Pseudo-boehmite with adjustable crystal size and preparation method and application thereof

Abstract

A method for preparing pseudo-boehmite with adjustable crystal size, comprising: (1) neutralizing sodium metaaluminate solution with carbon dioxide gas to form gel; (2) aging the formed slurry in a closed container by increasing temperature in stages; (3) filtering the aged slurry and washing with deionized water; and (4) drying the obtained filter cake after washing. The pseudo-boehmite prepared by the method has a crystallinity of not less than 90%, an adjustable crystal size of 5-12 nm, a specific surface area of 100-300 m 2 / g, and a pore volume of 0.4-1.0 mL / g. The method is green, environmentally friendly, low in cost, and simple in process, without adding any additives. By controlling suitable gelation pH value and temperature increasing aging conditions in stages, the obtained pseudo-boehmite has good peptization, pure crystal phase, and less impurities, and can be widely applied in the field of petroleum and chemical industry, especially in the preparation of catalysts.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing pseudoboehmite, in particular, a method for preparing pseudoboehmite with adjustable grain size and high crystallinity by carbonization method, and the pseudoboehmite obtained by the method and its application. BACKGROUND

[0002] Pseudoboehmite has a chemical formula of AlOOH·nH2O (0 < n < 1), and is an aluminum oxide compound with a water content greater than boehmite and a grain size smaller than boehmite. It is a crystal phase that is easily generated in the process of synthesizing aluminum hydroxide, and its crystallization is incomplete. Its typical crystal form is a very thin wrinkled sheet crystal. It is widely used in the petroleum refining process, and is commonly used as a binder for catalytic cracking catalysts, and a precursor for hydrogenation catalyst carriers (γ-Al2O3). There are many methods for preparing pseudoboehmite, mainly including alcohol alumina hydrolysis method and precipitation method, and the precipitation method is divided into acid method and alkali method.

[0003] Alcoholysis method is to use aluminum metal and higher alcohol (n-pentanol, n-hexanol, isopropyl alcohol) as raw materials, to form alcohol aluminum by the reaction of aluminum metal and alcohol in the presence of catalyst, and to obtain pseudoboehmite by hydrolysis. The alcoholysis method can produce pseudoboehmite with high purity and high crystallinity, but the production cost is high and the production process is complex. Alkaline precipitation method is to use alkali to neutralize and precipitate acidic aluminum salt to prepare pseudoboehmite. Commonly used aluminum salts include Al2(SO4)3, Al(NO3)3, AlCl3, etc. Commonly used alkali precipitants include NaOH, NH3·H2O, NaAlO2, Na2CO3, etc. Among them, the NaAlO2-Al2(SO4)3 method using sodium aluminate solution, an intermediate product of aluminum plant, as precipitant is widely used and is also called double aluminum method. The raw materials NaAlO2 and Al2(SO4)3 can both provide aluminum source, the reaction efficiency is high, and the production cost is relatively low. Therefore, the double aluminum method is the main technical route for producing pseudoboehmite for refining catalysts, especially hydrogenation catalysts in China. Acid precipitation method is to use acid to neutralize and precipitate basic aluminum salt to prepare pseudoboehmite. The basic aluminum salt is generally sodium aluminate, and the acid can be strong acid (HNO3, H2SO4, etc.), weak acid (NH4HCO3, NaHCO3, etc.) or CO2, etc. Among them, the NaAlO2-CO2 method is also called carbonation method. The carbonation method for preparing pseudoboehmite can rely on the sintering method for producing alumina, and use NaAlO2 solution, an intermediate product, and CO2, waste gas from aluminum plant, as raw materials. The process is simple, and the by-products and waste liquid in the production process can be returned to the production process of alumina for reuse. Therefore, the carbonation method is the method with the lowest cost for industrial production of pseudoboehmite. Moreover, the method is consistent with the theme of CO2 capture and utilization, and meets the requirements of green development in the era. However, the carbonation method is prone to generate trihydrate impurities, and the crystallinity is low. However, the particle size, morphology and crystallinity of pseudoboehmite have important influence on the properties of hydrogenation catalyst carrier and catalytic cracking binder, and are the main indicators for evaluating the quality of pseudoboehmite.

