CaLi-LSX molecular sieve as well as preparation method and application thereof

Abstract

The invention discloses a CaLi-LSX molecular sieve as well as a preparation method and application thereof. The framework of the CaLi-LSX molecular sieve is of an FAU topological structure, and the molar ratio of SiO2 to Al2O3 in the framework is 2.0-2.1; the calcium ion exchange degree is 45-65%, the lithium ion exchange degree is 35-55%, the nitrogen adsorption capacity of the CaLi-LSX molecular sieve at normal temperature and normal pressure is not less than 27 mL / g, and the nitrogen-oxygen separation coefficient of the CaLi-LSX molecular sieve at normal temperature and normal pressure is not less than 5. According to the method disclosed by the invention, the CaLSX molecular sieve is firstly obtained during preparation, and then lithium exchange is performed to obtain CaLi-LSX, so that most of lithium ions are fixed in a supercage of the LSX molecular sieve, are easy to exchange and have active SIII (SIII ') sites, while calcium ions are mostly filled in the LSX molecular sieve, and the lithium ions cannot generate active SII (SI') and SII (SII ') sites. The CaLi-LSX molecular sieve disclosed by the invention keeps excellent nitrogen and oxygen adsorption activity of Li-LSX to a certain extent, and has a relatively high nitrogen and oxygen separation coefficient while ensuring relatively high nitrogen adsorption capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve preparation, and specifically relates to CaLi-LSX molecular sieve, its preparation method and application. Background Art

[0002] Traditional oxygen production methods mainly include cryogenic method, pressure swing adsorption method, membrane separation method, etc. With the development of technology, pressure swing adsorption (PSA) oxygen production has gradually become the mainstream oxygen production method, and the adsorbent, which is the core of pressure swing adsorption oxygen production, is also a popular research direction.

[0003] Industrially, modified LSX molecular sieve is commonly used as an adsorbent. Among them, Ca-LSX molecular sieve has a large nitrogen adsorption capacity and low preparation cost, but its nitrogen-oxygen separation coefficient is relatively low, and the oxygen production efficiency is not high during actual use. Li-LSX molecular sieve has a large nitrogen adsorption capacity and a high nitrogen-oxygen separation coefficient, and is currently the most ideal adsorbent for pressure swing adsorption oxygen production. However, due to the development of the lithium battery industry in recent years, the price of lithium salts has been rising year by year, and the cost of fully lithium-exchanged molecular sieve is too high. Therefore, it is urgent to find a new type of adsorbent with high efficiency and low cost.

[0004] CN116177560A uses a combination of liquid-phase exchange method and solid-phase exchange method to prepare LSX molecular sieve mixed with lithium and other metals, which improves the lithium ion loading rate, reduces the generation of lithium ion waste liquid, and improves the nitrogen adsorption capacity and nitrogen selectivity. However, this method has complex operations and a long preparation cycle.

[0005] CN113772689B proposes to use ultra-high temperature hydrothermal exchange to improve the lithium ion exchange degree, and Li-LSX molecular sieve with an exchange degree of more than 97% can be obtained only by two exchanges at 220°C. However, LSX molecular sieve has poor hydrothermal stability, and ultra-high temperature hydrothermal may damage the molecular sieve structure, resulting in a decrease in nitrogen adsorption capacity. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problem of low nitrogen-oxygen separation coefficient of CaLi-LSX molecular sieve prepared by the prior art, and provide CaLi-LSX molecular sieve, its preparation method and application. The CaLi-LSX molecular sieve has a high nitrogen-oxygen separation coefficient while ensuring a high nitrogen adsorption capacity, and the preparation method is simple, easy to operate, and suitable for large-scale industrial applications.

[0007] To achieve the above purpose, in the first aspect of the present invention, a CaLi-LSX molecular sieve is provided. The framework of the CaLi-LSX molecular sieve is of FAU topology structure, and in the framework, SiO 2 and Al 2 O 3The molar ratio is 2.0 to 2.1; the calcium ion exchange degree is 45 to 65%, and the lithium ion exchange degree is 35 to 55%. The nitrogen adsorption capacity of the CaLi-LSX molecular sieve under normal temperature and pressure is not less than 27 mL / g, and the nitrogen-oxygen separation coefficient of the CaLi-LSX molecular sieve under normal temperature and pressure is not less than 5.

