A method for preparing highly dispersed nano titanium dioxide and its product

Abstract

The invention mainly relates to the technical field of high-performance ceramic filler nano titanium dioxide, and discloses a preparation method of highly dispersed nano titanium dioxide, comprising the following steps: slowly dripping a pretreated titanium source into a mixed solvent to obtain a titanium source solution; adding water and a mixed inhibitor into a reactor, stirring evenly, slowly dripping the prepared titanium source solution into the reactor, and continuously stirring during the dripping process; cooling the product to room temperature, adding a dispersant, aging for a period of time, and slowly adding a nano silica sol; washing the aged product and performing vacuum drying; calcining the dried product at 300-350°C for 1-1.5 hours, and then heating it to 480-550°C for 2-2.5 hours, and the heating rate is controlled at 1.5°C-2°C / min, and a nano titanium dioxide product with uniform particle size and high dispersibility is obtained after calcination. The invention optimizes the preparation process to achieve a particle size of nano titanium dioxide within a small range, while still maintaining good particle size uniformity and dispersibility.

Description

Technical Field

[0001] The invention mainly relates to the technical field of high-performance ceramic filler nano titanium dioxide, in particular to a highly dispersed nano titanium dioxide product and a preparation method thereof. Background Art

[0002] Ceramic fillers are ceramic substances used to fill various material systems to improve material properties. Ceramic fillers usually have the characteristics of high temperature resistance, good chemical stability, high hardness, and wear resistance. These characteristics enable them to play an important role in many industrial applications, such as enhancing the mechanical properties of composite materials and improving the corrosion resistance of materials.

[0003] Nano-titanium dioxide (TiO2) has good chemical stability, high hardness and wear resistance, and excellent optical properties, which makes it have good application prospects in ceramic fillers. For example, nano-titanium dioxide can be added as a filler in ceramic tool materials. Ceramic tools need to have high hardness, high wear resistance and good chemical stability. The addition of nano-titanium dioxide can effectively improve the cutting performance and service life of the tool. In electronic ceramic materials, nano-titanium dioxide can be used to adjust the dielectric and electrical properties of the material. Its good chemical stability also helps to ensure the normal operation of electronic ceramic components in complex working environments.

[0004] For high-performance ceramic fillers, the particle size of nano-titanium dioxide is usually at the nanometer level, such as 4-15nm, and the particle size distribution is uniform. Smaller particle size can increase the specific surface area, improve the bonding force with the ceramic matrix, and help improve the sintering performance and mechanical properties of the ceramic. If the particle size is too large or unevenly distributed, it is easy to cause agglomeration, affecting the dispersion of the filler in the ceramic, thereby reducing the performance of the ceramic.

[0005] Traditional preparation processes often fail to achieve good particle size uniformity and dispersibility of nano-titanium dioxide within a small range. For example, during the hydrolysis reaction, the hydrolysis rate of the titanium source is difficult to control, which can easily lead to too fast or uneven hydrolysis reaction, thereby generating particles with uneven particle sizes. Moreover, during particle formation and subsequent processing, particles are prone to agglomeration, which not only reduces the dispersibility of nano-titanium dioxide, but also affects its performance in applications. For example, in photocatalytic applications, agglomerated particles will reduce the exposure of active sites and reduce photocatalytic efficiency.

[0006] The agglomeration of nano-titanium dioxide particles during the preparation process is a problem that seriously affects its performance. The reasons are multifaceted. From the perspective of the interaction force between particles, nano-scale particles have higher surface energy. According to the principles of thermodynamics, they tend to reduce surface energy by agglomeration. In the solution, there are van der Waals forces between particles. When the particles are close, this attraction causes them to agglomerate together. At the same time, during the hydrolysis and aging process, if there are no appropriate dispersion measures, the active groups such as hydroxyl groups on the surface of the newly generated particles may cause the particles to agglomerate through hydrogen bonding interactions.

[0007] Some patent documents have been disclosed in the prior art on the research of nano titanium dioxide, such as the patent with application number 201810995545.9, which is entitled "A method for preparing highly dispersed nano titanium dioxide". Modified gel is added when preparing highly dispersed nano titanium dioxide. The porous structure of the modified gel after expansion is utilized to adsorb the precursor of nano titanium dioxide, reduce the agglomeration of the precursor of nano titanium dioxide, and thereby reduce the particle size of the product. In addition, during the calcination process, the substances in the modified gel will produce gas, which can reduce the oxygen content in the calcination furnace, cause incomplete combustion of fungal substances and glucose, and form tar, thereby preventing the agglomeration of nano titanium dioxide.

[0008] The above scheme is a good exploration of the preparation process of nano titanium dioxide, but the exploration of the preparation process of nano titanium dioxide by those skilled in the art has been ongoing. In order to further improve the application field and use effect of titanium dioxide nanomaterials, the present invention provides a highly dispersed nano titanium dioxide product and a preparation method thereof, aiming to develop a nano titanium dioxide powder with uniform particle size and good dispersibility. Summary of the invention

[0009] In order to solve the above technical problems, one of the purposes of the present invention is to provide a highly dispersed nano titanium dioxide product and a preparation method thereof, and through the optimization of the preparation process, the particle size of the nano titanium dioxide is kept within a smaller range while still maintaining good particle size uniformity and dispersibility.

[0010] The technical solution adopted by the present invention to solve the above technical problems is:

[0011] In a first aspect, the present invention provides a method for preparing highly dispersed nano titanium dioxide, comprising the following steps:

[0012] (1) Solution preparation: slowly dropwise adding the pretreated titanium source into the mixed solvent to obtain a titanium source solution;

[0013] (2) Hydrolysis reaction: Add water and mixed inhibitor to the reactor, stir evenly, then slowly drip the prepared titanium source solution into the reactor, stirring continuously during the dripping process; further, during the hydrolysis process, stirring continuously and performing mild ultrasonic treatment at the same time, wherein the ultrasonic power is 100-150 W. Slow dripping of water and ultrasonic treatment can make the hydrolysis reaction more uniform both locally and overall, preventing large particles from being generated due to excessive local hydrolysis, and mild ultrasonic energy can disperse the newly generated particles in time to avoid agglomeration.

[0014] (3) Addition of dispersant: After the hydrolysis reaction is completed, the product is cooled to room temperature, and the dispersant is added and stirred to make it fully mixed. The stirring time is 30 to 60 minutes and the speed is 260 to 350 rpm to make it fully mixed.

[0015] (4) Aging treatment: The reaction solution containing the dispersant is aged for a period of time under certain temperature conditions, wherein the aging temperature is 30°C to 35°C and the aging time is 18 to 24 hours.

[0016] The aging process has an important influence on the performance of nano titanium dioxide. Properly extending the aging time and controlling the aging temperature can make the generated titanium hydroxide particles undergo further condensation reaction, making the particle structure more stable and helping to improve the dispersibility of the particles. Too high an aging temperature or too long an aging time may lead to increased particle agglomeration, while too low a temperature or too short an aging time may make the particle structure imperfect and affect its performance.

[0017] (5) Inorganic coating treatment: After aging, slowly add nano-silica sol into the reactor and stir to make the silica evenly coat the surface of the titanium dioxide particles. The solid content of the nano-silica sol is 10%, and the amount used is the amount that can form a uniform coating layer on the surface of the titanium dioxide particles (the specific amount can be determined through experiments).

