Method for producing crystalline nanometer titania and method for improving dispersibility of crystalline nanometer titania

Abstract

A method for preparing titania and a method for improving the dispersibility of titania, wherein the method for preparing low-temperature crystallized titania includes the steps of (1) obtaining hydrated titanic acid through hydrolysis, separation, purification, and drying of a titanium compound, (2) heating the hydrated titanic acid to 100 to 200°C, and (3) introducing hydrogen chloride gas into the heated hydrated titanic acid system and reacting at constant pressure to obtain a crystalline nanotitania material. This low-temperature crystallized titania technology can improve the precipitation synthesis of nanotitania and promote the performance and application fields of titania nanomaterials.

Description

Cross-reference related reference

[0001] This application claims priority to Chinese Patent Applications filed on July 6, 2020, with Application No. 202010642220.X and Invention Title "Method for Crystallizing Titania at Low Temperature", and Application No. 202010642931.7 and Invention Title "Method for Improving the Dispersibility of Titania", the contents of which are hereby incorporated by reference in their entirety into this application.

Technical Field

[0002] This application relates to a method for producing titania and a method for improving the dispersibility of titania.

Background Art

[0003] Nanotitania refers to titania with a particle size of less than 100 nanometers, which has special effects such as a small particle size, a high specific surface area, excellent photocatalytic activity, stable chemical and thermal properties, and super hydrophilicity, and has irreplaceable application advantages in fields such as air management, disinfection, self-cleaning materials, sunscreen skin care, etc. For example, nanotitania can also be used for the decomposition of formaldehyde, benzene, TVOC, SOx, NOx, etc., and can also be used for removing the pollution odor of refrigerators and purifying air-conditioning gases, and can exert the effect of indoor and in-vehicle air management. Nanotitania is applied to the surfaces of glass, louvers, mirrors, street lights, etc. to achieve a self-cleaning effect. Nanotitania is also widely applied in fields such as medical devices, catheters, operating rooms, sunscreen cosmetics, sunscreen clothing, whitening products, and anti-aging paints. In addition, nanotitania can also be used in the field of energy conversion and storage such as the negative electrode material of lithium-ion batteries and the photocatalytic or photoelectrocatalytic extraction of hydrogen energy.

[0004] Currently, there are two main methods for producing nanotitania: gas-phase and liquid-phase. Liquid-phase synthesis is a widely used method for producing titania material in laboratories and industrial settings, offering advantages such as easy reaction control, simple equipment, and low energy consumption. Liquid-phase methods mainly include precipitation, hydrothermal, sol-gel, and microemulsion methods.

[0005] Here, the precipitation method refers to the process of hydrolyzing a titanium source in water by controlling the pH value of the solution at a constant temperature, forming an insoluble precipitate of hydrated titanic acid, and then obtaining titania powder through steps such as filtration, washing, drying, and calcination. In the precipitation method, in order to obtain highly crystalline titania material, the calcination temperature is usually exceeded 500°C. However, the high calcination temperature causes the particles in the resulting titania powder to become large, making it impossible to form a nanotitania particle material with good dispersibility. At the same time, the high calcination temperature increases the input of equipment and the energy consumption during synthesis.

[0006] Therefore, lowering the calcination temperature in the precipitation method is an important step in the synthesis of titania materials by precipitation, and is of great significance in improving the performance of the product and reducing costs.

[0007] Furthermore, the properties of a material are closely related to its size, and ultra-small nanoparticles can exhibit superior properties in terms of energy, environmental friendliness, and catalysis. For example, titania materials with a particle size of less than 100 nanometers possess special effects such as small particle size, high specific surface area, excellent photocatalytic activity, stable chemical and thermal performance, and superhydrophilicity, offering irreplaceable application advantages in fields such as air management, sterilization and disinfection, self-cleaning materials, and sunscreen skincare.

[0008] The concentration and stability of a dispersion of nanotitania particles significantly affect the reaction process and the final product. With the ever-expanding range of applications for titania, for example, in application fields such as air management, material molding, paints, and ink production, product performance largely depends on the degree of dispersion of titania powder in a liquid medium; the better the dispersion, the better the final application effect of the product. Typically, nanotitania particles are small in size, have many defects at their interfaces, have high surface activity, and are thermodynamically unstable. Nanoparticles dispersed in a liquid medium tend to condense and aggregate, settle, and fail to form a stable dispersion, losing the unique properties of nanoparticles and exhibiting significant practical drawbacks. As a main example, (1) in the field of photocatalysis, after being prepared as a photocatalyst, it cannot be applied to surfaces such as doors, windows, and leather because white spots are formed, negatively impacting the aesthetics, and the photocatalytic activity of aggregated nanoparticles is not high, resulting in little noticeable effect in removing contaminants such as formaldehyde. (2) In the field of self-cleaning, it cannot be used directly on transparent surfaces such as glass and mirrors due to its strong light scattering and reflection and poor light transmittance. (3) In the field of beauty and skincare products, it cannot be used to manufacture transparent and natural-colored skincare or sunscreen products, as it causes an unnatural white appearance on the skin. (4) In the field of film products, it cannot be widely applied to transparent film products, transparent durable topcoats, fine ceramics, and other surfaces.