[0008] The second aspect of the present invention provides a preparation method of a CaLi-LSX molecular sieve, and the preparation method includes the following steps:

[0009] (1) Carry out calcium ion exchange on a calcium salt solution and a KNa-LSX molecular sieve, and then through separation, washing and drying, obtain a Ca-LSX molecular sieve;

[0010] (2) Carry out lithium ion exchange on the Ca-LSX molecular sieve and a lithium salt solution, and through solid-liquid separation, obtain a solid phase and a liquid phase. Among them, the pH value of the lithium salt solution is 7-10, the solid phase is a CaLi-LSX molecular sieve, and the liquid phase is a mixed solution of a calcium salt and a lithium salt;

[0011] (3) Carry out lithium ion exchange on the solid phase obtained in the previous step and the lithium salt solution, and through solid-liquid separation, obtain a solid phase and a liquid phase;

[0012] (4) Repeat step (3), and then wash, dry and activate the separated solid phase to obtain a CaLi-LSX molecular sieve.

[0013] The third aspect of the present invention provides an oxygen production method, and the method includes: using the CaLi-LSX molecular sieve described in the first aspect or the CaLi-LSX molecular sieve prepared by the preparation method described in the second aspect as a selective adsorbent for PSA oxygen production or VPSA oxygen production.

[0014] Through the above technical solutions, the beneficial technical effects obtained by the present invention are as follows:

[0015] (1) The CaLi-LSX molecular sieve of the present invention maintains the excellent nitrogen-oxygen adsorption activity of Li-LSX to a certain extent. While ensuring a relatively high nitrogen adsorption capacity, it has a relatively high nitrogen-oxygen separation coefficient (not less than 5). Compared with commercial Li-LSX molecular sieves, the lithium content is significantly reduced, and the production cost is effectively reduced.

[0016] (2) In the preparation method of the present invention, first obtain a CaLSX molecular sieve, and then carry out lithium exchange to obtain CaLi-LSX, so that most lithium ions are fixed at the easily exchangeable and active SIII (SIII’) sites in the supercages of the LSX molecular sieve, while calcium ions are mostly filled in the SI (SI’) and SII (SII’) sites in the LSX molecular sieve where lithium ions cannot produce activity. The preparation process of the present invention is simple, easy to operate, and suitable for large-scale application and promotion. Detailed implementation mode

[0017] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0018] The first aspect of the present invention provides a CaLi-LSX molecular sieve, the framework of the CaLi-LSX molecular sieve is of FAU topological structure, and the molar ratio of SiO 2 and Al 2 O 3 in the framework is 2.0-2.1; the calcium ion exchange degree is 45-65%, the lithium ion exchange degree is 35-55%, the nitrogen adsorption capacity of the CaLi-LSX molecular sieve under normal temperature and pressure is not less than 27 mL / g, and the nitrogen-oxygen separation coefficient of the CaLi-LSX molecular sieve under normal temperature and pressure is not less than 5.

[0019] According to the present invention, the exchange degree represents the number of cations in the non-framework. The calcium ion exchange degree refers to the percentage of the calcium ion charge number in the total charge number among the non-framework cations; the lithium ion exchange degree refers to the percentage of the lithium ion charge number in the total charge number among the non-framework cations.

[0020] According to the present invention, both lithium ions and calcium ions play a certain adsorption role in the non-framework of the molecular sieve.

[0021] According to the present invention, the detection method for the lithium ion exchange degree and the calcium ion exchange degree: take 0.04 g of molecular sieve, add 10 mL of nitric acid with a mass concentration of about 23%, carry out microwave digestion at 200 °C and 10 MPa for 30 min, and after digestion, the liquid is diluted with nitric acid with a mass fraction of 1% for ICP testing, and the exchange degrees of lithium ions and calcium ions are obtained from the test results.

[0022] In the present invention, the method specified in GB-T 35109-2017 is used to test the nitrogen-oxygen adsorption capacity of the CaLi-LSX molecular sieve at normal temperature, and the nitrogen adsorption capacity, oxygen adsorption capacity and nitrogen-oxygen separation coefficient are obtained.

