,3-cyclohexanedimethylamine or 1,4-cyclohexanedimethylamine. This method solves the problem of low purity and high impurity content in halogen-containing ZSM-11 molecular sieve products. CN 102464335B discloses a method for synthesizing ZSM-11 molecular sieves using tetrabutylammonium bromide or tetrabutylammonium hydroxide as the organic template agent, while simultaneously adding EU-1 molecular sieve seed crystals. US 3709979 discloses a method for synthesizing ZSM-11 molecular sieves using tetrabutylammonium iodide as a template agent, US 5213786 discloses a method for synthesizing ZSM-11 molecular sieves using nonyltrimethylammonium bromide as a template agent, and CN 101348261A discloses a method for synthesizing binder-free ZSM-11 molecular sieves using tetrabutylammonium hydroxide as a template agent. All of the above synthesis methods use a single template agent, and the synthesized ZSM-11 molecular sieves are all microporous molecular sieves with small pore sizes, which have the problems of easy catalyst deactivation and short single-pass use cycle.

[0005] Currently, the industrial synthesis of toluene and xylene using ZSM-11 molecular sieve catalysts faces challenges due to low benzene conversion and high ethylbenzene byproduct content. Summary of the Invention

[0006] To address the problems of low benzene conversion and high ethylbenzene byproduct content in existing ZSM-11 molecular sieves used for the synthesis of toluene and xylene, this invention provides a ZSM-11 molecular sieve, its preparation method, and its application in the alkylation reaction of benzene and methanol to prepare toluene and xylene. Using the ZSM-11 molecular sieve catalyst of this invention in the alkylation reaction of benzene and methanol to prepare toluene and xylene features high benzene conversion and low ethylbenzene byproduct content.

[0007] The first aspect of the present invention provides a ZSM-11 molecular sieve, wherein the morphology of the molecular sieve is a cone-shaped particle formed by the orderly stacking of nanorods, the particle size is 500nm-2μm, the radial dimension of the nanorods is 20-60nm, and the bottom surface of the cone has protrusions.

[0008] In the above technical solution, the nanorods in the ZSM-11 molecular sieve have a cone-shaped structure with the bottom facing the top. Preferably, the size of the bottom protrusion is 50-400 nm.

[0009] In the above technical solution, the ZSM-11 molecular sieve is formed by the orderly stacking of nanorods into conical particles, which are then stacked in a secondary manner. Preferably, in the secondary stacking, the conical particles are stacked with their bottom surfaces facing outwards and their apexes facing inwards.

[0010] In the above technical solution, the SiO2 / Al2O3 molar ratio of the ZSM-11 molecular sieve is 15-200.

[0011] In the above technical solution, the specific surface area of ​​the ZSM-11 molecular sieve is 300-496 m². 2 / g, pore volume 0.1-0.6cm 3 / g, preferably 0.2-0.6cm 3 / g.

[0012] A second aspect of this invention provides a method for preparing ZSM-11 molecular sieves, comprising:

[0013] (1) Mix the first aluminum source, the first alkali source, the first template agent, the structural aid and water to obtain solution A; mix the first silicon source with solution A to obtain an initial gel, and crystallize it to obtain ZSM-11 molecular sieve seed crystals;

[0014] (2) Mix the second aluminum source, the second alkali source, the second template agent, the second silicon source and water to obtain solution B. Mix solution B with the ZSM-11 molecular sieve seed crystal obtained in step (1), and after crystallization, drying and calcination, obtain ZSM-11 molecular sieve.

[0015] The preparation method of the ZSM-11 molecular sieve in the above technical solution includes:

[0016] (1) First, mix the first aluminum source, the first alkali source and water to obtain solution A; mix the first silicon source with solution A, and then add the first template agent and the structural aid to obtain the initial gel. After crystallization, ZSM-11 molecular sieve seed crystals are obtained.

[0017] (2) First, mix the second aluminum source, the second alkali source and water to obtain solution B. Mix solution B with the ZSM-11 molecular sieve seed crystal obtained in step (1), then add the second template agent. After crystallization, drying and calcination, ZSM-11 molecular sieve is obtained.

[0018] In the above technical solution, the structural additive is selected from at least one of hexadecyltrimethylammonium bromide (CTAB) or polydiallyldimethylammonium chloride (PDDA).

[0019] In the above technical solution, the first template agent or the second template agent is independently selected from at least one of tetrabutylammonium hydroxide (TBAOH), tetrabutylammonium bromide (TBABr), and 1,8-octanediammonium.

[0020] In the above technical solution, the first silicon source or the second silicon source is independently selected from at least one of tetraethyl orthosilicate (TEOS), sodium silicate, atomized silica gel, or silica sol.

[0021] In the above technical solution, the first aluminum source or the second aluminum source is independently selected from at least one of boehmite, aluminum nitrate, sodium aluminate, aluminum sulfate or aluminum isopropoxide.

[0022] In the above technical solution, the first alkali source or the second alkali source is independently selected from at least one of sodium hydroxide or potassium hydroxide.

[0023] In the above technical solution, in step (1), the first aluminum source is calculated as Al2O3, the first silicon source is calculated as SiO2, the first alkali source is calculated as oxide (M2O, M represents alkali metal ion), and the molar ratio of the first template agent and water is as follows: 1SiO2: (0.10-1.0) First template agent: (0.01-0.005)Al2O3: (0.005-0.02)M2O: (15-300)H2O.

[0024] In the above technical solution, in step (1), the amount of the structural additive added is 10%-70% of the mass of the first silicon source based on SiO2.

