Pseudo-boehmite and preparation method thereof

Abstract

The present invention discloses a pseudo-boehmite and a preparation method thereof. The pseudo-boehmite of the present invention has the following properties: 1.0 < P1 ≤ 1.5, 1.5 < P2 ≤ 1.8, P1 = D(120) / D(031), P2 = D(120) / D(020); the 120 peak refers to the characteristic peak with 2θ of 25.5 - 29.9º in the XRD spectrum; the 031 peak refers to the characteristic peak with 2θ of 36.3 - 40.5º in the XRD spectrum; the 020 peak refers to the characteristic peak with 2θ of 12.0 - 16.2º in the XRD spectrum, D = Kλ / (Bcosθ), where K is the Scherrer constant, λ is the diffraction wavelength of the target, B is the half-peak width of the diffraction peak, and θ is the diffraction angle; the preparation method of the pseudo-boehmite includes the following steps: mixing γ-phase alumina powder, propylene oxide and water, and then performing rehydration treatment to obtain pseudo-boehmite. The present invention regulates the crystal plane size of the pseudo-boehmite by adding additives, and obtains a pseudo-boehmite product with larger grain size and probable pore diameter. This pseudo-boehmite product has broad application prospects in the fields of catalysis and adsorption.

Description

Technical Field

[0001] The invention belongs to the field of inorganic material preparation, and in particular relates to pseudo-boehmite and a preparation method thereof. Background Art

[0002] Alumina is widely used as a carrier material in various chemical fields due to its excellent physical and chemical properties, especially in the field of hydrogenation catalysts in petroleum processing. The main raw material for producing alumina carrier is pseudo-boehmite (A1OOH·nH 2 O, n = 0.08 ~ 0.62), also known as pseudo-boehmite, is a type of aluminum hydroxide with uncertain composition, incomplete crystallization, and thin folded sheets. It has the characteristics of high specific surface area and large pore volume. The performance of alumina carrier is mainly determined by the properties of its precursor pseudo-boehmite, especially the pore structure of pseudo-boehmite basically determines the pore structure of alumina carrier. Therefore, to prepare high-performance alumina carrier, high-performance pseudo-boehmite fraction must be prepared first. The main industrial preparation methods of pseudo-boehmite are: neutralization method, seed separation method, and alcohol aluminum method. Among them, the neutralization method is the most widely used production method in China, which can be specifically subdivided into aluminum nitrate method, aluminum sulfate method, carbonization method, double aluminum method, pH swing method, etc.

[0003] CN106938851A discloses a method for preparing high-purity pseudo-boehmite. The preparation process of the pseudo-boehmite in the method includes: (1) preparing alkoxy aluminum, (2) filtering, (3) hydrolysis reaction, (4) alcohol separation, (5) aging and alcohol distillation, (6) filtering, and drying. The pure pseudo-boehmite prepared by the method has a high purity.

[0004] CN105174293A discloses a method for preparing pseudo-boehmite with concentrated pore size distribution. The method comprises the following steps: neutralizing an aluminum source compound into a gel under normal pressure, adding the obtained slurry into a reactor and performing a hydrothermal treatment at 100-200° C. for 0.5-24 h; after the reaction is completed, performing solid-liquid separation and washing on the obtained slurry to obtain a product filter cake from which impurities are removed; and drying and crushing to obtain pseudo-boehmite powder with concentrated pore size distribution.

[0005] In the study “Morphological study of pseudo-boehmite prepared by rehydration of activated alumina” (Li Xiaoyun et al., Journal of Chinese Electron Microscopy Society, 2011, 30 (6) 517-520), pseudo-boehmite was prepared using activated alumina as raw material by hydrothermal method, and the effects of acidic, alkaline and neutral conditions on the properties of the product were studied. The study found that the pseudo-boehmite prepared under alkaline conditions had the largest specific surface area, pore volume and pore size, needle-shaped cluster powder was obtained under acidic conditions, and large-particle pseudo-boehmite powder was obtained under neutral conditions.

[0006] However, there are no methods or means to control the grain size on a certain crystal plane in existing research. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a pseudo-boehmite and a preparation method thereof. The present invention regulates the crystal face size of the pseudo-boehmite by adding an auxiliary agent, thereby obtaining a pseudo-boehmite product with a larger grain size and a larger pore size. The pseudo-boehmite product has broad application prospects in the fields of catalysis and adsorption.

[0008] The pseudo-boehmite of the present invention has the following properties: 1.0 <P 1 ≤1.5,1.5 <P 2 ≤1.8, P 1 =D(120) / D(031),P 2 =D(120) / D(020); the D(120) represents the grain size of the crystal plane corresponding to the (120) peak in the XRD spectrum of pseudo-boehmite grains; D(031) represents the grain size of the crystal plane corresponding to the (031) peak in the XRD spectrum of pseudo-boehmite grains; D(020) represents the grain size of the crystal plane corresponding to the (020) peak in the XRD spectrum of pseudo-boehmite grains; the 120 peak refers to the characteristic peak with 2θ of 25.5-29.9º in the XRD spectrum; the 031 peak refers to the characteristic peak with 2θ of 36.3-40.5º in the XRD spectrum; the 020 peak refers to the characteristic peak with 2θ of 12.0-16.2º in the XRD spectrum, D=Kλ / (Bcosθ), K is the Scherrer constant, λ is the diffraction wavelength of the target material, B is the half-peak width of the diffraction peak, and θ is the diffraction angle.

