Method for preparing nanoscale titanium dioxide through gas-liquid method

Abstract

The invention relates to a method for preparing nanoscale titanium dioxide by a gas-liquid method, which comprises the following steps: (1) introducing a carrier gas carrying titanium tetrachloride gas into an aqueous solution containing a dispersing agent, and hydrolyzing by the gas-liquid method to obtain metatitanic acid slurry; (2) carrying out solid-liquid separation, washing and drying on the metatitanic acid slurry obtained in the step (1) to obtain metatitanic acid; and (3) mixing the metatitanic acid obtained in the step (2) with a pyrolysis aid, and carrying out pyrolysis to obtain the nanoscale titanium dioxide. Nanoscale, high-dispersion and crystal-form-controllable preparation of titanium dioxide is realized by changing the introduction mode of titanium tetrachloride and matching with the dispersing agent and the pyrolysis aid. The titanium tetrachloride is introduced in a gas manner, so that the reaction temperature and speed can be adjusted, and the method has the advantages of improving the reaction efficiency, reducing the reaction temperature, being simple in preparation method, mild in reaction condition and the like.

Description

Technical Field

[0001] This invention relates to the field of inorganic nanomaterials technology, and in particular to a gas-liquid method for preparing nanoscale titanium dioxide. Background Technology

[0002] Nano-titanium dioxide, due to its unique physicochemical properties and excellent optical performance, has become an indispensable multifunctional material in modern industry. Because of its high refractive index, strong chemical stability, and non-toxicity, it is widely used in traditional fields such as coatings, plastics, papermaking, rubber, and food additives. At the same time, due to its high dielectric constant and resistivity, it also possesses semiconductor properties, playing an important role in high-tech industries such as electronic ceramics, semiconductor capacitors, thermistors, and specialty glasses.

[0003] The particle size and dispersibility of nano-titanium dioxide materials directly determine their application effects in various fields, and ultimately the performance of various derivative products developed based on nano-titanium dioxide materials. Nano-titanium dioxide mainly has three crystal forms: anatase, rutile, and brookite. Among them, anatase and rutile are the most widely used, while brookite is less studied due to its poor stability. Anatase phase has advantages such as high efficiency in separating photogenerated electron-hole pairs and strong photocatalytic activity, and is widely used in photocatalysis, solar cells, and environmental protection. Rutile phase has advantages such as high thermal and chemical stability, and is widely used in cosmetics, pigments, and electronic devices. Miscible nano-titanium dioxide (commonly found in Degussa P25, approximately 80% anatase + 20% rutile) enhances its overall performance through synergistic effects, especially in the field of photocatalysis, and is an important direction for future modification research.

[0004] Currently, there are two main methods for preparing nano-titanium dioxide: the gas-phase method and the liquid-phase method. The gas-phase method directly utilizes gas or transforms substances into gas through various means, causing physical or chemical changes in the gaseous state, and finally condenses and grows into nanoparticles during cooling. The gas-phase method typically involves high reaction temperatures, complex processes, high requirements for equipment and technology, and large investments, resulting in high product costs. The liquid-phase method involves diluting titanium tetrachloride solution in an ice-water bath or directly adding it dropwise to water, and then hydrolyzing it at a specific temperature. The liquid-phase method typically suffers from problems such as uncontrollable reaction temperature and rate, poor particle dispersibility, and difficulty in controlling crystal form.

[0005] In recent years, researchers have conducted studies on the preparation of nanoscale, well-dispersed, and controllable crystal form titanium dioxide. CN113896232A discloses a monodisperse, suspension-stable, and transparent rutile phase nano-titanium dioxide powder material and its preparation method. This method involves mixing titanium tetrachloride with water to form a mixture, stirring at low temperature to form a precipitate, separating and drying the precipitated solid powder, and then heating the precipitated solid powder in a sealed container to obtain the nano-titanium dioxide material. Although this method produces nanoscale, monodisperse particles, the controllable crystal form cannot be achieved due to process limitations.

[0006] CN117088408A discloses a method for preparing nano-titanium dioxide. The method involves mixing heated gaseous titanium tetrachloride with ammonia in a gas-phase reaction under anhydrous and oxygen-free atmosphere to obtain a solid intermediate product A. Intermediate product A is then heat-treated in a sealed container to obtain a solid intermediate product B. Intermediate product B is then placed in an aqueous liquid medium for hydration, followed by filtration and drying to obtain a solid intermediate product C. Finally, intermediate product C is calcined under an air or oxygen atmosphere to obtain nano-titanium dioxide. While this method achieves nano-titanium dioxide preparation, it still suffers from drawbacks such as poor dispersibility, uncontrollable crystal structure, and complex processing.

