JP4895929B2 - Low halogen low rutile ultrafine titanium oxide and method for producing the same - Google Patents

Description

  The present invention relates to a low-rutile low-chlorine ultrafine particle titanium oxide suitable for photocatalysts, solar cells, additives to silicone rubber, dielectric use, and the like, and a method for producing the same. More specifically, in vapor phase titanium oxide obtained by high-temperature oxidation of a gas containing halogen titanium with an oxidizing gas, the halogen content is low, the remaining halogen can be easily removed, and the dispersibility is low. The present invention relates to a rutile type low-halogen ultrafine particle titanium oxide and a method for producing the same.

  Ultra-fine particle titanium oxide has been used for a wide variety of applications such as UV shielding materials, additives to silicone rubber, dielectric materials, cosmetics, etc. (Titanium oxide is a combination of titanium dioxide and Japanese Industrial Standards (JIS)). Since titanium oxide is widely used as a general name, it is abbreviated as titanium oxide in this specification). Titanium oxide is also applied as a photocatalyst, a solar cell, and the like.

  There are three types of crystal forms of titanium oxide: rutile, anatase, and brookite. Of these, anatase and brookite, which have better photoelectrochemical activity than rutile, in the aforementioned photocatalyst and solar cell applications. A mold is used.

  The photocatalytic action of titanium oxide is used to decompose organic substances such as antibacterial tiles, self-cleaning building materials, and deodorant fibers, and the mechanism thereof is explained as follows. Titanium oxide absorbs ultraviolet rays and generates electrons and holes therein. Holes react with the adsorbed water of titanium oxide to generate hydroxy radicals, and decompose organic substances adsorbed on the surface of the titanium oxide particles into carbon dioxide gas and water ("Hikari Clean Revolution" Akira Fujishima, Kazuhito Hashimoto, Toshiya Watanabe, (CMC Co., pp. 143-145 (1997)). That is, conditions for titanium oxide having a strong photocatalytic action include that holes are likely to be generated and holes are likely to reach the surface of titanium oxide. “All about titanium oxide photocatalyst” (Kazuhito Hashimoto, Akira Fujishima, CMC Co., Ltd., 29-30 (1998)) describes anatase-type titanium oxide, which has high photocatalytic activity, and has few lattice defects. Titanium and titanium oxide with small particles and large specific surface area are mentioned.

  The application as a solar cell has been studied since Gretzell et al. Of Lausanne Institute of Technology reported a dye-sensitized solar cell combining titanium oxide and a ruthenium-based dye in 1991 (M. Graezel, Nature). , 353, 737, (1991)). In the dye-sensitized solar cell, titanium oxide has a role as a dye carrier and an n-type semiconductor, and is used as a dye electrode bound to a conductive glass electrode. The dye-sensitized solar cell has a structure in which an electrolytic layer is sandwiched between a dye electrode and a counter electrode, and the dye generates electrons and holes by absorbing light. The generated electrons reach the conductive glass electrode through the titanium oxide layer and are extracted to the outside. On the other hand, the generated holes are transported to the counter electrode through the electrolytic layer, and are combined with electrons supplied through the conductive glass electrode. One factor that improves the characteristics of the dye-sensitized solar cell is that the titanium oxide and the dye can be easily combined. As a crystal form of titanium oxide that can be easily bonded to a dye, for example, anatase is used in JP-A-10-255863, and brookite is a dye-sensitized type in JP-A 2000-340269. It is described that it is suitable for solar cells.

  Titanium oxide having good dispersibility is important for extracting its function. For example, when titanium oxide is used as a photocatalyst, if the dispersibility is poor, the concealing power becomes strong, so that the usable applications are limited. Also in the field of solar cells, titanium oxide with poor dispersibility is difficult to transmit light, so titanium oxide that can contribute to light absorption is limited, and photoelectric conversion efficiency is deteriorated. In general, light scattering (hiding power) is maximized when the particle size is about ½ of the visible light wavelength, and light scattering is said to be weaker when the particle size becomes smaller (“Titanium oxide” written by Manabu Seino, Gihodo (Co.), p.129, (1991)). Since the primary particle diameter of titanium oxide used in the above-mentioned field is often several to several tens of nm, if the dispersibility is good, the influence on light scattering is small. However, titanium oxide with poor dispersion and large aggregate particle size will increase light scattering.

  For the above reasons, in the above field, titanium oxide is required to have high dispersibility, and anatase type or brookite type ultrafine titanium oxide having good dispersibility is used. In general, the primary particle diameter of ultrafine particles is not clarified, but is usually referred to fine particles of about 0.1 μm or less.

  When titanium oxide is used in a photocatalyst or a solar cell, if a corrosive component such as chlorine is present, the base material is corroded or altered, so that the chlorine content of titanium oxide needs to be kept low. Also, it is better to keep Fe, Al, Si, S, etc. low. For example, if there is too much Fe in titanium oxide, it causes coloring and is not suitable for use in applications requiring transparency. If there are too many components such as Al and S inside the titanium oxide particles, lattice defects may occur, and the functions as a photocatalyst and a solar cell may be reduced.

  Titanium oxide production methods are roughly classified into a liquid phase method in which titanium tetrachloride and titanyl sulfate are hydrolyzed, and a gas phase method in which titanium halide is reacted with an oxidizing gas such as oxygen or water vapor. Titanium oxide obtained by the liquid phase method can obtain anatase as a main phase, but must be in a sol or slurry state. When used in this state, the application is limited. In order to use it as a powder, it is necessary to dry it, and the ultrafine particles wetted by the solvent become more agglomerated as the drying progresses ("Ultrafine Particles Handbook" supervised by Shinroku Saito, Fuji Techno System, page 388, ( 1990) When this titanium oxide is used for a photocatalyst or the like, it is necessary to strongly disintegrate or grind the titanium oxide in order to enhance dispersibility. May cause problems.

