Lithium ion modified zeolite molecular sieve and preparation method thereof
Through the simplified preparation method, the lithium salt solution is directly mixed with the 13X zeolite molecular sieve and stirred, heated, filtered and dried, and obtained a lithium ion modified zeolite molecular sieve with a high specific surface area and an optimized pore structure, which solves the problem of hydrogen production by ammonia cleavage and high hydrogen The problem of difficulty in obtaining purity hydrogen reduces production difficulty and cost and is suitable for industrial applications.
Patent Information
- Application Number
- CN202411342670.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-25
- Publication Date
- 2024-12-31
AI Technical Summary
It is difficult to obtain high-purity hydrogen during the hydrogen production process of ammonia cracking, and the preparation process of existing lithium-ion modified zeolite molecular sieve is cumbersome and costly, which affects industrial development.
The preparation process is simplified by directly mixing the 13X zeolite molecular sieve with the lithium salt solution to stir, heat, filter and drying, and the preparation process is obtained to obtain a lithium-ion modified zeolite molecular sieve with a large specific surface area and an optimized pore structure.
It realizes efficient ammonia adsorption, simplifies the preparation process, reduces production costs, improves the stability and mechanical strength of the materials, and is suitable for industrial applications.
Smart Images
Figure CN119219015A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of modified molecular sieves, and in particular to a lithium ion modified zeolite molecular sieve and a preparation method thereof. Background Art
[0002] As an important component of clean energy, the development of hydrogen energy is necessary to achieve energy transformation and carbon neutrality goals. With the continuous advancement of technology, hydrogen energy technology is developing in the direction of high efficiency, low cost and sustainability. As an important form of storage and conversion of hydrogen energy, ammonia cracking has the advantages of high energy density, low-cost storage and transportation, and zero carbon emissions at the terminal, and has attracted much attention. However, it is difficult to obtain high-purity hydrogen in the process of ammonia cracking hydrogen production, which has become a key technology and core issue restricting its widespread application. In order to overcome this problem, the development of high-performance adsorption materials has become the key.
[0003] Zeolite molecular sieve is a type of adsorption material with unique structure and excellent performance. It has uniform and controllable pore size, high specific surface area, and relatively stable skeleton structure. It is widely used in adsorption, purification, drying and other fields. 13X zeolite molecular sieve has a large pore structure and high pore volume, and its low silicon-aluminum ratio gives it certain thermal stability and mechanical strength. It is often used for hydrogen purification. However, a certain amount of ammonia usually remains in the hydrogen after adsorption separation and purification. The presence of ammonia impurities will have a significant adverse effect on subsequent hydrogen energy applications, such as hydrogen refueling stations, fuel cells, etc.
[0004] Therefore, modifying the molecular sieve and improving its selective adsorption performance is the key to achieving ammonia-hydrogen separation and obtaining high-purity hydrogen. The diameter of lithium ions is smaller than that of sodium ions, so they can occupy more positions in the crystal structure, and Li +The coordination effect with NH3 helps to achieve high-capacity capture of ammonia. Therefore, lithium-ion modified molecular sieves theoretically have higher adsorption capacity than sodium-type molecular sieves. At present, the modification methods of cationic zeolite molecular sieves mainly include: the preparation method of modified lithium low-silicon zeolite molecular sieves disclosed in patent CN113351157A and patent CN101125664A: a lithium ion modification method coupled with solution and solid-state modification, firstly modifying the calcined Na-LSX raw powder with lithium ion solution, and then modifying the product with lithium salt powder to obtain Li-LSX zeolite molecular sieve; patent CN101289196A discloses a preparation method of LiLSX molecular sieve, firstly exchanging LSX raw powder with K ion solution to obtain KLSX, and then exchanging KLSX with ammonium ion solution to obtain NH4LSX, and then modifying with lithium ion solution to obtain LiLS X, with lower Li ion consumption; Patent CN102502694A discloses a Li-modified X molecular sieve and a preparation method thereof, wherein NaX raw powder is first exchanged with an ammonium salt aqueous solution to obtain an NH4NaX molecular sieve, and then the NH4NaX molecular sieve is exchanged with a lithium salt solution, dried and calcined to obtain a Li-modified X molecular sieve; Patent CN103539150A discloses a preparation method for a low silicon-aluminum ratio X-type zeolite molecular sieve [(Li,Ca)-LSX], wherein the calcined and activated Na-LSX zeolite is first mixed with a lithium salt solution, water-bathed and repeated to obtain a (Li,Na)-LSX zeolite, and then the zeolite is placed in a calcium salt solution for mixing, water-bathed and repeated, and dried and calcined to obtain a (Li,Ca)-LSX zeolite molecular sieve.
