CN107311185A - A kind of preparation method of superelevation porosity porous silica - Google Patents

Abstract

The invention belongs to the technical field of materials, in particular to a preparation method of ultra-high porosity ultra-light porous silica. The present invention uses organosilicon prepolymers as stabilizers for water-in-oil emulsions. This organosilicon prepolymers will be hydrolyzed to form hydroxyl groups with interfacial activity after contacting with water at the oil-water interface, and further condense to form silicon-oxygen-silicon bonds. ; After the organic silicon precursor is hydrolyzed and condensed, a porous skeleton structure is formed on the oil-water interface, and then the oil phase and the water phase are removed at the same time, leaving the silica skeleton on the interface, and the porous silica with ultra-high porosity can be obtained Material. The method of the invention has simple operation process, and the porosity of the obtained porous material can reach 99%, and the specific surface area can reach 755 m ² /g.

Description

A kind of preparation method of ultrahigh porosity porous silica

technical field

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

Background technique

Porous materials have important applications in catalysis, adsorption and gas storage, separation, and tissue engineering scaffolds. At present, the methods for preparing porous materials include direct synthesis, phase separation, template method, and block copolymer, among which the high internal phase emulsion template method is widely used to prepare porous materials with high porosity and adjustable pore structure. High internal phase emulsion refers to a type of emulsion whose internal phase volume is higher than 74%, and pores will be formed after the internal phase of the emulsion is removed. Because the volume of the internal phase is limited by the stability of the emulsion, especially when the emulsion is easily broken during emulsion polymerization, the porosity of the porous material prepared by the high internal phase emulsion template method is generally not higher than 90%.

The invention uses the emulsion as a template to prepare a porous silicon dioxide material with a porosity as high as 99%. The first is to prepolymerize organosiloxane to obtain a hyperbranched siloxane prepolymer with good lipophilicity. This siloxane prepolymer molecule can adjust the degree of reaction with water to control the amount of hydroxyl groups formed. Obtain suitable hydrophilic and lipophilic properties, and then stabilize the water-in-oil high internal phase emulsion. At the oil-water interface, the sol-gel (sol-gel) will further generate a silica skeleton structure during the heating process, and then remove the oil phase solvent and the water phase to obtain ultra-high porosity porous silica Material.

Contents of the invention

The purpose of the present invention is to provide a method for preparing porous silica with ultra-high porosity. The silica porous material prepared by the method has a porosity as high as 99% and a specific surface area as high as 755 m ² /g.

The method for preparing porous silica with ultra-high porosity provided by the present invention comprises the following steps: firstly, prepolymerizing the organosilicon precursor to obtain a hyperbranched siloxane prepolymer with good lipophilicity; Oxyalkylene prepolymers can adjust the degree of reaction with water to control the amount of hydroxyl groups formed, obtain suitable hydrophilic and lipophilic properties, and then stabilize the water-in-oil high internal phase emulsion. The siloxane prepolymer molecules at the oil-water interface will further sol-gel to form a silica skeleton structure during the heating process, and then remove the oil phase solvent and the water phase to obtain a porous silica with ultra-high porosity. Silicon oxide material.

Concrete steps of the present invention are as follows:

(1) First, prepare a silicon prepolymer with a molecular weight of 500-5000 g mol ^-1 under the action of a titanium catalyst with a precursor of organosilicon and acetic anhydride at a molar ratio of 1:0.1-10;

(2) Take the above-mentioned silicon prepolymer dissolved in an organic solvent as the oil phase. The mass of the silicon prepolymer accounts for 1-80% of the total mass of the oil phase, and then accurately measure a certain amount of distilled water. The volume of water is the oil phase 1 to 6 times the total volume, mix and emulsify the measured water with the prepared oil phase to obtain a water-in-oil emulsion; the organic solvent can dissolve the silicone prepolymer and is insoluble with the water phase;

(3) Transfer the prepared emulsion above to a high-pressure reactor, and react in a blast oven at a temperature of 50-100°C for 10-20 h;

(4) Transfer the reaction product in step (3) to a Soxhlet extractor, extract with acetone as a solvent for 10-24 h, and dry to obtain a porous silica material with ultra-high porosity.

The silicon prepolymer prepared by the invention can stabilize the water-in-oil emulsion, and can undergo hydrolysis and condensation on the oil-water interface to form a skeleton structure on the interface, and finally remove the oil phase solvent and the water phase to obtain ultra-high porosity porous silicon material.

The organosilicon precursor used in the present invention is selected from methyltriethoxysilane, dimethyldiethoxysilane, tetraethoxysilane, or γ-methacryloxypropyltrimethoxy One or more of silanes.

The organic solvent used in the present invention can dissolve the organosilicon prepolymer and is insoluble with the water phase. It can be one of xylene, toluene, cyclohexane, and petroleum ether, or it can be a polymerizable monomer, such as benzene One of ethylene, stilbene, methyl methacrylate, and acrylonitrile.

The preparation method adopted in the present invention can prepare a porous silica material with a porosity as high as 99%, and its density is very light, reaching 20 mg·cm ^-1 .

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

The invention has simple operation process and low cost, can prepare porous silicon dioxide material with very high porosity, and has a specific surface area as high as 755 m ² ▪g ^-1 .