[0007] Therefore, how to develop a new process to prepare nano-titanium dioxide by the hydrolysis of titanium tetrachloride with controllable reaction temperature and rate, good product dispersibility, and adjustable crystal form ratio is a technical problem that urgently needs to be solved. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a gas-liquid method for preparing nano-sized titanium dioxide. This method achieves controllability of reaction temperature and rate by changing the way titanium tetrachloride is introduced, thus shortening the process flow, improving reaction efficiency, and reducing production costs. Furthermore, the addition of dispersants and pyrolysis aids enables the preparation of highly dispersed titanium dioxide with adjustable crystal structure ratios.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing nano-sized titanium dioxide using a gas-liquid method, the method comprising the following steps:

[0011] (1) Pass a carrier gas carrying titanium tetrachloride gas into an aqueous solution containing a dispersant, and hydrolyze it by gas-liquid method to obtain metatitanic acid slurry.

[0012] (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, washing and drying to obtain metatitanic acid;

[0013] (3) The metatitanic acid obtained in step (2) is mixed with the pyrolysis aid and then pyrolyzed to obtain nano-sized titanium dioxide.

[0014] The gas-liquid method for preparing nano-sized titanium dioxide provided by this invention lowers the reaction temperature and accelerates the hydrolysis rate by introducing titanium tetrachloride as a gas into an aqueous solution. The reaction rate can be controlled by adjusting the amount of titanium tetrachloride introduced through the carrier gas. The dispersant enables highly dispersed preparation of metatitanic acid. The addition of a pyrolysis aid can inhibit particle agglomeration and lower the crystal transformation temperature, thereby reducing production costs. This method has good application prospects and economic benefits.

[0015] Compared with the conventional method of direct hydrolysis using titanium tetrachloride solution, this invention lowers the reaction temperature and allows for control of the reaction rate by adjusting the amount of titanium tetrachloride introduced through the carrier gas flow rate. The reaction conditions provided by this invention are more mild and controllable. In contrast, the traditional liquid-phase method cannot control the hydrolysis rate, resulting in the agglomeration, poor dispersibility, and uneven particle size distribution of the prepared titanium dioxide.

[0016] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0017] Preferably, the carrier gas in step (1) includes any one or a combination of at least two of air, nitrogen or oxygen. Typical but non-limiting combinations include a combination of air and nitrogen, a combination of nitrogen and oxygen, a combination of air and oxygen, and a combination of air, nitrogen and oxygen.

[0018] Preferably, the water content of the carrier gas in step (1) is ≤0.002 g / m³. 3 For example, it could be 0g / m 3 0.0005g / m 3 0.001g / m 3 0.0015g / m 3 Or 0.002g / m 3 However, this does not limit the listed values; other unlisted values ​​within the range are also applicable.

[0019] This invention further controls the water content of the carrier gas to ≤0.002 g / m³. 3 If the carrier gas contains too much water, it will cause the titanium tetrachloride gas to hydrolyze with the gas in the gas tube during the introduction process and slowly accumulate, leading to blockage of the gas tube.

[0020] Preferably, the inlet flow rate of the carrier gas in step (1) is 0.1L / min-2L / min, for example, it can be 0.1L / min, 0.15L / min, 0.5L / min, 0.8L / min, 1L / min, 1.5L / min, 1.8L / min or 2L / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] This invention further controls the carrier gas flow rate to 0.1L / min-2L / min. If the carrier gas flow rate is too high, a large amount of titanium tetrachloride gas will escape without participating in the reaction, resulting in waste of raw materials. If the carrier gas flow rate is too low, the reaction efficiency will be slow, and primary particles of metatitanic acid will continuously accumulate on the surface of metatitanic acid, resulting in an increase in particle size.

[0022] Preferably, the titanium tetrachloride gas in step (1) is obtained by heating a titanium tetrachloride solution.

[0023] Preferably, the heating temperature is 135℃-200℃, for example, it can be 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃ or 200℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0024] Preferably, the molar concentration of the titanium tetrachloride solution is 0.05M-2M, for example, it can be 0.05M, 0.08M, 0.1M, 0.4M, 0.5M, 0.9M, 1.0M, 1.2M, 1.5M, 1.8M or 2M, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the dispersant in step (1) comprises any one or a combination of at least two of polyethylene glycol, ethylenediaminetetraacetic acid (EDTA), or polyvinylpyrrolidone (PVP). Typical but non-limiting combinations include combinations of polyethylene glycol and EDTA, combinations of EDTA and PVP, combinations of polyethylene glycol and PVP, and combinations of polyethylene glycol, EDTA, and PVP.

[0026] This invention selects polyethylene glycol, ethylenediaminetetraacetic acid, or polyvinylpyrrolidone as dispersants, utilizing steric hindrance and their interaction with Ti... 4+ The formation of stable complexes suppresses hydrolysis kinetics, thereby achieving particle dispersion.

