A method for preparing nanoscale high-purity titanium dioxide based on self-generated seed crystal hydrolysis

Abstract

This invention discloses a method for preparing nano-sized high-purity titanium dioxide based on self-generated seed hydrolysis, belonging to the technical field of titanium dioxide preparation by self-generated seed hydrolysis. The method includes the following steps: S1: titanium liquid preparation; S2: preheating; S3: hydrolysis reaction; S4: filtration and washing; S5: calcination. In this application, ultrasonic dispersion for 15-20 minutes is used in the titanium liquid preparation stage, resulting in a suspension with particles of 100-150 nm in size, which induces hydrolysis and "delays" the nucleation stage of the titanium liquid. Preheating at 80-85°C avoids premature hydrolysis. The use of a dispersant ensures the number of hydrolysis nuclei, increases the yield of hydrolysis products, and generates nano-sized titanium dioxide with good morphology and a uniform particle size distribution of approximately 40 nm, achieving a high purity of 99.8%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nanomaterial preparation, and particularly relates to a technology for preparing titanium dioxide by self-seeding hydrolysis. BACKGROUND

[0002] Nanometer titanium dioxide is widely used in lithium / sodium batteries, functional fibers, sewage treatment, medicine and cosmetics, etc. due to its strong UV shielding effect, antibacterial and bacteriostatic properties, photocatalysis, high hardness, high transparency, good dispersion performance, and non-toxic and odorless advantages. Titanium dioxide has three crystal structures, namely, brookite, rutile and anatase. Among them, anatase titanium dioxide, as one of the three crystal phases of titanium dioxide, has a special octahedral structure, showing excellent photocatalytic and electrochemical properties. At the same time, anatase titanium dioxide has a higher band gap, is more conducive to the generation of electron holes by light excitation, and has a higher redox capacity. The common methods for preparing nanometer titanium dioxide include sol-gel method, hydrothermal synthesis method, microemulsion method, chemical precipitation method and hydrolysis method, etc. According to the standard of the Chinese High-tech Products Export Catalog, high-purity titanium dioxide has a purity of >99.8%, which is used in chemical industry, environmental protection and electronic industry.

[0003] Titanium liquid hydrolysis method can be roughly divided into two processes of crystal nucleus generation and growth. In industrial production, there are mainly two ways to generate crystal nucleus: one is to add crystal seeds, that is, to prepare crystal nucleus separately and add it into titanium liquid; the other is to prepare crystal nucleus in the existing titanium liquid. Compared with the external crystal seeds, the self-seeding method has higher efficiency and saves the production cost of crystal seeds, and it is also more convenient to control the particle size and particle shape of the generated titanium dioxide, which is an important production method at present.

[0004] Unlike the hydrolysis of salts, the hydrolysis mechanism of titanium liquid is very complex. The hydrolysis process of the self-seeding hydrolysis method in the prior art is mainly divided into induction period, hydrolysis period and mature period. The induction period is mainly the formation stage of the crystallization center, that is, the crystal nucleus. The number, properties, structure and composition of the crystal nucleus lay the foundation for the properties and composition of the final hydrolysis product, and it is the most important link in the hydrolysis process. The hydrolysis period is the growth stage of the crystal nucleus. Titanium in the form of hydrated titanium dioxide gradually precipitates and grows on the formed crystal to become hydrated titanium dioxide particles, but it is not enough to precipitate, that is, after the "gray point" is generated, the hydrolysis reaction begins to proceed rapidly. In the mature period, the hydrated titanium dioxide particles gradually agglomerate and grow to precipitate. Due to the precipitation of the solid metatitanic acid particles from the solution, the hydrolysis balance in the original solution is broken, and the hydrolysis proceeds at a relatively large speed. The titanium dioxide component in the liquid phase is continuously converted into the precipitate of solid metatitanic acid, until the end of the hydrolysis process.

[0005] Generally, the self-seeding hydrolysis method needs to prepare crystal nucleus by high-temperature preheating, that is, in the induction period of the hydrolysis process, to ensure the number of self-seeding in the initial stage of hydrolysis, while avoiding early hydrolysis of the titanium liquid in the preheating stage. The sign of early hydrolysis is the appearance of turbidity of the titanium liquid, that is, the appearance of gray spots, which is usually observed by naked eye, supplemented by time and temperature control. Because the titanium liquid will quickly hydrolyze after the appearance of gray spots, it is very difficult to control the crystal nucleus in the preparation stage, and many control parameters are required, including: preheating temperature, bottom water amount, etc. If the temperature is too high, the crystal nucleus will be hydrolyzed in large scale in advance, and if it is too low, the hydrolysis rate will be too slow and the yield will be poor; the less the amount of bottom water, the fewer the number of crystal nucleus generated, and the coarser the primary aggregated particles, the smaller the secondary aggregated particles, and the poorer the crystal grain morphology.

