Active alumina with low attrition index and method for producing the same

Abstract

The application belongs to the technical field of inorganic functional materials, and particularly relates to a low-abrasion-index active alumina and a preparation method thereof. The method comprises the following steps: (1) dispersing an aluminum salt and tetramethylammonium-based cage-shaped poly siesquioxane into deionized water; (2) adding a meta-aluminate solution dropwise and heating for 0.5-1 hours; (3) adding the tetramethylammonium-based cage-shaped poly siesquioxane again and continuing the reaction; and (4) post-treatment and calcination, so that the low-abrasion-index active alumina is obtained. In the application, the aluminum salt and the meta-aluminate are co-precipitated, the tetramethylammonium-based cage-shaped poly siesquioxane is added in two stages before and after the precipitation reaction, the unique nano-cage structure of the tetramethylammonium-based cage-shaped poly siesquioxane is utilized to regulate the nucleation, growth, assembly and calcination process of the precipitation product, so that the abrasion index of the active alumina is significantly reduced, the specific surface area is maintained to be relatively high, and the application prospect is good.

Description

Technical Field

[0001] This invention belongs to the field of inorganic functional materials technology, specifically relating to a low-wear-index activated alumina and its preparation method. Background Technology

[0002] Activated alumina is an inorganic functional material with a high specific surface area. Due to its excellent adsorption and catalytic activity, it is widely used as an adsorbent, catalyst support, desiccant, and chromatographic packing material. From the crystal structure of activated alumina, its high specific surface area originates from its nanoscale grains and abundant mesoporous structure. However, there is often a trade-off between high specific surface area and high mechanical strength—the finer the grains and the more developed the pore structure, the weaker the internal bonding force of the particles, and the worse the wear resistance. Therefore, how to improve wear resistance while maintaining a high specific surface area has always been a technical challenge in the field of activated alumina preparation.

[0003] Currently, common activated alumina is mainly used as a catalyst support in petrochemical refining reactions. With the rapid development of high-end manufacturing, especially in high-value-added fields such as electronic-grade chemical production, new energy material processing, semiconductor device manufacturing, high-performance structural ceramics, and pharmaceutical chromatography, the performance requirements for activated alumina far exceed those of conventional industrial-grade products. For example, in the production of electronic-grade chemicals, such as in the distillation process of ultrapure reagents used in chip manufacturing, activated alumina, as a distillation packing or catalyst support, can cause fine powder generated during wear, directly contaminating downstream products and leading to substandard purity of electronic-grade chemicals. In the processing of new energy materials, the wear rate of the grinding media directly determines the amount of impurities introduced into the product. Although the wear rate of traditional high-purity alumina balls has been controlled at a low level, trace impurities are still introduced during ultrafine grinding, affecting the electrochemical performance and safety of batteries. In the field of pharmaceutical chromatography, when activated alumina is used as a chromatographic packing, the particles must have an extremely low wear rate under the impact of high-pressure mobile phase; otherwise, fine powder will clog the chromatographic column, increase column pressure, reduce separation efficiency, and affect the purification quality of pharmaceutical intermediates.

[0004] In summary, high-end applications place extremely stringent requirements on the wear index of activated alumina. Currently, the mainstream industrial method for preparing activated alumina uses boehmite as a precursor, through processes such as sol-gel, molding, and calcination. Boehmite is a layered alumina with a hydroxyl structure that can undergo sol-gel reaction in acidic media to form a stable sol system. By controlling the degree of sol-gel reaction, the wear index of the final product can be significantly affected. However, this method has high requirements for the sol-gel properties of the raw materials, and the sol-gel process requires precise control of multiple parameters such as acidity, temperature, and time. The process window is narrow, operational control is demanding, and batch-to-batch stability of the product is difficult to guarantee.

[0005] Coprecipitation has attracted widespread attention due to its advantages, including the ability to achieve uniform mixing of components at the molecular or atomic level, ease of operation, and suitability for industrial scale-up. In a typical coprecipitation process for preparing alumina precursors, an aluminum salt solution is usually reacted with an alkaline solution (such as ammonia, sodium carbonate, or sodium hydroxide) or an aluminate solution (such as sodium aluminate) to generate the precursor, which is then washed, dried, and calcined to obtain activated alumina. Compared to the sol-gel method, coprecipitation eliminates the separate sol-gel and gel-gel steps, resulting in a simpler process flow.

