Modified type molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the field of molecular sieves, and discloses a modified molecular sieve and a preparation method and application thereof. The method comprises the following steps: enabling a lithium salt solution to flow through an exchange column filled with a molded molecular sieve to carry out lithium ion exchange; wherein the exchange column is a hose exchange column, and the exchange column is placed in a water bath or an oil bath to control the temperature of lithium ion exchange. According to the method, the nitrogen adsorption capacity, the nitrogen-oxygen separation coefficient and the lithium salt utilization rate of the molecular sieve can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of molecular sieves, and particularly to a modified type molecular sieve, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-modified low-silica-alumina ratio X-type molecular sieves (LSX) and 13X molecular sieves have excellent nitrogen adsorption capacity and nitrogen-oxygen separation coefficient. In particular, the former has become the most widely used commercial adsorbent and is the core component of the pressure swing adsorption oxygen generation process. The pressure swing adsorption air separation technology has been widely applied in many fields such as home medical care, metallurgy, steelmaking, carbon black production, fertilizer gasification, chemical oxidation, glass processing, pulp bleaching, aquaculture, sewage treatment, and military. LiX molecular sieves exhibit great market potential.

[0003] The technical key to preparing LiX molecular sieve adsorbent is the exchange of Li + The synthesized X-type molecular sieve usually contains Na + or K + ions. After being exchanged with Li + , LiX molecular sieve can be obtained. The exchange degree is generally required to be above 88%. With the increase of the exchange degree of Li + , its performance will be better. Due to the small radius of Li + and its extremely strong hydration ability, it is quite difficult to carry out ion exchange in an aqueous solution using the existing tank exchange technology. Each time, the amount of lithium required for exchange is required to be more than 3-6 times in excess, the exchange time is quite long, and the number of exchange times is more than 5 times, resulting in extremely low utilization rate of lithium, long production cycle, and high cost of LiX molecular sieve due to the high price of lithium salts.

[0004] CN101289196A introduces a molecular sieve modification method with a relatively high utilization rate of lithium salts. The LSX zeolite raw powder is exchanged into KLSX molecular sieve by a leaching method, and then the potassium ions in the KLSX molecular sieve are replaced with ammonium ions using an ammonium-containing solution. Finally, Li + exchange is carried out with LiOH solution at low temperature to obtain LiLSX molecular sieve, and at the same time, air is introduced to discharge NH 3。In this process, lithium exchange always proceeds in the forward direction without being restricted by equilibrium, resulting in a lithium salt utilization rate higher than 90%. However, this solution is only applicable to the modification of molecular sieve powders. Due to mass transfer effects, it is difficult to achieve a good exchange degree for shaped molecular sieves such as spherical or bar-shaped ones through leaching. If the LiLSX molecular sieve powder prepared by the above patent is formed, the corresponding shaped adsorbent can also be obtained. However, the binder added during forming cannot be converted into molecular sieve by the commonly used alkali treatment means in the industry, so the activity of the shaped body is somewhat restricted. Traditional columnar exchange is equivalent to connecting multiple batch exchange reactors in series. As the total length of the exchange column increases, the lithium salt solution is continuously utilized in a stepped manner, thus effectively improving the utilization rate. It can carry out ion exchange on conventional molecular sieve balls or alkali-treated molecular sieve balls. However, it is difficult to extend the total length of the exchange column according to requirements after the completion of the columnar exchange industrial device, and each column needs to be insulated separately, resulting in high energy consumption and poor temperature control uniformity. Especially when conducting columnar exchange research in the laboratory, it is still difficult to adjust the total column length multiple times and ensure uniform temperature of the exchange column. Based on the current situation, it is still an urgent need and of great significance to develop a method for lithium exchange of shaped molecular sieves with convenient application and high metal salt utilization rate. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above problems existing in the prior art and provide a modified shaped molecular sieve, its preparation method and application.