[0023] The CaLi-LSX molecular sieve of the present invention maintains the excellent nitrogen-oxygen adsorption activity of Li-LSX to a certain extent. While ensuring a relatively high nitrogen adsorption capacity, it has a relatively high nitrogen-oxygen separation coefficient (not less than 5). Compared with commercial Li-LSX molecular sieves, the lithium content is significantly reduced, and the production cost is effectively reduced.

[0024] According to some embodiments of the present invention, the calcium ion exchange degree is 50-60%, and the lithium ion exchange degree is 40-50%.

[0025] The second aspect of the present invention provides a method for preparing CaLi-LSX molecular sieve, and the preparation method includes the following steps:

[0026] (1) Perform calcium ion exchange on the calcium salt solution and KNa-LSX molecular sieve, and then through separation, washing and drying, obtain Ca-LSX molecular sieve;

[0027] (2) Perform lithium ion exchange on the Ca-LSX molecular sieve and the lithium salt solution, and through solid-liquid separation, obtain a solid phase and a liquid phase. Among them, the pH value of the lithium salt solution is 7-10, the solid phase is CaLi-LSX molecular sieve, and the liquid phase is a mixed solution of calcium salt and lithium salt;

[0028] (3) Perform lithium ion exchange on the solid phase obtained in the previous step and the lithium salt solution, and through solid-liquid separation, obtain a solid phase and a liquid phase;

[0029] (4) Repeat step (3), and then wash, dry and activate the separated solid phase to obtain CaLi-LSX molecular sieve.

[0030] According to some embodiments of the present invention, the pH value of the lithium salt solution is 9-10.

[0031] According to some embodiments of the present invention, the calcium salt in the calcium salt solution is selected from one or more of anhydrous calcium chloride, calcium chloride dihydrate, calcium sulfate and calcium nitrate.

[0032] According to some embodiments of the present invention, the calcium ion concentration in the calcium salt solution is 0.1-1 mol / L.

[0033] According to some embodiments of the present invention, the mass ratio of the volume of the calcium salt solution to the mass of KNa-LSX molecular sieve is 10-40 mL / g.

[0034] According to some embodiments of the present invention, the temperature of the calcium ion exchange is 10-100 °C, the time is 2-6 h, and the number of exchange times is 3-6 times.

[0035] According to the present invention, the number of calcium ion exchanges can be adjusted as needed to finally obtain Ca-LSX molecular sieve.

[0036] According to some embodiments of the present invention, the lithium salt in the lithium salt solution is selected from one or more of lithium nitrate, lithium sulfate and lithium chloride.

[0037] According to some embodiments of the present invention, the lithium ion concentration in the lithium salt solution is 1-3 mol / L.

[0038] According to some embodiments of the present invention, the mass ratio of the volume of the lithium salt solution to the mass of the Ca-LSX molecular sieve is 10-40 mL / g.

[0039] According to some embodiments of the present invention, the temperature of the lithium ion exchange is 10-100 °C and the time is 2-6 h.

[0040] According to the present invention, in step (4), the number of repeated exchanges is determined according to actual needs, and preferably the number of repeated exchanges is 1-5 times. When performing repeated lithium ion exchanges, the lithium salt solution used each time is the same as the lithium salt solution in step (2), and the pH value of the lithium salt solution is controlled to be 7-10, such as 6-8, 8-9, 9-10, etc.

[0041] According to some embodiments of the present invention, the activation temperature is 300-400 °C and the time is 4-7 h.

[0042] According to the present invention, the activation is high-temperature activation, and preferably vacuum degassing is performed, and the vacuum degree is not less than 20 Pa.

[0043] The third aspect of the present invention provides an oxygen production method, which includes: using the CaLi-LSX molecular sieve described in the first aspect or the CaLi-LSX molecular sieve prepared by the preparation method described in the second aspect as a selective adsorbent for PSA oxygen production or VPSA oxygen production.

[0044] According to a particularly preferred embodiment of the present invention, a preparation method of a CaLi-LSX molecular sieve with a high nitrogen-oxygen separation coefficient specifically includes the following steps:

[0045] A. Preparation of Ca-LSX molecular sieve:

[0046] (1) Add deionized water to the calcium salt to completely dissolve it, and prepare a calcium salt solution with a calcium ion concentration of 0.1-1 mol / L;

[0047] (2) According to the mass ratio of the volume (mL) of the calcium salt solution to the mass (g) of the KNa-LSX molecular sieve being 10-40 ml / g, add the KNa-LSX molecular sieve to the calcium salt solution obtained in step (1) and stir evenly;

[0048] (3) Stir the slurry obtained in step (2) at a certain temperature for ion exchange several times;

[0049] (4) After the exchange, obtain a solid sample by suction filtration or centrifugation, wash it and dry it to obtain the Ca-LSX molecular sieve.

