Form LiLSX molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the field of molecular sieves, and discloses a LiLSX molecular sieve as well as a preparation method and application thereof. The method comprises the following steps: 1) carrying out first contact and first ion exchange on a form LSX molecular sieve and a potassium-containing solution; 2) carrying out second contact and second ion exchange on the form KLSX molecular sieve and an ammonium-containing solution; (3) in the first container, carrying out third contact on the molded NH4LSX molecular sieve and water, in the second container, introducing water and heating, and then carrying out circulating exchange on the liquid in the first container and the liquid in the second container; 4) blowing air into the liquid in the second container, and then performing fourth contact with the lithium hydroxide solution; and 5) activating the molecular sieve in the first container. When the method is used, the utilization rate of lithium ions is greater than 90%, and a cyclic exchange method is adopted, so that mechanical damage of air blowing and stirring to a sample and potential chemical damage of instantaneous high temperature to the sample are avoided, and final product particles are not damaged and have good integrity.

Description

Technical Field

[0001] The present invention relates to the field of molecular sieves, and in particular to a LiLSX molecular sieve and a preparation method and application thereof. Background Art

[0002] Low silicon X-type molecular sieve, referred to as LSX, its SiO 2 / Al 2 O 3 The molar ratio is 2.0-2.1, and the number of its cationic sites reaches the theoretical maximum value, with more adsorption centers. Currently, the commercial air separation oxygen production adsorbent with the best application effect is lithium-modified LSX molecular sieve (LiLSX). This adsorbent has a large nitrogen adsorption capacity and a high nitrogen-oxygen separation coefficient, and is the core component of the pressure swing adsorption oxygen production process. Pressure swing adsorption air separation technology has been widely used in many fields such as home health care, metallurgy, steelmaking, carbon black production, fertilizer gasification, chemical oxidation, glass processing, pulp bleaching, aquaculture, sewage treatment, and military. LiLSX molecular sieve has shown great market potential.

[0003] The key technology for preparing LiLSX molecular sieve adsorbent is Li + The synthesized X-type molecular sieve usually contains Na + or K + Ions, Li + LiLSX molecular sieve can only be obtained after the exchange of Li. Its exchange degree is generally required to be above 88%. + The higher the exchange rate, the better the performance. + The radius is small and the hydration ability is extremely strong. It is quite difficult to carry out ion exchange in aqueous solution using the existing tank exchange technology. The amount of lithium exchanged each time is required to be 3-6 times excessive, the exchange time is quite long and the number of exchanges is more than 5 times, resulting in extremely low lithium utilization and long production cycle. In addition, the price of lithium salt is expensive, which ultimately leads to high cost of LiLSX molecular sieve.

[0004] Chinese patent CN101289196A introduces a molecular sieve modification method with high lithium salt utilization rate. The LSX zeolite raw powder is exchanged into KLSX molecular sieve by elution, and then the potassium ions in the KLSX molecular sieve are replaced with ammonium ions by ammonium solution. Finally, LiOH solution is used at low temperature to + exchange to obtain LiLSX molecular sieve, and at the same time, air is introduced to discharge NH 3. In this process, the lithium exchange always proceeds in the forward direction and is not limited by equilibrium, so it has a lithium salt utilization rate of more than 90%. However, this scheme is only applicable to the modification of molecular sieve powders. Due to the influence of mass transfer, it is difficult for spherical or strip-shaped molecular sieves to achieve a good exchange degree through elution. Subsequent lithium exchange stirring and air blowing operations will also cause the molded product to break. If the LiLSX molecular sieve powder prepared by the above patent is molded, the corresponding molded adsorbent can also be obtained, but the binder added during molding can no longer be converted into a molecular sieve through the alkali treatment method commonly used in the industry, so the activity of the mold is subject to certain limitations. In summary, it is still necessary and of great significance to find a method for modifying molded molecular sieves with a higher lithium salt utilization rate to prepare LiLSX products. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of damage and low lithium ion utilization rate in the preparation process of molecular sieves in the prior art, and to provide a preparation method of a LiLSX molecular sieve. The method has a lithium ion utilization rate of more than 90%, can effectively control the production cost of the adsorbent, can achieve high exchange degree modification of molecular sieves obtained by direct molding and various LSX molecular sieves processed by alkali treatment after molding, and adopts a cyclic exchange method to avoid mechanical damage to the sample caused by aeration and stirring, and potential chemical damage to the sample caused by excessive local concentration of lithium hydroxide and instantaneous high temperature of the heating interface. The final product particles are free of damage and have good integrity, and can be effectively applied to the pressure swing adsorption oxygen production process.

