Preparation method of millimeter-scale alumina spherical carrier

Abstract

The invention discloses a preparation method of a millimeter-scale alumina spherical carrier, which comprises the following steps: carrying out oil column molding on molding sol to obtain the spherical carrier, and adding basic aluminum chloride sol and an alumina seed crystal solution in the preparation process of the molding sol, the mass of the alumina seed crystal solution accounts for 0.1-15% of the mass of the basic aluminum chloride sol. According to the preparation method of the millimeter-scale alumina spherical carrier, the hydrothermal stability of the carrier is improved, and the shrinkage rate of the obtained alumina carrier is higher.

Description

Technical Field

[0001] The invention belongs to the field of preparation of inorganic catalytic materials, and particularly relates to an oil column forming preparation method of spherical alumina with high hydrothermal stability. Background Art

[0002] As a catalyst and catalyst carrier, the shape of Al2O3 has a great influence on the catalyst reaction. Commonly used Al2O3 shapes include spheres, strips and clover-shaped. With the continuous advancement of the industrialization process of the moving bed process, spherical alumina carriers are widely used in moving bed reactors due to their good sphericity, smooth surface and high strength, and the demand is also increasing. At present, there are many studies on the preparation methods of millimeter-sized alumina ball carriers for fluidized beds at home and abroad. The main methods used are hot oil column method, oil ammonia column method and water column method.

[0003] The aluminum sol hot oil column molding method for preparing spherical alumina was first seen in patent US2620314. Aluminum sol is prepared by reacting metallic aluminum and hydrochloric acid solution. The sol is mixed with hexamethylenetetramine solution and molded in a hot oil column device. Spherical alumina is obtained by pressurized aging in an oil bath, water washing, drying, roasting, and steam expansion treatment. Many steps are required, and each step takes a long time. Hydrochloric acid seriously corrodes the equipment. At the same time, the hydrothermal stability of the obtained alumina balls is low.

[0004] The method disclosed in US4399119 includes reacting hydrochloric acid and gibbsite under high temperature and high pressure to obtain a basic aluminum chloride aqueous solution, supplementing part of aluminum to adjust the aluminum content in the sol, adding ammonia water to form an aluminum chloride aqueous sol containing ammonium chloride, mixing the sol with a gelling agent that can be decomposed during the heating process, forming through hot oil column, aging, water washing, drying, and roasting to form spherical alumina. The use of hydrochloric acid to digest metal aluminum or gibbsite needs to be carried out under high temperature and high pressure, which seriously corrodes the equipment, has a high impurity content in the raw materials, and takes a long time to age after forming, pressurized aging, and water washing.

[0005] Mitsche et al. prepared a 1.40 g·mL -1 The mass percentage of Al is 14.2% and the molar ratio of Al / Cl is 1.15. After forming and aging, a specific surface area of ​​421m 2 ·g -1 , pore volume is 0.32 mL·g -1 , spherical alumina particles with an average pore size of 3nm.

[0006] Moser et al. used an oil column with a length of 1.5 m as the experimental platform to investigate the effects of molding oils with different viscosities on the molding and morphology of spherical alumina. At 90 ° C, when the viscosity of the molding oil ranged from 80 to 150 mm 2 ·s-1 When the viscosity of the molding oil is low, the droplets fall in the oil column in a uniform spherical shape, and the molding effect is good. When the molding oil viscosity is low, the droplets fall quickly in the oil column, making it difficult to mold. When the molding oil viscosity is high, the droplets fall slowly in the oil column, which easily causes adhesion between the droplets, and the morphology of the resulting spherical gel particles is poor.

[0007] In CN114180607A disclosed by the team of Professor Li Dianqing of Beijing University of Chemical Technology, a spherical alumina with a flower cluster-like lamellar structure on the surface and a preparation method thereof are reported, which is characterized in that a long-chain compound containing a large number of hydroxyl and carboxyl groups is added during the preparation of the molding sol to modify the pore structure of the spherical alumina. During the molding process, the carbonyl and hydroxyl groups will form hydrogen bonds with the Al-OH in the aluminum sol, guiding the surface to form a lamellar structure, and preparing a spherical alumina with a flower cluster-like lamellar structure; at the same time, key technologies such as magnetic separation-process reduction and iron removal of aluminum sol, micro-flow injection molding, spray dispersion-oil column molding, etc. are developed, which can control the preparation of spherical alumina-based carrier materials with a particle size range of 0.1-3.0 mm. However, the long-chain compound containing a large number of hydroxyl and carboxyl groups introduced in this technology is an organic compound, which is decomposed in the subsequent high-temperature roasting process. Although it can increase the specific surface area and pore volume of the spherical alumina, it cannot improve its hydrothermal stability.

