Method for preparing nano titanium dioxide from titanium tetrachloride

Abstract

The invention discloses a method for preparing nano titanium dioxide from titanium tetrachloride, which comprises the following steps: dissolving a dispersing agent in pure water to serve as bottom water for reaction, then respectively preheating a titanium tetrachloride solution and the bottom water and preserving heat, then slowly dropwise adding the preheated titanium tetrachloride solution into the bottom water, uniformly stirring and mixing, heating to boiling, and cooling to room temperature to obtain the nano titanium dioxide. And finally, cooling the hydrolyzed slurry, filtering, washing, drying and calcining to obtain the nanoscale titanium dioxide. A low-temperature hydrolysis method is adopted, under the conditions of low temperature and low pressure, the grain size of a nano titanium dioxide product is accurately controlled by controlling the addition amount of bottom water and the dripping speed of a titanium tetrachloride solution into the bottom water, and the particle size distribution of the product is controlled by controlling the addition amount of a dispersing agent; the particle size and the particle size distribution of the nano titanium dioxide product are accurately controlled.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide preparation technology, and more specifically, to a method for preparing nano-titanium dioxide from titanium tetrachloride. Background Technology

[0002] Nanomaterials have a wide range of applications in various fields due to their unique physical and chemical properties. Among them, nano titanium dioxide is an important inorganic functional material with excellent photocatalytic performance, ultraviolet shielding performance, photoelectric conversion performance, etc., and is widely used in solar cells, photocatalytic degradation of pollutants, cosmetics and other fields. Currently, the most common method for preparing nano-titanium dioxide powder is the sol-gel method. Specifically, using titanium alkoxide as a precursor, a titanium dioxide sol with a small crystal size and dispersed particle size is first prepared, and then dried to remove organic solvents, water, catalysts, etc., to obtain nano-titanium dioxide powder. However, during the drying process, especially during high-temperature calcination, the nano-titanium dioxide powder gradually tends to agglomerate, and even severe adhesion can occur when the calcination temperature is too high or the calcination time is too long. Therefore, the nano-titanium dioxide powder obtained after drying needs to be further ground and dispersed, for example, by introducing dispersants such as polyammonium methacrylate and γ-aminopropyltriethoxysilane. By reducing the surface energy of the powder particles and adjusting the surface charge properties of the powder particles, the dispersion characteristics of the powder in a specific dispersion solvent system can be improved. However, after dispersion treatment, the photocatalytic activity of the titanium dioxide powder is poor, significantly lower than that of the titanium dioxide sol. Therefore, other preparation methods are needed to overcome this problem.

[0003] Low-temperature hydrolysis has advantages such as mild conditions, simple equipment, and ease of large-scale production, and is widely used in the preparation of nano-titanium dioxide. The existing low-temperature hydrolysis method for preparing nano-titanium dioxide mainly uses titanium tetrachloride as raw material. By controlling the hydrolysis conditions, such as temperature, pressure, pH value, and reaction time, the particle size and morphology of the product can be controlled. Specifically, the crystal form of titanium dioxide can be adjusted by changing the reaction temperature, thereby affecting its photocatalytic activity, and the particle size of titanium dioxide can be controlled by changing the reaction time, thereby affecting its application in different fields.

[0004] For example, invention patent CN109911934A provides a method for preparing rutile titanium dioxide, including the following steps: preparing a titanium tetrachloride dispersion solution by mixing titanium tetrachloride, a dispersant, and deionized water in a weight ratio of 1-1.5:0.0001-0.001:1, wherein the dispersant is a neutral salt formed by a polyamine amide and an acid; under stirring conditions, adding an ammonium polyacrylate solution dropwise to the titanium tetrachloride dispersion solution at a molar ratio of 1:1-10 to ammonium polyacrylate at 40-45 ml / h, and continuously stirring the reaction at 80-90°C for 0.5-1 hour, followed by cooling to obtain a metatitanic acid slurry; and then further processing the metatitanic acid slurry. The acid slurry undergoes solid-liquid separation to obtain a solid phase composition. This solid phase composition is then calcined at 600℃-700℃ to obtain rutile titanium dioxide with a purity ≥99.9%. This method incorporates a dispersant to ensure a uniformly dispersed raw material system, thereby guaranteeing uniform dispersion of reactants in the subsequent hydrolysis and even calcination systems, preventing agglomeration and controlling the particle size of rutile titanium dioxide from the source. The subsequent addition of ammonium polyacrylate further ensures uniform dispersion of titanium tetrachloride in the reaction system and adjusts the pH of the reaction system to a suitable level for hydrolysis, ensuring product purity. However, this method uses a large amount of dispersant, increasing the difficulty of post-processing.

