Flaky grain boehmite and preparation method thereof
阅读说明：本技术 一种片状晶粒薄水铝石及其制备方法 (Flaky grain boehmite and preparation method thereof ) 是由 杨彦鹏 马爱增 达志坚 聂骥 王学兵 于 2019-10-18 设计创作，主要内容包括：一种片状晶粒薄水铝石,其晶粒的D-((200))/D-((002))＝0.5～1.5,D-((002))/D-((020))＝10～40,所述的D-((020))、D-((200))和D-((002))分别为根据薄水铝石的X射线衍射曲线中沿(020)晶面、(200)晶面和(002)晶面方向衍射峰的半峰宽,由Sherrer公式计算的晶粒尺寸。由该薄水铝石焙烧制备的γ-Al-2O-3具有大的比表面积和大的孔体积,并含有较多的中强酸,弱酸和强酸占比较少,适宜用作催化剂载体。(Flake-grain boehmite, D of crystal grain thereof (200) /D (002) ＝0.5～1.5，D (002) /D (020) 10 to 40, the D (020) 、D (200) And D (002) The crystal grain sizes calculated by the Sherrer formula are respectively based on the half-peak widths of diffraction peaks in the directions of the (020) crystal plane, (200) crystal plane and the (002) crystal plane in the X-ray diffraction curve of boehmite. gamma-Al prepared by roasting boehmite 2 O 3 Has large specific surface area and large pore volume, contains more medium-strong acid, and contains less weak acid and strong acid, and is suitable for being used as a catalyst carrier.)
1. Flake-grain boehmite, D of crystal grain thereof(200)/D(002)＝0.5～1.5，D(002)/D(020)10 to 40, the D(020)、D(200)And D(002)The half-peak widths of diffraction peaks along the (020) crystal plane, the (200) crystal plane and the (002) crystal plane in the X-ray diffraction curve of boehmite are respectively the grain sizes calculated by Sherrer formula.
2. The boehmite as recited in claim 2 wherein D of said boehmite grains(200)/D(002)＝0.7～1.2，D(002)/D(020)＝20～35。
3. The boehmite according to claim 1 or 2, characterized in that the boehmite grains have a length of 60 to 110nm, a width of 60 to 120nm, and a thickness of 2 to 5 nm.
4. A method for preparing boehmite according to claim 1, comprising adding a grain structure regulator to an aluminum hydroxide slurry obtained after hydrolysis of an aluminum alkoxide, standing and aging at 60-260 ℃ for 0.5-72 hours, and then drying, wherein the grain structure regulator is hydroxycarboxylic acid and carboxylic acid, the mass ratio of hydroxycarboxylic acid to carboxylic acid is 0.1-2, and the molar ratio of hydroxycarboxylic acid to aluminum contained in the aluminum hydroxide slurry is 0.005-0.5.
5. The method according to claim 4, wherein the hydroxycarboxylic acid has 3 to 5 carbon atoms, 1 to 3 hydroxyl groups and 1 to 3 carboxyl groups.
6. The method according to claim 5, wherein the hydroxycarboxylic acid is one or more selected from the group consisting of hydroxypropionic acid, 2-hydroxysuccinic acid, 2, 3-dihydroxysuccinic acid, and 3-hydroxy-1, 3, 5-pentanedioic acid.
7. The method according to claim 4, wherein the carboxylic acid is a monocarboxylic acid or a dicarboxylic acid having 1 to 5 carbon atoms.
8. The method according to claim 4, wherein the aluminum hydroxide slurry is aged at a temperature of 100 to 220 ℃ for 2 to 24 hours.
9. The method according to claim 4, wherein the drying temperature is 100 to 240 ℃, and the drying is oven drying, spray drying or flash drying.
10. The method according to claim 9, wherein the drying is carried out at a temperature of 100 to 150 ℃ for 8 to 24 hours.
11. The method according to claim 9, wherein the spray drying is carried out at a spray dryer inlet temperature of 180 to 230 ℃ and an outlet temperature of 80 to 120 ℃.
12. The method according to claim 4, wherein the aluminum alkoxide is hydrolyzed at 60 to 100 ℃ for 0.3 to 3 hours at a water to aluminum alkoxide molar ratio of 3 to 40.
Technical Field
The invention relates to hydrated alumina and a preparation method thereof, in particular to (pseudo) boehmite with special grain morphology and a preparation method thereof.
