Method for improving cation exchange degree of X-type molecular sieve with low silica-alumina ratio and X-type molecular sieve with low silica-alumina ratio containing metal cations

Abstract

The invention provides a method for improving the cation exchange degree of a low-silica-alumina-ratio X-type molecular sieve and the low-silica-alumina-ratio X-type molecular sieve containing metal cations. The method comprises the following steps: uniformly dispersing a NaK-LSX molecular sieve into a potassium salt solution, performing ultrasonic treatment after the NaK-LSX molecular sieve is added, and performing post-treatment to complete a potassium ion exchange process; repeating the potassium ion exchange process for at least one time to obtain a K-LSX molecular sieve; the method comprises the following steps: adding a K-LSX molecular sieve into a mixed solution containing target metal ion salt and alkali, carrying out ultrasonic treatment after adding, and carrying out post-treatment to complete a target metal ion exchange process; and repeating the target metal ion exchange process for at least one time to obtain the LSX molecular sieve containing the target metal ions. The method can reduce energy consumption required by exchange and improve exchange efficiency and exchange degree, and is suitable for industrial production of molecular sieves.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve synthesis, and particularly to a method for improving the cation exchange degree of low silica-alumina ratio X-type molecular sieve and a low silica-alumina ratio X-type molecular sieve containing metal cations. Background Art

[0002] Low silica-alumina ratio X-type (LSX) molecular sieve is an faujasite (FAU) structure formed by connecting silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons through oxygen bridges, and its silica-alumina molar ratio is between 2.0 and 2.2. Compared with A-type molecular sieve, the framework pore size of X-type molecular sieve is larger and the adsorption capacity for materials is higher. Compared with conventional X-type molecular sieve (silica-alumina molar ratio between 2.2 and 3.0), LSX molecular sieve has more aluminum content. Since aluminum is trivalent, that is, the aluminum-oxygen tetrahedron has a negative charge and there are more anions on the framework, more cations are needed to neutralize the framework charge, and ion exchange is easier. The excellent ion exchange characteristics of LSX molecular sieve will change the original pore size and electric field of the molecular sieve, thereby improving the adsorption capacity and adsorption selectivity of the molecular sieve. For example, it has been reported in existing studies that Li-LSX molecular sieve or Ca-LSX molecular sieve after lithium ion or calcium ion exchange has a higher nitrogen adsorption capacity than Na-LSX or conventional X-type molecular sieve, and is widely used in the field of gas adsorption and separation. However, the lithium ion has a small radius and large polarity, and is easy to form hydrated lithium ions, and is not easy to exchange with sodium and potassium ions in the molecular sieve. Therefore, a large amount of high-price lithium salt solution needs to be consumed during the exchange process, and multiple repeated exchanges are required to achieve a high ion exchange degree, resulting in high production costs. The ion exchange of other cations such as calcium ions, barium ions, strontium ions, silver ions and other metal cations with Na-LSX also requires an excessive amount of salt solution and repeated exchanges many times to improve the ion exchange degree.

[0003] The existing cation exchange methods for Na-LSX molecular sieve have problems such as cumbersome steps, long exchange time, high reaction energy consumption, and low ion exchange degree, and a method for improving the cation exchange degree of LSX molecular sieve is needed. Summary of the Invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a method for improving the cation exchange degree of low silica-alumina ratio X-type molecular sieve and a low silica-alumina ratio X-type molecular sieve containing metal cations. This method can reduce the energy consumption required for exchange, improve the exchange efficiency and exchange degree, and is suitable for the industrial production of molecular sieves.

[0005] In order to achieve the above purpose, the present invention provides a method for improving the cation exchange degree of low silica-alumina ratio X-type molecular sieve, which method comprises:

[0006] S1. Uniformly disperse NaK-LSX molecular sieve into a potassium salt solution, perform ultrasonic treatment, then filter by suction, wash, and dry to complete one potassium ion exchange process;

[0007] Completely repeat the above potassium ion exchange process at least one more time to obtain K-LSX molecular sieve;

[0008] S2. Uniformly disperse K-LSX molecular sieve into a mixed solution of a salt solution of a target metal ion and an alkali solution of the target metal ion, perform ultrasonic treatment, then filter by suction, wash, and dry to complete one target metal ion exchange process;

[0009] Completely repeat the above target metal ion exchange process at least one more time to obtain LSX molecular sieve containing the target metal ion.

[0010] In the method of the present invention, further, ultrasonic treatment can be performed during the process of dispersing NaK-LSX molecular sieve in S1 to improve the dispersion degree of NaK-LSX molecular sieve in the potassium salt solution. S1 in the above method can include: S1. Uniformly disperse NaK-LSX molecular sieve into a potassium salt solution, perform ultrasonic treatment during the dispersion process of NaK-LSX molecular sieve, maintain ultrasonic treatment after the addition of NaK-LSX molecular sieve is completed, then filter by suction, wash, and dry to complete one potassium ion exchange process; completely repeat the above potassium ion exchange process at least one more time to obtain K-LSX molecular sieve.

[0011] In the method of the present invention, in S1, NaK-LSX molecular sieve can be dispersed into the potassium salt solution at one time, or can be divided into two or more portions and dispersed into the potassium salt solution.

[0012] In the method of the present invention, still further, in the process of S1, NaK-LSX molecular sieve can be added in two or more portions, and after each addition of a portion of NaK-LSX molecular sieve, a period of time can be interposed before adding the next portion of NaK-LSX molecular sieve. Specifically, the process of S1 can include:

[0013] S1. Divide NaK-LSX molecular sieve into m portions, m≥2, maintain ultrasonic treatment, and add the NaK-LSX molecular sieve portion by portion to the potassium salt solution; wherein, when adding the 1st to (m - 1)th portions of NaK-LSX molecular sieve, a first time interval is interposed between each addition of a portion of NaK-LSX molecular sieve (during the interval process, stop adding NaK-LSX molecular sieve and maintain the above ultrasonic treatment); after the addition of the last portion of NaK-LSX molecular sieve is completed, maintain the ultrasonic treatment for a second time, then filter by suction, wash, and dry to complete one potassium ion exchange process; completely repeat the above potassium ion exchange process at least one more time to obtain K-LSX molecular sieve.

[0014] In the method of the present invention, in S1, m can be further controlled to be 2-4. NaK-LSX molecular sieve can be added to the potassium salt solution in 2, 3, or 4 portions. By adding the raw powder of NaK-LSX molecular sieve to the potassium solution in small amounts and multiple times, the solid-liquid ratio in the system can be gradually increased (the solid-liquid ratio in the present invention refers to the ratio of the mass of the solid to the volume of the liquid), ensuring that the solid-liquid ratio is low at the initial stage of ion exchange, the potassium ion solution is sufficiently excessive, ensuring that the raw powder of the molecular sieve is in full contact with the potassium ion solution, and improving the ion exchange efficiency and ion exchange degree.

[0015] In the method of the present invention, the NaK-LSX molecular sieve is divided into 2-4 portions, and the mass of each portion of the molecular sieve may be equal or unequal.

