WO2022007764A1

WO2022007764A1 - Method for preparing titanium dioxide and method for improving titanium dioxide dispersibility

Info

Publication number: WO2022007764A1
Application number: PCT/CN2021/104594
Authority: WO
Inventors: 梁先华
Original assignee: 宁波极微纳新材料科技有限公司
Priority date: 2020-07-06
Filing date: 2021-07-05
Publication date: 2022-01-13
Also published as: JP2023532589A

Abstract

A method for preparing titanium dioxide and a method for improving titanium dioxide dispersibility. A method for preparing a low-temperature crystallized titanium dioxide, the method comprising the following steps: (1) subjecting a titanium compound to hydrolysis, separation, purification and drying processes to obtain hydrated titanic acid; (2) heating the hydrated titanic acid to 100°C to 200°C; and (3) introducing hydrogen chloride gas into the heated hydrated titanic acid system and carrying out a constant pressure reaction to obtain a crystalline nano titanium dioxide material. The technical method of the low-temperature crystallized titanium dioxide can improve the precipitation synthesis method of nano titanium dioxide, and can also improve the performances and application field of titanium dioxide nano materials.

Description

Method for preparing titanium dioxide and method for improving dispersibility of titanium dioxide

Cross-reference related references

This application requires the application number 202010642220.X submitted on July 6, 2020, the name of the invention is "Method for low-temperature crystallization of titanium dioxide", and the application number 202010642931.7 submitted on July 6, 2020, the name of the invention is "a Priority of the Chinese Patent Application for "Methods for Improving the Dispersibility of Titanium Dioxide", the entire contents of which are incorporated herein by reference.

technical field

The present application relates to a method for preparing titanium dioxide and a method for improving the dispersibility of titanium dioxide.

Background technique

Nano-titanium dioxide refers to titanium dioxide with a particle size of less than 100 nanometers. It has special effects such as small particle size, high specific surface area, excellent photocatalytic activity, stable chemical and thermal properties, and super affinity. Self-cleaning materials, sunscreen skin care products and other fields have irreplaceable application advantages. For example, nano-titanium dioxide can be used to decompose formaldehyde, benzene, TVOC, SOx, NOx, etc. It can also be used to remove pollution and odor in refrigerators, clean air conditioners, etc., and play the role of indoor and car air control; nano-titanium dioxide is used in glass, shutters, Mirrors, street lamps and other surfaces can achieve self-cleaning effect; nano-titanium dioxide is also widely used in medical equipment, catheters, operating rooms, sunscreen cosmetics, sunscreen clothing, whitening products, anti-aging coatings and other fields; in addition, nano-titanium dioxide can also be used in lithium Energy conversion and storage fields such as anode materials for ion batteries, photocatalysis or photoelectric catalytic production of hydrogen energy.

At present, the preparation methods of nano-titania mainly include gas-phase method and liquid-phase method. The liquid phase synthesis method has the advantages of easy control of the reaction, simple equipment, and low energy consumption, and is widely used in the laboratory and industry to prepare titanium dioxide materials. Liquid-phase methods mainly include precipitation method, hydrothermal method, sol-gel method, microemulsion method, etc.

Among them, the process route of the precipitation method means that at a certain temperature, by controlling the pH value of the solution, the titanium source is hydrolyzed in water to form insoluble hydrated titanic acid precipitation, and then the titanium dioxide powder is obtained by filtering, washing, drying, calcining and other steps. body. In the precipitation method, in order to obtain highly crystalline titania materials, the calcination temperature is usually greater than 500 degrees Celsius. The high calcination temperature also increases the equipment investment and energy consumption in the synthesis process.

Therefore, reducing the calcination temperature in the precipitation method is a key step to improve the synthesis of titania materials by the precipitation method, which is of great significance for improving product performance and reducing costs.

In addition, the properties of materials have a very important relationship with their size. Nanoparticles with ultra-small particle size can exhibit more excellent properties in energy, environment, and catalysis. For example, titanium dioxide materials with a particle size of less than 100 nanometers have special effects such as small particle size, high specific surface area, excellent photocatalytic activity, stable chemical and thermal properties, and super affinity, which are used in air treatment, sterilization and self-cleaning. Materials, sunscreen skin care products and other fields have irreplaceable application advantages.

The concentration and stability of the nano-titania particle dispersion have important effects on the reaction process and the final product. With the continuous expansion of the application range of titanium dioxide, such as in air treatment, material forming, coatings, ink preparation and other application fields, product performance largely depends on the dispersion degree of titanium dioxide powder in liquid medium. The better the dispersion, the better the final product. The application effect is also better. Generally, nano-TiO2 particles are small in size, have a large number of defects on the surface, large surface activity, and are in a thermodynamically unstable state. The nanoparticles dispersed in the liquid medium are easy to coagulate, agglomerate, and coagulate, and cannot form a stable dispersion. The unique properties of nanoparticles cause great defects in practical applications. Mainly in: (1) In the field of photocatalysts, they cannot be sprayed on the surfaces of doors, windows, leather goods, etc. after they are formulated into photocatalysts, because white spots will be formed, which will affect the appearance, and the photocatalytic activity of the agglomerated nanoparticles is not high, which can remove pollutants such as formaldehyde. The effect is not obvious; (2) In the field of self-cleaning, due to their strong light scattering and reflection, resulting in poor light transmittance, they cannot be directly used on transparent surfaces such as glass and mirrors; (3) In the field of beauty and skin care products, they cannot be used directly. Skin care and sunscreen products used to make transparent and natural skin tone will make the skin appear unnaturally white; (4) In the field of film products, it cannot be widely used in transparent film products, transparent durable topcoats, fine ceramics, etc.