[0027] For polyvinyl alcohol (PVA), a commonly used dispersant, its molecular structure (linear chain) provides some steric hindrance, but its adsorption capacity is weak. In the TiCl4 hydrolysis system, the surface of titanium oxide is usually positively charged (at low pH), and the neutral hydroxyl groups of PVA are difficult to stably adsorb through electrostatic interactions. In contrast, the polar amide groups of polyvinylpyrrolidone (PVP) or the ether oxygen atoms of polyethylene glycol (PEG) can more effectively coordinate with titanium species to form a stable coating layer. Ethylenediaminetetraacetic acid (EDTA) can also adsorb titanium oxides through electrostatic interactions. 4+ Coordination inhibits premature hydrolysis, controls particle growth, and achieves particle dispersion. Meanwhile, polyvinyl alcohol may precipitate or form insoluble complexes in highly acidic solutions, while polyethylene glycol, ethylenediaminetetraacetic acid, or polyvinylpyrrolidone exhibit better solubility over a wide pH range and are adaptable to the dynamic acid-base changes during TiCl4 hydrolysis. Therefore, polyvinyl alcohol is unsuitable as a dispersant for TiCl4 hydrolysis due to its insufficient dispersion mechanism and instability in acidic environments.

[0028] Preferably, the mass percentage of the dispersant in the aqueous solution containing the dispersant in step (1) is 0.01%-1%, for example, it can be 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the washing in step (2) includes sequential water washing and alcohol washing.

[0030] Preferably, the number of water washes is 2 to 5 times, for example, 2, 3, 4 or 5 times, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the washing solution after alcohol washing contains Cl - The mass ratio of the metatitanic acid to the metatitanic acid is (0.1-5):100, for example, it can be 0.1:100, 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100 or 5:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] This invention further controls the Cl content in the metatitanic acid solid after alcohol washing. - The mass ratio of Cl to metatitanic acid is (0.1-5):100. - As a mineralizing agent, Cl can effectively reduce the crystal transformation temperature during pyrolysis. - If the content is too high, it will result in residual Cl in the product. - This results in poor product purity; if Cl -If the content is too low, the crystal transformation temperature will not decrease as much, resulting in increased production costs.

[0033] Preferably, the pyrolysis aid in step (3) includes citric acid and / or oxalic acid.

[0034] This invention selects citric acid and oxalic acid as pyrolysis aids. By complexing with titanium ions, they decompose during calcination, inhibiting particle agglomeration. Moreover, they decompose completely at high temperatures, leaving little residue.

[0035] Preferably, the mass ratio of the pyrolysis aid to metatitanic acid in step (3) is (5-15):100, for example, it can be 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100 or 15:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the pyrolysis temperature in step (3) is 400℃-800℃, for example, it can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] This invention achieves complete decomposition of the pyrolysis aid by further controlling the pyrolysis temperature to 400℃-800℃, resulting in no impurities remaining in titanium dioxide. Furthermore, the crystal form (anatase phase and rutile phase) can be continuously adjusted by regulating the pyrolysis temperature.

[0038] Preferably, the pyrolysis time in step (3) is 0.5h-5h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1h-4h.

[0039] As a preferred embodiment of the method described in this invention, the method includes the following steps:

[0040] (1) Heating a titanium tetrachloride solution with a molar concentration of 0.05M-2M at 135℃-200℃ yields titanium tetrachloride gas with a water content ≤0.002g / m³. 3 Using any one or a combination of at least two of air, nitrogen, or oxygen as the carrier gas, the carrier gas carrying titanium tetrachloride gas is passed into an aqueous solution containing a dispersant at a flow rate of 0.1 L / min to 2 L / min, and gas-liquid hydrolysis is carried out at 25℃ to 100℃ to obtain metatitanic acid slurry.

[0041] The dispersant includes any one or a combination of at least two of polyethylene glycol, ethylenediaminetetraacetic acid, or polyvinylpyrrolidone; the mass percentage of the dispersant in the aqueous solution containing the dispersant is 0.01%-1%;

[0042] (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, water washing 2-5 times, and alcohol washing until Cl is added to the washing solution. - The mass ratio of metatitanic acid to metatitanic acid is (0.1-5):100, and after drying, metatitanic acid is obtained.

[0043] (3) Mix the metatitanic acid obtained in step (2) with the pyrolysis aid and pyrolyze at 400℃-800℃ for 1h-4h to obtain nano-sized titanium dioxide; the pyrolysis aid includes citric acid and / or oxalic acid; the mass ratio of the pyrolysis aid to metatitanic acid is (5-15):100.

[0044] Secondly, the present invention provides a nano-sized titanium dioxide, which is prepared by the method described in the first aspect.

