Process for the preparation of high strength alumina pellets with large pore volume

Abstract

The present application relates to a kind of preparation methods of high-strength alumina pellets with large pore volume, by the hydrolysis of aluminium alcohol in the organic solvent containing only hydrogen bond donor is transferred to kettle and is aged to obtain pseudo-boehmite, the prepared pseudo-boehmite is made into aluminium sol, add gelling agent, drop into hot oil column and form, then after washing, drying, calcination is prepared.The pseudo-boehmite prepared in the present application has the characteristics of large pore volume and high peptization, and the specific surface area of the alumina pellets prepared after hot oil column forming is 158~289 m 2 / g, the pore size distribution is 2~46 nm, the pore volume is 0.50~0.88 cm 3 / g, and the strength is 43~73 N / grain.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical synthesis technology, and particularly relates to a preparation method of macroporous high-strength gamma-alumina pellets. BACKGROUND

[0002] As a catalyst carrier, the gamma-alumina pellets have a very important use in the field of chemical refining. With the heavy oil processing, the alumina pellets are required to have a large pore volume and pore diameter to improve the diffusion rate of the reactant and product molecules in the reaction process, thereby improving the reaction efficiency. Meanwhile, the large pore volume of the carrier can increase its carbon accumulation capacity and slow down the deactivation rate of the catalyst. In addition, the alumina pellets should have high strength, so that the catalyst has high wear resistance during use and regeneration, thereby prolonging the service life of the catalyst.

[0003] In the synthesis process of the alumina pellets, the addition of the pore-expanding agent can improve the pore volume of the alumina pellets to a certain extent. However, the synthesis method has many deficiencies. The pore-expanding agent is difficult to recover after being added and can only be removed by calcination. This not only produces a large amount of polluting gas to pollute the environment, but also increases the preparation cost of the spherical alumina carrier. More importantly, the strength of the alumina pellets prepared by adding the pore-expanding agent is significantly reduced, which shortens the service life of the catalyst prepared by using the alumina pellets as the carrier.

[0004] CN101850997A discloses a method for preparing spherical alumina using oil-ammonia column forming. The method uses pseudo-boehmite powder as the raw material, acidifies the pseudo-boehmite powder to prepare a pseudo-boehmite dispersion slurry, adds kerosene as a pore-expanding agent, and simultaneously adds an emulsifier with a hydrophilic-lipophilic balance value greater than 10 to uniformly disperse the kerosene, to prepare an emulsified slurry. Then, the emulsified slurry is formed in an oil-ammonia column, the wet pellets are collected, dried, and calcined to obtain spherical alumina.

[0005] CN104402028A discloses an oil-water column forming method for spherical alumina. The method adds pseudo-boehmite and a pore-expanding agent (urea, urotropine, cellulose, or activated carbon) to a seaweed acid salt solution, stirs uniformly to prepare a seaweed acid-pseudo-boehmite suspension slurry. The suspension slurry is dropped into an oil-water column composed of an upper oil phase and a lower polyvalent metal cation salt solution phase to form composite spherical gel particles. The gel particles are taken out and treated with an acidic solution. Finally, the spherical alumina product is obtained by drying and calcination.

[0006] CN106111214A discloses that water, acid and at least one boehmite powder are mixed into a suspension, a solid pore-forming agent or a liquid pore-forming agent is added into the suspension, and a spherical particle is formed by gelation, and then the spherical particle is dried and calcined to obtain an alumina pellet. The solid pore-forming agent is selected from starch, flour, latex, polystyrene or acrylic particles, polysaccharide, carbon black particles and sawdust, the liquid pore-forming agent is selected from oil and fat, oil and mineral wax, fat, hydrocarbon and oil fraction, and the surfactant is selected from non-ionic or ionic surfactants.

[0007] Pseudo-boehmite is an important raw material for synthesizing alumina pellets, and its properties often determine the strength, specific surface area, pore volume and pore size of the alumina pellets. Pseudo-boehmite can be prepared by carbonization method, acid method, alkali method and alcohol aluminum hydrolysis method. The pseudo-boehmite prepared by the alcohol aluminum hydrolysis method has the advantages of high purity and good crystal phase. By adjusting various parameters in the hydrolysis process, the physicochemical properties of the pseudo-boehmite can be controlled to some extent. However, the existing control strategies for producing pseudo-boehmite have the disadvantages of small specific surface area, pore volume and pore size, and low strength.