Preventing the agglomeration of nano-titanium dioxide particles and obtaining monodisperse titanium dioxide nanoparticles can greatly improve the performance of titanium dioxide nanomaterials in the fields of optics, electricity, and catalysis. At present, it has been reported to prepare stable nanoparticle dispersions by physical dispersion and chemical dispersion. Among them, the physical dispersion method mainly uses external forces to disperse the nanoparticles, including mechanical stirring dispersion, ultrasonic dispersion and high-energy treatment dispersion. The disadvantage of the physical dispersion method is that if the external force stops, the particles will re-aggregate. The chemical dispersion method is to use surface chemical methods to add surface treatment agents for dispersion. For example, the preparation of water-phase dispersed nanoparticles is usually achieved by the induction and restraint of water-soluble surfactants or polymers, but the surface of the particles is covered with modified molecules such as organics. The contribution of dispersibility control to improving material properties is reduced, such as the preparation of water-soluble titanium dioxide nanoparticles by the reaction of titanium alkoxides and alkylamines, but the presence of such alkaline reagents passivates the surface activity of the product to make it photocatalytic At the same time, different application systems may also have adverse adverse effects with the surface-modified molecules, reducing the application performance of the final product. For example, the use of polyethylene glycol as a stabilizer makes the dispersibility of titanium dioxide nanoparticles somewhat improved. increased, but decreased its catalytic activity. In addition, the titanium dioxide dispersion product obtained by the above method is still a liquid suspension, the particles cannot be completely monodispersed and the particle size is uneven, and a stable colloidal dispersion cannot be formed, resulting in high transportation costs and practical application.

Therefore, it is urgent to develop a technical method that does not use any surface organic additives, and can greatly improve the dispersibility of nano-titania by processing at low temperature, so as to promote the application field and use effect of titania nanomaterials.

SUMMARY OF THE INVENTION

In view of the above deficiencies, the present invention provides a technical method for preparing low-temperature crystallized titanium dioxide, so as to improve the precipitation synthesis method of nano-titanium dioxide and promote the properties and application fields of titanium dioxide nanomaterials.

Another object of the present invention is to provide a technical method for greatly improving the dispersibility of nano-titanium dioxide, so as to promote the application field and use effect of nano-titanium dioxide materials.

To achieve the above object, the present invention adopts the following technical solutions:

A method for preparing low-temperature crystallized titanium dioxide, comprising the following steps:

(1) The titanium compound is hydrolyzed, separated, purified and dried to obtain hydrated titanic acid;

(2) heating the hydrated titanic acid to 100 degrees Celsius to 200 degrees Celsius;

(3) introducing hydrogen chloride gas into the heated hydrated titanic acid system and reacting at constant pressure to obtain a crystalline nano-titanium dioxide material.

As a preferred embodiment, the titanium compound is selected from one or a combination of titanium sulfate, titanium oxysulfate, titanium tetrachloride, titanium isopropoxide, and tetrabutyl titanate.

As a preferred embodiment, the hydrolysis process is to directly react the titanium compound with water; or, the hydrolysis process is to react the titanium compound with an alkaline aqueous solution.

As a preferred embodiment, the passing hydrogen chloride gas also contains water vapor.

As a preferred embodiment, the pressure of the constant pressure reaction is 0.5 atmospheres to 20 atmospheres; the preferred pressure is 1 atmosphere to 10 atmospheres.

As a preferred embodiment, the time of the constant pressure reaction is 3 hours to 24 hours.

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

As a preferred embodiment, the crystalline nano-titania material can be spontaneously dispersed in pure water without additives or dispersants to form a stable dispersion; the dispersion is mainly colloidal dispersion.

As a preferred embodiment, the crystalline nano-titanium dioxide material is nano-scale titanium dioxide particles with a particle size of less than 100 nanometers or nano-scale titanium dioxide particle agglomerates with a particle size of less than 100 nanometers; the surface of the crystalline nano-titanium dioxide material is Acidic.

A method for improving the dispersibility of titanium dioxide, comprising the following steps:

The precursor solid titanium dioxide A is thermally treated in a hydrogen chloride atmosphere to obtain a dispersed titanium dioxide B product.

A method and product for improving the dispersibility of titanium dioxide, comprising the following steps:

The precursor solid titanium dioxide A is placed in the container;

The container in which the precursor solid titanium dioxide A is placed is filled with hydrogen chloride gas and subjected to low temperature heating treatment to obtain a dispersible titanium dioxide B product.

As a preferred embodiment, compared with the precursor titanium dioxide A, the dispersibility of the dispersible titanium dioxide B product in water is increased by more than ten times.

As a preferred embodiment, compared with the precursor titanium dioxide A, the dispersion stability of the dispersible titanium dioxide B product in water is improved by more than ten times.

As a preferred embodiment, compared with the precursor titanium dioxide A, the transparency of the dispersible titanium dioxide B product after being dispersed in water is increased by more than ten times.

