An activated alumina ball, its preparation method and application

Abstract

This solution provides an activated alumina ball, its preparation method and application. 1) Prepare aluminum sol using pseudo-boehmite as the aluminum source; 2) Prepare a high-polymer crosslinked starch with a spatial network structure by reacting a crosslinking agent with the hydroxyl groups of amylose molecules; 3) Dry, calcine, crush and grind the colloid to obtain alumina powder; 4) Use an organic amine rich in amino groups as a modifier and load it into the inner pores and surface of alumina by physical impregnation; 5) Use the rotary disk granulation method to roll into balls, and then hydrate and calcine to obtain the finished activated alumina balls. The activated alumina balls prepared by this method optimize the pore structure and pore morphology characteristics, and can greatly improve their carbon dioxide adsorption capacity and adsorption cycle stability while basically ensuring the compressive strength and specific surface area of the balls.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorbent production, and particularly relates to an activated alumina ball, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, high-nickel ternary materials, which have advantages such as high energy density, large discharge capacity, and low comprehensive cost, have gradually become the main direction of the development of lithium battery cathode material technology. However, high-nickel ternary materials are extremely prone to react with water and carbon dioxide in the air during the preparation process and generate by-products, which affects the performance of such cathode materials. In view of the above problems, a patent for invention of a compressed air decarbonization and drying device and a use method disclosed in Chinese Patent Publication No. CN 118304741A discloses a purification device for reducing the carbon dioxide and moisture content in compressed air to meet the gas use requirements for the preparation of high-nickel ternary cathode materials.

[0003] In a compressed air decarbonization and drying device, molecular sieves, due to their crystalline substances with regular and uniform pore structures, can widely adsorb carbon dioxide molecules through their microporous structures by correspondingly regulating the pore size to match the molecular size. However, due to the limited strength of molecular sieves and the fact that their adsorption performance and separation effect under high-humidity conditions are inferior to those of activated alumina, it is often necessary to place some activated alumina at the lower part of the molecular sieve bed layer to absorb moisture and resist the impact of air flow. However, in the actual use process of such a compressed air decarbonization and drying device, on the one hand, a double-bed process of activated alumina and molecular sieve needs to be adopted, which not only leads to a complex structure of the adsorber, high cost, and the risk of mixed beds; on the other hand, although activated alumina has a large specific surface area and good chemical stability, its low carbon dioxide adsorption performance limits its possibility of independent application in compressed air decarbonization and drying devices.

[0004] For the above reasons, improving the carbon dioxide adsorption capacity of activated alumina by physical or chemical methods has gradually become an important way to solve the above problems. Currently, in this field, there has been some progress in the research of using activated alumina as a raw material, an ethanol solution of pentaethylenehexamine as a modifier, and the impregnation method to prepare modified activated alumina to increase the carbon dioxide adsorption amount of activated alumina. However, due to problems such as uneven pore size distribution and complex pore morphology characteristics of the carrier activated alumina, the activated alumina balls prepared by the above method still generally have problems such as limited improvement in adsorption performance and low adsorption sequence stability. Summary of the Invention

[0005] The purpose of the present invention is to provide an activated alumina ball and a preparation method and application thereof. By optimizing the pore structure and pore morphology characteristics of the activated alumina, its ability and effect of loading amino-rich organic amines are improved, and while basically ensuring the compressive strength and specific surface area of ​​the sphere, its carbon dioxide adsorption capacity and adsorption cycle stability can be greatly improved.

[0006] like Figure 1 To achieve the above purpose, the present technical solution provides a method for preparing activated alumina balls, comprising the following steps:

[0007] S1: adding pseudo-boehmite into deionized water at a temperature of 85-95° C. and stirring the mixture thoroughly to obtain a liquid-solid mixture slurry, adding nitric acid to the liquid-solid mixture slurry, stirring the mixture under a constant temperature, and aging and refluxing the mixture to obtain an aluminum sol;

[0008] S2: adding starch and sodium hydroxide solution into deionized water and stirring to obtain an alkaline starch suspension, adding a crosslinking agent to the alkaline starch suspension and reacting at 20-55° C. for a period of time, followed by filtering, washing and drying in sequence to obtain a high polymer cross-linked starch having a spatial network structure;

[0009] S3: mixing the polymer cross-linked starch with the aluminum sol, and then drying, calcining, crushing, and grinding the mixture to obtain aluminum oxide powder;

[0010] S4: using physical impregnation to load the modifier into the inner pores and surface of the alumina powder to obtain modified activated alumina powder, wherein the modifier is an organic amine rich in amino groups;

[0011] S5: spraying an aqueous solution containing an additive or a binder into a spheroidizing plate containing modified activated alumina powder and forming spheroids by a rotating plate spheroidizing method, rehydrating and calcining the spheroids to obtain activated alumina spheres.