[0045] The nano-sized titanium dioxide prepared by this invention has high dispersibility, uniform particle size, and controllable crystal form.

[0046] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] (1) This invention reduces the reaction temperature and accelerates the hydrolysis rate by introducing titanium tetrachloride into the aqueous solution in the form of gas. The reaction rate can be controlled by controlling the amount of titanium tetrachloride introduced. The dispersant can achieve high dispersion of metatitanic acid. The addition of pyrolysis aid can inhibit particle agglomeration and reduce the crystal transformation temperature, thereby reducing production costs. It has good application prospects and economic benefits.

[0049] (2) The nano-sized titanium dioxide prepared by this invention has high dispersibility, uniform particle size and controllable crystal form. Attached Figure Description

[0050] Figure 1 These are the XRD patterns of the nano-titanium dioxide prepared in Examples 1-7 of this invention;

[0051] Figure 2 Here is a SEM image of the nano-titanium dioxide prepared in Example 3 of this invention;

[0052] Figure 3Here is a SEM image of the nano-titanium dioxide prepared in Example 8 of this invention;

[0053] Figure 4 Here is a SEM image of the nano-titanium dioxide prepared in Example 9 of this invention;

[0054] Figure 5 This is a SEM image of the nano-titanium dioxide prepared in Comparative Example 1 of this invention.

[0055] Figure 6 This is a SEM image of the nano-titanium dioxide prepared in Comparative Example 2 of this invention;

[0056] Figure 7 This is a SEM image of the nano-titanium dioxide prepared in Comparative Example 3 of this invention.

[0057] Figure 8 This is a SEM image of the nano-titanium dioxide prepared in Comparative Example 4 of this invention. Detailed Implementation

[0058] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0059] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0060] Example 1

[0061] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide, the method comprising the following steps:

[0062] (1) A titanium tetrachloride solution with a molar concentration of 0.05 M was heated at 135 °C to obtain titanium tetrachloride gas with a water content of 0.0005 g / m³. 3 Using air as the carrier gas, the carrier gas carrying titanium tetrachloride gas was introduced into an aqueous solution containing 1% by mass of dispersant (polyethylene glycol) at a flow rate of 1 L / min, and gas-liquid hydrolysis was carried out at 100°C to obtain metatitanic acid slurry.

[0063] (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, washed with water three times, and washed with alcohol until the metatitanic acid solid is dissolved in Cl. - The mass ratio of metatitanic acid to metatitanic acid is 0.5:100, and after drying, metatitanic acid is obtained.

[0064] (3) Mix the metatitanic acid and citric acid obtained in step (2) and pyrolyze them at 600℃ for 2 hours to obtain nano-sized titanium dioxide; the mass ratio of citric acid to metatitanic acid is 11:100.

[0065] Example 2

[0066] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide, the method comprising the following steps:

[0067] (1) Heating a 0.9 M titanium tetrachloride solution at 145 °C yields titanium tetrachloride gas with a water content of 0.0015 g / m³. 3 Nitrogen gas was used as the carrier gas, and the carrier gas carrying titanium tetrachloride gas was introduced into an aqueous solution containing 0.5% by mass of dispersant (polyvinylpyrrolidone) at a flow rate of 1.5 L / min. Gas-liquid hydrolysis was carried out at 80 °C to obtain metatitanic acid slurry.

[0068] (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, washed twice with water, and washed with alcohol until the metatitanic acid solid is dissolved in Cl. - The mass ratio of metatitanic acid to metatitanic acid is 1:100, and after drying, metatitanic acid is obtained.

[0069] (3) The metatitanic acid and oxalic acid obtained in step (2) are mixed and pyrolyzed at 400℃ for 4 hours to obtain nano-sized titanium dioxide; the mass ratio of oxalic acid to metatitanic acid is 9:100.

[0070] Example 3

[0071] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide, the method comprising the following steps:

[0072] (1) Heating a titanium tetrachloride solution with a molar concentration of 0.08 M at 160 °C yields titanium tetrachloride gas with a water content of 0.0003 g / m³. 3 Using oxygen as the carrier gas, the carrier gas carrying titanium tetrachloride gas was introduced into an aqueous solution containing 0.05% by mass of dispersant (a mixture of polyethylene glycol and ethylenediaminetetraacetic acid in a mass ratio of 1:1) at a flow rate of 1.8 L / min. Gas-liquid hydrolysis was carried out at 40 °C to obtain metatitanic acid slurry.

[0073] (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, water washing five times, and alcohol washing until the metatitanic acid solid is dissolved in Cl. - The mass ratio of metatitanic acid to metatitanic acid is 0.1:100, and after drying, metatitanic acid is obtained.