[0005] However, the preparation process of the above existing methods is relatively complicated, difficult to implement, high in cost, and has a certain impact on the environment, which limits its industrial development. Summary of the invention
[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a lithium ion modified zeolite molecular sieve and a preparation method thereof. The prepared lithium ion modified zeolite molecular sieve has a larger specific surface area, a more optimized pore structure, and a higher ammonia adsorption capacity.
[0007] In order to achieve the above object, the present invention adopts the following technical solutions:
[0008] A lithium ion modified zeolite molecular sieve is composed of a plurality of beta cages, with a framework silicon-aluminum ratio (Si / Al) of 1 to 1.5 and a porosity of 0.45 to 0.65.
[0009] Preferably, the chemical composition of the molecular sieve is expressed as xLi2O·yNa2O·Al2O3·nSiO2·6H2O, wherein 0.25≤x≤0.95, 0.85≤x+y≤1.2, and 1.9≤n≤2.2.
[0010] Preferably, the BET specific surface area is 460 to 740 m 2 / g, and the pore size distribution is 1.25~1.85nm.
[0011] The present invention also provides a method for preparing a lithium ion modified zeolite molecular sieve, comprising the following steps:
[0012] Step 1, mixing: stirring and mixing a lithium salt solution of a certain concentration with 13X zeolite molecular sieve raw powder to obtain a mixed suspension;
[0013] Step 2, heating: heating the mixed suspension to a certain temperature, stirring continuously, stopping stirring after a certain reaction time, and cooling to room temperature;
[0014] Step 3, filtration: placing the mixed suspension obtained in the above step 2 in a centrifuge, separating the solid and liquid phases at a certain speed, filtering out the zeolite and washing it to obtain a modified zeolite molecular sieve solid powder;
[0015] Step 4, drying: the solid powder obtained in the above step 3 is placed in an oven for drying to obtain a lithium ion modified zeolite molecular sieve.
[0016] Preferably, in step 1, the lithium salt solution is a LiCl, LiF, Li2SO4 or LiNO3 solution, and the concentration of the lithium salt solution is 0.1 to 1.0 mol / L.
[0017] Preferably, in step 1, the stirring is performed mechanically by a magnetic stirrer, and the stirring speed of the magnetic stirrer is 200 to 2000 r / min.
[0018] Preferably, in step 2, the heating temperature is 60-110° C., and the reaction time is 4-24 hours. The heating is performed by a magnetic stirrer, and the mixture is naturally cooled to room temperature after the heating is completed.
[0019] Preferably, in step 3, the speed of the centrifuge is 1000-2000 rpm, the centrifugation time is 2-10 min, and the washing operation is repeated three or more times. During separation, the solid phase is filtered out with filter paper, and then washed with deionized water, and the centrifugation operation is repeated three or more times to wash away the attached ions.
[0020] Preferably, in step 4, the drying temperature is 100-150° C., and the drying time is 4-24 hours.
[0021] Preferably, the lithium ion modified zeolite molecular sieve has an ammonia adsorption capacity of 340 to 382 cm at 25°C and 0.6 MPa. 3 / g.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] 1. The present invention directly mixes and stirs 13X type zeolite with a lithium salt solution, reacts at a certain temperature, performs cation replacement, and obtains a modified zeolite after filtering and drying. No pretreatment of the molecular sieve is required, and no calcination or other processes are required. The modified molecular sieve is obtained by one-step replacement, which significantly simplifies the preparation process, reduces the production difficulty, reduces the production cost, and facilitates promotion and application.