Background
γ-Al2O3Is one of heterogeneous catalyst carriers with wide application, in particular to the fields of petroleum refining, petrochemical industry and fine chemical industry, such as the carrier of catalytic hydrogenation, catalytic reforming and isomerization catalysts. It is largeSpecific surface area (generally greater than 150 m)2The/g) is beneficial to the dispersion of active metal components, and the surface acidity also provides part of acid centers for certain catalytic reaction processes (such as catalytic reforming, isomerization of lower alkanes and the like). gamma-Al2O3As a catalytic material, the macroscopic physical properties and catalytic performance in various fields have been studied, and gamma-Al has been studied2O3The surface properties are relatively poorly studied. In recent years, researchers have found that gamma-Al2O3In particular gamma-Al2O3The type and proportion of exposed crystal faces of the support also affect the catalyst performance and, therefore, for gamma-Al2O3The exposed crystal face of the carrier crystal grain is regulated and controlled, which is a new way for improving the performance of the catalyst.
γ-Al2O3Is prepared by roasting boehmite at a certain temperature, and the existing research shows that the boehmite is converted into gamma-Al2O3The transformation process is a topological process of short-range rearrangement of Al and O atoms on the structure, and during the transformation process, the crystal grain appearance of boehmite is in gamma-Al2O3Well maintained, and the exposed crystal face of the boehmite and the gamma-Al2O3Have a defined correspondence between the exposed crystal planes. According to the results of the studies by Digne et al (Digne M, Sautet P, Raybaud P, et al Structure and stability of aluminum hydroxides: a the organic student [ J ]]J Phys Chem B,2002,106(20):5155-2O3In the process of (2), the (010) crystal face and the (100) crystal face of the boehmite crystal grain are converted into gamma-Al2O3The (110) crystal face of boehmite crystal grain, the (101) crystal face of boehmite crystal grain are converted into gamma-Al2O3The (111) crystal face of boehmite crystal grain, the (001) crystal face of boehmite crystal grain is converted into gamma-Al2O3The (100) crystal plane of (c). Therefore, it is desired to realize para-gamma-Al2O3The precise regulation and control of the crystal grain exposed crystal face is fundamentally in the precise regulation and control of the boehmite crystal grain exposed crystal face, namely the morphology of the boehmite crystal grain.
The existing research finds that in the preparation process of boehmite, the step which plays a decisive role in the crystal grain morphology is the aging stage of aluminum hydroxide slurry, in the aging process, boehmite crystal grains grow in a liquid phase environment, the coordination structure of atoms on the surface of solid-phase crystal grains and atoms in a bulk phase has a large difference, the atoms on the surface of the crystal grains are metastable, and the driving force of the crystal grain growth is to minimize the surface free energy, so that the crystal face with the lowest surface free energy becomes the dominant crystal face of the crystal grains. According to the Gibbs adsorption law, during the growth or dissolution of the crystal grains, the solid-phase crystal grains automatically adsorb or desorb species which can reduce their surface energy from or to the liquid phase, thereby maintaining the surface energy of the whole crystal grains at a minimum.
The addition of a grain structure regulator during the aging process of the aluminum hydroxide slurry is the most common method for regulating the morphology of boehmite grains. Chiche et al use Al (NO)3-NaAlO2Precipitation method for preparing boehmite (Chiche D, Chizallet C, Duruthy O, et al, growth of boehmite particles in the presence of xylene, collagen oriented by the new effect of hydroxide bonding [ J]And Phys Chem Phys,2009,11(47):11310-11323), wherein the morphology of the boehmite nanoparticles is regulated by adding polyol into the aluminum hydroxide slurry. The results show that the polyol molecules are easily adsorbed on the (101) crystal face of the boehmite crystal grains after being added, the surface tension between the crystal face and the liquid phase is reduced, and the exposure ratio of the (101) crystal face is increased while the boehmite crystal grains are reduced.
