Lsx molecular sieve, method for regulating size of lsx molecular sieve crystal clusters, and use thereof

Abstract

The present application relates to the field of molecular sieve preparation, and discloses a method for regulating the size of LSX molecular sieve clusters, which comprises the following steps: 1) sequentially performing first contact and first aging on a first silicon source, an aluminum source, a sodium source and a first water to obtain a cluster size regulator; 2) performing second contact on a second silicon source, an aluminum source, a sodium source, a potassium source and a second water to obtain a gel; and 3) performing third contact on the cluster size regulator and the gel, and sequentially performing second aging and crystallization treatment on the third contact product to obtain LSX molecular sieve. The second silicon source is water glass and / or sodium silicate, and the target average particle size of the LSX molecular sieve cluster and the amount of the cluster size regulator satisfy the formula: y = 1.6517 x (100 x) ‑0.274 . According to the method, LSX molecular sieves with various cluster sizes can be prepared according to requirements, and the cluster size of the prepared LSX molecular sieve is very uniform.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of molecular sieve preparation, in particular to a method for regulating the size of LSX molecular sieve clusters and application thereof, and LSX molecular sieve prepared by the method. BACKGROUND

[0002] The key to the air separation oxygen production technology by pressure swing adsorption method is to use an adsorbent with large nitrogen adsorption capacity and high nitrogen-oxygen separation coefficient. Since the low-silicon X-type molecular sieve (silicon-aluminum ratio of 2.0-2.1, referred to as LSX molecular sieve) has a low silicon-aluminum ratio, more cation sites, and a large pore size, the currently ideal adsorbent is usually obtained by modifying the LSX molecular sieve with Li or other bimetallic ions.

[0003] In addition, the LSX molecular sieve has better effect than the 4A molecular sieve when used as a detergent aid, and has a larger adjustment range of product performance when used as a catalyst or catalyst carrier than the conventional X-type molecular sieve.

[0004] During the formation of the X-type molecular sieve, the zeolite grains of the octagonal shape often gather together to form multi-ribbed spherical clusters, and these clusters are subsequently stacked into product particles under the action of the binder. In the application of the molecular sieve, its activity is usually closely related to physical indicators such as the cluster size and the grain size, and reducing the zeolite cluster or grain can increase the specific surface area, shorten the pore channel, thereby increasing the effective active site and improving the diffusion rate. However, the cluster or grain of the molecular sieve should not be too small, otherwise the effective cage structure for adsorption or catalysis will be reduced, which will adversely affect the material performance.

[0005] One of the important principles for designing adsorbents or catalysts and other products is to adjust the cluster size of the zeolite to make the intrinsic activity and mass transfer rate of the zeolite reach the best effect under the specified working conditions.

[0006] However, there is no feasible method for regulating the cluster size of the LSX molecular sieve at present, and the cluster size uniformity of the LSX molecular sieve prepared at present is poor, which leads to poor adsorption performance.

[0007] Based on the current situation, it is an important task to be solved in the field to develop a simple and efficient method for preparing LSX molecular sieve capable of controlling the cluster size in a large range. SUMMARY

[0008] The present application aims to overcome the problems of the prior art, such as the difficulty in adjusting the size of LSX molecular sieve clusters, and the uneven size of the prepared LSX molecular sieve clusters, and provides a method for regulating the size of LSX molecular sieve clusters, which can regulate the target average particle size of the prepared LSX molecular sieve clusters, so that LSX molecular sieves of various cluster sizes can be prepared according to requirements, and the LSX molecular sieve clusters prepared by the method are very uniform in size.

[0009] To achieve the above-mentioned purpose, the present application provides a method for regulating the size of LSX molecular sieve clusters, which comprises the following steps:

[0010] 1) sequentially performing first contact and first aging on a first silicon source, an aluminum source, a sodium source and a first water to obtain a cluster size regulator;

[0011] 2) performing second contact on a second silicon source, an aluminum source, a sodium source, a potassium source and a second water to obtain a gel;

[0012] 3) performing third contact on the cluster size regulator and the gel, and sequentially performing second aging and crystallization treatment on the third contact product to obtain LSX molecular sieve,

[0013] wherein the second silicon source is water glass and / or sodium silicate,

[0014] the target average particle size of the LSX molecular sieve clusters and the amount of the cluster size regulator in step 3) satisfy the following relationship:

[0015] y = 1.6517 x (100x) -0.274 ,

[0016] wherein y is the target average particle size of the LSX molecular sieve clusters, in units of μm, and the value range is 1-5.8; x is the weight ratio of the cluster size regulator to the gel in step 3).

[0017] Preferably, in step 1), the first silicon source, the aluminum source, the sodium source and the first water are subjected to the first contact in a molar ratio of SiO2:Al2O3:Na2O:water of 5.5-10.5:1:10-20:200-300.

[0018] Preferably, in step 1), the first silicon source is mixed with a part of the first water to obtain a mixture A1; the aluminum source, the sodium source and the remaining part of the first water are mixed to obtain a mixture A2, and the mixture A1 and the mixture A2 are subjected to the first contact.

[0019] Preferably, in step 1), the part of the first water accounts for 10-15 mole% of the total amount of water for the first contacting.

[0020] Preferably, the conditions of the first contacting include: temperature of 10-40℃, time of 1-2h.

[0021] Preferably, the conditions of the first aging include: temperature of 15-55℃, time of 5-40h.

