Method for synthesizing microspherical boron-containing mercerizing molecular sieve

Abstract

The invention relates to a method for synthesizing a microspherical boron-containing mercerizing molecular sieve, and belongs to the technical field of molecular sieve synthesis. The method comprises the following steps: dissolving sodium silicate in water, adding a certain amount of sodium metaaluminate and boric acid, stirring to uniformly mix, adding a certain amount of hydrogen peroxide aqueous solution, and finally filling the mixture into a crystallization kettle; sealing the crystallization kettle, introducing a certain amount of carbon dioxide gas while stirring, then introducing nitrogen to maintain the pressure, stirring and aging for a certain time at room temperature while maintaining the pressure, heating to a certain temperature, carrying out hydrothermal crystallization, carrying out solid-liquid separation on the product after crystallization is completed, and washing and drying the obtained solid to obtain the microspherical boron-containing mercerizing molecular sieve. According to the method, an organic template agent or an organic surfactant is not used, the obtained molecular sieve has good spherical morphology, secondary oil column forming or spray granulation forming is not needed in the preparation process, and the preparation process is simple, small in environmental pollution and low in energy consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular sieve synthesis, and particularly relates to a method for synthesizing microspherical boron-containing mordenite molecular sieve. Background Art

[0002] As an important molecular sieve material with MOR-type topological structure, regular pore structure and adjustable acidic sites, mordenite molecular sieve plays an important role in the fields of petroleum refining, petrochemical industry, fine chemical industry and environmental protection as a catalytic material or an adsorbent material.

[0003] However, when synthesizing mordenite molecular sieve, the traditional hydrothermal synthesis technology is limited by the crystal growth kinetics and often generates irregularly shaped aggregates. When used in a fluidized bed reactor, the irregular morphology of such aggregates will cause problems such as uneven bed density of industrial catalysts. Not only is the bed resistance large, it is easy to be entrained and lost by the gas flow, but also local carbon deposition deactivation is easily caused, the operation efficiency of the reactor is reduced, and the long-term stable operation of the device is affected. Therefore, the irregularly shaped mordenite molecular sieve directly synthesized is difficult to be directly used in a fluidized bed reactor.

[0004] To solve these problems, generally, forming technologies such as oil-ammonia column forming or spray granulation are required, and after adding a binder, the molecular sieve obtained by direct synthesis is subjected to secondary processing and forming to make it have a better spherical morphology.

[0005] Chinese Patent No. 201210100709.X, "Preparation Method of a Spherical Molecular Sieve Catalyst", discloses a method for producing spherical catalysts using a vortex or mixed vortex mixing reactor. In this method, the mixed solution is sprayed into the air through the nozzle of the vortex or mixed vortex mixing reactor, and the mixed solution undergoes polycondensation to form spherical gel particles containing molecular sieves; Chinese Patent No. 202311221080.9, "A Molecular Sieve-Based Microsphere Fluidized Bed Catalyst and Its Preparation Method and Application", discloses a transition metal-modified molecular sieve. It is dispersed in a straight-chain alkane with a carbon atom number ≥ 5 to form slurry A, and a matrix and a binder are mixed to form slurry B. Then, slurry A and slurry B are mixed, spray granulated, and calcined to prepare a fluidized bed catalyst; Chinese Patent No. 202410863414.0, "Molding Method of Titanium-Silicon Molecular Sieve Catalyst and Its Application", discloses a method using a microfluidic co-flow type device. The dispersed phase of the molecular sieve mixture flowing into the main channel from the capillary is cut and dispersed by the external fluid oil phase dispersant (continuous phase) injected into the main channel, thereby obtaining droplet microspheres; Chinese Patent No. 201210042471.X, "Method for Primary Molding of Titanium-Silicon Molecular Sieve", discloses that the crystallization solution of the synthesized titanium-silicon molecular sieve is directly added to matrix substances, binders, peptizing agents, and pore expanders for beating treatment, and then spray dried and calcined to obtain molded titanium-silicon molecular sieves; Chinese Patent No. 201811228437.5, "Method for Droplet Spheroidization Molding", discloses a method in which an oxide particle slurry is dropped into an oil-ammonia solution. The slurry first shrinks into a sphere in the upper oil phase and then enters the lower ammonia phase for gelation molding. After aging, gel spheres are obtained, and the gel spheres are taken out for drying and calcination to obtain spherical particles; Chinese Patent No. 202011172787.1, "A Catalyst Molding Device and Its Application", discloses an oil-ammonia column molding device. The catalyst colloid is dropped by a droplet dropper and solidified and molded in the short column of the U-shaped column. The molded gel spheres are collected in a sphere collection basket and lifted by a lifter and placed in the long column of the U-shaped column for aging. After aging, the spheres are lifted out of the column by the lifter.