[0016] In the method of the present invention, the mass of each portion of NaK-LSX molecular sieve can be 20%-80% of the total mass of all NaK-LSX molecular sieves. Further, the mass of each portion of NaK-LSX molecular sieve can be controlled to be equal.

[0017] In the method of the present invention, the molar ratio of silicon to aluminum in the NaK-LSX molecular sieve may be 2.0-2.2. Further, in the NaK-LSX molecular sieve, the molar ratio of sodium to sodium potassium may be 0.5-0.9:1.

[0018] In the method of the present invention, in the potassium ion exchange process of S1, the potassium salt solution K + The solid-liquid ratio of the NaK-LSX molecular sieve to the potassium salt solution is generally controlled to be 1:5-15, for example, it can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15 and other specific values, and a range with any two of the above specific values ​​as endpoints. In some specific embodiments, the solid-liquid ratio of the NaK-LSX molecular sieve to the potassium salt solution can be 1:5-10, and can be further controlled to be 1:10.

[0019] In the method of the present invention, the concentration of the potassium salt solution can be 0.5-1 mol / L, for example, it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L and other specific values, as well as a range with any two of the above specific values ​​as endpoints.

[0020] In the method of the present invention, the potassium salt is generally a soluble salt, and specifically may include KCl and / or K 2 SO 4 wait.

[0021] In the method of the present invention, in S1, by controlling the temperature of the ultrasonic treatment, the exchange efficiency and degree of exchange of potassium ions and sodium ions can be adjusted. The temperature of the ultrasonic treatment in S1 (including the ultrasonic treatment during the dispersion of NaK-LSX molecular sieve and the ultrasonic treatment after the addition is completed) is denoted as the first temperature, and the first temperature is 50-90 °C. For example, it can be specific values such as 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 90 °C, etc., and ranges with any two of the above specific values as endpoints. The temperature of the ultrasonic treatment during the dispersion of the NaK-LSX molecular sieve and the temperature of the ultrasonic treatment after the addition of the molecular sieve is completed can be the same or different.

[0022] In the method of the present invention, in S1, the first time is 3 min - 20 min. Specifically, the first time can be specific values such as 3 min, 5 min, 10 min, 15 min, 20 min, etc., and ranges with any two of the above specific values as endpoints.

[0023] In the method of the present invention, in S1, the second time is 30 min - 150 min. Specifically, the second time can be specific values such as 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, etc., and ranges with any two of the above specific values as endpoints. The second time can be further controlled to be 60 min - 120 min.

[0024] In the method of the present invention, in S1, the ultrasonic power of the ultrasonic treatment can be 500 - 2000 w. For example, it can be 1000 w, and the ultrasonic frequency of the ultrasonic treatment can be 30 - 100 KHz. For example, it can be 40 kHz.

[0025] In the method of the present invention, the complete potassium ion exchange process included in S1 can be carried out 2 to 5 times; that is, after one potassium ion exchange is completed, the potassium ion exchange process can be repeated 1 to 4 times. In each potassium ion exchange process, the NaK-LSX molecular sieve is divided into two or more portions and gradually added to a fresh potassium salt solution (a potassium salt solution that has not undergone exchange), and after each addition except the last one (that is, after adding the 1st to (m - 1)th portions of the molecular sieve), there is an interval of the first time (3 - 20 min). During the process of adding the NaK-LSX molecular sieve and the process of stopping adding the NaK-LSX molecular sieve (i.e., the interval process), ultrasonic treatment is maintained at 50 - 90 °C; after all the NaK-LSX molecular sieve is added, the above ultrasonic treatment at 50 - 90 °C is maintained for the second time (30 min - 150 min), followed by suction filtration, washing, and drying to complete one complete potassium ion exchange process, and then continue with the next complete potassium ion exchange process.

[0026] According to a specific embodiment of the present invention, in S1, the NaK-LSX molecular sieve can be added at one time or divided into m portions for addition, where m can be 2 - 4, preferably 3; the concentration of the potassium salt can be 0.5 - 1 mol / L, further preferably 0.8 mol / L; the first temperature of the ultrasonic treatment can be 50 - 90 °C, further can be 60 - 80 °C; the first time can be 3 - 20 min, further can be 5 - 10 min; the second time can be 30 min - 150 min, further can be 60 - 80 min; the solid-liquid ratio of all the NaK-LSX molecular sieve to the potassium salt solution can be 1:5 - 15, further can be 1:5 - 10.

[0027] In the method of the present invention, further, ultrasonic treatment can be carried out during the process of dispersing the K-LSX molecular sieve in S2 to improve the dispersion degree of the K-LSX molecular sieve in the mixed solution containing the target metal ions. S2 in the above method can include: S2. The K-LSX molecular sieve is uniformly dispersed into a mixed solution of a salt solution of the target metal ions and an alkali solution of the target metal ions. Ultrasonic treatment is carried out during the dispersion process of the K-LSX molecular sieve. After the addition of the K-LSX molecular sieve is completed, ultrasonic treatment is maintained, and then suction filtration, washing, and drying are carried out to complete one target metal ion exchange process; the above target metal ion exchange process is completely repeated at least once to obtain the LSX molecular sieve containing the target metal ions.

[0028] In the method of the present invention, in S2, the K-LSX molecular sieve can be dispersed into the mixed solution of the salt solution of the target metal ions and the alkali solution of the target metal ions at one time, or divided into two or more portions for dispersion into the mixed solution of the salt solution of the target metal ions and the alkali solution of the target metal ions.

[0029] In the method of the present invention, further, in the process of S2, the K-LSX molecular sieve can be divided into two or more portions for addition, and after adding each portion of the K-LSX molecular sieve, a period of time can be interposed before adding the next portion of the K-LSX molecular sieve. Specifically, the process of S2 may include:

[0030] S2. Divide the K-LSX molecular sieve into n portions, where n≥2, maintain ultrasonic treatment, and add the K-LSX molecular sieve portion by portion to the mixed solution of the salt solution of the target metal ion and the alkali solution of the target metal ion; wherein, when adding the 1st to (n - 1)th portions of the K-LSX molecular sieve, a third time interval is provided between the addition of each portion of the K-LSX molecular sieve (during the interval, the addition of the K-LSX molecular sieve is stopped, and the above ultrasonic treatment is maintained), after the last portion of the K-LSX molecular sieve is added, maintain the ultrasonic treatment for a fourth time, then perform suction filtration, washing, and drying to complete one target metal ion exchange process; completely repeat the above target metal ion exchange process at least once to obtain the LSX molecular sieve containing the target metal ion (denoted as M-LSX molecular sieve).

[0031] In the method of the present invention, in S2, n can be further controlled to be 2 - 4. The K-LSX molecular sieve can be divided into 2, 3, or 4 portions and added to the mixed solution of the salt solution of the target metal ion and the alkali solution of the target metal ion. By adding the K-LSX molecular sieve raw powder in small amounts and multiple times to the salt solution and alkali solution of the target metal ion, the solid-liquid ratio in the system can be gradually increased, ensuring a low solid-liquid ratio at the initial stage of ion exchange, with the target metal ion solution being sufficiently in excess, ensuring sufficient contact between the molecular sieve and the solution containing the target metal ion, and improving the ion exchange efficiency and ion exchange degree.

