A pseudo-boehmite and a method for producing the same

Abstract

A pseudo-boehmite and a preparation method thereof, the pseudo-boehmite has a crystal grain size D (130) of 4-10 nm, and a specific surface area D (130) / D (020) of 1.0-1.5. The preparation method comprises the following steps: reacting a sodium aluminate solution with carbon dioxide gas, aging under certain hydrothermal conditions, washing and drying. The pseudo-boehmite prepared by the method has high crystallinity, large crystal grain size, large pore diameter and good peptization performance. The pseudo-boehmite is applied to a catalytic cracking catalyst, can produce obvious mesopore distribution under the condition that the strength of the catalyst is qualified, and significantly improves the pore structure of the catalyst, which has important significance for promoting the efficient diffusion of heavy oil macromolecules, reaction intermediates and product molecules in the catalyst, reducing the coke yield and optimizing the product distribution. The preparation method of the pseudo-boehmite is green and environmentally friendly, low in cost and easy to implement.

Description

TECHNICAL FIELD

[0001] The present application relates to a pseudo-boehmite and a preparation method thereof. BACKGROUND

[0002] The chemical formula of the pseudo-boehmite is AlOOH·nH2O (0 < n < 1), which is an aluminum oxide compound with a water content greater than boehmite and a crystal grain size smaller than boehmite. It is a crystal phase that is easily generated in the process of synthesizing aluminum hydroxide, and its typical crystal form is a very thin wrinkled sheet crystal.

[0003] There are many methods for preparing the pseudo-boehmite, mainly including alcohol aluminum hydrolysis method and precipitation method, etc. The precipitation method is divided into acid method and alkali method. The alcohol aluminum hydrolysis method uses metal aluminum and high alcohol (n-pentanol, n-hexanol, isopropyl alcohol) as raw materials, and the pseudo-boehmite is obtained by reacting the metal aluminum with alcohol in the presence of a catalyst to form alcohol aluminum, and then hydrolyzing. However, this method has high production cost and complex production process. The alkali precipitation method refers to a method for preparing the pseudo-boehmite by neutralizing and precipitating an acid aluminum salt with an alkali. Common aluminum salts include Al2(SO4)3, Al(NO3)3, AlCl3, etc., and common alkali precipitants include NaOH, NH3·H2O, NaAlO2, Na2CO3, etc. The acid precipitation method refers to a method for preparing the pseudo-boehmite by neutralizing and precipitating an alkali aluminate with an acid. The alkali aluminate is generally sodium aluminate, and the acid used can be a strong acid (HNO3, H2SO4, etc.), a weak acid (NH4HCO3, NaHCO3, etc.), CO2, etc. The NaAlO2-CO2 method is also known as carbonization method. The pseudo-boehmite prepared by the carbonization method can rely on the sintering method for producing aluminum oxide, and use the intermediate product NaAlO2 solution and the waste gas CO2 of an aluminum plant as reaction 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 the aluminum oxide for reuse. It is the lowest cost method for industrial production of the pseudo-boehmite at present.

[0004] The pseudo-boehmite is widely used in petroleum refining and petrochemical catalysts, and is commonly used as a binder for catalytic cracking catalysts and a precursor for hydrogenation catalyst carriers (γ-Al2O3). The pseudo-boehmite has good binding performance after acidification, and can form a specific mesoporous structure after the catalyst is prepared and formed.

[0005] The pseudo-boehmite prepared by the conventional carbonization method has low crystallinity, and the mesopore size is only 3.8 nm. When the pseudo-boehmite is prepared into a catalytic cracking catalyst, it can only provide a mesoporous structure with a pore size of 3.8 nm. The diffusion of the catalytic cracking raw material molecules is obviously hindered in the 3.8 nm pore channel. This hindering effect limits the efficient diffusion and conversion of heavy oil raw material molecules, which is not conducive to reducing the coke yield and improving the product distribution. At present, there is no literature report that the pseudo-boehmite prepared by the carbonization method can provide a larger mesopore size distribution after acidification and peptization and be applied to the catalytic cracking catalyst.

