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

Abstract

The application provides a method for improving the cation exchange degree of a low-silicon aluminum ratio X-type molecular sieve and a low-silicon aluminum ratio X-type molecular sieve containing metal cations. The method comprises the following steps: uniformly dispersing NaK-LSX molecular sieve into a potassium salt solution, adding an ultrasonic treatment after the addition is completed, post-treatment, and completing a potassium ion exchange process; repeating the potassium ion exchange process at least once to obtain K-LSX molecular sieve; adding the K-LSX molecular sieve into a mixed solution containing a target metal ion salt and an alkali, adding an ultrasonic treatment after the addition is completed, post-treatment, and completing a target metal ion exchange process; and repeating the target metal ion exchange process at least once to obtain LSX molecular sieve containing the target metal ion. The method can reduce the energy consumption required for the exchange, improve the exchange efficiency and the exchange degree, and is suitable for industrial production of the molecular sieve.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve synthesis technology, and in particular to a method for improving the cation exchange capacity of low silica-alumina ratio X-type molecular sieves and a low silica-alumina ratio X-type molecular sieve containing metal cations. Background Technology

[0002] Low silica-to-alumina ratio (LSX) molecular sieves are octahedral zeolite (FAU) structures formed by connecting silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra through oxygen bridges, with a silica-to-alumina molar ratio between 2.0 and 2.2. Compared to type A molecular sieves, LSX molecular sieves have larger framework pore sizes and higher adsorption capacity. Compared to conventional X-type molecular sieves (silicon-to-alumina molar ratio between 2.2 and 3.0), LSX molecular sieves have a higher aluminum content. Since aluminum is trivalent, meaning the aluminum-oxygen tetrahedra carry a negative charge, there are more anions on the framework, requiring more cations to neutralize the framework charge, thus facilitating ion exchange. The excellent ion exchange characteristics of LSX molecular sieves alter the original pore size and electric field, thereby improving the adsorption capacity and selectivity. For example, studies have reported that Li-LSX or Ca-LSX molecular sieves after lithium or calcium ion exchange have higher nitrogen adsorption capacities than Na-LSX or conventional X-type molecular sieves, and are widely used in gas adsorption and separation applications. However, lithium ions have a small radius and high polarity, making them prone to forming hydrated lithium ions. They are not easily exchanged with sodium and potassium ions in the molecular sieve. Therefore, the exchange process requires a large amount of high-valence lithium salt solution and multiple repeated exchanges to achieve a high degree of ion exchange, resulting in high production costs. The ion exchange of other cations, such as calcium, barium, strontium, and silver ions, with Na-LSX also requires excess salt solution and repeated exchanges to improve the degree of ion exchange.

[0003] Existing cation exchange methods in Na-LSX molecular sieves suffer from problems such as cumbersome steps, long exchange time, high reaction energy consumption, and low ion exchange degree. Therefore, there is a need to provide a method to improve the cation exchange degree of LSX molecular sieves. Summary of the Invention

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

[0005] To achieve the above objectives, the present invention provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

[0006] S1. Disperse NaK-LSX molecular sieve uniformly into potassium salt solution, sonicate, then filter, wash and dry to complete one potassium ion exchange process;

[0007] The potassium ion exchange process described above is repeated at least once more to obtain K-LSX molecular sieves.

[0008] S2. The K-LSX molecular sieve is uniformly dispersed in a mixed solution of salt solution and alkaline solution of target metal ions, subjected to ultrasonic treatment, and then filtered, washed and dried to complete one target metal ion exchange process.

[0009] Repeat the above target metal ion exchange process at least once more to obtain LSX molecular sieves containing target metal ions.

[0010] In the method of the present invention, further, the above-mentioned S1 process of dispersing NaK-LSX molecular sieve can be subjected to ultrasonic treatment to improve the dispersion degree of NaK-LSX molecular sieve in potassium salt solution. S1 in the above method may include: S1, uniformly dispersing NaK-LSX molecular sieve into potassium salt solution, performing ultrasonic treatment during the NaK-LSX molecular sieve dispersion process, maintaining ultrasonic treatment after the NaK-LSX molecular sieve is added, then filtering, washing, and drying to complete one potassium ion exchange process; then completely repeating the above potassium ion exchange process at least once to obtain K-LSX molecular sieve.

[0011] In the method of the present invention, in S1, the NaK-LSX molecular sieve can be dispersed into the potassium salt solution in one step, or it can be dispersed into the potassium salt solution in two or more parts.

[0012] In the method of the present invention, furthermore, in the above-mentioned S1 process, the NaK-LSX molecular sieve can be added in two or more portions, and after each portion of NaK-LSX molecular sieve is added, a certain time interval can be observed before adding the next portion. Specifically, the S1 process may include:

[0013] S1. Divide the NaK-LSX molecular sieve into m portions, where m ≥ 2. Maintain ultrasonic treatment and add the NaK-LSX molecular sieve portion by portion to the potassium salt solution. When adding the first to (m-1) portions of NaK-LSX molecular sieve, the addition time interval between each portion is the first time (during the interval, stop adding NaK-LSX molecular sieve and maintain the above ultrasonic treatment). After the last portion of NaK-LSX molecular sieve is added, maintain the ultrasonic treatment for the second time, then filter, wash, and dry to complete one potassium ion exchange process. Repeat the above potassium ion exchange process at least once to obtain K-LSX molecular sieve.

