A nano-macroporous tubular γ-aluminum oxide powder and a preparation method thereof

Abstract

The present invention discloses a nano-macroporous tubular γ-alumina and a preparation method thereof, comprising the following steps: <subgt;3< / subgt;·6H<subgt;2< / subgt;O的水溶液中缓慢滴入氨水,通过调节pH至8‑10,快速加入无水乙醇经充分搅拌均匀后保温静置,沉淀反应结束后,将沉淀物进行过滤、洗涤、干燥和焙烧,得到纳米大孔列管式γ‑氧化铝。本发明方法在低温、无模板剂条件下制备得到大孔列管式γ‑氧化铝,制备成本低、环境友好;本发明制备的γ‑氧化铝结构独特,呈列管式单向排列、两端为贯穿孔,且具有大孔结构,易于作为催化剂及载体、吸附剂使用,尤其对甲基橙的吸附率高达99.4%。

Description

Technical Field

[0001] The present invention relates to a nano-macroporous tubular γ-aluminum oxide powder and a preparation method thereof, belonging to the field of inorganic material preparation. Background Art

[0002] Nano-aluminum oxide is a white powdery crystal with a particle size in the range of 1 nm - 100 nm. Different preparation methods and process conditions can obtain nano-aluminum oxide with different structures. Its characteristics are porosity, high dispersion, and high activity. As a porous material, nano-aluminum oxide is widely used as a catalyst or a carrier due to its good mechanical stability, excellent anti-wear and corrosion resistance, large specific surface area, excellent adsorption performance, and low price.

[0003] Hierarchical-structured nanomaterials can exhibit unique electrical, optical, thermal, and other properties due to their special morphologies and structures. With the development of three-dimensional nanomaterials, the preparation of alumina with hierarchical structures has also attracted extensive attention.

[0004] CN113735614B discloses a method for preparing spherical alumina. Boehmite is peptized with an acid solution to form an alumina sol, and the alumina sol is dropped into an oil-ammonia column to form wet gel spheres. The wet gel spheres at the bottom of the oil-ammonia column are taken out, aged in an organic solvent, and then dried and calcined to obtain spherical alumina.

[0005] CN107176617B discloses a method for preparing spherical alumina. An aluminum salt solution with a surfactant is ultrasonically treated, and a sodium salt and a precipitant are added under continuous stirring, and then ultrasonically treated to obtain a precursor solution; after heating and reacting, it is centrifuged, washed, filtered, dried, and calcined to obtain a white powder.

[0006] CN106186013A discloses a method for synthesizing flower-like mesoporous alumina by a rheological phase reaction method. A small amount of sodium cholate and lanthanum salt are used to construct a soft template, and inorganic aluminum or organic aluminum is used as an aluminum source. A small amount of a mixed solvent of an organic solvent / water is added and thoroughly mixed and ground into a rheological phase substance, and kept at a constant temperature in a sealed reaction kettle for a certain time to obtain a dry gel, and then mesoporous alumina is obtained by high-temperature calcination.

[0007] The preparation methods of the above hierarchical-structured alumina powders often use traditional template methods and hydrothermal methods, which require steps such as precipitation, hydrothermal aging, filtration, washing, drying, and calcination. At the same time, the hydrothermal reaction requires high temperature and high pressure, the preparation process is complex, the cost is high, and the use of a template agent will also increase the preparation cost. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention provides a method for preparing nano-macroporous tubular γ-alumina powder. This method requires no template, hydrothermal treatment, or aging, resulting in a simple and easy-to-use preparation process. Furthermore, the γ-alumina prepared by the present invention exhibits a unique structure, with a tubular, unidirectional arrangement and through-holes at both ends. This macroporous structure makes it suitable for use as a catalyst, catalyst carrier, or adsorbent.

[0009] The invention discloses a method for preparing nano-macroporous tubular γ-alumina, comprising the following steps: slowly dripping ammonia water into an AlCl3·6H2O aqueous solution, adjusting the pH to 8-10, quickly adding anhydrous ethanol, stirring thoroughly and evenly, and then heat-insulating and standing to perform a precipitation reaction; after the precipitation reaction is completed, filtering, washing, drying and calcining the precipitate to obtain the nano-macroporous tubular γ-alumina.

[0010] In the preparation method of the present invention, the molar concentration of the AlCl3·6H2O aqueous solution is 0.5 mol / L-1.0 mol / L.

