A method for preparing mesoporous silica without solvent and its application

Abstract

The present invention is applicable to the technical field of new nanomaterials, and provides a method and application for preparing mesoporous silica by a solvent-free method with the aid of a soft template. First, a specific soft template is selected, fully mixed with tetraethoxysilane, and a trace amount of acid is added, and the mixture is placed in a ball mill for ball milling; secondly, the obtained silica material with the template is placed in the air for calcination to form a mesoporous silica nanomaterial after the template is removed; finally, the obtained mesoporous silica is adsorbed with substances that are easily oxidized and difficult to store, so as to achieve the effect of sealing and sustained release. The synthesis method provided by the present invention is simple and easy, does not require the addition of solvents, has high yield, good porosity and high crystallinity, and has excellent adsorption and sustained release properties. The resulting new mesoporous silica nanomaterial provides a new idea for the solvent-free synthesis of other mesoporous materials, and provides a new way to seal and sustainably release substances that are easily oxidized and difficult to store.

Description

Technical Field

[0001] The invention belongs to the technical field of novel nanomaterials and relates to a method for preparing mesoporous silicon oxide using a solvent-free method and its application. Background Art

[0002] Mesoporous materials have large specific surface area and pore volume, and have important application potential in catalysis, biomedicine, gas sensors, energy storage and conversion and other fields. At present, the synthesis of mesoporous materials mainly relies on the hard template method. The process of synthesizing and removing the template by etching or calcination is cumbersome, costly, time-consuming, and not suitable for large-scale production. However, the soft template method is a more promising technology for preparing mesoporous materials. The soft template method uses block copolymers as templates, and driven by Coulomb interactions or hydrogen bonding interactions, it self-assembles with inorganic precursors into organic-inorganic hybrid composite materials, and then calcines and decomposes the block copolymers to obtain mesoporous nanomaterials.

[0003] Although the soft template method has greatly expanded the scope of mesoporous nanomaterials and achieved control over the type of mesostructure in the past few decades, there are still some problems that need to be solved. First, there are great restrictions on the choice of templates. Usually the reaction needs to be carried out in a solvent, and only soluble inorganic precursors are suitable for this technology, which greatly limits the diversification of the soft template method. At the same time, the traditional solution reaction method is extremely wasteful of solution, and the waste of templates cannot be ignored. It can also easily make the reaction difficult to control and make the mesoporous structure unstable. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a method and application for preparing mesoporous silica by a solvent-free method, aiming to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] 1. A method for preparing mesoporous silica by a solvent-free method, characterized in that it comprises the following steps:

[0007] Step S1: 15 g to 20 g of tetraethoxysilane, 3 g to 5 g of soft template, and 1-3 mL of weak acid were added to a ball mill at room temperature and reacted for 30 min to 60 min;

[0008] Step S2: centrifuging the product obtained in step S1, washing with ethanol / water to obtain a white product, and drying in an oven at 90° C. to 120° C. to obtain a silicon oxide material with a template;

[0009] Step S3: calcining the silicon oxide material with the template obtained in step S2 at 500° C. to 600° C. in air to form a mesoporous silicon oxide nanomaterial after removing the template;

[0010] Step S4: The obtained mesoporous silica is used to adsorb substances that are easily oxidized and difficult to store, thereby achieving the effects of sealing and slow release.

[0011] Furthermore, in step S1, the soft template includes one or a mixture of polypropylene imine, cetyltrimethylammonium bromide, and melamine-formaldehyde polymer.

[0012] Furthermore, in step S1, the weak acid includes one or more of carbonic acid, acetic acid, oxalic acid, and phosphoric acid.

[0013] Furthermore, in step S2, the ratio of ethanol to water is 2:1, 1:1 or 1:2.

[0014] Furthermore, in step S2, the drying time is 8-12 hours.

[0015] Furthermore, in step S3, the calcination instrument used is a muffle furnace.

[0016] Furthermore, in step S3, the calcination time is 3-6 hours.

[0017] Furthermore, in step S4, the sealed and slowly released substances include but are not limited to vitamin C, tea polyphenols, ergothioneine, etc.

[0018] Furthermore, any of the above-mentioned solvent-free methods for preparing mesoporous silica is used for sealing and slowly releasing easily oxidizable substances.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention is applicable to the fields of new materials and sealing and sustained-release technologies, and provides a method and application for preparing mesoporous silica by a solvent-free method. First, a specific soft template is selected, fully mixed with tetraethoxysilane, and a trace amount of acid is added, and the mixture is placed in a ball mill for ball milling; secondly, the obtained silica material with the template is placed in the air for calcination to form a mesoporous silica nanomaterial after the template is removed; finally, the obtained mesoporous silica is adsorbed with substances that are easily oxidized and difficult to store, thereby achieving the effects of sealing and sustained release. The synthesis method provided by the present invention is simple and easy to implement, does not require the addition of solvents, has high yield, good porosity and high crystallinity, and has excellent adsorption and sustained-release properties.

