Preparation method of near-flaky alumina carrier with ultrahigh specific surface area

Abstract

The invention relates to the technical field of catalysts, and particularly provides a preparation method of an ultra-high specific surface area near-sheet-shaped alumina carrier, which comprises the following steps: inducing an aluminum source to directionally grow into a uniform near-sheet-shaped structure through synergistic self-assembly of metal ions and a template agent in an acidic sol system, and combining an oil ammonia column biphase forming technology to prepare the ultra-high specific surface area near-sheet-shaped alumina carrier. Under the conditions of low-temperature gel forming and low-temperature calcination, the near-flaky alumina carrier with the high specific surface area is prepared. Compared with a molten salt method and a traditional extrusion process, the method has the advantages that toxic molten salt and fluorine-containing auxiliaries are thoroughly avoided, the morphology controllability is remarkably improved, and the method has remarkable application value in the field of catalyst carriers.

Description

Technical Field

[0001] The present invention relates to the field of catalyst technology, in particular to a method for preparing an ultra-high specific surface area near-flaky alumina carrier. Background Art

[0002] Alumina carriers are widely used in the fields of catalysts and adsorbents due to their high temperature resistance, high mechanical strength and excellent chemical stability. Among them, nearly lamellar alumina has an open pore structure, which can significantly improve the molecular diffusion efficiency and become an ideal carrier for high-performance functional materials. However, existing preparation technologies have significant limitations: although the molten salt method can control the morphology by adjusting parameters, some molten salts are expensive and toxic, the product uniformity is poor and the post-processing is complicated; the solid-phase sintering method needs to be carried out at a high temperature above 1400°C, and fluorine-containing additives (such as ammonium fluoride) are often introduced to reduce the sintering temperature, which leads to environmental pollution and difficulty in morphology control, and the specific surface area is low; and the template method (such as CN115259188A) can produce nearly lamellar alumina with a large diameter-to-thickness ratio, but the template removal process is easy to destroy the structure, and the specific surface area is usually less than 400m 2 / g, which limits the active site density. In addition, compared with oil-ammonia droplet molding, the traditional extrusion molding process requires the addition of a binder, which can easily lead to a sharp decrease in specific surface area and strength.

[0003] Therefore, developing a green, low-temperature, highly morphologically controllable method for preparing near-flake alumina that can simultaneously achieve ultra-high specific surface area has become a key requirement for breaking through industry bottlenecks. Summary of the Invention

[0004] In view of this, the present invention proposes a method for preparing an ultra-high specific surface area near-flaky alumina carrier.

[0005] The technical solution of the present invention is achieved as follows: The present invention provides a method for preparing an ultra-high surface area ratio near-flaky alumina carrier, comprising the following steps:

[0006] (1) Dissolving the template and metal precursor in an acidic aqueous solution at 60-70° C. to form a mixed solution;

[0007] (2) adding the aluminum source dropwise to the mixed solution of step (1) at 60-70° C. and stirring for 4-6 hours to form a sol;

[0008] (3) dropping the sol into a two-phase system containing an oil phase and an ammonia aqueous phase, so that the sol is spherical in the oil phase and gelled in the ammonia aqueous phase;

[0009] (4) The gelled spheres are aged in aqueous ammonia for 12-24 hours, separated and dried after aging, and calcined at 550-650° C. for 6-8 hours to obtain a nearly flaky alumina support.

[0010] In some embodiments, the metal precursor is a compound of at least one element selected from zirconium, titanium, and tin.

[0011] In some embodiments, the metal precursor is a soluble salt, including: a zirconium source: zirconium nitrate, zirconium oxychloride, or zirconium sulfate; a titanium source: titanium sulfate or titanium tetrachloride; and a tin source: tin tetrachloride pentahydrate.

[0012] In some embodiments, the aluminum source is an organic aluminum compound, including at least one of aluminum isopropoxide and aluminum tri-sec-butoxide.