[0050] B. Preparation of CaLi-LSX molecular sieve:

[0051] (5) Add deionized water to the lithium salt to completely dissolve it, and prepare a lithium salt solution with a lithium ion concentration of 1-3 mol / L, and adjust the pH value to 7-10;

[0052] (6) Add Ca-LSX molecular sieve to the lithium salt solution obtained in step (5) according to the ratio of the volume (mL) of the lithium salt solution to the mass (g) of the Ca-LSX molecular sieve being 10-40 ml / g, and stir evenly;

[0053] (7) Stir the slurry obtained in step (6) at a certain temperature for ion exchange;

[0054] (8) After the exchange is completed, separate the solid and liquid of the mixed slurry by suction filtration or centrifugation. At this time, the solid is CaLi-LSX molecular sieve with a lower lithium ion exchange degree;

[0055] (9) Prepare a lithium salt solution the same as that in step (6), and stir and mix it evenly with the solid separated in step (8), and stir at a certain temperature for ion exchange;

[0056] (10) Repeat step (9) several times, then separate to obtain a solid product, wash and dry it, and after high-temperature activation, CaLi-LSX molecular sieve with the target lithium ion exchange degree can be obtained.

[0057] The preparation process of the molecular sieve of the present invention includes: dispersing KNa-LSX molecular sieve in a calcium salt solution and exchanging it multiple times to obtain Ca-LSX molecular sieve, and then dispersing Ca-LSX molecular sieve in a lithium salt solution, and screening to obtain CaLi-LSX molecular sieve with the best calcium and lithium ion exchange degree by changing conditions such as exchange temperature, exchange time, exchange times, and water-to-sieve ratio, so that it has excellent nitrogen-oxygen separation coefficient, and at the same time, the nitrogen adsorption capacity is not significantly reduced compared with commercial Li-LSX.

[0058] The CaLi-LSX molecular sieve provided by the present invention solves the problems of low nitrogen-oxygen separation coefficient of Ca-LSX molecular sieve and high production cost of Li-LSX molecular sieve. The preparation method is simple and convenient, and is suitable for large-scale application and promotion.

[0059] The present invention will be described in detail below through preparation examples and implementation examples, but the protection scope of the present invention is not limited to the following description.

[0060] For those not specified in the following preparation examples, implementation examples and comparative examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial channels.

[0061] Preparation Example

[0062] Take 22.42 g of anhydrous calcium chloride, add deionized water to make up the volume to 200 ml to obtain a calcium salt solution for ion exchange; take 10.0 g of KNa-LSX molecular sieve and disperse it evenly in the calcium salt solution. The above system is stirred at room temperature for ion exchange 6 times, 6 hours each time, and the calcium salt solutions used are of the same concentration and volume. After the exchange, filter and wash with 1000 mL of deionized water, and place it in a dry and ventilated indoor environment for drying for 24 h. After vacuum degassing at 350 °C for 5 h, a Ca-LSX molecular sieve with a calcium ion exchange degree of 99.1% is obtained.

[0063] After testing, the molar ratio of SiO 2 and Al 2 in the molecular sieve framework is 2.08, maintaining the FAU topological structure. The Ca-LSX molecular sieve obtained in this preparation example was tested for the nitrogen and oxygen adsorption capacity at room temperature by the method specified in GB-T35109-2017. The results are as follows: nitrogen 35.03 cm 3 / g (STP, 760 mmHg), oxygen 8.69 cm 3 / g (STP, 760 mmHg), and the nitrogen-oxygen separation coefficient is 4.03 (STP, 760 mmHg).

