Mordenite and process for its synthesis

Abstract

The application discloses a mordenite and a synthesis process thereof, and the synthesis process comprises the following steps: (1) first preparing material A; (2) mixing the material A, an aluminum source, a thiourea, a directing agent, alcohol and water uniformly in the presence of an inorganic base to obtain material B; (4) performing a crystallization reaction on the material B obtained in the step (3), and then performing separation, drying and calcination to obtain the mordenite. The application further provides the mordenite obtained by using the synthesis process. The mordenite obtained by the application presents a nanosheet morphology characteristic and has high crystallinity, the synthesis process has good repeatability, the obtained product has stable properties, and the synthesized mordenite product can be efficiently guaranteed to have the nanosheet morphology.

Description

Technical Field

[0001] This invention relates to a mordenite zeolite and its synthesis process, belonging to the field of inorganic porous material synthesis, specifically to a mordenite zeolite with special morphological characteristics and its synthesis process. Background Technology

[0002] Mordenite zeolite is a crystalline microporous aluminosilicate. Due to its regularly arranged pores, high specific surface area, high stability, and strong acidity, it has significant industrial application value in adsorption, separation, catalytic cracking, and isomerization. However, due to its small pore size, its catalytic activity is greatly reduced in catalytic reactions involving large molecules because of the limited molecular diffusion rate. To address this problem, the diffusion rate of molecules within the crystal is improved by reducing the particle size of the zeolite molecular sieve, i.e., synthesizing nano-sized zeolite molecular sieves.

[0003] CN102060308A discloses a method for synthesizing nanofiber-like mordenite. The method uses silicon source, aluminum source, inorganic acid and deionized water as reaction raw materials. By adding an appropriate amount of molecular sieve seed crystals, the mordenite is crystallized for 30-160 hours under hydrothermal conditions of autogenous pressure and crystallization temperature of 130-200℃ to synthesize highly crystalline mordenite. The synthesized mordenite has a regular c-axis elongated fibrous morphology with a width of 20-100 nanometers and a length of 1-8 micrometers.

[0004] CN103601213A discloses a method for preparing low silica-to-alumina ratio nanofiber clustered mordenite molecular sieves. The preparation process is as follows: 1) Using silica sol as the silicon source, sodium aluminate as the aluminum source, and sodium hydroxide as the alkali source, sodium aluminate and sodium hydroxide are first added to deionized water and stirred to form a uniform solution. Then, silica sol is slowly added to the solution and aged for 30 minutes under stirring at room temperature to form a uniform white colloid. 2) The white colloid obtained in step 1) is transferred to a reaction vessel and subjected to hydrothermal reaction at 160-190℃ for 3-7 days. The obtained reaction product is vacuum filtered, washed with deionized water until the pH value of the washing solution is less than 9, dried at 120℃ for more than 12 hours, and finally calcined at 550℃ for 4-8 hours at a heating rate of 5℃ / min to obtain nanofiber clustered mordenite molecular sieves.

[0005] CN102718231A discloses a method for preparing layered nanofiber zeolite molecular sieves. The method uses hexadecyltrimethyl-p-methylbenzenesulfonate ammonium salt as the template agent. The specific steps are as follows: first, a silicon source is dissolved in an alkaline solution containing different aluminum sources and stirred at a constant temperature. Then, this solution is added dropwise to an aqueous solution containing the template agent, and stirring continues. After cooling to room temperature, the solution is transferred to a closed reactor for crystallization. Finally, the crystallized product is filtered, dried with a detergent, and calcined to obtain the layered nanofiber zeolite molecular sieve. This invention provides a sheet-like nanolayered zeolite. Summary of the Invention

[0006] Based on the above analysis, although some methods for controlling the morphology of mordenite have been reported in the prior art, they still have certain shortcomings. Repeated experiments using the methods reported in the prior art revealed that although the synthesized product is mordenite, its morphology remains typical of micron-sized disc-shaped or blocky crystals. Addressing the persistent problems in existing mordenite synthesis processes, the main contribution of this invention is to provide a synthesis process for mordenite that yields nanosheet-like morphology with high crystallinity. More importantly, the synthesis process provided by this invention exhibits good reproducibility, stable product properties, and can efficiently ensure that the synthesized mordenite product possesses a nanosheet morphology.