As a preferred embodiment, the dispersible titanium dioxide B product can spontaneously disperse in pure water without additives or dispersants to form a stable dispersion; the dispersion is mainly colloidal dispersion.

As a preferred embodiment, the dispersible titanium dioxide B product is nanoscale titanium dioxide particles with a particle size of less than 100 nanometers or nanoscale titanium dioxide particle agglomerates with a particle size of less than 100 nanometers; the surface of the dispersible titanium dioxide B product is Acidic.

As a preferred embodiment, the dispersible titanium dioxide B product is crystalline nano-titanium dioxide; the crystal phase of the crystalline nano-titanium dioxide is one or more of anatase phase, rutile phase, and brookite phase The combination.

As a preferred embodiment, the precursor solid titanium dioxide A is nanoscale titanium dioxide particles with a particle size of less than 100 nanometers or nanoscale titanium dioxide particle agglomerates with a particle size of less than 100 nanometers.

As a preferred embodiment, the precursor solid titanium dioxide A is nanoscale titanium dioxide particles with a particle size of less than 50 nanometers or nanoscale titanium dioxide particle agglomerates with a particle size of less than 50 nanometers.

As a preferred embodiment, the precursor solid titanium dioxide A is crystalline titanium dioxide particles or amorphous titanium dioxide particles.

As a preferred embodiment, the precursor solid titanium dioxide A further includes one or a combination of titanium hydroxide, titanium hydroxide hydrate, titanic acid, and titanic acid hydrate.

As a preferred embodiment, the hydrogen chloride atmosphere also contains water vapor; the pressure of the water vapor is 0.1 atm to 10 atm.

As a preferred embodiment, the pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere is 0.5 atm to 20 atm.

As a preferred embodiment, the pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere is 1 atmosphere to 10 atmospheres.

As a preferred embodiment, the pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere can be constant or changed.

As a preferred embodiment, the hydrogen chloride atmosphere is provided in a continuous manner or an intermittent manner.

As a preferred embodiment, the source of the hydrogen chloride atmosphere can be provided by the inside of the reaction system or provided by external input.

As a preferred embodiment, the temperature of the heat treatment is 80 degrees Celsius to 300 degrees Celsius; the preferred heat treatment temperature is 100 degrees Celsius to 200 degrees Celsius.

As a preferred embodiment, the time of the heat treatment is 2 hours to 48 hours.

As a preferred embodiment, the hydrogen chloride gas in the hydrogen chloride atmosphere fluctuates within a predetermined pressure range; the hydrogen chloride atmosphere is provided in a continuous manner; the hydrogen chloride atmosphere is provided by an external input.

The advantages of the present invention are:

1. The method for preparing low-temperature crystalline titanium dioxide greatly reduces the calcination temperature in the nano-titanium dioxide precipitation synthesis method, and reduces the calcination temperature from 500 degrees Celsius to a minimum of 100 degrees Celsius, saving energy consumption and equipment investment.

2. The nano-titanium dioxide material obtained by the method for preparing low-temperature crystalline titanium dioxide has a great improvement in specific surface area, dispersibility and catalytic performance.

3. The method for improving the dispersibility of titanium dioxide does not use any surface organic additives, which makes the application field of the nano-titanium dioxide dispersion liquid universal, and increases the application field and use effect of the dispersion liquid.

4. The method for improving the dispersibility of titanium dioxide has low processing temperature, simple operation steps and low price, which is favorable for large-scale industrialization and application.

With reference to the following description and drawings, specific embodiments of the invention are disclosed in detail, indicating the manner in which the principles of the invention may be employed. It should be understood that embodiments of the present invention are not thereby limited in scope.

Features described and/or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, in combination with, or instead of features in other embodiments .

It should be emphasized that the term "comprising/comprising" when used herein refers to the presence of a feature, integer, step or component, but does not exclude the presence or addition of one or more other features, integers, steps or components.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

FIG. 1 is a transmission electron microscope image observed after the titanium dioxide water dispersion droplets obtained in Example 1 are coated on a copper mesh and dried.

2 is an X-ray diffraction pattern of the titanium dioxide product prepared in Example 1, and the main crystal phase is anatase phase.

FIG. 3 is a colloidal water dispersion formed by mixing the titanium dioxide material obtained in Example 1 with water.

Fig. 4 is the photocatalytic degradation curve of rhodamine B of the nano-titania product obtained in Example 1 and P25.

Fig. 5 is that the mass fraction obtained after adding water to the nano-titania product obtained in Example 4 is an aqueous dispersion of 5/1000, which has a relatively stable dispersion state;

Figure 6 is an optical image of the precursor titanium hydroxide suspension with a mass fraction of 5/1000 standing for 2 hours, with obvious delamination phenomenon, and the suspension is unstable;

Fig. 7 is the SEM image obtained by drip-coating the product obtained in Example 4 on a silicon wafer after being dispersed in water, and observed after drying;

Fig. 8 is the scanning electron microscope image obtained after the precursor titanium hydroxide is dispersed in water and then drop-coated on the silicon wafer and observed after drying;

FIG. 9 is a scanning electron microscope image of the product obtained in Comparative Example 3, after being dispersed in water and then drop-coated on a silicon wafer, and observed after drying.

detailed description

In order to make those skilled in the art better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described The embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Example 1

First, slowly mix 0.25 mol per liter of titanium tetrachloride aqueous solution with 1 mol per liter of sodium hydroxide solution in a volume ratio of 1 to 1, wash and separate, and then dry at normal temperature and pressure to obtain hydrated titanic acid; Next, take 10 grams of the hydrated titanic acid prepared above and place it in a pressure-resistant anti-corrosion tube, and heat it to 160 degrees Celsius; then fill the pressure-resistant anti-corrosion tube with hydrogen chloride gas to keep the pressure inside the tube at 5 atmospheres, at 160 degrees Celsius Constant temperature for 12 hours to obtain nano titanium dioxide powder material.