[0022] Preferably, in step 2), the second silicon source, the aluminum source, the sodium source, the potassium source and the second water are subjected to the second contacting in a molar ratio of SiO2:Al2O3:(Na2O+K2O):water of 1.8-3:1:3-12:90-250, and wherein the molar ratio of Na2O:(Na2O+K2O) is 0.6-0.9:1.

[0023] Preferably, in step 2), the second silicon source is mixed with a part of the second water to obtain a mixture B1, the aluminum source, the sodium source, the potassium source and the rest of the second water are mixed to obtain a mixture B2, and the mixture B1 and the mixture B2 are subjected to the second contacting.

[0024] Preferably, in step 2), the part of the second water accounts for 10-35 mole% of the total amount of water for the second contacting.

[0025] Preferably, the conditions of the second contacting include: temperature of 10-40℃, time of 0.1-2h.

[0026] Preferably, the first silicon source is one or more of water glass, silica sol, sodium silicate, potassium silicate and amorphous silicon dioxide, and more preferably water glass and sodium silicate.

[0027] Preferably, the second silicon source is water glass.

[0028] Preferably, the water glass contains 4.25-9.25wt% of Na2O, 15.55-23.55wt% of SiO2 and 67.20-80.20wt% of water.

[0029] Preferably, the aluminum source is one or more of sodium aluminate, aluminum oxide and aluminum hydroxide, and preferably aluminum hydroxide.

[0030] Preferably, the sodium source is one or more of sodium hydroxide, sodium chloride and sodium sulfate.

[0031] Preferably, the potassium source is one or more of potassium hydroxide, potassium chloride and potassium sulfate.

[0032] Preferably, in step 3), the conditions of the third contacting include: temperature of 10-40℃, time of 0.1-2h.

[0033] Preferably, in step 3), the conditions of the second aging include: temperature of 30-90℃, time of 1-35h, more preferably, the conditions of the second aging can include: temperature of 60-80℃, time of 3-8h.

[0034] Preferably, in step 3), the conditions of the crystallization treatment include: temperature of 80-120℃, time of 0.5-10h, more preferably, the conditions of the crystallization treatment include: temperature of 90-110℃, time of 1-4h.

[0035] Preferably, the method further comprises: a step of subjecting the product of the crystallization treatment in step 3) to solid-liquid separation, washing and drying.

[0036] Preferably, the washing is such that the pH of the washing liquid is 7-8.

[0037] Preferably, the conditions of the drying include: temperature of 50-150℃, time of 8-24h.

[0038] The second aspect of the present application provides a LSX molecular sieve prepared by the method of the first aspect of the present application.

[0039] Preferably, the silicon-aluminum ratio of the LSX molecular sieve is 2.0-2.1.

[0040] The third aspect of the present application provides application of the method of the first aspect of the present application for regulating the size of LSX molecular sieve crystal clusters in the preparation of LSX molecular sieve.

[0041] Through the above technical solution, the addition amount of the corresponding crystal cluster size regulator can be calculated according to the target average particle size of the LSX molecular sieve crystal cluster, so that the size of the LSX molecular sieve crystal cluster can be flexibly regulated, and thus the LSX molecular sieve with the required crystal cluster size can be prepared as needed.

[0042] In addition, through the method of the present application, the LSX molecular sieve prepared has high uniformity of crystal cluster size, low content of impurities, high crystallinity, and the silicon-aluminum ratio can reach 2.0-2.1, and has excellent adsorption activity. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a scanning electron microscope image of the LSX molecular sieve prepared in Example 1;

[0044] Figure 2 is a scanning electron microscope image of the LSX molecular sieve prepared in Example 2;

[0045] Figure 3 is a scanning electron microscope image of LSX molecular sieve prepared in Example 3;

[0046] Figure 4 is a scanning electron microscope image of LSX molecular sieve prepared in Example 5;

[0047] Figure 5 is a scanning electron microscope image of LSX molecular sieve prepared in Example 6;

[0048] Figure 6 is a scanning electron microscope image of LSX molecular sieve prepared in Comparative Example 1;

[0049] Figure 7 is a scanning electron microscope image of LSX molecular sieve of Comparative Example 2. DETAILED DESCRIPTION

[0050] The endpoints of the ranges and any values claimed herein are not to be understood as being limited to the exact values recited as implicitly included within the range. The ranges include the endpoints.

[0051] In the present application, the silicon to aluminum ratio refers to the molar ratio of SiO2 and Al2O3.

[0052] In the present application, the LSX molecular sieve cluster refers to a polyhedral-like stack formed by a group of LSX molecular sieve grains gathered together.

[0053] In the present application, the particle size of the LSX molecular sieve cluster refers to the length of the longest axis of the LSX molecular sieve cluster.

[0054] In the present application, the average particle size of the LSX molecular sieve cluster is obtained by randomly selecting 30 LSX molecular sieve clusters in a scanning electron microscope (SEM) image and calculating the average of their particle sizes.

[0055] In the present application, the target average particle size of the LSX molecular sieve cluster refers to the average particle size of the LSX molecular sieve cluster to be prepared.