[0007] This invention provides a synthesis process for mordenite zeolite, the synthesis process comprising the following steps:

[0008] (1) Mix silica sol, fumed silica and water evenly, then add inorganic alkali until completely dissolved, and then dry and calcine.

[0009] (2) After the material in step (1) is roasted, it is further washed and dried to obtain material A;

[0010] (3) Under the condition of inorganic base, material A, aluminum source, thiourea, directing agent, alcohol and water are mixed evenly to obtain material B;

[0011] (4) The material B obtained in step (3) is subjected to a crystallization reaction, and then separated, dried and calcined to obtain mordenite.

[0012] In the above-mentioned synthesis process of mordenite zeolite, the silica sol and precipitated silica in step (1) are both common industrial commodities. Those skilled in the art can obtain them by purchasing them from relevant chemical manufacturers.

[0013] In the above-mentioned synthesis process of mordenite, the mass ratio of silicon oxide to water in the silica sol in step (1) is 7-30:200, preferably 10-25:200.

[0014] In the above-mentioned synthesis process of mordenite, the mass ratio of silica to water in step (1) is 7-30:200, preferably 10-25:200.

[0015] In the above-mentioned synthesis process of mordenite, the inorganic base mentioned in step (1) can be one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide, preferably sodium hydroxide.

[0016] In the above-mentioned synthesis process of silica zeolite, the mass ratio of silicon dioxide to inorganic alkali in the mixture of silica sol and fumed silica in step (1) is 10-35:1, preferably 15-30:1.

[0017] In the above synthesis process of mordenite, the drying conditions in step (1) can usually be controlled as follows: the drying temperature is 40-90℃, preferably 50-80℃.

[0018] In the above synthesis process of mordenite, the calcination conditions in step (1) can usually be controlled as follows: calcination temperature is 300-900℃, preferably 500-700℃; calcination time is 1-15h, preferably 3-10h.

[0019] In the above synthesis process of mordenite, the washing in step (2) is to wash with deionized water until neutral, and the drying conditions in step (2) can usually be controlled as follows: drying temperature is 100-140℃ and drying time is 5-15h.

[0020] In the above synthesis process of mordenite zeolite, the material A obtained in step (2) is solid silicon dioxide with a specific surface area of ​​50-180 m². 2 / g, its pore size distribution is concentrated in 9-12nm and 40-50nm, with the specific surface area of ​​9-12nm pores accounting for 50-65% of the total specific surface area, and the specific surface area of ​​40-50nm pores accounting for 25-35% of the total specific surface area.

[0021] In the above-mentioned synthesis process of mordenite, the directing agent mentioned in step (3) can be obtained by the following preparation method: mordenite, inorganic alkali and water are mixed and treated at 80-180℃ (preferably 100-140℃) for 0.5-8h (preferably 2-4h) under closed conditions, and the resulting suspension is the directing agent.

[0022] Furthermore, in the preparation method of the guiding agent, the mordenite can be homemade or commercially available mordenite.

[0023] Furthermore, in the preparation method of the directing agent, the inorganic base is at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0024] Furthermore, in the preparation method of the directing agent, the mass ratio of mordenite, inorganic alkali and water is 4-11:3-10:100, preferably 5-10:4-8:100.

[0025] In the above-mentioned synthesis process of mordenite, the alcohol in step (3) is at least one of ethanol, propanol, and butanol.

[0026] In the above-mentioned synthesis process of mordenite, the aluminum source in step (3) can be at least one of aluminum isopropoxide, aluminum butoxide, aluminum sec-butoxide, aluminum nitrate, aluminum sulfate, aluminum chloride, and sodium aluminate, preferably at least one of aluminum isopropoxide, aluminum nitrate, aluminum sulfate, and aluminum chloride.