[0074] (3) The metatitanic acid and oxalic acid obtained in step (2) are mixed and pyrolyzed at 700℃ for 2.5h to obtain nano-sized titanium dioxide; the mass ratio of oxalic acid to metatitanic acid is 7:100.

[0075] SEM images of the prepared nanoscale titanium dioxide obtained by the gas-liquid method are shown below. Figure 2 As shown, from Figure 2 As can be seen from the data, the prepared titanium dioxide is nanoscale and has good dispersibility.

[0076] Example 4

[0077] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide, the method comprising the following steps:

[0078] (1) Heating a 1.5 M titanium tetrachloride solution at 175 °C yields titanium tetrachloride gas with a water content of 0.001 g / m³. 3 A mixture of air and nitrogen (volume ratio 1:1) was used as the carrier gas. The carrier gas carrying titanium tetrachloride was passed into an aqueous solution containing 0.01% by mass of dispersant (a mixture of polyethylene glycol, ethylenediaminetetraacetic acid and polyvinylpyrrolidone in a mass ratio of 1:1:1) at a flow rate of 2 L / min. Gas-liquid hydrolysis was carried out at 60 °C to obtain metatitanic acid slurry.

[0079] (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, washed twice with water, and washed with alcohol until the metatitanic acid solid is dissolved in Cl. - The mass ratio of metatitanic acid to metatitanic acid is 4:100, and after drying, metatitanic acid is obtained.

[0080] (3) Mix the metatitanic acid and citric acid obtained in step (2) and pyrolyze them at 650℃ for 3 hours to obtain nano-sized titanium dioxide; the mass ratio of citric acid to metatitanic acid is 13:100.

[0081] Example 5

[0082] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide, the method comprising the following steps:

[0083] (1) Heating a 0.4 M titanium tetrachloride solution at 180 °C yields titanium tetrachloride gas with a water content of 0.002 g / m³. 3 A mixture of air and oxygen (volume ratio 1:1) was used as the carrier gas. The carrier gas carrying titanium tetrachloride gas was passed into an aqueous solution containing 0.1% by mass of dispersant (a mixture of polyethylene glycol and polyvinylpyrrolidone in a mass ratio of 1:1) at a flow rate of 0.1 L / min. Gas-liquid hydrolysis was carried out at 90 °C to obtain metatitanic acid slurry.

[0084] (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, water washing four times, and alcohol washing until the metatitanic acid solid is dissolved in Cl. -The mass ratio of metatitanic acid to metatitanic acid is 2:100, and after drying, metatitanic acid is obtained.

[0085] (3) The metatitanic acid obtained in step (2) is mixed with a pyrolysis aid (a mixture of citric acid and oxalic acid in a mass ratio of 1:2) and pyrolyzed at 500℃ for 3.5h to obtain nano-sized titanium dioxide; the mass ratio of the pyrolysis aid to metatitanic acid is 5:100.

[0086] Example 6

[0087] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide, the method comprising the following steps:

[0088] (1) Heating a 2M titanium tetrachloride solution at 190℃ yields titanium tetrachloride gas with a water content of 0.0018 g / m³. 3 A mixture of nitrogen and oxygen (volume ratio 1:1) was used as the carrier gas. The carrier gas carrying titanium tetrachloride was introduced into an aqueous solution containing 0.8% by mass of dispersant (ethylenediaminetetraacetic acid and polyvinylpyrrolidone in a mass ratio of 1:2) at a flow rate of 0.5 L / min. Gas-liquid hydrolysis was carried out at 50 °C to obtain metatitanic acid slurry.

[0089] (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, water washing four times, and alcohol washing until the metatitanic acid solid is dissolved in Cl. - The mass ratio of metatitanic acid to metatitanic acid is 0.8:100, and after drying, metatitanic acid is obtained.

[0090] (3) Mix the metatitanic acid and citric acid obtained in step (2) and pyrolyze them at 800℃ for 1 h to obtain nano-sized titanium dioxide; the mass ratio of citric acid to metatitanic acid is 15:100.

[0091] Example 7

[0092] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide, the method comprising the following steps:

[0093] (1) Heating a 0.1 M titanium tetrachloride solution at 200 °C yields titanium tetrachloride gas with a water content of 0.0005 g / m³. 3 Air, nitrogen, and oxygen (volume ratio 1:1:1) were used as carrier gas. The carrier gas carrying titanium tetrachloride gas was passed into an aqueous solution containing 0.2% by mass of dispersant (ethylenediaminetetraacetic acid) at a flow rate of 1 L / min. Gas-liquid hydrolysis was carried out at 25 °C to obtain metatitanic acid slurry.

[0094] (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, washed with water three times, and washed with alcohol until the metatitanic acid solid is dissolved in Cl. -The mass ratio of metatitanic acid to metatitanic acid is 0.5:100, and after drying, metatitanic acid is obtained.

