JP2010143783A - Method for producing low halogen titanium oxide powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing titanium oxide powder having low halogen content and the low variation of the halogen content reducing effect while suppressing the change of rutilated ratio or specific surface area. <P>SOLUTION: In the method of producing titanium oxide powder having low halogen content by heating of crude titanium oxide powder produced using titanium halide as a raw material in a cylindrical treating chamber, the treating chamber is arranged vertical and the crude titanium oxide powder is added and falls down in the treating chamber while supplying a dehalogenated gas from the upper part of the treating chamber into a heating chamber to form a descending air current flowing in the whole treating chamber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a titanium oxide powder having a low halogen content suitable for a catalyst, a solar cell, a dielectric material and the like.

  Titanium oxide powder is used in various applications such as pigments, dielectric materials, and ultraviolet shielding materials, and in recent years, its application to photocatalysts and solar cells is also in the spotlight. As described above, titanium oxide is used for various purposes, but fine titanium oxide having fine particles and good dispersibility has been demanded from demands for improvement in performance, miniaturization, high refractive index, transparency and the like.

  The production method of titanium oxide powder includes a liquid phase method in which titanyl sulfate, titanium tetrachloride, organic titanium and the like are hydrolyzed in a liquid phase, and a gas phase in which titanium halide is reacted with an oxidizing gas such as oxygen or water vapor in the gas phase. Broadly divided into law. Generally, titanium oxide obtained by a vapor phase method does not use a solvent, and therefore has finer particles and better dispersibility than titanium oxide obtained by a liquid phase method, and is excellent in crystallinity because it is a reaction at a high temperature. It has the features such as.

  When manufacturing titanium oxide powder using raw titanium oxide powder made from titanium halide such as titanium tetrachloride as the raw material, the presence of a halogen element such as chlorine in the resulting titanium oxide will result in production equipment and product bases. In order to corrode or alter the material, it is necessary to keep the halogen content in the obtained titanium oxide powder low.

  For example, when barium titanate is produced from barium carbonate and titanium oxide by a solid phase method, it is known that chlorine in titanium oxide causes abnormal grain growth of barium titanate (for example, Patent Documents). 1), in particular, when the particle size of the titanium oxide powder is reduced and the specific surface area is increased, the residual chlorine concentration tends to increase (for example, see Patent Document 2).

As a method for reducing the chlorination of titanium oxide, for example,
(I) A method of bringing titanium oxide into contact with water vapor while rolling in a cylindrical rotary heating furnace (see Patent Document 2),
(Ii) a method of contacting titanium oxide obtained by oxidizing titanium tetrachloride in a gas phase with gaseous alcohol in a temperature range of 300 ° C. or lower (see Patent Document 3),
(Iii) A metal oxide obtained by hydrolyzing a metal vapor halide in the presence of hydrolyzing or oxidizing gas, and wet air by countercurrent flow at a high temperature in an upright hollow cylindrical processing chamber. In refining by the treatment used, the oxide is introduced into a treatment chamber heated to about 400 to 600 ° C. opposite to an inert moist air flow that rises, and the flow rate of the mixed gas phase is increased to a highly dispersible oxide. Is known to keep it low so that a vortex layer cannot be formed (see Patent Document 4).
Paragraph [0012] of Japanese Patent Laid-Open No. 2006-76876 JP-A-10-251021 JP-A-6-171940 Japanese Patent Publication No. 48-13832

  However, as a result of studies by the present inventors, the methods described in Patent Document 2 and Patent Document 3 have a small effect of reducing the halogen content, and the method described in Patent Document 4 has an energy loss. In addition to being large, it was found that the variation of the halogen content reduction effect in the obtained titanium oxide powder was large.

  Under such circumstances, the present invention provides a method for producing a titanium oxide powder that reduces the halogen content and has little variation in the halogen content reduction effect while suppressing changes in the rutile ratio and specific surface area. It is intended.

  In order to solve the above technical problem, the present inventor has intensively studied. As a result, when the crude titanium oxide powder produced using titanium halide as a raw material is heat-treated in a cylindrical processing chamber, the processing chamber is set vertically. Heat treatment while adding crude titanium oxide powder to the processing chamber and dropping it while forming a descending airflow that flows through the entire processing chamber by supplying dehalogenated gas from the upper part of the processing chamber to the processing chamber. As a result, it has been found that the above technical problem can be solved, and the present invention has been completed based on this finding.

That is, the present invention
(1) When heat-treating crude titanium oxide powder produced using titanium halide as a raw material in a cylindrical processing chamber,
While arranging the processing chamber vertically,
While forming a descending airflow that circulates the entire processing chamber by supplying dehalogenated gas into the processing chamber from the upper part of the processing chamber,
A method for producing a low halogen titanium oxide powder, wherein the crude titanium oxide powder is added to the treatment chamber and dropped while being dropped,
(2) The method for producing low-halogen titanium oxide powder according to (1), wherein the crude titanium oxide powder is repeatedly dropped a plurality of times in the processing chamber,
(3) The method for producing a low halogen titanium oxide powder according to the above (1) or (2), wherein the dehalogenating gas contains one or more selected from water vapor, alcohol gas, or a mixed gas thereof,
(4) The method for producing a low halogen titanium oxide powder according to any one of (1) to (3), wherein the heat treatment temperature is 300 ° C. or higher,
(5) The method for producing a low halogen titanium oxide powder according to any one of (1) to (4) above, wherein the internal dimensions of the processing chamber are 50 to 300 mm in diameter, and (6) the crude titanium oxide powder is The method for producing a low halogen titanium oxide powder according to any one of the above (1) to (5), wherein the residence time per one time passing through the processing chamber is 5 seconds or less.