[0006] Secondary processing and molding often have a complex preparation process, high energy consumption and environmental protection costs, require the additional addition of binders, and various impurities are easily introduced during the molding process.

[0007] Chinese Patent No. 202411646712.0, "A Self-Assembled Microsphere Molecular Sieve with a Hierarchical Pore Structure and Its Preparation Method", discloses a method for forming microspheres of different sizes or densities by adding self-assembly regulators including organic amines or surfactants; Chinese Patent No. 202110878029.X, "An Efficient Single-Atom Molecular Sieve Molding Catalyst and Its Preparation Method", discloses a method in which a semi-crystallized state molecular sieve raw powder is first synthesized, then the semi-crystallized state molecular sieve raw powder is mixed evenly with a binder and molded, and the molded semi-crystallized molecular sieve is secondarily crystallized in an autoclave to obtain a molecular sieve molding catalyst.

[0008] Microspherical molecular sieves can also be obtained by methods such as adding organic template agents, surfactants, or secondary crystallization. However, the process flow is still relatively complex and various impurities are easily introduced. SUMMARY OF THE INVENTION

[0009] Based on the above problems existing in the prior art, the present invention provides a method for synthesizing microspherical boron-containing mordenite molecular sieves. This method does not use organic template agents or organic surfactants. The obtained molecular sieves have a good spherical morphology. The preparation process does not require secondary oil column forming or spray granulation forming. The preparation process is simple, has little environmental pollution, and low energy consumption.

[0010] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0011] A method for synthesizing microspherical boron-containing mordenite molecular sieves, comprising the following steps:

[0012] Step (1), dissolving sodium silicate in water, adding a certain amount of sodium aluminate and boric acid, stirring to mix them evenly, then adding a certain amount of hydrogen peroxide aqueous solution, and finally loading the mixture into a crystallization kettle;

[0013] Step (2), after sealing the crystallization kettle, introducing a certain amount of carbon dioxide gas under stirring, and then introducing nitrogen to maintain pressure;

[0014] Step (3), after stirring and aging at room temperature for a certain time under pressure, heating to a certain temperature for hydrothermal crystallization. After completion of crystallization, separating the product into solid and liquid, and washing and drying the obtained solid to obtain microspherical boron-containing mordenite molecular sieves.

[0015] Further, in the step (1), the molar ratio of sodium silicate, sodium aluminate, boric acid, water, and hydrogen peroxide in the mixture is Na2SiO3∶NaAlO2∶H3BO3∶H2O∶H2O2 = 1∶0.1 - 0.2∶0.05 - 0.1∶25 - 40∶0.5 - 1.

[0016] Further, in the step (2), the amount of carbon dioxide gas introduced is CO2∶Na2SiO3 molar ratio = 0.80 - 0.95∶1, and the stirring speed in the crystallization kettle is 100 - 500 revolutions per minute.

[0017] Further, in the step (2), introducing nitrogen to maintain pressure makes the pressure in the crystallization kettle 0.2 - 1 MPa.

[0018] Further, in the step (3), the aging time at room temperature is 2 - 12 hours, the hydrothermal crystallization temperature is 160 - 190 °C, and the hydrothermal crystallization time is 24 - 48 hours.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] The present method provides a method for synthesizing microspherical boron-containing mordenite zeolite. The organic template or organic surfactant is not used in the synthesis process. The obtained zeolite has a good spherical morphology, and the secondary oil column forming or spray granulation forming is not required in the preparation process. The preparation process is simple, with little environmental pollution and low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 XRD pattern of the synthesized sample of Comparative Example 1;

[0022] Figure 2 XRD pattern of the synthesized sample of Comparative Example 2;

[0023] Figure 3 XRD pattern of the synthesized sample of Example 1;

[0024] Figure 4 XRD pattern of the synthesized sample of Example 2;

[0025] Figure 5 XRD pattern of the synthesized sample of Example 3;

[0026] Figure 6 XRD pattern of the synthesized sample of Example 4;

[0027] Figure 7 XRD pattern of the synthesized sample of Example 5.