[0013] In some embodiments, the template is a cationic surfactant or an amphiphilic block copolymer, including at least one of hexadecyltrimethylammonium bromide, P123 or F127, and the concentration of the template in the mixed solution is 4-6 g / L.

[0014] In some embodiments, in steps (1) and (2), the acid in the acidic aqueous solution is a strong inorganic acid, including hydrochloric acid, nitric acid, or sulfuric acid; and the molar ratio of aluminum ion, hydrogen ion, and metal ion is 1:(0.05-0.10):(0.0125-0.05).

[0015] In some embodiments, in step (3), the oil phase is paraffin oil or kerosene, and the concentration of the ammonia aqueous phase is 6-8 wt %.

[0016] In some embodiments, in step (4), the drying temperature is 60-80°C, the drying time is 20-24 hours, and the calcination temperature is 600-650°C.

[0017] In a second aspect, the present invention also provides an ultra-high specific surface area near-flaky alumina carrier prepared by the above method, wherein the specific surface area is ≥500m 2 / g, with a nearly flake-like morphology, a flake diameter of 100-500nm, and an aspect ratio ≥10.

[0018] In a third aspect, the present invention further provides an application of an ultra-high specific surface area near-flaky alumina carrier in a catalyst carrier or adsorption material.

[0019] The present invention has the following beneficial effects compared to the prior art:

[0020] This invention uses a synergistic self-assembly mechanism between metal ions and templates to induce the directional growth of aluminum sources into uniform, near-lamellar structures in an acidic sol system. Combined with an oil-ammonia column dual-phase forming technique, this method achieves three breakthroughs: significantly increasing specific surface area, providing abundant active sites, and overcoming the bottleneck of morphology control. Metal ion doping effectively inhibits agglomeration, resulting in uniform, near-lamellar supports with a diameter of 100-500nm and an aspect ratio of ≥10, significantly enhancing molecular diffusion efficiency. The process is environmentally friendly and low-carbon, with an overall reaction temperature of ≤70°C and a calcination temperature of ≤650°C. This saves over 60% energy compared to solid-phase sintering methods and completely avoids the use of toxic molten salts and fluorine-containing additives, in line with green manufacturing trends. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a morphology diagram of the carrier prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0025] Unless otherwise specified, the methods used in the following examples are conventional methods. The materials, reagents, and instruments used are conventional materials, reagents, and instruments in the art, unless otherwise specified, and can be obtained commercially by those skilled in the art.

[0026] When an amount, concentration or other value or parameter is expressed as a range, a preferred range or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range. In the present specification and claims, range definitions may be combined and / or interchanged, and if not otherwise stated, such ranges include all subranges contained therein.

[0027] Example 1

[0028] Zr 4+ Doping system

[0029] step:

[0030] (1) Dissolve 0.5 g of CTAB in 100 mL of water at 60°C, add 0.26 g of Zr(NO3)4·5H2O and 0.14 mL of HNO3 (65%);

[0031] (2) Add 4.4 g of aluminum isopropoxide dropwise and stir at 70°C for 6 h to form a gel;

[0032] (3) The sol was dripped into a paraffin oil / 8% ammonia biphasic column, and the gelled balls were aged in 8% ammonia for 24 h;

[0033] (4) Dry at 65°C for 24 hours and calcine at 650°C for 6 hours.

[0034] The obtained aluminum oxide is nearly flaky and its morphology is as follows Figure 1 .

[0035] Example 2

[0036] Ti 4+ Doping system

[0037] step:

[0038] (1) Dissolve 0.5 g of CTAB in 100 mL of water at 60°C, add 0.10 g of TiCl4 and 0.14 mL of H2SO4 (98%);

[0039] (2) Add 4.4 g of aluminum isopropoxide dropwise and stir at 70°C for 6 h to form a gel;

[0040] (3) The sol was dripped into a paraffin oil / 8% ammonia biphasic column, and the gelled balls were aged in 8% ammonia for 24 h;

[0041] (4) Dry at 65°C for 24 hours and calcine at 650°C for 6 hours.