[0027] In the above-mentioned synthesis process of mordenite, the molar ratio of inorganic alkali, material A (calculated as SiO2), aluminum source (calculated as Al2O3), thiourea, alcohol and water in step (3) is 1-7:10-55:1:1-6:80-220:700-1850, preferably 2-6:15-50:1:2-5:100-200:800-1800.

[0028] In the above-mentioned synthesis process of mordenite, the mass ratio of the directing agent to water in step (3) is 8-25:100, preferably 10-20:100.

[0029] In the above-mentioned synthesis process of mordenite, the mixing of inorganic alkali, material A, aluminum source, thiourea, directing agent, alcohol and water in step (3) needs to be carried out at 0 to 10°C. The mixing time can usually be controlled at 0.5 to 6 hours, preferably 1 to 5 hours.

[0030] In the above-mentioned synthesis process of mordenite, the crystallization reaction in step (4) is generally controlled within the following conditions: the crystallization temperature is 150-220℃, preferably 160-200℃; the crystallization time is 50-130h, preferably 60-120h.

[0031] In the above-mentioned synthesis process of mordenite, the separation operation mentioned in step (4) can be carried out by at least one of the existing solid-liquid two-phase separation methods in the art. Those skilled in the art can make any choice according to specific requirements and conditions. Specifically, in the synthesis process of the present invention, filtration can be used, generally 1 to 10 times.

[0032] In the above synthesis process of mordenite, the drying temperature in step (4) is 80-150℃ and the drying time is 1-20h.

[0033] In the above synthesis process of mordenite, the calcination in step (4) is carried out at 400-600℃ for 1-10 hours. The calcination needs to be carried out in the presence of an oxygen-containing atmosphere, specifically in the presence of air or oxygen.

[0034] The present invention also provides a mordenite obtained by the above-described synthesis process.

[0035] Furthermore, the mordenite zeolite obtained by the above synthesis process is a solid inorganic crystalline material with a mordenite zeolite structure. Its main framework structural elements include silicon, aluminum, and oxygen, specifically composed of silicon-oxygen and aluminum-oxygen structures as basic structural units, ultimately forming a network of porous structures. Its crystal morphology consists of irregular nanosheets, with the first dimension measuring 0.8–3 μm, the second dimension measuring 0.8–3 μm, and the third dimension measuring 30–100 nm; the sheet-like crystals are curved.

[0036] Furthermore, in the X-ray diffraction pattern of mordenite obtained by the above synthesis process, the diffraction peak located near 25.68 is the diffraction peak with the highest intensity.

[0037] Furthermore, the total specific surface area of ​​the mordenite zeolite obtained by the above synthesis process is 350–810 m². 2 / g.

[0038] The most prominent characteristic of zeolite materials is their regular and complex pore structure. The micropores provide a vast surface area, serving as the primary site for catalytic or adsorption reactions. During the reaction, reactants enter the micropores, undergo chemical reactions within the pores, and are transformed into reaction products that overflow from the pores, completing one catalytic reaction. While the microporous systems of micron-sized, three-dimensional, two-dimensional, and one-dimensional nanozeolites are essentially the same, the lengths of their micropore channels vary significantly in different directions. Therefore, the residence time of reactants in the pores of zeolites at different scales varies, resulting in different degrees of reaction. Ultimately, the same reactant catalyzing a reaction on zeolites of different scales produces completely different types or compositions of reaction products. Morderne zeolite is an important catalytic material and adsorbent in the chemical industry. Its crystal morphology influences its catalytic and adsorption capabilities. Traditional micron-sized morderne zeolite has pores at the micron level in all three dimensions. This invention provides a pore system for mordenite that has both conventional micron-scale pores and nano-scale pores. Therefore, it can exhibit special properties different from traditional mordenite in reactions such as disproportionation, isomerization, alkylation, alkyl transfer of aromatics, disproportionation and isomerization of alkanes, esterification, etherification and amination of alcohols. It can change the type and composition of reaction products to meet different production requirements.