[0006] In order to achieve the above object, the present invention provides a method for preparing a LiLSX molecular sieve, characterized in that the method comprises the following steps:

[0007] 1) subjecting the LSX molecular sieve to a first contact and a first ion exchange with a potassium-containing solution to obtain a KLSX molecular sieve;

[0008] 2) The KLSX molecular sieve is contacted with the ammonium solution for the second time and the ion exchange is performed for the second time to obtain the NH 4 LSX molecular sieve;

[0009] 3) In the first container, make the NH 4 The LSX molecular sieve and water are contacted for the third time, water is introduced into the second container and heated, and then the liquids in the first container and the second container are circulated and exchanged;

[0010] 4) blowing air into the liquid in the second container, and then contacting the liquid with the lithium hydroxide solution for a fourth time;

[0011] 5) Activate the molecular sieve in the first container to obtain a LiLSX molecular sieve adsorbent.

[0012] Preferably, in step 1), the LSX molecular sieve is NaLSX molecular sieve or KNaLSX molecular sieve.

[0013] Preferably, the LSX molecular sieve is spherical with a diameter of 0.3-5 mm or strip-shaped with a length of 1-10 mm and a cross-sectional diameter of 1-3.5 mm.

[0014] Preferably, the potassium-containing solution is an aqueous solution containing one or more of potassium sulfate, potassium chloride and potassium nitrate.

[0015] Preferably, the potassium-containing solution is an aqueous solution of potassium sulfate.

[0016] Preferably, the concentration of potassium ions in the potassium-containing solution is 0.2-5 mol / L.

[0017] Preferably, the volume of the potassium-containing solution is 5-40 mL relative to 1 g of the LSX molecular sieve.

[0018] Preferably, in step 1), the conditions of the first ion exchange include: time of 10-180 min, temperature of 30-120° C., and number of exchanges of 2-9 times.

[0019] Preferably, in step 2), the ammonium-containing solution is an aqueous solution containing one or more of ammonium sulfate, ammonium chloride and ammonium nitrate.

[0020] Preferably, the ammonium-containing solution is an aqueous solution of ammonium sulfate.

[0021] Preferably, the concentration of ammonium ions in the ammonium-containing solution is 0.2-7 mol / L.

[0022] Preferably, relative to 1 g of the KLSX molecular sieve, the volume of the ammonium solution is 5-40 mL.

[0023] Preferably, in step 2), the conditions of the second ion exchange include: 10-180 min, temperature of 30-120° C., and exchange times of 2-9 times.

[0024] Preferably, in step 3), the body NH 4 The mass ratio of LSX molecular sieve to the water is 1:1-5.

[0025] Preferably, the circulation exchange method is a double pump circulation exchange method.

[0026] Preferably, the conditions for the liquid circulation exchange include: a temperature of 30-120° C. and a flow rate such that the liquids in the first container and the second container are completely replaced within 1-20 minutes.

[0027] Preferably, the flow rate of solution delivered from the bottom of the first container to the top of the second container is equal to the flow rate of solution delivered from the bottom of the second container to the top of the first container.

[0028] Preferably, in step 4), the mass concentration of lithium hydroxide in the lithium hydroxide solution is 1-10%.

[0029] Preferably, the amount of lithium hydroxide used is such that the pH value of the liquid in the second container is 11-12.

[0030] Preferably, when performing step 4), circulation exchange of the liquid in the first container and the liquid in the second container is maintained.

[0031] The second aspect of the present invention provides a LiLSX molecular sieve prepared by the method for preparing the LiLSX molecular sieve according to the first aspect of the present invention.

[0032] The third aspect of the present invention provides a method for preparing the LiLSX molecular sieve described in the first aspect of the present invention or use of the LiLSX molecular sieve described in the second aspect of the present invention in a pressure swing adsorption oxygen production process.

[0033] The present invention, through the preparation method, can overcome the problems of damage and low lithium ion utilization rate in the molecular sieve preparation process in the prior art, so that the single-pass lithium salt utilization rate of the exchange process is more than 90%, and adopts a cyclic exchange method to avoid mechanical damage to the sample caused by aeration and stirring, as well as potential chemical damage to the sample caused by excessive local concentration of lithium hydroxide and instantaneous high temperature of the heating interface. The final product particles are free of damage and have good integrity, and can be effectively applied to the pressure swing adsorption oxygen production process. DETAILED DESCRIPTION

[0034] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise 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, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0035] According to a first aspect of the present invention, a method for preparing a LiLSX molecular sieve is provided, wherein the method comprises the following steps:

[0036] 1) subjecting the LSX molecular sieve to a first contact and a first ion exchange with a potassium-containing solution to obtain a KLSX molecular sieve;

[0037] 2) The KLSX molecular sieve is contacted with the ammonium solution for the second time and the ion exchange is performed for the second time to obtain the NH 4 LSX molecular sieve;

[0038] 3) In the first container, make the NH 4 The LSX molecular sieve is contacted with water for the third time, water is introduced into the second container and heated, and then the liquids in the first container and the second container are circulated and exchanged;

[0039] 4) blowing air into the liquid in the second container, and then contacting the liquid with the lithium hydroxide solution for a fourth time;

[0040] 5) Activate the sample in the first container to obtain a LiLSX molecular sieve adsorbent.

