A method for controlling the particle size of titanium dioxide produced by hydrochloric acid process

Abstract

This invention discloses a method for controlling the particle size of titanium dioxide produced by hydrochloric acid purification. The method utilizes TiCl4 seed crystals as external seed crystals. Titanium liquid is purified using hydrochloric acid. 2.5%–10% (by weight of the purified titanium liquid) of TiCl4 seed crystals are heated to 70±1℃ and held at this temperature for 10–20 minutes. Then, under stirring, purified titanium liquid heated to the same temperature and held for the same time as the TiCl4 seed crystals is added uniformly to the TiCl4 seed crystals at a rate of 10–20 minutes to initiate a hydrolysis reaction. The titanium dioxide primary product is obtained through two micro-boiling, aging, and post-treatment steps. The preferred method is to add purified titanium liquid to 7.5% TiCl4 seed crystals for 15 minutes to obtain titanium dioxide with a particle size distribution range of 175-332 nm and a median particle size of 241 nm. This invention can better control the particle size distribution of titanium dioxide produced by hydrochloric acid method, and it is less expensive and less energy-intensive. The resulting metatitanic acid has stable quality, and the obtained titanium dioxide primary product has a narrow particle size distribution, making it a titanium dioxide product with good pigment properties.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of titanium dioxide preparation, and more particularly to a method for regulating the particle size of titanium dioxide. BACKGROUND

[0002] Titanium dioxide (TiO2) is an amphoteric oxide of white solid or powder, which has the advantages of good whiteness, strong tinting strength, strong hiding power, non-toxicity, non-pollution, strong chemical stability and the like, and is considered as the best white pigment in the world today, and is widely used in the industries of coating, chemical fiber, cosmetics, papermaking, printing ink, plastic, rubber, food and the like. At present, the industrial production methods of titanium dioxide mainly include the sulfuric acid method and the chlorination method. The sulfuric acid method has mature process technology, but the process needs to be acidolysis, hydrolysis, primary water washing, bleaching, secondary water washing, salt treatment, high-temperature calcination and post-treatment, and has long process, complex solid-liquid separation means, large amount of by-products, large consumption of sulfuric acid and water, and large environmental pollution. The chlorination method is more advanced than the sulfuric acid method in general, and has short process, but requires high quality of raw materials, needs to be imported in large amount from abroad, and needs the processes of compression, cooling and oxidation at high temperature of 1800 DEG C, which requires high equipment for the chlorination process, has large amount of waste water and waste acid, and has large dangerous coefficient. The hydrochloric acid method as a new technology has low requirement on the quality of raw materials, short process, does not need high-temperature operation, and can recycle the hydrochloric acid, which meets the national double control policy standard.

[0003] In addition, for pigment-grade titanium dioxide, the particle size and distribution are the key factors affecting the quality indexes of titanium dioxide product, and directly affect the pigment performance and application performance of titanium dioxide. The hydrolysis process is the most critical link in the production of titanium dioxide, and the factors such as the size of seed particle, the initial concentration of titanium liquid, the stirring speed, the aging time and the aging temperature in the hydrolysis process will affect the particle size of titanium dioxide product, and seriously affect the pigment performance and application performance of titanium dioxide. At present, the domestic main methods are self-grown seed hydrolysis method and external seed hydrolysis method by using sulfuric acid method, which controls the particle size, particle size distribution and crystal form of product by changing the technical parameters and reaction conditions such as hydrolysis process conditions, special salt treatment formula, calcination seed addition and calcination intensity, and heating rate, so as to affect the quality of final titanium dioxide.

