Preparation method of high-purity titanium dioxide

Abstract

The invention discloses a preparation method of high-purity titanium dioxide, which is characterized by comprising the following steps: (1) preparing a titanium solution: slowly adding a titanium tetrachloride solution into deionized water to obtain the titanium solution; (2) heat-preservation hydrolysis: adding an acidic dispersant into the titanium liquid obtained in the step (1), stirring and mixing uniformly at room temperature, heating to 80-85 DEG C, preserving heat, and carrying out hydrolysis reaction for 1-2 hours to obtain hydrolysis slurry; (3) obtaining a precursor: cooling, aging, filtering, washing and drying the hydrolyzed slurry obtained in the step (2) to obtain a metatitanic acid precursor; and (4) calcining: calcining the metatitanic acid precursor obtained in the step (3) at 400 DEG C to obtain the high-purity titanium dioxide. According to the preparation method of the high-purity titanium dioxide, provided by the invention, the high-purity (greater than or equal to 99.9%) titanium dioxide is prepared under mild process conditions of low-temperature hydrolysis and low-temperature calcination, the product yield reaches about 90%, and the obtained high-purity titanium dioxide is spherical titanium dioxide with a rutile structure and has good dispersity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterial preparation, and more particularly to a preparation method of high-purity titanium dioxide. BACKGROUND

[0002] Titanium dioxide (TiO2), commonly known as titanium white powder in industry, is a white inorganic functional material with excellent performance. The substance is a white powder with no smell and taste, soft texture, stable chemical properties, insoluble in water, dilute inorganic acid and organic solvents, slightly soluble in alkali, and soluble in concentrated sulfuric acid. Its unique physical and chemical properties make it an important raw material indispensable in modern industry. In recent years, with the continuous improvement of the performance requirements of materials, the excellent photochemical properties of titanium dioxide have made it widely used in high-end manufacturing, electronic components and catalysis. Especially in electronic components: resistance (thermistor, pressure-sensitive resistor VDR), capacitance (multilayer ceramic capacitor MLCC), inductance, piezoelectricity (piezoelectric ceramic), circuit board, integrated circuit, etc.; battery materials: lithium battery lithium titanate negative electrode, lithium battery titanium dioxide negative electrode, lithium battery positive electrode material additive, sodium ion battery negative electrode, fuel cell separator, solar cell, etc.; glass: glass additive, glass colorant, optical glass, microcrystalline glass, special glass, etc. and titanium dioxide film: vacuum sputtering film, vacuum evaporation film, etc. show irreplaceable important value.

[0003] However, the application of titanium dioxide has high requirements for its purity and impurity content. Generally, the purity of high-purity titanium dioxide is 99.0-99.9%, and the higher the purity, the more stable the performance of the product containing titanium; harmful impurities in titanium dioxide will have adverse effects on the subsequent finished products, especially silicon, aluminum, iron and other elements which have a fatal impact on the quality of the finished products.

[0004] In recent years, the main methods for producing titanium dioxide at home include gas phase method and liquid phase method. The gas phase method has become a research hotspot in the industry because of its excellent product quality and high degree of automation. At present, the gas phase method is used to produce high-purity electronic-grade titanium dioxide. In order to ensure uniform particle size and continuous operation of the oxidation reactor, a cooling device is often added at the tail of the high-temperature oxidation furnace to cool down the product. However, this will introduce impurities such as potassium, chlorine, and sodium ions. In order to minimize the insoluble impurities in high-purity titanium dioxide, inorganic surface treatment cannot be performed in the post-treatment process, which makes it difficult to form filter cake and weakens the impurity removal capacity during the washing process. The liquid phase method is a widely used method for preparing ultra-fine powder in laboratories and industries. The advantages of the liquid phase method mainly include good surface activity, wide raw material sources, low industrial production cost, simple equipment, and easy scale-up. However, this method also has some disadvantages, such as the difficulty in precisely controlling the size and morphology uniformity of the particles, and the tendency of particle agglomeration during the subsequent drying and high-temperature treatment stages, which reduces the dispersion performance of the product and adversely affects its practical application and application fields.

[0005] To solve these problems, homogeneous precipitation method, hydrothermal method, hydrolysis method, and microemulsion method can be introduced to control the particle size and size distribution. Some studies have reported the preparation of nano-titanium dioxide by hydrolysis method, mainly using titanium tetrachloride as raw material, and controlling the hydrolysis conditions such as temperature, pressure, pH value, and reaction time to control the particle size and morphology of titanium dioxide.

