Method for preparing molecular sieve adsorbent by using organic alcohol solution for ion exchange

Abstract

The invention discloses a method for preparing a molecular sieve adsorbent by using an organic alcohol solution for ion exchange, and belongs to the technical field of molecular sieve adsorbent preparation. The preparation method of the molecular sieve adsorbent provided by the invention comprises the following steps: carrying out vacuum drying on a molecular sieve to obtain an activated molecular sieve, carrying out ion exchange on an organic alcohol solution of specific metal ions and the activated molecular sieve to obtain an ion exchange molecular sieve, and carrying out suction filtration washing, vacuum drying and other operations on the obtained ion exchange molecular sieve to obtain the molecular sieve adsorbent. The ion exchange molecular sieve adsorbent is obtained. The alcohol solution is adopted for ion exchange, specific metal ions can be conveniently introduced into the molecular sieve, the adsorption selectivity of the molecular sieve to specific molecules is improved, and meanwhile structural part collapse and adsorption capacity reduction caused by hydrolysis of the molecular sieve in the ion exchange process can be effectively avoided. The prepared molecular sieve adsorbent has excellent adsorption capacity and adsorption selectivity.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of molecular sieve adsorbents, and particularly relates to a method for preparing molecular sieve adsorbents by ion exchange using an organic alcohol solution. Background Art

[0002] Purification of organic substances is an essential process in chemical production. Some organic substances are difficult to separate by traditional distillation processes due to their similar boiling points, especially the separation of olefins and alkanes, and the separation of benzene isomers, which are listed as "the seven separation processes that can change the world" (Nature. 2016, 532, 435 - 437) due to their high economic value and great separation difficulty.

[0003] Adsorption separation is considered a separation method with low energy consumption and high separation efficiency, and can be effectively used for the separation of organic substances with similar boiling points. The principle of adsorption separation is to achieve selective adsorption by utilizing the adsorption differences of different adsorbates in the adsorbent, and then desorb the adsorbate from the adsorbent by specific means to achieve the enrichment of specific component adsorbates. Therefore, the core part of adsorption separation is the adsorbent with adsorption selectivity.

[0004] Silicoaluminate molecular sieve materials are a class of inorganic crystalline materials with regular pore structures formed by covalent bonding of silicon - oxygen tetrahedrons and aluminum - oxygen tetrahedrons. Due to their large and adjustable pore sizes, regular and uniform pore sizes, easy modification of extra - framework cations in the pores, and many adsorption sites, they have very wide applications in the fields of adsorption separation, ion exchange, and catalysis. Commonly used silicoaluminate molecular sieves for adsorption separation are A, X, and Y type molecular sieves.

[0005] Generally speaking, selective adsorption of a certain type of adsorbate can be achieved by introducing specific metal ions into the adsorption sites of A, X, and Y type molecular sieves. Common ion introduction methods include impregnation method, in - situ introduction method, and ion exchange method. The impregnation method is to introduce specific metal salts into the pores of the molecular sieve, which is likely to block the pores of the molecular sieve and is not conducive to the molecular sieve as an adsorbent to adsorb subsequent adsorbates. The in - situ introduction method is to add specific metal cations to the molecular sieve synthesis mother liquor during the molecular sieve synthesis process. This method has a long R & D cycle, complex operation, and a narrow range of applicable metal ions. The ion exchange method is to add the molecular sieve to a solution containing specific metal ions for ion exchange. This principle is simple, the operation is convenient, and the application range is wide, and it is widely used in the synthesis of molecular sieve adsorbents.