[0095] (3) The metatitanic acid and citric acid obtained in step (2) are mixed and pyrolyzed at 750℃ for 1.5h to obtain nano-sized titanium dioxide; the mass ratio of citric acid to metatitanic acid is 10:100.

[0096] Example 8

[0097] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide, which differs from Example 1 only in that the water content of the carrier gas in step (1) is 0.02 g / m³. 3 The remaining steps remain unchanged.

[0098] SEM images of the prepared titanium dioxide are shown below. Figure 3 As shown in the figure, the dispersion of the obtained titanium dioxide is poor. The main reason is that some TiCl4 gas and water hydrolyze and agglomerate in the gas pipe. As the gas pressure increases, the hydrolysis products are blown into the liquid phase. Therefore, the dispersant does not play a good dispersing role.

[0099] Example 9

[0100] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide. The only difference from Embodiment 1 is that the flow rate of the carrier gas in step (1) is 0.05 L / min, while the other steps remain unchanged.

[0101] SEM images of the prepared titanium dioxide are shown below. Figure 4 As shown in the figure, some products agglomerate into micron-sized particles. The main reason for this is that the carrier gas flow rate is relatively low and the reaction time is relatively long, which leads to an increase in the collision frequency of particles. The particles overcome the energy barrier and form irreversible agglomeration.

[0102] Example 10

[0103] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide. The only difference from Embodiment 1 is that the flow rate of the carrier gas in step (1) is 5 L / min, while the other steps remain unchanged.

[0104] Example 11

[0105] This embodiment provides a gas-liquid method for preparing nano-sized titanium dioxide. The only difference from Example 1 is that the Cl in the washing solution after alcohol washing in step (2) is different. - The mass ratio of metatitanic acid to metatitanic acid is 10:100, and the remaining steps remain unchanged.

[0106] Comparative Example 1

[0107] This comparative example provides a method for preparing titanium dioxide. The only difference from Example 1 is that step (1) is replaced by adding a titanium tetrachloride solution with a molar concentration of 0.05M directly into an aqueous solution containing a dispersant, followed by liquid-phase hydrolysis to obtain a metatitanic acid slurry. The remaining steps remain unchanged.

[0108] SEM images of the prepared titanium dioxide are shown below. Figure 5 As shown in the figure, severe particle agglomeration is evident. The main reason is the instantaneous exothermic reaction upon adding the titanium tetrachloride solution to the liquid phase, causing the temperature to fluctuate significantly with that of Ti. 4+ Uneven concentration and exothermic reaction prevent the dispersant from forming a good coordination with metatitanic acid, resulting in severe agglomeration.

[0109] Comparative Example 2

[0110] This comparative example provides a method for preparing titanium dioxide, which differs from Example 1 only in that no dispersant is added in step (1), while the other steps remain unchanged.

[0111] SEM images of the prepared titanium dioxide are shown below. Figure 6 As shown in the figure, the particles are all micron-sized large particles. The main reason for this is that nanoparticles have a very large specific surface area, resulting in extremely high surface energy. Thermodynamically, they tend to agglomerate to reduce the total energy. Furthermore, no dispersant was added to disperse the particles, thus forming uneven micron-sized large particles.

[0112] Comparative Example 3

[0113] This comparative example provides a method for preparing titanium dioxide. The only difference from Example 1 is that no pyrolysis aid is added in step (3), while the other steps remain unchanged.

[0114] SEM images of the prepared titanium dioxide are shown below. Figure 7 As shown in the figure, the particles agglomerate due to the lack of pyrolysis aids, and molten particles can be seen on the particle surface, which is caused by the fusion of particles during pyrolysis. This indicates that pyrolysis aids have the function of maintaining particle morphology and dispersion.

[0115] Comparative Example 4

[0116] This comparative example provides a method for preparing titanium dioxide. The difference from Example 1 is that no dispersant is added in step (1) and no pyrolysis aid is added in step (3). The remaining steps are unchanged.

[0117] SEM images of the prepared titanium dioxide are shown below. Figure 8 As shown in the figure, the product particles prepared without the addition of dispersant and pyrolysis aid are micron-sized and have rough surfaces. The main reason for this is that the lattice shrinkage during pyrolysis leads to the release of internal stress in the particles, which manifests as roughness on a macroscopic scale.

[0118] test:

[0119] (1) Crystal content test: The content of rutile was calculated using the quantitative analysis formula.

[0120]

[0121] Wherein, Fr represents the rutile phase content; IA and IB are the diffraction intensities of the anatase (101) diffraction plane (2θ = 25.4°) and the rutile (110) diffraction plane (2θ = 27.4°) in the powder XRD curve, respectively.