[0056] The first aspect of the present application provides a method for regulating the size of LSX molecular sieve cluster, which comprises the following steps:

[0057] 1) sequentially performing first contact and first aging on a first silicon source, an aluminum source, a sodium source and a first water to obtain a cluster size regulator;

[0058] 2) performing second contact on a second silicon source, an aluminum source, a sodium source, a potassium source and a second water to obtain a gel;

[0059] 3) contacting the crystal cluster size regulator with the gel, and sequentially performing second aging and crystallization treatment on the third contact product to obtain LSX molecular sieve,

[0060] wherein the second silicon source is water glass and / or sodium silicate,

[0061] the target average particle size of the LSX molecular sieve crystal cluster and the amount of the crystal cluster size regulator in step 3) satisfy the following relationship:

[0062] y = 1.6517 x (100x) -0.274 ,

[0063] wherein y is the target average particle size of the LSX molecular sieve crystal cluster, in units of μm, and the value range is 1-5.8; and x is the weight ratio of the crystal cluster size regulator to the gel in step 3).

[0064] In the present application, the value range of y is not particularly limited, and can be any value in the range of 1-5.8. For example, y can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 and 5.8, etc.

[0065] The inventors of the present application accidentally found during the research that by using a specific second silicon source to prepare a gel, and adding a crystal cluster size regulator prepared according to the method of the present application to the gel, the crystal cluster size of the prepared LSX molecular sieve can be controlled by adjusting the amount of the crystal cluster size regulator added, thus completing the present application.

[0066] Hereinafter, first the preparation method of the crystal cluster size regulator in step 1) of the present application is described in detail.

[0067] In the present application, the crystal cluster size regulator is prepared by sequentially performing first contact and first aging on the first silicon source, the aluminum source, the sodium source and the first water.

[0068] In the present application, the first silicon source, the aluminum source and the sodium source are not particularly limited, and can be conventional choices in the art.

[0069] The first silicon source can be one or more of water glass, silica sol, sodium silicate, potassium silicate and amorphous silicon dioxide, preferably water glass and sodium silicate, and more preferably water glass. In this way, the uniformity of the crystal clusters of the LSX molecular sieve prepared can be further improved.

[0070] The aluminum source can be one or more of sodium aluminate, aluminum oxide and aluminum hydroxide, and is preferably aluminum hydroxide.

[0071] The sodium source can be one or more of sodium hydroxide, sodium chloride and sodium sulfate, and is preferably sodium hydroxide.

[0072] In addition, in the present application, the first water is preferably deionized water in order to reduce interference.

[0073] In the present application, there is no particular limitation on the amounts of the first silicon source, the aluminum source, the sodium source and the first water added when the first contact is performed.

[0074] In the present application, preferably, the first silicon source, the aluminum source, the sodium source and the first water are brought into the first contact in a molar ratio of SiO2:Al2O3:Na2O:water of 5.5-10.5:1:10-20:200-300. In this way, the adsorption performance of the LSX molecular sieve prepared can be further improved.

[0075] According to the present application, there is no particular limitation on the order of feeding the first silicon source, the aluminum source, the sodium source and the first water when the first contact is performed. For example, the first silicon source, the aluminum source and the sodium source can be added to the first water respectively, or the aluminum source and the sodium source can be mixed with the first water, and then the first silicon source can be added to the mixture. Alternatively, the first silicon source can be mixed with a part of the first water to obtain a mixture A1, the aluminum source and the sodium source can be mixed with the remaining part of the first water to obtain a mixture A2, and then the mixture A1 and the mixture A2 can be brought into the first contact.

[0076] The inventors of the present application have found that, when the first contact is performed, the first silicon source can be first mixed with a part of the first water to obtain a mixture A1 containing the first silicon source, the aluminum source and the sodium source can be uniformly mixed with the remaining part of the first water to obtain a mixture A2, and then the mixture A1 can be added to the mixture A2, which is mixed thoroughly and brought into the first contact. In this way, the dispersion of the above-mentioned raw materials can be very uniform, and the generation of different products in an intermediate process due to the non-uniform mixing of the raw materials in the first contact can be avoided. Thus, the uniformity of the LSX molecular sieve prepared can be significantly improved.

[0077] In addition, when the first contact is carried out in the above manner, i.e. when the first silicon source is mixed with a part of the first water to obtain mixture A1, the aluminum source, the sodium source and the rest of the first water are mixed to obtain mixture A2, and the mixture A1 and the mixture A2 are subjected to the first contact, the part of the first water accounts for 10-15 mole % of the total amount of water subjected to the first contact.

[0078] In the present application, it should be understood by those skilled in the art that when other raw materials used in the first contact contain water or ions that can be converted into water (for example, when the first silicon source is water glass, it contains part of water; when the sodium source is sodium hydroxide, it contains hydroxyl ions that can be converted into water), the total amount of water subjected to the first contact includes not only the amount of the first water, but also the amount of water contained in other raw materials or the amount of water that can be converted from other raw materials.

[0079] In addition, the conditions of the first contact are not particularly limited, for example, the conditions of the first contact can include a temperature of 10-40℃ and a time of 1-2h. In addition, in order to facilitate the progress of the first contact, preferably, the first contact is carried out under stirring.

[0080] In addition, the conditions of the first aging are also not particularly limited, for example, the conditions of the first aging can include a temperature of 15-55℃ and a time of 5-40h; preferably, the conditions of the first aging include a temperature of 20-40℃ and a time of 15-25h.