[0025] In the above technical solution, in step (1), the mixing conditions for preparing solution A are as follows: the temperature is 30-120℃, preferably 40-90℃, and the stirring time is 2-12 hours, preferably 2-8 hours.

[0026] In the above technical solution, the crystallization conditions in step (1) are as follows: the crystallization temperature is 140-220℃, preferably 150-180℃, and the crystallization time is 24-96 hours, preferably 48-96 hours.

[0027] In the above technical solution, in step (1), after crystallization, conventional steps such as separation and washing are performed first, and then the separated seed crystals are immediately placed in deionized water for storage. The separation can be performed by centrifugation. The washing can be performed by washing with deionized water until the pH value is 8-9.

[0028] In the above technical solution, in step (2), the molar ratios of the second aluminum source (calculated as Al2O3), the second silicon source (calculated as SiO2), the second alkali source (calculated as oxide (M2O, where M represents alkali metal ions), the second template agent, and water are as follows: 1SiO2: (0.30-1.0) Second template agent: (0.02-0.005)Al2O3: (0.01-0.02)M2O: (20-100)H2O.

[0029] In the above technical solution, in step (2), the amount of ZSM-11 molecular sieve seed crystals added is 1%-10% of the mass of the second silicon source based on SiO2.

[0030] In the above technical solution, in step (2), the mixing conditions for preparing solution B are as follows: the temperature is 30-120℃, preferably 40-90℃, and the stirring time is 2-12 hours, preferably 2-8 hours.

[0031] In the above technical solution, in step (2), the crystallization is a two-stage crystallization, and the crystallization conditions are as follows: the first-stage crystallization temperature is 30-60°C lower than the crystallization temperature in step (1), and the first-stage crystallization time is 12-36 hours, preferably 12-26 hours; the second-stage crystallization temperature is 40-60°C higher than the first-stage crystallization temperature, and the second-stage crystallization time is 12-60 hours, preferably 24-36 hours.

[0032] In the above technical solution, the drying conditions in step (2) are as follows: the drying temperature is 60-175℃, preferably 80-130℃, and the drying time is 3-124 hours, preferably 10-48 hours. The calcination conditions are as follows: the calcination temperature is 500-800℃, preferably 530-650℃, and the calcination time is 3-12 hours, preferably 4-8 hours.

[0033] In the above technical solution, after crystallization in step (2), conventional steps such as separation and washing can be performed. The separation can be performed by centrifugation. The washing can be performed with deionized water until the pH value is 8-9.

[0034] In the above technical solution, the morphology of the obtained ZSM-11 molecular sieve is a cone-shaped particle formed by the orderly stacking of nanorods, with a particle size of 500nm-2μm and a radial dimension of 20-60nm for the nanorods.

[0035] In the above technical solution, the obtained ZSM-11 molecular sieve has nanorods oriented with the bottom of a cone facing the top, and the bottom surface of the cone has protrusions. Preferably, the size of the bottom protrusions is 50-400 nm.

[0036] In the above technical solution, the obtained ZSM-11 molecular sieve is formed by the orderly stacking of nanorods into conical particles, which are then stacked in a secondary manner. Preferably, in the secondary stacking, the conical particles are stacked with their bottom surfaces facing outwards and their apexes facing inwards.

[0037] In the above technical solution, the specific surface area of ​​the obtained ZSM-11 molecular sieve is 300-496 m². 2 / g, pore volume 0.1-0.6cm 3 / g, preferably 0.3-0.6cm 3 / g.

[0038] The third aspect of this invention provides the application of the above-mentioned ZSM-11 molecular sieve in the preparation of toluene and xylene by the alkylation reaction of benzene and methanol.

[0039] In the above technical solution, the ZSM-11 molecular sieve undergoes ammonium exchange before being used as a catalyst, and the ammonium exchange adopts a conventional method.

[0040] In the above technical solution, the reaction conditions are as follows: the reaction temperature is 350-500℃, and the reaction pressure is 0.1-1.0MPa.

[0041] In the above technical solution, the molar ratio of benzene to methanol is 0.1-10, and the mass hourly space velocity (HHSV) of the reaction raw materials is 0.1-5.0 h⁻¹. -1 The carrier gas that carries the reactants into the catalyst bed is an inert gas, and the molar ratio of the carrier gas to the mixed feedstock is 5-20.

[0042] In the above technical solution, the inert gas is preferably nitrogen.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. This invention provides a novel ZSM-11 molecular sieve, which consists of nanorods arranged in an ordered primary stacking to form conical particles. The secondary stacking of these conical particles is such that the bottom surface faces outwards and the apex faces inwards, with protrusions distributed on the bottom surface. When the ZSM-11 molecular sieve of this invention is used as a catalyst in the alkylation reaction of benzene and methanol to prepare toluene and xylene, the benzene conversion rate reaches over 70%, and the selectivity for toluene and xylene reaches over 80%, demonstrating promising application prospects.

[0045] 2. The ZSM-11 molecular sieve with a specific morphology of the present invention is prepared by secondary crystallization with the assistance of a structural additive. The molecular sieve prepared by the method of the present invention exhibits high benzene conversion and toluene / xylene selectivity in the alkylation reaction of benzene and methanol to prepare toluene and xylene, while effectively reducing the content of byproducts such as ethylbenzene. Attached Figure Description

[0046] Figure 1 The images show the XRD patterns of the ZSM-11-F1 molecular sieve obtained in Example 1, the ZSM-11-F2 molecular sieve obtained in Example 2, the ZSM-11-F3 molecular sieve obtained in Example 3, the ZSM-11-D1 molecular sieve obtained in Comparative Example 1, and the ZSM-11-DF2 molecular sieve obtained in Comparative Example 2.

