Preparation method and application of amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst

Abstract

The present invention discloses a preparation method and application of an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst. The catalyst is prepared by mixing nano-SiO2 particles with absolute ethanol and tetrabutyl titanate at a certain temperature; then, deionized water and polyvinyl alcohol or sodium dodecyl benzene sulfonate are dropped into the obtained mixed solution, and stirring is continued for a certain time to obtain a suspension; finally, the obtained suspension is centrifuged to remove the supernatant, the precipitate is washed and centrifuged again, and finally the centrifuged precipitate is dried. The SiO2@TiO2 core-shell structure catalyst prepared by the present invention can achieve an effect close to total reflection, improve the reflectivity of light such as ultraviolet light, and further improve the photocatalytic effect on organic pollutants.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalysts, and specifically relates to a preparation method and application of a TiO2-based SiO2@TiO2 core-shell structure catalyst. Background Art

[0002] As the contradiction between the growing energy demand and the increasing energy shortage intensifies, the development and utilization of new energy, especially solar energy, has become more important. Photocatalysts have the advantages of mild reaction conditions and can directly convert light energy into chemical energy. They have attracted extensive attention from researchers in the degradation of organic pollutants, reduction of carbon dioxide, and realization of water splitting and hydrogen analysis, and are an ideal green material.

[0003] TiO2 is the most widely used photocatalyst with the advantages of low cost, good stability and strong photocatalytic ability, showing great application prospects in the fields of energy and environmental protection. However, due to its wide band gap (about 3.0eV), it has poor light absorption ability outside the ultraviolet region and its high recombination rate of photogenerated carriers, which further hinders its photocatalytic performance.

[0004] At present, most research focuses on improving the catalytic performance of crystalline TiO2. There are doping (Applied Catalysis B: Environmental, 242, 2019, 92-99; Applied Catalysis B: Environmental, 262, 2020, 118308), dye sensitization (Journal Of Materials Chemistry A, 34, 2019, 19852-19861; Applied Catalysis B: Environmental, 232, 2018, 260-267), precious metal composites (Nature Catalysis, 2, 2019, 873-881; Chemical Engineering Journal, 393, 2020, 124781), semiconductor composites (Journal Of Materials Chemistry A, 34, 2019, 19852-19861; Applied Catalysis B: Environmental, 232, 2018, 260-267), and so on. A, 6, 2018, 8289-8298) and other chemical modification methods are used to increase the number of defects, expand the light absorption range, and improve the separation efficiency of photogenerated electrons and holes, but these methods mainly focus on the regulation of the catalytic performance of crystalline TiO2 photocatalysts. How to achieve efficient utilization of solar energy by changing the physical structure of amorphous TiO2-based catalysts remains a challenge.

[0005] Although the prior art has conducted a lot of research on SiO2@TiO2 core-shell structure catalysts, these technologies still cannot change the physical structure of amorphous TiO2-based catalysts, thereby improving the efficient use of solar energy. For example, Patent Document 1 discloses a method for preparing a structurally stable color-forming material with a photocatalytic effect, which can prepare PA / SiO2@TiO2 amorphous photonic crystal structure color-forming materials, which can form black light-absorbing materials by forming oxygen defects in the TiO2 mesoporous shell after negative pressure treatment, so that multiple scattered light in the amorphous photonic crystal structure can be absorbed to prepare an amorphous photonic crystal structure color that is not angle-dependent. The appearance of oxygen vacancies makes the photocatalyst surface have more electrons than holes, and forms oxygen vacancy defect energy levels, which reduces the TiO2 bandgap width and effectively improves the photocatalytic efficiency. For example, Patent Document 2 discloses a method for preparing solar heat reflective TiO2@SiO2 core-shell particles, which first prepares TiO2 particles with a particle size range of 1.1 to 1.4 μm, and then prepares silica-coated titanium dioxide particles. The TiO2@SiO2 core-shell particles prepared by this method have a reflectivity of more than 80% in the infrared band. However, it does not give the reflectivity of low-band light (such as ultraviolet light), which is not very suitable for use scenarios such as photocatalytic degradation of organic pollutants.

