High-purity, large-pore-volume, high-strength spherical alumina and a preparation method thereof

Abstract

The application provides a high-purity, large-pore-volume and high-strength spherical alumina and a preparation method thereof. The method combines a micro-channel reactor and ultrasonic super dispersion, effectively controls the hydrolysis and polycondensation process of aluminum alkoxide through step-by-step hydrolysis, improves the related physical and chemical properties of the alumina hydrate intermediate product, and finally prepares the spherical alumina product with high purity, large pore volume, narrow pore size distribution and high strength through a hot oil column forming method, which can fully meet the requirements of the fluidized bed process on the alumina pellet carrier.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inorganic porous material synthesis and application, in particular, to a method for synthesizing aluminum oxide hydrate by controllable hydrolysis and polycondensation of aluminum alkoxide, and using the same as a precursor to prepare high-purity, large-pore-volume, high-strength spherical aluminum oxide by a hot oil column forming method, and a spherical aluminum oxide material prepared by the method. BACKGROUND

[0002] Aluminum oxide is inexpensive and readily available, has large specific surface area and pore volume, high mechanical strength and thermal stability, and is one of the most widely used catalyst support materials. In actual industrial applications, the support material needs to be made into a specific shape to meet the requirements of the reaction process used. For example, the mainstream process of fluidized bed for important chemical processes such as catalytic reforming and catalytic dehydrogenation of alkanes uses spherical aluminum oxide supported catalyst. The spherical aluminum oxide prepared by the drop ball forming method such as oil column forming and oil-ammonia column forming has high sphericity, uniform and controllable particle size, good mechanical properties and stable quality, and is the optimal method for preparing spherical aluminum oxide for fluidized bed at present. The crystal structure, particle morphology and size, and peptization properties of the aluminum oxide hydrate (pseudo-boehmite, boehmite, etc.) precursor used for drop ball forming have a significant impact on the properties of the ball product.

[0003] The synthesis method of aluminum oxide hydrate precursor can be divided into inorganic method and organic method, wherein the organic method mainly refers to the hydrolysis method of aluminum alkoxide, that is, pseudo-boehmite, boehmite, etc. are obtained by hydrolysis and polycondensation of organic aluminum alkoxide. Compared with the inorganic method, the raw material aluminum alkoxide used in the hydrolysis method of aluminum alkoxide is easy to purify, so the obtained aluminum oxide product has less impurities and high purity, which can meet the stringent requirements of catalyst support purity in the fields of catalytic reforming and catalytic dehydrogenation of alkanes.

[0004] The hydrolysis and polycondensation reaction of aluminum alkoxide is a complex process involving hydrolysis, dehydration and polycondensation, and dealcoholization. The whole process is initiated by hydrolysis reaction, followed by polycondensation between different degrees of hydrolysis products and between hydrolysis products and aluminum alkoxide. Hydrolysis and polycondensation reactions can occur simultaneously. The coordination of hydrolysis and polycondensation reactions will affect the grain size, morphology and texture properties of the generated aluminum oxide hydrate (Rolison, D. R. and B. Dunn, Journal of Materials Chemistry, 2001, 11(4): 963-980.), and ultimately affect the physicochemical properties and related performance of the aluminum oxide product. To adjust the properties of the hydrolysis and polycondensation products of aluminum alkoxide according to product requirements, the most fundamental thing is to control the progress of the above hydrolysis and polycondensation reactions, especially the degree of initial hydrolysis.

[0005] The method disclosed in patent CN104220373B controls the hydrolysis and polycondensation of alcohol aluminum by adding water to the alcohol aluminum solution twice. However, since the hydrolysis reaction of aluminum alcohol salt is extremely fast (Danks, A. E., et al., Materials Horizons, 2016, 3(2): 91-112), it is difficult to achieve uniform dispersion and mixing of alcohol aluminum and water before the reaction, even under stirring, and the composition of the reaction system is constantly changing as the reaction proceeds. Therefore, the above method cannot effectively control the hydrolysis and polycondensation reaction, and the pseudo-boehmite product is still uneven in space and time distribution. The method disclosed in patent CN113307293B controls the hydrolysis and polycondensation of aluminum alcohol salt by multiple hydrolysis processes through micro-reaction. In this method, the hydrolysis solution and aluminum alcohol salt are added to the reactor in sequence, and no other method is used to enhance dispersion and mixing. Therefore, uniform dispersion and reaction of the two materials cannot be achieved, and the internal channels of the reactor may be blocked by the gel or precipitate produced by the reaction.

[0006] The method disclosed in patent CN102718242B couples the esterification reaction of organic alcohol and organic acid with the hydrolysis reaction of aluminum alcohol salt, uses the slowly and uniformly produced water from the esterification reaction to hydrolyze the aluminum alcohol salt, delays the hydrolysis process of alcohol aluminum, and produces aluminum hydroxide with regular morphology and uniform dispersion. The method disclosed in patent CN105754106A first uses acetylacetone complexing agent to partially substitute the alkoxy group of isopropyl alcohol aluminum, reduces its hydrolysis reaction activity, and then adds water for controllable hydrolysis to prepare an alumina ceramic precursor with excellent performance. The above methods can delay the hydrolysis and polycondensation reaction of aluminum alcohol salt, and the method disclosed in patent CN106000245B controls the hydrolysis and polycondensation process of aluminum alcohol salt through two-step hydrolysis with the assistance of chelating agents such as ethyl acetoacetate and acetylacetone, to solve the problem that the aluminum hydroxide gel synthesized by the conventional alcohol aluminum method is prone to cracking during drying. The above methods for adjusting the hydrolysis of aluminum alcohol salt rely on other coupled reactions or modification of aluminum source by specific complex, and the process is complex, and the space and freedom for regulation are limited. SUMMARY

[0007] The purpose of the present application is to provide a method for synthesizing alumina hydrate with uniform composition and good peptization by controllable hydrolysis and polycondensation of organic aluminum alcohol salt, and preparing spherical alumina with high purity, large pore volume and high strength by using the alumina hydrate as a precursor through hot oil column method, and spherical alumina material prepared by the method.

