Stable alumina molded body and method for manufacturing an alumina molded body

Abstract

The present disclosure relates to calcined alumina compacts and methods for producing the calcined alumina compacts, which include hydrothermally aging alumina in an alumina suspension to achieve specific crystallite sizes, thereby further producing highly stable alumina in the form of calcined alumina compacts, particularly at temperatures above 1200°C.

Description

Technical Field

[0001] The present disclosure relates to a calcined product of an alumina formed body or a "calcined shaped alumina carrier" as used synonymously, and a method for producing a calcined product of a shaped alumina carrier / a calcined product of an alumina formed body.

Background Art

[0002] Activated alumina is widely used as a carrier for a number of heterogeneous catalyst applications. The above includes, on the one hand, applications in a fixed bed, also referred to as a packed bed, and on the other hand, applications in a moving bed or a fluidized bed. For applications in a fixed bed, it is important to prepare a catalyst that fills the layer uniformly in order to avoid channeling and temperature gradients. For applications in a fluidized bed and a moving bed, one important aspect is to prepare a stable and strong catalyst in order to avoid abrasion or disintegration of the catalyst particles due to collisions with the reactor wall or with each other. For some applications, shaping of alumina is effective. In particular, for fixed bed catalysts, a number of catalyst shapes have been proposed in the prior art in order to balance the impairment to catalyst activity and the pressure drop across the catalyst layer.

[0003] As used herein, "shaping" refers to a process and method of aggregating particles into a larger formed body, preferably such that part of the formed body becomes regular, and the meaning of "shaped" corresponds to the above. After such shaping, it is necessary to then calcine the formed body in order to provide strength and fix the formed body. Thus, those skilled in the art of the present disclosure will understand that the calcined product of an alumina formed body / the calcined product of a shaped alumina carrier means, for example, spheres of alumina preferably formed in a forming tube, extruded products of alumina, and tablets of alumina.

[0004] Patent Document 1 provides a process for preparing spherical alumina from boehmite alumina. The spheres obtained by the disclosed method have a diameter of 2-3 mm, a crushing strength per sphere of 200 N, a pore volume of 0.45-0.75 ml / g, and a surface area of ​​220-250 m². 2 It is stated that it is / g. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] U.S. Patent No. 4542113 [Overview of the project] [Problems that the invention aims to solve]

[0006] There is a need to improve the molded bodies of catalyst supports, which exhibit specific properties, particularly combinations of specific properties. [Means for solving the problem]

[0007] According to a first aspect of this disclosure, an alumina molded body or a ceramic / alumina carrier molded body or ceramic is provided. (a) The crushing strength is 30-70N, preferably 40-60N, and Characteristics (b) of monodisperse pore size distribution with a median pore radius of 5-12 nm, preferably 7-10 nm It is equipped with.

[0008] Preferably, the alumina molded body or the ceramic is Total pore volume is 0.4-1.2 cm³ 3 / g, preferably 0.7-1.0cm 3 The characteristic of being / g (c), The BET surface area is 10-100 m² after baking at 1200°C for 3 hours. 2 The ratio is / g, and preferably 40-80m after firing at 1200°C for 3 hours. 2 The characteristic of being / g (d), The characteristics (e) are that the content of Na impurities, Fe impurities, and Si impurities in the calcined alumina molded body is less than 100 ppm each, preferably less than 50 ppm each, and The characteristic (f) is that the α transition temperature exceeds 1200°C, preferably exceeding 1300°C. It further includes one or more of these, preferably all of them.

[0009] Preferably, a ceramic alumina molded body having properties (a) and (b) further has at least property (c).

[0010] The alumina molded body can be prepared by the method described later.

