Lilsx molecular sieve, method of making and use thereof

Abstract

The application relates to the field of LiLSX molecular sieve preparation and discloses a preparation method of LiLSX molecular sieve, which comprises the following steps: 1) mixing a crystal cluster size regulator with a gel, aging and crystallizing to obtain LSX molecular sieve; and 2) performing lithium ion exchange on the LSX molecular sieve by using an exchange solution containing lithium ions, wherein the preparation method of the crystal cluster size regulator comprises: first contacting a first silicon source, an aluminum source, a sodium source and first water; the preparation method of the gel comprises: second contacting a second silicon source, an aluminum source, a sodium source, a potassium source and second water, wherein the second silicon source is water glass and / or sodium silicate; the target average particle size of the LiLSX molecular sieve crystal cluster and the amount of the crystal cluster size regulator satisfy the relationship y = 1.6517 x (100 x) ‑0.274 . The method can not only regulate the crystal cluster size of the LiLSX molecular sieve, but also obtain LiLSX molecular sieve crystal clusters with good uniformity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of LiLSX molecular sieve preparation, in particular to a LiLSX molecular sieve and a preparation method and application thereof. BACKGROUND

[0002] Low-silica X-type molecular sieve, referred to as LSX molecular sieve, has a silicon-aluminum ratio of 2.0-2.1, the number of cation sites reaches a maximum, and has more adsorption centers. The best commercial air separation oxygen adsorbent is a lithium-modified LSX molecular sieve (LiLSX molecular sieve), which has a large nitrogen adsorption capacity and a high nitrogen-oxygen separation coefficient.

[0003] During the formation of the X-type molecular sieve, zeolite grain clusters are often aggregated together to form multi-ribbed spherical clusters, and these clusters are subsequently stacked into adsorbent product particles under the action of a binder. When the LiLSX molecular sieve is used as an adsorbent for air separation oxygen production, its adsorption performance is usually closely related to physical indexes such as the size of the clusters and the size of the grains, and reducing the size of the clusters or the grains can increase the specific surface area, shorten the pore channel, increase the effective active sites, and improve the diffusion rate. However, the clusters or grains 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 performance of the material.

[0004] One of the important principles for designing adsorbents or catalysts and other products is to adjust the size of the clusters so that the intrinsic activity and mass transfer rate of the zeolite can reach the best effect under the specified working conditions.

[0005] However, there is currently no feasible method for adjusting the size of the LiLSX molecular sieve clusters, and the uniformity of the size of the LiLSX molecular sieve clusters prepared at present is poor, which leads to poor adsorption performance.

[0006] Based on the current situation, it is an important task in the field to develop a simple and efficient method for preparing LiLSX molecular sieves that can adjust the size of the clusters in a wide range. SUMMARY

[0007] The purpose of the present application is to overcome the problems of difficulty in adjusting the size of the LiLSX molecular sieve clusters and poor uniformity of the size of the LiLSX molecular sieve clusters prepared in the prior art, and to provide a preparation method of LiLSX molecular sieve, which can not only adjust the size of the clusters of the LiLSX molecular sieve prepared as needed, but also has good uniformity of the size of the LiLSX molecular sieve clusters and excellent adsorption performance.

[0008] To achieve the above-mentioned purpose, the first aspect of the present application provides a preparation method of LiLSX molecular sieve, which comprises the following steps:

[0009] 1) sequentially mixing, aging and crystallizing a crystal cluster size regulator with a gel to obtain an LSX molecular sieve;

[0010] 2) performing lithium ion exchange on the LSX molecular sieve with an exchange solution containing lithium ions,

[0011] The preparation method of the crystal cluster size regulator comprises: first contacting a first silicon source, an aluminum source, a sodium source and a first water;

[0012] The preparation method of the gel comprises: second contacting a second silicon source, an aluminum source, a sodium source, a potassium source and a second water, and the second silicon source is water glass and / or sodium silicate;

[0013] The target average particle size of the LiLSX molecular sieve crystal cluster and the amount of the crystal cluster size regulator in step 1) satisfy the following relationship:

[0014] y = 1.6517 x (100x) -0.274 ,

[0015] Wherein, y is the target average particle size of the LiLSX molecular sieve crystal cluster, in units of μm, and the value range is 1-5.8; x is the weight ratio of the crystal cluster size regulator to the gel in step 1).

[0016] Preferably, in step 1), the aging conditions include: temperature of 30-90℃, time of 1-35h; more preferably, the aging conditions include: temperature of 60-80℃, time of 3-8h.

[0017] Preferably, in step 1), the crystallization conditions include: temperature of 80-120℃, time of 0.5-10h; more preferably, the crystallization conditions include: temperature of 90-110℃, time of 1-4h.

[0018] Preferably, in step 2), the concentration of lithium ions in the exchange solution containing lithium ions is 1-5mol / L, more preferably 2-3mol / L.

[0019] Preferably, the amount of the exchange solution containing lithium ions is 5-30mL, more preferably 10-20mL, relative to 1g of the LSX molecular sieve.

[0020] Preferably, in step 2), the lithium ion exchange conditions include: temperature of 60-120℃, time of 1-5h; more preferably, the lithium ion exchange conditions include: temperature of 80-100℃, time of 1-3h.

[0021] Preferably, the lithium ion exchange is repeated for 3-7 times.

[0022] Preferably, the lithium ion exchange is such that the degree of exchange of lithium ions is 95% or more, more preferably 97.5% or more.