[0028] Figure 8 SEM image of the synthesized sample of Comparative Example 1;

[0029] Figure 9 SEM image of the synthesized sample of Comparative Example 2;

[0030] Figure 10 SEM image of the synthesized sample of Example 1;

[0031] Figure 11 SEM image of the synthesized sample of Example 2;

[0032] Figure 12 SEM image of the synthesized sample of Example 3;

[0033] Figure 13 SEM image of the synthesized sample of Example 4;

[0034] Figure 14 SEM image of the synthesized sample of Example 5. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The technical solutions and effects of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0036] In the comparative examples and examples of the present invention, sodium silicate, sodium aluminate, boric acid, hydrogen peroxide aqueous solution, carbon dioxide, and nitrogen used are all commercially available products, and the mass fraction of the hydrogen peroxide aqueous solution used is 30%.

[0037] Comparative Example 1

[0038] Dissolve 284 g of sodium silicate (Na2SiO3·9H2O) in 386 g of water, then sequentially add 12.5 g of sodium aluminate and 4.6 g of boric acid, stir to make the mixture uniform, and then add 90.7 g of hydrogen peroxide aqueous solution (mass fraction 30%). Load this mixture into a crystallization kettle, and in terms of molar ratio, Na2SiO3∶NaAlO2∶H3BO3∶H2O∶H2O2 in the mixture = 1∶0.15∶0.075∶34∶0.8; after sealing the crystallization kettle, introduce nitrogen under stirring at 300 revolutions per minute to make the pressure in the crystallization kettle 0.6 MPa; after stirring and aging at room temperature under constant pressure for 6 hours, heat to 170 °C for hydrothermal crystallization for 36 hours. After crystallization is completed, separate the product into solid and liquid, wash the obtained solid, dry it, and collect the sample.

[0039] The XRD patterns and SEM images of the collected solid samples are shown in Figure 1 and Figure 8 respectively, and the elemental analysis results are shown in Table 1. It can be seen from the XRD patterns, SEM images and elemental analysis results that this sample is an amorphous species containing silicon, aluminum and boron, and the structure is non-spherical.

[0040] Comparative Example 2

[0041] Dissolve 284 g of sodium silicate (Na2SiO3·9H2O) in 450 g of water, then sequentially add 12.5 g of sodium aluminate and 4.6 g of boric acid, stir to make the mixture uniform, and load this mixture into a crystallization kettle. In terms of molar ratio, Na2SiO3∶NaAlO2∶H3BO3∶H2O in the mixture = 1∶0.15∶0.075∶34; after sealing the crystallization kettle, introduce 19 L of carbon dioxide gas (in terms of standard volume) under stirring at 300 revolutions per minute, and the amount of carbon dioxide gas introduced is CO2∶Na2SiO3 molar ratio = 0.85∶1, and then introduce nitrogen to make the pressure in the crystallization kettle 0.6 MPa; after stirring and aging at room temperature under constant pressure for 6 hours, heat to 170 °C for hydrothermal crystallization for 36 hours. After crystallization is completed, separate the product into solid and liquid, wash the obtained solid, dry it, and collect the sample.

[0042] The XRD patterns and SEM images of the collected solid samples are shown in Figure 2 and Figure 9 respectively, and the elemental analysis results are shown in Table 1. It can be seen from the XRD patterns, SEM images and elemental analysis results that this sample is a boron-containing mordenite zeolite with low crystallinity and irregular morphology (non-spherical).

[0043] Example 1

[0044] Dissolve 284 g of sodium silicate (Na2SiO3·9H2O) in 386 g of water, then successively add 12.5 g of sodium aluminate and 4.6 g of boric acid, stir to make the mixture uniform, and then add 90.7 g of hydrogen peroxide aqueous solution (mass fraction 30%). Load this mixture into a crystallization kettle. In terms of molar ratio, in the mixture, Na2SiO3∶NaAlO2∶H3BO3∶H2O∶H2O2 = 1∶0.15∶0.075∶34∶0.8; after sealing the crystallization kettle, introduce 19 L of carbon dioxide gas (in terms of standard condition volume) under stirring at 300 revolutions per minute. The amount of carbon dioxide gas introduced is CO2∶Na2SiO3 molar ratio = 0.85∶1, and then introduce nitrogen to make the pressure in the crystallization kettle 0.6 MPa; after stirring and aging at room temperature for 6 hours under constant pressure, heat to 170 °C for hydrothermal crystallization for 36 hours. After crystallization is completed, separate the solid and liquid of the product, wash the obtained solid, dry it, and collect the sample.