[0006] The Chinese patent with the application number CN201610427868.9 discloses a low-concentration hydrolysis method in the process of sulfuric acid method titanium dioxide, which comprises the following steps: (1) preheating water and adding it to the hydrolysis kettle as bottom water; (2) continuously adding 200-240 g / L high-concentration titanium liquid A and 160-199 g / L low-concentration titanium liquid B into the hydrolysis kettle within 15-25 minutes, the volume ratio of high-concentration titanium liquid A to low-concentration titanium liquid B being 1:9-20:1; (3) then operating according to the conventional hydrolysis method. The invention can reduce the concentration of titanium liquid, reduce the amount of bottom water, and reduce the production cost. However, the application needs to use two kinds of titanium liquid with different concentrations, and fails to prepare nano-titanium dioxide from self-seeding in one concentration of titanium liquid, resulting in a complicated process.

[0007] The Chinese patent with the application number CN201410225228.0 discloses a self-seeding normal-pressure hydrolysis method for sulfuric acid method titanium dioxide production, which specifically forms hydrolysis crystal nucleus by controlling the temperature, concentration and adding speed of titanium liquid in the hydrolysis tank with hot water, and controls the process conditions to complete the hydrolysis process. However, in the application, the concentration of titanium liquid used is high, the amount of bottom water is increased, and the preheating temperature mentioned in the claim of the application is high (90-96℃), which has a great possibility of causing early hydrolysis of the titanium liquid, making it difficult to control the composition and particle size of the crystal, and resulting in problems such as rough production process and poor titanium dioxide phase.

[0008] CN201110229322.X discloses a hydrolysis method for preparing high-brightness rutile titanium dioxide from low-concentration titanium liquid, which comprises preheating bottom water and titanium liquid with a concentration of 190-215 g / L at a volume ratio of 1:(4.5-6), mixing, heating the mixed system to boiling, and maintaining a micro-boiling state; when the system turns steel gray, stop the steam, stir for a period of time, continue heating and stirring to the second boiling, maintain the micro-boiling state of the system for a period of time, slowly add dilute water to the system, and maintain the micro-boiling state of the whole system until the hydrolysis is completed; the invention can reduce the concentration of titanium liquid, reduce the amount of bottom water, and reduce the production cost. Although the application can prepare titanium dioxide from low-concentration titanium liquid and reduce the amount of bottom water, the preheating temperature (90-98℃) in the application is very close to the boiling point (100℃), and the concentrated titanium liquid is also added to the bottom water to prepare the crystal seeds at a lower concentration and a higher temperature. The titanium liquid almost inevitably undergoes premature hydrolysis at a lower concentration and a higher temperature, even if the hydrolysis and precipitation are dissolved with the addition of concentrated titanium liquid, but due to the complex hydrolysis process of titanium dioxide, the precipitation is only partially dissolved, and a small amount of hydrolysis product still exists in the titanium liquid, resulting in poor product appearance and low yield of titanium dioxide. Therefore, the application does not indicate how to control the appearance of the final product in the process of preparing titanium dioxide by the autogenous crystal seed hydrolysis method.

[0009] In summary, the above patents all mention that titanium dioxide can be prepared by the autogenous crystal seed atmospheric hydrolysis method, and the amount of bottom water can be reduced by controlling the feeding process, titanium liquid concentration and other process conditions. However, a higher preheating temperature is needed to generate sufficient crystal nuclei, and a higher temperature can easily induce the growth process of the crystal nuclei, that is, the premature hydrolysis of the titanium liquid, particle agglomeration, making it difficult to control the appearance of titanium dioxide and reducing the yield. Therefore, how to generate sufficient crystal seeds to induce the subsequent hydrolysis process while effectively avoiding premature hydrolysis, and then generate high-purity nanoscale titanium dioxide with good appearance, has become a technical problem to be solved by those skilled in the art. SUMMARY

[0010] In view of the problems in the process of preparing titanium dioxide by the autogenous crystal seed atmospheric hydrolysis method, that is, a higher preheating temperature is generally needed to generate sufficient crystal seeds to induce the late hydrolysis, resulting in difficult control of the appearance of the crystals, the first purpose of the present application is to preheat the titanium liquid at a lower preheating temperature, so that the titanium liquid can generate sufficient crystal seeds without premature hydrolysis of the titanium liquid.

[0011] The second object of the present application is to provide a method for preparing nanoscale high-purity titanium dioxide based on self-seeding hydrolysis, which has simple operation and high yield, and can obtain nanoscale anatase titanium dioxide with a particle size of 40-60 nm, a purity of more than 99.8%, and a maximum of 99.9%, and a low content of main metal impurities.

