Method for preparing titanium suboxide from intermediate product of sulfuric acid method titanium dioxide

Abstract

The application belongs to the field of preparation of conductive titanium functional materials, and provides a method for preparing titanium suboxide from titanium white intermediate product prepared by sulfuric acid method, wherein the titanium white intermediate product comprises TiO2·0.06SO3·5H2O, and the method comprises the following steps: performing dehydration and desulfurization treatment on the titanium white intermediate product; grinding the titanium white intermediate product after the dehydration and desulfurization treatment into a solid powder; and reducing the solid powder by using a reducing agent to obtain titanium suboxide. The method uses high-purity intermediate product in the production process of titanium white prepared by sulfuric acid method as raw material, uses hydrogen gas or mixed gas of hydrogen and argon and carbon powder as reducing agent, and prepares titanium suboxide, especially high-purity Ti4O7, through high-temperature reduction reaction.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of conductive titanium functional materials, and particularly relates to a method for preparing titanium suboxide from an intermediate product of sulfuric acid process titanium white. Background Art

[0002] Titanium suboxide (Ti n O 2n-1 , 3 < n < 9), also known as Magnéli titanium oxide, is a group of conductive ceramic functional materials. Among them, Ti4O7 is a titanium oxide functional material with high conductivity and high corrosion resistance, which can be used to make various electrode materials, fuel cell catalysts, environmental photocatalysts, electronic materials, etc., and has broad application prospects. The existing methods for preparing Ti4O7 and other titanium suboxides generally use titanium dioxide (TiO2) as the titanium raw material, and hydrogen, carbon, or carbon-containing compounds as reducing agents to reduce titanium dioxide at high temperatures.

[0003] Patent US5173215A discloses a method for reducing TiO2 with hydrogen to prepare Ti4O7 and other titanium suboxides. Under the heating condition of 1230 °C, TiO2 is reduced in hydrogen for 6 hours to generate titanium suboxides Ti4O7 and Ti5O9. Radecka et al. used a mixed gas of 93% Ar and 7% H2 to reduce titanium dioxide at 947 - 1147 °C to prepare Ti4O7 and other titanium suboxides [J. Power Sources, 2007, 173, 816–821]. Toyoya et al. used polyvinyl alcohol to reduce titanium dioxide at 1100 °C to prepare Ti4O7 [Appl. Catal. B Environ. 88, 160, 2009]. Zhang et al. prepared Ti4O7 by reducing layered titanic acid (H2Ti3O7) with carbon powder at 1075 °C [J Mater Sci: Mater Electron (2016) 27:4861 - 4865], and the layered titanic acid was prepared by reacting titanium dioxide with sodium hydroxide, and the preparation process was complex. In addition, patent CN113104889A provides a method for preparing gram-scale titanium suboxide from metatitanic acid. In an inert atmosphere, the mixture of metatitanic acid and solid reducing agent is subjected to variable temperature treatment to prepare titanium suboxides Ti3O5, Ti4O7, Ti5O9 or Ti6O 11 . The solid reducing agent is citric acid, ammonium carbonate, ammonium bicarbonate, ammonium chloride or ammonium iodide. The inert atmosphere is nitrogen, helium or argon. The reaction temperature is between 987 - 1095 °C.

[0004] In summary, existing methods for producing Ti4O7 titanium suboxide generally use hydrogen, carbon, or carbon-containing compounds as reducing agents to reduce titanium dioxide (TiO2), titanic acid, and other titanium raw materials at high temperatures. These titanium raw materials generally have high impurity content, and the purity of the products prepared by reduction is generally low.

[0005] Therefore, existing technologies urgently need improvement. Summary of the Invention

[0006] To address existing technical problems, this invention proposes a method for preparing titanium suboxide (especially high-purity Ti4O7) through a high-temperature reduction reaction using high-purity intermediate products from the sulfuric acid process for titanium dioxide production as raw materials, and hydrogen or a mixture of hydrogen and argon gas and carbon powder as reducing agents.