[0041] The circulation exchange method can avoid mechanical damage to the sample caused by aeration and stirring, as well as potential chemical damage to the sample caused by excessive local concentration of lithium hydroxide and instantaneous high temperature of the heating interface, so that the final product particles are intact and have good integrity, and can be effectively used in the pressure swing adsorption oxygen production process.

[0042] According to the present invention, the LSX molecular sieve may be an untreated molecular sieve pellet A directly obtained by conventional molding, or may be a molecular sieve pellet B obtained by alkali treatment or other processing methods after molding, without limitation.

[0043] The preparation method of the untreated KNaLSX molecular sieve beads A can be as follows: KNaLSX molecular sieve beads: a certain amount of sodium silicate nonahydrate is mixed with deionized water, and stirred thoroughly to obtain a first solution; a certain amount of sodium aluminate, sodium hydroxide, and potassium hydroxide are mixed with deionized water, heated to dissolve, and insoluble impurities are filtered out to obtain a second solution; the first solution is added to the second solution, and a stirring state is maintained during the mixing process. After gelation occurs, the stirring rate is increased and the stirring is continued for 20 minutes to obtain n(SiO 2 )∶n(Al 2 O 3 )=2.1,n(Na 2 O+K 2 O)∶n(SiO 2 )=3.35,n(Na 2 O)∶n(Na 2 O+K 2 O)=0.72,n(H 2 O)∶n(Na 2 O+K 2O)=17; the above material precursor is transferred to a 100mL hydrothermal kettle, aged at 60℃ for 5h, and crystallized at 100℃ for 2h; after the reaction, the reaction system is cooled quickly, the obtained product is vacuum filtered, repeatedly washed until the pH of the washing liquid is close to 8, and dried in an oven at 80℃ for 10h to obtain KNaLSX raw powder. KNaLSX raw powder is mixed with a certain amount of kaolin in a mass ratio of 4:1, and after spraying an appropriate amount of water, the material is rolled into a target size ball using a ball rolling machine, and then dried at 80℃ overnight and calcined at 600℃ for 2h to finally obtain KNaLSX molecular sieve balls.

[0044] The preparation method of molecular sieve ball B (KNaLSX molecular sieve alkali treatment and crystallization method) is as follows: the KNaLSX molecular sieve ball is placed in a constant temperature and humidity chamber for pre-wetting, and then immersed in a hydrothermal kettle containing a certain amount of 60g / L sodium hydroxide solution for crystallization at 75°C for 5h, and then fully washed with deionized water until the pH value of the washing liquid is close to 8, and the product is placed in an 80°C oven for overnight drying to obtain an alkali-treated and crystallized product.

[0045] Preferably, the LSX molecular sieve is a NaLSX molecular sieve or a KNaLSX molecular sieve.

[0046] According to the present invention, due to the requirements of domestic oxygen production process or industrial oxygen production process for adsorbent bed pressure drop and mass transfer diffusion performance, the LSX molecular sieve is preferably spherical with a diameter of 0.3-5 mm or a strip with a length of 1-10 mm and a cross-sectional diameter of 1-3.5 mm.

[0047] According to the present invention, the amount of the potassium-containing solution depends on the amount of the LSX molecular sieve. Preferably, the volume of the potassium-containing solution is 5-40 mL relative to 1 g of the LSX molecular sieve; more preferably, the volume of the potassium-containing solution is 10-20 mL relative to 1 g of the LSX molecular sieve.

[0048] According to the present invention, the first contact refers to contacting the potassium-containing solution with the LSX molecular sieve.

[0049] According to the present invention, preferably, the concentration of potassium ions in the potassium-containing solution is 0.1-5 mol / L; more preferably, the concentration of potassium ions in the potassium-containing solution is 0.2-4.5 mol / L.

[0050] According to the present invention, preferably, the potassium-containing solution is an aqueous solution containing one or more of potassium sulfate, potassium chloride and potassium nitrate; more preferably, the potassium-containing solution is an aqueous potassium sulfate solution.

[0051] According to the present invention, since potassium solution is usually acidic and will destroy the unstable low silicon-aluminum ratio molecular sieve structure, step 1) also includes a step of controlling the pH of the potassium-containing solution before the first contact is performed. Preferably, the pH is controlled between 8-14; more preferably, the pH is controlled between 8.3-10.

[0052] According to the present invention, in step 1), a potassium hydroxide aqueous solution is preferably used for pH control, and preferably, the concentration of the potassium hydroxide aqueous solution is 1-10‰.

