A 13x molecular sieve and a method for making the same

Abstract

The application relates to a 13X type molecular sieve and a preparation method thereof, and the method comprises the following steps: obtaining a sodium aluminosilicate gel slurry through a reaction solution system with a first set silicon-aluminum ratio; adding crystal seeds into the sodium aluminosilicate gel slurry, and then performing aging to obtain a slurry containing 13X type molecular sieve crystals; adding a first aluminum source solution into the slurry containing the 13X type molecular sieve crystals to obtain a reaction solution system with a second set silicon-aluminum ratio, and then performing crystallization to obtain the 13X type molecular sieve. In the single-cation synthesis system, the aluminum source solution is added before crystallization, the silicon-aluminum ratio of the synthesis system is adjusted to 2.0-2.1, and the silicon-aluminum ratio of the product after crystallization can reach the low silicon-aluminum ratio requirement of 2.0-2.2. A 13X molecular sieve with a low silicon-aluminum ratio is obtained, and the problem of difficult mother liquor treatment is avoided, and the generated mother liquor can be directly recycled.

Description

Technical Field

[0001] This application relates to the field of preparation of octahedral zeolite molecular sieves, and more particularly to a 13X type molecular sieve and its preparation method. Background Technology

[0002] 13X zeolite, due to its excellent ion exchange, catalytic, and adsorption properties, has been widely used in petrochemical, environmental protection, building materials, and agriculture and animal husbandry. 13X zeolite has an octahedral zeolite structure, with its main body being a silicon (aluminum) oxygen framework. The lower the silicon-to-aluminum ratio, the more aluminum-oxygen tetrahedra are in the zeolite framework, the greater the cation charge density bonded to the aluminum-oxygen tetrahedra, and the better the adsorption and catalytic performance of the zeolite. Generally, X-type zeolite with a silicon-to-aluminum ratio above 2.5 is called high-silicon X-type zeolite, X-type zeolite with a silicon-to-aluminum ratio between 2.2 and 2.5 is called medium-silicon X-type zeolite, and X-type zeolite with a silicon-to-aluminum ratio between 2.0 and 2.2 is called low-silicon X-type zeolite. Low-silicon X-type zeolite has better adsorption capabilities for H2O and CO2, making it more suitable for deep gas drying, air separation, and other industries for removing moisture and CO2 from the air. Therefore, the adsorption performance of the molecular sieve directly affects its dehydration and CO2 removal capabilities.

[0003] Currently, the industrial production of low-silica 13X zeolite molecular sieves generally employs a dual-cation system for synthesis, followed by sodium chloride exchange after the material has undergone qualified crystallization. This process is cumbersome, and the treatment of the dual-cation mother liquor and the mother liquor after sodium chloride exchange is extremely difficult. Summary of the Invention

[0004] This application provides a 13X type molecular sieve and its preparation method to solve the following technical problem: how to reduce the silicon-to-aluminum ratio of the 13X type molecular sieve.

[0005] In a first aspect, this application provides a method for preparing a 13X type molecular sieve, the method comprising:

[0006] Sodium aluminosilicate gel slurry was obtained through a reaction solution system having a first predetermined silica-to-alumina ratio.

[0007] Seed crystals were added to the sodium aluminosilicate gel slurry, and then aged to obtain a slurry containing 13X type molecular sieve crystals;

[0008] A first aluminum source solution is added to the slurry containing 13X type molecular sieve crystals to obtain a reaction solution system with a set second set silicon-aluminum ratio, and then crystallization is performed to obtain 13X type molecular sieve.

[0009] Optionally, the first set silicon-to-aluminum ratio is 2.6 to 3.0.

[0010] Optionally, the reaction solution system having a first predetermined silicon-to-aluminum ratio includes: a silicon source solution and a second aluminum source solution; wherein,

[0011] The silicon source solution meets the following specifications: the SiO2 content is 200 g / L to 220 g / L, and the Na2O content is 80 g / L to 100 g / L.

[0012] The second aluminum source solution meets the following specifications: the content of Al2O3 is 70 g / L to 85 g / L, and the content of Nk is 60 g / L to 70 g / L.

[0013] Optionally, the reaction temperature of the reaction solution system is 20–25°C.

[0014] Optionally, the first aluminum source solution and the second aluminum source solution have the same specifications.

[0015] Optionally, the second set silicon-to-aluminum ratio is 2.0 to 2.1.