[0012] The technical scheme adopted by the present application to solve the technical problems is:

[0013] The method for preparing nanoscale high-purity titanium dioxide based on self-seeding hydrolysis comprises the following steps: S1: titanium liquid preparation; S2: preheating; S3: hydrolysis reaction; S4: filtration and washing; and S5: calcination. In the step S1, titanyl sulfate and water are mixed and ultrasonically dispersed for 15-20 min to obtain a suspension with a particle size of 100-150 nm, and then a titanium liquid is obtained by water bath heating, wherein the concentration (calculated based on TiO2) of the titanium liquid is 1-3 mol / L. In the step S2, a dispersant is added to water for preheating to obtain a dispersion liquid, and the titanium liquid and the dispersion liquid are separately preheated, and the preheating temperature is 80-85℃. In the step S3, the titanium liquid and the dispersion liquid are mixed to obtain a mixed liquid, and before the hydrolysis reaction of the mixed liquid, the system is dispersed with growth units Ti(OH) + (4- n n) (n=1, 2, 3, 4, 5, 6), and the particle size of the particles in the mixed liquid is 0.5-2 nm.

[0014] From the perspective of micro-dynamics, the nucleation mechanism of crystals mainly includes two processes of formation of growth units and connection between the growth units to form crystal nuclei. In the process of preparing titanium dioxide by self-seeding hydrolysis, the formation of growth units is mainly Ti 4+ hydrolysis to form Ti(OH) x and H + This process can also be carried out at low temperature (preheating temperature lower than 90℃), but since the system is acidic at this time, according to the basic knowledge of reversible reaction, the generated Ti(OH) x is less, that is, the number of nascent seeds is not large. The preheating temperature can affect the relative crystallization strength of the generated crystal nuclei, and as the temperature rises, the energy of the reaction system also rises, which can promote the generation of crystal nuclei. Therefore, the traditional self-seeding hydrolysis method needs a high preheating temperature to ensure the number of generated crystal nuclei.

[0015] In the titanium liquid preparation stage of S1 of the present application, the mixture of titanyl sulfate and water is first subjected to ultrasonic dispersion, and then heated in water bath until titanyl sulfate is dissolved to obtain the titanium liquid. The temperature required in this process is relatively low. The temperature of the whole titanium liquid system during the preheating stage of S2 does not induce early hydrolysis. When ultrasonic dispersion is used for dissolution, titanyl sulfate can be completely dissolved in water. At a relatively low preheating temperature, only a small amount of crystal nucleus can be generated in the titanium liquid, but a large amount of growth base Ti(OH) + (4- n n) (n = 1, 2, 3, 4, 5, 6), mainly Ti(OH) 2 6 - , with a concentration of about 170 g / L (calculated based on TiO2), to induce the subsequent high-temperature hydrolysis. The ultrasonic dispersion of the "titanium liquid" in advance enables titanyl sulfate to be well dissolved and dispersed in the aqueous solution, which is beneficial to the generation of more "nuclei" in the subsequent hydrolysis reaction, increases the nucleation rate, and effectively reduces the particle size of the subsequent hydrolysis product. In addition, the cavitation effect of ultrasonic waves continuously impacts the granular titanyl sulfate, making its internal microstructure more prone to generate crystal nucleus. Before the rapid hydrolysis of S3 occurs, a small amount of crystal nucleus and a large amount of growth base in the titanium liquid rapidly form "nuclei" at a sufficient temperature, and the hydrolysis reaction begins to rapidly proceed with the generation of gray spots.

[0016] The present application deviates from the conventional method of preparing sufficient crystal seeds in the preheating stage to induce the subsequent hydrolysis reaction, and significantly postpones the nucleation process. Only a small amount of crystal nucleus and a large amount of growth base are generated in the preheating stage to induce the hydrolysis reaction. Before the hydrolysis reaction of S3 occurs, that is, between S2 and S3 of the present application, the titanium liquid is mixed with the dispersion liquid before hydrolysis. At this time, the growth base has not formed a certain structure of crystal nucleus through the oxygen bridge cooperation and the protonation reaction of anion group. The number of crystal nucleus is small, and the particle size distribution is concentrated, all within 0.5-2 nm. The system undergoes hydrolysis under the induction of sufficient temperature, and a large amount of crystal nucleus is generated. Due to the previous dispersion operation, the particle size of the crystal nucleus is also generally within 0.5-2 nm. With the growth of the crystal nucleus, cluster materials between 2 nm and 40 nm appear in the solution until the hydrolysis is completed. At the same time, since the appearance of gray spots and the rapid occurrence of hydrolysis are sequential, the hydrolysis reaction directly occurs after nucleation, and no new impurities enter the crystal, so that the obtained titanium white product has high purity. The final titanium white product is tested, and the particle size of the obtained nanometer titanium dioxide can reach 40-100 nm. In terms of the common ion form of elements, the impurity elements that have a greater impact on the quality and purity of titanium dioxide are as follows: Cr ≤ 2 ppm, Cu ≤ 3 ppm, Mn ≤ 1 ppm, Fe ≤ 20 ppm, and the purity of TiO2 is ≥ 99.8%, and the highest can reach 99.9%. The obtained titanium dioxide product has good appearance.