[0053] In the present invention, the first ion exchange adopts a common ion exchange method in the art, without particular limitation, such as tank exchange or column exchange, etc. Preferably, tank exchange is used.

[0054] According to the present invention, preferably, the conditions for the first ion exchange include: time of 10-180 min, temperature of 30-120° C., and number of exchanges of 2-9 times; more preferably, the conditions for the first ion exchange include: time of 50-70 min, temperature of 90-110° C., and number of exchanges of 3-5 times.

[0055] In the present invention, after the first exchange, it is preferred to include a step of solid-liquid separation of the solution after the first exchange, and then perform a second exchange. The solid-liquid separation can be carried out by a method commonly used in the art, such as filtering, to remove the solution.

[0056] In a particularly preferred embodiment of the present invention, the first ion exchange step is as follows:

[0057] First exchange: the first contact product is subjected to a tank exchange at 98° C. for 60 min, and then the exchanged solution is filtered to remove the solution to obtain the first exchange product;

[0058] Second exchange: add fresh exchange solution to the first exchange product and perform tank exchange at 98°C for 60 minutes, then filter the exchanged solution to remove the solution to obtain the second exchange product;

[0059] And so on.

[0060] In the present invention, in order to prevent potassium ions from adhering to the surface or pores of the exchange product and contaminating the downstream exchange liquid, after the first ion exchange, the method further includes a step of first washing the molecular sieve with water, preferably, the water is deionized water.

[0061] In the present invention, after the first washing step, a step of drying the molecular sieve is also included. Preferably, the drying temperature includes: 70-130°C and the time is 6-24h; more preferably, the drying temperature includes: 90-110°C and the time is 8-12h.

[0062] Step 2) of the present invention is as follows:

[0063] According to the present invention, in order to obtain the NH 4 LSX molecular sieve, the KLSX molecular sieve obtained in step 1) is contacted with an ammonium-containing solution for a second time, preferably, the volume of the ammonium-containing solution is 5-40 mL relative to 1 g of the KLSX molecular sieve; more preferably, the volume of the ammonium-containing solution is 10-20 mL relative to 1 g of the KLSX molecular sieve.

[0064] In the present invention, the second contact refers to contacting the ammonium solution with the KLSX molecular sieve.

[0065] According to the present invention, preferably, the concentration of ammonium ions in the ammonium-containing solution is 0.2-7 mol / L; more preferably, the concentration of ammonium ions in the ammonium-containing solution is 1-5 mol / L.

[0066] According to the present invention, preferably, the ammonium-containing solution is an aqueous solution containing one or more of ammonium sulfate, ammonium chloride and ammonium nitrate; more preferably, the ammonium-containing solution is an aqueous solution of ammonium sulfate.

[0067] According to the present invention, since the ammonium solution is usually acidic and will destroy the unstable low silicon-aluminum ratio molecular sieve structure, step 2) also includes a step of controlling the pH of the ammonium solution before the second contact. Preferably, the pH is controlled between 8-14; more preferably, the pH is controlled between 8.3-10.

[0068] According to the present invention, in step 2), ammonia water is preferably used for pH control, and preferably, the mass concentration of the ammonia water is 20-30%.

[0069] In the present invention, the second ion exchange adopts a common ion exchange method in the art, without particular limitation, such as tank exchange or column exchange, etc. Preferably, tank exchange is used.

[0070] According to the present invention, preferably, the conditions for the second ion exchange include: time 10-180 min, temperature 30-120° C., and number of exchanges 2-9 times; more preferably, the conditions for the first ion exchange include: time 100-150 min, temperature 90-110° C., and number of exchanges 3-5 times.

[0071] In the present invention, after the first exchange, it is preferred to include a step of solid-liquid separation of the solution after the first exchange, and then perform a second exchange. The solid-liquid separation can be carried out by a method commonly used in the art, such as filtering, to remove the solution.

[0072] In a particularly preferred embodiment of the present invention, the second ion exchange step is as follows:

[0073] First exchange: the first contact product is subjected to a tank exchange at 98° C. for 120 min, and then the exchanged solution is filtered to remove the solution to obtain the first exchange product;

[0074] Second exchange: add fresh exchange solution to the first exchange product and perform tank exchange at 98°C for 120 min, then filter the exchanged solution to remove the solution to obtain the second exchange product;

[0075] And so on.

[0076] In the present invention, in order to prevent ammonium ions from adhering to the surface or pores of the exchange product and contaminating the downstream exchange liquid, after the second ion exchange, the molecular sieve is further washed with water for a second time. Preferably, the water is deionized water.

[0077] Step 3) of the present invention is as follows:

[0078] In the present invention, preferably, step 3) adopts a double pump circulation exchange method to circulate and exchange the liquids in the two containers. The specific operation is as follows: in the first container, the NH 4 The LSX molecular sieve and water are contacted for the third time. In the second container, water is introduced and heated. Then, the liquids in the first container and the second container are circulated and exchanged to form a double pump circulation.