[0006] However, the silicon - aluminum ratio of A, X, and Y type molecular sieves is relatively low, and their acid - base resistance is poor. They are prone to hydrolysis in aqueous solutions during the ion exchange process, resulting in the destruction of the molecular sieve framework structure and a decrease in adsorption capacity. Xiao et al. experimentally demonstrated by ab initio molecular simulation that the molecular sieve can hydrolyze and remove aluminum and silicon under acidic conditions, and the H in water+ It will attack the bridging oxygen in the molecular sieve framework (Geochim. Cosmochim. Acta. 1994, 58, 5379 - 5400). Jin et al. also used simulation calculations to explain the hydrolysis phenomenon of molecular sieves under alkaline conditions. OH in water - can act as a catalyst to catalyze the cleavage of Si - O bonds in the framework (Chem. Mater. 2021, 33, 9202 - 9212). Even under neutral conditions, molecular sieves will slowly undergo hydrolysis. Heard et al. used ab initio molecular dynamics simulations combined with experiments to prove that aluminosilicate molecular sieves also undergo hydrolysis in neutral aqueous solutions at room temperature (Nat. Commun. 2019, 10, 4690). The hydrolysis principle of molecular sieves in water can be summarized as that H + and OH - promote the cleavage of the bridging oxygen bonds in the molecular sieve framework. SUMMARY OF THE INVENTION

[0007] To solve the above problems, the purpose of the present invention is to provide a method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution. Using an alcohol solution for ion exchange can conveniently introduce specific metal ions into the molecular sieve, improve its adsorption selectivity for specific molecules, and effectively avoid the hydrolysis of the molecular sieve during ion exchange, resulting in partial collapse of the structure and reduction of the adsorption capacity.

[0008] To achieve the above object of the invention, the present invention adopts the following technical solutions:

[0009] A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution, comprising the following steps:

[0010] 1) Drying and activation: Place the molecular sieve raw material in a common oven at 95 - 105 °C for preliminary drying for 1.8 - 2.2 h, then take out the preliminarily dried molecular sieve and place it in a vacuum drying oven, and vacuum dry it at 0.5 - 10 Pa and 250 °C for 1.8 - 2.2 h to obtain the activated molecular sieve raw material;

[0011] 2) Ion exchange solution: Select an organic alcohol as the solvent, dissolve a salt containing metal ions in the organic alcohol solvent to prepare an organic alcohol solution with a metal ion concentration of 1 - 0.001 mol / L. The metal ions are Li + , K + , Rb + , Cs + , Mg 2 + , Ca 2+ , Sr 2+ , Ba 2+ , Ni 2+ , Cu2+ 、 Zn 2+ 、 Ag + or any one of the following;

[0012] 3) In a reflux device, mix the molecular sieve raw material activated in step 1) with the organic alcohol solution in step 2) for ion exchange. During the ion exchange process, the temperature of the exchange system is 25 - 100 °C, the exchange time is 1 - 72 h, and the number of exchange times is 1 - 8 times;

[0013] 4) Filter the ion-exchanged molecular sieve successively by suction filtration, washing, and vacuum drying to obtain an ion-exchanged molecular sieve adsorbent.

[0014] Preferably, the number of ion exchange times is 1 - 8 times, that is, steps 3) - 4) are repeated 1 - 8 times.

[0015] Preferably, the molecular sieve raw material described in step 1) is any one of A-type, X-type, or Y-type molecular sieves.

[0016] Preferably, the organic alcohol solvent described in step 2) is any one of methanol, ethanol, ethylene glycol, propanol, propylene glycol, glycerol, or a solution prepared by mixing these organic alcohols in any proportion, and the water content of the organic alcohol is not more than 1%.

[0017] Preferably, the mixing ratio of the activated molecular sieve raw material to the organic alcohol solution in step 3) is 1 g: 1 - 200 mL.

[0018] Preferably, the suction filtration temperature in step 4) is 50 - 100 °C.

[0019] Preferably, the washing in step 4) is carried out in an organic alcohol solvent, the washing temperature is 25 - 100 °C, the washing time is 0.1 - 1 h, and the number of washing times is 1 - 8 times.

[0020] Preferably, the absolute pressure of the vacuum drying in step 4) is 0.5 - 10 Pa, and the heating program is to heat to 95 - 105 °C at a rate of 1 - 10 °C / min and hold for 0.5 - 2 h, then heat to 240 - 260 °C at a rate of 1 - 10 °C / min and hold for 2 - 24 h.

[0021] The molecular sieve adsorbent prepared by the present invention has an exchange degree greater than 70% and a specific surface area greater than 600 m 2 / g and can be used for the adsorption separation of organic mixtures.