[0039] In industrial production, product stability is paramount; only mature and reliable processes can guarantee consistent product quality. Zeolite molecular sieves are metastable substances, and their synthesis is inherently challenging. Nanoscale zeolite molecular sieves, including one-dimensional, two-dimensional, and three-dimensional nanomaterials, possess higher surface energies than conventional micron-scale zeolite molecular sieves, thus naturally tending to eliminate nanoscale characteristics and transition to the micron scale. Compared to conventional micron-scale zeolite synthesis methods, many nanoscale zeolite synthesis methods exhibit poor stability. Some key factors controlling the size of nanomaterials may become ineffective due to factors such as raw material purity, resulting in insufficient synthesis stability of nanomaterials.

[0040] Compared with existing technologies, this invention overcomes the drawback of poor stability of mordenite products obtained by existing synthesis processes, provides mordenite with stable product characteristics and its synthesis method, and has the following advantages:

[0041] This invention utilizes a self-made silicon source to synthesize mordenite zeolite. This silicon source is a key factor in controlling the crystal morphology of zeolite, and experiments have shown that the silicon source significantly influences the crystallization process of zeolite. In existing technologies, when using conventional silicon sources (including but not limited to silica sol, silica, and water glass) to synthesize mordenite, the crystallized product is a large crystal, such as a micron-sized block crystal. Large crystals have lower surface energy and better stability than nanocrystals; therefore, existing conventional methods tend to synthesize large crystals rather than nanocrystals. In the synthesis process of this invention, the self-made silicon source behaves differently from other silicon sources during the crystallization process, effectively controlling the crystal morphology of mordenite zeolite.

[0042] In the mordenite synthesis process provided by this invention, thiourea is also a key factor in controlling the morphology of zeolite crystals. The reason for this may be that its adsorption force on different crystal faces of zeolite varies significantly. Therefore, the growth of certain crystal faces of zeolite crystals can be selectively restricted without affecting the growth of other crystal faces, thereby generating mordenite with a nanosheet morphology.

[0043] In the mordenite synthesis process provided by this invention, the use of a directing agent enables more efficient synthesis of nanosheet mordenite zeolite. This is because the directing agent is prepared from complete mordenite macrocrystals through alkali treatment, and its main components are mordenite fragments and primary and secondary structural units of mordenite. Therefore, these smaller directing agents can easily enter the pores of the silicon source and achieve sufficient contact with it. This is beneficial for the synthesis of mordenite zeolite. If micron-sized mordenite zeolite is used as the structural directing agent, it cannot enter the pores of the special silicon source of this invention, greatly reducing the effectiveness of the directing agent.

[0044] The mordenite synthesized in this invention exhibits unique X-ray diffraction spectral characteristics, specifically, the highest intensity diffraction peak is located near 25.68. In contrast, the highest intensity diffraction peak in conventional mordenite is located near 9.67. Attached Figure Description

[0045] Figure 1 The image shown is a scanning electron microscope image of the sample obtained in Example 1.

[0046] Figure 2 Scanning electron microscope images of the sample obtained for Comparative Example 1.

[0047] Figure 3 The XRD pattern of the sample obtained in Example 1 is shown.

[0048] Figure 4 The XRD pattern of the sample was obtained for comparison example 1. Detailed Implementation

[0049] The technical solutions and effects of the present invention will be further illustrated below with reference to the embodiments, but the invention is not limited to the following embodiments.

[0050] The pore structure of the material of this invention was characterized by N2 adsorption-desorption using a physical adsorption instrument from Micron Technology, USA. Before measurement, the sample was vacuum-treated at 300℃ for more than 4 hours. Parameters such as total specific surface area and pore size were calculated using the BET and BJH formulas.

[0051] The phase structure and crystallinity of the material of this invention were characterized by X-ray diffraction using a Rigaku D / max2500 X-ray diffractometer (Japan), with a Cu target, Kα radiation source, graphite monochromator, tube voltage of 40kV, tube current of 80mA, scanning range of 5° to 40°, step size of 0.1°, and scanning speed of 1° / min.