[0004] For example, Chinese patent CN116332229A discloses a method for controlling the particle size and size distribution of titanium dioxide by adjusting the oxygen content in the calcination atmosphere. This invention relates to a process for preparing rutile titanium dioxide by the sulfuric acid method, which controls the particle size and size distribution of titanium dioxide by adjusting the oxygen content in the calcination atmosphere. The specific method is as follows: after acidolysis, hydrolysis, primary water washing, bleaching, secondary water washing, and salt treatment, the metatitanic acid filter cake after salt treatment is calcined from room temperature to 1015-1020°C, the flow rate of the calcination atmosphere is adjusted to 300 mL / min, the oxygen concentration is 5-16%, and the rutile conversion rate of the titanium dioxide at the end of calcination is controlled to be above 98.5%. The obtained titanium dioxide has a particle size of 0.318-0.349 μm. This invention method adjusts the oxygen concentration in the calcination atmosphere, reduces the oxygen vacancies in the anatase TiO2 lattice, and inhibits the phase transition to rutile, thereby affecting the growth rate of rutile titanium dioxide crystals and optimizing the particle size and size distribution of titanium dioxide.

[0005] For another example, Chinese patent CN107500347A discloses a method for controlling the particle size of titanium dioxide in decorative base paper, which adjusts the particle size of titanium dioxide by controlling the hydrolysis process. First, the titanium sulfate solution is preheated to 96-98°C, and the desalted water is preheated to boiling; then the preheated titanium sulfate solution is added to the preheated desalted water under stirring, and the mixture is heated to micro-boiling for hydrolysis; when the hydrolysis rate reaches 50-65%, the stirring and heating are stopped, and the mixture is allowed to mature; after maturation, the mixture is stirred and heated again to micro-boiling for hydrolysis for 160-180 min; finally, boiling desalted water is added, the total titanium concentration in the slurry is controlled to be 160-180 g / L, and the mixture is kept at micro-boiling for 50-60 min. The obtained metatitanic acid particles are uniform in size, smooth, and consistent, and the particle size of metatitanic acid is 1.2-1.5 μm. This method controls the hydrolysis rate and time by two micro-boiling and maturation processes and the control of heating temperature, which ensures the uniformity of the metatitanic acid particles, but the obtained product has a large particle size.

[0006] For example, Chinese patent CN114772636A discloses a production method for regulating the particle size of titanium dioxide. In this method, the titanium liquid is divided into two parts, specifically titanium liquid A and titanium liquid B, and preheated separately. The temperature of preheated titanium liquid A is different from that of preheated titanium liquid B. Then, preheated titanium liquid A is added to preheated alkali liquid to obtain system A, and the pH of system A is controlled. After primary aging, preheated titanium liquid B is added to obtain system B, and the pH of system B is controlled. Subsequently, secondary aging is performed to obtain hydrolysis seed crystals. The hydrolysis seed crystals are then added to preheated titanium liquid C for hydrolysis. After washing, bleaching, secondary washing, salt treatment, and calcination, titanium dioxide is obtained. The particle size of the hydrolysis seed crystals prepared by this method ranges from 2.0 to 30 nm. After adding 2.5 wt% of the hydrolysis seed crystals, hydrolysis can produce titanium dioxide with an average particle size of 150-401 nm. This invention is a self-grown seed hydrolysis method. By regulating the particle size of the hydrolysis seed crystals of the titanium liquid, the particle size of the calcined titanium dioxide is directly regulated, and the effect is relatively obvious. However, this method requires the preparation of seed crystals with different particle sizes, and the operation is relatively complex.

[0007] For example, Chinese patent CN106946287A discloses a method for precise control of the particle size of titanium dioxide primary product. In this method, the titanium liquid is preheated to 96-98°C and then added dropwise into water while stirring to perform hydrolysis. Heating is stopped when the titanium liquid reaches the gray point. Then, the titanium liquid is aged, and after aging, the titanium liquid is heated. First, it is boiled for 0.5-1.5 h, then it is slightly diluted and boiled for 2-3 h to complete hydrolysis and obtain metatitanic acid. Then, potassium hydroxide, phosphoric acid, zinc chloride or zinc oxide powder are added to the obtained metatitanic acid in sequence, and stirred uniformly to obtain salt-treated metatitanic acid. Finally, the metatitanic acid is calcined at 600-650°C for the first stage, 650-800°C for the second stage, and 800-870°C for the third stage to obtain titanium dioxide primary product. This method regulates the initial concentration of the titanium liquid, the stirring speed and the hydrolysis temperature, and then uses special salt treatment measures and calcination process to jointly regulate the particle size of the titanium dioxide primary product. This method can effectively control the average particle size of the titanium dioxide primary product within the range of 250-270 nm, and the obtained titanium dioxide has large scattering force and good optical performance, which is suitable for general-purpose titanium dioxide powder used in the field of coatings.

