Synthesis method for controlling crystal form of nano titanium dioxide

Abstract

The invention discloses a synthesis method for controlling the crystal form of nano titanium dioxide, which specifically comprises the following steps: adding a titanium source into a mixed solution of ethanol and water, hydrolyzing, uniformly stirring, centrifugally washing the precipitate, dissolving the precipitate with an acid solution to obtain a mixed solution, carrying out hydrothermal treatment on the mixed solution at 100-200 DEG C for 1-24 hours, centrifugally washing the product, and drying to obtain the nano titanium dioxide. And drying and roasting to obtain nano titanium dioxide with different crystal forms. The synthesis process is simple, the operation is easy, the repeatability is good, the prepared nano titanium dioxide crystal form can be regulated and controlled among a pure anatase type, a mixed crystal form with different anatase and rutile proportions and a pure rutile type, the product purity is high, the specific surface area is large, the grain size is small, the granularity is uniform, and the good application prospect is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic materials, and particularly relates to a synthesis method for controlling the crystal form of nano-titanium dioxide. Background Art

[0002] Nano-titanium dioxide (TiO 2 ) is a multifunctional inorganic nano-material, which has the advantages of stable properties, low cost, non-toxicity, good biocompatibility, etc., and can be widely applied in the fields of catalysts, cosmetics, biomedicine, etc. TiO 2 has three crystal structures, namely anatase type, rutile type and brookite type. The most common, useful and studied crystal forms in practical applications are anatase type and rutile type. A large number of studies have shown that the crystal structure of TiO 2 has a very important influence on its physical and chemical properties such as catalytic performance and chemical reaction activity. Therefore, regulating the crystal structure of TiO 2 to improve the performance of TiO 2 has always been a hot topic in interdisciplinary research.

[0003] Traditionally, the methods for preparing nano-TiO 2 are mainly divided into gas-phase method and liquid-phase method. The nano-TiO 2 produced by the gas-phase method has the advantages of high chemical activity, good dispersion and less agglomeration, but the production requires high-temperature conditions and has high requirements for production equipment. In contrast, the nano-TiO 2 prepared by the liquid-phase method has the advantages of controllable powder particle size, relatively low synthesis temperature, low cost, etc., and is a method widely used in laboratories and industries at present.

[0004] In the process of preparing TiO 2 by the liquid-phase method, the crystal form of TiO 2 is mainly controlled by controlling the calcination temperature and adding impurity ions. High-temperature calcination of anatase-type TiO 2 is a simple method to obtain rutile-type TiO 2 , but this method will cause the rapid growth, agglomeration and even sintering of nano-TiO 2 . Patent CN102963926A discloses a method for preparing a mixed-crystal TiO 2 powder, and controls the crystal structure change of TiO 2 through a self-propagating combustion temperature of 300-600 °C. This method has problems such as high energy consumption, poor safety and poor control of the TiO 2 crystal form. Patent CN102701277A uses ion doping to control the crystal structure of nano-TiO 2 . The doping ions not only have a large dosage, but also remain in the final product as an impurity, which may affect the nano-TiO2 has an impact on the catalytic activity, etc. Patent CN109110806A discloses a preparation method of different crystal forms of bayberry-like TiO 2 , and the prepared TiO 2 has problems such as powder agglomeration and poor dispersibility. Therefore, in this field, it is necessary to improve the synthesis method of nano-TiO 2 , especially the synthesis method for precisely controlling different TiO 2 crystal structures. SUMMARY OF THE INVENTION

[0005] Aiming at the above defects and technical needs existing in the prior art, the purpose of the present invention is to provide a synthesis method for controlling the crystal form of nano-titanium dioxide. Specifically, a titanium source is added to a mixed solution of ethanol and water, and after hydrolysis and stirring evenly, the precipitate is centrifuged and washed. The precipitate is dissolved in an acid solution to obtain a precursor solution. The precursor solution is hydrothermally treated at 100-200 °C for 1-24 h, and the product is centrifuged and washed, and different crystal forms of nano-titanium dioxide are obtained after drying and calcination, including the following steps:

[0006] (1) A titanium source is added to a mixed solution of ethanol and water, and the volume ratio of ethanol to water is 0.5-5; after stirring and hydrolysis, centrifugation is carried out to obtain a precipitate; the preferred volume ratio of ethanol to water is 1-3; the titanium source includes one or more of titanium tetrachloride, tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate;