[0008] CN114180608A of the Petrochemical Research Institute of Sinopec Corporation discloses a method for preparing alumina pellets, including adding an acid solution to an alumina suspension to obtain an alumina sol, adding a water-soluble organic polymer monomer and a cross-linking agent to the alumina sol to prepare a mixture, and dripping the mixture into a hot oil column to form pellets. The method solidifies the alumina pellets by polymerizing the organic polymer monomer, and does not use hexamethylenetetramine as a gelling agent.

[0009] CN111792659A of Liming Chemical Research and Design Institute discloses a method for preparing spherical alumina by oil column forming process, characterized in that one or more of pseudo-boehmite powder and activated carbon are added to the aluminum sol to obtain spherical alumina with a bulk density of ≤0.45g / cm 3 , the average compressive strength is ≥40N. It was found in practice that when adding pseudo-boehmite powder to aluminum sol, the powder and aluminum sol are easily agglomerated into small particles and the material uniformity is poor. In the subsequent hot oil column forming process, when the material is dripped into the forming oil column through the dispersion dropper, the needle is seriously blocked, the forming efficiency is low, and the particle sphericity is poor.

[0010] CN1048229C of Tianjin Chemical Research Institute of the Ministry of Chemical Industry discloses a process for preparing low-density, large-pore-volume spherical alumina, characterized in that aluminum salt and aluminate are used as raw materials, firstly, large-grain pseudo-boehmite seeds are prepared at 60-80°C and pH 7-9, and then aluminum salt and aluminate are added in parallel to neutralize to generate alumina hydrate mainly composed of pseudo-boehmite. When the ratio of the amount of alumina in the prepared seeds to the amount of all alumina in the final neutralized product is controlled within the range of 0.05-0.45, the prepared spherical alumina has a large pore volume and a small bulk density. This technology first prepares large-grained pseudo-boehmite seeds with the reaction raw materials aluminum salt and aluminate under specific conditions, and then continues to carry out neutralization reaction with the aluminum salt and aluminate. The characteristics of the seeds are the same as the raw material composition of the neutralization reaction, but the reaction conditions are different, and there is no need to undergo pressurized aging, water washing, steam pore expansion treatment and other processes. It is particularly suitable as a carrier for immobilized enzymes. When used in high-temperature and high-pressure scenarios such as petrochemicals that require frequent regeneration treatments, it is prone to pore structure collapse and loss and insufficient hydrothermal stability.

[0011] In recent years, the application fields of spherical alumina prepared by the oil column forming method as a catalyst or catalyst carrier have been continuously expanded, involving petrochemical industry, fine chemical industry and coal chemical industry, etc., providing a broad development space for the technical system of preparing spherical alumina by the oil column forming method.

[0012] The oil column molding method is to prepare spherical alumina by reacting industrial-grade hydrochloric acid with aluminum powder to synthesize basic aluminum chloride sol, remove solid impurities in the aluminum sol, and fully mix it with a gelling agent hexamethylenetetramine solution. The mixed sol is dripped into a hot oil column at a temperature of 95-98°C to form it, and then aged, washed, dried, and roasted to obtain spherical alumina. The oil column molding method is used to prepare spherical alumina, and its application fields as catalysts or catalyst carriers are constantly expanding, involving petrochemicals, fine chemicals, and coal chemicals. The carrier has high sphericity, good strength, and low wear rate. The disadvantage is that the hydrothermal stability is low. Under high-temperature hydrothermal treatment conditions, the specific surface area decays rapidly, thereby affecting the high dispersion of active components and deteriorating the catalytic performance.

[0013] Compared with the oil column forming method, the oil-ammonia column forming method is a method improved and developed on the oil column forming device. This method uses pseudo-boehmite as the aluminum source and ammonia water as the coagulant. First, dilute acid (nitric acid, acetic acid, etc.) is used as a peptizing agent to react with the pseudo-boehmite precursor to prepare a sol with good fluidity. Then the sol is dripped into the oil-ammonia column with oil as the upper layer and ammonia water of a certain concentration as the lower layer through a dispersed dripper. A neutralization reaction occurs behind the ammonia water layer and the gel is quickly solidified to form gel balls. The spherical alumina prepared by the oil-ammonia column method has low cost and short time, and maintains the properties of the pseudo-boehmite raw powder, so it has high hydrothermal stability; the disadvantage is that the ammonia water accelerates the coagulation speed quickly, resulting in slightly poor sphericity and slightly higher wear rate.