[0011] A further aspect of this disclosure provides a method for preparing a ceramic alumina molded body, the method being: (i) A step of preparing an alumina suspension containing alumina and at least water, (ii) A step of hydrothermally aging the alumina suspension until the crystallite sizes along the (120) axis and (020) axis of the alumina in the alumina suspension are 60 to 140 Å, respectively, to form a hydrothermally aged alumina suspension. (iii) A step of selectively drying the hydrothermally aged alumina suspension to obtain alumina powder, (iv) A step of selectively preparing either an alumina paste derived from alumina powder, or an alumina dispersion derived from alumina powder or a hydrothermally aged alumina suspension, (v) A step of forming an alumina molded body by molding alumina powder, alumina paste, alumina dispersion, hydrothermally aged alumina suspension, or a mixture thereof, (vi) A step of drying the alumina molded body to form a dried alumina molded body, (vii) A process of forming a calcined alumina molded body by drying the alumina molded body. Includes.

[0012] Since the alumina powder in step (iii) can be directly formed in step (v), step (iv) is optional. Since the hydrothermally aged alumina suspension in step (ii) can be directly used in step (iv) or (v), step (iii) is optional.

Advantages of the Invention

[0013] The calcined product of the alumina molded body is either the calcined product of the molded body of the alumina carrier or can be used as a carrier for heterogeneous catalyst applications.

Brief Description of the Drawings

[0014] Here, the present invention will be described with reference to non-limiting examples and drawings:

[0015] [Figure 1] Figure 1 shows the pore size distributions of Comparative Example 1 and Comparative Example 2 (Sample 1 and Sample 2), as well as Example 1 and Example 6 (Sample 3a and Sample 7). [Figure 2] Figure 2 shows the pore size distributions of Example 1 and Example 2 calcined at various temperatures. [Figure 3] Figure 3 shows the pore size distributions for Example 4 and Example 5 (Sample 5 and Sample 6) containing various dopants. [Figure 4] Figure 4 shows the DSC (Differential Scanning Calorimetry) - TG (Thermal Gravimetric) analysis of Comparative Example 1 and Example 1. [Figure 5] Figure 5 shows the X-ray diffraction of Comparative Example 2 and Example 1 after calcination at 1200°C for 3 hours. [Figure 6] Figure 6 shows the pore size distribution of Comparative Example 3.

Modes for Carrying Out the Invention

[0016] [Detailed Description of the Present Disclosure] The alumina molded product can preferably be in the form of a spherical body formed in a molded tube, an extruded product or a tablet, or a mixture thereof. The alumina molded product is preferably a spherical body, i.e., spherical alumina. In this disclosure, "spheroid" or "spheroidal" preferably means a spherical body with a sphericity of 0.9 or greater.

[0017] The process of forming spherical alumina in a molded tube relies on introducing an alumina-containing sol, solution, or other mixture into a liquid as droplets that will later be converted into spherical bodies. Numerous variations and improvements particularly applicable to the formation of spherical alumina particles are known to those skilled in the art and are described, for example, in Patent Document 1 and the cited art in that document. The disclosure of Patent Document 1 is incorporated herein by reference, in particular, regarding formation using a molded tube.

[0018] The maximum dimensions of alumina molded or fired alumina are 0.5 mm or more (for spheres, the maximum dimensions are, for example, the diameter). When alumina molded or fired alumina is in the form of spherical alumina, it can have the additional characteristic of having a diameter of 0.5 mm to 3.0 mm.

[0019] The diameter of the spherical alumina is determined by the ASTM D1155 standard.

[0020] A ceramic alumina molded body according to one embodiment has a monodispersed pore radius distribution. "Monodispersed pore radius distribution" refers to a pore radius distribution obtained by mercury intrusion (DIN 66133), in which only one overall maximum value is identified for radii in the range of 1 to 100 nm, and no maximum value is identified (i.e., the pore radius distribution is unimodal). The foregoing is one of the advantages of the present disclosure, as in the past, a maximum value of 2 was expected. The ceramic alumina molded body of the present disclosure has a median pore radius in the range of 5 to 12 nm, preferably 7 to 10 nm.

[0021] The total pore volume, resulting from the pore size distribution, is measured using the standard DIN 66133 (measurement of pore volume distribution and specific surface area of ​​solids by mercury intrusion).

[0022] It is well known that α-alumina can ultimately be obtained through thermal transitions of various phases of alumina when the temperature is increased. Typically, the final step in thermal transition is the phase transition from the θ phase to the α phase. The transition to the α phase is accompanied by a decrease in porosity and surface area, and the α-alumina powder produced by high-temperature calcination is usually about 5 m 2 Characterized by a low BET surface area per g.