[0014] In the method of this invention, in S1, m can be further controlled to be 2-4. The NaK-LSX molecular sieve can be added to the potassium salt solution in 2, 3, or 4 portions. By adding the NaK-LSX molecular sieve powder to the potassium solution in small, frequent amounts, the solid-liquid ratio in the system (the solid-liquid ratio in this invention refers to the ratio of the mass of the solid to the volume of the liquid) can be gradually increased. This ensures a low solid-liquid ratio at the initial stage of ion exchange, a sufficient excess of potassium ion solution, and adequate contact between the molecular sieve powder and the potassium ion solution, thereby improving ion exchange efficiency and degree of ion exchange.

[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 molecular sieve may be equal or unequal.

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

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

[0018] In the method of the present invention, during the first potassium ion exchange process of S1, the potassium salt solution is used as the K + For a concentration of 0.5-1 mol / L, the solid-liquid ratio of the NaK-LSX molecular sieve to the potassium salt solution is generally controlled at 1:5-15. For example, it can be specific values ​​such as 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc., or a range with any two of these 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 more specifically, it can be controlled at 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 a specific value such as 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, or 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, specifically including KCl and / or K2SO4, etc.

[0021] In the method of this invention, in step S1, the exchange efficiency and degree of potassium and sodium ions can be adjusted by controlling the temperature of the ultrasonic treatment. The temperature of the ultrasonic treatment in step S1 (including ultrasonic treatment during the NaK-LSX molecular sieve dispersion process and ultrasonic treatment after addition) is denoted as a first temperature, which 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, and 90°C, or a range with any two of these specific values ​​as endpoints. The temperature of the ultrasonic treatment during the NaK-LSX molecular sieve dispersion process and the temperature of the ultrasonic treatment after the molecular sieve addition can be the same or different.

[0022] In the method of the present invention, in S1, the first time is 3 min to 20 min. Specifically, the first time can be a specific value such as 3 min, 5 min, 10 min, 15 min, 20 min, or a range 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 to 150 min. Specifically, the second time can be a specific value 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., or a range with any two of the above specific values ​​as endpoints. The second time can be further controlled to be 60 min to 120 min.

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

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

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

[0027] In the method of the present invention, further, the above-mentioned S2 process of dispersing K-LSX molecular sieve can be subjected to ultrasonic treatment to improve the dispersion degree of K-LSX molecular sieve in the mixed solution containing target metal ions. S2 in the above method may include: S2, uniformly dispersing K-LSX molecular sieve into a mixed solution of a salt solution and an alkaline solution of the target metal ions, performing ultrasonic treatment during the K-LSX molecular sieve dispersion process, maintaining ultrasonic treatment after the K-LSX molecular sieve is added, then filtering, washing, and drying to complete one target metal ion exchange process; then completely repeating the above target metal ion exchange process at least once to obtain 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 once in a mixed solution of the salt solution and the alkaline solution of the target metal ion, or it can be divided into two or more parts and dispersed in a mixed solution of the salt solution and the alkaline solution of the target metal ion.

[0029] Furthermore, in the method of this invention, during the S2 process described above, the K-LSX molecular sieve can be added in two or more portions, and after each portion of K-LSX molecular sieve is added, a certain time interval can be observed before adding the next portion. Specifically, the S2 process may include:

[0030] S2. Divide the K-LSX molecular sieve into n portions, n≥2, and maintain ultrasonic treatment. Add the K-LSX molecular sieve portion by portion to a mixed solution of the target metal ion's salt solution and the target metal ion's alkaline solution. When adding the first to (n-1) portions of K-LSX molecular sieve, the addition time interval between each portion is the third time (during the interval, stop adding K-LSX molecular sieve and maintain the above ultrasonic treatment). After the last portion of K-LSX molecular sieve is added, maintain ultrasonic treatment for the fourth time, then filter, wash, and dry to complete one target metal ion exchange process. Repeat the above target metal ion exchange process at least once to obtain LSX molecular sieve containing the target metal ion (denoted as M-LSX molecular sieve).

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

[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 molecular sieve may be equal or unequal.

[0033] In the method of the present invention, in S2, the mass of each batch of K-LSX molecular sieve can be 20%-80% of the total mass of all K-LSX molecular sieves. Further, the mass of each batch of 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 + One or more combinations of the following, 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 one or more of LiCl, CaCl2, SrCl2, BaCl2, AgNO3, etc.

[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 of the salt of the target metal ion. Specifically, the base of the target metal ion may include one or more of LiOH, Ca(OH)2, Sr(OH)2, Ba(OH)2, AgOH, etc.

[0037] In the method of the present invention, during the first target metal ion exchange process in S2, the target metal ion concentration in the salt solution of the target metal ion is 0.5-2 mol / L and the target metal ion concentration in the alkaline solution of the target metal ion is 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 alkaline solution of the target metal ion) is generally controlled to be 1:5-15. For example, it can be specific values ​​such as 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc., and a range with any two of the above specific values ​​as endpoints. In some specific implementations, the solid-liquid ratio of the K-LSX molecular sieve to the mixed solution can be 1:5-10, or more specifically 1:10, 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 alkaline solution of the target metal ion being 0.1-0.5 mol / L.