[0009] By preventing the aggregation of nanotitania particles and obtaining monodisperse titania nanoparticles, the usability of titania nanomaterials in fields such as optics, electrical engineering, and catalysis can be significantly improved. Currently, there are reports of the production of stable nanoparticle dispersions using physical dispersion methods and chemical dispersion methods. Physical dispersion methods mainly use external force to disperse nanoparticles and include dispersion by mechanical stirring, ultrasonic dispersion, and dispersion by high-energy processing methods. A drawback of physical dispersion methods is that the particles reaggregate when the external force stops. Chemical dispersion methods use interfacial chemistry to disperse materials by adding interfacial treatment agents. For example, the production of aqueous phase dispersed nanoparticles is usually achieved by inducing and constraining water-soluble surfactants or polymers. However, because the particle surface is coated with modifying molecules such as organic substances, the contribution to improving material performance through control of dispersibility is reduced. For example, when producing water-soluble titania nanoparticles using the reaction of titanium alkoxide and alkylamine, the presence of such alkaline agents slows down the surface activity of the product, reducing its photocatalytic performance. At the same time, different application systems may exhibit adverse reaction effects with the modified molecules at the interface, potentially reducing the application performance of the final product. For example, using polyethylene glycol as a stabilizer improves the dispersibility of titania nanoparticles but reduces their catalytic activity. Furthermore, the titania dispersion product obtained in the above manner is still a liquid suspension, making it impossible to completely monodisperse the particles, and the particle size is non-uniform, preventing the formation of a stable colloidal dispersion. This leads to difficulties such as high transportation costs and limitations on practical use.

[0010] Therefore, there is a pressing need to develop a technical method that can significantly improve the dispersibility of nanotitania by processing it at low temperatures without using any interfacial organic additives, thereby advancing the application fields and effectiveness of titania nanomaterials. [Overview of the project] [Problems that the invention aims to solve]

[0011] In view of these drawbacks, the present invention provides a technical method for producing low-temperature crystallized titania in order to improve the precipitation synthesis method of nanotitania and promote the performance and application fields of titania nanomaterials.

[0012] The present invention also aims to provide a technical method for significantly improving the dispersibility of nanotitania in order to promote the application fields and usage effects of titania nanomaterials. [Means for solving the problem]

[0013] To achieve the above objective, the present invention employs the following technical means. (1) A step of obtaining hydrated titanic acid by hydrolysis, separation, purification and drying of a titanium compound, (2) The step of heating the hydrated titanic acid from 100°C to 200°C, (3) A method for producing low-temperature crystallized titania, comprising the step of passing hydrogen chloride gas through the heated hydrated titanate system and carrying out a constant-pressure reaction to obtain a crystalline nanotitania material.

[0014] In a preferred embodiment, the titanium compound is one or a combination of several selected from titanium sulfate, titanyl sulfate, titanium tetrachloride, titanium isopropoxide, and tetrabutyl titanate.

[0015] In preferred embodiments, the hydrolysis process involves directly reacting the titanium compound with water, or reacting the titanium compound with an alkaline aqueous solution.

[0016] In a preferred embodiment, the hydrogen chloride gas being passed through further contains water vapor.

[0017] In a preferred embodiment, the pressure of the constant voltage reaction is 0.5 to 20 atmospheres, with a preferred pressure of 1 to 10 atmospheres.

[0018] As a preferred embodiment, the time of the constant-pressure reaction is from 3 hours to 24 hours.

[0019] As a preferred embodiment, the crystal phase of the crystalline nano-titania material is a rutile phase or anatase phase or a composite phase of rutile phase and anatase phase.

[0020] As a preferred embodiment, the crystalline nano-titania material can spontaneously disperse in pure water without additives or dispersants to form a stable dispersion mainly in colloidal dispersion.

[0021] As a preferred embodiment, the crystalline nano-titania material is nano-level titania particles with a particle size less than 100 nanometers or aggregates of nano-level titania particles with a particle size less than 100 nanometers, and the interface of the crystalline nano-titania material is acidic.

[0022] A method for improving the dispersibility of titania, which includes the step of heat-treating solid titania A as a precursor in an atmosphere of hydrogen chloride to obtain a product of dispersible titania B.

[0023] The step of putting solid titania A as a precursor into a container, A method for improving the dispersibility of titania and a product thereof, which include the step of filling the container containing solid titania A as the precursor with hydrogen chloride gas and performing low-temperature heat treatment to obtain a product of dispersible titania B.

[0024] As a preferred embodiment, compared with titania A as a precursor, the dispersibility of the product of dispersible titania B in water is improved by 10 times or more.

[0025] As a preferred embodiment, compared with titania A as a precursor, the dispersion stability of the product of dispersible titania B in water is improved by 10 times or more.

[0026] As a preferred embodiment, compared with the precursor titania A, the transparency of the product of the dispersible titania B after being dispersed in water is improved by 10 times or more.

[0027] As a preferred embodiment, the product of the dispersible titania B can spontaneously disperse in pure water without containing additives or dispersants to form a stable dispersion mainly in the form of colloidal dispersion.

[0028] As a preferred embodiment, the product of the dispersible titania B is nanoscale titania particles with a particle size of less than 100 nanometers or aggregates of nanoscale titania particles with a particle size of less than 100 nanometers, and the interface of the product of the dispersible titania B is acidic.

[0029] As a preferred embodiment, the product of the dispersible titania B is crystalline nanoscale titania, and the crystal phase of the crystalline nanoscale titania is one or a combination of more than one of anatase phase, rutile phase, and brookite phase.

