Preparation method and application of pseudo-boehmite

Abstract

The invention provides a preparation method and application of pseudo-boehmite. The method comprises the following steps: (1) mixing an aluminum-containing acidic solution with a sodium metaaluminate solution, and carrying out a neutralization gelling reaction; (2) directly filtering and washing the material obtained by the neutralization gelling reaction in the step (1) without aging to obtain aluminum hydroxide colloid; and (3) carrying out steam treatment on the aluminum hydroxide colloid obtained in the step (2) at least twice, carrying out steam treatment for the first time in an alkaline atmosphere, and drying to obtain the pseudo-boehmite powder. The pseudo-boehmite powder prepared by the method is used as a hydrotreating catalyst carrier material, and has good activity when being applied to the hydrotreating process of high-nitrogen inferior raw materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of inorganic material synthesis, and relates to a preparation method and application of pseudo-boehmite. BACKGROUND

[0002] Alumina is a widely used compound, which plays an important role in the fields of chemistry, electronics, building and aerospace. In the field of chemistry, alumina is widely used as a hydrogenation treatment catalyst carrier material due to its high specific surface area and good thermal stability.

[0003] CN1141821A discloses a preparation method of a hydrogenation catalyst carrier. The specific surface area of the carrier is 250-500 m 2 / g, and the average pore size is 7-12 nm. The preparation method is as follows: an acidic aqueous aluminum salt solution and an alkaline aqueous aluminum salt solution are neutralized at a temperature of 30-85℃ and a pH of 6-10 for 0.25-4 hours; aging is performed at a temperature of 30-85℃ and a pH of 6-10 for 0.25-8 hours; and the neutralization reaction process and the aging process are performed under the same conditions, so as to prepare a carrier with a pore size distribution concentrated in 7-12 nm.

[0004] CN105883871A discloses a preparation method of pseudo-boehmite. The preparation method uses sodium metaaluminate, a soluble sulfate and an acidic aluminum source as initial raw materials, first uses a titration method to add the sodium metaaluminate solution to the mixed solution of the soluble sulfate and the acidic aluminum source, then performs hydrothermal treatment, cools, washes after aging and crystallization, and finally dries to obtain the pseudo-boehmite.

[0005] The pseudo-boehmite prepared by the above patent method is used as a carrier material to prepare a hydrogenation treatment catalyst, which has yet to be further improved in activity when processing poor-quality raw materials, especially high-nitrogen poor-quality raw materials. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides a preparation method and application of pseudo-boehmite. The pseudo-boehmite powder prepared by the method has good activity when used as a hydrogenation treatment catalyst carrier material in the hydrogenation treatment process of high-nitrogen poor-quality raw materials.

[0007] The present application provides a preparation method of pseudo-boehmite in the first aspect, which includes the following contents:

[0008] (1) an acidic aluminum-containing solution is mixed with a sodium metaaluminate solution to perform a neutralization gelation reaction;

[0009] (2) the material obtained in the neutralization gelation reaction of step (1) is directly filtered and washed without aging to obtain an aluminum hydroxide gel;

[0010] (3) subjecting the aluminum hydroxide gel obtained in step (2) to at least two steam treatments, wherein the first steam treatment is carried out in an alkaline atmosphere, and the dried product is a boehmite powder.

[0011] In the above method for preparing boehmite, the aluminum-containing acidic solution in step (1) is selected from one or more of aluminum sulfate, aluminum nitrate, and aluminum chloride solution; and the concentration of the aluminum-containing acidic solution is 2-8 g / 100 mL of Al2O3, preferably 2.5-7.5 g / 100 mL.

[0012] In the above method for preparing boehmite, the concentration of the sodium aluminate solution in step (1) is 12-30 g / 100 mL of Al2O3, preferably 15-28 g / 100 mL.

