Metal ion exchange modified molecular sieve, preparation method and application

Abstract

The invention discloses a metal ion exchange modified molecular sieve as well as a preparation method and application thereof, the preparation method comprises the following steps: sequentially performing static aging and dynamic hydrothermal crystallization on mixed gel prepared from a silicon source, an aluminum source, water-soluble inorganic salt, alkali and water to obtain mixed slurry; and separating out a solid phase in the mixed slurry, and sequentially washing, drying and calcining the solid phase to obtain the metal ion exchange modified molecular sieve. The molecular sieve prepared by the method provided by the invention has abundant pore structures and excellent carbon dioxide adsorption performance, and especially has a better effect in adsorption of low-concentration carbon dioxide; and the preparation method is simple, convenient and feasible, is remarkable in cost benefit, has good large-scale production potential and is suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular sieve preparation and modification, in particular to a metal ion exchange modified molecular sieve, a preparation method and an application. BACKGROUND

[0002] With the progress of industry, the waste gas produced after the combustion of fossil energy leads to air pollution. Carbon dioxide (CO2) is contained in the waste gas, such as waste gas from internal combustion engines (cars and trucks), combustion devices (natural gas, oil or coal heated power plants) and chemical production plants. At present, various treatment methods have been developed to treat CO2 gas to reduce the content of CO2 in the atmosphere. For example: (1) solvent absorption method, which is to chemically absorb CO2 by alkaline solution to achieve the purpose of reducing emissions; (2) CO2 reduction process, in which hydrogen or low-carbon hydrocarbons are used as reducing agents to selectively reduce CO2 into CO or CH4 and other products under the action of electrocatalysis, thermal catalysis and photocatalysis. However, the above methods have the disadvantages of high cost, high energy consumption and complex process, which are not suitable for large-scale use in industrial scenarios. DAC technology has become an environmentally friendly and pollution-free process technology due to its high running safety and stability and operational flexibility.

[0003] CO2 is a stable acidic gas, which is colorless and odorless at normal temperature and pressure, although it can be liquefied or solidified under low temperature and high pressure conditions. Its high density and low viscosity characteristics make it easy to compress and transport, but low-temperature and high-pressure liquefaction or solidification are not suitable for treating CO2 gas emissions, which are of high cost and also increase the risk of leakage and explosion. Under certain conditions, CO2 can react with basic substances to form carbonates, and this property is widely used in CO2 chemical fixation. However, the formed carbonates are chemically stable and cannot be dissociated at normal temperature and pressure, so the method of using basic substances or alkaline solution to chemically absorb CO2 cannot realize the low-cost and green and pollution-free recycling of CO2. Especially for low concentration of CO2 in the air, the absorption efficiency of the chemical absorption method is lower and the cost is higher, while the physical adsorption method is a powerful way to solve this problem.

[0004] Molecular sieves, as a common adsorption material, have a wide range of applications in gas separation, catalysis and other fields due to their high specific surface area, good pore structure and chemical stability. In the field of CO2 capture, the adsorption performance of molecular sieves determines whether they can efficiently remove CO2, especially low-concentration CO2. Therefore, improving the adsorption capacity of molecular sieves, especially for low-concentration CO2, has become a hot research topic.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The application aims to provide a metal ion exchange modified molecular sieve, a preparation method and application, and overcomes the problem of poor adsorption capacity of low concentration CO2 in the prior art.

[0007] The application is implemented as follows: In a first aspect, the application provides a preparation method of a metal ion exchange modified molecular sieve, comprising: sequentially performing static aging and dynamic hydrothermal crystallization on a mixed gel prepared from a silicon source, an aluminum source, a water-soluble inorganic salt, an alkali and water to obtain a mixed slurry; Separating a solid phase from the mixed slurry and sequentially performing washing, drying and calcination on the solid phase to obtain the metal ion exchange modified molecular sieve.