  According to the present invention, when a crude titanium oxide powder produced using titanium halide as a raw material is heat-treated in a cylindrical processing chamber, the processing chamber is disposed vertically and the processing chamber is disposed from the upper portion of the processing chamber. By reducing the residence time in the processing chamber by supplying the dehalogenated gas to the chamber and forming a descending airflow that circulates throughout the processing chamber, heat treatment while adding and dropping the crude titanium oxide powder into the processing chamber In addition to reducing the change in the rutile rate of the raw titanium oxide powder as a raw material, and uniformizing the heating temperature of the individual particles constituting the crude titanium oxide powder, while suppressing the change in the rutile rate and specific surface area, A titanium oxide powder having a small halogen content and a small variation in the halogen content reducing effect can be produced.

  The method for producing a low-halogen titanium oxide powder of the present invention is such that when the crude titanium oxide powder produced using titanium halide as a raw material is heat-treated in a cylindrical processing chamber, the processing chamber is disposed vertically. Supplying a dehalogenating gas from the upper part of the processing chamber into the processing chamber to form a descending airflow flowing through the entire processing chamber, and adding the crude titanium oxide powder to the processing chamber and performing the heat treatment while dropping. It is a feature.

  First, the preparation method of the crude titanium oxide powder used as a raw material in the method of this invention is demonstrated.

  As a preparation method of the crude titanium oxide powder, a gas phase method in which a titanium halide-containing gas such as titanium tetrachloride is hydrolyzed or oxidized in the gas phase, and a titanium halide content such as titanium tetrachloride is contained. Examples thereof include a liquid phase method in which a solution is hydrolyzed and neutralized with an alkali or water.

In the method of the present invention, examples of the method for producing the raw titanium oxide powder as a raw material by a vapor phase method include a method of hydrolyzing or oxidizing titanium halide gas, for example,
(I) a gas phase oxidation method in which a titanium halide-containing gas is oxidized by contacting oxygen gas in the gas phase;
(II) A flame hydrolysis method in which a combustible gas such as hydrogen gas that generates water during combustion and oxygen gas is supplied to a combustion burner to form a flame, and a titanium halide-containing gas is introduced into the flame,
(III) a gas phase oxidation method in which a titanium halide-containing gas is contacted with water vapor in the gas phase and oxidized;
(IV) A flame hydrolysis method in which a combustible gas such as hydrogen gas that generates water during combustion and an oxygen gas are supplied to a combustion burner to form a flame, and a titanium halide-containing gas and water vapor are introduced into the flame,
Gas phase methods such as

  Examples of the halogenated titanium-containing gas include those containing titanium halide gas such as titanium tetrachloride gas, titanium tetrabromide gas, titanium tetraiodide gas, and the like. A mixed gas with an inert gas is also included.

  Further, instead of various gases for hydrolyzing or oxidizing the titanium halide, a mixed gas of a combustible gas such as hydrogen gas, oxygen gas and water vapor, and an inert gas such as nitrogen gas may be used. Good.

  When producing a crude titanium oxide powder by the vapor phase method, the resulting titanium dioxide powder is obtained by reacting the titanium halide-containing gas with a combustible gas such as hydrogen gas, oxygen gas or water vapor in the gas phase. As compared with the case where a crude titanium oxide powder is produced by a liquid phase method, an impurity element is less likely to be mixed in or remain.

  When producing a crude titanium oxide powder by a vapor phase method, the obtained crude titanium oxide powder usually contains about 1000 to 20000 mass ppm of a halogen element derived from a titanium halide-containing gas.

In the method of the present invention, the average particle size of the primary particles constituting the raw titanium oxide powder as a raw material is not particularly limited, but is usually 200 nm or less when the crude titanium oxide powder is obtained by a vapor phase method. The thickness is preferably 100 nm or less. The specific surface area of the crude titanium oxide powder is not particularly limited, but is usually 50 to ²⁰⁰ m ² / g in terms of BET specific surface area. In the method of the present invention, when the BET specific surface area of the raw titanium oxide powder as a raw material is within the above range, it is possible to provide a fine low halogen titanium oxide powder having excellent optical characteristics and catalytic activity.

  Hereinafter, a method for producing a crude titanium oxide powder by a vapor phase method using titanium tetrachloride gas as a raw material will be described in detail.

As a production method of the crude titanium oxide powder,
(I) a step of bringing titanium tetrachloride gas and oxygen gas into contact with each other, or
(Ii) a step of bringing titanium tetrachloride gas into contact with hydrogen gas and oxygen gas to react, or
(Iii) a step of bringing titanium tetrachloride gas into contact with water vapor to react, or
(Iv) It is preferable to include any step of contacting titanium tetrachloride gas with hydrogen gas, oxygen gas, and water vapor to cause the reaction to hydrolyze or oxidize titanium tetrachloride in a gas phase.

