Method for preparing alumina microspheres and alumina microspheres

Abstract

The application discloses a preparation method of alumina microspheres and the alumina microspheres. The preparation method comprises the following steps: hydrolyzing and concentrating soluble aluminum alcohol salt to obtain AlOOH solid sol; mixing the AlOOH solid sol with an acid solution after dilution to obtain stable AlOOH sol; performing solidification forming on the stable AlOOH sol to obtain alumina gel microspheres; and mixing the alumina gel microspheres with alcohol, and then sequentially performing drying and calcination to obtain the alumina microspheres. The alumina microspheres with high crushing strength can be prepared by using the method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial catalysts, in particular to a preparation method of alumina microspheres and alumina microspheres. BACKGROUND

[0002] Alumina has good chemical stability and thermal stability, and can maintain its original performance in high temperature and complex chemical environment, and is an ideal catalyst carrier and ion exchanger. When alumina is used as a catalyst carrier, it needs to be formed into a granular or spherical shape, so as to be uniformly filled in the reactor, which is beneficial to the loading of the catalyst.

[0003] The traditional alumina microsphere forming methods such as spray drying method, rotating ball forming method and oil column forming method have low crushing strength of the obtained alumina microspheres, which can cause the crushing problem of the alumina microspheres. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the related art. To this end, one object of the present application is to provide a preparation method of alumina microspheres and alumina microspheres. By using the method of the present application, alumina microspheres with high crushing strength can be obtained.

[0005] In one aspect of the present application, a preparation method of alumina microspheres is provided. According to an embodiment of the present application, the method comprises:

[0006] S1, hydrolyzing and concentrating a soluble aluminum alcohol salt to obtain an AlOOH solid sol;

[0007] S2, mixing the AlOOH solid sol with an acid solution after dilution to obtain a stable AlOOH sol;

[0008] S3, solidifying and forming the stable AlOOH sol to obtain an alumina gel microsphere;

[0009] S4, mixing the alumina gel microsphere with alcohol, and then sequentially drying and calcining to obtain an alumina microsphere.

[0010] According to the method of the above embodiment of the present application, the hydrolysis characteristics of the soluble aluminum alcohol salt are utilized, and by concentration, an AlOOH solid sol with high purity can be obtained; then the AlOOH solid sol is diluted and gelatinized to obtain a stable AlOOH sol; then the stable AlOOH sol is solidified and formed by the sol-gel method to obtain an alumina gel microsphere; the alumina gel microsphere is mixed with alcohol, and through the volatilization process of alcohol during drying, the stable removal of the remaining solvent in the alumina gel microsphere is induced, the crosslinking degree of the alumina gel microsphere is increased, and thus the crushing strength of the alumina microsphere after calcination can be improved.

[0011] In addition, the method according to the above-mentioned embodiments of the present application can further have the following additional technical features:

[0012] In some embodiments of the present application, the mass percentage of AlOOH in the AlOOH sol is 14wt%-15wt%. Thus, it is beneficial to obtain the alumina microspheres with high crushing strength.

[0013] In some embodiments of the present application, the concentration temperature is 85°C-98°C. Thus, the AlOOH sol with higher purity can be obtained, which is beneficial to improve the crushing strength of the alumina microspheres.

[0014] In some embodiments of the present application, the pH value of the stable AlOOH sol is 3-4. Thus, it is beneficial to promote the stable existence of the AlOOH sol, and improve the crushing strength of the alumina microspheres.

[0015] In some embodiments of the present application, the mass ratio of the alumina gel microspheres to the alcohol is 1:(15-20). Thus, it is beneficial to obtain the alumina microspheres with high crushing strength.

[0016] In some embodiments of the present application, the mixing time is 5min-10min. Thus, the alcohol and the alumina gel microspheres can be mixed uniformly, so that the alcohol can be immersed into the interior of the alumina gel microspheres, and then the alumina microspheres with high crushing strength can be obtained.

[0017] In some embodiments of the present application, the drying temperature is 20°C-40°C. Thus, it is beneficial to volatilize the alcohol, and then the alumina microspheres with high crushing strength can be obtained.

[0018] In some embodiments of the present application, the drying time is 8h-20h. Thus, it is beneficial to volatilize the alcohol, and then the alumina microspheres with high crushing strength can be obtained.

[0019] In some embodiments of the present application, the calcination temperature is 550°C-700°C. Thus, it is beneficial to obtain the alumina microspheres with high crushing strength.

[0020] In some embodiments of the present application, the calcination time is 3h-6h. Thus, it is beneficial to obtain the alumina microspheres with high crushing strength.

[0021] In some embodiments of the present application, the alcohol has 2-4 carbon atoms, and optionally, the alcohol includes at least one of ethanol or propanol. Thus, it is beneficial to obtain the alumina microspheres with high crushing strength.