[0008] In order to achieve the above purpose, the present application provides the following technical solution, i.e. a method for preparing spherical alumina with high purity, large pore volume and high strength, comprising the following steps:

[0009] (1) Dissolve the aluminum alkoxide in an organic solvent to form an aluminum alkoxide solution;

[0010] (2) Inject the aluminum alkoxide solution and water into two micro-channel reactors A respectively by two pumps at a constant flow rate, so that the two materials are mixed and reacted at a fixed water / aluminum molar ratio under a certain temperature and ultrasonic wave;

[0011] (3) Inject the output of reactor A and water into two micro-channel reactors B respectively by two pumps at a constant flow rate, so that the two materials are mixed and reacted at a fixed water / aluminum molar ratio under a certain temperature and ultrasonic wave;

[0012] (4) Transfer the material obtained in step (3) to an autoclave for aging, then filter and dry the aged mixture to obtain alumina hydrate powder;

[0013] (5) Mix the alumina hydrate powder with an acid solution for peptization, then add a gelling agent for gelation, drop into a hot oil column to form balls, and then age, wash, dry and calcine the collected balls to obtain spherical alumina products.

[0014] In the above preparation method, the aluminum alkoxide used can be selected from one of aluminum alkoxides with a single alkyl carbon atom number of 3-8.

[0015] In the above preparation method, the organic solvent used for dissolving the aluminum alkoxide can be selected from one or a mixture of two or more of C1-C8 alkanes, cycloalkanes, aromatic hydrocarbons and alcohols, and the molar ratio thereof to the aluminum alkoxide is in the range of 1-50:1.

[0016] In the above preparation method, the water / aluminum molar ratio in step (2) can be in the range of 0.5-2:1, the temperature is not lower than 20°C and not higher than the boiling point of all organic solvents, alcohols and water involved in the reaction, and the ultrasonic power can be adjusted according to the volume and flow rate of the channel of the reactor convergence section (i.e. downstream of the convergence point of the two materials) to make the ultrasonic energy density received by the material in the convergence section channel in the range of 0.1-10 J / mL;

[0017] In the above preparation method, the water / aluminum molar ratio in step (3) can be in the range of 2.5-20:1, the temperature is not lower than 20°C and not higher than the boiling point of all organic solvents, alcohols and water involved in the reaction, and the ultrasonic power can be adjusted according to the volume and flow rate of the channel of the reactor convergence section (i.e. downstream of the convergence point of the two materials) to make the ultrasonic energy density received by the material in the convergence section channel in the range of 0.5-40 J / mL;

[0018] In the preparation method, the channel diameter of the microreactor A can be in the range of 0.3-2 mm, the channel volume of the merging section can be in the range of 0.1-2 ml, the channel diameter of the microreactor B can be in the range of 1-3 mm, the channel volume of the merging section can be in the range of 1-20 ml, and the ultrasonic frequency used can be in the range of 17-40 kHz.

[0019] In the preparation method, the aging temperature of step (4) can be in the range of 80-220 ℃, and the time can be in the range of 0.5-72 h; the drying temperature can be in the range of 90-150 ℃, and the time can be in the range of 8-24 h, and the drying can be performed under a certain vacuum degree.

[0020] In the preparation method, the Al2O3 content in the gelatinization process of step (5) can be in the range of 15-25% (mass content), the acid used can be one or more of nitric acid, hydrochloric acid, acetic acid, and citric acid, the H + / Al2O3 molar ratio can be in the range of 0.03-0.15:1; the gelling agent used can be one or more of hexamethylene tetramine, urea, diethylamine, dilute ammonia, ammonium bicarbonate, and ammonium carbonate, wherein the equivalent NH4 + contained in the gelling agent and the H + added in the gelatinization process can have a molar ratio in the range of 1.2-4:1; the oil used in the hot oil column can be one of white oil, spindle oil, vacuum pump oil, diesel oil, and paraffin oil, the oil temperature can be in the range of 80-120 ℃, the aging temperature can be in the range of 100-200 ℃, the aging time can be in the range of 6-12 h, the drying temperature can be in the range of 100-150 ℃, the drying time can be in the range of 10-20 h, the calcination temperature can be in the range of 400-700 ℃, and the calcination time can be in the range of 2-6 h.