[0014] In summary, it is necessary to provide a method for preparing spherical alumina by an oil column molding process to solve the problems existing in the prior art. Summary of the invention

[0015] The purpose of the present invention is to solve the problems of poor hydrothermal stability of spherical alumina carriers obtained by the existing oil column molding technology route and large specific surface area loss during repeated regeneration, and to form a spherical alumina carrier preparation technology with high hydrothermal stability, good sphericity and high particle strength.

[0016] To achieve the above object, the present invention provides a method for preparing a millimeter-level alumina spherical carrier, the preparation method comprising:

[0017] The spherical carrier is obtained by subjecting the forming sol to oil column forming. The forming sol comprises basic aluminum chloride sol and aluminum oxide seed solution. The mass of the aluminum oxide seed solution accounts for 0.1% to 15% of the mass of the basic aluminum chloride sol.

[0018] In the method for preparing the millimeter-level alumina spherical carrier of the present invention, the mass of the alumina seed solution accounts for 0.8% to 13% of the mass of the basic aluminum chloride sol.

[0019] The method for preparing the millimeter-level alumina spherical carrier of the present invention comprises the following steps of preparing the forming sol:

[0020] The alumina seed solution is dropped into the basic aluminum chloride sol and then a coagulant is added to obtain a formed sol.

[0021] The method for preparing the millimeter-level alumina spherical carrier of the present invention comprises the following steps of preparing the basic aluminum chloride sol:

[0022] Aqueous hydrochloric acid solution is added to aluminum powder to react to obtain basic aluminum chloride sol.

[0023] The preparation method of the millimeter-level alumina spherical carrier of the present invention, the purity of the aluminum powder is ≥99%, and the particle size is 100μm-350μm;

[0024] The concentration of the hydrochloric acid aqueous solution is 12wt%-25wt%; the Al / Cl mass ratio in the reaction solution is controlled to be 0.4-2.5;

[0025] The reaction temperature is 80°C-100°C, and the reaction time is 2h-6h.

[0026] The method for preparing the millimeter-level alumina spherical carrier of the present invention comprises the following steps of preparing the alumina seed solution:

[0027] The pseudo-boehmite powder is dissolved in deionized water and stirred to obtain a suspension solution; a nitric acid aqueous solution is added thereto and ultrasonic treatment is performed to form a uniformly dispersed aluminum oxide seed solution.

[0028] The method for preparing the millimeter-level alumina spherical carrier of the present invention comprises the following steps: the particle size of the pseudo-boehmite powder is 150 μm-300 μm, and the peptization index of the pseudo-boehmite powder is ≥97%.

[0029] The pseudo-boehmite is at least one of SB powder, TM70 powder, and high-purity low-sodium aluminum hydroxide;

[0030] The concentration of the nitric acid aqueous solution is 10wt%-30wt%; the mass ratio of Al / NO3 in the alumina seed solution is controlled to be 0.1-5;

[0031] The ultrasonic treatment time is 1-10 min.

[0032] The method for preparing the millimeter-level alumina spherical carrier of the present invention, the mass fraction of the coagulant is 25%-45%; the coagulant accounts for 15%-30% of the total mass of the formed sol;

[0033] The coagulant is at least one of urea and hexamethylenetetramine aqueous solution, preferably a hexamethylenetetramine aqueous solution with a mass fraction of 25%-45%;

[0034] The molding sol of the present invention is prepared in a reactor with stirring and cold bath circulation, the temperature of the material in the reactor is 0-10°C, the stirring speed is 200r / min-400r / min, and the stirring time is 20min-40min.

[0035] The method for preparing the millimeter-level alumina spherical carrier of the present invention comprises the following steps of preparing the shaped sol by oil column shaping:

[0036] The forming sol is transported to the disperser through a peristaltic pump, and then dripped into the forming column through a dispersing dripper. The formed balls are collected at the bottom of the hot oil column and then transferred to an aging kettle for aging. After washing, drying and roasting, alumina balls are obtained.