[0008] In an optional embodiment, the silicon source is selected from at least one of kaolin, metakaolin or sodium silicate; And / or, the particle size of the silicon source is 800-1600 mesh.

[0009] In an optional embodiment, the aluminum source is selected from at least one of sodium metaaluminate, aluminum sulfate or aluminum isopropoxide; And / or, the molar ratio of Al2O3 to SiO2 in the metal ion exchange modified molecular sieve is 1:(17-25); And / or, the molar ratio of aluminum element to water in the mixed gel is 1:(82-110).

[0010] In an optional embodiment, the water-soluble inorganic salt is selected from at least one of lithium salt, sodium salt, potassium salt, magnesium salt, calcium salt, iron salt, copper salt, zinc salt, nickel salt and cobalt salt; And / or, the water-soluble inorganic salt is selected from at least one of hydrochloride, sulfate, nitrate and permanganate; And / or, the molar fraction of the water-soluble inorganic salt in the metal ion exchange modified molecular sieve is 7.4%-37.5%; And / or, the preparation of the mixed gel comprises: mixing a water-soluble inorganic salt solution with a concentration of 0.08 mol / L-0.6 mol / L with a gel prepared from a silicon source, an aluminum source, an alkali and water.

[0011] In an optional embodiment, the alkali is selected from at least one of sodium hydroxide, potassium hydroxide or calcium hydroxide; And / or, the molar ratio of the alkali to aluminum element in the aluminum source is (2.7-31):1.

[0012] In an optional embodiment, the temperature of the static aging step is 45℃-60℃, and the time is 20h-25h.

[0013] In an optional embodiment, the temperature of the dynamic hydrothermal crystallization step is 100-120 DEG C, the time is 24-48 h, and the pressure is 0.1-0.2 MPa; And / or, the temperature increasing rate of the dynamic hydrothermal crystallization step is 2-5 DEG C / min; And / or, the washing liquid used in the washing step is water, and the pH of the washing liquid after washing is 6.5-7.5; And / or, the temperature of the drying step is 110-130 DEG C, and the drying time is 6-9 h.

[0014] In an optional embodiment, before the drying step, the washed solid is first heated to 55-65 DEG C and kept for 50-70 min, and then heated for drying; And / or, the temperature of the calcination step is 450-550 DEG C, and the calcination time is 5-7 h; And / or, the air flow rate of the calcination step is controlled to be 50-100 mL / min; And / or, the temperature increasing rate of the calcination step is 2.5-3.5 DEG C / min.

[0015] In a second aspect, the present application provides a metal ion exchange modified molecular sieve prepared by the method for preparing a metal ion exchange modified molecular sieve according to any one of the preceding embodiments.

[0016] In a third aspect, the present application provides an application of the metal ion exchange modified molecular sieve according to the preceding embodiments in carbon dioxide adsorption.

[0017] The present application has the following beneficial effects: The molecular sieve prepared by the method of the present application has abundant pore structure and excellent carbon dioxide adsorption performance, especially in the adsorption of low-concentration carbon dioxide; and the preparation method is simple and easy to implement, has significant cost-effectiveness, has good potential for large-scale production, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0019] Figure 1 SEM image of the metal ion exchange modified molecular sieve prepared for the present application embodiment 1; Figure 2SEM image of the molecular sieve prepared for Comparative Example 2 of the present application; Figure 3 Breakthrough curve of the metal ion exchange modified molecular sieve prepared by using Example 1 of the present application for adsorbing N2, CO2 mixed gas with a CO2 volume fraction of 15% at 25℃; Figure 4 Breakthrough curve of the metal ion exchange modified molecular sieve prepared by using Example 1 of the present application for adsorbing N2, CO2 mixed gas with different CO2 volume fractions at 25℃. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions suggested by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased in the market.

[0021] The embodiment of the present application provides a preparation method of a metal ion exchange modified molecular sieve, comprising: sequentially performing static aging and dynamic hydrothermal crystallization on a mixed gel prepared from a silicon source, an aluminum source, a water-soluble inorganic salt, an alkali and water to obtain a mixed slurry; Separating the solid phase in the mixed slurry and sequentially performing washing, drying and calcination on the solid phase to obtain the metal ion exchange modified molecular sieve.