[0023] The calcined alumina bodies of the present disclosure are characterized, according to one embodiment, by remarkable thermal stability, i.e., by thermal stability that resists a phase transition to the α phase and remains in the θ phase. Even if a phase transition to the α phase occurs, the calcined alumina bodies of the present disclosure are characterized by a larger surface area than expected for typical α-alumina. As used herein, the term “thermostability” means thermal stability against changes in the surface and / or crystalline phase that occur due to external influences induced by expected temperature changes, along with other external influences such as water, chemicals, pressure, and mechanical loads. For example, thermal stability can be characterized by a surface area determined by the BET method using nitrogen according to DIN ISO 9277, which is maintained after calcining a sample in a muffle furnace at 1200°C for more than 3 hours, or after calcining at 1300°C (heating rate of 1K to 10K per minute (K / min)) for more than 3 hours.

[0024] The alumina molded body may further contain dopants. The dopants preferably include rare earth elements, transition elements (groups 3 to 11 of the periodic table, particularly group 4 to 11, particularly group 4 (IVb in the old IUPAC numbering system) and group 5 (Vb in the old IUPAC numbering system)), as well as tin and bismuth. The content of the added dopant is 0 to 1 weight percent or greater than 0 and less than or equal to 1 weight percent, preferably 0 to 0.5 weight percent or greater than 0 and less than or equal to 0.5 weight percent, where the weight of the dopant is calculated as an element and the weight percentage is relative to the alumina molded body. Preferably, the alumina molded body contains transition elements, rare earth elements, and elements from group 4 (IVb in the old IUPAC numbering system) and group 5 (Vb in the old IUPAC numbering system) of the periodic table, and more preferably, organic and inorganic salts of Sn and Bi. Most preferably, the alumina molded body is calcined to which SnCl4 or Bi(NO3)3·5H2O is added.

[0025] Preferred embodiments of the method described herein are further defined as follows:

[0026] The alumina molded product can preferably be in the form of a spherical body formed in a molded tube, an extruded product or a tablet, or a mixture thereof. The maximum dimension of the alumina molded product is 0.5 mm or more (for spheres, the maximum dimension is, for example, the diameter). The alumina molded product is preferably a spherical body, i.e., spherical alumina.

[0027] The alumina suspension contains alumina and at least water. The alumina content in the alumina suspension, measured as Al2O3, is preferably 2 to 20 weight percent, more preferably 5 to 10 weight percent, of the alumina suspension. The alumina suspension is preferably obtained by hydrolysis of an alkoxide.

[0028] The alumina in the alumina suspension can include boehmite, gibbsite, byelite, and transition alumina (containing at least γ-alumina, δ-alumina, and θ-alumina), with boehmite being the most preferred. The alumina in boehmite can be obtained, for example, by hydrolysis of aluminum alkoxide in water.

[0029] The predetermined crystallite sizes along the (120) axis and (020) axis are obtained by hydrothermal aging of the alumina suspension, and the hydrothermal aged alumina suspension contains at least boehmite. The hydrothermal aging reaction is generally carried out at 60-300°C, preferably 80-180°C, for 1-30 hours, preferably 15-30 hours, under stirring.

[0030] Temperature and time are selected separately. The crystallite sizes along the (120) axis and (020) axis of the hydrothermally aged boehmite are preferably 70 to 110 Å, respectively. More preferably, the ratio of the crystallite size along the (120) axis to the crystallite size along the (020) axis of the hydrothermally aged boehmite is 0.5:1 to 2.0:1, and more preferably 0.9:1 to 1.1:1.

[0031] The alumina dispersion contains alumina and at least water. The alumina content in the alumina dispersion, measured as Al2O3, is 10 to 40 weight percent, preferably 25 to 35 weight percent.

