Method for preparing spherical aluminum oxide by oil ammonia column forming process

Abstract

The invention belongs to the technical field of spherical aluminum oxide preparation, and particularly discloses a method for preparing spherical aluminum oxide through an oil ammonia column forming process. The preparation method comprises the following steps: firstly, uniformly mixing pseudo-boehmite or boehmite powder with a dilute acid solution to prepare aluminum sol; the upper layer of the oil ammonia column is an oil phase, the lower layer of the oil ammonia column is an ammonia water phase containing a macromolecular thickening agent, and a surfactant is added to an interface while the aluminum sol is dropped into the oil ammonia column through a forming needle, so that the aluminum sol is pelletized and gelled and cured. And finally, taking out the gel beads, drying and roasting to obtain the spherical alumina carrier. The spherical aluminum oxide prepared by the method is high in sphericity degree and high in crushing strength, and can be used as a catalyst carrier for various catalytic reactions.

Description

Technical Field

[0001] The present invention belongs to the technical field of spherical alumina preparation, and particularly relates to a method for preparing spherical alumina using an oil-ammonia column forming process. Background Art

[0002] Alumina has many excellent properties, such as high melting point, good thermal stability, developed pores, strong adsorption capacity, high surface activity, etc. It is an important multi-functional material and is often used as a catalyst support, adsorbent, heat stabilizer, fireproof material, ceramic material, etc., and is widely used in various fields, especially in the petrochemical industry.

[0003] In the field of petrochemical catalysis, when alumina is used as a catalyst support, it needs to be prepared into different shapes according to actual application requirements, including spherical, cylindrical, strip-shaped, clover-shaped, annular, honeycomb-shaped, etc. Among them, spherical alumina is widely used due to its advantages such as strong fluidity, good wear resistance, smooth surface, and high strength.

[0004] The forming methods of spherical alumina mainly include spray drying forming method, rotational forming method, hot oil column forming method, and oil-ammonia column forming method. Among them, the oil-ammonia column forming method has strong raw material adaptability, controllable product particle size, high strength, and high sphericity, and is suitable for large-scale production. The specific forming process in the oil-ammonia column is as follows: (1) The aluminum sol droplets first enter the upper-middle oil phase in the column and shrink into spheres under the action of the oil-water (aluminum sol) interfacial tension; (2) The spherical colloidal droplets continue to move downward and, under the action of a surfactant that can reduce the interfacial resistance, pass through the oil-water phase interface and enter the ammonia water phase, where a neutralization reaction occurs and gelation and solidification take place to obtain gel spheres with a certain strength; (3) The gel spheres are taken out and, after being dried, calcined and other treatments, spherical alumina products can be obtained.

[0005] During the falling process in the ammonia water phase, the spherical sol droplets that have not been fully solidified are easily deformed under the extrusion of gravity and movement resistance and the impact during bottom contact, resulting in a decrease in sphericity and strength. Chinese Patent CN110404591 A discloses a method for preparing a spherical alumina support. This method uses pseudo-boehmite as a raw material to prepare aluminum sol, and performs drop ball forming in an oil-ammonia column device. By adding a suitable gelling agent, the sol spheres can be quickly gelled and solidified in the ammonia water phase, which can improve the solidification degree of the sol spheres to a certain extent. However, the gelling agent may cause premature gelation and solidification of the aluminum sol droplets, affecting the sphericity, and even causing the fluidity of the aluminum sol to become poor and unable to form drops.