[0018] The surface of nano-titanium dioxide is coated with inorganic substances, such as aluminum oxide, silicon dioxide, etc. These inorganic coating layers can improve the surface properties of nano-titanium dioxide, reduce its surface energy, and reduce the agglomeration between particles. At the same time, the inorganic coating layer can also improve the compatibility of nano-titanium dioxide in different media and further enhance its dispersibility.

[0019] (6) Washing and drying: The aged product is washed and then vacuum dried. Specifically, the product is first washed twice with a mixture of ethanol and deionized water in a volume ratio of 1:1, and then washed three times with deionized water alone. After each washing, the product is centrifuged at a speed of 7000-9000 rpm. The washed product is first quickly frozen at below -50°C, then freeze-dried at a vacuum degree of less than 10 Pa for 25-33 hours, and then vacuum dried at 55-65°C for 10-14 hours.

[0020] Freeze drying can effectively avoid the agglomeration of particles caused by the surface tension of water during the conventional drying process. In the low-temperature frozen state, water directly sublimates from the solid state to the gas state, and does not form a liquid phase that causes the particles to agglomerate. This method is very effective in maintaining the dispersed state of the particles after washing. Subsequent vacuum drying at a lower temperature further removes the small amount of water and organic solvent that may remain, consolidates the dispersion of the particles, and avoids the influence of high temperature on the particle structure and dispersion.

[0021] Vacuum drying can quickly remove moisture at a lower temperature, avoiding agglomeration of particles due to evaporation of water, which is beneficial to maintaining good dispersion of nano-titanium dioxide. Drying temperature also needs to be strictly controlled. Too high a temperature may cause sintering or agglomeration between particles, reducing their dispersion.

[0022] (7) Staged calcination: The dried product is first calcined at 300-350°C for 1-1.5 hours, and then heated to 480-550°C for calcination for 2-2.5 hours. The heating rate is controlled at 1.5°C-2°C / min. After calcination, a nano-titanium dioxide product with uniform particle size and high dispersion is obtained.

[0023] During the pre-calcination process at a lower temperature, titanium hydroxide begins to decompose initially. At this time, the active groups such as hydroxyl groups on the surface of the particles gradually decrease, and the tendency of particles to agglomerate due to hydrogen bonds and other effects also weakens. At the same time, the lower temperature makes the growth and structural adjustment of the particles slower, which is conducive to the formation of a more uniform crystal nucleus. Later, during the calcination at a higher temperature, the particles continue to grow and improve the crystal structure on the basis of the uniform crystal nucleus that has been formed. Due to the good uniformity of the crystal nucleus in the early stage, titanium dioxide particles with more uniform particle size can be obtained in the end. Moreover, the slow heating rate during the staged calcination process can enable the particles to smoothly adjust their structure at different temperature stages, reduce the thermal stress caused by the rapid temperature change, thereby effectively preventing the particles from breaking and agglomerating, and further improving the dispersion of the particles.

[0024] In practice, an inert protective gas, such as nitrogen or argon, is introduced during the calcination process, and the gas flow rate is controlled at 50-100 ml / min. The introduction of protective gas can prevent the titanium dioxide particles from over-oxidizing with oxygen in the air during the calcination process. Excessive oxidation may cause changes in the surface properties of the particles, increase the interaction between the particles, and then cause agglomeration. The presence of protective gas can create a relatively stable calcination environment, reduce the impact of external factors on the particles, and enable the particles to undergo structural transformation and growth in a relatively pure atmosphere, which helps to maintain the dispersed state of the particles and improve the particle size uniformity and dispersibility of the product.

[0025] Furthermore, the use of dynamic calcination (rotating tube furnace) during the staged calcination process can ensure that the sample is heated more evenly throughout the calcination process, avoiding uneven particle growth and agglomeration caused by local overheating. The relative positions of the particles change continuously during the tumbling process, reducing the possibility of agglomeration caused by long-term contact, which helps to further improve the particle size uniformity and dispersibility of the nano-titanium dioxide particles.

[0026] Furthermore, a proper amount of an inorganic dispersant, such as sodium hexametaphosphate, may be added to the dried product in an amount of 1% to 3% of the mass of the product, and then calcination may be performed.

[0027] Inorganic dispersants such as sodium hexametaphosphate can be adsorbed on the surface of titanium dioxide particles during the calcination process to form an isolation layer to prevent direct contact and agglomeration between particles. During high-temperature calcination, the dispersant can reduce the energy barrier on the particle surface, making the particle growth more orderly and avoiding uneven particle size caused by irregular growth. At the same time, the presence of the dispersant can adjust the charge distribution on the particle surface, increase the electrostatic repulsion between particles, and further improve the dispersion stability of the particles, thereby obtaining a nano-titanium dioxide product with uniform particle size and high dispersibility after calcination.

[0028] Through the above optimization of calcination treatment, the agglomeration of titanium dioxide particles can be effectively prevented from different angles, the particle size uniformity and high dispersibility of nano titanium dioxide products can be improved, and the performance requirements of nano titanium dioxide in different application fields can be met.

[0029] The present invention can effectively improve the particle size uniformity and dispersibility of nano titanium dioxide through the synergistic effect of the above raw material formula and preparation process. Among them, the reasonable ratio of each raw material component and the precise control of each step and parameter in the preparation process have an important influence on the nucleation, growth, agglomeration and other processes of nano titanium dioxide, thereby realizing the preparation of highly dispersed nano titanium dioxide.

[0030] In the implementation of the first aspect, the surface functionalization step is also included:

[0031] The dried product was stirred in a toluene solution containing an appropriate amount of 3-aminopropyltriethoxysilane for 2-3 hours at a temperature of 60-70°C to introduce amino functional groups on the surface of the nano-titanium dioxide;

[0032] And / or, after the reaction is completed, the product is washed with toluene and ethanol for multiple times to remove unreacted 3-aminopropyltriethoxysilane, and then dried in a vacuum drying oven.

[0033] 3-Aminopropyltriethoxysilane (APTES) is used to perform surface functionalization on nano-titanium dioxide. The ethoxy groups in the APTES molecules can undergo hydrolysis and condensation reactions with the hydroxyl groups on the particle surface, thereby introducing amino functional groups onto the surface of nano-titanium dioxide.

[0034] The introduced amino functional groups have the following functions: first, they can increase the charge density on the particle surface and further improve the dispersibility of the particles through electrostatic repulsion; second, they can improve the compatibility of nano-titanium dioxide with other materials, especially in some systems containing amino-sensitive groups, so that nano-titanium dioxide can be better dispersed and applied; third, the amino functional groups have certain reactivity and can be used as reaction sites for further chemical modification or complexing with other substances, expanding the application range of nano-titanium dioxide.

[0035] In an achievable manner of the first aspect, the titanium source in the solution preparation is a composite titanium source, the composite titanium source includes tetrabutyl titanate and titanium sulfate, and the mass ratio of the tetrabutyl titanate to titanium sulfate is 8:2;

[0036] and / or, slowly adding tetrabutyl titanate and titanium sulfate into the mixed solvent respectively to obtain a titanium source solution;

[0037] And / or, tetrabutyl titanate and titanium sulfate are pretreated by reduced pressure distillation respectively.