[0007] According to the present invention, a method for preparing titanium suboxide from titanium dioxide intermediates produced by the sulfuric acid process is provided. The titanium dioxide intermediates contain TiO2·0.06SO3·5H2O. The method includes the following steps: dehydrating and desulfurizing the titanium dioxide intermediates; grinding the dehydrated and desulfurized titanium dioxide intermediates into solid powder; and reducing the solid powder with a reducing agent to obtain titanium suboxide.

[0008] According to one embodiment of the present invention, the dehydration and desulfurization treatment includes: keeping the titanium dioxide intermediate product at a temperature range of 100~700ºC for 1~4 hours.

[0009] According to one embodiment of the present invention, the dehydrated and desulfurized titanium dioxide intermediate product is ground into solid powder using an agate mortar.

[0010] According to one embodiment of the present invention, the reducing agent comprises hydrogen, carbon powder, or a carbon-containing compound.

[0011] According to one embodiment of the present invention, the reduction of the solid powder using a reducing agent comprises: placing a container containing the solid powder into a tube furnace and mixing it with a reducing agent; heating the tube furnace to 1000~1300ºC and holding it at that temperature for 2~4 hours to carry out the reduction reaction; and cooling to room temperature after the reduction reaction is completed.

[0012] According to one embodiment of the present invention, placing the container containing the solid powder into a tube furnace and mixing it with a reducing agent comprises: introducing hydrogen or a mixture of hydrogen and an inert gas into the tube furnace, controlling the gas flow rate to be 100~500 ml·min. -1 .

[0013] According to one embodiment of the present invention, the inert gas is argon, and the hydrogen content in the mixed gas is ≥10 wt.%.

[0014] According to one embodiment of the present invention, the step of placing the container containing the solid powder into a tube furnace and mixing it with a reducing agent comprises: premixing the solid powder and carbon powder uniformly in a ball mill; placing the container containing the mixture of the solid powder and carbon powder into a tube furnace; and introducing an inert gas into the tube furnace at a flow rate of 100~500 ml·min. -1 .

[0015] According to one embodiment of the present invention, the molar ratio of titanium compound to carbon powder in the solid powder is 3 to 9:1.

[0016] According to one embodiment of the present invention, when the molar ratio of titanium compound to carbon powder in the solid powder is 4:1, the titanium suboxide is Ti4O7.

[0017] By adopting the above technical solutions, compared with the prior art, the present invention has lower production costs, a stable supply of raw materials, a wide range of sources, and higher purity for producing high-purity titanium dioxide intermediates via the sulfuric acid process. Furthermore, the titanium raw material of the present invention has small solid-phase particles, is not sintered, and has a large specific surface area, which is beneficial for reaction with reducing gases or pre-mixing and reacting with solid reducing agents. The reaction rate is fast and stable, and the prepared product, Ti4O7, has advantages such as low cost, high purity, and excellent performance. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] The sulfuric acid process is one of the most important methods for industrial production of titanium dioxide. In the sulfuric acid process, ilmenite (FeTiO3) or titanium slag reacts with concentrated sulfuric acid: FeTiO3 + 2H2SO4 = TiOSO4 + FeSO4 + 2H2O. The resulting solution contains sulfates such as titanium sulfate (TiOSO4), ferrous sulfate (FeSO4), magnesium sulfate (MgSO4), and aluminum sulfate (Al2(SO4)3), as well as acid hydrolysis residues of ilmenite. Titanium dioxide intermediates are obtained through precipitation, crystallization, disc separation, concentration, and hydrolysis. However, these intermediates still contain large amounts of sulfates such as ferrous sulfate (FeSO4), magnesium sulfate (MgSO4), and aluminum sulfate (Al2(SO4)3). After washing and bleaching, a high-purity titanium dioxide intermediate (chemical composition: TiO2·0.06SO3·5H2O, hereinafter referred to as titanium dioxide intermediate) is obtained. Due to extensive desalination and bleaching, its impurity content is ≤20ppm. The basic components of this intermediate product are anatase ultrafine crystals with an average size of approximately 5 nm, along with some water and amorphous titanium dioxide particles. These ultrafine crystals aggregate to form porous primary particles with an average diameter of tens of nanometers. These primary particles further aggregate to form secondary porous particles with an average diameter of several hundred nanometers. These secondary particles have a large specific surface area and excellent adsorption and dispersibility, easily mixing uniformly with powdered materials such as carbon powder and adsorbing reducing gases, thus accelerating the reduction reaction. Furthermore, adding a small amount of TiO2 seed crystals to the titanium dioxide intermediate product, especially trace amounts of salt treatment agents such as KOH, ZnCl2, H3PO4, and Al2(SO4)3, can reduce the sintering of the reaction product, resulting in a product with better application performance.