[0030] As a preferred embodiment, the solid titania A as the precursor is nanoscale titania particles with a particle size of less than 100 nanometers or aggregates of nanoscale titania particles with a particle size of less than 100 nanometers.

[0031] As a preferred embodiment, the solid titania A as the precursor is nanoscale titania particles with a particle size of less than 50 nanometers or aggregates of nanoscale titania particles with a particle size of less than 50 nanometers.

[0032] As a preferred embodiment, the solid titania A as the precursor is crystalline titania particles or non-crystalline titania particles.

[0033] As a preferred embodiment, the solid titania A as the precursor further contains one or a combination of more than one of titanium hydroxide, titanium hydroxide hydrate, titanic acid, and titanic acid hydrate.

[0034] In a preferred embodiment, the hydrogen chloride atmosphere further contains water vapor, and the pressure of the water vapor is between 0.1 atmospheres and 10 atmospheres.

[0035] In a preferred embodiment, the pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere is between 0.5 atmospheres and 20 atmospheres.

[0036] In a preferred embodiment, the pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere is between 1 atmosphere and 10 atmospheres.

[0037] In a preferred embodiment, the pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere may be constant or may vary.

[0038] In a preferred embodiment, the hydrogen chloride atmosphere is provided continuously or intermittently.

[0039] In a preferred embodiment, the source of the hydrogen chloride atmosphere may be provided from within the reaction system or may be provided by inputting it from an external source.

[0040] In a preferred embodiment, the heat treatment temperature is 80°C to 300°C, and a preferred heat treatment temperature is 100°C to 200°C.

[0041] In a preferred embodiment, the heat treatment time is 2 to 48 hours.

[0042] In a preferred embodiment, the hydrogen chloride gas in the hydrogen chloride atmosphere fluctuates within a predetermined pressure range, the hydrogen chloride atmosphere is continuously supplied, and the hydrogen chloride atmosphere is supplied by external input. [Effects of the Invention]

[0043] The advantages of this invention are as follows: 1. This low-temperature crystallized titania preparation method significantly reduces the calcination temperature in the nanotitania precipitation synthesis method, lowering it from 500°C to a minimum of 100°C, thereby saving energy consumption and equipment input. 2. The nanotitania material obtained by this low-temperature crystallized titania production method exhibits significant improvements in specific surface area, dispersibility, and catalytic performance. 3. This method for improving the dispersibility of titania does not use any interfacial organic additives, thus giving the nanotitania dispersion universal applicability and improving the range of applications and effectiveness of the dispersion. 4. This method for improving the dispersibility of titania involves low processing temperatures, simple operating steps, low cost, and is advantageous for widespread industrialization.

[0044] Specific embodiments of the present invention are disclosed in detail with reference to the following description and drawings, and the embodiments in which the principles of the present invention may be employed are clearly shown. It should be understood that the embodiments of the present invention are not limited in scope.

[0045] Features described and / or shown in one embodiment may be used in the same or similar manner in one or more other embodiments, combined with or substituting features in other embodiments.

[0046] When used in this text, the term "include" refers to the presence of a feature, an entire component, a step, or a component, but it must be emphasized that it does not exclude the presence / addition of one or more other features, entire components, steps, or components. [Brief explanation of the drawing]

[0047] To more clearly describe embodiments of the present invention or technical solutions in the prior art, the accompanying drawings necessary for describing embodiments or the prior art are briefly introduced below. It is obvious that the drawings described below are merely embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without expending progressive effort.

[0048] [Figure 1] This is a transmission electron microscope image taken after the titania aqueous dispersion obtained in Example 1 was dropped onto a copper mesh and dried. [Figure 2] This is an X-ray diffraction pattern of the titania product prepared in Example 1, where the main crystalline phase is the anatase phase. [Figure 3] This is a colloidal aqueous dispersion obtained by mixing the titania material obtained in Example 1 with water. [Figure 4] This curve shows the photocatalytic decomposition of the nanotitania product obtained in Example 1 and rhodamine B in P25. [Figure 5] The aqueous dispersion obtained by adding water to the nanotitania obtained in Example 4 has a mass ratio of 5‰ and exhibits a relatively stable dispersion state. [Figure 6] This is an optical photograph of a titanium hydroxide suspension, a precursor with a mass ratio of 5‰, after standing for 2 hours. It clearly shows delamination, indicating that the suspension is unstable. [Figure 7] This is a scanning electron microscope image of the product obtained in Example 4, after being dispersed in water, dropped onto a silicon wafer, and then dried. [Figure 8] This is a scanning electron microscope image obtained by dispersing titanium hydroxide, a precursor, in water, then applying it dropwise to a silicon wafer, and observing it after drying. [Figure 9] This is a scanning electron microscope image obtained after the product obtained in Comparative Example 3 was dispersed in water, dropped onto a silicon wafer, and then dried. [Modes for carrying out the invention]

[0049] To enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below, accompanied by drawings of the embodiments. It is clear that the embodiments described are only a selection of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art without progressive effort based on the embodiments of the present invention should fall within the scope of the present invention.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art. In this text, terms used in the specification of the present invention are for the purpose of describing specific embodiments only and not to restrict the invention. The term "and / or" as used herein includes any and all combinations of one or more related listed items. [Examples]

[0051] First, a 0.25 mol / liter aqueous solution of titanium tetrachloride and a 1 mol / liter solution of sodium hydroxide were gradually mixed in a 1:1 volume ratio. After washing and separation, the mixture was dried at room temperature and pressure to obtain hydrated titanic acid. Next, 10 grams of the hydrated titanic acid prepared above were placed in a pressure-resistant rust-preventive tube and heated to 160°C. Subsequently, hydrogen chloride gas was filled into the pressure-resistant rust-preventive tube, the pressure inside the tube was maintained at 5 atmospheres, and the tube was kept at a constant temperature of 160°C for 12 hours to obtain nanotitania powder material.

