阅读说明：本技术 一种二氧化硅气凝胶微球及其制备方法和用途 (Silicon dioxide aerogel microsphere and preparation method and application thereof ) 是由 孔令汉 程量 詹建波 张莹 李赓 余婷婷 王浩 王旭 于 2020-04-08 设计创作，主要内容包括：本发明属于吸附技术领域,特别涉及一种二氧化硅气凝胶微球及其制备方法和用途。所述二氧化硅气凝胶微球具有疏水性,其粒径为250～1000μm,密度为0.05～0.20g/cm<Sup>3</Sup>,比表面积为400～1000m<Sup>2</Sup>/g。本发明还公开了所述二氧化硅气凝胶微球的制备方法和用途。本发明制备的气凝胶微球具有良好的疏水性和成球性,具有优异的吸附性能,可应用于香烟滤棒中,进行香烟的侧流烟气的吸附和香精香料的负载,还可应用于污水处理、色谱填料等更多具有特殊要求的领域。(The invention belongs to the technical field of adsorption, and particularly relates to a silicon dioxide aerogel microsphere as well as a preparation method and application thereof. The silica aerogel microspheres have hydrophobicity, the particle size of the silica aerogel microspheres is 250-1000 mu m, and the density of the silica aerogel microspheres is 0.05-0.20 g/cm 3 The specific surface area is 400-1000 m 2 (ii) in terms of/g. The invention also discloses a preparation method and application of the silicon dioxide aerogel microspheres. The aerogel microspheres prepared by the invention have good hydrophobicity and balling property and excellent adsorption performance, can be applied to cigarette filter sticks for adsorbing side-stream smoke of cigarettes and loading essence perfume, and can also be applied to more fields with special requirements such as sewage treatment, chromatographic packing and the like.)

1. The silica aerogel microspheres are characterized by having hydrophobicity, the particle size of the silica aerogel microspheres is 250-1000 mu m, and the density of the silica aerogel microspheres is 0.05-0.20 g/cm³The specific surface area is 400-1000 m²/g。

2. The method for preparing silica aerogel microspheres according to claim 1, comprising the steps of:

(1) respectively adding acid catalysts into the first silicon source and the second silicon source for hydrolysis to obtain a first precursor hydrolysate and a second precursor hydrolysate; wherein the first silicon source is hydrolyzed to generate silicon hydroxyl and does not contain organic groups; the second silicon source at least contains one non-hydrolytic group;

(2) mixing the first precursor hydrolysate and the second precursor hydrolysate in proportion to form mixed sol, adding an alkali catalyst, and adjusting the pH value of the solution;

(3) before the mixed sol obtained in the step (2) does not have an initial gel state, transferring the mixed sol into an emulsifier and stirring to form white wet gel balls;

(4) immersing the wet gel pellets obtained in the step (3) with a solvent, aging, and filtering to obtain solid pellets;

(5) drying the solid pellets obtained in the step (4) to obtain the silicon dioxide aerogel microspheres;

the preparation method of the silica aerogel microspheres does not comprise the steps of solvent exchange and surface modification.

3. The method of claim 2, wherein the second silicon source is an organosiloxane having one or more hydrocarbon groups.

4. The method of claim 2, wherein step (1) includes any one or a combination of the following features:

(a) the first silicon source is selected from tetraethyl orthosilicate, tetramethyl orthosilicate or water glass;

(b) the second silicon source is selected from methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane or dimethyldimethoxysilane;

(c) the acid catalyst is one or more of hydrofluoric acid, hydrochloric acid, sulfuric acid, oxalic acid and acetic acid;

(d) the concentration of the acid catalyst is 0.1-1 mol/L;

(e) the pH value is adjusted to 3.0-4.5.

5. The method of claim 2, wherein step (2) includes any one or a combination of the following features:

(a) the alkali catalyst is one of ammonia water, sodium carbonate, sodium bicarbonate, sodium hydroxide or potassium carbonate;

(b) the concentration of the alkali catalyst is 0.1-5 mol/L;

(c) adjusting the pH value to 7-8.

(d) The molar ratio of the first silicon source to the second silicon source is 0.1-4.

6. The method of claim 2, wherein step (3) includes any one or a combination of the following features:

(a) the emulsifier is one or more selected from n-hexane, polydimethylsiloxane, soybean oil, span 60 and span 80;

(b) the stirring speed is 500 r/min-1000 r/min.

7. The method according to claim 1, wherein the step (4) comprises any one or a combination of the following features:

(a) the solvent used for aging is one or more of ethanol, n-hexane, tert-butanol, methanol or n-heptane;

(b) the aging times are 1-4 times, and the aging time is 2-8 h.

8. The preparation method according to claim 2, wherein in the step (3), the stirring speed is controlled to control the particle size of the silica aerogel microspheres finally obtained.