[0020] The method for preparing titanium suboxide from the sulfuric acid process of titanium dioxide intermediates according to the present invention generally includes the following steps:

[0021] Step S1: Dehydration and desulfurization treatment of titanium dioxide intermediate product;

[0022] Step S2 involves grinding the dehydrated and desulfurized titanium dioxide intermediate into a solid powder; and

[0023] Step S3: Use a reducing agent to reduce the solid powder to obtain titanium suboxide.

[0024] In embodiments of the present invention, the titanium dioxide intermediate product can be kept at a temperature range of 100~700ºC for 1~4 hours, during which water and sulfides evaporate under high temperature conditions, obtaining a dehydrated and desulfurized titanium dioxide intermediate product. During this process, the holding time decreases as the temperature increases, and the temperature and holding time can be set according to actual production conditions. This dehydration and desulfurization method is simple to operate and low in cost. Alternatively, those skilled in the art can also use other methods to dehydrate and desulfurize the titanium dioxide intermediate product.

[0025] The titanium dioxide intermediate product after dehydration and desulfurization can be ground into a solid powder using an agate mortar or other grinding tools to facilitate the subsequent reduction reaction. Hydrogen, carbon powder, or other carbon-containing compounds can be used as reducing agents in the reduction reaction. These carbon-containing compounds can decompose into carbon under high-temperature conditions, thereby reducing the titanium dioxide intermediate product through carbon reduction.

[0026] In embodiments of the present invention, the reduction reaction step for producing titanium suboxide may specifically include:

[0027] Step S31: Place the container containing the solid powder into a tube furnace and mix it with the reducing agent;

[0028] Step S32: The tube furnace is heated to 1000~1300ºC and held at that temperature for 2~4 hours to carry out the reduction reaction; and

[0029] Step S33: After the reduction reaction is complete, cool to room temperature to obtain titanium suboxide.

[0030] When hydrogen is used as a reducing agent, step S31 includes: introducing hydrogen or a mixture of hydrogen and an inert gas into the tubular furnace, controlling the gas flow rate to be 100~500 ml·min. -1 Preferably, argon can be selected as the inert gas; when using a mixed gas, the hydrogen content can be any value between 10 wt.% and 100 wt.%, or equal to 10 wt.%; when the hydrogen content is 100 wt.%, it is pure hydrogen reduction.

[0031] When using carbon powder as a reducing agent, step S31 includes: premixing the solid powder and carbon powder evenly in a ball mill; placing a container containing the mixture of solid powder and carbon powder into a tube furnace; and introducing inert gas into the tube furnace at a flow rate of 100~500 ml·min. -1 Alternatively, this step can be replaced by a vacuum operation, whereby the solid powder can undergo a reduction reaction with the carbon powder under vacuum conditions. In embodiments of the present invention, the molar ratio of the titanium-containing compound to the carbon powder (referred to as the titanium-carbon molar ratio) in the solid powder can be 3 to 9:1. In actual production, Ti4O7 is the most commonly used titanium suboxide functional material. When the molar ratio of the titanium-containing compound to the carbon powder in the solid powder is 4:1, the titanium suboxide generated by the reduction reaction is Ti4O7.

[0032] This invention utilizes the intermediate products of the sulfuric acid process for titanium dioxide production as a substitute for traditional titanium dioxide. This not only enables the preparation of high-purity Ti4O7, but also allows the preparation of other titanium suboxide functional materials (Ti) by adjusting the reduction reaction temperature and time. n O 2n-1 Especially in the reduction process using toner as a reducing agent, the final reduction product can be further controlled by adjusting the molar ratio of solid powder to toner.

[0033] The following description is based on specific embodiments.