[0023] Preferably, in preparing the cluster size adjuster, the first contact is performed by bringing the first silicon source, the aluminum source, the sodium source, and the first water into contact in a molar ratio of SiO2:Al2O3:Na2O:water of 5.5-10.5:1:10-20:200-300.

[0024] Preferably, the first silicon source is mixed with a portion of the first water to obtain a mixture Al, and the aluminum source, the sodium source, and the remaining portion of the first water are mixed to obtain a mixture A2, and the mixture Al and the mixture A2 are brought into contact.

[0025] Preferably, the portion of the first water accounts for 10-15 mole% of the total amount of water used in the first contact.

[0026] Preferably, the conditions of the first contact include a temperature of 10-40°C and a time of 1-2h.

[0027] Preferably, the first contact is followed by a standing treatment.

[0028] More preferably, the conditions of the standing treatment include a temperature of 15-55°C and a time of 5-40h.

[0029] Preferably, in preparing the gel, the second contact is performed by bringing the second silicon source, the aluminum source, the sodium source, the potassium source, and the second water into contact 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.

[0030] Preferably, the second silicon source is mixed with a portion of the second water to obtain a mixture Bl, and the aluminum source, the sodium source, the potassium source, and the remaining portion of the second water are mixed to obtain a mixture B2, and the mixture Bl and the mixture B2 are brought into contact.

[0031] Preferably, the portion of the second water accounts for 10-35 mole% of the total amount of water used in the second contact.

[0032] Preferably, the conditions of the second contact include a temperature of 10-40°C and a time of 0.1-2h.

[0033] Preferably, the first silicon source is one or more of water glass, silica sol, sodium silicate, potassium silicate and amorphous silica, more preferably water glass and sodium silicate.

[0034] Preferably, the second silicon source is water glass; more 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.

[0035] Preferably, the aluminum source is one or more of sodium aluminate, aluminum oxide and aluminum hydroxide, preferably aluminum hydroxide.

[0036] Preferably, the sodium source is one or more of sodium hydroxide, sodium chloride and sodium sulfate.

[0037] Preferably, the potassium source is one or more of potassium hydroxide, potassium chloride and potassium sulfate.

[0038] Preferably, the method further comprises the steps of sequentially subjecting the product of step 1) to solid-liquid separation, washing and drying.

[0039] Preferably, the washing is such that the pH of the washing liquid is 7-8.

[0040] Preferably, the drying conditions include a temperature of 50-150℃ and a time of 8-24h.

[0041] The second aspect of the present application provides a LiLSX molecular sieve prepared by the method of the first aspect of the present application.

[0042] The third aspect of the present application provides the use of the LiLSX molecular sieve of the second aspect of the present application in air separation to produce oxygen.

[0043] Through the above technical solution, the size of the LiLSX molecular sieve crystal cluster can be flexibly regulated under the action of the crystal cluster size regulator, and the LiLSX molecular sieve with a crystal cluster size of 1-5.8 μm can be prepared according to the needs, so as to obtain the LiLSX molecular sieve meeting different industrial needs.

[0044] In addition, the LiLSX molecular sieve prepared by the method of the present application has uniform crystal cluster size, low impurity crystal content, high crystallinity and low silicon-aluminum ratio, and has excellent adsorption performance. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a scanning electron microscope image of the LiLSX molecular sieve prepared in Example 3. DETAILED DESCRIPTION

[0046] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0047] In this invention, the silicon-aluminum ratio refers to the molar ratio of SiO2 to Al2O3.

[0048] In this invention, the LSX molecular sieve cluster refers to a multi-faceted spherical stack formed by a group of LSX molecular sieve crystals aggregated together.

[0049] In this invention, the particle size of the LiLSX molecular sieve cluster refers to the length of the longest axis of the outer contour of the LiLSX molecular sieve cluster.

[0050] In this invention, the average particle size of the LiLSX molecular sieve clusters is obtained by randomly selecting 30 LiLSX molecular sieve clusters from scanning electron microscope (SEM) images and calculating the average particle size.

[0051] In this invention, the target average particle size of the LiLSX molecular sieve cluster refers to the average particle size of the LiLSX molecular sieve cluster to be prepared.

[0052] The first aspect of this invention provides a method for preparing LiLSX molecular sieves, wherein the method includes the following steps:

[0053] 1) The crystal cluster size regulator and the gel were mixed, aged, and crystallized sequentially to obtain LSX molecular sieve;

[0054] 2) The LSX molecular sieve is subjected to lithium-ion exchange with a lithium-ion-containing exchange solution.

[0055] The method for preparing the crystal cluster size regulator includes: bringing a first silicon source, an aluminum source, a sodium source, and a first water into a first contact;

[0056] The method for preparing the gel includes: making a second silicon source, an aluminum source, a sodium source, a potassium source, and a second water in a second contact, wherein the second silicon source is water glass and / or sodium silicate;

[0057] The target average particle size of the LiLSX molecular sieve clusters and the amount of cluster size regulator used in step 1) satisfy the following relationship:

[0058] y = 1.6517 × (100x) -0.274 ,

[0059] Wherein, y is the target average particle size of the LiLSX 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 1).

[0060] In this invention, there is no particular limitation on the range of values ​​for y, which can be any value from 1 to 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.