Take a small amount of the product obtained in this example and disperse it in deionized water and then take a small amount of drop-coating on a copper mesh, air dry naturally, and use for transmission electron microscopy to observe the morphology of the sample, as shown in Figure 1. It can be seen from FIG. 1 that the particle size of the product titanium dioxide nanoparticles is 5 nanometers to 10 nanometers, which further indicates that the nanometer titanium dioxide obtained in this example has a small particle size and good monodispersity.

Fig. 2 is the X-ray diffraction pattern of the titanium dioxide product prepared in this example, it can be seen from Fig. 2 that the main crystal phase of the nano-titanium dioxide obtained in this example is anatase phase, which has good crystallinity, and further illustrates the present invention The calcination temperature in the nano-titanium dioxide precipitation synthesis method can be greatly reduced, and the calcination temperature is reduced from 500 degrees Celsius to 160 degrees Celsius.

As shown in Figure 3, the nano-titanium dioxide product obtained in this example is added to water to obtain a nano-titanium dioxide dispersion with a mass fraction of 5/1000. The dispersion has good monodispersity and can form stable in an aqueous solution. The colloidal dispersion of the nanoparticle is stable in suspension, does not agglomerate and is not easy to settle, and the solution is placed for more than 6 months without stratification.

As shown in Figure 4, the nano-titania material obtained in this example has good photocatalytic activity, and the catalytic efficiency is 9 times that of commercial P25 material. 1 gram of Degussa) sample was dispersed in 100 ml of Rhodamine B solution with a concentration of 2.0×10-5 mol per liter, and was placed in a dark place with magnetic stirring for 30 minutes to achieve temperature equilibrium and adsorption equilibrium. Then turn on the simulated sunlight lamp, stir, take out 3 ml of samples at regular intervals, separate the particles by centrifugation, measure the absorbance of the solution at 550 nm with a UV-Vis spectrometer, and calculate the remaining concentration of Rhodamine B.

To sum up, the advantages of the present invention are: (1) the technical method greatly reduces the calcination temperature in the nano-titanium dioxide precipitation synthesis method, and reduces the calcination temperature from 500 degrees Celsius to 160 degrees Celsius, saving energy consumption and equipment investment. (2) The nano-titanium dioxide material obtained by this technical method is greatly improved in terms of specific surface area, dispersibility and catalytic performance.

Example 2

First, slowly add isopropyl titanate dropwise to deionized water at a volume ratio of 1:20, stir to form titanic acid precipitation, wash and separate, and then dry at normal pressure at 60 degrees Celsius to obtain hydrated titanic acid; secondly, Take 10 grams of the hydrated titanic acid prepared above and place it in a pressure-resistant anti-corrosion tube, and heat it to 120 degrees Celsius; then fill the pressure-resistant anti-corrosion tube with hydrogen chloride gas, keep the pressure inside the tube at 1 atmosphere, and keep it at 120 degrees Celsius at a constant temperature of 24 hours, to obtain nano titanium dioxide powder material.

Take a small amount of the product obtained in this example and disperse it in deionized water, and then take a small amount and drop it on a copper mesh, dry it naturally, and use it to observe the morphology of the sample with a transmission electron microscope. It can be seen that the particle size of the product titanium dioxide nanoparticles is 10 nanometers to 20 nanometers. Nanometer, and further illustrate that the nanometer titanium dioxide obtained in this example has a small particle size and good monodispersity.

The X-ray diffraction pattern confirms that the main crystal phase of the titanium dioxide product obtained in this implementation is anatase phase, which has good crystallinity, and further shows that the present invention can greatly reduce the calcination temperature in the nano-titanium dioxide precipitation synthesis method. Reduced from 500 degrees Celsius to 120 degrees Celsius.

The nano-titanium dioxide product obtained in this example is added to water to obtain a nano-titanium dioxide dispersion with a mass fraction of 5/1000. The dispersion has good monodispersity and can form a stable colloidal dispersion in an aqueous solution. Nanoparticles are stably suspended, do not agglomerate and are not easy to settle, and the solution has not been delaminated for 10 months.

The nano-titanium dioxide material obtained in this example has good photocatalytic activity, and the catalytic efficiency is 6 times that of commercial P25 material. The specific comparison method is to weigh the product obtained in this example and the P25 (Degusa) sample 1 gram respectively. Disperse in 100 ml of Rhodamine B solution with a concentration of 2.0 × 10-5 moles per liter, and place it in a dark place with magnetic stirring for 30 minutes to achieve temperature equilibrium and adsorption equilibrium. Then turn on the simulated sunlight lamp, stir, take out 3 ml of samples at regular intervals, separate the particles by centrifugation, measure the absorbance of the solution at 550 nm with a UV-Vis spectrometer, and calculate the remaining concentration of Rhodamine B.