[0022] In another aspect of the present application, the present application provides an alumina microsphere. According to an embodiment of the present application, the alumina microsphere is prepared by the method described above, and thus the alumina microsphere obtained by the present application has a high crushing strength.

[0023] In some embodiments of the present application, the diameter of the alumina microsphere is 600 μm to 800 μm.

[0024] In some embodiments of the present application, the pore size of the alumina microsphere is 8 nm to 15 nm.

[0025] In some embodiments of the present application, the specific surface area of the alumina microsphere is 260 m 2 / g to 300 m 2 / g.

[0026] In some embodiments of the present application, the crushing strength of the alumina microsphere is 40 N / mm 2 - 60 N / mm 2 .

[0027] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0028] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0029] Figure 1 A flow chart showing the method for preparing the alumina microsphere according to an embodiment of the present application is shown in FIG. 1.

[0030] Figure 2 A scanning electron microscope image of the alumina microsphere obtained in Example 1 is shown in FIG. 2.

[0031] Figure 3 A pore size distribution graph of the alumina microsphere obtained in Example 1 is shown in FIG. 3.

[0032] Figure 4 A scanning electron microscope image of the alumina microsphere obtained in Example 2 is shown in FIG. 4.

[0033] Figure 5 A nitrogen adsorption-desorption curve and a pore size distribution graph of the alumina microsphere obtained in Example 2 are shown in FIG. 5.

[0034] Figure 6 A scanning electron microscope image of the alumina microsphere obtained in Comparative Example 1 is shown in FIG. 6.

[0035] Figure 7The nitrogen adsorption-desorption curve and the pore size distribution of the alumina microspheres prepared in Comparative Example 1 are shown. DETAILED DESCRIPTION

[0036] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0037] The alumina is shaped into granular or spherical shape, which can be uniformly filled in the reactor. The conventional methods for shaping the alumina microspheres include spray drying, rotating ball forming, oil column shaping, etc. Although the equipment structure of these methods is simple and the production capacity is large, the microspheres prepared by these methods have wide particle size distribution, small pore size and pore volume, and poor sphericity, which leads to the difficulty in adapting to the reactors such as moving bed and fluidized bed which have high requirements for the morphology and strength of the carrier. At present, the high-performance alumina microspheres prepared by the microfluidic system based on the sol-gel method can overcome the above-mentioned shortcomings brought by the traditional preparation process. However, the crushing strength of the alumina microspheres prepared by this method is usually 20 N / mm 2 -30 N / mm 2 , which can cause the problems such as catalyst falling off and catalyst crushing caused by abrasion and collision of the alumina microspheres in the reactor. Therefore, it is of great significance to optimize the process parameters and process conditions for preparing the alumina microspheres, to improve the crushing strength of the final alumina microspheres, and to realize the large-scale controllable preparation of high-strength wear-resistant catalyst carrier microspheres, for realizing the long-period high-performance operation of the catalyst in the reactor.

[0038] In one aspect of the present application, a method for preparing alumina microspheres is provided. According to embodiments of the present application, the method comprises:

[0039] S1, hydrolyzing and concentrating a soluble aluminum alcohol salt to obtain an AlOOH solid sol.

[0040] In this step, the soluble aluminum alcohol salt is mixed with water for hydrolysis, and the product after hydrolysis is heated and concentrated to obtain an AlOOH solid sol with high content.

[0041] According to some embodiments of the present application, the mass ratio of the soluble alcohol aluminum salt to water can be 1:(8-15). For example, it can be 1:8, 1:9, 1:11, 1:13, 1:15, etc. If the water content is too low, the hydrolysis will not be complete; if the water content is too high, the time cost of subsequent concentration will be increased. Therefore, by limiting the mass ratio of the soluble alcohol aluminum salt to water within the above range, the soluble alcohol aluminum salt can be promoted to undergo hydrolysis reaction, and thus the alumina microspheres with high crushing strength can be obtained. The mass ratio of the soluble alcohol aluminum salt to water can be 1:10.

[0042] It should be noted that the crushing strength refers to the maximum load borne until the alumina microspheres are fractured when the pressure is uniformly applied on a unit area.

[0043] According to some embodiments of the present application, the soluble alcohol aluminum salt includes at least one of secondary butanol aluminum or isopropyl alcohol aluminum. The above-mentioned soluble alcohol aluminum salt can undergo hydrolysis reaction in hot water to generate the corresponding alcohol and AlOOH sol, and the generated alcohol can be removed by heating. For example, secondary butanol aluminum undergoes hydrolysis in hot water to generate secondary butanol and AlOOH sol, and the secondary butanol can be removed by further heating to obtain AlOOH sol with high purity. Therefore, by selecting the above-mentioned soluble alcohol aluminum salt, AlOOH sol with high purity can be obtained, which is beneficial to improve the crushing strength of the alumina microspheres.