[0022] The present invention has the following beneficial effects:

[0023] 1. Organic alcohols are not easily dissociated into H + , and at the same time, they will not dissociate into OH -, so it can be used as an excellent dispersion medium for zeolite ion exchange. The present invention uses an organic alcohol solution for ion exchange, which can conveniently introduce specific metal ions into the zeolite, improve its adsorption selectivity for specific molecules, and at the same time can maximize the avoidance of partial collapse of the zeolite structure caused by hydrolysis during ion exchange, and protect the integrity of the zeolite crystal structure as much as possible, ensuring that the zeolite adsorbent has a large specific surface area and adsorption capacity.

[0024] 2. The operation of the present invention is simple, and the range of applicable metal ions is wide, and specific metal cations can be conveniently and quickly introduced into the zeolite pores.

[0025] 3. After introducing specific metal ions, the zeolite adsorbent prepared by the present invention still has a complete crystal structure and a large adsorption capacity, so it has excellent adsorption and separation ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 XRD pattern of the Li + exchanged X-type zeolite adsorbent prepared in Example 1.

[0027] Figure 2 XRD pattern of the Li + exchanged X-type zeolite adsorbent prepared in Example 1.

[0028] Figure 3 Nitrogen adsorption and desorption isotherm of the Li + exchanged X-type zeolite adsorbent prepared in Example 1.

[0029] Figure 4 XRD pattern of the Ni 2+ exchanged X-type zeolite adsorbent prepared in Example 2.

[0030] Figure 5 Nitrogen adsorption and desorption isotherm of the Ni 2+ exchanged X-type zeolite adsorbent prepared in Example 2.

[0031] Figure 6 Adsorption breakthrough curve of the Ni 2+ exchanged X-type zeolite adsorbent for a mixture of acetylene and ethylene prepared in Example 2.

[0032] Figure 7 XRD pattern of the Ba 2+ exchanged X-type zeolite adsorbent prepared in Example 3.

[0033] Figure 8 Nitrogen adsorption and desorption isotherm of the Ba 2+ exchanged X-type zeolite adsorbent prepared in Example 3.

[0034] Figure 9 Ag prepared for Example 4 + XRD pattern of the Ag-exchanged Y-type molecular sieve adsorbent.

[0035] Figure 10 Ag prepared for Example 4 + N2 adsorption-desorption isotherm of the Ag-exchanged Y-type molecular sieve adsorbent.

[0036] Figure 11 Ag prepared for Example 4 + Isothermal adsorption curve of the Ag-exchanged Y-type molecular sieve adsorbent for propylene and propane.

[0037] Figure 12 Ag prepared for Example 5 + XRD pattern of the Ag-exchanged A-type molecular sieve adsorbent.

[0038] Figure 13 Ag prepared for Example 5 + N2 adsorption-desorption isotherm of the Ag-exchanged A-type molecular sieve adsorbent.

[0039] Figure 14 Ag prepared for Example 5 + Adsorption breakthrough curve of the Ag-exchanged A-type molecular sieve adsorbent for the ethylene and ethane mixture. Detailed implementation mode

[0040] The technical solution of the present invention will be further explained and illustrated through specific examples below. In the present invention, unless otherwise specified, all raw materials are commercially available products. The molecular sieves used in the examples were purchased from Tianjin Nanhua Catalyst Co., Ltd.

[0041] Example 1

[0042] A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution, comprising the following steps:

[0043] 1) Weigh 5 g of Na-X type molecular sieve powder with a silica-alumina ratio of 1.0 and put it into a crucible, then transfer it to an oven for preliminary drying at 100 °C for 2 h. Then take out the preliminarily dried molecular sieve and place it in a vacuum drying oven for vacuum drying at 0.5 Pa and 250 °C for 2 h to obtain the activated molecular sieve.

[0044] 2) Prepare 500 mL of a methanol solution of 0.1 mol / L LiCl. Quickly take out the activated molecular sieve powder from the vacuum drying oven and add it to the above solution. Slowly heat the turbid liquid mixed with the molecular sieve to 60 °C in a three-necked flask equipped with a condenser reflux tube. During the heating process, use magnetic stirring to make the solution heat evenly. Under this condition, maintain the exchange for 6 h. After the exchange is completed, filter the solution to obtain a filter cake.

