WO2019090660A1

WO2019090660A1 - Method for preparing size-selective nano-mesoporous sio2-tio2 composite photocatalytic material

Info

Publication number: WO2019090660A1
Application number: PCT/CN2017/110377
Authority: WO
Inventors: 冯泽云
Original assignee: 纳琦环保科技有限公司
Priority date: 2017-11-10
Filing date: 2017-11-10
Publication date: 2019-05-16
Also published as: CN110022972A; CN110022972B

Abstract

Disclosed is a method for preparing a nano-mesoporous SiO2-TiO2 composite photocatalytic material. The method comprises formulating a Ti-Si composite precursor solution, and formulating polyoxyethylene-polyoxypropylene-polyoxyethylene (P123), n-butyl alcohol and cetyl trimethyl ammonium bromide (CTAB), etc. into a template agent solution system, and then mixing the two solutions to obtain a precipitate, removing chloride ions by filtering and washing, then re-dissolving the precipitate by hydrogen peroxide to obtain a nano-mesoporous titanium dioxide/silicon dioxide composite photocatalytic material. The method achieves the in-situ synthesis of a nanometer silicon oxide-coated titanium oxide structure, avoiding the problems, readily caused by a process of synthesizing silicon oxide and then loading titanium oxide, that a catalyst blocks a mesoporous and is easy to fall off. Meanwhile, compared with the process of synthesizing titanium oxide and then coating with silicon oxide, the method has a simple flow, strong operability, and a relatively low cost, is suitable for batch preparation, has the possibility of industrial production, and has an extensive application prospect.

Description

Method for preparing size-selective nano mesoporous SiO2-TiO2 composite photocatalytic material

Technical field

The invention belongs to the field of preparation of inorganic metal oxides, in particular to a preparation method of nanostructured titanium dioxide/silica composite photocatalytic materials.

Background technique

As a mild advanced chemical oxidation technology, semiconductor photocatalytic technology can continuously convert the absorbed light energy into chemical energy, thereby effectively mineralizing volatile organic compounds in the air. It is considered to solve related industries, residential distribution and low. An effective solution to the concentration and high toxicity of organic volatile gases.

The main difficulty of semiconductor photocatalytic oxidation technology on the surface of organic substrates is the corrosion of photocatalytic materials on the organic substrate itself, that is, the polymer substrate itself can also be decomposed by the semiconductor photocatalytic process. Therefore, spraying the TiO ₂ coating directly on the surface of the substrate, or directly adding TiO ₂ in the polymer base material, causes corrosion of the substrate. However, most materials, especially building materials, are covered by organic coatings, whether based on functional requirements such as decoration or anti-corrosion. Therefore, the corrosion problem of organic substrate materials and polymer materials is the main technical bottleneck restricting the large-scale application of catalytic technology in various industries.

Mesoporous SiO ₂ coated TiO ₂ composite photocatalytic materials are considered as a method to provide size selectivity, in which silica forms nano-mesoporous structure, and nano-titanium oxide is dispersed in nano-silica mesopores. This allows small molecular contaminants such as formaldehyde and benzene to be decomposed by contact of mesopores with titanium oxide, while macromolecular polymers cannot directly contact nano-titanium oxide due to size effects, so that they are not decomposed. However, the currently reported synthesis method or the method of first synthesizing nanometer titanium oxide and then coating the surface of silicon oxide is cumbersome and not suitable for large-scale industrial production; or first synthesizing nanometer mesoporous nano-silica and then immersing in nano-oxidation Loading in titanium, but it will cause mesoporous blockage and catalyst shedding problems.

Summary of the invention

According to an aspect of the present invention, it is an object of the present invention to provide a method for preparing a size-selective nano-mesoporous SiO ₂ -TiO ₂ composite photocatalytic material which is simple, easy to control, and has good effects and is suitable for large-scale industrial production.

