Preparation method of spherical aluminum oxide

Abstract

The invention discloses a preparation method of spherical aluminum oxide, which comprises the following steps: mixing an aluminum source, water and acid to obtain pseudo sol, adding a pore-forming agent and a surfactant into the pseudo sol, uniformly stirring, carrying out ultrasonic treatment to obtain sol, molding the sol through an oil ammonia column to obtain gamma-Al2O3 spherical particles, and drying the gamma-Al2O3 spherical particles to obtain the spherical aluminum oxide. And then aging, washing, drying and calcining the gamma-Al2O3 spherical particles to obtain the spherical aluminum oxide. The preparation method comprises the following steps: introducing a surfactant and a pore-forming agent into pseudo sol, regulating related dosage and carrying out ultrasonic treatment, fully and uniformly dispersing the pore-forming agent to form a stable oil-in-water system, and carrying out oil ammonia column molding and curing to prepare the macroporous high-hydrothermal-stability aluminum oxide, so that the specific surface area and pore volume are remarkably increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst carriers, and particularly relates to a method for preparing spherical alumina. Background Art

[0002] Petrochemical industry is the lifeblood of a country's industry, and petroleum reforming is an important part of the petrochemical industry. In the petroleum catalytic reforming process, spherical γ-Al2O3 is usually selected as the catalyst carrier due to the presence of a large number of acidic sites on the surface and excellent chlorine-holding ability. The petroleum reforming catalyst mainly consists of an active component and a carrier, and the tiny particles of the active component are highly dispersed on the surface and pores of the carrier.

[0003] At present, the main forming methods of spherical alumina include rotary forming method, extrusion forming method, spray drying forming method, oil-ammonia column forming method, hot oil column forming method and water column forming method. However, it is still a challenge to prepare spherical alumina with high purity, narrow particle size distribution, high hydrothermal stability, high mechanical strength and suitable for industrial production.

[0004] Currently, the literature on the forming of spherical alumina mainly focuses on the hot oil column method and the oil-ammonia column method.

[0005] CN201110290343.2 reports a method for preparing spherical alumina by using an aluminum sol and a non-ionic surfactant and forming with an oil-ammonia column. According to the principle of adjusting the surface tension by the surfactant, the adhesion phenomenon at the dropper during the dropping process is effectively solved, the ball forming rate is significantly improved, and the post-treatment steps are simplified.

[0006] Journal of Inorganic Chemistry, 2010, 26(09): 1533-1538. Abandoning the commonly used precursors such as pseudo-boehmite and boehmite, using poly-chloride as the raw material, an aluminum sol was prepared by the sol-gel method, and then spherical alumina was prepared by forming with an oil-ammonia column.

[0007] The above patents and literature all focus on controlling the outer surface of the forming, and there is a lack of exploration of the internal structure of alumina, which is not conducive to fundamentally improving and enhancing the performance of the alumina carrier.

[0008] CN201280063512.1 discloses a method for manufacturing spherical alumina particles. A suspension is prepared with γ-alumina powder, boehmite powder, water and acid, and a pore-forming agent and a commercial emulsifier are added during the preparation of the suspension, and then the finished alumina spheres are obtained by forming with an oil-ammonia column. However, the bulk density and specific surface area of the finished alumina spheres obtained by this patent are generally less than 200m 2 / g, and the proportion of γ-alumina powder used in the raw materials is high, resulting in high preparation costs.

[0009] Therefore, in order to increase the specific surface area of spherical alumina, it is crucial to develop a preparation method for utilizing the internal space of spherical alumina, such as a method for uniformly creating pores. Summary of the Invention

[0010] The object of the present invention is to provide a method for preparing spherical alumina, in which the prepared spherical alumina has a large number of pores inside, thereby increasing its specific surface area and pore volume.

[0011] To achieve the above object, the present invention provides a method for preparing spherical alumina, which is characterized in that an aluminum source, water and an acid are mixed to obtain a pseudo sol, a pore-forming agent and a surfactant are added to the pseudo sol, and after stirring evenly, an ultrasonic treatment is carried out to obtain a shaped sol, the shaped sol is formed through an oil-ammonia column to obtain γ-Al2O3 spherical particles, and then the γ-Al2O3 spherical particles are aged, washed, dried and calcined to obtain the spherical alumina.

[0012] In the method for preparing spherical alumina of the present invention, the ultrasonic treatment conditions are: the voltage of the ultrasonic instrument is set to 12 - 24V, and the ultrasonic time is 0.5 - 10 min.