[0079] The double pump circulation exchange method is used to complete the conversion of lithium hydroxide to NH 4 The exchange of LSX molecular sieves separates the aeration, stirring, addition of lithium hydroxide and heating processes from the sample exchange process and carries them out simultaneously in two independent containers, thereby avoiding mechanical damage to the sample caused by aeration and stirring, as well as potential chemical damage to the sample caused by excessive local concentration of lithium hydroxide and instantaneous high temperature at the heating interface. The resulting product particles are free of damage, have good integrity and high crystallinity, and can be effectively used in the pressure swing adsorption oxygen production process.

[0080] According to the present invention, the amount of water can be adjusted according to the NH 4 The amount of LSX molecular sieve is selected, preferably, the type NH 4 The mass ratio of LSX molecular sieve to water is 1:1-7; more preferably, the type NH 4The mass ratio of LSX molecular sieve to the water is 1:2-5.

[0081] According to the present invention, in step 3), preferably, the exchange temperature is 30-120° C.; more preferably, the exchange temperature is 80-100° C. Preferably, the flow rate is such that the liquids in the first container and the second container are completely replaced within 1-20 minutes.

[0082] According to a particularly preferred embodiment of the present invention, the same amount of water as that of the first container is introduced into the second container, and the solution flow rate transported from the bottom of the first container to the top of the second container is equal to the solution flow rate transported from the bottom of the second container to the top of the first container.

[0083] Step 4) of the present invention is as follows:

[0084] According to the present invention, preferably, when performing step 4), the circulation exchange is maintained and the temperature thereof remains unchanged.

[0085] In the present invention, before the fourth contacting, an operation of preparing lithium hydroxide may also be included. First, the type NH 4 The ratio of the theoretical amount of lithium hydroxide required for all LSX molecular sieves to be exchanged with lithium ions is less than or equal to 1.1, for example, it can be 1.1:1, 1.09:1, 1.08:1, 1.07:1, 1.06:1, 1.05:1, 1.04:1, 1.03:1, 1.02:1, 1.01:1, 1:1, preferably, it is configured to a lithium hydroxide solution with a mass concentration of 1-10%; more preferably, it is configured to a lithium hydroxide solution with a mass concentration of 3-7%. For example, NH 4 The total mass of LSX molecular sieve is m, the relative molecular mass of lithium hydroxide is M, and the mass concentration of lithium hydroxide solution is y%. By using inductively coupled plasma spectrometer, the unit mass of NH 4 The molar number of aluminum ions in the LSX molecular sieve is x, and the theoretical molar number of lithium ions required is equivalent to the aluminum ions. 1.1 times of this value is the actual amount of lithium ions added, that is, 1.1x. The amount of lithium hydroxide used is 1.1xmM, and water is added to dissolve it to 1.1xmM / y%, thereby obtaining a lithium hydroxide exchange solution, thereby making the lithium ion utilization rate greater than 90%.

[0086] According to the present invention, air is first blown into the solution in the second container. The air may be air in daily life, which may include rare gases such as helium, neon, argon, krypton, xenon, and radon, and may also include impurity gases such as methane, ozone, and ethylene, etc., which are not particularly limited. Since acidic gases can react with lithium hydroxide, the air described in the present invention does not contain acidic gases. The content of rare gases and impurity gases is not particularly limited, as long as it does not exceed 10% of the normal content range. When particulate solids are contained in the gas, they may enter the molecular sieve container with the liquid and mix with the molecular sieve. Therefore, it is preferred to avoid the air described in the present invention containing impurity solids as much as possible.

[0087] According to the present invention, the content of the air to be blown in is not particularly limited, and sufficient air is blown in as long as the reaction can proceed normally and the ammonium ions can be exchanged.

[0088] According to the present invention, in order to avoid excessive gas concentration in the container, preferably, the air velocity of the blown air is 1-4min -1 (Air flow / liquid volume in container).

[0089] According to the present invention, in order to realize the NH formed by the exchanged ammonium ions, 3 In order to effectively discharge and fully mix the lithium hydroxide solution, the air blowing may also include a stirring operation. Preferably, the stirring speed is 200-500 rpm.

[0090] According to the present invention, the fourth contact refers to adding lithium hydroxide to the solution in the second container. Preferably, the amount of lithium hydroxide is such that the pH value of the solution in the second container is maintained between 10 and 14; more preferably, the amount of lithium hydroxide is such that the pH value of the solution in the second container is maintained between 11 and 12.

[0091] According to a particularly preferred embodiment of the present invention, as the lithium hydroxide solution is added, the amount of solution in the second container increases, and the circulation flow of the dual pumps can be continuously adjusted to ensure that the amount of liquid in the two containers is equivalent.