[0044] According to some embodiments of the present application, the temperature of the hydrolysis can be 85℃-98℃. For example, the temperature of the hydrolysis can be 85℃, 88℃, 90℃, 95℃, 98℃, etc. The time of the hydrolysis can be 20min-40min. For example, the time of the hydrolysis can be 20min, 25min, 30min, 35min, 40min, etc. Therefore, by limiting the parameters of the hydrolysis within the above range, the soluble alcohol aluminum salt can be rapidly hydrolyzed to generate AlOOH sol, which is beneficial to subsequent experimental operations, and the alumina microspheres with high crushing strength can be obtained.

[0045] According to some embodiments of the present application, the concentration temperature is 85℃-98℃. For example, the temperature can be 85℃, 88℃, 90℃, 95℃, 98℃, etc. If the concentration temperature is too low, the volatilization of impurities will be affected, and the time cost of concentration will be increased. If the concentration temperature is too high, the internal structure of AlOOH sol may be changed, which affects the crushing strength of the alumina microspheres. Therefore, by limiting the concentration temperature within the above range, the alcohol impurities generated by hydrolysis can be volatilized, and thus AlOOH sol with high purity can be obtained, which is beneficial to prepare alumina microspheres with high crushing strength.

[0046] In order to obtain the AlOOH sol with higher purity, the AlOOH sol needs to be washed after being concentrated, specifically, the AlOOH sol is washed with pure water for three times at a temperature of 50-60°C, for example, 50°C, 53°C, 55°C, 57°C, 60°C, etc., and the total amount of water added in the washing is consistent with the amount of water added in the hydrolysis. In this way, the impurities adhered to the surface of the sol can be further washed away by washing the sol with hot water, which is beneficial to obtain the AlOOH sol with higher purity, and further beneficial to prepare the oxide microspheres with higher crushing strength.

[0047] According to some embodiments of the present application, the mass percentage of AlOOH in the AlOOH sol is 14wt%-15wt%, for example, 14wt%, 14.3wt%, 14.5wt%, 14.7wt%, 15wt%, etc. Limiting the mass percentage of AlOOH in the AlOOH sol within the above range can make the hydrolysis of the soluble aluminum alcohol salt more complete, which is beneficial to obtain the AlOOH sol with higher purity, and further beneficial to prepare the oxide microspheres with higher crushing strength.

[0048] S2, the AlOOH sol after being diluted is mixed with an acid solution to obtain a stable AlOOH sol.

[0049] In this step, the AlOOH sol with high content obtained in step S1 is diluted and then mixed with an acid solution to cause gelation. In the process of gelation, part of the acid can react with the AlOOH produced by hydrolysis to generate aluminum ions; another part of the acid can gather on the surface of the AlOOH produced by hydrolysis to form a gel nucleus, and aluminum ions and hydrogen ions are adsorbed on the surface of the gel nucleus. Due to the effect of electrostatic repulsion, the colloidal particles are not easy to aggregate, so that a stable AlOOH sol can be generated.

[0050] The dilution method is not particularly limited in the present application. According to a specific embodiment of the present application, hot pure water is added to the AlOOH sol with high content obtained in step S1 to configure an AlOOH sol containing 5wt%-10wt% of AlOOH, for example, the mass percentage of AlOOH can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, etc. In this way, limiting the mass percentage of AlOOH in the diluted AlOOH sol within the above range can meet the minimum requirement of the content of AlOOH for solidification and crosslinking, and at the same time, it can prevent the viscosity of the AlOOH sol from being too large due to too high content of AlOOH, which can cause the risk of equipment blockage to be too high. Alternatively, the mass percentage of AlOOH in the diluted AlOOH sol is 8wt%.

[0051] According to some embodiments of the present application, the mass concentration of the acid solution is 5wt%-20wt%, for example, the mass concentration can be 5wt%, 8wt%, 10wt%, 14wt%, 16wt%, 20wt% and the like. Limiting the mass concentration of the acid solution in the above range can promote the peptization reaction between the acid solution and the AlOOH sol, and in turn can prepare the alumina microspheres with high crushing strength. Further, the type of the acid solution is not particularly limited, and a person skilled in the art can select it flexibly according to the actual situation. For example, the acid solution comprises at least one of nitric acid, acetic acid or citric acid.

[0052] According to some embodiments of the present application, the pH value of the stable AlOOH sol is 3-4, for example, the pH value can be 3, 3.2, 3.4, 3.6, 3.8, 4 and the like. Thus, limiting the pH value of the stable AlOOH sol in the above range can form an "acid bridge" of double-electron layer particles between the AlOOH, wherein the "acid bridge" can connect multiple AlOOH together in a network form to form a dynamic balance, and in turn can maintain the stability of the AlOOH sol, which is beneficial to prepare the alumina microspheres with high crushing strength.