[0013] In the above method for preparing boehmite, the neutralization and gelation reaction temperature in step (1) is 25-55°C, preferably 30-50°C; the pH value is 6.5-8.8, preferably 6.8-8.5; and the concentration of the material obtained from the neutralization and gelation reaction is 4.2-8.0 g / 100 mL of Al2O3.

[0014] In the above method for preparing boehmite, the filtration and washing process in step (2) can be carried out according to the prior art, and the above process can be repeated, for example, by multiple washing and separation.

[0015] In the above method for preparing boehmite, the dry basis of the aluminum hydroxide gel in step (2) is 20-40 wt%.

[0016] In the above method for preparing boehmite, the alkaline atmosphere in step (3) is a mixed gas of alkaline gas and steam, and the volume fraction of the alkaline gas in the mixed gas is 5%-20%, preferably 8%-18%; and the alkaline gas is at least one of ammonia, phosphine, and methylamine, preferably ammonia.

[0017] In the above method for preparing boehmite, in step (3), the first steam treatment is carried out in an atmosphere containing alkaline gas, and the second steam treatment is carried out in an atmosphere containing air; the atmosphere containing air is a mixed gas of air and steam, and the volume fraction of the steam in the mixed gas is 10%-40%, preferably 12%-35%.

[0018] In the preparation method of pseudo-boehmite, the first steam treatment in step (3) is performed at a temperature of 110-180℃, a pressure of 0.35-1.00 MPa, and a time of 20-50 min; the second steam treatment is performed at a temperature of 150-350℃, a pressure of 0.15-0.55 MPa, and a time of 10-30 min; preferably, the second steam treatment is performed at a temperature 60-120℃ higher than the first steam treatment.

[0019] In the preparation method of pseudo-boehmite, short-chain alcohol can be introduced in step (3) by mixing the aluminum hydroxide gel obtained in step (2) with short-chain alcohol and then performing N times of steam treatment; the short-chain alcohol can be one or more of methanol, ethanol and propanol; the amount of short-chain alcohol introduced is 0.3-3 wt% of the mass of the aluminum hydroxide gel (dry basis), preferably 0.5-2.5 wt%.

[0020] In the preparation method of pseudo-boehmite, the drying temperature in step (3) is 120-180℃, and the drying time is 2-8 h.

[0021] The second aspect of the present application provides a pseudo-boehmite powder obtained by the above preparation method.

[0022] The third aspect of the present application provides a preparation method of an alumina carrier, comprising the following steps: molding the pseudo-boehmite powder to obtain the alumina carrier.

[0023] In the above method, the molding can be performed by using existing technologies, such as kneading molding or rolling molding; the molding can be performed to prepare the carrier into any one of a spherical shape, a strip shape and a tooth ball shape according to needs.

[0024] The fourth aspect of the present application provides an alumina carrier obtained by the above method.

[0025] The fifth aspect of the present application provides a hydroprocessing catalyst containing the above alumina carrier.

[0026] The sixth aspect of the present application provides the use of the above hydroprocessing catalyst in a hydroprocessing process.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] 1. In the preparation method of boehmite of the present invention, an aluminum-containing acidic solution is mixed with a sodium aluminate solution for a neutralization and gelation reaction. The material obtained from the neutralization and gelation reaction is not aged but directly filtered and washed, and then aged in an atmosphere containing alkaline gas. In the above process, the particle size in the unaged material is relatively small. At the same time, immediate filtration and washing can effectively remove impurity elements, which is conducive to the uniform growth of particles, thus obtaining small and uniform particles. The particles have a relatively short and relatively uniform contact time with the gas in the atmosphere containing alkaline gas, which can more quickly and uniformly complete the particle growth process and avoid excessive aggregation between particles. Then, high-temperature steam treatment can remove alkaline gas, avoid excessive aging of particles, and help to improve the particle structure of powder. The boehmite powder prepared by the above method, as a catalyst support material for hydrogenation treatment, has good activity when applied to the hydrogenation treatment process of high nitrogen feedstock. Furthermore, controlling the temperature of the second steam treatment to be 60-120°C higher than that of the first steam treatment can further improve the catalyst performance.