[0006] To achieve the above purpose, in the first aspect of the present invention, a method for modifying a shaped molecular sieve is provided. The method includes: flowing a lithium salt solution through an exchange column filled with a shaped molecular sieve for lithium ion exchange;

[0007] Wherein, the exchange column is a flexible tube exchange column, and the exchange column is placed in a water bath or an oil bath to control the temperature of lithium ion exchange.

[0008] In the second aspect of the present invention, a modified shaped molecular sieve prepared by the above method is provided.

[0009] In the third aspect of the present invention, the application of the above modified shaped molecular sieve in pressure swing adsorption for oxygen production is provided.

[0010] The technical solution of the present invention has at least the following technical effects:

[0011] (1) The method of the present invention can effectively improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve. The method of the present invention has wide applicability and can carry out ion exchange on conventional molecular sieve balls or alkali-treated molecular sieve balls. The modified adsorbent has good nitrogen-oxygen separation activity and can be widely applied to the pressure swing adsorption oxygen production process. Compared with the heating of a conventional rigid tube exchange column, the flexible tube exchange column of the present invention is heated by a water bath or an oil bath, which can effectively improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve.

[0012] (2) The lithium exchange method of the present invention makes up for the deficiencies of traditional columnar exchange. By using a flexible exchange column to carry the shaped molecular sieve, the total column length can be conveniently adjusted, and the temperature of the exchange column can be uniformly controlled by water bath or oil bath, thereby increasing the stability and flexibility of columnar exchange in industry and laboratories. Description of the Drawings

[0013] Figure 1 It is a schematic diagram of the ion exchange device in Examples 1-7. Detailed Embodiments

[0014] 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, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values 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.

[0015] In the first aspect of the present invention, a method for modifying a shaped molecular sieve is provided, and the method includes: flowing a lithium salt solution through an exchange column filled with a shaped molecular sieve for lithium ion exchange; wherein, the exchange column is a flexible hose exchange column, and the exchange column is placed in a water bath or an oil bath to control the temperature of lithium ion exchange.

[0016] The inventors of the present invention have found that, compared with the traditional method using a hard tube for exchange, the flexible hose exchange column is spirally shaped in a special shape, which is beneficial to forming a certain disturbance when the solution inside the exchange column moves, and can kinetically improve the ion exchange rate. Moreover, the flexible hose exchange column can be uniformly heated by a water bath or an oil bath, thereby improving the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve.

[0017] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the flow rate of the lithium salt solution is 0.5-10 cm / min, and it can be 0.5 cm / min, 1 cm / min, 2 cm / min, 3 cm / min, 4 cm / min, 5 cm / min, 6 cm / min, 7 cm / min, 8 cm / min, 9 cm / min, 10 cm / min or any range and values within the range formed by any two of the above values.

[0018] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, Li in the lithium salt solution +The concentration is 0.1 - 3 mol / L, and it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L or any range formed by any two of the above values and the values within the range.

[0019] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, relative to a 1 m exchange column, the flow time of the lithium salt solution is 5 - 50 h, and it can be 5 h, 7 h, 9 h, 10 h, 12 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 24 h, 28 h, 30 h, 32 h, 36 h, 40 h, 44 h, 48 h, 50 h or any range formed by any two of the above values and the values within the range.

[0020] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the exchange column is selected from at least one of a silica gel tube, a rubber tube and a polytetrafluoroethylene tube. When performing the exchange, the exchange column is coiled into an irregular shape, and the irregular shape is a ring, a quadrilateral or a broken line shape.

[0021] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the inner diameter of the exchange column is 5 - 50 mm, for example, it can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm, 30 mm, 32 mm, 34 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, 46 mm, 48 mm, 50 mm or any range formed by any two of the above values and the values within the range.

[0022] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the temperature of the exchange is 35 - 120 °C, and it can be 35 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C or any range formed by any two of the above values and the values within the range.