[0047] Figure 2 This is one of the scanning electron microscope images of the ZSM-11-F1 molecular sieve obtained in Example 1;

[0048] Figure 3 This is the second scanning electron microscope image of the ZSM-11-F1 molecular sieve obtained in Example 1;

[0049] Figure 4 This is one of the transmission electron microscope images of the ZSM-11-F1 molecular sieve obtained in Example 1;

[0050] Figure 5 This is the second transmission electron microscope image of the ZSM-11-F1 molecular sieve obtained in Example 1;

[0051] Figure 6 This is a scanning electron microscope image of the ZSM-11-D1 molecular sieve obtained in Comparative Example 1;

[0052] Figure 7 This is a scanning electron microscope image of the ZSM-11-DF2 molecular sieve obtained in Comparative Example 2. Detailed Implementation

[0053] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the embodiments.

[0054] In this invention, a Bruker D8 Advance X-ray diffractometer (XRD) was used to analyze the crystal structure of the sample. The light source was a Cu Kα target with λ = 0.1542 nm, the tube voltage was 40 kV, and the tube current was 50 mA.

[0055] In this invention, the crystal morphology was observed using a Zeiss Merlin scanning electron microscope (SEM) and a Tecnai 20STWIN transmission electron microscope (TEM). The accelerating voltage of the SEM was 2kV. The sample was uniformly dispersed on a sample stage coated with conductive adhesive for testing. The accelerating voltage of the TEM was 200kV.

[0056] In this invention, the alkylation of benzene / methanol to produce toluene and xylene was carried out in an atmospheric pressure fixed-bed flow reactor. The products were analyzed using an Agilent 8890A gas chromatograph (GC). The product gas mixture was periodically analyzed using a GC equipped with a flame ionization detection (FID) device and an HP-PONA capillary column (50 m × 0.2 mm × 0.5 μm). The oven temperature was maintained at 343 K.

[0057] Example 1

[0058] 0.164 g of sodium aluminate and 0.052 g of potassium hydroxide were dissolved in 70.4 g of deionized water to form a clear solution. 20.8 g of TEOS was added to this solution, and the mixture was stirred to form a homogeneous clear solution A1. Then, 6.48 g of tetrabutylammonium hydroxide (TBAOH) and 14.5 g of cetyltrimethylammonium bromide (CTAB) were added as template agents. The mixture was stirred at 60 °C for 8 hours, transferred to a reaction vessel, and crystallized at 170 °C for 48 hours. After rapid cooling, centrifugation, and washing, the separated seed crystals were immediately placed in deionized water and stored, named ZSM-11-S1.

[0059] 0.164 g of sodium aluminate and 0.052 g of potassium hydroxide were dissolved in 60.33 g of deionized water to form a transparent solution. 18.75 g of TEOS was added to this solution, followed by 17.7 g of tetrabutylammonium hydroxide (TBAOH) as a template agent. The mixture was stirred at 60 °C for 2 hours. Then, 0.9 g of ZSM-11-S1 was added, and the mixture was stirred for 1 hour. The mixture was transferred to a reactor and crystallized at 140 °C for 12 hours, followed by further crystallization at 180 °C for 24 hours. The mixture was then rapidly cooled, centrifuged, dried at 100 °C for 10 hours, and calcined at 550 °C for 6 hours to obtain an ammonium-type molecular sieve. The obtained ammonium-type molecular sieve was then exchanged with a 0.1 mol / L ammonium chloride solution at a solid-liquid ratio of 1:50 at 80 °C for 4 hours. This process was repeated three times. After filtration, washing, and drying, the H-type catalyst ZSM-11-F1 was obtained.

[0060] The ZSM-11-F1 molecular sieve has a SiO2 / Al2O3 molar ratio of 100 and a specific surface area of ​​464 m². 2 / g, pore volume is 0.34cm 3 / g.

[0061] The XRD pattern of the above product ZSM-11-F1 ( Figure 1 As can be seen, it possesses a typical ZSM-11 molecular sieve structure. (Scanning electron microscopy image of ZSM-11-F1) Figure 2 ) and TEM images ( Figure 3 As can be seen, the morphology of the molecular sieve is that of conical particles formed by the orderly stacking of nanorods along the bottom to the top of the cone, with a particle size of 700nm to 2μm and a radial dimension of 20 to 60nm for the nanorods; protrusions with a size of 100-350nm are distributed on the bottom surface of the cone; and the conical particles are stacked in a secondary manner with the bottom surface facing outward and the top surface facing inward.

[0062] The ZSM-11-F1 powder was compressed into tablets and sieved to obtain 20-40 mesh catalyst particles (Cat1). Using a fixed-bed reactor, 3g of the shaped catalyst Cat1 was loaded. At room temperature, benzene and methanol were mixed in a 1:1 molar ratio, vaporized, and evenly dispersed before entering the reactor. The reaction was carried out at 500℃, with nitrogen as the carrier gas, at atmospheric pressure, and a benzene-methanol mass hourly space velocity (HHSV) of 2.0 h⁻¹. 1 The reaction was carried out under certain conditions, and a gaseous product stream was obtained after the reaction. After cooling, the stream was passed into a gas-liquid separator for separation. The liquid product was sampled and analyzed. See Table 1 for details.