[0029] 2. In the preparation method of pseudoboehmite of the present invention, the introduction of short-chain alcohol can further disperse the particles, reduce the probability of particle agglomeration, and more effectively promote the effective contact between alkaline vapor and particles, thereby further improving the properties of pseudoboehmite powder and helping to further improve the activity of the corresponding catalyst. Detailed Implementation

[0030] The technical features of the present invention are further described below through embodiments, but it should not be considered that the present invention is limited to these embodiments. The percentages mentioned are weight percentages.

[0031] In this invention, the dry basis is determined by taking an appropriate amount of sample with a mass of m1, calcining it at 500°C for 3 hours, and then measuring the mass of m2. The mass percentage of the calcined sample compared to the sample before calcination is calculated as m2 / m1×100%, which is the dry basis of the sample.

[0032] Example 1

[0033] 2 L of deionized water was added to the reaction vessel as the bottom water, and the temperature of the bottom water was controlled to rise to 50 °C. Simultaneously, an aluminum sulfate solution containing 4.3 g / 100 mL of Al₂O₃ and a sodium aluminate solution containing 19 g / 100 mL of Al₂O₃ were added. The pH value for the neutralization reaction was set to 7.9, and the concentration of the slurry after neutralization was 7.8 g / 100 mL (based on Al₂O₃). After the neutralization reaction, the obtained slurry was filtered and washed, and the above process was repeated three times. Then, 1.8 wt% ethanol (based on dry weight) of aluminum hydroxide colloid was added and mixed with the solution. The mixture was then filtered to obtain aluminum hydroxide colloid with a dry weight of 28 wt%.

[0034] The obtained aluminum hydroxide colloid was transferred to a first steam treatment device, the volume fraction of ammonia in the system was controlled at 10%, and the treatment was performed at a temperature of 180°C for 25 min under a treatment pressure of 0.25 MPa; then, the powder obtained by the first steam treatment was transferred to a second steam treatment device, the volume fraction of water vapor in the system was 13%, and the treatment was performed at a temperature of 270°C for 20 min under a treatment pressure of 0.18 MPa. Drying was performed at 150°C for 4 h to obtain the boehmite powder F1.

[0035] Example 2

[0036] 2 L of deionized water was added to a reaction tank as a reaction bottom water, and the bottom water temperature was controlled to rise to 40°C. An aluminum sulfate solution containing 6.4 g / 100 mL of Al2O3 and a sodium metaaluminate solution containing 15 g / 100 mL of Al2O3 were simultaneously added, and the pH value of the neutralization reaction was set to 6.8. The slurry concentration after the neutralization reaction was 4.2 g / 100 mL of Al2O3. After the neutralization reaction was completed, the obtained slurry was filtered and washed, the above process was repeated three times, then 2.4 wt% of ethanol based on the mass of the aluminum hydroxide colloid (dry basis) was added for mixing and stirring, and then a dry basis of 20 wt% of the aluminum hydroxide colloid was obtained by filtration.

[0037] The obtained aluminum hydroxide colloid was transferred to a first steam treatment device, the volume fraction of ammonia in the system was controlled at 18%, and the treatment was performed at a temperature of 150°C for 36 min under a treatment pressure of 0.22 MPa; then, the powder obtained by the first steam treatment was transferred to a second steam treatment device, the volume fraction of water vapor in the system was 20%, and the treatment was performed at a temperature of 210°C for 20 min under a treatment pressure of 0.48 MPa. Drying was performed at 150°C for 4 h to obtain the boehmite powder F2.