[0006] Patent document 3 discloses a SiO2@TiO2 nanocomposite material and a preparation method, which can increase the specific surface area of ​​TiO2 to improve the photocatalytic activity of the composite material by changing the concentration of the silicon source and the heat treatment method. Although the degradation rate of a methylene blue solution with a mass concentration of 20 mg / l in 90 minutes can reach 98.42%, its preparation process is relatively complicated and the reflectivity of light, especially ultraviolet light, needs to be improved.

[0007] Patent document 1: Publication No. CN112194143A;

[0008] Patent document 2: Publication No. CN104084096A;

[0009] Patent document 2: Publication No. CN112915989A.

[0010] In response to this problem, the researchers in this case proposed further improvement plans. Summary of the invention

[0011] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst and its application. The addition of polyvinyl alcohol or sodium dodecylbenzene sulfonate can promote the loading of amorphous TiO2 on the outer layer of SiO2 microspheres, so that TiO2 can be densely coated on the outer layer of SiO2 microspheres, and the prepared SiO2@TiO2 core-shell structure catalyst can achieve a near-total reflection effect, improve the reflectivity of light such as ultraviolet light, and thus improve the photocatalytic effect on organic pollutants.

[0012] To achieve the above-mentioned object of the invention, the present invention provides a method for preparing an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst, which comprises at least the following steps:

[0013] 1) Mix nano-SiO2 particles with anhydrous ethanol and butyl titanate at a certain temperature;

[0014] 2) adding deionized water and polyvinyl alcohol or sodium dodecylbenzene sulfonate dropwise to the mixed solution of step 1), and stirring for a certain period of time to obtain a suspension;

[0015] 3) Centrifuging the suspension in step 2), removing the supernatant, washing the precipitate, centrifuging again, and finally drying the precipitate after centrifugation to obtain a white precipitate, that is, obtaining an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst.

[0016] As a further improvement of the present invention, in step 1), the usage ratio of the nano-SiO2 particles to the butyl titanate is 0.5 g~1 g:3~15 ml.

[0017] As a further improvement of the present invention, in step 1), the usage ratio of the butyl titanate to the anhydrous ethanol is: 3-10 ml: 20-50 ml.

[0018] As a further improvement of the present invention, in step 1), the mixing temperature of the nano-SiO2 particles, anhydrous ethanol and butyl titanate is 70°C to 100°C.

[0019] As a further improvement of the present invention, the usage ratio of the polyvinyl alcohol in the step 2) to the butyl titanate in the step 1) is 0.05-0.2 g: 3-15 ml.

[0020] As a further improvement of the present invention, the dosage ratio of the sodium dodecylbenzene sulfonate in the step 2) to the butyl titanate in the step 1) is 0.05-0.3 g: 3-15 ml.

[0021] As a further improvement of the present invention, the nano-SiO2 particles in step 1) are mixed with anhydrous ethanol, deionized water, ammonia water, and tetraethyl orthosilicate solution, and stirred in a water bath at a certain temperature, and then the suspension obtained by stirring is centrifuged, the supernatant is removed and dried.

[0022] As a further improvement of the present invention, the volume ratio of the ammonia water, anhydrous ethanol, deionized water and tetraethyl orthosilicate solution is 3-13 ml: 20-50 ml: 1-5 ml: 1-5 ml.

[0023] At the same time, the present invention also proposes an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst, which can be prepared by the above-mentioned preparation method. The catalyst includes a plurality of core-shell structured nanoparticles, wherein the nanoparticles include SiO2 microspheres as a core and a plurality of TiO2 particles as an outer shell tightly covering the surface of the core, forming a fully reflective core-shell structure. The fully reflective core-shell structure has an absorbance of 0.25 for visible light with a wavelength of 400nm and an absorbance of 0.55 for ultraviolet light with a wavelength of 300nm.

[0024] At the same time, the present invention also relates to the application of an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst in photocatalytic degradation of organic pollutants.

[0025] The beneficial effects of the present invention are:

[0026] 1. The present invention can promote the loading of amorphous TiO2 in the outer layer of SiO2 microspheres by adding polyvinyl alcohol or sodium dodecylbenzene sulfonate, so that TiO2 can be densely coated in the outer layer of SiO2 microspheres, and then the prepared SiO2@TiO2 core-shell structure catalyst can obtain a near total reflection effect, improve the reflectivity of light such as ultraviolet light, and then improve the photocatalytic effect on organic pollutants.