[0045] The XRD pattern and SEM image of the collected solid sample are shown in Figure 3 and Figure 10 respectively, and the elemental analysis results are shown in Table 1. From the XRD pattern, SEM image and elemental analysis results, it can be seen that this sample is a microspherical boron-containing mordenite zeolite.

[0046] Example 2

[0047] Add 284 g of sodium silicate (Na2SiO3·9H2O) to 209 g of water, heat to dissolve it, then successively add 8.2 g of sodium aluminate and 6.2 g of boric acid, stir to make the mixture uniform, and then add 113 g of hydrogen peroxide aqueous solution (mass fraction 30%). Load this mixture into a crystallization kettle. In terms of molar ratio, in the mixture, Na2SiO3∶NaAlO2∶H3BO3∶H2O∶H2O2 = 1∶0.10∶0.10∶25∶1.0; after sealing the crystallization kettle, introduce 17.9 L of carbon dioxide gas (in terms of standard condition volume) under stirring at 500 revolutions per minute. The amount of carbon dioxide gas introduced is CO2∶Na2SiO3 molar ratio = 0.8∶1, and then introduce nitrogen to make the pressure in the crystallization kettle 0.6 MPa; after stirring and aging at room temperature for 6 hours under constant pressure, heat to 170 °C for hydrothermal crystallization for 36 hours. After crystallization is completed, separate the solid and liquid of the product, wash the obtained solid, dry it, and collect the sample.

[0048] The XRD pattern and SEM image of the collected solid sample are shown in Figure 4 and Figure 11 respectively, and the elemental analysis results are shown in Table 1. From the XRD pattern, SEM image and elemental analysis results, it can be seen that this sample is a microspherical boron-containing mordenite zeolite.

[0049] Example 3

[0050] 284 g of sodium silicate (Na2SiO3·9H2O) was added to 518 g of water, and heated to dissolve. Then, 16.5 g of sodium aluminate and 3.1 g of boric acid were added successively, and stirred to mix evenly. Next, 56.7 g of hydrogen peroxide aqueous solution (mass fraction 30%) was added. The mixture was loaded into a crystallization kettle, and in terms of molar ratio, Na2SiO3∶NaAlO2∶H3BO3∶H2O∶H2O2 in the mixture was 1∶0.20∶0.05∶40∶0.5; after sealing the crystallization kettle, 21.3 L of carbon dioxide gas (in terms of standard volume) was introduced under stirring at 100 revolutions per minute. The amount of carbon dioxide gas introduced was CO2∶Na2SiO3 molar ratio = 0.95∶1, and then nitrogen was introduced to make the pressure in the crystallization kettle 0.6 MPa; after aging at room temperature under constant pressure with stirring for 6 hours, it was heated to 170 °C for hydrothermal crystallization for 36 hours. After crystallization was completed, the product was separated into solid and liquid, and the obtained solid was washed, dried, and the sample was collected.

[0051] The XRD pattern and SEM image of the collected solid sample are shown respectively in Figure 5 and Figure 12 , and the elemental analysis results are shown in Table 1. From the XRD pattern, SEM image and elemental analysis results, it can be seen that the sample is microspherical boron-containing mordenite.

[0052] Example 4

[0053] 284 g of sodium silicate (Na2SiO3·9H2O) was dissolved in 386 g of water, and then 12.5 g of sodium aluminate and 4.6 g of boric acid were added successively, and stirred to mix evenly. Next, 90.7 g of hydrogen peroxide aqueous solution (mass fraction 30%) was added. The mixture was loaded into a crystallization kettle, and in terms of molar ratio, Na2SiO3∶NaAlO2∶H3BO3∶H2O∶H2O2 in the mixture was 1∶0.15∶0.075∶34∶0.8; after sealing the crystallization kettle, 19 L of carbon dioxide gas (in terms of standard volume) was introduced under stirring at 300 revolutions per minute. The amount of carbon dioxide gas introduced was CO2∶Na2SiO3 molar ratio = 0.85∶1, and then nitrogen was introduced to make the pressure in the crystallization kettle 1.0 MPa; after aging at room temperature under constant pressure with stirring for 2 hours, it was heated to 190 °C for hydrothermal crystallization for 24 hours. After crystallization was completed, the product was separated into solid and liquid, and the obtained solid was washed, dried, and the sample was collected.