[0005] For example, the invention patent with publication number CN115124072A provides a method and product for preparing high-purity nano-titanium dioxide using the sulfuric acid method, including the following steps: (1) using concentrated sulfuric acid to acid hydrolyze metatitanic acid powder to obtain an acid hydrolysate, and diluting the acid hydrolysate to obtain a titanium oxysulfate solution; (2) slowly adding the titanium oxysulfate solution to an organic dispersant solution for hydrolysis at a temperature of 30-90°C for 2-12 hours, and then aging it at a warm temperature to obtain a titanium dioxide slurry; (3) filtering and washing the titanium dioxide slurry and adjusting the pH to 8-10. After stirring and aging for 2-5 hours, ammonium sulfate is added, and the mixture is filtered and dried to obtain powder; (4) The powder obtained in step (3) is calcined at 400-700℃ to prepare high-purity nano-titanium dioxide; This method uses a relatively pure titanium oxysulfate solution for hydrolysis, without the influence of iron and magnesium ions, with a low hydrolysis temperature and low hydrolysis acidity. By controlling the hydrolysis temperature, hydrolysis time, and organic dispersant, the growth of the titanium dioxide particles obtained by hydrolysis can be controlled, and high-purity nano-titanium dioxide with good dispersibility can be obtained. However, this method is relatively complicated.

[0006] For example, the invention patent with publication number CN1248550A provides a method for preparing rutile phase titanium dioxide nanocrystals at room temperature. The method involves first adjusting the pH of an aqueous solution to between 0 and 1 using an inorganic acid, controlling the concentration of the titanium tetrachloride aqueous solution to 0.05–0.5 mol / L, then adding a polymeric surfactant, controlling the hydrolysis temperature to 40–90°C, and the time to 1–5 hours. After precipitation and aging, vacuum drying, and grinding or slight grinding, rutile phase titanium dioxide nanocrystals are obtained. This method uses a surfactant as a dispersant to ensure uniform dispersion of titanium dioxide, and controls the hydrolysis temperature and time to obtain nanoparticles with uniform particle size and no hard agglomerates, resulting in granular and columnar titanium dioxide nanocrystals with a product purity greater than 99%.

[0007] In summary, most existing technologies utilize dispersants to improve the dispersibility of titanium dioxide to control the uniformity of the final titanium dioxide particle size. The particle size is adjusted by controlling the hydrolysis temperature and time. However, due to the complexity of the hydrolysis reaction, the preparation of nano-titanium dioxide by low-temperature hydrolysis still faces some problems, such as the need for large amounts of organic solvents and surfactants and complex processes. This not only pollutes the environment but also increases the difficulty of post-processing and production costs. Therefore, how to prepare nano-titanium dioxide with uniform particle size and morphology under low-temperature and low-pressure conditions using a simple method remains a challenge. Summary of the Invention

[0008] In view of the above, the present invention provides a method for preparing nano-titanium dioxide from titanium tetrachloride, which precisely controls the grain size and particle size distribution range of the titanium dioxide product, and obtains nano-titanium dioxide with a specific particle size under low temperature and low pressure.

[0009] This invention provides a method for preparing nano-titanium dioxide from titanium tetrachloride, comprising the following steps:

[0010] (1) Add 0.05% to 0.5% of the total titanium mass of the dispersant to pure water and stir evenly to obtain bottom water;

[0011] (2) Preheat the titanium tetrachloride solution and the bottom water to 80-90°C and keep them at that temperature;

[0012] (3) The preheated titanium tetrachloride solution is added dropwise to the bottom water at a rate of 0.5 to 10 mL / min, stirred and mixed evenly, heated to boiling and kept warm to obtain hydrolyzed slurry, wherein the volume ratio of titanium tetrachloride solution to bottom water is 1:0.5 to 10.