[0006] However, pure-phase active alumina prepared by the traditional co-precipitation method in existing technologies generally suffers from a high wear index. The root cause of this problem lies in the difficulty of effectively controlling the nucleation, growth, and assembly processes of the precipitate in the traditional co-precipitation method. This results in a wide particle size distribution, irregular morphology, and loose internal structure in the precursor particles. After calcination, the alumina grains formed have weak bonding forces, making them prone to grain peeling and fine powder generation under mechanical action. Silsesquioxanes are polymer materials that have been extensively studied in recent years. CN119430987A and CN118360026A, among others, have investigated the effects of silsesquioxanes on alumina properties; however, these studies all involve post-modification processes, which are relatively cumbersome, and do not address the impact of silsesquioxanes on the wear resistance of alumina.

[0007] Therefore, developing a co-precipitation preparation method that can significantly reduce the wear index while maintaining a high specific surface area without changing the main components of activated alumina has important theoretical research value and industrial application prospects. Summary of the Invention

[0008] The purpose of this invention is to provide an activated alumina with a low wear index and its preparation method. This invention employs a co-precipitation system of aluminum salts and aluminates, and adds tetramethylammonium-based cage-like polysilsesquioxane in two stages, before and after the precipitation reaction. Utilizing its unique nanocage structure, positive surface charge, and thermal decomposition properties, the nucleation, growth, assembly, and calcination processes of the precipitated product are controlled, thereby significantly reducing the wear index of the activated alumina while maintaining a high specific surface area.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum salt and tetramethylammonium cage-like polysilsesquioxane in deionized water to obtain a mixed solution of aluminum salt; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum salt is (0.5-2):100; (2) Under stirring conditions, the aluminate solution is added dropwise to the aluminum salt mixture, then the pH of the solution is adjusted, and the reaction is heated for 0.5-1h; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction; (4) The material is obtained after filtration, washing, drying, crushing and sieving; calcination treatment is performed to obtain active alumina with low wear index.

[0010] Cage-shaped polysilsesquioxanes, as a novel organic-inorganic hybrid nanomaterial, exhibit unique application value in polymer modification, membrane separation, and biomedicine. Among them, tetramethylammonium-based cage-shaped polysilsesquioxanes, compared to other functional group types, are widely used in the preparation of inorganic materials due to their positively charged surface, complete water solubility, and ability to form a silica protective layer after thermal decomposition. As an organic-inorganic hybrid nanoparticle, tetramethylammonium-based cage-shaped polysilsesquioxane has a core of approximately 1.5 nm rigid silica cage-like framework, with tetramethylammonium groups attached to each of its eight vertices. The positively charged tetramethylammonium groups can electrostatically adsorb onto the surface of negatively charged precipitated particles, while the nanoscale cage-like framework acts as a steric hindrance, preventing particle aggregation. Furthermore, upon calcination, the tetramethylammonium-based cage-shaped polysilsesquioxane decomposes, transforming into a dense silica protective layer that provides bonding and reinforcement.

[0011] To fully utilize the large-volume exclusion effect of tetramethylammonium-based cage-like polysilsesquioxane, this invention involves the addition of tetramethylammonium-based cage-like polysilsesquioxane in two phases during the co-precipitation reaction of aluminum salts and aluminates. The first phase of addition occurs before the co-precipitation reaction, where the positively charged tetramethylammonium-based cage-like polysilsesquioxane is pre-mixed with aluminum ions. When the aluminate is added dropwise and the precipitation reaction begins, the tetramethylammonium-based cage-like polysilsesquioxane immediately adsorbs onto the surface of the newly formed aluminum hydroxide crystal nuclei. Through electrostatic repulsion and steric hindrance, it prevents the crystal nuclei from agglomerating. Simultaneously, the hydrophilic groups on the surface of the tetramethylammonium-based cage-like polysilsesquioxane provide additional heterogeneous nucleation sites, increasing the nucleation rate and resulting in a large number of fine and uniform initial crystal nuclei. If tetramethylammonium-based cage-like polysilsesquioxane is not added in the first phase, the initial crystal nuclei will rapidly agglomerate and grow, forming a coarse and loose structure.

[0012] The second stage of addition occurs after a period of co-precipitation reaction. At this stage, the newly added tetramethylammonium-based cage-like polysilsesquioxane adsorbs onto the surface of existing particles, filling surface defects and pores, making the particles smoother and denser. During the continued reaction, the tetramethylammonium-based cage-like polysilsesquioxane continuously inhibits the dissolution of small particles and the growth of large particles, maintaining the fine and uniform particle size.