[0037] The method for preparing the millimeter-level alumina spherical carrier of the present invention, the molding column is a jacketed molding column, and the jacket is heated in a water bath or an oil bath;

[0038] The dispersing dripper drips into the hot oil of the forming column, and the temperature of the hot oil is 80°C-100°C;

[0039] The hot oil is at least one of vacuum pump oil, paraffin oil and mineral oil;

[0040] The disperser is a needle-type disperser, and the needle is a single needle or multiple needles.

[0041] The preparation method of the millimeter-level alumina spherical carrier of the present invention, the aging temperature is 120° C.-150° C., the pressure is 0.5 MPa-1.0 MPa, and the time is 2 h-6 h;

[0042] The drying temperature is 60°C-120°C;

[0043] The calcination temperature is 500°C-1000°C and the calcination time is 4h-8h;

[0044] The particle size of the alumina spheres is 0.1 mm to 5 mm.

[0045] The invention discloses a method for preparing a millimeter-level alumina spherical carrier. The aluminum source in the aluminum sol comprises two parts, one part is a basic aluminum chloride sol, and the other part is an alumina seed solution. The alumina seed solution has excellent peptizing performance and strong adhesion. The alumina seed solution is introduced into the basic aluminum chloride sol, and the alumina seed solution maintains the characteristics of pseudo-boehmite raw powder and is spherical particles with narrow particle distribution. The surface hydroxyl groups of the alumina seed solution interact with Al-OH in the basic aluminum chloride sol to form hydrogen bonds, and the shrinkage degree of the particles increases during drying and roasting, and the chemical bond strength between species is enhanced, which effectively inhibits the high-temperature sintering and phase change of alumina. In terms of microscopic size, the particles are more evenly distributed, and the arrangement and bonding between the particles are tighter, thereby inhibiting the shrinkage and sintering between Al-OH under the action of high-temperature water vapor, improving the hydrothermal stability of the carrier, and obtaining a higher shrinkage rate of the alumina carrier.

[0046] The millimeter-sized alumina spherical carrier obtained by the preparation method of the present invention is mainly used as an industrial catalyst carrier or adsorbent, and is suitable for fixed bed processes and moving bed processes. When used in high temperature, high pressure, and frequent regeneration scenarios, the pore structure is not easily lost and the hydrothermal stability is good. The millimeter-sized alumina spherical carrier obtained by the preparation method of the present invention can be controlled within 5% for 24 hours of specific surface area attenuation in a fixed bed reactor at a temperature of 600°C-700°C and a water content of 8wt%-15wt%. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is the SEM image of the alumina seed crystal of Example 1, with a magnification of 1000.

[0048] Figure 2 This is the SEM image of the alumina seed crystal of Example 1: magnification 10000.

[0049] Figure 3This is the SEM image of the sample of Comparative Example 1 without the introduction of alumina seed crystals: magnification 10000.

[0050] Figure 4 This is the SEM image of the sample with introduced alumina seed crystals in Example 1: magnification 10,000. DETAILED DESCRIPTION

[0051] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Obviously, the embodiments specifically described below are only part of the embodiments of the present invention, not all of the embodiments, so the present invention is not limited to the following description.

[0052] Example 1

[0053] (1) Preparation of basic aluminum chloride sol

[0054] Weigh 100 g of aluminum powder with a purity of ≥99% and a size of 100 μm-200 μm, slowly add 1125 g of a 15 wt% aqueous hydrochloric acid solution (Al / Cl=0.8), control the reaction temperature to 98°C for heating and dissolving, condense and reflux for 4 hours to obtain basic aluminum chloride sol.

[0055] (2) Preparation of alumina seed solution

[0056] Weigh 2 g of pseudo-boehmite (peptization index 99%) with a particle size of 150 μm-200 μm, dissolve it in 10 g of deionized water, stir to obtain a suspension solution, add 10 g of a 10 wt% nitric acid aqueous solution (Al / NO3=1.5) thereto, and ultrasonically treat for 5 minutes to form a uniformly dispersed alumina seed solution.