[0032] In the method of the present invention, the K-LSX molecular sieve is divided into 2 - 4 portions, and the mass of each portion of the molecular sieve can be equal or unequal.

[0033] In the method of the present invention, in S2, the mass of each portion of the K-LSX molecular sieve can be 20% - 80% of the total mass of all the K-LSX molecular sieves. Further, the mass of each portion of the K-LSX molecular sieve can be controlled to be equal.

[0034] In the method of the present invention, in S2, the target metal ion may include Li + , Ca 2+ , Sr 2+ , Ba 2+ , Ag + or a combination of two or more of them. For example, the target metal ion may include Li + and / or Ca 2+ .

[0035] In the method of the present invention, in S2, the salt of the target metal ion is a soluble salt, and the salt of the target metal ion may specifically include LiCl, CaCl 2 , SrCl 2 , BaCl 2 , AgNO 3 and the like, or a combination of two or more of them.

[0036] In the method of the present invention, in S2, the cation of the base of the target metal ion is generally the same as the cation type of the salt of the target metal ion. The base of the target metal ion may specifically include LiOH, Ca(OH) 2 , Sr(OH) 2 , Ba(OH) 2 , AgOH and the like, or a combination of two or more of them.

[0037] In the method of the present invention, in one target metal ion exchange process of S2, calculated based on the target metal ion concentration in the salt solution of the target metal ion being 0.5 - 2 mol / L and the target metal ion concentration in the base solution of the target metal ion being 0.1 - 0.5 mol / L, the solid-liquid ratio of the K-LSX molecular sieve to the mixed solution (formed by the salt solution of the target metal ion and the base solution of the target metal ion) is generally controlled to be 1:5 - 15. For example, it can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15 and other specific values, as well as the ranges with any two of the above specific values as endpoints. In some specific embodiments, calculated based on the target metal ion concentration in the salt solution of the target metal ion being 0.5 - 2 mol / L and the target metal ion concentration in the base solution of the target metal ion being 0.1 - 0.5 mol / L, the solid-liquid ratio of the K-LSX molecular sieve to the mixed solution can be 1:5 - 10, and further can be 1:10.

[0038] In the above method, in S2, the solid-liquid ratio of the molecular sieve to the mixed solution containing the exchange ion is low (1:5 - 15), which can reduce the dosage of the target metal ion solution. Especially for the exchange process of noble metal ions such as Li + , Ag + and the like, it can significantly reduce the production cost while ensuring a high exchange degree.

[0039] In some specific embodiments, in S2, the concentration of the salt solution of the target metal ion can be 0.5 - 2 mol / L. For example, it can be 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L and other specific values, as well as the ranges with any two of the above specific values as endpoints.

[0040] In some specific embodiments, in S2, the concentration of the alkali solution of the target metal ion can be 0.1 - 0.5 mol / L. For example, it can be specific values such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc., and ranges with any two of the above specific values as endpoints.

[0041] In some specific embodiments, in S2, the volume of the salt solution of the target metal ion can be 20 - 100 times the volume of the alkali solution of the target metal ion.

[0042] In the method of the present invention, in S2, the pH value of the mixed solution is 7.0 - 8.0. For example, it can be specific values such as 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, etc., and ranges with any two of the above specific values as endpoints. The alkali solution of the target metal ion can adjust the pH value of the mixed solution. The above method utilizes a near-neutral environment for ion exchange, which not only inhibits the hydration of the target metal ion and protects the original structure to a certain extent, but also reduces the amount of alkali solution used, protects the instrument and equipment, and reduces the environmental impact.

[0043] In the method of the present invention, in S2, by controlling the temperature of the ultrasonic treatment, the exchange efficiency and exchange degree of the target metal ion and potassium ion can be adjusted. The temperature of the ultrasonic treatment in S2 (including the ultrasonic treatment during the dispersion of K-LSX molecular sieve and the ultrasonic treatment after the addition is completed) is denoted as the second temperature, and this second temperature can be controlled to be 50 - 90 °C. For example, it can be specific values such as 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, etc., and ranges with any two of the above specific values as endpoints. The temperature of the ultrasonic treatment during the dispersion of the K-LSX molecular sieve and the temperature of the ultrasonic treatment after the addition of the molecular sieve can be the same or different.

[0044] In the method of the present invention, in S2, the third time can be 3 min - 20 min. For example, it can be specific values such as 3 min, 5 min, 10 min, 15 min, 20 min, etc., and ranges with any two of the above specific values as endpoints.

[0045] In the method of the present invention, in S2, the fourth time may be 30 min - 150 min. For example, it may be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, 120 min, 130 min, 140 min, 150 min and other specific values, as well as the ranges with any two of the above specific values as endpoints. The fourth time can be further controlled to be 60 min - 120 min.

[0046] In the method of the present invention, in S2, the ultrasonic power of the ultrasonic treatment may be 500 - 2000 w. For example, it may be 1000 w. The ultrasonic frequency of the ultrasonic treatment may be 30 - 100 KHz. For example, it may be 40 kHz. In the present invention, the temperature, time, power and frequency of the ultrasonic treatment in S2 may be the same as or different from those of the ultrasonic treatment in S1.

[0047] In the method of the present invention, the target metal ion exchange process included in S2 may be 2 - 6 times; that is, after one exchange is completed, the target metal ion exchange process can be repeated 1 - 5 times. In each target metal ion exchange process, the K-LSX molecular sieve is divided into 2 parts or more, and then added portion by portion to the mixed solution of fresh target metal ion salt solution and target metal ion base solution (the mixed solution that has not undergone ion exchange). And after each addition except the last one (that is, after adding the 1st to (n - 1)th portion of the molecular sieve), there is an interval of the third time (3 - 20 min). During the process of adding the K-LSX molecular sieve and the process of stopping adding the K-LSX molecular sieve (i.e., the interval process), ultrasonic treatment is maintained at 50 - 90 °C. After the last portion of the K-LSX molecular sieve is added (that is, after all the K-LSX molecular sieves are added), ultrasonic treatment is maintained at the above 50 - 90 °C for the fourth time (30 - 150 min), followed by suction filtration, washing and drying to complete a complete target metal ion exchange process, and then continue with the next complete target metal ion exchange process.

[0048] According to a specific embodiment of the present invention, in S2, when the target metal ion is a lithium ion, the K-LSX molecular sieve can be added once or in n portions, where n can be 2-4, and further can be 3; the second temperature of the ultrasonic treatment can be 50-90°C, and further can be 70-80°C; the third time can be 3-20 min, and further can be 5-15 min; the fourth time can be 30-150 min, and further can be 80-100 min; the solid-liquid ratio of all the K-LSX molecular sieve to the lithium-containing mixed solution can be 1:5-15, and further can be 1:5-10.

[0049] In the method of the present invention, in S2, when the target metal ion is a calcium ion, the K-LSX molecular sieve can be added once or in n portions, where n can be 2-4, and further can be 3; the second temperature of the ultrasonic treatment can be 50-90°C, and further can be 70-80°C; the third time can be 3-20 min, and further can be 5-15 min; the fourth time can be 30-150 min, and further can be 80-100 min; the solid-liquid ratio of all the K-LSX molecular sieve to the calcium-containing mixed solution can be 1:5-15, and further can be 1:5-10.