Example 3

First, slowly mix 0.25 mol per liter of titanyl sulfate aqueous solution with 1 mol per liter of ammonia solution in a volume ratio of 1 to 1, wash and separate, and then dry at 80 degrees Celsius to obtain hydrated titanic acid; secondly, take 10 The hydrated titanic acid prepared above was placed in a pressure-resistant anti-corrosion tube and heated to 200 degrees Celsius; then the pressure-resistant anti-corrosion tube was filled with hydrogen chloride gas containing 30% water vapor by mass, and the pressure inside the tube was kept at 10 atmospheres of pressure, constant temperature at 200 degrees Celsius for 5 hours, to obtain nano titanium dioxide powder materials.

Take a small amount of the product obtained in this example and disperse it in deionized water, and then take a small amount and drop it on a copper mesh, dry it naturally, and use it to observe the morphology of the sample with a transmission electron microscope. It can be seen that the particle size of the product titanium dioxide nanoparticles is 20 nanometers to 50 nanometers. nanometer, indicating that the nanometer titanium dioxide obtained in this example has better dispersibility.

The X-ray diffraction pattern confirms that the main crystal phase of the titanium dioxide product obtained in this implementation is rutile phase, which has good crystallinity, and further shows that the present invention can greatly reduce the calcination temperature in the nano-titanium dioxide precipitation synthesis method, and the calcination temperature is increased from 500 Celsius decreased to 200 degrees Celsius.

The nano-titanium dioxide product obtained in this example is added to water to obtain a nano-titanium dioxide dispersion with a mass fraction of one thousandth. The dispersion has good monodispersity and can form a stable colloidal dispersion in an aqueous solution. Nanoparticles are stably suspended, do not agglomerate and are not easy to settle, and the solution does not delaminate after being placed for 1 month.

The nano-titania material obtained in this example has good photocatalytic activity, and the catalytic efficiency is twice that of commercial P25 material. The specific comparison method is to weigh the product obtained in this example and the P25 (Degussa) sample 1 gram respectively. Disperse in 100 ml of Rhodamine B solution with a concentration of 2.0 × 10-5 moles per liter, and place it in a dark place with magnetic stirring for 30 minutes to achieve temperature equilibrium and adsorption equilibrium. Then turn on the simulated sunlight lamp, stir, take out 3 ml of samples at regular intervals, separate the particles by centrifugation, measure the absorbance of the solution at 550 nm with a UV-Vis spectrometer, and calculate the remaining concentration of Rhodamine B. Comparative Example 1

First, slowly mix 0.25 mol per liter of titanium tetrachloride aqueous solution with 1 mol per liter of sodium hydroxide solution in a volume ratio of 1 to 1, wash and separate, and then dry at normal temperature and pressure to obtain hydrated titanic acid; Next, take 10 grams of the hydrated titanic acid prepared above and place it in a pressure-resistant anti-corrosion tube and heat it to 160 degrees Celsius; then fill the pressure-resistant anti-corrosion tube with air, keep the pressure inside the tube at 5 atmospheres, and keep the temperature at 160 degrees Celsius. After 12 hours, the product was obtained. After testing, the product obtained in this comparative example is still amorphous titanic acid, which cannot be converted into a nano-titanium dioxide material with a crystalline phase.

Comparative Example 2

First, slowly mix 0.25 mol per liter of titanium tetrachloride aqueous solution with 1 mol per liter of sodium hydroxide solution in a volume ratio of 1 to 1, wash and separate, and then dry at normal temperature and pressure to obtain hydrated titanic acid; Next, take 10 grams of the hydrated titanic acid prepared above, place it in a pressure-resistant anti-corrosion tube, heat it to 160 degrees Celsius under normal pressure and keep it at a constant temperature for 12 hours to obtain a product. After testing, the product obtained in this comparative example is still amorphous titanic acid, which cannot be converted into a nano-titanium dioxide material with a crystalline phase.

Example 4

First, 10 grams of titanium hydroxide (Guangdong Wengjiang Chemical Reagent Co., Ltd., CAS No.: 20338-08-3, purity ≥99%) powder was weighed and placed in a pressure-resistant anti-corrosion tube. Then, heat the pressure-resistant anti-corrosion pipe to 120 degrees Celsius, keep the pressure of the hydrogen chloride injection port in the pipe about 2 atmospheres (fluctuate between 1.5 atmospheres and 2 atmospheres), and the injection pressure of the water vapor port is about 1 atmosphere. Constant temperature at 120 degrees Celsius for 24 hours to obtain nano titanium dioxide powder materials with significantly improved dispersion, stability and transparency.

The main crystal phase of the titanium dioxide material obtained in Example 4 is anatase phase. The product is mixed with water, and can also spontaneously disperse without stirring to form an aqueous dispersion in which nano titanium dioxide particles are stably suspended. Figure 5 is an aqueous dispersion with a mass fraction of 5/1000 obtained after adding water to the nano-titania product obtained in this example, the dispersion has good monodispersity, and can form a relatively stable colloidal dispersion in the aqueous solution , with obvious Tyndall phenomenon; the nanoparticles are stably suspended, not easy to settle, and the solution is placed for more than 3 days without obvious stratification. For comparison, Figure 6 is an optical picture of the precursor titanium hydroxide suspension with a mass fraction of 5/1000 standing for 2 hours. It can be seen that there is an obvious layering phenomenon, and the suspension is unstable. It can be seen that this technology The suspension stability of the obtained product was increased by more than 36 times.