[0008] Currently, the solvent used for preparing pseudo-boehmite by alcohol aluminum hydrolysis method is C3-C6 alcohol. Through in-depth theoretical analysis of the process of preparing pseudo-boehmite by this method, it is found that there are a large number of hydroxyl groups on the pseudo-boehmite, and alcohol hydroxyl groups can form hydrogen bonds with the hydroxyl groups on the pseudo-boehmite. However, alcohol hydroxyl groups exist as both hydrogen bond donors and hydrogen bond acceptors, and the coexistence of hydrogen bond donors and hydrogen bond acceptors makes the pseudo-boehmite particles tightly packed through hydrogen bonding with alcohol hydroxyl groups. In addition, hydrogen bonds also form between the pseudo-boehmite particles themselves, resulting in tight packing of the pseudo-boehmite particles, and thus the specific surface area, pore volume and pore size of the prepared pseudo-boehmite are small, and the alumina pellets prepared from the pseudo-boehmite are difficult to meet the needs of oil processing. SUMMARY

[0009] The present application transfers the alcohol aluminum hydrolyzed in the non-alcohol organic solvent to the kettle to perform aging treatment to obtain pseudo-boehmite, and then the prepared pseudo-boehmite is made into aluminum sol, a gelling agent is added, and then dropped into a hot oil column to form, and then the formed alumina pellets are dried and calcined to obtain the γ-alumina pellets. In the present application, only hydrogen bond acceptors exist in the selected non-alcohol organic solvent, which can only form a hydrogen bond with the pseudo-boehmite, so that the pseudo-boehmite particles cannot be connected by hydrogen bond during the alcohol aluminum hydrolysis and aging process. In addition, since the solvent forms a hydrogen bond with the hydroxyl group on the pseudo-boehmite, the pseudo-boehmite particles are difficult to form hydrogen bonds between particles, so that larger pores can be formed between the pseudo-boehmite particles. In addition, the aging treatment of the pseudo-boehmite in the organic solvent can improve the peptization of the pseudo-boehmite, and then the strength of the alumina pellets is improved. The specific surface area of the alumina pellets prepared by the pseudo-boehmite produced in the present application is 158-289 m 2 / g, the pore size distribution is 2-46 nm, the pore volume is 0.50-0.88 cm 3 / g, and the strength is 43-73 N / pellet, which can completely meet the needs of oil processing.

[0010] The present application specifically adopts the following technical solutions:

[0011] A preparation method of large-pore-volume high-strength alumina pellets, comprising the following steps:

[0012] (1) Dissolve the alcohol aluminum in the organic solvent at a certain temperature, and slowly drop water into the alcohol aluminum until the alcohol aluminum is completely hydrolyzed;

[0013] (2) Transfer the mixture after the reaction in step (1) to the kettle to perform aging treatment at a certain temperature, and then filter and dry to obtain the pseudo-boehmite;

[0014] (3) Add the prepared pseudo-boehmite to water containing acid to prepare aluminum sol, add a gelling agent, and then drop into a hot oil column to form, and then transfer the formed alumina pellets and the forming oil to the kettle to perform aging treatment at a certain temperature;

[0015] (4) Separate the aged alumina pellets, wash with an organic solvent, and then dry and calcine to obtain the alumina pellets.

[0016] Preferably, the alcohol aluminum in step (1) is one of isopropyl alcohol aluminum, n-butyl alcohol aluminum, sec-butyl alcohol aluminum, n-pentyl alcohol aluminum, and n-hexyl alcohol aluminum.

[0017] Preferably, the organic solvent in step (1) is one of tetrahydrofuran, acetone, dimethyl sulfoxide, diethyl ether, ethyl acetate, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl pyrrolidone, acetonitrile, and 1,4-dioxane.

[0018] Preferably, the molar ratio of the alcohol aluminum and the organic solvent in step (1) is 1:1-1:60, and the molar ratio of the alcohol aluminum and water is 1:2-1:40.