[0022] The present application provides a preparation method of a metal ion exchange modified molecular sieve, and the prepared molecular sieve is an X-type molecular sieve. The molecular sieve prepared by the method has a rich pore structure and excellent carbon dioxide adsorption performance.

[0023] In addition, the preparation process of the present application is simple and easy to operate, has significant cost-effectiveness, and has good potential for large-scale production. First, the water-soluble inorganic salt is introduced as a modifier in the molecular sieve synthesis stage, which can reduce the energy consumption by about 50% compared with the modification after the synthesis of the molecular sieve. Second, the water-soluble inorganic salt as a modifier is low in cost. Finally, the modification process does not require special equipment and can be directly carried out on the existing molecular sieve production line, which is suitable for large-scale industrial production. The prepared molecular sieve can be widely used in the capture and separation of carbon dioxide in industrial flue gas and the capture and separation of low-concentration carbon dioxide in air, and provides effective technical support for achieving the carbon emission reduction target.

[0024] In optional embodiments, the silicon source is selected from at least one of kaolin, metakaolin or sodium silicate; the higher the purity of the silicon source in the present application, the more advantageous it is to reduce the adverse effects of impurities on the adsorption capacity of the molecular sieve. In some embodiments, the purity of kaolin or metakaolin can be greater than 90%, preferably greater than 95%; the purity of sodium silicate can be greater than 98%, preferably greater than 99%.

[0025] In optional embodiments, the particle size of the silicon source is 800-1600 mesh; a small particle size of the silicon source is advantageous for uniform dispersion of the silicon source in the mixed gel.

[0026] In optional embodiments, the aluminum source is selected from at least one of sodium metaaluminate, aluminum sulfate, aluminum isopropoxide; in some embodiments, the purity of the aluminum source can be greater than 98%, preferably greater than 99%.

[0027] and / or, the molar ratio of Al2O3 to SiO2 in the metal ion-exchanged modified molecular sieve is 1:(17-25); and / or, the molar ratio of aluminum element to water in the mixed gel is 1:(82-110).

[0028] In optional embodiments, the water-soluble inorganic salt is selected from at least one of lithium salt, sodium salt, potassium salt, magnesium salt, calcium salt, iron salt, copper salt, zinc salt, nickel salt and cobalt salt; and / or, the water-soluble inorganic salt is selected from at least one of hydrochloride, sulfate, nitrate, permanganate; and / or, the molar fraction of the water-soluble inorganic salt in the metal ion-exchanged modified molecular sieve is 7.4%-37.5%; at this ratio, the molecular sieve and the exchanged ions can work more effectively, without destroying the configuration of the molecular sieve, ensuring the integrity of the molecular sieve channels, and more effectively improving the adsorption capacity of the molecular sieve for carbon dioxide molecules. At the same time, at this ratio, the waste of ion modification reagents is avoided. Through comparative studies, when the molar fraction of the water-soluble inorganic salt in the metal ion-exchanged modified molecular sieve is in the range of 7.4%-37.5%, the molecular sieve framework structure remains intact, X-ray diffraction (XRD) analysis shows that the crystallinity is maintained at more than 95%, and the BET specific surface area is maintained at 550-600 m 2 / g. When the molar fraction is lower than the above range, the modification effect is not obvious, and the carbon dioxide adsorption capacity is only increased by 4%-6%; when the molar fraction is higher than the above range, the molecular sieve channels are partially blocked, and the specific surface area decreases by about 20%, which is not conducive to the adsorption of CO2.

[0029] In optional embodiments, the preparation of the mixed gel comprises: mixing a water-soluble inorganic salt solution with a concentration of 0.08 mol / L-0.6 mol / L with a gel prepared from a silicon source, an aluminum source, a base and water.

