Preparation method of molded alumina with high thermal stability

Abstract

The invention discloses a preparation method of molded alumina with high thermal stability. The method specifically comprises the following steps: titrating and mixing an aluminum sulfate solution and a sodium metaaluminate solution until the pH is 7-9, and adding water glass to obtain a mixed solution; then adding a phosphate solution and halloysite, and crystallizing to obtain slurry; filtering, washing, extruding and drying the slurry to obtain formed boehmite; and finally roasting at 500-700 DEG C for 1-4 hours to obtain the formed aluminum oxide with high thermal stability. The preparation method provided by the invention is green and clean, solves the problem that flaky boehmite is difficult to form, the formed alumina with large specific surface area and pore volume is obtained, the formed alumina has the specific surface area of 300-450 m < 2 > / g and the pore volume of 1.10-1.50 cm < 3 > / g after being roasted at 600 DEG C, and the crushing strength is 100-200 N / cm.

Description

Technical Field

[0001] The invention belongs to the technical field of alumina preparation, and particularly relates to a method for preparing shaped alumina with high thermal stability. Background Art

[0002] Alumina, with its large surface area and well-defined pore structure, is often used as an adsorbent, catalyst, and catalyst carrier. Molding is a crucial step in the preparation of catalyst carriers, as industrial reactors require both compressive strength and wear resistance.

[0003] Feng et al. successfully prepared a spherical γ-Al2O3 carrier with a bimodal pore structure consisting of macropores and mesopores by using dodecane as a pore-forming agent through an oil-ammonia column molding method. During the preparation process, when the surfactant concentration was 4‰ and an ultrasonic voltage of 20 V was applied, the average pore size of the obtained γ-Al2O3 was 100 nm and the porosity was 69.21%. In addition, after being treated at 600°C for 120 h, the sample still maintained a porosity of 170.9 m 2 / g specific surface area.

[0004] Patent CN119551697A discloses a modified alumina with a high hydroxyl density surface. This is achieved by adding an isoelectric point modifier and employing appropriate surface treatment methods. A sulfuric acid solution, boehmite powder, carboxymethyl cellulose, polyvinyl alcohol, and vanadium pentoxide are mixed, kneaded in a kneader, and then extruded into a columnar shape.

[0005] Patent CN111069750 discloses a method for preparing a modified alumina carrier. Graphene and ZSM-5 molecular sieves are added to a pseudo-boehmite slurry, stirred evenly, and then ethanol and tetraethoxysilane are added. After aging at 185°C for 24 hours, the mixture is filtered, and ethylenediamine and tetraethoxysilane are added and kneaded into a plastic. The mixture is then extruded into strips, dried, and calcined at 500°C for 4 hours. The final modified alumina carrier has a specific surface area of 353 m 2 / g, pore volume of 0.57cm 3 / g.

[0006] Although the above reports prepared shaped alumina supports, they all required the addition of organic additives, which were relatively expensive and had low pore volumes. Summary of the Invention

[0007] In view of the shortcomings of existing alumina forming technology, the present invention provides a method for preparing formed alumina with high thermal stability.

[0008] The preparation method of the shaped alumina with high thermal stability is as follows: aluminum sulfate solution and sodium aluminate solution are titrated and mixed to a pH of 7-9, and water glass is added to obtain a mixed solution; a phosphate solution and halloysite are then added, crystallized to obtain a slurry; the slurry is filtered, washed, extruded, and dried to obtain shaped boehmite; and finally, calcined at 500-700°C for 1-4 hours to obtain shaped alumina with high thermal stability.

[0009] The concentration of the aluminum sulfate solution is 0.1-0.7 mol / L.

[0010] In the sodium metaaluminate solution, the concentration of aluminum oxide is 3-8 wt %, preferably 3-6 wt %, and the molar ratio of sodium to aluminum is 2.5-6.5, preferably 4-6.

[0011] The concentration of the water glass is 20-30 wt %. The amount of water glass added, calculated as silicon dioxide, accounts for 2-20 wt %, preferably 2-10 wt %, of the total mass of silicon dioxide and aluminum oxide in the mixed solution.

[0012] The crystallization temperature is 100-200° C., and the crystallization time is 0.5-6 hours.

[0013] After the phosphate solution is added, the molar ratio of P to Al in the mixed solution is 0.02-0.1.

[0014] The mass ratio of the halloysite to the mass of the alumina in the mixed solution is 5%-70%.

[0015] The specific surface area of the formed alumina is 200-500 m 2 / g, pore volume of 0.8-2.0 cm 3 / g, and the crushing strength is 50-200 N / cm.