[0092] Step 5) of the present invention is as follows:

[0093] In the present invention, before performing the activation treatment, the reaction in the second container is preferably maintained until the pH of the solution in the second container remains unchanged, at which time the exchange is completed.

[0094] In the present invention, before the activation treatment is performed and after the exchange is completed, the method further includes the steps of performing solid-liquid separation on the solution in the first container, performing a third washing and a second drying on the solid sample.

[0095] According to the present invention, the solid-liquid separation can be performed using methods commonly used in the art, such as filtration, which is not particularly limited. A solid sample is obtained after solid-liquid separation.

[0096] According to the present invention, the third washing uses water to clean the solid sample.

[0097] According to the present invention, preferably, the third drying conditions include: temperature of 30-200°C, time of 0.5-24h; more preferably, the third drying conditions include: temperature of 80-150°C, time of 8-15h.

[0098] According to the present invention, the activation treatment can be carried out by methods commonly used in the art without particular limitation, such as vacuum roasting or flowing hot air roasting, wherein the temperature is 240-500°C for vacuum roasting and 450-700°C for flowing hot air roasting.

[0099] The present invention will be described in detail below by way of examples, but the present invention is not limited to the following examples.

[0100] The exchange degree of potassium ions refers to the ratio of the molar number of potassium ions to the sum of the molar numbers of potassium ions and sodium ions in the KLSX molecular sieve, that is, the exchange degree of potassium ions = (molar number of potassium ions) / (molar number of potassium ions + molar number of sodium ions). This parameter can be obtained by X-ray fluorescence spectrometry (XRF).

[0101] Lithium ion exchange degree: refers to the ratio of the molar number of lithium ions in the LiLSX molecular sieve to the total molar number of all cations in the molecular sieve (all cations in the system are monovalent), that is, the lithium ion exchange degree = (molar number of lithium ions) / (molar number of all cations).

[0102] The lithium ion exchange degree of Comparative Example 2 was obtained by inductively coupled plasma analysis (ICP).

[0103] The lithium ion exchange degree of the embodiment cannot be obtained intuitively, and needs to be indirectly reflected by the adsorption activity (nitrogen adsorption capacity and nitrogen-oxygen separation coefficient) of the molecular sieve. The nitrogen adsorption capacity test and the nitrogen-oxygen separation coefficient are tested by the method specified in the national standard (GB-T35109-2017). The better the adsorption activity of the molecular sieve, the higher the lithium ion exchange degree.

[0104] The NH 4 The potassium oxide content in LSX molecular sieve can also be obtained by dry sample testing (XRF).

[0105] Calculation method of lithium salt utilization rate: The actual content of lithium ions in the LiLSX product is calculated by inductively coupled plasma analysis (ICP), and the ratio of this content to the total amount of lithium ions used to prepare the LiLSX is the lithium salt utilization rate.

[0106] Example 1

[0107] 1) 150 mL of potassium sulfate aqueous solution containing 1 mol / L potassium ions was adjusted to pH 8.5 with 5‰ potassium hydroxide aqueous solution, 10 g of KNaLSX molecular sieve beads A with a diameter of 1.3-1.7 mm were added, the temperature was raised to 98° C., and the exchange was carried out in a tank exchange manner for 1 hour, and then the solution was filtered out, and fresh exchange solution was added to continue the above steps for a total of 5 exchanges; after the completion, the molecular sieve beads were washed with deionized water and dried at 100° C. for 10 hours to obtain a solid KLSX molecular sieve bead, and the potassium ion exchange degree was 99.1% as analyzed by X-ray fluorescence spectroscopy;

[0108] 2) 150 mL of ammonium sulfate aqueous solution containing 2 mol / L ammonium ions was adjusted to pH 8.5 with ammonia water (mass concentration of 25%), and the KLSX molecular sieve beads obtained in step 1) were added, and the temperature was raised to 98°C, and the exchange was carried out in a tank exchange manner for 2 hours, and then the solution was filtered out, and fresh exchange solution was added and continued to be processed according to the above steps for a total of 7 exchanges; after the end, the molecular sieve beads were washed with deionized water to obtain the NH 4 LSX molecular sieve, the potassium oxide content is reduced to 0.15% by dry sample test;

[0109] 3) The NH obtained in step 2) 4 All LSX molecular sieves were placed in the first container, and 20 g of deionized water was added. The same amount of deionized water was introduced into the second container and heated to 85°C. The liquids in the two containers were continuously exchanged using a double pump circulation exchange method, so that the flow rate of the solution transported from the bottom of container A to the top of container B was equal to the flow rate of the solution transported from the bottom of container B to the top of container A, and the flow rate was 10 mL / min, and finally the liquid temperature was kept constant at 85°C;