[0030] The concentration of the water-soluble inorganic salt solution is 0.08 mol / L-0.6 mol / L, preferably 0.2 mol / L-0.4 mol / L, and more preferably 0.3 mol / L.

[0031] The solvent in the water-soluble inorganic salt solution is selected from water, ethanol, and dichloromethane, and preferably the solvent is ethanol. Ethanol has a low boiling point and is easy to remove, which is conducive to simplifying the process and improving the production efficiency while ensuring the performance of the molecular sieve.

[0032] In optional embodiments, the base is selected from at least one of sodium hydroxide, potassium hydroxide, or calcium hydroxide; in some embodiments, the base can be of analytical grade, and the base can be added in multiple times when preparing the mixed gel, which is conducive to the uniform distribution of the components in the mixed gel.

[0033] The molar ratio of the base to the aluminum element in the aluminum source is (2.7-31):1.

[0034] It should be noted that the specific process of preparing the mixed gel in the present application can be as follows: the silicon source and the aluminum source are dissolved in deionized water to form a silicon-aluminum source solution, and then the base is added in multiple times and fully dissolved to form an alkaline solution. Then, the mixture is quickly stirred until the gel is uniformly formed, and the gel is mixed with a previously prepared water-soluble inorganic salt solution. Specifically, a magnetic stirrer can be used to continuously stir at a speed of 300 r / min for 2 h to ensure that the water-soluble inorganic salt is uniformly distributed in the gel matrix, and a mixed gel is obtained.

[0035] In optional embodiments, the temperature of the static aging step is 45 ℃-60 ℃, and the time is 20 h-25 h, so as to promote the interaction of the reactants.

[0036] In optional embodiments, the temperature of the dynamic hydrothermal crystallization step is 100 ℃-120 ℃, preferably 105-115 ℃, and more preferably 110 ℃; the time is 24 h-48 h, preferably 36 h; and the pressure is 0.1 MPa-0.2 MPa.

[0037] The gel crude product obtained after the static aging step can be transferred to a hydrothermal reaction kettle for dynamic hydrothermal crystallization. The hydrothermal reaction kettle can be a polytetrafluoroethylene-lined stainless steel reaction kettle. During the hydrothermal crystallization process, inorganic cations (such as calcium ions, sodium ions, or ferrous ions) gradually embed into the molecular sieve framework to form a preliminary mixed crystal. After the reaction is completed, the reaction kettle is naturally cooled to room temperature, and the mixed slurry in the reaction kettle is taken out for subsequent processing.

[0038] In optional embodiments, the temperature increasing rate of the dynamic hydrothermal crystallization step is 2-5 ℃ / min, preferably 2 ℃ / min, which is beneficial to prevent the deformation of the crystal structure.

[0039] In some embodiments, the washing step specifically comprises: washing the obtained mixed crystals with deionized water, the deionized water having a conductivity of less than 5 μS / cm, and the washing temperature being 25-35 ℃, preferably 30 ℃. An intermittent washing method is used, and after each washing, the mixture is allowed to stand for 5 min to separate the solid and liquid, and the washing is repeated for 3-5 times until the pH is 6.5-7.5, thereby obtaining the mixed crystals.

[0040] In some embodiments, the drying step is performed in a drying oven, and in optional embodiments, a vacuum drying method is used to dry the mixed crystals, and the vacuum degree is controlled to be 0.08-0.1 MPa. Preferably, a stepwise temperature increasing method is used in the drying process, i.e., the temperature is first increased to 55-65 ℃ at a rate of 5 ℃ / min and maintained for 50-70 min, and then increased to 110-130 ℃ at a rate of 1.5-2.5 ℃ / min and maintained for 6-9 h, so as to ensure the integrity of the crystal structure, thereby obtaining a white powder of the crude molecular sieve, and the specific surface area of the crude molecular sieve is 350-450 m 2 / g. 2 / g.

