Microporous FAU type molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the technical field of molecular sieves, and discloses a microporous FAU type molecular sieve and a preparation method and application thereof, and the preparation method comprises the following steps: 1, adding an aluminum source into a sodium hydroxide solution, and uniformly mixing to obtain a solution 1; step 2, adding tetrahydrofuran into the solution 1, uniformly mixing, and adding a silicon source to obtain a gel mixture; and step 3, crystallizing, cooling, washing, drying and roasting the gel mixture obtained in the step 2 to obtain the microporous FAU type molecular sieve. The microporous FAU type molecular sieve obtained by the invention has higher porosity and pore volume, and can adsorb more volatile organic pollutants.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and in particular to a microporous FAU type molecular sieve and a preparation method and application thereof. Background Art

[0002] In recent years, various environmental problems have become increasingly serious and have attracted widespread attention. Among them, volatile organic pollutants have become a hot topic. Volatile organic pollutants, or VOCs, are volatile organic compounds with a melting point below room temperature and a boiling point between 50°C and 260°C. VOCs can cause problems such as photochemical smog and haze, and seriously affect human health and the growth of plants and animals, causing neurological and various diseases. Therefore, the control of VOCs is imminent. At present, the commonly used treatment methods include adsorption, absorption, catalysis, and biological methods. Among them, the adsorption method for treating VOCs is simple to operate, low in cost, and has a good effect on the treatment of low-concentration VOCs, becoming one of the main treatment methods. The key to the adsorption method lies in the selection of adsorption materials. Activated carbon (AC) is the most commonly used adsorption material, but it is flammable and has certain safety issues. Compared with activated carbon, molecular sieves have high stability and good safety, making them better adsorption materials.

[0003] At present, some researchers have applied molecular sieves to adsorbents to adsorb volatile organic pollutants, but found that the adsorption effects of different types of molecular sieves are completely different, among which FAU molecular sieves have the best effect. FAU molecular sieves have a 12-membered ring structure. This type of molecular sieve has the characteristics of large rings, high pore volume, etc., and has good application potential for VOCs adsorption. The FAU molecular sieve with a microporous structure has a particularly outstanding adsorption effect on volatile organic pollutants, but the pore volume, porosity, specific surface area, etc. of the microporous FAU molecular sieve obtained in the prior art cannot be further improved, and structural collapse is prone to occur in the process of improving its pore structure from micropores to mesopores. Therefore, the microporous FAU molecular sieve is still limited in the adsorption of volatile organic pollutants. In addition, in the preparation process of molecular sieves, the selection of template agents is particularly important. The selection of template agents will affect the type of molecular sieve and the physical properties of the molecular sieve (pore volume, specific surface area, etc.). At present, organic template agents are expensive and toxic, and need to be calcined and removed at high temperatures, which will cause energy consumption. Therefore, it is of great significance to find non-toxic and low-cost template agents, reduce the synthesis cost of molecular sieves, and improve the solid phase yield of molecular sieves, which is of great significance for the further research and large-scale industrial application of synthetic microporous FAU molecular sieves. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a microporous FAU type molecular sieve and a preparation method and application thereof. The microporous FAU type molecular sieve obtained by the present invention has higher porosity and pore volume, and can adsorb more volatile organic pollutants.

[0005] The present invention provides a method for preparing a microporous FAU type molecular sieve, comprising the following steps: Step 1: adding an aluminum source to a sodium hydroxide solution and mixing well to obtain a solution 1; Step 2: Add tetrahydrofuran to solution 1, mix well, and add a silicon source to obtain a gel mixture; Step 3: Crystallize the gel mixture obtained in step 2, cool, wash, dry and calcine to obtain a microporous FAU type molecular sieve.

[0006] Furthermore, the preparation method of the sodium hydroxide solution includes: placing sodium hydroxide in deionized water.

[0007] Furthermore, the aluminum source includes one or more of sodium aluminate, pseudo-boehmite and alumina.

[0008] Furthermore, the silicon source includes one or more of white carbon black, silica sol, and sodium silicate.

[0009] Furthermore, in the gel mixture, the molar ratio of aluminum oxide: sodium oxide: silicon dioxide: tetrahydrofuran: water is 1:4-6:10:1.4-3.5:210.

[0010] In the present invention, sodium hydroxide, aluminum source, tetrahydrofuran, silicon source and water in the raw materials are used to obtain a gel mixture, and the added amounts of sodium hydroxide, aluminum source, tetrahydrofuran, silicon source and water are based on the molar ratio of aluminum oxide, sodium oxide, silicon dioxide, tetrahydrofuran and water formed in the gel mixture.