[0021] The present application also claims the spherical alumina obtained by the above preparation method, which has a purity of not less than 99.99 wt%, a pore volume of not less than 0.60 mL / g, a pore size in the range of 15-25 nm accounting for not less than 90 vol%, and a compressive strength of not less than 50 N / particle.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] (1) The method provided by the application combines a micro-channel reactor and the super dispersion effect of ultrasonic waves, controls the degree of hydrolysis of aluminum alkoxide in the first step by adding water twice and hydrolyzing step by step, so as to effectively control the subsequent hydrolysis and polycondensation reaction. In the conventional one-step hydrolysis process, the aluminum alkoxide is basically completely hydrolyzed before polycondensation, the alkoxy group is completely replaced by a hydroxyl group, the hydrolysis product -O-M(OH)3 has multiple hydroxyl sites for polycondensation, which leads to disordered and uncontrollable polycondensation, and small and highly branched agglomerates are generated, forming a colloidal gel, and the final product has small pore volume and uneven pore size distribution. In the application, the aluminum alkoxide solution and the hydrolysis solution are transported and mixed in the micro-channel reactor, and ultrasonic waves are applied, so that the two raw materials are uniformly mixed and reacted according to the set stoichiometric ratio at all times. By simply limiting the amount (flow) of water added in the first step, the aluminum alkoxide is not completely hydrolyzed, and a structure in which part of the alkoxy group is replaced by a hydroxyl group (-O-M(OR) 3-n (OH) n , n<3) is formed, so that the subsequent hydrolysis and polycondensation are more coordinated. Condensation mainly occurs on the terminal hydroxyl group, so that chain and network gels are easily assembled, and finally, primary and secondary aluminum oxide hydrate particles with higher crystallinity, more uniform morphology and size are formed, and the pore volume, pore distribution uniformity, peptization and other physical and chemical properties are improved. In addition, the ultrasonic waves can also promote the suspension and dispersion of solids in liquids, and avoid pipeline blockage.

[0024] (2) The spherical alumina product prepared by the method has large pore volume, concentrated pore size distribution, high sphericity and high strength, and can fully meet the requirements of the fluidized bed process for alumina pellet carriers. DETAILED DESCRIPTION

[0025] In order to make the purpose, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the application, not all embodiments. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor, such as changing the purpose without changing the basic principles involved in the claims, belong to the protection scope of the application.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials, reagents and the like used can be obtained from commercial channels.

[0027] In the following examples, the pore volume of the alumina sample is determined by using the ASAP 2460 specific surface area and pore size analyzer of the American Micromeritics company, and the total pore volume at a single point adsorption at a relative pressure P / P0=0.995 is taken; the sphericity is determined by using the CAMSIZER X2 dynamic image method particle size and shape analyzer of the MICROTRAC RETSCH company; and the compressive strength is determined by using the DL 3 type particle strength tester of the Dalian Penghui Science and Technology Development Co., Ltd.

[0028] Example 1

[0029] This example is used to specifically illustrate the preparation method of the spherical alumina provided by the present application, and the operation steps are as follows:

[0030] (1) Dissolve aluminum isopropoxide in isopropyl alcohol, wherein the molar ratio of isopropyl alcohol to aluminum isopropoxide is 9:1;

[0031] (2) Use two pumps to inject the aluminum isopropoxide solution and water into two microchannel reactors A installed on an ultrasonic vibration platform at a flow rate of 8.9 mL / min and 0.18 mL / min, respectively, so that the two materials are mixed and reacted at a fixed water / aluminum molar ratio of 1:1, the inner diameter of the channel of the convergence section of the microchannel reactor A is 1 mm, the volume is 1 mL, the set temperature is 80°C, the ultrasonic frequency is 40 kHz, and the ultrasonic energy density received by the material in the channel of the convergence section is 2 J / mL;

[0032] (3) Use two pumps to inject the outflow of the reactor A and water into two microchannel reactors B installed on an ultrasonic vibration platform at a flow rate of 9.1 mL / min and 1.08 mL / min, respectively, so that the two materials are mixed and reacted at a fixed water / aluminum molar ratio of 4:1, the inner diameter of the channel of the convergence section of the microchannel reactor B is 1 mm, the volume is 2 mL, the set temperature is 80°C, the ultrasonic frequency is 20 kHz, and the ultrasonic energy density received by the material in the channel of the convergence section is 6 J / mL;

[0033] (4) Transfer the material obtained in step (3) to an autoclave and age at a temperature of 120°C for 12 h;

[0034] (5) Filter the aged mixture, take the solid material to dry at a temperature of 100°C for 16 h, and obtain an alumina hydrate powder;

[0035] (6) Take a certain amount of alumina hydrate powder, disperse it in water, and prepare a mixture with an alumina mass content of 18%, add nitric acid to perform peptization at a H + / Al2O3 molar ratio of 0.04:1, add NH4 + / H +The diethylamine gelling agent was added in equivalent molar ratio, and then dropped into a hot oil column with diesel oil as oil phase and at a temperature of 95 ℃ to form a ball, and then the collected small ball was loaded into an autoclave for aging at 150 ℃ for 6 h, washed with ethanol, and then placed into an oven for drying at 110 ℃ for 12 h, and finally placed into a muffle furnace for calcination at 500 ℃ for 4 h to obtain a spherical alumina product, and the relevant physical property parameters are shown in Table 1.