[0027] 2. The amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst prepared by the present invention can obtain a good reflection effect in practical application, with an absorbance of 0.25 for visible light with a wavelength of 400nm and an absorbance of 0.55 for ultraviolet light with a wavelength of 300nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a diagram showing the mechanism of the photothermal effect of the amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst of the present invention promoting the catalytic performance of the SiO2@TiO2 catalyst;

[0029] Figure 2 The XRD diagram of the amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst of the present invention;

[0030] Figure 3 It is the ultraviolet diffuse reflection absorption spectrum of the amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst of the present invention;

[0031] Figure 4 It is a degradation rate curve diagram of the amorphous TiO2-based SiO2@TiO2 core-shell structure of the present invention degrading 17β-estradiol under visible light. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below in conjunction with specific embodiments.

[0033] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the specific embodiments, while other details that are not closely related to the present invention are omitted.

[0034] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0035] The present invention provides a method for preparing an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst, which comprises at least the following steps:

[0036] 1) Mix nano-SiO2 particles with anhydrous ethanol and butyl titanate at a certain temperature;

[0037] 2) adding deionized water and polyvinyl alcohol or sodium dodecylbenzene sulfonate dropwise to the mixed solution of step 1), and stirring for a certain period of time to obtain a suspension;

[0038] 3) Centrifuging the suspension in step 2), removing the supernatant, washing the precipitate, centrifuging again, and finally drying the precipitate after centrifugation to obtain a white precipitate, that is, obtaining an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst.

[0039] In step 1), the usage ratio of the nano-SiO2 particles to the butyl titanate is 0.5 g~1 g: 3~15 ml.

[0040] In step 1), the usage ratio of the butyl titanate to the anhydrous ethanol is: 3-10 ml: 20-50 ml.

[0041] In step 1), the mixing temperature of the nano-SiO2 particles, anhydrous ethanol and butyl titanate is 70°C to 100°C.

[0042] The usage ratio of the polyvinyl alcohol in the step 2) to the butyl titanate in the step 1) is 0.05-0.2 g: 3-15 ml.

[0043] The dosage ratio of the sodium dodecylbenzene sulfonate in the step 2) to the butyl titanate in the step 1) is 0.05-0.3 g: 3-15 ml.

[0044] The nano-SiO2 particles in step 1) are obtained by mixing anhydrous ethanol, deionized water, ammonia water and tetraethyl orthosilicate solution, stirring in a water bath at a certain temperature, and then centrifuging the suspension obtained by stirring, removing the supernatant and drying.

[0045] The volume ratio of the ammonia water, anhydrous ethanol, deionized water and tetraethyl orthosilicate solution is 3-13 ml: 20-50 ml: 1-5 ml: 1-5 ml.

[0046] The present invention will be further described below with reference to specific embodiments:

[0047] Example 1

[0048] A method for preparing an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst comprises the following steps:

[0049] Step 1: Mix 47 ml of anhydrous ethanol, 3 ml of deionized water, 3 ml of aqueous ammonia, and 3 ml of tetraethyl orthosilicate solution thoroughly, and stir at 1100 rpm for 3 h in a 60°C water bath.

[0050] Step 2: Centrifuge the suspension obtained in step 1, remove the supernatant, wash the white precipitate with ethanol, and centrifuge again; repeat the above steps two to three times: finally, vacuum dry the obtained particles at 60°C for 10 hours.

[0051] Step 3: Place 0.1 g of SiO2 particles obtained in step 2 in a beaker containing 35 ml of anhydrous ethanol and 10 ml of butyl titanate in an oil bath at 200°C, slowly drop 10 ml of deionized water into the mixed solution, add 0.1 g of polyvinyl alcohol (PVA), and continue stirring for 4 h.

[0052] Step 4: Centrifuge the suspension obtained in step 3, remove the supernatant, wash the precipitate with ethanol, and centrifuge again; repeat the above steps two to three times, and finally dry at 80°C to obtain a white precipitate, thereby obtaining an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst.