[0041] In optional embodiments, the calcination temperature is 450-550 ℃, and the calcination time is 5-7 h. In the calcination step, the crude molecular sieve is placed in a muffle furnace for high-temperature calcination, and the calcination process is performed in an air atmosphere, the air flow is controlled to be 50-100 mL / min, and the temperature increasing rate is 2.5-3.5 ℃ / min, preferably 3 ℃ / min. After high-temperature calcination, the adsorption sites in the molecular sieve are activated, and the metal ions are fully combined with the molecular sieve framework to form a stable metal ion exchange modified molecular sieve.

[0042] The present application also provides a metal ion exchange modified molecular sieve, which is prepared by the method for preparing a metal ion exchange modified molecular sieve according to any one of the preceding embodiments.

[0043] The application also provides application of the metal ion exchange modified molecular sieve in carbon dioxide adsorption, including adsorption of CO2 in mixed gas, and the specific application includes the following steps: the prepared molecular sieve is contacted with the gas (such as air, industrial waste gas) to be treated containing low concentration CO2 at 15-30 ℃ to adsorb; after the adsorption is completed, the molecular sieve is heated to 150-250 ℃ under the nitrogen component and is purged to realize regeneration of the molecular sieve; the regenerated modified X-type molecular sieve is used as a CO2 adsorbent again, and the above adsorption-desorption steps are repeated to realize cyclic utilization.

[0044] The metal ion exchange modified molecular sieve in the application has significant application value in the field of industrial flue gas CO2 capture. In the actual application in coal-fired power plants, the capture efficiency of low concentration CO2 with a volume fraction of 3%-5% can reach 85%-90%, and the regeneration energy consumption is reduced by 45% compared with the traditional amine method; in the application in cement plants and steel plants, the CO2 capture cost can be effectively reduced by about 40%. It is estimated that the CO2 capture cost per ton can be controlled at 150-200 yuan by using the technology, which is reduced by 25%-30% compared with the prior art. In addition, the CO2 adsorption capacity of the molecular sieve can still maintain more than 95% of the initial value after 200 adsorption-desorption cycles, which exhibits excellent cyclic stability.

[0045] The features and performances of the application are further described in detail below in combination with examples.

[0046] Example 1 The example provides a preparation method of a metal ion exchange modified molecular sieve, including the following steps: (a) sodium silicate (Na2SiO3) with a purity of ≥99% and sodium aluminate (NaAlO2) with a purity of ≥98% are taken, and the sodium aluminate and the sodium silicate are dissolved in deionized water to form a silicon-aluminum source solution. Analytically pure sodium hydroxide (NaOH) is added in multiple portions and is fully dissolved to form an alkaline solution. The molar ratio of the added alkali, sodium aluminate, sodium silicate and water is 5.5:1:17:220. Rapid stirring is performed until the mixture is uniform, a gel is formed, and the gel is mixed with a previously prepared FeCl3 aqueous solution, wherein the concentration of the FeCl3 solution is 0.3 mol / L. A magnetic stirrer is used to continuously stir at a speed of 300 r / min for 2 h to ensure that the modifier FeCl3 is uniformly distributed in the gel matrix. The obtained mixture is fully aged at 50 ℃, and the aging time is 22 h to promote the interaction of the reactants; (b) The aged gel crude product is transferred to a stainless steel reactor with a polytetrafluoroethylene liner for hydrothermal crystallization treatment. The hydrothermal crystallization process is carried out at 110 °C for 36 h. The temperature rising rate is controlled at 2 °C / min to prevent the deformation of the crystal structure. During the hydrothermal crystallization process, inorganic cations (such as calcium ions, sodium ions and iron ions) gradually embed into the molecular sieve framework to form a preliminary mixed crystal. After the reaction is completed, the reactor is naturally cooled to room temperature, and the product is taken out for subsequent treatment; (c) The obtained mixed crystal is washed with deionized water, and the conductivity of the deionized water is controlled to be below 5 μS / cm, and the washing temperature is 30 °C. An intermittent washing method is adopted, and the solid-liquid is fully separated after each washing for 5 min, and the washing is repeated 4 times until the neutral condition is reached. The washed mixed crystal is placed in a vacuum drying box for drying treatment, the drying temperature is 120 °C, the drying time is 8 h, and the vacuum degree is controlled to be 0.08-0.1 MPa. A segmented temperature rising mode is adopted during the drying process, first rising to 60 °C at a rate of 5 °C / min and keeping for 1 h, and then rising to 100 °C at a rate of 2 °C / min to ensure the integrity of the crystal structure. The obtained molecular sieve crude product is in the form of white powder, and the specific surface area reaches 350-450 m 2 / g. The molecular sieve crude product is placed in a muffle furnace for high-temperature calcination treatment, the calcination temperature is 500 °C, and the calcination time is 6 h. The calcination process is carried out in an air atmosphere, the air flow is controlled at 75 mL / min, and the temperature rising rate is 3 °C / min. After high-temperature calcination, the adsorption sites in the molecular sieve are activated, and the metal ions are fully combined with the molecular sieve framework to form a stable metal ion exchange modified molecular sieve, and the SEM diagram of the obtained molecular sieve is as shown in Figure 1