In order to achieve the above object of the present invention, a method for preparing a nanometer mesoporous titania/silica composite photocatalytic material of the present invention comprises the following steps:

(1) Ti-Si composite precursor configuration

Dissolving silicon tetrachloride in titanium tetrachloride to obtain a composite precursor solution, wherein the molar ratio of Si:Ti is 1:0.1 to 1:10;

(2) Template solution solution system configuration

Dissolving polyoxyethylene-polyoxypropylene-polyoxyethylene (P123) in n-butanol, adding cetyltrimethylammonium bromide (CTAB) to dissolve, and then dissolving the above solution in aqueous ammonia solution to form a template solution a system; wherein the final weight percent concentration of P123 is from 0.01 wt% to 0.05 wt%, the final weight percent concentration of n-butanol is from 5 to 25 wt%, and the final weight percent concentration of cetyltrimethylammonium bromide (CTAB) is From 0.05 wt% to 0.1 wt%, the final weight percentage concentration of NH ₃ ·H ₂ O is from 5 wt% to 15 wt%, and the weight ratio of P123 to CTAB is from 1:0.1 to 1:8.

(3) Hydrolysis of Ti-Si composite precursor

The Ti-Si composite precursor is added dropwise to the above templating solution solution system, and stirred vigorously at a stirring speed of 600-2000 rpm for 24 to 36 hours to obtain a white precipitate; wherein the Ti-Si composite precursor solution and the template solution are The volume ratio is from 1:0.2 to 1:10.

(4) Precipitation purification

The Ti-Si composite white precipitate of step (3) is repeatedly subjected to filtration washing to remove chloride ions, and finally the chloride ion concentration in the eluate does not exceed 0.001 mol/l;

(5) Preparation of mesoporous silica/titanium oxide composite

Re-dissolving the precipitate of step (3) into a solution state with a hydrogen peroxide solution having a mass concentration of 5 wt% to 30 wt%, a molar ratio of Ti:H ₂ O ₂ of 1 to 25; at a temperature of 90 to 100 ° C After refluxing for 2 to 6 hours, the nanometer mesoporous titania\silicon oxide composite was obtained by centrifugation.

Preferably, the molar ratio of Si:Ti in step 1) is from 1:0.3 to 1:5, more preferably from 1:0.5 to 1:3, more preferably from 1:0.5 to 1:2, for example, it may be 1:0.5 , 1:1 or 1:2.

Preferably, the weight ratio of P123 to CTAB in step 2) is from 1:0.2 to 1:8, more preferably from 1:0.5 to 1:2.

Preferably, the agitation in the step 3) is carried out at a stirring speed of 700 to 1,500 rpm, more preferably 700 to 1,500 rpm, and most preferably 800 rpm.

Preferably, the volume ratio of the Ti-Si composite precursor solution to the templating agent solution in the step 3) is from 1:0.2 to 1:5, more preferably from 1:0.5 to 1:2, most preferably from 1:0.66 to 1:1.5.

Preferably, the mass percentage of the hydrogen peroxide solution in step 5) is preferably from 20% by weight to 40% by weight, more preferably 30% by weight; the molecular molar ratio of H ₂ O ₂ to Ti is preferably controlled to be from 2 to 18, preferably 5 to 10.

According to an aspect of the present invention, an object of the present invention is to provide a nano-mesoporous SiO ₂ -TiO ₂ composite photocatalytic material, and a BJH fitting pore size of a nano-mesoporous SiO ₂ -TiO ₂ composite photocatalytic material is 2.00 nm. To 5.00 nm, preferably 2.50 nm to 4.50 nm, more preferably 3.00 to 3.50 nm, and most preferably 3.25 nm to 3.35 nm, the composite photocatalytic material is prepared by the above method.

According to an aspect of the present invention, it is an object of the present invention to provide a coating comprising a nano-mesoporous SiO ₂ -TiO ₂ composite photocatalytic material according to the present invention, and other conventional coating components such as a resin, an antibacterial agent , a leveling agent, a pigment, etc., as long as the conventional coating composition does not adversely affect the catalytic performance of the nano-mesoporous SiO ₂ -TiO ₂ composite photocatalytic material. Further, the coating material according to the present invention can be directly applied by spraying, rolling, brushing or the like.

Beneficial effect

Compared with the preparation method reported in the literature, the present invention realizes the in-situ synthesis of the nano-silica-coated titanium oxide structure, thereby avoiding the problem that the catalyst is clogged with mesopores and easy to fall off due to the subsequent loading of titanium oxide by the synthetic silicon oxide; Compared with the process of synthesizing titanium oxide and coating silicon oxide, the method of the invention has simple process, strong operability, low cost, is suitable for batch preparation, has the possibility of industrial production, and has wide application prospects.

