CN112337435A - A-type zeolite/ZIF-8 core-shell structure microsphere and preparation method and application thereof - Google Patents
A-type zeolite/ZIF-8 core-shell structure microsphere and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses an A-type zeolite/ZIF-8 core-shell structure microsphere and a preparation method and application thereof. The microsphere takes A-type zeolite as a core structure and A-type zeolite and ZIF-8 as shell layers to form the core-shell structure microsphere. Preparation: (1) adding a silicon source into alkali liquor, and curing to form microspheres; (2) soaking the microspheres in an aluminum source, crystallizing, washing, drying and calcining; (3) wetting the microspheres; preparing zinc nitrate hexahydrate aqueous solution and dimethyl imidazole aqueous solution; (4) respectively soaking the wetted microspheres in zinc nitrate hexahydrate aqueous solution and dimethyl imidazole aqueous solution for oscillation reaction to obtain a pre-product; (5) and washing and drying the pre-product to obtain the A-type zeolite/ZIF-8 core-shell structure microspheres. The preparation method disclosed by the invention is simple and low in preparation cost, solves the problem of small specific surface area of the binderless A-type zeolite microsphere, provides a rich pore channel structure for the A-type zeolite/ZIF-8 core-shell structure microsphere, improves the gas adsorption and separation performance, and has obvious economic value and social benefit.
Description
Technical Field
The invention relates to the field of inorganic materials, in particular to an A-type zeolite/ZIF-8 core-shell structure microsphere and a preparation method and application thereof.
Background
As an important inorganic material, zeolite has a regular and ordered three-dimensional microporous structure, and the traditional application of the zeolite is mainly focused in the fields of adsorption, separation, ion exchange, catalysis and the like. The zeolite exists mainly in powder form, and in practical application, the zeolite powder is formed into a certain shape under the action of a binder for the convenience of use, wherein the preparation of a binder-free zeolite shaped body has been the object of continuous efforts of researchers. Yu et al restrict the growth of type a zeolite to chitosan microspheres by using an in situ sol-gel synthesis method, and binder-free type a zeolite microspheres are obtained by removing chitosan by calcination. The specific surface area of the obtained material is 30m calculated by a BET method2The specific surface area of the superfine type A zeolite powder and the commercial zeolite adsorbent reported in the literature is larger, but compared with other zeolite materials, the pore structure performance of the binderless type A zeolite microspheres is still to be improved.
ZIF-8 as a typical zeolite imidazolate framework material (ZIFs), has the characteristics of high thermal stability and chemical stability, large porosity and specific surface area, uniform pore diameter and the like, and has potential application values in the fields of adsorption separation, catalysis, photoelectric magnetic materials, drug delivery and the like. Since synthetic ZIF-8 is also powder, researchers have used chitosan (microporus mesopous mater, 2013,165, 200-204), gelatin (j. mater.chem.,2013,1(1): 3678-3684), polyether sulfone polymer (polym.complex., 2018,39,3896-3902), cellulose (cell., 2018,25,1997-2008), etc. as the support for ZIF-8 to prepare the ZIF-8 composite molded body material. Most of the forming agents are high molecular polymers, and are easy to cover the surface of ZIF-8 to block the pore channels of crystals, so that the pore structure parameters of the forming agents are reduced, and the existence of the high molecular polymers is not favorable for adsorption and separation of gas.
Disclosure of Invention
The invention aims to provide an A-type zeolite/ZIF-8 core-shell structure microsphere and a preparation method and application thereof; the invention solves the problem of small specific surface area of the binderless A-type zeolite microspheres, and the binderless A-type zeolite microspheres are used for gas adsorption separation, have rich pore channel structures, improve the gas adsorption separation performance, and have obvious economic value and social benefit.
The invention is realized by the following technical scheme:
the A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers. The shell layer contains a very small amount of A-type zeolite; in combination with the need of improving the pore structure performance of the binderless A-type zeolite microspheres and the forming requirement of ZIF-8, the invention utilizes the adsorption performance of the binderless A-type zeolite microspheres to grow ZIF-8 with a certain thickness on the surface of the binderless A-type zeolite microspheres to form core-shell structure microspheres with A-type zeolite as a core structure and A-type zeolite and ZIF-8 as shell layers.