[0006] Chinese Patent CN 115739198 A discloses a method for preparing spherical alumina. The mixed slurry is dropped into the oil-ammonia column to form gel spheres, and then the gel spheres solidified at the bottom of the oil-ammonia column are taken out and then placed in C3~C 10Age in a fatty alcohol organic solvent, and obtain alumina spheres through drying and calcination. This method can significantly improve the crushing strength of spherical alumina, but fails to take into account the sphericity of the alumina spheres. Summary of the Invention

[0007] In view of the above problems, the present invention provides a method for preparing spherical alumina by an oil-ammonia column forming process. This method uses pseudo-boehmite or boehmite as raw materials to prepare aluminum sol, and adds a polymer thickener to the ammonia water phase of the oil-ammonia column to adjust the viscosity of the ammonia water phase, thereby reducing the movement speed of the aluminum sol droplets in the ammonia water phase, reducing the influence of the movement speed on its sphericity, and at the same time prolonging the falling and solidification time of the aluminum sol droplets in the ammonia water phase, improving the solidification degree before touching the bottom, reducing deformation, and obtaining spherical alumina with high sphericity and high strength.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing spherical alumina by an oil-ammonia column forming process, comprising the following steps: (1) Preparation of aluminum sol: Mix pseudo-boehmite or boehmite powder with a dilute acid solution, continuously stir for a period of time, and obtain aluminum sol with a certain solid content (mass fraction of Al2O3 in the aluminum sol) and acid-aluminum ratio (n(H + ) / n(Al2O3)) after sufficient peptization.

[0009] (2) Oil-ammonia column forming: The upper layer of the oil-ammonia column is the oil phase, the lower layer is the ammonia water phase added with a polymer thickener, and the middle is the interface layer. Drop the aluminum sol obtained in step (1) into the oil-ammonia column through a forming needle, and at the same time drop an aqueous surfactant solution at the oil-ammonia interface to form spheres of the aluminum sol droplets in the oil phase, and then pass through the phase interface into the ammonia water phase for gelation and solidification; then take out the solidified gel spheres, dry and calcine to obtain alumina spheres.

[0010] Further, the mass concentration of the dilute acid solution in step (1) is 3-30%, preferably 5-25%. The acid is selected from one or more of nitric acid, hydrochloric acid, formic acid, acetic acid, citric acid, and oxalic acid, preferably one or more of nitric acid, acetic acid, and citric acid.

[0011] Further, the aluminum solid content in step (1) is 5-35 wt%, preferably 18-28 wt%, and the acid-aluminum ratio is 0.01-0.4, preferably 0.03-0.15.

[0012] Further, the stirring speed in step (1) is 100-1000 r / min, preferably 350-750 r / min, and the stirring duration is 0.5-8 h, preferably 0.5-1 h.

[0013] Furthermore, in step (2), the height of the forming needle tip from the upper surface of the oil phase is 1-10 cm, preferably 2-6 cm.

[0014] Furthermore, in step (2), the oil phase is one or more of n-hexane, n-octane, n-decane, dodecane, kerosene, and light liquid paraffin, preferably one or more of n-decane, dodecane, and kerosene. The height of the oil phase is 3-30 cm, preferably 5-15 cm.

[0015] Furthermore, in step (2), the high molecular weight thickener is one or more of polyethylene glycol, polypropylene glycol, allyl polyethylene glycol, and methoxy polyethylene glycol, preferably polyethylene glycol or allyl polyethylene glycol. The addition amount of the high molecular weight thickener is 0.1%-10% of the total mass of the ammonia aqueous phase, preferably 0.5%-5%.

[0016] Furthermore, in step (2), the concentration of the ammonia aqueous phase is 5%-25%, preferably 15%-25%. The height of the ammonia aqueous phase is 10-100 cm, preferably 40-80 cm.

[0017] Furthermore, in step (2), the surfactant is one or more of the fatty alcohol polyoxyethylene ether series (AEO-3, AEO-4, AEO-5, AEO-7, AEO-9) or the octylphenol polyoxyethylene ether series (OP-2, OP-4, OP-7, OP-10, OP-13), preferably one or more of the fatty alcohol polyoxyethylene ether series (AEO-3, AEO-4, AEO-5, AEO-7, AEO-9). The mass concentration of the surfactant aqueous solution is 0.01%-5%, preferably 0.01%-1.5%. The addition amount of the surfactant aqueous solution is 3 mL.