[0017] Compared with the prior art, the embodiments of the present application have at least the following beneficial effects:

[0018] 1、The present application selects preheating at 80-85℃, which significantly reduces the preheating temperature of the titanium liquid in the preheating stage, and can effectively avoid the early hydrolysis of the titanium liquid.

[0019] 2、The present application uses the method of ultrasonic pre-dispersion in the preparation stage of the titanium liquid, which plays a role in inducing hydrolysis. By using the cavitation effect of ultrasonic waves, the nucleation stage of the titanium liquid can be "delayed", while the number of nucleation of the hydrolysis reaction is ensured, and the yield of the hydrolysis product is improved.

[0020] 3、The present application uses ultrasonic dispersion combined with dispersant to disperse the titanium liquid system twice, which can ensure the number of nucleation of hydrolysis, while reducing the surface tension between colloidal particles, preventing particle agglomeration, and generating nanoscale high-purity titanium dioxide with good morphology and uniform particle size distribution of about 40nm. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments and comparative examples. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0022] Figure 1 The flowchart of the embodiments of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0024] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to specific embodiments.

[0025] A method for preparing high-purity nanometer titanium dioxide based on self-grown seed hydrolysis, comprising the following steps:

[0026] S1: Preparation of titanium liquid: titanium oxysulfate and water are mixed, ultrasonic dispersion is carried out for 15-20min, the particle size of the obtained suspension is 100-150nm, and then water bath heating is carried out to obtain titanium liquid. The temperature during the process of dissolving titanium oxysulfate by water bath heating is less than 60℃.

[0027] In this step, the titanium oxysulfate and water are mixed, and then the granular titanium oxysulfate is continuously impacted for 15-20 min by ultrasonic dispersion, so that the titanium oxysulfate particles can be uniformly dissolved and dispersed in the aqueous solution, which is beneficial to generating more "nuclei" in the subsequent hydrolysis, increasing the nucleation rate, and reducing the particle size of the hydrolysis product. At the same time, the cavitation effect of the ultrasonic wave makes it easier to generate crystal nuclei in the internal microstructure of the titanium liquid. Moreover, the ultrasonic dispersion reduces the thermal dissolution temperature of the titanium oxysulfate particles, so that the titanium oxysulfate particles can be completely dissolved at a water bath heating temperature of 60°C or less, usually 50-55°C, which is much lower than the hydrolysis temperature of the titanium liquid.

[0028] It should be noted that the longer the ultrasonic dispersion time, the more obvious the cavitation effect, but for the present application, limiting the ultrasonic dispersion time to 20 min or less is more conducive to generating more "nuclei" in the subsequent hydrolysis process.

[0029] S2: Preheating: adding a dispersant to water to obtain a dispersion liquid, and separately preheating the above titanium liquid and the above dispersion liquid, both at a preheating temperature of 80-85°C.

[0030] In this step, the titanium liquid and the water with the dispersant are separately preheated to a temperature of 80-85°C, which can effectively prevent the premature hydrolysis of the titanium liquid and generate a small amount of crystal seeds. From the perspective of micro-dynamics, the nucleation mechanism of the crystal mainly includes the formation of growth units and the connection between the growth units to form crystal nuclei. The formation of growth units mainly includes Ti 4+ hydrolysis to generate Ti(OH) x and H + , which can also occur at low temperatures (i.e., the preheating temperature is lower than 90°C), but since the titanium liquid system is usually acidic, according to the basic knowledge of reversible reactions, the amount of Ti(OH) x generated is small, i.e., the number of crystal nuclei generated is not large. In the present application, this step mainly plays an inducing role, using the small amount of crystal nuclei and a large number of growth units generated in the preheating stage to induce the subsequent high-temperature hydrolysis. The lower preheating temperature also better cooperates with the ultrasonic dispersion, effectively preventing the agglomeration between the small particles, so that the subsequent high-temperature hydrolysis process can continue while controlling the particle size distribution of the titanium dioxide product.

[0031] The dispersant is added to further control the particle size of the titanium dioxide particles. The nanoparticles generated by hydrolysis have a large specific surface area and a large interfacial free energy, and are thermodynamically unstable. The organic polymer dispersant (i.e. surfactant) can be adsorbed on the surface of the nanoparticles, reduce the surface tension between the particles, and play a stabilizing role by using the electrostatic repulsion and steric hindrance of the surfactant, preventing the agglomeration of the nanoparticles. In combination with the ultrasonic dispersion in S1, the particle size of the nanometer titanium dioxide is ultimately controlled to 40-60 nm.