[0024] 2. The modified zeolite prepared by the present invention has a higher degree of ion substitution and a higher specific surface area; its low silicon-aluminum ratio gives it a stronger mechanical strength, which can ensure its pore structure when subjected to greater stress, and the modified zeolite has a higher stability. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 TEM image of the lithium ion modified zeolite molecular sieve of the present invention;
[0026] Figure 2 The SEM image of the morphology of the lithium ion modified zeolite molecular sieve of the present invention;
[0027] Figure 3 It is the XPS chart of the lithium ion modified zeolite molecular sieve of the present invention (including Li 1s peak). DETAILED DESCRIPTION
[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.
[0029] Please refer to Figure 1 A lithium ion modified zeolite molecular sieve provided in an embodiment of the present invention is composed of several β cages, with a framework silicon-aluminum ratio (Si / Al) of 1 to 1.5 and a porosity of 0.45 to 0.65, and can be used in gas adsorption, separation, drying and screening and other fields.
[0030] The present invention also provides a method for preparing the lithium ion modified zeolite molecular sieve, which specifically comprises the following steps:
[0031] (1) Mixing: A lithium salt solution of a certain concentration is stirred and mixed with a 13X zeolite molecular sieve to obtain a suspension, wherein the lithium salt solution is a LiCl, LiF, Li2SO4 or LiNO3 solution, and the concentration of the lithium salt solution is 0.1 to 1.0 mol / L. During the mixing, a magnetic stirrer is used for mechanical stirring, and the stirring speed of the magnetic stirrer is 200 to 2000 r / min.
[0032] (2) Heating: The suspension obtained in the above (1) is heated to a target temperature and continuously stirred. After a period of reaction, stirring is stopped and the suspension is cooled to room temperature to obtain a mixed suspension. The target temperature is 60 to 110° C. and the stirring time is 4 to 24 hours. The suspension is heated by a magnetic stirrer and then cooled naturally after heating.
[0033] (3) Filtration: The mixed suspension obtained in the above (2) is placed in a centrifuge, and the solid and liquid phases are separated at a certain speed. The zeolite is filtered out and then washed. The centrifuge speed is 1000-2000 rpm, and the centrifugation time is 2-10 min. The washing operation is repeated three times or more to obtain a modified molecular sieve powder.
[0034] In specific implementation, during separation, the solid phase is filtered out with filter paper, then washed with deionized water, and the centrifugation operation is repeated three times or more.
[0035] (4) Drying: The modified molecular sieve powder obtained in the above (3) is placed in an oven for drying at a temperature of 90 to 150° C. for a time of 4 to 24 h to obtain a lithium ion modified zeolite molecular sieve.
[0036] The structures of the lithium ion zeolite modified molecular sieve prepared by the above method observed under transmission electron microscope and scanning electron microscope are as follows: Figure 1 , Figure 2 shown.
[0037] Example 1
[0038] 13X zeolite molecular sieve produced by Hebei Shangsu New Material Technology Co., Ltd. and lithium nitrate with Aladdin reagent product number L100136 were used. The mass ratio of zeolite molecular sieve original powder to lithium salt solution was 1:40. The mixture was mixed at 80°C and stirred for 4 hours at a stirring speed of 500r / min. The suspension obtained after mixing was centrifuged in a centrifuge at a centrifugal speed of 2000r / min. After filtering the solid, it was washed five times with deionized water. The solid was dried in an oven at 110°C for 10 hours to obtain a lithium ion modified zeolite molecular sieve.
[0039] Example 2
[0040] 13X zeolite molecular sieve produced by Dalian Haixin Chemical Co., Ltd. and lithium chloride with Aladdin reagent product number L116327 were used. The mass ratio of zeolite molecular sieve original powder to lithium salt solution was 1:30. The mixture was mixed at 110°C and stirred for 8 hours at a stirring speed of 400 r / min. The suspension obtained after mixing was centrifuged in a centrifuge at a centrifugal speed of 1750 r / min. After filtering the solid, it was washed six times with deionized water. The solid was dried in an oven at 120°C for 16 hours to obtain a lithium ion modified zeolite molecular sieve.