[0057] (3) Preparation of molding sol

[0058] The basic aluminum chloride sol in step (1) is added into a reactor with stirring and cold bath circulation, the material temperature is controlled at 5°C, the stirring speed is 300r / min, the aluminum oxide seed solution in step (2) is added dropwise, the mass of the aluminum oxide seed solution accounts for 1.8% of the mass of the basic aluminum chloride sol, and stirred for 20 minutes; then 267 grams of a 40% by mass hexamethylenetetramine aqueous solution (coagulant) is added to the above solution, and the coagulant is controlled to account for 17.5% of the total mass of the molding sol to obtain a molding sol.

[0059] (4) Preparation of spherical carrier by oil column molding

[0060] The formed sol obtained in step (3) was transported to a disperser via a peristaltic pump, and then dripped into 95°C vacuum pump oil via a dispersing dropper (diameter 0.8 mm), and the formed balls were collected at the bottom of the hot oil column, and then transferred to an aging kettle, and aged for 6 hours at 150°C and 0.5 MPa to obtain alumina balls; after washing, the sol was dried at 60°C for 4 hours, then heated to 100°C for drying for 4 hours, and calcined at 600°C for 4 hours to obtain alumina balls with a particle size of 1.5 mm-2 mm. The physical and chemical properties test results are shown in Table 1.

[0061] Example 2

[0062] (1) Preparation of basic aluminum chloride sol

[0063] Weigh 50 grams of aluminum powder with a purity of ≥99% and a size of 100 μm-200 μm, add it to 1125 grams of a 15 wt% aqueous hydrochloric acid solution (Al / Cl=0.4), heat to dissolve at a controlled temperature of 95°C, and condense and reflux for 6 hours to obtain basic aluminum chloride sol.

[0064] (2) Preparation of alumina seed solution

[0065] Weigh 2 g of pseudo-boehmite (peptization index 98%) with a particle size of 200 μm-300 μm, dissolve it in 21 g of deionized water, stir to obtain a suspension solution, add 147 g of a 10 wt% nitric acid aqueous solution ((Al / NO3=0.1)) thereto, and ultrasonically treat for 5 minutes to form a uniformly dispersed alumina seed solution.

[0066] (3) Preparation of molding sol

[0067] The basic aluminum chloride sol in step (1) is added into a reactor with stirring and cold bath circulation, the material temperature is controlled at 10° C., the stirring speed is 200 r / min, and the aluminum oxide seed solution in step (2) is dripped in, the mass of the aluminum oxide seed solution accounts for 12.6% of the mass of the basic aluminum chloride sol, and stirred for 20 minutes; then 336 grams of a 40% hexamethylenetetramine aqueous solution (coagulant) is added to the above solution, and the coagulant is controlled to account for 20% of the total mass of the molding sol to obtain a molding sol.

[0068] (4) Preparation of spherical carrier by oil column molding

[0069] The formed sol obtained in step (3) was transported to a disperser via a peristaltic pump, and then dripped into 100°C vacuum pump oil via a dispersing dripper (diameter 0.8 mm), and the formed balls were collected at the bottom of the hot oil column, and then transferred to an aging kettle, and aged for 3 hours at 120°C and 0.8 MPa to obtain alumina balls; after washing, the sol was dried at 80°C for 4 hours, then heated to 110°C for 4 hours, and calcined at 600°C for 4 hours to obtain alumina balls with a particle size of 1.5 mm-2 mm. The physical and chemical properties test results are shown in Table 1.

[0070] Example 3

[0071] (1) Preparation of basic aluminum chloride sol

[0072] Weigh 50 grams of aluminum powder with a purity of ≥99% and a size of 100 μm-200 μm, add it to 108 grams of a 25 wt% aqueous hydrochloric acid solution (Al / Cl=2.5), heat to dissolve at a controlled temperature of 85°C, condense and reflux for 6 hours to obtain basic aluminum chloride sol.

[0073] (2) Preparation of alumina seed solution

[0074] Weigh 2 g of pseudo-boehmite (peptization index 97%) with a particle size of 250 μm-300 μm, dissolve it in 21 g of deionized water, stir to obtain a suspension solution, add 2.9 g of a 10 wt% nitric acid aqueous solution ((Al / NO3=5)) thereto, and ultrasonically treat for 1 min to form a uniformly dispersed alumina seed solution.

[0075] (3) Preparation of molding sol

[0076] The basic aluminum chloride sol in step (1) is added into a reactor with stirring and cold bath circulation, the material temperature is controlled at 2°C, the stirring speed is 300r / min, the aluminum oxide seed solution in step (2) is added dropwise, the mass of the aluminum oxide seed solution accounts for 14% of the mass of the basic aluminum chloride sol, and stirred for 20 minutes; then 28 grams of a 40% by mass hexamethylenetetramine aqueous solution (coagulant) is added to the above solution, and the coagulant is controlled to account for 15% of the total mass of the molding sol to obtain a molding sol.