[0019] Preferably, the aging temperature in step (2) is 80-280 ℃, and the aging time is 2-60 h.

[0020] Preferably, the acid in step (3) is one of nitric acid, hydrochloric acid, sulfuric acid, citric acid, oxalic acid, p-toluene sulfonic acid, and p-dodecyl benzene sulfonic acid.

[0021] Preferably, the gelling agent in step (3) is one of hexamethylenetetramine, urea, ammonium carbonate, ammonium bicarbonate, and ammonium chloride.

[0022] Preferably, the molar ratio of the pseudoboehmite and water in step (3) is 1:5-1:26.

[0023] Preferably, the molar ratio of the acid and the pseudoboehmite in step (3) is 0.02-0.4.

[0024] Preferably, the molar ratio of the gelling agent and the pseudoboehmite in step (3) is 0.01-0.4.

[0025] Preferably, the hot oil column oil phase in step (3) is one of silicone oil, vacuum pump oil, lubricating oil, kerosene, diesel oil, and aromatic oil.

[0026] Preferably, the temperature of the hot oil column in step (3) is 60-180 ℃.

[0027] Preferably, the aging temperature in step (3) is 70-210 ℃, and the aging time is 2-32 h.

[0028] Preferably, the organic solvent in step (4) is one of C1-C6 alcohols, petroleum ether, diethyl ether, toluene, acetone, tetrahydrofuran, acetonitrile, and dimethylbenzene.

[0029] Preferably, the calcination temperature in step (4) is 400-700 ℃.

[0030] The present application has the following beneficial effects: the non-alcohol organic solvent used in the present application enables the pseudoboehmite particles to form larger pores between the particles, so that the pseudoboehmite with large pore volume and high specific surface area can be obtained. In addition, the aging treatment of the pseudoboehmite in the organic solvent can improve its peptization, thereby improving the strength of the alumina pellets. DETAILED DESCRIPTION

[0031] In order to make the above features and advantages of the present application more obvious and easy to understand, the following examples are given for detailed description. The method of the present application is the conventional method in the art unless otherwise specified.

[0032] Example 1

[0033] Dissolve 1 mol of aluminum isopropoxide in 3 mol of tetrahydrofuran solvent, and add 4 mol of water dropwise thereto. Transfer the reacted mixture into a kettle, and age at 120°C for 24 hours. Filter and dry the aged mixture to obtain pseudoboehmite. Take 1 mol of the prepared pseudoboehmite, and add it to 19 mol of water. Add 0.06 mol of HNO3 to prepare an aluminum sol. Add 0.04 mol of hexamethyltetramine to the aluminum sol, and drop it into a hot oil column with kerosene as an oil phase at 120°C to form. Transfer the forming oil and the formed alumina pellets into a kettle, and age at 120°C for 10 hours. Filter, wash with ethanol, dry, and calcine at 630°C to obtain γ-alumina pellets. The obtained alumina pellets have a specific surface area of 243 m 2 / g, a pore size distribution of 2-36 nm, a pore volume of 0.72 cm 3 / g, and a strength of 63 N / pellet.

[0034] Example 2

[0035] Dissolve 1 mol of aluminum sec-butoxide in 20 mol of dimethyl sulfoxide, and add 6 mol of water dropwise thereto. Transfer the reacted mixture into a kettle, and age at 280°C for 2 hours. Filter and dry the aged mixture to obtain pseudoboehmite. Take 1 mol of the prepared pseudoboehmite, and add it to 26 mol of water. Add 0.2 mol of citric acid to prepare an aluminum sol. Add 0.08 mol of ammonium chloride to the aluminum sol, and drop it into a hot oil column with vacuum pump oil as an oil phase at 100°C to form. Transfer the forming oil and the formed alumina pellets into a kettle, and age at 105°C for 14 hours. Filter, wash with acetone, dry, and calcine at 700°C to obtain γ-alumina pellets. The obtained alumina pellets have a specific surface area of 180 m 2 / g, a pore size distribution of 2-43 nm, a pore volume of 0.69 cm 3 / g, and a strength of 57 N / pellet.