[0042] Example 3

[0043] Sn 4+ Doping system

[0044] step:

[0045] (1) Dissolve 0.5 g of P123 in 100 mL of water at 60°C, add 0.19 g of SnCl4 and 0.14 mL of HNO3 (65%);

[0046] (2) Add 4.4 g of aluminum isopropoxide dropwise and stir at 70°C for 6 h to form a gel;

[0047] (3) The sol was dripped into a paraffin oil / 8% ammonia biphasic column, and the gelled balls were aged in 8% ammonia for 24 h;

[0048] (4) Dry at 65°C for 24 hours and calcine at 650°C for 6 hours.

[0049] Comparative Example 1

[0050] No metal ion doping

[0051] step:

[0052] (1) Dissolve 0.5 g of CTAB in 100 mL of water at 60°C and add 0.14 mL of HNO3 (65%);

[0053] (2) Add 4.4 g of aluminum isopropoxide dropwise and stir at 70°C for 6 h to form a gel;

[0054] (3) The sol was dripped into a paraffin oil / 8% ammonia biphasic column, and the gelled balls were aged in 8% ammonia for 24 h;

[0055] (4) Dry at 65°C for 24 hours and calcine at 650°C for 6 hours.

[0056] Comparative Example 2

[0057] Traditional extrusion

[0058] step:

[0059] (1) Dissolve 0.5 g of CTAB in 100 mL of water at 60°C, add 0.26 g of Zr(NO3)4·5H2O and 0.14 mL of HNO3 (65%);

[0060] (2) Add 4.4 g of aluminum isopropoxide dropwise and stir at 70°C for 6 h to form a gel;

[0061] (3) The sol was transferred to a kneader and 10% of the sol mass of sesbania powder was added as an extrusion aid at a speed of 50 rpm. After kneading for 30 min, the sol was placed in an extruder and extruded into strips (1.5 mm in diameter) at a pressure of 20 MPa and pelletized (3 mm in length).

[0062] (4) Dry at 65°C for 24 hours and calcine at 650°C for 6 hours.

[0063] Comparative Example 3

[0064] step:

[0065] (1) Dissolve 0.5 g of CTAB in 100 mL of water at 60°C, add 0.26 g of Zr(NO3)4·5H2O and 0.02 mL of HNO3 (65%);

[0066] (2) Add 4.4 g of aluminum isopropoxide dropwise and stir at 70°C for 6 h to form a gel;

[0067] (3) The sol was dripped into a paraffin oil / 8% ammonia biphasic column, and the gelled balls were aged in 8% ammonia for 24 h;

[0068] (4) Drying at 65°C for 24 hours, calcining at 650°C for 6 hours

[0069] Comparative Example 4

[0070] step:

[0071] Same as Example 1, the calcination temperature is 800°C.

[0072] Comparative Example 5

[0073] The γ-Al2O3 carrier (specifically 350m 2 / g).

[0074] Application testing:

[0075] The carriers prepared in the examples and comparative examples were used to load 15% MoO3-CoO for diesel hydrodesulfurization reaction.

[0076] Preparation steps:

[0077] Prepare the impregnation solution: dissolve ammonium molybdate (NH4)6Mo7O 24 ·4H2O and cobalt nitrate Co(NO3)2·6H2O in deionized water, controlling MoO3:CoO=12%:3%;

[0078] Equal volume impregnation: impregnate the support for 24 h (25°C);

[0079] Drying: 120℃×4h;

[0080] Calcination: 500℃×4h (air atmosphere).