[0023] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the zeolite molecular sieve is NaX molecular sieve and / or KNaX molecular sieve; preferably, the NaX molecular sieve is NaLSX molecular sieve; preferably, the KNaX molecular sieve is KNaLSX molecular sieve; more preferably, for the preparation method of the LSX molecular sieve containing K, reference can be made to the patent application with the application number 202211394114.X.

[0024] In the present invention, the method for modifying the shaped molecular sieve can also be used for modifying NaLSX and KNaLSX.

[0025] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the shaped molecular sieve is spherical with a particle size of 0.3 - 5 mm, which can be 0.3 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm or any value within the range formed by any two of the above values.

[0026] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the shaped molecular sieve is strip-shaped, with a length of 1 - 10 mm, which can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm or any value within the range formed by any two of the above values, and the cross-sectional diameter is 1 - 3.5 mm, which can be 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm or any value within the range formed by any two of the above values.

[0027] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the exchange column is composed of N single-section exchange columns connected together, where N is 1 - 30, for example, it can be 1 section, 2 sections, 3 sections, 4 sections, 5 sections, 6 sections, 7 sections, 8 sections, 9 sections, 10 sections, 11 sections, 12 sections, 13 sections, 14 sections, 15 sections, 16 sections, 17 sections, 18 sections, 19 sections, 20 sections, 21 sections, 22 sections, 23 sections, 24 sections, 25 sections, 26 sections, 27 sections, 28 sections, 29 sections or 30 sections, preferably 5 - 20 sections. The length of the single-section exchange column is 0.1 - 5 m, which can be 0.1 m, 0.5 m, 1 m, 1.5 m, 2 m, 2.5 m, 3 m, 3.5 m, 4 m, 4.5 m, 5 m or any value within the range formed by any two of the above values, preferably 0.5 - 3 m.

[0028] In the present invention, in order to prevent the molecular sieve in adjacent single-section exchange columns from undergoing exchange, the adjacent single-section exchange columns are separated by gauze, and the pore size of the gauze is smaller than the particle size and cross-sectional diameter of the shaped molecular sieve.

[0029] In the present invention, both ends of the exchange tube are provided with connecting devices, which can connect two single-section exchange tubes.

[0030] In the present invention, in actual operation, the single-section exchange column into which the lithium salt solution is introduced is used as the starting single-section exchange column, and the single-section exchange column from which the lithium salt solution is discharged is used as the terminal single-section exchange column. After the exchange is completed in the starting single-section exchange column, it can be disassembled, and the adjacent single-section exchange column is used as the new starting single-section exchange column, and the new single-section exchange column is connected behind the terminal single-section exchange column. The new single-section exchange column is used as the new terminal single-section exchange column. For a 1m single-section exchange column, a new single-section exchange column is replaced every T / N (flow time of the lithium salt solution in the 1m exchange column / number of connection segments of the exchange column) hours; in some embodiments of the present invention, preferably, a new single-section exchange column is replaced every 0.5 - 20h, and more preferably 0.5 - 2h.

[0031] In the present invention, the molecular sieve can be a conventional molecular sieve or a molecular sieve treated with alkali. In order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the shaped molecular sieve is treated with alkali and crystallized. The alkali treatment and crystallization are not limited and are conventional methods in the art.

[0032] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the method includes: pre-wetting the shaped molecular sieve before the lithium salt solution flows through the exchange column filled with the shaped molecular sieve.

[0033] In the present invention, in order to further improve the nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the molecular sieve, the method further includes: cleaning, drying and activating the exchange product. The temperature of the drying is 30 - 200°C.

[0034] In the present invention, the activation conditions are not limited and are common activation conditions in the art. The activation conditions include: the temperature is 200 - 450°C, the time is 2 - 8h, and the pressure is 2 - 7Pa.

[0035] The second aspect of the present invention provides a modified shaped molecular sieve prepared by the above method.

[0036] The third aspect of the present invention provides the application of the above modified shaped molecular sieve in pressure swing adsorption for oxygen production.