[0053] S3, curing and forming the stable AlOOH sol to obtain alumina gel microspheres.

[0054] In this step, the alumina gel microspheres can be obtained by curing and forming the stable AlOOH sol to make it undergo gel reaction.

[0055] The specific method of curing and forming is not particularly limited in the present application, and a person skilled in the art can select it flexibly according to the actual situation. According to one specific embodiment of the present application, a micro-channel reactor is used to cure and form the AlOOH sol. It should be noted that the micro-channel reactor is a micro-reactor with a feature size of 10 to 300 microns (or 1000 microns) manufactured by precision machining technology. The "micro" of the micro-reactor refers to the channel of the process fluid in microns, rather than the small size of the micro-reaction device or the small output of the product.

[0056] According to some embodiments of the present application, the microchannel reactor can be a single-channel reactor or a multi-channel reactor, which is a common microchannel reactor in the prior art. Specifically, the stable AlOOH sol is mixed with the first curing agent and the second curing agent as a dispersed phase, and a mixed solution of the water extractant, the oil-soluble anionic surfactant, and the initiator is used as a continuous phase. Under the action of the continuous phase, the dispersed phase is first dispersed into droplets in the microchannel reactor, and then the droplets are cut in the microchannel under the action of the surface tension and fluid shear force of the continuous phase, to generate sol droplets with uniform size. The uniform sol droplets are formed into alumina gel microspheres in the subsequent solidification process.

[0057] According to some embodiments of the present application, in the solidification process, the solidification includes gelation and coagulation bath. The temperature of the gelation is 80-95°C, for example, 80°C, 83°C, 86°C, 90°C, 93°C, or 95°C. The time of the gelation is 1-3 min, for example, 1 min, 1.5 min, 2 min, 2.5 min, or 3 min. The temperature of the coagulation bath is 80-95°C, for example, 80°C, 83°C, 86°C, 90°C, 93°C, or 95°C. The time of the coagulation bath is 1-2 h, for example, 1 h, 1.2 h, 1.5 h, 1.8 h, or 2 h. In the solidification process, under the joint action of the continuous phase and the dispersed phase, the dispersed phase droplets can quickly gel in the microchannel and finally complete the solidification, to obtain the alumina gel microspheres.

[0058] According to some embodiments of the present application, in the dispersed phase, the mass ratio of the stable AlOOH sol, the first curing agent, and the second curing agent is 1:(0.005-0.3):(0.005-0.3), for example, 1:0.005:0.005, 1:0.005:0.3, 1:0.3:0.005, 1:0.1:0.2, or the like. The first curing agent is a temperature-induced curing agent, which has a reverse temperature-sensitive property. At low temperature, the temperature-induced curing agent is in a liquid state. At high temperature, the chains of the temperature-induced curing agent are entangled, and the temperature-induced curing agent is in a semi-solid form, to promote the sol-gel reaction. The second curing agent is an internal pH-induced curing agent, which is easy to decompose and generate ammonia gas at high temperature. The ammonia gas can neutralize the acid added in the AlOOH sol, destroy the most stable pH environment of the AlOOH sol, and make the AlOOH sol unstable and transform into a gel. Therefore, the mass ratio of the stable AlOOH sol, the first curing agent, and the second curing agent is limited in the above range, which is beneficial to promote the transformation of the stable AlOOH sol into a gel, and further obtain the alumina gel microspheres.

[0059] The kind of the first curing agent and the second curing agent is not particularly limited, and a person skilled in the art can flexibly select according to the actual situation. According to some embodiments of the present application, the first curing agent comprises at least one of methyl cellulose, polyvinyl alcohol, polyacrylamide or polyethylene glycol, and the second curing agent comprises at least one of hexamethylenetetramine and urea. Thus, by selecting the above-mentioned first curing agent and second curing agent, the stable AlOOH sol can be further promoted to transform into gel, and then the alumina gel microspheres can be obtained.

