13X type molecular sieve and preparation method thereof

Abstract

The invention relates to a 13X type molecular sieve and a preparation method thereof. The method comprises the following steps: obtaining sodium aluminosilicate gel slurry through a reaction solution system with a first set silica-alumina ratio; adding a seed crystal into the sodium aluminosilicate gel slurry, and aging to obtain slurry containing 13X type molecular sieve crystals; and 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 silica-alumina ratio, and then crystallizing to obtain the 13X type molecular sieve. In the monocation synthesis system, the aluminum source solution is added before crystallization, the silica-alumina ratio of the synthesis system is adjusted to 2.0-2.1, and the silica-alumina ratio of the crystallized product can reach the low silica-alumina ratio requirement of 2.0-2.2. The 13X molecular sieve with the low silica-alumina ratio is obtained, meanwhile, the problem that mother liquor is difficult to treat is solved, and the generated mother liquor can be directly recycled.

Description

Technical Field

[0001] The present application relates to the field of preparation of faujasite molecular sieves, and in particular to a 13X type molecular sieve and a preparation method thereof. Background Art

[0002] Zeolite 13X has been widely used in many fields such as petrochemical industry, environmental protection, building materials and agriculture and animal husbandry due to its good ion exchange, catalytic and adsorption properties. Zeolite 13X has an eight-sided zeolite structure, and its main body is a silicon (aluminum) oxygen skeleton. The lower the silicon-aluminum ratio, the more aluminum-oxygen tetrahedrons there are in the zeolite skeleton, the greater the cationic charge density combined with the aluminum-oxygen tetrahedron, and the better the adsorption and catalytic properties of the zeolite. Generally, the X-type zeolite with a silicon-aluminum ratio of more than 2.5 is called high-silicon X-type zeolite, the X-type zeolite with a silicon-aluminum ratio between 2.2 and 2.5 is called medium-silicon X-type zeolite, and the X-type zeolite with a silicon-aluminum ratio between 2.0 and 2.2 is called low-silicon X-type zeolite. Low-silicon X-type zeolite has better adsorption of H2O and CO2, and is more suitable for deep drying of gas, air separation and other industries, and is used to remove moisture and CO2 from the air. Therefore, the adsorption performance of the molecular sieve will affect the ability to dehydrate and remove CO2.

[0003] At present, the industrial production of low-silicon 13X zeolite molecular sieves generally adopts the synthesis of the double cation system, and the qualified crystallized material is exchanged with sodium chloride. This process is cumbersome, and the treatment of the double cation mother liquor and the mother liquor after sodium chloride exchange is very difficult. Summary of the invention

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

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

[0006] Obtaining sodium aluminosilicate gel slurry through a reaction solution system having a first set silicon-to-aluminum ratio;

[0007] adding seed crystals to the sodium aluminosilicate gel slurry, followed by aging to obtain a slurry containing 13X molecular sieve crystals;

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

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

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

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

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

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

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

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

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

[0019] In a second aspect, the present application provides a 13X molecular sieve prepared by the method described in any embodiment of the first aspect.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The preparation method of the 13X molecular sieve provided in an embodiment of the present application comprises: 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 to obtain a slurry containing 13X molecular sieve crystals; adding a first aluminum source solution to the slurry containing the 13X molecular sieve crystals to obtain a reaction solution system having a second set silicon-to-aluminum ratio, and then crystallizing to obtain a 13X molecular sieve. Adding seed crystals to the sodium aluminosilicate gel slurry can induce the formation of 13X crystal nuclei in the sodium aluminosilicate gel mother liquor to stabilize the 13X molecular sieve crystal system; the sodium aluminosilicate gel slurry after adding seed crystals is aged to promote the dispersion of the sodium aluminosilicate gel and the generation of crystal nuclei, and avoid the appearance of impurity crystals, so as to obtain a slurry containing uniform and pure 13X molecular sieve crystals; the concentrations of Al2O3 and SiO2 remaining in the mother liquor in the slurry containing 13X molecular sieve crystals are in a balanced state, and the first aluminum source solution reacts with the SiO2 remaining in the mother liquor to form sodium aluminosilicate gel, thereby reducing the concentration of Al2O3 and SiO2 in the mother liquor. The SiO2 content in the 13X molecular sieve crystals is reduced, thereby breaking the above dynamic balance; after breaking the dynamic balance, the crystallization stage is entered, and the sodium aluminosilicate gel quickly forms new 13X molecular sieve crystals under the induction of a large number of crystallized 13X molecular sieve crystals, and the whole system forms a new dynamic equilibrium stage. At the same time, the crystallized 13X molecular sieve crystals are dissolved and recrystallized. In this process, the SiO2 in the 13X molecular sieve crystals will enter the mother liquor, thereby increasing the SiO2 content in the mother liquor, thereby reducing the SiO2 content in the 13X molecular sieve crystals, and finally achieving the reduction of the silicon-to-aluminum ratio of the 13X molecular sieve. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 A schematic flow chart of a method for preparing a 13X molecular sieve provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