[0011] In the preparation method of the present invention, the concentration of the ammonia water is 25-30%.

[0012] In the preparation method of the present invention, the time for rapid addition of anhydrous ethanol and sufficient stirring is 1-5 minutes, the volume content of anhydrous ethanol added is 5-15% of the aqueous solution, the insulation and standing temperature is 60-90°C, and the precipitation reaction time is 6-24 hours.

[0013] In the preparation method of the present invention, the precipitation reaction time is preferably 6-12 hours.

[0014] In the preparation method of the present invention, the drying conditions are 105-130° C. and the drying time is 1-12 hours.

[0015] In the preparation method of the present invention, the roasting conditions are as follows: the roasting temperature is 450-600° C. and the roasting time is 2-8 hours.

[0016] The nano-macroporous tubular γ-alumina prepared by the method of the present invention has a tubular unidirectional arrangement with through holes at both ends, a tube diameter of 500-1000nm, a pore volume of 0.5-0.7ml / g, and a specific surface area of 200-270m 2 / g.

[0017] The present invention finds that the nano-macroporous tubular gamma-alumina has good adsorption performance, and the adsorption rate of methyl orange is as high as 99.4%.

[0018] Compared with existing technologies, this method offers a simple process, operates at low temperatures of 60-90°C, and does not require high-temperature, high-pressure hydrothermal reactions. Furthermore, it can produce alumina with a multi-dimensional hierarchical structure without the addition of a template. The resulting alumina powder exhibits a tubular microstructure, with an appropriate specific surface area and pore volume. The tubular channels and large specific surface area can be filled with active components, making it suitable for use as a catalyst or catalyst support. Furthermore, the tubular structure can absorb more organic pigments, particularly methyl orange, making it suitable for adsorption and impurity removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a scanning electron microscope photograph of the nano-γ-alumina prepared in Example 1.

[0020] Figure 2 This is a scanning electron microscope photograph of the nano-γ-alumina prepared in Example 2.

[0021] Figure 3 This is a scanning electron microscope photograph of the nano-γ-alumina prepared in Example 3.

[0022] Figure 4 This is a scanning electron microscope photograph of the nano-γ-alumina prepared in Example 4.

[0023] Figure 5 This is a scanning electron microscope photograph of the nano-γ-alumina prepared in Example 5.

[0024] Figure 6 This is a scanning electron microscope photograph of the nano-γ-alumina prepared in Example 6.

[0025] Figure 7 This is the XRD diffraction pattern of the nano γ-alumina prepared in Example 1.

[0026] Figure 8 This is the methyl orange adsorption curve of the nano-γ-alumina prepared in Example 1 and Example 6. DETAILED DESCRIPTION

[0027] The effects and results of the method of the present invention are further illustrated below with reference to the following examples, but are not limited to the following examples.

[0028] Example 1

[0029] Weigh 12.45 g of AlCl₃·6H₂O and place it in a beaker. Add 100 ml of deionized water to the beaker and stir magnetically to completely dissolve the solid substance, preparing an aqueous solution of AlCl₃·6H₂O. Add 30% ammonia water dropwise to the above solution to adjust the pH value of the solution to 9. Quickly add 10 ml of absolute ethanol and stir well for 2 minutes to obtain a homogeneous emulsion, and then place it in an oven at 80 °C for heat preservation and static settlement for 12 h. Filter the precipitate and wash it several times with distilled water; place the obtained white powder in a drying oven and dry it at 120 °C for 6 hours; calcine it in a muffle furnace at 500 °C for 6 hours to obtain the γ-alumina powder of the present invention. The scanning electron micrograph is as shown in Figure 1 shown, and the XRD diffraction pattern is as shown in Figure 7 shown. The XRD diffraction peaks show that the obtained alumina is in the γ-alumina crystal phase after calcination at 500 °C. The specific surface area of this alumina powder is 266 m 2 / g, the pore volume is 0.68 ml / g, and the scanning electron micrograph shows that the morphology of the obtained alumina is arranged in a unidirectional nano-tubular array, and the pipe diameter is 500 - 100 nm.

[0030] Example 2

[0031] Same as Example 1, only adjust the pH value of the solution to 8 to obtain the nano-γ-alumina powder of the present invention. The specific surface area of this alumina powder is 220 m 2 / g, the pore volume is 0.57 ml / g, and the product morphology is as shown in Figure 2 shown.