  In the method of the present invention, the raw titanium oxide powder used as a raw material is produced by supplying water vapor to the reaction by producing or supplying water vapor (ii) to (iv), particularly supplying water vapor to the reaction. A method having the steps (iii) and (iv) is preferred.

In the method for producing the crude titanium oxide powder, titanium tetrachloride gas is supplied to the reaction part, and oxygen, hydrogen gas and oxygen gas, water vapor, or hydrogen gas, oxygen gas is supplied to the reaction part. However, it is desirable that the supply amount of oxygen and water vapor be equal to or more than the chemical equivalent for oxidizing all of titanium tetrachloride with respect to the supply amount of titanium tetrachloride gas to the reaction section. In particular, when the supply amount of water vapor is equal to or more than the chemical equivalent of oxidizing all titanium tetrachloride, the titanium oxide production reaction is uniformly performed, so that it is easy to control the crystal of the produced titanium oxide, and the high specific surface area. It becomes easy to obtain a rutile type titanium oxide powder having a high rutile ratio (rutile content) or an anatase type titanium oxide powder having a high specific surface area. Here, the chemical equivalent that oxidizes all titanium tetrachloride means the chemical equivalent of oxygen or water vapor when titanium tetrachloride is reacted with oxygen or water vapor. In the case of oxygen, titanium tetrachloride (TiCl ₄ ) gas 1 In the case of 1 mol of oxygen (O ₂ ) gas and water vapor with respect to mol, water vapor (H ₂ O) is 2 mol with respect to 1 mol of titanium tetrachloride.

  In the method for producing the crude titanium oxide powder, specifically, when the supply gas supplied to the reaction section is in a standard state, the volume ratio of the gas, preferably 5 times or more of the titanium tetrachloride gas, Particularly preferably, the reaction is performed by supplying water vapor of 7 times or more of titanium tetrachloride gas.

  Further, in the method for producing the crude titanium oxide powder, it is preferable that the supply amount of oxygen gas is equal to or more than the chemical equivalent for burning all hydrogen with respect to the supply amount of hydrogen gas to the reaction section. When the supply gas supplied to the reaction section is in a standard state, it is preferable to supply and react oxygen gas at a volume ratio of gas that is twice or more that of hydrogen gas. Here, the chemical equivalent of burning all hydrogen is 1 mole of oxygen gas per 2 moles of hydrogen gas. The rutile ratio can be adjusted by the supply amount of hydrogen gas.

  In the method for producing the crude titanium oxide powder, the volume ratio of hydrogen gas, oxygen gas and water vapor to 1 liter of titanium tetrachloride gas when each supply gas is in a standard state with respect to the supply amount of the supply gas supplied to the reaction section Are shown in Tables 1 and 2. Table 1 shows a method for producing anatase-type crude titanium oxide powder, and Table 2 shows a method for producing a rutile-type crude titanium oxide powder.

  In the method for producing the crude titanium oxide powder, the supply rate of titanium tetrachloride gas, hydrogen gas, oxygen gas and water vapor varies depending on the reaction scale or the nozzle diameter for supplying each supply gas, etc. It is desirable to set the supply speed of each supply gas, particularly titanium tetrachloride gas, in the turbulent flow region.

  In the method for producing the crude titanium oxide powder, titanium tetrachloride gas, hydrogen gas, oxygen gas, and water vapor may be diluted with an inert gas such as argon or nitrogen, and supplied to the reaction section for reaction.

  In the method for producing the crude titanium oxide powder, the supply amount of hydrogen gas, oxygen gas and water vapor to the titanium tetrachloride gas is set to the supply amounts shown in Table 1, so that the specific surface area is high and the rutile ratio is low. Anatase type crude titanium oxide powder can be obtained. Moreover, by setting it as the supply amount shown in Table 2, a rutile type rough titanium oxide powder having a high specific surface area and a high rutile ratio can be obtained.

  Further, in the method for producing the crude titanium oxide powder, when supplying the titanium tetrachloride gas, the hydrogen gas, the oxygen gas and the water vapor to the reaction part, it is desirable to preheat and supply and react, and the preheating temperature Is preferably 500 ° C. or higher, and more preferably 500 to 900 ° C.

  And in the manufacturing method of the said rough titanium oxide powder, each supply gas reacts in the said reaction part, and a rough titanium oxide powder produces | generates. The reaction temperature in the reaction part is preferably equal to or higher than the temperature at which titanium oxide is generated, specifically 500 ° C or higher, and more preferably 550 to 800 ° C.

  In the method for producing the crude titanium oxide powder, by controlling the preheating temperature and reaction temperature of each supply gas, the rutile ratio (rutile titanium oxide content) of the produced crude titanium oxide powder can be controlled.

  When producing an anatase-type titanium oxide powder having a low rutile ratio such as a rutile ratio of 10% or less, the preheating temperature is preferably 500 to 700 ° C, and the reaction temperature is preferably 550 to 800 ° C.

  On the other hand, when manufacturing a rutile type titanium oxide powder having a high rutile ratio such as a rutile ratio of 90% or more, the preheating temperature is preferably 800 to 900 ° C and the reaction temperature is preferably 850 to 900 ° C.