[0013] (4) The hydrolyzed slurry is cooled, filtered, washed, dried and then calcined to obtain nano-sized titanium dioxide.

[0014] In this invention, a base water and a titanium tetrachloride solution are prepared separately, preheated separately, and then the titanium tetrachloride solution is slowly added dropwise to the base water. The preheating temperature of the base water and the titanium tetrachloride solution directly affects the seed crystal formation temperature. Too high or too low a temperature will affect the quantity and quality of the seed crystals. Too low a temperature will result in fewer seed crystals, while too high a temperature will cause the seed crystals to deactivate, ultimately affecting the particle size and yield of the product. Therefore, the preheating temperature of the base water and the titanium tetrachloride solution must be strictly controlled, and should not be too high or too low. 80-90°C is the suitable temperature range.

[0015] The titanium tetrachloride solution and the bottom water were preheated to 85°C and kept at that temperature.

[0016] Then, the preheated titanium tetrachloride solution is added dropwise to the bottom water at a dropping rate of 0.5–10 mL / min. The dropping rate affects the number and activity of the seed crystals, which in turn determines the particle size and particle size distribution of the hydrolyzed metatitanic acid. If the dropping rate is too fast, the seed crystals will not be fully matured, and the number of seed crystals will be too small, affecting particle size growth, widening the particle size distribution range, increasing the grain size, and even forming irregular morphologies, thus reducing the product yield. If the dropping rate is too slow, the number of seed crystals will increase, but prolonged maturation will reduce the activity of the seed crystals, affecting the product yield.

[0017] Furthermore, the ratio of the volume of titanium tetrachloride solution to the bottom water determines the number of seed crystals. Too much bottom water will result in too many seed crystals, while too little bottom water will result in insufficient seed crystals, thus affecting the hydrolysis rate and the particle size of metatitanic acid, which in turn affects the quality of the finished product. Therefore, it is necessary to precisely control the volume ratio of titanium tetrachloride solution to bottom water to be 1:0.5 to 10.

[0018] The volume ratio of titanium tetrachloride solution to bottom water is 1:7.

[0019] Meanwhile, the amount of dispersant added must also be appropriate. If the amount of dispersant is too small, the ion distribution on the particle surface will be uneven, the particles will not be effectively dispersed, and the probability of agglomeration will be high. If the amount of dispersant is too large, the interaction between the dispersant and the particles will be too great, making the particles easy to stick together, which is not conducive to dispersion and affects the particle size distribution of the product. Therefore, the amount of dispersant is 0.05% to 0.5% of the total titanium mass, which is conducive to the stable control of the particle size distribution of the product.

[0020] The mass of the dispersant is 0.2% of the total titanium mass.

[0021] The dispersant is one of PEG2000 and PEG20000.

[0022] Both PEG2000 and PEG20000 are long-chain molecules with strong steric hindrance and solvation effects, which can disperse particles and reduce the probability of flocculation. Among them, PEG20000 has a longer molecular chain, forming a thicker adsorption layer with a stronger steric hindrance effect. It also contains more ether bonds, resulting in stronger hydrogen bonding with water and forming a more stable solvation layer with more adsorption sites. Compared with PEG2000, it constructs a more stable dispersion barrier and can achieve better dispersion.

[0023] The calcination temperature in step (4) is 650-700℃.

[0024] The beneficial effects of this technical solution are as follows:

[0025] (1) This invention precisely controls the grain size and particle size distribution of nano-titanium dioxide products by controlling the amount of dispersant added, the amount of bottom water added, and the dropping time of titanium tetrachloride solution, thereby obtaining spherical titanium dioxide with a narrow particle size distribution range of rutile structure. It realizes the precise control of the grain size and particle size distribution of nano-titanium dioxide products by controlling the volume ratio of titanium tetrachloride solution and bottom water, the dropping time of titanium tetrachloride solution, and the amount of dispersant added, thus solving the problem of difficulty in accurately controlling the particle size and poor particle size distribution of products in the prior art.