[0038] In the above method, the solid-liquid ratio of the molecular sieve in S2 to the mixed solution containing exchanged ions is low (1:5-15), which can reduce the amount of target metal ion solution used, especially when the target metal ion is Li. + Ag + The exchange process of precious metal ions can significantly reduce production costs while ensuring a high degree of exchange.

[0039] In some specific implementations, 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 a specific value such as 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, or a range with any two of the above specific values ​​as endpoints.

[0040] In some specific implementations, in S2, the concentration of the alkaline solution of the target metal ion can be 0.1-0.5 mol / L, for example, it can be a specific value such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, or a range with any two of the above specific values ​​as endpoints.

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

[0042] In the method of this invention, in step S2, the pH value of the mixed solution is 7.0-8.0, for example, it can be a specific value such as 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, or a range with any two of the above specific values ​​as endpoints. The alkaline 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 to a certain extent and protects the original structure, but also reduces the amount of alkaline solution used, protects the equipment, and reduces environmental impact.

[0043] In the method of this invention, in step S2, the exchange efficiency and degree of exchange between the target metal ions and potassium ions can be adjusted by controlling the temperature of the ultrasonic treatment. The temperature of the ultrasonic treatment in S2 (including ultrasonic treatment during the K-LSX molecular sieve dispersion process and ultrasonic treatment after addition) is denoted as the second temperature. This second temperature can be controlled between 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., or a range with any two of the above specific values ​​as endpoints. The temperature of the ultrasonic treatment during the K-LSX molecular sieve dispersion process and the temperature of the ultrasonic treatment after the molecular sieve addition can be the same or different.

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

[0045] In the method of the present invention, in S2, the fourth time can be 30min-150min, for example, it can be a specific value such as 30min, 35min, 40min, 45min, 50min, 55min, 60min, 65min, 70min, 75min, 80min, 85min, 90min, 95min, 100min, 105min, 110min, 115min, 120min, 130min, 140min, 150min, etc., or a range with any two of the above specific values ​​as endpoints. The fourth time can be further controlled to be 60min-120min.

[0046] In the method of this invention, in S2, the ultrasonic power of the ultrasonic treatment can be 500-2000W, for example, 1000W, and the ultrasonic frequency of the ultrasonic treatment can be 30-100kHz, for example, 40kHz. In this invention, the temperature, time, power, and frequency of the ultrasonic treatment in S2 can be the same as or different from the temperature, time, power, and frequency of the ultrasonic treatment in S1.

[0047] In the method of this invention, the target metal ion exchange process included in S2 can be repeated 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 or more parts, and then added one part at a time to a mixed solution of fresh target metal ion salt solution and target metal ion alkaline solution (the mixed solution that has not undergone ion exchange). After each addition except the last one (that is, after adding the 1st to (n-1)th parts of molecular sieve), there is a third time interval (3-20 min). During the process of adding K-LSX molecular sieve and stopping the addition of K-LSX (that is, the interval process), ultrasonic treatment at 50-90°C is maintained. After the last part of K-LSX molecular sieve is added (that is, after all K-LSX molecular sieve is added), the above-mentioned ultrasonic treatment at 50-90°C is maintained for a fourth time (30-150 min), followed by filtration, washing and drying to complete one complete target metal ion exchange process, and then the next complete target metal ion exchange process is continued.

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

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

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

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

[0052] After an interval of 3-20 minutes, the second NaK-LSX molecular sieve was added to the above potassium salt solution, and the solution was subjected to ultrasonic treatment at 50-90℃.

[0053] After an interval of 3-20 minutes, the third NaK-LSX molecular sieve is added to the potassium salt solution. After all NaK-LSX molecular sieves have been added, the solution is ultrasonically treated at 50-90℃ for 30-150 minutes, filtered, washed, and dried to complete the first potassium ion exchange process and obtain 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℃, add the first portion of K'-LSX molecular sieve to a fresh (unexchanged) potassium salt solution and maintain ultrasonic treatment at 50-90℃.

[0055] After an interval of 3-20 minutes, the second portion of K'-LSX molecular sieve was added to the potassium salt solution and sonicated at 50-90°C.

[0056] After an interval of 3-20 minutes, the third K'-LSX molecular sieve is added to the potassium salt solution. After all K'-LSX molecular sieves have been added, the solution is ultrasonically treated at 50-90℃ for 30-150 minutes, filtered, washed, and dried to complete the second potassium ion exchange process and obtain K-LSX molecular sieves.

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

[0058] After an interval of 3-20 minutes, the second portion of K-LSX molecular sieve was added to the above mixed solution, and the mixture was sonicated at 50-90℃.

[0059] After an interval of 3-20 minutes, the third K-LSX molecular sieve is added to the above mixed solution. After all K-LSX molecular sieves have been added, the solution is ultrasonically treated at 50-90℃ for 30-150 minutes, filtered, washed and dried 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 3 portions. Under ultrasonic treatment at 50-90℃, add the first portion of M'-LSX molecular sieve to a mixed solution of fresh target metal ion salt solution and target metal ion alkaline solution, and maintain ultrasonic treatment at 50-90℃.