[0004] CN110304644A discloses a method for producing high-purity and high-stickiness pseudoboehmite by carbonation method. The method is to obtain high-purity sodium aluminate solution by pre-decomposition, and then react with carbon dioxide gas to obtain high-purity pseudoboehmite. Further, a high-carbon alcohol additive (urea or choline) is introduced in the preparation process to perform condensation reaction under high temperature and high pressure, and thus pseudoboehmite with crystallinity of 80-90%, crystal size of 5-6 nm, good stickiness and high purity is obtained.

[0005] CN105645446A discloses an aging method for preparing pseudoboehmite by carbonation method. After the pseudoboehmite is gelled, solid-liquid separation is performed rapidly, and the obtained filter cake is aged at 70-100℃ for 2-4h. The prepared pseudoboehmite has crystallinity of 70-80%, less impurities and good peptization index.

[0006] The crystallinity of the pseudo-boehmite product prepared by the prior art method needs to be improved, and there is a lack of attention to the crystal size of the pseudo-boehmite. In fact, the crystal size changes the packing mode of primary particles, which has an important influence on the pore structure of the pseudo-boehmite and the subsequent alumina. SUMMARY

[0007] In view of the deficiencies of the prior art, the present inventors have found, through a large number of experiments, that by controlling suitable gelation pH value and stepwise temperature aging conditions, a pseudo-boehmite with good peptization, pure crystal phase, few impurities and adjustable crystal size can be prepared.

[0008] Therefore, in one aspect, the present application provides a method for preparing a pseudo-boehmite with adjustable crystal size, comprising the following steps:

[0009] (1) neutralizing a sodium alumininate solution with carbon dioxide gas to gelation;

[0010] (2) stepwise temperature aging of the gelled slurry in a closed container;

[0011] (3) filtering and washing the aged slurry with deionized water; and

[0012] (4) drying the filter cake obtained after washing to obtain the pseudo-boehmite with adjustable crystal size.

[0013] In one embodiment of the method according to the present application, the concentration of the sodium alumininate solution in step (1) is 10-80 g Al2O3 / L, preferably 15-60 g Al2O3 / L; the volume concentration of the carbon dioxide gas is 15-50%, preferably 25-50%; the gelation temperature is below 50°C; and the gelation end point pH value is 9-11.

[0014] In another embodiment of the method according to the present application, the stepwise temperature aging in step (2) comprises: first programmed temperature rising to 50-100°C for aging for 30-120 min, preferably programmed temperature rising to 60-80°C for aging for 40-80 min; and then programmed temperature rising to 100-220°C for aging for 1-10 h, preferably programmed temperature rising to 120-180°C for aging for 2-6 h.

[0015] In another embodiment of the method according to the present application, step (3) can be intermittent washing of the filter cake obtained by filtering the aged slurry by slurring and filtering the filter cake with deionized water, and then slurring and filtering the filter cake thus obtained with deionized water; or can be continuous washing of the filter cake obtained by filtering the aged slurry by continuously adding deionized water to the filter cake; preferably, continuous washing is adopted.

[0016] In another embodiment of the method according to the present application, the temperature of the deionized water is 60-90°C, preferably 80-90°C.

[0017] In another embodiment of the method according to the present application, the intermittent washing can be performed 1-4 times.

[0018] In another embodiment of the method according to the present application, the drying in step (4) is performed at a temperature of 60-120°C, preferably 70-100°C, for 2-4 hours.

[0019] In another aspect, the present application provides a pseudo-boehmite prepared according to the method of the preceding embodiments, which has a crystallinity of not less than 90%, a crystallite size of 5-12 nm, a specific surface area of 100-300 m 2 / g, and a pore volume of 0.4-1.0 mL / g.

[0020] In one embodiment of the pseudo-boehmite according to the present application, the pseudo-boehmite has a crystallinity of 90-97%, a crystallite size of 5-10 nm, a specific surface area of 120-250 m 2 / g, and a pore volume of 0.5-0.8 mL / g.

[0021] In another aspect, the present application provides the use of the aforementioned pseudo-boehmite in the preparation of a catalyst.

[0022] The method for preparing a pseudo-boehmite according to the present application uses the carbonization method, which is green, environmentally friendly, and low in cost, and does not require the addition of any auxiliary agent, and the process is simple. By controlling the appropriate gelation pH value and the conditions of stepwise temperature increase and aging, the obtained pseudo-boehmite has good peptization, pure crystal phase, and few impurities, and can be widely used in the field of petroleum and chemical industry, especially in the preparation of catalysts.