[0013] In one embodiment, the aluminum salt in step (1) is one or more of aluminum nitrate, aluminum chloride, and aluminum sulfate; the concentration of aluminum salt in the mixed solution is 5-50 g / L. In particular, aluminum nitrate can be selected because the anions of aluminum nitrate are easily decomposed and volatilized during subsequent calcination, making it less likely to introduce impurities into the product. Further, the aluminum salt concentration can be 10-30 g / L. If the aluminum salt concentration is too low, the production efficiency will be low; if the aluminum salt concentration is too high, the precipitation reaction will be too vigorous, which is not conducive to the formation of fine and uniform particles.

[0014] In one embodiment, the mass ratio of tetramethylammonium-based cage-like polysilsesquioxane to aluminum salt can be 0.5:100, 1:100, 1.5:100, or 2:100. Further, the mass ratio of tetramethylammonium-based cage-like polysilsesquioxane to aluminum salt can be (1-1.5):100. Insufficient tetramethylammonium-based cage-like polysilsesquioxane has little regulatory effect, while excessive amounts can negatively impact the reaction process. Specifically, appropriate heating can be applied during the preparation of the aluminum salt mixed solution to promote the dissolution and dispersion of the components.

[0015] In one embodiment, step (2) specifically involves the following process: preheating the aluminum salt mixed solution to 40-70°C, and then adding the aluminate solution dropwise while stirring; the dropping rate is 8-12 mL / min. Specifically, the preheating temperature can be 50-60°C, and the dropping rate is 8-10 mL / min. The purpose of preheating and slow addition is to ensure the precipitation reaction proceeds under relatively mild conditions, avoiding excessive local supersaturation that could lead to explosive nucleation.

[0016] In one embodiment, the aluminate solution is an aqueous solution of aluminate. Specifically, in step (2), the aluminate is one or more of sodium aluminate or potassium aluminate.

[0017] In one embodiment, the mass ratio of aluminate to aluminum salt is (0.1-1):1. The concentration of aluminate in the aluminate solution is 5-50 g / L. Specifically, the aluminate concentration can be 5 g / L, 10 g / L, 20 g / L, 30 g / L, 40 g / L, or 50 g / L. Appropriate aluminate dosage can regulate the reaction process and is beneficial for increasing the specific surface area of ​​activated alumina.

[0018] In one embodiment, step (2) adjusts the pH to 8-11. Specifically, the pH is adjusted by adding acidic substances such as hydrochloric acid, nitric acid, or acetic acid, or by using alkaline substances such as sodium hydroxide or ammonia. The heating reaction temperature in step (2) is 75-85°C; specifically, the reaction temperature can be 75°C, 80°C, or 85°C. Further, the heating reaction temperature is 78-82°C, and a suitable heating reaction process helps to improve the precursor crystal form and remove impurities. It is worth noting that under the above pH and heating reaction temperature conditions, the reaction is relatively vigorous, and its reaction time should be controlled. If the reaction time is too long, the precipitated particles will agglomerate, and the subsequently added tetramethylammonium cage-like polysilsesquioxane cannot be effectively introduced, which can easily lead to a decrease in product performance.

[0019] In one embodiment, the mass ratio of tetramethylammonium-based cage-like polysilsesquioxane to aluminum salt in step (3) is (0.5-2):100. Specifically, the mass ratio of tetramethylammonium-based cage-like polysilsesquioxane to aluminum salt can be 0.5:100, 1:100, 1.5:100, or 2:100. Further, the mass ratio of tetramethylammonium-based cage-like polysilsesquioxane to aluminum salt can be (0.5-1.2):100. In particular, the amount of tetramethylammonium-based cage-like polysilsesquioxane used in step (3) can be less than that used in step (2) to better exert its regulatory effect, thus avoiding waste of tetramethylammonium-based cage-like polysilsesquioxane and allowing it to better exert its dispersing effect, preventing excessive use from hindering the dispersion of the precursor in step (3).

[0020] In one embodiment, the reaction temperature continues at the same level as in step (2), and the reaction time continues for 1-2 hours. Specifically, the reaction time can be 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, or 2 hours. Further, the reaction time continues for 1.2-1.8 hours. By adjusting the reaction time, the dispersing effect of tetramethylammonium-based cage-like polysilsesquioxane can be fully utilized, while the desorption of tetramethylammonium-based cage-like polysilsesquioxane, which leads to hard agglomeration, can be avoided.