  In general, titanium oxide produced by a vapor phase method is superior in dispersibility compared to a liquid phase method because a solvent is not used.

  There are many examples of obtaining ultrafine particles of titanium oxide by a gas phase method. For example, in JP-A-6-340423, in a method for producing titanium oxide by hydrolyzing titanium tetrachloride in a flame, oxygen, tetrachloride A method for obtaining a titanium oxide having a high rutile content by adjusting the molar ratio of titanium and hydrogen is disclosed. JP-A-7-316536 discloses a method for producing crystalline titanium oxide powder by hydrolyzing titanium tetrachloride in a high temperature gas phase and rapidly cooling the reaction product. A method for obtaining a crystalline transparent titanium oxide having an average primary particle size of 40 nm or more and 150 nm or less by specifying the titanium concentration is disclosed. However, in any case, only titanium oxide having fine particles but high rutile content is obtained, and is not suitable for use as a photocatalyst or solar cell.

  For example, Japanese Patent Application Laid-Open No. 3-252315 discloses a method for producing titanium oxide whose main phase is anatase by a gas phase method, by changing the ratio of hydrogen in a mixed gas of oxygen and hydrogen in a gas phase reaction. A production method for adjusting the ratio is disclosed, and titanium oxide having a rutile content of 9% is described. However, the particle size of the exemplified titanium oxide is 0.5 to 0.6 μm, which is coarser than the particle size range generally referred to as ultrafine particles.

  When titanium oxide is produced by a vapor phase method using titanium halide as a raw material, ultrafine particles can be easily obtained, but since halogen derived from the raw material remains in titanium oxide, dehalogenation by heating or washing with water is often required. However, ultrafine titanium oxide is subject to the sintering of particles by heating for low halogenation, and the specific surface area tends to decrease, and the crystal form transition from anatase type to rutile type may occur. . In order to suppress the decrease in the specific surface area and the crystal transition, it is necessary to perform heating at a low temperature or for a short time, but it is not possible to sufficiently dehalogenate. A method for reducing the chlorination of ultrafine titanium oxide is disclosed, for example, in JP-A-10-251102. In this method, titanium oxide is brought into contact with water vapor while rolling in a cylindrical rotary heating furnace to reduce the chlorine content. Moreover, the rutile content of the titanium oxide described therein was as high as 15%.

  On the other hand, halogen remaining on the surface of the titanium oxide particles can be removed by dehalogenation by washing with water or the like, but there is a problem that the internal halogen tends to remain because the halogen inside the particles is difficult to contact with water.

As described above, in the conventional vapor phase method, a low rutile type ultrafine particle titanium oxide having a low halogen content has not been obtained.
JP-A-10-255863 JP 2000-340269 A JP-A-6-340423 JP 7-316536 A JP-A-10-251021 "Light Clean Revolution" Akira Fujishima, Kazuhito Hashimoto, Toshiya Watanabe, CMC Co., pp.143-145 (1997) "All about titanium oxide photocatalysts" (Kazuhito Hashimoto, Akira Fujishima, CMC, 29-30 (1998)) M.M. Graezel, Nature, 353, 737, (1991) “Titanium oxide” written by Manabu Seino, Gihodo Co., Ltd., p. 129, (1991) ("Ultrafine particle handbook" supervised by Shinroku Saito, Fuji Techno System, p. 388, (1990)

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a low rutile type ultrafine titanium oxide having excellent dispersibility and low halogen content in a gas phase method, and a method for producing the same. Is to provide.

  As a result of diligent research in view of the above problems, the present inventors have found that it is possible to produce a low rutile ultrafine titanium oxide having excellent dispersibility in a gas phase method and having a low halogen content, and the above problems are solved. It came to solve.

  In the gas phase method in which a gas containing titanium halide and an oxidizing gas (oxygen, water vapor, or a mixed gas containing them) are reacted, the raw material gas is reacted while controlling the heating temperature and the heating time. After that, there is obtained a low rutile ultrafine titanium oxide having a high BET specific surface area and specific characteristics, which is obtained by dehalogenation and having a rutile content of 5% or less, and a method for producing the same. It is to provide.

That is, the present invention includes the following inventions.
(1) Titanium oxide obtained by reacting a gas containing titanium halide with an oxidizing gas, having a rutile content of 5% or less and a specific surface area of titanium oxide measured by the BET single point method B (m ² / g), when the total halogen content of titanium oxide is C (mass ppm),
C ≦ 650e ^0.02B
The specific surface area B of titanium oxide is 10 to ²⁰⁰ m ² / g, and when the aqueous suspension is 1% by mass, the aqueous suspension is allowed to stand at 20 ° C. for 30 minutes. Titanium oxide characterized in that 80% by mass or more of the halogen contained in is transferred to a liquid phase.
(2) The titanium oxide according to the above (1), wherein 90% by mass or more of the halogen contained in the titanium oxide is transferred to a liquid phase.
(3) Titanium oxide as described in said (1) or (2) in which a titanium oxide contains 100 mass ppm or less of each element of Fe, Al, Si, and S, respectively.
(4 ) The titanium oxide according to any one of (1) to ( 3 ), wherein the titanium oxide has a 90% cumulative mass particle size distribution diameter of 2.5 μm or less as measured by a laser diffraction particle size analyzer. .
( 5 ) The titanium oxide according to any one of (1) to ( 4 ), wherein the titanium halide is titanium tetrachloride, and the halogen is chlorine.
(6) In a vapor phase method for producing titanium oxide by reacting a gas containing titanium halide with an oxidizing gas, the gas containing titanium halide and the oxidizing gas are 600 ° C. or higher and lower than 1,100 ° C., respectively. When the gas containing titanium halide and the oxidizing gas are respectively introduced into the reactor and reacted, the temperature in the reactor is 800 ° C. or higher and lower than 1,100 ° C. A method for producing titanium oxide, wherein the gas containing titanium halide and the oxidizing gas have a residence time at a temperature of 800 ° C. or higher and lower than 1,100 ° C. in the reactor of 0.005 to 0.05 seconds. .
(7) A powder comprising titanium oxide produced by the production method described in ( 6 ) above.
( 8 ) A slurry containing titanium oxide produced by the production method described in ( 6 ) above.
( 9 ) A composition comprising titanium oxide produced by the production method described in ( 6 ) above.
( 10 ) A photocatalytic material comprising titanium oxide produced by the production method described in ( 6 ) above.
( 11 ) A wet solar cell material comprising titanium oxide produced by the production method described in ( 6 ) above.
( 12 ) A dielectric material comprising titanium oxide produced by the production method described in ( 6 ) above.
( 13 ) A silicone rubber additive comprising titanium oxide produced by the production method described in ( 6 ) above.
( 14 ) The rutile content is 5% or less, the specific surface area measured by the BET single point method is 10 to 200 m ² / g, and the 90% cumulative mass particle size distribution diameter measured by a laser diffraction particle size analyzer is 2.5 μm or less. When the specific surface area of the titanium oxide particles measured by the BET single point method is B (m ² / g) and the halogen content inside the titanium oxide particles is C _i (mass ppm), A titanium oxide particle, wherein the amount of halogen contained is represented by 0 ≦ C _i ≦ 650 ke ^0.02B (k is 0.20).
( 15 ) The titanium oxide particle according to ( 14 ), wherein the particle contains an amount of halogen represented by 10 <C _i ≦ 650 ke ^0.02B (k is 0.15).