[0063] Example 2

[0064] 0.144 g of sodium aluminate and 0.052 g of potassium hydroxide were dissolved in 70.4 g of deionized water to form a clear solution. 20.8 g of TEOS was added to this solution, and the mixture was stirred to form a homogeneous clear solution A2. Then, 8.05 g of tetrabutylammonium bromide (TBABr) and 14.5 g of hexadecyltrimethylammonium bromide were added. The mixture was stirred at 80 °C for 6 hours, transferred to a reaction vessel, and crystallized at 180 °C for 96 hours. After rapid cooling, centrifugation, and washing, the separated seed crystals were immediately placed in deionized water and stored, named ZSM-11-S2.

[0065] 0.144 g of sodium aluminate and 0.052 g of potassium hydroxide were dissolved in 70.4 g of deionized water to form a clear solution. 18.75 g of TEOS was added to this solution, followed by 22.0 g of tetrabutylammonium bromide (TBABr). The mixture was stirred at 60 °C for 2 hours. Then, 0.9 g of ZSM-11-S2 was added, and the mixture was stirred for 1 hour. The mixture was transferred to a reactor and crystallized at 120 °C for 24 hours, followed by further crystallization at 180 °C for another 24 hours. The mixture was then rapidly cooled, centrifuged, dried at 130 °C for 16 hours, and calcined at 550 °C for 6 hours to obtain an ammonium-type molecular sieve. The obtained ammonium-type molecular sieve was then exchanged with a 0.1 mol / L ammonium chloride solution at a solid-liquid ratio of 1:50 at 80 °C for 4 hours. This process was repeated three times. After filtration, washing, and drying, the H-type catalyst ZSM-11-F2 was obtained.

[0066] The SiO2 / Al2O3 molar ratio of ZSM-11-F2 molecular sieve is 1:13, and its specific surface area is 445 m². 2 / g, pore volume 0.44cm 3 / g.

[0067] The XRD pattern of the above product ZSM-11-F2 ( Figure 1As can be seen, it has a typical ZSM-11 molecular sieve structure. Its morphology is similar to ZSM-11-F1, consisting of cone-shaped particles formed by the orderly stacking of nanorods from the bottom to the top of the cone. The particle size is 700 nm to 3 μm, and the radial dimension of the nanorods is 20 to 60 nm. The bottom surface of the cone has protrusions with a size of 100-350 nm. The cone particles are stacked in a secondary manner with the bottom facing outward and the top facing inward.

[0068] The ZSM-11-F2 powder was compressed into tablets and sieved to obtain 20-40 mesh catalyst particles (Cat2). Using a fixed-bed reactor, 3g of the shaped catalyst Cat2 was loaded. At room temperature, benzene and methanol were mixed in a 1:1 molar ratio, vaporized, and evenly dispersed before entering the reactor. The reaction was carried out at 500℃, with nitrogen as the carrier gas, at atmospheric pressure, and a benzene-methanol mass hourly space velocity (HHSV) of 2.0 h⁻¹. 1 The reaction was carried out under certain conditions, and a gaseous product stream was obtained after the reaction. After cooling, the stream was passed into a gas-liquid separator for separation. The liquid product was sampled and analyzed. See Table 1 for details.

[0069] Example 3

[0070] 0.11 g of sodium aluminate and 0.052 g of potassium hydroxide were dissolved in 70.4 g of deionized water to form a transparent solution. 20.8 g of TEOS was added to this solution, and the mixture was stirred to form a homogeneous transparent solution A3. Then, 6.48 g of tetrabutylammonium hydroxide (TBAOH) and 2.1 g of polydiallyldimethylammonium chloride (PDDA) were added. The mixture was stirred at 60 °C for 8 hours, transferred to a reaction vessel, and crystallized at 180 °C for 48 hours. After rapid cooling, centrifugation, and washing, the separated seed crystals were immediately placed in deionized water and stored, named ZSM-11-S3.

[0071] 0.11 g of sodium aluminate and 0.061 g of potassium hydroxide were dissolved in 60.33 g of deionized water to form a transparent solution. 18.75 g of TEOS was added to this solution, followed by 17.7 g of tetrabutylammonium hydroxide (TBAOH) as a template agent. The mixture was stirred at 60 °C for 2 hours. Then, 1.88 g of ZSM-11-S3 was added, and the mixture was stirred for 1 hour. The mixture was transferred to a reactor and crystallized at 120 °C for 12 hours, followed by further crystallization at 160 °C for 24 hours. The mixture was then rapidly cooled, centrifuged, dried at 100 °C for 10 hours, and calcined at 550 °C for 6 hours to obtain an ammonium-type molecular sieve. The obtained ammonium-type molecular sieve was then exchanged with a 0.1 mol / L ammonium chloride solution at a solid-liquid ratio of 1:50 at 80 °C for 4 hours. This process was repeated three times. After filtration, washing, and drying, the H-type catalyst ZSM-11-F3 was obtained.

[0072] The ZSM-11-F3 molecular sieve has a SiO2 / Al2O3 molar ratio of 150 and a specific surface area of ​​404 m². 2 / g, pore volume 0.54cm 3 / g.

[0073] The XRD pattern of the above product ZSM-11-F3 ( Figure 1 As can be seen, it has a typical ZSM-11 molecular sieve structure. The morphology is similar to ZSM-11-F1, consisting of cone-shaped particles formed by the orderly stacking of nanorods from the bottom to the top of the cone. The particle size is 700 nm to 2 μm, and the radial dimension of the nanorods is 20 to 60 nm. The bottom surface of the cone has protrusions with a size of 100-350 nm. The cone particles are stacked in a secondary manner with the bottom facing outward and the top facing inward.