[0045] 3) Put the filter cake into methanol solvent, stir and wash it at 60 °C for 1 h, then filter the solution to obtain the filter cake. Repeat this step three times.

[0046] 4) Put the filter cake obtained in step 3) into a crucible, quickly transfer it to a vacuum drying oven. During the drying process, use a vacuum pump to evacuate to keep the absolute pressure in the vacuum drying oven less than 1.0 Pa. Heat the vacuum drying oven to 100 °C at a heating rate of 5 °C / min and hold for 1 h, then heat the vacuum drying oven to 250 °C at a heating rate of 1 °C / min and hold for 2 h. After drying, cool it to room temperature under the above vacuum conditions.

[0047] 5) During the whole implementation process, repeat steps 2) - 4) four times to obtain Li + The ion exchange degree of the Li-exchanged X-type molecular sieve adsorbent is greater than 98%, and the specific surface area is 859 m 2 / g.

[0048] The Li + The XRD pattern and nitrogen adsorption-desorption isotherm diagram of the exchanged X-type molecular sieve adsorbent are respectively as Figure 1 and Figure 2 shown. It can be seen from Figure 1 that all the XRD diffraction peaks belong to the crystal structure of the Li + exchanged X-type molecular sieve. It can be seen from Figure 2 that the nitrogen adsorption-desorption isotherm belongs to the type I isotherm adsorption line, and the nitrogen adsorption capacity is greater than 200 cm 3 / g, which conforms to the microporous structure characteristics of the Li + exchanged X-type molecular sieve. It shows that the Li + exchanged X-type molecular sieve with a complete structure and unobstructed pores is successfully synthesized in this example.

[0049] A breakthrough experiment of a mixed gas of propylene (C3H6) and propane (C3H8) was carried out on a fixed-bed device. The experimental conditions were as follows: 0.25 Mpa, 80 °C, the molar amounts of propylene and propane were equal, the flow rate of the mixed gas was 2.5 L / min, the diameter of the adsorbent particles was 0.60 - 1.18 mm, the length of the packed column was 85 mm, and the inner diameter was 10.5 mm. Before the experiment, the adsorbent was activated overnight at 320 °C under helium purging. The adsorption breakthrough curve diagram of the propylene and propane mixed gas of the adsorbent is as Figure 3 shown.

[0050] The calculation formula for the adsorption selectivity (α) is:

[0051]

[0052] In the formula, Q A and Q Brespectively refer to the adsorption amounts of component A and component B, F refers to the molar flow rate (mol / s) at the outlet of the packed column, and F0 represents the molar flow rate (mol / s) at the inlet of the packed column.

[0053] According to Figure 3 the adsorption evaluation results, the adsorption selectivity α(C3H6 / C3H8) of the adsorbent can be calculated to be 2.47, indicating that the Li + exchanged X-type molecular sieve synthesized in this example has good performance in separating propylene and propane, and also indicates that the pore structure of the molecular sieve is complete, and the exchanged Li + ions have selective adsorption activity.

[0054] Example 2

[0055] A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution, comprising the following steps:

[0056] 1) Weigh 5 g of Na-X type molecular sieve powder with a silica-alumina ratio of 1.25 and put it into a crucible, then transfer it to an oven for preliminary drying at 100 °C for 2 h. Then take out the preliminarily dried molecular sieve and place it in a vacuum drying oven for vacuum drying at 0.5 Pa and 250 °C for 2 h to obtain the activated molecular sieve.

[0057] 2) Prepare 100 mL of a 0.01 mol / L NiCl methanol solution. Quickly take out the activated molecular sieve from the vacuum drying oven and add it to the above solution. Slowly heat the turbid liquid mixed with the molecular sieve in a three-necked flask equipped with a condenser reflux tube to 60 °C. Use magnetic stirring during the heating process to make the solution heat evenly. Under this condition, maintain the exchange for 6 h. After the exchange is completed, filter the solution to obtain a filter cake.

[0058] 3) Put the filter cake into methanol solvent, stir and wash it at 60 °C for 1 h, then filter the solution to obtain a filter cake. Repeat this step five times.