[0047] Example 2 The embodiment provides a preparation method of a metal ion exchange modified molecular sieve, which is different from the embodiment 1 only in that an Fe2(SO4)3 aqueous solution with an equal amount of iron element is used instead of the FeCl3 aqueous solution.

[0048] Example 3 The embodiment provides a preparation method of a metal ion exchange modified molecular sieve, which is different from the embodiment 1 only in that an Fe(NO3)3 salt solution with an equal amount of iron element is used instead of the FeCl3 salt solution described in the embodiment 1.

[0049] Example 4 The embodiment provides a preparation method of a metal ion exchange modified molecular sieve, which is different from the embodiment 1 only in that a LiCl salt solution with an equal amount of iron element is used instead of the FeCl3 salt solution described in the embodiment 1.

[0050] ​Example 5 The present example provides a preparation method of metal ion-exchanged modified molecular sieve, which differs from example 1 only in that a Li2SO4 salt solution with equal amount of iron element is used instead of the FeCl3 salt solution described in example 1.

[0051] Example 6 The present example provides a preparation method of metal ion-exchanged modified molecular sieve, which differs from example 1 only in that a LiNO3 salt solution with equal amount of iron element is used instead of the FeCl3 salt solution described in example 1.

[0052] Example 7 The present example provides a preparation method of metal ion-exchanged modified molecular sieve, which differs from example 1 only in that a CuCl2 salt solution with equal amount of iron element is used instead of the FeCl3 salt solution described in example 1.

[0053] Example 8 The present example provides a preparation method of metal ion-exchanged modified molecular sieve, which differs from example 1 only in that a Cu(NO3)2 salt solution with equal amount of iron element is used instead of the FeCl3 salt solution described in example 1.

[0054] Example 9 The present example provides a preparation method of metal ion-exchanged modified molecular sieve, which differs from example 1 only in that a CuSO4 salt solution with equal amount of iron element is used instead of the FeCl3 salt solution described in example 1.

[0055] Example 10 The present example provides a preparation method of metal ion-exchanged modified molecular sieve, which differs from example 1 only in that a Na2SO4 salt solution with equal amount of iron element is used instead of the FeCl3 salt solution described in example 1.

[0056] Example 11 The present example provides a preparation method of metal ion-exchanged modified molecular sieve, which differs from example 1 only in that a FeCl3 salt solution with 2 times amount of iron element is used instead of the FeCl3 salt solution described in example 1.

[0057] Example 11 The present example provides a preparation method of metal ion-exchanged modified molecular sieve, which differs from example 1 only in that a FeCl3 salt solution with 0.1 times amount of iron element is used instead of the FeCl3 salt solution described in example 1.