[0032] The alumina dispersion preferably contains an acid. The usable acid can be an organic or inorganic acid, preferably nitric acid, acetic acid, formic acid, or a mixture thereof. The acid concentration in the alumina dispersion can be 0.1 to 1.5 weight percent, preferably 0.9 to 1.2 weight percent. The particle size of the alumina in the dispersion is preferably less than 1 μm, preferably less than 500 nm.

[0033] Furthermore, the alumina dispersion may contain hydrocarbons with a boiling point exceeding 250°C, particularly kerosene. The hydrocarbon content, especially kerosene, in the alumina dispersion can be 0 to 10 weight percent of the alumina dispersion, preferably 0 to 5 weight percent. "Kerosene" refers to a liquid mixture of branched-chain and unbranched-chain paraffins. Typical kerosene according to EINECS 232-384-2 has a specific gravity of 0.81 to 0.89 g / cm³. 3 Its boiling point exceeds 250°C.

[0034] Dopants can be added to alumina paste, alumina dispersion, hydrothermally aged alumina suspension, or mixtures thereof, before the process of molding to form an alumina molded body. Dopants preferably include rare earth elements, transition elements (periodic elements from groups 3 to 11, preferably from groups 4 to 11, especially group 4 (IVb in the old IUPAC numbering system) and group 5 (Vb in the old IUPAC numbering system)), as well as tin and bismuth. When dopants are added to an alumina dispersion, the alumina dispersion preferably contains 0 to 1 weight percent or more than 0 and 1 weight percent of dopant, preferably 0 to 0.5 weight percent or more than 0 and 0.5 weight percent of dopant, where the weight of the dopant is calculated as an element and the weight percentage is relative to the alumina molded body or ceramic.

[0035] Preferably, the alumina dispersion contains rare earth elements and transition elements, particularly elements from Group 4 (IVb in the old IUPAC numbering system) and Group 5 (Vb in the old IUPAC numbering system) of the periodic table, and more preferably, organic and inorganic salts of Sn and Bi. Most preferably, the alumina dispersion contains SnCl4 or Bi(NO3)3·5H2O. Tin and bismuth are generally included for catalytic purposes.

[0036] Alumina paste preferably contains alumina and an acid. The alumina content in the alumina paste, measured as Al2O3, can be 20 to 65 weight percent, preferably 40 to 60 weight percent. The acids that can be used are organic or inorganic acids, preferably nitric acid, acetic acid, formic acid, or mixtures thereof. The acid concentration in the alumina paste can be 0.1 to 4.0 weight percent, preferably 1.0 to 2.5 weight percent.

[0037] It is preferable to prepare an alumina dispersion from alumina powder.

[0038] The alumina molded articles of this disclosure are obtained by molding alumina powder, alumina paste, alumina dispersion, hydrothermally aged alumina suspension, or mixtures thereof using various techniques known in the art. For example, to prepare spherical bodies, an alumina dispersion is dropped into a molding tube in the form of droplets. To form extruded articles or tablets, alumina powder or alumina paste is extruded or pressed using techniques known in the art.

[0039] According to one embodiment of the present disclosure, the alumina molded article is preferably dried at a temperature of 90°C to 150°C, more preferably at 110°C to 130°C, and separately from the temperature, preferably using a standing oven or belt dryer, with a residence time of 2 to 24 hours. The above drying techniques are known to those skilled in the art of the present disclosure.

[0040] According to one embodiment of the present disclosure, the firing is carried out at a temperature of 450°C to 1100°C, preferably 550°C to 750°C, generally in a muffle furnace or kiln, with a residence time of 10 minutes to 10 hours, preferably 2 to 4 hours. The temperature and time are selected separately. [Examples]

[0041] 《Analysis Methods and Definitions》 The crystallite size of boehmite according to this disclosure is given by the general Scherrer formula: Crystallite size = (K × λ × 57.3) / (β × cosθ) It is determined along the (120) axis and the (020) axis using [this method].

[0042] In the above equation, K (formation factor) is 0.992, λ (X-ray wavelength) is 0.154 nm, β (correction value for linewidth expansion of the instrument) is reflection-dependent, and θ is also reflection-dependent.