[0006] CN110304644A discloses a method for producing high-purity high-viscosity pseudo-boehmite by carbonization. The method is to obtain high-purity sodium aluminate solution by pre-decomposition, and then react with carbon dioxide gas to obtain high-purity pseudo-boehmite. However, the pseudo-boehmite has a low pore size, which cannot provide a larger pore size in the preparation process of catalytic cracking catalyst. SUMMARY

[0007] One of the technical problems to be solved by the present application is to provide a pseudo-boehmite capable of generating larger mesopore structure after acidification. The second technical problem to be solved by the present application is to provide a preparation method of the pseudo-boehmite.

[0008] The present application provides a pseudo-boehmite, wherein the grain size D (130) of the pseudo-boehmite is 4 nm to 10 nm, and the ratio of D (130) / D (020) is 1.0 to 1.5. (130) Herein, D (020) represents the grain size of the crystal plane represented by the (130) peak (corresponding to 2θ = 38.3°) in the XRD spectrum of the pseudo-boehmite grain, and D (130) represents the grain size of the crystal plane represented by the (020) peak (corresponding to 2θ = 14.1°) in the XRD spectrum of the pseudo-boehmite grain.

[0009] The pseudo-boehmite provided by the present application has a pore size of greater than 4.5 nm and less than 12 nm, preferably 4.8 nm to 11 nm, for example, 5-10 nm or 5 nm to 9 nm or 6-8.5 nm or 7-9 nm. The pore size refers to the diameter.

[0010] The pseudo-boehmite provided by the present application has a grain size D (130) of 4 nm to 10 nm, preferably 5 nm to 8.5 nm, for example, 5.1-8.5 nm or 5.5-8.5 nm or 6-8.2 nm.

[0011] The pseudo-boehmite provided by the present application has a ratio of D (130) / D (020) of 1.0 to 1.5, for example, 1.1-1.4 or 1.2-1.35, preferably 1.1 to 1.3.

[0012] The pseudo-boehmite provided by the present application has a crystallinity of 85% to 110%, preferably 88% to 108%, for example, 90%-105%.

[0013] The pseudo-boehmite provided by the present application has a pore volume of 0.30 cm 3 / g to 0.58 cm 3 / g, preferably 0.31 cm 3 / g 0.52 cm 3 / g for example 0.33 to 0.5 cm 3 / g.

[0014] The pseudoboehmite provided by the present application has a peptization index of 90% to 100%, preferably 93% to 99%.

[0015] The present application provides a method for preparing the pseudoboehmite, which comprises the following steps:

[0016] (1) reacting a sodium aluminate solution with CO2 to form a first slurry;

[0017] (2) aging the first slurry under certain conditions to obtain an aged slurry, which is referred to as a second slurry; the certain conditions for aging are: first static aging, then aging under stirring, and the aging temperature is above 100°C and not more than 185°C;

[0018] (3) filtering, washing and drying the aged slurry.

[0019] According to the method for preparing the pseudoboehmite of the present application, in step (1), the concentration of the sodium aluminate solution is preferably 5 to 60 g / L in terms of Al2O3. The sodium aluminate solution can be commercially available or prepared according to the prior art. In one embodiment, the method for preparing the sodium aluminate solution comprises: reacting aluminum hydroxide and an alkali solution at a temperature of 90 to 120°C for 1 to 4 hours, and diluting to an Al2O3 concentration of 5 to 60 g / L. The alkali solution is for example a sodium hydroxide solution. The caustic ratio of the sodium metaaluminate solution is for example 1.0 to 3.2.

[0020] According to the method for preparing the pseudoboehmite of the present application, in step (1), the reaction of the sodium aluminate solution with CO2 can be carried out by bubbling a CO2-containing gas into the sodium metaaluminate solution, and the volume concentration of CO2 in the CO2-containing gas is 20 to 100%, for example 40 to 100% by volume.