[0006] Chinese patent CN117819598 discloses a method for preparing high-purity titanium dioxide. The specific steps include: slowly adding titanium tetrachloride with a purity of ≥99.99% after rectification into a hydrochloric acid solution, and then standing to obtain a first hydrolysis material; mixing the first hydrolysis material with water and reacting under certain conditions, then washing the filter cake with water to prepare a slurry, adjusting the pH to 6.0-8.0, and then washing with water, alcohol, and calcining to obtain high-purity titanium dioxide. Although this method achieves high hydrolysis rate through the hydrolysis process, it requires two hydrolysis processes, which is relatively complex. Moreover, the conditions for the two hydrolysis processes need to be accurately controlled, and the stability of industrial production is required to be high.

[0007] Chinese patent CN109704399B discloses a kind of high dispersion rutile titanium dioxide and its preparation method.The method is to prepare metatitanic acid by hydrolysis of titanium tetrachloride as raw material in prior art, prepare titanium dioxide powder by calcination, and improve the preparation process of titanium tetrachloride solution, calcination process, and the dispersion and size uniformity of the prepared titanium dioxide particles are effectively improved by adding additives in hot water and increasing slurry aging treatment.The specific improvement method is as follows:(1) under the condition of temperature lower than 35 DEG C, the way of adding water first and then adding titanium tetrachloride is used to prepare titanium tetrachloride solution with mass concentration of 40-50wt%;(2) metatitanic acid filter cake is subjected to first calcination treatment at 200-400 DEG C, and after crushing, second calcination treatment at 500-800 DEG C is continued, and the desired rutile titanium dioxide powder is obtained by crushing;(3) the flocculating agent is polyacrylamide (0.2-0.4wt%), and the surfactant is sodium dodecyl sulfate (0.2-0.4wt%);(4) aging time is 4-10h.Although the dispersion of titanium dioxide product is improved, the energy consumption and equipment cost are significantly increased by two calcinations and two crushing;And the chloride ion content in some examples is as high as 3322ppm, which affects the product purity and application field.

[0008] Chinese patent CN114853056B discloses a preparation method of nano-sized titanium dioxide with controllable particle size.The steps are as follows:(1) titanium tetrachloride is added dropwise into deionized water, and a process control agent is added during the process, stirring, hydrolysis at 65-95 DEG C, filtration, vacuum drying, to obtain metatitanic acid precursor;The control agent is ammonium carbonate or ammonium bicarbonate;(2) the obtained metatitanic acid precursor is subjected to two-step heat treatment in air atmosphere, the first step heat treatment temperature is 350-400 DEG C, and the time is 0.5-3h;The second step heat treatment temperature is 440-480 DEG C, and the reaction time is 0.5-3h;Natural cooling to room temperature, to obtain nano-sized titanium dioxide powder.However, high-purity nano titanium dioxide obtained by this method needs to be calcined twice, and the product particle size fluctuates greatly (5-94nm) in the examples, which cannot guarantee the stability of each production batch.

[0009] For example, the existing document "Titanium Tetrachloride Low Temperature Hydrolysis Directly Preparing Rutile Type Nano Titanium Dioxide" proposes: a mixture of isopropyl alcohol: water = 1:5 is configured as a dispersant, and hydrochloric acid is used to adjust the pH value to 0.5-3, then slowly add 0.5 mol / L titanium tetrachloride solution, and add ammonia water to adjust the pH value to about 8, heat to 70℃ and hydrolyze for 3h, age for 24h, filter, wash with anhydrous ethanol for 2-3 times, and dry at 80℃ to obtain TiO2 powder. Then calcine at 300, 400℃ respectively for 2h to obtain the sample. Under this method, the rutile phase mass fraction of the precipitate product directly generated by low temperature hydrolysis is 99.24%, the morphology is oval, and the particle size is 10-30nm. However, this method hydrolyzes in alkaline conditions, the hydrolysis reaction is instantaneous, the reaction is not easy to control, the crystal size and its distribution of the prepared sample are not easy to control, the specific surface area is too large, and the purity of titanium dioxide is also low, which needs to be further improved.