DRAWINGS

1a and 1b are transmission electron micrographs of a nanometer mesoporous titania/silica composite photocatalytic material prepared according to Example 1 of the present invention, respectively.

2 is a scanning electron microscope (SEM) analysis result of a nanometer mesoporous titania/silica composite photocatalytic material prepared according to Example 1 of the present invention.

3 is a photocatalytic result of a nanometer mesoporous titania/silica composite photocatalytic material prepared according to Example 1 of the present invention.

Detailed ways

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, the terms used in the specification and the appended claims should be understood and should not be construed as limited to the general and the meaning of the The principles are explained based on the meanings and concepts corresponding to the technical aspects of the present invention. Therefore, the description herein is for the purpose of illustration only, and is not intended to limit the scope of the invention, and it is understood that other equivalents and modifications may be made without departing from the spirit and scope of the invention.

The nano mesoporous SiO ₂ -TiO ₂ composite photocatalyst material provided by the invention uses a cationic surfactant and a nonionic block surfactant as a template, and uses titanium tetrachloride and silicon tetrachloride as a titanium source and a silicon source, respectively. Prepared under alkaline conditions, the diameter of the obtained microparticles is adjustable between 10 μm and 100 μm. After N ₂ adsorption-desorption analysis, the mesoporous pore diameter is 3 to 5 nm, and the specific surface area is 210 to 450 m ² /g. The obtained microparticles were analyzed by EDS to be TiO ₂ and SiO ₂ components.

The mesoporous pore size, specific surface area, and photocatalytic effect of the product in the preparation method of the nanometer mesoporous titania/silica composite photocatalytic material according to the present invention depend on various factors, which will be described in detail below.

Preferably, in the preparation method according to the present invention, the molar ratio of Si:Ti in the step 1) is from 1:0.3 to 1:5, more preferably from 1:0.5 to 1:3, more preferably from 1:0.5 to 1: 2, for example, can be 1:0.5, 1:1 or 1:2. When the molar ratio of Si:Ti is greater than 1:0.5, that is, Si is excessive, although the mesoporous structure does not change too much, the photocatalytic effect is not obvious because the relative proportion of Ti is too low; when Si:Ti mole When the ratio is less than 1:3, Ti is excessive. Due to the high proportion of titanium tetrachloride in the precursor, the hydrolysis rate in step 4) is too fast, and it is difficult to form a mesoporous material, which tends to cause a large amount of flocculation and precipitation.

In step 2) of the preparation method of the present invention, P123 and CTAB are used as a templating agent, wherein P123 is a nonionic block type surfactant and CTAB is a cationic surfactant, and the mixture of the two forms a mesoporous formation and The control of the pore size is very important. Preferably, the weight ratio of P123 to CTAB is from 1:0.2 to 1:8, more preferably from 1:0.5 to 1:2. When the weight ratio of P123 to CTAB is greater than 1:0.2, that is, P123 is excessive, the mesoporous pore size is difficult to control, and the microporous structure is often obtained; when the weight ratio of P123 to CTAB is less than 1:8, CTAB is excessive, since CTAB is cationic The surfactant has a charge effect, resulting in agglomeration of the formed TiO ₂ -SiO ₂ coprecipitation, and the formed particles are dense, and it is difficult to form a mesoporous structure.

The inventors of the present invention have surprisingly found that in the step 3) of the present invention, during the dropwise addition of the Ti-Si composite precursor to the templating solution system of the step 2), the degree of stirring of the solution is on the mesoporous size and The particle size has a significant effect. Preferably, the stirring is vigorously stirred at a stirring speed of 700 to 1500 rpm for 24 to 36 hours to obtain a white precipitate. The white precipitate is filtered, washed, dechlorinated and treated with hydrogen peroxide to obtain mesopores. suitable dimensions of TiO ₂ -SiO ₂ composite photocatalytic material. When the stirring speed is lower than 700 rpm, the distribution of TiO ₂ and SiO ₂ in the nanoparticles is not uniform enough; when the stirring speed is higher than 1500 rpm, the mesoporous structure may be incompletely formed and dense particles may be formed. More preferably, the agitation speed is from 700 to 1500 rpm, most preferably 800 rpm.