[0037] The present invention will be described in detail below through examples.

[0038] In the following examples, (1) the exchange degree of lithium ions refers to the ratio of the number of moles of lithium ions to the total number of moles of all cations in the LiLSX molecular sieve (all cations in the system are monovalent), that is, the lithium ion exchange degree = (number of moles of lithium ions) / (number of moles of all cations). In the examples, the lithium ion exchange degree can be obtained by statistically analyzing the number of moles of each cation through inductively coupled plasma analysis (ICP) and then calculating according to the above formula;

[0039] (2) The nitrogen adsorption capacity test and the nitrogen-oxygen separation coefficient are tested by the method specified in the national standard (GB / T 35109-2017).

[0040] (3) The lithium salt utilization rate is calculated by statistically analyzing the lithium content in all the outflowing lithium salt solution and the lithium content in all the fresh lithium salt solution used.

[0041] (4) Calculation of the lithium salt utilization rate: 1 - (lithium content in all the outflowing lithium salt solution / lithium content in all the fresh lithium salt solution used).

[0042] (5) Preparation of KNaLSX molecular sieve (with a K content of 10.1 wt% based on KO): 2 Prepare the crystal cluster size regulator according to the method in the preparation example of the patent application with the application number 202211394114.X.

[0043] Prepare the KNaLSX molecular sieve according to the method in Example 1 of the patent application with the application number 202211394114.X.

[0044] Differently, charge water glass, aluminum hydroxide, sodium hydroxide, potassium hydroxide and deionized water in a molar ratio of SiO:AlO:(NaO + KO):water of 2:1:7.5:127.5, and the molar ratio of NaO to NaO + KO is 0.74:1.

[0045] 2 2 3 2 2 2 2 2

[0046] Example 1

[0047] (1) Load 34.8 g of untreated NaLSX molecular sieve pellets with a diameter of 1.3 - 1.7 mm into a 1 m long and 8 mm inner diameter silica gel tube (as a flexible exchange column).

[0048] (2) Connect two sections of the silica gel tubes filled with the above molecular sieve through quick connectors. Install gauze at the tail end of each silica gel tube to prevent the materials in the column from flowing to the downstream, and then coil the connected silica gel tubes into multiple loops of a circular ring.

[0049] (3) Place the coiled silica gel tube in a 25°C water bath, slowly introduce pure water from one end of the connected silica gel tubes to pre-wet the shaped molecular sieve, and the pure water flowing through the bed layer is discharged from the other end of the connected silica gel tubes.

[0050] ​​​​​​​​​After the molecular sieve in the silica gel tube is completely pre-wetted, stop introducing purified water and heat the water bath to 95 °C;

[0051] (5) Pump a 0.7 mol / L lithium chloride solution into one end of the connected silica gel tube through a peristaltic pump at a flow rate of 4 cm / min, and the residual liquid after exchange is discharged and collected from the other end of the connected silica gel tube; after 18 h, the molecular sieve in the first exchange column is modified, disassemble it, and supplement a new silica gel column filled with molecular sieve (the third exchange column) at the tail end of the connected silica gel tube; after 9 h, the molecular sieve in the second exchange column is modified, disassemble it, and supplement a new silica gel column filled with molecular sieve (the fourth exchange column) at the tail end of the connected silica gel tube, and then proceed in turn, disassembling and supplementing an exchange column every 9 h to complete the lithium ion exchange of each exchange column;

[0052] (6) Pass purified water into the disassembled silica gel tube to wash the molecular sieve; the washed product is dried overnight at 80 °C and activated for 5 h under a vacuum condition of 5 Pa at 350 °C.

[0053] Thus, the shaped LiLSX molecular sieve adsorbent A is obtained. Figure 1 It is the schematic diagram of the said exchange method. The lithium ion exchange degree of this adsorbent is about 98.3%. The adsorption activity of the adsorbent is tested. Its nitrogen adsorption capacity is 24.34 mL / g at 25 °C and 760 mmHg pressure, and the nitrogen-oxygen separation coefficient is 6.56. The lithium salt utilization rate in this process is about 18%.