[0034] Example 1

[0035] The titanium dioxide intermediate was heated at 100ºC for 4 hours to remove moisture and sulfur. After cooling, it was ground into a solid powder using an agate mortar.

[0036] A corundum boat containing 6 grams of solid powder (containing 5% calcined TiO2 seed crystals and trace amounts of salt treatment agents such as KOH, ZnCl2, H3PO4, Al2(SO4)3, etc.) was placed into a tube furnace. A mixture of hydrogen and argon gas (H2: 30wt%, Ar: 70wt%) was introduced from one end of the tube furnace at a flow rate of 500 cm⁻¹. 3 ·min -1 The temperature of the tube furnace is set at 10ºC·min. -1 The temperature was increased from room temperature to 1200ºC and held at this temperature for 3 hours. Then the tube furnace temperature was allowed to cool naturally back to room temperature.

[0037] The product found in the corundum boat was a black powder. X-ray diffraction analysis showed that the black powder was Ti4O7, with a phase purity of 98.9% and a chemical purity greater than 99.9%.

[0038] Example 2

[0039] The titanium dioxide intermediate was heated at 400ºC for 2 hours to remove moisture and sulfur. After cooling, it was ground into a solid powder using an agate mortar.

[0040] A corundum boat containing 6 grams of solid powder (containing 5% calcined TiO2 seed crystals) was placed into a tube furnace. A mixture of hydrogen and argon gas (H2: 20 wt.%, Ar: 80 wt.%) was introduced from one end of the tube furnace at a flow rate of 200 cm⁻¹. 3 ·min -1 The temperature of the tube furnace is set at 10ºC·min. -1 The temperature was increased from room temperature to 1300ºC and held at this temperature for 2 hours. Then the tube furnace temperature was allowed to cool naturally back to room temperature.

[0041] The product found in the corundum boat was a black powder. X-ray diffraction analysis showed that the black powder was Ti4O7, with a phase purity of 99.0% and a chemical purity greater than 99.9%.

[0042] Example 3

[0043] The titanium dioxide intermediate was heated at 700ºC for 1 hour to remove moisture and sulfur. After cooling, it was ground into a solid powder using an agate mortar.

[0044] A corundum boat containing 6 grams of solid powder was placed into a tube furnace. 100 wt.% pure hydrogen gas was introduced from one end of the tube furnace at a flow rate of 100 cm³. 3 ·min -1 The temperature of the tube furnace is set at 10ºC·min. -1 The temperature was increased from room temperature to 1100ºC and held at this temperature for 4 hours. Then the tube furnace temperature was allowed to cool naturally back to room temperature.

[0045] The product found in the corundum boat was a black powder. X-ray diffraction analysis showed that the black powder was Ti4O7, with a phase purity of 97.5% and a chemical purity greater than 99.9%.

[0046] Example 4

[0047] The titanium dioxide intermediate was heated at 600ºC for 1.5 hours to remove moisture and sulfur. After cooling, it was ground into solid powder using an agate mortar.

[0048] A corundum boat containing 1 gram of solid powder (containing 5% calcined TiO2 seed crystals and trace amounts of salt treatment agents such as KOH, ZnCl2, H3PO4, Al2(SO4)3, etc.) and carbon powder (titanium-carbon molar ratio of 4:1) is placed into a tube furnace. Argon gas is introduced from one end of the tube furnace at a flow rate of 300 cm³. 3 ·min -1 The temperature of the tube furnace is set at 10ºC·min. -1 The temperature was increased from room temperature to 1220ºC and held at this temperature for 3 hours. Then the tube furnace temperature was allowed to cool naturally back to room temperature.

[0049] The product found in the corundum boat was a black powder. X-ray diffraction analysis showed that the black powder was Ti4O7, with a phase purity of 100.0% and a chemical purity greater than 99.9%.

[0050] Example 5

[0051] The titanium dioxide intermediate was heated at 700ºC for 2 hours to remove moisture and sulfur. After cooling, it was ground into a solid powder using an agate mortar.