[0036] Example 2

[0037] This example is used to specifically illustrate the method for preparing the spherical alumina provided by the present application, and the operation steps are as follows:

[0038] (1) The aluminum isopropoxide was dissolved in isopropyl alcohol, and the isopropyl alcohol and aluminum isopropoxide were in a molar ratio of 15:1;

[0039] (2) The aluminum isopropoxide solution and water were respectively injected into two micro-channel reactors A installed on an ultrasonic vibration platform by two pumps at a flow rate of 13.5 mL / min and 0.14 mL / min, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 0.8:1, the micro-channel reactor A had a converging section channel with an inner diameter of 0.5 mm and a volume of 0.5 mL, and was set at a temperature of 80 ℃, the ultrasonic frequency was 40 kHz, and the ultrasonic energy density received by the material in the converging section channel was 0.5 J / mL;

[0040] (3) The outflow of the reactor A and water were respectively injected into two micro-channel reactors B installed on an ultrasonic vibration platform by two pumps at a flow rate of 13.6 mL / min and 1.62 mL / min, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 6:1, the micro-channel reactor B had a converging section channel with an inner diameter of 2 mm and a volume of 15 mL, and was set at a temperature of 80 ℃, the ultrasonic frequency was 20 kHz, and the ultrasonic energy density received by the material in the converging section channel was 5 J / mL;

[0041] (4) The material obtained in step (3) was transferred to an autoclave for aging at a temperature of 160 ℃ for 12 h;

[0042] (5) The aged mixture was filtered, and the solid was dried at a temperature of 120 ℃ for 12 h to obtain an alumina hydrate powder;

[0043] (6) A certain amount of the alumina hydrate powder was dispersed in water to prepare a mixture with an alumina mass content of 25%, and H + NO3 was added in a molar ratio of 1.5:1 to perform peptization, and NH + 4OH was added in a molar ratio of 1.5:1 to perform peptization, and H +The diethylamine gelling agent was added in equivalent molar ratio, and then dropped into a hot oil column with spindle oil as oil phase and at a temperature of 100 ℃ to form a ball, and then the collected small ball was loaded into an autoclave for aging at 140 ℃ for 8 h, washed with ethanol, and then placed into an oven for drying at 120 ℃ for 15 h, and finally placed into a muffle furnace for calcination at 600 ℃ for 4 h to obtain a spherical alumina product, and the relevant property parameters are shown in Table 1.

[0044] Example 3

[0045] This example is used to specifically illustrate the method for preparing the spherical alumina provided by the present application, and the operation steps are as follows:

[0046] (1) The aluminum isopropoxide was dissolved in toluene, and the toluene / aluminum isopropoxide molar ratio was 6:1;

[0047] (2) The aluminum isopropoxide solution and water were respectively injected into two micro-channel reactors A installed on an ultrasonic vibration platform by two pumps at a flow rate of 8.3 mL / min and 0.18 mL / min, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 1:1, the micro-channel reactor A had a converging section channel with an inner diameter of 0.5 mm and a volume of 0.5 mL, and was set at a temperature of 90 ℃, the ultrasonic frequency was 40 kHz, and the ultrasonic energy density received by the material in the converging section channel was 5 J / mL;

[0048] (3) The reactor A effluent and water were respectively injected into two micro-channel reactors B installed on an ultrasonic vibration platform by two pumps at a flow rate of 8.5 mL / min and 0.68 mL / min, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 2.5:1, the micro-channel reactor B had a converging section channel with an inner diameter of 1 mm and a volume of 4 mL, and was set at a temperature of 90 ℃, the ultrasonic frequency was 20 kHz, and the ultrasonic energy density received by the material in the converging section channel was 12 J / mL;

[0049] (4) The material obtained in step (3) was transferred to an autoclave for aging at a temperature of 200 ℃ for 32 h;

[0050] (5) The aged mixture was filtered, and the solid was dried at a temperature of 100 ℃ for 12 h to obtain an alumina hydrate powder;

[0051] (6) A certain amount of the alumina hydrate powder was dispersed in water to prepare a mixture with an alumina mass content of 22%, and acetic acid was added in a H + / Al2O3 molar ratio of 0.1:1 for peptization, and NH4 + / H +The equivalent molar ratio of ammonium bicarbonate gelling agent was added, and then dropped into a hot oil column with white oil as the oil phase and a temperature of 110 ℃ to form balls. The collected balls were loaded into an autoclave and aged at 120 ℃ for 12 h. After washing with ethanol, the balls were placed in an oven and dried at 140 ℃ for 10 h. Finally, the balls were placed in a muffle furnace and calcined at 550 ℃ for 4 h to obtain spherical alumina products. The relevant physical property parameters are shown in Table 1.

[0052] Example 4

[0053] This example is used to specifically illustrate the method for preparing spherical alumina provided by the present application, and the operation steps are as follows:

[0054] (1) Aluminum isopropoxide was dissolved in toluene, and the molar ratio of toluene to aluminum isopropoxide was 30:1;

[0055] (2) Two pumps were used to inject the aluminum isopropoxide solution and water into two microchannel reactors A installed on an ultrasonic vibration platform at flow rates of 33.7 mL / min and 0.27 mL / min, respectively, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 1.5:1. The microchannel reactor A had a convergence section channel with an inner diameter of 1 mm and a volume of 1 mL, and was set to a temperature of 70 ℃. The ultrasonic frequency was 28 kHz, and the ultrasonic energy density received by the material in the convergence section channel was 5 J / mL;

[0056] (3) Two pumps were used to inject the reactor A effluent and water into two microchannel reactors B installed on an ultrasonic vibration platform at flow rates of 34.0 mL / min and 3.2 mL / min, respectively, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 12:1. The microchannel reactor B had a convergence section channel with an inner diameter of 2 mm and a volume of 4 mL, and was set to a temperature of 70 ℃. The ultrasonic frequency was 20 kHz, and the ultrasonic energy density received by the material in the convergence section channel was 15 J / mL;