A preparation method of A-type zeolite/ZIF-8 core-shell structure microspheres is characterized by comprising the following steps:
(1) adding a silicon source into alkali liquor, and curing to form microspheres; the silicon source is a silica sol aqueous solution in which chitosan is dissolved, and the formed microspheres are silica sol/chitosan hybrid microspheres;
(2) dipping the microspheres in an aluminum source, and then heating and crystallizing; washing, drying and calcining the crystallized microspheres; the aluminum source is a clear aqueous solution in which sodium hydroxide and sodium aluminate are dissolved;
(3) wetting the binderless A-type zeolite microspheres; preparing zinc nitrate hexahydrate aqueous solution and dimethyl imidazole aqueous solution;
(4) then respectively soaking the wetted A-type zeolite microspheres in zinc nitrate hexahydrate aqueous solution and dimethylimidazole aqueous solution for oscillation reaction (the A-type zeolite microspheres can be soaked in the zinc nitrate hexahydrate aqueous solution firstly and then soaked in the dimethylimidazole aqueous solution, or the soaking sequence can be reversed), so as to obtain a pre-product;
(5) and washing and drying the pre-product to obtain the A-type zeolite/ZIF-8 core-shell structure microspheres.
Furthermore, the feeding molar ratio of each raw material in the aqueous solution mixture of the silica sol/chitosan hybrid microspheres and the aluminum source is Na2O:Al2O3:SiO2:H2Calculated as O, 5.87: 1.0: 1.35: 185.
further, the alkali liquor in the step (1) is 2-5 wt% of sodium hydroxide solution.
Further, the dipping time in the step (2) is 18-24 hours; the temperature of the heating crystallization is 70-90 ℃, and the crystallization time is 2-5 hours; washing the crystallized microspheres to be neutral by using deionized water, and drying for 1-3 hours at 50-60 ℃; drying and then placing in a muffle furnace for heating and calcining; the heating rate is 1-10 ℃/min, the temperature is increased to 500-600 ℃, and the temperature is kept for 2-6 hours after the temperature is increased.
Further, in the step (3), the binderless A-type zeolite microspheres (binderless NaA zeolite microspheres) are placed above water vapor for wetting for 2-10 minutes; the concentration of the zinc nitrate hexahydrate aqueous solution is 2-30 wt%, and the concentration of the dimethylimidazole aqueous solution is 3-60 wt%.
Further, the mass-volume ratio of the A-type zeolite microspheres to the zinc nitrate hexahydrate aqueous solution in the step (4) is 0.01-0.05 g/mL; the mass-volume ratio of the A-type zeolite microspheres to the dimethyl imidazole aqueous solution is 0.01-0.05 g/mL; the time of each impregnation is 2-48 hours respectively; the oscillation is carried out at room temperature, and the oscillation time is 1-12 hours.
And further, washing the pre-product with a methanol solution and deionized water for 3-5 times in sequence in the step (5), and then drying in an oven at 50-60 ℃ for 2-5 hours to obtain the A-type zeolite/ZIF-8 core-shell structure microspheres.
The application of the A-type zeolite/ZIF-8 core-shell structure microspheres is characterized in that the A-type zeolite/ZIF-8 core-shell structure microspheres or the A-type zeolite/ZIF-8 core-shell structure microspheres prepared by the method are used for gas adsorption separation. The invention solves the problem of small specific surface area of the binderless A-type zeolite microspheres, improves the gas adsorption and separation performance by rich pore channel structures, and has obvious economic value and social benefit.
Compared with the prior art, the invention has the beneficial effects that:
the preparation method is simple and low in cost, solves the problem of small specific surface area of the binderless A-type zeolite microspheres, provides rich pore channel structures for the A-type zeolite/ZIF-8 core-shell structure microspheres, improves the gas adsorption and separation performance, and has obvious economic value and social benefit.
