A surface hydroxyl-rich mesoporous pseudoboehmite and a method for preparing the same

Abstract

A surface hydroxyl-rich mesoporous pseudo-boehmite and a preparation method thereof, the pseudo-boehmite has a probable pore diameter greater than 4.5 nm and not more than 12 nm, I 3000～3800 is 6.0 cm ‑1 · mg ‑1 ~ 8.5 cm ‑1 · mg ‑1 The preparation method comprises the following steps: reacting a sodium metaaluminate solution with carbon dioxide gas, aging in stages under hydrothermal conditions in the presence of a hydroxyl regulator, washing and drying. The pseudo-boehmite prepared by the method has high crystallinity, large crystal grain size, a large probable pore diameter, a rich surface hydroxyl and good peptization performance.

Description

Technical Field:

[0001] The present invention relates to mesoporous pseudoboehmite with surface-rich hydroxyl groups and a preparation method thereof. Background Art

[0002] Pseudoboehmite has a chemical formula of AlOOH·nH₂O (0<n<1), which is an aluminum oxy compound with a higher water content and smaller crystal grain size than boehmite. It is a crystal phase that is easily formed during the synthesis of aluminum hydroxide, with incomplete crystallization, and its typical crystal form is very thin folded lamellar crystals.

[0003] There are many preparation methods for pseudoboehmite, mainly including aluminum alkoxide hydrolysis method and precipitation method. The precipitation method is further divided into two categories: acid method and alkali method. The aluminum alkoxide hydrolysis method uses metallic aluminum and higher alcohols (n-pentanol, n-hexanol, isopropanol) as raw materials. Aluminum alkoxide is formed through the reaction of metallic aluminum and alcohol in the presence of a catalyst, and then hydrolyzed to obtain pseudoboehmite. However, this method has high production cost and complicated production process. The alkali precipitation method refers to a method for preparing pseudoboehmite by neutralizing and precipitating acidic aluminum salts with alkalis. Commonly used aluminum salts include Al₂(SO₄)₃, Al(NO₃)₃, AlCl₃, etc., and commonly used alkali precipitants include NaOH, NH₃·H₂O, NaAlO₂, Na₂CO₃, etc. The acid precipitation method refers to a method for preparing pseudoboehmite by neutralizing and precipitating alkaline aluminate with acid. The alkaline aluminate is generally sodium aluminate, and the acid used can be a strong acid (HNO₃, H₂SO₄, etc.), a weak acid (NH₄HCO₃, NaHCO₃, etc.) or CO₂. Among them, the NaAlO₂-CO₂ method is also called carbonization method. Preparation of pseudoboehmite by carbonization method can rely on the sintering process for alumina production, using the intermediate product NaAlO₂ solution and CO₂, the waste gas from aluminum plants, as reaction raw materials, with simple process. Moreover, by-products and waste liquid generated in the production process can be returned to the alumina production process for reuse, which is currently the method with the lowest cost for industrial production of pseudoboehmite.

[0004] Pseudoboehmite is widely used in petroleum refining and petrochemical catalysts, and is often used as a binder for fluid catalytic cracking catalysts and a precursor for hydrogenation catalyst supports (γ-Al₂O₃). Pseudoboehmite is an important raw material in semi-synthetic catalytic cracking catalysts. After acidification, pseudoboehmite has good bonding performance, and can also form a specific mesoporous structure after the catalyst is prepared and shaped.

[0005] Boehmite prepared by conventional carbonization has low crystallinity and a pore size of only 3.8 nm, providing only a mesoporous structure of 3.8 nm when used in catalytic cracking catalysts. Catalytic cracking feedstock molecules are relatively large, and diffusion within these 3.8 nm pores is significantly hindered. This hindering effect limits the efficient diffusion and conversion of heavy oil feedstock molecules, negatively impacting coke yield and product distribution. Currently, there are no reports in the literature of boehmite prepared by carbonization providing a larger pore size distribution in catalytic cracking catalysts. Furthermore, currently available boehmite with larger pore sizes exhibits poor wear resistance and cannot directly form a pore structure with a larger pore size after acidification. Summary of the Invention:

[0006] One of the technical problems to be solved by this invention is to provide a mesoporous pseudoboehmite with good bonding properties, which is rich in surface hydroxyl groups. A second technical problem to be solved by this invention is to provide a method for preparing this pseudoboehmite.