[0018] Furthermore, in step (2), the curing time is 0.1-3 h.

[0019] Furthermore, in step (2), the drying temperature is 50-150 °C, preferably 60-120 °C. The drying time is 8-24 h, preferably 12-16 h.

[0020] Furthermore, in step (2), the calcination temperature is 300-1000 °C, preferably 450-650 °C. The calcination time is 2-8 h, preferably 4-8 h.

[0021] The sphericity of the spherical alumina prepared by the above method is greater than 98%, and the crushing strength ≥75.

[0022] The beneficial effects of the present invention are as follows: When the aluminum sol droplets fall relatively fast in the ammonia water phase, they are prone to obvious deformation due to the large movement resistance. At the same time, due to the short falling time and insufficient curing, they are easily deformed by the impact when hitting the bottom. By adding a polymer thickener to the ammonia water phase, without changing the ammonia concentration of the ammonia water phase, the viscosity of the ammonia water phase is increased, so that the aluminum sol droplets can fall more slowly, thereby reducing the deformation caused by the large movement speed. And on the premise that the height of the ammonia water phase remains unchanged, the curing time is increased and the curing degree is improved. Therefore, the alumina spheres prepared by the present invention have the advantages of high sphericity and large crushing strength, and can effectively solve the problems of low sphericity and poor crushing strength of the spherical alumina prepared by the prior art. Detailed Embodiments

[0023] To make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0024] Example 1 (1) Preparation of aluminum sol: Add 2.09 g of 20% dilute nitric acid by mass to a beaker containing 54.45 g of deionized water. After stirring evenly, add 30 g of pseudo-boehmite while stirring. After adding, continue to stir at a speed of 650 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 26 wt% and an acid-aluminum ratio of 0.03 is prepared.

[0025] (2) Oil-ammonia column forming: The upper layer of the oil-ammonia column is a 12 cm high n-decane oil phase; the lower layer is a 75 cm high ammonia water phase, where the ammonia concentration is 20 wt%, and 5 wt% of polyethylene glycol (M w 6000) is added, and the middle is the interface layer. At 3 cm above the oil phase liquid surface, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of 0.8 wt% fatty alcohol polyoxyethylene ether (AEO-7) surfactant aqueous solution is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 10 h, and finally calcined at 550 °C for 4 h to obtain γ-phase spherical alumina.

[0026] Example 2 (1) Preparation of aluminum sol: Add 2.32 g of 20% dilute nitric acid by mass to a beaker containing 47.68 g of deionized water. After stirring evenly, add 25 g of boehmite while stirring. After adding, continue to stir at a speed of 550 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 25 wt% and an acid-aluminum ratio of 0.04 is prepared.

[0027] (2) Oil-ammonia column forming: The upper layer of the oil-ammonia column is a kerosene oil phase with a height of 12 cm; the lower layer is an ammonia water phase with a height of 65 cm, where the ammonia water concentration is 23 wt%, and allyl polyethylene glycol (M w 2000) polymer thickener with 5 wt% of the total mass of the ammonia water phase is added, and the middle is the interface layer. At 4 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of 0.9 wt% fatty alcohol polyoxyethylene ether (AEO-9) surfactant aqueous solution is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 10 h, and finally calcined at 600 °C for 4 h to obtain γ-phase spherical alumina.

[0028] Example 3 (1) Preparation of aluminum sol: 3.48 g of 20% dilute nitric acid by mass is added to a beaker containing 56.52 g of deionized water. After stirring evenly, 30 g of pseudoboehmite is added while stirring. After adding, it is continuously stirred at a speed of 650 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 25 wt% and an acid-aluminum ratio of 0.05 is prepared.