[0052] A small amount of the product obtained in this embodiment was taken, dispersed in deionized water, and then a small amount was dropped onto a copper mesh and air-dried. As shown in Figure 1, the sample was used to observe its morphology with a transmission electron microscope. From Figure 1, it was found that the particle size of the titania nanoparticles in the product ranged from 5 nanometers to 10 nanometers. Furthermore, it was shown that the nanotitania obtained in this embodiment has a small particle size and excellent monodispersibility.

[0053] Figure 2 shows the X-ray diffraction pattern of the titania product prepared in this embodiment. From Figure 2, it can be seen that the nanotitania obtained in this embodiment has an anatase phase as its main crystalline phase and exhibits good crystallinity. Furthermore, it has been shown that the present invention can significantly reduce the calcination temperature in the nanotitania precipitation synthesis method, lowering the calcination temperature from 500°C to 160°C.

[0054] As shown in Figure 3, the nanotitania product obtained in this embodiment was added to water to obtain a nanotitania dispersion with a mass ratio of 5‰. This dispersion exhibited excellent monodispersibility and could form a stable colloidal dispersion in aqueous solution. The suspension of nanoparticles was stable, and aggregation and sedimentation were unlikely to occur. Even after being left for more than 6 months, no delamination phenomenon occurred in the solution.

[0055] As shown in Figure 4, the nanotitania material obtained in this example exhibits good photocatalytic activity, with a catalytic efficiency nine times that of commercial P25 material. As a specific comparison method, 1 gram each of the product obtained in Example 1 and the P25 (Degsa) sample were weighed out and dispersed in 100 ml of a rhodamine B solution with a concentration of 2.0 × 10⁻⁵ mol / liter. The mixture was then magnetically stirred in the dark for 30 minutes to balance the temperature and adsorption. Subsequently, a simulated sunlight lamp was turned on, the mixture was stirred, and 3 ml of the sample was taken out at regular intervals. The particles were centrifuged, and the absorbance of the solution was measured at 550 nanometers using a UV-Vis spectrometer to calculate the remaining concentration of rhodamine B.

[0056] As described above, the advantages of the present invention are (1) that this technical method significantly reduces the calcination temperature in the nanotitania precipitation synthesis method, lowering the calcination temperature from 500°C to 160°C, thereby saving energy consumption and equipment input, and (2) that the nanotitania material obtained by this technical method is significantly improved in terms of specific surface area, dispersibility, and catalytic performance. [Examples]

[0057] First, isopropyl titanate was slowly added dropwise to deionized water in a volume ratio of 1:20, and stirred to form a titanic acid precipitate. After washing and separating, the precipitate was dried at atmospheric pressure at 60°C to obtain hydrated titanic acid. Next, 10 grams of the hydrated titanic acid prepared above was placed in a pressure-resistant corrosion-preventive tube and heated to 120°C. Subsequently, hydrogen chloride gas was filled into the pressure-resistant corrosion-preventive tube, the pressure inside the tube was maintained at 1 atmosphere, and the tube was kept at a constant temperature of 120°C for 24 hours to obtain nanotitania powder material.

[0058] A small amount of the product obtained in this example was taken, dispersed in deionized water, and then a small amount was dropped onto a copper mesh and air-dried. The sample was then used to observe its morphology with a transmission electron microscope. It was found that the particle size of the titania nanoparticles in the product was between 10 and 20 nanometers. Furthermore, it was shown that the nanotitania obtained in this example has a small particle size and excellent monodispersibility.

[0059] X-ray diffraction patterns confirmed that the titania product obtained in this embodiment had an anatase phase as its main crystalline phase and exhibited good crystallinity. Furthermore, it was demonstrated that the present invention significantly reduced the calcination temperature in the nanotitania precipitation synthesis method, lowering it from 500°C to 120°C.

[0060] The nanotitania product obtained in this example was added to water to obtain a nanotitania dispersion with a mass ratio of 5‰. This dispersion exhibited excellent monodispersibility and could form a stable colloidal dispersion in aqueous solution. The suspension of nanoparticles was stable, and aggregation and sedimentation were unlikely to occur. Even after being left for 10 months, no delamination occurred in the solution.