[0023] Compared with the prior art, the present application breaks through the limitation that it is difficult to prepare high-quality pseudo-boehmite by the traditional carbonization method, and shows great economic benefits, and can be widely used in the field of petroleum and chemical industry, especially as a binder for catalytic cracking catalysts, a carrier for hydrogenation catalysts, and a carrier for reforming catalysts. BRIEF DESCRIPTION OF DRAWINGS

[0024] The above and other characteristics and advantages of the present application will become more apparent from the following detailed description of the application taken in conjunction with the accompanying drawings, in which:

[0025] Figure 1 is an XRD spectrum of the pseudo-boehmite; DETAILED DESCRIPTION

[0026] The following examples will further illustrate the present application, which is intended to help the reader better understand the essence of the present application and the beneficial effects brought by the present application, but should not be understood as any limitation on the implementable scope of the present application.

[0027] The method for preparing pseudo-boehmite with adjustable grain size according to the present application comprises the following steps:

[0028] (1) neutralizing a sodium alumininate solution with carbon dioxide gas to form a gel;

[0029] (2) aging the formed gel slurry in a closed container in stages by increasing the temperature;

[0030] (3) filtering the aged slurry and washing it with deionized water; and

[0031] (4) drying the filter cake obtained after washing to obtain the pseudo-boehmite with adjustable grain size.

[0032] In one embodiment of the method according to the present application, the concentration of the sodium alumininate solution in step (1) is 10-80 g Al203 / L, preferably 15-60 g Al203 / L; the volume concentration of the carbon dioxide gas is 15-50%, preferably 25-50%; the gelation temperature is below 50°C; and the pH at the end of gelation is 9-11.

[0033] It should be noted that in the present application, the volume concentration of the carbon dioxide gas refers to the volume ratio of carbon dioxide and nitrogen; the gelation temperature refers to the temperature of the neutralization reaction of sodium alumininate and carbon dioxide; and the pH at the end of gelation refers to the pH at the end of the reaction of sodium alumininate and carbon dioxide.

[0034] In another embodiment of the method according to the present application, the aging in stages by increasing the temperature in step (2) comprises: first increasing the temperature in stages to 50-100°C for aging for 30-120 min, preferably increasing the temperature in stages to 60-80°C for aging for 40-80 min; and then increasing the temperature in stages to 100-220°C for aging for 1-10 h, preferably increasing the temperature in stages to 120-180°C for aging for 2-6 h.

[0035] It should be noted that in the present application, the container in step (2) is generally a container resistant to high temperature, pressure and acid and alkali corrosion, and can be a glass container, a stainless steel container or a reaction kettle, etc.; and the speed of increasing the temperature in stages is generally controlled within the range of 4-6°C / min. The suitable aging temperature and aging time have a significant influence on the nucleation and growth of grains, which is the reason why the aforementioned aging by increasing the temperature in stages is adopted in the present application.

[0036] In another embodiment of the method according to the present application, step (3) can be an intermittent washing in which the filter cake obtained by filtering the aged slurry is slurried with deionized water and filtered, and then the filter cake thus obtained is again slurried with deionized water and filtered; or a continuous washing in which the filter cake obtained by filtering the aged slurry is continuously added with deionized water; and preferably the continuous washing is used.

[0037] It should be noted that in the present application, the washing method in step (3) can be divided into intermittent washing and continuous washing, the former refers to that the slurry of the filter cake ~ filtration is one washing, and is repeated for several times, for example, if the washing is performed 4 times, the slurry is performed 4 times, and the filtration is performed 4 times; the latter refers to that the deionized water is continuously added during the filtration, and the slurry is not repeated after the first slurry, until the washing is completed. In the continuous washing, the water and solid system is always in dynamic balance, which is more conducive to reducing the Na2O content in the pseudo-boehmite product and promoting the grain growth.

[0038] In another embodiment of the method according to the present application, the temperature of the deionized water is 60-90°C, preferably 80-90°C.

[0039] In another embodiment of the method according to the present application, the drying in step (4) is performed at a temperature of 60-120°C, preferably 70-100°C, for 2-4h.

[0040] On the other hand, the present application provides a pseudo-boehmite prepared by the method according to the aforementioned embodiments, which has a crystallinity of not less than 90%, a grain size of 5-12nm, a specific surface area of 100-300m 2 / g, and a pore volume of 0.4-1.0mL / g.