[0060] According to some embodiments of the present application, in the continuous phase, the mass fraction of the water extractant, the oil-soluble anionic surfactant and the initiator is 67wt%-97.5wt%, 1.5wt%-3wt% and 1wt%-30wt% in turn. For example, the mass fraction of the water extractant can be 67wt%, 70wt%, 85wt%, 90wt%, 97.5wt% and the like, the mass fraction of the oil-soluble anionic surfactant can be 1.5wt%, 2wt%, 2.5wt%, 3wt% and the like, and the mass fraction of the initiator can be 1wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt% and the like. The water extractant can extract the water in the sol microspheres by the difference in water content between the inside of the AlOOH sol and the continuous phase, and accelerate the gelation transformation process of the sol. The oil-soluble anionic surfactant can be adsorbed on the outside of the droplets, reduce the surface tension and improve the interfacial interaction. The initiator is an external pH curing initiator, which can diffuse into the sol droplets from the continuous phase, neutralize the acid added in the sol, destroy the most stable pH environment of the sol, and make the sol unstable to transform into gel. Thus, by limiting the mass fraction of the water extractant, the oil-soluble anionic surfactant and the initiator within the above-mentioned range, the stable AlOOH sol can be promoted to transform into gel, and then the alumina gel microspheres can be obtained.

[0061] The kind of the water extractant, the oil-soluble anionic surfactant and the initiator is not particularly limited, and a person skilled in the art can flexibly select according to the actual situation. According to some embodiments of the present application, the water extractant comprises at least one of n-octanol, n-nonyl alcohol and ethyl oleate, the oil-soluble anionic surfactant comprises at least one of Span85 and Dow Corning 749, and the initiator comprises at least one of trioctylamine and N,N,N',N'-tetramethyl ethylenediamine. Thus, by selecting the above-mentioned water extractant, oil-soluble anionic surfactant and initiator, the stable AlOOH sol can be further promoted to transform into gel, and then the alumina gel microspheres can be obtained.

[0062] S4, after mixing the alumina gel microspheres with alcohol, sequentially drying and calcining, alumina microspheres are obtained.

[0063] In this step, by mixing the alumina gel microspheres with the alcohol solution, then drying and calcining, the alumina microspheres can be obtained. According to the embodiments of the present application, first, the alumina gel microspheres are immersed in the alcohol solution, so that the alcohol solution can enter the inside of the alumina gel microspheres and cross-link with the organic substances in the microspheres, thereby increasing the cross-linking degree inside the microspheres, then the soaked alumina gel microspheres are dried, in the process of volatilization of the alcohol, the stable removal of the remaining solvent in the alumina gel microspheres can be induced, and finally the dried alumina gel microspheres are calcined, which can make the AlOOH dehydrate and change into Al-O-Al structure, and the alumina microspheres with high crushing strength can be obtained.

[0064] According to some embodiments of the present application, the mass ratio of the alumina gel microspheres to the alcohol is 1:(15-30), for example, the mass ratio can be 1:15, 1:20, 1:25, 1:30, etc., which ensures that enough alcohol can immerse the alumina gel microspheres, and at the same time, ensures that the added alcohol does not reach the saturated water content, so that the water extraction process and the diffusion process into the inside of the gel microspheres can continue. Therefore, by limiting the mass ratio of the alumina gel microspheres to the alcohol within the above range, the alumina microspheres with high crushing strength can be obtained.

[0065] According to some embodiments of the present application, the mixing time of the alumina gel microspheres and the alcohol is 5min-10min, for example, it can be 5min, 6min, 7min, 8min, 9min, 10min, etc. By limiting the mixing time within the above range, the alumina gel microspheres can be fully mixed with the alcohol, which is beneficial to the alcohol entering the inside of the alumina gel microspheres and cross-linking with the organic substances therein, so as to increase the cross-linking degree inside the alumina gel microspheres, and further to obtain the alumina microspheres with high crushing strength.

[0066] According to some embodiments of the present application, the drying temperature is 20℃-40℃, for example, the drying temperature can be 20℃, 25℃, 30℃, 35℃, 40℃, etc., and the drying time is 8h-20h, for example, it can be 8h, 10h, 15h, 20h, etc. Therefore, by limiting the above drying parameters within the above range, the excess alcohol inside the alumina gel microspheres can be effectively removed, and the stable removal of the remaining solvent in the alumina gel microspheres can be induced with the volatilization of the alcohol, and further the alumina microspheres with high crushing strength can be obtained.

[0067] The kind of alcohol is not particularly limited, and those skilled in the art can select flexibly according to the actual situation. According to some embodiments of the present application, the number of carbon atoms of the alcohol is 2-4, for example, the number of carbon atoms can be 2, 3, 4, etc., which can promote the mutual solubility and diffusion between the alcohol and water, so that the alcohol can effectively diffuse into the inside of the alumina gel microspheres. Therefore, by limiting the number of carbon atoms of the alcohol in the above range, alumina microspheres with high crushing strength can be obtained. In some specific embodiments of the present application, the alcohol includes at least one of ethanol or propanol.

[0068] According to some embodiments of the present application, the temperature of the calcination is 550°C-700°C, for example, the calcination time can be 550°C, 600°C, 650°C, 700°C, etc., and the calcination time is 3h-6h, for example, it can be 3h, 4h, 5h, 6h, etc. Therefore, by limiting the parameters of calcination in the above range, the intermolecular dehydration of AlOOH can be further promoted to convert into Al-O-Al structure, and in turn alumina microspheres with high crushing strength can be obtained.