[0059] 4) Put the filter cake obtained after step 3) into a crucible, quickly transfer it to a vacuum drying oven, and keep the absolute pressure of the vacuum drying oven less than 1.0 Pa with a vacuum pump during the drying process. Heat the vacuum drying oven to 100 °C at a heating rate of 5 °C / min and keep it for 1 h, then heat the vacuum drying oven to 250 °C at a heating rate of 1 °C / min and keep it for 2 h. After the drying is completed, cool it to room temperature under the above vacuum condition.

[0060] 5) During the whole implementation process, repeat steps 2) to 4) five times, and the ion exchange degree of the obtained Ni 2+ exchanged X-type molecular sieve adsorbent is greater than 70%, and the specific surface area is 845 m 2 / g.

[0061] The Ni prepared in this example2+ The XRD pattern and nitrogen adsorption - desorption isotherm of the exchanged X - type molecular sieve adsorbent are shown in Figure 4 and Figure 5 respectively. As can be seen from Figure 4 , all XRD diffraction peaks belong to the crystal structure of the Ni - exchanged X - type molecular sieve. As can be seen from 2+ , the nitrogen adsorption - desorption isotherm belongs to the type - I isotherm, and has a large adsorption capacity, which is in line with the microporous structure characteristics of the Ni - exchanged X - type molecular sieve. This indicates that the Ni - exchanged X - type molecular sieve with a complete structure and unobstructed pores was successfully synthesized in this example. Figure 5 2+ 2+ 2+ 2+

[0062] A breakthrough experiment of a mixed gas of acetylene (C2H2) and ethylene (C2H4) was carried out on a fixed - bed device. The experimental conditions were as follows: 0.1 Mpa, 25 °C, the molar amounts of acetylene and ethylene were equal, helium was used to dilute the concentrations of both acetylene and ethylene to 2%, the flow rate of the mixed gas was 6 L / min, the diameter of the adsorbent particles was 0.60 - 1.18 mm, the length of the packed column was 11 mm, and the inner diameter was 6 mm. Before the experiment started, the adsorbent was activated overnight at 200 °C under helium purge. The adsorption breakthrough curve of the acetylene and ethylene mixed gas of the adsorbent is shown in Figure 6 respectively. According to the adsorption breakthrough curve in the figure, it is calculated that the adsorption selectivity α(C2H2 / C2 C2H4) = 10.54 of the adsorbent, indicating that the Ni - exchanged X - type molecular sieve can selectively adsorb acetylene in the mixed gas of acetylene and ethylene, the pore structure of the molecular sieve is complete, and the Ni 2+ ions exchanged into the molecular sieve have selective adsorption activity. 2+

[0063]

[0063] Example 3

[0064] A method for preparing a molecular sieve adsorbent by ion - exchange using an organic alcohol solution includes the following steps:

[0065] 1) Weigh 5 g of Na - X type molecular sieve powder with a silica - alumina ratio of 1.16 and put it into a crucible, then transfer it to an oven for preliminary drying at 100 °C for 2 h. Then take out the preliminarily dried molecular sieve and place it in a vacuum drying oven for vacuum drying at 0.5 Pa and 250 °C for 2 h to obtain the activated molecular sieve.

[0066] 2) Prepare 100 mL of a methanol solution of 0.2 mol / L BaCl2. Quickly take out the vacuum - dried molecular sieve powder from the vacuum drying oven and add it to the above solution. Slowly heat the turbid liquid mixed with the molecular sieve in a three - necked flask equipped with a condenser reflux tube to 60 °C. During the heating process, use magnetic stirring to make the solution heat evenly. Under this condition, keep the exchange for 4 h. After the exchange is completed, filter the solution to obtain a filter cake.

[0067] 3) Put the filter cake into methanol solvent, stir and wash it at 60 °C for 1 h, then filter the solution to obtain the filter cake. Repeat this step five times.