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

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

[0029] In a first aspect, the present application provides a method for preparing a 13X molecular sieve. Figure 1 A schematic diagram of a process for preparing a 13X molecular sieve provided in an embodiment of the present application; see Figure 1 , the method comprising:

[0030] S1, obtaining a sodium aluminosilicate gel slurry through a reaction solution system having a first set silicon-to-aluminum ratio;

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

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

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

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

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

[0036] In the embodiment of the present application, generally speaking, the silicon source solution is water glass, and the second aluminum source solution is sodium aluminate solution. The content of SiO2 in water glass can be 200g / L~220g / L, because: it can reduce the polymerization degree of water glass, so that it can accelerate the subsequent crystallization stage of crystal recrystallization under the premise of meeting the synthesis requirements of 13X, so that SiO2 can easily enter the mother liquor, thereby achieving the purpose of reducing the silicon-aluminum ratio of 13X type molecular sieve. The content of Na2O in water glass can be 80g / L~100g / L, because: to ensure the water glass modulus requirements, to ensure that the degree of polymerization of water glass meets the process requirements. Exemplarily, in the above-mentioned water glass, the content of SiO2 can be 200g / L, 205g / L, 210g / L, 215g / L, 220g / L, etc.; the content of Na2O can be 80g / L, 85g / L, 90g / L, 95g / L, 100g / L, etc.

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

[0038] Under the premise of meeting the above-mentioned indicators of water glass and the above-mentioned indicators of sodium aluminate solution, combined with the first set silicon-aluminum ratio, and the temperature at which the gel undergoes chemical reaction is 20-25°C, this temperature can make the sodium aluminosilicate gel generated by the reaction of water glass and sodium aluminate stable and conducive to later crystallization. Exemplarily, the above-mentioned first set silicon-aluminum 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, adding seed crystals to the sodium aluminosilicate gel slurry, and then aging to obtain a slurry containing 13X molecular sieve crystals;

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

[0041] In the embodiment of the present application, adding seed crystals to the sodium aluminosilicate gel having the first set silicon-aluminum ratio can induce the formation of 13X crystal nuclei in the sodium aluminosilicate gel slurry to stabilize the 13X type molecular sieve crystal system. Exemplarily, the seed crystals can be 1‰, 2‰, 3‰, etc. of the volume of the sodium aluminosilicate gel slurry.

[0042] In the examples of the present application, in some implementation methods, the aging process parameters include: an aging temperature of 40° C. to 50° C., and an aging time of 34 h to 36 h.

[0043] In the embodiment of the present application, the sodium aluminosilicate gel slurry after adding the seed crystal is aged to promote the dispersion of the sodium aluminosilicate gel and the generation of crystal nuclei, and to avoid the appearance of impurity crystals, so as to obtain a slurry containing uniform and pure 13X molecular sieve crystals. Exemplarily, the aging temperature can be 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, etc.; the aging time can be 34h, 35h, 36h, etc.

[0044] S3. Adding the first aluminum source solution to the slurry containing the 13X molecular sieve crystals to obtain a reaction solution system having a set second set silicon-aluminum ratio, and then performing crystallization to obtain the 13X 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 2.0-2.1.

[0047] In the embodiment of the present application, the first aluminum source solution and the second aluminum source solution are both sodium aluminate solutions and may have the same concentration. The addition amount of the silicon source solution and the second aluminum source solution is calculated by the first set silicon-aluminum ratio, and the addition amount of the first aluminum source solution is calculated by the second set silicon-aluminum ratio. Exemplarily, the second set silicon-aluminum ratio may 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 3 h to 6 h.