[0061] After an interval of 3-20 minutes, the second portion of M'-LSX molecular sieve was added to the above mixed solution, and the mixture was sonicated at 50-90℃.

[0062] After an interval of 3-20 minutes, the third M'-LSX molecular sieve is added to the above mixed solution. After all M'-LSX molecular sieves have been added, the solution is ultrasonically treated at 50-90℃ for 30-150 minutes, filtered, washed, and dried to complete the second target metal ion exchange process, thus obtaining M-LSX molecular sieve, i.e. LSX molecular sieve containing the target metal ions.

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

[0064] This invention also provides a low silica-to-alumina ratio X-type molecular sieve containing metal cations, comprising the LSX molecular sieve containing the target metal ion obtained by the above method. The LSX molecular sieve containing the target metal ion obtained by the above method has a high ion exchange capacity.

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

[0066] 1. This invention employs a two-step ion exchange process to prepare M-LSX. First, the original NaK-LSX molecular sieve powder is exchanged into K-LSX, and then further exchanged into M-LSX containing the target metal ions. The Na in the NaK-LSX molecular sieve... + Typically distributed in the SI sites at the center of the hexagonal column cage, the SI' and SII' sites in the β cage, and the SII and SII” sites in the octagonal zeolite cage. + Exchange to K + Afterwards, due to K + Than Na + Large volume, K + The SI sites in the center of the smaller hexagonal columnar cage are not easily stable, but rather tend to exist at the SI' and SII' sites in the larger β cages and the SII and SII” sites in the even larger octahedral zeolite cages. Compared to the center of the hexagonal columnar cage, the β cage and octahedral zeolite cage are larger, therefore potassium exchange can improve the distribution of metal cations in the molecular sieve, causing them to tend to be distributed in the larger constituent building units within the molecular sieve. In the subsequent exchange of target metal ions, K... + Located in larger building blocks, they are more easily replaced by target metal ions, thus effectively improving the exchange rate of target metal ions.

[0067] 2. The method provided by this invention can improve the exchange degree between sodium and potassium ions in low silica-to-alumina ratio X-type molecular sieve (NaK-LSX) raw powder and target metal cations in solution, reduce the number of exchange steps, shorten the exchange time, and efficiently synthesize LSX molecular sieves with high cation exchange degree, thereby increasing the adsorption capacity for non-hydrogen gases and enabling its application in the field of hydrogen pressure swing adsorption purification. Compared with existing ion exchange technologies for NaK-LSX molecular sieves, the ion exchange method of this invention is simpler, more time-saving, lower in cost, reduces the impact of alkaline solutions on instruments and the environment, and can achieve a high ion exchange degree. Attached Figure Description

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

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

[0070] Figure 3 The nitrogen adsorption isotherms at 298 K are for the NaK-LSX raw powder of this invention and the product after secondary calcium ion exchange in Example 12. Detailed Implementation

[0071] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0072] The silica-alumina molar ratio of the NaK-LSX molecular sieve used in the following examples and comparative examples is 2.0-2.2; the molar ratio of sodium to sodium-potassium in the NaK-LSX molecular sieve is 0.5-0.9:1.

[0073] The ultrasonic power used in the following examples and comparative examples is 1000W and the ultrasonic frequency is 40KHz.

[0074] Example 1

[0075] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

[0076] (1) Maintain ultrasonic treatment at 50℃. First, add 1.25g of NaK-LSX molecular sieve powder to 50mL of 0.5mol / L K2SO4 solution. After a 15min interval (i.e., the first time, during which ultrasonic treatment is maintained, and the interval process in other steps of this embodiment and other embodiments and comparative examples is also maintained by ultrasonic treatment), add another 1.25g of NaK-LSX molecular sieve powder to the above solution. After a 15min interval, add another 1.25g of NaK-LSX molecular sieve powder to the above solution. After a 15min interval, add a final 1.25g of NaK-LSX molecular sieve powder to the above solution. Maintain ultrasonic treatment for 90min (i.e., the second time). After filtration, washing and drying, one potassium ion exchange is completed. Repeat the above potassium ion exchange once to obtain K-LSX-1 molecular sieve with a potassium ion exchange degree of 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 until the pH of the solution reaches 8.0. Then, sonicate at 80°C. Add 5 g of K-LSX-1 molecular sieve to the solution at once and sonicate for 120 min (the fourth time). After filtration, washing and drying, one lithium-ion exchange is completed. Repeat the above lithium-ion exchange once to obtain Li-LSX-1 molecular sieve.

[0078] Example 2

[0079] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

[0080] (1) Maintain ultrasonic treatment at 60℃. First, add 1.67g of NaK-LSX molecular sieve raw powder to 50mL of 0.8mol / L K2SO4 solution. After a 10min interval, add another 1.67g of NaK-LSX molecular sieve raw powder to the above solution. After a 10min interval, add the last 1.67g of NaK-LSX molecular sieve raw powder to the above solution. Maintain ultrasonic treatment for 80min. After filtration, washing and drying, one potassium ion exchange is completed. Repeat the above potassium ion exchange once to obtain K-LSX-2 molecular sieve with a potassium ion exchange degree of 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 until the pH of the solution reaches 8.0. Then, maintain the temperature at 90°C and sonicate. Add 5 g of K-LSX-2 molecular sieve to the solution at once and maintain the sonication for 120 min. After filtration, washing and drying, one lithium-ion exchange is completed. Repeat the above lithium-ion exchange once to obtain Li-LSX-2 molecular sieve.