[0053] Example 2-12

[0054] Compared with Example 1, Example 2-12 is different in that the volumes of anhydrous ethanol, deionized water, ammonia water and tetraethyl orthosilicate in step 1 are different. The specific experimental conditions and parameters and the performance of the prepared SiO2@TiO2 core-shell structure catalyst are shown in Table 1.

[0055] Table 1

[0056]

[0057] It can be seen from the results of Examples 1-12 that the nano-SiO2 particles prepared under different material ratios will affect the catalytic performance of the core-shell structure catalyst prepared subsequently.

[0058] Examples 13-19

[0059] Compared with Example 1, Examples 13-19 differ in that the volumes of anhydrous ethanol, butyl titanate, deionized water and polyvinyl alcohol in step 3 are different. The specific experimental conditions and parameters and the performance of the prepared SiO2@TiO2 core-shell structure catalysts are shown in Table 2.

[0060] Table 2

[0061]

[0062] From the results of Example 14 and Examples 13, 15-19, it can be seen that the optimal ratio of anhydrous ethanol, butyl titanate, deionized water, and polyvinyl alcohol is (35ml:10ml:10ml:0.1g). Increasing butyl titanate and polyvinyl alcohol can increase the absorbance of the prepared catalyst. When the content of polyvinyl alcohol is constant, the increase in the content of butyl titanate leads to the thickening of TiO2 wrapped on the surface of SiO2, which is conducive to the total reflection of light, increasing the temperature of the catalytic system, and reducing the band gap of TiO2, thereby promoting the absorption of light. When the content of butyl titanate is constant, the absorbance increases with the increase of the content of polyvinyl alcohol. Since polyvinyl alcohol has a dispersing effect, it reduces the agglomeration of the core-shell catalyst, makes the catalyst have a more uniform structure, and increases its specific surface area, thereby promoting the improvement of catalytic performance.

[0063] Examples 20-29

[0064] Compared with Example 1, Examples 20-29 differ in that the usage ratios of nano-SiO2 particles and butyl titanate in step 3 are different. The specific experimental condition parameters and the performance of the prepared SiO2@TiO2 core-shell structure catalysts are shown in Table 3.

[0065] Table 3

[0066]

[0067] It can be seen from the results of Examples 20-29 that when the content of SiO2 is constant, as the content of butyl titanate increases, the absorbance of the prepared core-shell catalyst increases.

[0068] Embodiment 30

[0069] A method for preparing an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst comprises the following steps:

[0070] Step 1: Mix 47 ml of anhydrous ethanol, 3 ml of deionized water, 3 ml of aqueous ammonia, and 3 ml of tetraethyl orthosilicate solution thoroughly, and stir at 1100 rpm for 3 h in a 60°C water bath.

[0071] Step 2: Centrifuge the suspension obtained in step 1, remove the supernatant, wash the white precipitate with ethanol, and centrifuge again; repeat the above steps two to three times: finally, vacuum dry the obtained particles at 60°C for 10 hours.

[0072] Step 3: Place 0.1 g of SiO2 particles obtained in step 2 in a beaker containing 35 ml of anhydrous ethanol and 10 ml of butyl titanate in an oil bath at 200°C, slowly drop 10 ml of deionized water into the mixed solution, add 0.1 g of sodium dodecylbenzene sulfonate, and continue stirring for 4 h.

[0073] Step 4: Centrifuge the suspension obtained in step 3, remove the supernatant, wash the precipitate with ethanol, and centrifuge again; repeat the above steps two to three times, and finally dry at 80°C to obtain a white precipitate, thereby obtaining an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst.

[0074] Examples 31-36

[0075] Compared with Example 1, Examples 30-36 differ in that the volumes of anhydrous ethanol, butyl titanate, deionized water and sodium dodecylbenzene sulfonate in step 3 are different. The specific experimental conditions and parameters and the performance of the prepared SiO2@TiO2 core-shell structure catalysts are shown in Table 4.

[0076] Table 4

[0077]

[0078] From the results of Examples 30-36, it can be seen that the addition of sodium dodecylbenzene sulfonate has the same effect as polyvinyl alcohol.

[0079] Experimental Example 1

[0080] The amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst prepared by the above method of the present invention was subjected to a photocatalytic test. The test used 17β-estradiol as the target pollutant, a xenon lamp as the light source, and the amount of the amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst used was 0.5 g.