[0008] In summary, there are various methods for controlling the particle size of titanium dioxide on the market, such as controlling the hydrolysis speed, seed particle size, initial concentration of titanium liquid, and improving salt treatment and calcination process. However, there is no related technical literature that uses the amount of hydrolysis seed and the time of adding titanium liquid to the seed to cooperatively regulate the particle size of titanium dioxide. Moreover, titanium dioxide is basically produced using the complex sulfuric acid method. There are few cases or industrial applications of using hydrochloric acid method for hydrolysis process to prepare titanium dioxide with narrow particle size distribution and good pigment performance. SUMMARY

[0009] The application provides a method for regulating the particle size of titanium dioxide by hydrochloric acid method, which uses the amount of added hydrolysis TiCl4 seed and the time when the purified titanium liquid is added to the seed to cooperatively regulate the particle size of titanium dioxide, and the mass of metatitanic acid formed by the method is stable, the particle size distribution of the prepared titanium dioxide is narrow, and the titanium dioxide product has good pigment performance.

[0010] The application provides a method for regulating the particle size of titanium dioxide by hydrochloric acid method, which uses the amount of added hydrolysis TiCl4 seed and the time when the purified titanium liquid is added to the seed to cooperatively regulate the particle size of titanium dioxide, and the mass of metatitanic acid formed by the method is stable, the particle size distribution of the prepared titanium dioxide is narrow, and the titanium dioxide product has good pigment performance.

[0011] The purified titanium liquid is obtained by leaching a titanium ore with hydrochloric acid and separating and concentrating the titanium liquid to obtain a purified titanium liquid with a concentration of 180 g / L to 210 g / L, wherein the concentration of the purified titanium liquid is calculated based on the mass of TiO2.

[0012] The application adopts the mode of adding the purified titanium liquid to the TiCl4 seed, and first forms the seed, then after the crystal nucleus is formed, the purified titanium liquid is added to continue the hydrolysis, and the solidification of titanium occurs on the surface of the crystal nucleus. This promotes the gradual accumulation and growth of the crystal nucleus, and when the crystal nucleus reaches a certain size, it becomes a precipitate and is precipitated out. With the hydrolysis, the crystal continues to grow, which is beneficial to the formation of a product with uniform particle size and narrow distribution.

[0013] The main role of the hydrolysis seed is to act as a crystal nucleus, and the purified titanium liquid is hydrolyzed into metatitanic acid and attached to the crystal nucleus, and the crystal slowly grows. The addition of the hydrolysis seed can promote the progress of hydrolysis, improve the hydrolysis yield, and control the size and distribution of the particle size. The TiCl4 seed and the purified titanium liquid are heated to the same temperature to ensure that the hydrolysis reaction is carried out at 70±1℃, because if the preheating temperature is greater than 70±1℃, the stability of the purified titanium liquid will be affected, leading to premature hydrolysis. The preheating temperature of the purified titanium liquid and the seed directly affects the seed formation temperature, and too high or too low temperature will affect the quantity and quality of the seed. Since it is necessary to maintain the temperature of the purified titanium liquid and the seed constant during the process of adding the purified titanium liquid to the TiCl4 seed, the hydrolysis reaction is carried out at 70±1℃ to avoid uncontrolled temperature during the hydrolysis process.