[0007] (2) The precipitate in step (1) is dissolved in an acid solution, and the molar ratio of H + in the acid solution to Ti in the titanium source is 1-10, and a precursor solution is obtained after stirring for 1-24 h; preferably, the acid is one of hydrochloric acid, sulfuric acid, and nitric acid; preferably, the molar ratio of H + in the acid solution to Ti in the titanium source is 2-8; the preferred stirring time is 5-15 h;

[0008] (3) The precursor solution obtained in step (2) is transferred to a hydrothermal autoclave, the hydrothermal temperature is 100-200 °C, the hydrothermal time is 1-24 h, and the hydrothermally treated product is centrifuged to obtain a solid; the preferred hydrothermal temperature is 120-180 °C; the preferred hydrothermal time is 3-12 h;

[0009] (4) After the solid obtained in step (3) is dried and calcined at 200-600 °C, different crystal forms of nano-titanium dioxide are obtained; the preferred calcination temperature is 200-400 °C;

[0010] The beneficial effects of the present invention are as follows:

[0011] The synthesis process of the present invention is simple, easy to operate, and has good repeatability. The crystal form of the prepared nano-titanium dioxide can be regulated among pure anatase type, mixed crystal forms with different ratios of anatase and rutile, and pure rutile type. The product has high purity, large specific surface area, small grain size, uniform particle size, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 XRD diagrams of the nano-TiO prepared in Examples 1-5. 2

[0013] Figure 2 TEM photograph of the nano-TiO prepared in Example 1. 2

[0014] Figure 3 TEM photograph of the nano-TiO prepared in Example 2. 2

[0015] Figure 4 TEM photograph of the nano-TiO prepared in Example 3. 2

[0016] Figure 5 TEM photograph of the nano-TiO prepared in Example 4. 2

[0017] Figure 6 TEM photograph of the nano-TiO prepared in Example 5. 2 DETAILED DESCRIPTION OF THE INVENTION

[0018] The following examples will further illustrate the present invention, but the present invention is not limited to the following examples. At the same time, the examples only give some conditions for achieving this purpose, and it does not mean that these conditions must be met to achieve this purpose.

[0019] Example 1

[0020] Measure 10 mL of anhydrous ethanol and 10 mL of deionized water, mix them evenly, add 2 mL of tetrabutyl titanate dropwise thereto, stir for hydrolysis, then centrifuge to separate, and obtain a precipitate. Add 35 mL of 0.4 mol / L hydrochloric acid solution to the precipitate to dissolve and obtain a precursor solution. After stirring for 15 h, transfer the precursor solution to a hydrothermal autoclave and hydrothermally treat it at 180 °C for 12 h. After cooling, centrifuge and dry the product, and calcine it at 300 °C for 2 h to obtain nano-titanium dioxide.

[0021] Example 2

[0022] ​​​​​​Measure 10 mL of absolute ethanol and 10 mL of deionized water, mix them evenly, add 2 mL of tetrabutyl titanate dropwise thereto, stir for hydrolysis, then perform centrifugal separation to obtain a precipitate. Add 35 mL of 0.8 mol / L hydrochloric acid solution to the precipitate to dissolve and obtain a precursor solution. After stirring for 15 h, transfer the precursor solution to a hydrothermal reactor and hydrothermally treat it at 180 °C for 12 h. After cooling, centrifuge and dry the product, and calcine it at 300 °C for 2 h to obtain nano-titanium dioxide.

[0023] Example 3

[0024] Measure 10 mL of absolute ethanol and 10 mL of deionized water, mix them evenly, add 2 mL of tetrabutyl titanate dropwise thereto, stir for hydrolysis, then perform centrifugal separation to obtain a precipitate. Add 35 mL of 1.0 mol / L hydrochloric acid solution to the precipitate to dissolve and obtain a precursor solution. After stirring for 15 h, transfer the precursor solution to a hydrothermal reactor and hydrothermally treat it at 180 °C for 12 h. After cooling, centrifuge and dry the product, and calcine it at 300 °C for 2 h to obtain nano-titanium dioxide.

[0025] Example 4

[0026] Measure 10 mL of absolute ethanol and 10 mL of deionized water, mix them evenly, add 2 mL of tetrabutyl titanate dropwise thereto, stir for hydrolysis, then perform centrifugal separation to obtain a precipitate. Add 35 mL of 1.2 mol / L hydrochloric acid solution to the precipitate to dissolve and obtain a precursor solution. After stirring for 15 h, transfer the precursor solution to a hydrothermal reactor and hydrothermally treat it at 180 °C for 12 h. After cooling, centrifuge and dry the product, and calcine it at 300 °C for 2 h to obtain nano-titanium dioxide.