The invention develops a method for preparing the A-type zeolite/ZIF-8 core-shell structure microspheres by utilizing the adsorption effect of the NaA zeolite microspheres without the binding agent, and the method has the advantages of simple synthesis method, easy operation, high repeatability and easy industrialization. The synthesized A-type zeolite/ZIF-8 core-shell structure microsphere material is composed of an A-type zeolite serving as a core structure and an A-type zeolite and ZIF-8 serving as shell structures, and the thickness of a ZIF-8 shell layer can be effectively adjusted by simply controlling reaction conditions. The synthesized core-shell microspheres have higher specific surface area and better potential application value in the aspects of gas adsorption separation and the like.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is an XRD spectrum of zeolite A, ZIF-8, and zeolite A/ZIF-8 core-shell structure microspheres;
FIG. 2 is an SEM image of the zeolite A/ZIF-8 core-shell structure microspheres of example 1;
FIG. 3 is a nitrogen adsorption/desorption isotherm of the A-type zeolite/ZIF-8 core-shell microspheres of example 1.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the A-type zeolite/ZIF-8 core-shell structure microsphere comprises the following steps:
(1) adding a silicon source into an injector, inverting to remove bubbles, dropwise adding the silicon source into alkali liquor through a 0.35mm needle head, and curing to form microspheres; wherein the silicon source is a silica sol aqueous solution in which chitosan is dissolved, and the formed microspheres are silica sol/chitosan hybrid microspheres; the alkali liquor is 2 wt% of sodium hydroxide solution;
(2) adding the microspheres into an aluminum source, soaking for 24 hours, sealing, and then transferring into an oven at 80 ℃ for crystallization for 3 hours; washing the crystallized microspheres with deionized water to neutrality, drying at 50 ℃ for 3 hours, placing the dried microspheres in a muffle furnace, heating to 550 ℃ at a heating rate of 10 ℃/min, and carrying out heat preservation treatment for 4 hours; wherein the aluminum source is a clear aqueous solution in which sodium hydroxide and sodium aluminate are dissolved; the feeding molar ratio of each raw material in the aqueous solution mixture of the silica sol/chitosan hybrid microspheres and the aluminum source is Na2O:Al2O3:SiO2:H2Calculated as O, 5.87: 1.0: 1.35: 185 of the formula (I);
(3) wetting the prepared A-type zeolite microspheres for 5 minutes above water vapor; 10ml of zinc nitrate hexahydrate aqueous solution with the concentration of 10 weight percent and dimethyl imidazole aqueous solution with the concentration of 20 weight percent are prepared;
(4) then 0.1g of the binderless A-type zeolite microspheres wetted by water vapor are placed in 10ml of 10 wt% zinc nitrate hexahydrate aqueous solution for soaking for 24 hours, the binderless A-type zeolite microspheres are fished out after soaking and then are transferred into 10ml of 20 wt% dimethylimidazole aqueous solution for soaking for 24 hours (here, the binderless A-type zeolite microspheres can also be placed in the dimethylimidazole aqueous solution for soaking and then placed in the zinc nitrate hexahydrate aqueous solution for soaking), and the mixture is slowly vibrated at room temperature for reaction for 3 hours to obtain a pre-product;
(5) and (3) sequentially washing the pre-product with a methanol solution and deionized water for three times, and drying in an oven at 50 ℃ for 3 hours after washing to obtain the A-type zeolite/ZIF-8 core-shell structure microsphere product.
The A-type zeolite/ZIF-8 core-shell structure microspheres obtained in example 1 are taken and characterized by X-ray diffraction, and as shown in FIG. 1, the A-type zeolite/ZIF-8 core-shell structure microspheres have diffraction peaks of both A-type zeolite and ZIF-8 and do not affect crystal forms.
The core-shell structure microspheres were characterized by Scanning Electron Microscopy (SEM), as shown in FIG. 2, wherein (a) is an overall view of a cross-sectional view of the core-shell structure microspheres, (b) is an enlarged view of a center of the cross-section, (c-d) is an enlarged view of an edge of the cross-section, and (e) is an overall view of measurement of shell thickness, and it can be seen from (e) that the shell thickness composed of ZIF-8 and A-type zeolite is about 50 μm.