  In the method for producing the crude titanium oxide powder, after reacting each supply gas to produce the crude titanium oxide powder, in order to prevent aggregation of the produced particles, at least below the temperature at which the titanium oxide particles are sintered, specifically It is preferable to cool the crude titanium oxide powder as quickly as possible to below 300 ° C.

  Next, a method for producing a crude titanium oxide powder as a raw material by a liquid phase method in the method of the present invention will be described.

Examples of a method for producing a crude titanium oxide powder by a liquid phase method include a method of hydrolyzing a titanium halide or neutralizing a titanium halide-containing liquid.
(I) a method in which an aqueous solution of titanium chloride is contacted with an alkali and neutralized;
(II) A method in which water is added to titanium chloride and a hydrolysis treatment is performed.

  Examples of titanium chloride include titanium trichloride and titanium tetrachloride.

  Crude titanium oxide solids obtained by the above-mentioned preparation methods (I) to (II) of crude titanium oxide powder by the liquid phase method are rutile or anatase type titanium oxide, orthotitanic acid, metatitanic acid, titanium hydroxide or oxidized. It is a powder or colloid containing titanium hydrate.

  After performing the neutralization treatment or hydrolysis treatment, it is preferable to perform a washing treatment to remove impurities such as hydrochloric acid and alkaline components, and if necessary, perform separation and drying treatment to form a powder. If necessary, it is preferable to perform a drying treatment for removing water such as crystal water. Examples of the method for separating the crude titanium oxide solids include filtration with a filter or filter press, decantation, and a centrifugal separation method, and the drying treatment is preferably a method that can prevent aggregation of the solid titanium oxide solid particles. A spray dryer or a commercially available dryer can be preferably used.

  In the step of obtaining the crude titanium oxide solid by neutralization or hydrolysis, the crystal form of the obtained crude titanium oxide powder can be controlled by adjusting various conditions.

  For example, the rutile ratio of the resulting crude titanium oxide powder can be controlled by the time or speed of the neutralization treatment or hydrolysis treatment. Specifically, for example, when a titanium tetrachloride aqueous solution is neutralized with ammonia water or the like, a neutral titanium oxide powder having a low anatase-rich rutile ratio can be obtained by neutralizing in a short time. By slowing down, a crude titanium oxide powder having a high rutile ratio can be obtained. The neutralization rate is preferably a rate of neutralizing 50 to 500 g of titanium tetrachloride per minute in terms of titanium atomic weight, and a rate of neutralizing 100 to 300 g of titanium tetrachloride per minute in terms of titanium atomic weight. More preferred. When the neutralization rate is slower than the rate of neutralizing 200 g of titanium tetrachloride per minute in terms of titanium atomic weight, the rutile ratio becomes 50% or more.

  Further, the rutile ratio of the crude titanium oxide powder obtained can be controlled by the pH of the reaction system during the neutralization treatment or hydrolysis treatment.

  For example, after precipitation of the crude titanium oxide solid, a ripening reaction in a low pH atmosphere improves the rutile ratio, and a rutile type and anatase type mixed crystal can be obtained.

Moreover, the average particle diameter or specific surface area of the crude titanium oxide powder can be controlled by the hydrolysis treatment or the neutralization treatment conditions with alkali. Specifically, the average particle size can be controlled to usually 200 nm or less, preferably 100 nm or less, and the specific surface area can be controlled to 50 to 300 m ² / g.

  The crude titanium oxide powder obtained by the liquid phase method usually contains about 1000 to 20000 ppm by mass of a halogen element derived from titanium halide.

  In the method of the present invention, the crude titanium oxide powder may be anatase type, rutile type, brookite type, a mixed phase selected from these, or an amorphous titanium oxide.

  In the present specification, the rutile rate means that calculated by the following method.

That is, in this specification, the rutile ratio is obtained by performing X-ray diffraction measurement according to the method defined in ASTM D3720-84, and calculating the peak area (Ir) of the strongest diffraction line (surface index 110) of rutile-type crystalline titanium oxide. It means what is calculated | required by calculating | requiring the peak area (Ia) of the strongest diffraction line (surface index 101) of anatase type crystalline titanium oxide, and calculating with following Formula.
Rutile ratio (% by weight) = 100-100 / (1 + 1.2 × Ir / Ia)

  In the formula, the peak area (Ir) and the peak area (Ia) mean the area of the portion protruding from the base line in the corresponding diffraction line of the X-ray diffraction spectrum, and a known method can be used for the calculation method. For example, methods such as computer calculation and approximate triangulation can be used.

  In the method of the present invention, when the crude titanium oxide powder is heat-treated in a cylindrical processing chamber, the processing chamber is disposed vertically.

  As for the internal dimension of a cylindrical processing chamber, it is preferable that a diameter is 50-300 mm, It is more preferable that it is 70-200 mm, It is further more preferable that it is 80-100 mm. In addition, the internal dimensions of the cylindrical processing chamber may be set such that the residence time per one time that the crude titanium oxide powder passes through the processing chamber is 5 seconds or less. It is more preferable that the residence time is set to be 1 to 4 seconds, and it is more preferable that the residence time is set to be 2 to 3 seconds. Specifically, the height is usually preferably 3000 to 7000 mm, more preferably 3000 to 6000 mm, although depending on the relationship with the speed of the downdraft formed in the processing chamber. More preferably, it is 3000 to 5000 mm.

