A method for dynamically synthesizing multi-level pore ZSM-22 molecular sieve

Abstract

The present invention belongs to the technical field of molecular sieve preparation, and discloses a method for dynamically synthesizing a multi-level porous ZSM-22 molecular sieve. The method does not contain a microporous template agent, has a short crystallization time, is environmentally friendly, has a low production cost, and the product has potential application value for some important catalytic reactions.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieve preparation, and in particular relates to a method for dynamically synthesizing a multi-level pore ZSM-22 molecular sieve. Background Art

[0002] ZSM-22 molecular sieve is a kind of aluminosilicate molecular sieve with TON topological structure framework synthesized by Dwyer et al. of Mobil Corporation in the United States under hydrothermal conditions in the 1980s. The framework is composed of five-membered rings, six-membered rings and ten-membered rings. The main pore is a one-dimensional straight pore parallel to the (001) crystal plane, and the pore opening is an ellipse of 4.6Å×5.7Å. The unique one-dimensional straight pore structure of ZSM-22 molecular sieve shows good shape selectivity, and the suitable acidity reduces the incidence of cracking reaction while isomerizing at high isomerization, so it is widely used in the isomerization of olefins and isomerization of alkanes.

[0003] Since the one-dimensional micropore length of the ZSM-22 molecular sieve synthesized by the traditional method can reach 1-3μm, it severely limits the diffusion of carbon cation intermediates and isomerization reaction products, thus leading to an intensified cracking reaction and a low yield of isomerization products. Therefore, the synthesis of multi-level porous ZSM-22 molecular sieves with micro-mesoporous structures has become an effective means to improve the diffusion properties of reaction intermediates and products, inhibit the occurrence of cracking reactions, and achieve a significant increase in the yield of isomerization products.

[0004] CN201610222567.2 discloses a method for preparing a multi-level pore ZSM-22 molecular sieve by an alkali desiliconization post-treatment method, wherein the method is first used to prepare a microporous ZSM-22 molecular sieve raw powder, and then the multi-level pore ZSM-22 molecular sieve is obtained by alkali desiliconization treatment. This method forms mesopores in the molecular sieve by post-treatment, which easily makes the skeleton structure unstable.

[0005] CN201810566615.9 discloses a method for synthesizing a nano ZSM-22 zeolite assembly containing a mesoporous structure, and adopts a method for synthesizing a multi-level pore ZSM-22 molecular sieve in situ by adding a microporous template agent and a high molecular polymer as a mesoporous template agent. CN201610110252.9 discloses a method for preparing a ZSM-22 molecular sieve with a mesoporous-microporous hierarchical structure, and adopts a method for synthesizing a multi-level pore ZSM-22 molecular sieve in situ by adding a microporous template agent and starch as a mesoporous template agent. Both of the above methods are static synthesis and can only be used for laboratory synthesis, which is not conducive to industrial large-scale production.

[0006] At present, the dynamic synthesis technology of multi-level pore ZSM-22 molecular sieve still has a series of difficulties that need to be overcome. Therefore, reducing the synthesis cost, shortening the crystallization time, and developing a dynamic synthesis method suitable for industrial production are the main research contents. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, the present invention provides a method for dynamically synthesizing multi-level porous ZSM-22 molecular sieves, which does not require a microporous template, has a short crystallization time, is environmentally friendly, and has a low production cost. The product has potential application value for some important catalytic reactions.

[0008] The above object of the present invention is achieved by the following technical scheme: A method for dynamically synthesizing a multi-level pore ZSM-22 molecular sieve, comprising the steps of:

[0009] 1. Mix deionized water and aluminum source evenly, then add potassium source, stir and add silica sol at the same time;

[0010] 2. Mix TPOAC (dimethyloctadecyl[3-methoxysilylpropyl]ammonium chloride) and deionized water and stir;

[0011] 3. Pour the product obtained in step 2 into the silica-alumina sol formed in step 1 and stir evenly, then add ZSM-22 molecular sieve seed crystals and continue stirring;

[0012] 4. The product obtained in step 3 is placed in an ultrasonic oscillation high-pressure reactor, and the ultrasonic oscillation high-pressure reactor is placed in a dynamic reactor for crystallization, and the product is filtered and dried to obtain a ZSM-22 molecular sieve;

[0013] Among them, the structure of the ultrasonic oscillation high-pressure reactor is as follows: a discharge port is provided at the bottom of the reactor shell, a feeding port is provided at the top, an agitator is arranged inside the shell and the tail of the agitator passes through the center of the top of the shell and is connected to the motor above the shell, a thermocouple and a pH meter pass through the top of the shell and enter the interior of the shell, and an ultrasonic oscillator is also provided at the bottom of the shell.

[0014] Furthermore, in step 1, the aluminum source is specifically Al2O3, the potassium source is specifically K2O, and the silica sol component is specifically SiO2.