[0064] Example 1

[0065] Take 31.80 g of lithium chloride monohydrate, add deionized water to make up the volume to 200 mL, and adjust the pH to 8.0 with 1% LiOH solution to obtain a lithium salt solution for ion exchange (2.5 mol / L); take 10.0 g of the Ca-LSX molecular sieve (not activated) prepared in the preparation example and disperse it evenly in the lithium salt solution. Heat the above system to 50 °C and stir for ion exchange, repeat 3 times, 6 hours each time. The lithium salt solutions used are of the same concentration and volume. After the exchange, filter and wash with 1000 mL of deionized water, and place it in a dry and ventilated indoor environment for drying for 24 h. After vacuum degassing at 350 °C for 5 h, a CaLi-LSX molecular sieve with a lithium ion exchange degree of 43.7% and a calcium ion exchange degree of 55.8% is obtained.

[0066] After testing, the molar ratio of SiO 2 and Al 2 in the molecular sieve framework is 2.04, maintaining the FAU topological structure. The CaLi-LSX molecular sieve obtained in this example was tested for the nitrogen and oxygen adsorption capacity at room temperature by the method specified in GB-T35109-2017. The results are as follows: nitrogen 28.94 cm 3 O 3 / g (STP, 760 mmHg), oxygen 5.53 cm 3 / g (STP, 760 mmHg), 2 / g(STP, 760 mmHg), the nitrogen-oxygen separation coefficient is 5.23 (STP, 760 mmHg).

[0067] Example 2

[0068] Prepare the CaLi-LSX molecular sieve according to the method of Example 1. The difference is that 5.0 g of the Ca-LSX molecular sieve (not activated) prepared in the preparation example is taken for ion exchange, and finally a CaLi-LSX molecular sieve with a lithium ion exchange degree of 50.2% and a calcium ion exchange degree of 49.4% is obtained.

[0069] After testing, the molar ratio of SiO 2 and Al 2 O 3 in the molecular sieve framework is 2.07, maintaining the FAU topological structure. The CaLi-LSX molecular sieve obtained in this example was tested for normal temperature nitrogen and oxygen adsorption capacity by the method specified in GB-T35109-2017. The results are as follows: nitrogen 27.34 cm 3 / g(STP, 760 mmHg), oxygen 5.43 cm 3 / g(STP, 760 mmHg), the nitrogen-oxygen separation coefficient is 5.03 (STP, 760 mmHg).

[0070] Example 3

[0071] Take 19.07 g of lithium chloride monohydrate, add deionized water to make up the volume to 200 mL, and adjust the pH to 10.0 with 1% LiOH solution to obtain the lithium salt solution for exchange (1.5 mol / L); take 10.0 g of the Ca-LSX molecular sieve (not activated) prepared in the preparation example and disperse it evenly in the lithium salt solution. Heat the above system to 50 °C and stir for ion exchange, repeat 5 times, each time for 6 hours. The lithium salt solutions used are of the same concentration and volume. After exchange, filter and wash with 1000 mL of deionized water, and dry in a dry and ventilated indoor environment for 24 h. After vacuum degassing at 350 °C for 5 h, a CaLi-LSX molecular sieve with a lithium ion exchange degree of 40.5% and a calcium ion exchange degree of 59.0% is obtained.

[0072] After testing, the molar ratio of SiO 2 and Al 2 O 3 in the molecular sieve framework is 2.09, maintaining the FAU topological structure. The CaLi-LSX molecular sieve obtained in this example was tested for normal temperature nitrogen and oxygen adsorption capacity by the method specified in GB-T35109-2017. The results are as follows: nitrogen 28.20 cm 3 / g(STP, 760 mmHg), oxygen 5.57 cm 3 / g(STP, 760 mmHg), the nitrogen-oxygen separation coefficient is 5.06 (STP, 760 mmHg).

[0073] Example 4

[0074] Take 31.80 g of lithium chloride monohydrate, add deionized water to make up the volume to 200 mL, and adjust the pH to 7.0 with 1% LiOH solution to obtain a lithium salt solution for ion exchange (2.5 mol / L); take 10.0 g of the Ca-LSX molecular sieve prepared in the preparation example (not activated) and disperse it evenly in the lithium salt solution. Heat the above system to 50 °C and stir for ion exchange, repeat 4 times, each time for 4 hours. The lithium salt solutions used are of the same concentration and volume. After ion exchange, filter and wash with 1000 mL of deionized water, place it in a dry and ventilated indoor environment for drying for 24 h, and perform vacuum degassing at 350 °C for 5 h to obtain a CaLi-LSX molecular sieve with a lithium ion exchange degree of 46.6% and a calcium ion exchange degree of 52.7%.