[0016] Optionally, the aging process parameters include: an aging temperature of 40℃~50℃ and an aging time of 34h~36h.

[0017] Optionally, the crystallization process parameters include: a crystallization temperature of 90℃~100℃ and a crystallization time of 3h~6h.

[0018] Optionally, the seed crystal is 1‰ to 3‰ of the volume of the mother liquor containing 13X type molecular sieve crystals.

[0019] Secondly, this application provides a 13X type molecular sieve prepared by the method described in any one embodiment of the first aspect.

[0020] The technical solutions provided in this application have the following advantages compared with the prior art:

[0021] The method for preparing the 13X molecular sieve provided in this application includes: obtaining a sodium aluminosilicate gel slurry through a reaction solution system having a first set silicon-to-aluminum ratio; adding seed crystals to the sodium aluminosilicate gel slurry and then aging it to obtain a slurry containing 13X molecular sieve crystals; adding a first aluminum source solution to the slurry containing 13X molecular sieve crystals to obtain a reaction solution system having a second set silicon-to-aluminum ratio, and then crystallizing it to obtain the 13X molecular sieve. Adding seed crystals to sodium aluminosilicate gel slurry can induce the formation of 13X crystal nuclei in the sodium aluminosilicate gel mother liquor, thereby stabilizing the 13X molecular sieve crystal system. Aging of the sodium aluminosilicate gel slurry after seed crystal addition promotes the dispersion of the sodium aluminosilicate gel and the formation of crystal nuclei, while preventing the appearance of impurities, resulting in a slurry containing uniform and pure 13X molecular sieve crystals. The concentrations of residual Al2O3 and SiO2 in the mother liquor of the slurry containing 13X molecular sieve crystals are in equilibrium. The first aluminum source solution reacts with the residual SiO2 in the mother liquor to form sodium aluminosilicate gel, thereby reducing the concentration of impurities in the mother liquor. The SiO2 content is reduced, thus breaking the above dynamic equilibrium. After the dynamic equilibrium is broken, the crystallization stage begins. Under the induction of a large number of crystallized 13X molecular sieve crystals, the sodium aluminosilicate gel rapidly forms new 13X molecular sieve crystals, and the whole system forms a new dynamic equilibrium stage. At the same time, the crystallized 13X molecular sieve crystals undergo dissolution and recrystallization. During this process, the SiO2 in the 13X molecular sieve crystals enters the mother liquor, thereby increasing the SiO2 content in the mother liquor and reducing the SiO2 content in the 13X molecular sieve crystals, ultimately achieving a reduction in the Si-aluminum ratio of the 13X molecular sieve. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart illustrating a method for preparing a 13X type molecular sieve, as provided in an embodiment of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0027] In this application, the terms "including" or "comprising" mean "including but not limited to".

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0029] Firstly, this application provides a method for preparing 13X type molecular sieves. Figure 1 A schematic flowchart illustrating a method for preparing a 13X type molecular sieve provided in this application embodiment; please refer to... Figure 1 The method includes:

[0030] S1. A sodium aluminosilicate gel slurry is obtained through a reaction solution system having a first set silica-alumina ratio;

[0031] In some embodiments, the first set silicon-to-aluminum ratio is 2.6 to 3.0.

[0032] In some embodiments, the reaction solution system having a first predetermined silicon-to-aluminum ratio comprises: a silicon source solution and a second aluminum source solution; wherein,

[0033] The silicon source solution meets the following specifications: the SiO2 content is 200 g / L to 220 g / L, and the Na2O content is 80 g / L to 100 g / L.

[0034] The second aluminum source solution meets the following specifications: the content of Al2O3 is 70 g / L to 85 g / L, and the content of Nk is 60 g / L to 70 g / L.

[0035] Optionally, the reaction temperature of the reaction solution system is 20–25°C.

[0036] In the embodiments of this application, generally, the silicon source solution is water glass, and the second aluminum source solution is sodium aluminate solution. The SiO2 content in the water glass can be 200 g / L to 220 g / L. The reason is that it can reduce the degree of polymerization of the water glass, so that while meeting the requirements of 13X synthesis, it can accelerate the recrystallization of crystals in the subsequent crystallization stage, making it easier for SiO2 to enter the mother liquor, thereby achieving the purpose of reducing the silicon-to-aluminum ratio of the 13X molecular sieve. The Na2O content in the water glass can be 80 g / L to 100 g / L. The reason is that it can ensure the modulus requirements of the water glass and ensure that the degree of polymerization of the water glass meets the process requirements. For example, the SiO2 content in the above-mentioned water glass can be 200 g / L, 205 g / L, 210 g / L, 215 g / L, 220 g / L, etc.; and the Na2O content can be 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, etc.