[0081] According to a preferred embodiment of the present application, in the step 1), the first silicon source is sufficiently mixed with a part of the first water under stirring to obtain mixture A1; the aluminum source, the sodium source and the rest of the first water are mixed and stirred at 60-140℃ until all solids are dissolved to obtain mixture A2, then the mixture A1 is added dropwise into the mixture A2 under stirring, the stirring speed is increased after the appearance of gel, and the stirring is continued at 10-40℃ for 1-2h to carry out the first contact, then the stirring is stopped, and the first aging is carried out at 20-40℃, and the time of the first aging is 15-25h.

[0082] The crystal cluster size regulator thus obtained can further significantly improve the uniformity of the LSX molecular sieve crystal clusters when the LSX molecular sieve is prepared according to the method of the present application.

[0083] Hereinafter, the preparation method of the gel according to the first aspect of the present application will be described in detail.

[0084] In step 2), the second silicon source, the aluminum source, the sodium source, the potassium source and the second water are contacted to obtain a gel.

[0085] In the present application, the aluminum source, the sodium source and the potassium source in step 2) are not particularly limited and can be selected conventionally.

[0086] In addition, in step 2), the aluminum source and the sodium source can be consistent with the selection of the corresponding aluminum source and sodium source in step 1) described above, which will not be repeated here.

[0087] The potassium source can be various potassium sources conventionally used in the art, for example, can be one or more of potassium hydroxide, potassium chloride and potassium sulfate, and is preferably potassium hydroxide.

[0088] The inventors of the present application found in the research process that in step 2), the selection of the second silicon source is very critical, and the selection of the second silicon source plays a key role in the cluster size and uniformity of the LSX molecular sieve prepared by the specific method described in the present application.

[0089] In the present application, the second silicon source is water glass and / or sodium silicate, and more preferably water glass. By using water glass as the second silicon source, not only can the size of the LSX molecular sieve cluster be successfully adjusted by the method described in the present application, but also compared with sodium silicate, the LSX molecular sieve cluster prepared therefrom can further ensure that the cluster size is more uniform, the content of impurities is less, and the crystallinity is higher.

[0090] In addition, in the present application, the composition of the water glass is not particularly limited and a conventional commercially available water glass can be used.

[0091] Preferably, the water glass contains 4.25-9.25 wt% of Na2O, 15.55-23.55 wt% of SiO2 and 67.20-80.20 wt% of water. This can further ensure the uniformity of the LSX molecular sieve cluster prepared.

[0092] In addition, in step 2) of the present application, in order to reduce interference, the second water is preferably deionized water.

[0093] In the present application, when the second contact is performed, the addition amount of the second silicon source, the aluminum source, the sodium source and the second water is not particularly limited and can be the conventional amount used when preparing LSX molecular sieve gel in the art.

[0094] Preferably, in step 2), the second silicon source, the aluminum source, the sodium source, the potassium source and the second water are contacted in a molar ratio of SiO2:Al2O3:(Na2O+K2O):water of 1.8-3:1:3-12:90-250, and a molar ratio of Na2O:(Na2O+K2O) of 0.6-0.9:1, so that the adsorption performance of the prepared LSX molecular sieve can be further improved.

[0095] According to the present application, the order of adding the second silicon source, the aluminum source, the sodium source, the potassium source and the second water is not particularly limited when the second contact is performed. For example, the second silicon source, the aluminum source, the sodium source and the potassium source can be added into the second water respectively, or the aluminum source, the sodium source and the potassium source can be mixed with the second water, and then the second silicon source is added into the mixture, or the second silicon source is mixed with a part of the second water to obtain a mixture B1, and the aluminum source, the sodium source, the potassium source and the remaining part of the second water are mixed to obtain a mixture B2, and then the mixture B1 and the mixture B2 are contacted.

[0096] The inventors of the present application have found that, when the second contact is performed, the second silicon source is first mixed with a part of the second water to obtain a mixture B1 containing the second silicon source, and then the aluminum source, the sodium source, the potassium source and the remaining part of the second water are mixed to obtain a mixture B2, and then the mixture B1 is added into the mixture B2 and mixed thoroughly. In this way, the dispersion and mixing of the above-mentioned raw materials can be more uniform, and the generation of different products in some intermediate process due to the non-uniform mixing of the raw materials in the second contact can be avoided, so that the uniformity of the prepared LSX molecular sieve can be significantly improved.

[0097] In addition, when the second contact is performed in the above-mentioned way, i.e., the second silicon source is mixed with a part of the second water to obtain a mixture B1, the aluminum source, the sodium source, the potassium source and the remaining part of the second water are mixed to obtain a mixture B2, and then the mixture B1 and the mixture B2 are contacted, the part of the second water accounts for 10-35 mol% of the total amount of water used in the second contact, so that the uniformity of the LSX molecular sieve clusters prepared can be significantly improved.

[0098] In the present application, it is understood by those skilled in the art that when the other raw materials used in the second contacting contain water or ions that can be converted into water (for example, when the second silicon source is water glass, which contains part of water; when the sodium source is sodium hydroxide, which contains hydroxyl ions that can be converted into water), the total amount of water used in the second contacting includes not only the amount of the second water, but also the amount of water contained in the other raw materials or the amount of water that can be converted from the other raw materials.

[0099] In addition, in the present application, the conditions of the second contacting are not particularly limited, for example, the conditions of the second contacting can include a temperature of 10-40℃ and a time of 0.1-2h; preferably, the conditions of the second contacting include a temperature of 10-20℃ and a time of 0.2-0.5h.