The light transmittance of the titanium dioxide material aqueous dispersion obtained in this embodiment 4 at a wavelength of 550 nanometers is 85%, compared with 2.5% of the light transmittance of the same concentration of the precursor titanium hydroxide suspension, and the transparency is improved by 34 times. The specific experimental operation is as follows: take a small amount of the titanium dioxide material obtained in Example 1, prepare it into an aqueous dispersion with a mass fraction of 5/10,000, for comparison, and also prepare a precursor hydroxide with a mass fraction of 5/10,000. Titanium suspension; then respectively take the above dispersion in a 1 cm thick quartz cuvette, test the transmittance of the sample at a wavelength of 550 nm, and use pure water as a blank.

Take a small amount of the product obtained in Example 4 and disperse it in deionized water, drop a small amount on the silicon wafer, dry it naturally, and adhere the dried silicon wafer to the sample stage of the scanning electron microscope with conductive adhesive for scanning. The morphology of the sample was observed by electron microscope, as shown in Figure 7. It can be seen from Figure 7 that the product titanium dioxide nanoparticles have good dispersion and can be spread on silicon wafers. The size of the particles is about 50 nanometers, and the uniformity of the particles is good. For comparison, Figure 8 is a scanning electron microscope image of the precursor titanium hydroxide. It can be seen that the precursor is an aggregate of nanoparticles of about 50 nanometers, with poor dispersion, which further shows that the precursor is easy to settle and stratify in water. By separately counting the number of particles in the same area on the SEM image, it can be estimated that the dispersion degree of the titanium dioxide product obtained after the treatment by this technology has been significantly improved, and the dispersion degree has been increased by about 50 times. It can be seen that the titanium dioxide product processed by this technology has been significantly improved in terms of dispersibility, dispersion stability, and transparency after dispersion, which will greatly expand the application of titanium dioxide materials in the fields of ultraviolet absorption and aesthetics.

To sum up, the advantages of the present invention are: (1) The technical method does not use any surface organic additive, which makes the application field of the nano titanium dioxide dispersion universal, and increases the application field and effect of the dispersion. (2) The processing temperature of the technical method is low, the operation steps are simple, and the price is low, which is favorable for large-scale industrialization and application.

Example 5

First, 10 grams of titanium hydroxide (Guangdong Wengjiang Chemical Reagent Co., Ltd., CAS No.: 20338-08-3, purity ≥99%) powder was weighed and placed in a pressure-resistant anti-corrosion tube. Then, heat the pressure-resistant anti-corrosion pipe to 150 degrees Celsius, keep the pressure of the hydrogen chloride injection port in the pipe about 8 atmospheres, and the injection pressure of the water vapor port about 8 atmospheres, and keep the temperature at 150 degrees Celsius for 12 hours to obtain dispersion and stability. , Transparent and significantly improved nano titanium dioxide powder material.

The main crystal phase of the titanium dioxide material obtained in Example 5 is anatase phase and contains a trace amount of rutile phase. This product is mixed with water, and can spontaneously disperse without stirring to form an aqueous dispersion in which nano-titanium dioxide particles are stably suspended, with obvious Tyndall phenomenon. Significant delamination occurred. For comparison, when the precursor titanium hydroxide suspension was left standing for 2 hours, an obvious layering phenomenon appeared. It can be seen that the suspension stability of the product obtained by this technology has increased by more than 24 times.

The light transmittance of the titanium dioxide material aqueous dispersion obtained in this Example 5 at a wavelength of 550 nanometers is 67%, which is 27 times higher than that of the 2.5% light transmittance of the precursor titanium hydroxide suspension with the same concentration. Specifically, The experimental procedure is the same as that in Example 4. Using the same electron microscope observation method in Example 4, the dispersion degree of the titanium dioxide material aqueous dispersion obtained in Example 5 is approximately 20 times higher. It can be seen that the titanium dioxide product processed by this technology has been significantly improved in terms of dispersibility, dispersion stability, and transparency after dispersion, which will greatly expand the application of titanium dioxide materials in the fields of ultraviolet absorption and aesthetics.

Example 6

First, weigh 10 grams of self-made amorphous nano-titanium dioxide particles and place them in a pressure-resistant anti-corrosion tube. The preparation method of the amorphous nano-titanium dioxide particles is: slowly add an ethanol solution containing titanium isopropoxide dropwise to a pH value of 2 Hydrolyzed in nitric acid-ethanol aqueous solution, washed, separated and dried. Subsequently, the pressure-resistant anti-corrosion pipe was heated to 140 degrees Celsius, the pressure of the hydrogen chloride injection port in the pipe was kept unchanged at 2 atmospheres, and the temperature was kept at 140 degrees Celsius for 16 hours to obtain a water-phase monodispersion with significantly improved dispersion, stability and transparency. Nano titanium dioxide powder material.

The crystal phase of the titanium dioxide material obtained in Example 6 was an anatase phase. This product is mixed with water, and can spontaneously disperse without stirring to form an aqueous dispersion in which nano-titanium dioxide particles are stably suspended, with obvious Tyndall phenomenon. Significant delamination occurred. For comparison, when the precursor suspension was left standing for 5 hours, an obvious stratification phenomenon appeared. It can be seen that the suspension stability of the product obtained by this technology has increased by more than 288 times.

