A method for producing high-purity electronic-grade titanium dioxide

Abstract

A method for producing high-purity electronic-grade titanium dioxide involves preheating refined titanium tetrachloride, refined niobium chloride, and oxygen, respectively, before introducing them into a high-temperature oxidizer. Heat generated by toluene combustion is then used to preheat the hot oxygen to 1800°C to 1900°C in the high-temperature oxidation reactor for a gas-phase oxidation reaction. Simultaneously, a potassium chloride solution is introduced into the high-temperature oxidizer via a pipeline to refine the grains, producing a mixture of titanium dioxide particles containing niobium oxide and chlorine gas. This mixture undergoes gas-solid separation to yield a primary titanium dioxide product. Deionized water is used to prepare a titanium dioxide slurry, which is then dispersanted with a water slurry to deagglomerate the particles. The pH is adjusted with an inorganic base, and a water-based acrylic emulsion treatment agent is added. The mixture is then aged, washed, dried, and subjected to a steam-powder treatment to yield a high-purity electronic-grade titanium dioxide product. Advantages include a simple process, high titanium dioxide purity, low impurity content, uniform particle size with a narrow particle size distribution range, high rutile content, high specific surface area, and excellent electrical properties, meeting the application requirements of high-end electronic-grade titanium dioxide.

Description

Technical Field

[0001] The present invention relates to the field of high-purity titanium dioxide production, and in particular to a method for producing high-purity electronic-grade titanium dioxide. Background Art

[0002] High-purity electronic-grade titanium dioxide is primarily used in new electronic components such as BaTiO3-based PTC thermistors, SrTiO3-based or TiO2-based varistors, semiconductor capacitors, MLCCs, high-voltage ceramic capacitors, and PZT. Due to its semiconductor properties, it has become a fundamental raw material for the preparation of high-performance titanium-containing materials. With the rapid development of the domestic electronics industry, market demand for high-purity TiO2 has increased annually, making the research and development and production of high-purity TiO2 a key focus for various companies.

[0003] High-purity electronic-grade titanium dioxide has high requirements for TiO2 purity, impurity content, and specific surface area. The higher the purity of TiO2, the more stable the performance of titanium-containing electronic components. The content of harmful impurities will seriously affect the performance of electronic components. For example, Fe2O3 will reduce the dielectric strength of capacitors; Na2O and K2O will increase the conductivity of ceramics and reduce the insulation strength; SiO2 and Al2O3 will reduce the electromechanical coupling coefficient, etc. Therefore, the lower the content of harmful impurity elements, the better. The specific surface area affects the reaction efficiency and dimensional stability. Controlling the particle size and particle size distribution of high-purity TiO2 can also effectively increase the specific surface area. Especially in the preparation of precision devices, its specific surface area is required to be 7.8m 2 / g or above.

[0004] At present, there are two main methods for producing high-purity titanium dioxide in China: the gas phase method and the liquid phase method. Among them, the gas phase method has become a hot research topic in the industry due to its excellent product quality and high degree of automation. At present, the production of electronic-grade titanium dioxide by the gas phase method mainly focuses on the research of continuous production technology and impurity content control technology. There is little research on improving the functionality of high-purity titanium dioxide in the application of the electronics field, and there is no feasible solution. In addition, when using the gas phase method to produce high-purity electronic-grade titanium dioxide, in order to ensure uniform product particle size and continuous operation of the oxidation reactor, rock salt is often added to the tail of the high-temperature oxidation furnace for cooling, which will introduce K, Cl, Na and other ion impurities. In order to minimize the insoluble impurities in high-purity titanium dioxide, inorganic surface treatment cannot be performed in the post-processing process. As a result, it is difficult to form a filter cake during the washing and impurity removal process due to the lack of the bridging effect of the inorganic coating layer, and the impurity removal ability is weak. CN 116102058A discloses a "method for preparing high-purity electronic-grade titanium dioxide," which achieves a controllable average particle size within the range of 125nm to 370nm, a TiO2 purity of ≥99.90%, and a rutile crystal content of ≥98.00%. However, this method fails to address the product's particle size distribution, specific surface area, or functional enhancements to the high-purity titanium dioxide. Therefore, there is an urgent need to develop a production method that achieves high rutile content, high specific surface area, and excellent electrical properties without introducing impurities, thereby enhancing the functionality of high-purity electronic-grade titanium dioxide in the electronics field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a production method of high-purity electronic-grade titanium dioxide, which has a simple process, high titanium dioxide purity, low impurity content, uniform particle size, narrow distribution range, high rutile content, high specific surface area, and excellent electrical properties, and can meet the application needs of high-end electronic-grade fields.