CN104150513A discloses a strip-shaped crystal grain boehmite and a preparation method thereof, wherein the width of the strip-shaped crystal grain boehmite is 3-6 nm, and the length of the strip-shaped crystal grain boehmite is 20-107 nm. The preparation method of the strip-shaped crystal grain boehmite comprises the following steps of5～C7Hydrolyzing the alkoxy aluminum at the water/alkoxy aluminum molar ratio of 3-6 and at the temperature of 80-100 ℃, placing the slurry obtained after hydrolysis in a closed container, aging for 2-48 hours at the temperature of 100-200 ℃ and under the pressure of 0.2-1.0 MPa, and separating alcohol generated by hydrolysis to obtain the strip-shaped crystal grain boehmite. The preparation method of the strip-shaped crystal grain boehmite is simple and low in cost, only self-synthesized substances are used in the preparation process, other organic substances are not required to be added, and the preparation method is suitable for large-scale production.
CN105084397A is a further improvement of the method disclosed in CN104150513A, and is characterized in that a mixture of aluminum hydroxide slurry obtained by hydrolyzing alkoxy aluminum and alcohol is aged in a closed container for 2-72 hours at 60-250 ℃ and under the pressure of 0.2-1.0 MPa, the aged slurry is directly dried, and the alcohol is recovered in the drying process. The method can reduce the aggregation of the strip boehmite grains, and has simple process and low cost.
CN104724741A discloses a method for preparing flake alumina, which comprises preparing a solution from an aluminum source, an amine organic compound and an auxiliary agent according to a certain ratio, heating and stirring, volatilizing the solution, concentrating, and pyrolyzing to obtain precursor powder, wherein the aluminum source is a water-soluble inorganic aluminum salt, such as aluminum chloride, aluminum nitrate or aluminum sulfate; then reacting the precursor powder for 2-4 hours at 800-1700 ℃ in a flowing air atmosphere; finally, the flaky alumina with the granularity of 3-8 mu m and the diameter/thickness ratio of 25-80 is obtained.
CN105347377A discloses a preparation method of high-purity flake alumina, which comprises the steps of taking high-purity aluminum isopropoxide with the purity of 99.999%, pure water and isopropanol as main raw materials, taking ammonium bifluoride or ammonium fluoride as a crystal morphology control agent, dissolving the high-purity aluminum isopropoxide in the isopropanol to prepare a solution A, preparing the pure water, the isopropanol and the ammonium bifluoride into a solution B, gradually adding the solution A into the solution B at a certain dropping speed, reacting under the action of heating and stirring to generate hydrated alumina, and sequentially filtering, drying and roasting to obtain the high-purity flake alumina. The thickness of the high-purity flaky alumina crystal grain prepared by the method is less than or equal to 1.0 mu m, and the radial size is 5-20 mu m.
The above patents propose several methods for preparing boehmite or alumina with specific crystal grain morphology, but do not mention the specific characteristics of boehmite or alumina crystal grain prepared by the methods, and the process is complicated, the cost of the adopted crystal grain morphology control agent is amine organic matter or ammonium compound is high, and a large amount of waste gas is easily generated in the production process.
Disclosure of Invention
The invention aims to provide flaky grain boehmite and a preparation method thereof,the boehmite has regular grain structure and uniform grain size, and the gamma-Al prepared from the boehmite2O3The surface acid distribution of (2) has a large proportion of medium-strong acid.
The flake boehmite provided by the invention and D of the crystal grain thereof(200)/D(002)＝0.5～1.5，D(002)/D(020)10 to 40, the D(020)、D(200)And D(002)The half-peak widths of diffraction peaks along the (020) crystal plane, the (200) crystal plane and the (002) crystal plane in the X-ray diffraction curve of boehmite are respectively the grain sizes calculated by Sherrer formula.
The flaky grain boehmite provided by the invention has proper length/width ratio and thicker lamella, is prepared by adding a grain structure regulator to perform standing aging on aluminum hydroxide slurry, and is roasted to prepare gamma-Al2O3Contains more medium-strong acid, and is suitable for being used as a catalyst carrier.
Drawings
FIG. 1 is a scanning electron micrograph of boehmite prepared according to example 1 of the present invention.
FIG. 2 is a scanning electron micrograph of boehmite prepared according to example 4 of the present invention.
FIG. 3 is a scanning electron micrograph of boehmite prepared according to example 7 of the present invention.
FIG. 4 is a scanning electron micrograph of boehmite prepared according to example 10 of the present invention.