[0021] According to the method for preparing the pseudoboehmite of the present application, the pH value at the end of the reaction of the sodium aluminate solution with CO2 is 8.5 to 10.5.

[0022] According to the method for preparing the pseudoboehmite of the present application, in step (1), the initial reaction temperature is preferably 10 to 35°C, and the temperature at the end of the reaction is preferably 15 to 55°C.

[0023] According to the method for preparing the pseudoboehmite of the present application, in step (1), the reaction time of the sodium aluminate solution with CO2 is preferably 20 to 70 minutes.

[0024] In one embodiment, in step (1), the conditions for the reaction of sodium aluminate solution with CO2 include: an initial reaction temperature of 10–35°C, a reaction time of 20–70 minutes, and an ending reaction temperature of 15–55°C. The pH value at the endpoint of the reaction between sodium aluminate solution and CO2 is 8.5–10.5. Preferably, the reaction of sodium aluminate solution with CO2 involves contacting the sodium aluminate solution with a CO2-containing gas, wherein the volume concentration of CO2 in the CO2-containing gas is 20%–100%.

[0025] In step (2), the first slurry is aged under certain conditions. In one embodiment, the aging temperature is 100–185°C, for example, 120–180°C, preferably 135–180°C. The first slurry can be heated to 100–185°C, preferably 120–180°C or 135–180°C, and then aged at this temperature. Preferably, the time for the first slurry to rise from the reaction endpoint temperature to the aging temperature does not exceed 60 minutes. Preferably, the temperature from the start to the end of aging is constant, meaning that the temperature of static aging and stirring aging is kept substantially constant; for example, the difference between the static aging and stirring aging temperatures preferably does not exceed 2°C.

[0026] In step (2), the aging pressure is preferably 0.2 to 1 MPa.

[0027] In step (2), the stirring speed is controlled at 50–400 r / min. The stirring can be carried out using existing stirring methods. Through stirring, the aging slurry rotates in the aging tank under the action of the stirring paddle.

[0028] In step (2), the aging time is preferably 2 to 10 hours.

[0029] In step (2), the slurry is first statically aged at a certain temperature and then aged under stirring. During static aging, no stirring is performed, allowing the slurry to remain still for a period of time. Preferably, the first slurry is first statically aged at the aging temperature for 1-4 hours, for example, 2-3 hours, and then aged under stirring at the aging temperature for 1-6 hours. The stirring speed is 50-400 r / min, for example, 60-400 r / min.

[0030] In one embodiment, in step (2), the first slurry is aged under certain conditions, with an aging temperature of 100-185°C and a pressure of 0.2-1 MPa for 2-10 hours of constant temperature reaction; wherein, the first slurry is first allowed to stand for aging for 1-4 hours, for example 2-3 hours, and then the aging temperature and pressure are maintained, and stirring is applied, with the stirring speed controlled at 50-400 r / min, for example 60-400 r / min, and the stirring aging time is 1-6 hours.

[0031] Step (3), the slurry after aging is filtered, washed, and dried to obtain pseudo-boehmite with specific crystal characteristics and pore size distribution. In one embodiment, the washing condition is washing with deionized water at 70-100°C until the pH of the wet cake is 7-7.5. The drying temperature is preferably 60-98°C, for example 70-98°C, preferably 70-95°C, and the drying time is for example 2-4h.

[0032] The pseudo-boehmite provided by the present application has specific crystal characteristics, high crystallinity, large grain size, large pore size, and good peptization.

[0033] The preparation method of the pseudo-boehmite provided by the present application is green, environmentally friendly, low in cost, and easy to implement, and can obtain pseudo-boehmite with specific crystal characteristics and pore size distribution. The pseudo-boehmite has high crystallinity, large grain size, large pore size, and good peptization, and has a large pore size and good adhesion after acidification.