[0041] In one embodiment of the pseudo-boehmite according to the present application, the pseudo-boehmite has a crystallinity of 90-97%, a grain size of 5-10nm, a specific surface area of 120-250m 2 / g, and a pore volume of 0.5-0.8mL / g.

[0042] It should be noted that in the present application, the crystallinity refers to the percentage of the mass of the crystal state in the total mass, which is measured by X-ray powder diffraction (XRD).

[0043] It should be noted that in the present application, the grain size refers to the size of the grain size, which is measured by X-ray powder diffraction (XRD).

[0044] In the present application, the crystallinity and crystallite size of the sample are determined by X-ray powder diffraction method (XRD) using RIPP 145-90, RIPP 146-90 standard methods (see "Analysis Methods for Petroleum and Chemical Industry" (RIPP Test Methods) Yang Cuiding et al., Science Press, 1990). The formula for calculating the crystallite size is: wherein K = 1.075, λ is the wavelength of the anode radiation Kα1 spectrum, β1 is the integral width of the pseudo-boehmite 041, 130 diffraction peak, and θ is the Bragg diffraction angle of the diffraction peak.

[0045] In the present application, the specific surface area and total pore volume of the sample are determined by BET method, i.e. using an American Micromeritics Company ASAP 2405N V1.01 automatic adsorption instrument, low-temperature static nitrogen adsorption volumetric method, the sample is placed in a 1.33 x 10 -2 Pa, vacuum degassing at 300°C for 4 h, using N2 as the adsorption medium, and determining the adsorption-desorption isotherm of the sample at 77.4 K. The specific surface area (S BET ) of the sample is calculated according to the BET formula, the volume of N2 adsorbed by the sample at a relative pressure p / p0 = 0.98 is determined, which is converted into the liquid nitrogen volume, i.e. the total pore volume.

[0046] In the present application, the Na2O content is determined by X-ray fluorescence spectroscopy.

[0047] Example 1

[0048] A sodium metaaluminate solution with a concentration of 60 g Al2O3 / L is reacted with carbon dioxide gas with a volume fraction of 50% to form a gel, the carbon dioxide gas flow rate is 3 L / min, and the terminal pH value is controlled at 10. After the obtained slurry is transferred to a reaction kettle, it is first aged at 60°C for 50 min by programmed heating (heating rate 5°C / min), and then aged at 120°C for 3 h by programmed heating (heating rate 5°C / min). After the aging is completed, the obtained slurry is separated into solid and liquid, washed with 80°C deionized water for half an hour, and a filter cake of the product with impurities removed is obtained. The filter cake is dried at 100°C for 3 h, and then crushed to obtain a pseudo-boehmite powder A1, the physicochemical properties of which are shown in Table 1 below.

[0049] Example 2

[0050] A sodium aluminate solution with a concentration of 40 g Al2O3 / L was reacted with carbon dioxide gas with a volume fraction of 45% to form a gel, and the flow rate of the carbon dioxide gas was 2 L / min, with the end point pH value controlled at 10.5. After the obtained slurry was transferred to a reactor, it was first aged at 65°C for 45 min by programmed heating (heating rate 5°C / min), and then aged at 135°C for 4 h by programmed heating (heating rate 5°C / min). After the aging was completed, the obtained slurry was separated into solid and liquid, and washed with deionized water at 80°C for half an hour. The filter cake of the product after the impurities were removed was dried at 100°C for 3 h, and was crushed to obtain a boehmite powder A2, the physicochemical properties of which are shown in Table 1 below.

[0051] Example 3

[0052] A sodium aluminate solution with a concentration of 30 g Al2O3 / L was reacted with carbon dioxide gas with a volume fraction of 45% to form a gel, and the flow rate of the carbon dioxide gas was 2 L / min, with the end point pH value controlled at 10.5. After the obtained slurry was transferred to a reactor, it was first aged at 70°C for 50 min by programmed heating (heating rate 5°C / min), and then aged at 150°C for 4 h by programmed heating (heating rate 5°C / min). After the aging was completed, the obtained slurry was separated into solid and liquid, and washed with deionized water at 90°C for half an hour. The filter cake of the product after the impurities were removed was dried at 100°C for 3 h, and was crushed to obtain a boehmite powder A3, the physicochemical properties of which are shown in Table 1 below.