[0054] Example 2

[0055] Carry out according to the method described in Example 1, the difference is that

[0056] In step 2), connect 6 silica gel tubes filled with the above molecular sieve through quick connectors, install gauze at the tail end of each silica gel tube to prevent the materials in the column from flowing to the downstream, and then coil the connected silica gel tubes into a multi-turn ring.

[0057] In step 5), disassemble and supplement an exchange column every 3 h to complete the lithium ion exchange of each exchange column.

[0058] Thus, the shaped LiLSX molecular sieve adsorbent B is obtained. The lithium ion exchange degree of this adsorbent is about 98.3%. The adsorption activity of the adsorbent is tested. Its nitrogen adsorption capacity is 24.63 mL / g at 25 °C and 760 mmHg pressure, and the nitrogen-oxygen separation coefficient is 6.57. The lithium salt utilization rate in this process is about 45%, which is significantly higher than that of the 2-column exchange system.

[0059] Example 3

[0060] Carry out according to the method described in Example 1, the difference is that

[0061] In step 2), 15 silica gel tubes filled with the above molecular sieve are connected through quick connectors. A gauze is installed at the tail end of each silica gel tube to prevent the material in the column from flowing to the downstream, and then the connected silica gel tubes are coiled into a multi-turn ring.

[0062] In step 5), one exchange column is disassembled and replenished every 1.2 h to complete the lithium ion exchange of each exchange column.

[0063] Thus, the LiLSX molecular sieve adsorbent C of the form is obtained. The lithium ion exchange degree of this adsorbent is about 98.5%. The adsorption activity of the adsorbent is tested. Its nitrogen adsorption capacity is 24.66 mL / g at 25 °C and 760 mmHg pressure, and the nitrogen-oxygen separation coefficient is 6.56. The lithium salt utilization rate in this process is about 74%, which is higher than that of the 6-section exchange column system, indicating that this exchange method can adjust the lithium salt utilization rate and can indeed achieve the improvement of the lithium salt utilization rate.

[0064] Example 4

[0065] It is carried out according to the method described in Example 3, except that

[0066] In step 1), the molecular sieve pellets used are NaLSX molecular sieve pellets obtained after alkali treatment and recrystallization, and thus the LiLSX molecular sieve adsorbent D of the form is obtained.

[0067] The specific operation of the alkali treatment and recrystallization of the NaLSX molecular sieve pellets is as follows: The NaLSX molecular sieve pellets described in Example 1 are placed in a constant temperature and humidity box. After pre-wetting, they are immersed in a hydrothermal kettle containing a certain amount of 60 g / L sodium hydroxide solution and crystallized at 75 °C for 5 h. Then, they are washed thoroughly with deionized water until the pH value of the washing solution is close to 8, and the product is placed in an 80 °C oven and dried overnight to obtain the alkali-treated and crystallized NaLSX molecular sieve pellets.

[0068] The lithium ion exchange degree of this adsorbent D is about 99.3%. The adsorption activity of the adsorbent is tested. Its nitrogen adsorption capacity is 28.22 mL / g at 25 °C and 760 mmHg pressure, and the nitrogen-oxygen separation coefficient is 6.64. The lithium salt utilization rate in this process is about 76%, indicating that this exchange method can also be effectively applied to the molecular sieve of the form treated with alkali. Compared with Examples 3 and 4, the adsorption activity of the adsorbent D is significantly improved. On the one hand, because part of the binder in the form pellets is converted into active molecular sieve, and on the other hand, because the alkali treatment dredges the internal pores of the adsorbent, making the exchange more thorough and the lithium ion loading higher.

[0069] Example 5

[0070] According to the method of Example 3, except that the NaLSX molecular sieve is replaced with a NaKLSX molecular sieve, and the potassium content in its framework is K 2O is counted as 10.1% by weight (XRF test result).