[0052] The crystal morphology of the material of this invention was characterized by scanning electron microscopy using a JSM-6 301F SEM (equipped with Oxford EDS) from Nippon Electronics Corporation, with an operating voltage of 20kV, an operating distance of 15mm, and a resolution of 1.5nm.

[0053] In this document, the directing agents used in the examples and comparative examples were prepared by the following method.

[0054] Mix mordenite, sodium hydroxide, and deionized water in the following ratio (mass ratio of mordenite: sodium hydroxide: water = 8:7:100), stir well, and place in a sealed reaction vessel. Incubate in an oven at 120°C for 4 hours. The resulting suspension is the directing agent.

[0055] In this document, material A used in the examples and comparative examples was prepared by the following methods to prepare the first material A, the second material A, and the third material A, respectively, as follows:

[0056] Preparation of Material A:

[0057] Silica sol (silica:water = 23.5:200), silica, and distilled water were mixed in a ratio of 21.5:100 (total silica:water = 21.5:100) and stirred for 2 hours. Sodium hydroxide (inorganic alkali:silica = 1:18) was added to the mixture; then it was dried at 60°C for 12 hours. It was then calcined at 600°C for 5 hours; washed with deionized water until neutral, and dried at 120°C for 12 hours to obtain a silicon source with a specific surface area of ​​176.1 m². 2 / g, with pore sizes of 10nm and 45nm.

[0058] Preparation of the second material A:

[0059] Silica sol (silica:water mass = 20.3:100), fumed silica, and distilled water were mixed in a ratio of 20.5:200 (total silica:water mass = 20.3:100) and stirred for 2.5 h. Sodium hydroxide (inorganic alkali:silica = 1:22) was added to the mixture; then it was dried at 60°C for 12 h. It was then calcined at 550°C for 5 h; washed with deionized water until neutral, and dried at 120°C for 12 h to obtain a silicon source with a specific surface area of ​​176.7 m². 2 / g, with pore sizes of 10nm and 47nm.

[0060] Preparation of the third material A:

[0061] Silica sol (silica:water mass = 27.7:200), silica, and distilled water were mixed in a ratio of 25.5:100 (total silica:water mass = 25.5:100) and stirred for 2 hours. Sodium hydroxide (inorganic alkali:silica = 1:20) was added to the mixture; then it was dried at 70°C for 12 hours. It was then calcined at 630°C for 5 hours; washed with deionized water until neutral, and dried at 120°C for 12 hours to obtain a silicon source with a specific surface area of ​​151.2 m². 2 / g, with pore sizes of 11nm and 47nm.

[0062] Example 1

[0063] First, take a clean container and add sodium hydroxide, material A, aluminum nitrate, propanol, thiourea, deionized water, and the guiding agent according to the following ratio (molar ratio of inorganic alkali: material A: aluminum source: thiourea: alcohol: water = 5:35:1:4:150:1000, mass ratio of guiding agent: water = 15:100). Mix thoroughly. Then place the container in a circulating water system at 2℃ and stir for 2 hours. Next, transfer it to a high-pressure reactor and react at 170℃ for 80 hours. After the reaction, filter the resulting solid sample multiple times, then dry it in an oven at 110℃ for 12 hours. Finally, calcine it in air at 560℃ in a high-temperature furnace for 8 hours. The resulting sample is designated C1.

[0064] Its crystal structure belongs to mordenite, and its morphology is one-dimensional nanosheets, with the first dimension being 1.2 μm, the second dimension being 1 μm, and the third dimension being 75 nm; the sheet-like crystals are curved.

[0065] Example 2

[0066] First, take a clean container and add sodium hydroxide, material A, aluminum nitrate, butanol, thiourea, deionized water, and the guiding agent according to the following ratio (molar ratio of inorganic alkali: material A: aluminum source: thiourea: alcohol: water = 6:15:1:2:100:800, mass ratio of guiding agent: water = 10:100). Mix thoroughly. Then place the container in a circulating water system at 2℃ and stir for 2 hours. Next, transfer it to a high-pressure reactor and react at 160℃ for 60 hours. After the reaction, filter the resulting solid sample multiple times, then dry it in an oven at 110℃ for 12 hours. Finally, calcine it in air at 560℃ in a high-temperature furnace for 8 hours. The resulting sample is designated C2.