[0050] In the method of the present invention, taking m and n as 3 respectively, and taking the case where the complete ion exchange processes included in S1 and S2 are both 2 times as an example, the above method can specifically include:

[0051] 1. Divide the NaK-LSX molecular sieve into 3 portions. Under ultrasonic treatment at 50-90°C, add the first portion of the NaK-LSX molecular sieve to the potassium salt solution and maintain ultrasonic treatment at 50-90°C.

[0052] After an interval of 3-20 min, add the second portion of the NaK-LSX molecular sieve to the above potassium salt solution and maintain ultrasonic treatment at 50-90°C.

[0053] After an interval of 3-20 min, add the third portion of the NaK-LSX molecular sieve to the above potassium salt solution. After all the NaK-LSX molecular sieve is added, maintain ultrasonic treatment at 50-90°C for 30-150 min, filter, wash, and dry to complete the first potassium ion exchange process and obtain the K'-LSX molecular sieve.

[0054] 2. Divide the K'-LSX molecular sieve obtained in step 1 into 3 portions. Under ultrasonic treatment at 50-90°C, add the first portion of the K'-LSX molecular sieve to a fresh (not having undergone the ion exchange process) potassium salt solution and maintain ultrasonic treatment at 50-90°C.

[0055] After an interval of 3 - 20 min, add the second portion of K’-LSX molecular sieve to the above potassium salt solution and maintain ultrasonic treatment at 50 - 90 °C;

[0056] After an interval of 3 - 20 min, add the third portion of K’-LSX molecular sieve to the above potassium salt solution. After all the K’-LSX molecular sieves are added, maintain ultrasonic treatment at 50 - 90 °C for 30 - 150 min, perform suction filtration, washing, and drying to complete the second potassium ion exchange process and obtain K-LSX molecular sieve;

[0057] 3. Divide the K-LSX molecular sieve obtained in step 2 into three portions. Under ultrasonic treatment at 50 - 90 °C, add the first portion of K-LSX molecular sieve to the mixed solution of the salt solution of the target metal ion and the alkali solution of the target metal ion, and maintain ultrasonic treatment at 50 - 90 °C;

[0058] After an interval of 3 - 20 min, add the second portion of K-LSX molecular sieve to the above mixed solution and maintain ultrasonic treatment at 50 - 90 °C;

[0059] After an interval of 3 - 20 min, add the third portion of K-LSX molecular sieve to the above mixed solution. After all the K-LSX molecular sieves are added, maintain ultrasonic treatment at 50 - 90 °C for 30 - 150 min, perform suction filtration, washing, and drying to complete the first target metal ion exchange process and obtain M’-LSX molecular sieve;

[0060] 4. Divide the M’-LSX molecular sieve obtained in step 3 into three portions. Under ultrasonic treatment at 50 - 90 °C, add the first portion of M’-LSX molecular sieve to the mixed solution of the fresh salt solution of the target metal ion and the alkali solution of the target metal ion, and maintain ultrasonic treatment at 50 - 90 °C;

[0061] After an interval of 3 - 20 min, add the second portion of M’-LSX molecular sieve to the above mixed solution and maintain ultrasonic treatment at 50 - 90 °C;

[0062] After an interval of 3 - 20 min, add the third portion of M’-LSX molecular sieve to the above mixed solution. After all the M’-LSX molecular sieves are added, maintain ultrasonic treatment at 50 - 90 °C for 30 - 150 min, perform suction filtration, washing, and drying to complete the second target metal ion exchange process and obtain M-LSX molecular sieve, that is, LSX molecular sieve containing the target metal ion.

[0063] In the method of the present invention, the above method may further include activating the LSX molecular sieve containing the target metal ions. The activation treatment can improve the adsorption activity of the LSX molecular sieve containing the target metal ions. The activation treatment may specifically include calcining the LSX molecular sieve containing the target metal ions at 400-600 °C for 1-3 hours.

[0064] The present invention also provides a low-silica-alumina ratio X-type molecular sieve containing metal cations, which includes the LSX molecular sieve containing the target metal ions obtained by the above method. The ion exchange degree of the LSX molecular sieve containing the target metal ions obtained by the above method is relatively high.

[0065] The beneficial effects of the present invention are as follows:

[0066] 1. The present invention uses two-step ion exchange to prepare M-LSX. First, the NaK-LSX molecular sieve powder is exchanged into K-LSX, and then further exchanged into M-LSX containing the target metal ions. Na in the NaK-LSX molecular sieve + is usually distributed at the SI position in the center of the hexagonal prism cage, the SI' position, SII' position in the β cage, the SII position and SII" position in the faujasite cage. After Na + is exchanged into K + , due to the fact that K + is larger in volume than Na + , K + is not easily stably present at the SI position in the center of the relatively small-volume hexagonal prism cage, and is more likely to exist at the SI' position and SII' position in the relatively large-volume β cage and the SII position and SII" position in the even larger-volume faujasite cage. Compared with the center of the hexagonal prism cage, the β cage and the faujasite cage have a larger volume. Therefore, potassium exchange can improve the distribution of metal cations in the molecular sieve and make the metal cations tend to be distributed in the relatively large-volume building units within the molecular sieve. In the subsequent process of exchanging the target metal ions, K + is located in the relatively large-volume building units and is more easily replaced by the target metal ions. Therefore, the exchange degree of the target metal ions is effectively improved.

[0067] 2. The method provided by the present invention can improve the exchange degree of sodium and potassium ions in the low-silica-alumina ratio X-type molecular sieve (NaK-LSX) powder with the target metal cations in the solution, reduce the number of exchanges, shorten the exchange time, efficiently synthesize an LSX molecular sieve with a high cation exchange degree, improve the adsorption capacity for non-hydrogen gases, and thus be used in the field of hydrogen pressure swing adsorption purification. Compared with the existing ion exchange technology of NaK-LSX molecular sieve, the ion exchange method of the present invention is simple, time-saving, low-cost, reduces the impact of alkaline solution on instruments and the environment, and can achieve a high ion exchange degree. Description of the Drawings

[0068] Figure 1 XRD patterns of the NaK-LSX raw powder of the present invention and the product after the secondary calcium ion exchange in Example 12.

[0069] Figure 2 XRD patterns of the products after the secondary calcium ion exchange in Example 11 and Example 13.

[0070] Figure 3 Nitrogen adsorption isotherms of the NaK-LSX raw powder of the present invention and the product after the secondary calcium ion exchange in Example 12 at 298K. Detailed implementation manners

[0071] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention.

[0072] In the following examples and comparative examples, the silicon-aluminum molar ratio of the NaK-LSX molecular sieve is 2.0 - 2.2; in the NaK-LSX molecular sieve, the molar ratio of sodium to sodium and potassium is 0.5 - 0.9:1.

[0073] In the following examples and comparative examples, the power of the ultrasonic wave used is 1000w, and the frequency of the ultrasonic wave is 40KHz.