[0013] In the method for preparing spherical alumina of the present invention, the pore-forming agent is a water-insoluble liquid organic matter, preferably a liquid alkane, more preferably one or more of nonane, decane, undecane, dodecane and kerosene.

[0014] In the method for preparing spherical alumina of the present invention, the molar ratio of hydrogen ions in the acid to aluminum ions in the aluminum source in the pseudo sol is 0.03 - 0.10.

[0015] In the method for preparing spherical alumina of the present invention, the dosage of the pore-forming agent is 0.1% - 15% of the mass of the pseudo sol.

[0016] In the method for preparing spherical alumina of the present invention, the surfactant is one or more of an anionic surfactant, a cationic surfactant and a nonionic surfactant.

[0017] In the method for preparing spherical alumina of the present invention, the dosage of the surfactant is 0.01 - 2% of the mass of the pseudo sol.

[0018] In the method for preparing spherical alumina of the present invention, the calcination conditions are calcination at 550 - 650 °C for 2 - 4 h.

[0019] In the method for preparing spherical alumina of the present invention, the aluminum source is one or more of pseudo-boehmite, boehmite and gibbsite.

[0020] The preparation method of spherical alumina according to the present invention, the specific surface area of the spherical alumina is 200 - 600 m 2 / g, and the specific surface area remains at 160 - 420 m 2 / g after hydrothermal treatment at 600 °C.

[0021] Advantages of the present invention:

[0022] By introducing a surfactant and a pore-forming agent into the pseudo-sol, regulating the relevant dosages and ultrasonic treatment, the pore-forming agent is uniformly and fully dispersed in the sol in the form of fine particles and a stable oil-in-water system is formed. After forming and curing through an oil-ammonia column, alumina with large pores and high hydrothermal stability is prepared, significantly increasing the specific surface area and pore volume.

[0023] This preparation method is simple to operate, low in cost, stable in the production process, and easy for large-scale production.

[0024] After creating a large number of pores inside the alumina, the present invention greatly improves the specific surface area, which is beneficial to the loading of the catalyst inside the alumina.

[0025] The present invention uses an ultrasonic instrument to emit ultrasonic waves to break up the pore-forming agent inside the pseudo-sol, converting it from large droplets to small droplets, and can extend the demulsification time. After forming and curing, the pores formed inside the alumina are smaller, thereby further increasing the specific surface area of the alumina.

[0026] The alumina prepared by the present invention has a large specific surface area and high hydrothermal stability, which helps to significantly improve the stability of the catalyst in petroleum reforming and has industrial production utilization value and commercial value. Description of the drawings

[0027] Figure 1 Optical photograph of ultrasonic-assisted microvesicle spherical alumina prepared in Example 1.

[0028] Figure 2 XRD pattern of ultrasonic-assisted microvesicle spherical alumina prepared in Example 1.

[0029] Figure 3 SEM photograph of ultrasonic-assisted microvesicle spherical alumina prepared in Example 1.

[0030] Figure 4 XRD pattern of alumina prepared in Comparative Example 1.

[0031] Figure 5 SEM photograph of alumina prepared in Comparative Example 1.

[0032] Figure 6 SEM photograph of alumina prepared in Comparative Example 2. Detailed implementation manners

[0033] The present invention will be specifically described below through embodiments. It is necessary to point out here that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0034] Example 1

[0035] Step 1: 10 g of pseudoboehmite (pore volume 0.41 mL / g, pore diameter 5.3 nm) was used to prepare a suspension with a solid content of 15%. Keeping the hydrogen-aluminum ratio H + :Al 3+ = 0.05, 420 μL of concentrated nitric acid was added to obtain a pseudo sol;

[0036] Step 2: 3 g of dodecane was added as a pore-forming agent to the pseudo sol obtained in Step 1, and it was continuously stirred. Subsequently, 5 mg of cetyltrimethylammonium bromide CTAB was added as a surfactant, and it was stirred for 1 h. Then, it was subjected to ultrasonic dispersion treatment for 0.5 min using a 12 V ultrasonic device;

[0037] Step 3: The sol obtained in Step 2 was dropped into an oil-ammonia column: the oil phase was petroleum ether, with a height of 10 cm; the ammonia water phase was ammonia water with a mass fraction of 8 wt%, with a height of 1 m;

[0038] The collected spherical particles were aged in ammonia water for 12 h, then taken out and washed several times with deionized water. The product was placed in an 80°C oven and dried for 10 h; after drying, the product was placed in a 600°C furnace and calcined for 3 h to obtain the target product γ-aluminum oxide, with the chemical formula γ-Al2O3, its morphology being spherical particles, with an average diameter of 1 mm, a bulk density of 0.6 g / mL, a pore volume of 0.61 mL / g, and a specific surface area of 231.6 m 2 / g.