[0100] According to a preferred embodiment of the present application, in the step 2), the second silicon source and part of the second water are mixed under stirring to obtain a mixture B1; the aluminum source, the sodium source, the potassium source and the remaining part of the second water are mixed and stirred at 60-140℃ until all the solids are dissolved to obtain a mixture B2, then the mixture B1 is quickly added to the mixture B2 under stirring (for example, the stirring speed is 200-400rpm), the stirring speed is increased (for example, the stirring speed is 350-600rpm) after the appearance of the gel, and the stirring is continued at 10-20℃ for 0.2-0.5h. In this way, the prepared gel can further improve the uniformity of the subsequently obtained LSX molecular sieve crystal clusters.

[0101] In addition, it is understood by those skilled in the art that in the method for regulating the size of LSX molecular sieve crystal clusters in the first aspect of the present application, the order of the step 1) and the step 2) is not particularly limited, that is, the crystal cluster size regulator can be prepared by the step 1) first, or the gel can be prepared by the step 2) first, as long as the crystal cluster size regulator and the gel can be obtained. That is, the "step 1)" and "step 2)" here do not limit the order of the corresponding operations.

[0102] Then, the step 3) is performed, that is, the crystal cluster size regulator is subjected to a third contacting with the gel, and the third contacting product is sequentially subjected to a second aging and a crystallization treatment.

[0103] In the step 3), when the third contacting is performed, preferably, the crystal cluster size regulator is added to the gel, and more preferably, the stirring is performed at the same time.

[0104] In addition, the conditions of the third contacting can include a temperature of 10-40℃ and a time of 0.5-2h.

[0105] In the present application, the third contact product is subjected to second aging and crystallization in sequence.

[0106] Here, the conditions for the second aging are not particularly limited, for example, the conditions for the second aging can include: temperature of 30-90℃, time of 1-35h; preferably, the conditions for the second aging include: temperature of 60-80℃, time of 3-8h.

[0107] After the aging treatment, the crystallization treatment is continued.

[0108] In the present application, the conditions for the crystallization treatment are also not particularly limited, for example, the conditions for the crystallization treatment can include: temperature of 80-120℃, time of 0.5-10h. Preferably, the conditions for the crystallization treatment include: temperature of 90-110℃, time of 1-4h.

[0109] In addition, the method of the present application can further include the step of subjecting the product after the crystallization treatment in step 3) to solid-liquid separation, washing and drying.

[0110] Here, the method for the solid-liquid separation, washing and drying is not particularly limited and can be performed by various methods in the art.

[0111] The solid-liquid separation can be performed by vacuum filtration, for example.

[0112] The washing can be performed by elution with excess deionized water, for example. Preferably, the washing is performed so that the pH of the washing liquid is 7-8.

[0113] The conditions for the drying can include: temperature of 50-150℃, time of 8-24h, for example.

[0114] According to the present application, the size of the LSX molecular sieve crystal cluster to be prepared can be controlled according to the needs by the above method.

[0115] Specifically, first, the target average particle size (unit: μm) of the LSX molecular sieve crystal cluster required, i.e. y, is determined according to the actual needs, and then the corresponding value of x is calculated according to y = 1.6517 x (100x) -0.274 , so as to obtain the weight ratio of the crystal cluster size adjusting agent to the gel in step 3).

[0116] In addition, since errors are inevitably caused in the calculation and operation process, when the ratio of the actual average particle size y1 of the LSX molecular sieve cluster prepared by using the regulation method to the target average particle size y of the LSX molecular sieve cluster is 1±0.1 (i.e. y1 / y=0.9-1.1), it is considered that the relationship formula of the present application is satisfied.

[0117] The second aspect of the present application provides the LSX molecular sieve prepared by the method of the first aspect of the present application.

[0118] According to the second aspect of the present application, the LSX molecular sieve has a cluster with uniform size, and the standard deviation of the particle size between the LSX molecular sieve clusters is less than 0.8.

[0119] The silicon-aluminum ratio of the LSX molecular sieve of the second aspect of the present application can be as low as 2.0-2.1.

[0120] The third aspect of the present application provides the application of the method for regulating the size of the LSX molecular sieve cluster of the first aspect of the present application in the preparation of the LSX molecular sieve.

[0121] The present application will be described in detail below through examples.

[0122] In the following examples and comparative examples, the scanning electron microscope image is measured by a scanning electron microscope of model Apreo 2C produced by the United States Thermo Fisher Scientific Company.

[0123] In the following examples and comparative examples, the silicon-aluminum ratio is measured by X-ray fluorescence spectroscopy analysis (XRF).

[0124] Unless otherwise specified, the raw materials and products used in the following examples, preparation examples and comparative examples are all conventional commercially available products, or can be prepared by conventional methods.

[0125] In the following examples and comparative examples, the specific composition of the water glass used is: Na2O 6.50 wt%, SiO2 20.57 wt%, H2O 72.93 wt%; the mass fraction of aluminum hydroxide is 98.74 wt%; and the mass fraction of potassium hydroxide is 93 wt%.

[0126] Preparation Example

[0127] The cluster size regulator used in the following examples and comparative examples is prepared according to the following method.