[0012] Step S1 of this scheme uses pseudo-boehmite as a raw material, and uses the peptization characteristics of pseudo-boehmite under acidic conditions to form a stable aluminum sol, which provides a basic raw material for the subsequent preparation of activated alumina, and its pore structure and morphology are conducive to subsequent amino modification. It should be noted that pseudo-boehmite is a kind of incompletely crystallized boehmite, has a chemical composition similar to that of boehmite, contains 1.25~2.0 crystal waters, is a type of incompletely crystallized hydrated aluminum oxide, also known as monohydrated aluminum oxide, pseudo-monohydrate soft aluminum oxide, and the typical structure of pseudo-boehmite is an extremely thin pleated sheet, which is an aluminum oxide hydrate with a special spatial network structure, and has physical properties such as high specific surface area and large pore volume, and chemical properties of peptization and thixotropy under acidic conditions.

[0013] In some embodiments, pseudo-boehmite is prepared by any one of the following methods: gibbsite quick stripping method, aluminum salt neutralization method, alcohol aluminum method, alkali method, and nitric acid method. The specific preparation process is selected according to the source of the raw materials and the product performance.

[0014] In some embodiments, the grain size of pseudo-boehmite is 3.5-6.0 nm. The appropriate grain size helps to form a uniform aluminum sol, thereby better controlling the pore structure and morphology of the activated alumina balls in subsequent processes, thereby ensuring the consistency and stability of product performance.

[0015] In some embodiments, pseudo-boehmite is added to deionized water at a temperature of 85-95°C and fully stirred, wherein the stirring conditions are set to a stirring speed of 600-900 r / min, an aging time of 5-8 hours, and a reflux time of 2-3 hours, which can enable the pseudo-boehmite to be fully dispersed and reacted, promote the formation and stabilization of aluminum sol, and ensure the quality and performance of aluminum sol.

[0016] In some embodiments, the solid content in the liquid-solid mixture slurry is 60-80 g / L, which ensures the appropriate concentration of pseudo-boehmite in the reaction system, avoiding uneven reaction or excessive viscosity of the system due to excessively high concentration, and preventing production efficiency and product quality from being affected by excessively low concentration.

[0017] In some embodiments, nitric acid with a concentration of 3-5% is added to the liquid-solid mixture slurry at an acid-aluminum molar ratio of 0.06-0.1:1. The appropriate amount and concentration of nitric acid can ensure sufficient peptization of pseudo-boehmite while avoiding the adverse effects of excessive or insufficient nitric acid on the structure and properties of the aluminum sol, thereby ensuring the stability of the aluminum sol and the quality of subsequent products.

[0018] In step S2 of this scheme, starch and sodium hydroxide solution are mixed to obtain an alkaline starch suspension, and a cross-linking agent is added for reaction, followed by filtration, water washing and drying to obtain a high polymer cross-linked starch having a spatial network structure. The starch selected in this scheme is straight-chain starch to avoid excessive viscosity of the mixed system. The spatial network structure formed by the cross-linking reaction helps to regulate the pore structure of activated alumina during the subsequent mixing and treatment process with aluminum sol.

[0019] It should be noted that cross-linked starch is a new synthetic substance and belongs to one of the modified starches; it is also an important starch derivative. It is formed by the reaction of a cross-linking agent containing a binary or polyvalent functional group with the hydroxyl groups of starch molecules (generating groups such as diether bonds and diester groups), thereby cross-linking two or more starch molecules to form a cross-linked starch, a polymer with a three-dimensional network structure. Natural starch is composed of amylose and amylopectin. Most starches contain 10% - 12% amylose and 80% - 90% amylopectin. Corn starch contains 27% amylose; potato starch contains 20% amylose (the rest of both is amylopectin); glutinous rice starch is almost entirely amylopectin. In the present invention, amylose is used as the starch raw material to prepare cross-linked starch polymer. Its molecular structure is relatively simple, with a small molecular mass, high solubility and stability, and relatively low viscosity, which can avoid the excessive viscosity of the mixing system and caking during the preparation of activated alumina, and relatively improve the smoothness of the mixing system.