[0014] The TiCl4 seed crystal with the mass of 2.5% to 10% of the mass of the purified titanium liquid is added to control the hydrolysis rate and the particle size of metatitanic acid. The ratio of the amount of the seed crystal to the purified titanium liquid determines the amount of the seed crystal. If the amount of the seed crystal is not appropriate, the amount of the seed crystal will be too much or too little, the hydrolysis rate of the purified titanium liquid will be reduced, and the particle size of metatitanic acid will be too small or too large, thereby affecting the quality of the finished product. In addition, the purified titanium liquid is added to the TiCl4 seed crystal within 10 to 20 minutes to control the number of crystal nuclei and the hydrolysis efficiency in the hydrolysis process. If the adding time is too fast, the number of crystal nuclei will be too small, the gray point of the reaction will appear too early, the hydrolysis rate will be reduced, and the particle size of metatitanic acid will be too large. If the adding time is too slow, the number of crystal nuclei will be too large, the gray point of the reaction will appear too late, the hydrolysis rate will be reduced, and the particle size of metatitanic acid will be too small, thereby affecting the quality of the finished product.

[0015] Preferably, when the mass of the TiCl4 seed crystal is 2.5% of the mass of the purified titanium liquid, the heated purified titanium liquid is added to the heated TiCl4 seed crystal at a uniform speed within 10 minutes. Preferably, when the mass of the TiCl4 seed crystal is 5% of the mass of the purified titanium liquid, the heated purified titanium liquid is added to the heated TiCl4 seed crystal at a uniform speed within 15 minutes. Preferably, the mass of the TiCl4 seed crystal is 7.5% of the mass of the purified titanium liquid, and the heated purified titanium liquid is added to the heated TiCl4 seed crystal at a uniform speed within 15 minutes. Preferably, the mass of the TiCl4 seed crystal is 10% of the mass of the purified titanium liquid, and the heated purified titanium liquid is added to the heated TiCl4 seed crystal at a uniform speed within 20 minutes.

[0016] Through experiments, the inventors found that when the mass of the TiCl4 seed crystal is 7.5% of the mass of the purified titanium liquid, and the heated purified titanium liquid is added to the heated TiCl4 seed crystal at a uniform speed within 15 minutes, the particle size distribution range of the titanium dioxide primary product prepared under this condition is the narrowest, which is 175 to 332 nm, the median particle size is 241 nm, the whiteness is the highest, which is 97.3, and the b value is the smallest, which is 2.7. At the same time, it is indicated that the crystal growth and the hydrolysis speed under this condition are the best.

[0017] In addition, the temperature is maintained at 70±1°C during the process of adding the heated purified titanium liquid to the heated TiCl4 seed crystal, and the stirring speed is controlled at 50 r / min to 200 r / min during the adding process.

[0018] The purified titanium liquid is added to the TiCl4 seed at a constant speed and the temperature is kept constant during the adding process, so as to make the crystal grow stably, and the stirring speed is controlled at 50 r / min-200 r / min, so as to make the concentration and temperature distribution in the purified titanium liquid more uniform, to ensure that the particles grow under uniform conditions, and the hydrolysis process adopts twice ripening, so as to avoid that the hydrolysis speed is too fast to cause the particle size of the hydrolysis product to be different, and make the metatitanic acid crystal particle size grow more uniformly.

[0019] In summary, the application uses TiCl4 seed as an added seed, controls the seed adding amount and the time of adding the purified titanium liquid to the TiCl4 seed to carry out the hydrolysis test, so as to achieve the purpose of better controlling the particle size distribution of the hydrochloric acid method titanium dioxide, the process is a production method of added seed hydrolysis of titanium dioxide under normal pressure with less investment and lower energy consumption, the metatitanic acid formed is stable in quality, the titanium dioxide primary product prepared has narrow particle size distribution, and the titanium dioxide product has good pigment performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Preparation process flowchart of TiCl4 seed of hydrochloric acid method titanium dioxide

[0021] Figure 2 Preparation process flowchart of hydrochloric acid method titanium dioxide hydrolysis DETAILED DESCRIPTION

[0022] 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, but rather, the embodiments are provided so that the present application can be more thoroughly and completely understood. 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.