[0074] Example 1

[0075] This example provides a method for improving the cation exchange degree of a low silicon-aluminum ratio X-type molecular sieve, and the method includes:

[0076] (1) Maintain ultrasonic treatment at 50°C. First, add 1.25 g of the NaK-LSX molecular sieve raw powder to 50 mL of 0.5 mol / L K 2 SO 4 solution. After an interval of 15 min (i.e., the first time, and the ultrasonic treatment is maintained during the interval. The interval processes in other steps of this example and other examples and comparative examples are all maintained with ultrasonic treatment), then add another 1.25 g of the NaK-LSX molecular sieve raw powder to the above solution. After an interval of 15 min, continue to add 1.25 g of the NaK-LSX molecular sieve raw powder to the above solution. After an interval of 15 min, finally add 1.25 g of the NaK-LSX molecular sieve raw powder to the above solution. Maintain ultrasonic treatment for 90 min (i.e., the second time), then filter, wash, and dry to complete one potassium ion exchange; repeat the above potassium ion exchange once to obtain the K-LSX-1 molecular sieve, and the potassium ion exchange degree is 99.1%.

[0077] (2) Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker. After adjusting the pH of the solution to 8.0, maintain ultrasonic treatment at 80 °C. Add 5 g of K-LSX-1 molecular sieve to the above solution at one time, keep ultrasonic treatment for 120 min (i.e., the fourth time), then perform suction filtration, washing and drying to complete one lithium ion exchange; repeat the above lithium ion exchange once to obtain Li-LSX-1 molecular sieve.

[0078] Example 2

[0079] This example provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, which includes:

[0080] (1) Maintain ultrasonic treatment at 60 °C. First, add 1.67 g of NaK-LSX molecular sieve raw powder to 50 mL of 0.8 mol / L K 2 SO 4 solution. After an interval of 10 min, add another 1.67 g of NaK-LSX molecular sieve raw powder to the above solution. After an interval of 10 min, finally add 1.67 g of NaK-LSX molecular sieve raw powder to the above solution. Maintain ultrasonic treatment for 80 min, then perform suction filtration, washing and drying to complete one potassium ion exchange; repeat the above potassium ion exchange once to obtain K-LSX-2 molecular sieve, and the potassium ion exchange degree is 99.0%.

[0081] (2) Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker. After adjusting the pH of the solution to 8.0, maintain ultrasonic treatment at 90 °C. Add 5 g of K-LSX-2 molecular sieve to the above solution at one time, keep ultrasonic treatment for 120 min, then perform suction filtration, washing and drying to complete one lithium ion exchange; repeat the above lithium ion exchange once to obtain Li-LSX-2 molecular sieve.

[0082] Example 3

[0083] This example provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, which includes:

[0084] (1) Maintain ultrasonic treatment at 70 °C. First, add 2.5 g of NaK-LSX molecular sieve raw powder to 50 mL of 0.8 mol / L K 2 SO 4 solution. After an interval of 10 min, add another 2.5 g of NaK-LSX molecular sieve raw powder to the above solution. Maintain ultrasonic treatment for 70 min, then perform suction filtration, washing and drying to complete one potassium ion exchange; repeat the above potassium ion exchange once to obtain K-LSX-3 molecular sieve, and the potassium ion exchange degree is 99.3%.

[0085] (2) 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution were mixed in a beaker until the pH of the solution reached 8.0, and then ultrasonic treatment was maintained at 80° C. First, 2.5 g of K-LSX-3 molecular sieve was added to the above solution. After an interval of 5 minutes (i.e., the third time), another 2.5 g of K-LSX-3 molecular sieve was added to the above solution, and ultrasonic treatment was maintained for 90 minutes. After filtration, washing and drying, a lithium ion exchange was completed; the above lithium ion exchange was repeated once to obtain Li-LSX-3 molecular sieve.

[0086] Example 4

[0087] This embodiment provides a method for improving the cation exchange degree of a low silicon-aluminum ratio X-type molecular sieve, the method comprising:

[0088] (1) Maintaining ultrasonic treatment at 80°C, 5 g of NaK-LSX molecular sieve was added into 50 mL of 1 mol / L K 2 SO 4 The solution was subjected to ultrasound for 90 minutes, and potassium ion exchange was completed after filtration, washing and drying. The potassium ion exchange was repeated once to obtain K-LSX-4 molecular sieve with a potassium ion exchange degree of 99.0%.

[0089] (2) 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution were mixed in a beaker until the pH of the solution reached 8.0, and then ultrasonic treatment was performed at 90°C. 2.5 g of K-LSX-4 molecular sieve was first added to the above solution. After an interval of 5 minutes, another 2.5 g of K-LSX-4 molecular sieve was added to the above solution. The ultrasonic treatment was maintained for 80 minutes. After filtration, washing and drying, a lithium ion exchange was completed. The above lithium ion exchange was repeated once to obtain Li-LSX-4 molecular sieve.

[0090] Example 5

[0091] This embodiment provides a method for improving the cation exchange degree of a low silicon-aluminum ratio X-type molecular sieve, the method comprising:

[0092] (1) Maintaining ultrasonic treatment at 70°C, 1.67 g of NaK-LSX molecular sieve powder was added to 50 mL of 0.8 mol / L K 2 SO 4In the solution, after an interval of 5 min, another 1.67 g of the original NaK-LSX molecular sieve powder was added into the above solution. After an interval of 5 min, finally another 1.67 g of the original NaK-LSX molecular sieve powder was added into the above solution. Ultrasonic treatment was maintained for 60 min. After suction filtration, washing and drying, one potassium ion exchange was completed; the above potassium ion exchange was repeated once to obtain the K-LSX-5 molecular sieve, and the potassium ion exchange degree was 99.3%.

[0093] (2) After mixing 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker to make the pH of the solution reach 8.0, ultrasonic treatment was maintained at 70 °C. First, 1.67 g of the K-LSX-5 molecular sieve was added into the above solution. After an interval of 15 min, another 1.67 g of the K-LSX-5 molecular sieve was added into the above solution. After an interval of 15 min, finally another 1.67 g of the K-LSX-5 molecular sieve was added into the above solution. Ultrasonic treatment was maintained for 100 min. After suction filtration, washing and drying, one lithium ion exchange was completed; the above lithium ion exchange was repeated once to obtain the Li-LSX-5 molecular sieve.

[0094] Example 6

[0095] This example provides a method for improving the cation exchange degree of low silica-alumina ratio X-type molecular sieve, and the method includes:

[0096] (1) Ultrasonic treatment was maintained at 80 °C. First, 1.67 g of the original NaK-LSX molecular sieve powder was added into 50 mL of 1 mol / L K 2 SO 4 solution. After an interval of 5 min, another 1.67 g of the original NaK-LSX molecular sieve powder was added into the above solution. After an interval of 5 min, finally another 1.67 g of the original NaK-LSX molecular sieve powder was added into the above solution. Ultrasonic treatment was maintained for 60 min. After suction filtration, washing and drying, one potassium ion exchange was completed; the above potassium ion exchange was repeated once to obtain the K-LSX-6 molecular sieve, and the potassium ion exchange degree was 99.5%.