[0067] Its crystal structure belongs to mordenite, and its morphology is one-dimensional nanosheets, with the first dimension being 1.6 μm, the second dimension being 1.1 μm, and the third dimension being 65 nm; the sheet-like crystals are curved.

[0068] Example 3

[0069] First, take a clean container and add sodium hydroxide, third material A, aluminum nitrate, butanol, thiourea, deionized water, and the directing agent according to the following ratio (molar ratio of inorganic alkali: material A: aluminum source: thiourea: alcohol: water = 2:50:1:5:200:1800, mass ratio of directing agent: water = 20:100). Mix thoroughly. Then place the container in a circulating water system at 2℃ and stir for 2 hours. Next, transfer it to a high-pressure reactor and react at 200℃ for 120 hours. After the reaction, filter the resulting solid sample multiple times, then dry it in an oven at 110℃ for 12 hours. Finally, calcine it in air at 560℃ in a high-temperature furnace for 8 hours. The resulting sample is designated C3.

[0070] Its crystal structure belongs to mordenite, and its morphology is one-dimensional nanosheets. The first dimension is 1.8 μm, the second dimension is 1.5 μm, and the third dimension is 96 nm; the sheet-like crystals are curved.

[0071] Example 4

[0072] First, take a clean container and add potassium hydroxide, material A, aluminum sulfate, propanol, thiourea, deionized water, and the directing agent according to the following ratio (molar ratio of inorganic alkali: material A: aluminum source: thiourea: alcohol: water = 5.1:45:1:4.4:155:1050, mass ratio of directing agent: water = 18:100). Mix thoroughly. Then place the container in a circulating water system at 2℃ and stir for 2 hours. Next, transfer it to a high-pressure reactor and react at 166℃ for 100 hours. After the reaction, filter the resulting solid sample multiple times, then dry it in an oven at 110℃ for 12 hours. Finally, calcine it in air at 560℃ for 8 hours in a high-temperature furnace. The resulting sample is designated C4.

[0073] Its crystal structure belongs to mordenite, and its morphology is one-dimensional nanosheets. The first dimension is 2.3 μm, the second dimension is 1.3 μm, and the third dimension is 50 nm; the sheet-like crystals are curved.

[0074] Example 5

[0075] First, take a clean container and add potassium hydroxide, material A, aluminum sulfate, propanol, thiourea, deionized water, and the directing agent according to the following ratio (molar ratio of inorganic alkali: material A: aluminum source: thiourea: alcohol: water = 3.2:34:1:3.7:135:1200, mass ratio of directing agent: water = 16.5:100). Mix thoroughly. Then place the container in a circulating water system at 2℃ and stir for 2 hours. Next, transfer it to a high-pressure reactor and react at 170℃ for 85 hours. After the reaction, filter the resulting solid sample multiple times, then dry it in an oven at 110℃ for 12 hours. Finally, calcine it in air at 560℃ in a high-temperature furnace for 8 hours. The resulting sample is designated C5.

[0076] Its crystal structure belongs to mordenite, and its morphology is one-dimensional nanosheets. The first dimension is 2.5 μm, the second dimension is 1.3 μm, and the third dimension is 85 nm; the sheet-like crystals are curved.

[0077] Comparative Example 1

[0078] Synthesis experiments were conducted using silica as the silicon source.

[0079] Here, silica is used as the silicon source to replace material A in this invention as the synthesis raw material. First, take a clean container and add sodium hydroxide, silica, aluminum chloride, propanol, thiourea, deionized water, and structural directing agent according to the following ratio (molar ratio of inorganic alkali: silica: aluminum source: thiourea: alcohol: water = 5:35:1:4:150:1000, mass ratio of directing agent: water = 15:100), and mix thoroughly. Then place the container in a circulating water device at 2°C and stir for 2 hours. Then, load it into a high-pressure reactor and react at 170°C for 80 hours. After the reaction, filter the resulting solid sample several times, then dry it in an oven at 110°C for 12 hours, and finally calcine it in air at 560°C for 8 hours in a high-temperature furnace. The resulting sample is numbered C6.