[0082] Example 3

[0083] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

[0084] (1) Maintain ultrasonic treatment at 70℃. First, take 2.5g of NaK-LSX molecular sieve raw powder and add it to 50mL of 0.8mol / L K2SO4 solution. After an interval of 10min, take another 2.5g of NaK-LSX molecular sieve raw powder and add it to the above solution. Maintain ultrasonic treatment for 70min. After filtration, washing and drying, one potassium ion exchange is completed. Repeat the above potassium ion exchange once to obtain K-LSX-3 molecular sieve with a potassium ion exchange degree of 99.3%.

[0085] (2) Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker until the pH of the solution reaches 8.0. Then, maintain the sonication at 80°C. First, add 2.5 g of K-LSX-3 molecular sieve to the above solution. After a 5-minute interval (i.e., the third time), add another 2.5 g of K-LSX-3 molecular sieve to the above solution. Maintain sonication for 90 minutes. After filtration, washing, and drying, one lithium-ion exchange is completed. Repeat the above lithium-ion exchange once to obtain Li-LSX-3 molecular sieve.

[0086] Example 4

[0087] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

[0088] (1) Keep the ultrasonic treatment at 80℃, take 5g of NaK-LSX molecular sieve and add it into 50mL of 1mol / L K2SO4 solution at once, keep the ultrasonic treatment for 90min, filter, wash and dry to complete one potassium ion exchange; repeat the above potassium ion exchange once to obtain K-LSX-4 molecular sieve with a potassium ion exchange degree of 99.0%.

[0089] (2) Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker until the pH of the solution reaches 8.0. Then, maintain the sonication at 90°C. First, add 2.5 g of K-LSX-4 molecular sieve to the above solution. After a 5-minute interval, add another 2.5 g of K-LSX-4 molecular sieve to the above solution. Maintain sonication for 80 minutes. After filtration, washing and drying, one lithium-ion exchange is completed. Repeat the above lithium-ion exchange once to obtain Li-LSX-4 molecular sieve.

[0090] Example 5

[0091] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

[0092] (1) Maintain ultrasonic treatment at 70℃. First, add 1.67g of NaK-LSX molecular sieve raw powder to 50mL of 0.8mol / L K2SO4 solution. After a 5min interval, add another 1.67g of NaK-LSX molecular sieve raw powder to the above solution. After a 5min interval, add the last 1.67g of NaK-LSX molecular sieve raw powder to the above solution. Maintain ultrasonic treatment for 60min. After filtration, washing and drying, one potassium ion exchange is completed. Repeat the above potassium ion exchange once to obtain K-LSX-5 molecular sieve with a potassium ion exchange degree of 99.3%.

[0093] (2) Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker until the pH of the solution reaches 8.0. Then, sonicate at 70°C. First, add 1.67 g of K-LSX-5 molecular sieve to the above solution. After a 15-minute interval, add another 1.67 g of K-LSX-5 molecular sieve to the above solution. After a 15-minute interval, add the last 1.67 g of K-LSX-5 molecular sieve to the above solution. Sonicate for 100 minutes. After filtration, washing and drying, one lithium-ion exchange is completed. Repeat the above lithium-ion exchange once to obtain Li-LSX-5 molecular sieve.

[0094] Example 6

[0095] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

[0096] (1) Maintain ultrasonic treatment at 80℃. First, add 1.67g of NaK-LSX molecular sieve raw powder to 50mL of 1mol / L K2SO4 solution. After a 5min interval, add another 1.67g of NaK-LSX molecular sieve raw powder to the above solution. After a 5min interval, add the last 1.67g of NaK-LSX molecular sieve raw powder to the above solution. Maintain ultrasonic treatment for 60min. After filtration, washing and drying, one potassium ion exchange is completed. Repeat the above potassium ion exchange once to obtain K-LSX-6 molecular sieve with a potassium ion exchange degree of 99.5%.

[0097] (2) Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker until the pH of the solution reaches 8.0. Then, sonicate at 80°C. First, add 1.67 g of K-LSX-6 molecular sieve to the above solution. After a 5-minute interval, add another 1.67 g of K-LSX-6 molecular sieve to the above solution. After a 5-minute interval, add the last 1.67 g of K-LSX-6 molecular sieve to the above solution. Sonicate for 90 minutes. After filtration, washing and drying, one lithium-ion exchange is completed. Repeat the above lithium-ion exchange once to obtain Li-LSX-6 molecular sieve.

[0098] The static nitrogen adsorption capacity of Li-LSX-6 molecular sieve is 19.2 cm⁻¹. 3 / g.

[0099] Example 7

[0100] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

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

[0102] (2) Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker until the pH of the solution reaches 8.0. Then, maintain the solution at 60°C and sonicate. First, add 1.25 g of K-LSX-5 molecular sieve to the solution. After a 10-minute interval, add another 1.25 g of K-LSX-5 molecular sieve to the solution. After a 10-minute interval, add another 1.25 g of K-LSX-5 molecular sieve to the solution. Finally, add another 1.25 g of K-LSX-5 molecular sieve to the solution. Maintain sonication for 100 minutes. After filtration, washing, and drying, one lithium-ion exchange is completed. Repeat the above lithium-ion exchange once to obtain Li-LSX-7 molecular sieve.