[0097] (2) After mixing 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker to make the pH of the solution reach 8.0, ultrasonic treatment was maintained at 80 °C. First, 1.67 g of the K-LSX-6 molecular sieve was added into the above solution. After an interval of 5 min, another 1.67 g of the K-LSX-6 molecular sieve was added into the above solution. After an interval of 5 min, finally another 1.67 g of the K-LSX-6 molecular sieve was added into the above solution. Ultrasonic treatment was maintained for 90 min. After suction filtration, washing and drying, one lithium ion exchange was completed; the above lithium ion exchange was repeated once to obtain the Li-LSX-6 molecular sieve.

[0098] The static nitrogen adsorption capacity of Li-LSX-6 molecular sieve is 19.2 cm 3 / g.

[0099] Example 7

[0100] This example provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, and the method includes:

[0101] (1) Repeat step (1) of Example 5.

[0102] (2) After mixing 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker to make the solution pH reach 8.0, keep it under ultrasonic treatment at 60 °C. First, add 1.25 g of K-LSX-5 molecular sieve into the above solution. After an interval of 10 min, add another 1.25 g of K-LSX-5 molecular sieve into the above solution. After an interval of 10 min, continue to add 1.25 g of K-LSX-5 molecular sieve into the above solution. After an interval of 10 min, finally add 1.25 g of K-LSX-5 molecular sieve into the above solution. Keep ultrasonic treatment for 100 min, then perform suction filtration, washing and drying to complete one lithium ion exchange; repeat the above lithium ion exchange once to obtain Li-LSX-7 molecular sieve.

[0103] Example 8

[0104] This example provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, and the method includes:

[0105] (1) Repeat step (1) of Example 5.

[0106] (2) After mixing 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker to make the solution pH reach 8.0, keep it under ultrasonic treatment at 50 °C. First, add 1 g of K-LSX-5 molecular sieve into the above solution. After an interval of 15 min, add another 1 g of K-LSX-5 molecular sieve into the above solution. After an interval of 15 min, then add 1 g of K-LSX-5 molecular sieve into the above solution. After an interval of 15 min, continue to add 1 g of K-LSX-5 molecular sieve into the above solution. After an interval of 15 min, finally add 1 g of K-LSX-5 molecular sieve into the above solution. Keep ultrasonic treatment for 120 min, then perform suction filtration, washing and drying to complete one lithium ion exchange; repeat the above lithium ion exchange once to obtain Li-LSX-8 molecular sieve.

[0107] Example 9

[0108] This embodiment provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, and the method includes:

[0109] (1) Repeat step (1) of Example 5.

[0110] (2) After mixing 50 mL of 0.5 mol / L CaCl 2 solution and 0.5 mL of 0.5 mol / L Ca(OH) 2 solution in a beaker to make the solution pH reach 7.8, keep it under ultrasonic treatment at 90 °C, add 5 g of K-LSX-5 molecular sieve into the above solution at one time, keep ultrasonic treatment for 120 min, filter, wash and dry, then complete one calcium ion exchange; repeat the above calcium ion exchange once to obtain Ca-LSX-1 molecular sieve.

[0111] Example 10

[0112] This embodiment provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, and the method includes:

[0113] (1) Repeat step (1) of Example 5.

[0114] (2) After mixing 50 mL of 0.5 mol / L CaCl 2 solution and 0.5 mL of 0.5 mol / L Ca(OH) 2 solution in a beaker to make the solution pH reach 7.8, keep it under ultrasonic treatment at 70 °C, first add 2.5 g of K-LSX-5 molecular sieve into the above solution, after 15 min interval, add another 2.5 g of K-LSX-5 molecular sieve into the above solution, keep ultrasonic treatment for 100 min, filter, wash and dry, then complete one calcium ion exchange; repeat the above calcium ion exchange once to obtain Ca-LSX-2 molecular sieve.

[0115] Example 11

[0116] This embodiment provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, and the method includes:

[0117] (1) Repeat step (1) of Example 5.

[0118] (2) After mixing 50 mL of 0.5 mol / L CaCl 2 solution and 0.5 mL of 0.5 mol / L Ca(OH) 2After the solutions were mixed in a beaker to make the pH of the solution reach 7.8, ultrasonic treatment was carried out at 80 °C. First, 2.5 g of K-LSX-5 molecular sieve was added to the above solution. After 5 minutes, another 2.5 g of K-LSX-5 molecular sieve was added to the above solution. Ultrasonic treatment was maintained for 90 minutes, followed by suction filtration, washing, and drying to complete one calcium ion exchange; the above calcium ion exchange was repeated once to obtain Ca-LSX-3 molecular sieve.

[0119] Example 12

[0120] This example provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, and the method includes:

[0121] (1) Repeat step (1) of Example 5.

[0122] (2) Mix 50 mL of 0.5 mol / L CaCl 2 solution and 0.5 mL of 0.5 mol / L Ca(OH) 2 solution in a beaker to make the pH of the solution reach 7.8, then maintain ultrasonic treatment at 70 °C. First, 1.67 g of K-LSX-5 molecular sieve was added to the above solution. After 5 minutes, another 1.67 g of K-LSX-5 molecular sieve was added to the above solution. After another 5 minutes, finally 1.67 g of K-LSX-5 molecular sieve was added to the above solution. Ultrasonic treatment was maintained for 80 minutes, followed by suction filtration, washing, and drying to complete one calcium ion exchange; the above calcium ion exchange was repeated once to obtain Ca-LSX-4 molecular sieve.

[0123] The static nitrogen adsorption capacity of Ca-LSX-4 molecular sieve is 24.6 cm 3 / g.

[0124] Example 13

[0125] This example provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, and the method includes:

[0126] (1) Repeat step (1) of Example 5.

[0127] (2) Mix 50 mL of 0.5 mol / L CaCl 2 solution and 0.5 mL of 0.5 mol / L Ca(OH) 2After the solutions were mixed in a beaker to bring the pH of the solution to 7.8, ultrasonic treatment was carried out at 80 °C. First, 1.67 g of K-LSX-5 molecular sieve was added to the above solution. After an interval of 5 min, another 1.67 g of K-LSX-5 molecular sieve was added to the above solution. After an interval of 5 min, finally 1.67 g of K-LSX-5 molecular sieve was added to the above solution. Ultrasonic treatment was maintained for 90 min, followed by suction filtration, washing, and drying to complete one calcium ion exchange; the above calcium ion exchange was repeated once to obtain Ca-LSX-5 molecular sieve.

[0128] Example 14

[0129] This example provides a method for improving the cation exchange degree of low-silica-alumina ratio X-type molecular sieve, and the method includes:

[0130] (1) Repeat step (1) of Example 5.

[0131] (2) Mix 50 mL of 0.5 mol / L CaCl 2 solution and 0.5 mL of 0.5 mol / L Ca(OH) 2 solution in a beaker to bring the pH of the solution to 7.8, then maintain ultrasonic treatment at 60 °C. First, 1.25 g of K-LSX-5 molecular sieve was added to the above solution. After an interval of 10 min, another 1.25 g of K-LSX-5 molecular sieve was added to the above solution. After an interval of 10 min, continue to add 1.25 g of K-LSX-5 molecular sieve to the above solution. After an interval of 10 min, finally 1.25 g of K-LSX-5 molecular sieve was added to the above solution. Ultrasonic treatment was maintained for 100 min, followed by suction filtration, washing, and drying to complete one calcium ion exchange; the above calcium ion exchange was repeated once to obtain Ca-LSX-6 molecular sieve.