[0023] The term "comprising" used in the present application is open inclusion, that is, "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.

[0024] Embodiments 1-16 of the present application are implemented according to the following specific steps for preparing titanium dioxide except for the different conditions indicated, including the preparation of TiCl4 seed and the hydrolysis process steps:

[0025] 1. Preparation of TiCl4 seed:

[0026] (1) Take pure TiCl4 and add it dropwise into distilled water to prepare a 260 g / L TiCl4 aqueous solution, the mass concentration of which is calculated based on TiO2;

[0027] (2) Add the prepared TiCl4 aqueous solution dropwise to the 5% NaOH solution under stirring to neutralize it to a pH of 7.0. Filter and wash the neutralized solution.

[0028] (3) After washing, the filter cake is slurried with 200ml of distilled water and 41ml of hydrochloric acid is slowly added to ensure that the system has [H+] / Ti = 0.38;

[0029] (4) Slowly heat the system to 85°C and keep it at that temperature for 30 minutes. After the temperature is maintained, add the same volume of distilled water as the system to cool it down. When the system is at room temperature, slowly add 5% NaOH solution to neutralize it so that the pH is 7.0.

[0030] (5) The obtained slurry was allowed to stand and settle, and the supernatant was removed to obtain a suspension of seed crystals, thus obtaining TiCl4 seed crystals.

[0031] 2. Hydrolysis process:

[0032] (1) First, titanium ore is leached with hydrochloric acid and titanium liquid is separated and concentrated to obtain purified titanium liquid with a concentration of 180g / L to 210g / L, wherein the concentration of purified titanium liquid is calculated based on the mass of TiO2.

[0033] (2) Preheat the purified titanium liquid from step (1) to 70±1℃ and keep it at that temperature for 10 to 20 minutes.

[0034] (3) Depending on the amount of seed crystals added, 2.5% to 10% of the mass of the purified titanium liquid TiCl4 seed crystals are heated to 70±1℃ and held for 10 to 20 minutes.

[0035] (4) Start stirring and control the stirring speed at 50r / min to 200r / min. Add the heated purified titanium liquid to the heated TiCl4 seed crystals at a uniform rate over a period of 10min to 20min. Keep the temperature at 70±1℃ during the feeding process.

[0036] (5) After the addition of materials, start heating to boiling (first boiling point), maintain a gentle boil until the solution reaches the ash point, stop stirring and heating, and let it mature for 30 minutes.

[0037] (6) Restart heating and stirring, raise the temperature to boiling (second boiling point), start timing, and maintain a gentle boil for 60 min to 120 min; (7) After the reaction is complete, cool and filter the hydrolyzed slurry, wash the filter cake with acid and water to obtain a metatitanic acid filter cake, dry the metatitanic acid, and calcine it at 800℃ to 950℃ for 30 min to 120 min to obtain the initial titanium dioxide product.

[0038] The following are examples under different conditions:

[0039] Example 1: The mass of TiCl4 seed crystals is 2.5% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 10 minutes.

[0040] Example 2: The mass of TiCl4 seed crystals is 2.5% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 15 minutes.

[0041] Example 3: The mass of TiCl4 seed crystals is 2.5% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 20 minutes.

[0042] Example 4: The mass of TiCl4 seed crystals is 5% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 10 minutes.

[0043] Example 5: The mass of TiCl4 seed crystals is 5% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 15 minutes.

[0044] Example 6: The mass of TiCl4 seed crystals is 5% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 20 minutes.

[0045] Example 7: The mass of TiCl4 seed crystals is 7.5% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 10 minutes.