[0029] (2) Oil-ammonia column forming: The upper layer of the oil-ammonia column is a n-decane oil phase with a height of 12 cm, the lower layer is an ammonia water phase with a height of 55 cm, where the ammonia water concentration is 20 wt%, and polyethylene glycol (M w 6000) polymer thickener with 4 wt% of the total mass of the ammonia water phase is added, and the middle is the interface layer. At 3 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of 0.8 wt% fatty alcohol polyoxyethylene ether (AEO-5) surfactant aqueous solution is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 12 h, and finally calcined at 550 °C for 4 h to obtain γ-phase spherical alumina.

[0030] Example 4 (1) Preparation of aluminum sol: 2.90 g of 20% dilute nitric acid by mass is added to a beaker containing 50.23 g of deionized water. After stirring evenly, 25 g of boehmite is added while stirring. After adding, it is continuously stirred at a speed of 550 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 24 wt% and an acid-aluminum ratio of 0.05 is prepared.

[0031] (2) Oil-ammonia column forming: The upper layer of the oil-ammonia column is a kerosene oil phase with a height of 12 cm; the lower layer is an ammonia water phase with a height of 65 cm, where the ammonia water concentration is 22 wt%, and allyl polyethylene glycol (M w 2000) polymer thickener with 4 wt% of the total mass of the ammonia water phase is added; the middle is an interfacial layer containing the above surfactant. At 4 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of 1.2 wt% fatty alcohol polyoxyethylene ether (AEO-7) surfactant aqueous solution is added to the interface. After standing and solidifying for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 10 h, and finally calcined at 600 °C for 4 h to obtain γ-phase spherical alumina.

[0032] Example 5 (1) Preparation of aluminum sol: 2.09 g of 20% dilute nitric acid by mass is added to a beaker containing 54.45 g of deionized water. After stirring evenly, 30 g of pseudo-boehmite is added while stirring. After adding, it is continuously stirred at a speed of 650 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 26 wt% and an acid-aluminum ratio of 0.03 is prepared.

[0033] (2) Oil-ammonia column forming: The upper layer of the oil-ammonia column is a n-decane oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 75 cm, where the ammonia concentration is 18 wt%, and polyethylene glycol (M w 6000) polymer thickener with 3 wt% of the total mass of the ammonia water phase is added, and the middle is an interfacial layer. At 3 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of 0.5 wt% fatty alcohol polyoxyethylene ether (AEO-7) surfactant aqueous solution is added to the interface. After standing and solidifying for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 12 h, and finally calcined at 550 °C for 4 h to obtain γ-phase spherical alumina.

[0034] Example 6 (1) Preparation of aluminum sol: 2.32 g of 20% dilute nitric acid by mass is added to a beaker containing 47.68 g of deionized water. After stirring evenly, 25 g of boehmite is added while stirring. After adding, it is continuously stirred at a speed of 550 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 25 wt% and an acid-aluminum ratio of 0.04 is prepared.

[0035] (2) Formation of oil-ammonia column: The upper layer of the oil-ammonia column is a kerosene oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 65 cm, where the ammonia concentration is 15 wt%, and allyl polyethylene glycol (M w 2000) polymer thickener with 3 wt% of the total mass of the ammonia water phase is added; the middle is the interfacial layer. At 4 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of 0.8 wt% aqueous solution of fatty alcohol polyoxyethylene ether (AEO-9) surfactant is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 10 h, and finally calcined at 600 °C for 4 h to obtain γ-phase spherical alumina.

[0036] Example 7 (1) Preparation of aluminum sol: 3.48 g of 20% dilute nitric acid by mass is added to a beaker containing 56.52 g of deionized water. After stirring evenly, 30 g of pseudoboehmite is added while stirring. After adding, it is continuously stirred at a speed of 650 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 25 wt% and an acid-aluminum ratio of 0.05 is prepared.