[0010] Although some studies have used the relatively simple hydrolysis method to prepare titanium dioxide, the hydrolysis reaction rate is fast, which easily leads to agglomeration, forms irregular particles or wide particle size distribution, and the process conditions are relatively strict, and parameters such as pH, temperature and concentration need to be controlled, otherwise non-target crystal forms are easily generated. Therefore, it can be seen that the hydrolysis method has significant shortcomings in the control of particle size, purity and morphology of titanium dioxide. Therefore, how to prepare high-purity and well-dispersed titanium dioxide products by a simple method under the premise of synthesizing target crystal forms is a problem that needs to be solved for the existing hydrolysis method, and higher requirements are put forward for the hydrolysis process. SUMMARY

[0011] In view of the above, the present application provides a preparation method of high-purity titanium dioxide to solve the technical problems of uneven crystal size and distribution and low purity of titanium dioxide caused by instantaneous hydrolysis reaction.

[0012] The present application provides a preparation method of high-purity titanium dioxide, comprising the following steps:

[0013] (1) titanium liquid preparation: slowly add titanium tetrachloride solution to deionized water to obtain titanium liquid;

[0014] (2) low temperature hydrolysis: add an acidic dispersant to the titanium liquid obtained in step (1), stir uniformly at room temperature, heat to 80-85℃ and keep warm, and hydrolyze for 1-2h to obtain a hydrolysis slurry;

[0015] The addition of the acidic dispersant in this step is beneficial to the slow hydrolysis of the titanium liquid under acidic conditions, and the core value lies in that H + released by the acidic dispersant will inhibit the dissociation process through the common ion effect, thereby delaying the hydrolysis process.

[0016] Since the hydrolysis reaction is an endothermic process, temperature rise is conducive to accelerating the reaction rate, the temperature of the hydrolysis reaction is maintained at 80-85°C in this step, which can not only make the reaction complete within the time limit to ensure production efficiency, but also will not lead to out of control due to too fast reaction, so as to facilitate process control; at the same time, the hydrolysis is carried out at 80-85°C, so that the subsequently generated metatitanic acid is more inclined to arrange into the lattice structure of rutile phase, and then the crystal type conversion can be completed at a lower temperature in the subsequent calcination to obtain high-purity rutile titanium dioxide; in addition, at 80-85°C, in combination with the action of the dispersing agent, a large amount of TiO2 crystal nucleus generated by the hydrolysis of the titanium liquid can stably exist and slowly and uniformly grow, so as to facilitate the subsequent obtaining of spherical titanium dioxide with good dispersity. If the temperature is lower than 80°C, the reaction rate of the hydrolysis reaction will be too slow, and the hydrolysis will be incomplete, resulting in low yield; if the temperature is higher than 85°C, the hydrolysis reaction will be accelerated sharply, a large amount of TiO2 crystal nucleus will be generated instantaneously and grow rapidly, the reaction is difficult to control, and hard agglomeration between particles is prone to occur, finally irregular-shaped titanium dioxide is obtained.

[0017] The time of the hydrolysis reaction in this step is set to 1-2h, which can ensure that the hydrolysis reaction is complete and the maximum product yield is obtained; if the time of the hydrolysis reaction is less than 1h, the reaction will not be complete, resulting in low product yield; if the time of the hydrolysis reaction is more than 2h, the generated TiO2 particles will grow or agglomerate excessively, affecting the morphology of the finally obtained titanium dioxide.

[0018] In summary, the three of acidic dispersing agent, hydrolysis temperature and hydrolysis time synergistically act together to jointly regulate the hydrolysis process and product characteristics: the acidic environment inhibits the hydrolysis rate through the common ion effect, promotes uniform nucleation and electrostatic stability, and prevents agglomeration; the suitable temperature not only ensures that the reaction is fully completed, but also guides the metatitanic acid to form the rudiment of rutile phase, which is beneficial to the low-temperature crystal type conversion in the later stage; sufficient time ensures that the hydrolysis is complete and the TiO2 particles grow uniformly into spherical shape.

[0019] (3) obtaining a precursor: cooling, aging, filtering, washing and drying the hydrolysis slurry obtained in step (2) to obtain a metatitanic acid precursor;

[0020] (4) low-temperature calcination: calcining the metatitanic acid precursor obtained in step (3) at 400°C to obtain high-purity titanium dioxide; wherein the high-purity titanium dioxide is spherical titanium dioxide with rutile structure.