[0132] Comparative Example 1

[0133] This comparative example provides a method for cation exchange of low-silica-alumina ratio X-type molecular sieve, and the method includes:

[0134] Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker to bring the pH of the solution to 8.0, then maintain ultrasonic treatment at 70 °C. First, 1.67 g of NaK-LSX molecular sieve raw powder was added to the above solution. After an interval of 15 min, another 1.67 g of NaK-LSX molecular sieve raw powder was added to the above solution. After an interval of 15 min, finally 1.67 g of NaK-LSX molecular sieve raw powder was added to the above solution. Ultrasonic treatment was maintained for 100 min, followed by suction filtration, washing, and drying to complete one lithium ion exchange; the above lithium ion exchange was repeated once to obtain Li-LSX-9 molecular sieve.

[0135] Comparative Example 2

[0136] This comparative example provides a method for cation exchange of low silica-alumina ratio X-type zeolite, and the method includes:

[0137] (1) Repeat step (1) of Example 5.

[0138] (2) Keep ultrasonic treatment at 70 °C. First, add 1.67 g of K-LSX-5 zeolite into 50 mL of 1 mol / L LiCl solution. After 15 minutes, add another 1.67 g of K-LSX-5 zeolite into the above solution. After another 15 minutes, finally add 1.67 g of K-LSX-5 zeolite into the above solution. Keep ultrasonic treatment for 100 minutes, then perform suction filtration, washing and drying to complete one lithium ion exchange; repeat the above lithium ion exchange once to obtain Li-LSX-10 zeolite.

[0139] Comparative Example 3

[0140] This comparative example provides a method for cation exchange of low silica-alumina ratio X-type zeolite, and the method includes:

[0141] Mix 50 mL of 0.5 mol / L CaCl 2 solution and 0.5 mL of 0.5 mol / L Ca(OH) 2 solution in a beaker to make the pH of the solution reach 7.8, then keep ultrasonic treatment at 70 °C. First, add 1.67 g of NaK-LSX zeolite raw powder into the above solution. After 5 minutes, add another 1.67 g of NaK-LSX zeolite raw powder into the above solution. After another 5 minutes, finally add 1.67 g of NaK-LSX zeolite raw powder into the above solution. Keep ultrasonic treatment for 80 minutes, then perform suction filtration, washing and drying to complete one calcium ion exchange; repeat the above calcium ion exchange once to obtain Ca-LSX-7 zeolite.

[0142] Comparative Example 4

[0143] This comparative example provides a method for cation exchange of low silica-alumina ratio X-type zeolite, and the method includes:

[0144] (1) Repeat step (1) of Example 5.

[0145] (2) Keep ultrasonic treatment at 70 °C. First, add 1.67 g of K-LSX-5 zeolite into 50 mL of 0.5 mol / L CaCl 2In the solution, after an interval of 5 minutes, another 1.67 g of K-LSX-5 molecular sieve was added to the above solution. After an interval of 5 minutes, finally 1.67 g of K-LSX-5 molecular sieve was added to the above solution. Ultrasonic treatment was maintained for 80 minutes, followed by suction filtration, washing, and drying to complete one calcium ion exchange. The above calcium ion exchange was repeated once to obtain Ca-LSX-8 molecular sieve.

[0146] The molecular sieve products of the above examples were subjected to structural characterization and adsorption performance testing, and the results are as follows:

[0147] Figure 1 XRD patterns of NaK-LSX and Ca-LSX-4 molecular sieves. From Figure 1 It can be seen that the Ca-LSX-4 molecular sieve after potassium ion and calcium ion exchange in sequence shows characteristic diffraction peaks of X molecular sieve at 2θ of 6.1°, 10.0°, 11.7°, 15.4°, 18.4°, 20.1°, 23.3°, 26.6°, 30.3°, 30.9°, 33.6°, etc., indicating that the framework of the product after ion exchange is intact and it is still a pure X molecular sieve. From Figure 2 It can be seen that the Ca-LSX-3 and Ca-LSX-5 molecular sieves obtained after exchange in Example 11 and Example 13 also retain the framework and structure of pure X molecular sieve.

[0148] Figure 3 Nitrogen adsorption isotherms of NaK-LSX and Ca-LSX-4 molecular sieves at 298 K. From Figure 3 It can be seen that the nitrogen adsorption capacity of the low-silica X molecular sieve after calcium ion exchange is 24.6 cm 3 / g, which is significantly higher than that of the sodium-potassium type low-silica X molecular sieve without ion exchange, indicating that the low-silica X molecular sieve after ion exchange has excellent nitrogen adsorption ability.

[0149] Table 1 summarizes the ion exchange results of the above examples and comparative examples.

[0150] Table 1 shows the ion exchange degree of NaK-LSX molecular sieve

[0151] Sample <![CDATA[Li + Exchange degree]]> Sample <![CDATA[Ca 2+ Exchange degree]]> Li-LSX-1 92.0％ Ca-LSX-1 93.8％ Li-LSX-2 93.4％ Ca-LSX-2 94.0％ Li-LSX-3 94.7％ Ca-LSX-3 95.7％ Li-LSX-4 95.2％ Ca-LSX-4 98.3％ Li-LSX-5 93.9％ Ca-LSX-5 97.9％ Li-LSX-6 96.4％ Ca-LSX-6 93.5％ Li-LSX-7 92.0％ Ca-LSX-7 85.4％ Li-LSX-8 91.6％ Ca-LSX-8 81.8％ Li-LSX-9 79.1％ Li-LSX-10 75.3％

[0152] For potassium ion exchange, the K-LSX molecular sieves obtained by the methods of Examples 1 to 6 all have a relatively high potassium ion exchange degree, which can reach 99% or more. Among them, the experimental conditions of the first temperature of 70 °C, the first time of 5 minutes, the second time of 60 minutes, and the addition of NaK-LSX molecular sieve raw powder in 3 equal parts during S1 ultrasonic treatment (Example 5) have good effects. After repeating potassium ion exchange twice, the K +The exchange degree reaches 99.3%, and the required ultrasonic time is short, and the ultrasonic temperature is low, which is an efficient potassium ion exchange method.

[0153] For lithium ion exchange, the experimental conditions (Example 6) of the second temperature of ultrasonic treatment in S2 being 80 °C, the third time being 5 min, the fourth time being 90 min, and adding K-LSX molecular sieve in 3 equal portions are the conditions with better lithium ion exchange effect. After repeating the exchange twice, the Li + exchange degree reaches 96.4%.

[0154] It can be seen from Comparative Example 1 that the lithium ion exchange degree obtained by the method of first performing potassium ion exchange on the NaK-LSX molecular sieve powder and then performing target metal ion exchange is significantly higher than the lithium ion exchange degree obtained by directly performing target metal ion exchange on the NaK-LSX molecular sieve powder.