[0037] The Al₂O₃ content in the sodium aluminate solution can be 70 g / L to 85 g / L because it ensures the solid content of the gel reaction system, meeting the requirements of production efficiency. The Nk content in the sodium aluminate solution can be 60 g / L to 70 g / L because it provides an alkaline environment for the gel reaction system. For example, the Al₂O₃ content in the above-mentioned sodium aluminate solution can be 70 g / L, 75 g / L, 80 g / L, 85 g / L, etc.; and the Nk content can be 60 g / L, 65 g / L, 70 g / L, etc.

[0038] Under the premise of meeting the above-mentioned indicators of water glass and sodium aluminate solution, combined with the first set silica-alumina ratio and the chemical reaction temperature of the gel being 20-25°C, this temperature can make the sodium aluminosilicate gel formed by the reaction of water glass and sodium aluminate stable and conducive to subsequent crystallization. For example, the above-mentioned first set silica-alumina ratio can be 2.6, 2.7, 2.8, 2.9, 3.0, etc., and the reaction temperature of the above-mentioned reaction solution system can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, etc.

[0039] S2. Add seed crystals to the sodium aluminosilicate gel slurry, and then age it to obtain a slurry containing 13X type molecular sieve crystals;

[0040] In some embodiments, the seed crystal is 1‰ to 3‰ of the volume of the slurry containing 13X type molecular sieve crystals.

[0041] In this embodiment, adding seed crystals to a sodium aluminosilicate gel having a first predetermined silica-to-alumina ratio can induce the formation of 13X crystal nuclei in the sodium aluminosilicate gel slurry, thereby stabilizing the 13X type molecular sieve crystal system. For example, the seed crystals can be 1‰, 2‰, 3‰, or other fractions of the volume of the sodium aluminosilicate gel slurry.

[0042] In some embodiments of this application, the aging process parameters include: an aging temperature of 40℃~50℃ and an aging time of 34h~36h.

[0043] In this embodiment, the sodium aluminosilicate gel slurry with added seed crystals is aged to promote the dispersion of the sodium aluminosilicate gel and the generation of crystal nuclei, while avoiding the appearance of impurities, resulting in a slurry containing uniform and pure 13X type molecular sieve crystals. For example, the aging temperature can be 40℃, 42℃, 44℃, 46℃, 48℃, 50℃, etc.; the aging time can be 34h, 35h, 36h, etc.

[0044] S3. Add a first aluminum source solution to the slurry containing 13X type molecular sieve crystals to obtain a reaction solution system with a set second set silicon-aluminum ratio, and then crystallize to obtain 13X type molecular sieve.

[0045] In some embodiments, the first aluminum source solution and the second aluminum source solution have the same specifications.

[0046] In some embodiments, the second set silicon-to-aluminum ratio is 2.0 to 2.1.

[0047] In this embodiment, both the first aluminum source solution and the second aluminum source solution are sodium aluminate solutions and can have the same concentration. The amount of silicon source solution and the second aluminum source solution added is calculated based on a first predetermined silicon-to-aluminum ratio, and the amount of the first aluminum source solution added is calculated based on a second predetermined silicon-to-aluminum ratio. For example, the second predetermined silicon-to-aluminum ratio can be 2.0, 2.02, 2.04, 2.06, 2.08, 2.1, etc.

[0048] In some embodiments, the crystallization process parameters include: a crystallization temperature of 90°C to 100°C and a crystallization time of 3h to 6h.