[0038] Example 3

[0039] 2 L of deionized water was added to a reaction tank as a reaction bottom water, and the bottom water temperature was controlled to rise to 45°C. An aluminum sulfate solution containing 3.6 g / 100 mL of Al2O3 and a sodium metaaluminate solution containing 22 g / 100 mL of Al2O3 were simultaneously added, and the pH value of the neutralization reaction was set to 7.1. The slurry concentration after the neutralization reaction was 5.7 g / 100 mL of Al2O3. After the neutralization reaction was completed, the obtained slurry was filtered and washed, the above process was repeated three times, then 1.2 wt% of propanol based on the mass of the aluminum hydroxide colloid (dry basis) was added for mixing and stirring, and then a dry basis of 24 wt% of the aluminum hydroxide colloid was obtained by filtration.

[0040] The obtained aluminum hydroxide colloid was transferred to a primary steam treatment device, the volume fraction of ammonia in the system was controlled at 13%, and the treatment was carried out at a temperature of 175°C for 30 min, and the treatment pressure was 0.6 MPa; then, the powder obtained by the primary steam treatment was transferred to a secondary steam treatment device, the volume fraction of water vapor in the system was 17%, and the treatment was carried out at a temperature of 295°C for 11 min, and the treatment pressure was 0.32 MPa. Drying was carried out at 150°C for 4 h to obtain pseudoboehmite powder F3.

[0041] Example 4

[0042] 2.7 g / 100 mL of aluminum sulfate solution containing Al2O3 and 26 g / 100 mL of sodium metaaluminate solution containing Al2O3, and the pH value of the neutralization reaction was set to be 8.5. After the neutralization reaction, the concentration of the obtained slurry was 6.3 g / 100 mL in terms of Al2O3. After the neutralization reaction was completed, the obtained slurry was filtered and washed, the above process was repeated three times, then 0.9 wt% of propanol based on the mass of the aluminum hydroxide colloid (in dry basis) was added and mixed and stirred, then, the aluminum hydroxide colloid with a dry basis of 34 wt% was obtained by filtration.

[0043] The obtained aluminum hydroxide colloid was transferred to a primary steam treatment device, the volume fraction of ammonia in the system was controlled at 13%, and the treatment was carried out at a temperature of 175°C for 30 min, and the treatment pressure was 0.6 MPa; then, the powder obtained by the primary steam treatment was transferred to a secondary steam treatment device, the volume fraction of water vapor in the system was controlled at 17%, and the treatment was carried out at a temperature of 295°C for 11 min, and the treatment pressure was 0.32 MPa. Drying was carried out at 150°C for 4 h to obtain pseudoboehmite powder F3.

[0044] Example 5

[0045] 2.7 g / 100 mL of aluminum sulfate solution containing Al2O3 and 26 g / 100 mL of sodium metaaluminate solution containing Al2O3, and the pH value of the neutralization reaction was set to be 8.5. After the neutralization reaction, the concentration of the obtained slurry was 6.3 g / 100 mL in terms of Al2O3. After the neutralization reaction was completed, the obtained slurry was filtered and washed, the above process was repeated three times, then 0.9 wt% of propanol based on the mass of the aluminum hydroxide colloid (in dry basis) was added and mixed and stirred, then, the aluminum hydroxide colloid with a dry basis of 34 wt% was obtained by filtration.

[0046] The obtained aluminum hydroxide colloid was transferred to a primary steam treatment device, the volume fraction of ammonia in the system was controlled at 16%, and the treatment was carried out at a temperature of 180°C for 48 min, and the treatment pressure was 0.50 MPa; then, the powder obtained by the primary steam treatment was transferred to a secondary steam treatment device, the volume fraction of water vapor in the system was 24%, and the treatment was carried out at a temperature of 300°C for 15 min, and the treatment pressure was 0.42 MPa. Drying was carried out at 150°C for 4 h to obtain pseudoboehmite powder F5.