[0006] The technical solution adopted in the present invention is:

[0007] A method for producing high-purity electronic-grade titanium dioxide, the specific steps of which are as follows:

[0008] 1. Preheating refined titanium tetrachloride, refined niobium chloride, and oxygen at a pressure of 300 kPa to 500 kPa is followed by separate introduction into a high-temperature oxidizer, wherein the mass ratio of refined titanium tetrachloride to refined niobium chloride is 1000:0.5 to 1000:3, and the mass ratio of the mixture of refined titanium tetrachloride and refined niobium chloride to oxygen is 1:20. Heat generated by toluene combustion is used to preheat the hot oxygen to 1800° C. to 1900° C. in a high-temperature oxidation reactor for a gas-phase oxidation reaction. Simultaneously, potassium chloride solution is introduced into the high-temperature oxidizer via a pipeline to refine the grains, thereby obtaining a mixture of titanium dioxide particles containing niobium oxide and chlorine gas. A primary titanium dioxide product is obtained by gas-solid separation.

[0009] 2. Prepare titanium dioxide slurry with a mass concentration of 20% to 30% using deionized water, add a certain amount of water slurry dispersant, and deagglomerate the particles;

[0010] 3. Use inorganic alkali to adjust the pH value to 8.0-9.0, add water-based acrylic emulsion treatment agent, mature and wash;

[0011] 4. Dry at a certain temperature and treat with steam powder to obtain high-purity electronic grade titanium dioxide products.

[0012] Furthermore, the purity of refined titanium tetrachloride is ≥99.9%, and the purity of refined niobium chloride is ≥99.9%.

[0013] Furthermore, refined titanium tetrachloride and refined niobium chloride are preheated in a titanium tetrachloride preheater and introduced into a high-temperature reaction chamber at a temperature of 500°C to 600°C; oxygen is preheated in a hot oxygen preheater at a temperature of 700°C to 800°C.

[0014] Furthermore, the concentration of the potassium chloride solution is 300 g / L, and the amount added is 300 ppm based on the total mass of refined titanium tetrachloride and refined niobium chloride.

[0015] Furthermore, the water slurry dispersant is one of citric acid and ammonium citrate anion organic dispersants, and the added amount accounts for 0.1% to 0.3% of the mass of titanium dioxide.

[0016] Further, the inorganic base is sodium hydroxide solution or potassium hydroxide solution;

[0017] Furthermore, the mass fraction of acrylic acid in the aqueous acrylic emulsion is 40% to 60%, and the added amount is 0.5% to 1.5% based on the weight of acrylic emulsion to titanium dioxide; further, the aqueous acrylic emulsion is acrylic acid-acrylate copolymer emulsion or styrene-acrylic acid copolymer emulsion.

[0018] Furthermore, deionized water is used for washing, and the resistivity of the dry cake after washing is controlled to be ≥500Ω·m;

[0019] Furthermore, the drying medium is hot air, and the drying temperature is 350°C to 420°C.

[0020] Furthermore, during the steam powder treatment, high-pressure steam pulverization treatment is adopted, and the mass ratio of high-pressure steam to titanium dioxide is 1.5:1 to 1.8:1, so as to further refine the particle size and control the particle size distribution range.

[0021] The beneficial effects of the present invention are:

[0022] Using refined titanium tetrachloride, an intermediate product of the chlorination production process, as a raw material (titanium tetrachloride content ≥99.9%), refined niobium chloride (niobium chloride content ≥99.9%) is introduced during the gas phase reaction process, and chemically reacts with oxygen at high temperature to obtain a titanium dioxide and chlorine mixture containing niobium oxide. The introduction of niobium oxide, which can be used in the electronics field, improves the crystal conversion rate of titanium dioxide and simultaneously improves the electrical properties in the electronic-grade application field, thereby better meeting the needs of the high-end electronics field. In the water slurry post-treatment process, a citrate dispersant and an aqueous acrylic emulsion are added. Citric acid acts between titanium dioxide particles through steric hindrance and electrostatic repulsion to depolymerize the polymerized particles. The aqueous acrylic emulsion polymer acts as a skeleton and bridge on the surface of the titanium dioxide particles, thereby improving the cake-forming ability and filterability of the titanium dioxide water slurry without coating with an inorganic film. The combined use of two organic modifiers ensures that the high-purity electronic-grade titanium dioxide slurry possesses both excellent dispersibility and forms a loose filter layer on the filter cloth, improving the slurry's cake-forming properties and enhancing its ability to remove water-soluble impurities and salts. After hot air drying at 350°C to 420°C, the citric acid and aqueous acrylic emulsion undergo a decomposition reaction, ensuring the specifications of the high-purity electronic-grade titanium dioxide. The entire process is easy to control, ensuring high titanium dioxide purity, low ion content, and stable quality. Niobium oxide, a substance beneficial to electronic-grade applications, is also introduced to enhance the functionality of the electronic-grade high-purity titanium dioxide. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with specific embodiments, but the application scope of the present invention is not limited to the embodiments. Various replacements and changes made without departing from the technical concept of the present invention should be within the scope of the present invention.

[0024] Example 1

[0025] 1) Preheating a mixture of refined titanium tetrachloride and refined niobium chloride to 500° C. in a titanium tetrachloride preheater at a pressure of 300 kPa, wherein the mass ratio of refined titanium tetrachloride to refined niobium chloride is 1000:0.5, and the purity of refined titanium tetrachloride is ≥99.9%, and the purity of refined niobium chloride is ≥99.9%. Oxygen is preheated to 700° C. in a hot oxygen preheater and introduced into a high-temperature oxidation reactor, wherein the mass ratio of the mixture of refined titanium tetrachloride and refined niobium chloride to oxygen is 1:20. The hot oxygen is preheated to 1800° C. in the high-temperature oxidation reactor using heat generated by toluene combustion. Refined titanium tetrachloride, refined niobium chloride, and oxygen undergo a gas-phase oxidation reaction in a high-temperature reactor. Simultaneously, a 300 g / L potassium chloride aqueous solution is added to the high-temperature reactor, with the amount of KCl solid added being 300 ppm by mass of the mixture of refined titanium tetrachloride and refined niobium chloride. The solution is atomized in a spray gun using a carrier gas and then added to a hot oxygen flow within the oxidation reactor. The grains are refined to obtain a mixture of titanium dioxide particles containing niobium oxide and chlorine gas. The mixture is cooled through rock salt and a water bath conduit, and subjected to gas-solid separation using a bag filter. The chlorine gas is then returned to the chlorination production process to obtain a primary titanium dioxide product.

[0026] 2) adding the primary titanium dioxide to deionized water to prepare a 20% aqueous slurry, and adding 0.1% citric acid dispersant based on the mass of the titanium dioxide to deagglomerate the agglomerated particles;

[0027] 3) adjusting the pH to 8.0 with sodium hydroxide solution, adding acrylic acid-acrylate copolymer emulsion with a mass fraction of 45% (based on the weight of acrylic acid-acrylate copolymer emulsion to TiO2) in an amount of 0.5%; and washing with deionized water to obtain a titanium dioxide dry cake with a resistivity of 600 Ω·m;

[0028] 4) The material is dried with hot air at 350°C, conveyed to a steam pulverizer under positive pressure, and pulverized with high-pressure steam. The mass ratio of high-pressure steam to titanium dioxide is 1.5:1, and a high-purity electronic grade titanium dioxide product is obtained.

[0029] After testing, the TiO2 content reached 99.98%, the Fe2O3 content was 7ppm, the Na2O content was 10ppm, and the Cl - 、SO4 2- All less than 10ppm; specific surface area 7.9m 2 / g; average particle size 220nm; D10: 140nm; D50: 210nm; D90: 420nm; rutile conversion rate 98.1%.