As the titanium halide which is a raw material of the titanium oxide of the present invention, titanium chloride which is easily available industrially, particularly titanium tetrachloride is preferable. Therefore, hereinafter, the present invention will be described by way of a representative example where the halogen is chlorine, but the present invention can also be applied to the case where the halogen is bromine or iodine.
Although the low rutile ultrafine titanium oxide of the present invention is produced using titanium tetrachloride by a vapor phase method, there is almost no chlorine inside the particles. Chlorine remaining inside the particles may diffuse from the inside of the particles to the surface over time and corrode and alter the base material, but is difficult to remove by simple dechlorination treatment such as washing with water or drying. Therefore, it is desirable that chlorine is not present inside the titanium oxide particles.
Regarding the chlorine content in the particle in the total chlorine content on the particle surface and inside the particle, chlorine extracted from pure titanium with pure water (referred to as water-extracted chlorine) and total chlorine contained in the titanium oxide particles ( The ratio of total chlorine) is used as an index, and the following formula (1)
R = WCL / TCL × 100 (1)
(In the formula, R represents the surface chlorine ratio (%), WCL represents the content (mass%) of water-extracted chlorine contained in titanium oxide, and TCL represents the total chlorine content (mass%) contained in titanium oxide. )
The higher the value of R represented by is, the lower the chlorine content in the titanium oxide particles is. In the titanium oxide in the present invention, R is preferably 80% or more, and more preferably 90% or more.

The ultrafine particle titanium oxide obtained by the vapor phase method using titanium tetrachloride of the present invention as a raw material has a rutile content [the rutile content is abbreviated as a peak height (Hr) corresponding to a rutile crystal in X-ray diffraction. ), A ratio (= 100 × Hr / (Hr + Ha + Hb)) calculated from a peak height (abbreviated as Hb) corresponding to a brookite type crystal and a peak height (abbreviated as Ha) corresponding to an anatase type crystal. ] Is 5% or less of ultrafine titanium oxide (hereinafter sometimes referred to as low rutile ultrafine titanium oxide), and not only after the dechlorination step but also in some cases, the dechlorination step. Even before, the following general formula (2):
C ≦ 650 × e ^0.02B (2)
The total chlorine content represented by In formula, C shows total chlorine content (mass%). C, for example, a solution obtained by adding a hydrofluoric acid aqueous solution to titanium oxide and heating and dissolving with microwaves is measured by potentiometric titration with silver nitrate to obtain the mass of chlorine in titanium oxide. It is obtained by dividing by mass. B represents a BET specific surface area (m ² / g), and the range thereof is 10 to ²⁰⁰ m ² / g. It has the characteristic represented by this.

That is, the low rutile ultrafine particle titanium oxide of the present invention is a titanium oxide having a low total chlorine content that satisfies the condition of the general formula (2) in FIG. 1, and the R of the formula (1) is large. Titanium oxide particles with a small chlorine content inside the particles. Even if the conventional ultrafine particle titanium oxide by a vapor phase method using titanium tetrachloride as a raw material is a low rutile type titanium oxide, C = 650 × shown in FIG. 1 in relation to the BET specific surface area and the total chlorine content. e Titanium oxide particles having the characteristics of the region plotted at the top of the curve represented by ^0.02B , and also having a high chlorine content inside the particles. In particular, titanium oxide having a large specific surface area is less likely to be dechlorinated and the chlorine content tends to increase exponentially.

The low rutile titanium oxide of the present invention is a superfine particle in which the relationship between the chlorine content and the BET specific surface area satisfies the characteristics of the general formula (2), and the range of the BET specific surface area is usually 10 to ²⁰⁰ m ^2. / g, preferably those 40 to 200 m ² / g, more preferably having a range of 45~120m ² / g.

Further, the low rutile ultrafine titanium oxide of the present invention has Fe, Al, Si, and S contents of 100 ppm by mass or less, preferably 0.1 to 100 ppm by mass, more preferably 0.1 to 0.1 ppm by mass. -50 mass ppm, more preferably 0.1-10 mass ppm.
In order to make these impurity concentrations less than 0.1 ppm, it is necessary to make the raw material for producing titanium oxide highly pure and to use equipment materials with higher corrosion resistance. In applications in which the titanium oxide of the present invention is usually used, it is economically advantageous not to make each impurity less than 0.1 ppm by mass.