[0047] Example 6

[0048] In a reaction tank, 1.5 L of deionized water was added as a reaction bottom water, and the bottom water temperature was controlled to rise to 30°C. At the same time, an aluminum sulfate solution containing 7.2 g / 100 mL of Al2O3 and a sodium metaaluminate solution containing 27 g / 100 mL of Al2O3 were added, and the pH value of the neutralization reaction was set to 8.5. The slurry concentration obtained after the neutralization reaction was 7.2 g / 100 mL of Al2O3. After the neutralization reaction was completed, the obtained slurry was filtered and washed, the above process was repeated three times, and then a 38 wt% dry basis aluminum hydroxide colloid was obtained by filtration.

[0049] The obtained aluminum hydroxide colloid was transferred to a primary steam treatment device, the volume fraction of ammonia in the system was controlled at 16%, and the treatment was carried out at a temperature of 180°C for 48 min, and the treatment pressure was 0.50 MPa; then, the powder obtained by the primary steam treatment was transferred to a secondary steam treatment device, the volume fraction of water vapor in the system was 24%, and the treatment was carried out at a temperature of 300°C for 15 min, and the treatment pressure was 0.42 MPa. Drying was carried out at 150°C for 4 h to obtain pseudoboehmite powder F5.

[0050] Example 7

[0051] The aluminum hydroxide colloid was prepared according to the process of Example 6. The obtained aluminum hydroxide colloid was transferred to a primary steam treatment device, the volume fraction of ammonia in the system was controlled at 11%, and the treatment was carried out at a temperature of 180°C for 27 min, and the treatment pressure was 0.26 MPa; then, the powder obtained by the primary steam treatment was transferred to a secondary steam treatment device, the volume fraction of water vapor in the system was 25%, and the treatment was carried out at a temperature of 180°C for 18 min, and the treatment pressure was 0.22 MPa. Drying was carried out at 150°C for 4 h to obtain pseudoboehmite powder F7.

[0052] Example 8

[0053] The aluminum hydroxide gel was prepared according to the procedure of Example 6. The obtained aluminum hydroxide gel was transferred into a primary steam treatment device, the volume fraction of ammonia gas in the system was controlled at 9%, and the treatment was carried out at a temperature of 150°C for 25 min under a treatment pressure of 0.80 MPa. Then, the powder obtained from the primary steam treatment was transferred into a secondary steam treatment device, the volume fraction of water vapor in the system was 20%, and the treatment was carried out at a temperature of 150°C for 15 min under a treatment pressure of 0.24 MPa. Drying was carried out at 150°C for 4 h to obtain pseudoboehmite powder F8.

[0054] Comparative Example 1

[0055] The difference between Example 2 and the present example is that an aging process in the prior art was added after the neutralization reaction was completed. The specific procedure is as follows:

[0056] 2 L of deionized water was added into a reaction tank as a reaction bottom water, and the temperature of the bottom water was controlled to rise to 40°C. At the same time, an aluminum sulfate solution containing 6.4 g of Al2O3 per 100 mL and a sodium metaaluminate solution containing 15 g of Al2O3 per 100 mL were added, and the pH value of the neutralization reaction was set to 6.8. The concentration of the slurry obtained after the neutralization reaction was 4.2 g of Al2O3 per 100 mL. After the neutralization reaction was completed, the temperature and pH value of the neutralization reaction were maintained, and an aging process was carried out for 2 h. The obtained slurry was filtered and washed, the above process was repeated three times, and then a filter cake was obtained, which was a 20 wt% aluminum hydroxide gel on a dry basis.

[0057] The obtained aluminum hydroxide gel was transferred into a primary steam treatment device, the volume fraction of ammonia gas in the system was controlled at 18%, and the treatment was carried out at a temperature of 150°C for 36 min under a treatment pressure of 0.22 MPa. Then, the powder obtained from the primary steam treatment was transferred into a secondary steam treatment device, the volume fraction of water vapor in the system was 20%, and the treatment was carried out at a temperature of 210°C for 20 min under a treatment pressure of 0.48 MPa. Drying was carried out at 150°C for 4 h to obtain pseudoboehmite powder DF1.