[0030] Example 2

[0031] 1) Preheating a mixture of refined titanium tetrachloride and refined niobium chloride to 600° C. in a titanium tetrachloride preheater at a pressure of 500 kPa, wherein the mass ratio of refined titanium tetrachloride to refined niobium chloride is 1000:3, and the purity of refined titanium tetrachloride is ≥99.9%, and the purity of refined niobium chloride is ≥99.9%. Oxygen is preheated to 800° C. in a hot oxygen preheater and introduced into a high-temperature oxidation reactor, wherein the mass ratio of the mixture of refined titanium tetrachloride and refined niobium chloride to oxygen is 1:20. The hot oxygen is preheated to 1900° C. in the high-temperature oxidation reactor using heat generated by toluene combustion. A vapor-phase oxidation reaction is performed on refined titanium tetrachloride, refined niobium chloride, and oxygen in a high-temperature reactor. Simultaneously, a 300 g / L potassium chloride aqueous solution is added to the high-temperature reactor, with the amount of KCl solid added being 300 ppm based on the mass of the mixture of refined titanium tetrachloride and refined niobium chloride. The solution is atomized in a spray gun using a carrier gas and then added to a hot oxygen stream in the oxidation reactor to refine the grains, thereby obtaining a mixture of titanium dioxide particles containing niobium oxide and chlorine. The mixture is then cooled in a rock salt and water bath, separated by a bag filter, and the chlorine is returned to the chlorination production process to obtain a primary titanium dioxide product.

[0032] 2) adding the primary titanium dioxide product to deionized water to prepare a 30% aqueous slurry, and adding 0.3% ammonium citrate dispersant based on the mass of the titanium dioxide to deagglomerate the agglomerated particles;

[0033] 3) adjusting the pH to 9.0 with sodium hydroxide, adding a styrene-acrylic acid copolymer emulsion having a mass fraction of 60% styrene-acrylic acid copolymer in an amount of 1.5% based on the weight of the styrene-acrylic acid copolymer emulsion to the TiO2, and washing with deionized water to obtain a dry cake with a resistivity of 700 Ω·m;

[0034] 4) The material is dried with hot air at 420°C and conveyed to a steam pulverizer under positive pressure. It is then crushed with high-pressure steam at a mass ratio of high-pressure steam to titanium dioxide of 1.8:1 to obtain a high-purity electronic-grade titanium dioxide product.

[0035] After testing, the TiO2 content reached 99.90%, the Fe2O3 content was 5ppm, the Na2O content was 12ppm, and the Cl - 、SO4 2- All less than 5ppm; specific surface area 8.9m 2 / g; average particle size 180nm; D10, 135nm; D50, 181nm; D90, 401nm; rutile conversion rate 99.3%.

[0036] Example 3

[0037] 1) Preheating a mixture of refined titanium tetrachloride and refined niobium chloride to 520° C. in a titanium tetrachloride preheater at a pressure of 400 kPa, wherein the mass ratio of refined titanium tetrachloride to refined niobium chloride is 1000:1, and the purity of refined titanium tetrachloride is ≥99.9%, and the purity of refined niobium chloride is ≥99.9%. Oxygen is preheated to 725° C. in a hot oxygen preheater and introduced into a high-temperature oxidation reactor, wherein the mass ratio of the mixture of refined titanium tetrachloride and refined niobium chloride to oxygen is 1:20. The hot oxygen is preheated to 1820° C. in the high-temperature oxidation reactor using heat generated by toluene combustion. A gas-phase oxidation reaction is performed on refined titanium tetrachloride, refined niobium chloride and oxygen in a high-temperature reactor. Simultaneously, a 300 g / L potassium chloride aqueous solution is added to the high-temperature reactor in an amount of 300 ppm (based on KCl solid content as a percentage of the mass of the mixture of refined titanium tetrachloride and refined niobium chloride). The solution is atomized in a spray gun using a carrier gas and then added to a hot oxygen flow in the oxidation reactor to refine the grains, thereby obtaining a mixture of titanium dioxide particles containing niobium oxide and chlorine. The mixture is cooled in a rock salt and water bath, separated in a bag filter, and the chlorine is returned to the chlorination production process to obtain a primary titanium dioxide product.

[0038] 2) adding the primary titanium dioxide to deionized water to prepare a 24.6% aqueous slurry, and adding 0.15% citric acid dispersant based on the mass of the titanium dioxide to disaggregate the agglomerated particles;

[0039] 3) adjusting the pH to 8.7 with sodium hydroxide, adding an acrylic acid-acrylic acid ester copolymer emulsion having a mass fraction of 50% (based on the weight of the acrylic acid-acrylic acid ester copolymer emulsion being 1.0%) of the TiO2, and washing with deionized water to obtain a dry cake having a resistivity of 705 Ω·m;

[0040] 4) The material is dried with hot air at 400°C and conveyed to a steam pulverizer under positive pressure. It is then crushed with high-pressure steam at a mass ratio of high-pressure steam to titanium dioxide of 1.6:1 to obtain a high-purity electronic-grade titanium dioxide product.