[0009] The preparation method of pseudo-boehmite of the present invention comprises the following contents: mixing gamma-phase alumina powder with propylene oxide aqueous solution, and then performing rehydration treatment to obtain pseudo-boehmite.

[0010] In the method of the present invention, the γ-phase alumina powder can be a commercial product or can be prepared according to the existing technology. Generally, a pseudo-boehmite precursor that is commercially available or prepared by the existing technology is used as a raw material and calcined to obtain the γ-phase alumina powder; the calcination temperature is 400-600°C and the calcination time is 4-8 hours.

[0011] In the method of the present invention, the mass percentage concentration of the propylene oxide aqueous solution is 2.5%-12%, preferably 4%-8%, and the mass ratio of the propylene oxide aqueous solution to the alumina powder is 3:1-10:1, preferably 4:1-8:1. In the present invention, the γ-phase alumina powder can be mixed with propylene oxide and then mixed with water, or the γ-phase alumina powder can be mixed with water and then mixed with propylene oxide.

[0012] In the method of the present invention, preferably polyethylene glycol 2000-20000 is added simultaneously to the propylene oxide aqueous solution, and the mass ratio of the added amount of polyethylene glycol 2000-20000 to the aluminum oxide powder is 0.01:1-0.05:1.

[0013] In the method of the present invention, the rehydration treatment is a hydrothermal treatment in a sealed container, the sealed container is preferably an autoclave, the treatment temperature is 110-180°C, preferably 120-160°C, the treatment time is 4-8 hours, and the pressure in the sealed container during the rehydration treatment is autogenous pressure.

[0014] In the method of the present invention, the material after rehydration treatment is generally washed and dried, the drying temperature is 100-160° C., and the drying time is 6-10 hours.

[0015] The ratio of the approximate pore diameter of the pseudo-boehmite prepared by the method of the invention to the approximate pore diameter of the pseudo-boehmite precursor is 1.2:1-1.6:1.

[0016] Compared with the prior art, the pseudo-boehmite prepared by the method of the present invention has high crystallinity and good purity, and the crystal grain size represented by the (120) and (031) peaks is relatively large. The pseudo-boehmite can be used as a catalytic and adsorption material, for example, as a raw material for an alumina carrier of a hydrogenation catalyst, an adsorption material in a water treatment process, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1: A is the XRD spectrum of the pseudo-boehmite precursor in Example 1; B is the XRD spectrum of the pseudo-boehmite PB-1 prepared in Example 1; C is the XRD spectrum of the pseudo-boehmite PB-5 prepared in Comparative Example 1. DETAILED DESCRIPTION

[0018] The technical scheme and technical effects of the present invention are further illustrated below in conjunction with embodiments, but are not limited to the following embodiments.

[0019] X-ray diffraction (XRD) analysis was performed on a D / max-2500 fully automatic rotating target X-ray diffractometer produced by Rigaku Corporation, Japan, using a Cu target, Kα radiation source, graphite monochromator, tube voltage of 40 kV, and tube current of 80 mA.

[0020] Example 1

[0021] Weigh 500 g of pseudo-boehmite (prepared by aluminum sulfate-sodium aluminate method, dry weight content of 73%). Its pore structure and XRD spectrum are shown in Table 1 and Figure 1 As shown in Figure 1, γ-phase alumina was obtained by calcining at 450°C for 6 hours.

[0022] Weigh 100 g of the above-mentioned γ-phase alumina, add 550 g of propylene oxide aqueous solution with a mass percentage concentration of 4.5%, and stir magnetically for 30 minutes. Then, transfer the mixture into an autoclave, seal it, and heat it at 135°C for 6.5 hours. After cooling, filter and wash the solid material, and dry it at 110°C for 6 hours to obtain pseudo-boehmite PB-1. The properties of pseudo-boehmite are shown in Table 1, and the XRD spectrum is shown in Figure 1 -B.

[0023] Example 2

[0024] The same as Example 1, except that the calcination temperature of the pseudo-boehmite is 500°C. The amount of propylene oxide aqueous solution used is 450 g, and the mass percentage concentration of the solution is 5.5%. The heat treatment temperature is 145°C, and the treatment time is 5.5 hours to obtain pseudo-boehmite PB-2. The properties of the pseudo-boehmite are shown in Table 1.

[0025] Example 3

[0026] Same as Example 1, except that the amount of propylene oxide aqueous solution used was 350 g, and the mass percentage concentration of the solution was 7.0%. The heat treatment temperature was 125° C., and the treatment time was 7.5 hours to obtain pseudo-boehmite PB-3. The properties of the pseudo-boehmite are shown in Table 1.