  The low rutile type titanium oxide of the present invention is characterized by high dispersibility. In the present invention, the particle size distribution was measured by adopting a laser diffraction particle size distribution measuring method as an index of dispersibility. Dispersibility measurement methods include the “ultrafine particle handbook” supervised by Shinroku Saito, Fuji Techno System, p93, (1990), such as sedimentation, microscopy, light scattering, and direct counting. Among them, the sedimentation method and the direct counting method have a measurable particle size of several hundred nm or more and are not suitable for measuring the dispersibility of ultrafine particles. In addition, the microscopic method is not a preferable measuring method because the measured value may vary depending on the sampling of the target sample or the pretreatment of the sample. On the other hand, the light scattering method can measure the particle diameter in the range of several nm to several μm and is suitable for the measurement of ultrafine particles. The measurement procedure of the particle size distribution will be described below.

  A slurry obtained by adding 50 ml of pure water and 100 μl of 10% sodium hexametaphosphate aqueous solution to 0.05 g of titanium oxide is subjected to ultrasonic irradiation (46 KHz, 65 W) for 3 minutes. The slurry is subjected to a laser diffraction particle size distribution analyzer (SALD-2000J, manufactured by Shimadzu Corporation) to measure the particle size distribution. If the value of the 90% cumulative mass particle size distribution diameter (hereinafter sometimes abbreviated as D90) in the particle size distribution measured in this way is small, it is judged that the polymer exhibits good dispersibility in the hydrophilic solvent. Is done. Although it is possible to use the 50% cumulative mass particle size distribution diameter as an index of dispersibility, it is difficult to detect agglomerated particles having poor dispersibility. The ultrafine titanium oxide of the present invention preferably has a D90 of 2.5 μm or less.

  The ultrafine titanium oxide of the present invention is included as a raw material of various compositions, a pigment or a particle component utilizing the photocatalytic effect, and includes various materials such as cosmetics, ultraviolet shielding materials, dielectrics or silicone rubbers, solar cells, etc. It can be used as a raw material and additive for products.

Next, a manufacturing method will be described.
A general method for producing titanium oxide by a vapor phase method is known. When titanium tetrachloride is oxidized using an oxidizing gas such as oxygen or steam under a reaction condition of about 1,000 ° C., fine titanium oxide is obtained. can get.

  In order to obtain ultrafine titanium oxide in the vapor phase method, the growth time (growth zone) of the particles must be shortened. That is, grain growth due to sintering or the like can be suppressed by cooling and diluting immediately after the reaction and shortening the high temperature residence time as much as possible. Shortening the high temperature residence time also leads to suppression of thermal rearrangement from anatase to rutile, and particles having a high anatase content can be obtained.

Generally, 0.1 to 2% by mass of chlorine remains in titanium oxide obtained by a vapor phase method using titanium tetrachloride as a raw material. On the anatase type titanium oxide surface, there are 13 points / nm ² that can bind chlorine and the like (manufactured by Manabu Kiyono, “Titanium oxide”). The remaining chlorine content is theoretically expressed by the following formula (3).
Y = 0.077 × A (3)
(In the formula, Y represents the chlorine content (% by mass) remaining on the surface of the titanium oxide particles, and A represents the specific surface area (m ² / g).)
For example, the chlorine content remaining on the surface of the titanium oxide particles having a specific surface area of 100 m ² / g is about 8% by mass according to the formula (3).

  Actually, the chlorine content of titanium oxide can be obtained by the above formula (3) by replacing chlorine and oxidizing gas in the reaction and by the equilibrium transfer of chlorine due to the chlorine concentration difference between the titanium oxide particle surface and the gas phase. Although it may be slightly lower than the value, shortening the high-temperature residence time in the reaction will not complete the oxidation reaction of titanium tetrachloride, but will increase the titanium oxide that is partially chlorinated Conceivable. In addition, if the residual chlorine is left inside the titanium oxide particles, the amount of chlorine inside the particles is also increased, so that the heat treatment required for removing chlorine is increased in temperature and time, and the specific surface area is reduced. Therefore, conventionally, ultrafine particles obtained by the vapor phase method have a high anatase content but a high chlorine content, or a low chlorine content but a low anatase content.

In the present invention, in a gas phase method for producing titanium oxide by reacting a gas containing titanium tetrachloride and an oxidizing gas (high-temperature oxidation), titanium tetrachloride heated to 600 ° C. or more and less than 1,100 ° C. is contained. Gas and an oxidizing gas heated to 600 ° C. or higher and lower than 1,100 ° C. are respectively supplied to the reaction tube, and titanium oxide obtained by the reaction is 0.1 ° C. in a high temperature condition of 800 ° C. or higher and lower than 1,100 ° C. By staying in the reaction tube for a time of less than a second, a low rutile ultrafine particle titanium oxide having a low total chlorine content, particularly a low chlorine content inside the particle in relation to the BET specific surface area and the chlorine content, is obtained. It has been found that low rutile type ultrafine particle titanium oxide having a lower total chlorine content and a lower chlorine content inside the particles can be obtained by dechlorinating.
Here, dechlorination includes a dry method and a wet method. The dry dechlorination method includes, for example, a method of removing chlorine by heating titanium oxide using a heating device such as a cylindrical rotary heating furnace, a hot air circulation heating furnace, a fluidized drying furnace, a stirring drying furnace or the like. The present invention is not necessarily limited to these heating devices. In addition, the wet dechlorination method includes, for example, a method in which titanium oxide is suspended in pure water and chlorine transferred to the liquid phase is separated from the system. After separating chlorine out of the system, the obtained titanium oxide may be dried.