[0021] The concentration of the titanium liquid in the step (1) is 0.5-1.0 mol / L. In this step, the concentration of the titanium liquid is kept at 0.5-1.0 mol / L, which can produce appropriate and uniform crystal nucleus when the titanium liquid is hydrolyzed, and these crystal nucleus can be synchronously and slowly grown to form metatitanic acid with uniform particle size and good crystallization, which prepares for obtaining titanium dioxide with uniform particles and good dispersibility. In addition, the concentration range of 0.5-1.0 mol / L of the titanium liquid ensures that there is enough space between the initial TiO2 particles produced by hydrolysis, and under the action of the dispersant, the dispersant is effectively adsorbed on the surface of each TiO2 particle to form a stable space protection layer, which maximally inhibits the hard agglomeration between particles. If the concentration of the titanium liquid is less than 0.5 mol / L, the reaction rate of the hydrolysis reaction will be low, the number of TiO2 nucleation generated will be small, and the final obtained titanium dioxide will have a larger particle size and a wider distribution. If the concentration of the titanium liquid is greater than 1.0 mol / L, the hydrolysis reaction will be too violent, a large number of TiO2 crystal nucleus will be generated in a short time, the particle spacing will be small, and serious particle agglomeration will be formed. In addition, it is more difficult to remove impurities such as chloride ions by washing under high concentration, and the morphology and purity of the final obtained titanium dioxide will be affected.

[0022] In the step (2), the dispersant is citric acid, and the addition amount of the dispersant is 1%-2% of the total titanium mass (calculated as TiO2) in the titanium liquid. Citric acid is a small organic molecule that can be adsorbed on the surface of TiO2 particles through carboxyl groups. Its molecular chain forms an organic protective film around the particles, producing a steric hindrance effect to prevent particles from colliding with each other, thereby effectively inhibiting the hard agglomeration of particles. In addition, citric acid is a low-temperature decomposition type of organic acid that can be completely decomposed into CO2 and H2O and volatilized during subsequent calcination. In this step, the addition amount of the dispersant is 1%-2% of the total titanium mass (calculated as TiO2) in the titanium liquid, which can ensure that a sufficient number of citric acid molecules completely cover the surface of all generated TiO2 particles, which is beneficial to uniform nucleation and ordered growth of crystals, so that the final obtained titanium dioxide has a uniform particle size. If the addition amount of the dispersant is less than 1%, the coverage of the dispersant will be insufficient, which will lead to hard agglomeration of particles. If the addition amount of the dispersant is greater than 2%, the excess dispersant will cover the surface of the particles, which will inhibit the hydrolysis reaction.

[0023] In the step (3), the aging is performed under natural cooling conditions.

[0024] In the step (3), the aging time is 8-12 h. In this step, the aging time is set to 8-12 h, which is beneficial to the transformation of amorphous or metastable substances into stable rutile crystal structure, and eliminates the internal micro stress and crystal defects of the particles, so that the final obtained titanium dioxide has a refined particle size distribution and a more uniform particle morphology.

[0025] The calcination time in the step (4) is 1-2 h. The temperature for the calcination in this step is set at 400 DEG C, and the calcination time is set at 1-2 h. The metatitanic acid precursor prepared based on the above-mentioned titanium liquid preparation, low-temperature hydrolysis and precursor obtaining step has preliminarily possessed the rutile crystal structure characteristic. The low-temperature calcination (400 DEG C) in this step only causes the 'dehydration-crystallization' reaction, and the macro-morphology framework of the spherical metatitanic acid is completely retained. Meanwhile, the added citric acid is decomposed; the calcination time is set at 1-2 h, so as to ensure the completion of the crystal type conversion and impurity removal process. If the calcination time is less than 1 h, the crystal type conversion cannot be completed, and part of the anatase phase and amorphous component will be remained in the final obtained titanium dioxide product. Meanwhile, the impurity removal is not thorough, the citric acid can not be completely decomposed and volatilized, so that the carbon residue exists; if the calcination time is more than 2 h, the sintering between the particles will occur, the hard agglomerates which are difficult to disperse are formed, and the high-purity titanium dioxide with good dispersibility cannot be obtained.

[0026] The purity of the high-purity titanium dioxide is greater than or equal to 99.9%.

[0027] The beneficial effects of the present application are as follows:

[0028] The present application prepares the high-purity titanium dioxide through the mild process conditions of low-temperature hydrolysis and low-temperature calcination. The product is the spherical titanium dioxide with the rutile structure, and has good dispersibility.