The volume ratio of the Ti-Si composite precursor solution to the templating solution has a decisive influence on the product structure. Preferably, the volume ratio of the Ti-Si composite precursor solution to the templating solution in step 3) is 1:5 to 1 :0.2. When the volume ratio of the Ti-Si composite precursor solution to the templating solution is less than 1:5, that is, the amount of the templating agent is too high, the TiO ₂ /SiO ₂ nanoparticles are easily caused by the high content of the polymer as a templating solution in the solution. Agglomeration, especially when filtering, is easy to block the filter pores, so it is not suitable for large-scale industrial production; when the volume ratio of Ti-Si composite precursor solution to template solution is greater than 1:0.2, the amount of template is insufficient, mesopores The formation of the structure is incomplete and it is often easy to obtain dense particles. Further, the volume ratio of the Ti-Si composite precursor solution to the templating agent solution is more preferably 1:0.5 to 1:2, and most preferably 1:0.66 to 1:1.5.

The following examples are merely illustrative of the embodiments of the present invention, and are not intended to limit the scope of the present invention, and those skilled in the art can understand without departing from the spirit and scope of the present invention. Modifications fall within the scope of protection of the present invention. The reagents and instruments used in the following examples are commercially available products unless otherwise stated.

Example 1:

(1) slowly adding silicon tetrachloride to a solution of titanium tetrachloride to obtain a composite precursor solution, wherein the molar ratio of Si:Ti is 1:1;

(2) 1 g of polyoxyethylene-polyoxypropylene-polyoxyethylene (P123) was added to 25 ml of n-butanol, stirred for 10 minutes to make the solution uniform, and then 4 g of cetyltrimethyl bromide was added to the above solution. Ammonium (CTAB), stirring was continued for 5 minutes, then 500 ml of 10 wt% ammonia water was added to the solution, and the solution was stirred for 2 hours to thoroughly mix the solution;

(3) slowly adding 50 ml of the Ti-Si composite precursor solution prepared in the step (1) (the molar ratio of Si:Ti is 1:1) to the solution of the step (2) at a stirring speed of 800 rpm. Stir vigorously for 24 h to form a white precipitate.

(4) The resulting precipitate is washed with deionized water to remove chloride ions until the concentration of chloride ions in the eluate does not exceed 0.001 mol / l;

(5) The above precipitate is then dispersed in 200 ml of a 10% by weight aqueous solution of hydrogen peroxide, and the composite solution is heated to 90 ° C for 3 hours, and then centrifuged to obtain a nanometer mesoporous titania/silica composite photocatalytic material. .

1a and 1b are transmission electron micrographs of a nanometer mesoporous titania/silica composite photocatalytic material prepared according to the present embodiment, and FIG. 2 is a nanometer mesoporous titania/silicon dioxide composite prepared according to the embodiment. SEM analysis results of photocatalytic materials. It can be seen from the figure that the prepared nano-titanium dioxide is coated with silica to form a composite material according to the present embodiment, and the BET specific surface area of the sample is determined to be 380.2 m ² /g, and the BJH fitting pore diameter is 2.82 nm (see Table 1). ).

Example 2:

In addition to adding 2 g of polyoxyethylene-polyoxypropylene-polyoxyethylene (P123), 1 g of cetyltrimethylammonium bromide (CTAB) and Ti-Si composite precursor have a molar ratio of Ti:Si of 1:2. A nano mesoporous titania/silica composite photocatalytic material was prepared in the same manner as in Example 1.

3 is a N ₂ adsorption-desorption characterization of a nano-mesoporous titania/silica composite photocatalytic material prepared according to the present embodiment, and the results are shown in FIG. 3 . The BET specific surface area of the sample was measured to be 430.2 m ² /g, and the BJH fitting pore diameter was 2.46 nm. The silica microspheres synthesized under this condition have a mesoporous structure and a high specific surface area (see Table 1).