[0038] Tetrabutyl titanate in the composite titanium source provides a rapidly hydrolyzed titanium source to ensure the start of the reaction, while titanium sulfate hydrolyzes relatively slowly and the sulfate ions produced by hydrolysis can be adsorbed on the surface of titanium dioxide particles, reducing the tendency of agglomeration between particles through electrostatic repulsion. At the same time, the introduction of titanium sulfate can adjust the overall hydrolysis reaction rate, making the reaction more uniform and stable, thereby reducing the occurrence of agglomeration.

[0039] In an achievable manner of the first aspect, the hydrolysis reaction utilizes plasma-assisted hydrolysis, and water and an inhibitor are added step by step:

[0040] (21) Add the first part of water and inhibitor into the plasma reactor, stir evenly, then slowly drop the prepared titanium source solution into the reactor, keep stirring during the dropwise addition, turn on the plasma generator, the power is 200-300 W, the frequency is 13.56 MHz, and multi-frequency ultrasonic treatment is used at a power of 180-240 W. The pulse mode is: work for 5-8 s, and rest for 2-3 s.

[0041] (22) After the first part of the titanium source solution is added, the second part of the water is added, and the addition speed is maintained at 1-2 drops / second, during which stirring, ultrasound and plasma treatment are continued;

[0042] (23) After the second portion of water is added, the reaction is continued for 2 hours, and then the third portion of water is slowly added at an appropriate time according to the state of the reaction system.

[0043] The molar ratio of water to titanium source (in terms of titanium atoms) is 2.8:1. The high-purity deionized water is divided into three parts. The first part (accounting for 40% of the total water) is added at the initial stage of the reaction, the second part (accounting for 40% of the total water) is slowly added in drops in the middle of the reaction at a rate of 1.5 drops / second, and the third part (accounting for 20% of the total water) is added in small amounts in the late stage of the reaction according to the reaction conditions. This step-by-step water addition method can accurately control the hydrolysis reaction rate, make the hydrolysis process proceed smoothly, prevent particle agglomeration caused by explosive growth of the hydrolysis reaction caused by a large amount of water added at one time, and is conducive to the generation of nano titanium dioxide with uniform particle size.

[0044] Plasma is rich in a large number of highly active species, such as free radicals, ions and electrons. During the hydrolysis reaction, these active species can interact with the titanium source, solvent and water to initiate and promote the hydrolysis and polycondensation reactions of the titanium source. For example, hydroxyl radicals in the plasma can directly participate in the hydrolysis process of the titanium source, accelerate the reaction, and enable the reaction to start efficiently at a lower temperature. This low-temperature reaction characteristic is conducive to avoiding the problem of particle agglomeration caused by high temperature, because high temperature tends to intensify the Brownian motion of particles and increase the probability of collision and agglomeration.

[0045] Because plasma interacts with the surface of nano-titanium dioxide particles, it can change the chemical properties of the particle surface. On the one hand, plasma can remove some impurities and adsorbents on the particle surface, making the particle surface cleaner; on the other hand, plasma treatment can introduce some active groups on the particle surface, such as hydroxyl groups and peroxide groups, which can change the charge distribution and energy state on the particle surface, increase the electrostatic repulsion and steric hindrance between particles, and thus improve the dispersion of particles. In addition, the physical impact generated by plasma also helps prevent the newly generated particles from agglomerating, so that they remain well dispersed in the reaction system.

[0046] The above plasma-assisted method can accelerate the reaction process at a lower temperature, shorten the reaction time, and improve production efficiency. Compared with the traditional high-temperature and long-time reaction method, it not only reduces energy consumption, but also reduces the side reactions and waste that may be generated by long-time high-temperature reactions, which is more environmentally friendly.

[0047] In an achievable manner of the first aspect, the inhibitor in the hydrolysis reaction is a composite inhibitor, the composite inhibitor comprises glacial acetic acid, acetylacetone and 2-pyridinecarboxylic acid, and the molar ratio of the glacial acetic acid, acetylacetone and 2-pyridinecarboxylic acid is 10:1.5:1;

[0048] And / or, the molar ratio of the total amount of the composite inhibitor to the titanium source (calculated as titanium atoms) is 0.35:1.

[0049] The composite inhibitor system composed of glacial acetic acid, acetylacetone and 2-picolinic acid synergistically controls the hydrolysis rate of the titanium source by forming a variety of complexes with titanium ions. The nitrogen atom and carboxyl group in 2-picolinic acid have lone pairs of electrons and can form stable coordination bonds with titanium ions. This multi-component complexation can more effectively slow down the hydrolysis reaction than a single inhibitor, making the hydrolysis process more uniform and gentle. The reason is that different inhibitor molecules have different binding sites and binding strengths with titanium ions. Their cooperation can more comprehensively cover the active sites of the titanium source molecules, thereby more accurately regulating the start-up and progress of the hydrolysis reaction, reducing particle agglomeration caused by excessive hydrolysis, and facilitating the generation of nano-titanium dioxide with uniform particle size.

[0050] In addition, the composite inhibitor can also stabilize the intermediates in the hydrolysis reaction process and prevent the intermediates from undergoing polycondensation reactions too quickly. During the hydrolysis process, some intermediate hydrolysis products formed by the titanium source may have high activity and are easy to polymerize with each other. The presence of the composite inhibitor can interact with these intermediates, reduce their activity, and make them more stable in the system, further ensuring the stability of the reaction and helping to improve the dispersibility and particle size uniformity of nano-titanium dioxide.

[0051] The dispersant is a mixed dispersant, and the mixed dispersant includes hexadecyltrimethylammonium bromide and polyethylene glycol, and the mass ratio of the hexadecyltrimethylammonium bromide to the polyethylene glycol is 1:1;

[0052] Hexadecyltrimethylammonium bromide (CTAB) is a cationic surfactant. CTAB can be adsorbed on the surface of nano-titanium dioxide particles, making the particle surface positively charged. The electrostatic repulsion between particles is enhanced, which effectively prevents agglomeration and improves dispersibility. Polyethylene glycol (PEG) is a non-ionic surfactant that prevents the agglomeration of nano-titanium dioxide particles through steric hindrance. It forms a coating layer on the surface of the particles, increases the distance between the particles, reduces the mutual contact between the particles, and thus improves the dispersibility. The two are mixed in proportion to play a synergistic role and further improve the dispersion effect.

[0053] And / or, during the aging process, dilute ammonia water is added dropwise through an online pH monitoring system to maintain the pH value of the system in the range of 3 to 4.

[0054] In an achievable manner of the first aspect, during the solution preparation and hydrolysis reaction, dilute hydrochloric acid is added dropwise through an online pH monitoring system to maintain the pH value of the system within the range of 2 to 3.

[0055] During the hydrolysis reaction stage, the system pH value is maintained in the range of 2-3. A lower pH value helps control the hydrolysis rate of the titanium source and allows the hydrolysis process to proceed smoothly. At the same time, under this pH condition, the particle surface may be positively charged, reducing agglomeration through electrostatic repulsion. During the aging process, maintaining the pH value in the range of 3-4 is conducive to further maturation and structural stability of the particles. At this time, changes in pH will affect the charge state of the particle surface. Fine-tuning this charge state can further optimize the interaction between particles, enhance dispersibility, and avoid local precipitation or agglomeration caused by pH fluctuations.