[0029] (1) The present application realizes the accurate control of the purity, crystal type and crystal grain size of the titanium dioxide by accurately controlling the key process parameters such as the titanium liquid concentration, dispersant amount, hydrolysis temperature and time, aging time and calcination time, and solves the technical problems of uneven particle size and poor dispersibility of the product in the prior art.

[0030] (2) The present application adopts the mild process conditions of low-temperature hydrolysis and low-temperature calcination, avoids the harsh reaction conditions of high temperature and high pressure required in the traditional method, greatly reduces the energy consumption and production cost, and significantly improves the process safety and operation simplicity.

[0031] (3) The process flow of the present application is simple, and the reaction conditions are easy to control, which meets the needs of industrial production and is conducive to promoting the wide application of the high-purity titanium dioxide material. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the XRD pattern of the titanium dioxide prepared by the preparation method of the high-purity titanium dioxide provided in the embodiment 4 of the present application;

[0033] Figure 2 is the SEM image of the titanium dioxide prepared by the preparation method of the high-purity titanium dioxide provided in the embodiment 4 of the present application;

[0034] Figure 3 SEM image of titanium dioxide prepared by the preparation method of high-purity titanium dioxide provided by Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0035] The embodiments of the present application will be described in more detail below. The present application can be implemented in various forms and should not be interpreted as being limited to the embodiments set forth herein, which are provided for a more thorough and complete understanding of the present application. It should be understood that the embodiments of the present application are for exemplary purposes only and are not intended to limit the scope of protection of the present application.

[0036] The term "comprising" used in the present application is open and inclusive, i.e., "including but not limited to". The term "according to" is "at least partially according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment". Related definitions of other terms will be given in the following description.

[0037] All embodiments of the present application are implemented according to the following technical solutions to prepare high-purity titanium dioxide. The specific conditions of different embodiments are referred to Table 1, and the specific steps include:

[0038] (1) Preparation of titanium liquid: slowly add titanium tetrachloride solution to deionized water to prepare titanium liquid with a concentration of 1.0 mol / L, and stir uniformly;

[0039] (2) Hydrolysis under insulation: add a dispersing agent to the titanium liquid obtained in step (1), the dispersing agent is citric acid, and the addition amount is 1% of the total titanium mass (calculated as TiO2) in the titanium liquid. After stirring and mixing uniformly at room temperature, heat to 85℃ and keep warm, and carry out hydrolysis reaction for 1h to obtain hydrolysis slurry;

[0040] (3) Obtain precursor: naturally cool the hydrolysis slurry obtained in step (2) to room temperature, age for 12h under the condition of natural cooling, then perform suction filtration, and wash with deionized water to remove residual chloride ions, and dry the filter cake to obtain metatitanic acid precursor;

[0041] (4) Calcination: calcine the metatitanic acid precursor obtained in step (3) at 400℃ for 2h to obtain high-purity titanium dioxide powder; wherein the high-purity titanium dioxide is spherical titanium dioxide with rutile structure.

[0042] Comparative Example 1: high-purity titanium dioxide is prepared without adding a dispersing agent, and the specific steps include:

[0043] (1) Preparation of titanium liquid: slowly add titanium tetrachloride solution to deionized water to prepare titanium liquid with a concentration of 0.5 mol / L, and stir uniformly;

[0044] (2) Incubation and hydrolysis: the temperature was raised to 80°C and incubated, and the hydrolysis reaction was carried out for 1 h, to obtain a hydrolysis slurry;

[0045] (3) Obtaining the precursor: the hydrolysis slurry obtained in step (2) was naturally cooled to room temperature, and aged for 8 h under the condition of natural cooling, then filtered under suction, and washed with deionized water to remove residual chloride ions, and the filter cake was dried to obtain metatitanic acid precursor;

[0046] (4) Calcination: the metatitanic acid precursor obtained in step (3) was calcined at 400°C for 1 h to obtain high-purity titanium dioxide powder;

[0047] Comparative Example 2: high-purity titanium dioxide was prepared using polyvinylpyrrolidone (PVP) as a dispersant, and the specific steps included:

[0048] (1) Preparation of titanium solution: titanium tetrachloride solution was slowly added to deionized water to prepare a titanium solution with a concentration of 0.5 mol / L, and stirred uniformly;

[0049] (2) Incubation and hydrolysis: a dispersant was added to the titanium solution obtained in step (1), the dispersant was polyvinylpyrrolidone (PVP), and the addition amount was 1% of the total titanium mass (calculated as TiO2) in the titanium solution, after stirring and mixing uniformly at room temperature, the temperature was raised to 85°C and incubated, and the hydrolysis reaction was carried out for 1 h, to obtain a hydrolysis slurry;