[0128] The water glass, aluminum hydroxide, sodium hydroxide and deionized water are fed in a molar ratio of SiO2:Al2O3:Na2O:water of 10:1:12:280, specifically:

[0129] 1) Mix the water glass with a part of the deionized water under stirring until complete mixing, obtaining a mixture Al, wherein the part of the deionized water represents 14.6 mole% of the total amount of water (sum of the deionized water and the water contained in the other raw materials);

[0130] 2) Mix the aluminum hydroxide, the sodium hydroxide and the remaining part of the deionized water, stirring at 80°C until complete dissolution of the solids, then cooling to 10°C, obtaining a mixture A2;

[0131] 3) Slowly add the mixture Al to the mixture A2 under stirring at 375 rpm, increasing the stirring speed to 475 rpm after the appearance of the gel, stirring at 10°C for 1 h for the first contact, stopping the stirring and subjecting the obtained slurry to a first aging at 35°C for 20 h, obtaining the crystalline cluster size modifier.

[0132] Example 1

[0133] The target average particle size of the LSX molecular sieve crystalline clusters to be prepared in this example is 3.75 μm, i.e. y is 3.75 μm, and the crystalline cluster size modifier should have a weight ratio x with respect to the gel calculated as 0.0005, i.e. 0.05%.

[0134] The water glass, the aluminum hydroxide, the sodium hydroxide, the potassium hydroxide and the deionized water are dosed in the molar ratio Si02:Al203:(Na20+K20):water equal to 2:1:7.5:127.5, and the molar ratio Na20 to Na20+K20 is 0.77:1, in particular,

[0135] 1) Mix the water glass with a part of the deionized water under stirring until complete mixing, obtaining a mixture Bl, wherein the part of the deionized water represents 19.4 mole% of the total amount of water (sum of the deionized water and the water contained in the other raw materials);

[0136] 2) Mix the aluminum hydroxide, the sodium hydroxide, the potassium hydroxide and the remaining part of the deionized water, stirring at 80°C until complete dissolution of the solids, then cooling to 10°C, obtaining a mixture B2;

[0137] 3) Quickly add the mixture Bl to the mixture B2, mixing under stirring at 375 rpm, increasing the stirring speed to 475 rpm after the appearance of the gel, stirring at 10°C for 15 min for the second contact, obtaining the gel A;

[0138] 4) Add a cluster size regulator accounting for 0.05% by weight of the gel A to the gel A, and carry out a third contact at 25°C for 0.5 h with stirring, followed by static aging at 70°C for 5 h; then raise the temperature to 100°C with stirring and allow it to crystallize for 2 h, then vacuum filter the crystallized product, wash it 5 times until the pH is 8, and then dry it in an oven at 80°C for 10 h to obtain LSX molecular sieve raw powder S1, with a silicon-to-aluminum ratio of 2.00.

[0139] The scanning electron microscope image of S1 is as follows: Figure 1 As shown, by Figure 1 It can be seen that the S1 crystal clusters are uniform in size, with no obvious heterogeneous crystal morphology, and have a high degree of crystallinity.

[0140] The average grain size of the S1 cluster is calculated to be 3.62 μm with a standard deviation of 0.4.

[0141] Example 2

[0142] The target average particle size of the LSX molecular sieve clusters to be prepared in this embodiment is 2.57 μm. According to the calculation, the weight ratio of the cluster size regulator to the gel should be 0.002, that is, 0.2%.

[0143] The procedure is carried out according to the method described in Example 1), except that...

[0144] In step 4), a cluster size modifier accounting for 0.2% by weight of gel A is added to gel A.

[0145] Finally, LSX molecular sieve raw powder S2 was obtained, with a silicon-to-aluminum ratio of 2.01.

[0146] The scanning electron microscope image of S2 is as follows: Figure 2 As shown, by Figure 2 It can be seen that the prepared LSX molecular sieve clusters are uniform in size, without obvious impurity crystal morphology, and have high crystallinity.

[0147] The average grain size of the S2 crystal cluster is calculated to be 2.48 μm, with a standard deviation of 0.4.

[0148] Example 3

[0149] The target average particle size of the LSX molecular sieve clusters to be prepared in this embodiment is 1.65 μm. According to calculation, the weight ratio of the cluster size regulator to the gel should be 0.01, i.e. 1%.

[0150] The procedure is carried out according to the method described in Example 1), except that...

[0151] In step 4), a cluster size modifier accounting for % by weight of gel A1 is added to gel A.

[0152] Finally, LSX molecular sieve crude powder S3 is obtained, and the Si / Al ratio of S3 is 2.00.

[0153] The scanning electron microscope image of S3 is shown in Figure 3 Figure 3 It can be seen that the prepared LSX molecular sieve clusters are uniform in size, and no obvious impurity crystal morphology appears, and the crystallinity is high.

[0154] The average particle size of S3 clusters is calculated to be 1.57 μm, and the standard deviation is 0.3.

[0155] Example 4

[0156] In this example, the target average particle size of the prepared LSX molecular sieve clusters is 1 μm, and the weight ratio of the cluster size adjusting agent to the gel is calculated to be 0.06, i.e. 6%.

[0157] The method described in Example 1 is followed, except that,

[0158] In step 4), 6% of the cluster size adjusting agent by weight of the gel A is added to the gel A.

[0159] Finally, LSX molecular sieve crude powder S4 is obtained, and the Si / Al ratio of S4 is 2.01.

[0160] It can be seen from the scanning electron microscope image of S4 that the prepared LSX molecular sieve clusters are uniform in size, and no obvious impurity crystal morphology appears, and the crystallinity is high.

[0161] The average particle size of S4 clusters is calculated to be 0.99 μm, and the standard deviation is 0.5.