[0074] The ZSM-11-F3 powder was compressed into tablets and sieved to obtain 20-40 mesh catalyst particles (Cat3). A fixed-bed reactor was used, with 3g of the shaped catalyst Cat3 loaded. At room temperature, benzene and methanol were mixed in a 1:1 molar ratio, vaporized, and evenly dispersed before entering the reactor. The reaction was carried out at 500℃, with nitrogen as the carrier gas, at atmospheric pressure, and a benzene-methanol mass hourly space velocity (HHSV) of 2.0 h⁻¹. 1 The reaction was carried out under certain conditions, and a gaseous product stream was obtained after the reaction. After cooling, the stream was passed into a gas-liquid separator for separation. The liquid product was sampled and analyzed. See Table 1 for details.

[0075] Example 4

[0076] 0.08 g of sodium aluminate and 0.086 g of potassium hydroxide were dissolved in 541.2 g of deionized water to form a clear solution. 20.8 g of TEOS was added to this solution, and the mixture was stirred to form a homogeneous clear solution A4. Then, 14.41 g of 1,8-octanoic acid diammonium phosphate (CTAB) and 6.9 g of cetyltrimethylammonium bromide (CTAB) were added. The mixture was stirred at 60 °C for 8 hours, transferred to a reaction vessel, and crystallized at 170 °C for 48 hours. After rapid cooling, centrifugation, and washing, the separated seed crystals were immediately placed in deionized water and stored, named ZSM-11-S4.

[0077] 0.08 g of sodium aluminate and 0.086 g of potassium hydroxide were dissolved in 60.33 g of deionized water to form a transparent solution. 18.75 g of TEOS was added to this solution, followed by 9.84 g of 1,8-octanoic acid diammonium phosphate (1,8-octanoic acid diammonium phosphate) as a template agent. The mixture was stirred at 60 °C for 2 hours. Then, 1.88 g of ZSM-11-S4 was added, and the mixture was stirred for 1 hour. The mixture was transferred to a reactor and crystallized at 120 °C for 12 hours, followed by further crystallization at 180 °C for 24 hours. The mixture was then rapidly cooled, centrifuged, dried at 100 °C for 10 hours, and calcined at 550 °C for 6 hours to obtain an ammonium-type molecular sieve. The obtained ammonium-type molecular sieve was then exchanged with a 0.1 mol / L ammonium chloride solution at a solid-liquid ratio of 1:50 at 80 °C for 4 hours. This process was repeated three times. After filtration, washing, and drying, the H-type catalyst ZSM-11-F4 was obtained.

[0078] The ZSM-11-F4 molecular sieve has a SiO2 / Al2O3 molar ratio of 200 and a specific surface area of ​​455 m². 2 / g, pore volume 0.58cm 3 / g.

[0079] The XRD pattern of the above product ZSM-11-F4 is similar to Figure 1 Similar to ZSM-11, it has a typical ZSM-11 molecular sieve structure. Its morphology is similar to ZSM-11-F1, consisting of cone-shaped particles formed by the orderly stacking of nanorods from the bottom to the top of the cone. The particle size is 700 nm to 2 μm, and the radial dimension of the nanorods is 20 to 50 nm. The bottom surface of the cone has protrusions with a size of 100-200 nm. The cone particles are stacked in a secondary manner with the bottom facing outward and the top facing inward.

[0080] The ZSM-11-F4 powder was compressed into tablets and sieved to obtain 20-40 mesh catalyst particles (Cat4). A fixed-bed reactor was used, with 3g of shaped catalyst (Cat4) loaded. At room temperature, benzene and methanol were mixed in a 1:1 molar ratio, vaporized, and evenly dispersed before entering the reactor. The reaction was carried out at 500℃, with nitrogen as the carrier gas, at atmospheric pressure, and a benzene-methanol mass hourly space velocity (HHSV) of 2.0 h⁻¹. 1 The reaction was carried out under certain conditions, and a gaseous product stream was obtained after the reaction. After cooling, the stream was passed into a gas-liquid separator for separation. The liquid product was sampled and analyzed. See Table 1 for details.

[0081] Example 5

[0082] 1.09 g of sodium aluminate and 0.03 g of potassium hydroxide were dissolved in 180.1 g of deionized water to form a clear solution. 20.8 g of TEOS was added to this solution, and the mixture was stirred to form a homogeneous clear solution A5. Then, 3.56 g of 1,8-octanediamine (a template agent) and 14.5 g of polydiallyldimethylammonium chloride (PDDA) were added. The mixture was stirred at 60 °C for 8 hours, transferred to a reaction vessel, and crystallized at 170 °C for 48 hours. After rapid cooling, centrifugation, and washing, the separated seed crystals were immediately placed in deionized water and stored, named ZSM-11-S5.