[0041] After testing, the TiO2 content reached 99.92%, the Fe2O3 content was 4ppm; the Na2O content was 15ppm, and the Cl - 、SO4 2- All less than 5ppm; specific surface area 8.2m 2 / g; average particle size 210nm; D10, 143nm; D50, 211nm; D90, 419nm. Rutile conversion rate 98.6%.

[0042] Comparative Example 1 is based on Example 1, but refined niobium chloride is not added. The details are as follows:

[0043] 1) preheating refined titanium tetrachloride to 500° C. in a preheater at a pressure of 300 kPa (the purity of the refined titanium tetrachloride is ≥99.9%), and preheating oxygen to 700° C. in an oxygen preheater, and introducing the two into a high-temperature oxidation reactor, respectively, with a mass ratio of refined titanium tetrachloride to oxygen being 1:20; preheating the hot oxygen to 1800° C. in the high-temperature oxidation reactor using heat generated by toluene combustion, so that the refined titanium tetrachloride and oxygen undergo a gas-phase oxidation reaction in the high-temperature reactor; and simultaneously adding a 300 g / L potassium chloride aqueous solution to the high-temperature reactor (the amount added being 300 ppm based on the mass of KCl solid to the refined titanium tetrachloride), atomizing the solution in a spray gun using a carrier gas, and then adding the solution to the hot oxygen flow in the oxidation reactor to refine the crystals to obtain a mixture of titanium dioxide particles and chlorine gas, cooling the mixture through rock salt and a water bath conduit, and performing gas-solid separation through a bag filter. The chlorine gas is then returned to the chlorination production process to obtain a primary titanium dioxide product.

[0044] 2) adding the primary titanium dioxide to deionized water to prepare a 20% aqueous slurry, and adding 0.1% citric acid dispersant based on the mass of the titanium dioxide to deagglomerate the agglomerated particles;

[0045] 3) adjusting the pH to 8.0 with sodium hydroxide solution, adding acrylic acid-acrylate copolymer emulsion with a mass fraction of 45% (based on the weight of acrylic acid-acrylate copolymer emulsion to TiO2) in an amount of 0.5%; and washing with deionized water to obtain a titanium dioxide dry cake with a resistivity of 600 Ω·m;

[0046] 4) The material is dried with hot air at 350°C, conveyed to a steam pulverizer under positive pressure, and pulverized with high-pressure steam. The mass ratio of high-pressure steam to titanium dioxide is 1.5:1, and a high-purity electronic grade titanium dioxide product is obtained.

[0047] After testing, the TiO2 content reached 99.97%, the Fe2O3 content was 7.5ppm, the Na2O content was 14ppm, and the Cl - 、SO4 2- All less than 10ppm; specific surface area 5.8m 2 / g; average particle size 320nm; D10, 139nm; D50, 320nm; D90, 598nm; rutile conversion rate 85.4%.

[0048] Comparative Example 2 does not add citric acid dispersant. Other details are the same as in Example 1, as follows:

[0049] 1) Under a pressure of 300 kPa, a mixture of refined titanium tetrachloride and refined niobium chloride is preheated to 500° C. in a titanium tetrachloride preheater, wherein the mass ratio of refined titanium tetrachloride to refined niobium chloride is 1000:0.5, and the purity of refined titanium tetrachloride is ≥99.9%, and the purity of refined niobium chloride is ≥99.9%. Oxygen is preheated to 700° C. in a hot oxygen preheater and introduced into a high-temperature oxidation reactor, wherein the mass ratio of the refined titanium tetrachloride and refined niobium chloride mixture to oxygen is 1:20. The hot oxygen is preheated to 1800° C. in the high-temperature oxidation reactor using heat generated by toluene combustion. Refined titanium tetrachloride, refined niobium chloride, and oxygen undergo a gas-phase oxidation reaction in a high-temperature reactor. Simultaneously, a 300 g / L potassium chloride aqueous solution is added to the high-temperature reactor, with the amount of KCl solid added being 300 ppm by mass of the mixture of refined titanium tetrachloride and refined niobium chloride. The solution is atomized in a spray gun using a carrier gas and then added to a hot oxygen flow within the oxidation reactor. The grains are refined to obtain a mixture of titanium dioxide particles containing niobium oxide and chlorine gas. The mixture is cooled through rock salt and a water bath conduit, and subjected to gas-solid separation using a bag filter. The chlorine gas is then returned to the chlorination production process to obtain a primary titanium dioxide product.