[0020] In some embodiments, the starch in step S2 is amylose, selected from one or more of mung bean starch, soybean starch, white bean starch or retrograded starch.

[0021] In some embodiments, the starch content in the alkaline starch suspension is 90 - 130 g / L, and the pH value is 7.6 - 9. This starch content range can ensure that there is enough starch participating in the cross-linking reaction to form a suitable three-dimensional network structure. If the content is too low, the cross-linking effect is poor and the pore structure of activated alumina cannot be effectively regulated; if the content is too high, it may lead to excessive viscosity of the system, affecting the reaction progress and product performance. The suitable pH environment provides good conditions for the cross-linking reaction, promotes the reaction of the cross-linking agent with the hydroxyl groups of starch molecules, enables the cross-linking reaction to proceed smoothly, helps to form a cross-linked starch polymer with a stable and ideal three-dimensional network structure, and thus has a positive impact on the pore structure of activated alumina.

[0022] In some embodiments, the cross-linking agent is epichlorohydrin, trisodium metaphosphate or hexametaphosphate. These cross-linking agents contain binary or polyvalent functional groups, can react with the hydroxyl groups of starch molecules to generate groups such as diether bonds and diester groups, and cross-link two or more starch molecules to form a stable three-dimensional network structure. This structure can play a templating role during the processes of mixing with aluminum sol, subsequent drying and calcination, etc., helping to regulate the pore structure of activated alumina to make it more regular and uniform.

[0023] In some embodiments, the parts by mass of the crosslinking agent are 0.2-3% of the mass of the starch. This addition ratio can not only ensure that the crosslinking agent reacts fully with the starch to form an effective three-dimensional network structure, but also prevent the crosslinking degree from being too high due to excessive crosslinking agent, which may affect the performance of the starch and its subsequent synergistic effect with the aluminum sol; nor will the crosslinking reaction be insufficient due to too little crosslinking agent, failing to achieve the expected pore regulation effect.

[0024] In some embodiments, the crosslinking agent is added to the alkaline starch suspension and reacted for 3-4 h. This reaction time can ensure that the crosslinking agent reacts fully with the starch molecules, enabling the full formation and stabilization of the three-dimensional network structure. If the reaction time is too short, the crosslinking reaction is incomplete and the pores of the activated alumina cannot be effectively regulated; if the reaction time is too long, it may lead to over-crosslinking, causing changes in the starch structure and affecting the product performance.

[0025] In step S3 of this solution, the polymer crosslinked starch and the aluminum sol are mixed and then successively subjected to drying, calcination, crushing, and grinding to obtain alumina powder. It should be noted that the sol-gel method uses compounds containing highly chemically active components as precursors, uniformly mixes these raw materials in the liquid phase, and undergoes hydrolysis and condensation chemical reactions to form a stable transparent sol system in the solution. The sol is aged and the colloidal particles slowly polymerize to form a three-dimensional network structure gel. The gel network is filled with a solvent that has lost fluidity to form a gel. The gel is dried and sintered to prepare materials with molecular and even nano-substructures. In the present invention, pseudo-boehmite is used as the aluminum source, and the pore structure and morphological characteristics of the activated alumina prepared by the sol-gel method are more suitable for amination modification by the physical impregnation method.

[0026] In some embodiments, the mass ratio of the polymer crosslinked starch to the aluminum sol is (1.1-1.4):50. At this mass ratio, the crosslinked starch is evenly dispersed in the aluminum sol system, and the three-dimensional network structure formed by the crosslinked starch plays a template role in the subsequent drying and calcination processes. During high-temperature treatment, the crosslinked starch gradually decomposes, leaving evenly distributed pores. These pores cooperate with the alumina skeleton formed by the aluminum sol, helping to form a regular, uniform, and suitable pore structure, providing a good diffusion channel for gas molecules such as carbon dioxide, improving the adsorption efficiency, and optimizing the pore structure of the alumina powder. And the appropriate ratio can ensure that during the formation of the activated alumina balls, neither excessive crosslinked starch will cause excessive impurities to remain after calcination and affect the specific surface area, nor will too little crosslinked starch be unable to effectively regulate the pore structure, thus ensuring that the activated alumina balls have a high specific surface area. A larger specific surface area means more active sites, which can enhance the adsorption capacity for carbon dioxide.