The drying is normal pressure; the drying temperature is controlled to be 60-120 ℃, and the drying time is 6-48 h.

9. The method according to claim 2, wherein the hydrolysis in step (1), the aging in step (3) and the aging in step (4) are all carried out in a constant temperature water bath at 45 ℃.

10. Use of silica aerogel microspheres according to claim 1 for adsorbing cigarette sidestream smoke and flavor-laden flavors.

Technical Field

The invention belongs to the technical field of adsorption, and particularly relates to a silicon dioxide aerogel microsphere as well as a preparation method and application thereof.

Background

The porous material loading system is a relatively common depot sustained release system, and the storage and release of the fragrance material depends on the properties of the porous material, and generally has the following characteristics: (1) inert per se, or inert in the target environment, or have special effects; (2) the material has a porous structure and a large specific surface area; (3) for some objects (such as perfume), the inner surface of the porous material has certain special functional groups; (4) the price is low and is common; (5) green and non-toxic. The cyclodextrin, the porous starch, the porous silicon material and the like are widely applied in the field of flavor and fragrance. In recent years, the preparation process of the silicon-based porous material is well developed, and the silica aerogel is one of typical materials.

The silica aerogel is a light porous amorphous material, and the main structural formula of the silica aerogel is a continuous three-dimensional network structure formed by mutually aggregating silica nano-scale ultrafine particles. The silica aerogel structure consists of network pores with volume fraction of more than 90 percent and SiO with volume fraction of less than 10 percent₂The skeleton is composed of pores filled with gaseous dispersing medium. SiO 2₂The structure of the aerogel gives the aerogel extremely low thermal conductivityHigh heat resistance stability and excellent adsorption performance. Can be used for sidestream smoke adsorption of cigarette and loading of essence and spice.

The aerogel density is extremely low, and the current lightest silicon aerogel is only 3mg/cm³(the density of air is 1.29kg/m³) And is therefore also called "frozen smoke" or "blue smoke". This will also lead to the aerogel material in the use of cigarette products, once the control conditions to the aerogel powder is not enough, will lead to the aerogel powder to fly away in the form of "cigarette" in the burning process of cigarette, and then follow the flue gas and be inhaled by the human body in vivo, remain in the lung, harm human health. It is therefore contemplated to modify the morphological structure of the aerogel sample to reduce such hazards, as by replacing it with aerogel microspheres. The aerogel microspheres are prone to caking during combustion to form densified caking. The microspheres have certain roundness and certain form stability. During processing, storage, transportation and use, no environmental pollution and no human harm caused by powder floating.

In the process of implementing the invention, the inventor finds that the prior art has at least the following problems:

the specific surface area of the microspheres prepared by the existing method is usually 400m²About/g, and the performance of the adsorbent is not excellent enough when the adsorbent is applied to the adsorption field. And some preparation methods need sol exchange and surface modification steps, so that the use of solvents is increased, the preparation cost is higher, and the toxicity is increased.

The present invention has been made to solve the above problems.

Disclosure of Invention

The first aspect of the invention provides silica aerogel microspheres, wherein the silica aerogel microspheres have hydrophobicity, the particle size of the silica aerogel microspheres is 250-1000 microns, and the density of the silica aerogel microspheres is 0.05-0.20 g/cm³The specific surface area is 400-1000 m²/g。

The second aspect of the present invention provides a method for preparing the silica aerogel microspheres described in the first aspect, the method comprising the steps of:

(1) respectively adding acid catalysts into the first silicon source and the second silicon source for hydrolysis to obtain a first precursor hydrolysate and a second precursor hydrolysate; wherein the first silicon source is hydrolyzed to generate silicon hydroxyl and does not contain organic groups; the second silicon source at least contains one non-hydrolytic group;

(2) mixing the first precursor hydrolysate and the second precursor hydrolysate in proportion to form mixed sol, adding an alkali catalyst, and adjusting the pH value of the solution;

(3) before the mixed sol obtained in the step (2) does not have an initial gel state, transferring the mixed sol into an emulsifier and stirring to form white wet gel balls;

(4) immersing the wet gel pellets obtained in the step (3) with a solvent, aging, and filtering to obtain solid pellets;

(5) drying the solid pellets obtained in the step (4) to obtain the silicon dioxide aerogel microspheres;

the preparation method of the silica aerogel microspheres does not comprise the steps of solvent exchange and surface modification.

Preferably, the second silicon source is an organosiloxane containing one or more hydrocarbon groups.

Preferably, step (1) includes any one or a combination of the following features:

(a) the first silicon source is selected from tetraethyl orthosilicate, tetramethyl orthosilicate or water glass;

(b) the second silicon source is selected from methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane or dimethyldimethoxysilane;

(c) the acid catalyst is one or more of hydrofluoric acid, hydrochloric acid, sulfuric acid, oxalic acid and acetic acid;

(d) the concentration of the acid catalyst is 0.1-1 mol/L;

(e) the pH value is adjusted to 3.0-4.5.