[0043] The measurement was performed using Bruker's CubiX 3 The measurement is performed using a device. The measurement parameters for boehmite are θ=14 degrees for reflection along the (120) axis, θ=7 degrees for reflection along the (020) axis, and β=0.919 for both reflections.

[0044] The specific surface area provided herein is measured by the BET method using nitrogen according to DIN-ISO 9277.

[0045] Pore ​​volume (pore volume for pore radii up to 1000 Å) and pore size distribution are measured using mercury intrusion according to DIN 66133. The "median pore radius" is the radius corresponding to the 50th percentile of pore volume, that is, the radius at which half of the pore volume is found to be in the larger pores and half of the pore volume is found to be in the smaller pores.

[0046] The diameter of a spherical alumina is determined by ASTM D1155.

[0047] Crushing strength is determined according to ASTM D6175 for extruded products and ASTM D4179 for other shapes.

[0048] The DSC is determined by DIN 51007.

[0049] As described in ISO 13322-2 (2006), sphericity is determined by dynamic image analysis using Retsch's Camsizer P4. Sphericity (SPHT3) is calculated from the measured values ​​of the perimeter P and area A of the particle projection using the following formula.

[0050]

number

[0051] The determined value is dimensionless, being 1 for an ideal sphere and generally less than 1 for spherical particles that are not ideal spheres. In this case, the sphericity is greater than 0.9.

[0052] The above procedure was followed precisely as outlined in the prescribed method.

[0053] The particle size is determined using Mie theory and laser diffraction (Malvern's Mastersizer 2000).

[0054] Preparation of hydrothermally aged samples [Sample A] The hydrolysis of aluminum hexanolate was carried out at 98°C in a 2% aqueous solution of ammonium bicarbonate. The resulting alumina suspension (=boehmite suspension) containing 7.5 wt% Al2O3 was stirred at 105°C for 18 hours at a stirring speed of 3.2 m / s.

[0055] The matured alumina suspension was dried in a spray dryer (inlet temperature: 120°C). Boehmite powder was obtained with a crystallite size of 101 Å along the (120) axis and 104 Å along the (020) axis.

[0056] [Sample B] The hydrolysis of aluminum hexanolate was carried out at 98°C in a 2% aqueous solution of ammonium bicarbonate. The obtained alumina suspension (=boehmite suspension), containing 7.5 wt% alumina calculated as Al2O3, was stirred at 100°C for 16 hours at a stirring speed of 3.2 m / s. The matured alumina suspension was dried in a spray dryer (inlet temperature: 120°C). Boehmite powder was obtained with a crystallite size of 94 Å along the (120) axis and a crystallite size of 93 Å along the (020) axis.

[0057] "experiment" [Example 1] Sample 3a The alumina dispersion was prepared by dispersing boehmite from sample A in acidic water. The dispersion contained 32.5 wt percent boehmite, calculated as Al2O3, and 0.03 g of nitric acid per g of boehmite. After stirring for 10 minutes, the sol was supplied in droplet form to a molded tube according to Patent Document 1 at a temperature of 20°C to 25°C, and filled with an 8 wt percent ammonia solution. The unprocessed spherical bodies released from the molded tube were dried at 120°C until a certain weight was obtained. The dried spherical bodies were calcined at 650°C for 3 hours.

[0058] [Example 2] Sample 3b Example 2 was carried out in the same manner as Example 1, but the dried spherical body was baked at 950°C for 3 hours.

[0059] [Example 3] Sample 4 Example 3 was carried out in the same manner as Example 1, but the initial alumina, which is boehmite, is sample B.

[0060] [Example 4] Sample 5 Example 4 was carried out in the same manner as Example 3, but in addition to boehmite, water, and acid, the dispersion contained a dopant, SnCl4·2H2O, which was calculated as SnO2 and corresponds to 0.4 weight percent of Sn based on the alumina spheres or calcined material.

[0061] [Example 5] Sample 6 Example 5 was carried out in the same manner as Example 3, but in addition to boehmite, water, and acid, the dispersion contained a dopant called Bi(NO3)3·5H2O, which was calculated as Bi2O3 and corresponds to 0.1 weight percent Bi based on the calcined alumina spheres.