[0027] In some embodiments, in step S3, the drying temperature is 110~180°C and the drying time is 2~8 h; the calcination temperature is 550~650°C and the calcination time is 4.5~6 h. Further, in the calcination process, the temperature is first increased at a rate of 2.5~3.3°C / min until the calcination temperature reaches 330~350°C, and after maintaining the temperature for 0.5~1 h, the temperature is then increased to 550~650°C at a rate of 1.7~2.2°C / min under an oxygen-containing condition and maintained for 1~2 h.

[0028] In some embodiments, the particle size of the alumina powder prepared in step S3 is 320 mesh to 550 mesh.

[0029] In step S4 of this solution, an organic amine rich in amino groups is used as a modifier, and it is loaded into the inner pores and surface of the alumina powder by physical impregnation. The amino groups in the organic amine can react with carbon dioxide to form carbamate, enhancing the carbon dioxide adsorption capacity of activated alumina. It should be noted that the organic amine molecules can perform amination modification on the activated alumina, and enhance the affinity of the activated alumina for CO2 through the large number of amino groups contained therein, reacting with CO2 to form carbamate. Although the organic amine molecules are successfully loaded onto the activated alumina and do not destroy the original structure of the activated alumina, it causes a slight decrease in its specific surface area and pore volume.

[0030] In some embodiments, the organic amine is one or more selected from tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, polyethylenepolyamine, and hydroxyethyl ethylenediamine, which can maintain better cyclic regeneration ability and is more suitable for forming impregnated amino solids.

[0031] In step S5 of this solution, an aqueous solution containing an auxiliary agent or a binder is sprayed onto the modified activated alumina powder, and spheres are formed by the rotary disk granulation method, followed by hydration and calcination treatments. The auxiliary agent or binder helps the powder to form spheres. Hydration can further optimize the internal structure of the activated alumina spheres, and calcination removes impurities, adjusts the pore structure and morphology, improves the product performance, and enables the activated alumina spheres to have specific compressive strength, specific surface area, carbon dioxide adsorption performance, etc.

[0032] It should be noted that the calcination process is also one of the important factors affecting the pore structure and morphological characteristics of activated alumina. Calcination includes processes such as dehydration, dehydroxylation, particle sintering, decomposition or removal of volatile substances, and burning off organic substances, and these processes all affect the pore structure and morphological characteristics of the final activated alumina carrier. At different calcination temperatures, the pore structure of activated alumina will continuously change.

[0033] The test results show that as the calcination temperature increases, smaller pores collapse to form larger pores, resulting in a gradual increase in the average pore diameter and a corresponding gradual decrease in the specific surface area. When the calcination temperature is 380 - 450 °C, activated alumina with a high specific surface area and large pore volume can be obtained. In addition, by appropriately adjusting the heating rate, the moisture in the small pores can be completely removed, thus eliminating caking and fracture phenomena. Therefore, to ensure the properties of the activated alumina support, appropriate calcination temperature and calcination time must be controlled during its calcination process. In some embodiments, the calcination temperature is 380 - 450 °C and the calcination time is 30 - 40 min.

[0034] In a second aspect, the present solution provides an activated alumina ball, which is prepared according to the preparation method of the activated alumina ball mentioned in the first aspect.

[0035] In some embodiments, the pore morphology characteristics of most pores of the activated alumina ball are straight cylindrical, the specific surface area ≥ 280 m 2 / g, and the strength is greater than 150 N / particle; under the operating temperature of 25 °C and the operating pressure of 250 mmHg, the saturated adsorption capacity of CO2 ≥ 6 wt%.

[0036] In a third aspect, the present solution provides a compressed air decarbonization device, which uses the activated alumina ball described above as an adsorbent.

[0037] In some embodiments, the compressed air decarbonization device is used in the preparation scenario of high-nickel ternary cathode materials to reduce the carbon dioxide and moisture content in the compressed air.