[0122] The XRD patterns of the nano-titanium dioxide prepared in Examples 1-7 are shown below. Figure 1 As shown in the figure, the crystal structure of nano-titanium dioxide can be continuously adjusted by regulating the calcination temperature.

[0123] (2)Cl - Content test: Dissolve the metatitanic acid sample in dilute nitric acid or sodium hydroxide (choose according to the sample properties), filter to remove insoluble matter, adjust the pH to neutral or weakly alkaline (pH=7-9), add 5% potassium chromate indicator (1mL), and titrate with standard silver nitrate solution (e.g. 0.01mol / L) until a brick-red precipitate appears in the solution and does not fade.

[0124]

[0125] V: Volume of silver nitrate consumed (mL); C: Concentration of silver nitrate (mol / L); m: Mass of sample (g).

[0126] The titanium dioxide prepared in the examples and comparative examples was tested, and the test results are shown in Table 1 below.

[0127] Table 1

[0128] Anatase phase content (%) Rutile phase content (%) Example 1 64.8 35.2 Example 2 100 0 Example 3 26.2 73.8 Example 4 45 55 Example 5 84.6 15.4 Example 6 0 100 Example 7 5.2 94.8 Example 8 64.2 35.8 Example 9 64.5 35.5 Example 10 63.8 36.2 Example 11 51.3 48.7 Comparative Example 1 25.3 64.7 Comparative Example 2 5.7 94.3 Comparative Example 3 62.4 37.6 Comparative Example 4 4.2 95.8

[0129] The test results show that:

[0130] (1) As can be seen from Examples 1-7 and Table 1, the present invention reduces the reaction temperature and accelerates the hydrolysis rate by introducing titanium tetrachloride into the aqueous solution in the form of gas. The reaction rate can be controlled by controlling the amount of titanium tetrachloride introduced. The dispersant can achieve high dispersion of metatitanic acid. The addition of pyrolysis aid can inhibit particle agglomeration and reduce the crystal transformation temperature, thereby reducing the production cost and obtaining nanoscale titanium dioxide material with high dispersibility, uniform particle size and controllable crystal form. It has good application prospects and economic benefits. As can be seen from Table 1, the content of anatase phase gradually decreases and the content of rutile phase gradually increases with the increase of pyrolysis temperature. Therefore, it can be shown that the crystal form can be continuously adjusted by controlling the pyrolysis temperature.

[0131] (2) A comparison between Example 1 and Example 8 shows that the present invention further controls the water content of the carrier gas to ≤0.002 g / m³. 3 This method can better achieve the technical effect of stable and uniform preparation of metatitanic acid. If the carrier gas contains too much water, it will cause the titanium tetrachloride gas and water to hydrolyze in the gas pipe and cause blockage. At the same time, the prepared metatitanic acid will exhibit agglomeration.

[0132] (3) By comparing Example 1 with Examples 9-10, it can be seen that by further controlling the inlet flow rate of the carrier gas to 0.1L / min-2L / min, if the carrier gas flow rate is too large, a large amount of titanium tetrachloride gas will escape before it can react, and the absorption rate will decrease from about 75% to about 20%. If the carrier gas flow rate is too small, the reaction efficiency will be slow, and the primary particles of metatitanic acid will continuously accumulate on the surface of metatitanic acid, resulting in an increase in particle size.

[0133] (4) A comparison between Example 1 and Example 11 shows that the present invention further controls the Cl content in the washing solution after alcohol washing. - The mass ratio of Cl to metatitanic acid is (0.1-5):100. - As a mineralizing agent, Cl can effectively reduce the crystal transformation temperature during pyrolysis. - Excessive Cl content can significantly lower the awakening conversion temperature, but due to Cl... - The purity of titanium dioxide products will decrease; if Cl - If the content is too low, the crystal transformation temperature will be increased, resulting in a waste of resources.

[0134] (5) As can be seen from Example 1 and Comparative Example 1, the gas-liquid method of the present invention for preparing nano-sized titanium dioxide, compared with the liquid phase method in the prior art, achieves lower local reaction temperature and Ti content. 4+The concentration is controllable and uniform, so the prepared metatitanic acid has good dispersibility and small particle size. In contrast, the local high temperature in Comparative Example 1 accelerated the transformation of the anatase phase to the rutile phase, resulting in an increase in the rutile phase content. Therefore, this invention shows that the process has the advantages of uniform and controllable reaction temperature, simple process, high dispersibility of nano-sized titanium dioxide, and controllable crystal form.