[0052] A corundum boat containing 2.5 grams of solid powder (containing 5% calcined TiO2 seed crystals and trace amounts of salt treatment agents such as KOH, ZnCl2, and H3PO4) was placed into a tube furnace. A mixture of hydrogen and argon gas (H2: 30wt%, Ar: 70wt%) was introduced from one end of the tube furnace at a flow rate of 500 cm⁻¹. 3 ·min -1 The temperature of the tube furnace is set at 10ºC·min. -1The temperature was increased from room temperature to 1000ºC and held at this temperature for 2 hours. Then the tube furnace temperature was allowed to cool naturally back to room temperature.

[0053] The product from the corundum boat was a black powder. X-ray diffraction analysis indicated that the black powder was Ti9O. 17 Its phase purity is 100%, and its chemical purity is greater than 99.9%.

[0054] Example 6

[0055] The titanium dioxide intermediate was heated at 700ºC for 2 hours to remove moisture and sulfur. After cooling, it was ground into a solid powder using an agate mortar.

[0056] A corundum boat containing 1 gram of solid powder (containing 5% calcined TiO2 seed crystals and trace amounts of salt treatment agents such as KOH, ZnCl2, H3PO4, Al2(SO4)3, etc.) and carbon powder (titanium to carbon molar ratio of 6:1) is placed into a tube furnace. Argon gas is introduced from one end of the tube furnace at a flow rate of 500 cm³ / s. 3 ·min -1 The temperature of the tube furnace is set at 10ºC·min. -1 The temperature was increased from room temperature to 1120ºC and held at this temperature for 3 hours. Then the tube furnace temperature was allowed to cool naturally back to room temperature.

[0057] The product found in the corundum boat was a black powder. X-ray diffraction analysis indicated that the black powder was Ti6O. 11 Its phase purity is 100%, and its chemical purity is greater than 99.9%.

[0058] The titanium suboxide prepared in this application has low cost and high purity, especially the Ti4O7 phase purity which is close to 100%, much higher than the highest purity of 95.0% for commercially available Ti4O7 phase, resulting in better application performance.

[0059] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing titanium suboxide from sulfuric acid process titanium dioxide intermediates, characterized in that, The titanium dioxide intermediate product comprises TiO2·0.06SO3·5H2O, and the method comprises the following steps: The titanium dioxide intermediate product was subjected to dehydration and desulfurization treatment by holding it at a temperature range of 100~700ºC for 1~4h. The titanium dioxide intermediate product after dehydration and desulfurization treatment was ground into a solid powder; and The solid powder is reduced using hydrogen, carbon powder, or a carbon-containing compound as a reducing agent to obtain titanium suboxide; If hydrogen is used as a reducing agent, the container containing the solid powder is placed in a tube furnace, and hydrogen or a mixture of hydrogen and an inert gas is introduced into the tube furnace. The tube furnace is heated to 1000~1300ºC and held for 2~4 hours to carry out the reduction reaction. After the reduction reaction is completed, it is cooled to room temperature. If carbon powder or carbon-containing compounds are used as a reducing agent, the solid powder and carbon powder are premixed evenly in a ball mill. The container containing the mixture of solid powder and carbon powder is placed in a tube furnace, and the tube furnace is heated to 1000~1300ºC and held for 2~4 hours to carry out the reduction reaction. After the reduction reaction is completed, it is cooled to room temperature.

2. The method according to claim 1, characterized in that, The dehydrated and desulfurized titanium dioxide intermediate was ground into solid powder using an agate mortar and pestle.

3. The method according to claim 1, characterized in that, The step of placing the container containing the solid powder into a tube furnace and introducing hydrogen or a mixture of hydrogen and an inert gas into the tube furnace includes: Control the gas flow rate to 100~500 ml·min -1 .

4. The method according to claim 2, characterized in that, The inert gas is argon, and the hydrogen content in the mixed gas is ≥10 wt.%.

5. The method according to claim 1, characterized in that, After placing the container containing the mixture of solid powder and carbon powder into the tube furnace, Inert gas is introduced into the tubular furnace at a flow rate of 100~500 ml·min. -1 .

6. The method according to claim 1, characterized in that, The molar ratio of titanium compounds to carbon powder in the solid powder is 3~9:

1.

7. The method according to claim 6, characterized in that, When the molar ratio of titanium compound to carbon powder in the solid powder is 4:1, the sub-titanium oxide is Ti4O7.