[0032] S3: Hydrolysis reaction: The preheated titanium liquid is added to the dispersion liquid to obtain a mixed liquid, which is stirred. The growth units Ti(OH) + (4- n n) (n = 1, 2, 3, 4, 5, 6), and the particle size in the mixed liquid is 0.5-2 nm. The mixed liquid is heated to the first boiling point, and the micro-boiling state is maintained for 15 min. When the color of the mixed liquid becomes gray, the stirring and heating are stopped, and the aging is performed for 15 min. Then the heating is restarted, and the temperature is increased to the second boiling point. The micro-boiling state is maintained for 30-90 min to obtain a hydrolysis slurry.

[0033] In this step, on the basis of the enrichment of a small amount of crystal seeds and a large amount of growth units in the entire titanium liquid system, the titanium liquid is heated to induce a large number of crystal nuclei, and the heating is continued to micro-boiling for about 15 min. The metatitanic acid crystalline precipitate can be precipitated in the system, that is, the gray point appears. The heating and stirring are stopped, and the aging is performed for about 15 min. During this process, the crystallization continuously precipitates and grows. Then the heating is restarted, and the micro-boiling state is maintained for 30-90 min. During this process, the hydrolysis reaction continues and reaches equilibrium until the reaction is completed. During the hydrolysis reaction, due to the continuous precipitation of the titanium liquid system, the acidity of the solution increases. As the hydrolysis reaction gradually reaches equilibrium, the acid solution selectively dissolves other soluble impurities precipitated, so that the final obtained crystalline precipitate has good purity and particle size distribution.

[0034] S4: Filtration and washing: The hydrolysis slurry is filtered and washed until there is no SO4 2- present in the washing liquid. The filter cake is collected and dried at a temperature of 50-120°C.

[0035] In this step, the hydrolysis product will inevitably carry a part of the sulfate ions, and these ions cannot be removed in the subsequent calcination process, which will affect the grade of the final titanium dioxide. Therefore, the hydrolysis slurry is filtered to separate the metatitanic acid crystalline precipitate from the solution, and remove the excess dispersant and other soluble impurities. Then, the metatitanic acid precipitate is washed with deionized water to remove the adsorbed sulfate ions. The washing is continued until no white flocculent material is found in the sample when a 0.05M BaCl2 solution is used for testing, indicating that there is no SO42- The trace amount is reached, and washing is completed; then, drying is performed to remove the adsorbed water on the metatitanic acid precipitate, so that the purity of the final titanium dioxide product is higher.

[0036] S5: calcination: the filter cake is calcined at a temperature of 300-750 DEG C to obtain the above-mentioned nano-titanium dioxide product.

[0037] In this step, the metatitanic acid crystal precipitate is calcined and impurities are removed, and the temperature is controlled to obtain the anatase titanium dioxide product.

[0038] In some embodiments of the present application, in the above S1, the mass ratio of titanyl sulfate to water is ≥19:11.

[0039] Generally, the amount of water used is related to the concentration of the titanium liquid, and the mass ratio of titanyl sulfate to water is calculated according to the actual required titanium liquid concentration, and the mass ratio is preferably: water: titanyl sulfate ≥19:11, which can make the titanyl sulfate dissolve better.

[0040] In some embodiments of the present application, in the above S1, the concentration of titanyl sulfate in the above titanium liquid (calculated as TiO2) is 1-3 mol / L.

[0041] According to the crystal growth kinetics, when the concentration of titanyl sulfate is too high (the supersaturation degree is too large), the nucleation rate is higher than the growth rate, the particle size of the hydrolysis product is too fine, the surface free energy is too high, and the agglomeration effect is easy to occur, and at the same time, high concentration also has an inhibitory effect on the hydrolysis rate; similarly, when the concentration of titanyl sulfate is too low (the supersaturation degree is too small), the nucleation rate is lower than the growth rate, the particle size of the hydrolysis product is too coarse, and it is difficult to reach the nanometer level. Therefore, in order to ensure the particle size and hydrolysis rate of the hydrolysis product, the concentration of titanyl sulfate is preferably 1-3 mol / L.

[0042] In some embodiments of the present application, in the above S2, the volume ratio of the above titanium liquid to the above dispersion liquid is 4-20:1.

[0043] The dispersion liquid and the amount are provided, which can have a good dispersion effect on titanyl sulfate, can make the number of generated crystal nuclei better, and the dispersant is easy to remove in the subsequent treatment.

[0044] In some embodiments of the present application, in the above S2, the dispersant includes at least one of sorbitan laurate, polyethylene glycol-2000 and sodium dodecyl benzene sulfonate, and the amount of the dispersant is 0.1%-2% of the mass of the above titanium liquid, which can achieve a better dispersion effect and prevent the particles from agglomerating.

[0045] In some embodiments of the present application, in the above S3, 100 mL of the preheated above titanium liquid is added to the preheated above dispersant at a uniform speed within 16-20 min.