[0155] It can be seen from Comparative Example 2 that adding an appropriate amount of LiOH to adjust the pH value of the target metal ion salt solution during the lithium ion exchange process can significantly improve the lithium ion exchange degree.

[0156] For calcium ion exchange, the experimental conditions (Example 12) of the second temperature of ultrasonic treatment in S2 being 70 °C, the third time being 5 min, the fourth time being 80 min, and adding K-LSX molecular sieve in 3 equal portions are the conditions with better ion exchange effect. After repeating the exchange twice, the Ca 2+ exchange degree reaches 98.3%.

[0157] It can be seen from Comparative Example 3 that under the same calcium ion exchange conditions, the calcium ion exchange degree obtained by the method of first performing potassium ion exchange on the NaK-LSX molecular sieve powder and then performing target metal ion exchange is significantly higher than the calcium ion exchange degree obtained by directly performing target metal ion exchange on the NaK-LSX molecular sieve powder.

[0158] It can be seen from Comparative Example 4 that adding an appropriate amount of Ca(OH) 2 to adjust the pH value of the target metal ion solution can significantly improve the calcium ion exchange degree.

[0159] It can be seen from the above experimental results that the present invention can effectively improve the exchange degree of the target metal ion by successively performing potassium ion exchange and target metal ion exchange on the low silica-alumina ratio X-type molecular sieve, controlling the pH value of the solution during the target metal ion exchange process, and adopting the method of adding the molecular sieve at one time or in portions, while saving steps and exchange duration, saving reaction energy consumption. The obtained low silica-alumina ratio X-type molecular sieve containing the target metal ion can be applied to the field of hydrogen pressure swing adsorption purification.

Claims

1. A method for improving the cation exchange degree of X-type zeolite with low silica-alumina ratio, the method comprises: S1. Uniformly disperse NaK-LSX zeolite into a potassium salt solution, perform ultrasonic treatment, then filter, wash, and dry to complete one potassium ion exchange process; Completely repeat the above potassium ion exchange process at least once more to obtain K-LSX zeolite; S2. Uniformly disperse K-LSX zeolite into a mixed solution of a salt solution of a target metal ion and an alkali solution of the target metal ion, perform ultrasonic treatment, then filter, wash, and dry to complete one target metal ion exchange process; Completely repeat the above target metal ion exchange process at least once more to obtain LSX zeolite containing the target metal ion.

2. The method according to claim 1, wherein, S1 in the method comprises: S1. Uniformly disperse NaK-LSX zeolite into a potassium salt solution, perform ultrasonic treatment during the dispersion of NaK-LSX zeolite, maintain ultrasonic treatment after the addition of NaK-LSX zeolite is completed, then filter, wash, and dry to complete one potassium ion exchange process; Completely repeat the above potassium ion exchange process at least once more to obtain K-LSX zeolite.

3. The method according to claim 1 or 2, wherein, S1 in the method comprises: S1. Divide NaK-LSX zeolite into m parts, m≥2, maintain ultrasonic treatment, and add NaK-LSX zeolite to the potassium salt solution portion by portion; wherein, when adding the 1st to (m - 1)th portions of NaK-LSX zeolite, there is a first time interval between the addition of each portion of NaK-LSX zeolite; After the addition of the last portion of NaK-LSX zeolite is completed, maintain the ultrasonic treatment for a second time, then filter, wash, and dry to complete one potassium ion exchange process; Completely repeat the above potassium ion exchange process at least once more to obtain K-LSX zeolite; Preferably, m is 2 - 4.

4. The method according to any one of claims 1 - 3, wherein, the silica-aluminum molar ratio of the NaK-LSX zeolite is 2.0 - 2.2; Preferably, in the NaK-LSX zeolite, the molar ratio of sodium to sodium-potassium is 0.5 - 0.9:

1.

5. The method according to any one of claims 1 - 3, wherein, During a potassium ion exchange process in S1, calculated based on the concentration of potassium salt solution being 0.5 - 1 mol / L, the solid-liquid ratio of the NaK-LSX molecular sieve to the potassium salt solution is 1:5 - 15, preferably 1:5 - 10. + Calculated based on the concentration of potassium salt solution being 0.5 - 1 mol / L, the solid-liquid ratio of the NaK-LSX molecular sieve to the potassium salt solution is 1:5 - 15, preferably 1:5 - 10.

6. The method according to claim 3, wherein, the temperature of the ultrasonic treatment in S1 is 50 - 90°C; and / or, the first time is 3 min - 20 min; and / or, the second time is 30 min - 150 min, preferably 60 min - 120 min.

7. The method according to claim 1, wherein, S2 in the method comprises: S2. Uniformly disperse K-LSX zeolite into a mixed solution of a salt solution of a target metal ion and an alkali solution of the target metal ion, perform ultrasonic treatment during the dispersion of K-LSX zeolite, maintain ultrasonic treatment after the addition of K-LSX zeolite is completed, then filter, wash, and dry to complete one target metal ion exchange process; Repeat the above target metal ion exchange process at least once completely to obtain an LSX molecular sieve containing the target metal ion.

8. The method according to claim 1 or 7, wherein, S2 in this method includes: S2. Divide the K-LSX molecular sieve into n portions, n≥2, maintain ultrasonic treatment, and add the K-LSX molecular sieve portion by portion to the mixed solution of the salt solution of the target metal ion and the alkali solution of the target metal ion; wherein, when adding the 1st to (n - 1)th portions of the K-LSX molecular sieve, there is a third time interval between each addition of the K-LSX molecular sieve portion; After the addition of the last portion of the K-LSX molecular sieve is completed, maintain the ultrasonic treatment for a fourth time, then perform suction filtration, washing, and drying to complete one target metal ion exchange process; Repeat the above target metal ion exchange process at least once completely to obtain an LSX molecular sieve containing the target metal ion; preferably, n is 2 - 4.

9. The method according to claim 8, wherein, the temperature of the ultrasonic treatment in S2 is 50 - 90 °C; and / or, the third time is 3 min - 20 min; and / or, the fourth time is 30 min - 150 min, preferably 60 min - 120 min.

10. The method according to any one of claims 1, 7 - 8, wherein, The target metal ions include Li + , Ca 2+ , Sr 2 + , Ba 2+ , Ag + or a combination of two or more thereof.

11. The method according to any one of claims 1, 7 - 8, wherein, In one target metal ion exchange process of S2, calculated based on the concentration of the target metal ion in the salt solution of the target metal ion being 0.5 - 2 mol / L and the concentration of the target metal ion in the alkali solution of the target metal ion being 0.1 - 0.5 mol / L, the solid-liquid ratio of the K-LSX molecular sieve to the mixed solution in S2 is 1:5 - 15, preferably 1:5 - 10.

12. The method according to any one of claims 1, 7 - 8, wherein, the pH value of the mixed solution in S2 is 7.0 - 8.

0.

13. A low-silica-alumina ratio X-type molecular sieve containing metal cations, which comprises the LSX molecular sieve containing the target metal ion obtained by the method according to any one of claims 1 - 12.

Images