[0034] The pseudo-boehmite provided by the present application can be used for catalyst preparation. Its specific grain morphology makes it easier to accumulate and form a stable mesoporous structure during catalyst preparation, and a larger pore size can be obtained than in the prior art. The pseudo-boehmite can be directly acidified to obtain a catalyst with a larger pore size and good strength without the need for pore expansion treatment. For example, in the preparation of catalytic cracking catalysts, a significant mesopore distribution can be produced, and a catalytic cracking catalyst with a pore size greater than 5nm can be obtained, which maintains the strength of the catalyst while significantly improving the pore structure of the catalyst. The prepared catalytic cracking catalyst can promote the efficient diffusion of heavy oil macromolecules, reaction intermediates, and product molecules in the catalyst, reduce coke yield, and optimize product distribution. DETAILED DESCRIPTION

[0035] The following examples will further illustrate the present application, but should not be used to limit the present application.

[0036] In the present application, the crystallinity and grain size D of the sample are measured by X-ray powder diffraction (XRD) method, and are determined according to the RIPP145-90 and RIPP146-90 standard methods (see "Petroleum and Chemical Industry Analysis Methods" (RIPP Test Methods) edited by Yang Cuiding et al., published by Science Press in 1990). The crystallinity of the sample is calculated according to the peak at 2θ = 38.3° (130 crystal plane). The grain size is calculated according to the Scherrer formula where K = 1.075, λ is the wavelength of the anode radiation Kα1 spectrum, β is the half-peak width of the specific diffraction peak of the pseudo-boehmite, and θ is the Bragg diffraction angle of the diffraction peak. (130) D represents the grain size of the sample perpendicular to the (130) crystal plane, β 130 D is the half-maximum width of the diffraction peak of sample (130). (020) This indicates the grain size of the sample perpendicular to the (020) crystal plane. β 020 is the half-peak width of the (020) diffraction peak of the sample.

[0037] In this invention, the probabilistic pore size distribution and pore volume of the sample were determined by low-temperature nitrogen static capacity adsorption. Specific surface area and pore volume were calculated using the two-parameter BET formula, and pore size distribution was calculated using the BJH formula. The pore size corresponding to the highest point of the pore size distribution curve is the probabilistic pore size of the sample. An ASAP 2405NV1.01 automated adsorption instrument from Micromeritics (USA) was used, and the sample was at a temperature of 1.33 × 10⁻⁶. -2 The sample was degassed under vacuum at 300℃ for 4 hours, and the adsorption-desorption isotherm was measured at 77.4K using N2 as the adsorption medium.

[0038] In this invention, the determination of the gel solubility index is as follows: 10 grams of boehmite is weighed, calcined at 600℃ for 3 hours, cooled in a desiccator, and weighed to obtain W0 grams. The dry basis weight a0 = W0 / 10 is obtained. The weight of the boehmite m1 = 6 / a0 grams is weighed. m1 grams of boehmite is placed in a 100 mL polytetrafluoroethylene (PTFE) cup, and deionized water is added to a final volume of 40 grams. The mixture is stirred evenly using a magnetic rotor, and then 20 mL of 0.19 N dilute nitric acid solution is added. The mixture is stirred magnetically for 20 minutes. The entire solution is poured into a centrifuge tube and centrifuged at 1900 rpm for 20 minutes. The upper colloidal solution is poured off, placed in a weighed crucible, dried at 80℃, calcined at 600℃ for 3 hours, cooled in a desiccator, and weighed to obtain m2 grams. The gel solubility index DI = (m2 / 6) * 100%.

[0039] Sodium aluminate, produced by Shanghai Maclean Biochemical Technology Co., Ltd., caustic ratio 1, analytical grade.