[0083] 1.09 g of sodium aluminate and 0.03 g of potassium hydroxide were dissolved in 155.7 g of deionized water to form a transparent solution. 18.75 g of TEOS was added to this solution, followed by 23.3 g of tetrabutylammonium hydroxide (TBAOH) as a template agent. The mixture was stirred at 60 °C for 2 hours. Then, 0.9 g of ZSM-11-S5 was added, and the mixture was stirred for 1 hour. The mixture was transferred to a reactor and crystallized at 120 °C for 12 hours, followed by further crystallization at 180 °C for 24 hours. The mixture was then rapidly cooled, centrifuged, dried at 100 °C for 10 hours, and calcined at 550 °C for 6 hours to obtain an ammonium-type molecular sieve. The obtained ammonium-type molecular sieve was then exchanged with a 0.1 mol / L ammonium chloride solution at a solid-liquid ratio of 1:50 at 80 °C for 4 hours. This process was repeated three times. After filtration, washing, and drying, the H-type catalyst ZSM-11-F5 was obtained.

[0084] The ZSM-11-F5 molecular sieve has a SiO2 / Al2O3 molar ratio of 15 and a specific surface area of ​​485 m². 2 / g, pore volume is 0.44cm 3 / g.

[0085] The XRD pattern of the above product ZSM-11-F5 is similar to Figure 1 Similar to ZSM-11, it has a typical ZSM-11 molecular sieve structure. Its morphology is similar to ZSM-11-F1, consisting of cone-shaped particles formed by the orderly stacking of nanorods from the bottom to the top of the cone. The particle size is 700 nm to 2 μm, and the radial dimension of the nanorods is 20 to 50 nm. The bottom surface of the cone has protrusions with a size of 100-250 nm. The cone particles are stacked in a secondary manner with the bottom facing outward and the top facing inward.

[0086] The ZSM-11-F5 powder was compressed into tablets and sieved to obtain 20-40 mesh catalyst particles (Cat5). A fixed-bed reactor was used, with 3g of the shaped catalyst Cat5 loaded. At room temperature, benzene and methanol were mixed in a 1:1 molar ratio, vaporized, and evenly dispersed before entering the reactor. The reaction was carried out at 500℃, with nitrogen as the carrier gas, at atmospheric pressure, and a benzene-methanol mass hourly space velocity (HHSV) of 2.0 h⁻¹. 1The reaction was carried out under certain conditions, and a gaseous product stream was obtained after the reaction. After cooling, the stream was passed into a gas-liquid separator for separation. The liquid product was sampled and analyzed. See Table 1 for details.

[0087] Example 6

[0088] 0.41 g of sodium aluminate and 1.25 g of potassium hydroxide solution were dissolved in 70.4 g of deionized water to form a clear solution. 20.8 g of TEOS was added to this solution, and the mixture was stirred to form a homogeneous clear solution A6. Then, 2.59 g of tetrabutylammonium hydroxide (TBAOH) and 10.4 g of cetyltrimethylammonium bromide (CTAB) were added as template agents. The mixture was stirred at 60 °C for 8 hours, transferred to a reaction vessel, and then crystallized at 170 °C for 48 hours. After rapid cooling, centrifugation, and washing, the separated seed crystals were immediately placed in deionized water and stored, named ZSM-11-S6.

[0089] 0.41 g of sodium aluminate and 1.25 g of potassium hydroxide solution were dissolved in 60.33 g of deionized water to form a transparent solution. 18.75 g of TEOS was added to this solution, followed by 17.7 g of tetrabutylammonium hydroxide (TBAOH) as a template agent. The mixture was stirred at 60 °C for 2 hours. Then, 0.9 g of ZSM-11-S6 was added, and the mixture was stirred for 1 hour. The mixture was transferred to a reactor and crystallized at 120 °C for 12 hours, followed by further crystallization at 180 °C for 24 hours. After rapid cooling and centrifugation, the mixture was dried at 100 °C for 10 hours and calcined at 550 °C for 6 hours to obtain an ammonium-type molecular sieve. The solid-liquid ratio of the molecular sieve to 0.1 mol / L ammonium chloride solution was 1:50, and the mixture was exchanged at 80 °C for 4 hours. This process was repeated three times. After filtration, washing, and drying, the H-type catalyst ZSM-11-F6 was obtained.

[0090] The ZSM-11-F6 molecular sieve has a SiO2 / Al2O3 molar ratio of 40 and a specific surface area of ​​464 m². 2 / g, pore volume 0.34cm 3 / g.

[0091] The XRD pattern of the above product ZSM-11-F6 is similar to Figure 1 Similar to ZSM-11, it has a typical ZSM-11 molecular sieve structure. Its morphology is similar to ZSM-11-F1, consisting of cone-shaped particles formed by the orderly stacking of nanorods from the bottom to the top of the cone. The particle size is 700 nm-2 μm, and the radial dimension of the nanorods is 20-60 nm. The bottom surface of the cone has protrusions with a size of 100-350 nm. The cone particles are stacked in a secondary manner with the bottom facing outward and the top facing inward.

[0092] The ZSM-11-F6 powder was compressed into tablets and sieved to obtain 20-40 mesh catalyst particles (Cat6). A fixed-bed reactor was used, with 3g of the shaped catalyst Cat6 loaded. At room temperature, benzene and methanol were mixed in a 1:1 molar ratio, vaporized, and evenly dispersed before entering the reactor. The reaction was carried out at 500℃, with nitrogen as the carrier gas, at atmospheric pressure, and a benzene-methanol mass hourly space velocity (HHSV) of 2.0 h⁻¹. 1 The reaction was carried out under certain conditions, and a gaseous product stream was obtained after the reaction. After cooling, the stream was passed into a gas-liquid separator for separation. The liquid product was sampled and analyzed. See Table 1 for details.