[0037] (2) Formation of oil-ammonia column: The upper layer of the oil-ammonia column is a n-decane oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 75 cm, where the ammonia concentration is 20 wt%, and polyethylene glycol (M w 6000) polymer thickener with 2 wt% of the total mass of the ammonia water phase is added; the middle is the interfacial layer. At 3 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of 0.8 wt% aqueous solution of fatty alcohol polyoxyethylene ether (AEO-4) surfactant is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 10 h, and finally calcined at 550 °C for 4 h to obtain γ-phase spherical alumina.

[0038] Example 8 (1) Preparation of aluminum sol: 2.90 g of 20% dilute nitric acid by mass is added to a beaker containing 50.23 g of deionized water. After stirring evenly, 25 g of boehmite is added while stirring. After adding, it is continuously stirred at a speed of 550 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 24 wt% and an acid-aluminum ratio of 0.05 is prepared.

[0039] (2) Formation of oil-ammonia column: The upper layer of the oil-ammonia column is a kerosene oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 65 cm, where the ammonia concentration is 18 wt%, and allyl polyethylene glycol (M w 2000) polymer thickener accounting for 2 wt% of the total mass of the ammonia water phase is added. The middle is the interfacial layer. At a position 4 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of an aqueous solution of 0.8 wt% fatty alcohol polyoxyethylene ether (AEO-5) surfactant is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 10 h, and finally calcined at 600 °C for 4 h to obtain γ-phase spherical alumina.

[0040] Example 9 (1) Preparation of aluminum sol: 2.09 g of 20% dilute nitric acid by mass is added to a beaker containing 54.45 g of deionized water. After stirring evenly, 30 g of pseudo-boehmite is added while stirring. After adding, it is continuously stirred at a speed of 650 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 26 wt% and an acid-aluminum ratio of 0.03 is prepared.

[0041] (2) Formation of oil-ammonia column: The upper layer of the oil-ammonia column is a n-decane oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 75 cm, where the ammonia concentration is 20 wt%, and polyethylene glycol (M w 6000) polymer thickener accounting for 0.8 wt% of the total mass of the ammonia water phase is added; the middle is the interfacial layer. At a position 3 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of an aqueous solution of 1.0 wt% fatty alcohol polyoxyethylene ether (AEO-7) surfactant is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 10 h, and finally calcined at 550 °C for 4 h to obtain γ-phase spherical alumina.

[0042] Example 10 (1) Preparation of aluminum sol: 2.32 g of 20% dilute nitric acid by mass is added to a beaker containing 47.68 g of deionized water. After stirring evenly, 25 g of boehmite is added while stirring. After adding, it is continuously stirred at a speed of 550 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 25 wt% and an acid-aluminum ratio of 0.04 is prepared.

[0043] (2) Oil-ammonia column forming: The upper layer of the oil-ammonia column is a kerosene oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 65 cm, where the ammonia concentration is 18 wt%. 0.8 wt% of allyl polyethylene glycol (M w 2000) polymer thickener is added based on the total mass of the ammonia water phase, and the middle is the interface layer. At a position 4 cm above the liquid surface of the oil phase, the aluminum sol droplets are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify. While dropping the aluminum sol, 3 mL of 0.8 wt% aqueous solution of fatty alcohol polyoxyethylene ether (AEO-9) surfactant is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 85 °C for 10 h, and finally calcined at 600 °C for 4 h to obtain γ-phase spherical alumina.

[0044] Comparative Example 1 (1) Preparation of aluminum sol: 2.09 g of 20% dilute nitric acid by mass was added to a beaker containing 54.45 g of deionized water. After stirring evenly, 30 g of pseudoboehmite was added while stirring. After adding, it was continuously stirred at a speed of 650 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 26 wt% and an acid-to-aluminum ratio of 0.03 was prepared.