[0103] Example 8

[0104] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

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

[0106] (2) Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker until the pH of the solution reaches 8.0. Then, sonicate at 50°C. First, add 1 g of K-LSX-5 molecular sieve to the above solution. After a 15 min interval, add another 1 g of K-LSX-5 molecular sieve to the above solution. After a 15 min interval, add another 1 g of K-LSX-5 molecular sieve to the above solution. After a 15 min interval, add another 1 g of K-LSX-5 molecular sieve to the above solution. Finally, add another 1 g of K-LSX-5 molecular sieve to the above solution. Sonicate for 120 min. After filtration, washing and drying, one lithium-ion exchange is completed. 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 capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

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

[0110] (2) Mix 50 mL of 0.5 mol / L CaCl2 solution and 0.5 mL of 0.5 mol / L Ca(OH)2 solution in a beaker until the pH of the solution reaches 7.8. Then, maintain the temperature at 90°C and sonicate. Add 5 g of K-LSX-5 molecular sieve to the solution at once and maintain sonication for 120 min. After filtration, washing and drying, one calcium ion exchange is completed. 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 capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

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

[0114] (2) Mix 50 mL of 0.5 mol / L CaCl2 solution and 0.5 mL of 0.5 mol / L Ca(OH)2 solution in a beaker until the pH of the solution reaches 7.8. Then, maintain the sonication at 70°C. First, add 2.5 g of K-LSX-5 molecular sieve to the above solution. After an interval of 15 min, add another 2.5 g of K-LSX-5 molecular sieve to the above solution. Maintain sonication for 100 min. After filtration, washing and drying, one calcium ion exchange is completed. 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 capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

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

[0118] (2) Mix 50 mL of 0.5 mol / L CaCl2 solution and 0.5 mL of 0.5 mol / L Ca(OH)2 solution in a beaker until the pH of the solution reaches 7.8. Then, maintain the sonication at 80°C. First, add 2.5 g of K-LSX-5 molecular sieve to the above solution. After a 5-minute interval, add another 2.5 g of K-LSX-5 molecular sieve to the above solution. Maintain sonication for 90 minutes. After filtration, washing and drying, one calcium ion exchange is completed. Repeat the above calcium ion exchange once to obtain Ca-LSX-3 molecular sieve.

[0119] Example 12

[0120] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

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

[0122] (2) Mix 50 mL of 0.5 mol / L CaCl2 solution and 0.5 mL of 0.5 mol / L Ca(OH)2 solution in a beaker until the pH of the solution reaches 7.8. Then, maintain the solution at 70°C and sonicate. First, add 1.67 g of K-LSX-5 molecular sieve to the solution. After a 5-minute interval, add another 1.67 g of K-LSX-5 molecular sieve to the solution. After a 5-minute interval, add the last 1.67 g of K-LSX-5 molecular sieve to the solution. Maintain sonication for 80 minutes. After filtration, washing and drying, one calcium ion exchange is completed. Repeat the above calcium ion exchange once to obtain Ca-LSX-4 molecular sieve.

[0123] The static nitrogen adsorption capacity of Ca-LSX-4 molecular sieve is 24.6 cm⁻¹. 3 / g.

[0124] Example 13

[0125] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

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

[0127] (2) Mix 50 mL of 0.5 mol / L CaCl2 solution and 0.5 mL of 0.5 mol / L Ca(OH)2 solution in a beaker until the pH of the solution reaches 7.8. Then, maintain the solution at 80°C and sonicate. First, add 1.67 g of K-LSX-5 molecular sieve to the solution. After a 5-minute interval, add another 1.67 g of K-LSX-5 molecular sieve to the solution. After a 5-minute interval, add the last 1.67 g of K-LSX-5 molecular sieve to the solution. Maintain sonication for 90 minutes. After filtration, washing and drying, one calcium ion exchange is completed. Repeat the above calcium ion exchange once to obtain Ca-LSX-5 molecular sieve.

[0128] Example 14

[0129] This embodiment provides a method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising:

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

[0131] (2) Mix 50 mL of 0.5 mol / L CaCl2 solution and 0.5 mL of 0.5 mol / L Ca(OH)2 solution in a beaker until the pH of the solution reaches 7.8. Then, maintain the solution at 60°C and sonicate. First, add 1.25 g of K-LSX-5 molecular sieve to the solution. After a 10-minute interval, add another 1.25 g of K-LSX-5 molecular sieve to the solution. After a 10-minute interval, add another 1.25 g of K-LSX-5 molecular sieve to the solution. Finally, add another 1.25 g of K-LSX-5 molecular sieve to the solution. Maintain sonication for 100 minutes. After filtration, washing, and drying, one calcium ion exchange is completed. Repeat the above calcium ion exchange once to obtain Ca-LSX-6 molecular sieve.