[0046] The feeding time often affects the quantity and activity of the resulting seed crystals, which in turn determine the particle size and particle size distribution of the hydrolyzed metatitanic acid. If the feeding time is too short, the resulting seed crystals will not be fully matured, and the number of seed crystals will be too small. If the feeding time is too long, the number of seed crystals will increase, but prolonged maturation will lead to a decrease in seed crystal activity. Therefore, under laboratory conditions, it is preferable to add 100 ml of preheated titanium liquid to the bottom water at a uniform rate within 16–20 min.

[0047] In some embodiments of the present invention, in S3 above, the stirring process is uniform stirring at a speed of 200 to 300 r / min.

[0048] The stirring speed can significantly determine the size of the secondary aggregated metatitanic acid particles. The higher the speed, the smaller the secondary aggregated particles. Therefore, the stirring speed is preferably between 200 and 300 r / min.

[0049] In some embodiments of the present invention, the calcination temperature in S5 is 400-600°C.

[0050] Under laboratory conditions, anatase titanium dioxide will transform into rutile titanium dioxide at 730℃. However, in actual production, this transformation trend is weaker, and the calcination temperature can be preferably set between 400 and 600℃.

[0051] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0052] Example 1

[0053] like Figure 1 As shown, Figure 1 This is a flowchart of an embodiment of the present invention.

[0054] S1: Titanium solution preparation: Weigh 53.9 g of titanium oxysulfate dihydrate into a beaker, add 80 mL of deionized water and stir. Disperse ultrasonically at room temperature for 20 min. The resulting suspension contains particles with a diameter of 120–127 nm. Then, heat the suspension to 55 °C using a water bath to ensure complete dissolution. Cool and filter to obtain the titanium solution, which is then brought to a final volume of 100 mL. The titanium solution concentration (based on TiO2) is 220 g / L.

[0055] S2: Preheating: Preheat the titanium liquid and water with 1.5% SDBS added to 85°C respectively. The titanium liquid is heated by oil bath or water bath. The preheating time is 15 minutes.

[0056] S3: Hydrolysis reaction: Slowly add the preheated titanium liquid to the preheated SDBS at a volume ratio of 10:1. Stir at a constant speed, heat to boiling, maintain a gentle boil until ash spots appear, then stop stirring and heating, and mature for 30 minutes. Reheat and stir, and stop after a gentle boil for 60 minutes to obtain the hydrolyzed slurry.

[0057] S4: Filtration and washing: Cool, filter, and wash the above hydrolyzed slurry until no SO4 is present in the washing liquid. 2- The filter cake is collected and dried at 60°C.

[0058] S5: Calcination: The above filter cake is placed in a tube furnace and calcined at 400°C for 2 hours to obtain nano-titanium dioxide product.

[0059] The particle size of the product was measured using the XRD linebroadening method, the purity was tested using the aluminum reduction method, and the yield was calculated using the following formula:

[0060] ε=m(TiO2) 产品 / m(TiO2) 钛液 ×100%

[0061] The experiment showed that the nano-titanium dioxide product obtained in Example 1 had a particle size of 45 nm, a purity of 99.8%, and a hydrolysis yield of 90%.

[0062] Example 2

[0063] like Figure 1 As shown, Figure 1 This is a flowchart of an embodiment of the present invention.

[0064] S1: Titanium solution preparation: Weigh 26.95g of titanium oxysulfate dihydrate into a beaker, add 80mL of deionized water and stir. Disperse ultrasonically at room temperature for 15min. The resulting suspension contains particles with a diameter of 115-130nm. Then, heat the suspension to 55℃ using a water bath to ensure complete dissolution. Cool and filter to obtain the titanium solution, which is then brought to a final volume of 100mL. The titanium solution concentration (based on TiO2) is 110g / L.

[0065] S2: Preheating: Preheat the titanium liquid and water with 0.3% sorbitan laurate to 80°C respectively. The titanium liquid is heated by an oil bath or water bath. The preheating time is 10 minutes.

[0066] S3: Hydrolysis reaction: Slowly add the preheated titanium liquid to the preheated sorbitan laurate, with a volume ratio of 4:1. Stir at a constant speed, heat to boiling, maintain a gentle boil until ash spots appear, then stop stirring and heating, and mature for 30 minutes. Reheat and stir, and stop after a gentle boil for 60 minutes to obtain the hydrolyzed slurry.

[0067] S4: Filtration and washing: Cool, filter, and wash the above hydrolyzed slurry until no SO4 is present in the washing liquid. 2- The filter cake is collected and dried at 60°C.

[0068] S5: Calcination: The above filter cake is placed in a tube furnace and calcined at 500°C for 3 hours to obtain nano-titanium dioxide product.

[0069] The particle size of the product was measured using the XRD linebroadening method, the purity was tested using the aluminum reduction method, and the yield was calculated using the following formula:

[0070] ε=m(TiO2) 产品 / m(TiO2) 钛液 ×100%

[0071] The experiment showed that the nano-titanium dioxide product obtained in Example 2 had a particle size of 45 nm, a purity of 99.9%, and a hydrolysis yield of 87%.