Preferably, step (2) includes any one or a combination of the following features:

(a) the alkali catalyst is one of ammonia water, sodium carbonate, sodium bicarbonate, sodium hydroxide or potassium carbonate;

(b) the concentration of the alkali catalyst is 0.1-5 mol/L;

(c) adjusting the pH value to 7-8.

(d) The molar ratio of the first silicon source to the second silicon source is 0.1-4.

Preferably, step (3) includes any one or a combination of the following features:

(a) the emulsifier is one or more selected from n-hexane, polydimethylsiloxane, soybean oil, span 60 and span 80;

(b) the stirring speed is 500 r/min-1000 r/min.

Preferably, step (4) includes any one or combination of the following features:

(a) the solvent used for aging is one or more of ethanol, n-hexane, tert-butanol, methanol or n-heptane;

(b) the aging times are 1-4 times, and the aging time is 2-8 h.

Preferably, in the step (1), a proper amount of the first silicon source or the second silicon source is taken, the solvent and the water are added, the acid catalyst is added after stirring, the pH value is adjusted, and the first precursor hydrolysate or the second precursor hydrolysate is obtained after hydrolysis.

Preferably, in step (1), a surfactant is further added to the first silicon source and/or the second silicon source.

Preferably, in the step (3), the stirring speed is controlled to control the particle size of the silica aerogel microspheres finally obtained.

Preferably, in the step (5), the drying is normal pressure; the drying temperature is controlled to be 60-120 ℃, and the drying time is 6-48 h.

Preferably, the hydrolysis in the step (1), the step (3) and the aging in the step (4) are all carried out in a constant-temperature water bath at 45 ℃.

In a third aspect, the invention provides the use of the silica aerogel microspheres of the first aspect for adsorbing cigarette side stream smoke and carrying flavors and fragrances.

Preferably, the silica aerogel microspheres are used in cigarette filter rods.

The technical scheme can be freely combined on the premise of no contradiction.

The invention has the following beneficial effects:

(1) the method utilizes a co-precursor method to carefully select two silicon sources, omits the process of surface hydrophobic modification, greatly reduces the use of organic solvents and shortens the preparation period, the obtained aerogel microspheres have full particles, smooth surfaces and slightly static electricity, the microspheres are soft and light, the microsphere material has hydrophobicity, the particle size is 250-1000 mu m, and the density is 0.05-0.20 g/cm³The specific surface area is 400-1000 m²/g。

(2) According to the invention, the silicon dioxide aerogel is made into a small ball shape by an emulsion balling method, the balance weight is added, the problems of light weight and easy dispersion of aerogel powder are solved, and the application field of aerogel materials is increased.

(3) The existing sol-gel preparation process needs to carry out the steps of aging and solvent exchange in an alcoholic solution so as to replace ethanol in gel pores. Before the mixed sol does not have an initial gel state, the mixed sol is transferred into an emulsifier and stirred to form a white wet gel ball. Namely, the process of forming sol into gel is carried out in the emulsifier, the emulsifier is in the pores of the obtained gel, the subsequent solvent exchange process is not needed, and the specific surface area of the finally obtained microspheres is larger and is 400-1000 m²A lower density of 0.05 to 0.20g/cm³。

(4) The invention adopts a normal pressure drying method, and is safer and more environment-friendly compared with supercritical drying.

(5) The aerogel microspheres prepared by the invention have good hydrophobicity and balling property and excellent adsorption performance, can be applied to cigarette filter sticks for adsorbing side-stream smoke of cigarettes and loading essence perfume, and can also be applied to more fields with special requirements such as sewage treatment, chromatographic packing and the like.

Drawings

FIG. 1 is a flow chart of the preparation of silica aerogel microspheres according to example 1 of the present invention.

Fig. 2 is a photograph of an aerogel microsphere prepared according to example 1 of the present invention.

FIG. 3 is a hydrophobicity experiment of aerogel microspheres prepared in example 1 of the present invention.

Fig. 4 is a field emission Scanning Electron Microscope (SEM) image of aerogel microspheres prepared in example 2 of the present invention.

FIG. 5 is a Transmission Electron Micrograph (TEM) of aerogel microspheres prepared according to example 2 of the present invention.

FIG. 6 is a graph of isothermal nitrogen adsorption and desorption curves of aerogel microspheres prepared in example 3 of the present invention, wherein the abscissa is relative pressure (p/p)₀) The ordinate is the volume adsorption (cm)³/gSTP)。

FIG. 7 is a Fourier infrared spectrum of an aerogel sample prepared according to example 4 of the present invention.

FIG. 8 is a graph showing the distribution of particle sizes of aerogel samples prepared in example 2 of the present invention.

Detailed Description

The present invention will be further described with reference to the following embodiments.