[0027] Example 5

[0028] Measure 10 mL of absolute ethanol and 10 mL of deionized water, mix them evenly, add 2 mL of tetrabutyl titanate dropwise thereto, stir for hydrolysis, then perform centrifugal separation to obtain a precipitate. Add 35 mL of 1.4 mol / L hydrochloric acid solution to the precipitate to dissolve and obtain a precursor solution. After stirring for 15 h, transfer the precursor solution to a hydrothermal reactor and hydrothermally treat it at 180 °C for 12 h. After cooling, centrifuge and dry the product, and calcine it at 300 °C for 2 h to obtain nano-titanium dioxide.

[0029] The nano-TiO prepared in Examples 1 to 5 2 The XRD patterns are shown in Figure 1 .

[0030] It can be seen from Figure 1 that when the concentrations of the hydrochloric acid solutions are 0.4 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, and 1.4 mol / L, the prepared TiO 2Diffraction peaks of anatase TiO appeared at positions such as 2θ = 25.3°, 37.0°, 37.9°, etc., and diffraction peaks of rutile TiO appeared at positions such as 2θ = 27.3°, 36.1°, 41.2°, etc., indicating that the prepared TiO contains both anatase and rutile crystal forms. 2 Diffraction peaks of rutile TiO appeared at positions such as 2θ = 27.3°, 36.1°, 41.2°, etc., indicating that the prepared TiO contains both anatase and rutile crystal forms. 2 Diffraction peaks of rutile TiO appeared at positions such as 2θ = 27.3°, 36.1°, 41.2°, etc., indicating that the prepared TiO contains both anatase and rutile crystal forms. 2 Diffraction peaks of rutile TiO appeared at positions such as 2θ = 27.3°, 36.1°, 41.2°, etc., indicating that the prepared TiO contains both anatase and rutile crystal forms.

[0031] According to Figure 1 the diffraction peak intensities in, calculate the contents of anatase TiO and rutile TiO in the nano-TiO prepared in Examples 1-5. The formula is as follows: 2 the diffraction peak intensities in, calculate the contents of anatase TiO and rutile TiO in the nano-TiO prepared in Examples 1-5. The formula is as follows: 2 the diffraction peak intensities in, calculate the contents of anatase TiO and rutile TiO in the nano-TiO prepared in Examples 1-5. The formula is as follows: 2 the diffraction peak intensities in, calculate the contents of anatase TiO and rutile TiO in the nano-TiO prepared in Examples 1-5. The formula is as follows:

[0032] W R = I R / (0.886I A + I R )

[0033] where I A , I R represent the diffraction peak intensities of anatase TiO at 2θ = 25.3° and rutile TiO at 2θ = 27.3° in the XRD pattern respectively, and W 2 represents the percentage content of rutile in TiO. The results are shown in Table 1. 2 represent the diffraction peak intensities of anatase TiO at 2θ = 25.3° and rutile TiO at 2θ = 27.3° in the XRD pattern respectively, and W R represents the percentage content of rutile in TiO. The results are shown in Table 1. 2 represent the diffraction peak intensities of anatase TiO at 2θ = 25.3° and rutile TiO at 2θ = 27.3° in the XRD pattern respectively, and W

[0034] Table 1 Rutile and anatase crystal form ratios and N 2 physical adsorption results of TiO in Examples 1-5 2 physical adsorption results of TiO in Examples 1-5

[0035]

[0036]

[0037] The higher the acid concentration during the synthesis process, the lower the content of rutile TiO in the product and the higher the content of anatase TiO. Table 1 also shows the N 2 physical adsorption characterization results of the TiO products prepared in Examples 1-5. As the content of anatase TiO in the product increases, the specific surface area of the product increases, the pore volume remains almost unchanged, and the pore diameter becomes smaller. 2 physical adsorption characterization results of the TiO products prepared in Examples 1-5. As the content of anatase TiO in the product increases, the specific surface area of the product increases, the pore volume remains almost unchanged, and the pore diameter becomes smaller. 2 physical adsorption characterization results of the TiO products prepared in Examples 1-5. As the content of anatase TiO in the product increases, the specific surface area of the product increases, the pore volume remains almost unchanged, and the pore diameter becomes smaller. 2 physical adsorption characterization results of the TiO products prepared in Examples 1-5. As the content of anatase TiO in the product increases, the specific surface area of the product increases, the pore volume remains almost unchanged, and the pore diameter becomes smaller. 2 physical adsorption characterization results of the TiO products prepared in Examples 1-5. As the content of anatase TiO in the product increases, the specific surface area of the product increases, the pore volume remains almost unchanged, and the pore diameter becomes smaller.