[0056] In an achievable manner of the first aspect, the mixed solvent in the preparation of the solution includes anhydrous ethanol and isopropanol, and the anhydrous ethanol and isopropanol are configured in a volume ratio of 2:1. Furthermore, the molar ratio of the total amount of the mixed solvent to the titanium source (measured in titanium atoms) is 10:1.

[0057] Mixed solvents can better adjust the polarity and viscosity of the system. Anhydrous ethanol ensures the good solubility of the titanium source, and the addition of isopropanol further optimizes the solvent environment, making the titanium source molecules more evenly dispersed in the solution, which helps to generate titanium dioxide particles with uniform particle size, and can affect the hydrolysis rate to a certain extent, avoiding agglomeration caused by excessive hydrolysis. In addition, the appropriate amount of solvent can make the titanium source evenly dispersed in the solution, avoiding uneven hydrolysis reaction caused by excessive local concentration, thereby reducing agglomeration.

[0058] In an achievable manner of the first aspect, a centrifugal classification method is used to classify the obtained product into different particle size grades at a suitable rotation speed according to the size of the nano-titanium dioxide particles, and collect products with a particle size range that meets the requirements of the target application.

[0059] Centrifugal classification is a method of separating nano-titanium dioxide particles by using the difference in sedimentation velocity of nano-titanium dioxide particles in a centrifugal field. The classification process can classify the nano-titanium dioxide products produced during the preparation process according to different quality grades, so that products of different particle size ranges can be reasonably utilized, avoiding product waste due to particle size not meeting the requirements of a specific application, and improving the effective utilization of resources.

[0060] In a second aspect, the present invention provides a highly dispersed nano titanium dioxide product prepared by the above-mentioned preparation method.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] (1) The present invention adopts a series of measures, including raw material purity control, ultrasonic parameter optimization, precise control of reaction conditions, and dynamic calcination, to comprehensively ensure the uniformity of nano-titanium dioxide particles during the nucleation and growth process. For example, the high purity and pretreatment of the raw materials avoid the interference of impurities on particle growth. The multi-frequency combination and precise parameter control of ultrasound make the titanium source more evenly dispersed and the hydrolysis reaction more stable. The segmented calcination ensures that the particles are evenly heated during the calcination process, avoiding growth differences caused by local overheating, and ultimately making the prepared nano-titanium dioxide particle size more uniform.

[0063] (2) The present invention effectively solves the problem of particle agglomeration through the synergistic effect of multiple dispersing methods. The compound use of dispersants CTAB and PEG prevents the particles from approaching each other through the dual effects of electrostatic repulsion and steric hindrance; the introduction of inorganic coating agent silica further reduces the surface energy of the particles and enhances the isolation effect between the particles; the combination of freeze drying and vacuum drying avoids agglomeration caused by the surface tension of water during conventional drying, so that the nano-titanium dioxide particles can maintain a good dispersion state in various application systems, greatly improving their dispersibility.

[0064] (3) The combination of the composite inhibitor system and plasma-assisted preparation in the present invention more accurately controls the rate and uniformity of the hydrolysis reaction from the initial stage of the reaction, reducing the particle size differences caused by excessive local reactions. During the entire reaction process, the particle growth is more orderly, making the particle size distribution of the final product narrower and the particle size uniformity significantly improved.

[0065] (4) The present invention utilizes plasma to modify the particle surface, the use of dispersants, and surface functionalization treatment to synergistically enhance the dispersibility of nano-titanium dioxide particles. The electrostatic repulsion and steric hindrance effect between particles are optimized. Whether in the preparation process or in the subsequent application system, nano-titanium dioxide can maintain a good dispersion state and effectively avoid agglomeration.

[0066] (5) The surface functionalization treatment in the present invention gives nano-titanium dioxide specific functional groups, making its surface properties more in line with the needs of different application scenarios. For example, the introduced amino functional groups improve the compatibility and reactivity of the particles with other materials, creating better conditions for the application of nano-titanium dioxide in composite materials, biomedicine and other fields.

[0067] (6) Plasma-assisted preparation can accelerate the reaction process at a lower temperature, shorten the reaction time, and improve production efficiency. Compared with the traditional high-temperature and long-time reaction method, it not only reduces energy consumption, but also reduces the side reactions and waste that may be generated by long-time high-temperature reactions, which is more environmentally friendly.

[0068] (7) The good particle size uniformity and dispersibility of the present invention make the performance of nano-titanium dioxide more stable and reliable in practical applications. Taking the field of photocatalysis as an example, the uniformly dispersed nano-titanium dioxide particles can fully expose the active sites, more effectively absorb light energy and generate photogenerated carriers, thereby improving the photocatalytic efficiency. In addition, during multiple uses, since the particles are not easy to agglomerate, the photocatalytic performance can remain relatively stable, and the performance will not be greatly reduced due to the reduction of active sites caused by agglomeration.

[0069] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 is a process flow chart of an embodiment of the present invention;

[0071] Figure 2 It is a bar chart of particle size uniformity of the nano titanium dioxide products prepared in Examples 1-5 of the present invention;

[0072] Figure 3 It is a bar chart of particle size uniformity of the nano titanium dioxide products prepared in Examples 6-10 of the present invention;

[0073] Figure 4 This is a bar chart of the particle size uniformity of the nano titanium dioxide products obtained in Comparative Examples 1-6 of the present invention. DETAILED DESCRIPTION

[0074] To facilitate understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings, but the present invention can be implemented in different forms and is not limited to the embodiments described in the text. On the contrary, these embodiments are provided to make the content disclosed in the present invention more thorough and comprehensive.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly connected by technicians in the technical field to which the present invention belongs. The terminology used in the specification of the present invention is for the purpose of describing specific embodiments and is not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0076] Embodiment 1: In a first aspect, the present invention provides a method for preparing highly dispersed nano-titanium dioxide, comprising the following steps:

[0077] (1) Solution preparation: Take 8 g of tetrabutyl titanate and 2 g of titanium sulfate that have been pretreated by vacuum distillation, slowly add tetrabutyl titanate dropwise into 200 ml of a mixed solvent (133 ml of anhydrous ethanol and 67 ml of isopropanol), and simultaneously add dilute hydrochloric acid through an online pH monitoring system to maintain the pH value of the system at 2-3, to obtain a titanium source solution.

[0078] (2) Hydrolysis reaction: Add 10 ml of water (accounting for 40% of the total water volume) and a composite inhibitor (0.35 mol of glacial acetic acid, 0.0525 mol of acetylacetone, and 0.035 mol of 2-pyridinecarboxylic acid) to the plasma reactor. After stirring evenly, slowly drip the prepared titanium source solution. Stir continuously during the dripping process. Turn on the plasma generator (power 200 W, frequency 13.56 MHz) and use multi-frequency ultrasonic treatment (power 180 W, pulse mode: work 5 s, rest 2 s). After the titanium source solution is dripped, start dripping the second part of 10 ml of water (drip rate 1.5 drops / second), during which stirring, ultrasonication and plasma treatment are continued. After the second part of water is dripped, continue the reaction for 2 hours, and then slowly drip 5 ml of water.

[0079] (3) Addition of dispersant: After the hydrolysis reaction is completed, the product is cooled to room temperature, 5 g of hexadecyltrimethylammonium bromide and 5 g of polyethylene glycol are added, and stirred for 30 minutes at a speed of 260 rpm.