[0038] Compared with the prior art, the present technical solution has the following characteristics and beneficial effects:

[0039] (1) In the present invention, pseudo-boehmite is used as the aluminum source to prepare porous activated alumina, and then an organic amine rich in amino groups is used as a modifier. The obtained activated alumina ball prepared by the impregnation method has a uniform pore size distribution, and also provides sufficient confinement space for the amine modifier, promoting the amine modifier to form a highly spatially dispersed state, thereby exposing more hydrophilic groups. It has a higher carbon dioxide adsorption effect than ordinary activated alumina balls, and can be recycled with high stability.

[0040] (2) Through the reasonable selection and proportioning of raw materials, cross-linking agents, and modifiers, as well as the optimization of process parameters in aspects such as glue preparation, drying, cross-linking, calcination, modification, and activation, the pore structure and morphological characteristics of activated alumina balls are effectively improved, ensuring basic performance indicators such as the compressive strength of the formed balls, specific surface area, and static adsorption capacity. It should be noted that the pore structure and morphological characteristics of the adsorbent have a very important impact on its adsorption and desorption performance. According to different shapes, the pores of the adsorbent can be mainly divided into spherical pores, conical pores, cylindrical pores, fissure pores, etc. And using linear cross-linked starch as a pore-forming agent can make activated alumina produce cylindrical pores that are more conducive to the implementation of the impregnation process. The improvement of the carbon dioxide adsorption performance and cycle stability of activated alumina mainly benefits from this through the analysis of the experimental test data of the adsorbent performance.

[0041] (3) The present invention provides a method for producing activated alumina balls with a simple and efficient preparation process, low cost, and easy to scale up. The product prepared according to this method can effectively achieve the synchronous and efficient adsorption of water and carbon dioxide, significantly reducing the manufacturing cost and maintenance cost of compressed air decarbonization devices and similar equipment. Brief Description of the Drawings

[0042] Figure 1 It is a process flow chart of the preparation method of the activated alumina balls provided by this solution. Detailed Embodiments

[0043] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0044] Example 1

[0045] Weigh 7 g of pseudo-boehmite and add it to 100 ml of deionized water, and stir well at 90 °C to prepare a liquid-solid mixture slurry; add dilute nitric acid with a concentration of 3.5% to the above slurry according to the molar ratio of acid to aluminum of 0.06:1, and stir at a constant temperature of 800 r / min, age for 5.5 h, and reflux for 3 h to obtain an aluminum sol for standby;

[0046] Weigh 5 g of mung bean starch and add it to sodium hydroxide aqueous solution A (0.05 mol / L) to prepare a starch milk with a mass fraction of 12%, and adjust the pH value to 8.5 with sodium hydroxide aqueous solution B (mass fraction of 2%). Slowly add 1.5 mL of sodium hexametaphosphate solution (mass fraction of 4%) to the starch milk. After the cross-linking reaction is completed, take out the product, filter, wash with water, and leave it to stand in an oven at 40 °C for 3.5 h to obtain cross-linked starch.

[0047] Mix cross-linked starch with reserved aluminum sol at a mass ratio of 1.2:50. After drying the obtained colloid at a constant temperature of 160°C for 4 h, gradually heat it up to 350°C at a heating rate of 3°C / min, keep it at a constant temperature for 0.5 h, then heat it up to 650°C at a heating rate of 2°C / min under an oxygen-containing condition and keep it at a constant temperature for 2 h, and then crush and grind it to a powder particle size of 400 mesh.

[0048] Dissolve 2 g of tetraethylenepentamine in 50 mL of absolute ethanol, and stir it at a constant temperature and seal it at 40°C until it is completely dissolved. Weigh 5 g of activated alumina, place it in the above-mentioned well-stirred solution, and stir it at a constant temperature of 40°C for 4 h. After filtering and washing the impregnated activated alumina, place it in a vacuum drying oven and dry it at -0.095 MPa and 85°C for 12 h to obtain tetraethylenepentamine-modified activated alumina.

[0049] Take 15 g of ammonium bicarbonate and 8 g of sodium carbonate and add them to 100 ml of deionized water, and stir well to form a binder slurry. Place the modified activated alumina powder in a rotating balling pan, and spray the binder slurry to make the powder adhere to each other and gradually become spherical particles during rolling. After the formed balls are stored at room temperature for 24 h, perform hydrothermal treatment with steam at 120°C for 2 h. Then, calcine the balls after hydrothermal treatment at 450°C for 30 min to obtain the finished activated alumina balls.