[0050] (3) Obtaining the precursor: the hydrolysis slurry obtained in step (2) was naturally cooled to room temperature, and aged for 10 h under the condition of natural cooling, then filtered under suction, and washed with deionized water to remove residual chloride ions, and the filter cake was dried to obtain metatitanic acid precursor;

[0051] (4) Calcination: the metatitanic acid precursor obtained in step (3) was calcined at 400°C for 1 h to obtain high-purity titanium dioxide powder; wherein the high-purity titanium dioxide was spherical titanium dioxide with rutile structure.

[0052] Comparative Example 3: high-purity titanium dioxide was prepared using a titanium solution with a concentration of 2.0 mol / L and citric acid (0.5% of the total titanium mass (calculated as TiO2) in the titanium solution), and the specific steps included:

[0053] (1) Preparation of titanium solution: titanium tetrachloride solution was slowly added to deionized water to prepare a titanium solution with a concentration of 2.0 mol / L, and stirred uniformly;

[0054] (2) Incubation and hydrolysis: a dispersant was added to the titanium solution obtained in step (1), the dispersant was citric acid, and the addition amount was 0.5% of the total titanium mass (calculated as TiO2) in the titanium solution, after stirring and mixing uniformly at room temperature, the temperature was raised to 80°C and incubated, and the hydrolysis reaction was carried out for 2 h, to obtain a hydrolysis slurry;

[0055] (3) Obtaining precursor: the hydrolysis slurry obtained in step (2) is naturally cooled to room temperature, and then aged for 10 h under the condition of natural cooling, followed by suction filtration, and washed with deionized water to remove residual chloride ions, and the filter cake is dried to obtain metatitanic acid precursor;

[0056] (4) Calcination: the metatitanic acid precursor obtained in step (3) is calcined at 400°C for 1 h to obtain high-purity titanium dioxide powder.

[0057] Table 2 is the product test results of different examples and comparative examples. As shown in Table 2, the preparation method of high-purity titanium dioxide provided by the present application, the purity of titanium dioxide prepared in examples 1-4 is greater than 99.9%, and the crystal form is all in rutile type; and the grain size of titanium dioxide prepared in examples 1-4 is 24.5 nm, 28.7 nm, 33.5 nm, 22.6 nm respectively, which shows that the titanium dioxide has a smaller grain size, and the grain size of titanium dioxide in examples 1-4 is not much different, indicating that the titanium dioxide prepared according to the method provided by the present application has good uniformity. In addition, from Table 2, the product yield of examples 1-4 is about 90%, which shows that the preparation method of high-purity titanium dioxide provided by the present application has a high product yield. In order to further confirm the crystal form of the prepared titanium dioxide, the titanium dioxide is characterized by X-ray diffraction technology, and the results are shown in Figure 1 The characteristic diffraction peak appears at 27.48° in the spectrum, which belongs to the characteristic diffraction peak of rutile titanium dioxide.

[0058] From Table 2, examples 4 and comparative example 1 are compared. Under the same conditions of titanium liquid concentration, hydrolysis temperature, hydrolysis time, aging time and calcination time, citric acid is added as a dispersant in example 4, and the amount of addition is 2% of the total titanium mass (calculated as TiO2) in the titanium liquid in example 4, and the prepared titanium dioxide has a grain size of 24.5 nm; no dispersant is added in comparative example 1, and the prepared titanium dioxide has a grain size of 52.4 nm, and the grain size of the titanium dioxide prepared in example 4 is much smaller than that in comparative example 1. In addition, combined with Figure 2 and Figure 3 , Figure 2 The SEM image of titanium dioxide prepared in example 4 is shown in Figure 2 It can be seen that the morphology of titanium dioxide prepared in example 4 is spherical, and the particles are uniform, well dispersed, and have a large specific surface area; Figure 3 The SEM image of titanium dioxide prepared in comparative example 1 is shown in Figure 3It can be seen that the titanium dioxide prepared in Comparative Example 1 presents irregular blocks and the particle agglomeration is serious, and the specific surface area is small. It can be seen that the addition of dispersant can effectively prevent particle agglomeration, refine the grain size, and increase the dispersibility of titanium dioxide particles. At the same time, the spherical morphology and good dispersibility help to improve the specific surface area of the product.