[0049] In the embodiment of the present application, seed crystals are added to the sodium aluminosilicate gel slurry, and then aged. The slurry containing 13X molecular sieve crystals will enter a dynamic equilibrium, that is, the concentrations of Al2O3 and SiO2 in the mother liquor remain substantially unchanged for a period of time, and the entire system is about to enter the crystal dissolution recrystallization, crystal growth and improvement stage. At this time, sodium aluminate solution is added to react with the SiO2 residual in the mother liquor to form a gel, which sharply reduces the SiO2 in the mother liquor, thereby breaking the dynamic equilibrium that has been formed. Entering the crystallization stage, the gel quickly forms 13X crystals under the induction of a large number of 13X crystals, and the system enters a stage of establishing a new dynamic equilibrium. At the same time, driven by temperature, the 13X crystals dissolve and recrystallize. In this process, the SiO2 in the 13X crystals will enter 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 purpose of reducing the silicon-aluminum ratio of the 13X product. Therefore, when the product is aged to a crystallinity of 70-75%, the first aluminum source solution is added. At this time, the crystallized crystals are about to enter the dissolution and recrystallization stage. At the same time, the crystallized products in the system act as seeds, which play a good inducing role in the gel formed after the addition of sodium aluminate. The crystallization temperature can be 90°C to 100°C, and the crystallization time can be 3h to 6h, so that the system can quickly enter the crystallization stage, accelerate the establishment of a new equilibrium, and provide sufficient kinetic energy for crystallization, so that the dissolution and recrystallization of the crystals are faster and more sufficient. Exemplarily, the above-mentioned crystallization temperature can be 90°C, 92°C, 94°C, 96°C, 98°C, 100°C, etc.; the above-mentioned crystallization time can be 3h, 4h, 5h, 6h, etc.

[0050] In summary, the present application provides a method for preparing a 13X molecular sieve. In a single cation synthesis system, sodium aluminate solution is added before crystallization to adjust the silicon-aluminum ratio of the synthesis system 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. In this way, the problem of producing various types of 13X molecular sieves in one synthesis system can be solved, and the problem of difficulty in handling mother liquor can be avoided, and the generated mother liquor can be directly recycled.

[0051] In a second aspect, the present application provides a 13X molecular sieve prepared by the method described in any embodiment of the first aspect.

[0052] The 13X molecular sieve is realized based on the preparation method of the above-mentioned 13X molecular sieve. The specific steps of the preparation method of the 13X molecular sieve can refer to the above-mentioned embodiment. Since the 13X molecular sieve adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0053] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0054] Example 1

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

[0056] Example 2

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

[0058] Example 3

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

[0060] Comparative Example 1

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

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

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

[0064] serial number <![CDATA[SiO2 / wt%]]> <![CDATA[Al2O3 / wt%]]> <![CDATA[Na2O / wt%]]> Si / Al 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] It can be seen from Table 1 that a 13X molecular sieve and a preparation method thereof according to an embodiment of the present application can achieve a low silicon-to-aluminum ratio requirement of 2.0 to 2.2.

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

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

[0068] (2) When the product is aged to a crystallinity of 70-75%, sodium aluminate solution is added for the second time. At this time, the crystals that have already crystallized are about to enter the dissolution recrystallization stage. At the same time, 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 only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a 13X molecular sieve, characterized in that: The method comprises: Obtaining 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, followed by aging to obtain a mother liquor containing 13X molecular sieve crystals; A first aluminum source solution is added to the slurry containing the 13X molecular sieve crystals to obtain a reaction solution system having a second set silicon-aluminum ratio, and then crystallization is performed to obtain the 13X molecular sieve.

2. The method according to claim 1, characterized in that The first set silicon-to-aluminum ratio is 2.6-3.

0.

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

4. The method according to claim 3, characterized in that The reaction temperature of the reaction solution system is 20-25°C.

5. The method according to claim 3, characterized in that: The first aluminum source solution and the second aluminum source solution have the same index.

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

1.

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

8. The method according to claim 1, characterized in that The process parameters of the crystallization include: a crystallization temperature of 90° C. to 100° C. and a crystallization time of 3 h to 6 h.

9. The method according to claim 1, characterized in that: The seed crystals account for 1‰ to 3‰ of the volume of the slurry containing 13X molecular sieve crystals.

10. A 13X molecular sieve prepared by the method according to any one of claims 1 to 9.

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