[0011] Furthermore, in the gel mixture, the molar ratio of aluminum oxide: sodium oxide: silicon dioxide: tetrahydrofuran: water is 1:4:10:2.8:210.

[0012] Furthermore, in step 1, the mixing needs to be performed at room temperature.

[0013] Furthermore, in step 2, the mixing needs to be performed at room temperature. As an example, the mixing is performed at room temperature for 10 min to 60 min.

[0014] Furthermore, in the step 2, after adding the silicon source, stirring is performed at room temperature to mix evenly.

[0015] Furthermore, the crystallization temperature is 80° C.-110° C., and the crystallization time is 10 h-60 h.

[0016] Furthermore, the crystallization temperature is 100° C.-110° C., and the crystallization time is 24 h-48 h.

[0017] Furthermore, in step 3, the mixture is cooled to room temperature, which is 20°C-25°C.

[0018] Furthermore, the specific method of washing includes washing with deionized water at least 3 times.

[0019] Furthermore, the drying temperature is 80°C-150°C.

[0020] Furthermore, the specific method of calcination includes: calcining at 550° C. for 5 h to 6 h in an air atmosphere.

[0021] The present invention also provides a microporous FAU type molecular sieve obtained by the preparation method.

[0022] Furthermore, the specific surface area of ​​the microporous FAU type molecular sieve is greater than 650m 2 / g, micropore volume not less than 0.35cm 3 / g.

[0023] The present invention also provides the use of the microporous FAU type molecular sieve in adsorbing volatile organic pollutants.

[0024] The embodiments of the present invention have the following technical effects: 1. The low-priced tetrahydrofuran is used as a template agent, which greatly reduces the synthesis cost; in addition, the use of tetrahydrofuran as a template agent has a good effect in reducing the synthesis cost and improving the crystallinity during the synthesis process. Since the synthesized microporous FAU type molecular sieve of the present invention has a high solid phase yield, good crystallinity, and strong adsorption performance, it is of great significance for the further research and application of the synthetic FAU type molecular sieve.

[0025] 2. In the present invention, the sodium ions in the hydrated sodium ions in the gel mixture are used to balance the negative charge in the molecular sieve structure framework, thereby improving the stability of the molecular sieve framework. Tetrahydrofuran and water form a coating layer on the surface of the sodium ions to form hydrated sodium ions; in the process of molecular sieve formation, silicon, aluminum and oxygen begin to grow the molecular sieve framework structure with hydrated sodium ions as a template, and in the roasting process, tetrahydrofuran and water volatilize to form a microporous structure in the molecular sieve. Among them, tetrahydrofuran can not only promote tetrahydrofuran and water to be coated on the surface of the sodium ions, thereby obtaining more hydrated sodium ions, which is conducive to more hydrated sodium ions in the molecular sieve framework structure, thereby facilitating the formation of more microporous structures during the roasting process; and the -O- group in tetrahydrofuran will form relatively strong hydrogen bonds with silicon, aluminum and oxygen, thereby promoting silicon, aluminum and oxygen to form a stable connection structure with the sodium ions in the hydrated sodium ions during the growth process with hydrated sodium ions as a template, preventing the collapse of the molecular sieve structure during the roasting process, so that the microporous structure is converted into a mesoporous structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 1 is the XRD diagram of the embodiment of the present invention and the comparative example.

[0028] Figure 2 It is the change of the crystallinity of the molecular sieve with the crystallization time in the present invention.

[0029] Figure 3 It is the XRD diagram of Comparative Example 3 in the present invention.

[0030] Figure 4 It is the XRD diagram of Example 4 in the present invention.

[0031] Figure 5 It is a graph of N2 adsorption-desorption isotherm results tested in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0033] In a first aspect, some embodiments of the present invention provide a method for preparing a microporous FAU type molecular sieve, comprising the following steps: Step 1: adding an aluminum source to a sodium hydroxide solution and mixing well to obtain a solution 1; Step 2: Add tetrahydrofuran to solution 1, mix well, and add a silicon source to obtain a gel mixture; Step 3: Crystallize the gel mixture obtained in step 2, cool, wash, dry and calcine to obtain a microporous FAU type molecular sieve.