[0162] Example 5

[0163] In this example, the target average particle size of the prepared LSX molecular sieve clusters is 2.57 μm, and the weight ratio of the cluster size adjusting agent to the gel is calculated to be 0.002, i.e. 0.2%.

[0164] The method of Example 1 is followed, except that,

[0165] In step 1), the water glass is replaced with an equimolar amount of sodium silicate nonahydrate calculated as SiO2, and 19.4 mole% of the total amount of water is replaced with deionized water;

[0166] In step 2), the amounts of sodium hydroxide and deionized water are adjusted so that the molar ratio of SiO2, Al2O3, Na2O, K2O and H2O in the material is the same as in Example 1, and gel B is obtained;

[0167] In step 4), 0.2% of the cluster size adjusting agent by weight of the gel B is added to the gel B.​

[0168] Finally, LSX-type molecular sieve raw powder S5 was obtained, with a silicon-to-aluminum ratio of 2.00.

[0169] The scanning electron microscope image of S5 is shown below. Figure 4 As shown, by Figure 4 It can be seen that the crystal clusters of the prepared LSX molecular sieve are generally uniform in size, but there are a few slightly larger or smaller crystal clusters, and no obvious impurity crystal morphology appears.

[0170] The average grain size of the S5 crystal cluster is calculated to be 2.46 μm with a standard deviation of 0.6.

[0171] Example 6

[0172] The target average particle size of the LSX molecular sieve clusters to be prepared in this embodiment is 3.75 μm, that is, y is 3.75 μm. According to the calculation, the weight ratio of the cluster size regulator to the gel, x, should be 0.0005, that is, 0.05%.

[0173] The procedure is carried out according to the method described in Example 1, except that...

[0174] Replace steps 1)-3) of Example 1 with the following method:

[0175] Water glass, aluminum hydroxide, sodium hydroxide, potassium hydroxide, and deionized water were added in a molar ratio of SiO2:Al2O3:(Na2O+K2O):water of 2:1:7.5:127.5, with the molar ratio of Na2O to Na2O+K2O being 0.77:1. Specifically,

[0176] Water glass, aluminum hydroxide, sodium hydroxide, and potassium hydroxide were added to deionized water and stirred at 10°C for 90 minutes to obtain gel C.

[0177] In step 4), a cluster size regulator is added to the gel C, accounting for 0.05% by weight of the gel C.

[0178] Finally, LSX-type molecular sieve raw powder S6 was obtained, with a silicon-to-aluminum ratio of 2.03.

[0179] The scanning electron microscope image of S6 is shown below. Figure 5 As shown, by Figure 5 It can be seen that the crystal clusters of the prepared LSX molecular sieve are generally uniform in size, but there are some slightly larger or smaller crystal clusters, and no obvious impurity crystal morphology appears.

[0180] The average grain size of the S6 crystal cluster is calculated to be 3.82 μm with a standard deviation of 0.8.

[0181] Example 7

[0182] The target average particle size of LSX molecular sieve clusters to be prepared in this example is 4.82 μm. It is calculated that the weight ratio of cluster size adjusting agent to the gel should be 0.0002, i.e. 0.02%.

[0183] The method described in Example 1 is followed, except that,

[0184] In Step 4), 0.02% by weight of cluster size adjusting agent is added to the gel A.

[0185] Finally, LSX molecular sieve crude powder S7 is obtained, and the silicon-aluminum ratio of S7 is 2.04.

[0186] As can be seen from the scanning electron microscope image of S7, the LSX molecular sieve clusters prepared have uniform size, no obvious morphology of impurity crystals appears, and the crystallinity is high.

[0187] It is calculated that the average particle size of S7 clusters is 4.61 μm, and the standard deviation is 0.6.

[0188] Comparative Example 1

[0189] The target average particle size of LSX molecular sieve clusters to be prepared in this example is 3.75 μm. It is calculated that the weight ratio of cluster size adjusting agent to the gel should be 0.0005, i.e. 0.05%.

[0190] The method of Example 1 is followed, except that,

[0191] In Step 1), the water glass is replaced with an equal molar amount of silica sol (silica content of 30% by weight) calculated as SiO2, and the amount of deionized water is adjusted to 19.4 mole% of the total amount of water;

[0192] In Step 2), the amounts of sodium hydroxide and deionized water are adjusted so that the molar ratio of SiO2, Al2O3, Na2O, K2O and H2O in the material is the same as in Example 1, and gel D is obtained.

[0193] In Step 4), 0.05% by weight of cluster size adjusting agent is added to the gel D.

[0194] Finally, LSX molecular sieve crude powder D1 is obtained, and the silicon-aluminum ratio of D1 is 2.01.

[0195] The scanning electron microscope image of D1 is shown in Figure 6 As can be seen from the scanning electron microscope image of D1, Figure 6 the LSX molecular sieve clusters prepared have extremely uneven size and a certain amount of cubic A-type impurity crystals appear, which leads to a decrease in the crystallinity of the molecular sieve.

[0196] Calculations show that the average grain size of the D1 cluster is 3.12 μm, which is significantly different from 3.75 μm, with a standard deviation of 1.63.

[0197] Comparative Example 2

[0198] Commercially available LSX molecular sieve powder D2 was purchased for analysis and characterization. The silica-alumina ratio of D2 was 2.06.