[0132] Comparative Example 1

[0133] This comparative example provides a method for cation exchange using X-type molecular sieves with a low silica-to-alumina ratio, the method comprising:

[0134] Mix 50 mL of 1 mol / L LiCl solution and 1 mL of 0.5 mol / L LiOH solution in a beaker until the pH reaches 8.0. Then, sonicate at 70°C. First, add 1.67 g of NaK-LSX molecular sieve powder to the solution. After a 15-minute interval, add another 1.67 g of NaK-LSX molecular sieve powder. After another 15-minute interval, add the final 1.67 g of NaK-LSX molecular sieve powder. Sonicate for 100 minutes. After filtration, washing, and drying, one lithium-ion exchange is completed. Repeat the lithium-ion exchange once to obtain Li-LSX-9 molecular sieve.

[0135] Comparative Example 2

[0136] This comparative example provides a method for cation exchange using X-type molecular sieves with a low silica-to-alumina ratio, the method comprising:

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

[0138] (2) Maintain ultrasonic treatment at 70℃. First, add 1.67g of K-LSX-5 molecular sieve to 50mL of 1mol / L LiCl solution. After a 15min interval, add another 1.67g of K-LSX-5 molecular sieve to the above solution. After a 15min interval, add the last 1.67g of K-LSX-5 molecular sieve to the above solution. Maintain ultrasonic treatment for 100min. After filtration, washing and drying, one lithium-ion exchange is completed. Repeat the above lithium-ion exchange once to obtain Li-LSX-10 molecular sieve.

[0139] Comparative Example 3

[0140] This comparative example provides a method for cation exchange using X-type molecular sieves with a low silica-to-alumina ratio, the method comprising:

[0141] Mix 50 mL of 0.5 mol / L CaCl2 solution and 0.5 mL of 0.5 mol / L Ca(OH)2 solution in a beaker until the pH reaches 7.8. Then, sonicate at 70°C. First, add 1.67 g of NaK-LSX molecular sieve powder to the solution. After a 5-minute interval, add another 1.67 g of NaK-LSX molecular sieve powder. After another 5-minute interval, add the final 1.67 g of NaK-LSX molecular sieve powder. Sonicate for 80 minutes. After filtration, washing, and drying, one calcium ion exchange is completed. Repeat the calcium ion exchange once to obtain Ca-LSX-7 molecular sieve.

[0142] Comparative Example 4

[0143] This comparative example provides a method for cation exchange using X-type molecular sieves with a low silica-to-alumina ratio, the method comprising:

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

[0145] (2) Maintain ultrasonic treatment at 70℃. First, add 1.67g of K-LSX-5 molecular sieve to 50mL of 0.5mol / L CaCl2 solution. After a 5min interval, add another 1.67g of K-LSX-5 molecular sieve to the solution. After a 5min interval, add the last 1.67g of K-LSX-5 molecular sieve to the solution. Maintain ultrasonic treatment for 80min. After filtration, washing and drying, one calcium ion exchange is completed. Repeat the above calcium ion exchange once to obtain Ca-LSX-8 molecular sieve.

[0146] The molecular sieve products of the above embodiments were characterized structurally and their adsorption performance was tested. The results are as follows:

[0147] Figure 1 The XRD patterns of NaK-LSX and Ca-LSX-4 molecular sieves are shown. Figure 1 It can be seen that the Ca-LSX-4 molecular sieve, after successive potassium and calcium ion exchange, exhibits characteristic diffraction peaks of X molecular sieve at 2θ values ​​of 6.1°, 10.0°, 11.7°, 15.4°, 18.4°, 20.1°, 23.3°, 26.6°, 30.3°, 30.9°, and 33.6°, indicating that the product after ion exchange has an intact framework and remains pure X molecular sieve. Figure 2 It can be seen that the exchanged Ca-LSX-3 and Ca-LSX-5 molecular sieves obtained in Examples 11 and 13 also retain the framework and structure of pure X molecular sieves.

[0148] Figure 3 The figures show nitrogen adsorption isotherms for NaK-LSX and Ca-LSX-4 molecular sieves at 298 K. 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⁻¹. 3 / g, which is significantly higher than the nitrogen adsorption capacity of 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 capacity.

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

[0150] Table 1 shows the ion exchange capacity of NaK-LSX molecular sieves.

[0151] 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 in Examples 1 to 6 all exhibited high potassium ion exchange rates, reaching 99% or higher. Among them, the experimental conditions (Example 5) of ultrasonic treatment with a first temperature of 70°C, a first time of 5 min, a second time of 60 min, and the addition of NaK-LSX molecular sieve powder in three equal portions showed the best results. K-LSX molecular sieves obtained after two repeated potassium ion exchange processes... + With an exchange rate of 99.3%, and requiring short ultrasonic time and low ultrasonic temperature, it is a highly efficient potassium ion exchange method.

[0153] For lithium-ion exchange, the experimental conditions in S2—a second ultrasonic treatment at 80°C, a third time of 5 min, a fourth time of 90 min, and the addition of K-LSX molecular sieve in three equal portions (Example 6)—are the best for lithium-ion exchange. The Li-ion exchange was achieved after two repeated exchanges. + The exchange rate reached 96.4%.

[0154] As shown in Comparative Example 1, the lithium-ion exchange degree obtained by first exchanging potassium ions in the NaK-LSX molecular sieve raw powder and then exchanging it with the target metal ions is significantly improved compared with the lithium-ion exchange degree obtained by directly exchanging the target metal ions in the NaK-LSX molecular sieve raw powder.