  The temperature in the reaction tube into which the titanium tetrachloride-containing gas or oxidizing gas is introduced is preferably 800 ° C. or higher and lower than 1,100 ° C., more preferably 900 ° C. or higher and lower than 1,000 ° C. By increasing the temperature in the reaction tube, the reaction is completed simultaneously with mixing, so that uniform nucleation is promoted and the reaction (CVD) zone can be reduced. When the temperature in the reaction tube is lower than 800 ° C., titanium oxide having a high anatase content is easily obtained, but the reaction is insufficient and chlorine remains inside the titanium oxide particles. When the temperature in the reaction tube is 1,100 ° C. or higher, rutile transition and particle growth proceed, and low rutile type and ultrafine particles cannot be obtained.

  On the other hand, when the raw material gas is introduced into the reaction tube and the reaction proceeds, this reaction is an exothermic reaction, so that there is a reaction zone where the reaction temperature exceeds 1,100 ° C. Although there is some heat dissipation from the device, the titanium oxide particles grow more and more and the crystal form is transferred to rutile unless rapid cooling is performed. Therefore, in the present invention, the high temperature residence time of 800 ° C. or more and less than 1,100 ° C. is 0.1 seconds or less, preferably 0.005 to 0.1 seconds, particularly preferably 0.01 to 0.05 seconds. To do. If the high temperature residence time exceeds 0.1 seconds, the transition to rutile and particle sintering proceed, which is not preferable. When the high-temperature residence time is less than 0.005 seconds, the oxidation reaction time of titanium tetrachloride is also shortened. Therefore, it is necessary to carry out under conditions that facilitate oxidation, such as using a sufficiently excessive amount of oxygen compared to titanium tetrachloride. Insufficient oxidation leads to an increase in the amount of residual chlorine inside the particles.

  As the rapid cooling means, for example, a method of introducing a large amount of cooling air or nitrogen gas into the reaction mixture, a method of spraying water, or the like is employed.

  By controlling the temperature in the reaction tube to be 800 ° C. or more and less than 1,100 ° C., ultrafine particles having a low chlorine content inside the particles can be obtained, and the high temperature residence time is controlled to 0.1 seconds or less. Can suppress rutile transition and grain growth.

  In order to set the temperature in the reaction tube to 800 ° C. or higher and lower than 1,100 ° C., the heating temperature of the raw material gas is preferably adjusted to 600 ° C. or higher and 1,100 ° C. or lower. The heated source gas reacts and generates heat in the reaction tube, but if the source gas temperature is less than 600 ° C., the temperature in the reaction tube is unlikely to be 800 ° C. or higher. On the other hand, if the raw material gas temperature is 1,100 ° C. or higher, the temperature in the reaction tube tends to exceed 1,100 ° C. although there is heat dissipation from the apparatus.

  The raw material gas composition containing titanium tetrachloride is preferably 0.1 to 20 moles of inert gas, more preferably 4 to 20 moles per mole of titanium tetrachloride gas. When the inert gas is less than the above range, the titanium oxide particle density in the reaction zone increases, and it becomes easy to aggregate and sinter, so it is difficult to obtain ultrafine titanium oxide. When there are more inert gases than the said range, the reactivity will fall and the recovery rate as a titanium oxide will fall.

The amount of oxygen gas to be reacted with the raw material gas containing titanium tetrachloride is preferably 1 to 30 mol per 1 mol of titanium tetrachloride. More preferably, it is 5-30 mol. Increasing the amount of oxygen gas increases the number of nuclei generated and makes it easier to obtain ultrafine particles. However, even if the amount exceeds 30 mol, there is almost no effect of increasing the number of nuclei generated. Even if the amount of oxygen gas exceeds 30 moles, there is no influence on the characteristics of titanium oxide, but the upper limit is set from an economical point of view. On the other hand, when the amount of oxygen gas is insufficient with respect to titanium tetrachloride, titanium oxide with many oxygen defects is formed and colored. The oxidizing gas may contain water vapor in addition to oxygen.
As the oxidizing gas, for example, oxygen, oxygen including water vapor, air, or a gas obtained by mixing an inert gas (nitrogen, argon, etc.) with these oxidizing gases can be used, but the reaction temperature is easily controlled. Oxygen containing water vapor is preferred.

  Dechlorination by heating of titanium oxide is performed while bringing steam into contact with titanium oxide powder so that the mass ratio of water to titanium oxide (= mass of water vapor / mass of titanium oxide, the same applies hereinafter) is 0.01 or more. It is preferable to carry out at a temperature of 200 ° C. or higher and 500 ° C. or lower. More preferably, the mass ratio of water and titanium oxide is 0.04 or more, and the heating temperature is 250 ° C. or more and 450 ° C. or less. When the heating temperature exceeds 500 ° C., sintering of the titanium oxide particles proceeds and grain growth occurs. When the heating temperature is lower than 200 ° C., the efficiency of dechlorination is extremely reduced. Dechlorination proceeds by the substitution reaction of chlorine on the surface of titanium oxide with water near the particles or surface hydroxyl groups of adjacent particles. When chlorine on the surface of titanium oxide particles is replaced with water, it is dechlorinated without growing grains, but when it is replaced with hydroxyl groups on the adjacent particles, grains grow simultaneously with dechlorination. . In particular, the larger the specific surface area of titanium oxide, the higher the probability of substitution reaction with the adjacent particle surface hydroxyl groups, and thus the easier the grain growth. That is, the mass ratio of water and titanium oxide is also important for dechlorination while suppressing grain growth. If the mass ratio of water and titanium oxide is 0.01 or more, the effect of suppressing grain growth is achieved. Is recognized.

  The water vapor to be brought into contact with the titanium oxide is preferably used by mixing with a gas having a role of efficiently transferring chlorine separated from the titanium oxide out of the system. An example of such a gas is air. When air is used, water vapor is preferably contained in the air in an amount of 0.1% by volume or more, more preferably 5% by volume or more, and particularly preferably 10% by volume or more. The air containing water vapor is preferably heated to 200 ° C. or higher and 1,000 ° C. or lower.