[0057] (4) The material obtained in step (3) was transferred to an autoclave and aged at a temperature of 100 ℃ for 8 h;

[0058] (5) The aged mixture was filtered, and the solid was dried at a temperature of 140 ℃ for 12 h to obtain alumina hydrate powder;

[0059] (6) A certain amount of alumina hydrate powder was dispersed in water to prepare a mixture with an alumina mass content of 15%. Acetic acid was added for peptization at an H + / Al2O3 molar ratio of 0.1:1, and ammonium bicarbonate was added at an NH + / H +The equivalent molar ratio of urea gelling agent was added, and then dropped into a hot oil column with white oil as the oil phase and a temperature of 100 ℃ to form a ball. The collected small balls were loaded into an autoclave and aged at 140 ℃ for 12 h. After washing with ethanol, the product was dried in an oven at 120 ℃ for 12 h, and finally calcined in a muffle furnace at 550 ℃ for 4 h to obtain a spherical alumina product. The relevant physical property parameters are shown in Table 1.

[0060] Example 5

[0061] This example is used to specifically illustrate the method for preparing spherical alumina provided by the present application, and the operation steps are as follows:

[0062] (1) Dissolve aluminum isopropoxide in cyclohexane, wherein the molar ratio of cyclohexane to aluminum isopropoxide is 4:1;

[0063] (2) Use two pumps to inject the aluminum isopropoxide solution and water into two microchannel reactors A installed on an ultrasonic vibration platform at flow rates of 6.5 mL / min and 0.18 mL / min, respectively, so that the two materials are mixed and reacted at a fixed water / aluminum molar ratio of 1:1. The microchannel reactor A has a convergence section channel with an inner diameter of 0.5 mm and a volume of 0.5 mL, and is set at a temperature of 25 ℃. The ultrasonic frequency is 40 kHz, and the ultrasonic energy density received by the material in the convergence section channel is 6 J / mL.

[0064] (3) Use two pumps to inject the reactor A effluent and water into two microchannel reactors B installed on an ultrasonic vibration platform at flow rates of 6.7 mL / min and 0.81 mL / min, respectively, so that the two materials are mixed and reacted at a fixed water / aluminum molar ratio of 3:1. The microchannel reactor B has a convergence section channel with an inner diameter of 1 mm and a volume of 2 mL, and is set at a temperature of 80 ℃. The ultrasonic frequency is 25 kHz, and the ultrasonic energy density received by the material in the convergence section channel is 6 J / mL.

[0065] (4) Transfer the material obtained in step (3) to an autoclave and age at a temperature of 150 ℃ for 48 h;

[0066] (5) Filter the aged mixture, and dry the solid at a temperature of 120 ℃ for 12 h to obtain an alumina hydrate powder;

[0067] (6) Disperse a certain amount of alumina hydrate powder in water to prepare a mixture with an alumina mass content of 20%, and add citric acid for peptization at an H + / Al2O3 molar ratio of 0.1:1. Add NH4 + / H +The equivalent molar ratio of hexamethylenetetramine gelling agent was added, and then the mixture was dropped into a hot oil column with white oil as the oil phase and a temperature of 105 ℃ to form balls. The collected balls were placed in an autoclave and aged at 160 ℃ for 8 h. After being washed with petroleum ether, the balls were placed in an oven and dried at 120 ℃ for 12 h. Finally, the balls were placed in a muffle furnace and calcined at 550 ℃ for 4 h to obtain spherical alumina products. The relevant physical property parameters of the products are shown in Table 1.

[0068] Example 6

[0069] This example is used to specifically illustrate the method for preparing spherical alumina provided by the present application, and the operation steps are as follows:

[0070] (1) Aluminum sec-butoxide was dissolved in sec-butoxyl alcohol, and the molar ratio of sec-butoxyl alcohol to aluminum sec-butoxide was 6:1;

[0071] (2) Two pumps were used to inject the aluminum isopropoxide solution and water into two microchannel reactors A installed on an ultrasonic vibration platform at flow rates of 8.0 mL / min and 0.18 mL / min, respectively, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 1:1. The microchannel reactor A had a convergence section channel with an inner diameter of 1 mm and a volume of 1 mL, and was set at a temperature of 90 ℃. The ultrasonic frequency was 40 kHz, and the ultrasonic energy density received by the material in the convergence section channel was 5 J / mL.

[0072] (3) Two pumps were used to inject the reactor A effluent and water into two microchannel reactors B installed on an ultrasonic vibration platform at flow rates of 8.2 mL / min and 1.08 mL / min, respectively, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 4:1. The microchannel reactor B had a convergence section channel with an inner diameter of 2 mm and a volume of 4 mL, and was set at a temperature of 90 ℃. The ultrasonic frequency was 20 kHz, and the ultrasonic energy density received by the material in the convergence section channel was 15 J / mL.

[0073] (4) The material obtained in step (3) was transferred to an autoclave and aged at a temperature of 150 ℃ for 16 h.

[0074] (5) The aged mixture was filtered, and the solid was dried at 100 ℃ and a vacuum of 10 Pa for 10 h to obtain alumina hydrate powder.