[0021] In one embodiment, the drying in step (4) can be carried out in an oven at a temperature of 100-130°C. Specifically, the pulverization can be performed using conventional pulverization methods in the art; furthermore, rotary pulverization can be used to promote particle dispersion. After pulverization, the activated alumina precursor can be obtained by sieving. Specifically, the sieving particle size is not particularly limited; selectable sizes include 20 mesh, 30 mesh, 40 mesh, 50 mesh, 60 mesh, 70 mesh, or higher. Specifically, the size can also be within the range of 20-30 mesh, 30-40 mesh, 40-50 mesh, etc., and the specific size can be selected as needed.

[0022] In one embodiment, the calcination temperature in step (4) is 600-650℃, and the calcination time is 4-6h. The calcination temperature significantly affects the performance of alumina. If the temperature is too low, the precursor transformation is incomplete, and if the temperature is too high, the specific surface area will easily decrease significantly. During the calcination process, tetramethylammonium-based cage-like polysilsesquioxane further plays an in-situ reinforcing role. As the temperature rises, the tetramethylammonium-based cage-like polysilsesquioxane decomposes, forming uniform micropores inside the particles, which is beneficial to maintaining a high specific surface area. At the same time, the silicon-oxygen skeleton is transformed into silicon dioxide, which can form a dense protective layer, firmly bonding adjacent grains together and improving the mechanical properties of the product. Since the amount of tetramethylammonium-based cage-like polysilsesquioxane added is small, this reinforcing effect occurs at the grain interface without changing the grain body. Therefore, the wear index is significantly reduced while the specific surface area is maintained.

[0023] On the other hand, the present invention also provides an activated alumina with a low wear index prepared by the above method, which has a large surface area and good wear resistance; at the same time, the preparation process is simple, without the need to add various carbon-containing surfactants and special molding processes, and the resulting product has high purity, fine and uniform particles, and high mechanical strength, making it particularly suitable for high value-added fields such as electronic-grade chemical production, new energy material processing, semiconductor device manufacturing, high-performance structural ceramics, and pharmaceutical chromatographic separation.

[0024] Beneficial Effects: This invention employs a co-precipitation system of aluminum salts and aluminates, adding tetramethylammonium-based cage-like polysilsesquioxane in two stages—before and after the precipitation reaction. Utilizing its unique nanocage structure, positive surface charge, and thermal decomposition properties, the nucleation, growth, assembly, and calcination processes of the precipitate are controlled, significantly reducing the wear index of activated alumina while maintaining a high specific surface area and suitable pore structure. This invention does not alter the main components and intrinsic properties of activated alumina. The low addition amount of tetramethylammonium-based cage-like polysilsesquioxane does not change the phase structure or surface acidity of activated alumina. This characteristic is particularly crucial for systems sensitive to the surface properties of the support, such as pharmaceutical chromatography and electronic-grade chemical distillation, and is something that cannot be achieved by introducing second-phase reinforcing agents such as zirconium oxide. The product of this invention has significant economic value in high-value-added fields, especially in high-value-added applications such as electronic-grade chemical production, new energy material processing, semiconductor device manufacturing, high-performance structural ceramics, and pharmaceutical chromatography separation. The low wear rate can lead to improved product yield, reduced equipment maintenance costs, extended service life, and improved quality of downstream products, thus having good commercial prospects. Detailed Implementation

[0025] The embodiments described are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the embodiments described. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description are still within the scope of protection of the present invention.

[0026] Performance testing: The specific surface area (m²) of the low-wear-index activated alumina prepared in Examples 1-9 and Comparative Examples 1-3 was tested using the gas adsorption method. 2 / g), and its wear resistance (%) was tested using an abrasion tester.

[0027] Example 1

[0028] A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 0.5:100; (2) Preheat the aluminum nitrate mixed solution to 60°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate 8 mL / min), and adjust the pH of the solution to 10; then react at 85°C for 0.5 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.7:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1.8 h; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 2:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 600℃ for 6 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 265 m². 2 / g, with an abrasion rate of 0.14%.

[0029] Example 2

[0030] A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 2:100; (2) Preheat the aluminum nitrate mixed solution to 65°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 12 mL / min) to adjust the pH of the solution to 10; then react at 75°C for 1 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.75:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1 hour; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 0.5:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 650℃ for 4 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 279 m². 2 / g, with an abrasion rate of 0.08%.