[0110] 4) Calculate the NH type 4 The theoretical amount of lithium hydroxide required to completely exchange the LSX molecular sieve with lithium ions is calculated to be 1.35 g. Take 1.08 times of this amount, that is, take 1.46 g of LiOH to prepare a solution with a mass concentration of 5%; keep the double pump circulation, blow air into the liquid in container B, the liquid stirring rate is 350 rpm, and the air velocity of blowing air is 2.5 min -1 (ratio of air flow rate to liquid volume in container B), then slowly introduce lithium hydroxide solution to a pH value of 11, while continuously adjusting the circulation flow of the dual pumps to ensure that the liquid amounts in the two containers are equal and that the real-time liquids in the two containers can be replaced once every 5 minutes;

[0111] 5) After the lithium hydroxide solution is introduced, the reaction is maintained for a period of time until the pH of the liquid in container B remains unchanged, indicating that the exchange is completed. The sample in the first container is separated and washed with clean water, dried at 120° C. for 10 h, and activated at 350° C. and 5 Pa vacuum conditions for 5 h to obtain a LiLSX molecular sieve adsorbent product A.

[0112] The adsorbent particles have no damage on the surface and good integrity. The adsorbent was tested for adsorption activity, and its nitrogen adsorption capacity at 25°C and 760mmHg pressure was 24.46mL / g, and the nitrogen-oxygen separation coefficient was 6.54. According to calculations, the single-pass lithium salt utilization rate of the exchange process was 90.7%.

[0113] Example 2

[0114] The method described in Example 1 was followed, except that

[0115] In step 1), a 2 mol / L potassium chloride aqueous solution of potassium ions is used, and the number of exchanges is 4 times, and the potassium ion exchange degree of the obtained KLSX molecular sieve is 98.9%;

[0116] In step 2), 4 mol / L ammonium chloride aqueous solution of ammonium ions was used, and the number of exchanges was 4 times. The obtained NH 4 The potassium oxide content of LSX molecular sieve is reduced to 0.13%.

[0117] Obtain LiLSX molecular sieve adsorbent product B.

[0118] The adsorbent particles have no damage on the surface and good integrity. The adsorbent was tested for adsorption activity, and its nitrogen adsorption capacity at 25°C and 760 mmHg pressure was 24.62 mL / g, and the nitrogen-oxygen separation coefficient was 6.58. According to calculations, the single-pass lithium salt utilization rate of the exchange process is 90.8%.

[0119] Example 3

[0120] The method described in Example 1 was followed, except that

[0121] In step 1), the molecular sieve used is KNaLSX molecular sieve pellet B obtained by alkali treatment and recrystallization, and the potassium ion exchange degree of the obtained KLSX molecular sieve is 99.5%;

[0122] In step 2), the obtained NH 4 The potassium oxide content of LSX molecular sieve is reduced to 0.08%.

[0123] The LiLSX molecular sieve adsorbent product C was obtained. The adsorbent particles had no damage on the surface and good integrity. The adsorbent was tested for adsorption activity, and its nitrogen adsorption capacity at 25°C and 760 mmHg pressure was 28.31 mL / g, and the nitrogen-oxygen separation coefficient was 6.68. According to calculations, the single-pass lithium salt utilization rate of the exchange process was 91.9%.

[0124] Example 4

[0125] The method described in Example 1 was followed, except that

[0126] In step 5), the product is calcined and activated in flowing hot air at 550°C for 2 hours.

[0127] The LiLSX molecular sieve adsorbent product D was obtained. The adsorbent particles had no damage on the surface and good integrity. The adsorbent was tested for adsorption activity. Its nitrogen adsorption capacity at 25°C and 760 mmHg pressure was 24.23 mL / g, and the nitrogen-oxygen separation coefficient was 6.55, which was close to the activity of the product A obtained by activation at 350°C and 5 Pa vacuum conditions for 5 hours in Example 1, indicating that the two activation methods were equivalent. It was calculated that the single-pass lithium salt utilization rate of the exchange process was 90.7%.

[0128] Comparative Example 1

[0129] The method described in Example 1 was followed, except that

[0130] In step 3), without using the first container, the body NH obtained in step 2) is placed in the 4 Put the LSX molecular sieve into the second container, add 40g of deionized water and heat it to keep the liquid temperature constant at 85°C;

[0131] In step 4), the liquid stirring rate is 30 rpm.

[0132] The obtained product E is a LiLSX molecular sieve adsorbent. The adsorbent is severely broken, with many powdery and blocky particles, and the integrity of the small balls is poor. This is caused by the mechanical collision of bubbling and stirring. Even if the stirring speed is greatly reduced, it will still cause severe breakage. The adsorbent was tested for adsorption activity. Its nitrogen adsorption capacity at 25°C and 760mmHg pressure is 23.62mL / g, and the nitrogen-oxygen separation coefficient is 6.31. It is less active than the adsorbent A prepared by the double pump circulation exchange method. This is caused by the destruction of the molecular sieve structure caused by the excessive local concentration when adding lithium hydroxide solution and the local overheating of the heating medium.