Example 3:

A nanometer mesoporous titania/silica composite photocatalytic material was prepared in the same manner as in Example 1 except that the molar ratio of Ti:Si in the Ti-Si composite precursor was 2:1, and the BET specific surface area of the sample was determined to be 320.2. m ² /g, BJH fitted pore size was 3.28 nm (see Table 1).

Table 1

	实施例1Example 1	实施例2Example 2	实施例3Example 3
BET比表面积BET specific surface area	380.2m²/g380.2m ² /g	430.2m²/g430.2m ² /g	320.2m²/g320.2m ² /g
BJH拟合孔径BJH fitting aperture	2.82nm2.82nm	2.46nm2.46nm	3.28nm3.28nm

Comparative Example 1

The molar ratio of Ti:Si in the addition of 5 g of polyoxyethylene-polyoxypropylene-polyoxyethylene (P123), 0.7 g of cetyltrimethylammonium bromide (CTAB) and Ti-Si composite precursor is 1: A nano mesoporous titania/silica composite photocatalytic material was prepared in the same manner as in Example 1 except for 2. The BET specific surface area of the sample was measured to be 142.8 m ² /g, and the BJH fit pore diameter was 14.37 nm, which was not a mesoporous structure.

Comparative Example 2

In addition to adding 1 g of polyoxyethylene-polyoxypropylene-polyoxyethylene (P123), 10 g of cetyltrimethylammonium bromide (CTAB) and Ti-Si composite precursor have a molar ratio of Ti:Si of 1:2. A nano mesoporous titania/silica composite photocatalytic material was prepared in the same manner as in Example 1. The sample was measured to have a BET specific surface area of 133.7 m ² /g, dense nanoparticles, and no mesoporous structure was observed.

Comparative Example 3

A nano mesoporous titania/silica composite photocatalytic material was prepared in the same manner as in Example 1 except that the stirring speed was set to 2000 rpm. The sample was measured to have a BET specific surface area of 178.6 m ² /g, dense nanoparticles, and no mesoporous structure was observed.

Comparative Example 4

A nano mesoporous titania/silica composite photocatalytic material was prepared in the same manner as in Example 1 except that the stirring speed was set to 650 rpm. The obtained material is a large amount of agglomeration, and the composite photocatalytic material cannot be effectively obtained.

Comparative Example 5

In addition to adding 32 ml of the Ti-Si composite precursor solution prepared in the step (1) (the molar ratio of Si:Ti is 1:1), wherein the volume ratio of the Ti-Si composite precursor solution to the templating solution solution is 1:16, A nanometer mesoporous titania/silica composite photocatalytic material was prepared in the same manner as in Example 1. As a result, a large amount of agglomeration could not be filtered, and the pores were severely clogged, and the composite photocatalytic material could not be effectively obtained.

Comparative Example 6

In addition to adding 131 ml of the Ti-Si composite precursor solution prepared in the step (1) (the molar ratio of Si:Ti is 1:1), wherein the volume ratio of the Ti-Si composite precursor solution to the templating solution is about 1:4. A nanometer mesoporous titania/silica composite photocatalytic material was prepared in the same manner as in Example 1. The sample was measured to have a BET specific surface area of 194.6 m ² /g, dense nanoparticles, and no mesoporous structure was observed.

Experimental Example 1

The nanometer mesoporous titania/silica composite photocatalytic material prepared in Example 1 was placed in a uniform suspension of 0.01 g/ml, coated on a 4 cm×4 cm glass plate, dried overnight in an oven, and then placed separately. After being adsorbed and saturated in 0.04 mmol/L of 20 ml of methylene blue and disperse red, it was taken out and dried, and then placed in 0.02 mmol/L of 20 ml of methylene blue and dispersed red solution for degradation (UV light intensity ² mw/cm ^{2 ).} ), the absorbance change was measured using an ultraviolet-visible spectrophotometer. Figure 4 is a photocatalytic degradation diagram of the obtained product for methylene blue and dispersed red red.

As can be seen from the figure, the nanometer mesoporous titania/silica composite photocatalytic material according to the present invention has good photodegradability for small molecule methylene blue, but has little degradation performance for macromolecular carmine. This is mainly because the pore size of the shell layer is only about 3.25 nm. The small molecule methylene blue can be degraded by the shell pores reaching the surface of the titanium oxide, while the macromolecular carmine can not be degraded through the pores to the surface of the titanium oxide. Size-selective photocatalytic performance of nanometer mesoporous titania/silica composite photocatalytic materials.