[0046] Example 8: The mass of TiCl4 seed crystals was 7.5% of the mass of purified titanium liquid. The heated purified titanium liquid was added to the heated TiCl4 seed crystals at a uniform rate over a period of 15 minutes.

[0047] Example 9: The mass of TiCl4 seed crystals is 7.5% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 20 minutes.

[0048] Example 10: The mass of TiCl4 seed crystals is 10% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 10 minutes.

[0049] Example 11: The mass of TiCl4 seed crystals is 10% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 15 minutes.

[0050] Example 12: The mass of TiCl4 seed crystals is 10% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 20 minutes.

[0051] Example 13: The mass of TiCl4 seed crystals is 1.5% of the mass of purified titanium liquid. The heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform rate over a period of 15 minutes.

[0052] Example 14: The mass of TiCl4 seed crystals was 12.5% ​​of the mass of purified titanium liquid. The heated purified titanium liquid was added to the heated TiCl4 seed crystals at a uniform rate over a period of 15 minutes.

[0053] Example 15: The mass of TiCl4 seed crystals was 7.5% of the mass of purified titanium liquid. The heated purified titanium liquid was added to the heated TiCl4 seed crystals at a uniform rate over a period of 5 minutes.

[0054] Example 16: The mass of TiCl4 seed crystals was 7.5% of the mass of purified titanium liquid. The heated purified titanium liquid was added to the heated TiCl4 seed crystals at a uniform rate over a period of 25 minutes.

[0055] Through the above embodiments, the states of the titanium liquid filtration process for preparing titanium dioxide by this method are shown in Table 1, the whiteness and b-value of the initial titanium dioxide dry powder are shown in Table 2, and the particle size of the initial titanium dioxide is shown in Table 3.

[0056] Table 1 Properties of metatitanic acid

[0057]

[0058] As shown in Table 1, the filtration process of the hydrolyzed and purified titanium solution exhibited no filter breakage and almost no sedimentation. The less seed crystals added, the shorter the filtration time for the hydrolyzed and purified titanium solution. Simultaneously, with the same amount of seed crystals added, a shorter filtration time for the purified titanium solution also resulted in a shorter filtration time. The amount of seed crystals added and the filtration time determined the number of crystal nuclei formed. This indicates that too few or too many crystal nuclei in the solution, leading to the appearance of gray spots in the hydrolysis reaction too early or too late, would result in an unsatisfactory hydrolysis rate, thus affecting product quality.

[0059] Table 2 Whiteness of raw titanium dioxide

[0060]

[0061] Generally speaking, the higher the whiteness and the lower the b-value of titanium dioxide, the whiter the product will be. Titanium dioxide particles are also finer and have higher hiding power. As shown in Table 2, the titanium dioxide obtained using the method of this invention has a whiteness of 94-98 and a b-value of 2-15. The best result is achieved by adding 7.5% TiCl4 seed crystals (by mass of purified titanium liquid) and adding the heated purified titanium liquid to the heated TiCl4 seed crystals over 15 minutes. After hydrolysis and calcination, the resulting raw titanium dioxide powder has a whiteness of 97.3 and a b-value of 2.7. Conversely, by adding 7.5% TiCl4 seed crystals (by mass of purified titanium liquid) and adding the heated purified titanium liquid to the heated TiCl4 seed crystals over 5 minutes and 25 minutes respectively, the raw titanium dioxide powder has a whiteness of 96.5 and 96.7, and b-values ​​of 6.5 and 7.3 respectively. Considering that the raw titanium dioxide powder prepared under other conditions has relatively poor whiteness and b-value, this indicates that a suitable dropping rate of purified titanium liquid and the amount of seed crystals added will result in a good hydrolysis rate and the formation of suitable metatitanic acid particle size, leading to a product with high whiteness and low b-value.