[0053] Example 4

[0054] A sodium aluminate solution with a concentration of 20 g Al2O3 / L was reacted with carbon dioxide gas with a volume fraction of 33% to form a gel, and the flow rate of the carbon dioxide gas was 2 L / min, with the end point pH value controlled at 10.5. After the obtained slurry was transferred to a reactor, it was first aged at 70°C for 60 min by programmed heating (heating rate 5°C / min), and then aged at 170°C for 5 h by programmed heating (heating rate 5°C / min). After the aging was completed, the obtained slurry was separated into solid and liquid, and washed with deionized water at 90°C for half an hour. The filter cake of the product after the impurities were removed was dried at 100°C for 3 h, and was crushed to obtain a boehmite powder A4, the physicochemical properties of which are shown in Table 1 below.

[0055] Example 5

[0056] A sodium aluminate solution with a concentration of 15 g Al2O3 / L was reacted with carbon dioxide gas with a volume fraction of 25% to form a gel, and the flow rate of the carbon dioxide gas was 1 L / min, and the terminal pH value was controlled to be 11. After the obtained slurry was transferred to a reaction kettle, it was first programmed to heat (heating rate 5°C / min) to 75°C for aging for 70 min, and then programmed to heat (heating rate 5°C / min) to 180°C for aging for 5 h. After the aging was completed, the obtained slurry was subjected to solid-liquid separation, and was continuously washed with ionized water at 90°C for half an hour to obtain a filter cake of the product from which impurities were removed. The filter cake was dried at 100°C for 3 h, and was crushed to obtain pseudo-boehmite powder A5, and the physicochemical properties of the pseudo-boehmite powder A5 are shown in Table 1 below.

[0057] Comparative Example 1

[0058] A sodium aluminate solution with a concentration of 40 g Al2O3 / L was reacted with carbon dioxide gas with a volume fraction of 45% to form a gel, and the flow rate of the carbon dioxide gas was 2 L / min, and the terminal pH value was controlled to be 10.5. After the obtained slurry was transferred to a reaction kettle, it was hydrothermally aged at 100°C for 3 h. After the aging was completed, the obtained slurry was subjected to solid-liquid separation, and was continuously washed with deionized water at 80°C for half an hour to obtain a filter cake of the product from which impurities were removed. The filter cake was dried at 100°C for 3 h, and was crushed to obtain pseudo-boehmite powder D1, and the physicochemical properties of the pseudo-boehmite powder D1 are shown in Table 1 below.

[0059] Comparative Example 2

[0060] The pseudo-boehmite was prepared according to the method of Example 1, except that the deionized water was intermittently washed 4 times at 80°C. Pseudo-boehmite powder D2 was obtained, and the physicochemical properties of the pseudo-boehmite powder D2 are shown in Table 1 below.

[0061] Comparative Example 3

[0062] The pseudo-boehmite was prepared according to the method described in Example 4 of CN105645446A, and the specific steps are as follows:

[0063] A sodium aluminate solution with an alumina content of 60 g / l was used as a raw material, and carbon dioxide gas with a volume concentration of 30-40% was introduced. When the pH value of the slurry was 12, the obtained slurry was quickly subjected to liquid-solid separation. The separated filter cake was placed in a sealed flask and aged in a 95°C water bath for 3.5 hours. Then, hot water at 95°C was added to the slurry, and the slurry was repeatedly stirred and washed to remove impurities. The pseudo-boehmite D3 was obtained by drying in an oven, and the physicochemical properties of the pseudo-boehmite D3 are shown in Table 1 below.

[0064] Comparative Example 4

[0065] The pseudo-boehmite was prepared according to the method described in Example 1 of CN110304644A, and the specific steps are as follows:

[0066] First, the sodium aluminate solution is purified, and then a high-purity sodium aluminate solution with an Al2O3 content of 45 g / L is used as raw material, CO2 gas with a concentration of 40% is introduced to carry out the gelation reaction, the flow rate per hour is controlled at 3.0 m 3 / h, the reaction time is controlled at 40 minutes, the Al2O3 residual is controlled at 5 g / L, and the final temperature is controlled at 35°C. After the reaction, the slurry is separated and washed, the filter cake is washed with high-purity water at 85°C until the pH value of the filter cake is 7.0. The filter cake prepared above is added to high-purity water and stirred to form a slurry, urea with a concentration of 8 g / L is added, and after stirring for 50 min, the slurry is moved to an autoclave device, the autoclave temperature is controlled at 160°C, the pressure is controlled at 0.6 MPa, and the holding time is 4 h. After the reaction is completed, the temperature is lowered, the material is discharged, and the filter cake is washed. The amount of water used for washing is controlled according to the pH value of the filter cake, which is 7.0, and the product is dried at 100°C to control the water content at 15%, and the final product pseudoboehmite D4 is obtained by crushing. The physicochemical properties of the product are shown in Table 1 below.