The light transmittance of the titanium dioxide material aqueous dispersion obtained in Example 6 at a wavelength of 550 nanometers is 95%, compared with 6% of the light transmittance of the precursor suspension with the same concentration, the transparency is improved by 16 times. The specific experiment Operation is the same as Example 4. Using the same electron microscope observation method in Example 4, the dispersion degree of the titanium dioxide material aqueous dispersion obtained in Example 6 is increased by about 10 times. It can be seen that the titanium dioxide product processed by this technology has been significantly improved in terms of dispersibility, dispersion stability, and transparency after dispersion, which will greatly expand the application of titanium dioxide materials in the fields of ultraviolet absorption and aesthetics.

Example 7

First, weigh 10 grams of self-made crystalline nano-titanium dioxide particles and place them in a pressure-resistant anti-corrosion tube. The preparation method of the crystalline nano-titanium dioxide particles is as follows: slowly drop an ethanol solution containing titanium isopropoxide into a pH value of 2. Hydrolyzed in an aqueous nitric acid-ethanol solution, washed, separated and dried, and then annealed at 300 degrees Celsius for 3 hours, the crystalline phase is anatase phase. Subsequently, the pressure-resistant anti-corrosion pipe was heated to 200 degrees Celsius, the pressure of the hydrogen chloride injection port in the pipe was kept constant at 5 atmospheres, and the injection pressure of the water vapor port was 5 atmospheres, and the temperature was kept at 200 degrees Celsius for 10 hours to obtain dispersion and stability. , Transparent and significantly improved nano titanium dioxide powder material.

The crystal phase of the titanium dioxide material obtained in Example 7 was an anatase phase. This product is mixed with water, and can spontaneously disperse without stirring to form an aqueous dispersion in which nano-titanium dioxide particles are stably suspended, with obvious Tyndall phenomenon. Significant delamination occurred. For comparison, when the precursor suspension was left standing for 3 hours, an obvious stratification phenomenon appeared. It can be seen that the suspension stability of the product obtained by this technology has increased by more than 80 times.

The light transmittance of the titanium dioxide material aqueous dispersion obtained in Example 7 at a wavelength of 550 nanometers is 83%, which is 23 times higher than that of the 3.6% light transmittance of the precursor suspension with the same concentration. The specific experiment Operation is the same as Example 4. Using the same electron microscope observation method in Example 4, the dispersion degree of the titanium dioxide material aqueous dispersion obtained in Example 7 was increased by about 20 times. It can be seen that the titanium dioxide product processed by this technology has been significantly improved in terms of dispersibility, dispersion stability, and transparency after dispersion, which will greatly expand the application of titanium dioxide materials in the fields of ultraviolet absorption and aesthetics.

Comparative Example 3

First, weigh 10 grams of titanium hydroxide (Guangdong Wengjiang Chemical Reagent Co., Ltd., CAS No.: 20338-08-3, purity ≥99%, particle size 20-30nm) powder and place it in a pressure-resistant anti-corrosion tube. Subsequently, the pressure-resistant anti-corrosion pipe is heated to 120 degrees Celsius, and the injection pressure of the water vapor port in the pipe is maintained at about 1 atmosphere, and the product is obtained at a constant temperature of 120 degrees Celsius for 24 hours. The morphology of the product obtained in this comparative example is basically the same as that of the precursor, as shown in Fig. 9 of the scanning electron microscope; at the same time, the product cannot be dispersed in water to form a stable and transparent dispersion, the obtained product is a suspension liquid, and precipitation will appear within 2 hours. Floor. Therefore, the treatment of this comparative example cannot change the properties of the titanium dioxide product in terms of dispersion degree, dispersion stability, and transparency after dispersion.

Any numerical value recited herein includes all values of the lower value and the upper value in one unit increments from the lower value to the upper value, where there is an interval of at least two units between any lower value and any higher value, i.e. Can. For example, if the number of components or process variables (eg, temperature, pressure, time, etc.) are stated to have values from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, the intent is to illustrate that the The specification also explicitly lists values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32, and the like. For values less than 1, one unit is appropriately considered to be 0.0001, 0.001, 0.01, 0.1. These are merely examples of what is intended to be express, and all possible combinations of numerical values recited between the lowest value and the highest value are considered to be expressly set forth in this specification in a similar fashion.

Unless otherwise stated, all ranges include the endpoints and all numbers between the endpoints. "About" or "approximately" used with a range applies to both endpoints of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30," including at least the indicated endpoints.

It should be understood that the above description is for purposes of illustration and not limitation. From reading the above description, many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art. The scope of the present teachings should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated herein by reference for the purpose of being comprehensive. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to disclaim such subject matter, nor should it be construed that the inventor did not consider such subject matter to be part of the disclosed subject matter.