[0045] (2) Oil-ammonia column forming: The upper layer of the oil-ammonia column is a n-decane oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 75 cm, where the ammonia concentration is 20 wt%; the middle is the interface layer. At a position 3 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify. While dropping the aluminum sol, 3 mL of 0.8 wt% aqueous solution of fatty alcohol polyoxyethylene ether (AEO-7) surfactant is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 10 h, and finally calcined at 550 °C for 4 h to obtain γ-phase spherical alumina.

[0046] Comparative Example 2 (1) Preparation of aluminum sol: 2.32 g of 20% dilute nitric acid by mass was added to a beaker containing 47.68 g of deionized water. After stirring evenly, 25 g of boehmite was added while stirring. After adding, it was continuously stirred at a speed of 550 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 25 wt% and an acid-to-aluminum ratio of 0.04 was prepared.

[0047] (2) Formation of oil-ammonia column: The upper layer of the oil-ammonia column is a kerosene oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 65 cm, where the ammonia concentration is 23 wt%; the middle is the interface layer. At a position 4 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of an aqueous solution of 0.9 wt% fatty alcohol polyoxyethylene ether (AEO-9) surfactant is added to the interface. After standing and solidifying for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 10 h, and finally calcined at 600 °C for 4 h to obtain γ-phase spherical alumina.

[0048] Comparative Example 3 (1) Preparation of aluminum sol: 2.09 g of 20% dilute nitric acid by mass was added to a beaker containing 54.45 g of deionized water. After stirring evenly, 30 g of pseudo-boehmite was added while stirring. After adding, it was continuously stirred at a speed of 650 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 26 wt% and an acid-aluminum ratio of 0.03 was prepared.

[0049] (2) Formation of oil-ammonia column: The upper layer of the oil-ammonia column is a n-decane oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 75 cm, where the ammonia concentration is 18 wt%, and 3.0 wt% of polyacrylamide (M w 5500000) polymer thickener is added. The middle is the interface layer. At a position 3 cm above the liquid surface of the oil phase, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of an aqueous solution of 0.5 wt% fatty alcohol polyoxyethylene ether (AEO-7) surfactant is added to the interface. After standing and solidifying for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 12 h, and finally calcined at 550 °C for 4 h to obtain γ-phase spherical alumina.

[0050] Comparative Example 4 (1) Preparation of aluminum sol: 2.09 g of 20% dilute nitric acid by mass was added to a beaker containing 54.45 g of deionized water. After stirring evenly, 30 g of pseudo-boehmite was added while stirring. After adding, it was continuously stirred at a speed of 650 r / min for 0.5 h. After sufficient peptization, an aluminum sol with a solid content of 26 wt% and an acid-aluminum ratio of 0.03 was prepared.

[0051] (2) Formation of oil-ammonia column: The upper layer of the oil-ammonia column is a n-decane oil phase with a height of 12 cm, and the lower layer is an ammonia water phase with a height of 75 cm, where the ammonia concentration is 18 wt%, and 3.0 wt% of polydiallyldimethylammonium chloride (M w(150000) Polymer thickener; the middle is the interfacial layer. At a position 3 cm above the oil phase liquid surface, the aluminum sol droplets obtained in step (1) are dropped into the oil-ammonia column through a forming needle to form spheres and gel solidify; while dropping the aluminum sol, 3 mL of an aqueous solution of 0.5 wt% fatty alcohol polyoxyethylene ether (AEO-7) surfactant is added to the interface. After standing and curing for 1 h, the formed gel spheres are taken out, then dried at 80 °C for 12 h, and finally calcined at 550 °C for 4 h to obtain γ-phase spherical alumina.

[0052] Table 1 shows the performance test results of the alumina spheres prepared in the examples and comparative examples. Among them, the specific surface area and pore volume were measured by the nitrogen adsorption and desorption method using an ASAP 2460 type fully automatic adsorption instrument from Micromeritics, USA. The particle size and sphericity were measured using a Camsizer X2 type sphericity tester from Microtrac Mrb, Germany. The crushing strength was measured using a DL4 strength tester from Dalian Penghui Co., Ltd.