[0071] Thus, the shaped LiLSX molecular sieve adsorbent E is obtained. The lithium ion exchange degree of this adsorbent is about 98.7%. The adsorption activity of the adsorbent was tested. Its nitrogen adsorption capacity at 25 °C and 760 mmHg pressure is 24.98 mL / g, and the nitrogen-oxygen separation coefficient is 6.58. The utilization rate of lithium salt in this process is about 75%, indicating that the shaped KNaLSX molecular sieve is also applicable to this method.

[0072] Example 6

[0073] It is carried out according to the method described in Example 3, except that

[0074] In step 1), the particle size of the NaLSX molecular sieve pellets is 0.3 - 0.7 mm;

[0075] In step 3), the silica gel tube is placed in an oil bath;

[0076] In step 4), after the shaped molecular sieve in the silica gel tube is completely pre-wetted, the introduction of pure water is stopped, and the oil bath is heated to 115 °C;

[0077] In step 5), a 0.2 mol / L lithium chloride solution is pumped into one end of the connected silica gel tube through a peristaltic pump at a flow rate of 9 cm / min, and the residual liquid after exchange is discharged and collected from the other end of the connected silica gel tube; after 28 h, the molecular sieve in the first exchange column is modified, and it is disassembled, and a new silica gel column filled with molecular sieve is added to the tail end of the connected silica gel tube; after 1.9 h, the molecular sieve in the second exchange column is modified, and it is disassembled, and a new silica gel column filled with molecular sieve is added to the tail end of the connected silica gel tube, and then it is carried out in turn. Each 1.9 h, an exchange column is disassembled and a new one is added to complete the lithium ion exchange of each exchange column.

[0078] Thus, the shaped LiLSX molecular sieve adsorbent F is obtained. The lithium ion exchange degree of this adsorbent is about 97.5%. The adsorption activity of the adsorbent was tested. Its nitrogen adsorption capacity at 25 °C and 760 mmHg pressure is 23.45 mL / g, and the nitrogen-oxygen separation coefficient is 6.41. The utilization rate of lithium salt in this process is about 70%.

[0079] Example 7

[0080] It is carried out according to the method described in Example 3, except that

[0081] In step 1), the particle size of the NaLSX molecular sieve pellets is 4 - 5 mm;

[0082] In step 4), after the shaped molecular sieve in the silica gel tube is completely pre-wetted, the introduction of pure water is stopped, and the water bath is heated to 45 °C;

[0083] In step 5), a 2.5 mol / L lithium chloride solution is pumped into one end of the connected silica gel tubes through a peristaltic pump at a flow rate of 1 cm / min, and the residual liquid after exchange is discharged and collected from the other end of the connected silica gel tubes; after 21 h, the molecular sieve in the first exchange column is modified, and it is disassembled, and a new silica gel column filled with molecular sieve is added to the tail end of the connected silica gel tubes; after 1.4 h, the molecular sieve in the second exchange column is modified, and it is disassembled, and a new silica gel column filled with molecular sieve is added to the tail end of the connected silica gel tubes, and then it is carried out in turn. Each 1.4 h, an exchange column is disassembled and a new one is added to complete the lithium ion exchange of each exchange column.

[0084] Thus, the LiLSX molecular sieve adsorbent G of the form is obtained. The lithium ion exchange degree of this adsorbent is about 97.9%. The adsorption activity of the adsorbent is tested. Its nitrogen adsorption capacity is 24.06 mL / g at 25 °C and 760 mmHg pressure, and the nitrogen-oxygen separation coefficient is 6.48. The lithium salt utilization rate in this process is about 71%.

[0085] Comparative Example 1

[0086] According to the method of Example 1, the difference is that the silica gel tubes are replaced with polytetrafluoroethylene hard tubes, without coiling, and the temperature is maintained at 95 °C by winding an electric heating tape on the outer wall of the polytetrafluoroethylene hard tubes.