[0061] The nanotitania material obtained in this example exhibits good photocatalytic activity, with a catalytic efficiency six times that of commercial P25 material. As a specific comparison method, 1 gram each of the product obtained in this example and a P25 (detoxa) sample were weighed out and dispersed in 100 ml of a rhodamine B solution with a concentration of 2.0 × 10⁻⁵ mol / liter. The mixture was then magnetically stirred in the dark for 30 minutes to balance the temperature and adsorption. Subsequently, a simulated sunlight lamp was turned on, the mixture was stirred, and 3 ml of the sample was taken out at regular intervals. The particles were centrifuged, and the absorbance of the solution was measured at 550 nanometers using a UV-Vis spectrometer to calculate the remaining concentration of rhodamine B. [Examples]

[0062] First, a 0.25 mol / liter aqueous solution of titanyl sulfate and a 1 mol / liter aqueous solution of ammonia were gradually mixed in a 1:1 volume ratio. After washing and separation, the mixture was dried at 80°C to obtain hydrated titanic acid. Next, 10 grams of the hydrated titanic acid prepared above were placed in a pressure-resistant corrosion-preventive tube and heated to 200°C. Subsequently, the pressure-resistant corrosion-preventive tube was filled with hydrogen chloride gas containing 30% water vapor by mass, the pressure inside the tube was maintained at 10 atmospheres, and the tube was kept at a constant temperature of 200°C for 5 hours to obtain nanotitania powder material.

[0063] A small amount of the product obtained in this example was taken, dispersed in deionized water, and then a small amount was dropped onto a copper mesh and air-dried. The sample was then used to observe its morphology with a transmission electron microscope. The particle size of the titania nanoparticles in the product was found to be between 20 and 50 nanometers, demonstrating that the nanotitania obtained in this example has good dispersibility.

[0064] X-ray diffraction patterns confirmed that the titania product obtained in this embodiment had a rutile phase as its main crystalline phase and exhibited good crystallinity. Furthermore, it was demonstrated that the present invention significantly reduced the calcination temperature in the nanotitania precipitation synthesis method, lowering the calcination temperature from 500°C to 200°C.

[0065] The nanotitania product obtained in this example was added to water to obtain a nanotitania dispersion with a mass ratio of 1‰. This dispersion exhibited excellent monodispersibility and could form a stable colloidal dispersion in aqueous solution. The suspension of nanoparticles was stable, and aggregation and sedimentation were unlikely to occur. Even after being left for one month, no delamination phenomenon occurred in the solution.

[0066] The nanotitania material obtained in this example exhibits good photocatalytic activity, with a catalytic efficiency twice that of commercial P25 material. As a specific comparison method, 1 gram each of the product obtained in this example and a P25 (detoxa) sample were weighed out and dispersed in 100 ml of a rhodamine B solution with a concentration of 2.0 × 10⁻⁵ mol / liter. The mixture was then magnetically stirred in the dark for 30 minutes to balance the temperature and adsorption. Subsequently, a simulated sunlight lamp was turned on, the mixture was stirred, and 3 ml of the sample was taken out at regular intervals. The particles were centrifuged, and the absorbance of the solution was measured at 550 nanometers using a UV-Vis spectrometer to calculate the remaining concentration of rhodamine B.

[0067] Comparative Example 1 First, a 0.25 mol / liter aqueous solution of titanium tetrachloride and a 1 mol / liter solution of sodium hydroxide were gradually mixed in a 1:1 volume ratio. After washing and separation, the mixture was dried at room temperature and pressure to obtain hydrated titanic acid. Next, 10 grams of the hydrated titanic acid prepared above were placed in a pressure-resistant corrosion-preventive tube and heated to 160°C. Subsequently, air was filled into the pressure-resistant corrosion-preventive tube, the pressure inside the tube was maintained at 5 atmospheres, and the mixture was kept at a constant temperature of 160°C for 12 hours to obtain the product. Detection revealed that the product obtained in this comparative example was still non-crystalline titanic acid and could not be converted into a nanotitania material with a crystalline phase.

[0068] Comparative Example 2 First, a 0.25 mol / liter aqueous solution of titanium tetrachloride and a 1 mol / liter solution of sodium hydroxide were gradually mixed in a 1:1 volume ratio. After washing and separation, the mixture was dried at room temperature and pressure to obtain hydrated titanic acid. Next, 10 grams of the hydrated titanic acid prepared above was placed in a pressure-resistant rust-preventive tube, heated to 160°C at atmospheric pressure, and then kept at a constant temperature for 12 hours to obtain the product. Detection revealed that the product obtained in this comparative example was still non-crystalline titanic acid and could not be converted into a nanotitania material with a crystalline phase. [Examples]

[0069] First, 10 grams of titanium hydroxide powder (Guangdong Wengjiang Chemical Reagents Co., Ltd., CAS number: 20338-08-3, purity ≥ 99%) was measured out and placed in a pressure-resistant corrosion-preventive tube. Then, the pressure-resistant corrosion-preventive tube was heated to 120°C, the pressure at the hydrogen chloride injection port inside the tube was maintained at approximately 2 atmospheres (fluctuating between 1.5 and 2 atmospheres), and the injection pressure at the water vapor port was maintained at approximately 1 atmosphere. The tube was kept at a constant temperature of 120°C for 24 hours to obtain a nanotitania powder material with significantly improved dispersion, stability, and transparency.

[0070] The titania material obtained in Example 4 has anatase as its main crystalline phase. When this product is mixed with water, it spontaneously disperses without stirring, forming an aqueous dispersion in which nanotitania particles are stably suspended. Figure 5 shows an aqueous dispersion with a mass ratio of 5‰ obtained by adding water to the nanotitania product obtained in this example. This dispersion has good monodispersibility, can form a relatively stable colloidal dispersion in aqueous solution, and exhibits a clear Tyndall effect. The nanoparticles are stable in suspension, do not settle easily, and no clear delamination phenomenon occurred in the solution even after being left for more than 3 days. For comparison, Figure 6 is an optical photograph of a titanium hydroxide suspension, a precursor with a mass ratio of 5‰, after being left standing for 2 hours. Clear delamination is observed, indicating that the suspension is unstable, and it can be seen that the suspension stability of the product obtained in this technique has improved by more than 36 times.