[0053] Table 1 As can be seen from Table 1, when using pseudo-boehmite or boehmite as raw materials to prepare aluminum sol and using an oil-ammonia column with a polymer thickener added to the ammonia water phase for oil-ammonia column forming, the properties such as sphericity and crushing strength of the prepared spherical alumina (examples) are significantly better than those of the products prepared using other oil-ammonia columns (comparative example 1, comparative example 2, comparative example 3, comparative example 4). This proves that this method can effectively improve the sphericity and crushing strength of spherical alumina at the same time.

[0054] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A method for preparing spherical alumina by an oil-ammonia column forming process, characterized in that: It includes the following steps: (1) Preparation of aluminum sol: Mix pseudo-boehmite or boehmite powder with a dilute acid solution and stir to obtain an aluminum sol with a solid content of 5 - 35 wt% and an acid-to-aluminum ratio of 0.01 - 0.4; (2) Oil-ammonia column forming: The upper layer of the oil-ammonia column is the oil phase, the lower layer is the ammonia water phase added with a polymer thickener, and the middle is the interface layer. Drop the aluminum sol obtained in step (1) into the oil-ammonia column through a forming needle. At the same time, add an aqueous surfactant solution to the interface to make the aluminum sol droplets form spheres in the oil phase, and then pass through the phase interface into the ammonia water phase to gel and solidify. Take out the solidified gel spheres, dry and calcine them to obtain alumina spheres; The polymer thickener is one or more of polyethylene glycol, polypropylene glycol, allyl polyethylene glycol, and methoxy polyethylene glycol.

2. The method for preparing spherical alumina by the oil-ammonia column forming process according to claim 1, characterized in that: In step (1), the mass concentration of the dilute acid solution is 3 - 30%, and one or more of nitric acid, hydrochloric acid, formic acid, acetic acid, citric acid, and oxalic acid are selected.

3. The method for preparing spherical alumina by the oil-ammonia column forming process according to claim 1, characterized in that: In step (1), the stirring speed is 100 - 1000 r / min, and the stirring duration is 0.5 - 8 h.

4. The method for preparing spherical alumina by the oil-ammonia column forming process according to claim 1, characterized in that: In step (2), the height of the forming needle from the upper surface of the oil phase is 1 - 10 cm.

5. The method for preparing spherical alumina by the oil-ammonia column forming process according to claim 1, characterized in that: In step (2), the oil phase is a mixture of one or more of n-hexane, n-octane, n-decane, dodecane, kerosene, and light liquid paraffin, and the height of the oil phase is 3 - 30 cm.

6. The method for preparing spherical alumina by the oil-ammonia column forming process according to claim 1, characterized in that: In step (2), the addition amount of the polymer thickener is 0.1% - 10% of the total mass of the ammonia water phase.

7. The method for preparing spherical alumina by the oil-ammonia column forming process according to claim 1, characterized in that: In step (2), the concentration of the ammonia water phase is 5 - 25%, and the height of the ammonia water phase is 10 - 100 cm.

8. The method for preparing spherical alumina by the oil-ammonia column forming process according to claim 1, characterized in that: In step (2), the mass concentration of the aqueous surfactant solution is 0.01 - 5%, the addition amount of the surfactant is 3 mL, and the surfactant is selected from one or more of fatty alcohol polyoxyethylene ether and octylphenol polyoxyethylene ether.

9. The method for preparing spherical alumina by the oil-ammonia column forming process according to claim 1, characterized in that: In step (2), the solidification time is 0.1 - 3 h; the drying temperature is 50 - 150 °C, and the drying time is 8 - 24 h; the calcination temperature is 300 - 1000 °C, and the calcination time is 2 - 8 h.

10. The spherical alumina prepared by the method according to any one of claims 1-9, characterized in that: The sphericity of the spherical alumina is greater than 98%, and the crushing strength ≥ 75 N.

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