[0075] (6) A certain amount of alumina hydrate powder was dispersed in water to prepare a mixture with an alumina mass content of 20%. Hydrochloric acid was added at an H + / Al2O3 molar ratio of 0.08:1, and the mixture was gelled. Hydrochloric acid was added at an NH + / H +The equivalent molar ratio of hexamethylenetetramine gelling agent was added, and then the ball was formed by dropping into the hot oil column with white oil as the oil phase and a temperature of 115 ℃. Then the collected small balls were loaded into an autoclave and aged at 140 ℃ for 12 h. After being washed with petroleum ether, the product was dried in an oven at 120 ℃ for 12 h, and finally calcined in a muffle furnace at 550 ℃ for 4 h to obtain the spherical alumina product. The relevant physical property parameters are shown in Table 1.

[0076] Example 7

[0077] This example is used to specifically illustrate the preparation method of the spherical alumina provided by the present application, and the operation steps are as follows:

[0078] (1) The aluminum n-hexyl alcohol was dissolved in toluene, and the molar ratio of toluene to aluminum n-hexyl alcohol was 8:1;

[0079] (2) The aluminum isopropyl alcohol solution and water were injected into two microchannel reactors A installed on an ultrasonic vibration platform at a flow rate of 12.1 mL / min and 0.18 mL / min, respectively, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 1:1. The microchannel reactor A had a convergence section channel inner diameter of 1 mm, a volume of 1 mL, and a set temperature of 90 ℃. The ultrasonic frequency was 40 kHz, and the ultrasonic energy density received by the material in the convergence section channel was 8 J / mL;

[0080] (3) The reactor A effluent and water were injected into two microchannel reactors B installed on an ultrasonic vibration platform at a flow rate of 12.3 mL / min and 0.81 mL / min, respectively, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 3:1. The microchannel reactor B had a convergence section channel inner diameter of 2 mm, a volume of 10 mL, and a set temperature of 90 ℃. The ultrasonic frequency was 20 kHz, and the ultrasonic energy density received by the material in the convergence section channel was 25 J / mL;

[0081] (4) The material obtained in step (3) was transferred to an autoclave and aged at a temperature of 160 ℃ for 16 h;

[0082] (5) The aged mixture was filtered, and the solid was dried at 120 ℃ and a vacuum of 10 Pa for 10 h to obtain an alumina hydrate powder;

[0083] (6) A certain amount of alumina hydrate powder was dispersed in water to prepare a mixture with an alumina mass content of 20%, and hydrochloric acid was added at an H + / Al2O3 molar ratio of 0.08:1 for peptization, and NH4 + / H +The equivalent molar ratio of hexamethylenetetramine gelling agent was added, and then the ball was formed by dropping into a hot oil column with a temperature of 115 ℃ and a vacuum pump oil as an oil phase. Then, the collected small balls were loaded into an autoclave for aging at 140 ℃ for 12 h. After being washed with petroleum ether, the product was dried in an oven at 120 ℃ for 12 h, and finally, the product was calcined in a muffle furnace at 550 ℃ for 4 h to obtain a spherical alumina product. The relevant physical property parameters of the product are shown in Table 1.

[0084] Example 8

[0085] This example is used to specifically illustrate the method for preparing the spherical alumina provided by the present application, and the operation steps are as follows:

[0086] (1) Aluminum n-octyl alcohol was dissolved in toluene, and the molar ratio of toluene to aluminum n-octyl alcohol was 12:1;

[0087] (2) Two pumps were used to inject the aluminum isopropyl alcohol solution and water into two micro-channel reactors A installed on an ultrasonic vibration platform at flow rates of 17.6 mL / min and 0.18 mL / min, respectively, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 1:1. The micro-channel reactor A had a convergence section channel with an inner diameter of 1 mm and a volume of 1 mL, and was set at a temperature of 90 ℃. The ultrasonic frequency was 40 kHz, and the ultrasonic energy density received by the material in the convergence section channel was 4 J / mL.

[0088] (3) Two pumps were used to inject the reactor A effluent and water into two micro-channel reactors B installed on an ultrasonic vibration platform at flow rates of 17.8 mL / min and 1.35 mL / min, respectively, so that the two materials were mixed and reacted at a fixed water / aluminum molar ratio of 5:1. The micro-channel reactor B had a convergence section channel with an inner diameter of 2 mm and a volume of 10 mL, and was set at a temperature of 90 ℃. The ultrasonic frequency was 20 kHz, and the ultrasonic energy density received by the material in the convergence section channel was 35 J / mL.

[0089] (4) The material obtained in step (3) was transferred to an autoclave for aging at a temperature of 160 ℃ for 16 h;

[0090] (5) The aged mixture was filtered, and the solid was dried at 120 ℃ and a vacuum of 10 Pa for 10 h to obtain an alumina hydrate powder;

[0091] (6) A certain amount of alumina hydrate powder was dispersed in water to prepare a mixture with an alumina mass content of 20%. Hydrochloric acid was added at an H + / Al2O3 molar ratio of 0.08:1 for peptization, and NH4 + / H +The equivalent molar ratio of hexamethylenetetramine gelling agent was added, and then dropped into a hot oil column with a temperature of 115 ℃ and vacuum pump oil as the oil phase to form balls. The collected small balls were loaded into an autoclave and aged at 140 ℃ for 12 h. After being washed with petroleum ether, the product was dried in an oven at 120 ℃ for 12 h, and finally calcined in a muffle furnace at 550 ℃ for 4 h to obtain a spherical alumina product. The relevant physical property parameters are shown in Table 1.