Detailed Description
The strip boehmite provided by the invention has a regular grain structure and uniform grain size. The boehmite is prepared by adding a grain structure regulator consisting of hydroxycarboxylic acid and carboxylic acid into aluminum hydroxide slurry obtained by hydrolyzing alkoxy aluminum, aging the aluminum hydroxide slurry under a standing condition, and drying the aluminum hydroxide slurry. gamma-Al prepared by roasting boehmite2O3Has larger specific surface area and larger pore volume, contains more medium-strong acid, and contains less weak acid and strong acid, thus being suitable for being used as a catalyst carrier.
The length of the boehmite crystal grain is 60-110 nm, preferably 60-100 nm, the width is 60-120 nm, preferably 60-110 nm, and the thickness is preferably 2-5 nm.
According to the invention, D(200)Representing the grain length dimension, D(002)Representing the grain width dimension, D(020)Representing the grain thickness dimension. Preferably, D of the boehmite grains(200)/D(002)＝0.7～1.2，D(002)/D(020)＝20～35。
The grain size (D) of the boehmite X-ray diffraction curve along different diffraction directions is calculated by the Sherrer formula shown in formula (r).
In the formula I, D is the average value of the grain sizes in the normal direction of the crystal face of (HKL) and is unit nm; k is a constant, and can be approximately 0.89; lambda is X-ray wavelength, and the characteristic wavelength of CuK alpha 1 is 0.154056 nm; theta is a grazing angle corresponding to a diffraction peak of a (HKL) crystal face, also called a half-diffraction angle, and the unit is an angle; beta is the broadening amount of the diffraction peak caused by grain refinement, the unit is radian, and the relation between the broadening amount and the actually measured half-peak width B of the diffraction peak and the increasing width B of the diffraction peak caused by the instrument factors such as the absorption of the sample, the diaphragm size and the like is as follows:
in formula (I), D can be the crystal grain size D measured along the (020) crystal plane in the XRD diffraction curve(020)Crystal grain size D measured along the (200) crystal plane(200)Crystal grain size D measured along (002) crystal plane(002)。
The preparation method of the boehmite comprises the steps of adding a crystal grain structure regulating agent into aluminum hydroxide slurry obtained after hydrolysis of alkoxy aluminum, standing and aging at 60-260 ℃ for 0.5-72 hours, and then drying, wherein the crystal grain structure regulating agent is hydroxycarboxylic acid and carboxylic acid, the mass ratio of the hydroxycarboxylic acid to the carboxylic acid is 0.1-2, and the molar ratio of the hydroxycarboxylic acid to aluminum contained in the aluminum hydroxide slurry is 0.005-0.5.
In the method, the hydrolysis temperature of the aluminum alkoxide is preferably 60 to 100 ℃, more preferably 75 to 95 ℃, the hydrolysis time is preferably 0.3 to 3 hours, more preferably 0.5 to 2 hours, and the molar ratio of water to the aluminum alkoxide is preferably 3.5 to 40, more preferably 6 to 30. The hydrolysis of the aluminum alkoxide is preferably carried out under stirring, and the stirring speed is preferably 100 to 300rpm, preferably 120 to 250 rpm.
The alkoxy aluminum is hydrolyzed to generate aluminum hydroxide and alcohol, water is always contained in the reaction system due to excessive water, and a two-phase system with an upper layer being an alcohol phase and a lower layer being an aluminum hydroxide slurry phase is generated after hydrolysis. Separating the upper alcohol phase, aging the obtained aluminum hydroxide slurry, adding a grain structure regulator in the aging process, and then drying to obtain the boehmite.
In the method of the present invention, the aging of the aluminum hydroxide slurry is carried out under a standing condition. The aging temperature is preferably 100-220 ℃, and the time is preferably 2-24 hours.
The number of carbon atoms of the hydroxycarboxylic acid in the grain structure regulating agent is 3-5, the number of hydroxyl groups is 1-3, and the number of carboxyl groups is 1-3. Preferably, the hydroxycarboxylic acid is one or more of hydroxypropionic acid, 2-hydroxysuccinic acid, 2, 3-dihydroxysuccinic acid and 3-hydroxy-1, 3, 5-pentanedioic acid.
The carboxylic acid is monocarboxylic acid or dicarboxylic acid with 1-5 carbon atoms, such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, malonic acid or succinic acid.