Since the low rutile ultrafine particle titanium oxide according to the present invention has almost no chlorine inside the particles, it can be reduced in the wet state. Examples of the wet dechlorination method include a method in which titanium oxide is suspended in pure water, and chlorine transferred to the liquid phase is separated from the system by an ultrafiltration membrane, a reverse osmosis membrane, a filter press, or the like.
The low rutile ultrafine titanium oxide having a low total halogen content and a low halogen content inside the grain in the relationship between the BET specific surface area and the halogen content of the present invention thus produced is preferably a halogen on the grain surface. By completely dehalogenating, a low rutile ultrafine titanium oxide having a very low total halogen content in relation to the BET specific surface area can be obtained.
Therefore, the low rutile ultrafine titanium oxide of the present invention has a rutile content of 5% or less, a specific surface area measured by the BET single point method of 10 to 200 m ² / g, as described above, and measured by a laser diffraction particle size analyzer. The 90% cumulative mass particle size distribution diameter is 2.5 μm or less of titanium oxide particles and the specific surface area of titanium oxide measured by the BET single point method is B (m ² / g), and the halogen content inside the titanium oxide particles When the amount is C _i (ppm by mass), the amount of halogen contained in the particle is 0 ≦ C _i ≦ 650 ^{ke 0.02B} (k is 0.20), preferably 0 <C _i ≦ 650 ^{ke 0.02B} (k is 0 20), more preferably 10 <C _i ≦ 650 ^{ke 0.02B} (k is 0.15).

  Hereinafter, although an Example and a comparative example demonstrate concretely, this invention is not limited to these at all.

Reference example 1:
A titanium tetrachloride dilution gas obtained by diluting 11.8 Nm ³ / hr (N means standard state; the same shall apply hereinafter) gaseous titanium tetrachloride with 8 Nm ³ / hr of nitrogen gas is preheated to 900 ° C., and 8 Nm ³ An oxidizing gas in which / hr oxygen and 32 Nm ³ / hr water vapor were mixed was preheated to 800 ° C., and these raw material gases were introduced into a quartz glass reactor. Cooling air was introduced into the reaction tube so that the high-temperature residence time of 800 ° C. or more and less than 1,100 ° C. was 0.1 second, and then ultrafine titanium oxide powder was collected with a polytetrafluoroethylene bag filter.

The obtained titanium oxide was passed through a cylindrical rotary heating furnace and dechlorinated at a mass ratio of water to titanium oxide of 0.02 and a heating temperature of 450 ° C. Thereafter, the obtained titanium oxide had a BET specific surface area of 22 m ² / g, a rutile content ratio (also referred to as a rutile content) of 1%, a water extraction chlorine content of 900 mass ppm, and a total chlorine content of 1, It was 000 mass ppm. However, the BET specific surface area is measured with a specific surface area measuring device manufactured by Shimadzu Corporation (model is Flowsorb II, 2300), and the rutile content ratio is a peak height corresponding to a rutile crystal in X-ray diffraction (abbreviated as Hr). The ratio (= 100 × Hr / (Hr + Ha + Hb)) calculated from the peak height (abbreviated as Hb) corresponding to the brookite type crystal and the peak height (abbreviated as Ha) corresponding to the anatase type crystal. . The surface chlorine ratio calculated by substituting the water extraction chlorine content 900 mass ppm and the total chlorine content 1,000 mass ppm into the formula (1) is higher than 80%, and the total chlorine content is calculated by the formula (2) The numerical value smaller than the value calculated by substituting 22 m ² / g for the specific surface area is shown.

  Moreover, about the particle size distribution of the titanium oxide powder obtained here, it was 1.1 micrometers as a result of measuring 90% cumulative mass particle size distribution diameter D90 by the laser diffraction type particle size distribution measuring method. Table 1 shows the analysis results of rutile ratio, BET specific surface area, total chlorine content, surface chlorine ratio, D90, and Fe, Al, Si, and S.

Example 1 :
A titanium tetrachloride dilution gas obtained by diluting 5.9 Nm ³ / hr of gaseous titanium tetrachloride with 30 Nm ³ / hr of nitrogen gas is preheated to 1,000 ° C., and 4 Nm ³ / hr of oxygen and 16 Nm ³ / hr of water vapor The premixed oxidizing gas was preheated to 1,000 ° C., and these raw material gases were introduced into a quartz glass reactor. Cooling air was introduced into the reaction tube so that the high-temperature residence time of 800 ° C. or more and less than 1,100 ° C. was 0.03 seconds, and then the ultrafine titanium oxide powder was collected with a polytetrafluoroethylene bag filter.

The obtained titanium oxide was put into a hot air circulating heating furnace and dechlorinated at a water / titanium oxide mass ratio of 0.04 and a heating temperature of 450 ° C. The titanium oxide thus obtained had a BET specific surface area of 65 m ² / g, a rutile content of 3%, a water extraction chlorine content of 900 mass ppm, and a total chlorine content of 1,100 mass ppm. The surface chlorine ratio calculated by substituting the water extraction chlorine content 900 mass ppm and the total chlorine content 1,100 mass ppm into the formula (1) is higher than 80%, and the total chlorine content is calculated by the formula (2) A numerical value smaller than the value calculated by substituting for the specific surface area of 65 m ² / g was shown. The 90% cumulative mass particle size distribution diameter D90 in the particle size distribution measured by the laser diffraction particle size distribution measurement method of this powder was 1.9 μm. Table 1 shows the analysis results of rutile ratio, BET specific surface area, total chlorine content, surface chlorine ratio, D90, and Fe, Al, Si, and S.