[0036] Example 3

[0037] mol water was added dropwise, and the reacted mixture was transferred into a kettle and aged at 100°C for 40 h. The aged mixture was filtered, dried, and then the pseudo-boehmite was obtained. 1 mol of the pseudo-boehmite prepared above was added to 20 mol of water, and 0.04 mol of HCl was added to prepare an alumina sol. After 0.07 mol of ammonium bicarbonate was added to the alumina sol, the mixture was dropped into a hot oil column with diesel oil as an oil phase at 140°C to form a shaped product. The shaped oil and the formed alumina pellets were transferred into a kettle and aged at 140°C for 8 h. The product was filtered, washed with petroleum ether, dried, and then calcined at 500°C to obtain γ-alumina pellets. The obtained alumina pellets had a specific surface area of 289 m 2 / g, a pore size distribution of 3-46 nm, a pore volume of 0.88 cm 3 / g, and a strength of 50 N / pellet.

[0038] Example 4

[0039] mol water was added dropwise, and the reacted mixture was transferred into a kettle and aged at 100°C for 40 h. The aged mixture was filtered, dried, and then the pseudo-boehmite was obtained. 1 mol of the pseudo-boehmite prepared above was added to 20 mol of water, and 0.04 mol of HCl was added to prepare an alumina sol. After 0.07 mol of ammonium bicarbonate was added to the alumina sol, the mixture was dropped into a hot oil column with diesel oil as an oil phase at 140°C to form a shaped product. The shaped oil and the formed alumina pellets were transferred into a kettle and aged at 140°C for 8 h. The product was filtered, washed with petroleum ether, dried, and then calcined at 500°C to obtain γ-alumina pellets. The obtained alumina pellets had a specific surface area of 289 m 2 / g, a pore size distribution of 3-46 nm, a pore volume of 0.88 cm 3 / g, and a strength of 50 N / pellet.

[0040] Example 5

[0041] mol cyclohexanone, 20 mol water was added dropwise to the mixture, and the reacted mixture was transferred to a kettle, and aged at 140°C for 20 h. The aged mixture was filtered, dried, and then 1 mol of the thus-prepared pseudoboehmite was added to 22 mol of water, and 0.2 mol of oxalic acid was added to prepare an alumina sol. Then, 0.3 mol of hexamethyltetramine was added to the alumina sol, and the mixture was dropwise added to a hot oil column at 100°C using lubricating oil as an oil phase to form a shaped product. The shaped oil and the formed alumina pellets were transferred to a kettle, and aged at 70°C for 32 h. The aged product was filtered, washed with n-butanol, dried, and then calcined at 580°C to obtain γ-alumina pellets. The obtained γ-alumina pellets had a specific surface area of 251 m 2 / g, a pore size distribution of 2-39 nm, a pore volume of 0.69 cm 3 / g, and a strength of 51 N / pellet.

[0042] Example 6

[0043] mol n-butanol was dissolved in 10 mol of N,N-dimethylformamide, and 40 mol of water was added dropwise to the mixture. The reacted mixture was transferred to a kettle, and aged at 160°C for 18 h. The aged mixture was filtered, dried, and then 1 mol of the thus-prepared pseudoboehmite was added to 10 mol of water, and 0.4 mol of p-toluenesulfonic acid was added to prepare an alumina sol. Then, 0.4 mol of urea was added to the alumina sol, and the mixture was dropwise added to a hot oil column at 100°C using aromatic oil as an oil phase to form a shaped product. The shaped oil and the formed alumina pellets were transferred to a kettle, and aged at 160°C for 4 h. The aged product was filtered, washed with n-pentanol, dried, and then calcined at 620°C to obtain γ-alumina pellets. The obtained γ-alumina pellets had a specific surface area of 178 m 2 / g, a pore size distribution of 2-38 nm, a pore volume of 0.50 cm 3 / g, and a strength of 73 N / pellet.