[0071] The titania material aqueous dispersion obtained in Example 4 had a light transmittance of 85% at a wavelength of 550 nanometers, which is 34 times more transparent than the 2.5% light transmittance of the precursor titanium hydroxide suspension at the same concentration. Specifically, a small amount of the titania material obtained in Example 1 was taken and prepared as an aqueous dispersion with a mass ratio of 5 / 10,000. For comparison, a titanium hydroxide suspension with a mass ratio of 5 / 10,000 was also prepared. Then, each of the above dispersions was taken and placed in a 1 cm thick quartz colorimetric dish, and the light transmittance of the sample at a wavelength of 550 nanometers was measured, with pure water used as a blank.

[0072] A small amount of the product obtained in Example 4 was taken, dispersed in deionized water, and then a small amount was dropped onto a silicon wafer. After air drying, the dried silicon wafer was attached to the sample stage of a scanning electron microscope with conductive paste and used to observe the morphology of the sample with a scanning electron microscope, as shown in Figure 7. From Figure 7, it can be seen that the titania nanoparticles of the product had good dispersion, could be spread on the silicon wafer, had a particle size of about 50 nanometers, and exhibited good particle uniformity. For comparison, Figure 8 is a scanning electron microscope image of the precursor, titanium hydroxide. The precursor was an aggregate of nanoparticles of about 50 nanometers, showing poor dispersion, and it was also shown that the precursor was prone to delamination by settling in water. By statistically analyzing the number of particles in the same area on the scanning electron microscope images, it can be estimated that the dispersion of the titania product treated with this technology was significantly improved, with an improvement of approximately 50 times. As a result, the titania products treated with this technology show significant improvements in terms of dispersion, dispersion stability, and transparency after dispersion, indicating a substantial expansion of the applications of titania materials in product fields such as UV absorption and aesthetics.

[0073] As described above, the advantages of the present invention are (1) that this technical method does not use any interfacial organic additives, thus making it universally applicable to the fields of application of nanotitania dispersions and improving the fields of use and effects of the dispersions, and (2) that this technical method has a low processing temperature, simple operation steps, is inexpensive, and is advantageous for widespread adoption in large-scale industrialization. [Examples]

[0074] First, 10 grams of titanium hydroxide powder (Guangdong Wengjiang Chemical Reagents Co., Ltd., CAS number: 20338-08-3, purity ≥ 99%) was measured out and placed in a pressure-resistant corrosion-preventive tube. Then, the pressure-resistant corrosion-preventive tube was heated to 150°C, and the pressure at the hydrogen chloride injection port and the injection pressure at the water vapor port were maintained at approximately 8 atmospheres. The tube was kept at a constant temperature of 150°C for 12 hours to obtain a nanotitania powder material with significantly improved dispersion, stability, and transparency.

[0075] The titania material obtained in Example 5 has an anatase phase as its main crystalline phase and contains a trace amount of rutile phase. When this product is mixed with water, it spontaneously disperses without stirring to form an aqueous dispersion in which nanotitania particles are stably suspended, exhibiting a clear Tyndall effect. The nanoparticles in the dispersion are stable in suspension and do not settle easily, and no clear delamination phenomenon occurred in the solution even after being left for two days. For comparison, a clear delamination phenomenon appeared after a titanium hydroxide suspension, which is a precursor, was left to stand for two hours, indicating that the suspension stability of the product obtained with this technique has improved by more than 24 times.

[0076] The titania material aqueous dispersion obtained in Example 5 had a light transmittance of 67% at a wavelength of 550 nanometers, which is 27 times more transparent than the 2.5% light transmittance of the precursor titanium hydroxide suspension at the same concentration. The specific experiment was the same as in Example 4. Using the same electron microscope observation method as in Example 4, the dispersion of the titania material aqueous dispersion obtained in Example 5 was improved by approximately 20 times. As a result, the titania products treated with this technology show significant improvements in terms of dispersion, dispersion stability, and transparency after dispersion, indicating a substantial expansion of the applications of titania materials in product fields such as ultraviolet absorption and aesthetics. [Examples]

[0077] First, 10 grams of self-prepared non-crystalline nanotitania particles were measured out by slowly dropping an ethanol solution containing titanium isopropoxide into a nitric acid-ethanol aqueous solution with a pH of 2 to hydrolyze it, followed by washing, separation, and drying, and then placed into a pressure-resistant corrosion-preventive tube. Subsequently, the pressure-resistant corrosion-preventive tube was heated to 140°C, the pressure at the hydrogen chloride inlet inside the tube was maintained at a constant 2 atmospheres, and the tube was kept at a constant temperature of 140°C for 16 hours to obtain an aqueous-phase monodisperse nanotitania powder material with significantly improved dispersion, stability, and transparency.

[0078] The titania material obtained in this Example 6 has an anatase phase as its crystalline phase. When this product is mixed with water, it spontaneously disperses without stirring to form an aqueous dispersion in which nanotitania particles are stably suspended, exhibiting a clear Tyndall effect. The nanoparticles in the dispersion are stable in suspension and do not settle easily, and no clear delamination phenomenon occurred in the solution even after being left for 60 days. For comparison, a clear delamination phenomenon appeared after the precursor suspension was left to stand for 5 hours, indicating that the suspension stability of the product obtained by this technique has improved by more than 288 times.