[0080] (4) Aging treatment: The reaction solution was aged at 30°C for 18 h, and dilute ammonia water was added dropwise through an online pH monitoring system to maintain the pH value of the system at 3.

[0081] (5) Inorganic coating treatment: After aging, slowly add an appropriate amount of nano-silica sol (solid content 10%) into the reactor and stir to allow the silica to evenly coat the surface of the titanium dioxide particles.

[0082] (6) Washing and drying: Wash twice with a mixture of ethanol and deionized water (volume ratio 1:1), then wash three times with deionized water alone, and centrifuge at 7000 rpm after each wash. The washed product is first quickly frozen below -50°C, then freeze-dried for 25 hours under a vacuum degree of less than 10 Pa, and then vacuum-dried at 55°C for 10 hours.

[0083] (7) Staged calcination: The dried product was first calcined at 300°C for 1 hour, and then heated to 480°C for 2 hours at a heating rate of 1.5°C / min. Nitrogen was introduced during the calcination (gas flow rate 50 ml / min). Dynamic calcination was performed in a rotary tube furnace, and sodium hexametaphosphate (1% by mass of the product) was added to the dried product.

[0084] (8) Surface functionalization treatment: The dried product was stirred in a toluene solution containing an appropriate amount of 3-aminopropyltriethoxysilane for 2 hours (temperature controlled at 60°C) to introduce amino functional groups on the surface of the nano-titanium dioxide. The product was then washed with toluene and ethanol several times to remove unreacted 3-aminopropyltriethoxysilane and then dried in a vacuum drying oven.

[0085] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0086] The particle size uniformity of the nano-titanium dioxide sample prepared in the embodiment of the present invention is within ±5nm. This is because the reasonable ratio and pretreatment of the composite titanium source (tetrabutyl titanate and titanium sulfate) from the preparation of the solution ensure the stable start of the hydrolysis reaction. In the solution preparation, the titanium source is evenly dispersed in the solvent by controlling the ratio of the mixed solvent and maintaining a suitable pH value to avoid uneven hydrolysis caused by excessive local concentration. The plasma assistance (precise power and frequency), step-by-step water addition (precise control of the amount of water and the dripping speed of each part) and the composite inhibitor (synergistic effect of multiple components) in the hydrolysis reaction make the hydrolysis process smooth and uniform, and generate primary particles with uniform particle size. Subsequent steps such as addition of dispersants (cooperation of hexadecyltrimethylammonium bromide and polyethylene glycol), appropriate aging conditions (temperature and pH control), inorganic coating treatment (uniform coating of silica sol to reduce surface energy), special washing and drying methods (to avoid agglomeration caused by the surface tension of water) and staged calcination (control of temperature, heating rate, introduction of protective gas and dynamic calcination) further ensure the uniformity of particles during growth and processing, prevent agglomeration, and thus make the final product have good particle size uniformity.

[0087] The nano titanium dioxide sample prepared in the embodiment of the present invention was dispersed in water for 24 hours without obvious agglomeration. The dispersant hexadecyltrimethylammonium bromide makes the surface of the particles positively charged to generate electrostatic repulsion, and polyethylene glycol forms a steric hindrance, and the two work together to effectively prevent particle agglomeration. The inorganic coating layer of silica reduces the surface energy of the particles and reduces the interaction between particles. The combination of freeze drying and vacuum drying avoids agglomeration caused by the surface tension of water during conventional drying. Measures such as introducing protective gas during calcination, adopting dynamic calcination, and adding sodium hexametaphosphate further prevent particle agglomeration. The amino functional group introduced by the surface functionalization treatment increases the surface charge density of the particles and further improves the dispersibility through electrostatic repulsion.

[0088] serial number Particle size uniformity (mean particle size deviation) Dispersibility (24h dispersion in water) Example 1 Within ±5nm No obvious agglomeration Example 2 Within ±6nm Very little agglomeration Example 3 Within ±7nm A small amount of reunion Example 4 Within ±6nm Very little agglomeration Example 5 Within ±7nm A small amount of reunion Example 6 Within ±6nm Very little agglomeration Example 7 Within ±8nm A small amount of reunion Example 8 Within ±7nm A small amount of reunion Example 9 Within ±7nm Very little agglomeration Example 10 Within ±8nm A small amount of reunion Comparative Example 1 ±20nm or more There are a lot of reunions Comparative Example 2 ±15nm or so More reunions Comparative Example 3 ±12nm or so A certain amount of reunion Comparative Example 4 ±10nm or so More reunions Comparative Example 5 ±13nm or so More reunions Comparative Example 6 ±15nm or so There are a lot of reunions

[0089] Although the particle size uniformity data of the nano titanium dioxide samples prepared in Examples 1-10 fluctuated to a certain extent (such as within ±6nm in Example 2, within ±7nm in Example 3, etc.), the overall level was still maintained at a good level; there was no obvious agglomeration phenomenon or very little or small amount of agglomeration when dispersed in water for 24 hours. Due to the comprehensive effect of the dispersion measures in the overall preparation process, the agglomeration was still within a relatively small range, which shows that the nano titanium dioxide prepared in the embodiments of the present invention has a high dispersibility.

[0090] However, the average particle size deviation of the nano-titanium dioxide samples prepared in Comparative Examples 1-6 was more than ±20 nm, and the hydrolysis was uneven, which could not effectively prevent the particles from agglomerating, resulting in poor dispersibility.

[0091] Example 2: In the first aspect, the embodiment of the present invention provides a method for preparing highly dispersed nano-titanium dioxide, and the preparation method is basically consistent with Example 1, the difference being that in the hydrolysis reaction of this embodiment, the plasma generator power is 220W, the ultrasonic power is 200W, the working time is 6s, and the interval is 2.5s.

[0092] In the washing and drying steps of this embodiment, freeze drying is performed for 28 hours and vacuum drying is performed at 60° C. for 12 hours.

[0093] In the staged calcination step of this embodiment, the calcination was carried out at 320° C. for 1.2 hours, and then the temperature was raised to 500° C. for 2.2 hours, with a heating rate of 1.6° C. / min.

[0094] In the surface functionalization treatment step of this embodiment, the dried product was stirred and reacted in a toluene solution containing an appropriate amount of 3-aminopropyltriethoxysilane for 2.5 hours (the temperature was controlled at 65° C.).

[0095] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0096] Example 3: In the first aspect, the embodiment of the present invention provides a method for preparing highly dispersed nano-titanium dioxide, and the preparation method is basically consistent with Example 1, except that in the solution preparation step of this embodiment, the molar ratio of the total amount of the mixed solvent to the titanium source (measured in titanium atoms) is 11:1.

[0097] In the hydrolysis reaction of this embodiment, the first part of water is 12 ml, the second part of water is 8 ml, the third part of water is 5 ml, and the rest is the same as in Example 1.

[0098] In the dispersant adding step of this embodiment, stirring is performed for 50 minutes at a rotation speed of 320 rpm, and the rest is the same as in Embodiment 1.

[0099] In the aging treatment of this embodiment, the aging is carried out at a temperature of 33° C. for 22 hours, and the rest is the same as in Example 1.

[0100] In the inorganic coating treatment step of this embodiment, the amount of silica sol is increased to make the coating thicker, and the rest is the same as in Example 1.