[0039] Step 4: The γ-Al2O3 obtained in Step 3 was placed in a hydrothermal reaction bed, and at 600°C, it was hydrothermally treated with 10% water vapor for 120 h. After 120 h of hydrothermal treatment, the specific surface area could still be maintained at 173.5 m 2 / g, showing excellent hydrothermal stability.

[0040] Example 2

[0041] Step 1: 10 g of pseudoboehmite (the same as in Example 1) was used to prepare a suspension with a solid content of 18%. Keeping the hydrogen-aluminum ratio H + :Al 3+ = 0.05, 420 μL of concentrated nitric acid was added to obtain a pseudo sol;

[0042] Step 2: Add 3 g of nonane as a pore former to the pseudo sol described in Step 1, and continuously stir. Subsequently, add 5 mg of cetyltrimethylammonium chloride (CTAC) as a surfactant, stir for 1 h, and then perform ultrasonic dispersion treatment for 3 min using a 12V ultrasonic device;

[0043] Step 3: Drop the sol obtained in Step 2 into an oil-ammonia column: the oil phase is petroleum ether, with a height of 10 cm; the ammonia water phase is ammonia water with a mass fraction of 8 wt%, with a height of 1 m; the collected spherical particles are aged in ammonia water for 12 h, then taken out and washed several times with deionized water. The product is dried at 80 °C for 10 h; after drying, the product is calcined at 600 °C for 3 h to obtain the target product γ-aluminum oxide, whose chemical formula is γ-Al2O3, whose morphology is spherical particles, with an average diameter of 1.2 mm, a bulk density of 0.62 g / mL, a pore volume of 0.56 mL / g, and a specific surface area of 228.5 m 2 / g.

[0044] Step 4: Place the γ-Al2O3 obtained in Step 3 in a hydrothermal reaction bed and perform hydrothermal treatment at 600 °C using 10% water vapor for 120 h. After 120 h of hydrothermal treatment, the specific surface area can be maintained at 166.7 m 2 / g.

[0045] Example 3

[0046] Step 1: Prepare a suspension with a solid content of 15% using 5 g of pseudo-boehmite (the same as in Example 1) and 5 g of gibbsite, and keep the hydrogen-aluminum ratio H + :Al 3+ = 0.03, add 420 μL of concentrated nitric acid to obtain a pseudo sol;

[0047] Step 2: Add 5 g of kerosene as a pore former to the pseudo sol described in Step 1, and continuously stir. Subsequently, add 0.5 mg of polyvinylpyrrolidone (PVP) as a surfactant, stir for 1 h, and then perform ultrasonic dispersion treatment for 5 min using a 24V ultrasonic device;

[0048] Step 3: Drop the sol obtained in Step 2 into an oil-ammonia column: the oil phase is petroleum ether, with a height of 10 cm; the ammonia water phase is ammonia water with a mass fraction of 8 wt%, with a height of 1 m; the collected spherical particles are aged in ammonia water for 12 h, then taken out and washed several times with deionized water. The product is dried at 80 °C for 10 h; after drying, the product is calcined at 550 °C for 4 h to obtain the target product γ-aluminum oxide; its chemical formula is γ-Al2O3, its morphology is spherical particles, with an average diameter of 1 mm, a bulk density of 0.61 g / mL, a pore volume of 0.56 mL / g, and a specific surface area of 222.6 m 2 / g.

[0049] Step 4: Place the γ-Al2O3 obtained in Step 3 in a hydrothermal reaction bed, and carry out hydrothermal treatment at 600 °C with 10% water vapor for 120 h. After 120 h of hydrothermal treatment, the specific surface area can be maintained at 165.6 m 2 / g.