  By making the processing chamber cylindrical, it is possible to uniformly heat individual particles constituting the crude titanium oxide powder by suppressing the uneven temperature distribution in the processing chamber, and for the rough oxidation of the processing chamber wall. The adhesion of titanium powder can be reduced. When the diameter is larger than 300 mm, the uniformity of the temperature distribution in the processing chamber is reduced, and the variation of the halogen amount in the obtained low halogen titanium oxide powder is increased. When the diameter is smaller than 50 mm, the processing efficiency is reduced.

  The cylindrical processing chamber is preferably a cylindrical heating chamber formed inside the heating furnace, and more preferably a cylindrical heating chamber whose temperature and atmosphere can be controlled by the heating furnace.

  In the case where the cylindrical processing chamber is a heating chamber formed inside the heating furnace and the heating chamber is formed in a coaxial double cylindrical shape in the heating furnace, the heating furnace is made upright. By installing vertically in the state, the heating chamber can be arranged vertically.

  In the method of the present invention, dehalogenating gas is supplied from the upper part of the processing chamber into the processing chamber to form a descending airflow flowing through the entire processing chamber.

  The dehalogenation gas preferably contains at least one selected from an inert gas such as argon gas and helium gas, air, oxygen gas, nitrogen gas, etc., and is selected from water vapor, alcohol gas, or a mixture gas thereof. It is more preferable that it contains 1 or more types. When the dehalogenation gas contains one or more gases selected from water vapor, alcohol gas, or a mixed gas thereof, the effect of removing halogen elements can be enhanced, and particularly, a gas containing a mixed gas of water vapor and alcohol gas. Thus, the effect of removing the halogen element can be enhanced.

  When the dehalogenation gas contains an alcohol gas, examples of the alcohol gas include those that are gaseous at a temperature of 60 ° C. or higher, such as methanol gas, ethanol gas, propanol gas, and butanol gas. In particular, as the alcohol gas, methanol gas is preferable because of its high halogen element removal effect, low cost, and high safety (low explosion lower limit).

  When the dehalogenated gas is a mixed gas of water vapor and alcohol gas, the concentration of alcohol gas in the mixed gas ((volume of alcohol gas / volume of mixed gas) × 100) is 0.05 to 5 vol%. Is preferable, and it is more preferable that it is 1-4 vol%. When the concentration of alcohol in the mixed gas is less than 0.05 vol%, the effect of removing a halogen element is reduced, and when it is greater than 5 vol%, handling becomes difficult from the viewpoint of flammability and the like.

  Further, when the dehalogenation gas is composed of a mixed gas of water vapor and alcohol gas, the volume ratio of alcohol gas to water vapor in the mixed gas (alcohol gas / water vapor) is preferably 0.003 to 1, 01-0.1 is more preferable. When the volume ratio of the alcohol to the water vapor in the mixed gas is 0.003 to 1, the effect of removing the halogen element can be enhanced.

Further, when the dehalogenation gas is composed of a mixed gas of water vapor and alcohol gas, the ratio of the volume (Nm ³ ) of the alcohol gas to the mass (kg) of the crude titanium oxide (the volume of alcohol in the mixed gas (Nm ³ ) The mass (kg) of titanium oxide is preferably 0.003 or more. When the ratio of the volume of the alcohol gas to the mass of the crude titanium oxide is 0.003 or more, the halogen element removal effect can be improved. The ratio of the volume of the alcohol gas to the mass of the crude titanium oxide is preferably 0.006 or less from the viewpoint of economy.

  The descending airflow may be formed by ejecting a dehalogenated gas from the upper part of the processing chamber, or formed by sucking the dehalogenated gas from the lower part of the processing chamber while supplying the dehalogenated gas from the upper part of the processing chamber. May be.

  The dehalogenated gas may be supplied from the supply port provided at the upper end (top) of the vertically disposed processing chamber in the vertically downward direction in the processing chamber, or may be supplied from the vertically disposed processing chamber. Although it may be supplied downward from the supply port provided in the upper side surface, in consideration of processing efficiency, it is preferable to supply from the upper end (top) of the processing chamber in the vertical downward direction in the processing chamber. . In addition, the dehalogenated gas may be supplied into the process chamber from a plurality of supply ports provided in the upper part of the process chamber. However, in this case as well, considering the process efficiency, the dehalogenated gas is supplied only in the vertically downward direction in the process chamber. It is preferable to supply.

  Further, it is preferable not to supply a gas other than the dehalogenation gas into the processing chamber. When supplying a gas other than the dehalogenation gas, supply the gas so as to be in the same direction as the supply direction of the dehalogenation gas. Is preferred.

  The speed of the descending airflow is preferably 10 m / second or less, more preferably 5 m / second or less, and further preferably 3 m / second or less.

  In the method of the present invention, the crude titanium oxide powder is added and dropped from the upper part of the processing chamber into the processing chamber, and heat treatment is performed.

  The crude titanium oxide powder may be charged from an inlet provided in the upper part of the processing chamber, or may be supplied from an inlet provided separately in the middle of the processing chamber. It is preferable to feed from the inlet.