Claims

A method for preparing low-temperature crystallized titanium dioxide, comprising the following steps:

(1) The titanium compound is hydrolyzed, separated, purified and dried to obtain hydrated titanic acid;

(2) heating the hydrated titanic acid to 100 degrees Celsius to 200 degrees Celsius;

(3) introducing hydrogen chloride gas into the heated hydrated titanic acid system and reacting at constant pressure to obtain a crystalline nano-titanium dioxide material.
The method for preparing low-temperature crystalline titanium dioxide according to claim 1, wherein the titanium compound is selected from the group consisting of titanium sulfate, titanium oxysulfate, titanium tetrachloride, titanium isopropoxide, and tetrabutyl titanate. one or a combination of several.
The method for preparing low-temperature crystallized titanium dioxide according to claim 1, wherein the hydrolysis process is to directly react the titanium compound and water; or, the hydrolysis process is to react the titanium compound and an alkaline aqueous solution.
The method for preparing low-temperature crystallized titanium dioxide according to claim 1, characterized in that: the hydrogen chloride gas introduced into the gas also contains water vapor.
The method for preparing low-temperature crystallized titanium dioxide according to claim 1, wherein the pressure of the constant pressure reaction is 0.5 to 20 atmospheres; the preferred pressure is 1 to 10 atmospheres.
The method for preparing low-temperature crystalline titanium dioxide according to claim 1, wherein the time of the constant pressure reaction is 3 hours to 24 hours.
The method for preparing low-temperature crystalline titanium dioxide according to claim 1, wherein the crystal phase of the crystalline nano-titanium dioxide material is rutile phase or anatase phase or a composite phase of rutile phase and anatase phase .
The method for preparing low-temperature crystalline titanium dioxide according to claim 1, characterized in that: the crystalline nano-titanium dioxide material can be spontaneously dispersed in pure water without additives or dispersants to form a stable dispersion; the The dispersion is mainly colloidal dispersion.
The method for preparing low-temperature crystalline titanium dioxide according to claim 1, wherein the crystalline nano-titanium dioxide material is nano-scale titanium dioxide particles with a particle size of less than 100 nanometers or nano-scale titanium dioxide particles with a particle size of less than 100 nanometers Agglomerates; the surface of the crystalline nano-titania material is acidic.
A method for improving the dispersibility of titanium dioxide prepared by any one of the preparation methods of claims 1 to 9, wherein the method comprises the following steps:

The precursor solid titanium dioxide A is placed in the container;

The container in which the precursor solid titanium dioxide A is placed is filled with hydrogen chloride gas and subjected to low temperature heating treatment to obtain a dispersible titanium dioxide B product.
The method for improving the dispersibility of titanium dioxide according to claim 10, characterized in that compared with the precursor titanium dioxide A, the dispersibility of the product of the dispersible titanium dioxide B in water is increased by more than ten times.
The method for improving the dispersibility of titanium dioxide according to claim 10, characterized in that compared with the precursor titanium dioxide A, the dispersion stability of the dispersible titanium dioxide B product in water is improved by more than ten times.
The method for improving the dispersibility of titanium dioxide according to claim 10, characterized in that compared with the precursor titanium dioxide A, the transparency of the dispersible titanium dioxide B product after being dispersed in water is increased by more than ten times.
The method for improving the dispersibility of titanium dioxide according to claim 10, wherein the dispersible titanium dioxide B product can spontaneously disperse in pure water without additives or dispersants to form a stable dispersion; The liquid is mainly colloidal dispersion.
The method for improving the dispersibility of titanium dioxide according to claim 10, wherein the dispersible titanium dioxide B product is nanoscale titanium dioxide particles with a particle size of less than 100 nanometers or nanoscale titanium dioxide particles with a particle diameter of less than 100 nanometers. body; the surface of the dispersible titanium dioxide B product is acidic.
The method for improving the dispersibility of titanium dioxide according to claim 10, wherein the dispersive titanium dioxide B product is crystalline nano-titanium dioxide; the crystal phases of the crystalline nano-titanium dioxide are anatase phase, rutile phase , one or a combination of brookite phases.
The method for improving the dispersibility of titanium dioxide according to claim 10, wherein the precursor solid titanium dioxide A is nanoscale titanium dioxide particles with a particle size of less than 100 nanometers or nanoscale titanium dioxide particles with a particle diameter of less than 100 nanometers. Preferably, the precursor solid titanium dioxide A is nanoscale titanium dioxide particles with a particle size of less than 50 nanometers or nanoscale titanium dioxide particle agglomerates with a particle size of less than 50 nanometers.
The method for improving the dispersibility of titanium dioxide according to claim 10, wherein the precursor solid titanium dioxide A is crystalline titanium dioxide particles or amorphous titanium dioxide particles.
The method for improving the dispersibility of titanium dioxide according to claim 10, wherein the precursor solid titanium dioxide A further comprises one of titanium hydroxide, titanium hydroxide hydrate, titanic acid, and titanic acid hydrate or a combination of several.
The method for improving the dispersibility of titanium dioxide according to claim 10, wherein the hydrogen chloride atmosphere also contains water vapor; and the pressure of the water vapor is 0.1 atm to 10 atm.
The method for improving the dispersibility of titanium dioxide according to claim 10, wherein the pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere is 0.5 to 20 atmospheres, preferably, the pressure of the hydrogen chloride gas in the hydrogen chloride atmosphere From 1 atm to 10 atm.
The method for improving the dispersibility of titanium dioxide 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 provided in a continuous manner; the hydrogen chloride atmosphere is provided by an external Enter provided.
The method for improving the dispersibility of titanium dioxide according to claim 10, wherein: the temperature of the heat treatment is 80 degrees Celsius to 300 degrees Celsius; the preferred heat treatment temperature is 100 degrees Celsius to 200 degrees Celsius; the time of the heat treatment is 2 hours to 48 hours.