[0044] Example 7

[0045] mol water was added dropwise, and the reacted mixture was transferred to a kettle and aged at 100°C for 24 h. The aged mixture was filtered, dried, and then obtained pseudoboehmite. 1 mol of the obtained pseudoboehmite was added to 8 mol of water, and 0.1 mol of dodecylbenzenesulfonic acid was added to form an aluminum sol. After 0.06 mol of ammonium chloride was added to the aluminum sol, the aluminum sol was dropped into a hot oil column at 115°C with kerosene as the oil phase to form a shape. The shaped oil and the shaped alumina pellets were transferred to a kettle and aged at 110°C for 8 h. The aged mixture was filtered, washed with acetonitrile, dried, and then calcined at 650°C to obtain γ-alumina pellets. The obtained γ-alumina pellets had a specific surface area of 194 m 2 / g, a pore size distribution of 2-44 nm, a pore volume of 0.57 cm 3 / g, and a strength of 43 N / pellet.

[0046] Example 8

[0047] mol water was added dropwise, and the reacted mixture was transferred to a kettle and aged at 100°C for 24 h. The aged mixture was filtered, dried, and then obtained pseudoboehmite. 1 mol of the obtained pseudoboehmite was added to 8 mol of water, and 0.1 mol of dodecylbenzenesulfonic acid was added to form an aluminum sol. After 0.06 mol of ammonium chloride was added to the aluminum sol, the aluminum sol was dropped into a hot oil column at 115°C with kerosene as the oil phase to form a shape. The shaped oil and the shaped alumina pellets were transferred to a kettle and aged at 110°C for 8 h. The aged mixture was filtered, washed with acetonitrile, dried, and then calcined at 650°C to obtain γ-alumina pellets. The obtained γ-alumina pellets had a specific surface area of 194 m 2 / g, a pore size distribution of 2-44 nm, a pore volume of 0.57 cm 3 / g, and a strength of 43 N / pellet.

[0048] Example 9

[0049] mol water was added dropwise to the mixture, and the resultant mixture was transferred to a kettle and aged at 130°C for 16 hours. The aged mixture was filtered, dried, and then mixed with 1 mol of the pseudoboehmite prepared above and 10 mol of water. 0.01 mol of H2SO4 was added to the mixture to form an alumina sol, and 0.01 mol of ammonium bicarbonate was added to the alumina sol. The resultant mixture was dropped into a hot oil column at 180°C using silicone oil as the oil phase to form pellets. The forming oil and the formed pellets were transferred to a kettle and aged at 120°C for 7 hours. The pellets were filtered, washed with xylene, dried, and then calcined at 550°C to obtain γ-alumina pellets. The γ-alumina pellets had a specific surface area of 217 m 2 / g, a pore size distribution of 2-43 nm, a pore volume of 0.66 cm 3 / g, and a strength of 49 N / pellet.

[0050] Example 10

[0051] mol water was added dropwise to the mixture, and the resultant mixture was transferred to a kettle and aged at 130°C for 16 hours. The aged mixture was filtered, dried, and then mixed with 1 mol of the pseudoboehmite prepared above and 10 mol of water. 0.01 mol of H2SO4 was added to the mixture to form an alumina sol, and 0.01 mol of ammonium bicarbonate was added to the alumina sol. The resultant mixture was dropped into a hot oil column at 180°C using silicone oil as the oil phase to form pellets. The forming oil and the formed pellets were transferred to a kettle and aged at 120°C for 7 hours. The pellets were filtered, washed with xylene, dried, and then calcined at 550°C to obtain γ-alumina pellets. The γ-alumina pellets had a specific surface area of 217 m 2 / g, a pore size distribution of 2-43 nm, a pore volume of 0.66 cm 3 / g, and a strength of 49 N / pellet.

[0052] Example 11

[0053] 1 mol of aluminum sec-butoxide was dissolved in 7 mol of N-methylpyrrolidone, and 13 mol of water was added dropwise. The resulting mixture was transferred to a reactor and aged at 240 °C for 6 h. The aged mixture was then filtered and dried to obtain boehmite. 1 mol of the prepared boehmite was added to 22 mol of water, and 0.3 mol of p-toluenesulfonic acid was added to prepare an aluminum sol. 0.34 mol of ammonium carbonate was added to the aluminum sol, and the mixture was then dripped dropwise into a hot oil column at 105 °C with vacuum pump oil as the oil phase to form the granules. The forming oil and the formed alumina spheres were transferred to a reactor and aged at 130 °C for 8 h. After filtration, the granules were washed with toluene, dried, and calcined at 600 °C to obtain γ-alumina spheres with a specific surface area of ​​200 m². 2 / g, pore size distribution of 2~44 nm, pore volume of 0.60 cm³ 3 / g, strength is 60 N / particle.