[0092] Comparative Example 1

[0093] The operation steps are as follows:

[0094] (1) 100 g of aluminum isopropoxide was weighed into a 1000 mL three-necked round-bottom flask, isopropyl alcohol was added, and the molar ratio of isopropyl alcohol to aluminum isopropoxide was 9:1. Then the flask was placed in an 80 ℃ oil bath, a condensation reflux tube was added to the bottle mouth, and mechanical stirring was added to the bottle.

[0095] (2) After the aluminum isopropoxide was dissolved, a certain amount of water was added to the flask at a flow rate of 0.18 mL / min using a pump, and the molar ratio of water to aluminum was 1:1. After the water was added, heating and stirring were continued for 30 min.

[0096] (3) A certain amount of water was added to the flask at a flow rate of 1.08 mL / min using a pump, and the molar ratio of water to aluminum was 4:1. After the water was added, heating and stirring were continued for 30 min.

[0097] (4) The material obtained in step (3) was transferred to an autoclave and aged at a temperature of 120 ℃ for 12 h.

[0098] (5) The aged mixture was filtered, and the solid was dried at a temperature of 100 ℃ for 16 h to obtain alumina hydrate powder.

[0099] (6) A certain amount of alumina hydrate powder was dispersed in water to prepare a mixture with an alumina mass content of 18%, and H + NO3 was added in an equivalent molar ratio to perform peptization, and NH4 + / H + The equivalent molar ratio of hexamethylenetetramine gelling agent was added, and then dropped into a hot oil column with a temperature of 115 ℃ and vacuum pump oil as the oil phase to form balls. The collected small balls were loaded into an autoclave and aged at 140 ℃ for 12 h. After being washed with petroleum ether, the product was dried in an oven at 120 ℃ for 12 h, and finally calcined in a muffle furnace at 550 ℃ for 4 h to obtain a spherical alumina product. The relevant physical property parameters are shown in Table 1.

[0100] Comparative Example 2

[0101] The operation steps are as follows:

[0102] (1) Take 100 g of isopropyl aluminum alcohol in a 1000 mL three-necked round-bottom flask, add toluene, and the molar ratio of toluene to isopropyl aluminum alcohol is 6:1, then put the flask into a 90°C oil bath, add a condensation reflux tube to the bottle mouth, and add mechanical stirring to the bottle;

[0103] (2) After the isopropyl alcohol aluminum is dissolved, the ultrasonic is turned on, the power is set to 600 W, a certain amount of water is added to the flask at a flow rate of 0.63 ml / min by a pump, the molar ratio of water to aluminum is 3.5:1, and after the water is added, the heating and stirring is continued for 30 min;

[0104] (3) The material obtained in step (2) is transferred to an autoclave, and aged at a temperature of 200°C for 32 h;

[0105] (4) The aged mixture is filtered, and the solid is dried at a temperature of 100°C for 12 h to obtain an aluminum oxide hydrate powder;

[0106] (5) A certain amount of aluminum oxide hydrate powder is dispersed in water to prepare a mixture with an aluminum oxide mass content of 22%, H + / Al2O3 molar ratio of 0.1:1 is added to the acetic acid for peptization, NH4 + / H + equivalent molar ratio of ammonium bicarbonate gelling agent is added, then a hot oil column with white oil as the oil phase and a temperature of 110°C is dropped into the ball, the collected small balls are loaded into an autoclave and aged at 120°C for 12 h, washed with ethanol and then placed in an oven at 140°C for drying for 10 h, and finally placed in a muffle furnace at 550°C for calcination for 4 h to obtain a spherical aluminum oxide product, and the relevant physical property parameters are shown in Table 1.

[0107] Comparative Example 3

[0108] The operation steps are as follows:

[0109] (1) Mix 120 g of n-hexyl aluminum alcohol and toluene in a 1000 ml three-necked round-bottom flask, the molar ratio of toluene to n-hexyl aluminum alcohol is 8:1, then put the flask into an 80°C oil bath, add a condensation reflux tube to the bottle mouth, and add mechanical stirring to the bottle;

[0110] (2) After the n-hexyl aluminum alcohol is dissolved, the ultrasonic is turned on, the power is set to 800 W, a certain amount of water is added to the flask at a flow rate of 0.18 ml / min by a pump, the molar ratio of water to aluminum is 1:1, and after the water is added, the heating and stirring is continued for 30 min;

[0111] (3) A certain amount of water is added to the flask at a flow rate of 0.81 mL / min by a pump, the molar ratio of water to aluminum is 3:1, and after the water is added, the heating and stirring is continued for 30 min;

[0112] (4) The material obtained in step (3) is transferred to an autoclave and aged at a temperature of 160°C for 16 hours;

[0113] (5) The aged mixture is filtered, and the solid is dried at 120°C and under a vacuum of 10 Pa for 10 hours to obtain alumina hydrate powder;

[0114] (6) A certain amount of alumina hydrate powder is dispersed in water to prepare a mixture with an alumina mass content of 20%, and hydrochloric acid is added for peptization at a H + / Al2O3 molar ratio of 0.08:1, ammonium hydroxide is added for peptization at a NH + / H + equivalent molar ratio of 1.5:1, and then the mixture is dropped into a hot oil column with a temperature of 115°C to form balls, the collected balls are placed in an autoclave and aged at 140°C for 12 hours, washed with petroleum ether, and then placed in an oven and dried at 120°C for 12 hours, and finally placed in a muffle furnace and calcined at 550°C for 4 hours to obtain spherical alumina products, and the relevant physical property parameters are shown in Table 1.