[0135] (6) As can be seen from Example 1 and Comparative Examples 2-4, the present invention can obtain nanoscale titanium dioxide materials with high dispersibility, uniform particle size and controllable crystal form by adding a dispersant during the hydrolysis process to promote high dispersion of metatitanic acid and inhibit its hydrolysis rate to reduce the rutile phase content, and by adding a pyrolysis aid to inhibit particle agglomeration and reduce crystal transformation temperature during the pyrolysis process.

[0136] In summary, this invention lowers the reaction temperature and accelerates the hydrolysis rate by introducing titanium tetrachloride as a gas into an aqueous solution. The reaction rate can be controlled by adjusting the amount of titanium tetrachloride introduced through the carrier gas. The dispersant enables the high dispersion of metatitanic acid, and the addition of pyrolysis aids can inhibit particle agglomeration and lower the crystal transformation temperature, thereby reducing production costs. This results in nanoscale titanium dioxide materials with high dispersibility, uniform particle size, and controllable crystal structure, demonstrating promising application prospects and economic benefits.

[0137] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing nano-sized titanium dioxide using a gas-liquid process, characterized in that, The method includes the following steps: (1) Pass a carrier gas carrying titanium tetrachloride gas into an aqueous solution containing a dispersant, and hydrolyze it by gas-liquid method to obtain metatitanic acid slurry. (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, washing and drying to obtain metatitanic acid; (3) The metatitanic acid obtained in step (2) is mixed with the pyrolysis aid and then pyrolyzed to obtain nano-sized titanium dioxide.

2. The method according to claim 1, characterized in that, The carrier gas in step (1) includes any one or a combination of at least two of air, nitrogen, or oxygen.

3. The method according to claim 1 or 2, characterized in that, The water content of the carrier gas in step (1) is ≤0.002 g / m³. 3 ; Preferably, the flow rate of the carrier gas in step (1) is 0.1L / min-2L / min.

4. The method according to any one of claims 1-3, characterized in that, The titanium tetrachloride gas in step (1) is obtained by heating a titanium tetrachloride solution; Preferably, the heating temperature is 135℃-200℃; Preferably, the molar concentration of the titanium tetrachloride solution is 0.05M-2M.

5. The method according to any one of claims 1-4, characterized in that, The dispersant in step (1) includes any one or a combination of at least two of polyethylene glycol, ethylenediaminetetraacetic acid, or polyvinylpyrrolidone; Preferably, the mass percentage of the dispersant in the aqueous solution containing the dispersant in step (1) is 0.01%-1%.

6. The method according to any one of claims 1-5, characterized in that, The washing process in step (2) includes sequential water washing and alcohol washing; Preferably, the number of water washes is 2 to 5 times; Preferably, the Cl in the alcohol-washed metatitanic acid solid is... - The mass ratio of the metatitanic acid to the metatitanic acid is (0.1-5):

100.

7. The method according to any one of claims 1-6, characterized in that, The pyrolysis aids in step (3) include citric acid and / or oxalic acid; Preferably, the mass ratio of the pyrolysis aid to metatitanic acid in step (3) is (5-15):

100.

8. The method according to any one of claims 1-7, characterized in that, The pyrolysis temperature in step (3) is 400℃-800℃; Preferably, the pyrolysis time in step (3) is 0.5h-5h, and more preferably 1h-4h.

9. The method according to any one of claims 1-8, characterized in that, The method includes the following steps: (1) Heating a titanium tetrachloride solution with a molar concentration of 0.05M-2M at 135℃-200℃ yields titanium tetrachloride gas with a water content ≤0.002g / m³. 3 Using any one or a combination of at least two of air, nitrogen, or oxygen as the carrier gas, the carrier gas carrying titanium tetrachloride gas is passed into an aqueous solution containing a dispersant at a flow rate of 0.1 L / min to 2 L / min, and gas-liquid hydrolysis is carried out at 25℃ to 100℃ to obtain metatitanic acid slurry. The dispersant includes any one or a combination of at least two of polyethylene glycol, ethylenediaminetetraacetic acid, or polyvinylpyrrolidone; the mass percentage of the dispersant in the aqueous solution containing the dispersant is 0.01%-1%; (2) The metatitanic acid slurry obtained in step (1) is subjected to solid-liquid separation, water washing 2-5 times, and alcohol washing until Cl is added to the washing solution. - The mass ratio of metatitanic acid to metatitanic acid is (0.1-5):100, and after drying, metatitanic acid is obtained. (3) Mix the metatitanic acid obtained in step (2) with the pyrolysis aid, and pyrolyze at 400℃-800℃ for 1h-4h to obtain nano-sized titanium dioxide. The pyrolysis aid includes citric acid and / or oxalic acid; the mass ratio of the pyrolysis aid to metatitanic acid is (5-15):

100.

10. A nano-sized titanium dioxide, characterized in that, The nano-sized titanium dioxide is prepared by the method described in any one of claims 1-9.

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