[0007] This invention provides a pseudoboehmite, wherein the pseudoboehmite has a probable pore size greater than 4.5 nm and not exceeding 12 nm. 3000～3800 It is 6.0cm -1 ·mg -1 ~8.5cm -1 ·mg -1 I 3000～3800 This indicates that at an infrared wavelength of 3000cm -1 ~3800cm -1 Infrared absorption intensity of hydroxyl groups on the surface of pseudoboehmite within the range, I 3000～3800 The calculation method is based on the sample at 3000cm. -1 ~3800cm -1 The ratio of the area of ​​the absorption peak within the range to the sample mass.

[0008] Preferably, the pseudoboehmite provided by the present invention has a grain size D (130) The wavelength is greater than 4nm to 10nm, preferably 5nm to 8.5nm, for example 5.1nm to 8.5nm, 5.5nm to 8.5nm, or 6nm to 8.2nm. Preferably, the D of the pseudoboehmite provided by this invention... (130) / D (020) =1.0 to 1.5, for example 1.1 to 1.4 or 1.2 to 1.35, preferably 1.1 to 1.3. This pseudoboehmite can maintain a large pore size after acidification.

[0009] Where D (130) The grain size represented by the (130) peak (corresponding to 2θ = 38.3°) in the XRD pattern of pseudoboehmite grains is D. (020)The grain size represented by the (020) peak (corresponding to 2θ = 14.1°) in the XRD pattern of pseudoboehmite grains is indicated.

[0010] The pseudoboehmite provided by this invention has a pore size greater than 4.5 nm and less than 12 nm, preferably 4.8 nm to 11 nm, for example 5-10 nm, 5.5 nm to 9 nm, 6-8.5 nm, or 7-9 nm. The pore size refers to the diameter of the pore.

[0011] The crystallinity of the pseudoboehmite provided by the present invention is 85% to 110%, preferably 88% to 108%, for example 90% to 105%.

[0012] The pseudoboehmite provided by this invention has a pore volume of 0.30 cm³. 3 / g~0.58cm 3 / g, preferably 0.31cm 3 / g~0.52cm 3 / g, for example, 0.33~0.5cm 3 / g.

[0013] The pseudoboehmite provided by this invention, wherein I 3000～3800 It is 6.0cm -1 ·mg -1 ~8.5 / cm -1 ·mg -1 For example, 6.2–8.3 cm -1 ·mg -1 .

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

[0015] This invention provides a method for preparing the pseudoboehmite, the method comprising the following steps:

[0016] (1) React sodium aluminate solution with CO2 to generate the first slurry;

[0017] (2) The first slurry is aged under certain conditions. A hydroxyl modifier is added during the aging process. The hydroxyl modifier is urea and / or ammonia water. The aged slurry is called the second slurry. The aging temperature is above 100°C and does not exceed 185°C.

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

[0019] According to the method for preparing boehmite of the present invention, in step (1), the concentration of the sodium aluminate solution, calculated as Al2O3, is preferably 5-60 g / L. The sodium aluminate solution can be commercially available or prepared using existing methods. In one embodiment, the method for preparing the sodium aluminate solution includes: reacting aluminum hydroxide and an alkaline solution at a temperature of 90-120°C for 1-4 hours, and diluting to an Al2O3 concentration of 5-60 g / L. The alkaline solution is, for example, a sodium hydroxide solution. The caustic ratio of the sodium aluminate solution is, for example, 1.0-3.2.

[0020] According to the method for preparing boehmite according to the present invention, in step (1), sodium aluminate solution is reacted with CO2. The reaction can be carried out by passing a CO2-containing gas through the sodium aluminate solution. The volume concentration of CO2 in the CO2-containing gas is 20-100%, for example, 40-100% by volume.

[0021] According to the method for preparing pseudoboehmite of the present invention, the pH value at the endpoint of the reaction between sodium aluminate solution and CO2 is 8.5 to 10.5.

[0022] According to the method for preparing boehmite according to the present invention, in step (1), the reaction starting temperature is preferably 10-35°C, and the reaction ending temperature is preferably 15-55°C.

[0023] According to the method for preparing boehmite according to the present invention, in step (1), sodium aluminate solution is brought into contact with CO2 for reaction, and the reaction time of sodium aluminate solution and 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, an final reaction temperature of 15–55°C, and a reaction time of 20–70 minutes. The final pH value 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] Preferably, in step (2), the aging under certain conditions is: first static aging, then aging under stirring; the pseudoboehmite obtained by this method has a grain size D (130) =4nm~10nm, D (130) / D (020) The value is 1.0 to 1.5. Higher pore sizes are possible.