[0079] The titania material aqueous dispersion obtained in Example 6 had a light transmittance of 95% at a wavelength of 550 nanometers, which is 16 times more transparent than the 6% light transmittance of the precursor suspension of the same concentration. The specific experiment was the same as in Example 4. Using the same electron microscope observation method as in Example 4, the dispersion of the titania material aqueous dispersion obtained in Example 6 was improved by approximately 10 times. As a result, the titania products treated with this technology show significant improvements in terms of dispersion, dispersion stability, and transparency after dispersion, indicating a substantial expansion of the applications of titania materials in product fields such as ultraviolet absorption and aesthetics. [Examples]

[0080] First, 10 grams of self-produced crystalline nanotitania particles, in which the crystalline phase is anatase phase, were measured out by slowly adding an ethanol solution containing titanium isopropoxide dropwise to a nitric acid-ethanol aqueous solution with a pH of 2 to hydrolyze it, followed by washing, separation, and drying, and then annealing at 300°C for 3 hours, and placed in a pressure-resistant corrosion-preventive tube. Subsequently, the pressure-resistant corrosion-preventive tube was heated to 200°C, the pressure at the hydrogen chloride injection port inside the tube was maintained at a constant 5 atmospheres, the injection pressure at the water vapor port was set to 5 atmospheres, and the tube was kept at a constant temperature of 200°C for 10 hours to obtain a nanotitania powder material with significantly improved dispersion, stability, and transparency.

[0081] The titania material obtained in this Example 7 has an anatase phase as its crystalline phase. When this product is mixed with water, it spontaneously disperses without stirring to form an aqueous dispersion in which nanotitania particles are stably suspended, exhibiting a clear Tyndall effect. The nanoparticles in the dispersion are stable in suspension and do not settle easily, and no clear delamination phenomenon occurred in the solution even after being left for 10 days. For comparison, a clear delamination phenomenon appeared after the precursor suspension was left to stand for 3 hours, indicating that the suspension stability of the product obtained by this technique has improved by more than 80 times.

[0082] The titania material aqueous dispersion obtained in Example 7 had a light transmittance of 83% at a wavelength of 550 nanometers, which is 23 times higher in transparency compared to the 3.6% light transmittance of the precursor suspension of the same concentration. The specific experiment was the same as in Example 4. Using the same electron microscope observation method as in Example 4, the dispersion of the titania material aqueous dispersion obtained in Example 7 was improved by approximately 20 times. As a result, the titania products treated with this technology show significant improvements in terms of dispersion, dispersion stability, and transparency after dispersion, indicating a substantial expansion of the applications of titania materials in product fields such as ultraviolet absorption and aesthetics.

[0083] Comparative Example 3 First, 10 grams of titanium hydroxide powder (Guangdong Wengjiang Chemical Reagents Co., Ltd., CAS number: 20338-08-3, purity ≥ 99%, particle size 20-30 nm) was measured and placed in a pressure-resistant corrosion-preventive tube. Then, the pressure-resistant corrosion-preventive tube was heated to 120°C, the injection pressure at the steam port inside the tube was maintained at approximately 1 atmosphere, and the tube was kept at a constant temperature of 120°C for 24 hours to obtain the product. For example, as shown in Figure 9 of the scanning electron microscope image, the morphology of the product obtained in this comparative example is basically identical to that of the precursor. At the same time, the product could not form a stable, transparent dispersion in water; the obtained product was a suspension, and precipitation delamination appeared after 2 hours. Therefore, the treatment in this comparative example could not alter the performance of the titania product in terms of dispersibility, dispersion stability, or transparency after dispersion.

[0084] Any numerical value cited in this text includes all lower and upper values ​​that increase by one unit from the lower limit to the upper limit, provided that there is at least two units between any lower and upper value. For example, if the value of the number of components or process variables (e.g., temperature, pressure, time, etc.) is stated as being from 1 to 90, then 20 to 80 is preferred, 30 to 70 is more preferred, and this is intended to explain that the specification also clearly lists values ​​such as 15 to 85, 22 to 68, 43 to 51, and 30 to 32. For values ​​less than 1, one unit can be appropriately considered to be 0.0001, 0.001, 0.01, or 0.1. These are merely examples intended for clarity, and it is assumed that all possible combinations of numerical values ​​listed between the lowest and highest values ​​are clearly described in the specification in a similar manner.

[0085] Unless otherwise specified, all ranges include all numbers at and between the endpoints. The terms "approximately" or "approximately" used with a range apply to the two endpoints of that range. Therefore, "approximately 20 to 30" attempts to cover "approximately 20 to approximately 30," including at least the specified endpoints.

[0086] The above explanation should be understood as being for illustrative purposes only, and not for regulatory purposes.

[0087] By reviewing the above description, many embodiments and applications other than those provided will be obvious to those skilled in the art. Therefore, the scope of this teaching should not be determined by the above description, but rather by all the attached claims and their correspondings. For the purpose of comprehensiveness, all text and published materials, including patent applications and publications, are incorporated herein by reference. Any aspect of the subject matter disclosed herein, though omitted in the claims, is not intended to waive the subject matter, and it should not be considered that the inventor does not consider such subject matter to be part of the disclosed subject matter.