[0021] The advantages of this method are: 1. No solvent is required, which greatly reduces costs. Avoiding the use of solvents in the synthesis process not only greatly reduces the generation of waste and environmental pollution, but also saves costs and energy; in the selection process of the soft template, the solubility of the soft template does not need to be considered, and low-cost soft templates can be selected. At the same time, the soft template can be fully recycled and reused, which is not only beneficial to environmental protection, but also increases economic benefits. 2. The synthesis process is simple, the synthesis cycle is short, and the target product yield is high. The self-assembly process of the soft template can be completed by room temperature ball milling, and the calcination process can also be carried out in the air. The process is simple, time-consuming, and batch production can be achieved; at the same time, this method is extremely easy to achieve scale-up production and can maintain a very high product yield. 3. The mesoporous silica synthesized by the solvent-free method also has good porosity and high crystallinity. 4. The obtained mesoporous silica adsorbs substances that are easily oxidized and difficult to store, which not only achieves the purpose of sealing and protection, but also has the effect of on-demand sustained release. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a transmission electron microscope image of mesoporous silica.

[0023] Figure 2 This is the nitrogen adsorption-desorption isotherm of mesoporous silica.

[0024] Figure 3 This is the pore size distribution diagram of mesoporous silica.

[0025] Figure 4 This is a sustained release diagram of mesoporous silica emulsion. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0028] Example 1

[0029] An embodiment of the present invention provides a method for preparing mesoporous silica by a solvent-free method, comprising the following steps:

[0030] Step S1: 15 g of tetraethoxysilane, 3 g of polypropylene imine, and 1.5 mL of acetic acid were added to a ball mill at room temperature and reacted for 45 min;

[0031] Step S2: centrifuging the product obtained in step S1, washing with ethanol / water to obtain a white product, and drying in an oven at 105° C. to obtain a silicon oxide material with a template;

[0032] Step S3: calcining the silicon oxide material with the template obtained in step S2 at 550° C. in air to form a mesoporous silicon oxide nanomaterial after removing the template;

[0033] Step S4: The obtained mesoporous silica is used to adsorb vitamin C, thereby achieving the effects of sealing and sustained release.

[0034] Example 2

[0035] An embodiment of the present invention provides a method for preparing mesoporous silica by a solvent-free method, comprising the following steps:

[0036] Step S1: 17 g of tetraethoxysilane, 3.5 g of melamine-formaldehyde polymer, and 2 mL of oxalic acid were added to a ball mill at room temperature and reacted for 30 min;

[0037] Step S2: centrifuging the product obtained in step S1, washing with ethanol / water to obtain a white product, and drying in an oven at 105° C. to obtain a silicon oxide material with a template;

[0038] Step S3: calcining the silicon oxide material with the template obtained in step S2 at 600° C. in air to form a mesoporous silicon oxide nanomaterial after removing the template;

[0039] Step S4: Adsorbing tea polyphenols with the obtained mesoporous silica can achieve the effects of sealing and sustained release.

[0040] Example 3

[0041] An embodiment of the present invention provides a method for preparing mesoporous silica by a solvent-free method, comprising the following steps:

[0042] Step S1: 18 g of tetraethoxysilane, 3 g of melamine-formaldehyde polymer, and 2 mL of acetic acid were added to a ball mill at room temperature and reacted for 30 min;

[0043] Step S2: centrifuging the product obtained in step S1, washing with ethanol / water to obtain a white product, and drying in an oven at 100° C. to obtain a silicon oxide material with a template;

[0044] Step S3: calcining the silicon oxide material with the template obtained in step S2 at 600° C. in air to form a mesoporous silicon oxide nanomaterial after removing the template;

[0045] Step S4: The obtained mesoporous silica is used to adsorb ergothioneine, thereby achieving the effects of sealing and sustained release.

[0046] Example 4

[0047] An embodiment of the present invention provides a method for preparing mesoporous silica by a solvent-free method, comprising the following steps:

[0048] Step S1: 18 g of tetraethoxysilane, 4 g of polypropylene imine, and 1-3 mL of oxalic acid were added to a ball mill at room temperature and reacted for 30 min;

[0049] Step S2: centrifuging the product obtained in step S1, washing with ethanol / water to obtain a white product, and drying in an oven at 100° C. to obtain a silicon oxide material with a template;

[0050] Step S3: calcining the silicon oxide material with the template obtained in step S2 at 600° C. in air to form a mesoporous silicon oxide nanomaterial after removing the template;

[0051] Step S4: The obtained mesoporous silica is used to adsorb vitamin C, thereby achieving the effects of sealing and sustained release.