[0087] Thus, the LiLSX molecular sieve adsorbent H of the form is obtained. The lithium ion exchange degree of this adsorbent is about 95.1%. The adsorption activity of the adsorbent is tested. Its nitrogen adsorption capacity is 21.34 mL / g at 25 °C and 760 mmHg pressure, and the nitrogen-oxygen separation coefficient is 6.05. The lithium salt utilization rate in this process is about 14%.

[0088] The lithium ion exchange degree, nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate of the adsorbent H are all significantly lower than the results obtained in Example 1. This is because the hose exchange column is coiled in a special shape, which is conducive to forming a certain disturbance when the solution inside the exchange column moves. It promotes the ion exchange rate kinetically. At the same time, the hard tube cannot be uniformly heated by a water bath or an oil bath, and the heating tape heating usually causes the local temperature of the exchange column to be too low or too high, which will have a negative impact on the exchange process and the molecular sieve structure.

[0089] From the above results, it can be seen that by using the method of the present invention, higher nitrogen adsorption capacity, nitrogen-oxygen separation coefficient and lithium salt utilization rate can be obtained.

[0090] 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 the combination of each technical feature in any other suitable manner. 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 method for modifying a shaped molecular sieve, characterized in that, the method comprises: flowing a lithium salt solution through an exchange column filled with a shaped molecular sieve for lithium ion exchange; wherein, the exchange column is a flexible hose exchange column, and the exchange column is placed in a water bath or an oil bath to control the temperature of lithium ion exchange.

2. The method according to claim 1, wherein, the flow rate of the lithium salt solution is 0.5 - 10 cm / min; and / or, the concentration of Li in the lithium salt solution + is 0.1 - 3 mol / L; and / or, relative to a 1 m exchange column, the flow time of the lithium salt solution is 5 - 50 h.

3. The method according to claim 1 or 2, wherein, the exchange column is selected from at least one of a silica gel tube, a rubber tube and a polytetrafluoroethylene tube; and / or, during the exchange, the exchange column is coiled into an irregular shape, and the irregular shape is a circular ring, a quadrilateral or a broken line shape; and / or, the inner diameter of the exchange column is 5 - 50 mm.

4. The method according to claim 1 or 2, wherein, the temperature of the exchange is 35 - 120 °C; and / or, the shaped molecular sieve is a NaX molecular sieve and / or a KNaX molecular sieve; Preferably, the NaX molecular sieve is a NaLSX molecular sieve; Preferably, the KNaX molecular sieve is a KNaLSX molecular sieve.

5. The method according to claim 1 or 2, wherein, the shaped molecular sieve is spherical, with a particle size of 0.3 - 5 mm; and / or, the shaped molecular sieve is bar-shaped, with a length of 1 - 10 mm and a cross-sectional diameter of 1 - 3.5 mm.

6. The method according to claim 1 or 2, wherein, the exchange column is connected by 1 - 30 single-section exchange columns, and the length of each single-section exchange column is 0.1 - 5 m.

7. The method according to claim 6, wherein, the exchange column is connected by 5 - 20 single-section exchange columns; and / or, the length of each single-section exchange column is 0.5 - 3 m; and / or, the adjacent single-section exchange columns are separated by gauze, and the pore size of the gauze is smaller than the particle size and the cross-sectional diameter of the shaped molecular sieve.

8. The method according to claim 1 or 2, wherein, the shaped molecular sieve has been subjected to alkali treatment and crystallization; and / or, the method comprises: pre-wetting the shaped molecular sieve before flowing the lithium salt solution through the exchange column filled with the shaped molecular sieve; and / or, the method further comprises: cleaning, drying and activating the exchange product.

9. A modified shaped molecular sieve prepared by the method according to any one of claims 1 - 8.

10. Use of the modified shaped molecular sieve according to claim 9 in pressure swing adsorption for oxygen production.

Images