[0077] (4) Preparation of spherical carrier by oil column molding

[0078] The formed sol obtained in step (3) was transported to a disperser via a peristaltic pump, and then dripped into 90°C vacuum pump oil via a dispersing dripper (diameter 0.8 mm), and the formed balls were collected at the bottom of the hot oil column, and then transferred to an aging kettle, and aged for 4 hours at 140°C and 0.7 MPa to obtain alumina balls; after washing, the sol was dried at 60°C for 2 hours, then heated to 100°C for drying for 4 hours, and calcined at 600°C for 4 hours to obtain alumina balls with a particle size of 1.5 mm-2 mm. The results of the physical and chemical properties test are shown in Table 1.

[0079] Example 4

[0080] (1) Preparation of basic aluminum chloride sol

[0081] Weigh 100 g of aluminum powder with a purity of ≥99% and a size of 100 μm-200 μm, add it to 601 g of a 15 wt% aqueous hydrochloric acid solution (Al / Cl=1.5), heat to dissolve at a controlled temperature of 98°C, condense and reflux for 2 hours to obtain basic aluminum chloride sol.

[0082] (2) Preparation of alumina seed solution

[0083] Weigh 2 g of pseudo-boehmite (peptization index 98%) with a particle size of 150 μm-250 μm, dissolve it in 50 g of deionized water, stir to obtain a suspension solution, add 3.7 g of 20 wt% nitric acid aqueous solution (Al / NO3=2) thereto, and ultrasonically treat for 10 minutes to form a uniformly dispersed alumina seed solution.

[0084] (3) Preparation of molding sol

[0085] The basic aluminum chloride sol in step (1) is added into a reactor with stirring and cold bath circulation, the material temperature is controlled at 8°C, the stirring speed is 300r / min, the aluminum oxide seed solution in step (2) is added dropwise, the mass of the aluminum oxide seed solution accounts for 7.4% of the mass of the basic aluminum chloride sol, and stirred for 30 minutes; then 289 grams of a 45% by mass hexamethylenetetramine aqueous solution (coagulant) is added to the above solution, and the coagulant is controlled to account for 25% of the total mass of the molding sol to obtain a molding sol.

[0086] (4) Preparation of spherical carrier by oil column molding

[0087] The formed sol obtained in step (3) was transported to a disperser via a peristaltic pump, and then dripped into 95°C vacuum pump oil via a dispersing dripper (diameter 0.8 mm), and the formed balls were collected at the bottom of the hot oil column, and then transferred to an aging kettle, and aged for 6 hours at 150°C and 0.5 MPa to obtain alumina balls; after washing, the sol was dried at 60°C for 4 hours, then heated to 120°C for 4 hours, and calcined at 600°C for 4 hours to obtain alumina balls with a particle size of 1.5 mm-2 mm. The physical and chemical properties test results are shown in Table 1.

[0088] Example 5

[0089] (1) Preparation of basic aluminum chloride sol

[0090] Weigh 100 g of aluminum powder with a purity of ≥99% and a size of 100 μm-200 μm, add it to 1125 g of a 15 wt% aqueous hydrochloric acid solution (Al / Cl=0.8), heat to dissolve at a controlled temperature of 98°C, condense and reflux for 4 hours to obtain basic aluminum chloride sol.

[0091] (2) Preparation of alumina seed solution

[0092] Weigh 1 g of pseudo-boehmite (peptization index 99%) with a particle size of 250 μm-300 μm, dissolve it in 5 g of deionized water, stir to obtain a suspension solution, add 5 g of 30 wt% nitric acid aqueous solution (Al / NO3=0.7) thereto, and ultrasonically treat for 10 minutes to form a uniformly dispersed alumina seed solution.

[0093] (3) Preparation of molding sol

[0094] The basic aluminum chloride sol in step (1) is added into a reactor with stirring and cold bath circulation, the material temperature is controlled at 5°C, the stirring speed is 300r / min, the aluminum oxide seed solution in step (2) is added dropwise, the mass of the aluminum oxide seed solution accounts for 0.9% of the mass of the basic aluminum chloride sol, and stirred for 20 minutes; then 267 grams of a 40% by mass hexamethylenetetramine aqueous solution (coagulant) is added to the above solution, and the coagulant is controlled to account for 17.8% of the total mass of the molding sol to obtain a molding sol.