[0061] The inventors of this invention accidentally discovered during their research that by using a specific second silicon source to prepare a gel and adding a cluster size regulator prepared according to the method described in this invention to the gel, the size of the LiLSX molecular sieve clusters can be controlled by adjusting the amount of the cluster size regulator added, thus completing this invention.

[0062] The preparation methods of the crystal cluster size regulator and gel described in this invention will be described in detail below.

[0063] In this invention, the crystal cluster size regulator is prepared by sequentially bringing the first silicon source, the aluminum source, the sodium source, and the first water into a first contact.

[0064] In this invention, there are no particular limitations on the first silicon source, the aluminum source, and the sodium source; they can be conventional choices in the art.

[0065] The first silicon source can be one or more of water glass, silica sol, sodium silicate, potassium silicate, and amorphous silica, preferably water glass and sodium silicate; more preferably water glass. This can further improve the crystal cluster uniformity of the prepared LiLSX molecular sieve.

[0066] The aluminum source can be, for example, one or more of sodium aluminate, aluminum oxide, and aluminum hydroxide, preferably aluminum hydroxide.

[0067] The sodium source can be one or more of sodium hydroxide, sodium chloride, and sodium sulfate, preferably sodium hydroxide.

[0068] Furthermore, in order to reduce interference, the first water is preferably deionized water in this invention.

[0069] In this invention, there are no particular limitations on the amount of the first silicon source, aluminum source, sodium source and the first water added during the first contact.

[0070] In this invention, 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, thereby further improving the adsorption performance of the prepared LiLSX molecular sieve.

[0071] According to the present invention, when performing the first contact, there is no particular limitation on the order in which the first silicon source, the aluminum source, the sodium source, and the first water are added. 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 portion of the first water to obtain mixture A1, and the remaining portion of the aluminum source, the sodium source, and the first water can be mixed to obtain mixture A2. Then, mixture A1 and mixture A2 are subjected to the first contact.

[0072] The inventors of this invention have discovered that, during the first contact, by first mixing the first silicon source with a portion of the first water to obtain a uniformly mixed mixture A1 containing the first silicon source; then uniformly mixing the aluminum source, the sodium source, and the remaining portion of the first water to obtain a mixture A2; and then adding the mixture A1 to the mixture A2 to ensure thorough mixing and the first contact, the dispersion of the above raw materials can be made more uniform. This avoids the generation of multiple different products in a certain intermediate process due to uneven mixing of the raw materials during the first contact, thereby significantly improving the crystallinity and uniformity of the crystal cluster size of the prepared LiLSX molecular sieve.

[0073] Furthermore, when the first contact is performed in the manner described above, that is, when the first silicon source is mixed with a portion of the first water to obtain mixture A1; and the aluminum source, the sodium source, and the remaining portion of the first water are mixed to obtain mixture A2, and when mixture A1 and mixture A2 are brought into the first contact, a portion of the first water accounts for 10-15 moles of the total amount of water used in the first contact.

[0074] In this invention, those skilled in the art should understand that when the other raw materials used for the first contact contain water or contain ions that can be converted into water (for example, when the first silicon source is water glass, it contains some water; when the sodium source is sodium hydroxide, it contains hydroxide ions that can be converted into water), the total amount of water used for 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.

[0075] Furthermore, the conditions for the first contact are not particularly limited. For example, the conditions for the first contact may include a temperature of 10-40°C and a time of 1-2 hours. Additionally, to facilitate the first contact, it is preferable that the first contact is carried out under stirring.

[0076] In this invention, to further improve the performance of the crystal cluster size regulator, preferably, after the first contact, a settling treatment is performed. The conditions for the settling treatment may include: a temperature of 15-55°C and a time of 5-40 hours. Preferably, the conditions for the settling treatment include: a temperature of 20-40°C and a time of 15-25 hours.

[0077] According to a preferred embodiment of the present invention, in the preparation process of the crystal cluster size regulator, the first silicon source and a portion of the first water are thoroughly mixed under stirring to obtain mixture A1; the aluminum source, the sodium source and the remaining portion of the first water are mixed and stirred at 60-140°C until all the solids are dissolved to obtain mixture A2; then mixture A1 is added dropwise to mixture A2 under stirring; after gelation occurs, the stirring speed is increased, and stirring is continued at 10-40°C for 1-2 hours to achieve the first contact; then stirring is stopped, and the settling treatment is performed at 20-40°C for 15-25 hours.

[0078] The resulting cluster size regulator can significantly improve the uniformity of the prepared LiLSX molecular sieve clusters when used in the preparation of LiLSX molecular sieves according to the method of the present invention.

[0079] The preparation method of the gel described in this invention will be described in detail below.

[0080] According to the present invention, the method for preparing the gel includes: making a second silicon source, an aluminum source, a sodium source, a potassium source and a second water in a second contact, wherein the second silicon source is water glass and / or sodium silicate.

[0081] In this invention, there are no particular limitations on the aluminum, sodium, and potassium sources required for preparing the gel; they can be conventional choices in the field.

[0082] Furthermore, the aluminum source and the sodium source can be the same as those used in the preparation of the crystal cluster size regulator, and will not be elaborated further here.

[0083] The potassium source can be any potassium source commonly used in the art, such as one or more of potassium hydroxide, potassium chloride and potassium sulfate, preferably potassium hydroxide.

[0084] During the research process, the inventors of this invention discovered that the selection of the second silicon source is crucial in the preparation of the gel. The selection of the second silicon source plays a key role in the uniformity of the LiLSX molecular sieve crystal clusters prepared by the specific method described in this invention.