Example 2 :
A titanium tetrachloride dilution gas obtained by diluting 4.7 Nm ³ / hr of gaseous titanium tetrachloride with 36 Nm ³ / hr of nitrogen gas is preheated to 1,000 ° C., and then 36 Nm ³ / hr of air and 25 Nm ³ / hr of water vapor The premixed oxidizing gas was preheated to 1,000 ° C., and these raw material gases were introduced into a quartz glass reactor. Cooling air was introduced into the reaction tube so that the high temperature residence time of 800 ° C. or higher and lower than 1,100 ° C. was 0.02 seconds, and then the ultrafine titanium oxide powder was collected with a polytetrafluoroethylene bag filter.

The obtained titanium oxide was put into a hot air circulating heating furnace and dechlorinated at a water / titanium oxide mass ratio of 0.06 and a heating temperature of 350 ° C. The titanium oxide thus obtained had a BET specific surface area of 97 m ² / g, a rutile content of 1%, a water extraction chlorine content of 1,800 mass ppm, and a total chlorine content of 2,000 mass ppm. The surface chlorine ratio calculated by substituting the water extraction chlorine content of 1,800 mass ppm into the formula (1) and the total chlorine content of 2,000 mass ppm is higher than 80%. A numerical value smaller than the value calculated by substituting the specific surface area of 97 m ² / g into 2) was shown. The 90% cumulative mass particle size distribution diameter D90 in the particle size distribution measured by the laser diffraction particle size distribution measurement method of this powder was 2.2 μm. Table 1 shows the analysis results of rutile ratio, BET specific surface area, total chlorine content, surface chlorine ratio, D90, and Fe, Al, Si, and S.

Comparative Example 1:
11.8 nm ³ / hr of gaseous forty-four titanium chloride diluent gas diluted titanium tetrachloride with nitrogen gas 8 Nm ³ / hr and was preheated to 900 ° C., were mixed oxygen and 32 Nm ³ / hr of water vapor 8 Nm ³ / hr The oxidizing gas was preheated to 800 ° C., and these raw material gases were introduced into a quartz glass reactor. Cooling air was introduced into the reaction tube so that the high-temperature residence time of 800 ° C. or more and less than 1,100 ° C. was 0.2 seconds, and then ultrafine particulate titanium oxide powder was collected with a polytetrafluoroethylene bag filter. .

The obtained titanium oxide was passed through a cylindrical rotary heating furnace and dechlorinated at a water / titanium oxide mass ratio of 0.02 and a heating temperature of 450 ° C. The titanium oxide thus obtained had a BET specific surface area of 19 m ² / g, a rutile content ratio of 11%, a water extraction chlorine content of 300 mass ppm, and a total chlorine content of 300 mass ppm. The surface chlorine ratio calculated by substituting the water extraction chlorine content of 300 mass ppm and the total chlorine content of 300 mass ppm into the formula (1) is higher than 80%, and the total chlorine content is compared with the formula (2). A numerical value smaller than the value calculated by substituting the surface area of 19 m ² / g was shown. The 90% cumulative mass particle size distribution diameter D90 in the particle size distribution measured by the laser diffraction particle size distribution measurement method of this powder was 0.8 μm. Table 1 shows the analysis results of rutile ratio, BET specific surface area, total chlorine content, surface chlorine ratio, D90, and Fe, Al, Si, and S.

Comparative Example 2:
Preheated 4.7 nm ³ / hr of gaseous forty-four titanium chloride diluent gas diluted titanium tetrachloride with nitrogen gas 36 Nm ³ / hr to 800 ° C., mixing air and 25 Nm ³ / hr of steam 36 Nm ³ / hr The oxidized gas was preheated to 800 ° C., and these raw material gases were introduced into a quartz glass reactor. The reaction tube temperature was controlled at 750 ° C., and cooling air was introduced into the reaction tube so that the raw material gas was retained for 0.08 seconds, and then the ultrafine titanium oxide powder was collected with a polytetrafluoroethylene bag filter. .

The obtained titanium oxide was put into a hot air circulating heating furnace and dechlorinated at a water / titanium oxide mass ratio of 0.04 and a heating temperature of 350 ° C. The titanium oxide thus obtained had a BET specific surface area of 74 m ² / g, a rutile content of 2%, a water extraction chlorine content of 2,800 mass ppm, and a total chlorine content of 3,900 mass ppm. The surface chlorine ratio calculated by substituting the water extraction chlorine content of 2,800 mass ppm and the total chlorine content of 3,900 mass ppm into the formula (1) is lower than 80%. A value larger than the value calculated by substituting the specific surface area of 74 m ² / g for 2) was shown. The 90% cumulative mass particle size distribution diameter D90 in the particle size distribution measured by the laser diffraction particle size distribution measurement method of this powder was 3.6 μm. Table 1 shows the analysis results of rutile ratio, BET specific surface area, total chlorine content, surface chlorine ratio, D90, and Fe, Al, Si, and S.

Comparative Example 3:
A titanium tetrachloride dilution gas obtained by diluting 5.9 Nm ³ / hr of gaseous titanium tetrachloride with 30 Nm ³ / hr of nitrogen gas is preheated to 1,100 ° C., and 4 Nm ³ / hr of oxygen and 16 Nm ³ / hr of water vapor The premixed oxidizing gas was preheated to 1,100 ° C., and these source gases were introduced into a quartz glass reactor. The reaction tube temperature is controlled to 1,200 ° C., cooling air is introduced into the reaction tube so that the raw material gas stays for 0.04 seconds, and the ultrafine titanium oxide powder is captured by a polytetrafluoroethylene bag filter. Gathered.