[0199] The scanning electron microscope image of D2 is as follows: Figure 7 As shown, by Figure 7 It can be seen that the commercially available LSX molecular sieve clusters have poor size uniformity and are of varying sizes.

[0200] Calculations show that the average grain size of the D2 crystal cluster is 3.99 μm, with a standard deviation of 1.28.

[0201] As can be seen from the above embodiments and comparative examples, the method described in this invention can not only smoothly adjust the size of the LSX molecular sieve clusters, but also ensure that the LSX molecular sieve clusters prepared therefrom have uniform size, low impurity content, high crystallinity, and that the silicon-aluminum ratio can be controlled within a low range, making it very suitable for industrial production.

[0202] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for controlling the size of LSX molecular sieve clusters, characterized in that, The method includes the following steps: 1) The first silicon source, aluminum source, sodium source and first water are sequentially subjected to first contact and first aging to obtain a crystal cluster size regulator; 2) The second silicon source, aluminum source, sodium source, potassium source, and second water are brought into a second contact to obtain a gel; 3) The crystal cluster size regulator is brought into a third contact with the gel, and the product from the third contact is subjected to a second aging and crystallization treatment to obtain LSX molecular sieve. The second silicon source is water glass. The target average particle size of the LSX molecular sieve clusters and the amount of cluster size regulator used in step 3) satisfy the following relationship: y=1.6517×(100x) -0.274 , Wherein, y is the target average particle size of the LSX molecular sieve cluster, in μm, and ranges from 1 to 5.8; x is the weight ratio of the cluster size regulator to the gel in step 3).

2. The method according to claim 1, wherein, In step 1), the first silicon source, the aluminum source, the sodium source, and the first water are brought into the first contact in such a way that the molar ratio of SiO2:Al2O3:Na2O:water is 5.5-10.5:1:10-20:200-300.

3. The method according to claim 1, wherein, In step 1), the first silicon source is mixed with a portion of the first water to obtain mixture A1; the aluminum source, the sodium source and the remaining portion of the first water are mixed to obtain mixture A2; and mixture A1 and mixture A2 are brought into the first contact. In step 1), a portion of the first water accounts for 10-15 moles of the total amount of water used for the first contact.

4. The method according to claim 1, wherein, In step 1), the conditions for the first contact include: a temperature of 10-40℃ and a time of 1-2 hours; The conditions for the first aging process include a temperature of 15-55℃ and a time of 5-40 hours.

5. The method according to claim 1, wherein, In step 2), the second silicon source, the aluminum source, the sodium source, the potassium source and the second water are brought into the second contact in such a way that the molar ratio of SiO2:Al2O3:(Na2O+K2O):water is 1.8-3:1:3-12:90-250, and the molar ratio of Na2O:(Na2O+K2O) is 0.6-0.9:

1.

6. The method according to claim 1, wherein, In step 2), the second silicon source is mixed with a portion of the second water to obtain mixture B1, and the aluminum source, the sodium source, the potassium source and the remaining portion of the second water are mixed to obtain mixture B2. Mixture B1 and mixture B2 are then brought into the second contact. In step 2), a portion of the second water comprises 10-35 moles of the total water used for the second contact.

7. The method according to claim 1, wherein, In step 2), the conditions for the second contact include: a temperature of 10-40°C and a time of 0.1-2 hours.

8. The method according to any one of claims 1-7, wherein, The first silicon source is one or more of water glass, silica sol, and amorphous silica.

9. The method according to any one of claims 1-7, wherein, The first silicon source is water glass.

10. The method according to claim 1, wherein, The water glass contains 4.25-9.25% by weight of Na2O, 15.55-23.55% by weight of SiO2, and 67.20-80.20% by weight of water.

11. The method according to any one of claims 1-7, wherein, The aluminum source is one or more of sodium aluminate, aluminum oxide, and aluminum hydroxide. The sodium source is one or more of sodium hydroxide, sodium chloride, and sodium sulfate; The potassium source is one or more of potassium hydroxide, potassium chloride, and potassium sulfate.

12. The method according to any one of claims 1-7, wherein, In step 3), the conditions for the third contact include: a temperature of 10-40℃ and a time of 0.1-2h.

13. The method according to any one of claims 1-7, wherein, In step 3), the conditions for the second aging include: a temperature of 30-90℃ and a time of 1-35h.

14. The method according to any one of claims 1-7, wherein, In step 3), the conditions for the second aging include: a temperature of 60-80℃ and a time of 3-8h.

15. The method according to any one of claims 1-7, wherein, In step 3), the conditions for the crystallization treatment include: a temperature of 80-120℃ and a time of 0.5-10h.

16. The method according to any one of claims 1-7, wherein, In step 3), the conditions for the crystallization treatment include: a temperature of 90-110℃ and a time of 1-4h.

17. The method according to any one of claims 1-7, wherein, The method further includes the steps of solid-liquid separation, washing and drying of the crystallization product described in step 3).

18. The method according to claim 17, wherein, The washing process results in a washing solution with a pH of 7-8. The drying conditions include a temperature of 50-150℃ and a time of 8-24 hours.

19. The LSX molecular sieve prepared by the method according to any one of claims 1-18.

20. The LSX molecular sieve according to claim 19, wherein, The silica-alumina ratio of the LSX molecular sieve is 2.0-2.

1.

21. The application of the method for controlling the size of LSX molecular sieve clusters according to any one of claims 1-18 in the preparation of LSX molecular sieves.

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