[0069] According to the method of the above embodiments of the present application, the hydrolysis characteristics of soluble aluminum alcohol salt are utilized, and by concentration, AlOOH solid sol can be obtained with high purity; after dilution, the AlOOH solid sol can be gelatinized to obtain stable AlOOH sol; then the stable AlOOH sol is solidified and formed by the sol-gel method to obtain alumina gel microspheres; the alumina gel microspheres are mixed with alcohol, and through the volatilization process of alcohol during drying, the stable removal of the remaining solvent in the alumina gel microspheres is induced, and the crosslinking degree of the alumina gel microspheres is increased, thereby the crushing strength of the alumina microspheres after calcination can be improved.

[0070] According to some embodiments of the present application, the diameter of the alumina microspheres is 600μm-800μm, for example, the diameter can be 600μm, 650μm, 700μm, 750μm, 800μm, etc. Therefore, the diameter of the alumina microspheres prepared by the method provided in the present application can reach the above range, which is beneficial to the industrial application of the catalyst.

[0071] According to some embodiments of the present application, the pore size of the alumina microspheres is 8nm-15nm, for example, the pore size can be 8nm, 10nm, 12nm, 14nm, 15nm, etc. Therefore, the pore size of the alumina microspheres prepared by the method provided in the present application can reach the above range, which is beneficial to improve the crushing strength of the alumina microspheres.

[0072] According to some embodiments of the present application, the specific surface area of the alumina microspheres is 260m 2 / g-300m 2 / g, for example, the specific surface area can be 260m2 / g, 270 m 2 / g, 280 m 2 / g, 290 m 2 / g, 300 m 2 / g, etc., so that the specific surface area of the alumina microspheres prepared by the method provided in the present application can reach the above range, which is beneficial to the industrial application of the catalyst.

[0073] According to some embodiments of the present application, the crushing strength of the alumina microspheres is 40 N / mm 2 - 60 N / mm 2 , for example, the crushing strength can be 40 N / mm 2 , 45 N / mm 2 , 50 N / mm 2 , 55 N / mm 2 , 60 N / mm 2 , etc., so that the crushing strength of the alumina microspheres prepared by the method provided in the present application can reach the above range, so that the alumina microspheres have a higher crushing strength.

[0074] Embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application and cannot be understood as a limitation of the present application. If a specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product manual is used. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be obtained by purchase.

[0075] Example 1

[0076] 1) 2500 g of aluminum sec-butyl alcohol was added to 20000 g of pure water at 95°C, and hydrolysis was carried out under stirring at 300 r / min for 0.5 h, and then evaporation was carried out at 90°C for 30 min, and the obtained solid sol was washed with 6.6 L of hot water at 60°C for three times to obtain an AlOOH solid sol with a mass percentage of 14.4 wt%;

[0077] 2) 1000 g of the AlOOH solid sol was diluted with hot pure water to prepare an AlOOH solid sol with a mass percentage of 8 wt%, and then mixed with 90 g of 20 wt% nitric acid to obtain a stable AlOOH solid sol with a pH value of 4;

[0078] 3) The stable AlOOH sol was mixed with 11 g of methyl cellulose and 40 g of hexamethylenetetramine, and stirred at 250 r / min to form a dispersion phase. A n-octanol solution containing 15 wt% trioctylamine and 2 wt% Span 85 was prepared as a continuous phase. Then, the dispersion phase was sheared to form droplets by using the continuous phase with a flow rate of 1170 mL / min in a 200-channel T-shaped droplet shearing microfluidic module, and the droplets were subjected to preliminary gelation in the microfluidic system at 90°C for 3 min. The microspheres obtained by preliminary gelation were collected in an oil tank (the oil phase in the oil tank had the same formula as the continuous phase), and were allowed to further solidify at 90°C for 2 h to obtain alumina gel microspheres;

[0079] 4) The alumina gel microspheres were immersed in 1000 mL of ethanol, and the microspheres in the ethanol were slowly stirred. The immersion time was 10 min. The immersed alumina gel microspheres were dried at 25°C for 12 h, and then were calcined at 600°C for 6 h to obtain alumina microspheres.

[0080] Figure 2 The scanning electron microscope image of the alumina microspheres obtained in Example 1 is shown. As can be seen from the image, the alumina microspheres prepared in Example 1 are uniform in particle size, sphericity, surface smoothness and other properties, and the pores are uniformly distributed.