[0093] Comparative Example 1

[0094] Dissolve 0.164 g of sodium aluminate and 0.052 g of potassium hydroxide in 70.4 g of deionized water to prepare solution I. Add 20.8 g of TEOS to 30.5 g of an aqueous solution containing 6.48 g of TBAOH, then add 15 g of hexadecyltrimethylammonium bromide, and stir until homogeneous to form solution II. Slowly add solution II dropwise to solution I, stir the mixture at 60 °C for 8 hours, and then crystallize at 170 °C for 48 hours. Rapidly cool, centrifuge, and wash. Immediately store the separated seeds in deionized water and name them ZSM-11-D1.

[0095] ZSM-11-D1 has a SiO2 / Al2O3 molar ratio of 100 and a specific surface area of ​​339 m². 2 / g, pore volume 0.28cm 3 / g.

[0096] The XRD pattern of the above product ZSM-11-D1 ( Figure 1 As can be seen, it possesses a typical ZSM-11 molecular sieve structure. This is evident from the scanning electron microscope images of the above products (…). Figure 6 As can be seen, the molecular sieve is made up of nanospheres.

[0097] The ZSM-11-D1 powder was compressed into tablets and sieved to obtain 20-40 mesh catalyst particles (DCat1). Using a fixed-bed reactor, 3g of the shaped catalyst (DCat1) was loaded. At room temperature, benzene and methanol were mixed at a molar ratio of 1:1, vaporized, and uniformly dispersed before entering the reactor. The reaction was carried out at 500℃, with nitrogen as the carrier gas, at atmospheric pressure, and a benzene-methanol mass hourly space velocity (HHSV) of 2.0 h⁻¹. 1 The reaction was carried out under certain conditions, and a gaseous product stream was obtained after the reaction. After cooling, the stream was passed into a gas-liquid separator for separation. The liquid product was sampled and analyzed. See Table 1 for details.

[0098] Comparative Example 2

[0099] 0.052 g of potassium hydroxide was dissolved in 70.4 g of deionized water, and then 20.8 g of TEOS was added and stirred to form a homogeneous and transparent solution AD2. The mixture was stirred at 60 °C for 1 hour. 0.164 g of sodium aluminate was dissolved in 20 g of deionized water, and then tetrabutylammonium hydroxide (TBAOH) (6.48 g) and hexadecyltrimethylammonium bromide (CTAB) were added to form a transparent solution BD2. BD2 was slowly added to AD2, and the mixture was stirred at 60 °C for 8 hours. The mixture was then transferred to a reaction vessel and crystallized at 170 °C for 48 hours. After rapid cooling, centrifugation, and washing, the separated seed crystals were immediately placed in deionized water and stored, named ZSM-11-D2.

[0100] 0.164 g of sodium aluminate was added to 1.33 g of potassium hydroxide solution (46 mg / g solution) and 60.33 g of deionized water. 18.75 g of TEOS was added to this solution, followed by the template agent tetrabutylammonium hydroxide (TBAOH) (17.7 g). The mixture was stirred at 60 °C for 2 hours. Then, 0.9 g of ZSM-11-D2 was added, and the mixture was stirred for 1 hour. The mixture was transferred to a reactor and crystallized at 140 °C for 12 hours, followed by further crystallization at 180 °C for 24 hours. The mixture was then rapidly cooled, centrifuged, dried at 100 °C for 10 hours, and calcined at 550 °C for 6 hours to obtain an ammonium-type molecular sieve. The obtained ammonium-type molecular sieve was then exchanged with a 0.1 mol / L ammonium chloride solution at a solid-liquid ratio of 1:50 at 80 °C for 4 hours. This process was repeated three times. After filtration, washing, and drying, the H-type catalyst ZSM-11-DF2 was obtained.

[0101] The ZSM-11-DF2 molecular sieve has a SiO2 / Al2O3 molar ratio of 100 and a specific surface area of ​​378 m². 2 / g, pore volume is 0.31cm 3 / g.

[0102] The XRD pattern of the above product ZSM-11-DF2 ( Figure 1 As can be seen, it possesses a typical ZSM-11 molecular sieve structure. (Scanning electron microscopy image of ZSM-11-DF2) Figure 7 As can be seen, the molecular sieve has the morphology of spherical particles formed by stacked nanosheets, with a particle size of 1-2 μm and a thickness of 200-300 nm for the nanosheets.

[0103] The ZSM-11-DF2 powder was compressed into tablets and sieved to obtain 20-40 mesh catalyst particles (DCat2). A fixed-bed reactor was used, with 3g of the shaped catalyst DCat2 loaded. At room temperature, benzene and methanol were mixed in a 1:1 molar ratio, vaporized, and evenly dispersed before entering the reactor. The reaction was carried out at 500℃, with nitrogen as the carrier gas, at atmospheric pressure, and a benzene-methanol mass hourly space velocity (HHSV) of 2.0 h⁻¹. -1The reaction was carried out under certain conditions, and a gaseous product stream was obtained after the reaction. After cooling, the stream was passed into a gas-liquid separator for separation. The liquid product was sampled and analyzed. See Table 1 for details.