[0034] In the present invention, more hydrated sodium ions are formed by tetrahydrofuran (THF), water and sodium ion, and hydrated sodium ion can be used as a template for molecular sieve growth. In the molecular sieve crystallization process, silicon, aluminum and oxygen are used as templates to start growing molecular sieve framework structure. After the hydrated sodium ions in the molecular sieve framework increase, tetrahydrofuran (THF) also increases in the molecular sieve structure. In addition, the-O-group in tetrahydrofuran (THF) can form a relatively strong hydrogen bond with silicon, aluminum and oxygen, thereby promoting silicon, aluminum and oxygen to form a stable connection structure with the sodium ions in the hydrated sodium ions during the growth process. Therefore, when the molecular sieve is in the roasting process, tetrahydrofuran and water on the surface of the hydrated sodium ions are volatilized, and finally a microporous structure is formed in the FAU molecular sieve structure.

[0035] In some embodiments, the method for preparing the sodium hydroxide solution includes: placing sodium hydroxide in deionized water.

[0036] In some embodiments, the aluminum source includes one or more of sodium aluminate, pseudo-boehmite and alumina.

[0037] In some embodiments, the silicon source includes one or more of white carbon black, silica sol, and sodium silicate.

[0038] In some embodiments, in the gel mixture, the molar ratio of aluminum oxide: sodium oxide: silicon dioxide: tetrahydrofuran: water is 1:4-6:10:1.4-3.5:210.

[0039] In the present invention, sodium ions form hydrated sodium ions. On the one hand, it is necessary to balance the negative charge in the formation of the molecular sieve, so as to ensure the stability of the molecular sieve structure. On the other hand, tetrahydrofuran and water coated on the surface of the hydrated sodium ions are related to the microporous structure formed by the molecular sieve, that is, the content of sodium ions will affect the hydrated sodium ions, and further affect the formation of the microporous structure.

[0040] In the present invention, the amount of tetrahydrofuran and water added in the gel mixture has a direct relationship with the microporous structure in the FAU molecular sieve structure. When the tetrahydrofuran and water content is high, although more hydrated sodium ions can be formed, it may also cause the molecular sieve structure to be unstable and the collapse of the microporous structure occurs; when the tetrahydrofuran and water content is low, less hydrated sodium ions may be formed, resulting in the inability to improve the porosity of the molecular sieve. Therefore, in the present invention, in the gel mixture, the molar ratio of tetrahydrofuran: water is 1.4-3.5:210.

[0041] In the present invention, the water content in the gel mixture refers to the sum of the water in the solution and the crystal water in the raw materials.

[0042] In some embodiments, in the gel mixture, the molar ratio of aluminum oxide: sodium oxide: silicon dioxide: tetrahydrofuran: water is 1:4:10:2.8:210.

[0043] In the present invention, the appropriate sodium ion content, tetrahydrofuran and water content can not only improve the stability of the molecular sieve structure, but also further improve the microporous structure in the molecular sieve.

[0044] In some embodiments, in step 1, the mixing needs to be performed at room temperature.

[0045] In some embodiments, in step 2, the mixing needs to be performed at room temperature. As an example, the mixing is performed at room temperature for 10 min to 60 min.

[0046] In some embodiments, in step 2, the silicon source is added and then stirred at room temperature to mix evenly.

[0047] In some embodiments, the crystallization temperature is 80° C.-110° C., and the crystallization time is 10 h-60 h.

[0048] Under the conditions of the crystallization temperature and time of the present invention, the molecular sieve can be promoted to grow into the FAU type. When the crystallization temperature is not appropriate, the FAU type crystal form cannot be formed. When the crystallization time is too short, the morphology and crystallinity of the molecular sieve will be poor; and when the crystallization time is greater than 60h, the crystal form of the molecular sieve will change and the FAU molecular sieve cannot be formed.

[0049] In some embodiments, the crystallization temperature is 100° C.-110° C., and the crystallization time is 24 h-48 h.

[0050] In the present invention, further controlling the crystallization time and temperature can ensure that the molecular sieve can form a FAU crystal form and improve the crystallinity of the molecular sieve.

[0051] In some embodiments, in step 3, cooling to room temperature is performed, and the room temperature is 20°C-25°C.

[0052] In some embodiments, the specific method of washing includes washing with deionized water at least 3 times.

[0053] In some embodiments, the drying temperature is 80°C-150°C.

[0054] In some embodiments, the specific method of calcining includes: calcining at 550° C. for 5 h to 6 h in an air atmosphere.