[0072] Example 3

[0073] like Figure 1 As shown, Figure 1 This is a flowchart of an embodiment of the present invention.

[0074] S1: Titanium solution preparation: Weigh 53.9 g of titanium oxysulfate dihydrate into a beaker, add 80 mL of deionized water and stir. Disperse ultrasonically at room temperature for 20 min. The resulting suspension contains particles with a diameter of 130–145 nm. Then, heat the suspension to 50 °C using a water bath to fully dissolve the particles. Cool and filter to obtain the titanium solution, which is then brought to a final volume of 100 mL. The titanium solution concentration (based on TiO2) is 220 g / L.

[0075] S2: Preheating: Preheat the titanium liquid and water with 1% SDBS and 1% PEG-2000 added to 80°C respectively. The titanium liquid is heated by oil bath or water bath. The preheating time is 10 min.

[0076] S3: Hydrolysis reaction: Slowly add the preheated titanium liquid to the preheated SDBS and PEG-2000 blend at a volume ratio of 10:1. Stir at a uniform speed, heat to boiling, maintain a gentle boil until ash spots appear, stop stirring and heating, and mature for 30 minutes. Reheat and stir, and stop boiling for 60 minutes to obtain the hydrolyzed slurry.

[0077] S4: Filtration and washing: Cool, filter, and wash the above hydrolyzed slurry until no SO4 is present in the washing liquid. 2- The filter cake is collected and dried at 60°C.

[0078] S5: Calcination: The above filter cake is placed in a tube furnace and calcined at 600°C for 2 hours to obtain nano-titanium dioxide product.

[0079] The particle size of the product was measured using the XRD linebillization method, the purity was tested using the aluminum reduction method, and the yield was calculated using the following formula:

[0080] ε=m(TiO2) 产品 / m(TiO2) 钛液 ×100%

[0081] The experiment showed that the nano-titanium dioxide product obtained in Example 3 had a particle size of 52 nm, a purity of 99.8%, and a hydrolysis yield of 88%.

[0082] Comparative Example 1

[0083] The implementation method of Comparative Example 1 is basically the same as that of Example 1, except that the preheating temperature in S2 of Comparative Example 1 is 86°C.

[0084] Experiments revealed that premature hydrolysis occurred in the system at a preheating temperature of 86℃, resulting in slight turbidity in the titanium liquid during the preheating stage. Furthermore, the particle size of the product was measured using XRD linebroadening, purity was tested using the aluminum reduction method, and the yield was calculated using the following formula:

[0085] ε=m(TiO2) 产品 / m(TiO2) 钛液 ×100%

[0086] The experiment showed that in Comparative Example 1, during the preheating stage, the particles in the mixed liquid system agglomerated significantly, and the resulting nano-titanium dioxide product had an uneven particle size distribution of approximately 30–70 nm, a purity of 95.8%, and a high impurity content. Furthermore, the obtained titanium dioxide product contained impurities such as Cr (approximately 10 ppm), Cu (approximately 10 ppm), and K (approximately 3 g / L) (in the form of common elemental ions), with a yield of 75% and poor hydrolysis effect.

[0087] Comparative Example 2

[0088] Comparative Example 2 is basically the same as Example 1 in terms of implementation method, except that ultrasonic dispersion is not used to treat the titanium oxysulfate particles in the titanium liquid preparation stage.

[0089] Experiments revealed that without ultrasonic dispersion, the particle size in the resulting suspension was greater than 300 nm. Furthermore, during the hydrothermal dissolution stage of the S1 titanium solution preparation, significant agglomeration occurred between the particles in the mixed system, resulting in larger particle sizes. The granular titanium oxysulfate dihydrate could not be dispersed and dissolved at low temperatures (<60℃), and the reaction could not continue.

[0090] Comparative Example 3

[0091] Comparative Example 3 was implemented in a manner that was essentially the same as that of Example 1, except that no dispersant was used in Comparative Example 3.

[0092] Experiments showed that the reaction could continue after only one dispersion using ultrasonic dispersion, without the addition of a dispersant. However, the product particle size was measured by XRD line broadening, the purity was tested by aluminum reduction, and the yield was calculated using the following formula:

[0093] ε=m(TiO2) 产品 / m(TiO2) 钛液 ×100%

[0094] The experiment showed that in Comparative Example 3, during the first boiling and ripening stage of the S3 hydrolysis reaction, the particles in the mixed liquid system showed obvious agglomeration. The resulting nano-titanium dioxide product had an uneven particle size distribution, with particle sizes all around 100 nm. The particles were large and had poor morphology, with a purity of 95.3% and a high impurity content. Furthermore, the obtained titanium dioxide product contained impurities such as K (approximately 2 g / L) and Na (approximately 0.5 g / L) (in the form of common elemental ions). The yield was 80%, indicating poor hydrolysis performance.