[0085] In this invention, the second silicon source is water glass and / or sodium silicate, with water glass being more preferred. By using water glass as the second silicon source, not only can the size of the LiLSX molecular sieve clusters be smoothly adjusted using the method described in this invention, but compared with sodium silicate, it can further ensure that the LiLSX molecular sieve clusters prepared thereby have a more uniform size, less impurity content, and higher crystallinity.

[0086] Furthermore, in this invention, there are no particular limitations on the composition of the water glass, and commercially available water glass can be used.

[0087] Preferably, 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.

[0088] Furthermore, in order to reduce interference, the second water is preferably deionized water in this invention.

[0089] According to the present invention, when performing the second contact, there is no particular limitation on the amount of the second silicon source, aluminum source, sodium source and the second water added, and the amounts can be the conventional amounts used in the preparation of LSX molecular sieve gels in the art.

[0090] In this invention, when preparing the gel, preferably, the second silicon source, the aluminum source, the sodium source, the potassium source, and the second water are brought into the second contact 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, thereby further improving the adsorption performance of the prepared LiLSX molecular sieve.

[0091] According to the present invention, when performing the second contact, there is no particular limitation on the order in which the second silicon source, the aluminum source, the sodium source, the potassium source, and the second water are added. For example, the second silicon source, the aluminum source, the sodium source, and the potassium source can be added to the second water separately, or the aluminum source, the sodium source, and the potassium source can be mixed with the second water first, and then the second silicon source can be added to the mixture. Alternatively, the second silicon source can be mixed with a portion of the second water separately to obtain mixture B1. The remaining portion of the aluminum source, the sodium source, the potassium source, and the second water can be mixed to obtain mixture B2, and then mixture B1 and mixture B2 can be subjected to the second contact.

[0092] The inventors of this invention discovered that during the second contact, by first mixing the second silicon source with a portion of the second water to obtain a uniformly mixed mixture B1 containing the second silicon source; then uniformly mixing the aluminum source, the sodium source, the potassium source, and the remaining portion of the second water to obtain mixture B2; and finally adding mixture B1 to mixture B2 to ensure thorough mixing. This allows for more uniform dispersion and mixing of the various raw materials, preventing the formation of multiple different products in a certain intermediate stage due to uneven mixing of the raw materials during the second contact, thereby significantly improving the uniformity of the prepared LiLSX molecular sieve.

[0093] Furthermore, when the second contact is performed in the manner described above, that is, 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. When the second contact is performed between mixture B1 and mixture B2, a portion of the second water accounts for 10-35 mol% of the total amount of water used in the second contact.

[0094] In this invention, those skilled in the art should understand that when the other raw materials used for the second contact contain water or contain ions that can be converted into water (for example, when the second silicon source is water glass, it contains some water; when the sodium source is sodium hydroxide, it contains hydroxide ions that can be converted into water), the total amount of water used for the second contact includes not only the amount of the second 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.

[0095] Furthermore, in this invention, the conditions for the second contact are not particularly limited. For example, the conditions for the second contact may include: a temperature of 10-40°C and a time of 0.1-2h; preferably, the conditions for the second contact may include: a temperature of 10-20°C and a time of 0.2-0.5h.

[0096] In preparing the gel according to a preferred embodiment of the present invention, the second silicon source and a portion of the second water are thoroughly mixed under stirring to obtain mixture B1; the aluminum source, the sodium source, the potassium source, and the remaining portion of the second water are mixed and stirred at 60-140°C until all solids are dissolved to obtain mixture B2. Then, mixture B1 is rapidly added dropwise to mixture B2 under stirring (e.g., at a stirring speed of 200-400 rpm). After gelation, the stirring speed is increased (e.g., at a stirring speed of 350-600 rpm), and stirring continues at 10-20°C for 0.2-0.5 h. Thus, the prepared gel can further improve the uniformity of the subsequently obtained LiLSX molecular sieve clusters.

[0097] According to the method of the first aspect of the present invention, after obtaining the cluster size regulator and the gel, the cluster size regulator and the gel are sequentially mixed, aged and crystallized to obtain LSX molecular sieve.

[0098] In this invention, when mixing, preferably, the crystal cluster size adjuster is added to the gel; more preferably, stirring is performed simultaneously with the addition.

[0099] In addition, the mixing conditions include a temperature of 10-40°C and a time of 0.5-2 hours.

[0100] According to the present invention, the mixed product is subjected to the aging and crystallization processes in sequence.

[0101] Here, there is no particular limitation on the aging conditions. For example, the aging conditions may include: a temperature of 30-90°C and a time of 1-35 hours; preferably, the aging conditions include: a temperature of 60-80°C and a time of 3-8 hours.

[0102] In this invention, there are no particular limitations on the crystallization conditions. For example, the crystallization conditions may include: a temperature of 80-120°C and a time of 0.5-10 hours. Preferably, the crystallization treatment conditions include: a temperature of 90-110°C and a time of 1-4 hours.

[0103] Furthermore, the method of the present invention may further include: sequentially performing solid-liquid separation, washing, and drying on the product after crystallization treatment in step 1).

[0104] The methods for solid-liquid separation, washing, and drying are not particularly limited and can be carried out using various methods conventional in the art.

[0105] The solid-liquid separation can be performed, for example, by vacuum filtration.