[0050] Example 2

[0051] Weigh 7 g of pseudoboehmite and add it to 100 ml of deionized water, and stir it well at 85°C to prepare a liquid-solid mixture slurry; add dilute nitric acid with a concentration of 5% to the above slurry according to a molar ratio of acid to aluminum of 0.08:1, and stir it at a constant temperature of 800 r / min, age for 6.5 h, and reflux for 3 h to obtain reserved aluminum sol;

[0052] Weigh 5 g of soybean starch and add it to sodium hydroxide aqueous solution A (0.05 mol / L) to prepare a starch milk with a mass fraction of 12%, and adjust the pH value to 9 with sodium hydroxide aqueous solution B (mass fraction of 3%). Slowly drop 2.4 mL of epichlorohydrin solution (mass fraction of 2%) into the starch milk. After the cross-linking reaction is completed, take out the product, filter, wash it, and let it stand in an oven at 40°C for 3.5 h to obtain cross-linked starch.

[0053] Mix cross-linked starch with reserved aluminum sol at a mass ratio of 1.3:50. After drying the obtained colloid at a constant temperature of 160°C for 4 h, gradually heat it up to 330°C at a heating rate of 2.5°C / min, keep it at a constant temperature for 1 h, then heat it up to 550°C at a heating rate of 1.8°C / min under an oxygen-containing condition and keep it at a constant temperature for 1.5 h, and then crush and grind it to a powder particle size of 500 mesh.

[0054] Dissolve 2.5 g of pentaethylenehexamine in 50 mL of absolute ethanol, and stir it at a constant temperature and seal it at 40 °C until it is completely dissolved. Weigh 5 g of activated alumina and place it in the above-mentioned uniformly stirred solution, and stir it at a constant temperature and seal it at 40 °C for 4 h. After filtering and washing the impregnated activated alumina, place it in a vacuum drying oven and dry it at -0.095 MPa and 85 °C for 12 h to obtain pentaethylenehexamine-modified activated alumina.

[0055] Take 15 g of ammonium bicarbonate and 8 g of sodium carbonate and add them to 100 ml of deionized water, and stir well to form a binder slurry. Place the modified activated alumina powder in a rotating ball-forming pan, and spray the binder slurry to make the powder adhere to each other and gradually become spherical particles during rolling. After the formed balls are stored at room temperature for 24 hours, they are heat-treated with steam at 120 °C for 3 h. Then, the heat-treated balls are calcined at 400 °C for 30 min to obtain the finished activated alumina balls.

[0056] Example 3

[0057] Other raw materials, components, and parameters are the same as those in Example 1. The type, specification, and quantity of the cross-linking agent are changed from 1.5 mL of sodium hexametaphosphate solution (4%) to 2.4 mL of epichlorohydrin solution (mass fraction 2%); the type of starch is changed from mung bean starch to white bean starch.

[0058] Example 4

[0059] Other raw materials, components, and parameters are the same as those in Example 1. The type of organic amine is changed from tetraethylene pentamine to pentaethylene hexamine.

[0060] Example 5

[0061] Other raw materials, components, and parameters are the same as those in Example 1. Only the pH value of the alkaline starch suspension is adjusted to 10.5, and then 1.5 mL of sodium hexametaphosphate solution (4%) is added dropwise.

[0062] Example 6

[0063] Other raw materials, components, and parameters are the same as those in Example 2. Only during the preparation of the aluminum sol, the addition of dilute nitric acid is changed to a molar ratio of aluminum to acid of 0.08:1.

[0064] Example 7

[0065] Other raw materials, components, and parameters are the same as those in Example 2. Pentaethylenehexamine is changed to hexaethyleneheptamine.

[0066] Comparative Example 1

[0067] Other raw materials, components, and parameters are the same as those in Example 1. The mixing mass ratio of cross-linked starch to the spare aluminum sol is changed from 1.2:50 to 0.8:50.

[0068] Comparative Example 2

[0069] The other raw materials, components, and parameters are the same as those in Example 2, except that the dropping amount of epichlorohydrin solution (mass fraction 2%) is changed from 2.4 mL to 1 mL.