[0059] From Table 2, it can be seen that the grain sizes of the titanium dioxide prepared in Examples 1-4 are 24.5 nm, 28.7 nm, 33.5 nm, and 22.6 nm, respectively. Comparative Example 2 uses polyvinylpyrrolidone (PVP) as a dispersant, and the addition amount is 1% of the total titanium mass (calculated as TiO2) in the titanium liquid in Comparative Example 2. The grain size of the prepared titanium dioxide is 42.6 nm, which is much larger than that of Examples 1-4, which shows that compared with polyvinylpyrrolidone (PVP), citric acid can effectively inhibit the hard agglomeration of particles and is more suitable as a dispersant. In addition, the purity of the titanium dioxide prepared in Examples 1-4 is all higher than ≥99.9%, and the purity of the titanium dioxide prepared in Comparative Example 2 is 99.5%, which shows that compared with polyvinylpyrrolidone (PVP), citric acid as a dispersant can improve the purity of titanium dioxide to meet the requirements of high-purity titanium dioxide. At the same time, the product yield of Examples 1-4 is all about 90%, and the product yield of Comparative Example 2 is 88.46%, which shows that compared with polyvinylpyrrolidone (PVP), citric acid as a dispersant is beneficial to the improvement of product yield, thereby increasing the production efficiency of the product.

[0060] From Table 2, it can be seen that the product yield of the titanium dioxide prepared in Examples 1-4 is all about 90%. Comparative Example 3 reduces the addition amount of citric acid (0.5% of the total titanium mass (calculated as TiO2) in the titanium liquid) while increasing the concentration of the titanium liquid to 2.0 mol / L, and the product yield of the prepared titanium dioxide is 52.79%, which is much lower than that of Examples 1-4, which shows that too high concentration of the titanium liquid and too low amount of dispersant are not conducive to the improvement of product yield. In addition, the purity of the titanium dioxide in Examples 1-4 is all ≥99.9%, and the purity of the titanium dioxide in Comparative Example 3 is 99.15%, which shows that too high concentration of the titanium liquid and too low amount of dispersant also affect the purity of the product. It can be seen that the concentration of the titanium liquid and the amount of dispersant are both key variables affecting the product yield of titanium dioxide. Only when the concentration of the titanium liquid is maintained at 0.5-1.0 mol / L and the addition amount of the dispersant is maintained at 1%-2% of the total titanium mass (calculated as TiO2) in the titanium liquid, can the forward reaction be promoted, thereby improving the product yield and purity.

[0061] Table 1 Specific conditions of different examples

[0062]

[0063] Table 2 Product test results for different embodiments

[0064]

[0065] The above descriptions are only specific embodiments of the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, and all of them should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for producing high-purity titanium dioxide, characterized by, The method comprises the following steps: (1) titanium liquid preparation: slowly adding titanium tetrachloride solution into deionized water to obtain titanium liquid; (2) low-temperature hydrolysis: adding an acidic dispersant into the titanium liquid obtained in step (1), stirring and mixing uniformly at room temperature, heating to 80-85℃ and keeping the temperature, and carrying out hydrolysis reaction for 1-2h to obtain hydrolysis slurry; (3) obtaining precursor: cooling, aging, filtering, washing and drying the hydrolysis slurry obtained in step (2) to obtain metatitanic acid precursor; (4) low-temperature calcination: calcining the metatitanic acid precursor obtained in step (3) at 400℃ to obtain high-purity titanium dioxide; wherein the high-purity titanium dioxide is spherical titanium dioxide with rutile structure.

2. The method of producing high-purity titanium dioxide according to claim 1, characterized by, The concentration of the titanium liquid in step (1) is 0.5-1.0mol / L.

3. The method of producing high-purity titanium dioxide according to claim 1, characterized by, The acidic dispersant in step (2) is citric acid, and the addition amount is 1%-2% of the total titanium mass (calculated as TiO2) in the titanium liquid.

4. The method of producing high-purity titanium dioxide according to claim 1, characterized by, The aging in step (3) is carried out under natural cooling condition.

5. The method of producing high-purity titanium dioxide according to claim 1, characterized by, The aging time in step (3) is 8-12h.

6. The method of producing high-purity titanium dioxide according to claim 1, characterized by, The calcination time in step (4) is 1-2h.

7. The method of producing high-purity titanium dioxide according to claim 1, characterized by, The purity of the spherical titanium dioxide is ≥99.9%.

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