The mass ratio of the hydroxycarboxylic acid to the carboxylic acid is preferably 0.3 to 2, and the molar ratio of the hydroxycarboxylic acid to aluminum contained in the aluminum hydroxide slurry is preferably 0.01 to 0.2. The hydroxycarboxylic acid may be a combination of two hydroxycarboxylic acids, in which case the mass ratio of hydroxycarboxylic acid to carboxylic acid and the molar ratio of hydroxycarboxylic acid to aluminum contained in the aluminum hydroxide slurry are based on the total amount of hydroxycarboxylic acid used.
And drying the aluminum hydroxide slurry after aging, wherein the drying temperature is preferably 100-240 ℃. The drying can be drying, spray drying or flash drying. When drying is adopted, the drying temperature is preferably 100-150 ℃, and the drying time is preferably 8-24 hours, more preferably 8-12 hours. When spray drying is adopted, the inlet temperature of the spray dryer is preferably 180-230 ℃, and the outlet temperature of the spray dryer is preferably 80-120 ℃. Flash drying is carried out by conventional methods by evaporating water by heating under reduced pressure.
In the above process, the aluminum alkoxide is prepared by reacting metallic aluminum with an excess amount of fatty alcohol, and preferably, may be prepared by a two-step addition method comprising the steps of:
(1) adding aluminum and alcohol into a reaction kettle, initiating reaction at a reaction temperature of 5-50 ℃ lower than the boiling point of the alcohol until the reaction is stable,
(2) and adding alcohol into the reaction kettle, and continuing to react until the aluminum is completely dissolved.
The aluminum used for preparing the aluminum alkoxide in the above method may be at least one of aluminum wire, aluminum sheet, aluminum ingot, aluminum bean and aluminum powder, and the purity of the aluminum is not less than 99.7 mass%, preferably not less than 99.85 mass%. Preferably, the purity of the aluminum used for the initiation reaction in the step (1) is higher than that of the aluminum used for the preparation of the aluminum alkoxide in the step (2).
The alcohol may be C3～C12Fatty alcohols of (2), preferably C6～C8Such as n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, isooctanol. The purity of the alcohol is not less than 99.5 mass%, preferably not less than 99.8 mass%.
The alcohol dosage in the step (1) is 5-40%, preferably 10-35% of the total alcohol dosage required by the whole reaction.
In all reactions of the method, the molar ratio of alcohol to aluminum is 3-10: 1. preferably 4-6: 1.
in the above step (2), it is preferable to control the reaction temperature within. + -. 20 ℃ from the boiling point of the alcohol in order to make the reaction proceed smoothly.
The present invention is further illustrated by the following examples, but the present invention is not limited thereto.
D of boehmite sample grains(020)、D(200)And D(002)Calculated by Sherrer formula according to the half-peak widths of diffraction peaks along the (020) crystal plane, the (200) crystal plane and the (002) crystal plane in the XRD diffraction curve of boehmite. XRD diffraction CurveObtained using a Philips X' pert X-ray diffractometer using a Cu target, K α radiation, Ni filtering, λ 0.154056 nm. The voltage of the solid detector is 40kV, the current of the solid detector is 40mA, and the scanning range is 5-90 degrees.
The shape of the crystal grains of the boehmite is observed by an S-4800 type scanning electron microscope produced by Hitachi company, the accelerating voltage is 5.0kV, and the magnification is 1-300 k.
γ-Al2O3Is prepared from boehmite by calcining at 600 deg.C in air atmosphere for 3 hr.
γ-Al2O3The pore volume and the specific surface area of the catalyst are measured by a nitrogen adsorption and desorption method, and the method is GB/T5816-1995.
γ-Al2O3The surface acidity of the catalyst is desorbed by ammonia gas-temperature programming (NH)3-Temperature Programmed Desorption，NH3TPD), the used instrument is an Autochem II 2920 type automatic chemical adsorption instrument, and the specific steps are as follows: 0.1g of gamma-Al is weighed2O3Loading the particles into a sample tube, placing in a heating furnace, heating to 600 deg.C at 20 deg.C/min with He as carrier gas, purging for 60min to remove γ -Al2O3Surface adsorbed impurities; then cooling to 100 ℃, keeping the temperature for 10min, and switching the gas into NH3NH with a volume fraction of 10%3Adsorbing with mixed gas of/He for 30min, and purging with He for 90min to remove NH adsorbed by physical adsorption3(ii) a And (3) heating to 550 ℃ at the speed of 10 ℃/min for desorption, and monitoring and recording the gas component change information by adopting a TCD (thermal conductivity detector). By applying NH to the sample3Calculating the total acid amount by integrating the peak areas of the TPD curves, and calculating the proportion of strong acid, medium acid and weak acid by adopting Gaussian fitting, wherein the peak generated at the desorption temperature of 100-260 ℃ is weak acid, the peak generated at 260-420 ℃ is medium acid, and the peak generated at 420-580 ℃ is strong acid.