Claims

A method for preparing a size-selective nano-mesoporous SiO 2 -TiO 2 composite photocatalytic material, the method comprising the steps of:

(1) Ti-Si composite precursor configuration

Dissolving silicon tetrachloride in titanium tetrachloride to obtain a composite precursor solution, wherein the molar ratio of Si:Ti is 1:0.1 to 1:10;

(2) Template solution solution system configuration

Dissolving polyoxyethylene-polyoxypropylene-polyoxyethylene (P123) in n-butanol, adding cetyltrimethylammonium bromide (CTAB) to dissolve, and then dissolving the above solution in aqueous ammonia solution to form a template solution a system; wherein the final weight percent concentration of P123 is from 0.01 wt% to 0.05 wt%, the final weight percent concentration of n-butanol is from 5 to 25 wt%, and the final weight percent concentration of cetyltrimethylammonium bromide (CTAB) is 0.05wt% to 0.1wt%, the final weight percentage concentration of NH 3 ·H 2 O is 5wt% to 15wt%, the weight ratio of P123 to CTAB is 1:0.1 to 1:8;

(3) Hydrolysis of Ti-Si composite precursor

The Ti-Si composite precursor is added dropwise to the above templating solution solution system, and stirred vigorously at a stirring speed of 600-2000 rpm for 24 to 36 hours to obtain a white precipitate; wherein the Ti-Si composite precursor solution and the template solution are The volume ratio is 1:0.2 to 1:10;

(4) Precipitation purification

The Ti-Si composite white precipitate of step (3) is repeatedly subjected to filtration washing to remove chloride ions, and finally the chloride ion concentration in the eluate does not exceed 0.001 mol/l;

(5) Preparation of mesoporous silica/titanium oxide composite

Re-dissolving the precipitate of step (3) into a solution state with a hydrogen peroxide solution having a mass concentration of 5 wt% to 30 wt%, a molar ratio of Ti:H 2 O 2 of 1 to 25; at a temperature of 90 to 100 ° C After refluxing for 2 to 6 hours, the nanometer mesoporous titania\silicon oxide composite was obtained by centrifugation.
The preparation method according to claim 1, wherein the molar ratio of the Si:Ti in the step 1) is from 1:0.3 to 1:5, more preferably from 1:0.5 to 1:3, more preferably 1 : 0.5 to 1:2, for example, may be 1:0.5, 1:1 or 1:2.
The preparation method according to claim 1, wherein the weight ratio of the P123 to the CTAB in the step 2) is from 1:0.2 to 1:8, more preferably from 1:0.5 to 1:2.
The production method according to claim 1, wherein the stirring in the step 3) is carried out at a stirring speed of 700 to 1,500 rpm, more preferably 700 to 1,500 rpm, and most preferably 800 rpm. .
The preparation method according to claim 1, wherein the volume ratio of the Ti-Si composite precursor solution to the templating agent solution in the step 3) is from 1:0.2 to 1:5, more preferably from 1:0.5 to 1:2, most preferably 1:0.66 to 1:1.5.
The preparation method according to claim 1, wherein the mass percentage of the hydrogen peroxide solution in the step 5) is preferably 20% by weight to 40% by weight, more preferably 30% by weight; the molecules of H 2 O 2 and Ti The molar ratio is preferably controlled to be from 2 to 18, preferably from 5 to 10.
A nanometer mesoporous SiO 2 -TiO 2 composite photocatalytic material, the BJH fitting pore size of the nano mesoporous SiO 2 -TiO 2 composite photocatalytic material is 2.00 nm to 5.00 nm, preferably 2.50 nm to 4.50 nm, more preferably The composite photocatalytic material is prepared by the preparation method according to any one of claims 1 to 6 at 3.00 to 3.50 nm, most preferably from 3.25 nm to 3.35 nm.
Mesoporous SiO 2 -TiO 2 composite photocatalytic material, and other conventional coating composition a coating, said coating comprising according to claim 7, for example a resin, an antibacterial agent, a leveling agent, a pigment and the like.