[0050] 2) adding the primary titanium dioxide product to deionized water to prepare a 20% water slurry;

[0051] 3) adjusting the pH of the slurry to 8.0 using sodium hydroxide solution, adding acrylic acid-acrylate copolymer emulsion with a mass fraction of 45% (the amount of acrylic acid-acrylate copolymer emulsion added is 0.5% based on the weight of the acrylic acid-acrylate copolymer emulsion to the TiO2), and washing with deionized water to obtain a dry cake with a resistivity of 300 Ω·m;

[0052] 4) The material is dried with hot air at 350°C, conveyed to a steam pulverizer under positive pressure, and pulverized with high-pressure steam. The mass ratio of high-pressure steam to titanium dioxide is 1.5:1, and a high-purity electronic grade titanium dioxide product is obtained.

[0053] After testing, the TiO2 content reached 98.4%, the Fe2O3 content was 30ppm, the Na2O content was 170ppm, and the Cl - Content 73ppm, SO4 2- Less than 5ppm; specific surface area 6.2m 2 / g; average particle size 309nm; D10, 189nmD50, 311nm; D90, 528nm; rutile conversion rate 98.1%.

[0054] Comparative Example 3 does not add water-based acrylic emulsion, and the rest is the same as Example 1. The details are as follows:

[0055] 1) Under a pressure of 300 kPa, a mixture of refined titanium tetrachloride and refined niobium chloride is preheated to 500° C. in a titanium tetrachloride preheater, wherein the mass ratio of refined titanium tetrachloride to refined niobium chloride is 1000:0.5, and the purity of refined titanium tetrachloride is ≥99.9%, and the purity of refined niobium chloride is ≥99.9%. Oxygen is preheated to 700° C. in a hot oxygen preheater and introduced into a high-temperature oxidation reactor, wherein the mass ratio of the refined titanium tetrachloride and refined niobium chloride mixture to oxygen is 1:20. The hot oxygen is preheated to 1800° C. in the high-temperature oxidation reactor using heat generated by toluene combustion. Refined titanium tetrachloride, refined niobium chloride, and oxygen undergo a gas-phase oxidation reaction in a high-temperature reactor. Simultaneously, a 300 g / L potassium chloride aqueous solution is added to the high-temperature reactor, with the amount of KCl solid added being 300 ppm by mass of the mixture of refined titanium tetrachloride and refined niobium chloride. The solution is atomized in a spray gun using a carrier gas and then added to a hot oxygen flow within the oxidation reactor. The grains are refined to obtain a mixture of titanium dioxide particles containing niobium oxide and chlorine gas. The mixture is cooled through rock salt and a water bath conduit, and subjected to gas-solid separation using a bag filter. The chlorine gas is then returned to the chlorination production process to obtain a primary titanium dioxide product.

[0056] 2) adding the primary titanium dioxide to deionized water to prepare a 20% aqueous slurry, and adding 0.1% citric acid dispersant based on the mass of the titanium dioxide to deagglomerate the agglomerated particles;

[0057] 3) adjusting the pH to 8.0 with sodium hydroxide and washing with deionized water to obtain a dry cake with a resistivity of 200 Ω·m;

[0058] 4) The material is dried with hot air at 350°C, conveyed to a steam pulverizer under positive pressure, and pulverized with high-pressure steam. The mass ratio of high-pressure steam to titanium dioxide is 1.5:1, and a high-purity electronic grade titanium dioxide product is obtained.

[0059] After testing, the TiO2 content reached 99.87%, the Fe2O3 content was 36ppm, the Na2O content was 360ppm, and the Cl - Content 157ppm, SO4 2- Less than 5ppm; specific surface area 6.7m 2 / g; average particle size 240nm; D10, 176nmD50, 242nm; D90, 458nm; rutile conversion rate 98.0%.

[0060] In Comparative Example 4, the citric acid dispersant was replaced with sodium dodecylbenzenesulfonate dispersant, and the other procedures were the same as in Example 1.