[0058] Example 12 The embodiment provides a preparation method of a metal ion-exchanged modified molecular sieve, which is different from the embodiment 1 only in that the aging temperature in the step (a) is 25 DEG C.

[0059] Embodiment 13 The embodiment provides a preparation method of a metal ion-exchanged modified molecular sieve, which is different from the embodiment 1 only in that the crystallization time in the step (b) is 12 h.

[0060] Comparative example 1 The embodiment provides a preparation method of a metal ion-exchanged modified molecular sieve, which is different from the embodiment 1 only in that the aging temperature in the step (a) is 25 DEG C.

[0061] Comparative example 2 The embodiment provides a preparation method of a molecular sieve, which is different from the embodiment 1 only in that the step (a) is replaced by an equal volume of water instead of the FeCl3 aqueous solution, and the SEM image of the obtained molecular sieve is as shown in Figure 2 .

[0062] From Figure 1 , Figure 2 it can be seen that the molecular sieves in the embodiment 1 and the comparative example 2 have little difference in micro-morphology, and the metal ion-exchanged modified molecular sieve maintains the FAU configuration and structure.

[0063] The molecular sieve obtained in the embodiment 1 is tested by using a Belsorb BSD-MAB type penetration adsorber, the sample is loaded into a penetration column, heated to 120 DEG C for activation treatment, and cooled to room temperature 25 DEG C. Meanwhile, experimental materials such as carrier gas N2, adsorption gas CO2 and calibration gas CO2 are prepared. The gas is switched to the required adsorption gas or adsorption gas mixture through a six-way valve, and the outlet gas flow is controlled to be 400 sccm, and the test temperature is 25 DEG C. Then, the concentration change of the outlet gas is monitored by using a mass spectrometer or other detector. During the experiment, the inlet and outlet gas concentration data at different time points are recorded, and a penetration curve is drawn, part of the curve is as shown in Figure 3 , 4 the adsorption capacity of CO2 and the CO2 / N2 selectivity coefficient are shown in Table 1, wherein the CO2 / N2 selective adsorption coefficient is the ratio of the adsorption capacity of CO2 to the adsorption capacity of N2.

[0064] wherein, Figure 3 is the N2 and CO2 gas mass adsorption capacity test result of the N2 and CO2 mixed gas with a CO2 volume fraction of 15% at 25 DEG C, according to Figure 3It can be seen that the outlet volume concentration of N2 as the interference component carrier gas may fluctuate slightly with the experiment, but it should be relatively stable overall. It can be seen from the figure that there is basically only N2 at the gas outlet at the initial adsorption, and the outlet concentration approaches the inlet concentration, which means that the adsorbent obtained in Example 1 has no significant adsorption effect on N2. With the passage of time, more and more CO2 is adsorbed onto the adsorbent until all the adsorption sites are occupied (or reach the saturation state) at 2800 s. At this time, the outlet concentration of CO2 will start to rise rapidly, forming a so-called "breakthrough point". After the breakthrough point, the outlet concentration of CO2 will continue to rise until it approaches the inlet concentration at 3000 s. At this time, the adsorption capacity of the adsorbent for CO2 has been basically exhausted, and the selective adsorption amount of the molecular sieve for CO2 reaches 0.141 kg / kg.

[0065] Figure 4 The results of N2 and CO2 gas mass adsorption capacity tests on N2 and CO2 mixed gas with CO2 volume fractions of 1%, 3%, 5%, 10%, 12% and 15% at 25°C, respectively. From Figure 4 It can be seen that even if the concentration of CO2 is gradually reduced to a concentration of 3%, the molecular sieve obtained in Example 1 can still obtain a CO2 gas mass adsorption capacity of more than 0.1 kg / kg, and the results show that the modified molecular sieve has high adsorption performance for low concentration CO2 gas.