[0015] Furthermore, the mass ratio of SiO2, Al2O3, K2O and TPOAC is: (0.008-0.02): (0.05-0.1): (0.1-0.5): (20-50), the mass ratio of the ZSM-22 molecular sieve seed to SiO2 is 0.2%~5%, and the balance is deionized water.

[0016] Furthermore, in step 2, the stirring process is specifically stirring at room temperature for 12 hours.

[0017] Furthermore, in step 3, ZSM-22 molecular sieve seed crystals are added and stirring is continued for 1 hour.

[0018] Furthermore, in step 4, the rotation speed of the dynamic reactor is set to 10-30 r / min.

[0019] Furthermore, in step 4, the crystallization temperature is 140-160° C., and the crystallization time is 0.5-2 days.

[0020] The beneficial effects of the present invention compared with the prior art are:

[0021] Compared with the existing method for preparing ZSM-22 molecular sieve, the technical method provided by the present invention has no microporous template, short crystallization time, environmental friendliness, low production cost, and the product has potential application value for some important catalytic reactions;

[0022] The method provided by the present invention can synthesize micro-mesoporous composite ZSM-22 molecular sieve in one step, which is simple and quick, and maintains a high crystallinity of the molecular sieve while forming mesopores, so that the product maintains good crystallinity and purity while having good catalytic reaction activity.

[0023] The invention provides a dynamic crystallization method, which has important significance in the field of actual chemical production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0025] Figure 1 It is a schematic diagram of the structure of the ultrasonic oscillation high-pressure reactor of the present invention;

[0026] Figure 2 is the XRD spectrum of the sample in Example 1 of the present invention;

[0027] Figure 3 It is a graph of N2 physical adsorption data of the samples in Examples 1-4 of the present invention.

[0028] In the figure, 1. discharge port; 2. agitator; 3. housing; 4. feeding port; 5. motor; 6. thermocouple; 7. pH meter; 8. ultrasonic oscillator. DETAILED DESCRIPTION

[0029] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0030] The implementation principle of the present invention:

[0031] The seed synthesis method is based on the direct synthesis method. ZSM-22 is added as a seed into the system to synthesize ZSM-22 zeolite molecular sieve in a relatively short time. By adding a small amount of ZSM-22 seed crystals, the crystallization can be accelerated quickly to obtain ZSM-22 crystals with high crystallinity and good purity.

[0032] Dimethyloctadecyl[3-methoxysilylpropyl]ammonium chloride is used as a mesoporous template and as a silicon source to participate in crystallization. After the silicon atom enters the framework, the organic atoms are removed by calcination, and a ZSM-22 molecular sieve containing mesopores can be formed. Example 1

[0033] First, mix 50g of deionized water and 1g of aluminum sulfate 18hydrate evenly, then add 0.01g of KOH, stir to clarify, add 20.03g of 30w% silica sol, continue stirring until the solution becomes uniform to form a silica-alumina sol, and at the same time, mix 30g of dimethyloctadecyl[3-methoxysilylpropyl]ammonium chloride (TPOAC) with 40g of deionized water and stir evenly, add the aqueous solution of TPOAC to the above-mentioned silica-alumina sol, and add 5% ZSM-22 molecular sieve as a seed (the amount of seed is calculated as a percentage of the mass of the input SiO2). Then add the reaction raw materials to a polytetrafluoroethylene stainless steel reactor, put the reactor into a KLJX-12A dynamic reactor, stir at a speed of 15r / min, and crystallize at 160°C for 12 h. After the crystallization is completed, cool naturally, filter, and wash, and the product is baked at 80°C for 12 hours until dry. The XRD diffraction peak of the product is shown in Figure 1 The product was determined to be ZSM-22 molecular sieve, and N2 physical adsorption characterization confirmed that the product contained mesopores. Example 2

[0034] First, 40g of deionized water and 1.33g of aluminum sulfate 18hydrate were mixed evenly, and then 0.0125g of KOH was added thereto. After stirring and clarifying, 20.03g of 30w% silica sol was added, and stirring was continued until the solution became uniform to form a silica-alumina sol. At the same time, 37.5g of dimethyloctadecyl [3-methoxysilylpropyl] ammonium chloride (TPOAC) was mixed and stirred with 32g of deionized water, and the aqueous solution of TPOAC was added to the above silica-alumina sol, and 0.2% ZSM-22 molecular sieve was added as a seed (the amount of seed was calculated as a percentage of the mass of the input SiO2). Then the reaction raw materials were added to a polytetrafluoroethylene stainless steel reactor, and the reactor was placed in a KLJX-12A dynamic reactor, with a stirring speed of 15r / min, and crystallized at 140°C for 2 days. After the crystallization was completed, it was naturally cooled, filtered, and washed, and the product was baked at 80°C for 12 hours until dry to obtain a multi-level pore ZSM-22 molecular sieve. Example 3