[0026] In step (2), the first slurry is aged under certain conditions. In one embodiment, the aging temperature is 100–185°C, preferably 120–160°C or 135–160°C. The first slurry can be heated to 100–185°C, preferably 120–160°C or 135–160°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, which means controlling the temperature of static aging and stirring aging to remain constant. For example, the temperature difference between static aging and stirring aging preferably does not exceed 2°C.

[0027] In step (2), the aging pressure is preferably 0.2 to 1 MPa.

[0028] 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.

[0029] In step (2), the aging time is preferably 2 to 10 hours.

[0030] 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 in a static state; for example, it can be left to stand for aging. Preferably, the first slurry is first left to stand 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 can be 50–400 r / min, for example, 60–400 r / min.

[0031] 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.

[0032] Step (2) involves adding a hydroxyl modifier, preferably urea or ammonia, in an amount of 0.5 to 2% by weight of the alumina content in the boehmite. The concentration of the ammonia (as NH3) is 15 to 25% by weight.

[0033] Preferably, the hydroxyl modifier is added after the reaction with CO2 is stopped in step (1) and before stirring aging. Typically, the hydroxyl modifier is added after a period of static aging, for example, during static aging or after static aging is completed and before stirring aging begins.

[0034] Step (3): After aging, the slurry is filtered, washed, and dried to obtain macroporous pseudoboehmite with a specific pore size distribution and rich in hydroxyl groups on the surface. Through static aging followed by agitated aging, a crystal with specific crystal characteristics can be obtained, with a grain size D... (130) For wavelengths greater than 4nm to 10nm, such as 4.5-9nm or 5-8nm, D (130) / D (020) =1.0 to 1.5, for example, 1.1 to 1.3. In one embodiment, the washing conditions are washing with deionized water at 70 to 100°C until the pH of the wet filter cake is 7 to 7.5. The drying temperature is preferably 60 to 98°C, for example, 70 to 98°C, more preferably 70 to 95°C, and the drying time is, for example, 2 to 4 hours.

[0035] The boehmite provided by this invention has abundant surface hydroxyl groups, a large pore size, high crystallinity, and good colloidal solubility. The boehmite provided by this invention also exhibits good binding properties and, when applied to catalytic cracking catalysts, can reduce coke selectivity in hydrocarbon oil conversion.

[0036] The method for preparing boehmite provided by this invention is green, environmentally friendly, low-cost, and easy to implement, filling the technological gap in the production of boehmite suitable for catalytic cracking catalysts via carbonization. It yields boehmite with good binding properties and a high probability pore size distribution, exhibiting high crystallinity, large grain size, a specific crystal structure, and good colloidal solubility.

[0037] The pseudoboehmite provided by this invention can be used for catalyst preparation. After acidification, the resulting catalyst can have a large pore size and good strength. For example, it can be used for the preparation of catalytic cracking catalysts. It can be directly acidified without pore expansion treatment to obtain catalytic cracking catalysts with a large pore size, such as a pore size greater than 5 nm and good wear resistance.

[0038] Compared with existing boehmite, this boehmite, when applied to the preparation of catalytic cracking catalysts, can provide more mesoporous structures, have higher pore sizes, and better catalyst strength (lower attrition index). The resulting catalytic cracking catalyst has lower coke selectivity and better product distribution, for example, it can increase the yield of liquefied petroleum gas and gasoline. Detailed Implementation

[0039] The following embodiments will further illustrate the present invention, but should not be used to limit the present invention.

[0040] In this application, the crystallinity and grain size D of the sample were measured by X-ray powder diffraction (XRD) using the RIPP 145-90 and RIPP 146-90 standard methods (see *Analytical Methods for Petrochemical Products* (RIPP Test Methods), edited by Yang Cuiding et al., Science Press, 1990). The crystallinity of the sample was calculated based on the peak at 2θ = 38.3° (130 crystal plane). The crystallinity was determined according to the Scherrer formula. Calculate the grain size, where K = 1.075, λ is the wavelength of the Kα1 spectral line of the anodic radiation, β is the full width at half maximum (FWHM) of the specific diffraction peak of the pseudoboehmite, and θ is the Bragg diffraction angle of the diffraction peak. D (130) This indicates 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.

[0041] In this application, 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.