[0027] Example 4

[0028] Same as Example 1, except that the amount of propylene oxide aqueous solution used is 700 g, the mass percentage concentration of the solution is 3.5%, and an appropriate amount of polyethylene glycol-20000 is added to the mixed material, and the amount of polyethylene glycol-20000 added is 1 g. The heat treatment temperature is 155°C, and the treatment time is 4.5 hours to obtain pseudo-boehmite PB-4. The properties of the pseudo-boehmite are shown in Table 1.

[0029] Comparative Example 1

[0030] The same as Example 1, except that the mixed material was not transferred into the autoclave for sealing treatment, but was refluxed at normal pressure in the condensation reflux device. After analysis, it was found that the γ-phase alumina was not rehydrated into pseudo-boehmite.

[0031] Comparative Example 2

[0032] The same as Example 1, except that propylene oxide was replaced with the same amount of ethylene oxide, to obtain pseudo-boehmite PB-5. The properties of the pseudo-boehmite are shown in Table 1, and the XRD spectrum is shown in Figure 1 -C.

[0033] Comparative Example 3

[0034] The same method as Example 1 was used, except that the propylene oxide was replaced with the same amount of distilled water to obtain pseudo-boehmite PB-6. The properties of the pseudo-boehmite are shown in Table 1.

[0035] Table 1 Properties of pseudo-boehmite

[0036]

[0037] from Figure 1 It can be seen from Table 1 that, compared with the comparative example, the pseudo-boehmite prepared by the method of the present invention has higher pore volume and specific surface area, and larger pore diameter, while the pseudo-boehmite prepared by the comparative example has lower pore volume and pore diameter; at the same time, the pseudo-boehmite prepared by the method of the present invention has higher crystallinity, and the crystal grain size corresponding to the (120) peak and the (031) peak is larger.

Claims

1. A pseudo-boehmite, Features Has the following properties: 1.0 <P 1 ≤1.5,1.5 <P 2 ≤1.8, P 1 =D(120) / D(031),P 2 =D(120) / D(020); D(120) represents the grain size of the crystal plane corresponding to the (120) peak in the XRD spectrum of pseudo-boehmite grains; D(031) represents the grain size of the crystal plane corresponding to the (031) peak in the XRD spectrum of pseudo-boehmite grains; D(020) represents the grain size of the crystal plane corresponding to the (020) peak in the XRD spectrum of pseudo-boehmite grains; the (120) peak refers to the characteristic peak with 2θ of 25.5-29.9º in the XRD spectrum; the (031) peak refers to the characteristic peak with 2θ of 36.3-40.5º in the XRD spectrum; the (020) peak refers to the characteristic peak with 2θ of 36.3-40.5º in the XRD spectrum. 2θ is a characteristic peak of 12.0-16.2º, D=Kλ / (Bcosθ), K is the Scherrer constant, λ is the diffraction wavelength of the target material, B is the half-peak width of the diffraction peak, and θ is the diffraction angle. The preparation method of pseudo-boehmite comprises the following contents: mixing γ-phase alumina powder with propylene oxide aqueous solution, and then performing rehydration treatment to obtain pseudo-boehmite; the rehydration treatment is a hydrothermal treatment in a closed container, the treatment temperature is 110-180°C, the treatment time is 4-8 hours, and the pressure in the sealed container is autogenous pressure; the mass ratio of the propylene oxide aqueous solution to the alumina powder is 3:1-10:

1.

2. A method for preparing the pseudo-boehmite according to claim 1, Features The method comprises the following contents: mixing γ-phase alumina powder with propylene oxide aqueous solution, and then performing rehydration treatment to obtain pseudo-boehmite; the rehydration treatment is a hydrothermal treatment in a sealed container, the treatment temperature is 110-180°C, the treatment time is 4-8 hours, and the pressure in the sealed container is autogenous pressure; the mass ratio of the propylene oxide aqueous solution to the alumina powder is 3:1-10:

1.

3. The method according to claim 2, Features: The gamma-phase alumina powder is obtained by calcining a pseudo-boehmite precursor as a raw material; the calcination temperature is 400-600° C. and the calcination time is 4-8 hours.

4. The method according to claim 2, Features: The mass percentage concentration of the propylene oxide aqueous solution is 2.5%-12%.

5. The method according to claim 2, Features: The mass percentage concentration of the propylene oxide aqueous solution is 4%-8%.

6. The method according to claim 2, Features: The mass ratio of the propylene oxide aqueous solution to the aluminum oxide powder is 4:1-8:

1.

7. The method according to claim 2, Features: The gamma-phase alumina powder is mixed with propylene oxide and then mixed with water, or the gamma-phase alumina powder is mixed with water and then mixed with propylene oxide.

8. The method according to claim 2, Features: Polyethylene glycol 2000-20000 is added to the propylene oxide aqueous solution, and the mass ratio of the added amount of polyethylene glycol 2000-20000 to the aluminum oxide powder is 0.01:1-0.05:

1.

9. The method according to claim 3, Features: The approximate pore size ratio of pseudo-boehmite to pseudo-boehmite precursor is 1.2:1-1.6:

1.

10. Use of the pseudo-boehmite according to claim 1 in the fields of catalysis and adsorption.

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