[0040] Example 1

[0041] A sodium aluminate solution with a concentration of 20 g Al2O3 / L was reacted with carbon dioxide gas with a volume fraction of 40% (the volume fraction of carbon dioxide was 40%, and the rest was nitrogen) to form a gel, and the end point pH value was controlled to be 9.5. After the obtained slurry was transferred to an aging kettle, it was aged at 135°C and 0.35 MPa for 3 h. Under the conditions of temperature and pressure, stirring was started, the stirring rate was kept at 150 r / min, and the aging was continued for 1 h. After the aging was completed, the obtained slurry was separated into solid and liquid, and the wet cake was washed with deionized water at 85°C for half an hour until the pH value of the wet cake was 7.1, to obtain a wet cake of impurity-removed pseudoboehmite. The wet cake was dried at 80°C for 3 h, and was crushed to obtain a pseudoboehmite powder S1, the physicochemical properties of which are shown in Table 1.

[0042] Example 2

[0043] A sodium aluminate solution with a concentration of 45 g Al2O3 / L was reacted with carbon dioxide gas with a volume fraction of 60% (the volume fraction of carbon dioxide was 60%, and the rest was nitrogen) to form a gel, and the end point pH value was controlled to be 10.3. After the obtained slurry was transferred to an aging kettle, it was aged at 180°C and 1.0 MPa for 2.5 h. Under the conditions of temperature and pressure of 180°C and 1.0 MPa, stirring was started, the stirring rate was kept at 450 r / min, and the aging was continued for 1 h. After the aging was completed, the obtained slurry was separated into solid and liquid, and the wet cake was washed with deionized water at 95°C for half an hour until the pH value of the wet cake was 7.3, to obtain a wet cake of impurity-removed pseudoboehmite. The wet cake was dried at 90°C for 4 h, and was crushed to obtain a pseudoboehmite powder S2, the physicochemical properties of which are shown in Table 1.

[0044] Example 3

[0045] A sodium aluminate solution with a concentration of 8 g Al2O3 / L was reacted with carbon dioxide gas with a volume fraction of 35% (the volume fraction of carbon dioxide was 35%, and the rest was nitrogen) to form a gel, and the end point pH value was controlled to be 9.3. After the obtained slurry was transferred to an aging kettle, it was aged at 120°C and 0.2 MPa for 4 h. Under the conditions of temperature and pressure of 120°C and 0.2 MPa, stirring was started, the stirring rate was kept at 100 r / min, and the aging was continued for 2.5 h. After the aging was completed, the obtained slurry was separated into solid and liquid, and the wet cake was washed with deionized water at 75°C for half an hour until the pH value of the wet cake was 7.1, to obtain a wet cake of impurity-removed pseudoboehmite. The wet cake was dried at 75°C for 4 h, and was crushed to obtain a pseudoboehmite powder S3, the physicochemical properties of which are shown in Table 1.

[0046] Example 4

[0047] A sodium aluminate solution with a concentration of 15 g Al2O3 / L was contacted with carbon dioxide gas (CO2volume fraction 50%, the rest being nitrogen) to form a slurry with a final pH of 9.7. The slurry was transferred to an aging kettle and aged at 150°C and 0.48 MPa for 5 h. Then, while maintaining the temperature and pressure at 150°C and 0.48 MPa, the slurry was stirred at a rate of 250 r / min for 4 h. After the aging was completed, the slurry was separated into solid and liquid, and the wet cake was washed with deionized water at 80°C for half an hour until the pH of the wet cake was 7.3. The impurity-removed pseudoboehmite wet cake was obtained. The wet cake was dried at 85°C for 4 h, and the pseudoboehmite powder S4 was obtained by crushing. The physicochemical properties of the pseudoboehmite powder S4 are shown in Table 1.

[0048] Example 5

[0049] A sodium aluminate solution with a concentration of 55 g Al2O3 / L was contacted with carbon dioxide gas (CO2volume fraction 90%, the rest being nitrogen) to form a slurry with a final pH of 10.0. The slurry was transferred to an aging kettle and aged at 160°C and 0.62 MPa for 7 h. Then, while maintaining the temperature and pressure at 160°C and 0.62 MPa, the slurry was stirred at a rate of 350 r / min for 5 h. After the aging was completed, the slurry was separated into solid and liquid, and the wet cake was washed with deionized water at 90°C for half an hour until the pH of the wet cake was 7.4. The impurity-removed pseudoboehmite wet cake was obtained. The wet cake was dried at 95°C for 4 h, and the pseudoboehmite powder S5 was obtained by crushing. The physicochemical properties of the pseudoboehmite powder S5 are shown in Table 1.