[0050] Example 4

[0051] Step 1: Prepare a suspension with a solid content of 15% using 10 g of pseudo-boehmite (the same as in Example 1), keep the hydrogen-aluminum ratio H + :Al 3+ = 0.05, add 420 μL of concentrated nitric acid to obtain a pseudo-sol;

[0052] Step 2: Add 10 g of dodecane as a pore-forming agent to the pseudo-sol described in Step 1, and continuously stir. Then add 1200 mg of Tween 80 as a surfactant, stir for 1 h, and then use a 24 V ultrasonic device for ultrasonic dispersion treatment for 10 min;

[0053] Step 3: Drop the sol obtained in Step 2 into an oil-ammonia column: the oil phase is petroleum ether, with a height of 10 cm; the ammonia water phase is ammonia water with a mass fraction of 8 wt%, with a height of 1 m; the collected spherical particles are aged in ammonia water for 12 h, then taken out and washed several times with deionized water, and the product is dried at 80 °C for 10 h; after drying, the product is calcined at 600 °C for 3 h to obtain the target product γ-aluminum oxide, with the chemical formula γ-Al2O3, its morphology is spherical particles, the average diameter is 1.1 mm, the bulk density is 0.52 g / mL, the pore volume is 0.66 mL / g, and the specific surface area is 223.9 m 2 / g.

[0054] Step 4: Place the γ-Al2O3 obtained in Step 3 in a hydrothermal reaction bed, and carry out hydrothermal treatment at 600 °C with 10% water vapor for 120 h. After 120 h of hydrothermal treatment, the specific surface area can be maintained at 167.9 m 2 / g.

[0055] Example 5

[0056] Step 1: Prepare a suspension with a solid content of 15% using 10 g of pseudo-boehmite (the same as in Example 1), keep the hydrogen-aluminum ratio H + :Al 3+ = 0.05, add 420 μL of concentrated nitric acid to obtain a pseudo-sol;

[0057] Step 2: Add 3 g of dodecane as a pore-forming agent to the pseudo-sol described in Step 1, and continuously stir. Then add 50 mg of sodium dodecyl sulfate (SDS) as a surfactant, stir for 1 h, and then use a 12 V ultrasonic device for ultrasonic dispersion treatment for 1 min;

[0058] Step 3: Drop the sol obtained in Step 2 into an oil-ammonia column: The oil phase is petroleum ether with a height of 10 cm; the ammonia water phase is ammonia water with a mass fraction of 15 wt%, with a height of 1 m; the collected spherical particles are aged in ammonia water for 6 h, then taken out and washed several times with deionized water, and the product is dried at 80 °C for 10 h; after drying, the product is calcined at 650 °C for 2 h to obtain the target product γ-aluminum oxide, with the chemical formula γ-Al2O3, its morphology is spherical particles, the average diameter is 1 mm, the bulk density is 0.60 g / mL, the pore volume is 0.53 mL / g, and the specific surface area is 224.8 m 2 / g.

[0059] Step 4: Place the γ-Al2O3 obtained in Step 3 in a hydrothermal reaction bed and perform hydrothermal treatment at 600 °C with 10% water vapor for 120 h. After 120 h of hydrothermal treatment, the specific surface area can be maintained at 168.5 m 2 / g.

[0060] Example 6

[0061] Step 1: Prepare a suspension with a solid content of 20% using 10 g of pseudo-boehmite (the same as in Example 1), keep the hydrogen-aluminum ratio H + :Al 3+ = 0.1, add 840 μL of concentrated nitric acid to obtain a pseudo-sol;

[0062] Step 2: Add 0.05 g of dodecane as a pore-forming agent to the pseudo-sol described in Step 1, and continuously stir, then add 1 mg of sodium dodecyl sulfate (SDS) as a surfactant, stir for 1 h, and then perform ultrasonic dispersion treatment for 1 min using a 12V ultrasonic device;

[0063] Step 3: Drop the sol obtained in Step 2 into an oil-ammonia column: The oil phase is petroleum ether with a height of 10 cm; the ammonia water phase is ammonia water with a mass fraction of 15 wt%, with a height of 1 m; the collected spherical particles are aged in ammonia water for 6 h, then taken out and washed several times with deionized water, and the product is dried at 80 °C for 10 h; after drying, the product is calcined at 650 °C for 2 h to obtain the target product γ-aluminum oxide, with the chemical formula γ-Al2O3, its morphology is spherical particles, the average diameter is 1 mm, the bulk density is 0.78 g / mL, the pore volume is 0.42 mL / g, and the specific surface area is 208.3 m 2 / g.

[0064] Step 4: Place the γ-Al2O3 obtained in Step 3 in a hydrothermal reaction bed and perform hydrothermal treatment at 600 °C with 10% water vapor for 120 h. After 120 h of hydrothermal treatment, the specific surface area can be maintained at 135.5 m 2 / g.