[0081] Reaction evaluation system:

[0082] In a fixed-bed microreactor (10 mm diameter stainless steel tube), the feedstock was diesel fuel (containing benzothiophene) with a sulfur content of 1.5 wt%. At 360°C, 4.0 MPa, a hydrogen-to-oil ratio of 300:1, and a space velocity of 2.0 / h, the total sulfur content of the product was measured using the microcoulometry method (GB / T11060) and the desulfurization rate was calculated. The results are shown in the following table:

[0083]

[0084] In the above data, Examples 1-3 all exhibit near-lamellar structures, high specific surface areas, and high desulfurization rates. Comparative Example 5 has a lower specific surface area and a lower desulfurization rate of only 86.2%. Comparative Example 1 lacks a near-lamellar structure, and its desulfurization rate decreases by 16.2% compared to Example 1. Comparative Example 2 uses conventional extrusion molding. After 100 hours of reaction, the crushing strength decreases from 15 N / cm to 8.2 N / cm, a 45% reduction in strength. In contrast, Example 1 only loses strength by 37%, and its initial mechanical strength reaches 32 N / cm. This results in a longer service life.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an ultra-high surface area-to-plate alumina carrier, characterized in that: The following steps are involved: (1) Dissolving the template and metal precursor in an acidic aqueous solution at 60-70° C. to form a mixed solution; (2) adding the aluminum source dropwise to the mixed solution of step (1) at 60-70° C. and stirring for 4-6 hours to form a sol; (3) dropping the sol into a two-phase system containing an oil phase and an ammonia aqueous phase, so that the sol is spherical in the oil phase and gelled in the ammonia aqueous phase; (4) The gelled spheres are aged in aqueous ammonia for 12-24 hours, separated and dried after aging, and calcined at 550-650° C. for 6-8 hours to obtain a nearly flaky alumina support.

2. The method for preparing the ultra-high surface area-to-plate alumina carrier according to claim 1, wherein: The metal precursor is a compound of at least one element selected from zirconium, titanium and tin.

3. The method for preparing the ultra-high surface area ratio flaky alumina carrier according to claim 2, wherein: The metal precursor is a soluble salt, including: a zirconium source: zirconium nitrate, zirconium oxychloride or zirconium sulfate; a titanium source: titanium sulfate or titanium tetrachloride; and a tin source: tin tetrachloride pentahydrate.

4. The method for preparing the ultra-high surface area-to-plate alumina carrier according to claim 1, wherein: The aluminum source is an organic aluminum compound, including at least one of aluminum isopropoxide and aluminum tri-sec-butoxide.

5. The method for preparing the ultra-high surface area ratio flaky alumina carrier according to claim 1, wherein: The template agent is a cationic surfactant or an amphiphilic block copolymer, including at least one of hexadecyltrimethylammonium bromide, P123 or F127, and the concentration of the template agent in the mixed solution is 4-6 g / L.

6. The method for preparing the ultra-high surface area ratio flaky alumina carrier according to claim 1, wherein: In step (1) and step (2), the acid in the acidic aqueous solution is an inorganic strong acid, including hydrochloric acid, nitric acid or sulfuric acid; and the molar ratio of aluminum ion, hydrogen ion and metal ion is 1:(0.05-0.10):(0.0125-0.05).

7. The method for preparing the ultra-high surface area-to-plate alumina carrier according to claim 1, wherein: In step (3), the oil phase is paraffin oil or kerosene, and the concentration of the ammonia water phase is 6-8wt%.

8. The method for preparing the ultra-high surface area-to-plate alumina carrier according to claim 1, wherein: In step (4), the drying temperature is 60-80°C, the drying time is 20-24h; and the calcination temperature is 600-650°C.

9. An ultra-high surface area-to-plate alumina carrier, characterized in that: Prepared by the preparation method described in any one of claims 1 to 8, the specific surface area is ≥500m 2 / g, with a nearly flake-like morphology, a flake diameter of 100-500nm, and an aspect ratio ≥10.

10. Use of the ultra-high surface area ratio nearly flaky alumina carrier according to claim 9 in catalyst carriers or adsorption materials.

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