The obtained titanium oxide was put into a hot air circulating heating furnace and dechlorinated at a water / titanium oxide mass ratio of 0.06 and a heating temperature of 450 ° C. The titanium oxide thus obtained had a BET specific surface area of 44 m ² / g, a rutile content of 12%, a water extracted chlorine content of 1,200 mass ppm, and a total chlorine content of 1,300 mass ppm. The surface chlorine ratio calculated by substituting the water extraction chlorine content of 1,200 mass ppm and the total chlorine content of 1,300 mass ppm into the formula (1) is higher than 80%. A numerical value smaller than the value calculated by substituting the specific surface area 44 m ² / g into 2) was shown. The 90% cumulative mass particle size distribution diameter D90 in the particle size distribution measured by the laser diffraction particle size distribution measurement method of this powder was 1.2 μm. Table 1 shows the analysis results of rutile ratio, BET specific surface area, total chlorine content, surface chlorine ratio, D90, and Fe, Al, Si, and S.
Comparative Example 4:
A commercially available titanyl sulfate solution (manufactured by Kanto Chemical Co., Ltd., reagent grade 1) was boiled, and the resulting precipitate was washed with pure water to obtain hydrous titanium oxide. In order to remove the residual sulfuric acid of the hydrous titanium oxide, pure water was added to form a slurry, and the aqueous solution was adjusted to pH 5 with stirring while stirring, and stirred for 12 hours. Thereafter, the hydrous titanium oxide concentration was concentrated to 20% by mass with an ultrafiltration membrane. An aqueous ammonia solution was added to the concentrate again to adjust to pH 5. After stirring for 12 hours, the solution was filtered through an ultrafiltration membrane while adding pure water to obtain a titania sol. The obtained titania sol was dried at 300 ° C. for 2 hours to obtain ultrafine titanium oxide by a liquid phase method.
The obtained titanium oxide had a BET specific surface area of 212 m ² / g and a rutile content of 1%. Both the water-extracted chlorine content and the total chlorine content were 0 ppm by mass. The titanium oxide was crushed in a mortar and the particle size distribution was measured by a laser diffraction particle size distribution measurement method. As a result, the 90% cumulative mass particle size D90 was 26.1 μm. Table 1 shows the analysis results of rutile ratio, BET specific surface area, total chlorine content, surface chlorine ratio, D90, and Fe, Al, Si, and S.

  According to the present invention, an anatase-type ultrafine titanium oxide by a vapor phase method, which has a low halogen content inside a particle and is particularly excellent in dispersibility, compared with a conventional titanium oxide having an equivalent BET specific surface area, is obtained by dehalogenation. Titanium oxide in which the relationship between the BET specific surface area (B) and the halogen content (C) satisfies the condition of the above formula (2), D90 measured by the laser diffraction particle size distribution measurement method is 2.5 μm or less Titanium oxides and methods for their production are provided.

  The titanium oxide of the present invention is suitable for photocatalyst use, solar cell use and the like. Particularly, since it has excellent dispersibility in aqueous solvents, it can be suitably used for photocatalyst use in water, and can be crushed as a powder. A process or the like is unnecessary, or an extremely light facility is required, and it has an industrially very large practical value.

The relationship between the halogen content rate of a microparticulate titanium oxide and a BET specific surface area is shown.

Claims (15)

Titanium oxide obtained by reacting a gas containing titanium halide with an oxidizing gas, the rutile content is 5% or less, and the specific surface area of titanium oxide measured by the BET one-point method is B (m ² / g), when the total halogen content of titanium oxide is C (mass ppm),
C ≦ 650e ^0.02B
The specific surface area B of titanium oxide is 10 to ²⁰⁰ m ² / g, and when the aqueous suspension is 1% by mass, the aqueous suspension is allowed to stand at 20 ° C. for 30 minutes. Titanium oxide characterized in that 80% by mass or more of the halogen contained in is transferred to a liquid phase.   The titanium oxide according to claim 1, wherein 90% by mass or more of the halogen contained in the titanium oxide is transferred to a liquid phase.   The titanium oxide according to claim 1 or 2, wherein the titanium oxide contains 100 mass ppm or less of each element of Fe, Al, Si, and S. The titanium oxide according to any one of claims 1 to 3 , wherein the titanium oxide has a 90% cumulative mass particle size distribution diameter of 2.5 µm or less as measured by a laser diffraction particle size analyzer. The titanium oxide according to any one of claims 1 to 4 , wherein the titanium halide is titanium tetrachloride and the halogen is chlorine. In a vapor phase method for producing titanium oxide by reacting a gas containing titanium halide with an oxidizing gas, the gas containing the titanium halide and the oxidizing gas are preheated to 600 ° C. or more and less than 1,100 ° C., respectively. When introduced into the reactor, a gas containing titanium halide and an oxidizing gas were introduced into the reactor and reacted, the temperature in the reactor was 800 ° C. or higher and lower than 1,100 ° C. A method for producing titanium oxide, wherein the gas containing and the oxidizing gas have a residence time at a temperature of 800 ° C. or higher and lower than 1,100 ° C. in the reactor of 0.005 to 0.05 seconds . A powder comprising titanium oxide produced by the production method according to claim 6 . A slurry comprising titanium oxide produced by the production method according to claim 6 . A composition comprising titanium oxide produced by the production method according to claim 6 . A photocatalytic material comprising titanium oxide produced by the production method according to claim 6 . A wet solar cell material comprising titanium oxide produced by the production method according to claim 6 . A dielectric material comprising titanium oxide produced by the production method according to claim 6 . A silicone rubber additive comprising titanium oxide produced by the production method according to claim 6 . Titanium oxide particles having a rutile content of 5% or less, a specific surface area measured by the BET one-point method of 10 to 200 m ² / g, and a 90% cumulative mass particle size distribution measured by a laser diffraction particle size analyzer of 2.5 μm or less And the specific surface area of titanium oxide measured by the BET single-point method is B (m ² / g), and the halogen content in the titanium oxide particles is C _i (mass ppm), the halogen contained in the particles Titanium oxide particles characterized in that the amount is represented by 0 ≦ C _i ≦ 650 ke ^0.02B (k is 0.20). The titanium oxide particle according to claim 14 , wherein an amount of halogen represented by 10 <C _i ≦ 650 ke ^0.02B (k is 0.15) is contained inside the particle.

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