Example 1
In a 1L three-neck flask with a reflux condenser, 27 g of aluminum beans with the purity of 99.9 mass% were added, while 90ml (0.7mol) of n-hexanol with the purity of 99.8 mass% was added, the reaction was started after refluxing at 130 ℃ for 20min, 362ml (2.9mol) of n-hexanol was slowly added to the three-neck flask, the temperature was maintained at 140 ℃, and the reaction was refluxed for 2hr to obtain a mixture of n-hexyloxy aluminum and n-hexanol.
Cooling the mixed solution of n-hexyloxy aluminum and n-hexylalcohol to 90 ℃, adding 468g of deionized water into the mixed solution at the stirring speed of 120rpm for hydrolysis, wherein the hydrolysis time is 45min, and the hydrolysis temperature is 90 ℃. Hydrolyzing to obtain a two-phase system with an upper alcohol phase and a lower aluminum hydroxide slurry phase. Decanting to separate the upper aqueous hexanol phase, adding crystal grain structure regulator composed of 9g 2-hydroxypropionic acid (lactic acid) and 6g formic acid into the lower aluminum hydroxide slurry, transferring the aluminum hydroxide slurry into a stainless steel pressure kettle, standing at 120 deg.C for aging for 6hr, washing the aged slurry with deionized water, and drying at 120 deg.C for 12hr in an oven to obtain boehmite A. Calculation of D from its XRD diffraction Curve(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)The results are shown in Table 1. The scanning electron micrograph of boehmite A is shown in FIG. 1, which shows that the crystal grains are flaky and regular.
Calcining boehmite A at 600 deg.C under air atmosphere for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of the carrier a are shown in Table 2, and the surface acid distribution is shown in Table 3.
Example 2
Boehmite was prepared according to the procedure of example 1, except that the grain structure modifier used consisted of 9g of 2-hydroxypropionic acid (lactic acid) and 9g of acetic acid, and the aluminum hydroxide slurry to which the grain structure modifier was added was allowed to stand at 120 ℃ for aging for 6hr to obtain boehmite B, D of which(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1. Calcining boehmite B at 600 deg.C in air for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of support b are shown in Table 2, and the surface acid distribution is shown in Table 3.
Example 3
Boehmite was prepared according to example 1 except that the grain structure modifier was added to the aluminum hydroxide slurry from 9g of 3-hydroxypropionic acid and 9g of acetic acidAging and drying the aluminum hydroxide slurry added with the grain structure regulator to obtain boehmite C and D(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1. Calcining boehmite C at 600 deg.C in air for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of support c are shown in Table 2, and the surface acid distribution is shown in Table 3.
Example 4
Boehmite was prepared as in example 1, except that the grain structure modifier added to the aluminum hydroxide slurry consisted of 8g of 2-hydroxysuccinic acid (malic acid) and 6.5g of propionic acid, and the aluminum hydroxide slurry added with the grain structure modifier was aged and dried to obtain boehmite D, D of which(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1 and scanning electron micrographs in figure 2. Calcining boehmite D at 600 deg.C in air for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of support c are shown in Table 2, and the surface acid distribution is shown in Table 3.
Example 5
Boehmite was prepared as in example 1, except that the grain structure modifier added to the aluminum hydroxide slurry consisted of 8g of 2-hydroxysuccinic acid (malic acid) and 9.8g of butyric acid, and the aluminum hydroxide slurry added with the grain structure modifier was aged and dried to obtain boehmite E, D of which(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1. Calcining boehmite E at 600 deg.C in air for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of support e are shown in Table 2, and the surface acid distribution is shown in Table 3.