[0035] First, 25g of deionized water and 0.005g of aluminum sulfate 18hydrate were mixed evenly, and then 0.06g of KOH was added thereto. After stirring and clarifying, 20.03g of 30w% silica sol was added, and stirring was continued until the solution became uniform to form a silica-alumina sol. At the same time, 7.5g of dimethyloctadecyl [3-methoxysilylpropyl] ammonium chloride (TPOAC) was mixed and stirred with 11g of deionized water, and the aqueous solution of TPOAC was added to the above silica-alumina sol, and 0.4% ZSM-22 molecular sieve was added as a seed (the amount of seed was calculated as a mass percentage of the input SiO2). Then the reaction raw materials were added to a polytetrafluoroethylene stainless steel reactor, and the reactor was placed in a KLJX-12A dynamic reactor, with a stirring speed of 15r / min, and crystallized at 150°C for 19h. After the crystallization was completed, it was naturally cooled, filtered, and washed, and the product was baked at 80°C for 12 hours until dry to obtain a multi-level pore ZSM-22 molecular sieve. Example 4

[0036] First, 40g of deionized water and 1.13g of aluminum sulfate 18hydrate were mixed evenly, and then 0.075g of KOH was added thereto. After stirring and clarifying, 20.03g of 30w% silica sol was added, and stirring was continued until the solution became uniform to form a silica-alumina sol. At the same time, 33.75g of dimethyloctadecyl [3-methoxysilylpropyl] ammonium chloride (TPOAC) was mixed and stirred with 24.8g of deionized water, and the aqueous solution of TPOAC was added to the above silica-alumina sol, and 2% ZSM-22 molecular sieve was added as a seed (the amount of seed was calculated as a percentage of the mass of the input SiO2). Then the reaction raw materials were added to a polytetrafluoroethylene stainless steel reactor, and the reactor was placed in a KLJX-12A dynamic reactor, with a stirring speed of 15r / min, and crystallized at 155°C for 14h. After the crystallization was completed, it was naturally cooled, filtered, and washed, and the product was baked at 80°C for 12 hours until dry to obtain a multi-level pore ZSM-22 molecular sieve.

[0037] Table 1 Texture properties of different samples

[0038]

[0039] It can be seen from Table 1 that the mesopore volume of the samples provided in Examples 1 to 4 of the present application is 0.25-0.32 cm 3 / g, indicating that the technical solution provided in the present application can obtain a ZSM-22 molecular sieve containing a large number of mesopores, which has high application value and prospect in the field of molecular sieve synthesis and catalysis.

[0040] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for dynamically synthesizing a multi-level porous ZSM-22 molecular sieve, characterized in that the steps include: S1. The deionized water and the aluminum source are mixed evenly, and then the potassium source is added, stirred and silica sol is added at the same time, wherein the aluminum source is Al2O3, the potassium source is K2O, and the silica sol component is SiO2; S2. Mix TPOAC and deionized water and stir; S3. The product obtained in step S2 is poured into the silica-alumina sol formed in step S1 and stirred evenly, and then ZSM-22 molecular sieve seed crystals are added and stirring is continued; S4. The product obtained in step S3 is placed in an ultrasonic oscillation autoclave, and the ultrasonic oscillation autoclave is placed in a dynamic reactor for crystallization. The product is filtered and dried to obtain a ZSM-22 molecular sieve, the crystallization temperature is 140-160 ° C, and the crystallization time is 0.5-2 days; The mass ratio of SiO2, Al2O3, K2O and TPOAC is: (0.008-0.02): (0.05-0.1): (0.1-0.5): (20-50), the mass ratio of ZSM-22 molecular sieve seed to SiO2 is 0.2% to 5%, and the balance is deionized water; Among them, the structure of the ultrasonic oscillation high-pressure reactor is as follows: a discharge port is provided at the bottom of the reactor shell, a feeding port is provided at the top, an agitator is arranged inside the shell and the tail of the agitator passes through the center of the top of the shell and is connected to the motor above the shell, a thermocouple and a pH meter pass through the top of the shell and enter the interior of the shell, and an ultrasonic oscillator is also provided at the bottom of the shell.

2. The method for dynamically synthesizing multi-level pore ZSM-22 molecular sieve according to claim 1, characterized in that: In step S2, the stirring process is specifically stirring at room temperature for 12 hours.

3. The method for dynamically synthesizing multi-level pore ZSM-22 molecular sieve according to claim 1, characterized in that: In step S3, ZSM-22 molecular sieve seed crystals are added and stirring is continued for 1 hour.

4. The method for dynamically synthesizing multi-level pore ZSM-22 molecular sieve according to claim 1, characterized in that: In step S4, the rotation speed of the dynamic reactor is set to 10-30 r / min.

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