[0050] Comparative Example 1

[0051] A sodium aluminate solution with a concentration of 20 g Al2O3 / L was contacted with carbon dioxide gas (CO2volume fraction 40%, the rest being nitrogen) to form a slurry with a final pH of 9.5. The slurry was transferred to an aging kettle and aged at 90°C for 3 h. After the aging was completed, the slurry was separated into solid and liquid, and the wet cake was washed with deionized water at 78°C for half an hour. The impurity-removed product wet cake was obtained. The wet cake was dried at 90°C for 3 h, and the pseudoboehmite powder D1 was obtained by crushing. The physicochemical properties of the pseudoboehmite powder D1 are shown in Table 1.

[0052] Comparative Example 2

[0053] A sodium aluminate solution with a concentration of 20 g Al2O3 / L was contacted with carbon dioxide gas (CO2volume fraction 40%, the rest being nitrogen) to form a slurry with a final pH of 9.5. The slurry was transferred to an aging kettle and aged at 135°C and 0.35 MPa for 3.5 h. After the aging was completed, the slurry was separated into solid and liquid, and the wet cake was washed with deionized water at 80°C for half an hour. The impurity-removed pseudoboehmite wet cake was obtained. The wet cake was dried at 80°C for 3 h, and the pseudoboehmite powder D2 was obtained by crushing. The physicochemical properties of the pseudoboehmite powder D2 are shown in Table 1.

[0054] Comparative Example 3

[0055] A sodium aluminate solution with a high purity and an Al2O3 content of 45 g / L was used as a raw material, and CO2 with a concentration of 40% was introduced to perform a gelation reaction, a flow rate per hour was controlled at 3.0 m 3 / h, a reaction time was controlled at 40 minutes, Al2O3 residue was controlled at 5 g / L, and a final temperature was controlled at 35℃. After the reaction, the slurry was separated and washed, the filter cake was washed with high-purity water at 85℃ until the pH value of the filter cake was 7.0. The filter cake prepared above was stirred in high-purity water, and urea with a concentration of 8 g / L was added. After stirring for 50 minutes, the slurry was moved to an autoclave device, the autoclave temperature was controlled at 150℃, the pressure was controlled at 0.6 MPa, and the slurry was aged for 3 hours. After the aging, the slurry was continuously washed with deionized water at 85℃ for half an hour, and then filtered and dried at 90℃. The final product pseudoboehmite D3 was obtained by crushing, and the physicochemical properties of the product are shown in Table 1.

[0056] Comparative Example 4

[0057] A sodium metaaluminate solution with a concentration of 45 g Al2O3 / L was contacted with carbon dioxide gas (CO2 with a volume fraction of 60%, and the rest was nitrogen) to perform a reaction, and the final pH value was controlled at 10.3. After the reaction, the obtained slurry was transferred to an aging autoclave, and the slurry was kept at 180℃, 1.0 MPa, and a stirring rate of 450 r / min for 3.5 hours. After the aging, the obtained slurry was separated into solid and liquid, and the wet filter cake was continuously washed with deionized water at 95℃ for half an hour until the pH value of the wet filter cake was 7.3, to obtain a wet filter cake of impurity-removed pseudoboehmite. The wet filter cake was dried at 90℃ for 4 hours, and the pseudoboehmite powder D4 was obtained by crushing, and the physicochemical properties of the product are shown in Table 1.

[0058] Table 1 Properties of pseudoboehmite

[0059]

[0060] * Acidification conditions: the acid-to-aluminum ratio (concentration of 36% by weight HCl: Al2O3 mass ratio) was 0.2, the solid content of the acidification mixture was 10% by weight; the calcination temperature was 550℃, and the calcination time was 2 hours.