[0061] The details are as follows:

[0062] 1) Under a pressure of 300 kPa, a mixture of refined titanium tetrachloride and refined niobium chloride is preheated to 500° C. in a titanium tetrachloride preheater, wherein the mass ratio of refined titanium tetrachloride to refined niobium chloride is 1000:0.5, and the purity of refined titanium tetrachloride is ≥99.9%, and the purity of refined niobium chloride is ≥99.9%. Oxygen is preheated to 700° C. in a hot oxygen preheater and introduced into a high-temperature oxidation reactor, wherein the mass ratio of the refined titanium tetrachloride and refined niobium chloride mixture to oxygen is 1:20. The hot oxygen is preheated to 1800° C. in the high-temperature oxidation reactor using heat generated by toluene combustion. Refined titanium tetrachloride, refined niobium chloride, and oxygen undergo a gas-phase oxidation reaction in a high-temperature reactor. Simultaneously, a 300 g / L potassium chloride aqueous solution is added to the high-temperature reactor, with the amount of KCl solid added being 300 ppm by mass of the mixture of refined titanium tetrachloride and refined niobium chloride. The solution is atomized in a spray gun using a carrier gas and then added to a hot oxygen flow within the oxidation reactor. The grains are refined to obtain a mixture of titanium dioxide particles containing niobium oxide and chlorine gas. The mixture is cooled through rock salt and a water bath conduit, and subjected to gas-solid separation using a bag filter. The chlorine gas is then returned to the chlorination production process to obtain a primary titanium dioxide product.

[0063] 2) adding the primary titanium dioxide to deionized water to prepare a 20% aqueous slurry, and adding 0.1% sodium dodecylbenzenesulfonate dispersant based on the mass of the titanium dioxide to deagglomerate the agglomerated particles;

[0064] 3) Adjusting the pH to 8.0 with sodium hydroxide solution, adding 45% by weight of acrylic acid-acrylate copolymer emulsion (0.5% by weight of acrylic acid-acrylate copolymer emulsion relative to the weight of TiO2), and washing with deionized water to obtain a titanium dioxide dry cake with a resistivity of 540 Ω·m.

[0065] 4) The material is dried with hot air at 350°C, conveyed to a steam pulverizer under positive pressure, and pulverized with high-pressure steam. The mass ratio of high-pressure steam to titanium dioxide is 1.5:1, and a high-purity electronic grade titanium dioxide product is obtained.

[0066] After testing, the TiO2 content reached 99.93%, the Fe2O3 content was 12ppm; the Na2O content was 15ppm, and the Cl - 、SO4 2- All less than 5ppm; specific surface area 7.5m 2 / g; average particle size 229nm; D10, 143nm; D50, 231nm; D90, 437nm. Rutile conversion rate 98.4%.

[0067] In the present invention, niobium oxide with good electrical properties is introduced into the oxidation process, which improves the functionality of titanium dioxide in electronic applications while ensuring high purity of titanium dioxide. As can be seen from Comparative Example 1, without adding niobium oxide, the crystal conversion rate of titanium dioxide is only 85.4%, and it is a mixed crystal form with a specific surface area of 5.8m 2 / g, with an average particle size of 320nm. As can be seen from Examples 1-3, adding a small amount of niobium oxide can ensure a rutile conversion rate of more than 98.0%, significantly improving the rutile crystal conversion rate of titanium dioxide, and the specific surface area is greater than 7.8m 2 / g, with an average particle size below 220nm. The above comparison shows that the addition of niobium oxide increases the rutile conversion rate and specific surface area, while reducing the average TiO2 particle size. The addition of niobium oxide stabilizes the rutile structure, increases TiO2 surface defects, and improves the dielectric constant, resulting in superior performance in the resulting electronic components.

[0068] During the wet impurity removal process, a citric acid dispersant with a low decomposition temperature and an aqueous acrylic emulsion are introduced. The citric acid dispersant has a good deagglomeration effect, providing high dispersibility of the TiO2 water slurry. After adjusting the pH, a water-soluble acrylic emulsion is added. The acrylic copolymer emulsion has a chain structure, and the mechanical entanglement and hydrogen bonds between the chains form a network structure, which provides a bridging effect for the titanium dioxide slurry that has not undergone inorganic surface treatment, significantly improving the permeability of the filter cake, enhancing the washing effect of soluble ions, and improving the purity of titanium dioxide. In Comparative Example 2, no citric acid dispersant was added, only an aqueous acrylic emulsion was added. Due to severe agglomeration and other reasons, under the same washing conditions, the removal rate of soluble salt impurities was low, the Na2O content was 170ppm, and the Cl - The content is 73ppm, which does not meet the requirements of high-purity electronic grade products and affects the average particle size and distribution width of the final product. In Comparative Example 3, no aqueous acrylic emulsion was added, and only citric acid dispersant was added. Due to the good dispersion state and strong fluidity of the slurry, no filter cake could be formed. Under the same washing conditions, the removal rate of soluble salt impurities was still low, with a Na2O content of 360ppm and Cl - The content is 157ppm, which does not meet the requirements of high-purity electronic-grade products and cannot be produced normally. In addition, the citrate dispersant and the aqueous acrylic emulsion are decomposed and removed during the hot air drying process at 350℃~420℃, further ensuring the stability of the high-purity titanium dioxide content. In Comparative Example 4, sodium dodecylbenzenesulfonate dispersant is used instead of citric acid dispersant. The specific surface area of the product is slightly lower, the average particle size is larger, and other indicators are normal. However, because sodium dodecylbenzenesulfonate remains in the final electronic-grade titanium dioxide product, the organic residue will affect the stability of electronic components and other indicators and affect the electrical properties of PTC thermistor ceramics.