  The heat treatment temperature of the crude titanium oxide powder in the treatment chamber is preferably 300 ° C or higher, more preferably 300 ° C to 1500 ° C, and further preferably 300 ° C to 500 ° C.

  When the heat treatment temperature is lower than 300 ° C., it is difficult to obtain a sufficient desalting effect. In addition, as the heat treatment temperature increases, the desalting effect increases, but the specific surface area of the obtained titanium oxide powder slightly decreases compared to the specific surface area of the crude titanium oxide powder. This becomes noticeable when titanium oxide powder is used. For this reason, it is preferable to determine the upper limit of heat processing temperature according to the specific surface area of a rough titanium oxide powder.

  In the method of the present invention, since the crude titanium oxide powder is heat-treated with the descending air flow while dropping in the processing chamber, the residence time of the crude titanium oxide powder in the processing chamber can be shortened. Even when the anatase type crude titanium oxide powder is heated at a temperature of 550 ° C. or higher, the phase transition from the anatase type to the rutile type can be suppressed.

  In the method of the present invention, the heat treatment may be performed while repeatedly dropping the crude titanium oxide powder a plurality of times in the processing chamber. By repeatedly dropping the crude titanium oxide powder in the processing chamber a plurality of times, even if the halogen element cannot be sufficiently removed by passing through the processing chamber only once, the halogen element can be removed to a desired level. . In the method of the present invention, the change in the specific surface area and the phase transition of titanium oxide can be suppressed even when the heat treatment is performed while dropping the crude titanium oxide powder a plurality of times in the treatment chamber. What is necessary is just to determine suitably the frequency | count (repetition number) to which a rough titanium oxide is dropped, considering the reduction amount of a halogen element.

  The residence time per time that the crude titanium oxide powder passes through the processing chamber is preferably 5 seconds or less, more preferably 1 to 4 seconds, and even more preferably 2 to 3 seconds. If the time per one time that the crude titanium oxide powder passes through the processing chamber is longer than 5 seconds, the grain growth and crystallinity of the titanium oxide particles change.

  When the crude titanium oxide powder is repeatedly dropped in the treatment chamber a plurality of times, the total residence time for the crude titanium oxide powder to pass through the treatment chamber (the total time for the crude titanium oxide powder to pass through the treatment chamber) is 8 to 40 seconds. It is preferable that it is, It is more preferable that it is 8 to 32 seconds, It is further more preferable that it is 8 to 24 seconds.

  In the method of the present invention, the low halogen titanium oxide powder obtained by the above treatment is further subjected to other dehalogenation element treatment, for example, heat treatment under normal pressure, reduced pressure or vacuum, water vapor or alcohol gas. You may perform a contact process with the gas containing this.

  In the method of the present invention, the method of the present invention may be applied after subjecting the crude titanium oxide powder to the other dehalogenation element treatment.

  In the method of the present invention, the obtained low halogen titanium oxide powder may be classified or sieved as necessary.

  In the method of the present invention, by subjecting the crude titanium oxide powder to heat treatment while dropping vertically downward, the contact frequency between the crude titanium oxide powders is reduced compared to a conventional desalting apparatus using a fluidized bed, Sintering of particles constituting the powder can be avoided, and individual particles constituting the powder can be uniformly heat-treated.

  Further, in the method of the present invention, the coarse titanium oxide powder is dropped in the processing chamber while forming a descending airflow flowing through the entire processing chamber, and the moving direction of the coarse titanium oxide powder is matched with the flow direction of the airflow. In addition, the residence time of the particles constituting the crude titanium oxide powder is made uniform in the processing chamber (with uniform heating conditions for each particle) to suppress variation in the halogen element content reduction effect and minimize energy loss. The adhesion of the crude titanium oxide powder to the processing chamber wall surface can be reduced.

In the method of the present invention, the crude titanium oxide powder is heated while being dropped together with the downdraft flowing through the entire processing chamber in the processing chamber, so that the residence time of the crude titanium oxide powder in the processing chamber is shortened, For example, a low halogen titanium oxide powder can be obtained while reducing the change in the rutile ratio of the titanium oxide powder to 5% or less, and the crude titanium oxide powder can be uniformly heat-treated. A low halogen titanium oxide powder can be produced while suppressing variations in the element content reduction effect. Furthermore, since the moving direction of the crude titanium oxide powder and the flow direction of the airflow in the processing chamber are the same in the method of the present invention, the contact frequency between the particles constituting the crude titanium oxide powder is reduced and the particles are sintered. Since it is possible to suppress the occurrence of condensation, since the heating time per time is short, even if the heat treatment is repeatedly performed in the processing chamber, the change in the specific surface area hardly occurs after the second heat treatment, Even when a low halogen-participated titanium powder is produced from a crude titanium oxide powder having a specific surface area of 50 m ² / g or more, the halogen concentration can be reduced while suppressing changes in the specific surface area and the rutile ratio.

  When used for an electronic material such as barium titanate, the low halogen titanium oxide powder obtained by the method of the present invention can give excellent electrical characteristics in terms of dielectric characteristics and the like.