Example 2
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the A-type zeolite/ZIF-8 core-shell structure microsphere comprises the following steps:
(1) adding a silicon source into an injector, inverting to remove bubbles, dropwise adding the silicon source into alkali liquor through a 0.35mm needle head, and curing to form microspheres; wherein the silicon source is a silica sol aqueous solution in which chitosan is dissolved, and the formed microspheres are silica sol/chitosan hybrid microspheres; the alkali liquor is 3 wt% of sodium hydroxide solution;
(2) adding the microspheres into an aluminum source, soaking for 20 hours, sealing, and then transferring into a drying oven at 90 ℃ for crystallization for 2 hours; washing the crystallized microspheres with deionized water to neutrality, drying at 55 ℃ for 2 hours, placing the dried microspheres in a muffle furnace, heating to 600 ℃ at a heating rate of 2 ℃/min, and carrying out heat preservation treatment for 3 hours; wherein the aluminum source is a clear aqueous solution in which sodium hydroxide and sodium aluminate are dissolved; the feeding molar ratio of each raw material in the aqueous solution mixture of the silica sol/chitosan hybrid microspheres and the aluminum source is Na2O:Al2O3:SiO2:H2Calculated as O, 5.87: 1.0: 1.35: 185 of the formula (I);
(3) wetting the prepared A-type zeolite microspheres for 2 minutes above water vapor; 10ml of zinc nitrate hexahydrate aqueous solution with the concentration of 5 weight percent and dimethyl imidazole aqueous solution with the concentration of 60 weight percent are prepared;
(4) then 0.3g of the binderless A-type zeolite microspheres wetted by water vapor are placed in 10ml of 5 wt% zinc nitrate hexahydrate aqueous solution to be soaked for 15 hours, the binderless A-type zeolite microspheres are fished out after soaking and then are transferred into 10ml of 20 wt% dimethylimidazole aqueous solution to be soaked for 15 hours (here, the binderless A-type zeolite microspheres can also be soaked in the dimethylimidazole aqueous solution firstly and then are placed in the zinc nitrate hexahydrate aqueous solution to be soaked), and the mixture is slowly oscillated and reacted for 8 hours at room temperature to obtain a pre-product;
(5) and (3) sequentially washing the pre-product with a methanol solution and deionized water for five times respectively, and drying in an oven at 60 ℃ for 2 hours after washing to obtain the A-type zeolite/ZIF-8 core-shell structure microsphere product.
Example 3
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the A-type zeolite/ZIF-8 core-shell structure microsphere comprises the following steps:
(1) adding a silicon source into an injector, inverting to remove bubbles, dropwise adding the silicon source into alkali liquor through a 0.35mm needle head, and curing to form microspheres; wherein the silicon source is a silica sol aqueous solution in which chitosan is dissolved, and the formed microspheres are silica sol/chitosan hybrid microspheres; the alkali liquor is 5 wt% of sodium hydroxide solution;
(2) adding the microspheres into an aluminum source, soaking for 18 hours, sealing, and then transferring into an oven at 70 ℃ for crystallization for 5 hours; washing the crystallized microspheres to be neutral by using deionized water, drying the microspheres for 1 hour at 60 ℃, putting the dried microspheres into a muffle furnace, heating the microspheres to 500 ℃ at the heating rate of 5 ℃/min, and carrying out heat preservation treatment for 6 hours after heating; wherein the aluminum source is a clear aqueous solution in which sodium hydroxide and sodium aluminate are dissolved; the feeding molar ratio of each raw material in the aqueous solution mixture of the silica sol/chitosan hybrid microspheres and the aluminum source is Na2O:Al2O3:SiO2:H2Calculated as O, 5.87: 1.0: 1.35: 185 of the formula (I);
(3) wetting the prepared A-type zeolite microspheres for 10 minutes above water vapor; 10ml of zinc nitrate hexahydrate aqueous solution with the concentration of 30 weight percent and dimethyl imidazole aqueous solution with the concentration of 3 weight percent are prepared;
(4) then 0.5g of the binderless A-type zeolite microspheres wetted by water vapor are placed in 10ml of 30 wt% zinc nitrate hexahydrate aqueous solution for dipping for 1 hour, the binderless A-type zeolite microspheres are fished out after dipping and then transferred into 10ml of 3 wt% dimethylimidazole aqueous solution for dipping for 1 hour (here, the binderless A-type zeolite microspheres can also be dipped in the dimethylimidazole aqueous solution and then dipped in the zinc nitrate hexahydrate aqueous solution), and the mixture is slowly oscillated and reacted for 10 hours at room temperature to obtain a pre-product;
(5) and (3) washing the pre-product with a methanol solution and deionized water for four times respectively, and drying in an oven at 55 ℃ for 3 hours after washing to obtain the A-type zeolite/ZIF-8 core-shell structure microsphere product.
Example 4
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the zeolite a/ZIF-8 core-shell structure microspheres of example 4 is the same as that of example 1, except that the impregnation time of the binderless zeolite a microspheres in the zinc nitrate hexahydrate aqueous solution in example 1 is changed, and the rest is unchanged; the binder-free type a zeolite microspheres of example 4 were immersed in an aqueous solution of zinc nitrate hexahydrate for 2 hours.