[0069] The above are merely specific embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for producing high-purity electronic-grade titanium dioxide, characterized in that: The specific steps are as follows: 1) Preheating refined titanium tetrachloride, refined niobium chloride, and oxygen at a pressure of 300 kPa to 500 kPa, respectively, and introducing them into a high-temperature oxidizer, wherein the mass ratio of refined titanium tetrachloride to refined niobium chloride is 1000:0.5 to 1000:3, and the mass ratio of refined titanium tetrachloride to oxygen is 1:20; using the heat generated by the combustion of toluene, the hot oxygen is preheated to 1800° C. to 1900° C. in the high-temperature oxidation reactor to undergo a gas-phase oxidation reaction, and simultaneously, potassium chloride solution is introduced into the high-temperature oxidizer through a pipeline to obtain a mixture of titanium dioxide particles containing niobium oxide and chlorine gas; and after gas-solid separation, a primary titanium dioxide product is obtained; 2) Prepare titanium dioxide slurry with a mass concentration of 20% to 30% using deionized water, add a certain amount of water slurry dispersant to deagglomerate the particles; the water slurry dispersant is one of citric acid and ammonium citrate anion organic dispersants; 3) Use inorganic alkali to adjust the pH value to 8.0-9.0, add water-based acrylic emulsion treatment agent, mature and wash; 4) Dry at a certain temperature and treat with steam powder to obtain high-purity electronic grade titanium dioxide products.

2. The method for producing high-purity electronic-grade titanium dioxide according to claim 1, wherein: The purity of refined titanium tetrachloride is ≥99.9%, and the purity of refined niobium chloride is ≥99.9%.

3. The method for producing high-purity electronic-grade titanium dioxide according to claim 1, wherein: Refined titanium tetrachloride and refined niobium chloride are preheated in a titanium tetrachloride preheater and then introduced into a high-temperature reaction chamber at a preheating temperature of 500°C to 600°C; oxygen is preheated in a hot oxygen preheater at a temperature of 700°C to 800°C.

4. The method for producing high-purity electronic-grade titanium dioxide according to claim 1, wherein: The concentration of the potassium chloride solution is 300 g / L, and the amount added is 300 ppm based on the total mass of refined titanium tetrachloride and refined niobium chloride.

5. The method for producing high-purity electronic-grade titanium dioxide according to claim 1, wherein: The amount of water slurry dispersant added is 0.1% to 0.3% of the mass of titanium dioxide.

6. The method for producing high-purity electronic-grade titanium dioxide according to claim 1, wherein: The inorganic base is sodium hydroxide solution or potassium hydroxide solution.

7. The method for producing high-purity electronic-grade titanium dioxide according to claim 1, wherein: The mass fraction of the aqueous acrylic acid in the aqueous acrylic emulsion is 40% to 60%, and the added amount is 0.5% to 1.5% of the weight of the titanium dioxide based on the aqueous acrylic emulsion.

8. The method for producing high-purity electronic-grade titanium dioxide according to claim 1, wherein: The water-based acrylic emulsion is acrylic acid-acrylate copolymer emulsion or styrene-acrylic acid copolymer emulsion.

9. The method for producing high-purity electronic-grade titanium dioxide according to claim 1, wherein: Use deionized water for washing and control the resistivity of the dry cake after washing to be ≥500Ω.m.

10. The method for producing high-purity electronic-grade titanium dioxide according to claim 1, wherein: The drying medium is hot air, and the drying temperature is 350℃~420℃; for steam-powder treatment, the steam-solid mass ratio is controlled at 1.5:1~1.8:1.