[0106] The washing process can be performed, for example, by rinsing with an excess of deionized water. Preferably, the washing process results in a washing solution with a pH of 7-8.

[0107] The drying conditions may include, for example, a temperature of 50-150°C and a time of 8-24 hours.

[0108] According to the present invention, the method described in the first aspect of the present invention can not only prepare LiLSX molecular sieves with uniform crystal cluster size, but also adjust the size of the LiLSX molecular sieve crystal clusters to be prepared according to the requirements.

[0109] Specifically, first, the target average particle size (in μm), y, of the required LiLSX molecular sieve clusters is determined based on actual needs. Then, according to y = 1.6517 × (100x) -0.274 The corresponding value of x is calculated, and the weight ratio of the crystal cluster size regulator to the gel in step 1) can be obtained.

[0110] Furthermore, since errors inevitably occur during calculation and operation, when the ratio of the actual average particle size y1 of the LiLSX molecular sieve cluster prepared by the control method described in this invention to the target average particle size y of the LiLSX molecular sieve cluster is 1 ± 0.1 (i.e., y1 / y = 0.9 - 1.1), it is considered to satisfy the relationship described in this invention.

[0111] According to a first aspect of the present invention, in step 2), the LSX molecular sieve is then subjected to lithium-ion exchange with a lithium-ion-containing exchange solution.

[0112] According to the present invention, the concentration of lithium ions in the lithium ion exchange solution is not particularly limited. For example, the concentration of lithium ions in the lithium ion exchange solution can be 1-5 mol / L, preferably 2-3 mol / L.

[0113] Furthermore, the source of lithium ions in the lithium ion exchange solution is not particularly limited, and various lithium-ion-containing raw materials commonly used in the art can be used. For example, the lithium ions can come from lithium salts, such as lithium chloride monohydrate, anhydrous lithium chloride, and lithium nitrate. There is no particular limitation in this invention.

[0114] In this invention, the amount of the exchange liquid can be determined according to the amount of the LSX molecular sieve. For example, relative to 1g of the LSX molecular sieve, the amount of the lithium-ion-containing exchange liquid can be 5-30mL, preferably 10-20mL.

[0115] Furthermore, the specific method for lithium-ion exchange is not particularly limited in this invention, and various methods conventional in the art can be used. For example, in a preferred embodiment of this invention, a tank exchange method is used for lithium-ion exchange.

[0116] Furthermore, the conditions for lithium-ion exchange can be conventionally chosen in the art. For example, the conditions for lithium-ion exchange may include a temperature of 60-120°C and a time of 1-5 hours; preferably, the conditions for lithium-ion exchange include a temperature of 80-100°C and a time of 1-3 hours. By performing lithium-ion exchange under the above conditions, the degree of lithium-ion exchange can be further improved.

[0117] Furthermore, in order to improve the lithium ion exchange rate, preferably, the lithium ion exchange can be repeated multiple times, for example, 3-7 times.

[0118] When performing the repeated exchange, the molecular sieve obtained from the previous lithium-ion exchange is used for the next lithium-ion exchange. Fresh lithium-ion-containing exchange solution is used for the next exchange. The composition of the exchange solution and the exchange conditions can be the same as described above. This is a conventional method in the field and will not be described in detail here.

[0119] In this invention, the degree of lithium ion exchange refers to the ratio of the number of moles of lithium ions to the sum of the number of moles of lithium ions, sodium ions, and potassium ions in the LiLSX molecular sieve after exchange, that is, the degree of lithium ion exchange = (number of moles of lithium ions) / (number of moles of lithium ions + number of moles of sodium ions + number of moles of potassium ions).

[0120] Furthermore, in this invention, preferably, the lithium ion exchange results in an exchange rate of 95% or higher, more preferably 97.5% or higher.

[0121] According to the present invention, after the lithium-ion exchange is performed, the lithium-ion exchange product is preferably washed. The washing can be performed using deionized water, and the washing ensures that no chloride ions are present in the washing solution.

[0122] In addition, the washed product can be dried after washing. There are no special requirements for the drying conditions. For example, it can be dried at 50-150℃ for 8-24 hours.

[0123] In addition, in order to activate the obtained exchange product, the method may further include an activation step. The activation method is not particularly limited and can be carried out by conventional methods in the art. For example, the lithium-ion exchange product can be placed in a degassing device and activated at 1-10 Pa and 250-650 °C for 1-10 h to obtain LiLSX molecular sieve.

[0124] The above method can not only prepare LiLSX molecular sieves with very uniform crystal cluster size, but also control the size of the LiLSX molecular sieves to be prepared by controlling the amount of crystal cluster size regulator, thereby meeting the application needs of various industrial scenarios.

[0125] The second aspect of the present invention provides a LiLSX molecular sieve prepared by the method described in the first aspect of the present invention.

[0126] According to a second aspect of the invention, the LiLSX molecular sieve has uniformly sized crystal clusters, and the standard deviation of the particle size between the LiLSX molecular sieve crystal clusters is less than 0.8.

[0127] The silica-to-alumina ratio of the LSX molecular sieve described in the second aspect of the present invention can be as low as 2.0-2.1.

[0128] The third aspect of the present invention provides the application of the LiLSX molecular sieve described in the second aspect of the present invention in air separation oxygen production.