[0065] Comparative Example 1

[0066] As a comparative example of Example 1, alumina was prepared without using a pore-forming agent. The specific method was to first prepare a suspension with a solid content of 15% using pseudo-boehmite (the same as in Example 1), and maintain the hydrogen-aluminum ratio H + :Al 3+ = 0.05, and add 420 μL of concentrated nitric acid to obtain a pseudo sol; then directly drop the obtained pseudo sol into an oil-ammonia column: the oil phase is petroleum ether, with a height of 10 cm; the ammonia water phase is ammonia water with a mass fraction of 8 wt%, with a height of 1 m; the subsequent steps were carried out according to the method of Example 1.

[0067] The characterization test results showed that the prepared alumina had obvious alumina diffraction peaks, no obvious macropores were seen inside, only wrinkles formed by pseudo-boehmite, and its specific surface area was 207.6 m 2 / g. After 120 h of hydrothermal treatment, the specific surface area remained at 125.2 m 2 / g.

[0068] Comparative Example 2

[0069] As a comparative example of Example 1, alumina was prepared without using ultrasonic treatment.

[0070] Step 1: Prepare a suspension with a solid content of 15% using 10 g of pseudo-boehmite (the same as in Example 1), and maintain the hydrogen-aluminum ratio H + :Al 3+ = 0.05, and add 420 μL of concentrated nitric acid to obtain a pseudo sol;

[0071] Step 2: Add 3 g of dodecane as a pore-forming agent to the pseudo sol described in Step 1, and continuously stir, then add 5 mg of CTAB as a surfactant and stir for 1 h;

[0072] Step 3: Drop the sol obtained in Step 2 into an oil-ammonia column: the oil phase is petroleum ether, with a height of 10 cm; the ammonia water phase is ammonia water with a mass fraction of 8 wt%, with a height of 1 m;

[0073] The collected spherical particles were aged in ammonia water for 12 h, then taken out and washed several times with deionized water, and the product was dried at 80 °C for 10 h; after drying, the product was calcined at 600 °C for 3 h to obtain the target product γ-alumina; its chemical formula is γ-Al2O3, its morphology is spherical particles, the average diameter is 1 mm, the bulk density is 0.67 g / mL, the pore volume is 0.55 mL / g, and the specific surface area is 203.5 m 2 / g. Figure 6 The results showed that the internal pore size was much larger than that of the alumina after ultrasonic treatment.

[0074] Step 4: Place the γ-Al2O3 obtained in Step 3 in a hydrothermal reaction bed and perform hydrothermal treatment at 600 °C using 10% water vapor for 120 h. After 120 h of hydrothermal treatment, the specific surface area can be maintained at 132.6 m 2 / g.

[0075] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention. However, these corresponding changes and deformations should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing spherical alumina, characterized in that, Mix an aluminum source, water and an acid to obtain a pseudo sol. Add a pore former and a surfactant to the pseudo sol, stir evenly, and then obtain a shaped sol through ultrasonic treatment. Form the shaped sol into γ-Al2O3 spherical particles through an oil-ammonia column, and then obtain the spherical alumina after aging, washing, drying and calcining the γ-Al2O3 spherical particles.

2. The preparation method of spherical alumina according to claim 1, characterized in that, The conditions of the ultrasonic treatment are as follows: the voltage of the ultrasonic instrument is set to 12-24 V, and the ultrasonic time is 0.5-10 min.

3. The preparation method of spherical alumina according to claim 1, characterized in that, The pore former is a water-insoluble liquid organic substance, preferably a liquid alkane, more preferably one or several of nonane, decane, undecane, dodecane and kerosene.

4. The preparation method of spherical alumina according to claim 1, characterized in that, The molar ratio of hydrogen ions in the acid to aluminum ions in the aluminum source in the pseudo sol is 0.03-0.

10.

5. The preparation method of spherical alumina according to claim 1, characterized in that, The dosage of the pore former is 0.1%-15% of the mass of the pseudo sol.

6. The preparation method of spherical alumina according to claim 1, characterized in that, The surfactant is one or several of an anionic surfactant, a cationic surfactant and a nonionic surfactant.

7. The preparation method of spherical alumina according to claim 1, characterized in that, The dosage of the surfactant is 0.0005%-2% of the mass of the pseudo sol.

8. The preparation method of spherical alumina according to claim 1, characterized in that, The calcination conditions are calcination at 550-650 °C for 2-4 h.

9. The preparation method of spherical alumina according to claim 1, characterized in that, The aluminum source is one or several of pseudo-boehmite, boehmite and gibbsite.

10. The method for preparing spherical alumina according to claim 1, wherein, The specific surface area of the spherical alumina is 200 - 600 m 2 / g, and after hydrothermal treatment at 600 °C, the specific surface area is maintained at 160 - 420 m 2 / g.

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