[0066] The molecular sieves prepared in the above examples and comparative examples were tested by X-ray diffraction (XRD) and nitrogen adsorption-desorption isotherms, and the results showed that the molecular sieves prepared in the above examples maintained the FAU type framework structure, the crystallinity was more than 98%, and the specific surface area was maintained in the range of 550-600 m 2 The pore size distribution of the molecular sieves prepared in each example is basically consistent with that of the molecular sieve prepared in Comparative Example 2, mainly concentrated in the range of 0.7-0.8 nm, which is beneficial to the selective adsorption of CO2 molecules.

[0067] Table 1

[0068] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing a metal ion-exchanged modified molecular sieve, characterized by, The preparation method comprises the following steps: The mixed gel prepared from a silicon source, an aluminum source, a water-soluble inorganic salt, an alkali and water is sequentially subjected to static aging and dynamic hydrothermal crystallization to obtain a mixed slurry; The solid phase in the mixed slurry is separated and sequentially subjected to washing, drying and calcination to obtain the metal ion exchange modified molecular sieve.

2. The method for preparing metal ion exchange modified molecular sieves according to claim 1, characterized in that, The silicon source is at least one selected from kaolin, metakaolin or sodium silicate; And / or, the particle size of the silicon source is 800-1600 mesh.

3. The method for preparing metal ion exchange modified molecular sieves according to claim 1, characterized in that, The aluminum source is at least one selected from sodium metaaluminate, aluminum sulfate and aluminum isopropoxide; And / or, the molar ratio of Al2O3 to SiO2 in the metal ion exchange modified molecular sieve is 1:(17-25); And / or, the molar ratio of aluminum element to water in the mixed gel is 1:(82-110).

4. The method for preparing metal ion exchange modified molecular sieves according to claim 1, characterized in that, The water-soluble inorganic salt is at least one selected from lithium salt, sodium salt, potassium salt, magnesium salt, calcium salt, iron salt, copper salt, zinc salt, nickel salt and cobalt salt; And / or, the water-soluble inorganic salt is at least one selected from hydrochloride, sulfate, nitrate and permanganate; And / or, the molar fraction of the water-soluble inorganic salt in the metal ion exchange modified molecular sieve is 7.4%-37.5%; And / or, the preparation of the mixed gel comprises mixing a water-soluble inorganic salt solution with a concentration of 0.08 mol / L-0.6 mol / L and a gel prepared from a silicon source, an aluminum source, an alkali and water.

5. The method for preparing metal ion exchange modified molecular sieves according to claim 1, characterized in that, The alkali is at least one selected from sodium hydroxide, potassium hydroxide and calcium hydroxide; And / or, the molar ratio of the alkali to aluminum element in the aluminum source is (2.7-31):

1.

6. The method for preparing metal ion exchange modified molecular sieves according to claim 1, characterized in that, The temperature of the static aging step is 45-60 ℃, and the time is 20-25 h.

7. The method for preparing metal ion exchange modified molecular sieves according to claim 1, characterized in that, The temperature of the dynamic hydrothermal crystallization step is 100-120 ℃, the time is 24-48 h, and the pressure is 0.1-0.2 MPa; And / or, the temperature increasing rate of the dynamic hydrothermal crystallization step is 2-5 ℃ / min; And / or, the washing liquid used in the washing step is water, and the pH of the washing liquid after washing is 6.5-7.5; And / or, the temperature of the drying step is 110-130 ℃, and the time is 6-9 h.

8. The method for preparing metal ion exchange modified molecular sieves according to claim 1, characterized in that, Before the drying step, the washed solid is first heated to 55-65 ℃ and kept for 50-70 min, and then dried by heating; And / or, the temperature of the calcination step is 450-550 ℃, and the time is 5-7 h; And / or, the air flow rate in the calcination step is controlled to be 50-100 mL / min; And / or, the temperature increasing rate of the calcination step is 2.5-3.5 ℃ / min.

9. A metal ion-exchanged modified molecular sieve characterized by, The metal ion exchange modified molecular sieve is prepared by the preparation method of any one of claims 1-8.

10. The metal ion exchange modified molecular sieve of claim 9 is used in carbon dioxide adsorption.

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