[0042] In this application, the determination of the colloidal index is as follows: 10 grams of boehmite was weighed, calcined at 600℃ for 3 hours, cooled in a desiccator, and weighed to obtain W0 grams. The dry basis weight a0 = W0 / 10 was obtained. The weight of the boehmite was weighed m1 = 6 / a0 grams. m1 grams of boehmite was placed in a 100 mL polytetrafluoroethylene (PTFE) cup, and deionized water was added to a final volume of 40 grams. The mixture was stirred evenly using a magnetic rotor, and then 20 mL of 0.19 N dilute nitric acid solution was added. The mixture was stirred magnetically for 20 minutes. The entire solution was poured into a centrifuge tube and centrifuged at 1900 rpm for 20 minutes. The upper colloidal solution was 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 colloidal index DI = (m2 / 6) * 100%.

[0043] In this application, I 3000～3800The measurement method is as follows: The infrared hydroxyl content of the sample was determined using a Nicolet 6700 Fourier transform infrared spectrometer manufactured by Thermo Fisher Scientific, USA. Test conditions: resolution 4.0 cm⁻¹ -1 Scanning range 400cm -1 ~4000cm -1 All samples need to be tested under a high vacuum of 1.0 × 10⁻⁶. -3 Purification for 2 hours at 450℃ and Pa. 3000～3800 The calculation method is based on the sample at an infrared wavelength of 3000 cm⁻¹. -1 ~3800cm -1 The ratio of the area of ​​the infrared absorption peak of hydroxyl groups on the surface of pseudoboehmite within the specified range to the sample mass.

[0044] Sodium aluminate, produced by Shanghai Maclean Biochemical Technology Co., Ltd., caustic ratio 1, analytical grade.

[0045] Example 1

[0046] A 20g / L sodium aluminate solution was reacted with 40% (v / v) carbon dioxide gas (the remainder being nitrogen) to form a gel, with the final pH value controlled at 9.5. The resulting slurry was transferred to an aging reactor and aged at 135℃ and 0.35MPa for 3 hours. Then, 0.8% (w / w) urea (based on the weight of the slurry, calculated from alumina) was added. Under the same temperature and pressure conditions, stirring was started and maintained at a stirring rate of 150 r / min for another hour. After aging, the resulting slurry was separated into solid and liquid components. The slurry was washed continuously with deionized water at 85℃ for half an hour until the pH of the wet filter cake reached 7.1, yielding a purified boehmite wet filter cake. The wet filter cake was dried at 80℃ for 3 hours and then pulverized to obtain boehmite powder S1, the physicochemical properties of which are shown in Table 1.

[0047] Example 2

[0048] A sodium aluminate solution with a concentration of 45 g Al2O3 / L was reacted with 60% carbon dioxide gas (60% CO2, the remainder being nitrogen) to control the final pH value at 10.3. The resulting slurry was transferred to an aging reactor and aged at 180℃ and 1.0 MPa for 2.5 h. Then, 1.5% (based on the mass of alumina in the slurry) of ammonia water (20% by weight of NH3) was added, and the mixture was stirred at 450 r / min for 1 h while maintaining the temperature at 180℃ and the pressure at 1.0 MPa. After aging, the resulting slurry was separated into solid and liquid components and washed continuously with 95℃ deionized water for half an hour until the pH value of the wet filter cake reached 7.3, yielding a purified boehmite wet filter cake. The wet filter cake was dried at 90℃ for 4 h and pulverized to obtain boehmite powder S2, the physicochemical properties of which are shown in Table 1.

[0049] Example 3

[0050] A sodium aluminate solution with a concentration of 8 g Al2O3 / L was reacted with 35% carbon dioxide gas (35% CO2, the remainder being nitrogen) to achieve a final pH of 9.2. The resulting slurry was transferred to an aging reactor, and 1.8% (based on the mass of alumina) ammonia water (20% by weight of NH3) was added. The mixture was stirred until homogeneous and then aged at 120℃ and 0.2 MPa for 3.5 h. Then, while maintaining the temperature and pressure at 120℃ and 0.2 MPa, stirring was started and maintained at a stirring rate of 120 r / min for 2.5 h. After aging, the resulting slurry was separated into solid and liquid components. The solid was continuously washed with deionized water at 75℃ for half an hour until the pH of the wet filter cake reached 7.2, yielding a purified boehmite wet filter cake. The wet filter cake was dried at 75℃ for 4 h and pulverized to obtain boehmite powder S3. Its physicochemical properties are shown in Table 1.