[0081] Figure 3 The pore size distribution diagram of the alumina microspheres obtained in Example 1 is shown. As can be seen from the diagram, the specific surface area of the alumina microspheres obtained in Example 1 is 221 m 2 / g, the pore volume is 0.97 mL / g, and the average pore size is 10.9 nm.

[0082] Example 2

[0083] 1) 2500 g of aluminum sec-butoxide was added to 20000 g of pure water at 95°C, and the mixture was stirred at 300 r / min for hydrolysis for 0.5 h. Then, the mixture was evaporated at 90°C for 30 min to obtain a sol, which was washed with 6.6 L of hot water at 60°C in three batches to obtain an AlOOH sol with a mass percentage of 15 wt%;

[0084] 2) 1000 g of the AlOOH sol was diluted with hot pure water to obtain an AlOOH sol with a mass percentage of 8 wt%, and then was mixed with 90 g of 20 wt% nitric acid to obtain a stable AlOOH sol with a pH value of 3;

[0085] 3) The stable AlOOH sol was mixed with 11 g of methyl cellulose and 40 g of hexamethylenetetramine, and stirred at 250 r / min to form a dispersion phase. A n-octanol solution containing 15 wt% trioctylamine and 2 wt% Span 85 was prepared as a continuous phase. Then, the dispersion phase was sheared to form droplets by using the continuous phase with a flow rate of 1170 mL / min in a 200-channel T-shaped droplet shearing microfluidic module, and the droplets were subjected to preliminary gelation in the microfluidic system at 90°C for 3 min. The microspheres obtained by preliminary gelation were collected in an oil tank (the oil phase in the oil tank had the same formula as the continuous phase), and were allowed to further solidify at 90°C for 2 h to obtain alumina gel microspheres;

[0086] 4) The alumina gel microspheres were immersed in 1000 mL of ethanol, and the microspheres in the ethanol were slowly stirred. The immersion time was 10 min. The immersed alumina gel microspheres were naturally air-dried at 25°C for 12 h, and then the dried alumina gel microspheres were calcined at 600°C for 6 h to obtain alumina microspheres.

[0087] Figure 4 The scanning electron microscope image of the alumina microspheres prepared in Example 2 is shown. As can be seen from the figure, the properties such as particle size, sphericity, surface smoothness, etc. of the alumina microspheres prepared in Example 2 are uniform, and the pores are uniformly distributed.

[0088] Figure 5 The nitrogen adsorption-desorption curve and pore size distribution diagram of the alumina microspheres prepared in Example 2 are shown. As can be seen from the figure, the specific surface area of the alumina microspheres prepared in this example is 288 m 2 / g, the pore volume is 0.797 mL / g, and the average pore size is 7.0 nm.

[0089] Comparative Example 1

[0090] 1) 2500 g of aluminum sec-butoxide was added to 20000 g of pure water at 95°C, and stirred at 300 r / min to hydrolyze for 0.5 h. Then, evaporation was performed at 90°C for 30 min to obtain a sol, which was washed with 6.6 L of hot water at 60°C in three times to obtain an AlOOH sol with a mass percentage of 15 wt%;

[0091] 2) 1000 g of the AlOOH sol was diluted with hot pure water to prepare an AlOOH sol with a mass percentage of 8 wt%, and then mixed with 90 g of 20 wt% nitric acid to obtain a stable AlOOH sol with a pH value of 3;

[0092] 3) The stable AlOOH sol was mixed with 11 g of methyl cellulose and 40 g of hexamethylenetetramine, and stirred at 250 r / min to form a dispersion phase; a n-octanol solution containing 15 wt% trioctylamine and 2 wt% Span 85 was prepared as a continuous phase; then, in a 200-channel T-shaped droplet shearing microfluidic module, the dispersion phase with a flow rate of 140 mL / min was sheared by the continuous phase with a flow rate of 1170 mL / min to form droplets of the dispersion phase, the droplets of the dispersion phase were subjected to preliminary gelation in the microfluidic system at 90°C for 3 min, and then the microspheres obtained by preliminary gelation were collected in an oil tank (the oil phase in the oil tank had the same formula as the continuous phase), and were allowed to further solidify at 90°C for 2 h to obtain alumina gel microspheres;

[0093] 4) The alumina gel microspheres were dried at 90°C for 10 h, and then the dried alumina gel microspheres were calcined at 600°C for 6 h to obtain alumina microspheres.

[0094] Figure 6 shows the scanning electron microscope image of the alumina microspheres prepared in Comparative Example 1, Figure 7 shows the nitrogen adsorption-desorption curve and pore size distribution of the alumina microspheres prepared in Comparative Example 1, and it can be seen from the figure that the specific surface area of the alumina microspheres prepared in Comparative Example 1 is 296 m 2 / g, the pore volume is 1.18 mL / g, and the average pore size is 9.93 nm.