[0031] Example 3

[0032] A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 0.8:100; (2) Preheat the aluminum nitrate mixed solution to 62°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 9 mL / min) to adjust the pH of the solution to 10; then react at 79°C for 0.6 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.72:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1.2 h; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 0.8:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 610℃ for 5.5 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 257 m². 2 / g, with an abrasion rate of 0.13%.

[0033] Example 4

[0034] A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage-like polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 1.2:100; (2) Preheat the aluminum nitrate mixed solution to 60°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 10 mL / min) to adjust the pH of the solution to 10; then react at 80°C for 0.7 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.75:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1.5 h; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 1.6:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 620℃ for 5 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 266 m².2 / g, with an abrasion rate of 0.12%.

[0035] Example 5

[0036] A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 1.4:100; (2) Preheat the aluminum nitrate mixed solution to 65°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 11 mL / min) to adjust the pH of the solution to 10; then react at 82°C for 0.8 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.7:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1.7 h; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 1.8:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 640℃ for 4.5 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 277 m². 2 / g, with an abrasion rate of 0.13%.

[0037] Example 6

[0038] A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 1.6:100; (2) Preheat the aluminum nitrate mixed solution to 60°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 10 mL / min) to adjust the pH of the solution to 10; then react at 80°C for 0.7 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.75:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 2 hours; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 1.2:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 620℃ for 5 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 256 m². 2 / g, with an abrasion rate of 0.07%.

[0039] Example 7

[0040] A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 1:100; (2) Preheat the aluminum nitrate mixed solution to 64℃, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 10 mL / min), and adjust the pH of the solution to 10; then react at 84℃ for 0.6 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.72:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1.4 h; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 1:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 630℃ for 4 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 265 m². 2 / g, with an abrasion rate of 0.09%.

[0041] Example 8

[0042] A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 1.8:100; (2) Preheat the aluminum nitrate mixed solution to 65°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 11 mL / min) to adjust the pH of the solution to 10; then react at 85°C for 1 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.7:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1.6 h; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 0.7:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 600℃ for 4 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 267 m². 2 / g, with an abrasion rate of 0.07%.

[0043] Example 9

[0044] A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 1.6:100; (2) Preheat the aluminum nitrate mixed solution to 60°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 10 mL / min) to adjust the pH of the solution to 10; then react at 80°C for 0.7 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.75:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1.5 h; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 1.2:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 620℃ for 5 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 272 m² / g. 2 / g, with an abrasion rate of 0.06%.

[0045] Comparative Example 1 A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage-like polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 2.8:100; (2) Preheat the aluminum nitrate mixed solution to 60°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 10 mL / min), and adjust the pH of the solution to 10; then react at 80°C for 2.2 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.75:1; (3) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 620℃ for 5 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 234 m². 2 / g, with an abrasion rate of 0.48%.

[0046] Comparative Example 2 A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 5:100; (2) Preheat the aluminum nitrate mixed solution to 60°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 10 mL / min) to adjust the pH of the solution to 10; then react at 80°C for 0.7 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.75:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1.5 h; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 1.2:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 620℃ for 5 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 245 m². 2 / g, with an abrasion rate of 0.42%.

[0047] Comparative Example 3 A method for preparing activated alumina with a low wear index includes the following steps: (1) Disperse aluminum nitrate and tetramethylammonium cage polysilsesquioxane in deionized water to obtain a mixed solution of aluminum nitrate with a concentration of 18 g / L; the mass ratio of tetramethylammonium cage polysilsesquioxane to aluminum nitrate is 1.6:100; (2) Preheat the aluminum nitrate mixed solution to 60°C, and add 10 g / L sodium aluminate solution dropwise while stirring (dropping rate is 10 mL / min) to adjust the pH of the solution to 10; then react at 80°C for 2 h; the mass ratio of sodium aluminate to aluminum nitrate is 0.75:1; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction for 1.5 h; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum nitrate is 1.2:100; (4) After filtration, washing, drying in an oven at 110℃, pulverizing, and sieving, the material is obtained; calcination at 620℃ for 5 hours yields activated alumina with a low abrasion index. Its specific surface area is measured to be 240 m². 2 / g, with an abrasion rate of 0.29%.