[0058] Comparative Example 2

[0059] The difference between Example 2 and the present example is that the first steam treatment was carried out in an atmosphere without ammonia gas. The specific procedure is as follows:

[0060] In a reaction tank, 2 L of deionized water was added as the reaction bottom water, and the temperature of the bottom water was controlled to 40°C. At the same time, aluminum sulfate solution containing 6.4 g / 100 mL of Al2O3 and sodium metaaluminate solution containing 15 g / 100 mL of Al2O3 were added, and the pH value of the neutralization reaction was set to 6.8. The slurry concentration after the neutralization reaction was 4.2 g / 100 mL of Al2O3. The obtained slurry was filtered and washed, the above process was repeated three times, and then the filter cake was obtained to give aluminum hydroxide colloid with a dry basis of 20 wt%.

[0061] The obtained aluminum hydroxide colloid was transferred to a primary steam treatment device, the volume fraction of water vapor in the system was controlled to 18%, and the treatment was performed at a temperature of 150°C for 36 min under a treatment pressure of 0.22 MPa. Then, the powder obtained by the primary steam treatment was transferred to a secondary steam treatment device, the volume fraction of water vapor in the system was 20%, and the treatment was performed at a temperature of 210°C for 20 min under a treatment pressure of 0.48 MPa. The powder was dried at 150°C for 4 h to obtain boehmite powder DF2.

[0062] 400 g of boehmite powder F1 was mixed with 6.5 g of citric acid and 6.5 g of sesbania powder, and then 376 g of nitric acid aqueous solution (containing 6.6 g of nitric acid) was slowly and uniformly added. After the addition of the acid solution, the material was continuously rolled and pressed for 20 min to form a plastic body, and then the plastic body was extruded into a strip through a three-leaf clover hole plate with a diameter of 1.7 mm. The strip was dried at 120°C for 6 h and then calcined at 500°C for 4 h. The support after calcination was denoted as Z1. The same method was used to prepare supports Z2, Z3, Z4, Z5, Z6, Z7, Z8, DZ1 and DZ2 using F2, F3, F4, F5, F6, F7, F8, DF1 and DF2 boehmite powders, respectively.

[0063] The calcined support strip Z2, Z4, Z5, Z6, Z7 and Z8 was used as the carrier, and a solution containing Mo and Ni was used for impregnation at the same volume for 2 h. After drying at 120°C for 6 h, the hydrogenation catalysts were obtained by calcination at 450°C for 3 h, and were denoted as C2, C4, C5, C6, C7 and C8, respectively. The physicochemical properties of the prepared catalysts are shown in Table 1.

[0064] DZ1 and DZ2 were used as the carrier, and a solution containing Mo and Ni was used for impregnation at the same volume for 2 h. After drying at 120°C for 6 h, the hydrogenation catalysts DC1 and DC2 were obtained by calcination at 450°C for 3 h. The physicochemical properties of the prepared catalysts are shown in Table 2.

[0065] Table 2 Physicochemical properties of the catalysts

[0066] Catalyst C2 C4 C5 C6 C7 C8 DC1 DC2 MoO3, wt.% 21.24 21.35 21.40 21.29 21.27 21.30 21.33 21.33 NiO, wt% 3.36 3.42 3.44 3.40 3.23 3.37 3.40 3.40

[0067] The catalyst activity evaluation experiment was carried out on a micro hydrogenation device, and the catalyst was pre-sulfided before the activity evaluation. The catalyst evaluation conditions were that the total reaction pressure was 7.0 MPa, the volume space velocity was 2.0 h -1 -1, the reaction temperature was 350 DEG C. The raw material for the activity evaluation was a mixed solution of α-methylnaphthalene and quinoline, and the nitrogen content was 1860 ppm. The activity evaluation results are shown in Table 3.