[0095] Comparative Example 2

[0096] Alumina microspheres were prepared by a traditional oil column forming method. Specifically, hexamethylenetetramine and urea were added to a mixed solution of Al(NO3)3 and NH4OH, and the mixture was extruded through a needle into a hot oil column to form droplets by surface tension and solidify at high temperature to obtain alumina microspheres. The average diameter of the alumina microspheres prepared in Comparative Example 2 was 690 μm.

[0097] The alumina microspheres of Examples 3-15 were prepared in the same manner as Example 2, except that the experimental parameters were different (see Table 1).

[0098] The experimental parameters of Examples 1-15 and Comparative Example 1 of the present application are shown in Table 1.

[0099] Table 1 Experimental parameters of Examples 1-15 and Comparative Example 1

[0100]

[0101] " / " means none.

[0102] Testing and analysis

[0103] The crushing strength of the alumina microspheres prepared in the above Examples 1-15 and Comparative Examples 1-2 was tested under the same conditions, and the specific testing method was as follows:

[0104] Crushing strength: YHKC-2A particle strength tester was used for testing. One microsphere was taken out and placed in the tester. The pressure detection element was turned on to continuously press the microsphere. When the microsphere was broken, the tester displayed the maximum pressure value that the microsphere was subjected to. The average value of the maximum pressure that the microsphere was subjected to was obtained by repeating the experiment 10 times. The crushing strength = the average value of the maximum pressure / (π x microsphere radius 2 ).

[0105] The test results are shown in Table 2.

[0106] Table 2 Test results of Examples 1-15 and Comparative Examples 1-2

[0107] Group Crushing strength (N / mm 2 )]]> Example 1 57 Example 2 60 Example 3 58 Example 4 52 Example 5 57 Example 6 50 Example 7 58 Example 8 44 Example 9 52 Example 10 60 Example 11 46 Example 12 50 Example 13 59 Example 14 51 Example 15 42 Comparative Example 1 15 Comparative Example 2 8

[0108] Results and discussion

[0109] As can be seen from Tables 1-2, compared with Comparative Example 2, Comparative Example 1 was not mixed with alcohol, nor was it soaked with alcohol, and Comparative Example 2 was prepared by using the existing method. The alumina microspheres prepared in the above Examples 1-15 of the present application have high crushing strength, which indicates that by using the method of the above Examples of the present application, alumina gel microspheres can be prepared based on the sol-gel method. The alumina gel microspheres are washed and soaked with low-carbon alcohol, and the process of volatilization of low-carbon alcohol at room temperature induces the stable removal of the remaining solvent in the alumina gel microspheres, increases the crosslinking degree of the alumina gel microspheres, and then the crushing strength of the alumina microspheres can be improved by calcination, so as to realize the preparation of high-strength alumina microspheres for catalyst carrier.

[0110] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0111] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and that variations, modifications, substitutions and changes can be made by those skilled in the art without departing from the scope of the present application.

Claims

1. A method for producing alumina microspheres, characterized by, The application relates to a method for preparing an alumina microsphere. The method comprises the following steps: S1, hydrolyzing and concentrating a soluble alcohol aluminum salt to obtain an AlOOH solid sol; S2, mixing the AlOOH solid sol with an acid solution after dilution to obtain a stable AlOOH sol; S3, solidifying and forming the stable AlOOH sol to obtain an alumina gel microsphere; S4, mixing the alumina gel microsphere with alcohol, and then sequentially performing drying and calcination to obtain the alumina microsphere. In step S2, the mass percentage of AlOOH in the AlOOH solid sol is 14wt%-15wt%, the concentration temperature is 85-98 DEG C, and the pH value of the stable AlOOH sol is 3-4.

2. The method of claim 1, wherein, In step S4, the mass ratio of the alumina gel microsphere to the alcohol is 1: (15-20), the mixing time is 5-10 min, the drying temperature is 20-40 DEG C, the drying time is 8-20 h, and the carbon atom number of the alcohol is 2-4. In step S4, the calcination temperature is 550-700 DEG C, and / or, 3. The method of claim 1, wherein, The calcination time is 3-6 h.

4. An alumina microsphere characterized by, The alcohol comprises at least one of ethanol or propanol.

5. The alumina microspheres of claim 4, wherein, The alumina microsphere is prepared by the method in any one of claims 1-3. The diameter of the alumina microsphere is 600-800 mu m, and / or, The pore size of the alumina microsphere is 8-15 nm.

6. The alumina microspheres of claim 4, wherein, The specific surface area of the alumina microspheres is 260 m 2 / g-300 m 2 / g.

7. The alumina microspheres of claim 4, wherein, The crush strength of the alumina microspheres is 40 N / mm 2 - 60 N / mm 2 .

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