[0095] Comparative Example 4

[0096] Comparative Example 4 is basically the same as Example 1 in terms of implementation method, except that the preheating temperature in S2 of Comparative Example 4 is 78°C.

[0097] Experiments showed that at a preheating temperature of 78℃, although the system did not undergo premature hydrolysis, the hydrolysis effect was extremely poor. The particle size of the product was measured using the XRD linebillization method, the purity was tested using the aluminum reduction method, and the yield was calculated using the following formula:

[0098] ε=m(TiO2) 产品 / m(TiO2) 钛液 ×100%

[0099] The experiment showed that in Comparative Example 4, during the second ripening and boiling stage of the S3 hydrolysis reaction, the particles in the mixed liquid system showed obvious agglomeration. The particle size of the obtained nano-titanium dioxide product was also unevenly distributed, ranging from about 30 to 100 nm, with a purity of 94.2% and a high impurity content. Furthermore, the obtained titanium dioxide product contained impurities such as K (about 3 g / L) and Ca (0.5 g / L) (in the form of common elemental ions). The hydrolysis yield was less than 40%, indicating poor hydrolysis effect.

[0100] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing nanoscale high-purity titanium dioxide based on autogenous seed hydrolysis, characterized in that, The method comprises the following steps: S1: titanium liquid preparation; S2: preheating; S3: hydrolysis reaction; S4: filtration washing; S5: calcination; in the S1, titanium oxysulfate and water are mixed and ultrasonic dispersed for 15-20 min, the particle size of the obtained suspension is 100-150 nm, and the titanium liquid is obtained by water bath heating, the concentration of the titanium liquid is 1-3 mol / L in terms of TiO2; in the S2, the dispersant is added into the preheated water to obtain a dispersion liquid, and the titanium liquid and the dispersion liquid are preheated respectively, and the preheating temperature is 80-85 ℃; in the S3, the titanium liquid and the dispersion liquid are mixed to obtain a mixed liquid, and the mixed liquid is dispersed with growth units of the formula (I) before the hydrolysis reaction, wherein n is 1, 2, 3, 4, 5 or 6; the particle size of the particles in the mixed liquid is 0.5-2 nm.

2. The method for preparing nanoscale high-purity titanium dioxide based on self-grown seed hydrolysis according to claim 1, characterized in that, In the S1, the temperature during the process of water bath heating and dissolving to prepare the titanium liquid is less than 60℃.

3. The method for preparing nanoscale high-purity titanium dioxide based on self-grown seed hydrolysis according to claim 1, characterized in that, In the S1, the mass ratio of titanyl sulfate to water is greater than or equal to 19:

11.

4. The method for preparing nanoscale high-purity titanium dioxide based on self-grown seed hydrolysis according to claim 1, characterized in that, In the S2, the volume ratio of the titanium liquid to the dispersion liquid is 4-20:

1.

5. The method for preparing nanoscale high-purity titanium dioxide based on self-grown seed hydrolysis according to claim 1, characterized in that, In the S2, the dispersant comprises at least one of sorbitan laurate, polyethylene glycol-2000 and sodium dodecyl benzene sulfonate, and the amount of the dispersant is 0.1%-2% of the mass of the titanium liquid.

6. The method for preparing nanoscale high-purity titanium dioxide based on self-grown seed hydrolysis according to claim 1, characterized in that, In the S3, after the preheated titanium liquid is added to the dispersion liquid to obtain the mixed liquid, stirring and heating are performed to the first boiling, the mixed liquid is kept in the state of micro-boiling for 15 min, the color of the mixed liquid is changed to gray, the stirring and heating are stopped, and aging is performed for 15 min; then, heating is performed again, the temperature is increased to the second boiling, the mixed liquid is kept in the state of micro-boiling for 30-90 min, and the hydrolysis slurry is obtained.

7. The method according to claim 6, wherein the method is characterized by, In the S3, 100 mL of the preheated titanium liquid is added to the dispersion liquid at a uniform speed within 16-20 min.

8. The method for preparing nanoscale high-purity titanium dioxide based on self-grown seed hydrolysis according to claim 6, characterized in that, In the S3, the stirring process is uniform stirring at a rotating speed of 200-300 r / min.

9. The method for preparing nanoscale high-purity titanium dioxide based on self-grown seed hydrolysis according to claim 6, characterized in that, In the S4, the hydrolysis slurry is filtered, washed until no SO4 2﹣ The filter cake is collected and dried at a temperature of 50-120°C.

10. The method for preparing nanoscale high-purity titanium dioxide based on self-grown seed hydrolysis according to claim 9, characterized in that, In the S5, the filter cake is calcined at a temperature of 300-750℃, and the temperature is kept for 1-3 h, so that the nanoscale high-purity titanium dioxide is obtained.

11. The method for preparing nanoscale high-purity titanium dioxide based on self-grown seed hydrolysis according to claim 10, characterized in that, In the S5, the calcination temperature is 400-600℃.

Images