EXAMPLES Next, although an Example is given and this invention is demonstrated further more concretely, this invention is not restrict | limited at all by the following examples.
Example 1
(1) Production of Crude Titanium Oxide Powder a Crude titanium oxide powder was prepared by a vapor phase method in which titanium tetrachloride was oxidized in contact with oxygen gas, hydrogen gas and water vapor in the gas phase.
First, using a gas phase reaction tube having an inner diameter of 200 mm equipped with a multi-tube burner, titanium tetrachloride gas preheated to 850 ° C. and vaporized is supplied to the multi-tube burner while being diluted with nitrogen gas. Then, steam preheated to 850 ° C. was supplied from another supply nozzle, and titanium tetrachloride was oxidized at 900 ° C. in the gas phase reaction tube to produce crude titanium oxide powder a. At this time, the supply amount (supply rate) of each supply gas was 42 liters / minute of titanium tetrachloride and 1280 liters / minute of water vapor in terms of standard conditions.
Thereafter, dry air at room temperature was supplied at 600 liters / minute to a cooling unit located at the lower part of the gas phase reaction tube to cool the produced crude titanium oxide powder a.

The crude titanium oxide powder a had a chlorine content of 2.2%, a specific surface area of 99 m ² / g, and a rutile ratio of 3.2%.

(2) Heat treatment The heating chamber is prepared by preparing a vertical heating furnace having a cylindrical heating chamber having an internal dimension of 100 mm in diameter and a height of 5900 mm, and vertically installing the heating furnace upright. Were arranged vertically.
From the upper part of the heating chamber toward the heating chamber, a mixed gas of methanol, water vapor and air (volume mixing ratio: methanol / water vapor / air = 4/20/76) as a dehalogenating gas is supplied at a rate of 35 liters / minute. A descending airflow that circulates throughout the heating chamber was formed by feeding vertically downward.
Heating by maintaining the temperature of the heating chamber at 350 ° C. while adding and dropping the crude titanium oxide powder a prepared in (1) above from the upper part of the heating part of the heating furnace at a rate of 4 kg / hr. Processed. After passing the crude titanium oxide powder a so that the residence time in the heating chamber was about 3 seconds, it was passed through the heating furnace four times under the same conditions (total contact between the descending airflow and the crude titanium oxide powder) It was heated by a total of 5 passes so that the time was about 15 seconds).
Table 3 shows the rutile ratio (%), the BET specific surface area, and the chlorine content in the obtained titanium oxide powder.
In this example, the rutile ratio (%) was calculated by the same method as described above, and X-ray diffraction measurement conditions, specific surface area calculation method, and chlorine content when the rutile ratio was calculated. The measuring method is as follows.

<X-ray diffraction measurement conditions>
Diffraction device: RAD-1C (manufactured by Rigaku Corporation)
X-ray tube: Cu
Tube voltage, tube current: 40 kV, 30 mA
Slit DS-SS: 1 degree, RS: 0.15mm
Monochromator: Graphite Measurement interval: 0.002 degrees Counting method: Constant clock method

<Specific surface area measurement method>
The specific surface area was measured by the BET method.

<Chlorine content measurement method>
The chlorine content is measured by the following.
The titanium oxide powder was weighed (x1) and dissolved by boiling in a hydrofluoric acid solution. Next, the mass (y1) of chlorine in the hydrofluoric acid solution after dissolving the titanium oxide powder was determined by a silver nitrate titration method. And the chlorine content of the titanium oxide powder was calculated from the mass of chlorine in the hydrofluoric acid solution after dissolving the titanium oxide powder by the following formula.
Chlorine content of titanium oxide powder (ppm) = (y1 / x1) × 100,000
(In the above formula, x1 represents the mass (g) of the weighed titanium oxide powder, and y1 represents the mass (g) of chlorine in the hydrofluoric acid solution determined by the silver nitrate titration method.)

(Comparative Example 1)
In a container, 1 kg of crude titanium oxide powder obtained in the same manner as in Example 1 (1) was placed in a container, and a mixed gas of water vapor and air (volume mixing ratio: water vapor / air = 24/76) was changed to 13 While supplying at a flow rate of 1 liter / min, the crude titanium oxide powder was brought into contact with the mixed gas at 350 ° C. for 20 hours. The characteristics of the obtained titanium oxide powder were measured in the same manner as in Example 1. The results are shown in Table 3.

  From Table 3, it can be seen that in the method for producing a low halogen titanium oxide powder of the present invention, the chlorine content can be reduced in a short time without substantially changing the specific surface area. Moreover, it turns out that the obtained low halogen titanium oxide powder has a homogeneity with little dispersion | variation in chlorine content.

(Example 2)
In Example 1 (2), a titanium oxide powder was obtained in the same manner as in Example 1 except that the temperature of the heating chamber was changed to 450 ° C. In the obtained titanium oxide powder, the rutile ratio (%), the BET specific surface area, and the chlorine content were measured in the same manner as in Example 1. The results are shown in Table 4.

(Examples 3 to 6)
In Example 2, the number of times that the crude titanium oxide powder a passed through the heating chamber was 1 to 4 times (the number of repetitions of the heat treatment was 0 (none) to 3 times). Thus, titanium oxide powder was obtained. In each obtained titanium oxide powder, the rutile ratio (%), the BET specific surface area, and the chlorine content were measured in the same manner as in Example 1. The results are shown in Table 5.