[0054] Comparative Example 1

[0055] 1 mol of aluminum isopropoxide was dissolved in 3 mol of isopropanol solvent, and 4 mol of water was added dropwise. The resulting mixture was transferred to a reactor and aged at 120 °C for 24 h. The aged mixture was then filtered and dried to obtain boehmite. 1 mol of the prepared boehmite was added to 19 mol of water, and 0.06 mol of HNO3 was added to prepare an aluminum sol. 0.04 mol of hexamethylenetetramine was added to the aluminum sol, and the mixture was then dripped dropwise into a hot oil column at 120 °C with kerosene as the oil phase to form the granules. The formed oil and the formed alumina spheres were transferred to a reactor and aged at 120 °C for 10 h. After filtration, the granules were washed with ethanol, dried, and calcined at 630 °C to obtain γ-alumina spheres with a specific surface area of ​​86 m². 2 / g, pore size distribution of 2~19 nm, pore volume of 0.36 cm³ 3 / g, strength is 45 N / particle.

[0056] Comparative Example 2

[0057] mol water was added dropwise thereto, and the reacted mixture was transferred to a kettle, and aged at 280°C for 2 hours. The aged mixture was filtered, dried, and then pseudo-boehmite was obtained. 1 mol of the pseudo-boehmite prepared above was added to 26 mol of water, and 0.2 mol of citric acid was added to prepare an alumina sol. After 0.08 mol of ammonium chloride was added to the alumina sol, the alumina sol was dropped into a hot oil column with a vacuum pump oil as an oil phase at 100°C to form a shape. The shaped oil and the shaped alumina pellets were transferred to a kettle, and aged at 105°C for 14 hours. The aged mixture was filtered, washed with acetone, dried, and then calcined at 550°C to obtain γ-alumina pellets. The obtained γ-alumina pellets had a specific surface area of 109 m 2 / g, a pore size distribution of 2-26 nm, a pore volume of 0.40 cm 3 / g, and a strength of 33 N / pellet.

[0058] Comparative Example 3

[0059] mol water was added dropwise thereto, and the reacted mixture was transferred to a kettle, and aged at 280°C for 2 hours. The aged mixture was filtered, dried, and then pseudo-boehmite was obtained. 1 mol of the pseudo-boehmite prepared above was added to 26 mol of water, and 0.2 mol of citric acid was added to prepare an alumina sol. After 0.08 mol of ammonium chloride was added to the alumina sol, the alumina sol was dropped into a hot oil column with a vacuum pump oil as an oil phase at 100°C to form a shape. The shaped oil and the shaped alumina pellets were transferred to a kettle, and aged at 105°C for 14 hours. The aged mixture was filtered, washed with acetone, dried, and then calcined at 550°C to obtain γ-alumina pellets. The obtained γ-alumina pellets had a specific surface area of 109 m 2 / g, a pore size distribution of 2-26 nm, a pore volume of 0.40 cm 3 / g, and a strength of 33 N / pellet.

[0060] Comparative Example 4

[0061] mol water was added dropwise, and the reacted mixture was transferred into a kettle, and aged at 110 ℃ for 30 h. The aged mixture was filtered, dried, and then 1 mol of the pseudo-boehmite was added into 5 mol of water, and 0.08 mol of HNO3 was added to form an aluminum sol. Then, 0.08 mol of ammonium carbonate was added into the aluminum sol, and the mixture was dropwise added into a hot oil column with oil pump oil as the oil phase at 100 ℃ to form a shape. The shaped oil and the shaped alumina pellets were transferred into a kettle, and aged at 210 ℃ for 2 h. The pellets were filtered, washed with methanol, dried, and then calcined at 700 ℃ to obtain γ-alumina pellets. The specific surface area of the obtained alumina pellets was 86 m 2 / g, the pore size distribution was 2-24 nm, the pore volume was 0.33 cm 3 / g, and the strength was 42 N / pellet.