[0048] As can be seen from the above examples and comparative examples, the present invention involves the addition of tetramethylammonium-based cage-like polysilsesquioxane in two stages during the co-precipitation reaction of aluminum salts and aluminates. The first stage of addition occurs before the co-precipitation reaction, at which point the positively charged tetramethylammonium-based cage-like polysilsesquioxane is pre-mixed with aluminum ions. When the aluminate begins to be added dropwise and the precipitation reaction starts, the tetramethylammonium-based cage-like polysilsesquioxane immediately adsorbs onto the surface of the newly formed aluminum hydroxide crystal nuclei. Through electrostatic repulsion and steric hindrance, it prevents crystal nucleus aggregation, increases the nucleation rate, and generates a large number of fine and uniform initial crystal nuclei. The second stage of addition occurs after a period of time during the co-precipitation reaction. At this time, the newly added tetramethylammonium-based cage-like polysilsesquioxane adsorbs onto the surface of existing particles, filling surface defects and pores, making the particles smoother and denser. During the continued reaction, the tetramethylammonium-based cage-like polysilsesquioxane continuously inhibits the dissolution of small particles and the growth of large particles, maintaining the uniformity of particle size.

[0049] Specifically, compared to Example 9, Comparative Example 1 changed the tetramethylammonium-based cage-like polysilsesquioxane used in step (3) to be added in step (1), resulting in a smaller specific surface area and increased wear. This is because Comparative Example 1 only added tetramethylammonium-based cage-like polysilsesquioxane in step (1). Although the initial nucleation was controlled, the growth stage lacked continuous inhibition, leading to secondary agglomeration of particles, a decrease in specific surface area, and an increase in the wear index. At the same time, due to the large volume effect of tetramethylammonium-based cage-like polysilsesquioxane and its own large positive charge, attention should be paid to its dosage and timing of addition. It can also be seen from Comparative Example 2 that the excessive amount of tetramethylammonium-based cage-like polysilsesquioxane in step (1) not only affects the precipitation reaction process due to its large volume effect, but also agglomerates to form large aggregates, which is not conducive to improving product performance. Meanwhile, as can be seen from Comparative Example 3, attention should be paid to the timing of adding tetramethylammonium cage-like polysilsesquioxane in step (3). In Comparative Example 3, tetramethylammonium cage-like polysilsesquioxane was added 2 hours after the reaction in step (2). The precipitated particles had already agglomerated, and tetramethylammonium cage-like polysilsesquioxane could not effectively intervene, resulting in a reduction in product performance.

[0050] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing activated alumina with a low wear index, characterized in that, Includes the following steps: (1) Disperse aluminum salt and tetramethylammonium cage-like polysilsesquioxane in deionized water to obtain a mixed solution of aluminum salt; the mass ratio of tetramethylammonium cage-like polysilsesquioxane to aluminum salt is (0.5-2):100; (2) Under stirring conditions, the aluminate solution is added dropwise to the aluminum salt mixture, then the pH of the solution is adjusted, and the reaction is heated for 0.5-1h; (3) Add tetramethylammonium cage-like polysilsesquioxane again and continue the reaction; (4) The material is obtained after filtration, washing, drying, crushing and sieving; calcination treatment is performed to obtain active alumina with low wear index.

2. The method for preparing low-wear-index activated alumina as described in claim 1, characterized in that, In step (1), the mass ratio of tetramethylammonium cage-shaped polysilsesquioxane to aluminum salt is (1-1.5):

100.

3. The method for preparing low-wear-index activated alumina as described in claim 1, characterized in that, In step (2), the aluminate solution drop rate is 8-12 mL / min.

4. The method for preparing low-wear-index activated alumina as described in claim 1, characterized in that, In step (2), the aluminate is one or more of sodium aluminate or potassium aluminate.

5. The method for preparing low-wear-index activated alumina as described in claim 1, characterized in that, The heating reaction temperature in step (2) is 75-85℃.

6. The method for preparing low-wear-index activated alumina as described in claim 1, characterized in that, In step (3), the mass ratio of tetramethylammonium cage-shaped polysilsesquioxane to aluminum salt is (0.5-2):

100.

7. The method for preparing low-wear-index activated alumina as described in claim 1, characterized in that, The reaction time in step (3) is 1-2 hours.

8. The method for preparing low-wear-index activated alumina as described in claim 1, characterized in that, In step (4), the drying is carried out in an oven at a temperature of 100-130℃.

9. The method for preparing low-wear-index activated alumina as described in claim 1, characterized in that, In step (4), the calcination temperature is 600-650℃ and the calcination time is 4-6h.

10. A low-wear-index activated alumina, characterized in that, It is prepared by the method for preparing a low wear index activated alumina according to any one of claims 1-9.