[0104] Table 1

[0105] catalyst Benzene conversion rate, % Toluene and xylene selectivity, % Toluene and xylene yields, % Cat1 72.3 83.9 60.7 Cat2 72.7 83.8 60.9 Cat3 70.3 81.2 57.1 Cat4 70.3 81.9 57.6 Cat5 73.9 80.9 59.8 Cat6 74.3 81.9 60.9 DCat1 50.8 68.2 34.6 DCat2 53.3 70.2 37.4

Claims

1. A method for preparing ZSM-11 molecular sieve, wherein the ZSM-11 molecular sieve has a morphology of conical particles formed by ordered stacking of nanorods, with a particle size of 500 nm-2 µm and a radial dimension of 20-60 nm for the nanorods; the bottom surface of the conical particles has protrusions; the method for preparing the ZSM-11 molecular sieve includes: (1) Mix the first aluminum source, the first alkali source, the first template agent, the structural aid and water to obtain solution A; The first silicon source was mixed with solution A to obtain an initial gel, which was then crystallized to obtain ZSM-11 molecular sieve seed crystals. (2) Mix the second aluminum source, the second alkali source, the second template agent, the second silicon source and water to obtain solution B. Mix solution B with the ZSM-11 molecular sieve seed crystal obtained in step (1), and after crystallization, drying and calcination, obtain ZSM-11 molecular sieve.

2. The preparation method according to claim 1, characterized in that, The structural additive is selected from at least one of hexadecyltrimethylammonium bromide or polydiallyldimethylammonium chloride.

3. The preparation method according to claim 1, characterized in that, The first template agent or the second template agent is independently selected from at least one of tetrabutylammonium hydroxide, tetrabutylammonium bromide, and 1,8-octanediammonium; the first silicon source or the second silicon source is independently selected from at least one of tetraethyl orthosilicate, sodium silicate, fumigated silica gel, or silica sol; the first aluminum source or the second aluminum source is independently selected from at least one of boehmite, aluminum nitrate, sodium aluminate, aluminum sulfate, or aluminum isopropoxide; and the first alkali source or the second alkali source is independently selected from at least one of sodium hydroxide or potassium hydroxide.

4. The preparation method according to claim 1, characterized in that, In step (1), the molar ratios of the first aluminum source (calculated as Al2O3), the first silicon source (calculated as SiO2), the first alkali source, the first template agent, and water are as follows: 1SiO2: (0.10-1.0) First template agent: (0.01-0.005)Al2O3: (0.005-0.02)M2O: (15-300)H2O; and / or, in step (2), the molar ratios of the second aluminum source (calculated as Al2O3), the second silicon source (calculated as SiO2), the second alkali source (calculated as oxide), the second template agent, and water are as follows: 1SiO2: (0.30-1.0) Second template agent: (0.02-0.005)Al2O3: (0.01-0.02)M2O: (20-100)H2O.

5. The preparation method according to claim 1, characterized in that, In step (1), the amount of the structural additive added is 10%-70% of the mass of the first silicon source based on SiO2; and / or, in step (2), the amount of the ZSM-11 molecular sieve seed crystal added is 1%-10% of the mass of the second silicon source based on SiO2.

6. The preparation method according to claim 1, characterized in that, In step (1), the crystallization conditions are as follows: the crystallization temperature is 140-220 ℃ and the crystallization time is 24-96 hours.

7. The preparation method according to claim 6, characterized in that, In step (1), the crystallization conditions are as follows: the crystallization temperature is 150-180 ℃ and the crystallization time is 48-96 hours.

8. The preparation method according to claim 1, characterized in that, In step (2), the crystallization is a two-stage crystallization with the following crystallization conditions: the first-stage crystallization temperature is 30-60 ℃ lower than the crystallization temperature in step (1), and the first-stage crystallization time is 12-36 hours; the second-stage crystallization temperature is 40-60 ℃ higher than the first-stage crystallization temperature, and the second-stage crystallization time is 12-60 hours.

9. The preparation method according to claim 8, characterized in that, In step (2), the first crystallization time is 12-26 hours; the second crystallization time is 24-36 hours.

10. The preparation method according to claim 1, characterized in that, In step (2), the calcination conditions are as follows: the calcination temperature is 500-800 ℃ and the calcination time is 3-12 hours.

11. The preparation method according to claim 10, characterized in that, In step (2), the calcination conditions are as follows: the calcination temperature is 530-650 ℃ and the calcination time is 4-8 hours.

12. The ZSM-11 molecular sieve prepared by any one of the preparation methods described in claims 1-11.

13. The ZSM-11 molecular sieve according to claim 12, characterized in that, In the ZSM-11 molecular sieve, the nanorods are axially conical with the bottom facing the top, and / or the size of the bottom protrusion is 50-400 nm.

14. The ZSM-11 molecular sieve according to claim 12, characterized in that, The SiO2 / Al2O3 molar ratio of the ZSM-11 molecular sieve is 15-200.

15. The ZSM-11 molecular sieve according to claim 12, characterized in that, The specific surface area of ​​the ZSM-11 molecular sieve is 300-496 m². 2 / g, pore volume 0.1-0.6 cm³ 3 / g.

16. The ZSM-11 molecular sieve according to claim 15, characterized in that, The ZSM-11 molecular sieve has a pore volume of 0.3-0.6 cm³. 3 / g.

17. The use of the ZSM-11 molecular sieve according to any one of claims 12-16 in the preparation of toluene and xylene by the alkylation reaction of benzene and methanol.

18. The application according to claim 17, characterized in that, The reaction conditions are as follows: reaction temperature 350-500 ℃, reaction pressure 0.1-1.0 MPa; the molar ratio of benzene to methanol is 0.1-10, and the mass hourly space velocity (HHSV) of the reactants is 0.1-5.0 h⁻¹. -1 The carrier gas that carries the reactants into the catalyst bed is an inert gas, and the molar ratio of the carrier gas to the mixed feedstock is 5-20.

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