[0075] After testing, the molar ratio of SiO 2 and Al 2 O 3 in the molecular sieve framework is 2.08, maintaining the FAU topological structure. The CaLi-LSX molecular sieve obtained in this example was tested for nitrogen and oxygen adsorption capacity at room temperature using the method specified in GB-T35109-2017. The results are as follows: nitrogen 27.68 cm 3 / g(STP, 760 mmHg), oxygen 5.50 cm 3 / g(STP, 760 mmHg), the nitrogen-oxygen separation coefficient is 5.03 (STP, 760 mmHg).

[0076] Comparative Example 1

[0077] Take 31.80 g of lithium chloride monohydrate, add deionized water to make up the volume to 200 mL, and adjust the pH to 8.0 with 1% LiOH solution to obtain a lithium salt solution for ion exchange (2.5 mol / L); take 10.0 g of the Ca-LSX molecular sieve prepared in the preparation example (not activated) and disperse it evenly in the lithium salt solution. Heat the above system to 30 °C and stir for ion exchange for 6 hours. After ion exchange, filter and wash with 1000 mL of deionized water, place it in a dry and ventilated indoor environment for drying for 24 h, and perform vacuum degassing at 350 °C for 5 h to obtain a CaLi-LSX molecular sieve with a lithium ion exchange degree of 20.3% and a calcium ion exchange degree of 79.0%.

[0078] After testing, the SiO in the molecular sieve framework 2 and Al 2 O 3The molar ratio is 2.04, maintaining the FAU topological structure. The CaLi-LSX molecular sieve obtained in this comparative example was tested for the normal-temperature nitrogen and oxygen adsorption capacities using the method specified in GB-T35109-2017. The results were: nitrogen 30.89 cm 3 / g (STP, 760 mmHg), oxygen 7.09 cm 3 / g (STP, 760 mmHg), and the nitrogen-oxygen separation coefficient was 4.35 (STP, 760 mmHg).

[0079] Comparative Example 2

[0080] Take 31.80 g of lithium chloride monohydrate, add deionized water to make up the volume to 200 mL, and adjust the pH to 8.0 with 1% LiOH solution to obtain the lithium salt solution for ion exchange (2.5 mol / L); take 10.0 g of the Ca-LSX molecular sieve (not activated) prepared in the preparation example and disperse it evenly in the lithium salt solution. The above system was heated to 30 °C and stirred for ion exchange, and this was repeated 2 times, 6 hours each time. The lithium salt solutions used were of the same concentration and volume. After the exchange, it was filtered and washed with 1000 mL of deionized water, placed in a dry and well-ventilated indoor environment for drying for 24 h, and degassed under vacuum at 350 °C for 5 h to obtain a CaLi-LSX molecular sieve with a lithium ion exchange degree of 31.0% and a calcium ion exchange degree of 68.4%.

[0081] Upon detection, the SiO 2 and Al 2 O 3 molar ratio of this molecular sieve was 2.04, maintaining the FAU topological structure. The CaLi-LSX molecular sieve obtained in this comparative example was tested for the normal-temperature nitrogen and oxygen adsorption capacities using the method specified in GB-T35109-2017). The results were: nitrogen 28.81 cm 3 / g (STP, 760 mmHg), oxygen 6.42 cm 3 / g (STP, 760 mmHg), and the nitrogen-oxygen separation coefficient was 4.49 (STP, 760 mmHg).

[0082] The lithium ion exchange degrees, calcium ion exchange degrees, nitrogen adsorption capacities, and nitrogen-oxygen separation coefficients of the products obtained in the preparation example, Examples 1-3, and Comparative Examples 1-2 were listed in Table 1 respectively.

[0083] Comparative Example 3

[0084] According to the method of Example 1, the difference was that the pH value of the lithium salt solution for ion exchange was 6.5, and the other steps were the same as in Example 1. The results are shown in Table 1.

[0085] Table 1 Detection Results

[0086]

[0087] As can be seen from the results in Table 1, when the lithium ion exchange degree and calcium ion exchange degree of the CaLi-LSX molecular sieve prepared in Examples 1-4 of the present invention are within a certain range, the nitrogen adsorption capacity can be not less than 27 cm 3 / g (STP, 760 mmHg), and the nitrogen-oxygen separation factor is greater than 5 (STP, 760 mmHg).