[0115] Table 1

[0116]

[0117] As can be seen from Table 1, the spherical alumina (Examples 1-8) prepared by the method provided by the present application has a pore volume of not less than 0.62 mL / g, the pore volume of the pores with a pore size in the range of 15-25 nm accounts for not less than 91% of the total pore volume, and the compressive strength is not less than 52 N / particle. Comparative Example 1 uses stepwise hydrolysis, but injects the hydrolysis solution into the aluminum isopropoxide solution in a conventional manner without ultrasonic; Comparative Example 2 applies ultrasonic during the hydrolysis process, but uses one-step hydrolysis; Comparative Example 3 uses stepwise hydrolysis and applies ultrasonic, but injects the hydrolysis solution into the aluminum isopropoxide solution in a conventional manner. The spherical alumina prepared by the above comparative examples has a pore volume of not more than 0.49 mL / g, the pore volume of the pores with a pore size in the range of 15-25 nm accounts for not more than 83% of the total pore volume, and only the spherical alumina prepared by Comparative Example 3 has a compressive strength higher than 50 N / particle. Therefore, compared with the comparative examples, the spherical alumina prepared by the method provided by the present application is superior in terms of pore volume, pore size distribution concentration, and compressive strength.

[0118] The above only describes preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

Claims

1. A method for preparing high-purity, large-pore-volume, high-strength spherical alumina, characterized in that, The method comprises the following steps: (1) dissolving aluminum alkoxide in an organic solvent to prepare an aluminum alkoxide solution; (2) using two pumps to inject the aluminum alkoxide solution and water into a microchannel reactor A at a constant flow rate, so that the two materials are mixed and reacted at a fixed water / aluminum molar ratio under a certain temperature and ultrasonic wave; (3) using two pumps to inject the output of the reactor A and water into a microchannel reactor B at a constant flow rate, so that the two materials are mixed and reacted at a fixed water / aluminum molar ratio under a certain temperature and ultrasonic wave; (4) transferring the material obtained in step (3) to an autoclave for aging, and then filtering and drying the aged mixture to obtain an aluminum hydroxide powder; (5) mixing the aluminum hydroxide powder with an acid solution for peptization, then adding a gelling agent for gelation, and then dropping into a hot oil column to form a ball, and then aging, washing, drying and calcining the collected small balls to obtain a spherical aluminum oxide product; The water / aluminum molar ratio in step (2) is in the range of 0.5-2:1, the reaction temperature is not lower than 20 DEG C and not higher than the boiling point of all organic solvents, alcohols and water involved in the reaction, and the ultrasonic power is set according to the ultrasonic energy density received by the material in the confluence section channel in the range of 0.1-10 J / mL; The water / aluminum molar ratio in step (3) is in the range of 2.5-20:1, the reaction temperature is not lower than 20 DEG C and not higher than the boiling point of all organic solvents, alcohols and water involved in the reaction, and the ultrasonic power is set according to the ultrasonic energy density received by the material in the confluence section channel in the range of 0.5-40 J / mL.

2. The preparation method according to claim 1, characterized in that, The aluminum alkoxide used is selected from one of aluminum alkoxides with carbon atoms in a single alkyl group ranging from 3 to 8.

3. The method of claim 1, wherein The organic solvent used for dissolving aluminum alkoxide is selected from one or a mixture of two or more of C1-C8 alkanes, cycloalkanes, aromatic hydrocarbons and alcohols, and the molar ratio thereof to aluminum alkoxide is in the range of 1-50:

1.

4. The method of claim 1, wherein The channel diameter of the microchannel reactor A is in the range of 0.3-2 mm, the confluence section channel volume is in the range of 0.1-2 mL, the channel diameter of the microchannel reactor B is in the range of 1-3 mm, the confluence section channel volume is in the range of 1-20 mL, and the ultrasonic frequency used is in the range of 17-40 kHz.

5. The method of claim 1, wherein The aging temperature in step (4) is in the range of 80-220 DEG C, and the time is in the range of 0.5-72 h; the drying temperature is in the range of 90-150 DEG C, and the time is in the range of 8-24 h, and the drying is carried out under a certain vacuum degree.

6. The method of claim 1, wherein Step (5) The Al2O3 content in the process of peptization is in the range of 15-25wt%, the acid used is one or more of nitric acid, hydrochloric acid, acetic acid, and citric acid, H + The molar ratio of / Al2O3 is in the range of 0.03-0.15:1; the gelling agent used is one or more of hexamethylenetetramine, urea, diethylamine, dilute ammonia, ammonium bicarbonate, and ammonium carbonate, wherein the equivalent NH4 + The molar ratio of H + added in the peptization is in the range of 1.2-4:1; the oil used in the hot oil column is one of white oil, spindle oil, vacuum pump oil, diesel oil, and paraffin oil, the oil temperature is in the range of 80-120℃, the aging temperature is in the range of 100-200℃, the aging time is in the range of 6-12h, the drying temperature is in the range of 100-150℃, the drying time is in the range of 10-20h, the calcination temperature is in the range of 400-700℃, and the calcination time is in the range of 2-6h.

7. Spherical alumina prepared according to the production process according to any one of claims 1 to 6, characterized in that The purity is not less than 99.99wt%, the pore volume is not less than 0.60 mL / g, the pore size in the range of 15-25 nm accounts for not less than 90vol%, and the compressive strength is not less than 50 N / particle.

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