[0068] 4) Put the filter cake obtained after step 3) into a crucible, quickly transfer it to a vacuum drying oven, and keep the absolute pressure in the vacuum drying oven less than 1.0 Pa by pumping vacuum with a vacuum pump during the drying process. Heat the vacuum drying oven to 100 °C at a heating rate of 5 °C / min and keep it for 1 h, then heat the vacuum drying oven to 250 °C at a heating rate of 1 °C / min and keep it for 2 h. After drying, cool it to room temperature under the above vacuum condition.

[0069] 5) During the whole implementation process, repeat steps 2) - 4) eight times to obtain Ba 2+ The ion exchange degree of the exchanged X-type molecular sieve adsorbent is greater than 90%, and the specific surface area is 682 m 2 / g.

[0070] The Ba 2+ exchanged X-type molecular sieve adsorbent prepared in this example has XRD patterns and nitrogen adsorption and desorption isotherm diagrams as shown in Figure 7 and Figure 8 respectively. As can be seen from Figure 7 , all XRD diffraction peaks belong to the crystal structure of the Ba 2+ exchanged X-type molecular sieve. As can be seen from Figure 8 , the nitrogen adsorption and desorption isotherm belongs to the type I isothermal adsorption line, and the nitrogen adsorption amount is around 170 cm 3 / g, which is in line with the microporous structure characteristics of the Ba 2+ exchanged X-type molecular sieve. It shows that the Ba 2+ exchanged X-type molecular sieve with a complete structure and unobstructed pores is successfully synthesized in this example.

[0071] Use the liquid-phase static adsorption experiment to evaluate the adsorption selectivity of the adsorbent. Experimental conditions: Weigh 0.1 g of the Ba 2+ exchanged X-type molecular sieve adsorbent with 5% water content and put it into 10 mL of a n-nonane solution of xylene. The concentrations of p-xylene (pX), m-xylene (mX), and o-xylene (oX) in this solution are all 10%, the adsorption time is 12 h, and the temperature is 40 °C. After adsorption, take the supernatant of the solution for analysis. The adsorption selectivity α(pX / mX) of the adsorbent is 6.50, and α(pX / oX) is 8.75. It shows that the Ba 2+ exchanged X-type molecular sieve can selectively adsorb p-xylene in the mixed xylene, and the Ba 2+ ions exchanged into the molecular sieve have selective adsorption activity.

[0072] Example 4

[0073] A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution, comprising the following steps:

[0074] 1) Weigh 5 g of Na-Y type molecular sieve powder with a silica-alumina ratio of 2.5 and put it into a crucible, then transfer it to an oven and dry it at 100 °C for 2 h. Then take out the preliminarily dried molecular sieve and place it in a vacuum drying oven, and vacuum dry it at 0.5 Pa and 250 °C for 2 h to obtain the activated molecular sieve.

[0075] 2) Prepare 100 mL of an ethanol solution of 0.05 mol / L AgNO3. Quickly take out the activated molecular sieve powder from the vacuum drying oven and add it to the above solution. Slowly heat the turbid liquid mixed with the molecular sieve in a three-necked flask equipped with a condenser reflux tube to 80 °C. Use magnetic stirring during the heating process to make the solution heat evenly. Under this condition, maintain the exchange for 14 h. After the exchange is completed, filter the solution to obtain a filter cake.

[0076] 3) Put the filter cake into an ethanol solvent, stir and wash it at 80 °C for 2 h, then filter the solution to obtain a filter cake. Repeat this step four times.

[0077] 4) Put the filter cake obtained after step 3) into a crucible, quickly transfer it to a vacuum drying oven, and use a vacuum pump to evacuate during the drying process to keep the absolute pressure in the vacuum drying oven less than 1.0 Pa. Heat the vacuum drying oven to 100 °C at a heating rate of 5 °C / min and maintain it for 1 h, then heat the vacuum drying oven to 200 °C at a heating rate of 1 °C / min and maintain it for 2 h. After drying, cool it to room temperature under the above vacuum condition.

[0078] 5) During the whole implementation process, repeat steps 2) to 4) eight times to obtain an Ag + -exchanged Y-type molecular sieve adsorbent with an ion exchange degree greater than 90% and a specific surface area of 727 m 2 / g.