[0095] (4) Preparation of spherical carrier by oil column molding

[0096] The formed sol obtained in step (3) was transported to a disperser via a peristaltic pump, and then dripped into 95°C vacuum pump oil via a dispersing dripper (diameter 0.8 mm), and the formed balls were collected at the bottom of the hot oil column, and then transferred to an aging kettle, and aged for 6 hours at 150°C and 0.5 MPa to obtain alumina balls; after washing, the sol was dried at 60°C for 4 hours, then heated to 120°C for 4 hours, and calcined at 600°C for 4 hours to obtain alumina balls with a particle size of 1.5 mm-2 mm. The physical and chemical properties test results are shown in Table 1.

[0097] Example 6

[0098] Alumina spheres were prepared according to the method of Example 1, except that the oil phase used in the oil column molding to prepare the spherical carrier in step (4) was mineral oil, and the molding temperature was 100° C. The results of the physical and chemical properties test are shown in Table 1.

[0099] Example 7

[0100] Alumina beads were prepared according to the method of Example 1, except that in the preparation of the molding sol in step (3), the concentration of the hexamethylenetetramine aqueous solution was 30%. The results of the physical and chemical properties test are shown in Table 1.

[0101] Example 8

[0102] Alumina beads were prepared according to the method of Example 1, except that in the preparation of the molding sol in step (3), the coagulant was 305 g of urea solution with a mass fraction of 30%. The results of the physical and chemical properties test are shown in Table 1.

[0103] Comparative Example 1

[0104] (1) Preparation of basic aluminum chloride sol

[0105] Weigh 100 g of aluminum powder with a purity of ≥99% and a size of 100 μm-200 μm, add it to 1125 g of a 15 wt% aqueous hydrochloric acid solution (Al / Cl=0.8), control the reaction temperature to 98°C for heating and dissolving, and condense and reflux for 4 hours to obtain basic aluminum chloride sol.

[0106] (2) Preparation of molding sol

[0107] The basic aluminum chloride sol in step (1) is added to a reactor with stirring and cold bath circulation, the material temperature is controlled at 5°C, the stirring speed is 300r / min, and then 267g of a 40% by mass hexamethylenetetramine aqueous solution (coagulant) is added to the above solution, and the coagulant is controlled to account for 17.9% of the total mass of the molding sol to obtain a molding sol.

[0108] (3) Preparation of spherical carrier by oil column molding

[0109] The formed sol obtained in step (2) was transported to a disperser via a peristaltic pump, and then dripped into 95°C vacuum pump oil via a dispersing dropper (diameter 0.8 mm), and the formed balls were collected at the bottom of the hot oil column, and then transferred to an aging kettle, and aged for 6 hours at 150°C and 0.5 MPa to obtain alumina balls; after washing, the sol was dried at 60°C for 4 hours, then heated to 100°C for drying for 4 hours, and calcined at 600°C for 4 hours to obtain alumina balls with a particle size of 1.5 mm-2 mm. The results of the physical and chemical properties test are shown in Table 1.

[0110] Comparative Example 2

[0111] (1) Preparation of basic aluminum chloride sol

[0112] Weigh 100 g of aluminum powder with a purity of ≥99% and a size of 100 μm-200 μm, add it to 1350 g of a 10 wt% aqueous hydrochloric acid solution, control the reaction temperature to 95°C for heating and dissolving, and condense and reflux for 4 hours to obtain basic aluminum chloride sol.

[0113] (2) Add 7% by mass of pseudo-boehmite and 400 g by mass of 35% by mass of hexamethylenetetramine aqueous solution, mix well and then drip into the oil column at a temperature of 95°C through a dispersing dropper.

[0114] The test process found that during the mixing process of basic aluminum chloride sol and pseudo-boehmite, more agglomerated particles appeared in the basic aluminum chloride sol. After further ultrasonic dispersion, the uniformity of the material was still poor; when dripping out through the dispersion dropper, the needle was easily blocked, the particle size uniformity of the formed particles was poor, and the forming efficiency was low. The test results of its physical and chemical properties are shown in Table 1.