[0054] The XRD pattern and SEM image of the collected solid sample are shown respectively in Figure 6 and Figure 13 , and the elemental analysis results are shown in Table 1. From the XRD pattern, SEM image and elemental analysis results, it can be seen that the sample is microspherical boron-containing mordenite.

[0055] Example 5

[0056] Dissolve 284 g of sodium silicate (Na2SiO3·9H2O) in 386 g of water, then successively add 12.5 g of sodium aluminate and 4.6 g of boric acid, stir to make the mixture uniform, and then add 90.7 g of hydrogen peroxide aqueous solution (mass fraction 30%). Load the mixture into a crystallization kettle, and the molar ratio of the mixture is Na2SiO3∶NaAlO2∶H3BO3∶H2O∶H2O2 = 1∶0.15∶0.075∶34∶0.8; after sealing the crystallization kettle, introduce 19 L of carbon dioxide gas (in terms of standard volume) under stirring at 300 rpm. The amount of carbon dioxide gas introduced is CO2∶Na2SiO3 molar ratio = 0.85∶1, and then introduce nitrogen to make the pressure in the crystallization kettle 0.2 MPa; after aging at room temperature with stirring under constant pressure for 12 hours, heat to 160 °C for hydrothermal crystallization for 48 hours. After crystallization is completed, separate the solid and liquid of the product, wash the obtained solid, dry it, and collect the sample.

[0057] The XRD pattern and SEM image of the collected solid sample are shown in Figure 7 and Figure 14 , and the elemental analysis results are shown in Table 1. From the XRD pattern, SEM image, and elemental analysis results, it can be seen that the sample is a microspherical boron-containing mordenite zeolite.

[0058] Table 1 Silicon, aluminum, and boron element contents (mass fraction) of the solid samples obtained in the comparative example and the examples

[0059]

[0060] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing microspherical boron-containing mordenite zeolite, characterized in that, It includes the following steps: Step (1): Dissolve sodium silicate in water, add a certain amount of sodium aluminate and boric acid, stir to mix them evenly, then add a certain amount of hydrogen peroxide aqueous solution, and finally load the mixture into a crystallization kettle. Step (2): After sealing the crystallization kettle, introduce a certain amount of carbon dioxide gas under stirring, and then introduce nitrogen to maintain the pressure. Step (3): After aging at room temperature under pressure for a certain time with stirring, heat to a certain temperature for hydrothermal crystallization. After the crystallization is completed, separate the solid and liquid of the product. The obtained solid is washed and dried to obtain microspherical boron-containing mordenite zeolite.

2. The method for synthesizing microspherical boron-containing mordenite zeolite according to claim 1, wherein In the said step (1), the molar ratio of sodium silicate, sodium aluminate, boric acid, water and hydrogen peroxide in the mixture is Na2SiO3∶NaAlO2∶H3BO3∶H2O∶H2O2 = 1∶0.1 - 0.2∶0.05 - 0.1∶25 - 40∶0.5 - 1.

3. The method for synthesizing microspherical boron-containing mordenite zeolite according to claim 1, characterized in that, In the said step (2), the amount of carbon dioxide gas introduced is such that the molar ratio of CO2∶Na2SiO3 = 0.80 - 0.95∶1, and the stirring speed in the crystallization kettle is 100 - 500 revolutions per minute.

4. The method for synthesizing microspherical boron-containing mordenite zeolite according to claim 1, characterized in that, In the said step (2), introducing nitrogen to maintain the pressure makes the pressure in the crystallization kettle 0.2 - 1 MPa.

5. The method for synthesizing microspherical boron-containing mordenite zeolite according to claim 1, wherein, In the said step (3), the aging time at room temperature is 2 - 12 hours, the hydrothermal crystallization temperature is 160 - 190 °C, and the hydrothermal crystallization time is 24 - 48 hours.

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