[0080] Its crystal structure belongs to mordenite, but its crystal morphology is a bulk crystal at the micrometer scale. This indicates that the silicon source is the key factor in the morphology of the mordenite described in this invention, and the mordenite with the morphology described in this invention cannot be synthesized using ordinary silicon sources.

[0081] Comparative Example 2

[0082] Thiourea was not used in the synthesis experiments.

[0083] First, take a clean container and add sodium hydroxide, material A, aluminum nitrate, propanol, deionized water, and the directing agent according to the following ratio (molar ratio of inorganic alkali: material A: aluminum source: thiourea: alcohol: water = 5:35:1:4:150:1000, mass ratio of directing agent: water = 15:100), and mix thoroughly. Then place the container in a circulating water system at 2℃ and stir for 2 hours. Next, transfer it to a high-pressure reactor and react at 170℃ for 80 hours. After the reaction, filter the resulting solid sample multiple times, then dry it in an oven at 110℃ for 12 hours, and finally calcine it in air at 560℃ for 8 hours. The resulting sample is designated C7.

[0084] Its crystal structure belongs to mordenite, but its crystal morphology is a bulk crystal at the micrometer scale. This indicates that the organic additive of the present invention is a key factor in the synthesis of the mordenite with the morphology described in the present invention; without the organic additive of the present invention, it is impossible to synthesize the mordenite with the morphology described in the present invention.

[0085] Comparative Example 3

[0086] Instead of using a directing agent, mordenite was used as a seed crystal in the synthesis experiment.

[0087] First, take a clean container and add sodium hydroxide, material A, aluminum nitrate, propanol, thiourea, deionized water, and mordenite seed crystals according to the following ratio (molar ratio of inorganic alkali: material A: aluminum source: thiourea: alcohol: water = 5:35:1:4:150:1000, mass ratio of mordenite: water = 5:100). Mix thoroughly. Then place the container in a circulating water system at 2℃ and stir for 2 hours. Next, transfer it to a high-pressure reactor and react at 170℃ for 80 hours. After the reaction, filter the resulting solid sample multiple times, then dry it in an oven at 110℃ for 12 hours. Finally, calcine it in air at 560℃ in a high-temperature furnace for 8 hours. The resulting sample is designated C8.

[0088] Its crystal structure belongs to mordenite, and its morphology is one-dimensional nanosheets, but its crystallinity is low.

[0089] Table 1. Physicochemical properties of samples obtained from each example and comparative example.

[0090]

[0091] Note: The sample obtained in Example 1 is used as a reference in this invention, and its crystallinity is set to 100%. The relative crystallinity of all other samples is obtained by comparing it with the crystallinity of the reference.

Claims

1. A synthesis process for mordenite zeolite, the synthesis process comprising the following steps: (1) Mix silica sol, fumed silica and water evenly, then add inorganic alkali until completely dissolved, and then dry and calcine. (2) After the material in step (1) is roasted, it is further washed and dried to obtain material A; (3) Under the condition of inorganic base, material A, aluminum source, thiourea, directing agent, alcohol and water are mixed evenly to obtain material B; (4) The material B obtained in step (3) is subjected to crystallization reaction, and then separated, dried and calcined to obtain mordenite.

2. The synthesis process of mordenite according to claim 1, wherein, The mass ratio of silicon oxide to water in the silica sol described in step (1) is 7-30:100, preferably 10-25:

200.

3. The synthesis process of mordenite according to claim 1, wherein, The mass ratio of silica to water in step (1) is 7-30:200, preferably 10-25:

200.

4. The synthesis process of mordenite according to claim 1, wherein, The inorganic base mentioned in step (1) is one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide, preferably sodium hydroxide.