[0081] It should be noted that the above-mentioned light source can be any one of a natural light source containing ultraviolet light and / or visible light band, a xenon lamp, an ultraviolet lamp and an LED lamp.

[0082] like Figure 3 As shown, the amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst prepared by the present invention can obtain a good reflection effect, with an absorbance of 0.25 for visible light with a wavelength of 400nm and an absorbance of 0.55 for ultraviolet light with a wavelength of 300nm. Compared with the traditional photocatalyst P25 ( Figure 3 P25 is titanium dioxide particles of mixed phases of anatase crystals and rutile crystals with an average particle size of 25 nanometers, and its absorbance for visible light with a wavelength of 400 nm is 0.1.

[0083] like Figure 4 As shown in the figure, the photocatalytic degradation rate and degradation rate of the amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst prepared by the present invention can be effectively improved when photocatalytic degradation is carried out. When the degradation time reaches 90min and 120min, the degradation rate can reach 84% and 92%. The degradation rate is also very outstanding. When the degradation rate reaches 60%, the time used is about 27min, while P25 ( Figure 4 The time required for P25, which is a titanium dioxide particle with a mixed phase of anatase crystal and rutile crystal and an average particle size of 25 nanometers, is 90 minutes, which is 2 times shorter.

[0084] In summary, the present invention can promote the loading of amorphous TiO2 in the outer layer of SiO2 microspheres by adding polyvinyl alcohol or sodium dodecylbenzene sulfonate, so that TiO2 can be densely coated in the outer layer of SiO2 microspheres, and then the prepared SiO2@TiO2 core-shell structure catalyst can obtain a near-total reflection effect, improve the reflectivity of light such as ultraviolet light, and then improve the photocatalytic effect on organic pollutants. In addition, in practical applications, a better reflection effect can be obtained, the absorbance for visible light with a wavelength of 400nm is 0.25, and the absorbance for ultraviolet light with a wavelength of 300nm is 0.55; when the degradation time reaches 90min and 120min, the degradation rate can reach 84% and 92%, respectively, which is significant in photocatalytic degradation effect compared with traditional P25.

[0085] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst for photocatalytic degradation of organic pollutants, characterized in that: At least the following steps are included: 1) Mix nano-SiO2 particles with anhydrous ethanol and butyl titanate at 70℃~100℃; 2) adding deionized water and polyvinyl alcohol, or adding deionized water and sodium dodecylbenzene sulfonate, to the mixed solution of step 1) and stirring for a certain period of time to obtain a suspension; 3) Centrifuging the suspension in step 2), removing the supernatant, washing the precipitate, centrifuging again, and finally drying the precipitate after centrifugation to obtain a white precipitate, that is, obtaining an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst; In step 1), the usage ratio of the nano-SiO2 particles to the butyl titanate is: 0.5g~1g:3~15ml; In step 1), the usage ratio of the butyl titanate to the anhydrous ethanol is: 3-10 ml: 20-50 ml.

2. The preparation method according to claim 1, characterized in that: The usage ratio of the polyvinyl alcohol in the step 2) to the butyl titanate in the step 1) is 0.05-0.2 g: 3-15 ml.

3. The preparation method according to claim 1, characterized in that: The dosage ratio of the sodium dodecylbenzene sulfonate in the step 2) to the butyl titanate in the step 1) is 0.05-0.3 g: 3-15 ml.

4. The preparation method according to claim 1, characterized in that: The nano-SiO2 particles in step 1) are obtained by mixing anhydrous ethanol, deionized water, ammonia water and tetraethyl orthosilicate solution, stirring in a water bath at a certain temperature, and then centrifuging the suspension obtained by stirring, removing the supernatant and drying.

5. The preparation method according to claim 4, characterized in that: The volume ratio of the ammonia water, anhydrous ethanol, deionized water and tetraethyl orthosilicate solution is 3-13 ml: 20-50 ml: 1-5 ml: 1-5 ml.

6. Use of an amorphous TiO2-based SiO2@TiO2 core-shell structure catalyst for photocatalytic degradation of organic pollutants prepared by the method according to any one of claims 1 to 5 in photocatalytic degradation of organic pollutants.

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