CN-118343773-B - Method for synthesizing SBA-15 mesoporous silica under near neutral pH condition

Abstract

The invention relates to a method for synthesizing SBA-15 mesoporous silica under a near neutral pH condition, which can overcome the technical problems of strong acidity requirement and environment unfriendly in the prior art. The method takes a nonionic block copolymer as a template agent, polyacrylic acid as a template auxiliary agent and aminosilane as a co-structure guiding agent, synthesizes the SBA-15 mesoporous silica material under the near neutral pH condition, particularly improves the pH value of a liquid environment required by SBA-15 synthesis from the common pH value of <1 to the near neutral pH value, and greatly reduces the acid amount required by synthesis. The product obtained by the method has uniform aperture and high order, adopts environment-friendly and low-cost polyacrylic acid as a template auxiliary agent, avoids using strong acid or ammonium fluoride and other raw materials which pollute the environment, and is easy to popularize.

Inventors

• CHEN TIEHONG
• LIU JIAWEI
• DU GUO

Assignees

• 南开大学

Dates

Publication Date

20260505

Application Date

20240422

Claims (5)

1. 1. The method for synthesizing SBA-15 mesoporous silica under the near neutral pH condition is characterized by comprising the following steps: 1) Mixing the aqueous solution of the P123 template agent and the polyacrylic acid template assisting agent at room temperature, stirring for 0.5-1 h to obtain a mixed solution, slowly dripping an acid solution to ensure that the pH value is 4-5, and fully stirring for 0.5-1 h to obtain emulsion; 2) Dropwise adding aminosilane into the emulsion under stirring, simultaneously dropwise adding a silicon source, heating with a water bath and preserving heat at 30-35 ℃, and fully stirring for 4-6 h; 3) Standing and crystallizing the emulsion in the step 2) for 24-48h at 80 ℃, centrifuging and separating a reaction mixture after standing and crystallizing are finished, washing a product for 1-3 times, and drying at 50-60 ℃ to obtain a white solid product; 4) Calcining the white solid product at 400-600 ℃ to obtain SBA-15 mesoporous silica, wherein the white solid product is 3-6 h; The mass ratio of the P123 template agent to the polyacrylic acid in the step 1) is=1:2, and the molecular weight of the polyacrylic acid is 3000-240000; the molar ratio of the aminosilane to the silicon source in the step 2) is 1:15-20, the mass ratio of the P123 template agent to the silicon source is=1:1.5-2.1, and the silicon source is ethyl orthosilicate or methyl orthosilicate.
2. 2. The process according to claim 1, characterized in that the acid of step 1) is 0.1M HCl or 0.1M tartaric acid.
3. 3. The method according to claim 1, characterized in that the aminosilane of step 2) is 3-aminopropyl trimethoxysilane.
4. 4. The method according to claim 1, wherein the emulsion of step 3) is crystallized at 80 ℃ by standing for 24 h.
5. 5. The process according to claim 1, characterized in that the white solid product of step 4) is calcined 6 h at 400-600 ℃.

Description

Method for synthesizing SBA-15 mesoporous silica under near neutral pH condition Technical Field The invention relates to a preparation method of a mesoporous silica molecular sieve, in particular to a method for synthesizing SBA-15 mesoporous silica under a near neutral pH condition. Background SBA-15 mesoporous silica belongs to one of the series of mesoporous silica materials developed by Stucky research groups of California university in the United states, and has a highly ordered hexagonal structure and regular pore distribution. Compared with MCM-41, the SBA-15 has thicker pore wall, larger pore diameter, greatly improved thermal stability and hydrothermal stability, so that the SBA-15 mesoporous material has good application prospect in the fields of catalysis, adsorption, separation, biomedicine and the like. However, SBA-15 synthesis needs to be carried out in a strong acid medium, and the use of a large amount of acid not only corrodes industrial reactors but also causes serious environmental pollution, so that the industrial application of SBA-15 is very limited. At present, the most common method for synthesizing SBA-15 is a method for preparing SBA-15 under hydrothermal conditions by taking an amphiphilic triblock copolymer as a template agent, which is proposed by Stucky et al (patent publication No. US7763665B 2). The method can prepare the SBA-15 with the pore canal structure being highly ordered and the pore canal size being adjustable. However, this method requires a strongly acidic solution environment (pH < 1), and is not suitable for industrial mass production. Stucky et al describe a method for synthesizing SBA-15 under near neutral conditions using fluoride as a catalyst (chem. Commun., 2000, 24, 2437-2438.). However, this method uses ammonium fluoride, in which a large amount of fluoride ions would pose a threat to the environment and organisms, and is not suitable for industrial production. Finding a synthetic method of SBA-15 mesoporous silica that is prepared at near neutral pH and is environmentally friendly is the direction of exploration by the materialist. Chinese patent CN 108483453A provides a method for preparing SBA-15 mesoporous silica microsphere, using polyvinyl alcohol as additive and using classical P123/silicon source/dilute hydrochloric acid system, the silica precursor is sodium silicate, ethyl orthosilicate or methyl orthosilicate. So far, no report exists on the preparation method for synthesizing mesoporous silica material SBA-15 under the condition of near neutral pH. Disclosure of Invention The invention aims to provide a method for synthesizing SBA-15 mesoporous silica under a near neutral pH condition, which can overcome the technical problems of strong acidity requirement and environment unfriendly in the prior art. The method takes a nonionic block copolymer as a template agent, polyacrylic acid as a template auxiliary agent and aminosilane as a co-structure guiding agent, synthesizes the SBA-15 mesoporous silica material under the near neutral pH condition, particularly improves the pH value of a liquid environment required by SBA-15 synthesis from the common pH value of <1 to the near neutral pH value, and greatly reduces the acid amount required by synthesis. The product obtained by the method has uniform aperture and high order, is environment-friendly and low-cost polyacrylic acid is used as a template auxiliary agent, avoids using a catalyst such as ammonium fluoride which causes pollution to the environment, and is easy to popularize. The invention provides a method for synthesizing mesoporous silica material SBA-15 under near neutral pH condition, which comprises the following steps: 1) Mixing an aqueous solution of a P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) template agent with a polyacrylic acid template auxiliary agent at room temperature, stirring for 0.5-1h to obtain a mixed solution, slowly dripping an acid solution to ensure that the pH=4-5, and fully stirring for 0.5-1h to obtain an emulsion; 2) Dropwise adding aminosilane into the emulsion under stirring, simultaneously dropwise adding a silicon source, heating with a water bath and preserving heat at 30-35 ℃, and fully stirring for 4-6 h; 3) Standing and crystallizing the emulsion in the step 2) for 24-48 hours, preferably 24 hours at 80 ℃, centrifuging and separating a reaction mixture after standing and crystallizing, washing a product for 1-3 times, and drying at 50-60 ℃ to obtain a white solid product; 4) Calcining the white solid product at 400-600 ℃ for 3-6 h, preferably 6h, to obtain the SBA-15 mesoporous silica. The mass ratio of the P123 to the polyacrylic acid in the step 1) is=1:2, the molecular weight of the polyacrylic acid is 3000-240000, and the HCl dosage is 0.7-1ml, preferably 0.9ml. The molecular weight of P123 was 5800. The mass ratio of P123 to silicon source in the step 2) is=1:1.5-2.1. The molar ratio of the aminosilane to th