[0129] According to the present invention, the LiLSX molecular sieve described in the second aspect of the present invention has uniform size and excellent adsorption performance. Therefore, when applied to air separation oxygen production, it can not only significantly improve the nitrogen adsorption capacity, but also has excellent nitrogen selectivity, and can achieve a high degree of nitrogen-oxygen separation.

[0130] The present invention will be described in detail below through embodiments.

[0131] In the following examples and comparative examples, the silicon-to-aluminum ratio was determined by X-ray fluorescence spectroscopy (XRF).

[0132] The scanning electron microscope (SEM) images were obtained using an Apreo2C scanning electron microscope manufactured by Thermo Fisher Scientific, Inc.

[0133] Unless otherwise specified, the raw materials and products used in the following examples, preparation examples and comparative examples are all commercially available products, or can be prepared by conventional methods.

[0134] In the following examples and comparative examples, the water glass used had the following specific composition: Na2O 6.50 wt%, SiO2 20.57 wt%, H2O 72.93 wt%; aluminum hydroxide 98.74 wt%; and potassium hydroxide 93 wt%.

[0135] Preparation Example 1 - Preparation of Cluster Size Modifier

[0136] Water glass, aluminum hydroxide, sodium hydroxide, and deionized water were added in a molar ratio of SiO2:Al2O3:Na2O:water of 10:1:12:280. Specifically:

[0137] 1) A portion of water glass and deionized water are thoroughly mixed under stirring to obtain mixture A1, wherein the portion of deionized water accounts for 14.6 mol% of the total water (the sum of water contained in the deionized water and other raw materials).

[0138] 2) Mix aluminum hydroxide, sodium hydroxide and the remaining deionized water, stir at 80°C until all the solids are dissolved, then cool to 10°C to obtain mixture A2;

[0139] 3) At a stirring rate of 375 rpm, mixture A1 is slowly added dropwise to mixture A2. After gelation occurs, the stirring speed is increased to 475 rpm and stirred at 10°C for 1 hour to achieve the first contact. Stirring is then stopped, and the resulting slurry is allowed to stand at 35°C for 20 hours to obtain the crystal cluster size regulator.

[0140] Preparation Example 2 - Preparation of Gel A

[0141] 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,

[0142] 1) A portion of water glass and deionized water are thoroughly mixed under stirring to obtain mixture B1, wherein the portion of deionized water accounts for 19.4 mol% of the total water (the sum of water contained in the deionized water and other raw materials).

[0143] 2) Mix aluminum hydroxide, sodium hydroxide, potassium hydroxide and the remaining deionized water, stir at 80°C until all the solids are dissolved, then cool to 10°C to obtain mixture B2;

[0144] 3) Quickly add mixture B1 to mixture B2 and mix at a stirring rate of 375 rpm. After gelation occurs, increase the stirring speed to 475 rpm and stir at 10°C for 15 min to achieve the second contact, thus obtaining gel A.

[0145] Preparation Example 3 - Preparation of Gel B

[0146] The procedure was carried out according to the method of Preparation Example 2, with the following differences:

[0147] In step 1), the water glass is replaced with sodium silicate nonahydrate in an equimolar amount based on SiO2, and a portion of the deionized water accounts for 19.4 mol% of the total water volume.

[0148] In step 2), the amount of sodium hydroxide and deionized water added is adjusted so that the molar ratio of SiO2, Al2O3, Na2O, K2O and H2O in the material is the same as in preparation example 2, and gel B is obtained.

[0149] Preparation Example 4 - Preparation of Gel C

[0150] 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.

[0151] In this process, water glass, aluminum hydroxide, sodium hydroxide, potassium hydroxide, and deionized water are added in a molar ratio of SiO2:Al2O3:(Na2O+K2O):water of 2:1:7.5:127.5, and the molar ratio of Na2O to Na2O+K2O is 0.77:1.

[0152] Comparative Preparation Example 1 - Preparation of Gel D

[0153] The procedure was carried out according to the method of Preparation Example 2, with the following differences:

[0154] In step 1), the water glass is replaced with silica sol (silica content of 30% by weight) in equimolar amounts based on SiO2, and a portion of the deionized water accounts for 19.4 mol% of the total water volume.

[0155] In step 2), the amount of sodium hydroxide and deionized water added is adjusted so that the molar ratio of SiO2, Al2O3, Na2O, K2O and H2O in the material is the same as in preparation example 2, and gel D is obtained.

[0156] Example 1

[0157] The target average particle size of the LiLSX molecular sieve clusters to be prepared in this embodiment is 1.19 μm, that is, y is 1.19 μm. According to the calculation, the weight ratio of the cluster size regulator to the gel, x, should be 0.033, that is, 3.3%.

[0158] 1) Add the cluster size regulator to gel A, wherein the amount of the cluster size regulator added is 3.3% by weight of gel A. Stir and mix at 25°C for 0.5 h, then let it stand at 70°C for 5 h. After that, heat to 100°C with stirring, let it stand and 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.

[0159] 2) An exchange solution with a lithium ion concentration of 2.2 mol / L was prepared using anhydrous lithium chloride. Then, LSX molecular sieve was added to the exchange solution. The amount of lithium ion-containing exchange solution used was 10 mL relative to 1 g of LSX molecular sieve. The exchange was then stirred at 90 °C for 2 h. After 2 h, the first exchange product was subjected to solid-liquid separation. The solid phase was collected and transferred to fresh exchange solution for a second lithium ion exchange. This process was repeated 5 times to obtain the exchanged molecular sieve. The sieve was then repeatedly washed with deionized water until no chloride ions were found. Finally, it was dried in an oven at 80 °C for 10 h to obtain LiLSX molecular sieve, denoted as S1.

