Preparation of silicon-aluminum precursor with high silicon content and compound
The high-silicon content silicon-aluminum composites are prepared by hydrolysis of aluminum alcohol and alkoxy silicon deposition, which solves the problem of impurities introduced in the traditional method and realizes the preparation of high-performance catalyst support.
Patent Information
- Application Number
- CN202510444489.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2025-07-11
AI Technical Summary
It is difficult to prepare silicon-aluminum composites with high silicon content in the prior art, and impurities are often introduced into the silicon-aluminum composites in traditional methods, which affect their performance.
After hydrolysis of aluminum alcohol, acid additives were added, and alkoxy silicon was added for deposition, a high silicon content silicon-aluminum precursor was prepared, and a high silicon content silicon-aluminum composite was obtained through heat treatment to avoid the introduction of other impurities.
The prepared silicon-aluminum composite has a high specific surface and a large pore structure, which can adjust the characteristics of B acid and L acid, and is suitable for catalysts and catalyst support, and improves catalytic activity.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the field of chemical production processes, and particularly relates to a method for preparing a silicon-aluminum precursor and a composite with a high silicon content. Background Art
[0002] Since 1942, synthetic "low-alumina" amorphous silica-alumina catalysts have been applied, with the weight / weight of Al2O3 being approximately 13%. Since 1955, "high-alumina" silica-alumina catalysts containing up to 30% Al2O3 weight / weight have been introduced. Alumina and silica-alumina have many applications as acid catalysts in industrial chemistry. On the other hand, silica, alumina, and amorphous silica-alumina are also widely used as supports for oxide catalysts.
[0003] Early interest in these materials was related to the fossil fuel era, but it will be further enhanced in the era of renewable raw materials that has arrived. In fact, solid acids have a very relevant potential role as catalysts and catalyst supports, for example, in the conversion of lignocellulosic biomass and waste into useful products, in several steps of the new green organic chemistry based on renewable energy, and for many environmental applications.
[0004] In the field of heterogeneous catalysis, high-purity catalyst supports are required. Boehmite prepared by the alcohol-aluminum method has a sodium content of less than 50 ppm Na2O, and has the advantages of narrow pore size distribution, good colloidal solubility, relatively high specific surface area and high purity. It is the most commonly used material and catalyst support in the chemical and catalytic fields. For single-atom catalysts, the role of the support material in the active component is even more important, because the support not only allows for a fine distribution of the active component on the surface, but also enables ideal mass transfer through a specific pore structure. The SiO2 content and acidity are correlated with the catalytically active substances as a function of the pore volume and acid amount.
[0005] The structure and formation of the catalytic center inherently depend on the selected synthesis route and subsequent post-synthesis treatment. In the existing methods for preparing silicon-aluminum composites by the alcohol-aluminum method, the silicon content in the obtained composite is 40%, such as the high-silicon-content silicon-aluminum composite of Sasol, and its thermal stability and specific surface area are significantly improved. Doping with silica can change the pore structure of alumina and can form a material with both B and L acids, but the preparation method of low-silicon boehmite is not suitable for the preparation of high-silicon aluminum composites. Therefore, a new method is needed to prepare silicon-aluminum composites with a high silicon content. Summary of the Invention
[0006] The object of the present invention is to prepare a silicon-aluminum composite with a high silicon content. During the preparation process, only silicon and alcohol are introduced, without introducing other impurities and without waste discharge. The obtained silicon-aluminum composite has a high specific surface area, a large pore structure, and adjustable Bronsted acid and Lewis acid. The technical solution of the present invention is to prepare a silicon-aluminum composite with a high silicon content by adding silicon after activating pseudo-boehmite. The method adopted is to add an acid assistant after the hydrolysis of aluminum alkoxide, and then add alkoxysilane for deposition. The obtained silicon-aluminum composite precursor is then heat-treated to directly become a catalytic material or a catalyst support.
[0007] The technical solution of the present invention is as follows: A method for preparing a high-silicon-content silicon-aluminum precursor and composite, which is based on the hydrolysis product of aluminum alkoxide plus alkoxysilane, includes the following steps: The first step is to hydrolyze aluminum alkoxide to prepare pseudo-boehmite, add acid and then add alkoxysilane to obtain a silicon-aluminum precursor solution.
[0008] The second step is to heat-treat and calcine the silicon-aluminum solution with an excessive silicon content to obtain a precursor and a composite.
[0009] According to the above method, when hydrolyzing C3-C6 aluminum alkoxide, C6 aluminum alkoxide is preferably used.
[0010] According to the above method, when hydrolyzing aluminum alkoxide, the hydrolysis temperature is 70-95°C and the hydrolysis time is 1h-4h.
[0011] According to the above method, the mixture obtained after hydrolysis is acid-hydrolyzed, and the acid used can be HCl, HNO3, acetic acid or citric acid.