[0062] Comparative Example 5

[0063] mol water was added dropwise, and the reacted mixture was transferred into a kettle, and aged at 110 ℃ for 30 h. The aged mixture was filtered, dried, and then 1 mol of the pseudo-boehmite was added into 5 mol of water, and 0.08 mol of HNO3 was added to form an aluminum sol. Then, 0.08 mol of ammonium carbonate was added into the aluminum sol, and the mixture was dropwise added into a hot oil column with oil pump oil as the oil phase at 100 ℃ to form a shape. The shaped oil and the shaped alumina pellets were transferred into a kettle, and aged at 210 ℃ for 2 h. The pellets were filtered, washed with methanol, dried, and then calcined at 700 ℃ to obtain γ-alumina pellets. The specific surface area of the obtained alumina pellets was 86 m 2 / g, the pore size distribution was 2-24 nm, the pore volume was 0.33 cm 3 / g, and the strength was 42 N / pellet.

[0064] In Comparative Examples 1-5, organic alcohols were used as solvents, and the pore volume of the pseudo-boehmite pellets obtained was less than 0.40 cm 3 / g, and the strength was low. The pores formed by the organic alcohols in the pseudo-boehmite are unstable pores, and these pores are very easy to collapse during the heat treatment process, resulting in small pore volume of the obtained alumina. In the present application, the non-alcohol organic solvent used enables the pseudo-boehmite particles to form large and stable pores between the particles, and thus the pseudo-boehmite with large pore volume and high specific surface area can be obtained.

[0065] The above description is only the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the present application should be included in the scope of the present application.

Claims

1. A process for the production of high strength alumina pellets having a large pore volume, characterized in that, It comprises the following steps: (1) dissolving aluminum alcohol in an organic solvent at a certain temperature, slowly dropping water into it until the aluminum alcohol is completely hydrolyzed; (2) transferring the mixture after reaction in step (1) to a kettle for aging treatment at a certain temperature, then filtering and drying to obtain pseudo-boehmite; (3) adding the prepared pseudo-boehmite into water containing acid to prepare an aluminum sol, then adding a gelling agent and dropping into a hot oil column for shaping, transferring the shaped alumina pellets and the shaping oil to a kettle for aging treatment at a certain temperature; (4) separating the aged alumina pellets, washing with an organic solvent, drying and calcining to obtain alumina pellets. The organic solvent in step (1) is one of tetrahydrofuran, acetone, dimethyl sulfoxide, diethyl ether, ethyl acetate, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl pyrrolidone, acetonitrile and 1,4-dioxane. The molar ratio of aluminum alcohol to organic solvent in step (1) is 1:1-1:60, and the molar ratio of aluminum alcohol to water is 1:2-1:

40.

2. The method of claim 1, wherein, The aluminum alcohol in step (1) is one of isopropyl alcohol aluminum, n-butyl alcohol aluminum, sec-butyl alcohol aluminum, n-pentyl alcohol aluminum and n-hexyl alcohol aluminum.

3. The method of claim 1, wherein, The aging temperature in step (2) is 80-280 ℃, and the aging time is 2-60 h.

4. The method of claim 1, wherein, The acid in step (3) is one of nitric acid, hydrochloric acid, sulfuric acid, citric acid, oxalic acid, p-toluenesulfonic acid and p-dodecylbenzenesulfonic acid.

5. The method of claim 1, wherein, The gelling agent in step (3) is one of hexamethyltetramine, urea, ammonium carbonate, ammonium bicarbonate and ammonium chloride.

6. The method of claim 1, wherein, The molar ratio of pseudo-boehmite to water in step (3) is 1:5-1:26, the molar ratio of acid to pseudo-boehmite is 0.02-0.4, and the molar ratio of gelling agent to pseudo-boehmite is 0.01-0.

4.

7. The method of claim 1, wherein, The oil phase of the hot oil column in step (3) is one of silicone oil, vacuum pump oil, lubricating oil, kerosene, diesel oil and aromatic oil; the temperature of the hot oil column is 60-180 ℃; the aging temperature is 70-210 ℃, and the aging time is 2-32 h.

8. The method of claim 1, wherein, The organic solvent in step (4) refers to one of C1-C6 alcohols, petroleum ether, diethyl ether, toluene, acetone, tetrahydrofuran, acetonitrile and dimethylbenzene; the calcination temperature is 400-700 ℃.