[0070] Comparative Example 3

[0071] The other parameters and steps are the same as those in Example 1, but crosslinked starch is not added, and the aluminum sol is directly subjected to drying, calcination, crushing, grinding, and modification treatments in sequence.

[0072] Performance detection:

[0073] Take the activated alumina balls prepared in the above Examples 1-7 and Comparative Examples 1-3, fill them in adsorption tubes respectively, heat and activate them with high-purity nitrogen at 250 °C for 1 h, cool them in a closed state, and then detect their compressive strength, specific surface area, and static water adsorption capacity in accordance with the standard of "HG / T 3927-2020 Industrial Activated Alumina"; detect their CO2 static adsorption capacity with reference to "HG / T 2690-2012 13X Molecular Sieve", and then heat and regenerate the test sample in vacuum, repeat the above steps 10 times, and evaluate the adsorption-desorption cycle stability of the activated alumina ball sample according to the mass change range of the activated alumina ball sample in each adsorption-desorption cycle process. The detection results of each example and comparative example are shown in Table 1 below:

[0074] Table 1 Detection Results of Each Example and Comparative Example

[0075]

[0076] It can be known from the detection results that the activated alumina balls obtained by the preparation method of the present application can greatly improve the static CO2 adsorption capacity and adsorption cycle stability while basically ensuring the compressive strength of the balls and the static water adsorption capacity.

[0077] The above examples only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for preparing activated alumina balls, characterized in that: The following steps are involved: S1: adding pseudo-boehmite into deionized water at a temperature of 85-95° C. and stirring the mixture thoroughly to obtain a liquid-solid mixture slurry, adding nitric acid to the liquid-solid mixture slurry, stirring the mixture under a constant temperature, and aging and refluxing the mixture to obtain an aluminum sol; S2: Add starch and sodium hydroxide solution into deionized water and stir to obtain an alkaline starch suspension, add a cross-linking agent to the alkaline starch suspension and react at 20-55°C for a period of time, then filter, wash and dry in sequence to obtain a high polymer cross-linked starch with a spatial network structure, wherein the mass fraction of the cross-linking agent is 0.2-3% of the mass fraction of the starch; S3: mixing polymer cross-linked starch and aluminum sol, and then drying, calcining, crushing and grinding to obtain alumina powder, wherein the mass ratio of polymer cross-linked starch to aluminum sol is (1.1-1.4):50; S4: using physical impregnation to load the modifier into the inner pores and surface of the alumina powder to obtain modified activated alumina powder, wherein the modifier is an organic amine rich in amino groups; S5: spraying an aqueous solution containing an additive or a binder into a spheroidizing plate containing modified activated alumina powder and forming spheroids by a rotating plate spheroidizing method, rehydrating and calcining the spheroids to obtain activated alumina spheres.

2. The method for preparing activated alumina balls according to claim 1, characterized in that: Pseudo-boehmite is added into deionized water at a temperature of 85-95°C and stirred thoroughly, wherein the stirring conditions are set at a stirring speed of 600-900 r / min, an aging time of 5-8 h, and a reflux time of 2-3 h.

3. The method for preparing activated alumina balls according to claim 1, characterized in that: Add nitric acid with a concentration of 3-5% into the liquid-solid mixture slurry at an acid-aluminum molar ratio of 0.06-0.1:

1.

4. The method for preparing activated alumina balls according to claim 1, characterized in that: The starch is straight-chain starch, and the cross-linking agent is epichlorohydrin, trisodium metaphosphate or hexametaphosphate.

5. The method for preparing activated alumina balls according to claim 1, characterized in that: The starch content in the alkaline starch suspension is 90~130g / L, and the pH value is 7.6~9.

6. The method for preparing activated alumina balls according to claim 1, characterized in that: The organic amine is one or more selected from tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, and hydroxyethylethylenediamine.

7. The method for preparing activated alumina balls according to claim 1, characterized in that: The calcination temperature is 380~450℃ and the calcination time is 30~40min.

8. An activated alumina ball, characterized in that: The activated alumina balls are prepared according to the preparation method of any one of claims 1 to 7.

9. A compressed air decarbonization device, characterized in that: The activated alumina balls according to claim 8 are used as adsorbent.

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