[0051] Example 4

[0052] A sodium aluminate solution with a concentration of 15 g Al2O3 / L was reacted with 50% carbon dioxide gas (50% CO2, the remainder being nitrogen) to achieve a final pH of 9.9. The resulting slurry was transferred to an aging reactor, and 1.8% urea (based on the mass of alumina) was added. The mixture was allowed to stand at 150℃ and 0.48 MPa for 4 hours. Then, while maintaining the temperature and pressure at 150℃ and 0.48 MPa, stirring was started and maintained at a stirring rate of 250 r / min for 3 hours. After aging, the resulting slurry was separated into solid and liquid components. The solid was continuously washed with deionized water at 80℃ for half an hour until the pH of the wet filter cake reached 7.2, yielding a purified boehmite wet filter cake. The wet filter cake was dried at 85℃ for 4 hours and then pulverized to obtain boehmite powder S4. Its physicochemical properties are shown in Table 1.

[0053] Example 5

[0054] A sodium aluminate solution with a concentration of 55 g Al2O3 / L was reacted with 90% carbon dioxide gas (90% CO2 volume fraction, the remainder being nitrogen gas) to control the final pH value at 10.3. The resulting slurry was transferred to an aging reactor, and 0.7% (based on the mass of alumina) ammonia water (ammonia concentration as 20% by weight, calculated as NH3) was added. The mixture was allowed to stand at 160℃ and 0.62 MPa for 6 hours. Then, while maintaining the temperature and pressure at 160℃ and 0.62 MPa, stirring was started and maintained at a stirring rate of 350 r / min for 4.5 hours. After aging, the resulting slurry was separated into solid and liquid components. The slurry was continuously washed with deionized water at 90℃ for half an hour until the pH value of the wet filter cake reached 7.2, obtaining a boehmite wet filter cake with impurities removed. The wet filter cake was dried at 95℃ for 4 hours and pulverized to obtain boehmite powder S5, the physicochemical properties of which are shown in Table 1.

[0055] Comparative Example 1

[0056] A sodium aluminate solution with a concentration of 20 g Al2O3 / L was reacted with carbon dioxide gas at a volume fraction of 40% to form a gel, with the final pH value controlled at 9.5. The resulting slurry was transferred to an aging reactor and aged at 90°C for 3 hours. After aging, the slurry was separated into solid and liquid components, and washed continuously with deionized water at 78°C for half an hour to obtain a filter cake with impurities removed. The filter cake was dried at 90°C for 3 hours and then pulverized to obtain boehmite powder D1. Its physicochemical properties are shown in Table 1.

[0057] Comparative Example 2

[0058] A 20 g / L sodium aluminate solution was reacted with 40% (v / v) carbon dioxide gas to form a gel, with the final pH value controlled at 9.5. The resulting slurry was transferred to an aging reactor and aged at 135 °C and 0.35 MPa for 3.5 h. After aging, the slurry was separated into solid and liquid components, and continuously washed with deionized water at 80 °C for half an hour to obtain a boehmite wet filter cake with impurities removed. The wet filter cake was dried at 80 °C for 3 h and pulverized to obtain boehmite powder D2, the physicochemical properties of which are shown in Table 1.

[0059] Comparative Example 3

[0060] Using a high-purity sodium aluminate solution with an Al2O3 content of 45 g / L as raw material, a gelation reaction was initiated by introducing 40% CO2, with the flow rate controlled at 3.0 m³ / h. 3The reaction time was controlled at 40 minutes, with Al2O3 residue controlled at 5 g / L, and the final temperature controlled at 35℃. After the reaction, the slurry was separated and washed, and 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 obtained above was added to high-purity water and stirred, and then urea with a concentration of 8 g / L was added. After stirring for 50 minutes, the slurry was transferred to a high-pressure reactor, and the reactor temperature was controlled at 150℃ and the pressure at 0.6 MPa. It was allowed to stand for 3 hours for aging. After aging, it was continuously washed with deionized water at 85℃ for half an hour, filtered, and dried at 90℃. The final product, pseudoboehmite D3, was obtained by pulverization, and its physicochemical properties are shown in Table 1.

[0061] Comparative Example 4

[0062] A sodium aluminate solution with a concentration of 45 g Al₂O₃ / L was reacted with 60% (v / v) carbon dioxide gas (60% CO₂, the remainder being nitrogen), and the final pH value was controlled to be 10.3. The resulting slurry was transferred to an aging reactor and aged at 180℃ and 1.0 MPa with a stirring rate of 450 r / min for 3.5 h. After aging, the slurry was separated into solid and liquid components, and continuously washed with 95℃ deionized water for half an hour until the pH of the wet filter cake reached 7.3, yielding a boehmite wet filter cake with impurities removed. The wet filter cake was dried at 90℃ for 4 h and pulverized to obtain boehmite powder D4, the physicochemical properties of which are shown in Table 1.