[0101] In the washing and drying steps of this embodiment, the mixture is first washed twice with a mixture of ethanol and deionized water (volume ratio of 1:1), and then washed three times with deionized water alone. After each washing, the mixture is centrifuged at 8000 rpm. The washed product is first quickly frozen below -50°C, and then freeze-dried for 30 hours under a vacuum degree of less than 10 Pa, and then vacuum-dried at 62°C for 13 hours.

[0102] In the staged calcination step of this embodiment, the dried product is first calcined at 330°C for 1.3 hours, then heated to 520°C for 2.3 hours, with a heating rate of 1.7°C / min. The rest is the same as in Embodiment 1.

[0103] In the surface functionalization treatment of this embodiment, the dried product was stirred in a toluene solution containing an appropriate amount of 3-aminopropyltriethoxysilane at 68° C. for 2.8 hours.

[0104] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0105] Example 4: In the first aspect, the embodiment of the present invention provides a method for preparing highly dispersed nano-titanium dioxide, and the preparation method is basically consistent with that in Example 1, the difference is that in the hydrolysis reaction of this embodiment, the plasma generator power is 250W, the ultrasonic power is 220W (working 7s, rest 3s), and the rest is the same as Example 1.

[0106] In the dispersant addition of this embodiment, after the hydrolysis reaction is completed, the product is cooled to room temperature, 6 g of hexadecyltrimethylammonium bromide and 6 g of polyethylene glycol are added, and stirred for 30 minutes at a speed of 280 rpm.

[0107] In the aging treatment of this embodiment, the reaction solution was aged at 34° C. for 21 h, and the rest was the same as in Example 1.

[0108] In the washing and drying steps of this embodiment, the washed product is firstly quickly frozen at below -50°C, then freeze-dried for 31 hours under the condition of vacuum degree less than 10 Pa, and vacuum-dried for 11 hours at 63°C, and the rest is the same as in Example 1.

[0109] In the staged calcination step of this embodiment, the dried product is first calcined at 340°C for 1.4 hours, then heated to 530°C for 2.4 hours, with a heating rate of 1.8°C / min. The rest is the same as in Embodiment 1.

[0110] In the surface functionalization treatment of this embodiment, the dried product was stirred in a toluene solution containing an appropriate amount of 3-aminopropyltriethoxysilane for reaction for 2.2 hours (the temperature was controlled at 62° C.), and the rest was the same as in Example 1.

[0111] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0112] Example 5: In the first aspect, the embodiment of the present invention provides a method for preparing highly dispersed nano-titanium dioxide, and its preparation method is basically consistent with Example 1, the difference being that in the hydrolysis reaction of this embodiment, the amount of water added is 9 ml for the first part, 9 ml for the second part, and 7 ml for the third part, and the rest is the same as Example 1.

[0113] In the dispersant adding step of this embodiment, after the hydrolysis reaction is completed, the product is cooled to room temperature, 5 g of hexadecyltrimethylammonium bromide and 5 g of polyethylene glycol are added, and stirred for 45 minutes (rotation speed 330 rpm).

[0114] In the aging treatment of this embodiment, the reaction solution was aged at 31° C. for 23 h, and the rest was the same as in Example 1.

[0115] The inorganic coating treatment in this embodiment is the same as that in Embodiment 1, but the solid content of the silica sol is 12%.

[0116] The washing and drying steps of this embodiment are the same as those of embodiment 1, but centrifugation at 8500 rpm, freeze drying for 29 hours, and vacuum drying at 61° C. for 12.5 hours are adopted.

[0117] In the staged calcination of this embodiment, the calcination was carried out at 310° C. for 1.1 hours, and then the temperature was raised to 510° C. for 2.1 hours. The heating rate was 1.6° C. / min. The rest was the same as in Embodiment 1.

[0118] The surface functionalization treatment in this example is the same as that in Example 1, but the reaction is carried out at 66° C. for 2.6 hours.

[0119] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0120] Example 6: In the first aspect, the embodiment of the present invention provides a method for preparing highly dispersed nano-titanium dioxide, and the preparation method is basically consistent with that of Example 1, the difference being that the solution of this embodiment is prepared the same as that of Example 1, but the volume ratio of anhydrous ethanol to isopropanol in the mixed solvent is changed to 3:1.

[0121] The hydrolysis reaction in this example is the same as that in Example 1, but the composite inhibitor contains 0.38 mol of glacial acetic acid, 0.057 mol of acetylacetone, and 0.038 mol of 2-pyridinecarboxylic acid.

[0122] The dispersant addition in this embodiment is the same as that in Embodiment 1, but 12 g of cetyltrimethylammonium bromide and polyethylene glycol are added in a mass ratio of 1:1.

[0123] In this embodiment, the reaction solution was aged at 30° C. for 20 h, and the rest was the same as in Example 1.

[0124] The washing and drying of this embodiment are the same as those of embodiment 1, but freeze drying is performed for 30 hours and vacuum drying is performed at 60°C for 13 hours.

[0125] In the staged calcination of this embodiment, the dried product was calcined at 320°C for 1.3 hours, and then heated to 500°C for 2.3 hours. The heating rate was 1.7°C / min. The rest was the same as in Embodiment 1.

[0126] The surface functionalization treatment in this example is the same as that in Example 1, but the reaction is carried out at 64° C. for 2.4 hours.

[0127] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0128] Example 7: In the first aspect, the embodiment of the present invention provides a method for preparing highly dispersed nano-titanium dioxide, and the preparation method is basically consistent with that of Example 1, except that the solution of this embodiment is prepared the same as that of Example 1, but the temperature is controlled at 15°C when tetrabutyl titanate and titanium sulfate are added dropwise.

[0129] The hydrolysis reaction in this embodiment is the same as that in embodiment 1, but the frequency of the plasma generator is 14 MHz and the ultrasonic power is 210 W (operating for 6 s and resting for 2.5 s).

[0130] During the addition of the dispersant in this embodiment, stirring was performed for 55 minutes (rotation speed: 340 rpm), and the rest was the same as in Embodiment 1.

[0131] In the aging treatment of this embodiment, the reaction solution was aged at 35° C. for 24 h, and the rest was the same as in Example 1.

[0132] The washing and drying of this embodiment are the same as those of embodiment 1, but freeze drying is performed for 32 hours and vacuum drying is performed at 64°C for 13.5 hours.

[0133] In the staged calcination of this embodiment, the dried product was calcined at 350°C for 1.5 hours, and then heated to 550°C for 2.5 hours at a heating rate of 2°C / min. The rest was the same as in Embodiment 1.

[0134] The surface functionalization treatment in this example is the same as that in Example 1, but the reaction is carried out at 70° C. for 3 hours.

[0135] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0136] Example 8: In the first aspect, the embodiment of the present invention provides a method for preparing highly dispersed nano-titanium dioxide, and the preparation method is basically consistent with that of Example 1, except that the hydrolysis reaction of this embodiment is the same as that of Example 1, but the overall speed of adding water is slightly slower.

[0137] The dispersant addition in this example is the same as in Example 1, but 10 g of cetyltrimethylammonium bromide and polyethylene glycol in a mass ratio of 1:1 are added, and stirring is carried out for 50 minutes (rotation speed 300 rpm).

[0138] In the aging treatment of this embodiment, the reaction solution was aged at 33° C. for 21 h, and the rest was the same as in Example 1.

[0139] The washing and drying of this embodiment are the same as those of embodiment 1, but freeze drying is performed for 30 hours and vacuum drying is performed at 62°C for 12 hours.