[0055] In the present invention, the calcination temperature and time can promote the volatilization of tetrahydrofuran and water in the molecular sieve to form a microporous structure. In a second aspect, some embodiments of the present invention also provide a microporous FAU type molecular sieve obtained by the preparation method.

[0056] In a third aspect, some embodiments of the present invention also provide the use of the microporous FAU type molecular sieve in the adsorption of volatile organic pollutants.

[0057] The following is described in conjunction with specific embodiments and comparative examples: Embodiment 1: Step 1: Weigh 2.29 g of sodium hydroxide and dissolve it in deionized water. Then add sodium aluminate as an aluminum source into the sodium hydroxide solution and stir thoroughly until it is completely dissolved.

[0058] Step 2: Weigh 2.02g of tetrahydrofuran and add it to the solution in step 1, and stir it at room temperature for 30 minutes. Then, take silica sol (SiO2 content 40%) as the silicon source, weigh 15.00g of silica sol and add it to the above mixed solution, and stir it at room temperature for 1 hour to form a uniform gel mixture. The final gel mixture molar ratio is Al2O3:Na2O:SiO2:tetrahydrofuran:H2O=1:4:10:2.8:210.

[0059] Step 3: Transfer the uniform gel mixture obtained in step 2 to a stainless steel hydrothermal reactor with a polytetrafluoroethylene lining and crystallize at 105°C for 24 hours; cool naturally to room temperature, recover the solid phase product by filtration, wash it with deionized water for many times, dry it, and finally calcine it at 550°C in air to obtain a FAU type molecular sieve.

[0060] Example 2: A method for preparing FAU type molecular sieve using tetrahydrofuran as a template. The basic steps of the preparation are the same as those of Example 1, except that the crystallization conditions in step 3 are changed from crystallization at 105°C for 24h to crystallization at 105°C for 10h, and finally a FAU type molecular sieve is obtained.

[0061] Example 3: A method for preparing FAU type molecular sieve using tetrahydrofuran as a template. The basic steps of the preparation are the same as those of Example 1, except that the crystallization conditions in step 3 are changed from crystallization at 105°C for 24 hours to crystallization at 105°C for 48 hours. Finally, a FAU type molecular sieve is synthesized with high crystallinity.

[0062] Example 4: A method for preparing FAU type molecular sieve using tetrahydrofuran as a template. The basic preparation steps are the same as those in Example 1, except that the molar ratio of the gel mixture is Al2O3:Na2O:SiO2:tetrahydrofuran:H2O=1:6:10:2.8:210. Finally, FAU type molecular sieve is synthesized. Increasing the Na2O content is beneficial to the crystallization of FAU type molecular sieve.

[0063] Example 5: A method for preparing FAU type molecular sieve using tetrahydrofuran as a template. The basic preparation steps are the same as those in Example 1, except that the molar ratio of the gel mixture is Al2O3:Na2O:SiO2:tetrahydrofuran:H2O=1:4:10:1.4:210, and finally a FAU type molecular sieve is synthesized.

[0064] Example 6: A method for preparing FAU type molecular sieve using tetrahydrofuran as a template. The basic preparation steps are the same as those in Example 1, except that the molar ratio of the gel mixture is Al2O3:Na2O:SiO2:tetrahydrofuran:H2O=1:4:10:3.5:210, and finally a FAU type molecular sieve is synthesized.

[0065] Comparative Example 1: A method for synthesizing a FAU type molecular sieve using tetrahydrofuran as a template. The basic steps of the preparation are the same as those of Example 1, except that the crystallization conditions in step 3 are changed from crystallization at 105°C for 24h to crystallization at 120°C for 60h. Finally, a FAU type molecular sieve is synthesized, but the synthesized FAU type molecular sieve is impure and contains impurities, such as Figure 1 XRD spectrum shown.

[0066] Comparative Example 2: A method for preparing FAU molecular sieves using tetrahydrofuran as a template, wherein the basic steps of the preparation are the same as those of Example 1, except that tetrahydrofuran is not added in this step.

[0067] Comparative Example 3: A method for preparing FAU type molecular sieve using tetrahydrofuran as a template. The basic preparation steps are the same as those in Example 1, except that the molar ratio of the gel mixture is Al2O3:Na2O:SiO2:tetrahydrofuran:H2O=1:3:10:2.8:210. When the Na2O content is low, no molecular sieve structure is formed.