[0068] Table 3 Catalyst activity evaluation results

[0069] Catalyst C2 C4 C5 C6 C7 C8 DC1 DC2 Relative denitration activity, % 118 116 112 111 108 106 102 100

Claims

1. A method for preparing pseudo-boehmite, characterized by: The method comprises the following steps: (1) mixing an aluminum-containing acidic solution with a sodium metaaluminate solution to perform a neutralization and gelation reaction; (2) directly filtering and washing the material obtained in the neutralization and gelation reaction in step (1) without aging to obtain an aluminum hydroxide gel; (3) performing water vapor treatment on the aluminum hydroxide gel obtained in step (2) for at least two times, wherein the first time of water vapor treatment is performed in an alkaline atmosphere, and the pseudo-boehmite powder is obtained after drying.

2. The method of claim 1, wherein: The aluminum-containing acidic solution in step (1) is selected from one or more of aluminum sulfate, aluminum nitrate and aluminum chloride solution; the concentration of the aluminum-containing acidic solution is 2-8 g / 100 mL of Al2O3, preferably 2.5-7.5 g / 100 mL of Al2O3.

3. The method of claim 1, wherein: The concentration of the sodium metaaluminate solution in step (1) is 12-30 g / 100 mL of Al2O3, preferably 15-28 g / 100 mL of Al2O3.

4. The method of claim 1, wherein: The neutralization and gelation reaction in step (1) is performed at a temperature of 25-55°C, preferably 30-50°C, and a pH value of 6.5-8.8, preferably 6.8-8.5; the concentration of the material obtained in the neutralization and gelation reaction is 4.2-8.0 g / 100 mL of Al2O3.

5. The method of claim 1, wherein: The dry basis of the aluminum hydroxide gel in step (2) is 20-40 wt%.

6. The method of claim 1, wherein: The alkaline atmosphere in step (3) is a mixed gas of an alkaline gas and water vapor, wherein the volume fraction of the alkaline gas in the mixed gas is 5%-20%, preferably 8%-18%; the alkaline gas is at least one of ammonia, phosphine and methylamine, preferably ammonia.

7. The method of claim 1, wherein: In step (3), the first time of steam treatment is performed in an atmosphere containing the alkaline gas, and the second time of steam treatment is performed in an atmosphere containing air, wherein the atmosphere containing air is a mixed gas of air and water vapor, and the volume fraction of water vapor in the mixed gas is 10%-40%, preferably 12%-35%.

8. The method of claim 1, wherein: In step (3), the first time of steam treatment is performed at a temperature of 110-180°C, a pressure of 0.35-1.00 MPa and for a time of 20-50 min; the second time of steam treatment is performed at a temperature of 150-350°C, a pressure of 0.15-0.55 MPa and for a time of 10-30 min; preferably, the temperature of the second time of steam treatment is 60-120°C higher than that of the first time of steam treatment.

9. The method of claim 1, wherein: In step (3), a short-chain alcohol is further introduced, and the introduction is performed by uniformly mixing the aluminum hydroxide gel obtained in step (2) with the short-chain alcohol and then performing N times of steam treatment; the short-chain alcohol is one or more of methanol, ethanol and propanol; the introduction amount of the short-chain alcohol is 0.3-3 wt% of the mass of the aluminum hydroxide gel (based on the dry basis), preferably 0.5-2.5 wt% of the mass of the aluminum hydroxide gel (based on the dry basis).

10. The method of claim 1, wherein: In step (3), the drying temperature is 120-180°C, and the drying time is 2-8 h.

11. A pseudo-boehmite powder prepared by the method of any one of claims 1-10.

12. A method for the preparation of an alumina support, characterized in that: The method comprises the following steps: molding the pseudo-boehmite powder of claim 11 to obtain an aluminum oxide carrier.

13. An aluminum oxide carrier prepared by the method of claim 12.

14. A hydroprocessing catalyst comprising the alumina support of claim 13.