[0079] The Ag + -exchanged Y-type molecular sieve adsorbent prepared in this example has XRD patterns and nitrogen adsorption-desorption isotherms as shown in Figure 9 and Figure 10 respectively. It can be seen from Figure 9 that all XRD diffraction peaks belong to the crystal structure of the Ag + -exchanged Y-type molecular sieve. It can be seen from Figure 10 that the nitrogen adsorption-desorption isotherm belongs to the type I isothermal adsorption line, and the nitrogen adsorption capacity is about 175 cm 3 / g, which is in line with the microporous structure characteristics of the Ag + -exchanged Y-type molecular sieve. This shows that this example successfully synthesizes an Ag + -exchanged Y-type molecular sieve with a complete structure and unobstructed pores.

[0080] The static adsorption capacity of the adsorbent for propylene and propane was evaluated using a gas-phase static adsorption experiment. Experimental conditions: 0.050 g of Ag + exchanged Y-type molecular sieve was placed in an intelligent gravimetric analyzer. After vacuum degassing at 200 °C for 6 h, a single-component propylene or propane gas was introduced at 25 °C, and the isothermal adsorption curves of the adsorbent at different propylene or propane gas pressures were measured. The isothermal adsorption curves of the adsorbent for propylene and propane are as Figure 11 shown. As can be seen from the figure, Ag + exchanged Y-type molecular sieve has a stronger ability to adsorb propylene than propane, indicating that the molecular sieve has a selective adsorption ability for propylene. The Ag + ions exchanged into the molecular sieve have selective adsorption activity.

[0081] Example 5

[0082] A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution, comprising the following steps:

[0083] 1) Weigh 5 g of Na-A type molecular sieve powder with a silica-alumina ratio of 1 and place it in a crucible. Then transfer it to an oven and dry it at 100 °C for 2 h. Then take out the preliminarily dried molecular sieve and place it in a vacuum drying oven for vacuum drying at 0.5 Pa and 250 °C for 2 h to obtain the activated molecular sieve.

[0084] 2) Prepare 1000 mL of an ethanol solution of 0.01 mol / L AgNO3. Quickly take out the activated molecular sieve powder from the vacuum drying oven and add it to the above solution. Slowly heat the turbid solution mixed with the molecular sieve in a three-necked flask equipped with a condenser reflux tube to 80 °C. Use a magnetic stirrer to make the solution heat evenly during the heating process. Under this condition, maintain the exchange for 14 h. After the exchange is completed, filter the solution to obtain a filter cake.

[0085] 3) Place the filter cake in an ethanol solvent, stir and wash it at 80 °C for 2 h, then filter the solution to obtain a filter cake. Repeat this step four times.

[0086] 4) Place the filter cake obtained after step 3) in a crucible and quickly transfer it to a vacuum drying oven. During the drying process, use a vacuum pump to evacuate to keep the absolute pressure in the vacuum drying oven less than 1.0 Pa. Heat the vacuum drying oven to 100 °C at a heating rate of 5 °C / min and hold for 1 h, then heat the vacuum drying oven to 200 °C at a heating rate of 1 °C / min and hold for 2 h. After drying, cool it to room temperature under the above vacuum conditions.

[0087] 5) Throughout the implementation process, repeat steps 2) to 4) eight times to obtain an Ag + exchanged A-type molecular sieve adsorbent with an ion exchange degree greater than 90% and a specific surface area of 691 m2 / g.

[0088] The Ag prepared in this example + The XRD pattern and nitrogen adsorption - desorption isotherm of the Ag - exchanged A - type molecular sieve adsorbent are respectively as Figure 12 and Figure 13 shown. From Figure 12 it can be seen that all XRD diffraction peaks belong to the crystal structure of the Ag - exchanged A - type molecular sieve. From + it can be seen that the nitrogen adsorption - desorption isotherm belongs to the type - I isotherm, and the nitrogen adsorption capacity is about 170 cm Figure 13 / g, which is in line with the microporous structure characteristics of the Ag - exchanged A - type molecular sieve. It shows that the structure - complete and pore - unobstructed Ag - exchanged A - type molecular sieve is successfully synthesized in this example. 3 exchanged A - type molecular sieve. + exchanged A - type molecular sieve. + exchanged A - type molecular sieve.