[0026] (2) The present invention uses a low-temperature hydrolysis method with mild reaction conditions. Under low temperature and low pressure conditions, nano-titanium dioxide with uniform particle size is prepared by a simple method, which reduces production costs and safety risks.

[0027] (3) The preparation method of the present invention is simple and easy to mass-produce, which meets the needs of industrial production and is conducive to promoting the widespread application of nano-titanium dioxide materials. Attached Figure Description

[0028] Figure 1 This is a process flow diagram for preparing nano-titanium dioxide from titanium tetrachloride.

[0029] Figure 2 This is the XRD pattern of the titanium dioxide product obtained in Example 1.

[0030] Figure 3 This is a SEM image of the titanium dioxide product obtained in Example 1. Detailed Implementation

[0031] The embodiments of this application will now be described in more detail. This application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to provide a more thorough and complete understanding of the application. It should be understood that the embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0032] The process flow diagram for preparing nano-titanium dioxide from titanium tetrachloride according to the present invention is attached. Figure 1 As shown, the embodiments and comparative examples of the present invention are implemented according to the following technical solutions, specifically including:

[0033] (1) Add the dispersant to pure water and stir evenly to obtain bottom water; wherein the dispersant is one of PEG2000 and PEG20000, and its amount is 0.05% to 0.5% of the total titanium mass;

[0034] (2) Preheat the titanium tetrachloride solution and the bottom water to 85°C and keep them at that temperature; wherein the volume ratio of the titanium tetrachloride solution to the bottom water is 1:0.5 to 10.

[0035] (3) Add the preheated titanium tetrachloride solution dropwise to the bottom water at a rate of 0.5-10 mL / min, stir and mix evenly, heat to boiling, and age in boiling state to obtain hydrolyzed slurry;

[0036] (4) The hydrolyzed slurry is cooled, filtered, washed, dried, and calcined at 650-700℃ to obtain nano-sized titanium dioxide.

[0037] Table 1 shows the specific implementation conditions of the embodiments and comparative examples of the present invention. The titanium dioxide products obtained from the embodiments and comparative examples were sent for testing, and the main titanium dioxide content was greater than 99.5%. The product crystal form was rutile, as shown in the attached table. Figure 2 As shown in the XRD pattern, the grown particles are of uniform size, as shown in the attached image. Figure 3 As shown in the SEM images, the particle size distribution and particle size test results of the products obtained in the examples and comparative examples are shown in Table 2.

[0038] The grain size refers to the primary particle size of the product, and the particle size distribution refers to the secondary particle size of the product. Table 2 shows that the titanium dioxide prepared by the method of this invention has a narrower particle size distribution and a better product yield. In Comparative Example 1, the excessive dropping rate resulted in a larger grain size and particle size distribution range for the obtained titanium dioxide, leading to a lower product yield. In Comparative Example 2, the excessive amount of bottom water resulted in a smaller grain size and particle size distribution range for the obtained titanium dioxide, but also a lower product yield. This demonstrates that the method of this invention requires precise control of the volume ratio of titanium tetrachloride solution to bottom water, the dropping time of the titanium tetrachloride solution, and the amount of dispersant added to accurately control the grain size and particle size distribution of the nano-titanium dioxide product, thereby obtaining nano-titanium dioxide with better performance and yield.