[0038] Figure 2 is the TiO prepared in Example 1 2TEM image of the product. It can be seen that the product morphology of Example 1 is a long rod-like structure with a length of 200 - 250 nm and a width of 40 - 60 nm.

[0039] Figure 3 is the TiO prepared in Example 2 2 TEM image of the product. It can be seen that the product morphology of Example 3 is a physical mixture state of a short rod-like structure with a length of 50 - 70 nm and a width of 20 - 30 nm and a spherical particle structure with a diameter of 20 - 40 nm.

[0040] Figure 4 is the TiO prepared in Example 3 2 TEM image of the product. It can be seen that the product morphology of Example 3 is a physical mixture state of a short rod-like structure with a length of 50 - 70 nm and a width of 20 - 30 nm and a spherical particle structure with a diameter of 20 - 40 nm.

[0041] Figure 5 is the TiO prepared in Example 4 2 TEM image of the product. It can be seen that the product morphology of Example 3 is a physical mixture state of a short rod-like structure with a length of 40 - 70 nm and a width of 20 - 30 nm and a spherical particle structure with a diameter of 20 - 40 nm.

[0042] Figure 6 is the TiO prepared in Example 5 2 TEM image of the product. It can be seen that the product morphology of Example 5 is mainly a spherical particle structure with a diameter of 20 - 40 nm.

Claims

1. A synthetic method for controlling the crystal form of nano-titanium dioxide, characterized in that: Add a titanium source to a mixed solution of ethanol and water. After hydrolysis and stirring evenly, centrifuge and wash the precipitate. Dissolve the precipitate with an acid solution to obtain a precursor solution. After hydrothermal treatment of the precursor solution, centrifuge and wash the product. After drying and calcination, rutile-type and / or anatase-type TiO 2 nanotitanium dioxide is obtained.

2. The method according to claim 1, characterized in that: comprises the following steps, (1) Add a titanium source to a mixed solution of ethanol and water. After stirring and hydrolyzing at a volume ratio of ethanol to water of 0.5 to 5, centrifuge to obtain a precipitate; (2) Dissolve the precipitate in step (1) in an acid solution, and the molar ratio of H + in the acid solution to Ti in the titanium source is 1 to 10. After stirring for 1 to 24 hours, a precursor solution is obtained; (3) Transfer the precursor solution obtained in step (2) to a hydrothermal autoclave. The hydrothermal temperature is 100 to 200 °C, and the hydrothermal time is 1 to 24 h. Centrifuge the product after hydrothermal treatment to obtain a solid; (4) Dry the solid obtained in step (3) and calcine it at 200 to 600 °C to obtain nano-titanium dioxide with different crystal forms.

3. The method according to claim 1, characterized in that: the titanium source in step (1) includes one or more of titanium tetrachloride, tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate; the volume ratio of the mixed solution to the titanium source is 5 to 20.

4. The method according to claim 1, characterized in that: the preferred volume ratio of ethanol to water in step (1) is 1 to 3.

5. The method according to claim 1, characterized in that: In the step (2), the acid solution is one or more of hydrochloric acid, sulfuric acid, and nitric acid; the molar concentration of the acid solution is 0.5 to 1.5 mol / L; in the preferred acid solution in the step (2), the molar ratio of H + to Ti in the titanium source is 2 to 8.

6. The method according to claim 1, characterized in that: the preferred stirring time in step (2) is 5 to 15 h.

7. The method according to claim 1, characterized in that: the preferred hydrothermal temperature in step (3) is 120 to 180 °C; the preferred hydrothermal time in step (3) is 3 to 12 h.

8. The method according to claim 1, characterized in that: the preferred calcination temperature in step (4) is 200 to 400 °C; the time is 3 to 24 h.

9. The method according to any one of claims 1 to 8, characterized in that: Roasted to obtain rutile and / or anatase TiO 2 nano-titanium dioxide; the higher the acid concentration in the synthesis process, the lower the content of rutile TiO 2 in the product, and the higher the content of anatase TiO 2 in the product.

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