[0155] As shown in Comparative Example 2, 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 degree of lithium ion exchange.

[0156] For calcium ion exchange, the conditions for optimal ion exchange were: a second ultrasonic treatment temperature of 70°C, a third time of 5 min, a fourth time of 80 min, and the addition of K-LSX molecular sieve in three equal portions (Example 12). Repeating the exchange twice resulted in better calcium ion exchange performance.2+ The exchange rate reached 98.3%.

[0157] As shown in Comparative Example 3, under the same calcium ion exchange conditions, the calcium ion exchange degree obtained by first exchanging NaK-LSX molecular sieve raw powder with potassium ions and then exchanging it with the target metal ions is significantly improved compared with the calcium ion exchange degree obtained by directly exchanging NaK-LSX molecular sieve raw powder with the target metal ions.

[0158] As shown in Comparative Example 4, adding an appropriate amount of Ca(OH)2 to adjust the pH value of the target metal ion solution during calcium ion exchange can significantly improve the degree of calcium ion exchange.

[0159] The experimental results above show that the present invention can effectively improve the degree of exchange of target metal ions by sequentially performing potassium ion exchange and target metal ion exchange on low-silicon-aluminum ratio X-type molecular sieves, controlling the pH value of the solution during the target metal ion exchange process, and using a method of adding molecular sieves once or in stages. At the same time, it saves steps and exchange time, and saves reaction energy consumption. The resulting low-silicon-aluminum ratio X-type molecular sieve containing target metal ions can be applied to the field of hydrogen pressure swing adsorption purification.

Claims

1. A method for improving the cation exchange capacity of low silica-to-alumina ratio X-type molecular sieves, the method comprising: S1. Divide NaK-LSX molecular sieve into m portions, where m≥2. Maintain ultrasonic treatment and add the NaK-LSX molecular sieve portions one by one to the potassium salt solution. Ultrasonic treatment is performed during the dispersion of NaK-LSX molecular sieve. When adding the first to (m-1) portions of NaK-LSX molecular sieve, the time interval between each portion of NaK-LSX molecular sieve addition is the first time. After the last portion of NaK-LSX molecular sieve is added, maintain the ultrasonic treatment for the second time, then filter, wash, and dry to complete one potassium ion exchange process. Repeat the potassium ion exchange process described above one more time to obtain K-LSX molecular sieve; S2. Divide the K-LSX molecular sieve into n portions, n≥2, and maintain ultrasonic treatment. Add the K-LSX molecular sieve portion by portion to a mixed solution of the target metal ion's salt solution and the target metal ion's alkaline solution. Ultrasonic treatment is performed during the dispersion of the K-LSX molecular sieve. When adding the first to (n-1) portions of K-LSX molecular sieve, the addition time interval between each portion of K-LSX molecular sieve is the third time interval. After the last portion of K-LSX molecular sieve is added, maintain the ultrasonic treatment for the fourth time, and then filter, wash, and dry to complete one target metal ion exchange process. Repeat the target metal ion exchange process completely once more to obtain LSX molecular sieves containing the target metal ions; The pH of the mixed solution in S2 is 7.0-8.0; the target metal ions include Li. + Ca 2+ 、Sr 2+ Ba 2+ Ag + One or more combinations of the above.

2. The method according to claim 1, wherein, m is 2-4.

3. The method according to claim 1, wherein, The silicon-aluminum molar ratio of the NaK-LSX molecular sieve is 2.0-2.

2.

4. The method according to claim 3, wherein, In the NaK-LSX molecular sieve, the molar ratio of sodium to sodium potassium is 0.5-0.9:

1.

5. The method according to claim 1, wherein, In a single potassium ion exchange process in S1, the potassium salt solution's K... + Based on a concentration of 0.5-1 mol / L, the solid-liquid ratio of the NaK-LSX molecular sieve to the potassium salt solution is 1:5-15.

6. The method according to claim 5, wherein, In a single potassium ion exchange process in S1, the potassium salt solution's K... + Based on a concentration of 0.5-1 mol / L, the solid-liquid ratio of the NaK-LSX molecular sieve to the potassium salt solution is 1:5-10.

7. The method according to claim 1, wherein, The temperature of the ultrasonic treatment in S1 is 50-90℃; And / or, the first time is 3 min to 20 min; And / or, the second time is 30 min to 150 min.

8. The method according to claim 7, wherein, The second time is 60min-120min.

9. The method according to claim 1, wherein, n is 2-4.

10. The method according to claim 1, wherein, The ultrasonic treatment temperature in S2 is 50-90℃; and / or the third time is 3min-20min. And / or, the fourth time is 30 min to 150 min.

11. The method according to claim 10, wherein, The fourth time period is 60 min to 120 min.

12. The method according to claim 1, wherein, In one target metal ion exchange process of S2, the solid-liquid ratio of the K-LSX molecular sieve to the mixed solution in S2 is 1:5-15, 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 alkaline solution of the target metal ion being 0.1-0.5 mol / L.

13. The method according to claim 12, wherein, In one target metal ion exchange process of S2, the solid-liquid ratio of the K-LSX molecular sieve to the mixed solution in S2 is 1:5-10, 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 alkaline solution of the target metal ion being 0.1-0.5 mol / L.

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