[0160] The silicon-to-aluminum ratio of S1 was tested to be 2.07.

[0161] As can be seen from the scanning electron microscope image of S1, the prepared LiLSX molecular sieve clusters are relatively uniform in size, with no obvious impurity crystal morphology, and have a high degree of crystallinity.

[0162] The average grain size of the S1 crystal cluster is 1.28 μm, with a standard deviation of 0.6.

[0163] Example 2

[0164] The target average particle size of the LiLSX molecular sieve clusters to be prepared in this embodiment is 2.14 μm, that is, y is 2.14 μm. According to the calculation, the weight ratio of the cluster size regulator to the gel, x, should be 0.0039, that is, 0.39%.

[0165] The method described in Example 1 is followed, except that:

[0166] In step 1), the amount of the crystal cluster size regulator added is 0.39% by weight of gel A.

[0167] The LiLSX molecular sieve was obtained and denoted as S2.

[0168] The silicon-to-aluminum ratio of S2 was tested to be 2.09.

[0169] As can be seen from the scanning electron microscope image of S2, the prepared LiLSX molecular sieve clusters are relatively uniform in size, with no obvious impurity crystal morphology, and have a high degree of crystallinity.

[0170] The average grain size of the S2 crystal cluster is calculated to be 2.07 μm, with a standard deviation of 0.6.

[0171] Example 3

[0172] The target average particle size of the LiLSX molecular sieve clusters to be prepared in this embodiment is 3.3 μm, that is, y is 3.3 μm. According to the calculation, the weight ratio of the cluster size regulator to the gel, x, should be 0.0008, that is, 0.08%.

[0173] The method described in Example 1 is followed, except that:

[0174] In step 1), the amount of the crystal cluster size regulator added is 0.08% by weight of gel A.

[0175] The LiLSX molecular sieve was obtained and denoted as S3.

[0176] The silicon-to-aluminum ratio of S3 was tested to be 2.08.

[0177] The scanning electron microscope image of S3 is as follows: Figure 1 As shown, by Figure 1 It can be seen that the prepared LiLSX molecular sieve clusters are relatively uniform in size, with no obvious impurity crystal morphology, and have a high degree of crystallinity.

[0178] The average grain size of the S3 crystal cluster is calculated to be 3.21 μm with a standard deviation of 0.4.

[0179] Example 4

[0180] The target average particle size of the LiLSX molecular sieve clusters to be prepared in this embodiment is 4.54 μm, that is, y is 4.54 μm. According to the calculation, the weight ratio of the cluster size regulator to the gel, x, should be 0.00025, that is, 0.025%.

[0181] The method described in Example 1 is followed, except that:

[0182] In step 1), the amount of the crystal cluster size adjuster added is 0.025% by weight of gel A.

[0183] The LiLSX molecular sieve was obtained and denoted as S4.

[0184] The silicon-to-aluminum ratio of S4 was tested to be 2.09.

[0185] As can be seen from the scanning electron microscope image of S4, the prepared LiLSX molecular sieve clusters are relatively uniform in size, with no obvious impurity crystal morphology, and have a high degree of crystallinity.

[0186] The average grain size of the S4 crystal cluster is calculated to be 4.24 μm with a standard deviation of 0.5.

[0187] Example 5

[0188] The target average particle size of the LiLSX molecular sieve clusters to be prepared in this embodiment is 5.22 μm, that is, y is 5.22 μm. According to the calculation, the weight ratio of the cluster size regulator to the gel, x, should be 0.00015, that is, 0.015%.

[0189] The method described in Example 1 is followed, except that:

[0190] In step 1), the amount of the crystal cluster size adjuster added is 0.015% by weight of gel A.

[0191] The LiLSX molecular sieve was obtained and denoted as S5.

[0192] According to testing, the silicon-to-aluminum ratio of S5 is 2.1.

[0193] As can be seen from the scanning electron microscope image of S5, the prepared LiLSX molecular sieve clusters are relatively uniform in size, with no obvious impurity crystal morphology, and have a high degree of crystallinity.

[0194] The average grain size of the S5 crystal cluster is calculated to be 5.01 μm with a standard deviation of 0.6.

[0195] Example 6

[0196] The method is carried out according to Example 3, with the following difference:

[0197] In step 1), gel B is used instead of gel A, that is, a cluster size regulator is added to gel B, wherein the amount of the cluster size regulator added is 0.08% by weight of gel B.

[0198] The LiLSX molecular sieve was obtained and denoted as S6.

[0199] According to testing, the silicon-to-aluminum ratio of S6 is 2.08.

[0200] As can be seen from the scanning electron microscope image of S6, the prepared LiLSX molecular sieve clusters are generally uniform in size, but there are some slightly larger or smaller clusters, and no obvious impurity crystal morphology appears.

[0201] The average grain size of the S6 crystal cluster is calculated to be 3.11 μm with a standard deviation of 0.7.

[0202] Example 7

[0203] The method is carried out according to Example 3, with the following difference:

[0204] In step 1), gel C is used instead of gel A, that is, a cluster size regulator is added to gel C, wherein the amount of the cluster size regulator added is 0.08% by weight of gel C.

[0205] The LiLSX molecular sieve was obtained and denoted as S7.