Description of drawings

FIG. 1 is a field emission scanning electron micrograph of the ultrahigh-porosity porous silica material prepared in Example 1.

detailed description

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Any simple modification, equivalent transformation or modification made to the following examples according to the technical essence of the present invention still belong to the scope of the technical solution of the present invention.

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

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

Example 1

1. Mix methyltriethoxysilane and acetic anhydride in a molar ratio of 1:0.5, and then add tetraethoxytitanium with a molar ratio of 1% of methyltriethoxysilane as a catalyst, at a temperature of 140 °C The reaction was carried out for 4 h, and the prepolymer of light yellow methyltriethoxysilane was obtained by distillation under reduced pressure.

2. Dissolve 160 g of the prepolymer of methyltriethoxysilane in 230 g of xylene, then slowly add 1600 g of distilled water with a pH of 7 to the mixture and homogeneously emulsify for 5 min at a speed of 10000 rpm , to obtain a water-in-oil emulsion.

3. Transfer the above emulsion to a closed reactor, and react for 10 hours in a blast oven at a temperature of 80°C.

4. Transfer the reaction product in step 3 to a Soxhlet extractor, extract with acetone for 10 h, and dry it in a blast oven at 80°C to obtain a porous silica material with ultra-high porosity. 98.9%.

Example 2

1. The experimental device and operation are the same as in Example 1, the methyltriethoxysilane is replaced by tetraethoxysilane, the molar ratio of tetraethoxysilane and acetic anhydride is replaced by 1:10, and the tetraethoxytitanium is replaced by Tetramethoxytitanium is used as a catalyst, and the proportion of tetramethoxytitanium is 0.1% of that of tetraethoxysilane.

2. Experimental device and operation are the same as embodiment 1, the prepolymer of 160 g methyltriethoxysilane is changed into the prepolymer of 100 g tetraethoxysilane, 230 g xylene is changed into 1000 g toluene, 1600 g of distilled water with a pH of 7 was replaced with 1200 g of distilled water with a pH of 1, and the pH of the distilled water was adjusted by hydrochloric acid.

3. The experimental device and operation are the same as in Example 1, but the heating in the blast oven is replaced by water bath heating, the temperature is replaced by 50 °C, and the reaction time is replaced by 20 h.

4. The reaction product in step 3 was directly dried in an 80°C blast oven to obtain a porous silica material with an ultra-high porosity of 99.0%.

Example 3

1. The experimental device and operation are the same as in Example 1, and the methyltriethoxysilane is replaced by a mixture of γ-methacryloxypropyl trimethoxysilane and tetraethoxysilane, and γ-methacryl The molar ratio of oxypropyltrimethoxysilane to tetraethoxysilane is 1:5, the ratio of total moles of siloxane to acetic anhydride is 1:1, and tetraethoxytitanium accounts for the total moles of siloxane 0.1% of.

2. The experimental device and operation are the same as in Example 1, and the prepolymer of methyltriethoxysilane is replaced by γ-methacryloxypropyltrimethoxysilane and tetraethoxysilane after prepolymerization. For the prepolymer, 230 g xylene is replaced with a mixture of 230 g xylene and styrene, and styrene accounts for 5% of the xylene mass fraction, and the initiator AIBN whose mass fraction accounts for 0.5% of the styrene mass fraction is added.

3. The experimental device and operation are the same as in Example 1.

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

Claims (4)

1. a preparation method of ultrahigh porosity porous silica, is characterized in that, concrete steps are as follows: (1) First, prepare the silicon prepolymer with a molecular weight of 500-5000 g mol ^-1 under the action of a titanium catalyst with the precursor of organic silicon and acetic anhydride at a molar ratio of 1:0.1-10; (2) Take the above-mentioned silicon prepolymer dissolved in an organic solvent as the oil phase, the mass of the silicon prepolymer accounts for 1-80% of the total mass of the oil phase, and then mix and emulsify the distilled water with the prepared oil phase to obtain the oil phase Water-in-water emulsion; wherein, the volume of distilled water is 1 to 6 times the total volume of the oil phase; the organic solvent can dissolve the silicone prepolymer and is insoluble with the water phase; (3) Transfer the prepared emulsion above to a high-pressure reactor, and react in a blast oven at a temperature of 50-100°C for 10-20 h; (4) Transfer the reaction product in step (3) to a Soxhlet extractor, extract with acetone as a solvent for 10-24 h, and dry to obtain a porous silica material with ultra-high porosity. 2. The preparation method according to claim 1, wherein the silicon precursor is selected from methyltriethoxysilane, dimethyldiethoxysilane, tetraethoxysilane, or γ- One or more of methacryloxypropyltrimethoxysilane. 3. preparation method according to claim 1, is characterized in that, described organic solvent is xylene, toluene, hexanaphthene, a kind of in sherwood oil, or is styrene, toluene, methyl methacrylate One of ester or acrylonitrile. 4. The preparation method according to claim 1, wherein the prepared porous silica material has a hierarchical porous structure, the size of the macropore is 2 ~ 20 μm, and the size of the small hole is 2 ~ 4 nm; The rate is as high as 99%.