[0049] In this embodiment, seed crystals are added to the sodium aluminosilicate gel slurry, followed by aging. The slurry containing 13X molecular sieve crystals enters a dynamic equilibrium, meaning the concentrations of Al2O3 and SiO2 in the mother liquor remain relatively constant for a period of time. The entire system is about to enter the crystal dissolution-recrystallization, crystal growth, and maturation stage. At this point, sodium aluminate solution is added, reacting with the residual SiO2 in the mother liquor to form a gel, causing a sharp decrease in SiO2 in the mother liquor, thus breaking the established dynamic equilibrium. Entering the crystallization stage, the gel rapidly forms 13X crystals under the induction of a large number of 13X crystals, and the system enters a new dynamic equilibrium stage. Simultaneously, driven by temperature, the 13X crystals dissolve and recrystallize. During this process, SiO2 from the 13X crystals enters the mother liquor, causing the SiO2 content in the mother liquor to slowly increase, thereby reducing the SiO2 content in the 13X crystals and achieving the goal of reducing the silicon-aluminum ratio of the 13X product. Therefore, when the product's crystallinity reaches 70-75% after aging, the first aluminum source solution is added. At this point, the already crystallized crystals are about to enter the dissolution-recrystallization stage. Simultaneously, the already crystallized product in the system acts as a seed crystal, effectively inducing the gel formed after the addition of sodium aluminate. The crystallization temperature can be 90℃-100℃, and the crystallization time can be 3h-6h, allowing the system to quickly enter the crystallization stage, accelerating the establishment of a new equilibrium, and providing sufficient kinetic energy for faster and more complete dissolution-recrystallization. For example, the crystallization temperatures can be 90℃, 92℃, 94℃, 96℃, 98℃, 100℃, etc.; and the crystallization times can be 3h, 4h, 5h, 6h, etc.

[0050] In summary, the method for preparing 13X molecular sieves provided in this application involves adding sodium aluminate solution to a single-cation synthesis system before crystallization to adjust the silica-alumina ratio of the synthesis system to 2.0–2.1. The resulting crystallized product achieves a low silica-alumina ratio of 2.0–2.2. This method solves the problem of producing various types of 13X molecular sieves using a single synthesis system while avoiding the difficulty of mother liquor treatment, as the generated mother liquor can be directly recycled.

[0051] Secondly, this application provides a 13X type molecular sieve prepared by the method described in any one embodiment of the first aspect.

[0052] The 13X molecular sieve is realized based on the preparation method of the 13X molecular sieve described above. The specific steps of the preparation method of the 13X molecular sieve can be referred to the above embodiments. Since the 13X molecular sieve adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0053] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0054] Example 1

[0055] 5m of water glass with a temperature of 21.5℃ and a concentration of SiO2: 202.3g / L and Na2O: 92.6g / L was prepared. 3 The solution was poured into a synthesis tank, and under stirring, 8.1 m³ of sodium aluminate solution at a temperature of 23.2℃, a concentration of Al₂O₃: 74.8 g / L, and Nk: 63.7 g / L was continuously injected. 3 At this point, the silicon-to-aluminum ratio was 2.83. After the reaction, 3‰ of the volume of sodium aluminosilicate gel slurry was added as a guiding agent. After aging at 43℃ for 36 hours, 3.4m³ of sodium aluminate solution was added. 3 At this point, the silicon-to-aluminum ratio is 2.0. After crystallizing at a crystallization temperature of 97°C for 3 hours, the material is discharged. After separation, washing, and drying, it becomes the low-silicon 13X molecular sieve product.

[0056] Example 2

[0057] 5m of water glass at 24.5℃ with a concentration of SiO2: 212.6 g / L and Na2O: 96.4 g / L was prepared. 3 The solution was poured into a synthesis tank, and under stirring, 8.2 m³ of sodium aluminate solution at a temperature of 23.5℃ with a concentration of Al₂O₃: 81.2 g / L and Nk: 69.1 g / L was continuously injected. 3 At this point, the silicon-to-aluminum ratio was 2.70. After the reaction, 3‰ of the volume of sodium aluminosilicate gel slurry was added as a guiding agent. After aging at 43℃ for 36 hours, 2.6m of sodium aluminate solution was added. 3 At this point, the silicon-to-aluminum ratio is 2.06. After crystallizing at a crystallization temperature of 90℃ for 3 hours, the material is discharged. After separation, washing, and drying, it becomes the low-silicon 13X molecular sieve product.

[0058] Example 3

[0059] 5m of water glass at 24.5℃ with a concentration of SiO2: 212.6 g / L and Na2O: 96.4 g / L was prepared. 3 The solution was poured into a synthesis tank, and under stirring, 7.5 mL of a sodium aluminate solution at a temperature of 23.5℃ with a concentration of Al₂O₃: 81.2 g / L and Nk: 69.1 g / L was continuously injected. 3At this point, the silicon-to-aluminum ratio was 2.96. After the reaction, 3‰ of the volume of sodium aluminosilicate gel slurry was added as a guiding agent. After aging at 43℃ for 36 hours, 6.0 ml of sodium aluminate solution was added. 3 At this point, the silicon-to-aluminum ratio is 2.0. After crystallizing at a crystallization temperature of 90℃ for 3 hours, the material is discharged. After separation, washing, and drying, it becomes the low-silicon 13X molecular sieve product.