[0063] Table 1 Properties of Boehmite

[0064]

[0065] *Acidification conditions: Acid-to-aluminum ratio (concentration 36 wt% HCl:Al2O3 mass ratio) is 0.2, solid content of acidified mixture is 10 wt%; calcination temperature is 550℃, calcination time is 2h.

[0066] As shown in Table 1, the pseudoboehmite provided by the present invention has abundant hydroxyl groups on its surface, large pore size, high crystallinity, large grain size, large D(130) / D(020) ratio, good gelation properties, and the pore size of the calcined sample after gelation is still large.

Claims

1. A mesoporous pseudoboehmite with hydroxyl-rich surface, wherein the probable pore size of the pseudoboehmite is greater than 4.8 nm and not more than 12 nm. 3000~3800 It is 6.0cm -1 ·mg -1 ~8.5cm -1 ·mg -1 I 3000~3800 This indicates that at an infrared wavelength of 3000cm -1 ~3800cm -1 Infrared absorption intensity of hydroxyl groups on the surface of pseudoboehmite within the range, I 3000~3800 The calculation method is based on the sample at 3000cm. -1 ~3800cm -1 The ratio of the area of ​​the absorption peak within the range to the sample mass; The grain size D of the pseudoboehmite （130） =4nm~10nm; D （130） / D （020） The value is 1.0~1.5, D （130） The grain size represented by the (130) peak in the XRD pattern of pseudoboehmite grains, corresponding to the crystal plane represented by 2θ=38.3°, is D. （020） The (020) peak in the XRD pattern of pseudoboehmite grains represents the grain size of the crystal plane represented by 2θ=14.1°; The pseudoboehmite has a crystallinity of 85%~110%; a colloidal index of 90%~100%; and a pore volume of 0.3 cm³. 3 / g~0.58cm 3 / g.

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

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

4. The pseudoboehmite according to claim 1, characterized in that, The grain size D of the pseudoboehmite （130） =5~8.5nm; The D of the pseudoboehmite （130） / D （020） It is 1.1~1.

3.

5. The pseudoboehmite according to claim 4, characterized in that, The pseudoboehmite has a crystallinity of 88%~108%; a colloidal index of 93%~99%; and a pore volume of 0.31 cm³. 3 / g~0.52cm 3 / g.

6. A method for preparing boehmite according to any one of claims 1 to 5, the method comprising the following steps: (1) React sodium aluminate solution with CO2 to form the first slurry; (2) The first slurry is aged under certain conditions, and a hydroxyl modifier is added during the aging process to obtain an aged slurry; the aging under certain conditions is: first static aging, and then aging under stirring; the hydroxyl modifier is added during static aging or before the start of aging under stirring after static aging is completed; the hydroxyl modifier accounts for 0.5~2% by weight of the first slurry based on alumina; the hydroxyl modifier is urea and / or ammonia; the aging temperature is above 100℃ and does not exceed 185℃; (3) Filtration, washing and drying of the slurry after aging.

7. The method according to claim 6, characterized in that, In step (1), the final pH value of the reaction between the sodium aluminate solution and CO2 is 8.5~10.5, and the Al2O3 concentration of the sodium aluminate solution is 5~60g / L.

8. The method according to claim 6 or 7, characterized in that, In step (1), the conditions for the reaction between the sodium aluminate solution and CO2 include passing CO2 gas with a concentration of 20% to 100% by volume into the sodium aluminate solution for the reaction, and the initial reaction temperature being 10 to 35°C.

9. The method according to claim 6 or 7, characterized in that, In step (2), the aging temperature of the slurry is 100~185℃, the aging pressure is 0.2~1Mpa, and the aging time is 2~10h.

10. The method according to claim 6, characterized in that, In step (2), the static aging time is 1~4h, and the aging time under stirring is 1~6h.

11. The method according to claim 10, characterized in that, The static aging time is 2-3 hours.

12. The method according to claim 6, characterized in that, The stirring speed for aging under stirring is 50~400 r / min.

13. The method according to claim 6, 10, 11 or 12, characterized in that, The aging temperature is 120~160℃.

14. The method according to claim 6, characterized in that, The concentration of ammonia in the ammonia solution is 15-25% by weight.

15. The method according to claim 8, characterized in that, The reaction endpoint temperature is 15~55℃.

16. The use of boehmite as described in any one of claims 1 to 5 in the preparation of catalysts.

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