[0062] Table 3 Particle size of raw titanium dioxide

[0063]

[0064] As shown in Table 3, when TiCl4 seed crystals were added at a mass of 7.5% of the purified titanium liquid mass, and the heated purified titanium liquid was added to the heated TiCl4 seed crystals over 15 minutes, the initial titanium dioxide obtained after hydrolysis and calcination had a minimum particle size distribution range of 175–332 nm and a median particle size of 241 nm. When TiCl4 seed crystals were added at a mass of 10% of the purified titanium liquid mass, and the heated purified titanium liquid was added to the heated TiCl4 seed crystals over 10 minutes, the initial titanium dioxide obtained after hydrolysis and calcination had a maximum particle size distribution range of 174–683 nm and a median particle size of 306 nm. The experimental results indicate that selecting appropriate seed crystal dosage and the dropping speed of purified titanium liquid can improve the hydrolysis reaction effect, allowing particles to grow under uniform conditions, and ultimately producing titanium dioxide products with smaller particles and narrower particle size distribution.

[0065] In summary, the purified titanium liquid obtained after purifying the hydrolyzed titanium liquid in the hydrochloric acid method for titanium dioxide production was added to TiCl4 seed crystals for hydrolysis experiments. By simultaneously controlling the amount of TiCl4 seed crystals added and the time when the purified titanium liquid was added to the TiCl4 seed crystals, the particle size of the calcined titanium dioxide can be directly controlled. The operation is simple and the effect is obvious.

[0066] 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 regulating the particle size of titanium dioxide hydrochloric acid process, after hydrolysis, acid washing, water washing, drying and calcination to obtain titanium dioxide, characterized in that, The hydrolysis reaction step comprises: (1) heating the purified titanium liquid to 70±1℃ and keeping for 10-20 minutes; (2) heating TiCl4 seed crystals with a mass of 2.5-10% of the mass of the purified titanium liquid to 70±1℃ and keeping for 10-20 minutes; (3) adding the heated purified titanium liquid to the heated TiCl4 seed crystals at a uniform speed under the conditions of a temperature of 70±1℃ and stirring for 10-20 minutes.

2. The method for regulating the particle size of hydrochloric acid process titanium dioxide according to claim 1, characterized in that, The mass of the TiCl4 seed crystals is 2.5% of the mass of the purified titanium liquid.

3. The method for controlling the particle size of hydrochloric acid process titanium dioxide according to claim 1, characterized in that, The mass of the TiCl4 seed crystals is 5% of the mass of the purified titanium liquid.

4. The method for controlling the particle size of hydrochloric acid process titanium dioxide according to claim 1, characterized in that, The mass of the TiCl4 seed crystals is 7.5% of the mass of the purified titanium liquid.

5. The method for controlling the particle size of hydrochloric acid process titanium dioxide according to claim 1, characterized in that, The mass of the TiCl4 seed crystals is 10% of the mass of the purified titanium liquid.

6. The method for regulating the particle size of titanium dioxide according to claim 1 or 2, characterized in that, The mass of the TiCl4 seed crystals is 2.5% of the mass of the purified titanium liquid, and the heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform speed for 10 minutes.

7. The method for regulating the particle size of titanium dioxide according to claim 1 or 3, characterized in that, The mass of the TiCl4 seed crystals is 5% of the mass of the purified titanium liquid, and the heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform speed for 15 minutes.

8. The method for regulating the particle size of titanium dioxide according to claim 1 or 4, characterized in that, The mass of the TiCl4 seed crystals is 7.5% of the mass of the purified titanium liquid, and the heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform speed for 15 minutes.

9. The method for regulating the particle size of titanium dioxide according to claim 1 or 5, characterized in that, The mass of the TiCl4 seed crystals is 10% of the mass of the purified titanium liquid, and the heated purified titanium liquid is added to the heated TiCl4 seed crystals at a uniform speed for 20 minutes.

10. The method for controlling the particle size of titanium dioxide according to any one of claims 1 to 5, characterized in that, The stirring speed during the process of adding the heated purified titanium liquid to the heated TiCl4 seed crystals is controlled at 50-200 r / min.

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