[0041] Example 3
[0042] A 13X zeolite molecular sieve with a porosity of 0.5 produced by Jianlong Micro-Nano in Yanshi, Henan, and lithium sulfate with Aladdin reagent product number L116327 were used. The mass ratio of the zeolite molecular sieve original powder to the lithium salt solution was 1:50. The mixture was mixed at 100°C and stirred for 10 hours at a stirring speed of 300 r / min. The suspension obtained after mixing was centrifuged in a centrifuge at a centrifugal speed of 1500 r / min. After filtering the solid, it was washed four times with deionized water. The solid was dried in an oven at 100°C for 20 hours to obtain a lithium ion modified zeolite molecular sieve.
[0043] In summary, the lithium ion modified zeolite molecular sieve prepared by the present invention has a larger specific surface area, a more optimized pore structure, and a higher ammonia adsorption capacity. At the same time, the present invention simplifies the preparation process, does not require roasting or multiple replacement reaction processes, reduces production difficulty, reduces production costs, and is easy to industrialize.
[0044] The description and practice disclosed in the present invention are easy to think and understand for ordinary technicians in the technical field, and several improvements and modifications can be made without departing from the principles of the present invention. Therefore, modifications or improvements made without departing from the spirit of the present invention should also be regarded as the protection scope of the present invention.
Claims
1. A lithium ion modified zeolite molecular sieve, characterized in that: It is composed of several β cages, with a framework silicon-aluminum ratio of 1 to 1.5 and a porosity of 0.45 to 0.
65.
2. A lithium ion modified zeolite molecular sieve according to claim 1, characterized in that: The chemical composition of the molecular sieve is expressed as xLi2O·yNa2O·Al2O3·nSiO2·6H2O, wherein 0.25≤x≤0.95, 0.85≤x+y≤1.2, and 1.9≤n≤2.
2.
3. The lithium ion modified zeolite molecular sieve according to claim 1, characterized in that: Its BET specific surface area is 460~740m 2 / g, and the pore size distribution is 1.25~1.85nm.
4. A method for preparing a lithium ion modified zeolite molecular sieve according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1, mixing: stirring and mixing a lithium salt solution of a certain concentration with 13X zeolite molecular sieve raw powder to obtain a mixed suspension; Step 2, heating: heating the mixed suspension to a certain temperature, stirring continuously, stopping stirring after a certain reaction time, and cooling to room temperature; Step 3, filtration: placing the mixed suspension obtained in the above step 2 in a centrifuge, separating the solid and liquid phases at a certain speed, filtering out the zeolite and washing it to obtain a modified zeolite molecular sieve solid powder; Step 4, drying: the solid powder obtained in the above step 3 is placed in an oven for drying to obtain a lithium ion modified zeolite molecular sieve.
5. The method for preparing a lithium ion modified zeolite molecular sieve according to claim 4, characterized in that: In step 1, the lithium salt solution is a LiCl, LiF, Li2SO4 or LiNO3 solution, and the concentration of the lithium salt solution is 0.1 to 1.0 mol / L.
6. The method for preparing a lithium ion modified zeolite molecular sieve according to claim 4, characterized in that: In step 2, the heating temperature is 60 to 110° C., and the reaction time is 4 to 24 hours.
7. The method for preparing a lithium ion modified zeolite molecular sieve according to claim 4, characterized in that: In step 1, the stirring is performed mechanically by a magnetic stirrer, and the stirring speed of the magnetic stirrer is 200 to 2000 r / min.
8. The method for preparing a lithium ion modified zeolite molecular sieve according to claim 4, characterized in that: In step 3, the rotation speed of the centrifuge is 1000-2000 rpm, the centrifugation time is 2-10 min, and the washing operation is repeated more than three times.
9. The method for preparing a lithium ion modified zeolite molecular sieve according to claim 4, characterized in that: In step 4, the drying temperature is 100-150° C., and the drying time is 4-24 hours.
10. The method for preparing a lithium ion modified zeolite molecular sieve according to claim 4, characterized in that: The lithium ion modified zeolite molecular sieve has an ammonia adsorption capacity of 340-382 cm at 25°C and 0.6 MPa. 3 / g.