[0060] Comparative Example 1

[0061] 5m of water glass with a temperature of 21.5℃ and a concentration of SiO2: 202.3g / L and Na2O: 92.6g / L was prepared. 3 The solution was poured into a synthesis tank, and under stirring, 8.1 m³ of sodium aluminate solution at a temperature of 23.2℃, a concentration of Al₂O₃: 74.8 g / L, and Nk: 63.7 g / L was continuously injected. 3 At this point, the silicon-to-aluminum ratio is 2.83. After the reaction, 3‰ of the volume of sodium aluminosilicate gel slurry is added as a guiding agent. After aging at 43℃ for 36 hours, the temperature is raised to enter the crystallization process. After crystallization at 95℃ for 3 hours, the material is discharged. After separation, washing, and drying, it becomes the 13X molecular sieve product.

[0062] The composition of the 13X molecular sieve products obtained in Examples 1-3 and Comparative Example 1 was analyzed. Please refer to Table 1 for the composition (wt%) of the 13X molecular sieve products.

[0063] Table 1. Composition (wt%) of 13X molecular sieve products

[0064] Example 1 32.45 27.44 15.68 2.01 Example 2 32.58 26.29 15.59 2.11 Example 3 33.11 27.37 15.78 2.06 Comparative Example 1 34.74 24.29 13.80 2.43

[0065] As shown in Table 1, a low silicon-to-aluminum ratio of 2.0 to 2.2 can be obtained by using a 13X type molecular sieve and its preparation method according to the embodiments of this application.

[0066] One or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0067] (1) In the single-cation synthesis system, sodium aluminate solution is added before crystallization to adjust the silicon-to-aluminum ratio of the synthesis system to 2.0–2.1. The silicon-to-aluminum ratio of the crystallized product can reach the low silicon-to-aluminum ratio requirement of 2.0–2.2. In this way, a 13X molecular sieve with a low silicon-to-aluminum ratio is obtained, while avoiding the problem of difficult mother liquor treatment. The resulting mother liquor can be directly recycled.

[0068] (2) When the product crystallinity reaches 70-75%, sodium aluminate solution is added a second time. At this time, the crystallized crystals are about to enter the dissolution and recrystallization stage. Meanwhile, the crystallized product in the system acts as a seed crystal, which plays a good inducing role in the gel formed after the addition of sodium aluminate.

[0069] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing 13X type molecular sieve, characterized in that, The method includes: Sodium aluminosilicate gel slurry was obtained through a reaction solution system having a first predetermined silica-to-alumina ratio. Seed crystals were added to the sodium aluminosilicate gel slurry, followed by aging, to obtain a mother liquor containing 13X type molecular sieve crystals; A first aluminum source solution is added to the mother liquor containing 13X molecular sieve crystals to obtain a reaction solution system with a set second set silicon-aluminum ratio, and then crystallization is performed to obtain 13X molecular sieve. The first set silicon-to-aluminum ratio is 2.6 to 3.

0.

2. The method according to claim 1, characterized in that, The reaction solution system having a first predetermined silicon-to-aluminum ratio comprises: a silicon source solution and a second aluminum source solution; wherein... The silicon source solution meets the following specifications: the SiO2 content is 200g / L~220g / L, and the Na2O content is 80g / L~100g / L. The second aluminum source solution meets the following specifications: the content of Al2O3 is 70 g / L to 85 g / L, and the content of Nk is 60 g / L to 70 g / L.

3. The method according to claim 2, characterized in that, The reaction temperature of the reaction solution system is 20~25℃.

4. The method according to claim 2, characterized in that, The first aluminum source solution has the same specifications as the second aluminum source solution.

5. The method according to claim 1, characterized in that, The second set silicon-to-aluminum ratio is 2.0 to 2.

1.

6. The method according to claim 1, characterized in that, The aging process parameters include: aging temperature of 40℃~50℃ and aging time of 34h~36h.

7. The method according to claim 1, characterized in that, The crystallization process parameters include: crystallization temperature of 90℃~100℃ and crystallization time of 3h~6h.

8. The method according to claim 1, characterized in that, The seed crystal is 1‰ to 3‰ of the volume of the slurry containing 13X type molecular sieve crystals.

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