[0068] Comparative Example 4: A method for preparing FAU type molecular sieve using tetrahydrofuran as a template. The basic preparation steps are the same as those in Example 1, except that the molar ratio of the gel mixture is Al2O3:Na2O:SiO2:tetrahydrofuran:H2O=1:1:10:1:175, and a FAU type molecular sieve is synthesized.

[0069] The molecular sieves in the embodiments and comparative examples were tested: (1) Test methods for specific surface area and micropore volume: N2 adsorption-desorption isotherm is mainly used to test the adsorption isotherm, specific surface area, pore volume and pore size distribution of samples. Before testing, the samples need to be degassed at 300℃ for 5h. The specific surface area and micropore volume are calculated by Brunauer-Emmett-Teller (BET) and t-plot method, respectively.

[0070] (2) Test method for acetone adsorption: 0.10g sample (20-40 mesh) is placed in the quartz tube of the reactor, a certain amount of nitrogen is introduced, the temperature is raised to 200°C, and the sample is pretreated for 2 hours by heating and purging to remove impurities and adsorbed water in the sample. After the pretreatment, it is cooled to room temperature and 1000ppm of VOCs gas is introduced for adsorption test. The gas concentration is detected by a gas chromatograph with an FID detector. When the outlet concentration is consistent with the inlet concentration, it indicates that the adsorption is completed.

[0071] Results and analysis: Table 1 Pore structure parameters of microporous molecular sieves of Examples and Comparative Examples

[0072] The method of the present invention successfully obtains a microporous FAU molecular sieve, which ensures the microporous structure (such as Figure 5As shown in the figure, the specific surface area and micropore volume of the microporous FAU molecular sieve are further improved, which are significantly higher than those of the comparative example and the prior art NaY molecular sieve (see Ding RD, Zu Y, et al., Journal of Fuel Chemistry and Technology, 46(4):451-458), ZEOflair®100 molecular sieve (see Blommaerts N, Dingenen F, et al., Separation and Purification Technology, 207(22):284-290), Y (FAZ-Y3) molecular sieve (see Ren XY, Liu, et al., Journal of Fuel Chemistry and Technology, 2018, 46(4):451-458), ZEOflair®100 molecular sieve (see Blommaerts N, Dingenen F, et al., Separation and Purification Technology, 2018, 207(22):284-290), and Y (FAZ-Y3) molecular sieve (see Ren XY, Liu, et al., Journal of Fuel Chemistry and Technology, 2018, 46(4):451-458). SJ et al., Microporous and Mesoporous Materials, Vol. 295, No. 15 (2020) p. 109940 (Ren XY, Liu SJ, et al., Microporous and Mesoporous Materials, 2020, 295(15): 109940.)), MFI molecular sieves (see Cosseron AF, Daou TJ et al., Microporous and Mesoporous Materials, Vol. 173 (2013) pp. 147-154 (Cosseron AF, Daou TJ, et al., Microporous and Mesoporous Materials, 2013, 173: 147-154)), so that the molecular sieve has a better adsorption effect on the adsorption of volatile organic compounds, as shown in Table 1.

[0073] In the preparation method of the present invention, at different crystallization temperatures, the crystal form of the generated molecular sieve may change, resulting in the generated molecular sieve being not the FAU type of the present invention. Therefore, the crystallization temperature is further selected to be 80°C-110°C. The crystallization time is related to the crystallinity of the molecular sieve. When the crystallization time is too short, the crystallinity of the molecular sieve will be poor. When the crystallization time is too long, not only will the crystal form of the molecular sieve change, but the FAU molecular sieve cannot be formed, and the crystallinity of the molecular sieve cannot be improved, resulting in a waste of energy (such as Figure 2 As shown in Figure 2, therefore, in the present invention, the crystallization time is 10h-60h. Figure 1 It was found that, further preferably, the crystallization time is 24h-48h.

[0074] In the present invention, sodium ions form hydrated sodium ions. On the one hand, it is necessary to balance the negative charge in the formation of the molecular sieve, so as to ensure the stability of the molecular sieve structure. On the other hand, the tetrahydrofuran and water coated on the surface of the hydrated sodium ions are related to the microporous structure formed by the molecular sieve. Figure 3 and Figure 4 As shown), it is found that in Comparative Example 3, due to the low sodium ion content, the FAU molecular sieve cannot be formed in the end. In Comparative Example 3, it may be because the formed hydrated sodium ion content is low, and the FAU crystal cannot be formed. In addition, when the hydrated sodium ions are low, the negative charge cannot be balanced, the stability of the molecular sieve structure decreases, and the adsorption capacity of the molecular sieve finally formed is significantly reduced. Therefore, in the present invention, in the gel mixture, the molar ratio of aluminum oxide: sodium oxide: silicon dioxide: tetrahydrofuran: water is 1:4-6:10:1.4-3.5:210.