[0088] When the lithium ion exchange degree of Comparative Example 1 is 20.3%, the molecular sieve has a relatively high nitrogen adsorption capacity, but the nitrogen-oxygen separation factor is relatively low because at this time, there is less Li + in the molecular sieve, and the main component playing the adsorption role is Ca 2+ .

[0089] Compared with Example 1, the nitrogen adsorption capacity and the nitrogen-oxygen separation factor of Comparative Example 2 are both reduced, indicating that increasing the lithium ion exchange degree is beneficial to improving the nitrogen-oxygen separation factor.

[0090] Compared with Example 1, when the pH value of the lithium salt solution used for exchange in Comparative Example 3 is 6.5, both the nitrogen adsorption capacity and the nitrogen-oxygen separation factor are reduced, indicating that adjusting the pH value of the lithium salt solution used for exchange can affect the nitrogen adsorption capacity and the nitrogen-oxygen separation factor.

[0091] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A CaLi-LSX molecular sieve, characterized in that, The framework of the CaLi-LSX molecular sieve is of FAU topology, and in the framework, the molar ratio of SiO 2 and Al 2 O 3 is 2.0 to 2.1; the calcium ion exchange degree is 45 to 65%, and the lithium ion exchange degree is 35 to 55%. The nitrogen adsorption capacity of the CaLi-LSX molecular sieve under normal temperature and pressure is not less than 27 mL / g, and the nitrogen-oxygen separation coefficient of the CaLi-LSX molecular sieve under normal temperature and pressure is not less than 5.

2. The CaLi-LSX molecular sieve according to claim 1, wherein, the calcium ion exchange degree is 50-60%, and the lithium ion exchange degree is 40-50%.

3. A preparation method of a CaLi-LSX molecular sieve, characterized in that, the preparation method comprises the following steps: (1) Carry out calcium ion exchange on a calcium salt solution and a KNa-LSX molecular sieve, and then through separation, washing and drying, obtain a Ca-LSX molecular sieve; (2) Carry out lithium ion exchange on the Ca-LSX molecular sieve and a lithium salt solution, through solid-liquid separation, obtain a solid phase and a liquid phase, wherein, the pH value of the lithium salt solution is 7-10, the solid phase is a CaLi-LSX molecular sieve, and the liquid phase is a mixed solution of a calcium salt and a lithium salt; (3) Carry out lithium ion exchange on the solid phase obtained in the previous step and the lithium salt solution, through solid-liquid separation, obtain a solid phase and a liquid phase; (4) Repeat step (3), and then wash, dry and activate the separated solid phase to obtain a CaLi-LSX molecular sieve.

4. The preparation method according to claim 3, wherein, the pH value of the lithium salt solution is 9-10.

5. The preparation method according to claim 3 or 4, wherein, the calcium salt in the calcium salt solution is selected from one or more of anhydrous calcium chloride, calcium chloride dihydrate, calcium sulfate and calcium nitrate; and / or, the calcium ion concentration in the calcium salt solution is 0.1-1 mol / L; and / or, the mass ratio of the volume of the calcium salt solution to the mass of the KNa-LSX molecular sieve is 10-40 mL / g.

6. The preparation method according to claim 3 or 4, wherein, the lithium salt in the lithium salt solution is selected from one or more of lithium nitrate, lithium sulfate and lithium chloride; and / or, the lithium ion concentration in the lithium salt solution is 1-3 mol / L; and / or, the mass ratio of the volume of the lithium salt solution to the mass of the Ca-LSX molecular sieve is 10-40 mL / g.

7. The preparation method according to claim 3 or 4, wherein, the temperature of the calcium ion exchange is 10-100 °C, the time is 2-6 h, and the number of exchange times is 3-6 times.

8. The preparation method according to claim 3 or 4, wherein, the temperature of the lithium ion exchange is 10-100 °C, the time is 2-6 h.

9. The preparation method according to claim 3 or 4, wherein, the temperature of the activation is 300-400 °C, the time is 4-7 h.

10. An oxygen production method, characterized in that, the method comprises: using the CaLi-LSX molecular sieve according to claim 1 or 2 or the CaLi-LSX molecular sieve prepared by the preparation method according to any one of claims 3-9 as a selective adsorbent for PSA oxygen production or VPSA oxygen production.

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