Example 5
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the zeolite A/ZIF-8 core-shell structure microspheres of example 5 is the same as that of example 1, except that the impregnation time of the binderless zeolite A microspheres in the zinc nitrate hexahydrate aqueous solution in example 1 is changed, and the rest is unchanged; the binder-free type a zeolite microspheres of example 5 were immersed in an aqueous solution of zinc nitrate hexahydrate for 12 hours.
Example 6
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the zeolite a/ZIF-8 core-shell structure microspheres of example 6 is the same as that of example 1, except that the impregnation time of the binderless zeolite a microspheres in the zinc nitrate hexahydrate aqueous solution in example 1 is changed, and the rest is unchanged; the binder-free type a zeolite microspheres of example 6 were immersed in an aqueous solution of zinc nitrate hexahydrate for a period of 36 hours.
Example 7
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the zeolite a/ZIF-8 core-shell structure microspheres of example 7 is the same as that of example 1, except that the impregnation time of the binderless zeolite a microspheres in the zinc nitrate hexahydrate aqueous solution in example 1 is changed, and the rest is unchanged; the binder-free type a zeolite microspheres of example 7 were immersed in an aqueous solution of zinc nitrate hexahydrate for 48 hours.
The above examples 4 to 7 are different from example 1 in that the immersion time of the binderless a-type zeolite microspheres in an aqueous solution of zinc nitrate hexahydrate was changed to 2 hours, 12 hours, 36 hours and 48 hours in this order, and the rest conditions were not changed, and the experimental results showed that the thickness of the ZIF-8 shell layer in the microspheres could be effectively adjusted by changing the immersion time of the binderless a-type zeolite microspheres in an aqueous solution of zinc nitrate hexahydrate.
Example 8
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the A-type zeolite/ZIF-8 core-shell structure microsphere in the embodiment 8 is the same as that in the embodiment 1, except that the slow oscillation time at room temperature in the embodiment 1 is changed, and the rest is unchanged; the shaking time in example 8 was 1 hour.
Example 9
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the a-type zeolite/ZIF-8 core-shell structure microsphere of example 9 is the same as that of example 1, except that the slow oscillation time at room temperature in example 1 is changed, and the rest is unchanged; the shaking time in example 9 was 6 hours.
Example 10
The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
The preparation method of the a-type zeolite/ZIF-8 core-shell structure microsphere of example 10 is the same as that of example 1, except that the slow oscillation time at room temperature in example 1 is changed, and the rest is unchanged; the shaking time in example 10 was 12 hours.
The above examples 8 to 10 are different from example 1 in that the oscillation time at room temperature was changed to 1 hour, 6 hours and 12 hours in this order, and the rest of the conditions were not changed, and the experimental results showed that the thickness of the ZIF-8 shell layer and the size of the ZIF-8 particles in the microspheres could be effectively adjusted by changing the oscillation time.
According to the embodiment, the method for preparing the core-shell structure microspheres with the A-type zeolite and the ZIF-8 shell layers by using the A-type zeolite as the neutralizing structure is developed, the preparation method is simple, easy to operate, high in repeatability and easy to industrialize, and the synthesized microspheres have good potential application values in the aspects of gas adsorption separation and the like.
Application example 1
Carrying out nitrogen adsorption and desorption on the A-type zeolite/ZIF-8 core-shell structure microspheres obtained in the example 1: degassing the sample at 200 deg.C for 3h, measuring the adsorption-desorption isotherm of the sample at 77K with ASAP 2020 specific surface pore size analyzer according to 77K N2The adsorption isotherm was used to calculate the specific surface area of the sample using the BET equation, and the results are shown in fig. 3. As can be seen from the figure, the nitrogen adsorption and desorption isotherm of the A-type zeolite/ZIF-8 core-shell structure microsphere is a class II isotherm, and a small amount of micropores are adsorbed in a low-pressure region; at P/P0Between 0.65 and 0.99, there is a relatively pronounced H4And (3) type hysteresis loop, which indicates that mesopores exist in the zeolite microspheres. When relative pressure (P/P)0) When the adsorption capacity is close to 1, the adsorption capacity to nitrogen is obviously increased, and the existence of macropores in the zeolite microspheres is indicated. The specific surface area of the obtained material was 265.4m as calculated by the BET method2Per g, which is far larger than 30m of A-type zeolite microspheres reported in literature2/g(Ind.Eng.Chem.Res.,2012,51,2299-2308)。
The above-mentioned preferred embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention. Obvious variations or modifications of the present invention are within the scope of the present invention.