[0067] Table 1: Pseudoboehmite performance index

[0068] Examples Crystallinity, % Grain size, nm Na20, % Specific surface area, m 2 / g]] Total pore volume, mL / g A1 93.3 5.7 0.0723 252.36 0.53 A2 92.7 6.7 0.0692 204.58 0.58 A3 94.1 7.5 0.0633 189.33 0.63 A4 96.4 8.5 0.0572 177.21 0.67 A5 95.6 9.2 0.049 128.41 0.74 D1 78.2 3.7 0.0671 329.24 0.43 D2 90.9 4.9 0.0884 250.76 0.5 D3 75.8 3.4 0.07534 351.75 0.42 D4 88.1 4.9 0.03895 182.4 0.50

[0069] The data in Table 1 show that the crystallinity of the pseudoboehmite prepared according to the method of the present application is significantly higher than that of the pseudoboehmite prepared by other methods, and the grain size of the pseudoboehmite can be adjusted.

[0070] The above describes the present application in combination with preferred embodiments, but these embodiments are only exemplary and serve only to illustrate the present application. On this basis, various substitutions and improvements can be made to the present application, and these all fall within the protection scope of the present application.

Claims

1. A method for preparing pseudo-boehmite with adjustable grain size, comprising the following steps: (1) neutralizing the sodium aluminate solution with carbon dioxide gas to form a gel; (2) subjecting the gelled slurry to temperature aging in a sealed container in stages; (3) filtering the aged slurry and washing with deionized water; and (4) drying the filter cake obtained after washing to obtain the pseudo-boehmite with adjustable grain size; in, The concentration of the sodium aluminate solution in step (1) is 10 to 80 gAl2O3 / L; the volume concentration of the carbon dioxide gas is 15 to 50%; the gelling temperature is lower than 50°C; and the pH value at the gelling endpoint is 9 to 11; The staged temperature aging in step (2) includes: firstly raising the temperature to 60-75°C for aging for 45-70 minutes; and then raising the temperature to 120-180°C for aging for 3-5 hours.

2. The method according to claim 1, wherein the concentration of the sodium metaaluminate solution in step (1) is 15 to 60 gAl2O3 / L; and the volume concentration of the carbon dioxide gas is 25 to 50%.

3. The method according to claim 1, wherein step (3) comprises intermittent washing of the filter cake obtained by filtering the aged slurry with deionized water and filtering, and then slurrying and filtering the filter cake obtained by filtering the aged slurry with deionized water; or continuous washing of the filter cake obtained by filtering the aged slurry with deionized water without interruption.

4. The method according to claim 3, wherein step (3) adopts continuous washing.

5. The method according to claim 3 or 4, wherein the temperature of the deionized water is 60 to 90°C. The method according to claim 5 , wherein the temperature of the deionized water is 80-90° C.

7. The method according to claim 3, wherein the intermittent washing is performed 1 to 4 times.

8. The method according to claim 1, wherein the drying in step (4) is carried out at a temperature of 60 to 120°C for 2 to 4 hours.

9. The method according to claim 8, wherein the drying in step (4) is carried out at a temperature of 70 to 100°C.

10. Pseudo-boehmite prepared according to the method of any one of claims 1 to 9, characterized in that The pseudo-boehmite has: a crystallinity of not less than 90%, a grain size of 5 to 12 nm, and a 2 / g specific surface area and 0.4~1.0mL / g pore volume.

11. Pseudoboehmite according to claim 10, characterized in that The pseudo-boehmite has: 90-97% crystallinity, 5-10nm grain size, 120-250nm 2 / g specific surface area and 0.5~0.8mL / g pore volume.

12. Use of the pseudo-boehmite according to claim 10 or 11 in the preparation of a catalyst.

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