[0075] On this basis, tetrahydrofuran and water form a coating layer on the surface of sodium ions to form hydrated sodium ions; during the calcination process, tetrahydrofuran and water volatilize to form a microporous structure in the molecular sieve. Among them, tetrahydrofuran can not only promote tetrahydrofuran and water to coat the surface of sodium ions, thereby obtaining more hydrated sodium ions, which is conducive to more hydrated sodium ions in the molecular sieve framework structure, forming more microporous structures; but also the -O- group in tetrahydrofuran will form relatively strong hydrogen bonds with silicon, aluminum and oxygen, thereby promoting silicon, aluminum and oxygen to form a stable connection structure with sodium ions in the hydrated sodium ions during the growth process with hydrated sodium ions as templates, preventing the collapse of the molecular sieve structure, so that the microporous structure is converted into a mesoporous structure.

[0076] By comparing Example 1, Example 5-Example 6 with Comparative Example 4, it is found that the molecular sieve obtained in Example 1 has a better specific surface area and micropore volume, and therefore has a better adsorption effect, while the adsorption capacity of Comparative Example 4 is significantly reduced. It is speculated that the change in the ratio between tetrahydrofuran and water will cause the structure of the final molecular sieve to change. For example, when the content of tetrahydrofuran and water is high, although more hydrated sodium ions can be formed, it may also cause the molecular sieve structure to be unstable and the micropore structure to collapse; when the content of tetrahydrofuran and water is low, as shown in Comparative Example 4, less hydrated sodium ions may be formed, resulting in the inability to improve the porosity of the molecular sieve and a decrease in the adsorption of acetone.

[0077] On this basis, the addition amount relationship between tetrahydrofuran and water is further optimized. Tetrahydrofuran can promote tetrahydrofuran and water to be coated on the surface of sodium ions. During the roasting process, tetrahydrofuran and water volatilize to form a microporous structure in the molecular sieve. It can be seen that the addition amount relationship between tetrahydrofuran and water can further improve the microporous structure. In Table 1, as shown in Example 1, Example 5-Example 6 and Comparative Example 2, it is found that by changing the relationship between tetrahydrofuran and water content, the specific surface area and micropore volume of the molecular sieve can indeed be further improved. Therefore, it is further preferred that the molar ratio of tetrahydrofuran: water is 2.8:210.

[0078] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0079] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a microporous FAU type molecular sieve, characterized in that: The steps include: Step 1: adding an aluminum source to a sodium hydroxide solution and mixing well to obtain a solution 1; Step 2: Add tetrahydrofuran to solution 1, mix well, and add a silicon source to obtain a gel mixture; Step 3: Crystallize the gel mixture obtained in step 2, cool, wash, dry and calcine to obtain a microporous FAU type molecular sieve.

2. The preparation method according to claim 1, characterized in that: The preparation method of the sodium hydroxide solution comprises: placing sodium hydroxide in deionized water.

3. The preparation method according to claim 1, characterized in that: The aluminum source includes one or more of sodium metaaluminate, pseudo-boehmite and alumina; The silicon source includes one or more of white carbon black, silica sol and sodium silicate.

4. The preparation method according to claim 1, characterized in that: In the gel mixture, the molar ratio of aluminum oxide: sodium oxide: silicon dioxide: tetrahydrofuran: water is 1:4-6:10:1.4-3.5:

210.

5. The preparation method according to claim 1, characterized in that: In the gel mixture, the molar ratio of aluminum oxide: sodium oxide: silicon dioxide: tetrahydrofuran: water is 1:4:10:2.8:

210.

6. The preparation method according to claim 1, characterized in that: The crystallization temperature is 80° C.-110° C., and the crystallization time is 10 h-60 h.

7. The preparation method according to claim 1, characterized in that: The crystallization temperature is 100° C.-110° C., and the crystallization time is 24 h-48 h.

8. The preparation method according to claim 1, characterized in that: The specific method of calcination includes: calcining at 550° C. for 5 h to 6 h in an air atmosphere.

9. The microporous FAU type molecular sieve obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the microporous FAU type molecular sieve according to claim 9 in adsorbing volatile organic pollutants.

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