[0206] According to tests, the silicon-to-aluminum ratio of S7 is 2.09.

[0207] As can be seen from the scanning electron microscope image of S7, the prepared LiLSX molecular sieve clusters are generally uniform in size, but there are some slightly larger or smaller clusters, and no obvious impurity crystal morphology appears.

[0208] The average grain size of the S7 cluster is calculated to be 3.04 μm with a standard deviation of 0.8.

[0209] Comparative Example 1

[0210] The method is carried out according to Example 3, with the following difference:

[0211] In step 1), gel D is used instead of gel A, that is, a cluster size regulator is added to gel D, wherein the amount of the cluster size regulator added is 0.08% by weight of gel D.

[0212] The LiLSX molecular sieve was obtained and denoted as D1.

[0213] The silicon-to-aluminum ratio of D1 was tested to be 2.07.

[0214] As can be seen from the scanning electron microscope image of D1, the prepared LiLSX molecular sieve clusters are extremely uneven in size and a certain amount of cubic A-type impurities appear, which leads to a decrease in the crystallinity of the molecular sieve.

[0215] The average grain size of the D1 cluster was calculated to be 2.85 μm with a standard deviation of 1.49.

[0216] 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 LiLSX molecular sieve clusters, but also ensure that the LiLSX molecular sieve clusters prepared therefrom have uniform size, low impurity content, high crystallinity, and that the silicon-to-aluminum ratio can be controlled within a low range, making it very suitable for industrial production.

[0217] 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 preparing LiLSX molecular sieves, characterized in that, The method includes the following steps: 1) The crystal cluster size regulator and the gel were mixed, aged, and crystallized sequentially to obtain LSX molecular sieve; 2) The LSX molecular sieve is subjected to lithium-ion exchange with a lithium-ion-containing exchange solution. The method for preparing the crystal cluster size regulator includes: bringing a first silicon source, an aluminum source, a sodium source, and a first water into a first contact; The method for preparing the gel includes: making a second silicon source, an aluminum source, a sodium source, a potassium source, and a second water in a second contact, wherein the second silicon source is water glass; The target average particle size of the LiLSX molecular sieve clusters and the amount of cluster size regulator used in step 1) satisfy the following relationship: y=1.6517×(100x) -0.274 , Wherein, y is the target average particle size of the LiLSX 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 1).

2. The preparation method according to claim 1, wherein, In step 1), the aging conditions include: a temperature of 30-90℃ and a time of 1-35h.

3. The preparation method according to claim 1, wherein, In step 1), the aging conditions include: a temperature of 60-80℃ and a time of 3-8h.

4. The preparation method according to claim 1, wherein, In step 1), the crystallization conditions include: a temperature of 80-120℃ and a time of 0.5-10h.

5. The preparation method according to claim 1, wherein, In step 1), the crystallization conditions include: a temperature of 90-110℃ and a time of 1-4h.

6. The preparation method according to claim 1, wherein, In step 2), the concentration of lithium ions in the lithium-ion-containing exchange solution is 1-5 mol / L; The amount of lithium-ion-containing exchange solution used is 5-30 mL relative to 1 g of the LSX molecular sieve.

7. The preparation method according to claim 1, wherein, In step 2), the concentration of lithium ions in the lithium-ion-containing exchange solution is 2-3 mol / L; The amount of lithium-ion-containing exchange solution used is 10-20 mL relative to 1 g of the LSX molecular sieve.

8. The preparation method according to claim 1, wherein, In step 2), the conditions for lithium-ion exchange include: a temperature of 60-120℃ and a time of 1-5h.

9. The method according to claim 1, wherein, In step 2), the lithium-ion exchange is repeated 3-7 times; The lithium-ion exchange achieves an exchange rate of over 95%.

10. The preparation method according to any one of claims 1-9, wherein, When preparing the crystal cluster size regulator, 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. 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. The first water comprises 10-15 moles of the total amount of water used in the first contact.

11. The preparation method according to any one of claims 1-9, wherein, The conditions for the first contact include: a temperature of 10-40℃ and a time of 1-2 hours; After the first contact, a settling process is also performed. The conditions for the static treatment include: a temperature of 15-55℃ and a time of 5-40h.

12. The preparation method according to any one of claims 1-9, wherein, When preparing the gel, the second silicon source, the aluminum source, the sodium source, the potassium source, and the second water are brought into the second contact in a molar ratio of SiO2:Al2O3:(Na2O+K2O):water of 1.8-3:1:3-12:90-250, wherein the molar ratio of Na2O:(Na2O+K2O) is 0.6-0.9:1; The second silicon source is mixed with a portion of the second water to obtain mixture B1. 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. The second water comprises 10-35 mol% of the total water used in the second contact. The conditions for the second contact include a temperature of 10-40°C and a time of 0.1-2 hours.

13. The preparation method according to any one of claims 1-9, wherein, The first silicon source is one or more of water glass, silica sol, and amorphous silica.

14. The preparation method according to any one of claims 1-9, 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.

15. The preparation method according to any one of claims 1-9, 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.

16. The preparation method according to any one of claims 1-9, wherein, The method further includes the steps of sequentially performing solid-liquid separation, washing, and drying on the crystallized product described in step 1).

17. The preparation method according to claim 16, 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.

18. The LiLSX molecular sieve prepared by the method according to any one of claims 1-17.

19. The application of the LiLSX molecular sieve of claim 18 in air separation oxygen production.

Images