[0089] A breakthrough experiment of the mixed gas of ethylene (C2H4) and ethane (C2H6) was carried out on a fixed - bed device. The experimental conditions were as follows: 0.1 Mpa, 30 °C, the molar amounts of ethylene and ethane were equal, helium was used to dilute the concentrations of acetylene and ethylene to 10%, the flow rate of the mixed gas was 15 L / min, the diameter of the adsorbent particles was 0.425 - 0.600 mm, the length of the packed column was 100 mm, and the inner diameter was 2.16 mm. Before the experiment started, the adsorbent was activated at 200 °C for 2 h under helium purge. The adsorption breakthrough curve of the ethylene and ethane mixed gas of the adsorbent is as Figure 14 shown. According to the adsorption breakthrough curve in the figure, it is calculated that the adsorption selectivity α(C2H4 / C2H6) of the adsorbent is 3.42, indicating that the Ag - exchanged A - type molecular sieve can selectively adsorb ethylene in the mixed gas of ethylene and ethane, the pore structure of the molecular sieve is complete, and the Ag + exchanged A - type molecular sieve, the Ag ions exchanged into the molecular sieve have selective adsorption activity. + ions have selective adsorption activity.

Claims

1. A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution, characterized in that, It includes the following steps: 1) Place the molecular sieve raw material in an oven at 95 - 105 o °C for preliminary drying for 1.8 - 2.2 h. Then take out the preliminarily dried molecular sieve and place it in a vacuum drying oven. Vacuum dry it at 0.5 - 10 Pa and 250 o °C for 1.8 - 2.2 h to obtain the activated molecular sieve raw material; 2) Dissolve the salt containing metal ions in an organic alcohol solvent to obtain an organic alcohol solution with a metal ion concentration of 1 to 0.001 mol / L, and the metal ion is Li + , K + , Rb + , Cs + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Ag + ; any one of them 3) In a reflux device, mix the molecular sieve raw material activated in step 1) with the organic alcohol solution in step 2) for ion exchange. During the ion exchange process, the temperature of the exchange system is 25~100 o °C, and the exchange time is 1~72 h; 4) The ion-exchanged molecular sieve is successively subjected to suction filtration, washing, and vacuum drying to obtain an ion-exchanged molecular sieve adsorbent.

2. A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution according to claim 1, characterized in that, The molecular sieve raw material described in step 1) is any one of A-type, X-type or Y-type molecular sieves.

3. A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution according to claim 1, characterized in that, The organic alcohol solvent described in step 2) is any one of methanol, ethanol, ethylene glycol, propanol, propylene glycol, glycerol or a solution prepared by mixing these organic alcohols in any proportion, and the water content of the organic alcohol is not more than 1%.

4. A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution according to claim 1, characterized in that, The mixing ratio of the activated molecular sieve raw material and the organic alcohol solution in step 3) is 1 g : 10 - 200 mL.

5. A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution according to claim 1, characterized in that, The suction filtration temperature described in step 4) is 50~100 o °C.

6. A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution according to claim 1, characterized in that, The washing described in step 4) is carried out in an organic alcohol solvent, and the washing temperature is 25~100 o °C, the washing time is 0.1~1 h, and the number of washing times is 1~8 times.

7. A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution as claimed in claim 1, wherein The absolute pressure of the vacuum drying in step 4) is 0.5 to 10 Pa, and the heating program is to heat up to 95 to 105 o °C at a rate of 1 to 10 o °C / min, hold at this temperature for 0.5 to 2 h, and then heat up to 240 to 260 o °C at a rate of 1 to 10 o °C / min and hold for 2 to 24 h.

8. A method for preparing a molecular sieve adsorbent by ion exchange using an organic alcohol solution according to claim 1, characterized in that, The number of ion exchange times is 1 - 8 times.

9. A molecular sieve adsorbent obtained by the preparation method according to any one of claims 1 - 8.

10. The molecular sieve adsorbent according to claim 9, characterized in that, The exchanged degree of the molecular sieve adsorbent is greater than 70%, and the specific surface area is greater than 600 m 2 / g.

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