[0016] The method for preparing shaped alumina with high thermal stability is green and clean, which solves the problem that thin-plate boehmite is difficult to shape, and obtains shaped alumina with large specific surface area and pore volume. After calcination at 600℃, the alumina has a surface area of 300-450m 2 / g and a specific surface area of 1.10-1.50cm 3 / g pore volume and a crushing strength of 100-200 N / cm. DETAILED DESCRIPTION

[0017] In the following examples and comparative examples, the specific surface area and pore volume parameters were measured by a TriStar II 3020 instrument from Micromeritics, USA; and the crushing strength was measured by a DL-3 intelligent particle strength tester from Dalian Penghui Technology Development Co., Ltd. Example 1

[0018] (1) A 0.7 mol / L aluminum sulfate solution and a sodium aluminate solution (3 wt% in terms of alumina, with a sodium to aluminum molar ratio of 4.5) were titrated and mixed to a pH of 8, and water glass was added to obtain a mixed solution; the concentration of water glass was 27 wt%, and the amount of water glass added, calculated as silica, accounted for 8 wt% of the total mass of the mixed solution calculated as silica and alumina.

[0019] (2) adding a saturated disodium hydrogen phosphate solution to the mixed solution at a P / Al molar ratio of 0.08 and 30 wt % of halloysite calculated as alumina in the mixed solution, and crystallizing at 160° C. for 2 h to obtain a slurry; (3) filtering, washing, extruding and drying the slurry to obtain formed boehmite; (4) The boehmite obtained above was calcined at 600°C and 1000°C for 2 h, respectively, to obtain shaped alumina. The specific surface area and pore volume data of the shaped alumina are shown in Table 1. Table 1 shows the specific surface area and pore volume of alumina prepared at different calcination temperatures.

[0020] Table 1

[0021] Example 2

[0022] (1) A 0.7 mol / kg aluminum sulfate solution and a sodium aluminate solution (3 wt % in terms of alumina, with a sodium to aluminum molar ratio of 4.5) were titrated and mixed to a pH of 8, and water glass was added to obtain a mixed solution; the concentration of water glass was 27 wt %, and the amount of water glass added, calculated as silica, accounted for 8 wt % of the total mass of the mixed solution calculated as silica and alumina.

[0023] (2) adding a saturated disodium hydrogen phosphate solution to the mixed solution at a P / Al molar ratio of 0.08, and adding 10-50 wt % of halloysite calculated as alumina to the mixed solution, and crystallizing at 160° C. for 2 h to obtain a slurry; (3) filtering, washing, extruding and drying the slurry to obtain formed boehmite; (4) The shaped boehmite obtained above was calcined at 600 °C for 2 h to obtain shaped alumina. The specific surface area, pore volume and crushing strength data of the shaped alumina are shown in Table 2.

[0024] Table 2

[0025] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing shaped alumina with high thermal stability, characterized in that: The specific operations of the preparation method are: titrating and mixing an aluminum sulfate solution and a sodium aluminate solution to a pH of 7-9, adding water glass to obtain a mixed solution; then adding a phosphate solution and halloysite, crystallizing to obtain a slurry; filtering, washing, extruding, and drying the slurry to obtain shaped boehmite; and finally calcining at 500-700°C for 1-4 hours to obtain shaped alumina with high thermal stability.

2. The preparation method according to claim 1, characterized in that The concentration of the aluminum sulfate solution is 0.1-0.7 mol / L.

3. The preparation method according to claim 1, characterized in that In the sodium metaaluminate solution, the concentration of aluminum oxide is 3-8 wt %, preferably 3-6 wt %, and the molar ratio of sodium to aluminum is 2.5-6.5, preferably 4-6.

4. The preparation method according to claim 1, characterized in that The concentration of the water glass is 20-30 wt %. The amount of water glass added, calculated as silicon dioxide, accounts for 2-20 wt %, preferably 2-10 wt %, of the total mass of silicon dioxide and aluminum oxide in the mixed solution.

5. The preparation method according to claim 1, characterized in that The crystallization temperature is 100-200° C., and the crystallization time is 0.5-6 hours.

6. The preparation method according to claim 1, characterized in that After the phosphate solution is added, the molar ratio of P to Al in the mixed solution is 0.02-0.

1.

7. The preparation method according to claim 1, characterized in that The mass ratio of the halloysite to the mass of the alumina in the mixed solution is 5%-70%.

8. A shaped alumina having high thermal stability prepared by the method according to any one of claims 1 to 7.

9. The shaped alumina with high thermal stability according to claim 8, characterized in that The specific surface area of the formed alumina is 200-500 m 2 / g, pore volume of 0.8-2.0 cm 3 / g, and the crushing strength is 50-200 N / cm.

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