[0039] In Example 1, using PEG20000 as a dispersant, and with the dispersant dosage at 0.2% of the total titanium mass, a titanium tetrachloride solution to bottom water volume ratio of 1:7, and a titanium tetrachloride solution dropping rate of 0.5 mL / min, the prepared titanium dioxide exhibited good grain size and particle size distribution range, and achieved the best product yield of 95.58%. Compared to Example 2, using PEG20000 as a dispersant resulted in increased grain size and particle size distribution range, but a decreased product yield, indicating that... PEG20000 is more effective as a dispersant in controlling the particle size and particle size distribution of the product. Compared with Example 3, Example 3 used more bottom water, resulting in smaller crystal size and particle size distribution, but the product yield was significantly reduced. This indicates that a volume ratio of titanium tetrachloride solution to bottom water of 1:7 is required to obtain nano-titanium dioxide with good crystal size, particle size distribution, and product yield. Compared with Example 4, Example 4 used less bottom water, resulting in larger crystal size and particle size distribution, but the product yield was also reduced. Similarly, This indicates that a titanium tetrachloride solution to water volume ratio of 1:7 is necessary to obtain nano-titanium dioxide with good grain size, particle size distribution, and product yield. A ratio less than or greater than 1:7 does not yield the optimal product. Compared to Example 5, Example 5, with a titanium tetrachloride solution drop rate of 10 mL / min, exhibited larger grain size and lower product yield. This demonstrates that a titanium tetrachloride solution drop rate of 0.5 mL / min is sufficient to obtain nano-titanium dioxide with good grain size, particle size distribution, and product yield. Better yield of nano-titanium dioxide; Compared with Example 6, Example 6 had a dispersant dosage of 0.5%, resulting in a wider particle size distribution and a lower product yield, indicating that the product performance is better when the dispersant dosage is 0.2% of the total titanium mass; Compared with Example 7, Example 7 had a dispersant dosage of 0.05%, which was too low, resulting in a wider particle size distribution and a lower product yield, further indicating that when the dispersant dosage is 0.2% of the total titanium mass, nano-titanium dioxide with better grain size, particle size distribution range and product yield can be obtained.

[0040] In summary, the method of this invention precisely controls the grain size and particle size distribution of nano-titanium dioxide products by precisely controlling the volume ratio of titanium tetrachloride solution to bottom water, the dropping time of titanium tetrachloride solution, and the amount of dispersant added, thus obtaining nano-titanium dioxide with better performance and yield. Among them, the titanium dioxide prepared under the following conditions—using PEG20000 as dispersant, with the dispersant amount being 0.2% of the total titanium mass, the volume ratio of titanium tetrachloride solution to bottom water being 1:7, and the dropping rate of titanium tetrachloride solution being 0.5 mL / min—has the most ideal grain size, particle size distribution range, and product yield.

[0041] Table 1. Specific Implementation Conditions of Embodiments and Comparative Examples of the Present Invention

[0042]

[0043]

[0044] Table 2. Particle size, dimensions, and product yield data of titanium dioxide prepared in the embodiments and comparative examples of the present invention.

[0045]

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A method for preparing nano-titanium dioxide from titanium tetrachloride, characterized in that, Includes the following steps: (1) Add 0.05% to 0.5% of the total titanium mass of the dispersant to pure water and stir evenly to obtain bottom water; (2) Preheat the titanium tetrachloride solution and the bottom water to 80-90°C and keep them at that temperature; (3) The preheated titanium tetrachloride solution is added dropwise to the bottom water at a rate of 0.5 to 10 mL / min, stirred and mixed evenly, heated to boiling and kept warm to obtain hydrolyzed slurry, wherein the volume ratio of titanium tetrachloride solution to bottom water is 1:0.5 to 10. (4) The hydrolyzed slurry is cooled, filtered, washed, dried and then calcined to obtain nano-sized titanium dioxide.

2. The method for preparing nano-titanium dioxide from titanium tetrachloride according to claim 1, characterized in that, The dispersant is one of PEG2000 and PEG20000.

3. The method for preparing nano-titanium dioxide from titanium tetrachloride according to claim 1, characterized in that, The mass of the dispersant is 0.2% of the total titanium mass.

4. The method for preparing nano-titanium dioxide from titanium tetrachloride according to claim 1, characterized in that, The volume ratio of the titanium tetrachloride solution to the bottom water is 1:

7.

5. The method for preparing nano-titanium dioxide from titanium tetrachloride according to claim 1, characterized in that, The titanium tetrachloride solution and the bottom water are preheated to 85°C and kept at that temperature.

6. The method for preparing nano-titanium dioxide from titanium tetrachloride according to claim 1, characterized in that, The calcination temperature mentioned in step (4) is 650-700℃.

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