[0115] Performance Evaluation

[0116] The alumina ball samples prepared in the examples and comparative examples were added into a fixed bed reactor and hydrothermally treated for 24 hours at a temperature of 650° C. and a water content of 12 wt %. The specific surface area results of the alumina ball samples are shown in Table 1.

[0117] Table 1 Performance parameters of samples prepared in Examples and Comparative Examples

[0118]

[0119]

[0120] It can be found from the results in Table 1 that the alumina spherical carrier prepared in the present invention has the advantages of high particle strength and strong hydrothermal stability compared with the spherical alumina prepared without adding alumina seeds.

[0121] The alumina balls obtained in Example 1 and Comparative Example 1 were characterized. Figure 1-Figure 4 .Depend on Figure 1 , Figure 2 It can be seen that the SEM magnifications of the alumina seed crystals are 1000 and 10000 respectively, and the alumina seed crystal solution retains the characteristics of the pseudo-boehmite raw powder, which is a spherical particle with a narrow particle distribution; Figure 3 , Figure 4 The SEM images of the carriers obtained before and after the addition of alumina seeds are shown in Comparative Example 1 and Example 1, respectively. It can be seen that after the addition of the alumina seed solution, the particle distribution is more uniform in microscopic size, and the arrangement and bonding between the particles are tighter.

[0122] The above-described embodiments are only preferred embodiments of the present invention and are by no means limitations on the embodiments of the present invention. For those skilled in the art, other equivalent embodiments with different forms of changes or modifications can be made based on the above description. It is impossible to list all the embodiments here. However, any obvious changes or modifications, equivalent modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a millimeter-sized alumina spherical carrier, characterized in that: include: The spherical carrier is obtained by subjecting the forming sol to oil column forming. The forming sol comprises basic aluminum chloride sol and aluminum oxide seed solution. The mass of the aluminum oxide seed solution accounts for 0.1% to 15% of the mass of the basic aluminum chloride sol.

2. The method for preparing the millimeter-level alumina spherical carrier according to claim 1, characterized in that: The mass of the aluminum oxide seed solution accounts for 0.8% to 13% of the mass of the basic aluminum chloride sol.

3. The method for preparing the millimeter-level alumina spherical carrier according to claim 1, characterized in that: The preparation process of the forming sol comprises: dropping an aluminum oxide seed solution into a basic aluminum chloride sol, and then adding a coagulant to obtain the forming sol.

4. The method for preparing the millimeter-level alumina spherical carrier according to claim 1 or 3, characterized in that: The preparation process of the basic aluminum chloride sol comprises: adding hydrochloric acid aqueous solution into aluminum powder to react to obtain the basic aluminum chloride sol.

5. The method for preparing the millimeter-level alumina spherical carrier according to claim 4, characterized in that: The particle size of the aluminum powder is 100 μm-350 μm; the mass ratio of Al / Cl in the reaction solution is controlled to be 0.4-2.

5.

6. The method for preparing the millimeter-level alumina spherical carrier according to claim 1 or 3, characterized in that: The preparation process of the alumina seed solution comprises: dissolving pseudo-boehmite powder in deionized water and stirring to obtain a suspension solution; adding nitric acid aqueous solution thereto and ultrasonically treating to form a uniformly dispersed alumina seed solution.

7. The method for preparing the millimeter-level alumina spherical carrier according to claim 6, characterized in that: The peptization index of the pseudo-boehmite powder is ≥97%, and the particle size of the pseudo-boehmite powder is 150 μm-300 μm.

8. The method for preparing the millimeter-level alumina spherical carrier according to claim 6, characterized in that: The pseudo-boehmite is at least one of SB powder, TM70 powder, and high-purity low-sodium aluminum hydroxide.

9. The method for preparing the millimeter-level alumina spherical carrier according to claim 6, characterized in that: The concentration of the nitric acid aqueous solution is 10wt%-30wt%, and the mass ratio of Al / NO3 in the alumina seed solution is controlled to be 0.1-5.

10. The method for preparing the millimeter-level alumina spherical carrier according to claim 6, characterized in that: The ultrasonic treatment time is 1-10 min.

11. The method for preparing the millimeter-level alumina spherical carrier according to claim 3, characterized in that: The mass fraction of the coagulant is 25%-45%; the coagulant accounts for 15%-30% of the total mass of the formed sol; the coagulant is at least one of urea and hexamethylenetetramine aqueous solution.

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