5. The synthesis process of mordenite according to claim 1, wherein, The mass ratio of silicon dioxide to inorganic alkali in the mixture of silica sol and precipitated silica in step (1) is 10 to 35:1, preferably 15 to 30:

1.

6. The synthesis process of mordenite according to claim 1, wherein, The drying conditions in step (1) are: the drying temperature is 40-90℃, preferably 50-80℃.

7. The synthesis process of mordenite according to claim 1, wherein, The roasting conditions in step (1) are: roasting temperature of 300-900℃, preferably 500-700℃; roasting time of 1-15h, preferably 3-10h.

8. The synthesis process of mordenite according to claim 1, wherein, The drying conditions in step (2) are: drying temperature of 100-140℃ and drying time of 5-15h.

9. The synthesis process of mordenite according to claim 1, wherein, Material A obtained in step (2) is solid silicon dioxide with a specific surface area of ​​50–180 m². 2 / g, its pore size distribution is concentrated in 9-12nm and 40-50nm, with the specific surface area of ​​9-12nm pores accounting for 50-65% of the total specific surface area, and the specific surface area of ​​40-50nm pores accounting for 25-35% of the total specific surface area.

10. The synthesis process of mordenite according to claim 1, wherein, The directing agent mentioned in step (3) is obtained by the following preparation method: mordenite, inorganic alkali and water are mixed and treated at 80-180℃ (preferably 100-140℃) for 0.5-8h (preferably 2-4h) under closed conditions, and the resulting suspension is the directing agent.

11. The synthesis process of mordenite according to claim 10, wherein, The inorganic base is at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

12. The synthesis process of mordenite according to claim 10, wherein, The mass ratio of mordenite, inorganic alkali, and water is 4–11:3–10:100, preferably 5–10:4–8:

100.

13. The synthesis process of mordenite according to claim 1, wherein, The alcohol in step (3) is at least one of ethanol, propanol, and butanol.

14. The synthesis process of mordenite according to claim 1, wherein, The aluminum source in step (3) is at least one of aluminum isopropoxide, aluminum butoxide, aluminum sec-butoxide, aluminum nitrate, aluminum sulfate, aluminum chloride, and sodium aluminate, preferably at least one of aluminum isopropoxide, aluminum nitrate, aluminum sulfate, and aluminum chloride.

15. The synthesis process of mordenite according to claim 1, wherein, In step (3), the molar ratio of inorganic alkali, material A (calculated as SiO2), aluminum source (calculated as Al2O3), thiourea, alcohol, and water is 1-7:10-55:1:1-6:80-220:700-1850, preferably 2-6:15-50:1:2-5:100-200:800-1800.

16. The synthesis process of mordenite according to claim 1, wherein, The mass ratio of the guiding agent to water in step (3) is 8-25:100, preferably 10-20:

100.

17. The synthesis process of mordenite according to claim 1, wherein, The mixing of inorganic alkali, material A, aluminum source, thiourea, directing agent, alcohol and water in step (3) is carried out at 0-10℃.

18. The synthesis process of mordenite according to claim 1, wherein, The crystallization reaction conditions in step (4) are: crystallization temperature of 150-220℃, preferably 160-200℃; and crystallization time of 50-130h, preferably 60-120h.

19. The synthesis process of mordenite according to claim 1, wherein, The drying temperature in step (4) is 80-150℃ and the drying time is 1-20h.

20. The synthesis process of mordenite according to claim 1, wherein, The roasting in step (4) is carried out at 400-600℃ for 1-10 hours; the roasting needs to be carried out in the presence of an oxygen-containing atmosphere.

21. A type of mordenite obtained by the synthesis process described in any one of claims 1-20.

22. The mordenite according to claim 21, wherein, The crystal morphology of mordenite is irregular nanosheets, with the first dimension measuring 0.8–3 μm, the second dimension measuring 0.8–3 μm, and the third dimension measuring 30–100 nm; the sheet-like crystals are curved.

23. The mordenite according to claim 21, wherein, In the X-ray diffraction pattern of mordenite, the diffraction peak located near 25.68 is the diffraction peak with the highest intensity.

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