CN107311185B

CN107311185B - Preparation method of ultrahigh-porosity porous silicon dioxide

Info

Publication number: CN107311185B
Application number: CN201710486735.3A
Authority: CN
Inventors: 涂书画; 余恒; 谭昊天; 赵永亮; 王海涛
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 2017-06-23
Filing date: 2017-06-23
Publication date: 2020-12-22
Anticipated expiration: 2037-06-23
Also published as: CN107311185A

Abstract

The invention belongs to the technical field of materials, and particularly relates to a preparation method of ultra-light porous silicon dioxide with ultra-high porosity. The invention adopts the prepolymer of the organic silicon as the stabilizer of the water-in-oil emulsion, and the prepolymer of the organic silicon can be hydrolyzed to generate hydroxyl with hydroxyl after being contacted with water on an oil-water interfaceInterface activity and further condensation to generate silicon-oxygen-silicon bonds; after the organic silicon precursor is hydrolyzed and condensed, a porous framework structure is formed on an oil-water interface, then the oil phase and the water phase are simultaneously removed, and a silicon dioxide framework on the interface is left, so that the porous silicon dioxide material with ultrahigh porosity can be obtained. The method has simple operation process, the porosity of the obtained porous material can reach 99 percent, and the specific surface area can reach 755 m²/g。

Description

Preparation method of ultrahigh-porosity porous silicon dioxide

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a preparation method of porous silicon dioxide with ultrahigh porosity.

Background

The porous material has important application in catalysis, adsorption and gas storage, separation, tissue engineering scaffold and other aspects. The existing methods for preparing the porous material include a direct synthesis method, a phase separation method, a template method and a block copolymer, wherein the high internal phase emulsion template method is widely used for preparing the porous material with high porosity and adjustable pore structure. High internal phase emulsions are those emulsions having an internal phase volume greater than 74% that will result in voids upon removal of the internal phase of the emulsion. Porous materials prepared using the high internal phase emulsion templating method typically have a porosity of no more than 90% because the internal phase volume is limited by the stability of the emulsion, particularly the tendency to break upon emulsion polymerization.

The invention takes the emulsion as a template to prepare the porous silicon dioxide material with the porosity up to 99 percent. Firstly, organic siloxane is prepolymerized to obtain a hyperbranched siloxane prepolymer with good lipophilicity, and the siloxane prepolymer molecule can adjust the degree of reaction with water to control the amount of generated hydroxyl groups, so as to obtain proper hydrophily and lipophilicity and further stabilize water-in-oil high internal phase emulsion. And further sol-gel (sol-gel) is generated on the oil-water interface during heating to form a silica skeleton structure, and then the oil phase solvent and the water phase are removed to obtain the porous silica material with ultrahigh porosity.

Disclosure of Invention

The invention aims to provide a preparation method for preparing porous silica with ultrahigh porosity, and the porous silica material prepared by the method has the porosity of up to 99 percent and the porosity of up to 755 m²Specific surface area in g.

The method for preparing the porous silicon dioxide with the ultrahigh porosity comprises the specific steps of firstly pre-polymerizing an organic silicon precursor to obtain a hyperbranched siloxane prepolymer with good lipophilicity, wherein the siloxane prepolymer can adjust the degree of reaction with water to control the amount of generated hydroxyl groups, so that appropriate hydrophily and lipophilicity are obtained, and further a water-in-oil high internal phase emulsion is stabilized. And (3) further sol-gel to generate a skeleton structure of silicon dioxide in the heating process of siloxane prepolymer molecules on an oil-water interface, and then removing an oil phase solvent and a water phase to obtain the porous silicon dioxide material with ultrahigh porosity.

The method comprises the following specific steps:

(1) firstly, a precursor of organosilicon and acetic anhydride are prepared according to the molar ratio of 1: 0.1-10 under the action of a titanium catalyst, wherein the molecular weight of the precursor is 500-5000 g as mol^-1The silicon prepolymer of (1);

(2) dissolving the silicon prepolymer in an organic solvent to serve as an oil phase, wherein the mass of the silicon prepolymer accounts for 1-80% of the total mass of the oil phase, accurately measuring a certain amount of distilled water, the volume of the water is 1-6 times of the total volume of the oil phase, and mixing and emulsifying the measured water and the prepared oil phase to obtain a water-in-oil emulsion; the organic solvent can dissolve the organic silicon prepolymer and is insoluble in a water phase;

(3) transferring the prepared emulsion into a high-pressure reaction kettle, and reacting for 10-20 hours in a blast oven at the temperature of 50-100 ℃;

(4) and (4) transferring the reaction product in the step (3) to a Soxhlet extractor, extracting for 10-24 h by taking acetone as a solvent, and drying to obtain the porous silicon dioxide material with ultrahigh porosity.

The silicon prepolymer prepared by the invention can stabilize water-in-oil emulsion, can be subjected to hydrolytic condensation on an oil-water interface to form a skeleton structure on the interface, and finally removes an oil phase solvent and a water phase to obtain the porous silicon material with ultrahigh porosity.

The organosilicon precursor adopted in the invention is selected from one or more of methyltriethoxysilane, dimethyldiethoxysilane, tetraethoxysilane or gamma-methacryloxypropyltrimethoxysilane.

The organic solvent adopted in the invention can dissolve the organic silicon prepolymer and is insoluble to the water phase, and can be one of xylene, toluene, cyclohexane and petroleum ether, and also can be one of polymerizable monomers such as styrene, stilbene, methyl methacrylate and acrylonitrile.