[0062] [Example 6] Sample 7 Example 6 was carried out in the same manner as Example 3, but in addition to boehmite, water, and acid, the dispersion contained 0.1 g of kerosene per g of boehmite.

[0063] [Example 7] Sample 8 (Extruded product) Alumina paste was prepared by mixing 1500 g of sample B with 1250 g of 4 wt percent acetic acid in a high-shear stirrer for 15 minutes. The paste was pressed onto a hole disk to obtain an extruded product with a diameter of 1.69 mm. The unprocessed product was dried at 120°C until it reached a certain weight. The dried extruded product was baked at 650°C for 3 hours.

[0064] [Example 8] Sample 9 (tablet) Tablets (5.1 × 5.2 mm) were pressed using boehmite powder of sample B by a process known in the art, and then baked at 650°C for 3 hours.

[0065] [Comparative Example 1] Sample 1 (without kerosene) An alumina dispersion was prepared by mixing boehmite powder, which had a crystallite size of 38 Å along the (120) axis and a crystallite size of 30 Å along the (020) axis, in acidic water without a maturation step. The dispersion contained 32.5 wt percent solids per gram of boehmite and 0.03 g of nitric acid. After stirring for 10 minutes, the sol was supplied in droplet form to a molded tube at a temperature of 20°C to 25°C and filled with an 8 wt percent ammonia solution. The raw spherical bodies released from the molded tube were dried at 120°C until their weight was constant. The dried spherical bodies were calcined at 650°C for 3 hours.

[0066] [Comparative Example 2] Sample 2 (with kerosene) Comparative Example 2 was conducted in the same manner as Comparative Example 1, but in addition to boehmite, water, and acid, the dispersion contained 0.1 g of kerosene per g of boehmite.

[0067] The examples and summaries of Comparative Examples 1 and 2, including the results, are included in Table 1 below.

[0068] Figure 1 compares the pore size distributions of Comparative Example 1 (Sample 1) and Comparative Example 2 (Sample 2), as well as Example 1 (Sample 3a) and Example 6 (Sample 7). Figure 1 clearly shows that the median pore radius of Comparative Example 1 is less than the median pore radius of the examples in this disclosure. Figure 2 shows the pore size distributions of Example 1 and Example 2, which use the same initial material but are calcined at different temperatures. Figure 3 shows the pore size distributions of Example 4 and Example 5 (Sample 5 and Sample 6), which use different dopants. Figure 4 shows the DSC (Differential Scanning Calorimetry) curves indicating the phase transition of alumina in Comparative Example 1 (Sample 1) and Example 1 (Sample 3a). As shown, Comparative Example 1 (Sample 1) is characterized by a phase transition to the α phase at 1188.6°C, while Example 1 (Sample 3a) prepared according to this disclosure exhibits a phase transition to the α phase at 1314°C. The phase transition to the α phase is accompanied by a decrease in surface area. Figure 5 shows a comparison of Comparative Example 2 (Sample 2) and Example 1 (Sample 3a) after being baked at 1200°C for 3 hours. Comparative Example 2 shows the α phase, while Example 2 shows only the θ phase.

[0069] [Table 1]

[0070] [Comparative Example 3] (Example 5 of Patent Document 1) Comparative Example 3 was prepared by reproducing Example 5 of Patent Document 1. The exact same experimental procedure was used. The raw materials were a mixture of two boehmite with the following properties.

[0071] [Table 2]

[0072] Comparing the material properties of the resulting product with those reported in Example 5 of Patent Document 1, it can be concluded that the remanufactured product is typical (see Table 3).

[0073] [Table 3]

[0074] Figure 6 shows the pore size distribution of Comparative Example 3. The median pore size measurement was 4.9 nm, and the pore size distribution is bimodal.

Claims

1. (a) The characteristic of having a crushing strength of 30 to 70 N, Characteristics of a monodisperse pore size distribution with a median pore radius of 5–12 nm (b) Equipped with A ceramic product made from alumina, The alumina molded body is fired, It is in the form of a spherical body with a sphericity of 0.9 or greater, an extruded product or a tablet, or a mixture thereof. Alumina molded material or ceramic.