Example 6
Boehmite was prepared according to example 1 except that the grain structure modifier consisting of 12g of 2, 3-dihydroxybutanoic acid (tartaric acid) and 8g of acetic acid was added to the aluminum hydroxide slurry, and the aluminum hydroxide slurry added with the grain structure modifier was aged and dried to obtainBoehmite F, D thereof(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1. Calcining boehmite F at 600 deg.C in air for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of the carrier f are shown in Table 2, and the surface acid distribution is shown in Table 3.
Example 7
Boehmite was prepared as in example 1, except that the grain structure modifier consisting of 12G of 2, 3-dihydroxybutanoic acid (tartaric acid) and 12G of oxalic acid was added to the aluminum hydroxide slurry, and the aluminum hydroxide slurry added with the grain structure modifier was aged and dried to obtain boehmite G, D thereof(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1 and scanning electron micrographs in figure 3. Calcining boehmite G in air at 600 deg.C for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of the support g are shown in Table 2, and the surface acid distribution is shown in Table 3.
Example 8
Boehmite was prepared as in example 1, except that the grain structure modifier added to the aluminum hydroxide slurry consisted of 15.4g of 3-hydroxy-1, 3,5 pentanedionic acid (citric acid) and 10.3g of acetic acid, and the aluminum hydroxide slurry with the grain structure modifier was aged and dried to give boehmite H, D thereof(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1. Calcining boehmite H at 600 deg.C in air for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of the carrier h are shown in Table 2, and the surface acid distribution is shown in Table 3.
Example 9
Boehmite was prepared as in example 1, except that the grain structure modifier added to the aluminum hydroxide slurry consisted of 15.4g of 3-hydroxy-1, 3,5 pentanedioic acid (citric acid) and 15.4g of oxalic acid, and the aluminum hydroxide slurry with the grain structure modifier was aged and dried to give boehmite I, D, thereof(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1. Calcining boehmite I at 600 deg.C in air for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of the carrier i are shown in Table 2, and the surface acid distribution is shown in Table 3.
Example 10
Boehmite was prepared as in example 1, except that the grain structure modifier added to the aluminum hydroxide slurry consisted of 4.5g of 2-hydroxypropionic acid (lactic acid), 4g of 2-hydroxysuccinic acid (malic acid), and 8.5g of acetic acid, and the aluminum hydroxide slurry with the grain structure modifier added was aged and dried to give boehmite J, D of which(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1, scanning electron micrographs see fig. 4. Calcining boehmite J at 600 deg.C in air for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of support j are shown in Table 2, and the surface acid distribution is shown in Table 3.
Comparative example 1
Boehmite was prepared according to example 1 except that, without adding a grain structure modifier to the aluminum hydroxide slurry, the aluminum hydroxide slurry was aged and dried to give boehmite M, D thereof(020)、D(200)And D(002)And D(200)/D(002)And D(002)/D(020)See table 1. Calcining boehmite M at 600 deg.C in air for 6hr to obtain gamma-Al2O3The specific surface area and pore volume of the carrier m are shown in Table 2, and the surface acid distribution is shown in Table 3.
Comparative example 2
Boehmite was prepared according to the method of example 1 except that 15.2g xylitol (pentanol) was added to the aluminum hydroxide slurry as a grain structure modifier, and the resulting aluminum hydroxide slurry was aged and dried to obtain boehmite N, D thereof(020)、D(200)And D(002)And l, D(200)/D(002)And D(020)The/l is shown in Table 1.
Calcining boehmite N at 600 deg.C in air for 6hr,to obtain gamma-Al2O3The specific surface area and pore volume of the support n are shown in Table 2, and the surface acid distribution is shown in Table 3.
As can be seen from Table 2, gamma-Al prepared from boehmite of the invention2O3Has larger specific surface area and pore volume. Table 3 shows the gamma-Al obtained according to the invention2O3The surface acid distribution of (2) is such that the proportion of the medium strong acid is relatively high, about 50%, and the proportions of the strong acid and the weak acid are relatively low.
TABLE 1
TABLE 2
Example number
γ-Al2O3Numbering
Specific surface area, m2/g
Pore volume, cm3/g
1
a
223
0.49
2
b
212
0.51
3
c
207
0.53
4
d
203
0.59
5
e
197
0.63
6
f
206
0.55
7
g
192
0.68
8
h
207
0.61
9
i
185
0.73
Comparative example 1
m
263
0.32
Comparative example 2
n
241
0.41
TABLE 3
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