[0032] Example 3

[0033] Same as Example 1, only weigh 24.9 g of AlCl₃·6H₂O and adjust the pH value of the solution to 10 to obtain the nano-γ-alumina powder of the present invention. The specific surface area of this alumina powder is 207 m 2 / g, the pore volume is 0.55 ml / g, and the product morphology is as shown in Figure 3 shown.

[0034] Example 4

[0035] Same as Example 1, only adjust the pH value of the solution to 7 to obtain an alumina product. The specific surface area of this alumina powder is 241 m 2 / g, the pore volume is 0.6 ml / g, and the product morphology is as shown in Figure 4 shown.

[0036] Example 5

[0037] Same as Example 1, only add absolute ethanol dropwise and stir for a total of 30 minutes to obtain an alumina product. The specific surface area of this alumina is 211 m 2 / g, the pore volume is 0.53 ml / g, and the product morphology is as shown in Figure 5 shown.

[0038] Example 6

[0039] Same as Example 1, except that anhydrous ethanol was added once during the preparation of the AlCl3·6H2O aqueous solution to obtain an alumina product having a specific surface area of 295 m 2 / g, pore volume 0.84ml / g, product morphology Figure 6 shown.

[0040] Examples 1-3 all produced γ-alumina with a tubular morphology. While Example 5 employed the dropwise addition of anhydrous ethanol, and Example 6 also added anhydrous ethanol, alumina with comparable specific surface area and pore volume was obtained, the morphology was irregular and lacked a hierarchical tubular structure. Electron microscopy images of Example 4 at a pH of 7 revealed a disordered alumina structure, also possessing a large specific surface area and pore volume.

[0041] The present invention finds that the prepared nano-macroporous tubular γ-alumina has good adsorption performance. 20 mg of the alumina prepared in Example 1 and Example 6 were weighed and put into 100 mL of a 50 mg / L methyl orange solution for adsorption experiments. The concentration of methyl orange in the solution was measured using an ultraviolet-visible spectrophotometer (UV-2550). The absorbance at 465 nm was used as a reference, and the adsorption capacity at different adsorption time intervals was characterized by Ci / C0, where Ci represents the instantaneous solution concentration and C0 represents the initial methyl orange solution concentration. The alumina prepared in Example 1 can quickly complete adsorption in 10 minutes, with an adsorption rate of up to 99.4%. The alumina prepared in Example 6 has an adsorption rate of 90.7% after 10 minutes. The tubular nano-alumina in Example 1 has good adsorption capacity for methyl orange.

[0042] 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 and improvements 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 preparation method of nano-macroporous tubular γ-aluminum oxide, characterized in that It includes the following process: Prepare an aqueous solution of AlCl3·6H2O with a molar concentration of 0.5 mol / L - 1.0 mol / L. Slowly drop ammonia water into the aqueous solution of AlCl3·6H2O. The concentration of the ammonia water used is 25 - 30%, adjust the pH to 8 - 10, quickly add absolute ethanol, stir well, keep warm and stand still for precipitation reaction. After the precipitation reaction is completed, filter, wash, dry and calcine the precipitate to obtain nano-porous tubular γ-aluminum oxide; the time for quickly adding absolute ethanol and stirring well is 1 - 5 minutes, and the volume content of the added absolute ethanol is 5 - 15% of the aqueous solution.

2. The method according to claim 1, wherein: The temperature for keeping warm and standing still is 60 - 90 °C, and the precipitation reaction time is 6 - 24 hours.

3. The method according to claim 1, wherein: The drying temperature condition is 105 - 130 °C, and the drying time is 1 - 12 hours.

4. The method according to claim 1, wherein: The calcination temperature is 450 - 600 °C, and the calcination time is 2 - 8 hours.

5. The nano-macroporous tubular γ-aluminum oxide prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The microstructure of the nano-macroporous tubular γ-alumina is arranged in a unidirectional tubular pattern with through-holes at both ends. The tube diameter is 500 - 1000 nm, the pore volume is 0.5 - 0.7 ml / g, and the specific surface area is 200 - 270 m 2 / g.

6. Application of the nano-porous tubular γ-aluminum oxide according to claim 5 as a catalyst or a catalyst carrier, an adsorbent.

7. According to the application described in claim 6, the adsorption rate for methyl orange is as high as 99.4%.

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