[0140] In the staged calcination of this embodiment, the dried product was calcined at 330°C for 1.3 hours, and then heated to 520°C for 2.3 hours. The heating rate was 1.8°C / min. The rest was the same as in Embodiment 1.

[0141] The surface functionalization treatment in this example is the same as that in Example 1, but the reaction is carried out at 67° C. for 2.7 hours.

[0142] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0143] Example 9: In the first aspect, the embodiment of the present invention provides a method for preparing highly dispersed nano-titanium dioxide, and the preparation method is basically consistent with that of Example 1, except that the solution of this embodiment is prepared the same as that of Example 1, but titanium sulfate is changed to 60% of the total amount added first, and the remaining 40% is added when half of the tetrabutyl titanate is added.

[0144] The hydrolysis reaction in this example was the same as in Example 1, but a small amount of hydrogen peroxide (0.5 ml) was added during the hydrolysis reaction.

[0145] The addition of dispersant in this embodiment is the same as in embodiment 1, but stirring is performed for 40 minutes at a speed of 280 rpm.

[0146] In the aging treatment of this embodiment, the reaction solution was aged at 32° C. for 20 h, and the rest was the same as in Example 1.

[0147] The washing and drying of this embodiment are the same as those of embodiment 1, but freeze drying is performed for 27 hours and vacuum drying is performed at 60°C for 11 hours.

[0148] In the staged calcination of this embodiment, the dried product was calcined at 320°C for 1.2 hours, and then heated to 500°C for 2.2 hours. The heating rate was 1.6°C / min. The rest was the same as in Embodiment 1.

[0149] The surface functionalization treatment in this example is the same as that in Example 1, but the reaction is carried out at 63° C. for 2.3 hours.

[0150] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0151] Example 10: In the first aspect, the embodiment of the present invention provides a method for preparing highly dispersed nano-titanium dioxide, and the preparation method is basically consistent with that in Example 1, the difference is that in the aging treatment of this embodiment, the reaction liquid is aged at 34°C for 22 hours, and the rest is the same as Example 1.

[0152] The washing and drying of this embodiment are the same as those of embodiment 1, but freeze drying is performed for 31 hours and vacuum drying is performed at 63°C for 12.5 hours.

[0153] In the staged calcination of this embodiment, the dried product was calcined at 340°C for 1.4 hours, and then heated to 530°C for 2.4 hours at a heating rate of 1.9°C / min. The rest was the same as in Embodiment 1.

[0154] The surface functionalization treatment in this example is the same as that in Example 1, but the reaction is carried out at 68° C. for 2.8 hours.

[0155] In a second aspect, an embodiment of the present invention provides a highly dispersed nano-titanium dioxide product prepared by the above-mentioned preparation method.

[0156] Comparative Example 1: The comparative example of the present invention provides a method for preparing nano titanium dioxide, and its preparation method is basically consistent with that of Example 1, except that the preparation method of this comparative example comprises the following steps:

[0157] (1) Solution preparation: Take 10 g of tetrabutyl titanate (without titanium sulfate) and add it dropwise into 200 ml of a mixed solvent (133 ml of anhydrous ethanol and 67 ml of isopropanol) without controlling the pH value.

[0158] (2) Hydrolysis reaction: Add 25 ml of water and glacial acetic acid (0.35 mol) into an ordinary reactor (without plasma assistance). After stirring evenly, slowly add the prepared titanium source solution dropwise. Stir continuously during the addition process without ultrasonic treatment.

[0159] (3) Addition of dispersant: After the hydrolysis reaction is completed, the product is cooled to room temperature, 5 g of hexadecyltrimethylammonium bromide is added, and stirred for 30 minutes (speed 260 rpm).

[0160] (4) Aging treatment: The reaction solution was aged at 30°C for 18 h without pH control.

[0161] (5) Washing and drying: Wash three times with deionized water only, centrifuge at 7000 rpm after each wash, and then dry at 80°C under normal pressure.

[0162] (6) Staged calcination: The dried product was calcined at 500 °C for 3 h with a heating rate of 5 °C / min without protective gas, dynamic calcination or addition of dispersant.

[0163] Comparative Example 2: The comparative example of the present invention provides a method for preparing nano titanium dioxide, and the preparation method thereof is basically consistent with that of Example 1, except that the preparation method of this comparative example comprises the following steps:

[0164] (1) Solution preparation: Same as Example 1, except that the titanium source was not pretreated and the mixed solvent was improperly used (the volume ratio of anhydrous ethanol to isopropanol was 1:1, and the molar ratio of the total amount to the titanium source was 8:1).

[0165] (2) Hydrolysis reaction: Same as Example 1, but using a single inhibitor, glacial acetic acid (0.35 mol), and adding all the water at once.

[0166] (3) Dispersant addition: Same as Example 1, but only 10 g of polyethylene glycol is used.

[0167] (4) Aging treatment: same as in Example 1.

[0168] (5) Inorganic coating treatment: same as in Example 1.

[0169] (6) Washing and drying: Same as in Example 1, but only ordinary vacuum drying (no freeze drying) is performed.

[0170] (7) Staged calcination: Same as Example 1, but with a heating rate of 5°C / min, without protective gas and dynamic calcination.

[0171] Comparative Example 3: The comparative example of the present invention provides a method for preparing nano titanium dioxide, and the preparation method thereof is basically consistent with that of Example 1, except that the preparation method of this comparative example comprises the following steps:

[0172] (1) Solution preparation: same as in Example 1.

[0173] (2) Hydrolysis reaction: Same as Example 1, but without plasma assistance and with an ultrasonic power of 300 W (continuous ultrasound).

[0174] (3) Addition of dispersant: same as in Example 1.

[0175] (4) Aging treatment: same as in Example 1.

[0176] (5) Inorganic coating treatment: same as in Example 1.

[0177] (6) Washing and drying: Same as in Example 1.

[0178] (7) Calcination: Use traditional static calcination instead of staged calcination.

[0179] (8) Surface functionalization treatment: same as in Example 1.

[0180] Comparative Example 4: The comparative example of the present invention provides a method for preparing nano titanium dioxide, and the preparation method thereof is basically consistent with that of Example 1, except that the preparation method of this comparative example comprises the following steps:

[0181] (1) Solution preparation: same as in Example 1.

[0182] (2) Hydrolysis reaction: Same as Example 1.

[0183] (3) Dispersant addition: After the hydrolysis reaction is completed, the product is cooled to room temperature without adding dispersant.

[0184] (4) Aging treatment: same as in Example 1.

[0185] (5) Washing and drying: Same as in Example 1.

[0186] (6) Staged calcination: same as in Example 1.

[0187] (7) Surface functionalization treatment: same as in Example 1.

[0188] Comparative Example 5: The comparative example of the present invention provides a method for preparing nano titanium dioxide, and the preparation method thereof is basically consistent with that of Example 1, except that the preparation method of this comparative example comprises the following steps:

[0189] (1) Solution preparation: same as in Example 1.

[0190] (2) Hydrolysis reaction: Add water and inhibitor into the plasma reactor at one time.

[0191] (3) Addition of dispersant: same as in Example 1.

[0192] (4) Aging treatment: Aging the reaction solution at 40°C for 30 h (the temperature is too high and the time is too long).

[0193] (5) Inorganic coating treatment: same as in Example 1.