  From the results of Table 4 and Table 5, in the method for producing low halogen titanium oxide powders of the present invention, the chlorine content is reduced with little influence on the specific surface area and the rutile ratio even if repeated heat treatment is performed. I can see that

(Example 7)
(1) Production of Crude Titanium Oxide Powder b Crude titanium oxide powder was prepared by a vapor phase method in which titanium tetrachloride was oxidized in contact with oxygen gas, hydrogen gas and water vapor in the gas phase.
First, using a gas phase reaction tube having an inner diameter of 200 mm equipped with a multi-tube burner, titanium tetrachloride gas preheated to 850 ° C. and vaporized is supplied to the multi-tube burner while being diluted with nitrogen gas. By supplying hydrogen gas, oxygen gas and water vapor preheated to 850 ° C. from separate supply nozzles, and performing oxidation reaction of titanium tetrachloride at 850 ° C. in the gas phase reaction tube, crude titanium oxide Powder b was produced. At this time, the supply amount (supply speed) of each supply gas was 34 liters / minute of titanium tetrachloride and 1052 liters / minute of water vapor in terms of standard conditions.
Thereafter, dry air at room temperature was supplied at 600 liters / minute to the cooling unit located at the lower part of the gas phase reaction tube to cool the produced crude titanium oxide powder b.
The crude titanium oxide powder b had a chlorine content of 1.4%, a BET specific surface area of 77 m ² / g, and a rutile ratio of less than 1%.

(2) Heat treatment From the top of the heating chamber toward the heating chamber, a mixed gas of water vapor and air (volume mixing ratio: water vapor / air = 20/80) as a dehalogenated gas is vertically applied at a rate of 35 liters / minute. A downward airflow that circulates through the entire heating chamber was formed by supplying downward.
Heating by maintaining the temperature of the heating chamber at 550 ° C. while adding and dropping the crude titanium oxide powder b prepared in (1) above from the upper part of the heating part of the heating furnace at a rate of 4 kg / hr. Processed.
After passing the crude titanium oxide powder b so that the residence time in the heating section was about 3 seconds, the same heating furnace was repeated twice under the same conditions (total contact between the descending airflow and the crude titanium oxide powder) It was heated by passing a total of three times so that the time was about 9 seconds).
The rutile ratio (%), BET specific surface area, and chlorine content in the obtained titanium oxide powder were measured in the same manner as in Example 1. The results are shown in Table 6.

(Example 8)
In Example 7 (2), instead of a mixed gas of water vapor and air (volume mixing ratio: water vapor / air = 20/80) as a dehalogenating gas, a mixed gas of ethanol, water vapor and air (volume mixing ratio: ethanol) Titanium oxide powder was obtained by performing heat treatment in the same manner as in Example 7 except that / water vapor / air = 4/20/76) was used. The rutile ratio (%), BET specific surface area, and chlorine content in the obtained titanium oxide powder were measured in the same manner as in Example 1. The results are shown in Table 6.

Example 9
Titanium oxide powder was obtained by performing heat treatment in the same manner as in Example 8 except that the temperature of the heating furnace was changed from 550 ° C. to 650 ° C. The rutile ratio (%), BET specific surface area, and chlorine content in the obtained titanium oxide powder were measured in the same manner as in Example 1. The results are shown in Table 6.

From Table 6, in the manufacturing method of the titanium oxide powder of the present invention, even when the crude titanium oxide powder having a BET specific surface area of 50 m ² / g or higher and a high specific surface area is processed, the rutile ratio and specific surface area are determined. It turns out that the titanium oxide powder excellent in the chlorine removal effect can be obtained without changing. Moreover, it turns out that a chlorine removal effect increases by processing in a mixed gas atmosphere of alcohol, water vapor | steam, and air rather than the mixed gas of water vapor | steam and air as a downdraft.

  ADVANTAGE OF THE INVENTION According to this invention, the method of manufacturing a titanium oxide powder which reduces halogen content and has a small dispersion | variation in a halogen content reduction effect can be provided, suppressing the change of a rutile rate or a specific surface area.

Claims (6)

When the crude titanium oxide powder produced using titanium halide as a raw material is heat-treated in a cylindrical processing chamber,
While arranging the processing chamber vertically,
While forming a descending airflow that circulates the entire processing chamber by supplying dehalogenated gas into the processing chamber from the upper part of the processing chamber,
A method for producing a low halogen titanium oxide powder, wherein the crude titanium oxide powder is added to the treatment chamber and dropped while being dropped.   The method for producing a low halogen titanium oxide powder according to claim 1, wherein the crude titanium oxide powder is repeatedly dropped a plurality of times in the processing chamber.   The method for producing a low halogen titanium oxide powder according to claim 1 or 2, wherein the dehalogenating gas contains one or more selected from water vapor, alcohol gas, or a mixed gas thereof.   The said heat processing temperature is 300 degreeC or more, The manufacturing method of the low halogen titanium oxide powder in any one of Claims 1-3.   The method for producing a low halogen titanium oxide powder according to any one of claims 1 to 4, wherein an internal dimension of the cylindrical processing chamber is 50 to 300 mm in diameter.   The method for producing a low-halogen titanium oxide powder according to any one of claims 1 to 5, wherein a residence time per one time that the crude titanium oxide powder passes through the processing chamber is 5 seconds or less.