Claims (9)
1. The A-type zeolite/ZIF-8 core-shell structure microsphere is characterized in that the core-shell structure microsphere is formed by taking A-type zeolite as a core structure and taking A-type zeolite and ZIF-8 as shell layers.
2. The preparation method of the A-type zeolite/ZIF-8 core-shell structure microsphere according to claim 1, characterized by comprising the following steps:
(1) adding a silicon source into alkali liquor, and curing to form microspheres; the silicon source is a silica sol aqueous solution in which chitosan is dissolved, and the formed microspheres are silica sol/chitosan hybrid microspheres;
(2) dipping the microspheres in an aluminum source, and then heating and crystallizing; washing, drying and calcining the crystallized microspheres; the aluminum source is a clear aqueous solution in which sodium hydroxide and sodium aluminate are dissolved;
(3) wetting the binderless A-type zeolite microspheres; preparing zinc nitrate hexahydrate aqueous solution and dimethyl imidazole aqueous solution;
(4) then respectively soaking the wetted A-type zeolite microspheres in zinc nitrate hexahydrate aqueous solution and dimethyl imidazole aqueous solution for oscillation reaction to obtain a pre-product;
(5) and washing and drying the pre-product to obtain the A-type zeolite/ZIF-8 core-shell structure microspheres.
3. The method for preparing A-type zeolite/ZIF-8 core-shell structure microspheres according to claim 2, wherein the molar ratio of raw materials in the aqueous solution mixture of the silica sol/chitosan hybrid microspheres and the aluminum source is Na2O:Al2O3:SiO2:H2Calculated as O, 5.87: 1.0: 1.35: 185.
4. the preparation method of the A-type zeolite/ZIF-8 core-shell structure microspheres according to claim 2, wherein the alkali solution in the step (1) is 2-5 wt% of sodium hydroxide solution.
5. The preparation method of the A-type zeolite/ZIF-8 core-shell structure microspheres according to claim 2, wherein the impregnation time in the step (2) is 18-24 hours; the temperature of the heating crystallization is 70-90 ℃, and the crystallization time is 2-5 hours; washing the crystallized microspheres to be neutral by using deionized water, and drying for 1-3 hours at 50-60 ℃; drying and then placing in a muffle furnace for heating and calcining; the heating rate is 1-10 ℃/min, the temperature is increased to 500-600 ℃, and the temperature is kept for 2-6 hours after the temperature is increased.
6. The preparation method of the A-type zeolite/ZIF-8 core-shell structure microspheres according to claim 2, wherein in the step (3), the binderless A-type zeolite microspheres are wetted for 2-10 minutes above water vapor; the concentration of the zinc nitrate hexahydrate aqueous solution is 2-30 wt%, and the concentration of the dimethylimidazole aqueous solution is 3-60 wt%.
7. The preparation method of the zeolite A/ZIF-8 core-shell structure microspheres of claim 2, wherein the mass-to-volume ratio of the zeolite A microspheres to the zinc nitrate hexahydrate aqueous solution in step (4) is 0.01-0.05 g/mL; the mass-volume ratio of the A-type zeolite microspheres to the dimethyl imidazole aqueous solution is 0.01-0.05 g/mL; the time of each impregnation is 2-48 hours respectively; the oscillation is carried out at room temperature, and the oscillation time is 1-12 hours.
8. The preparation method of the A-type zeolite/ZIF-8 core-shell structure microspheres according to claim 2, wherein the pre-product is sequentially washed with a methanol solution and deionized water for 3-5 times in step (5), and then dried in an oven at 50-60 ℃ for 2-5 hours to obtain the A-type zeolite/ZIF-8 core-shell structure microspheres.
9. An application of A-type zeolite/ZIF-8 core-shell structure microspheres is characterized in that the A-type zeolite/ZIF-8 core-shell structure microspheres in claim 1 or the A-type zeolite/ZIF-8 core-shell structure microspheres prepared by the method in any one of claims 2 to 8 are used for gas adsorption separation.
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