[0194] (6) Washing and drying: Same as in Example 1.

[0195] (7) Calcination: Use traditional static calcination instead of staged calcination.

[0196] (8) Surface functionalization treatment: same as in Example 1.

[0197] Comparative Example 6: The comparative example of the present invention provides a method for preparing nano titanium dioxide, and the preparation method thereof is basically consistent with that of Example 1, except that the preparation method of this comparative example comprises the following steps:

[0198] (1) Solution preparation: same as in Example 1.

[0199] (2) Hydrolysis reaction: Same as Example 1.

[0200] (3) Addition of dispersant: same as in Example 1.

[0201] (4) Aging treatment: same as in Example 1.

[0202] (5) Inorganic coating treatment: same as in Example 1.

[0203] (6) Washing and drying: Same as in Example 1.

[0204] (7) Staged calcination: The dried product was calcined at 600 °C for 4 hours (the temperature was too high and the time was too long), with a heating rate of 5 °C / min, without protective gas, dynamic calcination, and without adding dispersant.

[0205] (8) Surface functionalization treatment: same as in Example 1.

[0206] Any numerical value cited herein includes all values ​​of lower and upper values ​​that increase by one unit from the lower limit to the upper limit, and there is at least a two-unit interval between any lower value and any higher value. For example, if the value of the quantity of a component or a process variable (such as temperature, pressure, time, etc.) is stated to be from 1 to 90, preferably from 20 to 80, and more preferably from 30 to 70, the purpose is to illustrate that values ​​such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 are also explicitly listed in the specification. For values ​​less than 1, one unit is appropriately considered to be 0.0001, 0.001, 0.01, 0.1. These are merely examples that are intended to be clearly expressed, and it can be considered that all possible combinations of numerical values ​​listed between the lowest value and the highest value are clearly stated in the specification in a similar manner.

[0207] Unless otherwise indicated, 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 specified endpoints.

[0208] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but should be determined with reference to the appended claims and the full scope of equivalents possessed by such claims. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a waiver of the subject matter, nor should it be considered that the inventors did not consider the subject matter to be part of the disclosed inventive subject matter.

[0209] The above is an exemplary description of the present invention in combination with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as such non-substantial improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for preparing highly dispersed nano titanium dioxide, characterized in that: The following steps are involved: (1) Solution preparation: slowly dropwise adding the pretreated titanium source into the mixed solvent to obtain a titanium source solution; (2) Hydrolysis reaction: Add water and mixed inhibitor into the reactor, stir evenly, then slowly drop the prepared titanium source solution into the reactor, stirring continuously during the dropwise addition process; (3) Addition of dispersant: After the hydrolysis reaction is completed, the product is cooled to room temperature, and the dispersant is added and stirred to make it fully mixed; (4) Aging treatment: The reaction solution containing the dispersant is aged for a period of time under certain temperature conditions; (5) Inorganic coating treatment: After aging, slowly add nano-silica sol into the reactor and stir to make the silica evenly coat the surface of the titanium dioxide particles; (6) Washing and drying: The aged product is washed and then vacuum dried; (7) Staged calcination: The dried product is first calcined at 300-350°C for 1-1.5 hours, and then heated to 480-550°C for calcination for 2-2.5 hours. The heating rate is controlled at 1.5°C-2°C / min. After calcination, a nano-titanium dioxide product with uniform particle size and high dispersion is obtained.

2. The method for preparing highly dispersed nano titanium dioxide according to claim 1, characterized in that: It also includes surface functionalization steps: The dried product was stirred in a toluene solution containing an appropriate amount of 3-aminopropyltriethoxysilane for 2-3 hours at a temperature of 60-70°C to introduce amino functional groups on the surface of the nano-titanium dioxide; And / or, after the reaction is completed, the product is washed with toluene and ethanol for multiple times to remove unreacted 3-aminopropyltriethoxysilane, and then dried in a vacuum drying oven.

3. The method for preparing highly dispersed nano titanium dioxide according to claim 1, characterized in that: The titanium source in the solution preparation is a composite titanium source, and the composite titanium source includes tetrabutyl titanate and titanium sulfate, and the mass ratio of the tetrabutyl titanate to titanium sulfate is 8:2; and / or, slowly adding tetrabutyl titanate and titanium sulfate into the mixed solvent respectively to obtain a titanium source solution; And / or, tetrabutyl titanate and titanium sulfate are pretreated by reduced pressure distillation respectively.

4. The method for preparing highly dispersed nano titanium dioxide according to claim 1, characterized in that: The hydrolysis reaction utilizes plasma-assisted hydrolysis, and water and inhibitors are added step by step: The first part of water and the inhibitor are added to the plasma reactor, and after being stirred evenly, the prepared titanium source solution is slowly dripped into the reactor, and stirring is continued during the dripping process. The plasma generator is turned on, and multi-frequency ultrasonic treatment is performed at the same time; After the first part of the titanium source solution is added, the second part of the water is added, and the dropping speed is maintained at 1-2 drops / second, during which stirring, ultrasound and plasma treatment are continued; After the second portion of water was added, the reaction was continued for 2 hours, and then the third portion of water was slowly added at an appropriate time according to the state of the reaction system.

5. The method for preparing highly dispersed nano titanium dioxide according to claim 1, characterized in that: The inhibitor in the hydrolysis reaction is a composite inhibitor, which includes glacial acetic acid, acetylacetone and 2-pyridinecarboxylic acid, and the molar ratio of the glacial acetic acid, acetylacetone and 2-pyridinecarboxylic acid is 10:1.5:1; and / or, the molar ratio of the total amount of the composite inhibitor to the titanium source calculated as titanium atoms is 0.35:1; The dispersant in the aging step is a mixed dispersant, and the mixed dispersant includes hexadecyltrimethylammonium bromide and polyethylene glycol, and the mass ratio of the hexadecyltrimethylammonium bromide to the polyethylene glycol is 1:1; And / or, during the aging process, dilute ammonia water is added dropwise through an online pH monitoring system to maintain the pH value of the system in the range of 3 to 4.

6. The method for preparing highly dispersed nano titanium dioxide according to claim 1, characterized in that: During the solution preparation and hydrolysis reaction, dilute hydrochloric acid is added dropwise through an online pH monitoring system to maintain the pH value of the system within the range of 2-3.

7. The method for preparing highly dispersed nano titanium dioxide according to claim 1, characterized in that: The mixed solvent in the solution preparation includes anhydrous ethanol and isopropanol, and the anhydrous ethanol and isopropanol are configured in a volume ratio of 2:1; And / or, the molar ratio of the total amount of the mixed solvent to the titanium source calculated as titanium atoms is 10:

1.

8. The method for preparing highly dispersed nano titanium dioxide according to claim 1, characterized in that: Add an appropriate amount of inorganic dispersant to the dried product, the amount of which is 1% to 3% of the product mass, and then calcine; And / or, an inert protective gas is introduced during the calcination process, and the gas flow rate is controlled at 50-100 ml / min.

9. The method for preparing highly dispersed nano titanium dioxide according to any one of claims 1 to 8, characterized in that: The centrifugal classification method is used to classify the obtained product into different particle size grades according to the size of the nano titanium dioxide particles at a suitable rotation speed, and the products with a particle size range that meets the requirements of the target application are collected.

10. A highly dispersed nano titanium dioxide product, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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