Claims

1. (1) obtaining hydrated titanic acid from a titanium compound through hydrolysis, separation, purification and drying processes; (2) heating the hydrated titanic acid to 100°C to 200°C; (3) A method for producing low-temperature crystallized titania, comprising the steps of: passing hydrogen chloride gas through the heated hydrated titanic acid system and reacting it at constant pressure to obtain a crystalline nanotitania material.

2. 2. The method for producing low-temperature crystallized titania according to claim 1, wherein the titanium compound is one or a combination of two or more selected from the group consisting of titanium sulfate, titanyl sulfate, titanium tetrachloride, titanium isopropoxide, and tetrabutyl titanate.

3. 2. The method for producing low-temperature crystallized titania according to claim 1, wherein the hydrolysis process is a direct reaction between the titanium compound and water, or a reaction between the titanium compound and an alkaline aqueous solution.

4. 2. The method for producing low-temperature crystallized titania according to claim 1, wherein the hydrogen chloride gas passed through the method further contains water vapor.

5. 2. The method for preparing low-temperature crystallized titania according to claim 1, wherein the pressure of the constant-voltage reaction is 0.5 to 20 atmospheres, preferably 1 to 10 atmospheres.

6. 2. The method for preparing low-temperature crystallized titania according to claim 1, wherein the time for the constant pressure reaction is 3 to 24 hours.

7. 2. The method for producing low-temperature crystallized titania according to claim 1, wherein the crystalline phase of the crystalline nanotitania material is a rutile phase, an anatase phase, or a composite phase of the rutile phase and the anatase phase.

8. The method for preparing low-temperature crystallized titania according to claim 1, characterized in that the crystalline nanotitania material can be spontaneously dispersed in pure water without any additives or dispersants to form a stable dispersion that is primarily a colloidal dispersion.

9. The method for producing low-temperature crystallized titania according to claim 1, characterized in that the crystalline nano-titania material is nano-level titania particles having a particle size of less than 100 nanometers or an aggregate of nano-level titania particles having a particle size of less than 100 nanometers, and the interface of the crystalline nano-titania material is acidic.

10. placing a precursor solid titania A in a container; and filling a vessel containing the precursor solid titania A with hydrogen chloride gas and carrying out a low-temperature heat treatment to obtain a product of dispersed titania B. A method for improving the dispersibility of titania obtained by the production method of any one of claims 1 to 9.

11. The method for improving the dispersibility of titania according to claim 10, characterized in that the dispersibility of the product of dispersible titania B in water is improved by 10 times or more compared to the precursor titania A.

12. The method for improving the dispersibility of titania according to claim 10, characterized in that the dispersion stability of the dispersible titania B product in water is improved by 10 times or more compared to the precursor titania A.

13. The method for improving the dispersibility of titania according to claim 10, characterized in that the transparency of the dispersible titania B product after dispersion in water is improved by 10 times or more compared to that of the precursor titania A.

14. The method for improving the dispersibility of titania according to claim 10, characterized in that the dispersible titania B product can be spontaneously dispersed in pure water containing no additives or dispersants to form a stable dispersion that is mainly colloidal.

15. The method for improving the dispersibility of titania according to claim 10, characterized in that the product of dispersible titania B is nano-level titania particles having a particle size of less than 100 nanometers or aggregates of nano-level titania particles having a particle size of less than 100 nanometers, and the interface of the product of dispersible titania B is acidic.

16. The method for improving the dispersibility of titania according to claim 10, characterized in that the product of dispersible titania B is crystalline nanotitania, and the crystalline phase of the crystalline nanotitania is one or a combination of two or more of anatase phase, rutile phase, and brookite phase.

17. The method for improving the dispersibility of titania according to claim 10, wherein the precursor solid titania A is nano-level titania particles having a particle size of less than 100 nanometers or an aggregate of nano-level titania particles having a particle size of less than 100 nanometers, and preferably the precursor solid titania A is nano-level titania particles having a particle size of less than 50 nanometers or an aggregate of nano-level titania particles having a particle size of less than 50 nanometers.

18. 11. The method for improving the dispersibility of titania according to claim 10, wherein the solid titania A precursor is crystalline titania particles or non-crystalline titania particles.

19. 11. The method for improving the dispersibility of titania according to claim 10, wherein the precursor solid titania A further contains one or a combination of titanium hydroxide, titanium hydroxide hydrate, titanic acid, and titanic acid hydrate.

20. 11. The method for improving the dispersibility of titania according to claim 10, wherein the hydrogen chloride atmosphere further contains water vapor, and the pressure of the water vapor is from 0.1 atmosphere to 10 atmospheres.

21. The pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere is 0.5 to 20 atmospheres, and preferably, the pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere is 1 to 10 atmospheres.

11. The method for improving the dispersibility of titania according to claim 10.

22. 11. The method for improving the dispersibility of titania according to claim 10, wherein the hydrogen chloride gas in the hydrogen chloride atmosphere fluctuates within a predetermined pressure range, the hydrogen chloride atmosphere is continuously provided, or the hydrogen chloride atmosphere is provided by inputting it from an external source.

23. The method for improving the dispersibility of titania according to claim 10, characterized in that the heat treatment temperature is 80 to 300°C, preferably 100 to 200°C, and the heat treatment time is 2 to 48 hours.

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