[0052] Mesoporous silica adsorption process: Add easily oxidizable substances (vitamin C, tea polyphenols, ergothioneine, etc.) to a phosphate buffer solution and place it in a sealed glass jar, add mesoporous silica, stir and adsorb at room temperature, centrifuge and wash, and then freeze-dry to obtain mesoporous silica loaded with easily oxidizable substances.

[0053] Determination of release of easily oxidized substances in emulsion: Purchase commercial emulsion on the market, completely dissolve the sample of mesoporous silica loaded with easily oxidized substances in the emulsion, and then place it in a dialysis bag. After 1, 2, 3, 5, 8, 10, 15, and 20 hours, take out the test solution and detect its concentration by fluorescence method to verify its sustained release effect. The results are as follows Figure 4 As shown, compared with the system without adding mesoporous silica, the sustained release effect is greatly improved.

[0054] The working principle of the present invention is:

[0055] The present invention uses amino-rich polymers such as polypropyleneimine and melamine-formaldehyde polymer as soft templates. The amino groups in these polymers can act as hydrogen bond donors, interacting with hydrogen bond acceptors through hydrogen bonding or coordination. Weak acids such as acetic acid and oxalic acid serve as ligands, binding to the Si center to form a charged acetic acid / silicon oxalate coordination complex, while simultaneously generating the corresponding alcohol. The alcohol and weak acid further form an ester, releasing water and catalyzing the hydrolysis of tetraethoxysilane. This hydrolysis process achieves distributed hydrolysis, controlling the hydrolysis rate and intensity, and providing an ideal foundation for the production of nano-silicon oxide materials. Furthermore, during the calcination process, the soft template is largely removed, while ensuring the integrity of the mesoporous channels and the preservation of the entire crystal structure. Oxidizable substances, due to their diffusion and charge properties, can better enter the mesoporous channels and are effectively sealed by components such as silicone oil in the emulsion, providing excellent protection. Upon contact with the human body, they can be slowly released, laying a good foundation for the optimal absorption of active ingredients.

[0056] The entire process does not require solvents, significantly reducing costs. Avoiding the use of solvents during the synthesis process not only greatly reduces waste generation and environmental pollution, but also saves costs and energy. During the selection of soft templates, the solubility properties of the soft template do not need to be considered, and low-cost soft templates can be selected. At the same time, the soft template can be fully recycled and reused, which is not only beneficial to environmental protection but also increases economic benefits. The synthesis process is simple, the synthesis cycle is short, and the target product yield is high. The self-assembly process of the soft template can be completed by room temperature ball milling, and the calcination process can also be carried out in air. The process is simple, time-consuming, and can achieve mass production. At the same time, this method is extremely easy to scale up and can maintain a very high product yield. The mesoporous silica synthesized using the solvent-free method also has good porosity and high crystallinity. The obtained mesoporous silica can be used to adsorb substances that are easily oxidized and difficult to store, which not only achieves the purpose of sealing and protection, but also has the effect of on-demand sustained release.

[0057] The above are only preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention. These should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for preparing mesoporous silica without solvent, characterized in that: The following steps are involved: Step S1: 15 g to 20 g of tetraethoxysilane, 3 g to 5 g of soft template, and 1-3 mL of weak acid were added to a ball mill at room temperature and reacted for 30 min to 60 min; Step S2: centrifuging the product obtained in step S1, washing with ethanol / water to obtain a white product, and drying in an oven at 90° C. to 120° C. to obtain a silicon oxide material with a template; Step S3: calcining the silicon oxide material with the template obtained in step S2 at 500° C. to 600° C. in air to form a mesoporous silicon oxide nanomaterial after removing the template; Step S4: The obtained mesoporous silica is used to adsorb substances that are easily oxidized and difficult to store, thereby achieving the effects of sealing and slow release; In step S1, the soft template is hexadecyltrimethylammonium bromide; In step S1, oxalic acid is used as the weak acid.

2. The method for preparing mesoporous silica without solvent according to claim 1, characterized in that: In step S2, the ratio of ethanol to water is 2:1, 1:1 or 1:

2.

3. The method for preparing mesoporous silica without solvent according to claim 1, characterized in that: In step S2, the drying time is 8-12 hours.

4. The method for preparing mesoporous silica without solvent according to claim 1, characterized in that: In step S3, the calcination instrument used is a muffle furnace.

5. The method for preparing mesoporous silica without solvent according to claim 1, characterized in that: In step S3, the calcination time is 3-6 hours.

6. The method for preparing mesoporous silica without solvent according to claim 1, characterized in that: In step S4, the sealed and slowly released substances include vitamin C, tea polyphenols, and ergothioneine.

7. Use of a solvent-free mesoporous silica prepared according to the method of any one of claims 1 to 6 in the storage and sustained release of easily oxidizable substances.

Images