2. Total pore volume is 0.4–1.2 cm ３ If it is / g, then the characteristic (c) The BET surface area is 10 to 100 m² after firing at 1200°C for 3 hours. ２ The characteristic (d) is that it is / g. The characteristic (e) that the content of Na impurities, Fe impurities, and Si impurities in the calcined alumina molded body is each less than 100 ppm, and The characteristic of having an α-transition temperature exceeding 1200°C (f) It further comprises one or more of the following: A ceramic alumina molded body according to claim 1.

3. It possesses characteristic (c). A ceramic alumina molded body according to claim 2.

4. The alumina molded body is in the form of a spherical body with a sphericity of more than 0.

9. A ceramic alumina molded body according to any one of claims 1 to 3.

5. The alumina molded body is spherical in shape, and the spherical body has a diameter of 0.5 mm to 3.0 mm. A ceramic alumina molded body according to any one of claims 1 to 4.

6. comprising one or more dopants selected from the group consisting of tin, bismuth, transition elements, and rare earth elements. A ceramic alumina molded body according to any one of claims 1 to 5.

7. A method for preparing a ceramic product from an alumina molded body, (i) A step of preparing an alumina suspension containing alumina and at least water, (ii) A step of hydrothermating the alumina suspension until the crystallite sizes along the (120) axis and (020) axis of the alumina in the alumina suspension are 70 to 110 Å, respectively, to form a hydrothermally aged alumina suspension. (iii) A step of selectively drying the hydrothermally aged alumina suspension to obtain alumina powder, (iv) A step of selectively preparing either an alumina paste derived from the alumina powder, or an alumina dispersion derived from the alumina powder or the hydrothermally aged alumina suspension, (v) A step of forming an alumina molded body by molding the alumina powder, the alumina paste, the alumina dispersion, the hydrothermally aged alumina suspension, or a mixture thereof, (vi) A step of drying the alumina molded body to form a dried alumina molded body, (vii) A step of performing a calcination of the dried alumina molded body to form a calcined alumina molded body. Includes, The alumina molded body is fired, It is in the form of a spherical body with a sphericity of 0.9 or greater, an extruded product or a tablet, or a mixture thereof. method.

8. The alumina molded body is in the form of a spherical body with a sphericity of more than 0.

9. The method according to claim 7.

9. Al ２ O ３ The alumina content in the alumina suspension calculated as follows is 2 to 20 weight percent. The method according to claim 7 or 8.

10. Al ２ O ３ The alumina content in the alumina dispersion, calculated as follows, is 10 to 40 weight percent. The method according to any one of claims 7 to 9.

11. The alumina dispersion contains an acid The method according to any one of claims 7 to 10.

12. The alumina dispersion contains kerosene, The kerosene content in the alumina dispersion is 0 to 10 weight percent of the alumina dispersion. The method according to any one of claims 7 to 11.

13. Prior to the step of forming the alumina molded body by molding, one or more dopants are added to the alumina paste, the alumina dispersion, the hydrothermally aged alumina suspension, or a mixture thereof, and the one or more dopants are selected from the group consisting of tin, bismuth, transition elements, and rare earth elements. The method according to any one of claims 7 to 12.

14. The alumina in the alumina suspension is boehmite, gibbsite, byelite, and one or more transition aluminas. The method according to any one of claims 7 to 13.

15. The alumina suspension after hydrothermal aging contains or consists of boehmite. The method according to any one of claims 7 to 14.

16. The ratio of crystallite size along the (120) axis to crystallite size along the (020) axis of boehmite after hydrothermal aging is 0.5:1 to 2.0:

1. The method according to claim 14 or 15.

17. The aforementioned hydrothermal aging reaction is carried out at a temperature of 60°C to 300°C for 1 to 30 hours. The method according to any one of claims 7 to 16.

18. The alumina molded body is dried at a temperature of 90°C to 150°C for 2 to 24 hours. The method according to any one of claims 7 to 17.

19. The aforementioned baking process is carried out at a temperature of 450°C to 1100°C for 10 minutes to 10 hours. The method according to any one of claims 7 to 18.

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