[0012] According to the above method, the mixture obtained after hydrolysis is acid-hydrolyzed, and the acid-hydrolysis temperature is 70-110°C.
[0013] According to the above method, when adding alkoxysilane, the addition amount can be 50-90%.
[0014] According to the above method, the treatment temperature of the obtained silicon-aluminum composite is 90-120°C, the time is 6-8h, the calcination temperature is 550-600°C, and the calcination time is 4-7h.
[0015] Compared with the existing silicon-modified pseudo-boehmite, this method can obtain a silicon-aluminum composite with a high silicon content, without introducing other impurities at the same time, the preparation process is simple, and the obtained silicon-aluminum composite with a high silicon content has a high specific surface area, large pores and more than two acid characteristics. Description of the Drawings
[0016] Figure 1 XRD diffraction pattern of the high-silicon-content silicon-aluminum precursor in Example 1 Figure 2TG-DTG of the high-silica-content silicon-aluminum precursor in Example 1 Figure 3 Pore size distribution diagram of the high-silica-content silicon-aluminum composite in Example 1 Detailed implementation manners
[0017] Example 1: First, add 16.2 g of aluminum isopropoxide into a four-necked flask, heat up to 80 °C, then add 22 mL of deionized water for hydrolysis for 2 h, and then add 3 mL of HNO3 (0.1 mol / L). React at 85 °C for 30 min. Add the isopropanol mixture of 10 g of tetraethyl orthosilicate (TEOS) to the above solution and react for 3 h. Distill off the alcohol at 110 °C to obtain a silicon-aluminum solution, and place it in an oven at 110 °C for 6 h to obtain a 50% high-silica-content silicon-aluminum precursor. Calcinate it in a muffle furnace at 550 °C for 5 h to obtain a 50% high-silica-content silicon-aluminum composite.
[0018] Example 2: First, add 16.2 g of aluminum isopropoxide into a four-necked flask, heat up to 80 °C, then add 22 mL of deionized water for hydrolysis for 2 h, and then add 3 mL of HNO3 (0.1 mol / L). React at 85 °C for 30 min. Add the isopropanol mixture of 13.33 g of TEOS to the above solution and react for 3 h. Distill off the alcohol at 110 °C to obtain a silicon-aluminum solution, and place it in an oven at 110 °C for 6 h to obtain a 60% high-silica-content silicon-aluminum precursor. Calcinate it in a muffle furnace at 550 °C for 5 h to obtain a 60% high-silica-content silicon-aluminum composite.
[0019] Example 3: First, add 16.2 g of aluminum isopropoxide into a four-necked flask, heat up to 80 °C, then add 22 mL of deionized water for hydrolysis for 2 h, and then add 3 mL of HNO3 (0.1 mol / L). React at 85 °C for 30 min. Add the isopropanol mixture of 19.89 g of TEOS to the above solution and react for 3 h. Distill off the alcohol at 110 °C to obtain a silicon-aluminum solution, and place it in an oven at 110 °C for 6 h to obtain a 70% high-silica-content silicon-aluminum precursor. Calcinate it in a muffle furnace at 550 °C for 5 h to obtain a 70% high-silica-content silicon-aluminum composite.
[0020] The silicon-aluminum composite obtained in this invention patent has a relatively high specific surface area, large pore volume and pore size, and contains both B acid and L acid at the same time. The catalyst with this structure is particularly suitable for the reforming of complex reactant mixtures where several different types of reactions occur simultaneously.
[0021] The above are only the preferred implementation manners of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the creative concept of the present invention, making several improvements and transformations all fall within the protection scope of the present invention.
Claims
1. A method for preparing a silicon-aluminum composite with a high silicon content, which is based on an alcohol aluminum hydrolyzate plus an alkoxysilane, comprising the following steps: In the first step, hydrolyze the alcohol aluminum to prepare pseudoboehmite, and then add the alkoxysilane to obtain a silicon-aluminum composite. In the second step, heat-treat the silicon-aluminum composite.
2. The method according to claim 1, characterized in that When hydrolyzing the alcohol aluminum, the alcohol aluminum used is an alcohol aluminum of C3-C6, preferably C6 alcohol aluminum.
3. The method according to claim 1, wherein The hydrolysis temperature is 70-95 °C, and the hydrolysis time is 1-4 h.
4. According to the method described in claim 1, acidify the mixture obtained after hydrolysis. The acid used can be HCl, HNO3, acetic acid or citric acid.
5. The method according to claim 1, wherein The temperature for acidifying the mixture obtained after hydrolysis is 70-95 °C.
6. The method according to claim 1, characterized in that Add the alkoxysilane, and its addition amount can be 50-90% by weight.
7. According to the method described in claim 1, the treatment temperature of the obtained silicon-aluminum composite is 90-120 °C, the time is 6-8 h, the calcination temperature is 550-600 °C, and the calcination time is 4-7 h.