[0133] Comparative Example 2

[0134] Prepare 150mL of lithium chloride solution containing 2.2mol / L lithium ions, adjust the pH value to 8.5 with 5‰ lithium hydroxide solution, add 10g of KNaLSX molecular sieve beads A with a diameter of 1.3-1.7mm, heat to 95℃, exchange by tank exchange for 2h, then filter out the solution, add fresh exchange solution and continue to process according to the above steps, exchange 5 times in total; after completion, wash the molecular sieve beads with deionized water, dry at 120℃ for 10h, and activate at 350℃ and 5Pa vacuum conditions for 5h.

[0135] The LiLSX molecular sieve adsorbent product F was obtained. The adsorbent particles had no damage on the surface and good integrity. The lithium ion exchange degree was 98.2%. The adsorbent was tested for adsorption activity, and its nitrogen adsorption capacity at 25°C and 760mmHg pressure was 24.22mL / g, and the nitrogen-oxygen separation coefficient was 6.57. According to calculations, the single-pass lithium salt utilization rate of the exchange process was less than 5%.

[0136] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a LiLSX molecular sieve. It is characterized in that The method comprises the following steps: 1) subjecting the LSX molecular sieve to a first contact and a first ion exchange with a potassium-containing solution to obtain a KLSX molecular sieve; 2) The KLSX molecular sieve is contacted with the ammonium solution for the second time and the ion exchange is performed for the second time to obtain the NH 4 LSX molecular sieve; 3) In the first container, make the NH 4 The LSX molecular sieve and water are contacted for the third time, water is introduced into the second container and heated, and then the liquids in the first container and the second container are circulated and exchanged; 4) blowing air into the liquid in the second container, and then contacting the liquid with the lithium hydroxide solution for a fourth time; 5) Activate the molecular sieve in the first container to obtain a LiLSX molecular sieve adsorbent.

2. The method according to claim 1, in, In step 1), the LSX molecular sieve is NaLSX molecular sieve or KNaLSX molecular sieve; Preferably, the LSX molecular sieve is spherical with a diameter of 0.3-5 mm or strip-shaped with a length of 1-10 mm and a cross-sectional diameter of 1-3.5 mm; Preferably, the potassium-containing solution is an aqueous solution containing one or more of potassium sulfate, potassium chloride and potassium nitrate; Preferably, the potassium-containing solution is an aqueous solution of potassium sulfate; Preferably, the concentration of potassium ions in the potassium-containing solution is 0.2-5 mol / L; Preferably, the volume of the potassium-containing solution is 5-40 mL relative to 1 g of the LSX molecular sieve.

3. The method according to claim 1, in, In step 1), the conditions of the first ion exchange include: time of 10-180 min, temperature of 30-120° C., and exchange times of 2-9 times.

4. The method according to claim 1, in, In step 2), the ammonium-containing solution is an aqueous solution containing one or more of ammonium sulfate, ammonium chloride and ammonium nitrate; Preferably, the ammonium-containing solution is an aqueous solution of ammonium sulfate; Preferably, the concentration of ammonium ions in the ammonium-containing solution is 0.2-7 mol / L; Preferably, relative to 1 g of the KLSX molecular sieve, the volume of the ammonium solution is 5-40 mL.

5. The method according to claim 1, in, In step 2), the conditions of the second ion exchange include: 10-180 min, temperature of 30-120° C., and exchange times of 2-9 times.

6. The method according to claim 1, in, In step 3), the NH 4 The mass ratio of LSX molecular sieve to water is 1:1-5; Preferably, the method for performing the circulation exchange is a double pump circulation exchange method; Preferably, the conditions for the liquid circulation exchange include: a temperature of 30-120° C. and a flow rate such that the liquids in the first container and the second container are completely replaced within 1-20 minutes; Preferably, the flow rate of solution delivered from the bottom of the first container to the top of the second container is equal to the flow rate of solution delivered from the bottom of the second container to the top of the first container.

7. The method according to claim 1, in, In step 4), the mass concentration of lithium hydroxide in the lithium hydroxide solution is 1-10%; Preferably, the amount of lithium hydroxide used is such that the pH value of the liquid in the second container is 11-12.

8. The method according to claim 1, in, When performing step 4), the circulation exchange of the liquid in the first container and the liquid in the second container is maintained.

9. A bulk LiLSX molecular sieve adsorbent prepared by the method for preparing the bulk LiLSX molecular sieve according to claims 1-8.

10. The method for preparing the LiLSX molecular sieve according to claims 1 to 8 or the use of the LiLSX molecular sieve adsorbent according to claim 9 in a pressure swing adsorption oxygen production process.