[0061] As shown in Table 1, the pseudoboehmite provided by the present application has a high crystallinity, a large crystal size, a large D(130) / D(020), a large pore size, good peptization performance, and a large pore size of the calcined sample after peptization. It can be seen that, compared with the existing pseudoboehmite, the pseudoboehmite provided by the present application has a larger pore size and can provide more mesoporous structures when used for preparing a catalytic cracking catalyst.

Claims

1. A pseudoboehmite, characterized in that, The crystallite size D of the pseudoboehmite (130) = 4 nm to 10 nm, D (130) / D (020) = 1.0 to 1.5, the pore diameter of the pseudoboehmite is greater than 4.5 nm and not more than 12 nm, the pore volume of the pseudoboehmite is 0.3 cm 3 / g to 0.58 cm 3 / g; wherein D (130) represents the crystallite size of the crystal plane represented by 2θ = 38.3° corresponding to the (130) peak in the XRD pattern of the pseudoboehmite crystallites, and D (020) represents the crystallite size of the crystal plane represented by 2θ = 14.1° corresponding to the (020) peak in the XRD pattern of the pseudoboehmite crystallites.

2. Pseudo-boehmite according to claim 1, characterized in that The pseudoboehmite has a pore size of 4.8 nm to 11 nm.

3. Pseudo-boehmite according to claim 1 or 2, characterized in that The pseudo-boehmite has a D (130) / D (020) of 1.1 to 1.

3.

4. Pseudo-boehmite according to claim 1 or 2, characterized in that The pseudoboehmite has a colloidal index of 90%–100% and a crystallinity of 85%–110%.

5. The pseudoboehmite according to claim 2, characterized in that The pseudoboehmite has a pore size of 5 nm to 10 nm.

6. The pseudoboehmite according to claim 4, characterized in that The peptization index of the pseudoboehmite is 93% to 99%; the crystallinity of the pseudoboehmite is 88% to 108%; the pore volume of the pseudoboehmite is 0.31 cm 3 / g to 0.52 cm 3 / g.

7. A method for preparing pseudoboehmite, comprising the following steps: (1) React sodium aluminate solution with CO2 to form a first slurry; the conditions for the reaction of sodium aluminate solution with CO2 include an initial reaction temperature of 10-35°C and an endpoint pH value of 8.5-10.

5. (2) The first slurry is aged under certain conditions to obtain an aged slurry; the aging under certain conditions is: first static aging, then aging under stirring, the aging temperature is above 100℃ and not exceeding 185℃; the static aging time is 1 to 4 hours, and the aging time under stirring is 1 to 6 hours. (3) Filtering, washing and drying of the aged slurry.

8. The method of claim 7, wherein, In step (1), the concentration of the sodium aluminate solution, calculated as Al2O3, is 5-60 g / L; In step (3), the drying temperature is 60-98°C, and the washing conditions are washing with deionized water at 70-100°C until the pH of the wet filter cake is 7-7.

5.

9. The method according to claim 7 or 8, characterized in that In step (1), CO2 gas with a concentration of 20% to 100% by volume is introduced into the sodium aluminate solution to carry out the reaction, and the reaction endpoint temperature is 15 to 55°C.

10. The method according to claim 7 or 8, characterized in that In step (2), the aging temperature of the slurry is 120-180℃, the aging pressure is 0.2-1 MPa, the aging time is 2-10 hours, and the time for the first slurry to rise from the reaction endpoint temperature to the aging temperature does not exceed 60 minutes.

11. The method of claim 7, wherein, The static aging time in step (2) is 2 to 3 hours.

12. The method of claim 7, wherein, The aging temperature is 135–180°C.

13. The method of claim 7, wherein, The aging process is constant temperature aging.

14. The method of claim 7, wherein, The stirring speed for the aging process is 50–400 r / min.

15. The use of boehmite according to any one of claims 1 to 6 in the preparation of catalysts.

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