The preparation method adopted by the invention can prepare the porous silicon dioxide material with the porosity up to 99 percent, has light density and can reach 20 mg as much as cm^-1。

The ultrahigh-porosity porous silica material prepared by the invention has a hierarchical porous structure, the size of large pores is 2-20 mu m, and the size of small pores is 2-4 nm.

The invention has simple operation process and lower cost, can prepare the porous silicon dioxide material with very high porosity and the porosity of the porous silicon dioxide material is as high as 755 m²▪g^-1Specific surface area of (2).

Drawings

FIG. 1 is a SEM photograph of the ultra-high porosity porous silica material prepared in example 1.

Detailed Description

The following examples are intended to illustrate the present invention, but not to limit the scope of the present invention, and any simple modification, equivalent transformation or modification made to the following examples according to the technical spirit of the present invention still falls within the technical scope of the present invention.

In the following examples, the organosiloxanes used are methyltriethoxysilane, tetraethoxysilane, or gamma-methacryloxypropyltrimethoxysilane

The starting materials in the following examples are all commercially available products.

Example 1

1. Mixing methyltriethoxysilane and acetic anhydride according to a molar ratio of 1:0.5, adding tetraethoxytitanium accounting for 1% of methyltriethoxysilane as a catalyst, reacting at 140 ℃ for 4 hours, and distilling under reduced pressure to obtain a light yellow methyltriethoxysilane prepolymer.

2. 160 g of methyl triethoxysilane prepolymer is dissolved in 230 g of xylene, 1600 g of distilled water with pH of 7 is slowly added into the mixed solution and homogenized and emulsified for 5 min at the rotation speed of 10000 rpm, and a water-in-oil emulsion is obtained.

3. And transferring the emulsion into a closed reactor, and reacting for 10 hours in a forced air oven at the temperature of 80 ℃.

4. And (3) transferring the reaction product in the step (3) into a Soxhlet extractor, extracting for 10h by taking acetone as a solvent, and drying in a blast oven at 80 ℃ to obtain the porous silica material with ultrahigh porosity, wherein the porosity is 98.9%.

Example 2

1. Experimental apparatus and operation As in example 1, methyltriethoxysilane was changed to tetraethoxysilane, the molar ratio of tetraethoxysilane to acetic anhydride was changed to 1:10, and tetraethoxytitanium was changed to tetramethoxytitanium as a catalyst, the ratio of tetramethoxytitanium being 0.1% of tetraethoxysilane.

2. Experimental apparatus and operation As in example 1, a prepolymer of 160 g of methyltriethoxysilane was replaced with a prepolymer of 100 g of tetraethoxysilane, 230 g of xylene was replaced with 1000 g of toluene, 1600 g of distilled water having a pH of 7 was replaced with 1200 g of distilled water having a pH of 1, and the pH of the distilled water was adjusted with hydrochloric acid.

3. The experimental setup and operation were the same as in example 1, the temperature was changed to 50 ℃ and the reaction time was changed to 20 h, with the water bath heating being replaced by the forced air oven heating.

4. And (3) directly placing the reaction product in the step (3) in a blast oven at 80 ℃ for drying to obtain the porous silica material with ultrahigh porosity, wherein the porosity is 99.0%.

Example 3

1. Experimental setup and procedure as in example 1, methyltriethoxysilane was changed to a mixture of gamma-methacryloxypropyltrimethoxysilane and tetraethoxysilane, the molar ratio of gamma-methacryloxypropyltrimethoxysilane to tetraethoxysilane being 1: 5, the ratio of the total moles of siloxane to acetic anhydride is 1:1, and the tetraethoxytitanium accounts for 0.1 percent of the total moles of siloxane.

2. The experimental setup and operation were the same as in example 1, the prepolymer of methyltriethoxysilane was replaced with a prepolymer prepared by prepolymerization of gamma-methacryloxypropyltrimethoxysilane and tetraethoxysilane, 230 g of xylene was replaced with a mixture of 230 g of xylene and styrene, the mass fraction of styrene in xylene was 5%, and AIBN, the mass fraction of which was 0.5% of the mass of styrene, was added.

3. The experimental setup and procedure were the same as in example 1.

4. The experimental device and operation are the same as those of example 1, and the porosity of the prepared porous material can reach 98.5%.

Claims

1. A preparation method of porous silica with ultrahigh porosity is characterized by comprising the following specific steps:

(1) firstly, preparing a precursor of organosilicon and acetic anhydride according to the molar ratio of 1: 0.1-10, and making the molecular weight of the organosilicon be 500-5000 g as mol under the action of a titanium catalyst^-1The silicon prepolymer of (1);

(2) dissolving the silicon prepolymer in an organic solvent to serve as an oil phase, wherein the mass of the silicon prepolymer accounts for 1-80% of the total mass of the oil phase, and then mixing distilled water with the prepared oil phase and emulsifying to obtain a water-in-oil emulsion; wherein the volume of the distilled water is 1-6 times of the total volume of the oil phase; the organic solvent can dissolve the organic silicon prepolymer and is insoluble in a water phase;

(4) transferring the reaction product in the step (3) into a Soxhlet extractor, extracting for 10-24 h by taking acetone as a solvent, and drying to obtain a porous silicon dioxide material with ultrahigh porosity; the porous material has a hierarchical porous structure, the size of large pores is 2-20 mu m, and the size of small pores is 2-4 nm; the porosity reaches 99 percent;

the precursor of the silicon is selected from one or more of methyltriethoxysilane, dimethyldiethoxysilane, tetraethoxysilane or gamma-methacryloxypropyltrimethoxysilane.

2. The method according to claim 1, wherein the organic solvent is one of xylene, toluene, cyclohexane, petroleum ether, or one of styrene, stilbene, methyl methacrylate, and acrylonitrile.